Mitsubishi Electric KD Series User Manual page 25

2-3 Definition
【 Depth of Focus 】
Definition of resolution
Object Image (erected and
same size)
Depth of Focus on KD series
Focal point
（12mm above from
glass surface）
Scan images
4.0mm 3.0mm 2.0mm
TM-XG537C
【Definition of CIS output】
6. DOF : Depth of Focus
Depth of Focus indicates a tolerance of a resolution on
various positions of the object from focal position in a lens-
axis direction.
Generally, the resolution is getting 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.
•lp/inch: lp/inch indicates the resolution. The resolution
will be defined by reading the black and white stripe chart.
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
(Focal point)
are printed in 1 inch.
1.0mm 0.0mm
For example, "150 lp/inch chart" means the chart with
150 pairs of black and white stripes are printed in 1 inch,
which shall be calculated as 25.4 / 300 = 84.66, about
85μm width strips are printed .
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DVEp max. － DVEp min.
MTF =
DVEp max. + DVEp min.
× 100 (%)
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