【Depth of Focus】
Definition of resolution
Object
Image (erected and
Depth of Focus on KD series
Distance from the focal point (mm)
Scan images
3mm
2mm
TM-XH719C
2-3 Definition
same size)
Focal point
(12mm above from
glass surface)
1mm
0mm
(focal point)
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【Definition of CIS output】
6. DOF : Depth of Focus
Depth of Focus indicates a change of a focus performance
on various positions of the object from focal position on a
lens-axis.
Generally, the resolution becomes lower or defocused
when the scanning position is moved away from a focal
point.
The resolution is defined as MTF (Modulation Transfer
Function) value.
The MTF value is calculated by the following formula when
scanning a reference chart having a respective width and
pitch of the white and black areas.
MTF =
•lp/inch: lp/inch explains the resolution. The resolution is
defined by reading the black and white same-width stripes.
This pair of the same-width black and white stripe is called
as "line pair" (lp), and the "lp/inch " shows how many "lp"s
are printed in 1 inch.
-1mm
For example, "150 lp/inch chart" means that 150 pairs of
black and white stripes are printed in 1 inch on the chart.
And, the calculation of the resolution is 25.4 (mm) / 300
(stripes) = 84.66, which is about 85μm width strips are
printed .
Vpmax. -Vpmin.
× 100 (%)
Vpmax. + Vpmin.
28