MTF Graph and Its Discussion

Figure 3. Typical MTF versus Distance

See Figure 3, Typical MTF versus Distance. This graph essentially shows the working

depth-of-focus. Two curves indicates the spread among the modules. Note that MTF is

greater than 40% out to distance greater than 0.4 mm from the glass surface. Since this

module is a 200DPI module, a pixel density of 200 pixel per inch, the MTF was measured

with a 100 DPI or a 50 line-pair per inch optical bar pattern. The test was conducted with

pixel rate set to 2.5MHz.

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, .....1728

Operating Conditions (25 °C)

Item

Symbol

Min

Typical

Max

Units

Vdd (positive)

4.5

5.0

5.5

V

Vn (negative)

-10

-5

-4.0

V

Idd (positive)

60

66

75

ma

Power Supply

20

20

20

ma

Input voltage at digital high Vih

Vdd-1.0

Vdd-.5

Vdd

V

Input voltage at digital low

Vil

0

0.6

V

Clock frequency

Fclk

MHz

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)

PAGE 7 OF 10 - PI227/228/229, 01-31-04