Microsoft AR/VR Patent Proposes Multi-Directional Scanning with a Single Reflector in a Non-Dual-Gimbal Structure

CheckCitation/SourcePlease click:XR Navigation Network

(XR Navigation Network January 30, 2024) Scanning mirrors may be used in different types of optical devices, such as head-up display devices. Among other things, a time-of-flight depth sensing system of a head-up display device may utilize one or more microelectromechanical system (MEMS) mirrors to direct light into an environment, and each pixel of said depth image may represent a distance to a corresponding point in said environment.

The scanning mirror system may include two mirrors and rotate each along a transverse axis to scan light. The use of separate mirrors at each axis of rotation helps to provide stability and control because off-axis motion can be prevented. However, systems that include two or more mirrors are larger than systems based on a single mirror.

For other solutions, it is possible that a reflector can be mounted in a dual head structure. In this case, the reflector is suspended within the inner gimbal, while the inner gimbal is nested within the outer gimbal. In this way, the reflector can be controlled to scan light in multiple directions. However, controlling the direction of the reflector is a challenge. In addition, wires or other electrical conduits used to detect the direction of the reflector and provide feedback to the controller may be susceptible to strain and breakage due to the movement of the inner and outer heads.

In a patent application titled "Scanning mirror device," Microsoft proposes a solution in which a single mirror can scan in multiple directions without using a dual-head structure.

Briefly, two or more pairs of actuators are attached to a bracket supporting the mirrors. Each pair of actuators is operably configured to tilt the mirror with respect to one of two or more different rotation axes. This allows the mirrors to perform controlled scanning in different directions, such as directing the incident light into a grating pattern.

Advantageously, the actuator may be used to tilt the reflector in the direction of the target. In a depth sensing system, the image sensor uses positioning optics to form a depth image of the illuminated environment, so a precise light direction through the reflector is not required. In addition, the actuator arrangement described by the invention may allow the scanning mirror device to take up less space than other scanning mirror suits.

FIG. 1 illustrates an exemplary electronic device that may use a scanning mirror device in a depth sensing system. The device 100D is a head unit that includes a depth sensing system 102D.

FIG. 2 illustrates a schematic of an example time-of-flight (ToF) depth imaging system 200 that may utilize a scanning mirror system.The ToF depth imaging system includes a ToF camera 202.

The ToF camera 202 includes a sensor array 204, the sensor array 204 includes a plurality of ToF pixels 206, each pixel 206 configured to acquire a sample of light, and the controller 208 and the objective system 210 configured to focus an image of the target 220 onto the sensor array 204.The controller 208 is configured to collect and process the ToF pixel 206 from the sensor array 204 data to construct a depth image.

FIG. 3 illustrates a scanning mirror device 302. the scanning mirror device 302 includes a reflector 304 configured to reflect incident electromagnetic radiation, such as visible light, infrared light, or microwave radiation, in a controlled direction.

Said reflector 304 is located within an aperture 308 in the center region of the frame 306 of said scanning reflector device 302. The location of said reflector 304 within the center region of the aperture 308 allows other components of said scanning reflector device 302 to be arranged around said reflector 304. Such a configuration can take up less space.

In other embodiments, the reflector may be located in any other suitable region of the scanning mirror device. FIG. 4 illustrates another example of a scanning mirror device 402.

Like the scanning mirror device 302 in FIG. 3, the scanning mirror device 402 also includes a reflector 404. but in FIG. 4, the reflector 404 is located at a corner of an aperture 408 within the frame 406 of the scanning reflector device 402.

As shown in Figure 4, this configuration can provide different design possibilities. The mirrors located outside the center region can be configured to have relatively large dimensions and/or can be configured to have different characteristics.

Referring again to FIG. 3, said mirror 304 is provided in a mirror holder 310. in the example described, the holder 310 takes the form of a rod, but other forms may be used in other examples. The holder 310 couples the reflector mirror 304 to a plurality of actuators, said actuators being operatively configured to move said mirror 304.

In the described embodiment, the reflector holder 310 is oriented diagonally with respect to the sides of the frame 306 of the scanning reflector device 302. Said reflector holder 310 extends from one corner of said aperture 308 toward a center region of said aperture 308.

The scanning mirror device 302 also includes a counterweight 318, which is provided in the mirror support 310 opposite the mirror 304. the counterweight 318 can help prevent the weight of the mirror 304 from deflecting the mirror support 310 from the XY plane. The counterweight 318 may also help prevent rotation of the mirror from coupling to linear acceleration, thereby stabilizing the mirror.

The counterweight 318 of the scanning mirror device 302 is provided at the end of the bracket 310 closest to the frame 306. In other embodiments, the counterweight 318 may be located at any other suitable location. For example, the scanning mirror device 402 of FIG. 4 includes a counterweight 418 disposed in the center region of the bracket 406, wherein the center of the counterweight 418 is disposed within the aperture 408.

The scanning mirror device 302 also includes a first actuator pair including a first actuator 322A and a second actuator 322B. The first actuator 322A is disposed on a first side 324 of the reflector holder 310, and the second actuator 322B is disposed on a second side 326 of the reflector holder 310 opposite the first side 324 of the reflector holder 310.

The first actuator 322A and the second actuator 322B are coupled to the reflector holder 310 along the first axis of rotation 328. the first actuator 322A is anchored to the frame 306 at the distal end 334 of the first actuator 322A opposite the reflector holder 310, and the second actuator 322B is anchored to the frame 306 at the distal end 336 of the second actuator 322B opposite the reflector holder 310. frame 306.

In one embodiment, each of the first actuator 322A and the second actuator 322B includes a piezoelectric material operable by applying a suitable voltage. The application of the voltage can be controlled to rotate or tilt the mirror holder 310 along the first axis of rotation 328.

The scanning mirror device 302 also includes a second pair of actuators including a third actuator 330A and a fourth actuator 330B. The third actuator 330A is disposed on a first side 324 of the reflector bracket 310. the fourth actuator 330B is disposed on a second side 326 of the reflector bracket 310. the third actuator 330A and the fourth actuator 330B are connected along a second axis of rotation 332 to the reflector holder 310.

In one embodiment, the third actuator 330A is anchored to the frame 306 at a distal end 338 of the third actuator 330A opposite the reflector holder 310, and the fourth actuator 330B is anchored to the frame 306 at a distal end 340 of the fourth actuator 330B opposite the reflector holder 310.

In this manner, the third actuator 330A and the fourth actuator 330B are configured to tilt the reflector 304 about the Y-axis. In one example, each of the third actuator 330A and the fourth actuator 330B includes a piezoelectric material operable by applying a suitable voltage. The application of the voltage can be controlled to tilt the reflector holder 310 along the second axis of rotation 332.

The voltage applied to operate the third actuator 330A and the fourth actuator 330B may be the same as or different from the voltage applied to operate the first actuator 322A and the second actuator 322B.

In one embodiment, the third actuator 330A and the fourth actuator 330B are operated to move at half of the same maximum displacement as the first actuator 322A and the second actuator 322B. In examples where less displacement is required along one of the two axes (, this can reduce the complexity of the scanning mirror device.

In one embodiment, the first axis of rotation 328 and the second axis of rotation 332 are offset from the center region of the aperture 308. This allows said actuators 322A, 322B, 330A, 330B to be arranged around said mirror 304 and to connect said mirror holder 310 near the corner 314.Thus, the scanning reflector device 302 can take up less space than the other arrangements of the actuators 322A, 322B, 330A, 330B and the mirror 304.

In one embodiment, the first axis of 328 is orthogonal to the second axis of 332. For example, the first axis of rotation 328 shown in the embodiment of FIG. 3 is parallel to the x-axis. The second axis of rotation 332 is parallel to the y-axis.

In this way, the driver can control the mirrors to scan in the x- and y-axis directions with less off-axis motion than with non-orthogonal axes.

The scanning mirror device 400 of FIG. 4 similarly includes a first actuator 420A, 420B pair connected to the mirror holder 410 along a first axis of rotation, and a second actuator 422A, 422B pair connected to the mirror holder 410 along a second axis of rotation.

Similar to the actuators 322A, 322B, 330A, 330B of FIG. 3, the actuators 420A, 420B, 422A, 422B of FIG. 4 have a diagonal mirror symmetry with respect to the reflector holder 410. Such a structure can take up less space than other structures, such as those having an asymmetric orientation of the actuator.

Each of the actuators 322A, 322B, 330A, 330B of FIG. 3, and each of the actuators 420A, 420B, 422A, 422B of FIG. 4 may include a piezoelectric actuator. Movement of the piezoelectric actuator is proportional to the magnitude of an electric field applied to the layer of piezoelectric material of the actuator, with the magnitude of the electric field inducing mechanical changes in the layer of piezoelectric material.

Referring to FIG. 3, therefore, applying a higher voltage to the piezoelectric actuator results in a greater displacement of the mirror 304 compared to applying a lower voltage. In this way, the actuator can tilt the mirror to the target direction by controlling the voltage applied to the actuator.

Continuing with FIG. 3, each actuator is connected to the reflector bracket via a connector. For example, a first actuator 322A is coupled to the reflector holder 310 via connector 342A. a second actuator 322B is coupled to the reflector holder 310 via connector 342B. a third actuator 330A is coupled to the reflector holder 310 via connector 344A, and a fourth actuator 330B is coupled to the reflector holder 310 via connector 344B. connectors 342A , 342B, 344A, and 344B are schematically shown in FIG. 3.

The torsional portion and the bending portion of each connector are configured to have relative stiffness with respect to linear bending and rotational torsion. For example, the stiffness of the bending portion relative to the linear bending and the rotational torsion bending may be expressed in terms of a bending modulus and a torsional modulus of the connector.

When the drive reflector is tilted along the x-axis, connectors 344A and 344B function as actuator couplers for the linear bending mode, and connectors 342A and 342B function as mirror supports for the torsional yielding mode. When the y-axis is tilted, the function of the connectors is reversed. When driven to a +x +y angle, the connector's flexion and torsion modes are mixed and activated simultaneously. The frequency response range can be increased by using stiffer connector flexures.

Referring to connector 342A, upward actuator movement of actuator 322A is indicated by arrow 354A. The tab 346 attached to the connector 342A is relatively rigid in the direction of motion of the actuator 322A and therefore moves in a similar direction and with a similar magnitude as indicated by arrow 354B. The torsion portion 356A is oriented in a different direction than the actuator 322 and produces direct bending due to the nature of the connection symmetry experienced during the actuator movement, but at the same time produces a torsional pattern.

As a result, the 356A torsion portion undergoes some torsional deformation, as shown by arrow 360, while transmitting some of the linear motion of the actuator upward. This causes the bracket to tilt in the negative y-axis direction (or rotate along the x-axis). This tilt causes torsional yielding of connectors 344A and 344B, while the reflector bracket is tilted.

The scanning mirror devices 300, 400 each include two pairs of actuators. In other examples, said scanning mirror device may include any other suitable number of actuators and arrangement of actuators.

FIG. 5 illustrates an example of a scanning mirror device 502 comprising a first actuator 504A coupled to the mirror holder 506 at a first angle relative to the mirror holder, a second actuator 504B coupled to the mirror holder 506 at a second angle relative to the mirror holder, and a third actuator 504C coupled to the mirror holder 506 at a third angle relative to the mirror holder.

A first actuator 504A is connected to the mirror bracket 506 via a first connector 510A. a second actuator 504B is connected to the mirror bracket 506 via a second connector 510B. a third actuator 504C is connected to the mirror bracket 506 via a third connector 510C.

Each of said connectors 510A-510C may be similar to said connectors 342A, 342B, 344A, 344B. for example, the first connector 510A comprises a first flexural portion 512A, the second connector 510B comprises a second flexural portion 512B, and the third connector 510C comprises a third flexural portion 512C. this allows each connector to have sufficient strength and stiffness to transmit movement of the actuator to tilt the mirror, and sufficient flexibility to prevent the actuator from exerting a force on the connector that exceeds the yield strength or breaking strength of the connector.

The first actuator 504A, the second actuator 504B, and the third actuator 504C can be controlled to tilt the reflector 508 in various directions. In one example embodiment, the first actuator 504A, the second actuator 504B, and the third actuator 504C are approximately 120 degrees apart. In other embodiments, the actuators 504A, 504B, and 504C may have any other suitable relative orientation. The three-actuator structure of FIG. 5 may allow for a more compact structure than a structure having a greater number of actuators.

FIG. 6 shows an example of a ToF projector device 602, where the device 602 may include a scanning mirror device according to the description above.The ToF projection device 602 is an example of the projection device 230 of FIG. 2. The ToF projector device 602 includes a light source 604, such as a vertical cavity surface emitting laser (VCSEL).

The vertical cavity surface emitting laser includes a plurality of laser cavities, each of which is operably configured to emit light 606. the light source 606 illuminates a portion 608 of the field of view 610 of the partitioned ToF camera 612. the ToF camera 612 images the portion 608 illuminated by the light source 606 to determine a depth value of the portion 608 of the field of view 610.

The ToF projector device 602 also includes a scanning mirror device 614, where the scanning mirror device 614 is controlled by a controller 616 and is used to project light 606 from a light source 604 into the environment. The scanning mirror device 614 optionally receives the light 606 through a focusing lens 618, a diffusion lens 620, and/or relay lenses 622, 624. the controller 616 may include a computing system.

Said scanning mirror device 614 is configured to direct said light 606 to portion 608 of the field of view 610 of said camera 612. scanning mirror device 614 is further configured to move light source 606 in a predetermined pattern to scan field of view 610.

In one embodiment, the scanning mirror device 614 is configured to raster scan the field of view 610 at a frame rate of up to 100- 1000hz. In other examples, the scanning mirror device 614 is configured to scan the view 610 at a frame rate greater than 1000hz or less than 100hz. by imaging each of the illuminated portions 608 of said field of view 610, said camera 612 may construct a 3D depth image of said field of view 610.

Additionally, imaging the field of view 610 using the ToF method allows for the construction of a depth image using a relatively low-intensity light source 604 to illuminate a portion of the field of view, rather than using a high-intensity light source projected over a larger portion of the field of view. This allows the ToF projector device 602 to take up less space and consume less power than other ToF depth sensing devices.

In one embodiment, said scanning mirror device 614 is alternatively configured to act as a microwave reflector. For example, the scanning mirror device 614 may project microwaves with frequencies in the range of 0.1 GHz to 1000 GHz into the environment in a predetermined pattern similar to that of light 606, which may be used by the camera 612 to obtain a microwave image of the environment.

微波对天气条件和光照的弹性，以及它们穿过许多障碍物的能力，会导致比使用其他电磁波谱更可靠的ToF深度测绘和/或手势检测。

名为“Scanning mirror 设备”的微软专利申请最初在2022年6月提交，并在日前由美国专利商标局公布。

Generally speaking, after a U.S. patent application is examined, it will be automatically published 18 months from the filing date or priority date, or it will be published within 18 months from the filing date at the request of the applicant. Note that publication of a patent application does not mean that the patent is approved. After a patent application is filed, the USPTO requires actual review, which can take anywhere from 1 to 3 years.

In addition, this is only a patent application, which does not necessarily mean that it will be adopted, and it is also uncertain whether it will be actually commercialized and the actual results of its application.