IEC TS 61496-4-3:2022
(Main)Safety of machinery - Electro-sensitive protective equipment - Part 4-3: Particular requirements for equipment using vision based protective devices (VBPD) - Additional requirements when using stereo vision techniques (VBPDST)
Safety of machinery - Electro-sensitive protective equipment - Part 4-3: Particular requirements for equipment using vision based protective devices (VBPD) - Additional requirements when using stereo vision techniques (VBPDST)
IEC TS 61496-4-3:2022 specifies requirements for the design, construction and testing of non-contact electro-sensitive protective equipment (ESPE) designed specifically to detect persons or parts of persons as part of a safety-related system, employing vision-based protective devices (VBPDs) using stereo vision techniques (VBPDST) for the sensing function. Special attention is directed to features which ensure that an appropriate safety-related performance is achieved. An ESPE can include optional safety-related functions, the requirements for which are given in Annex A of IEC 61496-1:2020 and this document. Where this document does not contain all necessary provisions, IEC TS 62998-1 applies. It is also possible, for those aspects not considered in this document, to use provisions from IEC TS 62998-1 additionally. This document does not specify the dimensions or configurations of the detection zone and its disposition in relation to hazardous parts for any particular application, nor what constitutes a hazardous state of any machine. It is restricted to the functioning of the ESPE and how it interfaces with the machine. The detection principle is based on the evaluation of images from different viewing points (stereoscopic view) for the determination of distance information. This distance information is used to determine the position of an object(s).
– This document is limited to vision based ESPEs with fixed distances (stereo base) and fixed directions of the optical axes using a fixed focal length.
– It is limited to vision based ESPEs that do not require human intervention for detection.
– It is limited to vision based ESPEs that detect objects entering into or being present in a detection zone(s).
– It is limited to VBPDSTs employing radiation at wavelengths within the range 400 nm to 1 500 nm.
– This document does not address those aspects required for complex classification or differentiation of the object detected.
– This document does not consider the aspects of a moving ESPE installation.
Additional requirements and tests can apply in the following cases:
– Use of multi-spectral (colour) techniques;
– Setups other than as shown in Figure 2 and Figure 3 (e.g. changing backgrounds, horizontal orientation of the optical axis with respect to the floor);
– Intended for outdoor applications.
This document is relevant for VBPDSTs having a stated detection capability up to 200 mm. This document can be relevant to applications other than those for the protection of persons or parts of persons like arm or fingers (in the range 14 mm to 200 mm), for example the protection of machinery or products from mechanical damage. In those applications, additional requirements can be necessary, for example when the materials that are to be recognized by the sensing function have different properties from those of persons. This document does not deal with EMC emission requirements.
IEC TS 61496-4-3:2022 cancels and replaces the first edition published in 2015-05. This edition constitutes a technical revision. This edition includes the following technical changes with respect to the previous edition:
a) Some requirement clauses and test procedures have been adapted or removed because they have been consolidated in IEC 61496-1:2020 (e.g. 5.4.6.2 Light sources or Clause A.9).
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Standards Content (Sample)
IEC TS 61496-4-3 ®
Edition 2.0 2022-09
TECHNICAL
SPECIFICATION
colour
inside
Safety of machinery – Electro-sensitive protective equipment –
Part 4-3: Particular requirements for equipment using vision based protective
devices (VBPD) – Additional requirements when using stereo vision techniques
(VBPDST)
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IEC TS 61496-4-3 ®
Edition 1.0 2022-09
TECHNICAL
SPECIFICATION
colour
inside
Safety of machinery – Electro-sensitive protective equipment –
Part 4-3: Particular requirements for equipment using vision based protective
devices (VBPD) – Additional requirements when using stereo vision techniques
(VBPDST)
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 13.110; 29.260.99 ISBN 978-2-8322-5739-5
– 2 – IEC TS 61496-4-3:2022 © IEC 2022
CONTENTS
FOREWORD . 4
INTRODUCTION . 6
1 Scope . 7
2 Normative references . 8
3 Terms and definitions . 8
4 Functional, design and environmental requirements . 12
5 Testing . 21
6 Marking for identification and for safe use . 34
7 Accompanying documents . 34
Annex A (normative) Optional functions of the ESPE . 36
Annex B (normative) Catalogue of single faults affecting the electrical equipment of
the ESPE, to be applied as specified in 5.3 . 38
Annex AA (informative) The positioning of VBPDST employing a volume as a
detection zone in respect of parts of the human body . 39
Annex BB (informative) Relationship between position accuracy and tolerance zones
for VBPDST . 48
Annex CC (informative) Basic principles of physics for contrast of convex
homogeneous bodies . 54
Bibliography . 61
Figure 1 – Image planes in imaging device of a VBPDST . 9
Figure 2 – 3D view of a vision based protective device using stereo vision techniques
(VBPDST) . 12
Figure 3 – 2D view of a vision based protective device using stereo vision techniques
(VBPDST) . 13
Figure 4 – Examples for periodic surface structures on the background . 25
Figure 5 – Test setup for indirect light interference on the background. 30
Figure 6 – Test setup for VBPDST of identical design with PAPT . 31
Figure 7 – Test setup for direct light interference on the sensing device . 32
Figure AA.1 – Minimum distance S – Example 1 . 42
Figure AA.2 – Overall minimum distance S without tolerance zone – Example 1 . 42
o
Figure AA.3 – Overall minimum distance S including tolerance zone – Example 1 . 43
o
Figure AA.4 – Minimum distance S – Example 2 . 44
Figure AA.5 – Overall minimum distance S without tolerance zone – Example 2 . 45
o
Figure AA.6 – Overall minimum distance S including tolerance zone – Example 2 . 45
o
Figure AA.7 – Application example for body detection of a VBPDST employing a
volume as a detection zone . 47
Figure BB.1 – Relationship between test piece position and the probability of detection . 49
Figure BB.2 – Example for measurement of the probability of detection . 50
Figure BB.3 – Relationship between detection zone and tolerance zone . 52
Figure BB.4 – Overall minimum distance S including tolerance zone . 53
o
Figure CC.1 – Illumination model – Sphere illuminated by a point source . 55
Figure CC.2 – Illumination model – Sphere illuminated by a half-Ulbricht sphere . 55
Figure CC.3 – Brightness of a surface element of a sphere in spherical coordinates . 56
Figure CC.4 – Brightness distribution in an image of a sphere . 56
Figure CC.5 – Grey value profile over a sphere with low contrast for a typical imaging
contrast (Modulation Transfer Function) . 57
Figure CC.6 – Grey value profile over a sphere with the same colour as the
background . 57
Figure CC.7 – Grey value profile over a sphere in front of a background that is half as
bright . 58
Figure CC.8 – Grey value profile over a sphere in front of a background that is twice as
bright . 58
Figure CC.9 – Grey value profile over a sphere by low contrast . 59
Figure CC.10 – Grey value profile over the sphere from Figure CC.9 but with the
direction to the imaging device changed by 10° . 59
Figure CC.11 – Grey value profile over a small sphere that results in an image that is 5
pixels in diameter . 60
Table 431 – Verification of detection capability requirements (see also 4.2.12) . 23
Table 432 – Overview of light interference tests . 28
– 4 – IEC TS 61496-4-3:2022 © IEC 2022
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
SAFETY OF MACHINERY –
ELECTRO-SENSITIVE PROTECTIVE EQUIPMENT –
Part 4-3: Particular requirements for equipment using
vision based protective devices (VBPD) –
Additional requirements when using stereo
vision techniques (VBPDST)
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote international
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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of patent
rights. IEC shall not be held responsible for identifying any or all such patent rights.
IEC TS 61496-4-3 has been prepared by IEC technical committee TC 44: Safety of machinery
– Electrotechnical aspects. It is a Technical Specification.
This second edition cancels and replaces the first edition published in 2015-05. This edition
constitutes a technical revision.
This edition includes the following technical changes with respect to the previous edition:
a) Some requirement clauses and test procedures have been adapted or removed because
they have been consolidated in IEC 61496-1:2020 (e.g. 5.4.6.2 Light sources or
Clause A.9).
The text of this document is based on the following documents:
Draft Report on voting
44/934/DTS 44/957A/RVDTS
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this document is English.
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
described in greater detail at https://www.iec.ch/publications.
This document is to be used in conjunction with IEC 61496-1:2020.
This document supplements or modifies the corresponding clauses in IEC 61496-1:2020 to
specify particular requirements for the design, construction and testing of electro-sensitive
protective equipment (ESPE) for the safeguarding of machinery, employing vision based
protective devices (VBPD) using stereo vision techniques (VBPDST) for the sensing function.
Where a particular clause or subclause of IEC 61496-1:2020 is not mentioned in this document,
that clause or subclause applies as far as is reasonable. Where this document states "addition",
"modification" or "replacement", the relevant text of IEC 61496-1:2020 is adapted accordingly.
Clauses and subclauses which are additional to those of IEC 61496-1:2020 are numbered
sequentially, following on the last available number in IEC 61496-1:2020. Terminological entries
(in Clause 3) which are additional to those in IEC 61496-1:2020 are numbered starting from
3.4301. Additional annexes are lettered from AA onwards and additional tables are numbered
with prefix 43.
A list of all parts in the IEC 61496 series, published under the general title Safety of machinery
– Electro-sensitive protective equipment, can be found on the IEC website.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under webstore.iec.ch in the data related to the
specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
IMPORTANT – The "colour inside" logo on the cover page of this document indicates that it
contains colours which are considered to be useful for the correct understanding of its
contents. Users should therefore print this document using a colour printer.
– 6 – IEC TS 61496-4-3:2022 © IEC 2022
INTRODUCTION
An electro-sensitive protective equipment (ESPE) is applied to machinery presenting a risk of
personal injury. It provides protection by causing the machine to revert to a safe condition before
a person can be placed in a hazardous situation.
The working group responsible for drafting this document was concerned that, due to the
complexity of the technology, there are many issues that are highly dependent on analysis and
expertise in specific test and measurement techniques. In order to provide a high level of
confidence, independent review by relevant expertise is recommended. They considered that if
this high level of confidence could not be established these devices would not be suitable for
use in safety related applications.
SAFETY OF MACHINERY –
ELECTRO-SENSITIVE PROTECTIVE EQUIPMENT –
Part 4-3: Particular requirements for equipment using
vision based protective devices (VBPD) –
Additional requirements when using stereo
vision techniques (VBPDST)
1 Scope
Replacement:
This document specifies requirements for the design, construction and testing of non-contact
electro-sensitive protective equipment (ESPE) designed specifically to detect persons or parts
of persons as part of a safety-related system, employing vision-based protective devices
(VBPDs) using stereo vision techniques (VBPDST) for the sensing function. Special attention
is directed to features which ensure that an appropriate safety-related performance is achieved.
An ESPE can include optional safety-related functions, the requirements for which are given in
Annex A of IEC 61496-1:2020 and this document.
NOTE "Non-contact" means that physical contact is not required for sensing.
Where this document does not contain all necessary provisions, IEC TS 62998-1 applies.
It is also possible, for those aspects not considered in this document, to use provisions from
IEC TS 62998-1 additionally.
This document does not specify the dimensions or configurations of the detection zone and its
disposition in relation to hazardous parts for any particular application, nor what constitutes a
hazardous state of any machine. It is restricted to the functioning of the ESPE and how it
interfaces with the machine.
The detection principle is based on the evaluation of images from different viewing points
(stereoscopic view) for the determination of distance information. This distance information is
used to determine the position of an object(s).
– This document is limited to vision based ESPEs with fixed distances (stereo base) and fixed
directions of the optical axes using a fixed focal length.
– It is limited to vision based ESPEs that do not require human intervention for detection.
– It is limited to vision based ESPEs that detect objects entering into or being present in a
detection zone(s).
– It is limited to VBPDSTs employing radiation at wavelengths within the range 400 nm to
1 500 nm.
– This document does not address those aspects required for complex classification or
differentiation of the object detected.
– This document does not consider the aspects of a moving ESPE installation.
Additional requirements and tests can apply in the following cases:
– Use of multi-spectral (colour) techniques;
– Setups other than as shown in Figure 2 and Figure 3 (e.g. changing backgrounds, horizontal
orientation of the optical axis with respect to the floor);
– 8 – IEC TS 61496-4-3:2022 © IEC 2022
– Intended for outdoor applications.
This document is relevant for VBPDSTs having a stated detection capability up to 200 mm.
This document can be relevant to applications other than those for the protection of persons or
parts of persons like arm or fingers (in the range 14 mm to 200 mm), for example the protection
of machinery or products from mechanical damage. In those applications, additional
requirements can be necessary, for example when the materials that are to be recognized by
the sensing function have different properties from those of persons.
This document does not deal with EMC emission requirements.
2 Normative references
Addition:
IEC 60825-1:2014, Safety of laser products – Part 1: Equipment classification and requirements
IEC 61496-1:2020, Safety of machinery – Electro-sensitive protective equipment – Part 1:
General requirements and tests
IEC 62471:2006, Photobiological safety of lamps and lamp systems
ISO 13855:2010, Safety of machinery – Positioning of safeguards with respect to the approach
speeds of parts of the human body
ISO 20471:2013, High visibility clothing – Test methods and requirements
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
This clause of IEC 61496-1:2020 is applicable except as follows:
Replacement:
3.3
detection capability
ability to detect the specified test pieces (see 4.2.13) in the specified detection zone
Note 1 to entry: Detection capability is measured by the size of an object that can be detected. An increase in
detection capability means that a smaller object can be detected.
[SOURCE: IEC 61496-1:2020, 3.3, modified – The text has been changed to make it more
relevant to vision based sensors and Note 1 has been added.]
3.4
detection zone,
three-dimensional volume within which a specified test piece will be detected by the VBPDST
Note 1 to entry: Example for three-dimensional volume are a pyramid or a cone
3.5
electro-sensitive protective equipment
ESPE
Addition:
Note 3 to entry: Illumination unit(s), if applicable, is/are part(s) of the sensing device.
Addition:
3.4301
minimum detection zone
lowest dimension of the detection zone for a test piece moving with maximum speed
Note 1 to entry: This is the lowest dimension that ensures the integrity of the detection capability.
3.4302
evaluation images, pl
set of images which are used by the detection algorithms
SEE: Figure 1.
Figure 1 – Image planes in imaging device of a VBPDST
3.4303
Image
snapshot representation of the scene in different planes of the VBPDST in form of a two
dimensional pixel matrix
3.4304
vision-based protective device
VBPD
ESPE using an imaging sensor, operating in the visible and near infrared light spectrum to
detect an object in a defined field of view
Note 1 to entry: This note applies to the French language only.
– 10 – IEC TS 61496-4-3:2022 © IEC 2022
3.4305
vision based protective device using stereo vision techniques
VBPDST
VBPD with two or more imaging devices using stereo vision techniques and with or without
active illumination
3.4306
imaging sensor
opto-electronic device which produces electrical signals representing the characteristics of an
image
SEE: Figure 1.
3.4307
imaging device
combination of an imaging sensor, optics and the processing unit (if applicable)
SEE: Figure 1.
Note 1 to entry: The imaging devices are part of the sensing device.
3.4308
operating distance
distance measured along the z-axis of the sensing device coordinate system
3.4309
Pixel
smallest light sensitive element of an imaging sensor
3.4310
Pixel
area of the smallest element that can be distinguished from its neighbouring elements
3.4311
ambient illumination technique
AIT
technique that relies on scene lighting for illumination and contrast to obtain range
measurements
3.4312
pattern projection technique
PAPT
technique that uses a special projection to enhance the contrast of a scene
3.4313
sensing device coordinate system
coordinate system oriented to the sensing device
Note 1 to entry: Typically, the z-axis is parallel to the optical axis of one imaging device.
3.4314
tolerance zone
zone outside of and adjacent to the detection zone within which the specified test piece is
detected with a probability of detection lower than the required probability within the detection
zone
Note 1 to entry: The tolerance zone is necessary to achieve the required probability of detection of the specified
test piece within the detection zone. For explanation of the concept of probability of detection and the tolerance zone,
see Annex BB.
3.4315
user coordinate system
coordinate system that may be configured by the user
3.4316
zone with limited detection capability
volume between the detection zone and the front of the sensing device in which the stated
detection capability is not achieved
3.4317
stereo base
distance between the centres of the entrance pupils of two imaging devices
Note 1 to entry: The expression baseline is often used as synonym for stereo base.
3.4318
position accuracy
accuracy in three dimensions of the position of an object as measured by VBPDST
Addition:
Abbreviated terms
AIT Ambient illumination technique
BTP Black test piece
GB Grey background
GTP Grey test piece
lx Lux
LC Low contrast
OD Operating distance
P1 Position 1 of the light source
P2 Position 2 of the light source
PAPT Pattern projection techniques
PTZ Tolerance zone related to probability
RRTP Retro-reflective test piece
STZ Tolerance zone related to systematic influences
TTC Typical test condition (test condition for normal operation tests)
TI Typical illumination (illumination used for normal operation tests)
VBPDST Vision based protective devices using stereo vision techniques
WTP White test piece
– 12 – IEC TS 61496-4-3:2022 © IEC 2022
4 Functional, design and environmental requirements
This clause of IEC 61496-1:2020 is applicable except as follows:
4.1 Functional requirements
Replacement:
4.1.2 Sensing function
4.1.2.1 General
The detection zone shall begin at the border of the zone with limited detection capability and
end within the maximum operating distance (see Figure 2 and Figure 3).
Object(s) in the zone with limited detection capability shall not reduce the detection capability
within the detection zone. Any reduction of the detection capability shall be detected and the
VBPDST shall go to lock-out condition (see 4.2.2.4).
Key
1 – Maximum operating distance 4 – Sensing device 7 – Detection zone
2 – User coordinate system 5 – Zone with limited detection 8 – Tolerance zone
capability
3 – Sensing device coordinate 6 – Stereo base 9 – Stereo field of view
system
NOTE The figure shows a system with the sensing device coordinate system parallel to the stereo base and a
maximum operating distance on a plane perpendicular to the sensing device coordinate system axis.
Figure 2 – 3D view of a vision based protective device using
stereo vision techniques (VBPDST)
Key
1 – Maximum operating distance 4 – Sensing device 7 – Detection zone
2 – User coordinate system 5 – Zone with limited detection 8 – Tolerance zone
capability
3 – Sensing device coordinate 6 – Stereo base 9 – Stereo field of view
system
NOTE The figure shows a system with the sensing device coordinate system parallel to the stereo base and a
maximum operating distance on a plane perpendicular to the sensing device coordinate system axis.
Figure 3 – 2D view of a vision based protective device using
stereo vision techniques (VBPDST)
4.1.2.2 Additional functional requirements
The sensing function shall be effective over the detection zone. No adjustment of the detection
zone or detection capability shall be possible without the use of a security measure (e.g. key,
keyword, or tool).
The VBPDST shall respond by giving appropriate output signal(s) when a test piece is present
anywhere within the detection zone whether static or moving with respect to the VBPDST.
– 14 – IEC TS 61496-4-3:2022 © IEC 2022
The supplier shall specify the limits of detection capability. The supplier shall take into account
worst case scenario considering all influences listed in this document including, for example:
– signal-to-noise ratio;
– light intensity in the image in sensor plane (see Figure 1);
– contrast on the image in sensor plane;
– position of the image in sensor plane.
4.1.2.3 Optical performance
The VBPDST shall be designed and constructed to:
a) limit the possibility of malfunction during exposure to extraneous radiation in the range of
400 nm to 1 500 nm;
b) limit the effects of environmental influences (temperature, vibration and shocks, dust,
moisture, ambient light, extraneous reflections, changing illumination, shadows on
background, background reflectivity);
c) limit the misalignment at which normal operation is possible.
4.1.3 Types of ESPE
Replacement:
In this document, only a type 3 ESPE is considered. It is the responsibility of the machine
supplier and/or the user to specify which type is required for a particular application.
A type 3 ESPE shall fulfil the fault detection requirements of 4.2.2.4.
In normal operation, the output circuit of each of at least two output signal switching devices
(OSSDs) of the type 3 ESPE shall go to the OFF-state when the sensing device is actuated, or
when the power is removed from the ESPE.
When a single safety-related data interface is used to perform the functions of the OSSD(s),
then the data interface and associated safety-related communication interface shall meet the
requirements of 4.2.4.4 of IEC 61496-1:2020. In this case, a single safety-related data interface
can substitute for two OSSDs in a type 3 ESPE.
Addition:
4.1.6 Zone with limited detection capability
A zone between the optical window and the beginning of the detection zone is referred to as a
zone with limited detection capability. In order to ensure that no hazard can arise in a particular
application due to the presence of objects in the zone between the optical window and the
detection zone, its dimensions and appropriate information for use shall be provided by the
supplier.
4.2 Design requirements
4.2.2 Fault detection requirements
4.2.2.2 Particular requirements for a type 1 ESPE
This subclause of IEC 61496-1:2020 is not applicable.
4.2.2.3 Particular requirements for a type 2 ESPE
This subclause of IEC 61496-1:2020 is not applicable.
4.2.2.4 Particular requirements for a type 3 ESPE
Addition:
EXAMPLE of deterioration of the VBPDST detection capability include:
– increase of the minimum detectable object size;
– increase in the minimum detectable contrast;
– decrease of position accuracy.
4.2.2.5 Particular requirements for a type 4 ESPE
This subclause of IEC 61496-1:2020 is not applicable.
4.2.12 Integrity of the ESPE detection capability
Replacement:
4.2.12.1 General
The design of the VBPDST shall ensure that the detection capability is not decreased below
the limits specified by the supplier and in this document by any of, but not limited to, the
following:
a) low contrast between an object and background on the evaluation images;
b) the position of the object within the detection zone;
c) the number of objects within the detection zone;
d) the size of object(s) within the detection zone;
e) auto-adjustment of optical and electrical characteristics;
f) properties/limitations of optical and electrical components;
g) accuracy of object position in image(s);
h) at the limits of alignment and/or adjustment;
i) ageing of components;
j) performance and limitations of the optical components;
k) component tolerances;
l) changing of internal and external references to ensure the detection capability;
m) environmental conditions specified in 4.3.
4.2.12.2 Detection zone(s) and tolerance zone(s)
The supplier shall define values up to 200 mm as the minimum detectable object size of the
VBPDST within the detection zone. The minimum detectable object size may be distance
dependent.
The test pieces (see 4.2.13) shall be detected with a minimum probability of detection of
–7
1 – 2,9 × 10 throughout the detection zone(s). To achieve this minimum probability of
detection, the tolerance zone has to be considered in addition to the detection zone. The
tolerance zone depends on position accuracy composed of systematic (STZ) and random
influences (PTZ). Even if a measured distance value of a test piece falls into the tolerance zone,
this test piece will be determined as detected (see Annex BB for further Information). If a part
of the position error does not result in failure to danger, then it does not need to be included in
the tolerance zone.
NOTE 1 Under the assumption that errors are normally distributed, the PTZ will be 5 times the standard deviation
of the error distribution (5 sigma).
NOTE 2 Within the tolerance zone there is no requirement for maintaining a minimum probability of detection.
– 16 – IEC TS 61496-4-3:2022 © IEC 2022
NOTE 3 The dimensions of the tolerance zone in the three axes can be different.
NOTE 4 An example to determine the tolerance zone is given in Annex BB.
The supplier shall specify the tolerance zone(s) and take into account worst-case
considerations according to the influences listed in 4.2.12.7.
When using reference markers or parts of the environment such as walls or the floor during
setup, errors in determining the correct distance and position of these references shall be taken
into account when specifying the tolerance zone(s).
NOTE 5 The dimension of the tolerance zone can be influenced by the method of approach (for example walking,
crawling, sliding along a wall). If such information is used to calculate the tolerance zone, then appropriate analysis
or tests can be required.
NOTE 6 If the required probability of detection can be satisfied by partial intrusion of an object into the detection
zone, then a smaller tolerance zone can be used for safety distance determination. Further details can be found in
Annex AA.
4.2.12.3 Response time
Objects of the minimum detectable size that are either stationary or moving within the detection
zone at any speed up to 1,6 m/s shall be detected by the ESPE within the specified response
time. The supplier shall specify the maximum response time. The supplier shall take into
account worst case conditions.
EXAMPLES for worst case conditions for maximum response time are
– frame rate;
– evaluation time;
– minimum diameter of the test piece;
– maximum speed of the test piece;
– number of objects in the detection zone;
– values of the minimum detection zone;
– environmental influences.
Where the supplier states that a VBPDST can be used to detect objects moving at speeds
greater than 1,6 m/s, the requirements shall be met at any speed up to and including the stated
maximum speed.
4.2.12.4 Object detection at low contrast
At low contrast the test piece shall be detected when the VBPDST is in normal operation.
NOTE A physical contrast results in a difference of intensity that is detected. For more information, see Annex CC.
4.2.12.5 Object detection at high contrast
At high contrast the test piece shall be detected when the VBPDST is in normal operation.
NOTE A high contrast results from a big difference of the coefficient of diffuse reflection and/or lighting variation
between the background and the test piece. The contrast could be higher than the dynamic range of the imaging
sensor.
4.2.12.6 Minimum detection zone
The supplier shall specify the minimum detection zone(s). The supplier shall take into account
worst case conditions including, for example:
– response time;
– minimum diameter of the test piece;
– maximum speed of the test piece.
4.2.12.7 Position accuracy
When determining the position accuracy, the following influences shall be taken into account if
applicable, but not limited to:
a) the calibration of the sensing device;
b) characteristics of the optical/imaging sensor, such as
1) the number of pixels and pixel size
2) signal-to-noise ratio
3) modulation transfer function of the optics
c) algorithmic influences, such as:
1) smoothing algorithm
2) feature based detection algorithm, e.g. edge detection algorithm
3) template matching
4) colour sensor and algorithm
5) global algorithms, e.g. cluster algorithm
6) optical flow analysis algorithm
7) object tracking algorithm
8) stereo algorithm
d) synchronization between imaging sensors;
e) characteristics of the test piece;
f) limits of illumination;
g) Ageing and tolerances of components and references.
4.2.12.8 Pattern projection techniques (PAPT)
If pattern projection techniques are used to enhance the contrast in the scene, then the pattern
projector shall be considered as part of the VBPDST. This illumination module shall have the
capability to project sufficient contrast onto the scene anywhere within the specified detection
zone such that the system fulfils the requirements of this document. The detection capability
shall not be decreased below the limits specified by the supplier by any influences, including
but not limited to the following:
a) contrast between projected pattern elements;
b) contrast changes within projected pattern elements;
c) size and differentiation of projected pattern elements and number of projected pattern
elements used for contrast enhancement;
d) size of pixels and numbers of pixels compared to used projected pattern elements;
e) automatic adaptation of algorithm/routines;
f) size, shape, colour, reflectivity, position and surface structure of object and scene compared
to projected pattern;
g) resulting superposition of natural object/scene contrast and contrast produced by pattern
projection;
h) position and location of pattern projector.
4.2.12.9 Influence of periodic surface structures on the background
Periodic surface structures on the background shall not lead to a failure to danger.
Periodic surface structures resulting in a complete loss of the stated VBPDST detection
capability shall cause the ESPE to go to the OFF-state and remain in it as long as the periodic
structure is present.
– 18 – IEC TS 61496-4-3:2022 © IEC 2022
Periodic surface structures resulting in a deterioration of the stated VBPDST detection
capability shall cause the ESPE to go to the OFF-state within a time period of 5 s following the
occurrence of periodic surface structures and remain in it as long as the periodic structure is
present.
These requirements are verified by the tests of 5.2.1.5.
4.2.13 Test piece
Replacement:
4.2.13.1 General
The test pieces shall be provided by the supplier for use in the type tests of Clause 5. They
shall be marked with a type reference and identification of the VBPDST with which they are
intended to be used.
The test pieces shall be opaque. Different test pieces can be required for different phases of
the test procedures.
The characteristics of the test piece which shall be considered are:
a) size;
b) shape;
c) colour;
d) reflectivity;
– at the wavelength of the illumination for VBPDST with PAPT
– at the wavelength of maximum sensitivity of the sensor for VBPDST with AIT
e) contrast with background;
f) texture.
When defining the characteristics of the test piece, protection against camouflage with the
background shall be taken into account. Unless the analysis shows that other test pieces are
appropriate the following test pieces shall be used.
4.2.13.2 Cylindrical test piece
The test piece shall be cylindrical if the VBPDST is intended to be used for finger detection.
The cylindrical test piece shall have a diameter of 14 mm and a length for ease of use.
4.2.13.3 Conical test pieces
The test piece shall be a truncated cone if the VBPDST is intended to be used for hand
detection. The test piece starts with a diameter of 20 mm increasing up to 40 mm over a length
of 160 mm.
The test piece shall be a truncated cone in combination with a cylinder if the VBPDST is
intended to be used for arm detection. The test piece starts with a diameter of 40 mm increasing
up to 55 mm as a cone over a length of 180 mm and continues as a cylinder with a diameter of
55 mm to an overall length of 440 mm.
The test piece shall be a truncated cone if the VBPDST is intended to be used for leg detection.
The test piece starts with a diameter of 50 mm increasing up to 117 mm over a length of
1 000 mm.
If the VBPDST is intended to be used for detection of different parts of a body, the selection of
the most appropriate test pieces shall be dependent on the analysis of the design and intended
application. In some cases, all test pieces can be required or their combination to represent
more realistic the human body.
4.2.13.4 Spherical test piece
If the VBPDST is intended to be used for whole body detection, then the test piece shall be a
sphere with a maximum diameter of 200 mm attached to a cylinder with a maximum diameter
of 50 mm and a length selected for ease of use.
NOTE A spherical test piece with a diameter of 200 mm is intended to represent the thickness of a body.
4.2.13.5 Grey test piece (GTP)
The test piece shall have a coefficient of diffuse reflection of 27 % to 33 %.
4.2.13.6 Black test piece (BTP)
The test piece shall have a coefficient of diffuse reflection of less than 5 %.
4.2.13.7 White test piece (WTP)
The test piece shall have a coefficient of diffuse reflection of more than 70 %.
4.2.13.8 Retro-reflective test piece (RRTP)
The test piece shall have a retro-reflective surface that complies with the requirements for
separate performance retro-reflective material of ISO 20471 or equivalent.
NOTE Table 4 of ISO 20471:2013 defines the minimum coefficient of retro-reflection for separate performance retro-
reflective material as 330 cd · lx–1 · m–2 with an entrance angle of 5° and an observation angle of 0,2° (12').
Addition:
4.2.14 Wavelength
VBPDSTs shall operate at a wavelength within the range 400 nm to 1 500 nm.
4.2.15 Radiation intensity
If the emitting element(s) of the PAPT device uses LED technology, the radiation intensity
generated and emitted by the VBPDST shall meet the requirements of the exempt group in
accordance with IEC 62471.
NOTE Exempt group is equal to risk group zero (IEC 62471).
If the emitting element(s) of the PAPT device uses laser technology, the radiation intensity
generated and emitted by the VBPDST shall not exceed the maximum power or energy levels
for a class 1M laser in accordance with IEC 60825-1 (even in the presence of a component
failure). The marking as class 1 or class 1M laser shall be carried out as required in 5.2 of
IEC 60825-1:2014.
4.2.16 Mecha
...
IEC TS 61496-4-3 ®
Edition 2.0 2022-09
REDLINE VERSION
TECHNICAL
SPECIFICATION
colour
inside
Safety of machinery – Electro-sensitive protective equipment –
Part 4-3: Particular requirements for equipment using vision based protective
devices (VBPD) – Additional requirements when using stereo vision techniques
(VBPDST)
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IEC TS 61496-4-3 ®
Edition 2.0 2022-09
REDLINE VERSION
TECHNICAL
SPECIFICATION
colour
inside
Safety of machinery – Electro-sensitive protective equipment –
Part 4-3: Particular requirements for equipment using vision based protective
devices (VBPD) – Additional requirements when using stereo vision techniques
(VBPDST)
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 13.110; 29.260.99 ISBN 978-2-8322-5815-6
– 2 – IEC TS 61496-4-3:2022 RLV © IEC 2022
CONTENTS
FOREWORD . 4
INTRODUCTION . 2
1 Scope . 8
2 Normative references . 9
3 Terms and definitions . 9
4 Functional, design and environmental requirements . 13
5 Testing . 23
6 Marking for identification and for safe use . 39
7 Accompanying documents . 39
Annex A (normative) Optional functions of the ESPE . 41
Annex B (normative) Catalogue of single faults affecting the electrical equipment of
the ESPE, to be applied as specified in 5.3 . 43
Annex AA (informative) The positioning of VBPDST employing a volume as a
detection zone in respect of parts of the human body . 44
Annex BB (informative) Relationship between position accuracy and tolerance zones
for VBPDST . 53
Annex CC (informative) Basic principles of physics for contrast of convex
homogeneous bodies . 59
Bibliography . 66
Figure 1 – Image planes in imaging device of a VBPDST . 10
Figure 2 – 3D view of a vision based protective device using stereo vision techniques
(VBPDST) . 13
Figure 3 – 2D view of a vision based protective device using stereo vision techniques
(VBPDST) . 14
Figure 4 – Examples for periodic surface structures on the background . 28
Figure 5 – Test setup for indirect light interference on the background. 35
Figure 6 – Test setup for VBPDST of identical design with PAPT . 36
Figure 7 – Test setup for direct light interference on the sensing device . 37
Figure AA.1 – Minimum distance S – Example 1 . 47
Figure AA.2 – Overall minimum distance S without tolerance zone – Example 1 . 47
o
Figure AA.3 – Overall minimum distance S including tolerance zone – Example 1 . 48
o
Figure AA.4 – Minimum distance S – Example 2 . 49
Figure AA.5 – Overall minimum distance S without tolerance zone – Example 2 . 50
o
Figure AA.6 – Overall minimum distance S including tolerance zone – Example 2 . 50
o
Figure AA.7 – Application example for body detection of a VBPDST employing a
volume as a detection zone . 52
Figure BB.1 – Relationship between test piece position and the probability of detection . 54
Figure BB.2 – Example for measurement of the probability of detection . 55
Figure BB.3 – Relationship between detection zone and tolerance zone . 57
Figure BB.4 – Overall minimum distance S including tolerance zone . 58
o
Figure CC.1 – Illumination model – Sphere illuminated by a point source . 60
Figure CC.2 – Illumination model – Sphere illuminated by a half-Ulbricht sphere . 60
Figure CC.3 – Brightness of a surface element of a sphere in spherical coordinates . 61
Figure CC.4 – Brightness distribution in an image of a sphere . 61
Figure CC.5 – Grey value profile over a sphere with low contrast for a typical imaging
contrast (Modulation Transfer Function) . 62
Figure CC.6 – Grey value profile over a sphere with the same colour as the
background . 62
Figure CC.7 – Grey value profile over a sphere in front of a background that is half as
bright . 63
Figure CC.8 – Grey value profile over a sphere in front of a background that is twice as
bright . 63
Figure CC.9 – Grey value profile over a sphere by low contrast . 64
Figure CC.10 – Grey value profile over the sphere from Figure CC.9 but with the
direction to the imaging device changed by 10° . 64
Figure CC.11 – Grey value profile over a small sphere that results in an image that is 5
pixels in diameter . 65
Table 1 431 – Verification of detection capability requirements (see also 4.2.12) . 26
Table 2 432 – Overview of light interference tests . 31
– 4 – IEC TS 61496-4-3:2022 RLV © IEC 2022
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
SAFETY OF MACHINERY –
ELECTRO-SENSITIVE PROTECTIVE EQUIPMENT –
Part 4-3: Particular requirements for equipment using
vision based protective devices (VBPD) –
Additional requirements when using stereo
vision techniques (VBPDST)
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote international
co-operation on all questions concerning standardization in the electrical and electronic fields. To this end and
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6) All users should ensure that they have the latest edition of this publication.
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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of patent
rights. IEC shall not be held responsible for identifying any or all such patent rights.
This redline version of the official IEC Standard allows the user to identify the changes made to
the previous edition IEC TS 61496-4-3:2015. A vertical bar appears in the margin wherever a
change has been made. Additions are in green text, deletions are in strikethrough red text.
IEC TS 61496-4-3 has been prepared by IEC technical committee TC 44: Safety of machinery
– Electrotechnical aspects. It is a Technical Specification.
This second edition cancels and replaces the first edition published in 2015-05. This edition
constitutes a technical revision.
This edition includes the following technical changes with respect to the previous edition:
a) Some requirement clauses and test procedures have been adapted or removed because
they have been consolidated in IEC 61496-1:2020 (e.g. 5.4.6.2 Light sources or
Clause A.9).
The text of this document is based on the following documents:
Draft Report on voting
44/934/DTS 44/957A/RVDTS
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this document is English.
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
described in greater detail at https://www.iec.ch/publications.
This document is to be used in conjunction with IEC 61496-1:2020.
This document supplements or modifies the corresponding clauses in IEC 61496-1:2020 to
specify particular requirements for the design, construction and testing of electro-sensitive
protective equipment (ESPE) for the safeguarding of machinery, employing vision based
protective devices (VBPD) using stereo vision techniques (VBPDST) for the sensing function.
Where a particular clause or subclause of IEC 61496-1:2020 is not mentioned in this document,
that clause or subclause applies as far as is reasonable. Where this document states "addition",
"modification" or "replacement", the relevant text of IEC 61496-1:2020 is adapted accordingly.
Clauses and subclauses which are additional to those of IEC 61496-1:2020 are numbered
sequentially, following on the last available number in IEC 61496-1:2020. Terminological entries
(in Clause 3) which are additional to those in IEC 61496-1:2020 are numbered starting from
3.4301. Additional annexes are lettered from AA onwards and additional tables are numbered
with prefix 43.
A list of all parts in the IEC 61496 series, published under the general title Safety of machinery
– Electro-sensitive protective equipment, can be found on the IEC website.
– 6 – IEC TS 61496-4-3:2022 RLV © IEC 2022
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under webstore.iec.ch in the data related to the
specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
IMPORTANT – The "colour inside" logo on the cover page of this document indicates that it
contains colours which are considered to be useful for the correct understanding of its
contents. Users should therefore print this document using a colour printer.
INTRODUCTION
An electro-sensitive protective equipment (ESPE) is applied to machinery presenting a risk of
personal injury. It provides protection by causing the machine to revert to a safe condition before
a person can be placed in a hazardous situation.
The working group responsible for drafting this document was concerned that, due to the
complexity of the technology, there are many issues that are highly dependent on analysis and
expertise in specific test and measurement techniques. In order to provide a high level of
confidence, independent review by relevant expertise is required recommended. They
considered that if this high level of confidence could not be established these devices would
not be suitable for use in safety related applications.
– 8 – IEC TS 61496-4-3:2022 RLV © IEC 2022
SAFETY OF MACHINERY –
ELECTRO-SENSITIVE PROTECTIVE EQUIPMENT –
Part 4-3: Particular requirements for equipment using
vision based protective devices (VBPD) –
Additional requirements when using stereo
vision techniques (VBPDST)
1 Scope
Replacement:
This document specifies requirements for the design, construction and testing of non-contact
electro-sensitive protective equipment (ESPE) designed specifically to detect persons or parts
of persons as part of a safety-related system, employing vision-based protective devices
(VBPDs) using stereo vision techniques (VBPDST) for the sensing function. Special attention
is directed to features which ensure that an appropriate safety-related performance is achieved.
An ESPE may can include optional safety-related functions, the requirements for which are
given in Annex A of IEC 61496-1:20122020 and this document.
NOTE "Non-contact" means that physical contact is not required for sensing.
Where this document does not contain all necessary provisions, IEC TS 62998-1 applies.
It is also possible, for those aspects not considered in this document, to use provisions from
IEC TS 62998-1 additionally.
This document does not specify the dimensions or configurations of the detection zone and its
disposition in relation to hazardous parts for any particular application, nor what constitutes a
hazardous state of any machine. It is restricted to the functioning of the ESPE and how it
interfaces with the machine.
The detection principle is based on the evaluation of images from different viewing points
(stereoscopic view) for the determination of distance information. This distance information is
used to determine the location position of an object(s).
– This document is limited to vision based ESPEs with fixed distances (stereo base) and fixed
directions between the different imaging devices fixed during manufacture of the optical
axes using a fixed focal length.
– It is limited to vision based ESPEs, with a minimum distance from the sensing device to the
detection zone of 4 times of the stereo base.
– It is limited to vision based ESPEs that can detect objects with at least 5 pixel diameter in
the image plane.
– It is limited to vision based ESPEs that do not require human intervention for detection.
– It is limited to vision based ESPEs that detect objects entering into or being present in a
detection zone(s).
– It is limited to VBPDSTs employing radiation at wavelengths within the range 400 nm to
1 500 nm.
– This document does not address those aspects required for complex classification or
differentiation of the object detected.
– This document does not consider the aspects of a moving ESPE installation.
Additional requirements and tests can apply in the following cases:
– Use of multi-spectral (colour) techniques;
– Setups other than as shown in Figure 2 and Figure 3 (e.g. changing backgrounds, horizontal
orientation of the optical axis with respect to the floor);
– Intended for outdoor applications.
This document is relevant for VBPDSTs having a stated detection capability up to 200 mm.
This document may can be relevant to applications other than those for the protection of
persons or parts of persons like arm or fingers (in the range 14 mm to 200 mm), for example
the protection of machinery or products from mechanical damage. In those applications,
additional requirements can be necessary, for example when the materials that are to be
recognized by the sensing function have different properties from those of persons.
This document does not deal with EMC emission requirements.
2 Normative references
Addition:
IEC 60825-1:2014, Safety of laser products – Part 1: Equipment classification and requirements
IEC 61496-1:20122020, Safety of machinery – Electro-sensitive protective equipment – Part 1:
General requirements and tests
IEC 62471:2006, Photobiological safety of lamps and lamp systems
ISO 13855:2010, Safety of machinery – Positioning of safeguards with respect to the approach
speeds of parts of the human body
ISO 20471:2013, High visibility clothing – Test methods and requirements
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
This clause of IEC 61496-1:2020 is applicable except as follows:
Replacement:
3.3
detection capability
ability to detect the specified test pieces (see 4.2.13) in the specified detection zone
Note 1 to entry: Detection capability is measured by the size of an object that can be detected. An increase in
detection capability means that a smaller object can be detected.
– 10 – IEC TS 61496-4-3:2022 RLV © IEC 2022
[SOURCE: IEC 61496-1:20122020, 3.3, modified – The text has been changed to make it more
relevant to vision based sensors and Note 1 has been added.]
3.4
detection zone,
three-dimensional volume (for example, in the shape of a pyramid or cone) within which a
specified test piece will be detected by the VBPDST
Note 1 to entry: Example for three-dimensional volume are a pyramid or a cone
3.5
electro-sensitive protective equipment
ESPE
Addition:
Note 3 to entry: Illumination unit(s), if applicable, is/are part(s) of the sensing device.
Addition:
3.4301
minimum detection zone
lowest dimension of the detection zone for a test piece moving with maximum speed
Note 1 to entry: This is the lowest dimension that ensures the integrity of the detection capability.
3.4302
evaluation images, pl
set of images which are used by the detection algorithms
SEE: Figure 1.
Figure 1 – Image planes in imaging device of a VBPDST
3.4303
Image
snapshot representation of the scene in different planes of the VBPDST in form of a two
dimensional pixel matrix
3.4304
vision-based protective device
VBPD
ESPE using an imaging sensor, operating in the visible and near infrared light spectrum to
detect an object in a defined field of view
Note 1 to entry: This note applies to the French language only.
3.4305
vision based protective device using stereo vision techniques
VBPDST
VBPD with two or more imaging devices using stereo vision techniques and with or without
active illumination
3.4306
imaging sensor
opto-electronic device which produces electrical signals representing the characteristics of an
image
SEE: Figure 1.
3.4307
imaging device
combination of an imaging sensor, optics and the processing unit (if applicable)
SEE: Figure 1.
Note 1 to entry: The imaging devices are part of the sensing device.
3.4308
operating distance
distance measured along the z-axis of the sensing device coordinate system
3.4309
Pixel
smallest light sensitive element of an imaging sensor
3.4310
Pixel
area of the smallest element that can be distinguished from its neighbouring elements
3.4311
ambient illumination technique
AIT
technique that relies on scene lighting for illumination and contrast to obtain range
measurements
3.4312
pattern projection technique
PAPT
technique that uses a special projection to enhance the contrast of a scene
3.4313
sensing device coordinate system
coordinate system oriented to the sensing device
Note 1 to entry: Typically, the z-axis is parallel to the optical axis of one imaging device.
– 12 – IEC TS 61496-4-3:2022 RLV © IEC 2022
3.4314
tolerance zone
zone outside of and adjacent to the detection zone within which the specified test piece is
detected with a probability of detection lower than the required probability within the detection
zone
Note 1 to entry: The tolerance zone is necessary to achieve the required probability of detection of the specified
test piece within the detection zone. For explanation of the concept of probability of detection and the tolerance zone,
see Annex BB.
3.4315
user coordinate system
coordinate system that may be configured by the user
3.4316
zone with limited detection capability
volume between the detection zone and the front of the sensing device in which the stated
detection capability is not achieved
3.4317
stereo base
distance between the centres of the entrance pupils of two imaging devices
Note 1 to entry: The expression baseline is often used as synonym for stereo base.
3.4318
position accuracy
accuracy in three dimensions of the position of an object as measured by VBPDST
Addition:
Abbreviated terms
AIT Ambient illumination technique
BTP Black test piece
GB Grey background
GTP Grey test piece
lx Lux
LC Low contrast
OD Operating distance
P1 Position 1 of the light source
P2 Position 2 of the light source
PAPT Pattern projection techniques
PTZ Tolerance zone related to probability
RRTP Retro-reflective test piece
STZ Tolerance zone related to systematic influences
TTC Typical test condition (test condition for normal operation tests)
TI Typical illumination (illumination used for normal operation tests)
VBPDST Vision based protective devices using stereo vision techniques
WTP White test piece
4 Functional, design and environmental requirements
This clause of IEC 61496-1:2020 is applicable except as follows:
4.1 Functional requirements
Replacement:
4.1.2 Sensing function
4.1.2.1 General
The detection zone shall begin at the border of the zone with limited detection capability and
end at within the maximum operating distance (see Figure 2 and Figure 3).
Object(s) in the zone with limited detection capability shall not reduce the detection capability
within the detection zone. Any reduction of the detection capability shall be detected and the
VBPDST shall go to lock-out condition (see 4.2.2.4).
Key
1 – Maximum operating distance 4 – Sensing device 7 – Detection zone
2 – User coordinate system 5 – Zone with limited detection 8 – Tolerance zone
capability
3 – Sensing device coordinate 6 – Stereo base 9 – Stereo field of view
system
NOTE The figure shows a system with parallel axes the sensing device coordinate system parallel to the stereo
base and a maximum operating distance on a plane perpendicular to the axes the sensing device coordinate system
axis.
Figure 2 – 3D view of a vision based protective device using
stereo vision techniques (VBPDST)
– 14 – IEC TS 61496-4-3:2022 RLV © IEC 2022
Key
1 – Maximum operating distance 4 – Sensing device 7 – Detection zone
2 – User coordinate system 5 – Zone with limited detection 8 – Tolerance zone
capability
3 – Sensing device coordinate 6 – Stereo base 9 – Stereo field of view
system
NOTE The figure shows a system with parallel axes the sensing device coordinate system parallel to the stereo
base and a maximum operating distance on a plane perpendicular to the axes the sensing device coordinate system
axis.
Figure 3 – 2D view of a vision based protective device using
stereo vision techniques (VBPDST)
4.1.2.2 Additional functional requirements
4.1.2.1 General
The sensing function shall be effective over the detection zone. No adjustment of the detection
zone or detection capability shall be possible without the use of a security measure (e.g. key,
keyword, or tool).
The VBPDST shall respond by giving appropriate output signal(s) when a test piece is present
anywhere within the detection zone whether static or moving with respect to the VBPDST.
The supplier shall specify the limits of detection capability. The supplier shall take into account
worst case scenario considering all influences listed in this document including, for example:
– signal-to-noise ratio;
– light intensity in the image in sensor plane (see Figure 1);
– contrast on the image in sensor plane;
– position of the image in sensor plane.
4.1.2.3 Optical performance
The VBPDST shall be designed and constructed to:
a) limit the possibility of malfunction during exposure to extraneous radiation in the range of
400 nm to 1 500 nm;
b) limit the effects of environmental influences (temperature, vibration and bumps shocks, dust,
moisture, ambient light, extraneous reflections, changing illumination, shadows on
background, background reflectivity);
c) limit the misalignment at which normal operation is possible.
4.1.3 Types of ESPE
Replacement:
In this document, only a type 3 ESPE is considered. It is the responsibility of the machine
supplier and/or the user to prescribe if this specify which type is suitable required for a particular
application.
A type 3 ESPE shall fulfil the fault detection requirements of 4.2.2.4.
In normal operation, the output circuit of each of at least two output signal switching devices
(OSSDs) of the type 3 ESPE shall go to the OFF-state when the sensing device is actuated, or
when the power is removed from the device ESPE.
When a single safety-related data interface is used to perform the functions of the OSSD(s),
then the data interface and associated safety-related communication interface shall meet the
requirements of 4.2.4.4 of IEC 61496-1:2020. In this case, a single safety-related data interface
can substitute for two OSSDs in a type 3 ESPE.
Addition:
4.1.6 Zone with limited detection capability
A zone between the optical window and the beginning of the detection zone is referred to as a
zone with limited detection capability. In order to ensure that no hazard can arise in a particular
application due to the presence of objects in the zone between the optical window and the
detection zone, its dimensions and appropriate information for use shall be provided by the
supplier.
4.2 Design requirements
4.2.2 Fault detection requirements
4.2.2.2 Particular requirements for a type 1 ESPE
This subclause of IEC 61496-1:2020 is not applicable.
– 16 – IEC TS 61496-4-3:2022 RLV © IEC 2022
4.2.2.3 Particular requirements for a type 2 ESPE
This subclause of IEC 61496-1:2020 is not applicable.
4.2.2.4 Particular requirements for a type 3 ESPE
Replacement:
A single fault in the sensing device resulting in a complete loss of the stated VBPDST detection
capability shall cause the ESPE to go to a lock-out condition within the specified response time.
A single fault resulting in a deterioration of the stated VBPDST detection capability shall cause
the ESPE to go to the lock-out condition within a time period of 5 s following the occurrence of
that fault.
Addition:
NOTE EXAMPLE of deterioration of the VBPDST detection capability include:
– increase of the minimum detectable object size;
– increase in the minimum detectable contrast;
– decrease of position accuracy.
A single fault resulting in an increase in response time beyond the specified value or preventing
at least one OSSD going to the OFF-state shall cause the ESPE to go to a lock-out condition
immediately, i.e. within the response time, or immediately upon any of the following demand
events where fault detection requires a change in state:
– on actuation of the sensing function;
– on switch off/on;
– on reset of the start interlock or the restart interlock, if provided (see Clauses A.5 and A.6
of IEC 61496-1:2012).
It shall not be possible for the ESPE to achieve a reset from a lock-out condition, for example,
by interruption and restoration of the mains power supply or by any other means, when the fault
which initiated the lock-out condition is still present.
In cases where a single fault which does not cause a failure to danger of the ESPE is not
detected, the occurrence of one additional fault shall not cause a failure to danger.
For verification of this requirement, see 5.3.4.
4.2.2.5 Particular requirements for a type 4 ESPE
This subclause of IEC 61496-1:2020 is not applicable.
Additional design requirements:
4.2.12 Integrity of the VBPDST ESPE detection capability
Replacement:
4.2.12.1 General
The design of the VBPDST shall ensure that the detection capability is not degraded decreased
below the limits specified by the supplier and in this document by any of, but not limited to, the
following:
a) low contrast between an object and background on the evaluation images;
b) the position of the object within the detection zone;
c) the number of objects within the detection zone;
d) the size of object(s) within the detection zone;
e) auto-adjustment of optical and electrical characteristics;
f) properties/limitations of optical and electrical components;
g) accuracy of object position in image(s);
h) at the limits of alignment and/or adjustment;
i) ageing of components;
j) performance and limitations of the optical components;
k) component tolerances;
l) changing of internal and external references to ensure the detection capability;
m) environmental conditions specified in 4.3.
If a single fault, which under normal operating conditions (see 5.1.2.1) would not result in a loss
of the stated VBPDST detection capability but, when occurring with a combination of the above
conditions, would result in such a loss, that fault together with that combination of conditions
(as determined to be relevant during the analysis of the design) shall be considered as a single
fault and the VBPDST shall respond to such a single fault as required in 4.2.2.4.
4.2.12.2 Detection zone(s) and tolerance zone(s)
The supplier shall define values up to 200 mm as the minimum detectable object size of the
VBPDST within the detection zone. The minimum detectable object size may be distance
dependent.
The test pieces (see 4.2.13) shall be detected with a minimum probability of detection of
–7
1 – 2,9 × 10 throughout the detection zone(s). To achieve this minimum probability of
detection, the tolerance zone has to be considered in addition to the detection zone. The
tolerance zone depends on position accuracy composed of systematic (STZ) and random
influences (PTZ). Even if a measured distance value of a test piece falls into the tolerance zone,
this test piece will be determined as detected and the OSSDs shall go to the OFF-state or
remain in the OFF-state (see Annex BB for further Information). If a part of the position error
does not result in failure to danger, then it does not need to be included in the tolerance zone.
NOTE 1 Under the assumption that errors are normally distributed, the PTZ will be 5 times the standard deviation
of the error distribution (5 sigma).
NOTE 2 Within the tolerance zone there is no requirement for maintaining a minimum probability of detection.
NOTE 3 The dimensions of the tolerance zone in the three axes can be different.
NOTE 4 An example to determine the tolerance zone is given in Annex BB.
The supplier shall specify the tolerance zone(s) and take into account worst-case
considerations according to the influences listed in 4.2.12.7.
When using reference markers or parts of the environment such as walls or the floor during
setup, errors in determining the correct distance and position of these references shall be taken
into account when specifying the tolerance zone(s).
NOTE 5 The dimension of the tolerance zone can be influenced by the method of approach (for example walking,
crawling, sliding along a wall). If such information is used to calculate the tolerance zone, then appropriate analysis
or tests can be required.
NOTE 6 If the required probability of detection can be satisfied by partial intrusion of an object into the detection
zone, then a smaller tolerance zone can be used for safety distance determination. Further details can be found in
Annex AA.
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4.2.12.3 Response time
Objects of the minimum detectable size that are either stationary or moving within the detection
zone at any speed up to 1,6 m/s shall be detected by the ESPE within the specified response
time. The supplier shall specify the maximum response time.
The supplier shall take into account worst case conditions.
EXAMPLES for worst case conditions for maximum response time are
– frame rate;
– evaluation time;
– minimum diameter of the test piece;
– maximum speed of the test piece;
– number of objects in the detection zone;
– values of the minimum detection zone;
– environmental influences.
Where the supplier states that a VBPDST can be used to detect objects moving at speeds
greater than 1,6 m/s, the requirements shall be met at any speed up to and including the stated
maximum speed.
4.2.12.4 Object detection at low contrast
At low contrast the test piece shall be detected when the VBPDST is in normal operation.
NOTE A physical contrast results in a difference of intensity that is detected. For more information, see Annex CC.
4.2.12.5 Object detection at high contrast
At high contrast the test piece shall be detected when the VBPDST is in normal operation.
NOTE A high contrast results from a big difference of the coefficient of diffuse reflection and/or lighting variation
between the background and the test piece. The contrast could be higher than the dynamic range of the imaging
sensor.
4.2.12.6 Minimum detection zone
The supplier shall specify the minimum detection zone(s). The supplier shall take into account
worst case conditions including, for example:
– response time;
– minimum diameter of the test piece;
– maximum speed of the test piece.
4.2.12.7 Position accuracy
When determining the position accuracy, the following systematic and random influences shall
be taken into account if applicable, but not limited to:
a) the calibration of the sensing device;
b) characteristics of the optical/imaging sensor, such as
1) the number of pixels and pixel size
2) signal-to-noise ratio
3) modulation transfer function of the optics
c) algorithmic influences, such as:
1) smoothing algorithm
2) feature based detection algorithm, e.g. edge detection algorithm
3) template matching
4) colour sensor and algorithm
5) global algorithms, e.g. cluster algorithm
6) optical flow analysis algorithm
7) object tracking algorithm
8) stereo algorithm
d) synchronization between imaging sensors;
e) characteristics of the test piece;
f) limits of illumination;
g) Ageing and tolerances of components and references.
4.2.12.8 Pattern projection techniques (PAPT)
If pattern projection techniques are used to enhance the contrast in the scene, then the pattern
projector shall be considered as part of the VBPDST. This illumination module shall have the
capability to project sufficient contrast onto the scene anywhere within the specified detection
zone such that the system fulfils the requirements of this document. The detection capability
shall not be decreased below the limits specified by the supplier by any influences, including
but not limited to the following:
a) contrast between projected pattern elements;
b) contrast changes within projected pattern elements;
c) size and differentiation of projected pattern elements and number of projected pattern
elements used for contrast enhancement;
d) size of pixels and numbers of pixels compared to used projected pattern elements;
e) automatic adaptation of algorithm/routines;
f) size, shape, colour, reflectivity, position and surface structure of object and scene compared
to projected pattern;
g) resulting superposition of natural object/scene contrast and contrast produced by pattern
projection;
h) position and location of pattern projector.
4.2.12.9 Influence of periodic surface structures on the background
Periodic surface structures on the background shall not lead to a failure to danger.
Periodic surface structures resulting in a complete loss of the stated VBPDST detection
capability shall cause the ESPE to go to a lock-out condition within the specified response time
the OFF-state and remain in it as long as the periodic structure is present.
Periodic surface structures resulting in a deterioration of the stated VBPDST detection
capability shall cause the ESPE to go to the lock-out condition OFF-state within a time period
of 5 s following the occurrence of periodic surface structures and remain in it as long as the
periodic structure is present.
These requirements are verified by the tests of 5.2.1.5.
4.2.13 Test pieces for type testing
Replacement:
– 20 – IEC TS 61496-4-3:2022 RLV © IEC 2022
4.2.13.1 General
The test pieces shall be provided by the supplier for use in the type tests of Clause 5. They
shall be marked with a type reference and identification of the VBPDST with which they are
intended to be used.
The test pieces shall be opaque. Different test pieces can be required for different phases of
the test procedures.
The characteristics of the test piece which shall be considered are:
a) size;
b) shape;
c) colour;
d) reflectivity;
– at the wavelength of the illumination for VBPDST with PAPT
– at the wavelength of maximum sensitivity of the sensor for VBPDST with AIT
e) contrast with background;
f) texture.
When defining the characteristics of the test piece, protection against camouflage with the
background shall be taken into account. Unless the analysis shows that other test pieces are
appropriate the following test pieces shall be used.
4.2.13.2 Cylindrical test piece
The test piece shall be cylindrical if the VBPDST is intended to be used for finger detection.
The cylindrical test piece shall have a diameter of 14 mm and a length for ease of use.
4.2.13.3 C
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