Defective IR frames for short exposure times (<70usec) [USB2.1]

[MZimm4]

Setup InfoCamera ModelD435FW version5.10.3SDK version2.16.0

Did anyone else experience issues when setting the IR camera to very short exposure times?

When connected to a USB2.1 port I observe weird artifacts and damaged frames for exposure times shorter than 70usec

On a USB3.2 port however, this behavior is not visible.

Issue Description

When connected to a USB2.1 port one cannot set the depth exposure time shorter than 70usec.

Exp times shorter than 70usec will lead to artifacts and over-exposed frames.

Steps to Reproduce

* Connect a D435 to a USB 2.1 port and open realsense-viewer

* Enable infra1 stream and set "enable auto exposure" to OFF

* Set exposure time to something like 100usec and you get unaffected frames

* Set exposure time to any value lower than 70usec and the frame becomes over-exposed (it looks brighter than at 100usec) and will show artifacts.

ATTENTION: When using a USB3.2 port we could not observe this issue

Example of an IR frame taken at 1usec exposure:

(Visible salt and pepper artifacts, foggy)

Comparison 60us vs 90us exposureUSB2.1, 90usec exposureUSB2.1, 60usec exposure

[MartyG]

Whilst I do not have an answer for the USB 2.1 aspect of this question, I did find an interesting case about artifacts in under-exposure and over-exposure that may provide useful insights.

https://github.com/IntelRealSense/librealsense/issues/1912 Over-exposure Artifacts in Depth · Issue # 1912 · IntelRealSense/librealsense · GitHub

[idata]

Hi,

We were able to reproduce this issue in the lab and have notified the RealSense Engineering Team about your findings.Trying a different frame rate might help. According to our tests, at 30 frames per second, exposure times below 60 μs still look good. Please let me know if you have any further questions!Regards,Sahira

[MZimm4]

Thanks for putting it on the todo list.

You are right: At 30fps I can go as low as 21usec without any issues. Only at <=20usec I get defective frames

[idata]

Hi,

After looking in to this problem, we found that after downgrading the camera's firmware to 5.09.14, we were able to set exposure times to lower than 60 μs and were not getting over-exposed frames while streaming at 15 frames per second. To downgrade your camera's firmware to v 5.09.14, follow this link: https://downloadcenter.intel.com/download/27954/Latest-Firmware-for-Intel-RealSense-D400-Product-FamilyPlease be sure to downgrade your camera's firmware using a USB 3.0 port. Let me know if this information is helpful!Regards,Sahira

[MZimm4]

Thank you for looking into this!

I don't know if downgrading is an option for me, though. We use hw sync which only came with FW 5.10. Correct if I am wrong

best, Moritz

[MartyG]

Hi m0oz! The firmware support for sync in D415 was introduced in firmware version 5.9.14. Firmware sync for D435 was introduced in firmware 5.10.3 So yes, if you need sync and have a D435, it would be difficult to go further back than 5.10.3.

Using hardware sync with D435 did exist before that in less easy to use forms though, such as using a commercial flash to create a spike in camera data that acted as a trigger.