Microscan Quadrus EZ, User Manual, Page: 328 / 366

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Quadrus EZ Reader User’s Manual
Field of View and Lenses
Appendix J — Field of View and Lenses
Representations of two lens type views are shown in the drawing below. Notice that while
FOVs vary considerably by lens type and focal distance (the distance from the front of the
reader—also called “object distance”), the image sensor sizes are fixed. This is the case
with the both the CMOS and CCD which use the same sensor size for all lens types.
Pixels and Resolution
Wider lenses mean a wider
FOV, but lower resolutions.
This is because the number
of pixels on the image sen-
sor, whether CCD or CMOS,
is the same for all lens
types. So if you increase the
FOV—by going to a larger
lens type or a longer focal
distance—the resolution
(the number of pixels avail-
able for a given area) dimin-
ishes. In the representations
to the right, the extra-wide
lens has the same number of pixels available as the wide angle at similar distances, but
since the wide angle’s FOV is about half that of the extra-wide’s FOV, its resolution is
therefore double.
This can be stated in two rules:
1. At any given focal distance, the smaller the lens type, the higher the resolution.
2. For any given lens type, the shorter the focal distance, the higher the resolution.
Wide lens
Extra wide
angle lens
FOV
Image sen-
sor
Image sen-
sor
FOV
Image sen-
sor
Wide angle lens
Extra-wide angle lens