Systems, devices, and methods for laser projectors

• US 10,277,874 B2
• Filed: 07/27/2017
• Issued: 04/30/2019
• Est. Priority Date: 07/27/2016
• Status: Active Grant

• Current Assignee: Google LLC (Alphabet Inc.)
• Original Assignee: North Inc.
• Inventors: Xu, Kai
• Primary Examiner(s): Chow, Van N
• Application Number:
  US15/661,415
• Publication Number:
  US 20180035087A1
• Time in Patent Office: 642 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 laser projector comprising:

at least one laser diode;

a power source;

a photodetector responsive to laser light output by the at least one laser diode;

a beam splitter positioned and oriented to direct a first portion of laser light from the at least one laser diode along a first optical path towards the photodetector and a second portion of laser light from the at least one laser diode along a second optical path towards an output of the laser projector; and

a laser safety circuit communicatively coupled to the photodetector and responsive to signals therefrom, the laser safety circuit comprising a switch that mediates an electrical coupling between the power source and the at least one laser diode, wherein in response to a signal from the photodetector indicative that a power of the laser light output by the at least one laser diode exceeds a threshold, the switch interrupts a supply of power to the at least one laser diode from the power source.

2. The laser projector of claim 1 wherein the laser safety circuit further includes a latch that is communicatively coupled to the photodetector and to the switch, and wherein:

a state of the latch is responsive to signals from the photodetector and the switch is responsive to the state of the latch;

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

the switch interrupts the 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 laser projector of claim 2 wherein the latch is operable to store a current state selected from the first state and the second state and maintain the current state during a reboot event.

4. The laser projector of claim 1, further comprising:

a processor communicatively coupled to the at least one laser diode and to the photodetector, the processor to modulate the at least one laser diode, wherein, in response to the signal from the photodetector indicative that the power of the laser light output by the at least one laser diode exceeds the threshold, the processor stops modulating the at least one laser diode and prevents further modulations of the at least one laser diode.

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

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

upon boot-up of the laser projector, the processor accesses the non-transitory processor-readable storage medium to check for the flag, wherein in response to the processor finding the flag stored in the non-transitory processor-readable storage medium the processor prevents modulations of the at least one laser diode.

6. The laser projector 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

the photodetector is responsive to laser light from each of the red laser diode, the green laser diode, and the blue laser diode, wherein the signal from the photodetector is indicative of a total combined power of red laser light from the red laser diode, green laser light from the green laser diode, and blue laser light from the blue laser diode.

7. The laser projector of claim 6 wherein:

the at least one laser diode further includes an infrared laser diode; and

the photodetector is responsive to infrared laser light from the infrared laser diode, wherein the signal from the photodetector is indicative of a total combined power of red laser light from the red laser diode, green laser light from the green laser diode, blue laser light from the blue laser diode, and infrared laser light from the infrared laser diode.

8. The laser projector of claim 7, further comprising:

a beam combiner oriented to receive red laser light from the red laser diode, green laser light from the green laser diode, blue laser light from the blue laser diode, and infrared laser light from the infrared laser diode and to combine the red laser light, the green laser light, the blue laser light, and the infrared laser light into an aggregate laser beam, at least a portion of the beam combiner positioned upstream from the beam splitter with respect to an optical path of the laser light.

9. The laser projector of claim 1, further comprising:

a support structure that in use is worn on a head of the user, wherein the laser projector is carried by the support structure; and

a transparent combiner carried by the support structure and positioned within a field of view of the user, the transparent combiner to direct the second portion of laser light from the output of the laser projector to the field of view of the user.

10. The laser projector of claim 1 wherein the threshold is an independent, non-varying threshold.