Gain And Brightness - Basler A101f User Manual

3.6 Gain and Brightness

The major components in the camera electronics
include: a CCD sensor, a VGC (Variable Gain Control),
and an ADC (Analog to Digital Converter). The pixels in
the CCD sensor output voltage signals when they are
exposed to light. These voltages are amplified by the
VGC and transferred to the ADC which converts the
voltages to digital output signals.
Two parameters, gain and brightness are associated
with the VGC. As shown in Figures 3-9 and 3-10,
increasing or decreasing the gain increases or
decreases the amplitude of the signal that is input to
the ADC. Increasing or decreasing the brightness
moves the signal up or down the measurement scale
but does not change the signal amplitude.
The default gain and brightness are set so that with
optimal lighting and exposure, the linear output range
of the CCD sensor maps to the input range of the ADC.
Under these conditions, black will produce a gray value
of 1 from the ADC and white will produce a gray value
of 254.
For most applications, black should have a gray value
of 1 and white should have a gray value of 254. Attempt
to achieve this by varying exposure and illumination
rather than changing the camera's gain. The default
gain is the optimal operating point (minimum noise) and
should be used if possible.
Because increasing gain increases both signal and noise, the signal to noise ratio does
not change significantly when gain is increased.
f
BASLER A101
DRAFT
input
signal
to ADC
to ADC
Operation and Features
[V]
increasing gain
increases the
amplitude of
the input signal
light intensity [µJ/cm
Figure 3-9: Gain
input
signal
[V]
increasing brightness
moves the input
signal up the
measurement scale
offset
light intensity [µJ/cm
Figure 3-10: Brightness
2
]
2
]
3-11