MAXIMUM LINE SPEED AND EXPOSURE TIME CALCULATIONS
PRODUCT REFERENCE GUIDE
121
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.
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 (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 depends on the Matrix reader model
selected for the application (internal lighting system, optical lens, reading distance) and
on any external lighting system. It may also depend on code printing quality, and reader
position.
Example
A Matrix 320 using:
Internal Lighting Mode = Very High Power Strobe
Exposure Time (
s) = 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 blur-
ring for the given application line speed and code resolution. Therefore:
X / LS = T
exp
(max)
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
To Next Page
Loading...
Need help?
General
