Piezoelectric drive circuit structure, scanning display device and signal feedback method

Abstract

This invention discloses a piezoelectric driving circuit structure, a scanning display device, and a signal feedback method. The piezoelectric driving circuit structure includes a driving circuit and a detection circuit. The driving circuit includes a piezoelectric actuator, an inductor connected in series with the piezoelectric actuator, and a voltage source. When the scanning display device is in operation, the piezoelectric actuator acts as a capacitor, forming an LC resonant circuit with the inductor. The detection circuit is used to collect the voltage signal across the piezoelectric actuator or the inductor as a feedback signal. By using the voltage signal across the piezoelectric actuator or the inductor as the feedback signal, the addition of an extra sensor is avoided, thereby alleviating the technical problems of increased scanner module size, power consumption, cost, and production assembly complexity caused by adding sensors.

Description

Technical Field

[0001] This invention relates to the field of scanning display, and more particularly to a piezoelectric drive circuit structure, a scanning display device, and a signal feedback method. Background Technology

[0002] The imaging principle of fiber scanning display (FSD) is that a fiber scanner drives an optical fiber to move along a predetermined two-dimensional scanning trajectory, and modulates the light output of the light corresponding to each pixel of the image to be displayed. Then, the light corresponding to each pixel of the image to be displayed is projected onto the projection surface one by one through the optical fiber to form a projected image.

[0003] During projection display, precise control of the scanner's fiber optic scanning trajectory is required. Current technologies typically achieve scanner feedback control by adding external sensors to measure the vibration of the scanner or fiber optic cable. Methods include measuring scanner deformation, measuring scanner vibration information through magnetic or electric fields, or detecting the content of the image projected by the scanner using optical devices. These solutions all require additional sensors, inevitably increasing the size, power consumption, and cost of the scanner module, as well as increasing the complexity of production and assembly. Summary of the Invention

[0004] The purpose of this invention is to provide a piezoelectric drive circuit structure, a scanning display device, and a signal feedback method to solve the technical problems in the prior art where feedback control schemes all require additional sensors, which increases the size, power consumption, cost, and production assembly complexity of the scanner module.

[0005] To achieve the above-mentioned objectives, a first aspect of the present invention provides a piezoelectric driving circuit structure for use in a scanning display device. The circuit structure includes a driving circuit and a detection circuit. The driving circuit includes a piezoelectric actuator, an inductor connected in series with the piezoelectric actuator, and a voltage source. When the scanning display device is in operation, the piezoelectric actuator acts as a capacitor and forms an LC resonant circuit with the inductor. The detection circuit is used to collect the voltage signal across the piezoelectric actuator or the inductor as a feedback signal.

[0006] Optionally, the resonant frequency of the LC resonant circuit is greater than the resonant frequency of the piezoelectric actuator, the resonant frequency of the optical fiber, and the driving frequency of the driving signal output by the voltage source.

[0007] Optionally, one end of the inductor is connected to the positive terminal of the voltage source, and the other end of the inductor is connected to the positive electrode of the piezoelectric actuator; the negative electrode of the piezoelectric actuator is grounded to the negative terminal of the voltage source; the detection circuit is used to acquire the voltage signal across the piezoelectric actuator.

[0008] Optionally, the positive electrode of the piezoelectric actuator is connected to the positive terminal of the voltage source, and the negative electrode of the piezoelectric actuator is connected to one end of the inductor; the second end of the inductor is grounded to the negative terminal of the voltage source; and the detection circuit is used to acquire the voltage signal across the inductor.

[0009] A second aspect of the present invention provides a scanning display device, the scanning display device including the circuit structure and processor as described in the first aspect, the processor being configured to receive feedback signals acquired by the detection circuit and to correct the drive signals output by the voltage source based on the feedback signals.

[0010] A third aspect of this invention provides a signal feedback method applied in a scanning display device, wherein the scanning display device includes a driving circuit and a detection circuit, the driving circuit includes a piezoelectric actuator, an inductor connected in series with the piezoelectric actuator, and a voltage source; the method includes:

[0011] When the scanning display device is in operation, the voltage signal across the piezoelectric actuator or the inductor is collected by the detection circuit as a feedback signal.

[0012] Optionally, the method includes:

[0013] The feedback signal is received, and the drive signal output by the voltage source is corrected according to the feedback signal.

[0014] One or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages:

[0015] In the embodiments of this invention, the scanning display device employs LC resonant drive. When the scanning display device is in operation, the voltage signal across the piezoelectric actuator or inductor is used as the feedback signal, avoiding the need for additional sensors. This alleviates the technical problems associated with adding sensors, such as increased scanner module size, power consumption, cost, and increased production and assembly complexity. This solution enables scanner feedback control without adding additional sensors, ensuring that the displayed image remains unchanged despite variations in external operating conditions. Simultaneously, it reduces the size and weight of the feedback portion of the scanner display module, lowering the power consumption and cost of the scanner display module. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 A schematic diagram of a possible LC resonant drive circuit provided in an embodiment of the present invention;

[0018] Figure 2 This is a schematic diagram of the voltage-frequency curve across the inductor provided in an embodiment of the present invention;

[0019] Figure 3 This is a schematic diagram of the voltage frequency curve across the capacitor provided in an embodiment of the present invention;

[0020] Figure 4 A schematic diagram of another possible LC resonant drive circuit provided in an embodiment of the present invention;

[0021] Figure 5 This is a schematic diagram of another possible LC resonant drive circuit provided in an embodiment of the present invention. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] Please refer to Figure 1 , Figure 1 This is a schematic diagram of the piezoelectric drive circuit structure provided in an embodiment of the present invention. In this embodiment, the scanning display device uses LC resonant drive and takes the voltage signal across the piezoelectric actuator or inductor as the feedback signal.

[0024] The piezoelectric drive circuit structure consists of two parts: a drive circuit and a detection circuit. The drive circuit includes a piezoelectric actuator C1, an inductor L1 connected in series with the piezoelectric actuator C1, and a voltage source V1. When the scanning display device is in operation, the piezoelectric actuator C1 acts as a capacitor, forming an LC resonant circuit with the inductor L1. The detection circuit is used to collect the voltage signal across the piezoelectric actuator or the inductor as a feedback signal; the signal output from the FB terminal is the voltage signal across the piezoelectric ceramic.

[0025] In this embodiment of the invention, the piezoelectric actuator C1 is mainly composed of piezoelectric ceramics. Utilizing the inverse piezoelectric effect of the piezoelectric ceramics, it converts electrical signals into mechanical vibrations. Taking a fiber optic scanning display device as an example, an optical fiber is fixed to the piezoelectric actuator. The vibration of the piezoelectric actuator drives the vibration of the optical fiber fixed to the piezoelectric actuator, and image scanning is achieved through light output from the optical fiber.

[0026] For raster scanning display devices, the piezoelectric actuator includes two actuating units, providing drive in the X-axis and Y-axis directions respectively. Generally, the drive frequency in the Y-axis direction is lower than that in the X-axis direction. Therefore, the two actuating units can also be called the slow-axis (Y-axis) actuating unit and the fast-axis (X-axis) actuating unit, respectively. The optical fiber sweeps along a raster-like trajectory under the synergistic effect of the vibrations generated by the two actuating units. Therefore, for raster scanning, the two actuating units can be considered as the two drive axes of the fiber optic scanning display device. Since the fast-axis trajectory is amplified by fiber resonance, it is more susceptible to external influences. Changes in the trajectory can lead to changes in the displayed image and display anomalies, such as changes in fast-axis swing, image ellipticity, image squareness, and odd / even line overlap. Therefore, for raster scanning, feedback control of the fast-axis vibration is generally required.

[0027] For scanning display devices using Lissajous scanning or spiral scanning, the X-axis and Y-axis scanning trajectories are both amplified by fiber resonance. Therefore, feedback control of the vibration in both directions of the fiber is required.

[0028] In this embodiment of the invention, the piezoelectric actuator can be an X-axis actuator or a Y-axis actuator. The feedback signal is directly sampled from the drive circuit, without the need to lead the feedback signal lead out from the piezoelectric actuator. The X-axis and Y-axis signals will not be coupled, and the X-axis and Y-axis can be independently controlled by feedback, so there is no need to perform signal decoupling processing.

[0029] In this embodiment of the invention, within the scanner's operating temperature range, it is necessary to maintain the resonant frequency f of the LC resonant circuit. lc Greater than the actuator resonant frequency f p Fiber resonant frequency f f and driving frequency f d .

[0030] Temperature changes alter the response characteristics of piezoelectric ceramics, causing shifts in their impedance and frequency response curves. The resonant frequency f of an LC resonant circuit... lc The actuator resonant frequency f p fiber resonant frequency f f The frequency of the piezoelectric actuator will also change accordingly. For scanning display devices, the driving frequency of the piezoelectric actuator is determined by the display requirements of the scanning display device; therefore, the driving frequency f... d The positional relationship between the resonant peaks of the impedance / frequency response curve and the resonant peaks will change, requiring assurance that f... d It always remains on one side of the resonance peak of the impedance / frequency response curve.

[0031] The impedance curve is obtained by sweeping the frequency of an AC voltage signal of a certain amplitude applied to the piezoelectric ceramic, measuring the amplitude and phase of its current waveform, and then calculating the impedance curve and frequency response curve. Under the drive of an AC voltage signal, the piezoelectric ceramic deforms, causing overall vibration. The vibration mode of the piezoelectric ceramic changes with frequency, and the internal stress distribution of the ceramic also changes. Under the action of positive piezoelectricity, the internal charge distribution changes, ultimately leading to a change in the driving current. Therefore, the impedance curve and frequency response curve measured by the impedance analyzer can reflect its mechanical vibration frequency response characteristics.

[0032] like Figure 2 and Figure 3 The figure shows a schematic diagram of the voltage frequency curves across the inductor and capacitor near the resonance peak of the impedance curve in an LC series resonant circuit. Figure 2 Here are the amplitude-frequency curves of the voltage across the inductor (a) and the amplitude-frequency curve of the total circuit current (b). Figure 3 Here are the frequency curves of the voltage across the capacitor (c) and the amplitude-frequency curve of the total current in the circuit (d).

[0033] like Figure 2 and Figure 3 As shown, the inductor voltage amplitude-frequency curve 'a' has a higher slope to the left of the resonance peak, while the capacitor voltage amplitude-frequency curve 'c' has a higher slope to the right. When used as a feedback signal, high signal sensitivity is required; therefore, the curve slope should be as high as possible. Thus, the voltage signal across the piezoelectric actuator or inductor can be selected as the feedback signal based on the driving frequency of the piezoelectric actuator.

[0034] In one possible implementation, during the driving of the scanning display device, capacitor C is replaced by piezoelectric ceramic on the driving shaft of the scanning display device. As the temperature changes, the equivalent capacitance of the driving electrode of the scanning display device changes with the temperature. The voltage signal across capacitor C can be selected as the feedback signal; correspondingly, the right side of the LC resonant peak needs to be selected as the driving frequency.

[0035] When the voltage signal across capacitor C is selected as the feedback signal, the LC circuit connection method is as follows: Figure 1 As shown, inductor L1 is at the upper end of capacitor C1. The signal drawn from the FB terminal is the voltage across the piezoelectric ceramic. After voltage division, it is directly sent to the detection circuit. Since the signal amplitude is large, no amplification circuit is required in this embodiment of the invention.

[0036] If C is at the top of L, then it needs to be done as follows: Figure 4 The signal is extracted in the manner shown. Since the piezoelectric ceramic driving voltage is high, a sampling circuit with high voltage differential input is required.

[0037] When the voltage signal across inductor L is selected as the feedback signal, the LC circuit connection method is as follows: Figure 5As shown, inductor L2 is located at the lower end of capacitor C2. The signal drawn from the FB terminal is the voltage across the inductor, which is then directly fed into the detection circuit after voltage division.

[0038] Next, the feedback control process in the embodiments of the present invention will be described.

[0039] First possible implementation

[0040] Within a relatively small temperature range, the changes in the impedance and frequency response curves of the scanning display device are mainly overall shifts. Therefore, feedback control can be implemented in the following way: First, initialize the scanner and record the initial value of the current feedback signal. Then, during the operation of the scanning display device, sample the amplitude and phase of the feedback signal in real time, calculate the error between the sampled amplitude and phase of the feedback signal and the initial value of the feedback signal, and send the error to the PID controller to adjust the amplitude and phase of the drive signal respectively.

[0041] Second possible implementation

[0042] When feedback control is achieved through temperature calibration, and the control accuracy requirements for scanning display devices are high, the nonlinear changes in the scanner impedance curve and frequency response curve need to be considered.

[0043] When the temperature range is too wide, the shape of the impedance curve of the piezoelectric actuator may change slightly, which is reflected in the change of the slope of the resonant peak. Furthermore, when the driving voltage applied to the piezoelectric actuator varies too much, the frequency response curve of the piezoelectric ceramic in the scanning display device will also show nonlinear changes. Therefore, feedback control of the scanning display device can be implemented using the following method.

[0044] First, the scanner is initialized at different temperatures, and the amplitude and phase of its driving voltage, as well as the amplitude and phase of the feedback signal, are recorded.

[0045] With the feedback signal amplitude as the independent variable and the driving voltage as the dependent variable, the fitting function F vd (v fb ).

[0046] With the driving voltage amplitude as the independent variable and the feedback signal phase as the dependent variable, the fitting function F θ (v d ).

[0047] When performing amplitude feedback control, the amplitude of the feedback signal is acquired and substituted into the function F. vd (v fb The calculation error is e = F. vd (v fb )-V d Where e is the error value, V d V is the current driving voltage. fbThe amplitude of the feedback signal is then used, and the error e is fed into the PID controller to achieve amplitude feedback control.

[0048] During phase feedback control, the phase of the feedback signal is acquired and substituted into the function F. θ (v d ), calculation error e θ =θ-F θ (v d ), where e θ V is the error value. d Let be the current driving voltage, and θ be the phase of the feedback signal. Then, e θ The signal is fed into a PID controller to achieve amplitude feedback control.

[0049] Based on the same inventive concept, embodiments of the present invention also provide a scanning display device, which includes the circuit structure and processor described in the above embodiments. The processor is used to receive the feedback signal acquired by the detection circuit and to correct the drive signal output by the voltage source according to the feedback signal. The specific correction process has been described in the feedback control flow of the foregoing embodiments and will not be detailed here.

[0050] All features disclosed in this specification, or all steps in all disclosed methods or processes, may be combined in any way, except for mutually exclusive features and / or steps.

[0051] Any feature disclosed in this specification (including any appended claims, abstract, and drawings) may be replaced by other equivalent or similar features, unless specifically stated otherwise. That is, unless specifically stated otherwise, each feature is merely one example of a series of equivalent or similar features.

[0052] This invention is not limited to the specific embodiments described above. The invention extends to any new feature or combination disclosed in this specification, as well as any new method or process step or combination disclosed herein.

Claims

1. A piezoelectric drive circuit structure, applied in a scanning display device, characterized in that, The circuit structure comprises a driving circuit and a detection circuit; the driving circuit comprises a piezoelectric actuator, an inductor connected in series with the piezoelectric actuator, and a voltage source; when the scanning display device is in a working state, the piezoelectric actuator forms an LC resonant circuit with the inductor as a capacitor; the detection circuit is used to select a voltage signal across the piezoelectric actuator or the inductor as a feedback signal according to a driving frequency of the piezoelectric actuator.

2. The circuit structure of claim 1, wherein, The resonant frequency of the LC resonant circuit is greater than the resonant frequency of the piezoelectric actuator, the resonant frequency of an optical fiber, and the driving frequency of a driving signal output by the voltage source.

3. The circuit structure of claim 1, wherein, One end of the inductor is connected to a positive electrode of the voltage source, and the other end of the inductor is connected to a positive electrode of the piezoelectric actuator; a negative electrode of the piezoelectric actuator is grounded to a negative electrode of the voltage source; and the detection circuit is used to collect a voltage signal across the piezoelectric actuator.

4. The circuit structure of claim 1, wherein, The positive electrode of the piezoelectric actuator is connected to the positive electrode of the voltage source, and the negative electrode of the piezoelectric actuator is connected to one end of the inductor; the second end of the inductor is grounded to the negative electrode of the voltage source; and the detection circuit is used to collect a voltage signal across the inductor.

5. A scanning display device, characterized by The scanning display device comprises the circuit structure according to any one of claims 1-4 and a processor, and the processor is used to receive the feedback signal collected by the detection circuit and correct a driving signal output by the voltage source according to the feedback signal.

6. A signal feedback method applied to a scanning display device, characterized in that, The scanning display device comprises a driving circuit and a detection circuit, the driving circuit comprises a piezoelectric actuator, an inductor connected in series with the piezoelectric actuator, and a voltage source; the method comprises: When the scanning display device is in a working state, the detection circuit is used to select a voltage signal across the piezoelectric actuator or the inductor as a feedback signal according to a driving frequency of the piezoelectric actuator.

7. The method of claim 6, wherein, The method comprises: Receiving the feedback signal and correcting a driving signal output by the voltage source according to the feedback signal.

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