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3 Camera Control and Performing a Scan
Synchronization of the Imaging Procedure and the Object Scan Velocity
•
A two-dimensional image is generated by moving either the object or the camera. The direction of the translation
movement must be orthogonal to the sensor axis of the CCD line scan camera.
•
To obtain a proportional image with the correct aspect ratio, a line synchronous transport with the laterally
correct pixel assignment is required. The line frequency and the constant object velocity have to be adapted to
each other.
In cases of a variable object velocity or for particular high accuracy requirements then an external synchroni-
•
zation is necessary. The various trigger modes are described below.
CCD Sensor
Pixel #1
Scan Object
FOV
W
/ ß
P
Example 1:
Calculating the object scan velocity for a given field of view and line frequency:
Pixel width
Line frequency
S
FOV
Example 2:
Calculating the line frequency for a given field of view and object scan velocity:
Pixel width
Object scan velocity
S
FOV
© 2015
Schäfter + Kirchhoff GmbH • Hamburg
S
Pixel #1
V
0
= 14 µm
= 9.28 kHz
= 29.3 mm
= 50 mm
= 14 µm
= 200 mm/s
= 29.3 mm
= 50 mm
SK6288GKOC-L Instruction Manual (06.2015)
The optimum object scan velocity is calculated from:
V
=
O
If the velocity of the object carrier is not adjustable
then the line frequency of the camera must be adjusted
to provide an image with the correct aspect ratio,
where:
f
=
L
V
=
O
W
=
P
f
=
L
S
=
FOV
=
ß
=
=
14 µm · 9.28 kHz
V
=
O
(29.3 mm / 50 mm)
=
222 mm/s
200 mm/s · (29.3 mm / 50 mm)
f
=
L
14 µm
=
8.4 kHz
·
W
f
P
L
ß
·
V
ß
O
W
P
object scan velocity
pixel width
line frequency
sensor length
field of view
magnification
S / FOV
19
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