Wavelength stabilization of laser diodes by temperature control
Systems, devices, and methods for providing optical engines and laser projectors that are well-suited for use in wearable heads-up displays (WHUDs) are described. The optical engines of the present disclosure may integrate a plurality of laser diodes (e.g., 3 laser diodes, 4 laser diodes) within a single, hermetically or partially hermetically sealed, encapsulated package. Wavelength stabilization for the laser diodes is achieved by controlling the temperature of the lasers to always be in a particular range of operating specifications which provides wavelength stabilization that meets particular performance criteria. The lasers themselves may be used for temperature control by selectively switching them on to maintain their temperature within a specified range. Alternatively, compact resistive heaters may be positioned proximate the laser diodes to control the temperature of the laser diodes during operation. WHUDs that employ such optical engines and laser projectors are also described. Additionally, optical systems for collimating and shifting light beams are described.
1. A wearable heads-up display (WHUD), comprising:
an optical engine, comprising:
a laser diode; and
at least one temperature sensor configured to generate temperature sensor data indicative of a temperature of the laser diode;
at least one scan mirror positioned to receive light output by the laser diode; and
at least one processor configured to:
determine, based on the temperature sensor data, whether the temperature of the laser diode is below an operating temperature range; and
in response to determining that the temperature of the laser diode is below the operating temperature range:
cause the scan mirror to move to or remain in an out-of-view position where light emitted by the laser diode is redirected by the scan mirror to a position outside of an eyebox of the WHUD; and
cause the laser diode to emit light while the scan mirror is positioned in the out-of-view position.
2. The WHUD of claim 1 , wherein, in response to determining that the temperature of the laser diode is below the operating temperature range, the at least one processor is configured to cause the laser diode to emit light until the at least one processor determines that the temperature of the laser diode has reached a threshold temperature value within the operating temperature range.
3. The WHUD of claim 2 , wherein the threshold temperature value is equal to an upper end of the operating temperature range.
4. The WHUD of claim 2 , wherein the threshold temperature value is below an upper end of the operating temperature range.
5. The WHUD of claim 2 , wherein, in response to determining that the temperature of the laser diode is below the operating temperature range, the at least one processor is configured to alternatingly cause the laser diode to emit light while the scan mirror is positioned in the out-of-view position and while the scan mirror is positioned in an in-view position where light emitted by the laser diode is configured to be redirected by the scan mirror to a position within the eyebox.
6. The WHUD of claim 1 , wherein the optical engine comprises a plurality of laser diodes, and wherein the at least one processor is configured to:
in response to determining that the temperature of at least one of the plurality of laser diodes is below the operating temperature range:
cause the scan mirror to move to or remain in the out-of-view position; and
cause the at least one of the plurality of laser diodes to emit light while the scan mirror is positioned in the out-of-view position.
7. The WHUD of claim 6 , wherein the at least one temperature sensor comprises a plurality of temperature sensors, and wherein each of the plurality of temperature sensors is associated with a respective one of the plurality of laser diodes.
8. The WHUD of claim 1 , wherein the operating temperature range is between 50° C. and 70° C.
9. A method comprising:
receiving, by at least one processor of a wearable heads-up display (WHUD), temperature sensor data from at least one temperature sensor;
determining, by the at least one processor based on the temperature sensor data, whether a temperature of a laser diode is below an operating temperature range; and
in response to determining that the temperature of the laser diode is below the operating temperature range,
causing, by the at least one processor, a scan mirror to move to an out-of-view position where light emitted by the laser diode is redirected by the scan mirror to a position outside of an eyebox of the WHUD; and
causing, by the at least one processor, the laser diode to emit light while the scan mirror is positioned in the out-of-view position.
10. The method of claim 9 , further comprising, in response to determining that the temperature of the laser diode has reached a threshold temperature value, causing the scan mirror to move to an in-view position where the light emitted by the laser diode is redirected to a position within the eyebox of the WHUD.
11. The method of claim 9 , wherein causing the laser diode to emit light comprises instructing a laser diode driver circuit corresponding to the laser diode to drive current to the laser diode.
12. The method of claim 11 , wherein the laser diode driver circuit is a constant current driver, a constant voltage driver, a pulsing driver, a low power driver, or a high power driver.