ISO 18221:2025
(Main)Microscopes — Microscopes with digital imaging displays — Information provided to the user regarding imaging performance
Microscopes — Microscopes with digital imaging displays — Information provided to the user regarding imaging performance
This document specifies the minimum information to be provided to the user by the manufacturers of microscopes with digital displays regarding imaging performance. It further specifies terms and definitions for describing the optical performance of the digital imaging path of microscopy systems including the observation of the image on digital displays. This standard does not apply to confocal microscopes. NOTE Terms and definitions for the direct visual observation with eyepieces are specified in ISO 8039 and ISO 10934.
Microscopes — Microscopes avec écrans d'affichage numérique — Informations fournies à l'utilisateur concernant la performance d'affichage
General Information
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Standards Content (Sample)
International
Standard
ISO 18221
Second edition
Microscopes — Microscopes
2025-06
with digital imaging displays —
Information provided to the user
regarding imaging performance
Microscopes — Microscopes avec écrans d'affichage numérique
— Informations fournies à l'utilisateur concernant la
performance d'affichage
Reference number
© ISO 2025
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Published in Switzerland
ii
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols and abbreviated terms. 2
5 Magnification . 3
5.1 Optical magnification, M .3
TOT,PROJ
5.2 Display magnification, M .3
DIS
5.3 Visual display magnification, M .3
DIS,VIS
6 Resolving power limit . 4
6.1 Optical resolving power limit, R .4
L,OPT
6.2 Sensor resolving power limit, R .4
L,SEN
6.3 Display resolving power limit, R .5
L,DIS
6.4 System resolving power limit, R .5
L,SYS
7 Useful range of magnification . . 5
7.1 Useful range of viewing distance .5
7.2 Useful range of visual magnification .6
7.3 Empty magnification .6
8 Object field . . 6
8.1 Object field limited by the sensor .6
8.2 Object field limited by the display . .7
8.3 Object field of the microscopy system .8
8.4 Pixel size in object space .8
9 Depth of field . 8
10 Information to be provided to the user by manufacturers . 9
10.1 General information.9
10.2 Imaging performance data .9
Annex A (informative) Examples for information to be provided to the user .11
Bibliography .15
iii
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
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with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO document should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
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related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 172, Optics and photonics, Subcommittee SC 5,
Microscopes and endoscopes.
This second edition cancels and replaces the first edition (ISO 18221:2016), which has been technically
revised.
The main changes are as follows:
— addition of formula expression to 8.1 and 8.2;
— addition of subclause 8.4 Pixel size in object space;
— addition of content to Clause 9;
— revision of formula for depth of field in Clause 9;
— addition of f) in 10.2;
— addition of content to Tables A.1 to A.5.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
iv
International Standard ISO 18221:2025(en)
Microscopes — Microscopes with digital imaging displays
— Information provided to the user regarding imaging
performance
1 Scope
This document specifies the minimum information to be provided to the user by the manufacturers of
microscopes with digital displays regarding imaging performance.
It further specifies terms and definitions for describing the optical performance of the digital imaging path
of microscopy systems including the observation of the image on digital displays.
This standard does not apply to confocal microscopes.
NOTE Terms and definitions for the direct visual observation with eyepieces are specified in ISO 8039 and
ISO 10934.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO 10934, Microscopes — Vocabulary for light microscopy
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 10934 and the following apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
digital microscopy system
instrument consisting of an objective, an image sensor (3.2) and a digital display (3.3) to make visible minute
details that are not seen with unaided eye
Note 1 to entry: The system might include means for image enhancement, image analysis, archiving, etc.
3.2
image sensor
device to transform an optical image into a digital image
3.3
digital display
output device for the visual presentation of a digital image and other information
3.4
resolving power limit
maximum spatial frequency distinguishable in object space, expressed in line pairs per millimetre (lp/mm)
Note 1 to entry: The resolving power actually achieved will always be lower than the resolving power limit due to
reduced contrast, Moiré patterns, etc. In addition, it depends on sensor type, object structure, illumination, etc.
3.5
pixel pitch
distance between the centres of adjacent pixels (picture elements) in an image sensor (3.2) or a digital
display (3.3)
3.6
line pair
one line and one space between the lines of a spatial grid with equal line thickness and space width between lines
3.7
viewing distance
distance between the digital display (3.3) and the observer’s eye
4 Symbols and abbreviated terms
c coefficient related to the operation mode of the image sensor
d depth of field for observation of the image presented on the digital display
AX,SYS
d actual viewing distance
VIEW
d useful range of viewing distance
VIEW,USEF
h height of the object field limited by the image area in the display
LIM,DIS
h height of the object field limited by the sensor
LIM,SEN
h height of the object field of the microscopy system
SYS
λ wavelength
lp line pair
M display lateral magnification
DIS
M visual display magnification
DIS,VIS
M useful range of the perceived visual display magnification
DIS,VIS,USEF
M lateral magnification at the image projected onto the sensor
TOT,PROJ
M total visual magnification of the virtual microscope image formed by the eyepiece
TOT,VIS
NA numerical aperture
N number of image pixels in the display in x-direction
xDIS
N number of active image sensor pixels in x-direction
xSEN
N number of image pixels in the display in y-direction
yDIS
N number of active image sensor pixels in y-direction
ySEN
n refractive index of the object or of the immersion media
p pixel pitch of the digital display
p,DIS
p pixel pitch in object space
p,OBJ
p pixel pitch of the image sensor
p,SEN
R display resolving power limit in object space
L,DIS
R optical resolving power limit in object space
L,OPT
R sensor resolving power limit in object space
L,SEN
R system resolving power limit in object space
L,SYS
w width of the object field limited by the image area in the display
LIM,DIS
w width of the object field limited by the sensor
LIM,SEN
w width of the object field of the microscopy system
SYS
5 Magnification
5.1 Optical magnification, M
TOT,PROJ
M is the lateral magnification of the image projected onto the image sensor. It should be expressed in
TOT,PROJ
proportional form, e.g. 10:1.
5.2 Display magnification, M
DIS
M is the lateral magnification of the digital image
...
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