1、 Reference number ISO/IEC TR 29158:2011(E) ISO/IEC 2011TECHNICAL REPORT ISO/IEC TR 29158 First edition 2011-10-15Information technology Automatic identification and data capture techniques Direct Part Mark (DPM) Quality Guideline Technologies de linformation Techniques automatiques didentification e
2、t de capture de donnes Ligne directrice de qualit du marquage direct sur pice (DPM) ISO/IEC TR 29158:2011(E) COPYRIGHT PROTECTED DOCUMENT ISO/IEC 2011 All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic or
3、 mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or ISOs member body in the country of the requester. ISO copyright office Case postale 56 CH-1211 Geneva 20 Tel. + 41 22 749 01 11 Fax + 41 22 749 09 47 E-mail copyrightiso.org Web w
4、ww.iso.org Published in Switzerland ii ISO/IEC 2011 All rights reservedISO/IEC TR 29158:2011(E) ISO/IEC 2011 All rights reserved iiiContents Page Foreword iv Introduction . v 1 Scope 1 2 Normative references 1 3 Terms and definitions . 1 4 Abbreviated terms . 2 5 Overview of methodology 3 5.1 Proces
5、s differences from 15415 3 5.2 Lighting. 3 6 Obtaining the image 3 6.1 Orientation of the symbol to the camera 3 6.2 Lighting. 4 6.3 Image focus 4 6.4 Reflectance calibration . 4 6.5 Initial image reflectance level of the symbol under test 5 7 Obtaining the test image . 5 7.1 Binarize image . 5 7.2
6、Apply Reference Decode Algorithm 5 7.3 Connect areas of the same colour . 6 7.4 Final image adjustment . 7 8 Determine contrast parameters . 7 8.1 Calculate Cell Contrast (CC) 8 8.2 Calculate Cell Modulation (CM) 8 8.3 Calculate % Reflectance of Symbol (Rtarget) 8 9 Grading . 8 9.1 Cell Contrast (CC
7、) 8 9.2 Minimum Reflectance 8 9.3 Cell Modulation (CM) . 8 9.4 Fixed pattern damage . 9 9.5 Final grade . 9 10 Communicating grade requirements and results 9 10.1 Communication from Application to Verifier 9 10.2 Communicating from Verifier to Application 9 10.3 Communicating Lighting 9 10.4 Communi
8、cating the use of a proprietary decode 10 Annex A (normative) Threshold determination method . 11 Annex B (informative) Communicating the grade . 15 Annex C (informative) Cross-reference to ISO/IEC 15415 18 ISO/IEC TR 29158:2011(E) iv ISO/IEC 2011 All rights reservedForeword ISO (the International O
9、rganization for Standardization) and IEC (the International Electrotechnical Commission) form the specialized system for worldwide standardization. National bodies that are members of ISO or IEC participate in the development of International Standards through technical committees established by the
10、 respective organization to deal with particular fields of technical activity. ISO and IEC technical committees collaborate in fields of mutual interest. Other international organizations, governmental and non-governmental, in liaison with ISO and IEC, also take part in the work. In the field of inf
11、ormation technology, ISO and IEC have established a joint technical committee, ISO/IEC JTC 1. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2. The main task of the joint technical committee is to prepare International Standards. Draft Internat
12、ional Standards adopted by the joint technical committee are circulated to national bodies for voting. Publication as an International Standard requires approval by at least 75 % of the national bodies casting a vote. In exceptional circumstances, when the joint technical committee has collected dat
13、a of a different kind from that which is normally published as an International Standard (“state of the art”, for example) it may decide to publish a Technical Report. A Technical Report is entirely informative in nature and shall be subject to review every five years in the same manner as an Intern
14、ational Standard. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO and IEC shall not be held responsible for identifying any or all such patent rights. ISO/IEC TR 29158 was prepared jointly by Joint Technical Committee ISO/IEC
15、JTC 1, Information technology, Subcommittee SC 31, Automatic identification and data capture techniques. ISO/IEC TR 29158:2011(E) ISO/IEC 2011 All rights reserved vIntroduction Direct Part Marking (DPM) is a technology whereby, generally, an item is physically altered to produce two different surfac
16、e conditions. This alteration can be accomplished by various means including, but not limited to, dot peen, laser, ink jet, 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 pattern defined by a ba
17、r code symbology specification, is called “a symbol”. 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 ha
18、s 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
19、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 diffuse reflectance. In addition, from the scanner point-of-view, some marking and printing methods generate dots and are not
20、 capable of producing smooth lines. 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. This is intended to act as a bridge between the existing specifications a
21、nd the DPM environment in order to provide a standardized image-based measurement method for DPM that is predictive of scanner performance. As with all symbology and quality standards, it is the responsibility of the applicator to define the appropriate parameters of this guideline for use in conjun
22、ction with a particular application. TECHNICAL REPORT ISO/IEC TR 29158:2011(E) ISO/IEC 2011 All rights reserved 1Information technology Automatic identification and data capture techniques Direct Part Mark (DPM) Quality Guideline 1 Scope This Technical Report is an engineering document intended for
23、verifier manufacturers and application specification developers. This Technical Report 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 ne
24、w terms and parameters, modifications to the measurement and grading of certain parameters, and the reporting of the grading results. This Technical Report 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
25、 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 repo
26、rted as a DPM grade rather than as an ISO/IEC 15415 grade. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (in
27、cluding any amendments) applies. ISO/IEC 15415, Information technology Automatic identification and data capture techniques Bar code print quality test specification Two-dimensional symbols ISO/IEC 15416, Information technology Automatic identification and data capture techniques Bar code print qual
28、ity test specification Linear symbols ISO/IEC 19762-1, Information technology Automatic identification and data capture (AIDC) techniques Harmonized vocabulary Part 1: General terms relating to AIDC ISO/IEC 19762-2, Information technology Automatic identification and data capture (AIDC) techniques H
29、armonized vocabulary Part 2: Optically readable media (ORM) 3 Terms and definitions For the purposes of this document, the terms and definitions given in ISO/IEC 15415, ISO/IEC 15416, ISO/IEC 19762-1, ISO/IEC 19762-2 and the following apply. 3.1 MLcal mean of the light lobe from a histogram of the c
30、alibrated standard ISO/IEC TR 29158:2011(E) 2 ISO/IEC 2011 All rights reserved3.2 MLtarget mean of the light lobe from the final grid-point histogram of the symbol under test 3.3 reference symbol high-contrast printed calibration card EXAMPLE The GS1 Data Matrix calibrated conformance standard test
31、card. 3.4 Rcal reported reflectance value, Rmax, from a calibration standard 3.5 Rtarget measured percent reflectance of the light elements of the symbol under test relative to the calibrated standard 3.6 SRcal system response parameters (such as exposure and/or gain) used to create an image of the
32、calibration standard 3.7 SRtarget system response parameters (such as exposure and/or gain) used to create an image of the symbol under test 3.8 stick line segment comprised of image pixels that is used to connect areas of the same colour that are near to each other 3.9 T1 threshold created using a
33、histogram of the defined grey-scale pixel values in a circular area twenty times the aperture size in diameter, centred on the image centre using the algorithm defined in Annex A 3.10 T2 threshold created using the histogram of the reference grey-scale image pixel values at each intersection point o
34、f the grid using the method defined in Annex A 4 Abbreviated terms CM Cell Modulation CC Cell Contrast FPD Fixed pattern damage LED Light emitting diode MD MeanDark ISO/IEC TR 29158:2011(E) ISO/IEC 2011 All rights reserved 35 Overview of methodology 5.1 Process differences from 15415 All parameters
35、in the symbology and print quality specifications apply except for: - A different method for setting the image contrast. - A different method for creating the binary image. - A new method for choosing the aperture size. - An image pre-process methodology for joining disconnected modules in a symbol.
36、 - A different process for determining the Modulation and Reflectance Margin parameter renamed Cell Modulation. - A different process for determining the Symbol Contrast parameter which has been renamed Cell Contrast. - A difference process for computing Fixed Pattern Damage - A new parameter called
37、 Minimum Reflectance. This guideline explains how to both specify and report quality grades in a manner complementary to, yet distinct from, the method in ISO/IEC 15415. 5.2 Lighting This guideline recommends three specific lighting environments consisting of two forms of diffuse lighting (non-direc
38、tional): - diffuse on-axis illumination uses a diffuse light source illuminating the symbol nominally perpendicular to its surface (nominally parallel to the optical axis of the camera). - diffuse off-axis illumination uses light from an array of LEDs reflected from the inside of a diffusely reflect
39、ing surface of a hemisphere, with the symbol at its centre, to provide even incident illumination from all directions. - Directional illumination is oriented at a low angle (approximately 30 degrees) to the mark surface. 6 Obtaining the image 6.1 Orientation of the symbol to the camera 6.1.1 Camera
40、position The camera is positioned such that the plane of the image sensor is parallel to the plane of the symbol area. 6.1.2 Orienting the symbol The part is placed such that the symbol is in the centre of the field of view and oriented so that the horizontal lines in the symbol are parallel with a
41、line formed by the edge of the image sensor to within +/- 5 degrees. ISO/IEC TR 29158:2011(E) 4 ISO/IEC 2011 All rights reserved6.2 Lighting Two lighting environments each with sub-options are defined in this document. The defined lighting environments are denoted in the reported grade using the for
42、mat defined in ISO/IEC 15415 using the angle specifier with a combination of numbers and letters as defined below. Note: This does not limit the prerogative of an Application Specification to choose different lighting environments based on application requirements. Alternate lighting environments sh
43、ould include specifiers consistent with the format of those below which can be used for communicating quality requirements and quality grades. 6.2.1 Diffuse perpendicular (on-axis/bright field) (90) A flat diffusing material is oriented such that the plane of the material is parallel to the plane of
44、 the symbol area. The symbol is uniformly illuminated with diffuse light incident at 90 +/- 15 degrees relative to the optical axis to the plane of the symbol. The angle specifier shall be 90 to denote this lighting environment. 6.2.2 Diffuse off-axis (D) A diffusely reflecting dome is illuminated f
45、rom 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 angle specifier shall be D. 6.2.3 Low angle, four direction (30Q) Light is aimed at the part at an angle of 30 +/- 3 degrees from the plane
46、 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 w
47、ithin +/- 5 degrees. The lighting shall illuminate the entire symbol area with uniform energy. The angle specifier shall be 30Q. 6.2.4 Low angle, two direction (30T) Light is aimed at the part at an angle of 30 +/- 3 degrees from two sides. The light may be incident from either of the two possible o
48、rientations 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 30T. 6.2.5 Low angle, one direction
49、(30S) Light is aimed at the part at an angle of 30 +/- 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 30S. 6.3 Image focus The camera is adjusted such that the s
