Systems, devices, and methods for laser projectors

• US 10,250,856 B2
• Filed: 12/12/2017
• Issued: 04/02/2019
• Est. Priority Date: 07/27/2016
• Status: Active Grant

• Current Assignee: Google LLC (Alphabet Inc.)
• Original Assignee: North Inc. (Alphabet Inc.)
• Inventors: Xu, Kai
• Primary Examiner(s): Chow, Van N
• Application Number:
  US15/839,058
• Publication Number:
  US 20180115755A1
• Time in Patent Office: 476 Days
• CPC Class Codes: G02B 2027/0112 comprising device for genereting colour display
• CPC Class Codes: G02B 2027/0178 Eyeglass type eyeglass details G02C
• CPC Class Codes: G02B 27/0172 characterised by optical features
• CPC Class Codes: H01S 5/0014 Measuring characteristics or properties thereof measuring techniques per se G01J, G01K, G01N, G01R
• CPC Class Codes: H01S 5/042 Electrical excitation ; Circuits therefor monolithically integrated laser drive components H01S5/0261
• CPC Class Codes: H01S 5/06825 Protecting the laser, e.g. during switch-on/off, detection of malfunctioning or degradation
• CPC Class Codes: H01S 5/4093 Red, green and blue [RGB] generated directly by laser action or by a combination of laser action with nonlinear frequency conversion
• CPC Class Codes: H04N 9/3155 for controlling the light source light source control per se H05B35/00 – H05B47/00; control of an illumination source for displays in general G09G3/3406
• CPC Class Codes: H04N 9/3161 using laser light sources using laser beams scanning the display screen H04N9/3129
• CPC Class Codes: H04N 9/3194 including sensor feedback

Abstract

Laser safety systems, devices, and methods for use in laser projectors are described. A laser projector includes any number of laser diodes that each emit laser light, a shared laser diode power source, a photodetector to detect a power/intensity of a portion of the laser light, a beam splitter to direct a first portion of the light towards the photodetector and a second portion of the light towards an output on the projector, and a laser safety circuit responsive to signals from the photodetector. The laser safety circuit selectively electrically couples/uncouples the laser diodes from the power source depending on the power/intensity of the laser light detected by the photodetector. Particular applications of the laser safety systems, devices, and methods in a wearable heads-up display are described.

Claims

1. A method of operating a laser projector, the method comprising:

providing power to at least one laser diode by a power source electrically coupled to the at least one laser diode;

generating a laser light by the at least one laser diode;

splitting the laser light into a first portion and a second portion by a beam splitter;

directing the first portion of the laser light from the at least one laser diode along a first optical path towards a photodetector by the beam splitter;

directing the second portion of the laser light from the at least one laser diode along a second optical path towards an output of the laser projector by the beam splitter;

detecting the first portion of the laser light by the photodetector;

outputting a signal by the photodetector in response to detecting the first portion of the laser light by the photodetector, the signal indicative of a power of the laser light generated by the at least one laser diode;

receiving the signal from the photodetector by a laser safety circuit communicatively coupled to the photodetector, wherein the laser safety circuit includes a switch that mediates the electrical coupling between the power source and the at least one laser diode; and

in response to the signal from the photodetector indicating that the power of the laser light generated by the at least one laser diode exceeds a threshold, interrupting, by the switch, a supply of power to the at least one laser diode from the power source.

2. The method of claim 1 wherein the laser safety circuit includes a latch that is communicatively coupled to the photodetector and to the switch, a state of the latch responsive to the signal from the photodetector and the switch responsive to the state of the latch, and further comprising:

in response to the signal from the photodetector indicating that the power of the laser light output by the at least one laser diode exceeds the threshold, changing, by the latch, the state of the latch from a first state to a second state; and

wherein interrupting, by the switch, a supply of power to the at least one laser diode from the power source includes interrupting, by the switch, a supply of power to the at least one laser diode from the power source in response to the state of the latch changing from the first state to the second state.

3. The method of claim 2, further comprising:

storing a current state of the latch; and

maintaining the current state of the latch during a reboot event.

4. The method of claim 1 wherein the laser projector includes a processor, the processor is communicatively coupled to the photodetector, and wherein generating a laser light by the at least one laser diode includes modulating the at least one laser diode by the processor, and further comprising:

in response to the signal from the photodetector indicating that the power of the laser light generated by the at least one laser diode exceeds the threshold;

stopping modulation of the at least one laser diode by the processor; and

preventing further modulations of the at least one laser diode by the processor.

5. The method of claim 4 wherein the laser projector includes a non-transitory processor-readable storage medium communicatively coupled to the processor, and further comprising:

in response to the signal from the photodetector indicating that the power of the laser light generated by the at least one laser diode exceeds the threshold, storing, by the processor, a flag in the non-transitory processor-readable storage medium; and

upon boot-up of the laser projector, checking for the flag stored in the non-transitory processor-readable storage medium by the processor and, in response to finding the flag stored in the non-transitory processor-readable storage medium by the processor, preventing modulations of the at least one laser diode by the processor.

6. The method of claim 1 wherein the at least one laser diode includes a red laser diode, a green laser diode, and a blue laser diode, and:

generating a laser light by the at least one laser diode includes generating a red laser light by the red laser diode, a green laser light by the green laser diode, and a blue laser light by the blue laser diode;

detecting the first portion of the laser light by the photodetector includes detecting, by the photodetector, respective first portions of each of the red laser light, the green laser light, and the blue laser light; and

outputting a signal by the photodetector in response to detecting the first portion of the laser light by the photodetector includes outputting by the photodetector, a signal indicative of a total combined power of the red laser light generated by red laser diode, the green laser light generated by the green laser diode, and the blue laser light generated by the blue laser diode.

7. The method of claim 6 wherein the at least one laser diode further includes an infrared laser diode, and:

generating a laser light by the at least one laser diode further includes generating an infrared laser light by the infrared laser diode;

detecting, by the photodetector, respective first portions of each of the red laser light, the green laser light, and the blue laser light further includes detecting a first portion of the infrared laser light by the photodetector; and

outputting by the photodetector, a signal indicative of a total combined power of the red laser light generated by red laser diode, the green laser light generated by the green laser diode, and the blue laser light generated by the blue laser diode includes outputting by the photodetector, a signal indicative of a total combined power of the red laser light generated by red laser diode, the green laser light generated by the green laser diode, the blue laser light generated by the blue laser diode, and the infrared laser light generated by the infrared laser diode.

8. The method of claim 7 wherein the laser projector further includes a beam combiner, and further comprising:

combining the red laser light, the green laser light, the blue laser light, and the infrared laser light into an aggregate laser beam by the beam combiner before splitting the laser light into a first portion and a second portion by the beam splitter.

9. The method of claim 1 wherein, in response to the signal from the photodetector indicating that the laser light generated by the at least one laser diode exceeds the threshold, interrupting, by the switch, a supply of power to the at least one laser diode from the power source includes:

in response to the signal from the photodetector indicating that the laser light generated by the at least one laser diode exceeds an independent, non-varying threshold, interrupting, by the switch, a supply of power to the at least one laser diode from the power source.