Patent Description:
<CIT> describes a piezo MEMS mirror system that includes a drive system that drives a piezo MEMS mirror that generates an image on a portable device display. The drive system includes a DC-AC converter that operates to convert the DC power provided by the battery to AC power. The DC-AC converter may generate the AC power having a peak voltage that is at an intermediate level - being between the DC voltage of the battery, and the peak AC voltage generated by the drive system. The drive system also includes an output filter that uses a series -coupled inductance system (perhaps inductively coupled inductors in a differential mode circuit) in conjunction with a capacitance of the piezo MEMS mirror (and perhaps tuning capacitors to account for minor fabrication deviations) to amplify the AC voltage of the AC power at a mechanical resonant frequency of the piezo MEMS mirror.

<CIT> Al describes a motor driver circuit for a Micro-electro-mechanical systems (MEMS) micro-mirror device, the motor driver circuit comprising: a non-inverting buffer circuit; an inverting buffer circuit; and a scalar circuit, the scalar circuit comprising a Supply Tracked Common Mode Voltage (VCMSC) generation circuit, wherein the non-inverting buffer circuit, the inverting buffer circuit, and the scalar circuit are configured, together with the VCMSC generation circuit, to provide a common mode voltage to a motor in response to a VCMSC voltage generated by the VCMSC generation circuit, and wherein the VCMSC voltage is generated by the VCMSC generation circuit in response to a control supply voltage and a driver supply voltage provided to the VCMSC generation circuit.

Embodiments of the invention are described in the dependent claims.

Examples are disclosed herein that relate to driving a resonant scanning mirror system using a linear LC resonant driving scheme. In one example, a resonant scanning mirror system includes a scanning mirror, first and second mirror drive elements, and a drive circuit to drive the scanning mirror at a resonant frequency. The drive circuit includes one or more signal sources configured to create a first source signal and a second source signal that is <NUM> degrees out of phase with the first source signal. The drive circuit further includes a buffer stage configured to receive the first and second source signals and output first and second drive signals, a first resonant LC stage configured to amplify the first drive signal for provision to the first mirror drive element, and a second resonant LC stage configured to amplify the second drive signal for provision to the second mirror drive element.

A resonant scanning mirror system in a display device utilizes an alternating current (AC) drive voltage to actuate a scanning mirror at a mechanical resonant frequency of the mirror. The AC drive voltage is significantly higher than a maximum direct current (DC) voltage that can be provided by a battery of the display device. As such, a drive circuit may be configured to convert the available DC voltage to a higher AC voltage. As one example, a drive circuit can include an H-bridge comprising a plurality of switches to generate a suitably high AC voltage. However, such a drive circuit utilizes a boost converter, which can be relatively large and thus complicate the design of a small device. Additionally, the switching behavior of the H-bridge results in some power loss that reduces the efficiency of such a drive circuit.

Accordingly, the present description is directed to a display device comprising a resonant scanning mirror system and a drive circuit configured to drive the resonant scanning mirror system at a resonant frequency using a linear LC resonant driving scheme. Such a configuration boosts voltages only at and adjacent to the resonant frequency of the resonant scanning mirror system, and thus may be more power efficient than circuits that amplify all frequencies. Moreover, controlling the AC voltage in this manner can help to increase a reliability of the drive circuit, as the electrical components of the drive circuit are exposed to high AC voltages less often. Additionally, the disclosed circuits may be smaller in size than prior drive circuits. Furthermore, as described below, in some implementations the drive circuit may have a resonant LC stage that includes a coupled inductor that is configured to amplify a drive signal for driving mirror drive elements of the resonant scanning mirror system. By using the coupled inductor, a size of the drive circuit may be reduced relative to a drive circuit that employs two or more discreate inductors.

<FIG> shows an example head-mounted device (HMD) <NUM> worn by a user <NUM>. The HMD <NUM> includes a see-through display <NUM> configured to present virtual imagery to provide the user <NUM> with an augmented reality experience. The HMD <NUM> comprises a MEMS resonant scanning mirror system as an image source for visually presenting virtual imagery on the see-through display <NUM>. The HMD <NUM> is provided as a non-limiting example of a display device that comprises a resonant scanning mirror system and corresponding drive circuit, and the disclosed examples of resonant scanning mirror systems and drive circuits may be implemented in any suitable type of display device.

<FIG> shows an example resonant scanning mirror system <NUM>. The resonant scanning mirror system <NUM> comprises a scanning mirror <NUM> that is supported along two orthogonally pivoting axes <NUM>, <NUM>. Vertical scan and horizontal scan are controlled via mirror drive elements that pivot the scanning mirror <NUM> about the axes <NUM>, <NUM>. In this example, the first mirror drive element comprises a first piezoelectric actuator 208A and a second piezoelectric actuator 208B, which are operable to drive the mirror in a first scan direction via harmonic oscillation. This scan direction can be referred to as a fast scan direction. In the fast scan direction, the mirror scans a beam of light in a sinusoidal manner at a relatively higher frequency. The second mirror drive element comprises a third piezoelectric actuator 210A and a fourth piezoelectric actuator 210B, which drive the mirror in a second scan direction orthogonal to the first scan direction. This scan direction can be referred to as a slow scan direction. In the slow scan direction, the mirror can be driven via a control signal having a sawtooth-type nature, such that the mirror angle changes more slowly while the beam of light is scanned back and forth in the fast direction to scan an image. Upon completion of scanning an image, the resonant scanning mirror system <NUM> resets more quickly in the slow scan direction (e.g. following a steeper portion of a sawtooth-like control signal) to begin scanning a next image.

The first and second mirror drive elements 208A, 208B for the fast scan direction are driven by <NUM> degree out-of-phase sinusoidal signals. By applying oscillating electrical alternating current (AC) voltages to the respective drive elements, the scanning mirror <NUM> is caused to oscillate, thereby causing appropriate scanning to occur. Such oscillation can be efficiently obtained and maintained based on the first and second drive elements 208a, 208b being driven at a mechanical resonant frequency of the resonant scanning mirror system <NUM> in the fast scan direction.

As mentioned above, the AC drive voltages required to actuate the resonant scanning mirror system <NUM> may be significantly higher than a maximum DC voltage that can be provided by a battery of the HMD <NUM> (shown in <FIG>). For example, the AC drive voltage may be in the order of <NUM> to <NUM> volts, whereas the DC voltage provided by the battery may be in the order of <NUM>-<NUM> volts. As such, in accordance with the concepts described herein, a high AC drive voltage is attained at the mechanical resonant frequency of the scanning mirror system <NUM> using a linear inductive-capacitive (LC) resonant driving scheme employed by a drive circuit so as to efficiently drive the resonant scanning mirror system <NUM>. Such a drive circuit may have increased power efficiency and a smaller form factor compared to previous drive circuits.

<FIG> shows an example drive circuit <NUM> configured to drive the scanning mirror system <NUM> (or any other suitable resonant scanning mirror system) at a resonant frequency. The drive circuit <NUM> comprises a voltage source <NUM> configured to output a DC source voltage. The voltage source <NUM> may take any suitable form, such as one or more batteries.

The drive circuit <NUM> comprises a first signal source <NUM> configured to create a first source signal <NUM> (SS1) (illustrated here by a conductor that carries the first source signal <NUM>) based on the DC source voltage (DC_SV), and a second signal source <NUM> configured to create a second source signal <NUM> (SS2) based on the DC source voltage. The first and second signal sources <NUM>, <NUM> are configured such that the first source signal <NUM> is <NUM> degrees out of phase with the second source signal <NUM>. For example, the first and second signal sources <NUM>, <NUM> may be configured to convert the DC power provided by the voltage source <NUM> to differential mode AC power. In the depicted example, the first and second source signals are sinusoidal signals. In other examples, the first and second source signals may take other forms, such as triangle waves or square waves. In some examples, the first and second signal sources comprise outputs of a digital micro-controller. In other examples, the first and second signal sources may comprise discrete electronic components. In still other examples, the first and second source signals may be created by a single signal source and either of the source signals may be converted to be <NUM> degrees out of phase with the other source signal.

The drive circuit <NUM> comprises a buffer stage <NUM> configured to receive the first source signal <NUM> and the second source signal <NUM> and to output a first drive signal <NUM> (DS1) and a second drive signal <NUM> (DS2). In the depicted example, the buffer stage <NUM> comprises an operational amplifier stage including a first operational amplifier <NUM> and a second operational amplifier <NUM>, wherein the high input impedance and low output impedance of the operational amplifiers buffer the signal sources from circuit elements downstream of the operational amplifiers. In the depicted example, the first and second operational amplifiers <NUM>, <NUM> comprise unity gain amplifiers, such that the first and second drive signals <NUM>, <NUM> have effectively a same voltage as the first and second source signals <NUM>, <NUM> provided as input to the buffer stage <NUM>. In other examples, the buffer stage <NUM> may provide a different gain. In other examples, which are not covered by the claims, components other than operational amplifiers may be used for the buffer stage <NUM>. The buffer stage <NUM> may comprise any suitable electrical component(s) that are configured to buffer the source signals <NUM>, <NUM>.

The drive circuit <NUM> comprises a first resonant LC stage <NUM> and a second resonant LC stage <NUM>. The first resonant LC stage <NUM> is configured to amplify the first drive signal <NUM> for provision to the mirror drive element 208a (shown in <FIG>) of the resonant scanning mirror system <NUM>, and the second resonant LC stage <NUM> is configured to amplify the second drive signal <NUM> for provision to the mirror drive element 208b. The first resonant LC stage <NUM> is configured to use an inductance in conjunction with a capacitance Cpar of a first modeled parasitic capacitor <NUM> of the resonant scanning mirror system <NUM> to amplify a differential AC voltage of the first drive signal <NUM> at a mechanical resonant frequency of the resonant scanning mirror system <NUM>. Similarly, the second resonant LC stage <NUM> is configured to use an inductance in conjunction with a capacitance Cpar of a second modeled parasitic capacitor <NUM> of the resonant scanning mirror system <NUM> to amplify a differential AC voltage of the second drive signal <NUM> at a mechanical resonant frequency of the resonant scanning mirror system <NUM>. The first and second modeled parasitic capacitors <NUM>, <NUM> represent capacitances Cpar that are inherent to the resonant scanning mirror system <NUM>.

In the depicted example, the first resonant LC stage <NUM> comprises a first winding <NUM> of a coupled inductor <NUM> and the second resonant LC stage <NUM> comprises a second winding <NUM> of the coupled inductor <NUM>. The core of the coupled inductor <NUM> may take any suitable form. In one example, the core may have a toroidal shape. By employing the coupled inductor <NUM> in the drive circuit <NUM>, an overall size of the coupled inductor <NUM> may be less than a size of other drive circuit configuration that employ two discrete inductors. Moreover, the coupled inductor <NUM> may provide a greater inductance than discrete inductors due to the mutual inductance between the first and second windings. In this way, the first and second LC stages <NUM>, <NUM> amplify the first and second drive signals <NUM>, <NUM> at the resonant frequency of the resonant mirror system <NUM> in an efficient manner, since the first and second drive signals <NUM>, <NUM> are amplified less, or not all, at frequencies other than those close to or at the mechanical resonant frequency of the resonant scanning mirror system <NUM>.

The inductors and capacitors of the first and second resonant LC stages <NUM>, <NUM> may have any suitable values to amplify the drive signals to the resonant frequency of the resonant scanning mirror system <NUM>. In one example, the inductances of the first and second windings <NUM>, <NUM> are approximately the same. Likewise, the first and second modeled parasitic capacitors <NUM>, <NUM> may have approximately the same capacitances. In other examples, the inductors may have different inductances and/or the capacitors may have different capacitances.

In some examples, the first and second resonant LC stages <NUM>, <NUM> optionally may comprise first and second tuning capacitors <NUM>, <NUM>. The first and second tuning capacitors <NUM>, <NUM> coupled between an output of the coupled inductor <NUM> and a fixed voltage terminal, which may be common ground. The optional tuning capacitor(s) <NUM>, <NUM> allow for some deviation in the actual capacitance Cpar of the resonant scanning mirror system <NUM> that may occur due, for example, to manufacturing tolerances used in fabrication of the resonant scanning mirror system <NUM>. In particular, slight fabrication deviations in the resonant scanning mirror system <NUM> can cause the actual mechanical resonant frequency of the resonant scanning mirror system <NUM> to vary from the designed mechanical resonant frequency. In other examples, either or both tuning capacitors may be omitted.

The drive circuit <NUM> provides a linear LC resonant driving scheme that boosts signals near the resonant frequency and shows unity gain at other operating frequencies below the target resonant frequency. Such operation enables driving performance having increased reliability and efficiency relative to other drive circuit configurations. For example, a drive circuit that directly drives high voltage signals to drive elements of a resonant scanning mirror system can have excessive voltage swings due to process, voltage, and temperature (PVT) variations of the resonant scanning mirror system, which can cause damage to the resonant scanning mirror system. Moreover, since the drive signals are amplified only near the target resonant frequency, less stress may be applied to the electrical components of the drive circuit <NUM> relative to other drive circuits that amplify voltages across different frequencies. Additionally, the cross-coupled inductor employed in the resonant LC stages provides a compact design that reduces a size of the drive circuit <NUM> relative to other drive circuits that comprise discrete inductors and/or other electronic components. Further, by employing linear LC resonant amplification, power efficiency may be increased relative to a drive circuit configuration that employs a switching device (e.g., an H-bridges) that suffers power losses due to switching behavior.

<FIG> shows another example drive circuit <NUM>. The drive circuit <NUM> differs from the drive circuit <NUM> in that the first resonant LC stage <NUM> comprises a first discrete inductor <NUM> and the second resonant LC stage <NUM> comprises a second discrete inductor <NUM>. These discrete inductors <NUM>, <NUM> may work in conjunction with the modeled parasitic capacitors <NUM>, <NUM> (and optionally the tuning capacitors <NUM>, <NUM>) to amplify the drive signals <NUM>, <NUM> at the resonant frequency of the resonant scanning mirror system <NUM>. The discrete inductors <NUM>, <NUM> may be less efficient and larger in size than the coupled inductor <NUM> of the drive circuit <NUM> (shown in <FIG>), but otherwise may provide suitable amplification of the drive signals <NUM>, <NUM> to appropriately operate the resonant scanning mirror system <NUM>.

<FIG> shows another example drive circuit <NUM>. The drive circuit <NUM> differs from the drive circuit <NUM> in that the buffer stage <NUM> includes operational amplifiers that not only buffer the source signals <NUM>, <NUM>, but also provide gain, such that the drive signals <NUM>, <NUM> have a different (e.g. higher) voltage than the source signals. In this example, the buffer stage <NUM> comprises a noninverting operational amplifier stage including a first operational amplifier <NUM> and a second operational amplifier <NUM>. A first resistor <NUM> is electrically connected between a negative input terminal of the first operational amplifier <NUM> and an output terminal of the first operational amplifier <NUM>. A second resistor <NUM> is electrically connected between the negative input terminal of the first operational amplifier <NUM> and common ground (or another suitable reference). The first and second resistors <NUM>, <NUM> form a simple potential divider across the non-inverting amplifier terminal of the first operational amplifier <NUM> with the voltage gain of the first operational amplifier <NUM> being determined based on the ratio of the resistance values of the first and second resistors <NUM>, <NUM>. The first and second resistors <NUM>, <NUM> may have any suitable resistance values to provide any suitable gain to the first source signal <NUM> to generate the first drive signal <NUM>.

Furthermore, a third resistor <NUM> is electrically connected between a negative input terminal of the second operational amplifier <NUM> and an output terminal of the second operational amplifier <NUM>. A fourth resistor <NUM> is electrically connected between the negative input terminal of the second operational amplifier <NUM> and common ground. The third and fourth resistors <NUM>, <NUM> form a simple potential divider across the non-inverting amplifier terminal of the second operational amplifier <NUM> with the voltage gain of the second operational amplifier <NUM> being determined based on the ratio of the resistance values of the third and fourth resistors <NUM>, <NUM>. The third and fourth resistors <NUM>, <NUM> may have any suitable resistance values to provide any suitable gain to the second source signal <NUM> to generate the second drive signal <NUM>. In other examples, the buffer stage may utilize inverting amplifiers, and/or may be configured as differentiators, integrators, and/or any other suitable type of amplifier.

<FIG> shows another example drive circuit <NUM>. The drive circuit <NUM> differs from the drive circuit <NUM> in that a single signal source <NUM> provides a single source signal <NUM> to the buffer stage <NUM>. In the depicted example, the source signal <NUM> (SS) is a sinusoidal signal. The buffer stage <NUM> comprises a unity gain noninverting amplifier <NUM> that is configured to receive the source signal <NUM> and output the first drive signal <NUM>. The buffer stage <NUM> further comprises an inverting amplifier <NUM> that is configured to invert the signal, thereby outputting a signal that is <NUM> degrees out of phase with the output of the noninverting amplifier <NUM>. The resistance values of the first and second resistors <NUM>, <NUM> may be configured such that the differential operational amplifier <NUM> inverts the source signal <NUM> with unity gain to generate the second drive signal <NUM> that is <NUM> degrees out of phase with the first drive signal <NUM>.

The above described drive circuits are intended to be non-limiting and other drive circuit configurations that enable the linear LC resonant drive scheme to be performed as described herein are within the scope of the present disclosure.

<FIG> is a graph <NUM> showing an example frequency response of a drive signal for driving a resonant scanning mirror system at a resonant frequency, such as the resonant scanning mirror system <NUM> shown in <FIG>. For example, the drive signal may be generated by any of the drive circuits <NUM>, <NUM>, <NUM>, and/or <NUM> shown in <FIG>. The horizontal axis of the graph <NUM> represents frequency and the vertical axis of the graph <NUM> represents gain. In particular, the frequency response <NUM> of the drive signal is indicated by the solid line and the phase <NUM> of the drive signal is indicated by the dotted line. It can be seen that the gain comprises a peak <NUM> of the at the mechanical resonant frequency of the resonant scanning mirror system (~<NUM>), and the declining values above and below the peak <NUM>. It can be seen that the peak <NUM> of the frequency response <NUM> is offset from the phase <NUM>.

<FIG> is a graph <NUM> showing example transient responses of source signals for driving a resonant scanning mirror system, such as the resonant scanning mirror system <NUM> shown in <FIG>. The horizontal axis of the graph <NUM> represents time and the vertical axis of the graph <NUM> represents peak to peak voltage of the source signals. In particular, the first source signal <NUM> is indicated by a solid line and the second source signal <NUM> is indicated by a dotted line. Note that the first and second source signals <NUM>, <NUM> are sinusoidal signals that are <NUM> degrees out of phase relative to each other.

<FIG> is a graph <NUM> showing example differential source and drive signals of a drive circuit for driving a resonant scanning mirror system, such as the resonant scanning mirror system <NUM> shown in <FIG>. For example, the drive signal may be generated by any of the drive circuits <NUM>, <NUM>, <NUM>, and/or <NUM> shown in <FIG>. The horizontal axis of the graph <NUM> represents time and the vertical axis of the graph <NUM> represents peak to peak voltage of the input and out signals. In particular, the differential input signal <NUM> is indicated by a dotted line and the differential output signal <NUM> is indicated by a solid line. The differential input signal <NUM> has a peak to peak voltage of ~ <NUM> volts while the differential output signal <NUM> has a peak to peal voltage of ~ <NUM> volts. Note that the amplitude ranges of these differential input and output signals are presented for the purpose of example and are not limiting. It will be appreciated that a drive circuit may use a linear LC drive scheme to amplify an input signal having any suitable input amplitude to output an amplified output signal having any suitable output amplitude. Also, note that the differential output signal <NUM> is phase shifted relative to the differential input signal <NUM> as a result of the resonant peak having a phase offset (as shown in <FIG>).

<FIG> shows an example method <NUM> of operating a resonant scanning mirror system of a display device. The method <NUM> may be performed by any of the drive circuits <NUM>, <NUM>, <NUM>, and/or <NUM> shown in <FIG> to operate the resonant scanning mirror system <NUM> shown in <FIG>, as examples. At <NUM>, a first source signal and a second source signal may be generated, such that the first source signal and the second source signal are <NUM> degrees out of phase. The first and second source signals may be generated by one or more signals sources, such as the first and second signal sources <NUM>, <NUM> shown in <FIG>. At <NUM>, the first source signal and the second source signal are input into a buffer stage and a first drive signal and a second drive signal are output from the buffer stage. For example, the buffer stage <NUM> shown in <FIG> may buffer the first and second source signals <NUM>, <NUM> to output the first and second drive signals <NUM>, <NUM>. In some examples, inputting the first source signal and the second source signal into a buffer stage comprises inputting the first source signal and the second source signal into a unity gain stage.

At <NUM>, the first drive signal is amplified at a resonant frequency of a resonant mirror via a first resonant LC stage. For example, the first drive signal <NUM> may be amplified by the first resonant LC stage <NUM> shown in <FIG>. At <NUM>, the second drive signal is amplified at the resonant frequency of the resonant mirror via a second resonant LC stage. For example, the second drive signal <NUM> may be amplified by the second resonant LC stage <NUM> shown in <FIG>. In some example, the first drive signal may be amplified at the resonant frequency of the resonant mirror via the first resonant LC stage by utilizing a first winding of a coupled inductor, and the second drive signal may be amplified at the resonant frequency of the resonant mirror via a second resonant LC stage by utilizing a second winding of the coupled inductor. In other examples, discrete inductors may be used. Further, in some examples, the first drive signal may be amplified at the resonant frequency of the resonant mirror via the first resonant LC stage by utilizing a first parasitic capacitance of the scanning mirror system, and the second drive signal may be amplified at the resonant frequency of the resonant mirror via a second resonant LC stage by utilizing a second parasitic capacitance of the scanning mirror system inductor. In some examples, the first drive signal may be amplified at the resonant frequency of the resonant mirror via the first resonant LC stage by utilizing one or more tuning capacitors. At <NUM>, the first drive signal is provided to a first mirror drive element. For example, the first drive signal may be provided to the first drive element <NUM> of the resonant mirror drive system <NUM> shown in <FIG>. At <NUM>, the second drive signal is provided to a second mirror drive element. For example, the second drive signal may be provided to the second drive element <NUM> of the resonant mirror drive system <NUM> shown in <FIG>.

By operating a resonant scanning mirror system of a display device according to the method <NUM> that employs a linear LC resonant drive scheme, the resonant scanning mirror system may be driven in a power efficient and reliable manner. Furthermore, since peak voltage is applied only near the resonant frequency of the resonant scanning mirror system, the resonant scanning mirror system and other electrical components of the drive circuit may be less susceptible to PVT variations and other over voltage conditions that can cause degradation of such electrical components.

In an example, a display device comprises a resonant scanning mirror system comprising a scanning mirror, a first mirror drive element, and a second mirror drive element, and a drive circuit configured to drive the scanning mirror at a resonant frequency, the drive circuit comprising one or more signal sources configured to create a first source signal and a second source signal, the first source signal being <NUM> degrees out of phase with the second source signal, a buffer stage configured to receive the first source signal and the second source signal and to output a first drive signal and a second drive signal, a first resonant LC stage configured to amplify the first drive signal for provision to the first mirror drive element, and a second resonant LC stage configured to amplify the second drive signal for provision to the second mirror drive element. In this example and/or other examples, the buffer stage optionally may comprise an operational amplifier stage. In this example and/or other examples, the operational amplifier stage optionally may comprise a unity gain stage. In this example and/or other examples, the first resonant LC stage optionally may comprise a first winding of a coupled inductor, and the second resonant LC stage optionally may comprise a second winding of the coupled inductor. In this example and/or other examples, the first resonant LC stage optionally may utilize a first parasitic capacitance of the scanning mirror system, and the second resonant LC stage optionally may utilize a second parasitic capacitance of the scanning mirror system. In this example and/or other examples, the first resonant LC stage optionally may further comprise a first tuning capacitor. In this example and/or other examples, the first mirror drive element optionally may comprise a first piezoelectric drive element, and the second mirror drive element optionally may comprise a second piezoelectric drive element. In this example and/or other examples, the display device optionally may comprise a head-mounted display.

In another example, a display device, comprises a resonant scanning mirror system comprising a scanning mirror, a first mirror drive element, and a second mirror drive element, and a drive circuit configured to drive the scanning mirror at a resonant frequency, the drive circuit comprising one or more signal sources configured to create a first source signal and a second source signal, the first source signal being <NUM> degrees out of phase with the second source signal, a buffer stage configured to receive the first source signal and the second source signal and to output a first drive signal and a second drive signal respectively based upon the first source signal and the second source signal, a first resonant LC stage configured to amplify the first drive signal for provision to the first mirror drive element, the first resonant LC stage comprising a first winding of a coupled inductor, and a second resonant LC stage configured to amplify the second drive signal for provision to the second mirror drive element, the second resonant LC stage comprising a second winding of a coupled inductor. In this example and/or other examples, the operational amplifier stage optionally may comprise a unity gain stage. In this example and/or other examples, the first resonant LC stage optionally may utilize a first parasitic capacitance of the scanning mirror system, and the second resonant LC stage optionally may utilize a second parasitic capacitance of the scanning mirror system. In this example and/or other examples, the first resonant LC stage optionally may further comprise a first tuning capacitor. In this example and/or other examples, the first mirror drive element optionally may comprise a first piezoelectric drive element, and the second mirror drive element optionally may comprise a second piezoelectric drive element. In this example and/or other examples, the display device optionally may comprise a head-mounted display.

In yet another example, a method of operating a scanning mirror system of a display device comprises generating a first source signal and a second source signal, the first source signal and the second source signal being <NUM> degrees out of phase, inputting the first source signal and the second source signal into a buffer stage and outputting a first drive signal and a second drive signal from the buffer stage, amplifying the first drive signal at a resonant frequency of a resonant mirror via a first resonant LC stage, amplifying the second drive signal at the resonant frequency of the resonant mirror via a second resonant LC stage, providing the first drive signal to a first mirror drive element, and providing the second drive signal to a second mirror drive element. In this example and/or other examples, inputting the first source signal and the second source signal into a buffer stage optionally may comprise inputting the first source signal and the second source signal into a unity gain stage. In this example and/or other examples, amplifying the first drive signal at the resonant frequency of the resonant mirror via the first resonant LC stage optionally may comprise utilizing a first winding of a coupled inductor, and amplifying the second drive signal at the resonant frequency of the resonant mirror via a second resonant LC stage optionally may comprise utilizing a second winding of the coupled inductor. In this example and/or other examples, amplifying the first drive signal at the resonant frequency of the resonant mirror via the first resonant LC stage optionally may comprise utilizing a first parasitic capacitance of the scanning mirror system, and amplifying the second drive signal at the resonant frequency of the resonant mirror via a second resonant LC stage optionally may comprise utilizing a second parasitic capacitance of the scanning mirror system inductor. In this example and/or other examples, amplifying the first drive signal at the resonant frequency of the resonant mirror via the first resonant LC stage optionally further comprise utilizing a first tuning capacitor. In this example and/or other examples, the display device optionally may comprise a head-mounted display.

Claim 1:
A display device (<NUM>), comprising:
a resonant scanning mirror system (<NUM>) comprising a scanning mirror (<NUM>), a first mirror drive element (208A), and a second mirror drive element (208B); and
a drive circuit (<NUM>) configured to drive the scanning mirror by driving the first and second mirror drive elements at a resonant frequency, the drive circuit comprising
a first signal source (<NUM>) and a second signal source (<NUM>) configured to create a first source signal (<NUM>) and a second source signal (<NUM>) such that the first source signal (<NUM>) is <NUM> degrees out of phase with the second source signal (<NUM>);
a buffer stage (<NUM>) comprising an operational amplifier stage including a first operational amplifier (<NUM>) and a second operational amplifier (<NUM>) configured to receive the first source signal and the second source signal and to output a first drive signal and a second drive signal, respectively;
a first resonant LC stage (<NUM>) configured to amplify the first drive signal for provision to the first mirror drive element; and
a second resonant LC stage (<NUM>) configured to amplify the second drive signal for provision to the second mirror drive element.