3D TOF camera with masked illumination
View Patent ↗A method and system for reducing multi-path effects (stray light and multiple reflections) in 3D time of flight cameras by partly masking the camera's illumination elements.
1. A time of flight three dimensional imaging system, comprising:
an illumination module that generates modulated light to illuminate a scene, the modulated light being intensity modulated, the illumination module comprising illumination elements;
a mask for the illumination module for defining a field of illumination of the illumination module, wherein the mask has a plurality of illumination apertures through which light of the illumination elements is transmitted, and wherein each illumination aperture is provided for a respective one of the illumination elements, the illumination apertures including at least two apertures differing in shape from one another;
a sensor that detects the modulated light from the scene with demodulation pixels of an array, wherein a field of view of the sensor is at least partially within the field of illumination, and wherein the mask is arranged to suppress an amount of light power generated by the illumination module outside the field of view of the sensor; and
a controller that generates a three dimensional image from the detected modulated light by determining a phase delay between the modulated light generated by the illumination module and the modulated light detected by the demodulation pixels of the array of the sensor to determine a time of flight of the modulated light from the illumination module to the scene and back to the sensor.
2. A system as claimed in claim 1 , wherein the illumination elements of the illumination module comprise a light emitting diode.
3. A system as claimed in claim 1 , wherein the illumination elements of the illumination module comprise a laser diode.
4. A system as claimed in claim 1 , wherein the illumination apertures are shaped based on a particular field of illumination.
5. A system as claimed in claim 1 , wherein the mask comprises illumination apertures that provide varying levels of attenuation laterally across the width of the illumination aperture.
6. A system as claimed in claim 1 , wherein the field of illumination is selected to be substantially coextensive with the field of view.
7. A system as claimed in claim 1 , wherein the field of illumination is selected to be smaller than the field of view.
8. A system as claimed in claim 1 , wherein the field of illumination varies laterally across its width.
9. A system as claimed in claim 1 , wherein the mask provides a non-uniform field of illumination.