Datalogic Matrix 400, Справочное руководство

Страница: 109 / 142

READING FEATURES
99
7
7.3 MAXIMUM LINE SPEED AND EXPOSURE TIME CALCULATIONS
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 system, 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

T
exp

X
The maximum (theoretical) line speed
LS can be calculated as follows:
X / T
exp (max)
= LS
(max)
Example:
A Matrix 400™ 600-010 using:
Internal Lighting Mode = Very High Power Strobe
Exposure Time (x10

s) = 10 (100

s)
Code Resolution (X) = 0.254 mm (10 mils)
has a maximum line speed of:
0.254 (mm) / 0.0001 (s) = 2540 mm/s
Likewise,
T
exp (max)
is the maximum Exposure Time value that can be used without blurring
for the given application line speed and code resolution. Therefore:
X / LS
(max)
= T
exp (max)