XIIMUS R-GB-IR CL User Manual. Version 1.2
The data byte for this command can range from 0 to 63 (decimal). 0 corresponds to –2 dB
input stage gain and 63 10 dB gain. The default setting for this register is +4 dB,
which equals 31 decimal.
Decimal
Range
Range in
decibels
0-10
-2 to 0
10-21
0 to 2
21-31
2 to 4
31-42
4 to 6
42-53
6 to 8
53-63
8 to 10
Increasing preamp gain can be useful in low light applications as it improves overall signal to
noise ratio. It is first recommended to increase the preamp gain setting and then increase the
analog gains if there still isn’t enough signal. Setting the preamp gain too low can cause the
digital output to never reach saturation even though the CCD itself is in saturated state.
3.13.
Dark level (addresses 217 to 222)
The input clamp circuit of each channel removes the CCD’s optical black offset to maximise
system headroom and the effect of gain change on the black level. The dark level register
can be used to set the positive offset in the output data, if desired. If this parameter is set, the
dark level of channel in question will have an offset equal to the dark level setting.
Function decimal
hexadecimal
binary
Dark Level, Infrared odd
channel
217 D9 1101
1001
Dark Level, Infrared even
channel
218 DA 1101
1010
Dark Level, Red odd
channel
219 DB 1101
1011
Dark Level, Red even
channel
220 DC 1101
1100
Dark Level, Bluegreen
odd channel
221 DD 1101
1101
Dark Level, Bluegreen
even channel
222 DE 1101
1110
The data byte of this command has 8-bit range from 0 to 255 (decimal).
3.14.
Offset register (addresses 223 to 228)
The offset can be digitally removed by sending a value to the respective address. This value
is subtracted from all the pixel values prior to sending them out. The offset value is any
number between 0 and 1023. The MSB contains the topmost 8 bits and the LSB the bottom
most two bits of the 10-bit offset range. Offset is subtracted from the original 12-bit pixel
values.
Offset should be set by first sending the most significant byte of the channel and then
sending the least significant byte to the channel in question. The offset will not be updated if
only the MSB or the LSB byte of the desired offset setting is sent.
© TVI Vision, 18 October 2006 page 48 ( 57 )
