LT-400CL
17
6.3.7 Knee correction
If the relationship of input and output is linear (1:1), the output level will be clipped at a
certain input level and cannot reproduce the details in the clipped area. The knee
compensation circuit can keep the linear relationship until the knee point, while after
the knee point, the output signal is compressed to reproduce the details. This
compression area can be set by a knee slope.
The knee point and knee slope can be set individually.
Function
Length
Variable type
Setting range
Knee Point
10bit
Unsigned integer
0LSB
~
1023LSB
Knee Slope
16bit
Unsigned fixed point 0001h(x0.000015)
~
FFFFh(x1.0000)
The following drawing shows the characteristics of Knee Point 890LSB and Knee Slope
1000h.
O
u
tp
u
t C
amer
a
Li
n
k
D
at
a
Le
ve
l
1023
890
0
0
4095
Input Data Level
2848
Knee Point = 37Ah (890)
Knee Slope = 1000h (1/16)
In this case : Maximum Value is 968 LSB.
968
[100%]
32
[0%]
Knee Point
1279
102
1/16
Fig.15 Knee and knee slope characteristics
6.3.8 PRNU (Pixel Response Non-Uniformity ) correction
PRNU (Pixel Response Non-Uniformity) is, as the name implies, a non-uniformity of the
response of each individual pixel. This means that for a fixed light level each pixel will
have a slightly different output level (response).
Fig.16 Conceptual drawing for PRNU correction (1)
Max
Min
Multiply
by
Factor > 1
Multiply
by
Factor < 1
Before correction: Non-uniform response from pixel to pixel
Average