d435 IR Projector Issues

[JSmit77]

We just recently got our hands on a d435.

We are currently using the d415 to project a pattern on a subject, then in addition to grabbing depth data from the d415, we also pick up the pattern using external cameras for other processing needs. Our current issue is that we would also like to use the d435 for this purpose; however upon sampling images from an external camera we found that the d435's projected pattern is not constant like the d415, but rather it flickers at a rate, consistent with framerate being sampled. (e.g. if we set the d435 to record depth at 30 fps, it flickers at close to 30Hz).

Is there any current way to keep the d435's projector outputting continuously, like the d415's? Any suggestions would be very much appreciated.

[MartyG · Accepted solution]

The tuning best-practices guide for the 400 Series says "Ordinarily, no tuning needs to be done in the D4 VPU when you use any external projectors as long as it is on continuously or flickering at >50KHz, so as not to interfere with the rolling shutter or auto-exposure properties of the sensor."

The discussion linked to below also mentions a user's apparent projector behavior differences with D415 and D435.

https://github.com/IntelRealSense/librealsense/issues/1512 D435 projector fails to turn on using set_option · Issue # 1512 · IntelRealSense/librealsense · GitHub

[JSmit77]

Thanks for the response Marty,

My current issue is that I would like to use the d435's projector as an external projector for another camera. Ideally I would like to adjust the frequency of the projector to be either 50KHz or simply constant. I read through that discussion which noted a suspected firmware synchronization issue for the d415, though they seemed to work around it by using a higher framerate (15 fps from 6 fps). In my case I am already sampling at the highest framerate (90 fps), yet I still see differences in projector intensity between frames. Is there a method to either modify the projector frequency or to get/send hardware triggers from the camera?

[MartyG]

SDK support for hardware sync for multiple cameras has been programmed but Intel are still working on the firmware component of that feature. Without the firmware half of the system, the SDK half will not function. There is no date available yet for when the firmware support for hardware sync will be available.

In regard to a frequency option, I found:

RS2_OPTION_POWER_LINE_FREQUENCY

/**< Power Line Frequency control for anti-flickering Off/50Hz/60Hz

[FChau1]

firmware support for hardware sync : I think a lot of people here are waiting for that !