In general we recommend using the DUO M/MLX sensors within 0.23-2.5m using the provided Dense3D and Calibration Applications. With this you should expect to receive around 0.1-0.3mm accuracy with epipolar lines that are aligned to within 0.05 pixels RMS error based on a stereo resolution of 320×240.
The resulting depth map accuracy or the sensor depends on several factors:
- The algorithm used for extraction
- The framerate, resolution and FOV
- Illumination and texture
- Distance from sensor
- Calibration quality
Starting with the algorithm, we offer our Dense3D Middleware which uses a standard block matching method to perform stereo correlation. This is the most standard method used in the industry and acts as a base to test device functionality. For advanced users and developers please reference research into different stereo algorithms methods which can be used with DUO.
Resolution, Framerate and FOV
The increase of resolution will result in better accuracy at cost of performance. Framerate will not influence the resulting depth map accuracy, however, it will affect the illumination properties of a scene; the higher the framerate the more light required. By default on the DUO M/MLX devices we use a very high FOV (>150 degrees) if you are looking to achieve more accuracy at a distance consider using a more narrow field-of-view lenses as it improves the accuracy at long ranges.
Illumination and textures
For the stereo method to work properly it requires the objects in the scene are somewhat illuminated and have enough texture to differentiate themselves from other shapes in the scene. The DUO MLX ships with a programmable LED array which helps provide IR illumination even in dark scenes.
Distance from sensor
As we utilize the stereo effect our accuracy is directly tied to the distance from the imagers to the object. Thus we provide an accuracy calculator which provides both theoretical and applied accuracy measurements shown as a curve. The DUO M/MLX were specifically designed for short range sensing with the optimal accuracy with objects that fall within 0.25-1m.
The proper calibration is critical in a stereo system. Please follow our Calibration Guide in full to get best results while calibrating your devices.