Lookup Table - Basler A620f User Manual

DRAFT
Smart Features

6.7.8 Lookup Table

cameras have a sensor that provides pixel data at 12 bit depth. Internally, the camera has
A620
f
a processing block that uses the 12 bit data to perform image correction functions and to perform
the gain and offset functions. The output from the processing block is 10 bit pixel data. As
mentioned in Section 3.8, the camera can be set to transmit the output from the processing block
at either 10 bit depth or at 8 bit depth.
When the camera is set for 8 bit pixel depth, it normally just drops the two least significant bits
(LSBs) for each pixel and only transmits pixel data at 8 bit depth. The A620 includes a smart
f
feature that lets you use a custom lookup table to map the 10 bit pixel values output from the
processing block to the 8 bit values that will be transmitted from the camera rather than just
dropping the two LSBs. The lookup table is essentially just a list of 1024 values. Each value in the
table represents the 8 bit value that will be transmitted out of the camera when the processing
block reports a particular 10 bit value for a pixel. The first number in the table represents the 8 bit
value that will be transmitted out of the camera when the processing block reports that a pixel has
a value of 0. The second number in the table represents the 8 bit value that will be transmitted out
of the camera when the processing block reports that a pixel has a value of 1. The third number
in the table represents the 8 bit value that will be transmitted out of the camera when the
processing block reports that a pixel has a value of 2. And so on.
The advantage of the lookup table feature is that it allows the user to customize the response
curve of the camera. The graphs below represent the contents of two typical lookup tables. The
first graph is for a lookup table where the values are arranged so that the output of the camera
increases linearly as the sensor output increases. The second graph is for a lookup table where
the values are arranged so that the camera output increases quickly as the sensor output moves
from 0 through 511 and increases gradually as the sensor output moves from 512 through 1023.
Figure 6-5: LUT with Values Mapped in a Linear Fashion
Figure 6-6: LUT with Values Mapped for Higher Camera Output at Low Sensor Readings
6-23
BASLER A620
f