Technical Requirement for the use of RealSense cameras – in particular depth accuracy for short range use
Dear RealSense Community,
We are a start-up company in the UK trying to use your depth cameras in a short range (less than 1 m) medical application which requires high precision 3D information. Our camera system should meet the following technical requirements:
- Should be able to work in indoor condition under relatively intense visible light illumination.
- Range of work: 0.2 to 1 m
- Depth (z) accuracy: 0.2 mm
- Outputting accurate 3D (x, y and z point cloud) in real time at least 10 fps
Looking at the datasheets provided for your cameras, we were uncertain about z accuracy if some your cameras (particularly SR 305 as the datasheet did not provide a specific value).
Can you please tell us which of RealSense camera systems suites the technical specifications that we are after?
Can you also specify if Intel RealSence hold ISO 13485 certificate for application of the cameras for medical purposes?
Many thanks in advance for your help and we very much look forward to hearing back from you.
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Hi Hamidreza Alidousti 82 The D435 or D435i should meet your needs, as it has a minimum depth sensing distance of 0.1 meters, whilst the D415 model's minimum distance is 0.3 meters. The difference between the D435 and D435i is that the D435i contains an Inertial Measurement Unit (IMU) for measuring the camera's velocity and tilt angle.
All RealSense 400 Series models contain a Vision Processor D4 chip that enables automatic adjustment to changing lighting conditions in real-time, and they can be used both indoors and outdoors. The Vision Processor D4 hardware performs processing of data inside the camera at the point of capture, enabling the 400 Series cameras to be used on computers / computing devices with a low-end technical specification (as the D4 does work that the computer CPU and GPU would otherwise have to perform).
The 400 Series cameras work excellently in strong light, as explained in the link below.
All 400 Series cameras are able to meet your requirement of outputting a real-time XYZ point cloud. The D435 and D435i support FPS speeds of 6, 15, 25, 30, 60, 90, 100 and 300.
The accuracy of the 400 Series cameras is less than 1% of the distance from the camera. This translates to around 2.5mm to 5 mm at 1 meter range. The amount of error over distance (RMS Error) starts at around zero at the camera lenses and increases linearly over distance. The chart below illustrates how RMS error increases over distance, with the D435 represented by the upper orange line.
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In regard to ISO 13485 certification: as far as I know, the RealSense range does not have that medical certification, but is a safe Class 1 laser device.
The international regulatory information and certificates for the full range of RealSense cameras can be found at the link below.
https://www.intelrealsense.com/regulatory-information/
An extract of the EU Declaration of Conformity certification covering the D435 / D435i is shown below (though it is unclear how this may affect your UK-based start-up after Brexit on January 1 2021):
LV Directive 2014/35/EU
EN 60950-1:2006 + A11:2009+ A12:2011 + A1:2010 + A2:2013
EMC Directive 2014/30/EU
EN 55032: 2012 +AC: 2013
EN 55024: 2010
EN 61000-3-2: 2014
EN 61000-3-3: 2013
RoHS Directive 2011/65/EU
EN 50581: 2012
Additional declarations
FCC, 47 CFR Part 15, Class B digital device (USA)
AU / NZ -
Hi MartyG,
Thank you very much for your prompt and thorough reply. Looking closely at the graph you kindly provided, it seems that in shorter distance range (between 0.3 and 1 m) which is within our operating range, the D415 camera provides a scanning accuracy which may be 30-40% more accurate than the D435 camera (green vs orange curves). So, if we compromise on our technical requirement of minimum distance of 0.2 m and change it to 0.3m, would you suggest that D415 camera would give us a more accurate depth (z) data acquisition than D435 camera?
Again, many thanks for your kind help and I look forward to hearing from you.
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The D415 does have around 2x less depth error over distance than the D435 (though at close range the difference between models is very small).
D415 also has optimal depth accuracy at 1280x720, compared to the D435's optimal depth accuracy resolution of 848x480. Higher resolution = greater accuracy. The section of Intel's camera tuning guide linked to below describes these principles.
The D415 is also well suited to scanning static objects, whilst the D435's advantage is in tracking fast motion and its wider field of view.
It is worth mentioning that you may still be able to use 0.2 meters distance with the D415 if you use a function called Disparity Shift. Increasing its value reduces the minimum distance (MinZ) of the camera and enables it to get closer to objects, though it reduces the maximum observable depth distance (MaxZ) at the same time. This is not as significant an issue when performing close-range sensing though.
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Hi MartyG,
Thanks again for your thorough reply. To finalise this enquiry, can you please kindly clarify the following two points also:
The depth accuracy is important for our application. Based on the link you provided, our understating is that using the disparity shift function, enables us to scan objects as close as 0.2 mm while losing the ability to see objects beyond approximately 1m. This is fine for us as we are not interested in distant objects. However, does using the disparity shift function - to see close objects - continue to improve the depth accuracy as theoretically projected by the green line below (D415)?
In our application, we do not expect to scan fast moving objects but the object may still move ( around 10 cm/s). Is D415 still suitable for such motions?
Again, many thanks for your help and we look forward to hearing from you.
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If the camera moves significantly below the recommended minimum distance, the image is likely to become blurred and have problems with non-flat objects, so there is a finite restriction on image quality at extreme close range. The Chief Technical Officer of the RealSense Group at Intel (agrunnet) describes this in the discussion about close-range sensing in the link below.
https://github.com/IntelRealSense/librealsense/issues/7631
Whilst the depth-sensing shutter on the D415 is slower than the one on the D435, it should be able to handle capture of movement speeds at human walking pace and below. So the amount of movement that you describe (10 cm/s) should be within that range.
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Thanks for the link. However, I could not find the answer specific to my question regarding the effect of disparity shift function on the depth accuracy of D415 camera. Let rephrase my question:
1) For camera D415, what is the effect of disparity shift function on depth accuracy just before the image goes blur (say in the range between 0.2 and 0.3 m)?
2) At what distance (or disparity shift value) the image goes blur for camera 415?
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These two questions are covered by further advice from agrunnet in the link below. Please read the comment I have linked to and the additional comment by agrunnet beneath it, as these two comments should address questions 1 and 2 above.
https://github.com/IntelRealSense/librealsense/issues/1171#issuecomment-365119754
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