Instruction manual
Marlin Technical ManualV.2.7.0
86
Description of the data path
DSNU & blemish correction
(Marlin F-131B only)
In order to further reduce the dark signal non uniformity (DSNU) of the CMOS
sensor to levels similar to CCD sensors, the Marlin F-131B is equipped with a spe-
cial DSNU reduction function, extending the shading correction.
The DSNU function applies an additive correction to every pixel in order to equal-
ize the dark level of the pixels. This function also enables correction of single
and double blemished pixels by replacing them with their neighborhood pixels.
DSNU and blemish pixel correction are generated simultaneously but can be
switched on/off separately.
The following screenshots demonstrate how it works:
On the left picture (without correction) it can be seen that over the complete
field of view there is a certain spread of the histogram, indicating non uniform
dark pixels and blemished pixel(s) with brightness around 192(). With pure
DSNU correction the spread is considerably smaller.
The table below shows the advanced register map, required to control this func-
tionality.
Having generated the correction data it is possible to separately control the
blemish pixel correction with the help of the following register:
The effect of the additional blemish correction can be demonstrated with the
next screenshot. Not only is the spread now smaller, there are also no pixels
above a considerably lower grey level ( at. app. 96 in this case).
Figure 46: Effect of DSNU correction
Note
Configuration
To configure this feature in an advanced register:
•See Table 111: Advanced register: DSNU on page 210.
• Table 112: Advanced register: Blemish on page 211