Advice: D405 / D435 Considerations for 3D object reconstruction and tracking at 30 cm working distance
Hi,
I am currently evaluating RealSense D400 depth cameras for a system that requires 3D object reconstruction and online tracking
At this stage, I am considering the RealSense D405 & D435, and I would appreciate your guidance to better understand their suitability and possible alternatives within the RealSense family.
My use case can be described at a high level as follows:
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Working distance of approximately 30 cm
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Object is curved and has low natural texture
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The solution needs to be eye-safe
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The camera is intended to be integrated into a larger system, with constraints on size, weight, and overall compactness
Based on this, I would be grateful if you could help answer the following questions:
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What depth and reconstruction accuracy can be expected from the D405 & D435 at a ~30 cm working distance?
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Are there recommended approaches to improve reconstruction and tracking accuracy for curved, low-texture objects at this distance?
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Does adding artificial texture (e.g., patterns, speckles, or markers) typically improve performance in such scenarios?
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Given these constraints, are the D405 / 435 the most suitable options, or are there other RealSense models you would recommend for this type of application?
Thank you in advance for your support.
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Hi Lola Bismuth The D405 will meet most of your requirements, particularly in regard to weight and compactness. Although RealSense cameras are Class 1 eye-safe devices, the D405's lack of an infrared laser projector component may provide you with additional reassurance regarding eye safety. D405 is also designed to provide high quality, high accuracy images at close range and is the only model in the RealSense range that officially has sub-millimeter accuracy as a feature.
Although D405 has high accuracy at close range, it works best with surfaces that are textured due to the absence of an IR projector that can compensate for low surface detail by projecting a pattern of invisible dots onto a surface to aid analysis of that surface for depth information. RealSense 400 Series cameras can though also use ambient light to aid depth analysis, so if the location that the camera is used in is well lit then this may compensate for the lack of a projector.
Using a visible pattern projector component to cast a visible pattern onto a surface may help a D405 to depth-analyze it by giving the surface a grain that is readable by the camera, but this may not be practical if compactness is important to your system.
The success at analyzing curved surfaces may depend on how curved and how wide the surface is. For example, with a three-dimensional curvature like the human head a camera may be able to capture the front of the face but the side of the head, including the ears, would be excluded from the image because the camera would not be able to see around the sides of the head when positioned directly in front of the face.
D405 has a fast Global Shutter on its sensors whilst D435 has a slower Rolling shutter on its RGB sensor, so if your tracking system involves use of RGB images and fast movement of the camera or the capturing of fast moving objects, a D435 may experience lag or blurring on the RGB image during fast motion.
In summary, D405 will best meet your needs if you can work around issues caused by the absence of a pattern projector and the difficulties with low-texture / no-texture surfaces resulting from no projector (which increased external surface illumination may help to compensate for, so long as the surface is not reflective).
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Thanks, MartyX Grover for the thorough explanation - very helpful.
I have a few follow-up questions:
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Do you have any measured data for depth accuracy at a ~30 cm working distance (ideally more detailed than just “sub-mm”)?
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Regarding improving surface reconstruction quality with the D405: beyond projected patterns, are there specific types of passive texturization that work well in practice (e.g., printed patterns or markers attached to the object)? Any guidance on pattern type, contrast, or feature size?
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For the D435: in your experience, can it operate effectively at ~30 cm and achieve close to sub-millimeter accuracy, or is it fundamentally not well-suited for this range and therefore not worth testing for this use case?
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1. Actual real-world accuracy (or rather, the amount of depth error) can depend on a range of factors including lighting level and surface texture detail & reflectivity. So the best approach would be to find out what accuracy you can achieve and then identify the strategies that can improve accuracy in your specific scenario (including location and the kind of materials being analyzed).
2. For best results I would recommend a texture grain that resembles the one in the camera tuning guide at the link below.
3. Yes, D435 can operate effectively at 30 cm. Its official minimum depth distance is 28 cm. Whilst it is not designed for very close range like the D405 is (which has an optimal depth range of 7 to 50 cm), at 30 cm it will be able to operate as well as a D405 that is at that distance and will also have the benefit of the eye-safe IR pattern projector for better depth results on low-texture surfaces.
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