SR305 - Performance Variations on Different Surfaces
Hello,
I am currently using an SR305 camera for an object tracking program. Recently, I have noticed that the SR305 achieves very different depth performance for different surfaces. Please see the image below for the depth map achieved for two different fabrics. I have noticed that objects with dark and/or objects with glossy or shiny surfaces typically have poorer depth performance. Is this a limitation of structured light cameras due to the absorbance or refractance of IR light, or is there some settings or processing I could tweak to get better performance on these surfaces? Any advice is greatly appreciated.
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The issues that you describe are related to the physics of depth sensing cameras (not just RealSense). Dark surfaces such as black / dark grey are difficult for the camera to read depth detail from because the dark surface absorbs light. It is like how a person wearing a black t-shirt on a warm day may heat up faster than somebody in a white t-shirt. Affected areas may appear to be a plain single color such as black, because those areas of the image are actually empty of depth detail.
For example, if a black cable is scanned then it may seem to be represented on the image but is actually a cable-shaped black empty area.
Likewise, glossy / shiny surfaces will be difficult for the camera to read depth detail from, especially if there is a strong light-source projecting onto those surfaces.
There may not be much that can be done to rectify the problem with the technology inside the SR305, which is a couple of years older than that of the 400 Series cameras and has a smaller range of options. You can track objects or fabrics that are not black / grey in order to make them more readable to the camera. Spraying a fine powder such as baby powder or foot powder onto dark or reflective surfaces may make them more visible.
There are also professional 3D scanning sprays that can dampen reflections, and these are used for applications such as making 3D scans of shiny jewelry.
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A way to get around the technological limitations may be to purchase a physical optical filter and position it over the camera lens. The Intel paper on the subject in the link below was designed for the 400 Series cameras. But the principles of using filters to alter light to change camera properties should apply to other cameras such as SR305 too.
https://dev.intelrealsense.com/docs/optical-filters-for-intel-realsense-depth-cameras-d400
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