Gain Settings In More Detail - Basler A202K Manual

Operation and Features

3.5.1 Gain Settings in More Detail

When the gain is set to default, the sensor's
linear output range directly matches the
input voltage range of the ADCs. Thus, with
the default gain of 0 dB, a gray value of 0 is
produced when the pixels are exposed to no
light and a gray value of 255 (8-bit mode) or
1023 (10-bit mode) is produced when the
pixels are exposed to bright light.
The 0 dB default gain is achieved when gain
is programmed to a decimal value of 288.
(Due to tolerances in the electronic com-
ponents in your camera, you may find that
the 0 dB default gain is achieved with a
slightly different setting.) Increasing the gain
setting to more than 288 maps a smaller
portion of the sensor's linear output range to
the ADC's input.
Increasing the gain is useful when at your brightest exposure, a gray value lower than 255 is
reached. For example, if you found that at your brightest exposure your gray values were no
higher than 127, you could increase the gain to 6 dB (amplification factor of 2) and thus reach gray
values of 254 (see Figure 3-11).
Gain is adjustable and can be programmed on a decimal scale that ranges from 288 to 1023
(0x0120 to 0x03FF). The settings result in the following amplifications:
Decimal Number (DN)
288
1023
Table 3-1: Gain Settings
If you know the decimal number (DN) setting for the gain on your camera, the equivalent decibel
value can be calculated using the following equations:
When DN setting = 288 ... 511
When DN setting = 512 ... 1023
In normal operation, a gain setting lower than 288 (0x0120) should not be used. When
the gain setting is lower than 288, the sensor output signal that is mapped to the input
of the ADCs will not be linear.
3-14
DRAFT
Hexadecimal dB
0x0120 0
0x03FF 28.06
Gain in dB
Gain in dB
Gray Values
12 dB
1023 255
(10-bit) (8-bit)
0
0 25
Figure 3-11: Gain Settings in dB
Factor
x1
x25
658
æ
--------------------------- -
= 20 log
è
10
658 DN
= .0354 (DN) – 8.15
6 dB 0 dB
50 100
Sensor output
signal [%]
+ DN
ö
– 8.15
–
k
BASLER A202