BS ISO-IEC 16480-2015 pdf free download – Information technology — Automatic identification and data capture techniques — Reading and display of ORM by mobile devices
NOTE Eigure 2 shows a magnified portion of the bar code displayed on the screen (see Figure 1) of a mobiledevice showing the individual pixels of the screen.
5.1.1 Reading and illumination conditions
Generally, mobile devices do not have a diffuse reflective surface.Therefore it is generally not successfulto attempt to read the bar code with a flying spot device (e.g. a visible laser beam).
Generally,mobile devices have a flat polished screen surface (e.g. glass) that is highly reflective.Consequently it is not generally appropriate for a bar code scanning device to illuminate the surface.ln addition,generally, the only type of scanning devices capable of reading images produced on mobiledevices contains linear or area sensors or arrays and are sometimes called “linear imagers”, “2Dimagers” or simply “imagers”.
Generally, mobile devices produce light (i.e. backlighting) that is used directly by imagers to readsymbols on the screen.The amount of backlight produced is called Luminescence. Luminescence ismeasured with an optometer (luminance-meter) set to the units candelas per metre squared (cd/m2).The optometer shall be configured so that the only light collected is from pixels on the display at theirmaximum output.
Mobile devices should produce background illumination of greater than 90 cd/m2 for dependable scannerperformance. Displays with illumination less than 40 cd/m2 may not be readable by some scanners.
5.1.2 Display pixel conditions
The pixels on a mobile device screen should be controlled directly and individually in order to producea readable symbol. Specifically a black module should be rendered with exactly the same number ofpixels as what would be a white module of the same size.
For instance, in Figure 2 above, the smallest black module is made up of an array of four by four pixelsthat have been directly controlled to exclude the background light. Similarly, precisely the same arrayof pixels is left open to produce a bright module.
5.1.3Appropriate range of symbol X-dimensions
The X-dimension of a bar code symbol on a mobile device screen is the physical size of an individualpixel times the number of pixels per module.An alternate way to calculate the X-dimension is tomeasure the size of many modules and divide by the number of modules (often referred to as theZ-dimension).See Figure 3.
NOTE There are 32 modules in 10 mm (0,4 in) (between the “1” and the “5”). Therefore the Z-dimension is0,3 mm(0,012 5 in or equivalently 12,5 mils).Therefore, the module size on this display is too small.
The appropriate range of X-dimensions for bar code symbol rendered on the display of a mobile deviceis 0,38 mm to 0,63 mm (0,015 in to 0,025 in).
5.1.4 Capturing an image
To capture an image for quality analysis,use a verification device that has its lights turned off or whichdoes not have auxiliary lighting.The image should be taken in ambient lighting conditions. The imagetime should be such that the white areas reach between70 and 85 percent of image sensor saturation.
5.1.5 Grading an image
5.1.5.1 Relation to 15415 and 15416
For 2D bar code symbol quality analysis, the methods of ISO/IEC 15415 shall be used with the exceptionthat Rmax is set to 90 % and Symbol Contrast is not graded or reported.A synthetic aperture of 0,38 mm(15 mils) shall be used to process the image to produce the reference gray scale image.The aperturesize used for grading is 0,25 mm (10 mils).
While less common, if the symbol is a linear bar code, then the methods of lSO/IEC 15416 shall be usedexcept that the scan reflectance profile set is produced in software from an image using an aperture sizethat is 80 % of the symbol X-dimension with Rmax set to 90 % and Symbol Contrast not graded or reported.
5.1.5.2 Luminescence
Luminescence is graded per Table 1.BS ISO-IEC 16480 pdf download.