Description of the data path
GUPPY Technical Manual
V4.0.1
84
Look-up table (LUT) and gamma function
The AVT GUPPY camera provides one user-defined look-up table (LUT). The
use of this LUT allows any function (in the form Output = F(Input)) to be
stored in the camera's RAM and applied to the individual pixels of an image
at run-time.
The address lines of the RAM are connected to the incoming digital data,
these in turn point to the values of functions which are calculated offline,
e.g. with a spreadsheet program.
This function needs to be loaded into the camera's RAM before use.
One example of using a LUT is the gamma LUT:
Output = (Input)
0.5
This is used with all CCD models. This is known as compensation for the non-
linear brightness response of many displays e.g. CRT monitors. The look-up
table converts the 10 bits from the digitizer to 8 bits.
Figure 37: Gamma LUT
Output = (Input)
gamma
0
50
100
150
200
250
0
200
400
600
800
1000
Input
Ou
tp
u
t
Guppy, gamma=0.5