D415 Laser Intensity

• MartyG

  • September 26, 2020 14:53

  Hi Ajg206  The 'average' Laser Power of 150 mw represents a default value, and is set as the default value for the changeable Laser Power option in the RealSense SDK's RealSense Viewer program.  In the Viewer, the Laser Power option's maximum settable value is 360 mw.

  Laser Power has a direct relationship with the amount of detail on a depth image.  Decreasing the Laser Power makes the depth image more sparse (i.e more gaps / holes on the image), and increasing Laser Power makes the depth image less sparse (i.e less gaps / holes). 

  Section 4.1 of Intel's white-paper document about projectors discusses the Laser Power of the 400 Series' in-built projector and its effect on fill rate over a power range from 0 to 360 mw.

  https://dev.intelrealsense.com/docs/projectors#section-4-increasing-range 

  The same document states in Section 9 that by default the D435 model pulses its light to coincide with camera exposure, whilst the D415's default is that the projector stays on all the time.

  https://dev.intelrealsense.com/docs/projectors#section-9-using-multiple-depth-cameras 

  I could not locate an official reference regarding to intensity across the FOV.

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• Ajg206

  • September 26, 2020 15:38

  Thanks, MartyG. 

  Regarding the maximum laser power, I was wondering what is referred to by peak optical power in Table 3-14 here: https://www.intelrealsense.com/wp-content/uploads/2020/06/Intel-RealSense-D400-Series-Datasheet-June-2020.pdf and the circumstances under which it will be emitted.

  Is it possible to have the D415 pulse its light to coincide with exposure as the D435 does? Is that what the emitter enabled: laser auto is for?

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• MartyG

  • September 26, 2020 16:03
  • Edited

  Laser Auto is a deprecated feature that I understand was originally designed to toggle the emitter on and off.  Intel later added a mode to alternate the emitter on-off on a per-frame basis, though it only works for camera models with a fast global shutter such as D430 / D435 / D435i (the D415 has a slower rolling shutter).  The link below to information about this mode has an animated image with a fast-strobing light, so beware if you have epileptic sensitivity.

  https://github.com/IntelRealSense/librealsense/pull/3066 

  As far as I know, the lack of a global shutter on the D415 prevents replication of the D43x models' support for per-frame emitter strobing.

  The data sheet is the only publicly available document that makes reference to optical power so I would prefer not to make a guess at its meaning that might be incorrect.

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