Hi!
First of all, I'm not entirely sure if this is the right forum for this issue, but a quick search showed that there are several QHY-related threads here. I hope this post isn't considered spammy.
I recently acquired a QHY 268M Pro CMOS camera. I’d like to use it for more scientific purposes, which require precise time measurement. The camera is equipped with a 6-pin GPIO port.
Based on what I’ve found (specifically, the "GPXBOX-QHY600Pro High Precise Time Measurement" section on this page: https://www.qhyccd.c...y600pro-imx455/), it seems I can use the ERIS Framework to switch the GPIO port to Mode 2. In this mode, I am able to use a custom-made circuit board to record the time of the rising edge of the TrigOut pin. If I understand correctly, the rising edge of TrigOut marks the end of the exposure of row 0.
Additionally, I can measure the signal period from the LinePeriod pin using an oscilloscope. This measurement should provide the time offset between two rows due to the rolling shutter.
In theory, this would allow me to determine precise exposure timing as follows:
Use the TrigOut signal to get the time of the end of exposure for row 0.
Subtract the exposure time to calculate the start time of exposure for row 0.
For row N, multiply the LinePeriod by N and add it to the exposure start time of row 0.
Does this approach sound correct?
T_end_0 = T_trigout
T_start_0 = T_trigout - ExpTime
T_start_N = T_start_0 + N * LinePeriod
T_end_N = T_end_0 + N * LinePeriod
But something seems off. I set the exposure time to 500 ms and started a continuous, unlimited capture in SharpCap (which shows 2.0 FPS), but the period of T_trigout is slightly longer than 500 ms.
Additionally, there’s a hand-drawn diagram in the section I linked above, which I don’t fully understand. However, I have a feeling it might help solving this issue.
Does anyone here have experience with precise exposure time measurement?