QHYCCD QHY168C User Manual page 21

QHY168C
the power, if the "Cooler Power" value is very big, you should gradually turn it down before turn
off the power.
8. The FPS of cameras sometimes suddenly drops to zero under DDR mode on
SharpCap, what's the solution for this problem?
Recently, we have been told by our users that the FPS of their cameras sometimes suddenly drops
to zero under DDR mode on SharpCap. It is caused by the fact that the receiving speed of computer
is relatively slower than the sending speed of camera. Once CMOS sensor starts working, it will
incessantly conduct exposure and output image data over and over again, and it cannot be
interrupted. If USB transmission was interrupted too often by the operating system, the data
overflow of DDR would ensue resulting in bad frame. Therefore, not a single frame is a complete
frame, and the FPS will drop to zero.
Solutions:
The first solution to this problem is to increase the value of USB traffic to decrease the FPS of the
cameras. Note that by using previous version of SharpCap Patch, the value of USB traffic cannot be
set to a value large enough, so you should go to our website to download the latest version of
SharpCap Patch.
The second solution to this problem is to turn off the DDR mode, but for computers whose
performance isn't very good, this solution may not work very well.
9. What should I set my "gain" and "offset" to?
GAIN is the pre-ADC (analog-to-digital converter) programmable gain amplifier setting. OFFSET is
the ADC voltage offset setting. The correct setting of OFFSET and GAIN can change the CCD's system
gain, making the CCD output signal range matches the ADC quantization range, so as to get the
best dynamic range.
1. Set the gain=0, set the exposure time to 0, cover the lens, then take a BIAS frame.
2. Watch the local average value of the captured images (you can use the Noise Analyze function
of EZCAP, image process->noise analyze).The ideal average value is around 500 to 3000. If the value
is higher, then you should reduce the OFFSET. If the value is lower, then you should increase the
OFFSET. Repeat steps 1-2 to obtain the ideal OFFSET value.
3. Open the lens cover, increase the exposure time, then aim the camera at something bright or
just put it on your desk with no lens or lens cap on. Take a picture. Check the local average value
of the captured images. If the value is less than 60000, you should increase the value of GAIN. If
the value is 65535, you should reduce the value of GAIN. Repeat this step to obtain the appropriate
GAIN value.
4. Under this GAIN value, repeat steps 1-2 to obtain a more accurate OFFSET value.
For CMOS camera, its sampling depth is usually less than 16 bit, so there's a concept named Unity
Gain, which is gain value when System Gain = 1 e-/adu, i.e. 1 adu corresponds to 1 electron. If the
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