PI627MC-A4 / PI628MC-A4 / PI629MC-A4 Engineering Data Sheet

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Depth of Focus

Figure 4 shows the typical MTF versus Distance, which can be used to define the working depth of focus.

Two curves indicate the spread among the modules. Note that the MTF is greater than 40% out to a

distance greater than 0.3 mm from the glass surface. Since this module is a 600DPI module, a pixel density

of 600 pixels per inch, the MTF was measured with a 300 DPI or a 150 line-pair per inch optical bar pattern.

The test was conducted with pixel rate set to 5.0MHz.

The effective algorithm used in the measurements is as described by the following equation:

MTF={[Vp(n)+Vp(n+1)]/2-[Vp(n+2)+Vp(n+3)]/2}/{[Vp(n)+Vp(n+1)]/2+[Vp(n+2)+Vp(n+3)]/2}

Where n is 1, 2, .....5184

TYPICAL MTF VS DEPTH OF FOCUS

0

10

20

30

40

50

60

0

0.2

0.4

0.6

DEPTH FROM THE WINDOW SURFACE(mm)

Figure 4. Typical MTF versus Distance

Page 11 of 13, Revised 2-23-04