Apple invents advancements for their TrueDepth camera to improve Face ID and 3D Mapping for iDevices, future MR Headset and Smartglasses
In January of this year Patently Apple posted a report titled "Apple refines the Foldable Projection System that's part of Face ID's camera System found within the iPhone Notch." Last Thursday, the US Patent & Trademark Office published another patent application from Apple that relates to optoelectronic devices, and particularly to sources of optical radiation. More specifically, Apple has invented an advancement for their TrueDepth camera that is used for Face ID and general 3D mapping for AR applications. This will improve the TrueDepth camera for future iDevices and headsets (AV/AR/MR) and smartglasses.
Apple has invented a way to illuminate a subject target with two different projected dot patterns. To handle the heat generated from these two lasers, Apple patent also covers a new heat sink system.
Apple notes that various sorts of portable computing devices such as smartphones, augmented reality (AR) devices, virtual reality (VR) devices and smart glasses, comprise compact sources of optical radiation. (The terms "optical rays," "optical radiation," and "light," as used in the present description and in the claims, refer generally to any and all of visible, infrared, and ultraviolet radiation.)
For example, one source may emit flood radiation, illuminating a target region with a broad and uniform illumination for the purpose of feature illumination and recognition.
Another source may, for example, project patterned radiation so as to illuminate the target region with a pattern of dots for three-dimensional (3D) mapping of the region. Effective heat dissipation is one of the major challenges in design of high-power optoelectronic emitters, such as vertical-cavity surface-emitting lasers (VCSELs). Such devices generate large amounts of heat in the emitter active regions, resulting in high emitter junction temperatures, which tend to reduce VCSEL efficiency and lead to a reduced optical power output at a given drive current, shift the emission wavelength, degrade the quality of the laser modes, and reduce operating lifetime and reliability.
In VCSEL array devices, inefficient heat dissipation causes temperature non-uniformity among emitters, leading to variations in emitter optical power and wavelength across the array.
In response to this problem, U.S. Pat. No. 9,735,539, whose disclosure is incorporated herein by reference, describes an optoelectronic device, which includes a semiconductor substrate, having front and back sides and having at least one cavity extending from the back side through the semiconductor substrate into proximity with the front side. At least one optoelectronic emitter is formed on the front side of the semiconductor substrate in proximity with the at least one cavity. A heat-conducting material at least partially fills the at least one cavity and is configured to serve as a heat sink for the at least one optoelectronic emitter.
In embodiments of the present invention, radiation sources of different focal qualities are combined into a single optoelectronic apparatus comprising an optical element, such as a lens, and two monolithic emitter arrays, both of which emit optical beams through the optical element. One of the arrays is positioned at the rear focal plane of the optical element, while the other array is displaced from the rear focal plane, for example by axial shift of 100 .mu.m or more.
The beams emitted by the array at the rear focal plane are projected by the element as collimated beams, thus projecting patterned radiation on a target region in a pattern corresponding to the layout of the emitters in the array. The beams emitted by the array that is displaced from the rear focal plane are defocused. In the disclosed embodiments, the monolithic arrays comprise arrays of vertical-cavity surface-emitting lasers (VCSELs), disposed on semiconductor substrates, such as a gallium-arsenide (GaAs) substrate; but alternatively, other types of emitters may be used.
The position of the defocused array is chosen depending on the desired degree of defocus. In some embodiments, the defocus is sufficient so that the projected beams create a broad and largely uniform field of flood illumination.
In an alternative embodiment, the defocus is chosen so that the beams projected from the defocused array also create patterned radiation. The apparatus thus projects two different patterns, with pattern elements (such as spots) whose sizes vary differently as a function of distance from the apparatus.
Positioning the two arrays precisely within the required range of distances from the optical element can be difficult. This difficulty is exacerbated by the need to sink away the substantial amount of heat that is generated by the emitters.
Apple's invention addresses these problems by providing a heat sink, which is shaped to define two platforms at different elevations above the base of the heat sink. The two monolithic arrays of emitters are mounted respectively on the two platforms, thus positioning the two arrays at different elevations.
The invention further describes mounting the two monolithic arrays on the two platforms provides the required differential focal distances (distances from the optical element) for the two arrays.
Apple's patent FIGS. 2a and 2b below are schematic side views of optoelectronic apparatus illuminating a target region with patterned radiation and flood radiation; FIGS. 2c and 2d are schematic side views of optoelectronic apparatus illuminating a target region by patterned radiation with different focal properties.
Apple's patent FIG. 9 above is a flow chart that schematically illustrates a method for depth mapping using patterned radiation of different focal qualities.
For more details, review Apple's patent application number 20210364902 that was published last Thursday by USPTO.
Apple's patent in January and last week illustrate that changes could be on the table for their TrueDepth camera system that is four years old this month. It first debuted with the 2017 iPhone X.
Considering that this is a patent application, the timing of such a device to market is unknown at this time.