Piezoelectric actuator for focal power control using capacitive sensing

Abstract

A piezoelectric actuator for focal power control using capacitive sensing is disclosed. A method of operating a tunable lens includes determining a relationship between a power of the tunable lens and a capacitance of a piezoelectric element configured to deform the tunable lens; measuring the capacitance of the piezoelectric element; and applying a driving voltage to the piezoelectric element based on the measured capacitance to induce a desired power in the tunable lens.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. Provisional Application No. 63 / 579,227 filed on August 28, 2023, and U.S. Non-Provisional Application No. 18 / 776,689 filed on July 18, 2024, the contents of both applications are incorporated herein by reference in their entirety. Technical Field

[0003] The present disclosure relates generally to optical elements such as tunable lenses, and more particularly to a closed-loop control paradigm for predictably and reproducibly manipulating the optical power of a lens through capacitive sensing of an associated piezoelectric element. Background Art

[0004] There is a growing demand for optical systems with adjustable focus, including adaptive optics. Summary of the invention

[0005] For a tunable lens that can be operated using a piezoelectric driven actuator, an optical model establishes a relationship between the optical power of the lens and the capacitance of the piezoelectric element. The model is configured to dynamically apply a waveform to the piezoelectric element in a manner that effectively accounts for thermal and temporal variations of both the optical power and the capacitance to achieve a target focus condition. Therefore, the capacitance of the piezoelectric element can be used to adjust the system optical power in real time through closed-loop control. Closed-loop control can provide fast and accurate focusing. This allows high-quality images to be produced and maintained in an associated display. Using the disclosed model, the relationship between the system optical power and the component optical power can be used to determine a reference capacitance for a specific focus condition.

[0006] In some approaches, electronic circuitry can be used to actively measure the capacitance of a piezoelectric element during use. The sensing excitation waveform and sampling frequency can be superimposed on the drive voltage in a non-interfering manner to achieve closed-loop control. The drive voltage waveform can control the focusing condition of the lens while avoiding overshoot and excessive stress on lens components, including its deformable glass membrane. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The accompanying drawings illustrate several exemplary embodiments and are a part of this specification. Together with the following description, these drawings illustrate and explain various principles of the present disclosure.

[0008] Figure 1 Various sources of nonlinearity in the operation of a lens driven by a piezoelectric actuator are shown in accordance with some embodiments.

[0009] Figure 2An optical model for determining a voltage curve that produces a target optical power in a lens controlled by a piezoelectric actuator is depicted in accordance with various embodiments.

[0010] Figure 3 According to some embodiments, Figure 2 Example circuit diagram of the optical model.

[0011] Figure 4 is a graph of drive voltage with a capacitance measurement signal superimposed according to some embodiments.

[0012] Figure 5 Various methods for measuring capacitance of a piezoelectric element according to some embodiments are described.

[0013] Figure 6 is a simplified circuit diagram depicting a method for measuring capacitance according to some embodiments.

[0014] Figure 7 is a schematic diagram of an example closed-loop control configuration for driving a piezoelectric actuator in accordance with certain embodiments.

[0015] Figure 8 Methods for operating a piezoelectric actuator controlled tunable lens are described in accordance with some embodiments.

[0016] Fig. 9 is a cross-sectional view of a tunable lens operable by closed-loop control of one or more piezoelectric actuators, according to various embodiments.

[0017] Fig.10 is an isometric view of an example piezoelectric actuator according to some embodiments.

[0018] Fig.11 is a graph of optical power versus applied voltage illustrating the hysteresis behavior of an optical model according to certain embodiments.

[0019] Fig.12 is a graph of optical power versus applied voltage illustrating operation of a piezoelectric actuator controlled tunable lens according to some embodiments.

[0020] Fig.13 is a graph of optical power versus applied voltage illustrating operation of a piezoelectric actuator controlled tunable lens according to some embodiments.

[0021] Fig.14 is an illustration of exemplary augmented reality glasses that may be used in conjunction with embodiments of the present disclosure.

[0022] Fig.15is an illustration of an exemplary virtual reality head mounted device (headset) that may be used in conjunction with embodiments of the present disclosure.

[0023] In all figures, the same reference numerals and descriptions refer to similar but not necessarily identical elements. Although the exemplary embodiments described herein are susceptible to various modifications and alternative forms, a plurality of specific embodiments are shown in the drawings by way of example, and these specific embodiments will be described in detail herein. However, the exemplary embodiments described herein are not intended to be limited to the specific forms disclosed. Instead, the present disclosure covers all modifications, equivalents, and alternatives that fall within the scope of the appended claims. DETAILED DESCRIPTION

[0024] There is a growing demand for optical systems with adjustable focal length, including adaptive optics. For example, adaptive optics technology can be incorporated into wearable devices (e.g., augmented and virtual reality devices and head-mounted devices). Example architectures for actively changing the focal length of optical systems include large-scale deformable optics, macro-scale and micro-electromechanical system (MEMS) scale translatable lenses, and electrostatic actuation devices. However, there is still a need for high-speed and consistent adjustment of focal length over a wide tuning range, which is a problem that the aforementioned platforms do not adequately address.

[0025] Despite recent advances, it would be advantageous to provide an autofocus solution for tunable lenses. The present disclosure relates generally to optical elements such as tunable lenses, and more particularly to a closed-loop control paradigm for predictably and reproducibly manipulating the optical power of a lens through capacitive sensing of an associated piezoelectric element.

[0026] For a tunable lens that can be operated using a piezoelectric driven actuator, an optical model establishes a relationship between the optical power of the lens and the capacitance of the piezoelectric element. The model is configured to dynamically apply a waveform to the piezoelectric element in a manner that effectively accounts for thermal and temporal variations of both the optical power and the capacitance to achieve a target focus condition. Therefore, the capacitance of the piezoelectric element can be used to adjust the system optical power in real time through closed-loop control. Closed-loop control can provide fast and accurate focusing. This allows high-quality images to be produced and maintained in an associated display. Using the disclosed model, the relationship between the system optical power and the component optical power can be used to determine a reference capacitance for a specific focus condition.

[0027] In some approaches, electronic circuitry can be used to actively measure the capacitance of a piezoelectric element during use. The sensing excitation waveform and sampling frequency can be superimposed on the drive voltage in a non-interfering manner to achieve closed-loop control. The drive voltage waveform can control the focusing condition of the lens while avoiding overshoot and excessive stress on lens components, including its deformable glass membrane.

[0028] The following will refer to Figures 1 to 14 A detailed description of apparatus and related methods associated with the operation of a tunable lens is provided. Figure 1 The associated discussion includes a description of the various sources of optical power nonlinearity in piezoelectrically driven lenses. Figure 2 The associated discussion includes a description of an optical model for accurate and precise control of tunable lenses. Figures 3 to 8 The associated discussion includes a description of an actuation and sensing architecture for controlling a piezoelectrically driven tunable lens. Fig. 9 and Fig.10 The associated discussion includes a description of an example tunable lens architecture. Figures 11 to 13 The associated discussion includes a description of the operation of a piezoelectric actuator controlled tunable lens. Fig.14 and Fig.15 The associated discussion relates to exemplary virtual reality devices and exemplary augmented reality devices that may include one or more piezoelectrically actuated tunable lenses as disclosed herein.

[0029] As will be appreciated, accurate and precise control of a piezoelectrically actuated tunable lens can be complicated by a variety of effects. Figure 1 The sources of nonlinearity are schematically shown in FIG, and may include: (A) piezoelectric hysteresis; (B) thermal drift; (C) creep; and (D) intrinsic surface deformation, which may vary from lens to lens due to internal stresses and variations in manufacturing. For example, piezoelectric hysteresis may cause optical power nonlinearity when an increasing electric field changes to a decreasing electric field, and vice versa. Despite the aforementioned challenges, an optical model that can be implemented to consistently adjust the optical power of a lens is disclosed herein.

[0030] Reference Figure 2 The optical model uses capacitive sensing and combines various sources of nonlinearity (including intrinsic optical power) to determine the drive waveform required to induce the deformation required to produce the desired optical power in the tunable lens. For example, the drive voltage curve (P) can be represented as a linear and weighted combination of terms related to intrinsic optical power (P0), piezoelectric hysteresis (H(V)), thermal drift (P1(V,T)), and viscoelastic creep C(V,T,t).

[0031] In various embodiments, the model can: (i) determine a desired optical focal length based on one or more of an applied voltage, an operating time, and an operating temperature; (ii) determine and evaluate the relationship between the actual optical focal length of the lens and the capacitance of the piezoelectric element, and (iii) measure the capacitance of the piezoelectric element to determine and apply a drive voltage that effectively produces the desired optical focal length.

[0032] Reference Figure 3 , shown is a schematic diagram outlining closed-loop control of a lens driven by a piezoelectric actuator. An internal control loop for capacitive sensing, feedback, and actuation is included. Within the capacitive measurement circuit and during calibration and / or use thereof, a relationship between optical power and capacitance can be established. The calibration actions can include: (a) determining an initial optical power of a tunable lens; (b) evaluating the hysteresis behavior of the tunable lens with applied voltage for the initial optical power; (c) evaluating the thermal drift of the initial optical power with applied voltage; (d) evaluating the creep behavior of the tunable lens for a given applied voltage; and (e) determining the relationship between module-level optical power and component-level optical power. As further disclosed herein, capacitive sensing can be performed in a variety of ways.

[0033] According to some embodiments, a constant voltage may be applied to a piezoelectric actuator to cause deformation of the associated lens and adjust its optical power. Figure 4 As shown, a low amplitude, high frequency alternating current (AC) signal for synchronous capacitive sensing can be superimposed on the drive signal, and capacitance measurements can be performed within a specified sampling window. In some embodiments, the AC waveform for capacitance measurement can be superimposed on the drive signal with a peak-to-peak amplitude of less than about 0.1V and at a frequency (e.g., greater than 100 kilohertz (kHz)) that effectively avoids membrane resonance. The sampling rate can be selected to measure the response of the piezoelectric layer. For example, the sampling rate can range from about 10kHz to about 50kHz, but when combined with a low-pass filter, a higher sampling rate can be used. Figure 5 Selected capacitance sensing techniques are shown and may include: (A) charge and discharge time measurement; (B) reactance / impedance type measurement, or (C) bridge measurement. For example, the reactance / impedance type measurement may be configured to provide a large and nearly constant applied voltage for actuating the piezoelectric element, and a small but oscillating high frequency voltage for capacitance measurement.

[0034] Go to Figure 6 , depicted is an example of an impedance-based capacitance measurement scheme that can include generating an AC signal, directing the AC signal to a piezoelectric element along with a drive signal, sensing the capacitance of the piezoelectric element by modifying the AC signal, and measuring the capacitance by detecting the modified AC signal. A filter and a meter can be used to isolate and measure the modified AC signal. Figure 7 A flow chart depicting actuator control co-integrated with capacitive sensing is shown. In some embodiments, capacitive sensing and voltage drivers may be combined onto a single integrated circuit or printed circuit board.

[0035] Reference Figure 8 According to some embodiments, the drive signal and the sense signal may be configured to avoid mutual interference. Figure 8 As depicted in Figure 1, the lens actuator (e.g., piezoelectric transducer (PZT)) can behave as an ultrasonic transducer / resonator (greater than 20kHz), while the polymer layer can behave as a second resonator (about 8kHz). Actuation of the lens between the two resonance peaks (8kHz to 20kHz) may cause phase instability and generate large stresses in the glass membrane. However, referring to Figure 8 In B, the waveform used to actuate the lens can be designed to avoid resonance, where the ramp time can range from about 0.125 milliseconds (ms) to about 1 ms. For example, when a fast or sharp focus adjustment is required, a faster ramp time (e.g., 0.05 ms) can be used to intentionally cause performance overshoot. Go to Figure 8 In C, a smooth waveform, such as an S-curve, may be applied, which may further reduce the tendency to excite the mechanical resonance mode. The duration of the smooth (S-curve) type waveform may be about 0.1 ms to about 1.0 ms.

[0036] Fig. 9 900 is an example configuration of a tunable lens having a power range including both negative and positive values ​​according to one or more embodiments. Configuration 900 includes a tunable lens 910 and a tunable lens 920. The tunable lens 910 and the tunable lens 920 are optically connected in series with each other along an optical axis 935. As shown, the tunable lens 920 is substantially the same as the tunable lens 910, but is inverted relative to the tunable lens 910. Thus, the tunable lens 910 can have a positive range of power (e.g., 0 to +N diopters, where N is a number greater than or equal to zero), and the tunable lens 920 can have a negative range of power (e.g., 0 to -N diopters). In alternative embodiments, the tunable lens 910 can be different from the tunable lens 920 such that they have different power ranges (e.g., 0 to +N diopters and 0 to -0.5N diopters, respectively). Likewise, in alternative embodiments, tunable lens 920 may not be inverted relative to tunable lens 910 .

[0037] The tunable lens 910 can be configured to adjust its optical power according to an applied signal. The tunable lens 910 includes a window 930, a deformable medium 940 (e.g., a polymer), a deformable membrane 950 (e.g., a deformable glass membrane), a piezoelectric actuator assembly 960, and an aperture 970. The piezoelectric actuator assembly 960 can include one or more piezoelectric actuators adapted to control the surface profile of the deformable membrane 950 in response to an applied electrical signal (e.g., via an integrated electrode). As shown, the tunable lens 910 is in a first position in which the deformable membrane 950 is substantially flat (0 diopters) relative to the optical axis 935. However, the piezoelectric actuator assembly 960 applies one or more forces to the deformable membrane 950 in response to the received electrical signal to bend it and introduce curvature into the surface profile of the deformable membrane 950. In this way, the optical power of the tunable lens 910 can be adjusted from zero diopters to +N diopters.

[0038] As described above, the tunable lens 920 can be substantially the same as the tunable lens 910, but inverted relative to the tunable lens 910. Thus, application of an electrical signal to the tunable lens 920 (via the piezoelectric actuator assembly of the tunable lens 920) causes the deformable membrane 980 to bend toward the tunable lens 910, thereby introducing curvature into the surface profile of the deformable membrane 980. In this manner, the optical power of the tunable lens 920 can be dynamically adjusted from zero diopters to -N diopters. Thus, the illustrated configuration 900 has an optical range of (-N to +N) diopters.

[0039] Fig.10 Another example tunable lens configuration is shown. The tunable lens 1010 includes a window 1030 , a deformable medium 1040 (eg, a polymer lens), a deformable membrane 1050 (eg, a deformable glass membrane), and a piezoelectric actuator 1060 located at the periphery of the deformable membrane 1050 .

[0040] Reference Fig.11 , depicted is a pair of hysteresis loops showing the effect of applied voltage (i.e. applied voltage history) on the deformation of a piezoelectric actuator controlled tunable lens and thereby on the optical power. As will be appreciated, Fig.11 The response function of can represent the combined effects of: (A) piezoelectric hysteresis; (B) thermal drift; (C) creep; and (D) intrinsic surface deformation.

[0041] Fig.11The hysteresis loop of includes a main loop ABCDA, where point A may correspond to zero applied voltage or finite applied voltage, and / or zero deformation or finite deformation. Starting at point A, proceeding along the main loop, applying a positive applied voltage V1 may cause a deformation D1 associated with point B. Starting at point B, and continuing along the main loop, applying a positive voltage V2 may cause a deformation D2 (associated with point C). Starting at point C, a reduction in the applied voltage to a value V3 may cause a deformation D3, as depicted along the main loop back to point D.

[0042] Therefore, refer to Fig.11 , an example method of operating a piezoelectric actuator controlled tunable lens may include: applying a first drive voltage to the piezoelectric actuator in an amount effective to produce a first optical focal length in the tunable lens, and then applying a second drive voltage greater than the first drive voltage to produce a second optical focal length in the tunable lens, wherein the second optical focal length is greater than the first optical focal length. The method may also include: applying a third drive voltage less than the second drive voltage to produce a third optical focal length in the tunable lens, wherein the third optical focal length is less than the second optical focal length.

[0043] Applicants have shown that the relationship between applied voltage and deformation (or optical power) can be simplified by setting the applied voltage to a reset value rather than decreasing the applied voltage between successive set points, thereby avoiding navigation along one of a plurality of small loops (e.g. Fig.11 loop ABB1A).

[0044] Reference Fig.12 , shown as part of the main hysteresis loop. During operation of a piezoelectric actuator controlled tunable lens using a reset paradigm, starting at point A and proceeding along the main loop, applying a positive applied voltage V1 may cause a deformation D1 associated with point B. Starting at point B and continuing along the main loop, applying a positive voltage V2 may cause a deformation D2 (associated with point C). Starting at point C, the applied voltage may be first reduced to a reset value V0, and then a positive voltage V3 may be applied to cause a deformation D3 associated with point D.

[0045] According to some embodiments, a method may include: applying a first drive voltage to a piezoelectric actuator to produce a first optical power in a tunable lens; applying a second drive voltage greater than the first drive voltage to produce a second optical power in the tunable lens, wherein the second optical power is greater than the first optical power; applying a reset voltage less than the first drive voltage to reset the tunable lens; and applying a third drive voltage less than the second drive voltage to produce a third optical power in the tunable lens. The third optical power may be less than the second optical power, and in some examples, the third optical power may be less than the first optical power. As used herein, applying the reset voltage may include applying a zero volt voltage or a negative voltage to the piezoelectric actuator.

[0046] Reference Fig.13 , a portion of another main hysteresis loop is shown. During operation of a piezoelectric actuator controlled tunable lens using a reset paradigm, starting from point A and proceeding along the main loop, applying a positive applied voltage V1 may cause a deformation D1 associated with point B. Starting from point B, the applied voltage may first be reduced to a reset value V0, and then a positive voltage V2 may be applied to cause a deformation D2 associated with point C. Voltage V2 may be less than voltage V1, and deformation D2 may be less than deformation D1.

[0047] Therefore, another method may include: applying a first driving voltage to a piezoelectric actuator to produce a first optical focal length in a tunable lens; applying a reset voltage less than the first driving voltage to reset the tunable lens; and applying a second driving voltage to the piezoelectric actuator to produce a second optical focal length in the tunable lens, wherein the second driving voltage is less than the first driving voltage.

[0048] A system and method for controllable and reproducible operation of a tunable lens is disclosed, and more particularly, relates to using such operation to implement a unified model for addressing various sources of nonlinearity, including hysteresis, thermal drift, creep, and device-to-device variability in manufactured optical power. The capacitance of a piezoelectric actuator can be measured in real time to provide closed-loop control of the optical power of the lens.

[0049] Example Embodiments

[0050] Example 1: A method comprising: determining a relationship between an optical focal length of a tunable lens and a capacitance of a piezoelectric element configured to deform the tunable lens; measuring the capacitance of the piezoelectric element; and applying a drive voltage to the piezoelectric element based on the measured capacitance to induce a desired optical focal length in the tunable lens.

[0051] Example 2: A method according to Example 1, wherein determining the relationship between optical focal length and capacitance includes: evaluating at least two conditions selected from the following conditions: initial optical focal length of the tunable lens; piezoelectric hysteresis of the piezoelectric element; thermal drift of the optical focal length; and viscoelastic creep of components of the tunable lens.

[0052] Example 3: The method according to any one of Examples 1 and 2, comprising: applying a sensing voltage while applying a driving voltage to the piezoelectric element.

[0053] Example 4: A method according to any one of Examples 1 to 3, wherein applying a driving voltage includes: applying a first driving voltage to the piezoelectric element to produce a first optical focal length in the tunable lens; applying a reset voltage less than the first driving voltage to the piezoelectric element to reset the tunable lens; and applying a second driving voltage less than the first driving voltage to the piezoelectric element to produce a second optical focal length in the tunable lens.

[0054] Example 5: A method according to any one of Examples 1 to 3, wherein applying a driving voltage includes: applying a first driving voltage to the piezoelectric element to generate a first optical focal length in the tunable lens; applying a second driving voltage greater than the first driving voltage to the piezoelectric element to generate a second optical focal length in the tunable lens; applying a reset voltage less than the first driving voltage to the piezoelectric element to reset the tunable lens; and applying a third driving voltage less than the second driving voltage to the piezoelectric element to generate a third optical focal length in the tunable lens.

[0055] Example 6: A method comprising: applying a first driving voltage to a piezoelectric element to produce a first optical focal length in a tunable lens; applying a reset voltage less than the first driving voltage to the piezoelectric element to reset the tunable lens; and applying a second driving voltage to the piezoelectric element to produce a second optical focal length in the tunable lens, wherein the second driving voltage is less than the first driving voltage.

[0056] Example 7: The method of Example 6, wherein applying the reset voltage comprises applying a zero volt voltage or a negative voltage to the piezoelectric element.

[0057] Example 8: A method according to any one of Examples 6 and 7, wherein the first optical focal length is less than the second optical focal length.

[0058] Example 9: The method according to any one of Examples 6 to 8 includes: applying a sensing voltage while applying a first driving voltage and a second driving voltage to the piezoelectric element.

[0059] Example 10: The method of any one of Examples 6 to 9, comprising: sensing the capacitance of the piezoelectric element.

[0060] Example 11: A method according to any one of Examples 6 to 10, wherein the first drive voltage and the second drive voltage are determined based on corresponding capacitance measurement results of the piezoelectric element.

[0061] Example 12: A method comprising: applying a first driving voltage to a piezoelectric element to produce a first optical focal length in a tunable lens; applying a second driving voltage greater than the first driving voltage to the piezoelectric element to produce a second optical focal length in the tunable lens; applying a reset voltage less than the first driving voltage to the piezoelectric element to reset the tunable lens; and applying a third driving voltage less than the second driving voltage to the piezoelectric element to produce a third optical focal length in the tunable lens.

[0062] Example 13: The method of Example 12, wherein applying the reset voltage comprises applying a zero volt voltage or a negative voltage to the piezoelectric element.

[0063] Example 14: The method of any one of Examples 12 and 13, wherein the third driving voltage is greater than the first driving voltage.

[0064] Example 15: A method according to any one of Examples 12 to 14, wherein the second optical focal length is greater than the first optical focal length.

[0065] Example 16: The method of any one of Examples 12 to 15, wherein the third driving voltage is less than the second driving voltage.

[0066] Example 17: The method of any one of Examples 12 to 16, wherein the third driving voltage is less than the first driving voltage.

[0067] Example 18: The method according to any one of Examples 12 to 17, comprising: applying a sensing voltage while applying a first driving voltage, a second driving voltage, and a third driving voltage to the piezoelectric element.

[0068] Example 19: The method of any one of Examples 12 to 18, comprising: sensing the capacitance of the piezoelectric element.

[0069] Example 20: A method according to any one of Examples 12 to 19, wherein the first drive voltage, the second drive voltage and the third drive voltage are determined based on corresponding capacitance measurement results of the piezoelectric element.

[0070] Some parts of this specification may describe various embodiments in terms of algorithms and symbolic representations of operations on information. Although these operations are described functionally, computationally, or logically, these operations should be understood to be implemented by computer programs or equivalent circuits or microcodes, etc. In addition, without loss of generality, it sometimes proves convenient to refer to these arrangements of operations as modules. The described operations and their associated modules can be implemented in software, firmware, hardware, or any combination thereof.

[0071] Any of the steps, operations or processes described herein may be performed or implemented using one or more hardware or software modules, either alone or in combination with other devices. In some embodiments, the software module is implemented using a computer program product that includes a computer-readable medium containing a computer program code that can be executed by a computer processor to perform any or all of the steps, operations or processes described.

[0072] Embodiments may also relate to an apparatus for performing the operations described herein. The apparatus may be specially constructed for the desired purpose, and / or the apparatus may include a general-purpose computing device that is selectively activated or reconfigured by a computer program stored in a computer. Such a computer program may be stored in a non-transitory, tangible computer-readable storage medium, or in any type of medium suitable for storing electronic instructions that may be coupled to a computer system bus. In addition, any computing system referred to herein may include a single processor or architecture that employs a multi-processor design to increase computing power.

[0073] Embodiments may also relate to products produced by the computing process described herein. Such products may include information produced by the computing process, wherein the information is stored on a non-transitory, tangible computer-readable storage medium, and may include any embodiment of a computer program product or other data combination described herein.

[0074] The various embodiments of the present disclosure may include various types of artificial reality systems, or may be implemented in combination with various types of artificial reality systems. Artificial reality is a form of reality that has been adjusted in some way before being presented to the user, and artificial reality may include, for example, virtual reality, augmented reality, mixed reality, hybrid reality, or some combination and / or derivative thereof. Artificial reality content may include completely computer-generated content, or computer-generated content combined with collected (e.g., real-world) content. Artificial reality content may include video, audio, tactile feedback, or some combination thereof, any of which may be presented in a single channel or in multiple channels (e.g., stereoscopic video that produces a three-dimensional (3D) effect to the viewer). In addition, in some embodiments, artificial reality may also be associated with applications, products, accessories, services, or some combination thereof, which are used, for example, to create content in artificial reality and / or to be used in artificial reality in other ways (e.g., to perform activities in artificial reality).

[0075] Artificial reality systems can be implemented in a variety of different form factors and configurations. Some artificial reality systems can be designed to work without the use of a near-eye display (NED). Other artificial reality systems can include an NED that also provides visibility into the real world (e.g., Fig.14 ), or visually immersing a user in an artificial reality (e.g., Fig.15 1500 in the virtual reality system 1500). Although some artificial reality devices may be stand-alone systems, other artificial reality devices may communicate and / or cooperate with external devices to provide an artificial reality experience to a user. Examples of such external devices include handheld controllers, mobile devices, desktop computers, devices worn by a user, devices worn by one or more other users, and / or any other suitable external system.

[0076] Go to Fig.14 , the augmented reality system 1400 may include an eyewear device 1402 having a frame 1410 configured to hold a left display device 1415(A) and a right display device 1415(B) in front of the user's eyes. The left display device 1415(A) and the right display device 1415(B) may act together or independently to present an image or series of images to the user. Although the augmented reality system 1400 includes two displays, embodiments of the present disclosure may be implemented in an augmented reality system having a single NED or more than two NEDs.

[0077] In some embodiments, the augmented reality system 1400 may include one or more sensors, such as sensor 1440. Sensor 1440 may generate measurement signals in response to the movement of the augmented reality system 1400 and may be located substantially on any portion of the frame 1410. Sensor 1440 may represent a position sensor, an inertial measurement unit (IMU), a depth camera assembly, a structured light emitter and / or detector, or any combination thereof. In some embodiments, the augmented reality system 1400 may or may not include sensor 1440, or may include more than one sensor. In embodiments where sensor 1440 includes an IMU, the IMU may generate calibration data based on the measurement signals from sensor 1440. Examples of sensor 1440 may include, but are not limited to, accelerometers, gyroscopes, magnetometers, other suitable types of sensors that detect movement, sensors for error correction of IMUs, or some combination thereof.

[0078] The augmented reality system 1400 may also include a microphone array having a plurality of acoustic transducers 1420(A) to 1420(J), which are collectively referred to as acoustic transducers 1420. The acoustic transducer 1420 may be a transducer that detects changes in air pressure caused by sound waves. Each acoustic transducer 1420 may be configured to detect sound and convert the detected sound into an electronic format (e.g., an analog format or a digital format). Fig.14 The microphone array in may, for example, include ten acoustic transducers: acoustic transducers 1420(A) and 1420(B) that may be designed to be placed in corresponding ears of a user; acoustic transducers 1420(C), 1420(D), 1420(E), 1420(F), 1420(G) and 1420(H) that may be positioned at various locations on the frame 1410; and / or acoustic transducers 1420(I) and 1420(J) that may be positioned on the corresponding neckband 1405.

[0079] In some embodiments, one or more of acoustic transducers 1420(A) to 1420(F) can be used as output transducers (e.g., speakers). For example, acoustic transducer 1420(A) and / or acoustic transducer 1420(B) can be earbuds, or any other suitable type of earphones or speakers.

[0080] The configuration of each acoustic transducer 1420 in the microphone array can be varied. Fig.14 1410, but the number of acoustic transducers 1420 can be more or less than ten. In some embodiments, using a greater number of acoustic transducers 1420 can increase the amount of audio information collected and / or improve the sensitivity and accuracy of the audio information. In contrast, using a smaller number of acoustic transducers 1420 can reduce the computing power required for the associated controller 1450 to process the collected audio information. In addition, the position of each acoustic transducer 1420 in the microphone array can be changed. For example, the position of the acoustic transducer 1420 can include a defined position on the user, a defined coordinate on the frame 1410, an orientation associated with each acoustic transducer 1420, or some combination thereof.

[0081] The acoustic transducers 1420(A) and 1420(B) can be positioned at different parts of the user's ear, such as behind the pinna, behind the tragus, and / or in the auricle or ear cavity. Alternatively, in addition to the acoustic transducer 1420 in the ear canal, additional acoustic transducers 1420 can be present on or around the ear. Positioning the acoustic transducers 1420 near the user's ear canal can enable the microphone array to collect information about how sound reaches the ear canal. By positioning at least two of the acoustic transducers 1420 on both sides of the user's head (e.g., as binaural microphones), the augmented reality system 1400 can simulate binaural hearing and capture a 3D stereo sound field around the user's head. In some embodiments, acoustic transducers 1420(A) and 1420(B) may be connected to augmented reality system 1400 via wired connection 1430, while in other embodiments, acoustic transducers 1420(A) and 1420(B) may be connected to augmented reality system 1400 via a wireless connection (e.g., a Bluetooth connection). In other embodiments, acoustic transducers 1420(A) and 1420(B) may not be used in conjunction with augmented reality system 1400 at all.

[0082] The acoustic transducers 1420 on the frame 1410 may be positioned in a variety of ways: along the length of the temples, across the bridge of the nose, above or below the left display device 1415(A) and the right display device 1415(B), or some combination thereof. The acoustic transducers 1420 may be oriented so that the microphone array can detect sounds in a wide range of directions around the user who is wearing the augmented reality system 1400. In some embodiments, an optimization process may be performed during the manufacture of the augmented reality system 1400 to determine the relative positioning of the acoustic transducers 1420 in the microphone array.

[0083] In some examples, the augmented reality system 1400 can include or be connected to an external device (e.g., a paired device), such as a neckband 1405. Neckband 1405 generally represents any type or form of paired device. Therefore, the following discussion of neckband 1405 can also be applied to various other paired devices, such as charging boxes, smart watches, smart phones, wristbands, other wearable devices, handheld controllers, tablet computers, laptop computers, other external computing devices, etc.

[0084] As shown, the neckband 1405 can be coupled to the eyeglass device 1402 via one or more connectors. These connectors can be wired or wireless and can include electronic components and / or non-electronic components (e.g., structural components). In some cases, the eyeglass device 1402 and the neckband 1405 can operate independently without any wired or wireless connection between them. Although Fig.14 The components of the eyeglass device 1402 and the neckband 1405 are shown as being located at example locations on the eyeglass device 1402 and the neckband 1405, but the components may be located at other locations on the eyeglass device 1402 and / or the neckband 1405 and / or distributed in different ways on the eyeglass device and / or the neckband. In some embodiments, the components of the eyeglass device 1402 and the neckband 1405 may be located on one or more additional peripheral devices that are paired with the eyeglass device 1402, the neckband 1405, or some combination thereof.

[0085] Pairing an external device (e.g., a neckband 1405) with an augmented reality eyewear device can enable the eyewear device to achieve the form factor of a pair of glasses while still providing sufficient battery power and computing power for the expanded capabilities. Some or all of the battery power, computing resources, and / or additional features of the augmented reality system 1400 can be provided by a paired device, or shared between a paired device and the eyewear device, thereby reducing the weight, heat distribution, and form factor of the eyewear device as a whole while still maintaining the desired functionality. For example, the neckband 1405 can allow components that were originally included on the eyewear device to be included in the neckband 1405 because the user can bear a heavier weight load on their shoulders than the weight load on their head. The neckband 1405 can also have a larger surface area through which heat is diffused and dissipated to the surrounding environment. Therefore, the neckband 1405 can allow for greater battery power and greater computing power than would otherwise be possible on a standalone eyewear device. Because the weight carried in the neckband 1405 can be less intrusive to the user than the weight carried in the eyeglass device 1402, the user can tolerate wearing a lighter eyeglass device and carrying or wearing a paired device for longer periods of time than the user could tolerate wearing a heavy stand-alone eyeglass device, thereby enabling the user to more fully integrate the artificial reality environment into their daily activities.

[0086] The neckband 1405 can be communicatively coupled to the eyewear device 1402 and / or communicatively coupled to other devices. These other devices can provide certain functions (e.g., tracking, positioning, depth map construction, processing, storage, etc.) to the augmented reality system 1400. Fig.14 In an embodiment of the present invention, the neckband 1405 may include two acoustic transducers (e.g., acoustic transducers 1420 (I) and 1420 (J)) that are part of a microphone array (or potentially form their own microphone subarray). The neckband 1405 may also include a controller 1425 and a power supply 1435.

[0087] The acoustic transducers 1420(I) and 1420(J) of the neckband 1405 may be configured to detect sound and convert the detected sound into an electronic format (analog or digital). Fig.14 In an embodiment of the present invention, the acoustic transducers 1420(I) and 1420(J) can be positioned on the neckband 1405, thereby increasing the distance between the acoustic transducers 1420(I) and 1420(J) of the neckband and other acoustic transducers 1420 positioned on the eyeglass device 1402. In some cases, increasing the distance between the acoustic transducers 1420 in the microphone array can improve the accuracy of the beamforming performed via the microphone array. For example, if the acoustic transducers 1420(C) and 1420(D) detect a sound, and the distance between the acoustic transducers 1420(C) and 1420(D) is greater than the distance between the acoustic transducers 1420(D) and 1420(E), the determined source location of the detected sound can be more accurate than when the sound is detected by the acoustic transducers 1420(D) and 1420(E).

[0088] The controller 1425 of the neckband 1405 can process information generated by multiple sensors on the neckband 1405 and / or the augmented reality system 1400. For example, the controller 1425 can process information from a microphone array that describes the sound detected by the microphone array. For each detected sound, the controller 1425 can perform a direction-of-arrival (DOA) estimate to estimate from which direction the detected sound arrives at the microphone array. When the microphone array detects a sound, the controller 1425 can use the information to fill the audio data set. In an embodiment where the augmented reality system 1400 includes an inertial measurement unit, the controller 1425 can calculate all inertial calculations and spatial calculations from the IMU located on the eyeglass device 1402. The connector can transmit information between the augmented reality system 1400 and the neckband 1405, and between the augmented reality system 1400 and the controller 1425. The information can be in the form of optical data, electronic data, wireless data, or any other transmittable data form. Moving the processing of information generated by the augmented reality system 1400 to the neckband 1405 can reduce the weight and heat of the eyewear device 1402, making the eyewear device more comfortable for the user.

[0089] The power supply 1435 in the neckband 1405 can provide power to the eyeglass device 1402 and / or the neckband 1405. The power supply 1435 can include, but is not limited to, a lithium-ion battery, a lithium-polymer battery, a disposable lithium battery, an alkaline battery, or any other form of power storage device. In some cases, the power supply 1435 can be a wired power supply. Including the power supply 1435 on the neckband 1405 instead of the eyeglass device 1402 can help to better disperse the weight and heat generated by the power supply 1435.

[0090] As mentioned, some artificial reality systems may use virtual experiences to substantially replace one or more of a user's multiple sensory perceptions of the real world, rather than merging the artificial reality with the real reality. An example of this type of system is a head-mounted display system that mostly or completely covers the user's field of view, e.g. Fig.15 Virtual reality system 1500 in FIG. Virtual reality system 1500 may include a front rigid body 1502 and a band 1504 shaped to fit around a user's head. Virtual reality system 1500 may also include output audio transducers 1506 (A) and 1506 (B). In addition, although Fig.15 Not shown, but front rigid body 1502 may include one or more electronic components including one or more electronic displays, one or more inertial measurement units (IMUs), one or more tracking transmitters or detectors, and / or any other suitable device or system for creating an artificial reality experience.

[0091] Artificial reality systems may include various types of visual feedback mechanisms. For example, the display devices in the augmented reality system 1400 and / or the virtual reality system 1500 may include one or more liquid crystal displays (LCD), one or more light emitting diode (LED) displays, one or more organic LED (OLED) displays, one or more digital light project (DLP) micro displays, one or more liquid crystal on silicon (LCoS) micro displays, and / or any other suitable type of display screen. The artificial reality system may include a single display screen for both eyes, or a display screen may be provided for each eye, which may provide additional flexibility for zoom adjustment or correction of the user's refractive error. Some artificial reality systems may also include multiple optical subsystems having one or more lenses (e.g., traditional concave or convex lenses, Fresnel lenses, adjustable liquid lenses, etc.), through which the user can view the display screen. These optical subsystems can be used for a variety of purposes, including collimating light (e.g., making an object appear to be at a greater distance than it is physically at), magnifying light (e.g., making an object appear larger than it actually is), and / or delivering light (e.g., delivering light to a viewer's eye). These optical subsystems can be used in a direct-view architecture (e.g., a single lens configuration that directly collimates light but produces so-called pincushion distortion) and / or a non-direct-view architecture (e.g., a multi-lens configuration that produces so-called barrel distortion to eliminate pincushion distortion).

[0092] In addition to or instead of using a display screen, some artificial reality systems may include one or more projection systems. For example, each display device in the augmented reality system 1400 and / or the virtual reality system 1500 may include a micro LED projector that projects light into a display device (e.g., using a waveguide) such as a transparent combination lens that allows ambient light to pass through. The display device may refract the projected light toward the user's pupil and may enable the user to simultaneously view both the artificial reality content and the real world. The display device may achieve this using any of a variety of different optical components, including waveguide components (e.g., holographic waveguide elements, planar waveguide elements, diffractive waveguide elements, polarizing waveguide elements, and / or reflective waveguide elements), light manipulation surfaces and elements (e.g., diffractive elements and gratings, reflective elements and gratings, and refractive elements and gratings), coupling elements, and the like. The artificial reality system may also be configured with any other suitable type or form of image projection system, such as a retinal projector for a virtual retinal display.

[0093] The artificial reality system may also include various types of computer vision components and subsystems. For example, the augmented reality system 1400 and / or the virtual reality system 1500 may include one or more optical sensors, such as a two-dimensional (2D) camera or a 3D camera, a structured light emitter and detector, a time-of-flight depth sensor, a single beam rangefinder or a scanning laser rangefinder, a 3D laser radar (LiDAR) sensor, and / or any other suitable type or form of optical sensor. The artificial reality system may process data from one or more of these sensors to identify the user's location, map the real world, provide the user with context related to the real-world surroundings, and / or perform various other functions.

[0094] The artificial reality system may also include one or more input audio transducers and / or output audio transducers. Fig.15 In the example shown, the output audio transducers 1506(A) and 1506(B) may include voice coil speakers, ribbon speakers, electrostatic speakers, piezoelectric speakers, bone conduction transducers, cartilage conduction transducers, tragus vibration transducers, and / or any other suitable type or form of audio transducers. Similarly, the input audio transducers may include condenser microphones, dynamic microphones, ribbon microphones, and / or any other type or form of input transducers. In some embodiments, a single transducer may be used for both audio input and audio output.

[0095] Despite Fig.14Not shown, but the artificial reality system may include a tactile (i.e., haptic) feedback system that can be incorporated into headwear, gloves, clothing, handheld controllers, environmental devices (e.g., chairs, floor mats, etc.), and / or any other type of device or system. The tactile feedback system can provide various types of skin feedback, including vibration, thrust, pull, texture, and / or temperature. The tactile feedback system can also provide various types of kinesthetic feedback, such as motion and compliance. Tactile feedback can be implemented using motors, piezoelectric actuators, fluid systems, and / or various other types of feedback mechanisms. The tactile feedback system can be implemented independently of other artificial reality devices, implemented within other artificial reality devices, and / or implemented in combination with other artificial reality devices.

[0096] By providing tactile perception, auditory content, and / or visual content, artificial reality systems can create a complete virtual experience or enhance the user's real-world experience in various contexts and environments. For example, an artificial reality system can assist or expand a user's perception, memory, or cognition in a specific environment. Some systems can enhance the user's interaction with other people in the real world, or can achieve a more immersive interaction with other people in the virtual world. Artificial reality systems can also be used for educational purposes (e.g., for teaching or training in schools, hospitals, government agencies, military agencies, enterprises, etc.), entertainment purposes (e.g., for playing video games, listening to music, watching video content, etc.), and / or for accessibility purposes (e.g., as a hearing aid, visual aid, etc.). The various embodiments disclosed herein can implement or enhance the user's artificial reality experience in one or more of these contexts and environments, and / or in other contexts and environments.

[0097] The process parameters and step sequences described and / or shown herein are provided by way of example only and may be changed as desired. For example, although the steps shown and / or described herein may be shown or discussed in a particular order, the steps do not necessarily need to be performed in the order shown or discussed. The various exemplary methods described and / or shown herein may also omit one or more of the steps described or shown herein, or may include additional steps in addition to those disclosed.

[0098] The foregoing description has been provided to enable others skilled in the art to optimally utilize the various aspects of the exemplary embodiments disclosed herein. This exemplary description is not intended to be exhaustive or to be limited to any precise form disclosed. Many modifications and variations are possible without departing from the spirit and scope of the present disclosure. The various embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. In determining the scope of the present disclosure, reference should be made to the attached claims and their equivalents.

[0099] Unless otherwise indicated, the terms "connected to" and "coupled to" (and their derivatives) as used in this specification and claims will be interpreted as allowing both direct and indirect connections (i.e., connection via other elements or components). In addition, the terms "a" or "an" as used in this specification and claims will be interpreted to mean "at least one of..." Finally, for ease of use, the terms "including" and "having" (and their derivatives) as used in this specification and claims may be interchangeable with the word "comprising" and have the same meaning as the word "comprising".

[0100] It will be understood that when an element such as a layer or region is referred to as being formed on, deposited on, or disposed “on” or “over” another element, the element may be directly on at least a portion of the other element, or one or more intervening elements may also be present. Conversely, when an element is referred to as being “directly on” or “directly over” another element, the element may be on at least a portion of the other element without intervening elements.

[0101] As used herein, in certain embodiments, the term "about" with respect to a particular numerical value or numerical range means and includes the numerical value, and all values ​​within 10% of the numerical value. Thus, for example, in certain embodiments, referring to the numerical value "50" as "about 50" may include values ​​equal to 50±5, i.e., values ​​in the range of 45 to 55.

[0102] As used herein, the term "substantially" with respect to a given parameter, property, or condition may mean and include the degree to which one of ordinary skill in the art would understand that the given parameter, property, or condition is met to a small degree of variation, such as within acceptable manufacturing tolerances. For example, depending on the particular parameter, property, or condition that is substantially met, the parameter, property, or condition may be met by at least about 90%, by at least about 95%, or even by at least about 99%.

[0103] Although the transition phrase "comprising" may be used to disclose various features, elements, or steps in a particular embodiment, it should be understood that alternative embodiments are implied that include those features, elements, or steps that may be described using the transition phrases "consisting of" or "consisting essentially of." Thus, for example, implied alternative embodiments of a piezoelectric element that comprises or includes lead zirconate titanate (PZT) include embodiments in which the piezoelectric element consists essentially of lead zirconate titanate and embodiments in which the piezoelectric element consists of lead zirconate titanate.

Claims

1. A method comprising: determining a relationship between an optical power of a tunable lens and a capacitance of a piezoelectric element configured to deform the tunable lens; measuring the capacitance of the piezoelectric element; as well as A driving voltage is applied to the piezoelectric element based on the measured capacitance to induce a desired optical power in the tunable lens.

2. The method according to claim 1, wherein: Determining the relationship between the optical power and the capacitance comprises evaluating at least two conditions selected from the group consisting of: an initial optical power of the tunable lens; a piezoelectric hysteresis of the piezoelectric element; a thermal drift of the optical power; and a viscoelastic creep of a component of the tunable lens.

3. The method according to claim 1, comprising: A sensing voltage is applied while the driving voltage is applied to the piezoelectric element.

4. The method according to claim 1, wherein: Applying the driving voltage comprises: applying a first driving voltage to the piezoelectric element to generate a first optical power in the tunable lens; applying a reset voltage less than the first driving voltage to the piezoelectric element to reset the tunable lens; and A second driving voltage less than the first driving voltage is applied to the piezoelectric element to generate a second optical power in the tunable lens.

5. The method according to claim 1, wherein: Applying the driving voltage comprises: applying a first driving voltage to the piezoelectric element to generate a first optical power in the tunable lens; applying a second drive voltage greater than the first drive voltage to the piezoelectric element to generate a second optical power in the tunable lens; applying a reset voltage less than the first driving voltage to the piezoelectric element to reset the tunable lens; and A third driving voltage less than the second driving voltage is applied to the piezoelectric element to generate a third optical power in the tunable lens.

6. A method comprising: applying a first driving voltage to the piezoelectric element to generate a first optical power in the tunable lens; Applying a reset voltage less than the first driving voltage to the piezoelectric element to reset the tunable lens; as well as A second driving voltage is applied to the piezoelectric element to generate a second optical power in the tunable lens, wherein the second driving voltage is less than the first driving voltage.

7. The method according to claim 6, wherein: Applying the reset voltage includes applying a zero volt voltage or a negative voltage to the piezoelectric element.

8. The method according to claim 6, wherein: The first optical power is less than the second optical power.

9. The method according to claim 6, comprising: A sensing voltage is applied while the first driving voltage and the second driving voltage are applied to the piezoelectric element.

10. The method according to claim 6, comprising: The capacitance of the piezoelectric element is sensed.

11. The method according to claim 6, wherein: The first drive voltage and the second drive voltage are determined based on corresponding capacitance measurements of the piezoelectric element.

12. A method comprising: applying a first driving voltage to the piezoelectric element to generate a first optical power in the tunable lens; applying a second drive voltage greater than the first drive voltage to the piezoelectric element to generate a second optical power in the tunable lens; Applying a reset voltage less than the first driving voltage to the piezoelectric element to reset the tunable lens; as well as A third driving voltage less than the second driving voltage is applied to the piezoelectric element to generate a third optical power in the tunable lens.

13. The method according to claim 12, wherein: Applying the reset voltage includes applying a zero volt voltage or a negative voltage to the piezoelectric element.

14. The method according to claim 12, wherein: The third driving voltage is greater than the first driving voltage.

15. The method according to claim 12, wherein: The second optical power is greater than the first optical power.

16. The method according to claim 12, wherein: The third driving voltage is lower than the second driving voltage.

17. The method according to claim 12, wherein: The third optical power is smaller than the first optical power.

18. The method according to claim 12, comprising: A sensing voltage is applied while the first driving voltage, the second driving voltage, and the third driving voltage are applied to the piezoelectric element.

19. The method according to claim 12, comprising: The capacitance of the piezoelectric element is sensed.

20. The method according to claim 12, wherein: The first drive voltage, the second drive voltage, and the third drive voltage are determined based on corresponding capacitance measurements of the piezoelectric element.

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