2020 年 6 月， In June 2020 Patently Apple posted a report titled "Alphabet has Reportedly Acquired Canadian AR Smartglasses Company called 'North' which gives us a Peek at their Future." And while Google has shut down their "enterprise" smartglasses project, their consumer project is still alive and well. Below is a video from "North" the smartglasses company Google/Alphabet acquired.
For those that are interested, one of Google's acquired patents from the smartglasses company North' has now been published under Google.
Integrated Laser Package with Light Intensity Package
Google's acquired patent describes systems and methods for providing laser projectors having laser-based optical engines as well as light intensity and/or laser output power measuring (e.g. monitoring) capabilities. According to the various embodiments described herein, an optical engine of a laser projector includes at least one laser source (e.g., a laser diode or a plurality of laser diodes) that may be enclosed in a (e.g. partially or completely hermetically sealed) enclosure. The enclosure may include an optical window (sometimes referred to herein as an “exit window”) that may be integrated with one of its side walls or top surface or that forms one of its side walls or top surface.
Laser light beams output by the laser source(s) may pass through the exit window to exit the enclosure during active operation of the laser projector. The optical engine may support a relatively small substrate area for power monitoring, reducing the overall size of the optical engine. The laser projector or the optical engine can therefore be flexibly employed in a variety of display designs, including wearable heads-up displays or other head-mounted displays.
In some embodiments, after passing through the exit window, the light beams are passed through respective collimating lenses to a dichroic filter/beam combiner, at which light beams of different wavelengths are combined. The combined light beams may then be directed to one or more scanning elements that project the light beams across a display surface of an object,such as the holographic lens of a pair of smart glassesor another type of wearable heads-up display.
While various embodiments described are provided in the context of a wearable heads-up display, it should be understood that the laser projector and optical engine of the present patent application can instead be included in other systems, such as projection engines, lidar systems, sensing systems, ranging systems, external cavity laser diodes (e.g., as an integrated intensity stabilization servo), and/or the like.
It is generally desirable to monitor the laser output power of the laser sources of the optical engine of the laser projector, which allows for improved control over the quality of the projected image or video and enables a controller or processor of the device that includes the laser projector to dynamically limit the maximum output power of the optical engine based on real-time or near-real-time measurements of the laser output power.
For example, laser output power monitoring tends to be particularly important for the design of laser projectors used in wearable heads-up displays due to the generally limited availability of power and space (e.g., volume) in such wearable devices. Conventional methods for designing a laser projector with laser output power monitoring capabilities require a relatively large footprint on the laser projector substrate, which may be a printed circuit board (PCB) to be dedicated to the placement of a photodetector such as a photodiode, to the placement of optical components such as a pickoff mirror, and to maintaining a clear optical path to the photodetector.
In some instances, this footprint may be as large as that of the optical engine itself. Accordingly, it would be advantageous to reduce the substrate area taken up by the photodetector(s) and/or optical component(s) (sometimes referred to collectively herein as “laser output power monitoring component(s)”) that implement laser output power monitoring for an optical engine of a laser projector.
The systems, devices, and techniques described in the patent application may provide a reduction in the substrate area required for laser power output monitoring components, e.g. by utilizing an exit window of an enclosure of an optical engine having e.g. a diffraction grating that may be disposed in or on a primary output surface of the exit window and that may redirect (e.g., via diffraction) a portion of the incident light from the laser light beam(s) output by the laser source(s) toward one or more photodetectors, which may be photodiodes, and which may be disposed across from one or more surfaces of the exit window.
According to various embodiments, the exit window includes a diffraction grating that can be disposed or formed on or in the exit window, and that redirects the incident light from the laser sources toward the one or more photodetectors. In some embodiments, one or more photodetectors may be disposed on a top surface of the substrate so as to receive light that is redirected by the diffraction grating and that is output through a one or both side walls of the exit window. A “side wall” or “side surface” of the exit window may be defined as a surface of the exit window that extends between the primary input surface of the exit window and the primary output surface of the exit window that defines a plane that intersects (e.g., that is perpendicular to) the surface of the substrate upon which the optical engine is disposed.
In some embodiments, one or more photodetectors may be disposed below the exit window and completely or partially embedded in the substrate, such that the one or more photodetectors receive light that is redirected by the diffraction grating and that is output through a bottom surface of the exit window. In some embodiments, the exit window is disposed on a first side of the substrate and one or more photodetectors, which may be photodiodes, may be disposed below the exit window on a second side of the substrate that is opposite the first side, such that the one or more photodetectors receive light that is redirected by the diffraction grating and that is output through a bottom surface of the exit window, which passes through one or more apertures that extend through the entire thickness of the substrate to reach the one or more photodetectors. In some embodiments, one or more photodetectors may be disposed above the exit window on the surface of a second substrate that opposes the surface of the first substrate on which the window is disposed, such that the one or more photodetectors receive light that is redirected by the diffraction grating and that passes through a top surface of the window.
Google's patent FIG. 1 below is an illustrative diagram showing a side view of awearable heads-up display (WHUD) #100 #100that employs a laser projector #110, which may be a scanning laser projector. For example, the WHUD 100 may be a pair of smartglasses or a virtual reality (VR) headset. The laser projector comprises an optical engine #111 that includes a red laser diode (labeled “R” in FIG. 1), a green laser diode (labeled “G” in FIG. 1), and a blue laser diode (labeled “B” in FIG. 1), and a scan mirror #112 that is controllably rotatable about two axes of freedom
Generally, it is desirable to monitor laser output power in the laser projector in order to better control the image or video projected onto theHolographic Optical Element (HOE) #130and to limit the maximum output power of the WHUD. Monitoring laser output power in a laser projector such as the laser projector is typically performed using a discrete pickoff component to redirect a portion of the laser light #120 to an on-chip photodetector. However, such laser output power monitoring approaches require a relatively large footprint on the laser projector substrate. In order to reduce the footprint of laser output power monitoring components, an exit window of an enclosure that includes some or all of the components of the optical engine may be configured to redirect a portion of the laser light through the top, bottom, or side walls of the exit window toward one or more photodetectors placed across from and in the optical path of the top, bottom, or side walls of the exit window.
Google's patent FIG. 2 below is an isometric view of a wearable heads-up display with a laser projector that includes an optical engine.
Google's patent FIG. 4 above is a block diagram of a top-down view of a laser projector having an optical engine that includes an exit window having a holographic diffraction grating.
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