ISO/IEC DIS 29158

DRAFT INTERNATIONAL STANDARD
ISO/IEC DIS 29158
ISO/IEC JTC 1/SC 31 Secretariat: ANSI
Voting begins on: Voting terminates on:
2020-01-22 2020-04-15
Information technology — Automatic identification and
data capture techniques — Direct Part Mark (DPM) Quality
Guideline

Technologies de l'information — Techniques automatiques d'identification et de capture de données —

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Foreword ..........................................................................................................................................................................................................................................v

Introduction ................................................................................................................................................................................................................................vi

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Symbols (and abbreviated terms) ...................................................................................................................................................... 2

5 Overview of methodology ........................................................................................................................................................................... 2

5.1 Process differences from ISO/IEC 15415......................................................................................................................... 2

5.2 Lighting .......................................................................................................................................................................................................... 3

5.3 Tilted coaxial lighting and camera position (TCL). .................................................................................................. 3

6 Obtaining the image .......................................................................................................................................................................................... 4

6.1 Camera position and Symbol orientation ........................................................................................................................ 4

6.1.1 Symbol placement .......................................................................................................................................................... 4

6.1.2 Camera position in a 90 degree camera angle set up ....................................................................... 4

6.1.3 TCL setup ................................................................................................................................................................................ 5

6.2 Lighting environments ..................................................................................................................................................................... 5

6.2.1 Perpendicular coaxial (90) ...................................................................................................................................... 5

6.2.2 Diffuse off-axis (D) ......................................................................................................................................................... 5

6.2.3 Four direction (angle Q) ............................................................................................................................................ 5

6.2.4 Two direction (angle T) ............................................................................................................................................. 5

6.2.5 One direction (angle S) ............................................................................................................................................... 6

6.2.6 TCL Setup ............................................................................................................................................................................... 6

6.3 Image focus ................................................................................................................................................................................................ 6

6.4 Depth of field ............................................................................................................................................................................................ 6

6.5 System response adjustment and reflectance calibration ................................................................................. 6

7 Verifying a symbol ............................................................................................................................................................................................... 7

7.1 Initial image reflectance.................................................................................................................................................................. 7

7.1.1 Initialize aperture size ................................................................................................................................................ 7

7.1.2 Create initial histogram.............................................................................................................................................. 7

7.1.3 Compute mean ................................................................................................................................................................... 7

7.1.4 Optimize image ................................................................................................................................................................. 7

7.2 Obtaining the test image ................................................................................................................................................................. 7

7.2.1 Binarize image ................................................................................................................................................................... 7

7.3 Apply Reference Decode Algorithm ...................................................................................................................................... 7

7.3.1 Repeat if necessary ........................................................................................................................................................ 8

7.3.2 Continue until end .......................................................................................................................................................... 8

7.4 Final image adjustment ................................................................................................................................................................... 8

7.4.1 Determine grid-point reflectance with two apertures .................................................................... 8

7.4.2 Create a grid-point histogram .............................................................................................................................. 8

7.4.3 Measure MeanLight ....................................................................................................................................................... 8

7.4.4 Record parameters ........................................................................................................................................... .............. 8

7.4.5 Create binarized images for the Symbology Reference Decode .............................................. 8

7.4.6 Decode ...................................................................................................................................................................................... 8

8 Determine contrast parameters ........................................................................................................................................................... 9

8.1 Calculate Cell Contrast (CC) ......................................................................................................................................................... 9

8.2 Calculate Cell Module Modulation (CMOD) .................................................................................................................... 9

8.3 Calculate Minimum Reflectance (Rtarget) ...................................................................................................................... 9

9 Grading ........................................................................................................................................................................................................................... 9

9.1 Cell Contrast (CC) .................................................................................................................................................................................. 9

9.2 Minimum Reflectance (Rtarget) ............................................................................................................................................10

9.3 Cell Modulation (CM)......................................................................................................................................................................10

9.4 Fixed pattern damage ....................................................................................................................................................................11

9.5 Final grade ...............................................................................................................................................................................................11

10 Communicating grade requirements and results ...........................................................................................................11

10.1 Communication of Application requirements...........................................................................................................11

10.2 Communicating from Verifier to Application ............................................................................................................12

10.3 Communicating the use of a proprietary decode ...................................................................................................12

Annex A (normative) Threshold determination method .............................................................................................................13

Annex B (informative) Evaluation of image at virtual 90° camera position from real tilted

camera position ..................................................................................................................................................................................................17

Annex C (normative) Continuous Grading for ISO/IEC15415 Parameters ................................................................21

Annex D (normative) Dot connecting algorithm ...................................................................................................................................26

Annex E (informative) Communicating the grade ...............................................................................................................................28

Annex F (informative) Cross reference to ISO/IEC 15415 ...........................................................................................................31

Bibliography .............................................................................................................................................................................................................................32

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bodies (ISO member bodies). The work of preparing International Standards is normally carried out

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ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of

International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.

The main task of technical committees is to prepare International Standards. Draft International

Standards adopted by the technical committees are circulated to the member bodies for voting.

Publication as an International Standard requires approval by at least 75 % of the member bodies

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights.

ISO/IEC 29158 was prepared by Technical Committee ISO/TC JTC 1, Information Technology,

Direct Part Marking (DPM) is a technology whereby, generally, an item is physically altered to produce

two different surface conditions. This alteration can be accomplished by various means including, but

not limited to, dot peen, laser mark, ink jetting, and electro-chemical etch. The area of the alteration

is called "the mark." The area that includes the mark and background as a whole, when containing a

When light illuminates a symbol, it reflects differently depending on whether it impinges on the

background of the part or on the physical alteration. In most non-DPM bar code scanning environments,

light is reflected off a smooth surface that has been coloured to produce two different diffuse reflected

states. The DPM environment generally does not fit this model because the two different reflected

states depend on at least one of the states having material oriented to the lighting such that the angle

of incidence is equal to the angle of reflection. Sometimes the material so oriented produces a specular

(mirror like) reflectance that results in a signal that is orders of magnitude greater than the signal from

In addition, from the scanner point-of-view, some marking and printing methods generate dots and are

not capable of producing smooth lines. This is important for symbologies such as Data Matrix which is

specified to contain smooth continuous lines but is sometimes marked with disconnected dots in a DPM

Current specifications for matrix symbologies and two-dimensional print quality are not exactly suited

to reading situations that have either specular reflection or unconnected dots or both. Additionally

symbologies specified to consist of smooth continuous lines may appear with unconnected dots. This

is intended to act as a bridge between the existing specifications and the DPM environment in order

to provide a standardized image based measurement method for DPM that is predictive of scanner

As with all symbology and quality standards, it is the responsibility of the application to define the

appropriate parameters of this guideline for use in conjunction with a particular application.

This standard is an engineering document intended for verifier manufacturers and application

This standard describes modifications which are to be considered in conjunction with the symbol

quality methodology defined in ISO/IEC 15415 and a symbology specification. It defines alternative

illumination conditions, some new terms and parameters, modifications to the measurement and

subsequent grading of certain parameters and the reporting of the grading results.

This standard was developed to assess the symbol quality of direct marked parts, where the mark is

applied directly to the surface of the item and the reading device is a two-dimensional imager.

When application specifications allow, this method may also be applied to symbols produced by other

methods. This is appropriate when direct part marked (DPM) symbols and non-DPM symbols are being

scanned in the same scanning environment. The symbol grade is reported as a DPM grade rather than

ISO/IEC 15415, Information technology — Automatic identification and data capture techniques — Bar

ISO/IEC 19762, Information technology — Automatic identification and data capture (AIDC) techniques —

The terms and definitions given in ISO/IEC 19762, ISO/IEC 15416 and ISO/IEC 15415 apply, together

Mean of the light lobe from the final grid-point histogram of the symbol under test.

High-contrast printed calibration card for which results are traceable back to national or international

Measured percent reflectance of the light elements of the symbol under test relative to the calibrated

standard. Rtarget is graded and reported as the parameter named “Minimum Reflectance”.

System Response parameters (such as exposure and/or gain) used to create an image of the calibration

System Response parameters (such as exposure and/or gain) used to create an image of the symbol

Line segment comprised of image pixels that is used to connect areas of the same colour that are near

Threshold created using a histogram of the defined grey-scale pixel values in a circular area 20 times

the aperture size in diameter, centred on the image centre using the algorithm defined in Annex A.

Threshold created using the histogram of the reference grey-scale image pixel values at each

All parameters in the symbology and print quality specifications apply except for:

— An image pre-process methodology for joining disconnected modules in a symbol (where applicable).

— A different process for determining the Modulation and Reflectance Margin parameter renamed

— A different process for determining the Symbol Contrast parameter which has been renamed Cell

Axial Nonuniformity, Grid Nonuniformity and Unused Error Correction are applied with their

continuous grading grades as defined in Annex C, so long as 15415 does not provide information on

continuous grading for these parameters. If/when 15415 does provide continuous grading on these

parameters, that information will be used. This standard explains how to both specify and report

quality grades in a manner complementary to, yet distinct from, the method in ISO/IEC 15415.

Lighting environments shall be reported according to chapter 6.2 and 10.2. The chosen lighting

environment shall be selected under recognizing the properties of the mark and the scanning equipment

DPM applications that uses a geometrical mark which is peened, drilled or carved into a surface.

Reading camera and unidirectional illumination are located at a coaxial position with a known fixed tilt

To read dot-peened codes, there are multiple reading setups possible. This standard defines several

This specific TCL environment is focussing on the system response of the mark (e.g., the image a camera

sees). SAE Standard AS9132 takes a different approach to specify the mark geometry.

Figure 1 illustrates the setup. The essential parameter is the camera reading angle. Typical camera

Note The camera angle is defined in a compatible way to the lighting angle of ISO/IEC15415 (Figure 3).

Note Within the dot peen industry, it is common to specify the stylus angle which is twice the camera angle

Note In practice, the condition "coaxial lighting" may be implemented by an approximate setup like a high

It is not feasible to grade this setup with a camera angle of 90°. The result will not be significant for this

Note that a general purpose verifier device may not cover this application, as it requires a special

Camera to object position is described in this chapter. By default, the horizontal and vertical axis of

the symbol are parallel to a line formed by the edge of the image sensor within +/- 3 degrees (i.e. no

rotation). This symbol orientation should be maintained unless an application specification requires

or allows a different orientation. An application specification may specify a different symbol rotation.

Since the symbol rotation is determined after decoding, the actual rotation angle should be reported

so that the setup can be reproduced easily. In applications in which the rotation angle is specified, the

rotation angle shall be reported to confirm conformance to specified requirements.

The camera is positioned such that the plane of the image sensor is parallel to the plane of the symbol

Within the TCL setup, camera and symbol position differs in the following points:

• The raw image is geometrically transformed to correspond to a test image with a virtual camera

• The symbol rotation angle needs to be specified by the application and shall be respected by +/-5°.

The lighting environment is specified by the application. This shall include a direction specifier or an

angle or both. The format is an extension of the angle specifier used in ISO/IEC 15415. Several examples

The symbol is illuminated with diffuse light such that the specular reflection from the entire field of

A diffusely reflecting dome is illuminated from below so that the reflected light falls non-directionally

on the part and does not cast defined shadows. This is commonly used for reading curved parts. The

Light is aimed at the part at the given angle +/- 3 degrees from the plane of the surface of the symbol

from four sides such that the lines describing the centre of the beams from opposing pairs of lights

are co-planar and the planes at right angles to each other. One lighting plane is aligned to be parallel

to the line formed by a horizontal edge of the image sensor to within +/- 5 degrees. The lighting shall

illuminate the entire symbol area with uniform energy. The angle specifier shall be angle Q.

Light is aimed at the part at the given angle +/- 3 degrees from two sides. The light may be incident from

either of the two possible orientations with respect to the symbol. The lighting plane is aligned to be

parallel to the line formed by one edge of the image sensor to within +/- 5 degrees. The lighting shall

illuminate the entire symbol area with uniform energy. The angle specifier shall be "angle T".

Since there are two possible orientations in this setup (above and below, and left and right) the

particular orientation actually used should be reported. The reporting method may be to indicate the

location of the lights with respect to the symbol such as “north-south” when the light is incident from

above and below the natural “top” and “bottom” of a symbol. The orientation of a symbol is known after

decoding and related to the normal orientation of a symbol as specified in its Symbology Specification

(e.g. a Data Matrix symbol’s natural orientation has the solid borders on left and bottom, and for QR

code the normal orientation has Finder Patterns in the upper left, lower left and upper right corners but

Light is aimed at the part at the given angle +/- 3 degrees from one side. The light may be incident from

any of the four possible orientations with respect to the symbol. The plane perpendicular to the symbol

surface containing the centre of the beam is aligned to be parallel to the line formed by one edge of

the image sensor to within +/- 5 degrees. The lighting shall illuminate the entire symbol area with

uniform energy. The angle specifier shall be angle S. Since there are four possible orientations in this