Datalogic Matrix 210N, Справочное руководство, Страница: 103 / 167

READING FEATURES
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6
6.4 MAXIMUM LINE SPEED CALCULATION
The
Exposure Time (or Shutter ) parameter defines the time during which the image will be
exposed to the reader sensor to be acquired. This parameter depends heavily on the
environmental conditions (external lighting, image contrast etc.).
In general, a longer time corresponds to a lighter image but is susceptible to blurring due to
the code movement; a shorter exposure time corresponds to a darker image.
NOTE:
The following considerations must be applied only when the internal
lighting system and 2D codes are used. The Maximum line speed allowed for
linear codes or postal code reading applications heavily depends on the
direction of symbol movement. When the direction of movement is parallel to
the elements of the code, the maximum speed is greater.
Assuming:

X : Code Resolution (mm)

T
exp
: Exposure Time (s)

LS : Line Speed (mm/s)
The essential condition to avoid blurring effects between two adjacent elements in a dynamic
reading application is:
LS x T
exp

X
The maximum (theoretical) line speed (LS) can be calculated as follows:
X / T
exp (min)
= LS
(max)
T
exp
(min) is the minimum Exposure Time value obtainable for the specific application. It can
be evaluated in static reading conditions and may depend on code printing quality, reader
position, etc.
Using the formulas previously explained it is possible to calculate the theoretical maximum
line (target) speed expected for the application, based on the maximum code resolution and
the minimum suitable
Exposure Time value.
The minimum
Exposure Time value depends on the reading distance and on external
lighting.