In article <h8EOf.11802$(E-Mail Removed)>,

(E-Mail Removed) says...

> Unless there is an uncommon amount of crosstalk, most CCD chips come

> close to their theoretical capability, which is about 0.7 of the line

> frequency of the detectors. That is, if there are 100 detectors per mm,

> then the chip will usually test out at about 70 lines (35 lp) per mm.

> While the mtf curve for a discrete sensor is shaped a bit different than

> for a scanning sensor (Kell factor), the curves are close near the

> cutoff frequency or the 2% contrast point.
Where do you get this 70%? If a pattern with n white lines and n black

lines falls exactly on the lines of the CCD, so that each CCD line sees

either a black line or a white line, the CCD will have a resolution of

100% of the nominal pixel count. Maximum MTF. On the other hand if each

CCD line sees half of a black line and half of a white line, the CCD

will see a uniform gray (zero MTF).

--

Alfred Molon

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