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A-24 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

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Microscan Quadrus EZ Bedienungsanleitung Seite 328