D435 False Object Detection
Hello Team,
We are using a D435 on-board a drone for object detection for safety purposes.
We need to be able to detect any objects within 5 meters of the drone, outdoors in a variety of conditions (oftentimes over water where the sun glint is problematic). Typically, we are much further than 5 meters away from objects, as in 20-40 meters.
The issue we are seeing is where the D435 sees false objects near to the camera. So for example, the system is in the air and 20+ meters from everything, but sometimes at least one pixel in the D435 detects a false object at a distance < 5 meters, which trips the safety system. We aren't concerned about the precise distance to objects that are > 5 meters.
This problem has been hard to recreate/diagnose for us but we think it may be related to some of the following possible causes:
- Featureless images
- Bad calibration caused by high temperatures or vibrations
- Poorly tuned settings
Here is some relevant information regarding how we currently have the D435 configured:
- Firmware Version: 5.12.3
- Visual Preset: Default
- Emitter: Disabled
- Auto Exposure: Disabled
- Exposure: 1
- Gain: 16
We also have been re-calibrating the D435’s after purchasing them by pointing the D435 at a checkered floor and using the on-chip calibration in the RealSense viewer.
Do you have any insight regarding what is currently causing this issue and what we should try changing? I get the feeling we are pushing the limits of what the D435 is capable of. Do any of you have experience using the D435 outdoors on a drone and if so, what are some settings we should look into changing? Is loss of calibration from high temperatures/vibrations something we should be concerned about? Is there anything we should try in post-processing?
Thank You
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Hi Bgarby The D435 has been used successfully on drones, yes.
The links below should be a good place to start in seeking solutions to your drone false-depth issues.
https://github.com/IntelRealSense/librealsense/issues/6713
https://dev.intelrealsense.com/docs/depth-map-improvements-for-stereo-based-depth-cameras-on-drones
In Section 4.4 of Intel's white-paper document about applying physical optical filters over the camera lenses, Linear Polarizer filters are recommended as a means to significantly negate glare from reflections.
https://dev.intelrealsense.com/docs/optical-filters-for-intel-realsense-depth-cameras-d400
In regard to vibration, the stereo depth algorithm of the 400 Series cameras is very robust against vibration, but you could add vibration damping pads to the camera mounting point on the drone for additional protection.
Excessive temperature is a possible cause of sensor mis-calibration in theory, though a mis-calibration is unlikely to occur by this way in practice.
A correctly proportioned checkerboard target should be used for calibration. The official calibration target image for the 400 Series cameras can be downloaded here:
https://dev.intelrealsense.com/docs/dynamic-calibration-print-target
A professional OEM calibration target system with large target board can also be purchased from the official RealSense store:
https://store.intelrealsense.com/buy-intel-realsense-d400-cameras-calibration-target.html
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Intel's RealSense official blog article about the use of D435 on Everdrone emergency medical drones is also worth reading.
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