Range imaging devices and methods
View Patent ↗An array of laser diode emitters is used as an illumination source for a range imaging system. The laser diode emitters are disposed on a common substrate. When one of the emitters fails, the remaining emitters emit enough light to meet the output optical power specification. The emitters can be disposed with a tight spacing. The tight spacing facilitates packaging of the entire array into a compact single package on a common heat sink.
1. An apparatus for range imaging, comprising:
an illuminator for providing pulsed or modulated illumination of an object, and
an optical camera for time-gated or phase-sensitive imaging of the object illuminated with the illuminator,
wherein the illuminator comprises a laser diode array including a plurality of laser diode emitters on a common semiconductor substrate, and wherein the laser diode emitters have a non-uniform emitter spacing along the laser diode array, the emitter spacing decreasing from a middle of the laser diode array to edges thereof, to reduce thermal gradients and associated emitter-to-emitter wavelength spread during operation of the laser diode array.
2. The apparatus of claim 1 , further comprising a controller coupled to the illuminator and to the optical camera, for providing an object depth map from phase or time delays resulting from propagation of light emitted by the illuminator to the object and back to the optical camera.
3. The apparatus of claim 1 , wherein the laser diode emitters are single spatial mode emitters.
4. The apparatus of claim 3 , wherein the laser diode emitters have a width of no more than 10 micron.
5. The apparatus of claim 1 , wherein the emitter spacing at the middle of the laser diode array is smaller than 40 micron, and the emitter spacing at the edges of the laser diode array is larger than 10 micron.
6. The apparatus of claim 1 , wherein a width of the laser diode array is less than one millimeter.
7. The apparatus of claim 1 , wherein the laser diode emitters are electrically connected in parallel.
8. A method for range imaging of an object, comprising:
providing a laser diode array including a plurality of laser diode emitters on a common semiconductor substrate, wherein the laser diode emitters have a non-uniform emitter spacing along the laser diode array, the emitter spacing decreasing from a middle of the laser diode array to edges thereof, to reduce thermal gradients and associated emitter-to-emitter wavelength spread during operation of the laser diode array;
operating the laser diode array to provide pulsed or modulated illumination of the object; and
operating, in synchronism with the laser diode array, an optical camera for time-gated or phase-sensitive imaging of the object, to provide an object depth map from phase or time delays resulting from propagation of light emitted by the laser diode array to the object and back to the optical camera.
9. The method of claim 8 , wherein the laser diode emitters are single spatial mode emitters.
10. The method of claim 8 , further comprising heat sinking the semiconductor substrate.
11. The method of claim 8 , further comprising monitoring output optical power of the laser diode array, and increasing an electrical current supplied to the laser diode array upon determining a drop of output optical power due to a failure of at least one of the plurality of the laser diode emitters of the laser diode array.