Detection circuit and image generation apparatus

Abstract

A mirror position detection circuit (45) (detection circuit) is provided with: an I / V converter (210) that converts an energizing current flowing through a piezoelectric element (112) into a voltage; an integrator (220) that integrates the converted voltage; and a first switch (231) and a second switch (232), the first switch (231) and the second switch (232) resetting the integrator (220) according to a reset pulse. When a reset pulse is applied to the terminal (T1), the first switch (231) and the second switch (232) are closed, and the accumulated charge of the capacitor (222) is discharged. As a result, the integrator (220) is reset.

Description

Technical Field

[0001] The present invention relates to a detection circuit for detecting the scanning position of light and an image generation device including the detection circuit. Background Art

[0002] Conventionally, an image generation device is known that generates an image by scanning light modulated according to an image signal. In this device, for example, while scanning light in the horizontal direction at a first period, the light is scanned in the vertical direction at a second period longer than the first period to generate an image of one frame. The first period corresponds to the period of one line of the image signal, and the second period corresponds to the frame period of the image signal.

[0003] Such an image generation device is described, for example, in Patent Document 1 below. In this device, a light deflector using a piezoelectric actuator is used to scan light in the horizontal and vertical directions. In this case, the position of the image area in the vertical direction can be smoothly controlled by detecting the scanning position of the light in the vertical direction. In the light deflector, for example, a piezoelectric element is arranged for such position detection.

[0004] As a detection circuit using a piezoelectric element, for example, a detection circuit described in Patent Document 2 below is known. It is known that, generally, the magnitude of the current flowing through the piezoelectric element is proportional to the speed of expansion and contraction of the piezoelectric element. That is, the energization current of the piezoelectric element is obtained by differentiating the expansion and contraction state of the piezoelectric element. Accordingly, in the above detection circuit, the energization current of the piezoelectric element is converted into a voltage by an I / V converter, and the converted voltage is integrated by an integrator to generate a detection signal representing the expansion and contraction state of the piezoelectric element.

[0005] Prior Art Documents

[0006] Patent Documents

[0007] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2018-155989

[0008] Patent Document 2: Japanese Unexamined Patent Application Publication No. 2008-033567 Summary of the Invention

[0009] Problems to be Solved by the Invention

[0010] In the image generation device having the above-described structure, for example, control can be performed to shift the drawing area in the vertical direction according to changes in the user's line of sight. In this case, by changing the scanning range of light in the vertical direction, the drawing range of the image is shifted in the vertical direction. In this control, by monitoring the scanning position of light in the vertical direction, the control unit can determine whether the scanning range of light is applied to the position in the vertical direction based on the line-of-sight detection signal. When the scanning position of light is not properly applied, the control unit can correct the applied drive signal.

[0011] However, in the detection circuit described in Patent Document 2 above, it takes time until the integration value of the integrator stabilizes. Therefore, it is difficult to use its detection signal for feedback control in a short cycle (one frame period) such as in this image generation device.

[0012] In view of this problem, an object of the present invention is to provide a detection circuit and an image generation device that can accurately and smoothly detect the scanning position of light.

[0013] Means for Solving the Problem

[0014] A first aspect of the present invention relates to a detection circuit. The detection circuit according to this aspect includes: an I / V converter that converts the electric current flowing through a piezoelectric element into a voltage; an integrator that integrates the voltage; and a switch that resets the integrator according to a reset pulse.

[0015] According to the detection circuit according to this aspect, the integrator can be reset according to the reset pulse, so there is no need to wait for the integration value of the integrator to stabilize. Therefore, by using this detection circuit for detecting the scanning position of light in an image generation device, the scanning position of light can be detected quickly and accurately.

[0016] A second aspect of the present invention relates to an image generation device. The image generation device according to this aspect includes: a light source; a scanning unit that scans the light emitted from the light source; a detection circuit that detects the scanning position of the light; and a control unit that controls the light source and the scanning unit based on an image signal. The scanning unit includes a piezoelectric element for detecting the scanning position of the light. The detection circuit includes: an I / V converter that converts the electric current flowing through the piezoelectric element into a voltage; an integrator that integrates the voltage; and a switch that resets the integrator according to a reset pulse, and the control unit outputs the reset pulse to the detection circuit at a predetermined timing to cause the switch to operate.

[0017] According to the image generation device related to this mode, the scanning position of light is detected by a detection circuit having the same structure as that of the first mode described above. Therefore, the scanning position of light can be detected quickly and accurately. Therefore, even in the case of performing control to shift the drawing area according to changes in the user's line of sight as described above, the scanning position of light can also be smoothly and highly accurately controlled at a specified position based on the detection signal from the detection circuit.

[0018] Effects of the Invention

[0019] As described above, according to the present invention, it is possible to provide a detection circuit capable of quickly and accurately detecting the scanning position of light and an image generation device using the detection circuit.

[0020] Through the description of the embodiments shown below, the effects and significance of the present invention should become clearer. However, the embodiments shown below are merely examples when implementing the present invention, and the present invention is not limited by any of the contents described in the following embodiments. Brief Description of the Drawings

[0021] Figure 1 It is a perspective view schematically showing the structure of the AR glasses related to the embodiment.

[0022] Figure 2 It is a diagram schematically showing the structure of the projection unit related to the embodiment.

[0023] Figure 3 It is a diagram showing the structure of the circuit unit of the image generation device related to the embodiment.

[0024] Figure 4 It is a top view showing the structure of the second scanning unit related to the embodiment.

[0025] Figure 5 (a) of is a diagram showing the analog waveform of the drive signal (voltage) in the case where the drawing area of the image changes in the vertical direction for each frame in the embodiment. Figure 5 (b) of is showing in the embodiment by Figure 5 (a) of is a diagram showing the waveform obtained by simulating the current (monitoring current) flowing through the piezoelectric element when the piezoelectric actuator is driven by the drive signal of.

[0026] Figure 6 It is showing in the embodiment by the I / V converter Figure 5 (b) of is a diagram showing the voltage waveform (analog waveform) when the monitoring current is converted into voltage.

[0027] Figure 7 It is a diagram showing the structure of the mirror position detection circuit related to the embodiment.

[0028] Figure 8 It is a diagram showing the structure of the mirror position detection circuit related to the comparative example.

[0029] Figure 9 (a) of is a diagram showing the simulated waveform of the detection signal in the case of using the mirror position detection circuit related to the comparative example. Figure 9 (b) of is a diagram showing the waveform of the detection signal in the case of using the mirror position detection circuit related to the embodiment.

[0030] Figure 10 It is a timing chart showing the application timing of the reset pulse related to the embodiment.

[0031] Figure 11 It is a diagram showing the simulated waveform of the detection signal in the case of applying the reset pulse during the flyback period related to the embodiment.

[0032] Figure 12 It is a timing chart showing the application timing of the reset pulse related to Modification 1.

[0033] Figure 13 It is a diagram showing the simulated waveform of the detection signal in the case of applying the reset pulse during the DC period related to Modification 1.

[0034] Figure 14 It is a diagram showing the structure of the mirror position detection circuit related to Modification 2.

[0035] However, the drawings are for illustrative purposes only and do not limit the scope of the present invention. Detailed Embodiments

[0036] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following embodiments, an example of applying the present invention to an image generation device of AR glasses is shown. However, the following embodiments are one embodiment of the present invention, and the present invention is not limited by any of the following embodiments. For example, the present invention is not limited to being applied to an image generation device of AR glasses, and can also be applied to image generation devices such as AR goggles, VR glasses, VR goggles, and in-vehicle head-up displays.

[0037] Figure 1 It is a perspective view schematically showing the structure of the AR glasses 1.

[0038] In Figure 1 , the X, Y, and Z axes orthogonal to each other are noted together with the front, rear, left, right, up, and down directions of the AR glasses 1. The positive directions of the X axis, Y axis, and Z axis correspond to the right direction, rear direction, and upper direction of the AR glasses 1, respectively.

[0039] The AR glasses 1 include a frame 2 and a pair of image generation devices 3. The pair of image generation devices 3 are symmetric with respect to the Y-Z plane passing through the center of the AR glasses 1. The image generation device 3 includes a projection unit 4, a semi-transmissive semi-reflective mirror 5, and a detection unit 6. Like ordinary glasses, the AR glasses 1 are worn on the user's head.

[0040] The frame 2 is composed of a front surface portion 2a and a pair of support portions 2b. The pair of support portions 2b extend rearward from the right end and the left end of the front surface portion 2a. When the frame 2 is worn by the user, the front surface portion 2a is positioned in front of the pair of eyes E of the user. The front surface portion 2a is made of a transparent material (such as resin, etc.).

[0041] The projection unit 4 is provided on the inner side surface of the support portion 2b. The projection unit 4 projects light modulated according to an image signal onto the corresponding semi-transmissive semi-reflective mirror 5.

[0042] The semi-transmissive semi-reflective mirror 5 is provided on the inner side surface of the front surface portion 2a. The semi-transmissive semi-reflective mirror 5 reflects the light projected from the corresponding projection unit 4 toward the user's eyes E, and allows the light traveling in the front-rear direction to pass through. The light from the projection unit 4 reflected by the semi-transmissive semi-reflective mirror 5 irradiates the fovea located at the center of the retina in the eyes E. Thus, the user can visually recognize the frame image 20 generated by the image generation device 3 (refer to Figure 2 ). In addition, since the user can observe the front of the AR glasses 1 through the semi-transmissive semi-reflective mirror 5, the user can visually recognize the state in front of the AR glasses 1 and the frame image 20 generated by the image generation device 3 in a superimposed manner.

[0043] A pair of detection units 6 are provided on the inner side surface of the front surface portion 2a and are positioned between the pair of semi-transmissive semi-reflective mirrors 5. The detection unit 6 is used to detect the user's line of sight. Regarding the detection of the user's line of sight, it will be described later with reference to Figure 3 .

[0044] Figure 2 is a diagram schematically showing the structure of the projection unit 4.

[0045] The projection unit 4 includes light sources 11a, 11b, 11c, collimating lenses 12a, 12b, 12c, apertures 13a, 13b, 13c, mirrors 14a, dichroic mirrors 14b, 14c, a first scanning unit 15, a relay optical system 16, and a second scanning unit 17.

[0046] The light sources 11a, 11b, and 11c are, for example, semiconductor laser light sources. The light source 11a emits laser light having a red wavelength within the range of 635 nm or more and 645 nm or less. The light source 11b emits laser light having a green wavelength within the range of 510 nm or more and 530 nm or less. The light source 11c emits laser light having a blue wavelength within the range of 440 nm or more and 460 nm or less.

[0047] In the present embodiment, a color image is generated as the frame image 20 described later. Therefore, the projection unit 4 includes the light sources 11a, 11b, and 11c that can emit red, green, and blue laser lights. When a monochromatic image is displayed as the frame image 20, the projection unit 4 may include only one light source corresponding to the color of the image. In addition, the projection unit 4 may have a structure including two light sources having different emission wavelengths.

[0048] The light emitted from the light sources 11a, 11b, and 11c is converted into parallel light by the collimating lenses 12a, 12b, and 12c, respectively. The light passing through the collimating lenses 12a, 12b, and 12c is shaped into a substantially circular light beam by the apertures 13a, 13b, and 13c, respectively.

[0049] The mirror 14a substantially totally reflects the red light passing through the aperture 13a. The dichroic mirror 14b reflects the green light passing through the aperture 13b and transmits the red light reflected by the mirror 14a. The dichroic mirror 14c reflects the blue light passing through the aperture 13c and transmits the red light and the green light that have passed through the dichroic mirror 14b. The mirror 14a and the two dichroic mirrors 14b and 14c are arranged so that the optical axes of the light of each color emitted from the light sources 11a, 11b, and 11c coincide.

[0050] The first scanning unit 15 reflects the light that has passed through the dichroic mirror 14c. The first scanning unit 15 is, for example, a MEMS (Micro Electro Mechanical System) mirror. The first scanning unit 15 has the following structure: The first mirror M1 that receives the light passing through the dichroic mirror 14c rotates about a rotation axis R1 parallel to the Z-axis direction according to a drive signal. By rotating the first mirror M1, the reflection direction of the light changes. As a result, the light reflected by the first mirror M1 is scanned in the X-axis direction (horizontal direction) on the retina of the eye E.

[0051] The relay optical system 16 directs the light reflected by the first scanning unit 15 towards the center of the second mirror M2 of the second scanning unit 17. That is, the light incident on the first scanning unit 15 swings at a prescribed swing angle through the first mirror M1. The relay optical system 16 directs the light at each swing angle towards the center of the second mirror M2. The relay optical system 16 includes a plurality of mirrors, and reflects the light reflected by the first scanning unit 15 through the plurality of mirrors, thereby directing it towards the second scanning unit 17. Thereby, a longer optical path length can be achieved inside the relay optical system 16, and the swing angle of the light when viewed from the second mirror M2 can be suppressed.

[0052] The second scanning unit 17 reflects the light that has passed through the relay optical system 16. The second scanning unit 17 is a MEMS mirror. The second scanning unit 17 rotates the second mirror M2 that receives the light incident after passing through the relay optical system 16 around a rotation axis R2 parallel to the X-Y plane according to a drive signal. By rotating the second mirror M2, the reflection direction of the light changes. Thereby, on the retina of the eye E, the light that is scanned in the X-axis direction (horizontal direction) by the first scanning unit 15 is also scanned in the Z-axis direction (vertical direction).

[0053] In addition, the structure of the second scanning unit 17 will be described later with reference to Figure 4 this.

[0054] The light reflected by the second scanning unit 17, that is, the light emitted from the projection unit 4, is reflected by the half mirror 5, and a frame image 20 is formed on the retina of the eye E. That is, the light modulated according to the video signal (the light emitted from the light sources 11a to 11c) is scanned in the horizontal direction (X-axis direction) and the vertical direction (Z-axis direction) through the first scanning unit 15 and the second scanning unit 17, thereby forming a frame image 20 of one frame on the retina of the eye E.

[0055] Figure 3 FIG. is a diagram showing the structure of the circuit unit of the image generation device 3.

[0056] The detection unit 6 includes a light source 61 and an imaging element 62, and the detection unit 6 is connected to the control unit 41 of the projection unit 4. The light source 61 is, for example, an LED that emits light having an infrared wavelength. The imaging element 62 is, for example, a CMOS image sensor or a CCD image sensor. The light source 61 irradiates the user's eye E with light according to an instruction from the control unit 41. The imaging element 62 captures an image of the user's eye E according to an instruction from the control unit 41, and outputs the captured image to the control unit 41.

[0057] The projection unit 4 includes a control unit 41, a first mirror drive circuit 42, a second mirror drive circuit 43, a laser drive circuit 44, and a mirror position detection circuit 45.

[0058] The control unit 41 includes an arithmetic processing unit such as a CPU and an FPGA, and a memory. The control unit 41 processes the image signal from an external device and controls each part of the projection unit 4. In addition, the control unit 41 detects the user's line of sight based on the captured image from the detection unit 6, for example, by the dark pupil method, the bright pupil method, the corneal reflection method, etc. The control unit 41 obtains the viewpoint position in the frame image 20 formed on the user's retina based on the detected user's line of sight.

[0059] The first mirror drive circuit 42 drives the first mirror M1 of the first scanning unit 15 according to the drive signal from the control unit 41. The second mirror drive circuit 43 drives the second mirror M2 of the second scanning unit 17 according to the drive signal from the control unit 41.

[0060] The mirror position detection circuit 45 outputs a detection signal corresponding to the drive state of the second mirror M2 in the second scanning unit 17, that is, the scanning position in the vertical direction (Z-axis direction) of light, to the control unit 41. Regarding the structure of the mirror position detection circuit 45, it will be described later with reference to Figure 7 for illustration.

[0061] The control unit 41 outputs a drive signal to the second mirror drive circuit 43 based on the detection signal from the mirror position detection circuit 45, so that the second mirror M2 rotates in the vertical direction (Z-axis direction) with a desired drive waveform. In addition, the control unit 41 controls the second mirror drive circuit 43 based on the user's line of sight detected by the detection unit 6 and the detection signal from the mirror position detection circuit 45 to draw the frame image 20 at the position of the line of sight.

[0062] In addition, the image generation device 3 may further include a detection circuit for detecting the drive state of the first mirror M1 in the first scanning unit 15, that is, the scanning position in the horizontal direction (X-axis direction) of light. In this case, the control unit 41 controls the first mirror drive circuit 42 based on the detection signal from this detection circuit, so that the first mirror M1 rotates in the horizontal direction (X-axis direction) with a desired drive waveform.

[0063] Figure 4 is a top view showing the structure of the second scanning unit 17.

[0064] As Figure 4 shown, in the present embodiment, the second scanning unit 17 is composed of a meander-type MEMS mirror (light deflector). However, the second scanning unit 17 is not limited to the meander-type MEMS mirror, and may also be a light deflector with other structures.

[0065] The second scanning unit 17 includes a support portion 101, a pair of drive portions 102, and a movable portion 103. The support portion 101 is a frame-shaped member with a specified thickness, and is made of, for example, a silicon substrate. In a top view, the support portion 101 has a rectangular outline.

[0066] The drive unit 102 includes a substrate 110 having one end connected to the support unit 101 and the other end connected to the movable unit 103, and four piezoelectric actuators 111 formed on the upper surface of the substrate 110. The substrate 110 has a meandering shape that meanders in a direction perpendicular to the rotation axis R2. The thickness of the substrate 110 is constant. The substrate 110 is integrally formed with the support unit 101 from the same material as the support unit 101.

[0067] The four piezoelectric actuators 111 are respectively disposed on the upper surfaces of four regions 110a of the substrate 110 that extend in a direction perpendicular to the rotation axis R2. The piezoelectric actuator 111 has a structure in which a piezoelectric body with a constant thickness is sandwiched between an upper electrode and a lower electrode. The piezoelectric body is formed of, for example, PZT. The upper electrode and the lower electrode are formed of, for example, platinum. By applying a voltage (drive signal) between the upper electrode and the lower electrode, the piezoelectric actuator 111 (the piezoelectric body) expands and contracts. As a result, the substrate 110 flexes, generating a driving force for driving the movable unit 103.

[0068] The movable unit 103 is supported by a pair of drive units 102. The movable unit 103 is integrally formed with the substrate 110 and the support unit 101 from the same material as the substrate 110 of the drive unit 102. In a plan view, the movable unit 103 is circular. The shape of the movable unit 103 may also be other shapes such as a square. The thickness of the movable unit 103 is the same as the thickness of the substrate 110. Ribs for suppressing warping of the movable unit 103 may be formed on the back surface of the movable unit 103. The above-described second mirror M2 is formed on the upper surface of the movable unit 103. When the reflectivity of the upper surface of the movable unit 103 is high, the upper surface of the movable unit 103 may be the second mirror M2.

[0069] When drive voltages with the same phase are applied to the odd-numbered piezoelectric actuators 111 starting from the movable unit 103 side, the piezoelectric bodies of these piezoelectric actuators 111 are deformed, and the odd-numbered substrates 110 (regions 110a) vibrate in a flexural manner. At this time, a drive voltage with a phase opposite to that applied to the odd-numbered piezoelectric actuators 111 is applied to the even-numbered piezoelectric actuators 111 starting from the movable unit 103 side. As a result, the piezoelectric bodies in the piezoelectric actuators 111 are deformed, and the even-numbered substrates 110 (regions 110a) are deformed in a flexural manner. In this way, by deforming each substrate 110, the movable unit 103 rotates around the rotation axis R2.

[0070] Moreover, piezoelectric elements 112 are disposed on the upper surfaces of the portions of the substrates 110 of the respective drive units 102 that are connected to the support unit 101. The piezoelectric elements 112, like the piezoelectric actuators 111, have a structure in which a piezoelectric body is sandwiched between an upper electrode and a lower electrode.

[0071] Figure 3The mirror position detection circuit 45 shown outputs detection signals corresponding to the deformations of the two piezoelectric elements 112, respectively. Here, when the movable portion 103 and the second mirror M2 rotate by driving the piezoelectric actuator 111 and, accordingly, the piezoelectric element 112 deforms, based on the piezoelectric effect, a current corresponding to this deformation flows in the piezoelectric element 112. It is known that, generally, the magnitude of the current flowing in the piezoelectric element 112 is proportional to the speed of expansion and contraction of the piezoelectric element 112. That is, the current flowing through the piezoelectric element 112 is obtained by differentiating the expansion and contraction state of the piezoelectric element 112. Therefore, this current flowing through the piezoelectric element 112 corresponds to the rotational position of the second mirror M2, that is, the scanning position of light in the vertical direction.

[0072] Figure 5 Fig. (a) is a diagram showing an analog waveform of the drive signal (voltage) applied to the piezoelectric actuator 111 when the drawing area of the image changes in the vertical direction for each frame. Figure 5 Fig. (b) is a diagram showing a waveform obtained by analog calculation of the current (monitoring current) flowing through the piezoelectric element 112 when the piezoelectric actuator 111 is driven by the drive signal of Figure 5 Fig. (a). In Figure 5 Fig. (a), the drive signal for one piezoelectric actuator 111 is shown, and in Figure 5 Fig. (b), the monitoring current flowing through one piezoelectric element 112 is shown.

[0073] For convenience, in Figure 5 Fig. (a), the vertical axis is normalized with the maximum and minimum values of the drive signal. In addition, in Figure 5 Fig. (b), the vertical axis is normalized with the current values corresponding to 1 and -1 on the vertical axis.

[0074] In Figure 5 Fig. (a), Fk is the k-th frame period (a period corresponding to one frame). The frame period Fk includes a flyback period Tfb for returning the scanning position from the scanning end position in the previous frame period Fk-1 to the scanning start position in the current frame period Fk, and a drawing period Td of the image.

[0075] In all frames, the slope of the drive signal during the drawing period Td, that is, the scanning speed in the vertical direction, is constant. The slope of the drive signal during the flyback period Tfb, that is, the scanning speed in the vertical direction, is also constant in all frames. In addition, the slope of the drive signal during the period between the flyback period Tfb and the drawing period Td is also constant in all frames.

[0076] In this simulation, the range of the drive signal during the drawing period Td is different between adjacent frames. Specifically, the value of the drive signal at the start time point of the drawing period Td within the frame period Fn+1 is slightly smaller than the value of the drive signal at the end time point of the drawing period Td within the frame period Fn. Additionally, the value of the drive signal at the start time point of the drawing period Td within the frame period Fn+2 is slightly smaller than the value of the drive signal at the end time point of the drawing period Td within the frame period Fn+1. The range of the drive signal during the drawing period Td within the frame period Fn+3 is the same as that within the frame period Fn+1. During the frame period Fn+3, the cycle continues with the same frame periods as those from the frame period Fn to Fn+3.

[0077] In this way, when the drawing period Td is set for each frame period, the range of the drive signal for drawing the image, that is, the range of the drawing area in the vertical direction, cyclically switches among three stages: upper, middle, and lower.

[0078] In this case, the monitoring current flowing through the piezoelectric element 112 changes as shown in Figure 5 (b). As described above, the slope of the drive signal during the flyback period Tfb is constant. Therefore, after the monitoring current during the flyback period Tfb rises to a current value corresponding to this slope, it remains constant at this current value. Additionally, the slope of the drive signal during the drawing period Td is constant. Thus, after the monitoring current during the drawing period Td drops to a current value corresponding to this slope, it remains constant at this current value. The slope of the drive signal during the period between the flyback period Tfb and the drawing period Td is also constant. Hence, the monitoring current during this period remains constant at a current value corresponding to this slope.

[0079] As Figure 5 (b) shows, the monitoring current flowing through the piezoelectric element 112 is a waveform obtained by differentiating the expansion and contraction state of the piezoelectric element 112 when the piezoelectric actuator 111 is driven by the drive signal in Figure 5 (a). Therefore, by converting the monitoring current into a voltage using an I / V converter and integrating the converted voltage using an integrator, a detection signal representing the expansion and contraction state of the piezoelectric element 112, that is, the scanning position of light in the vertical direction, can be obtained. When the monitoring current in Figure 5 (b) is converted into a voltage using an I / V converter, the waveform shown in Figure 6 is obtained. This waveform is integrated using an integrator to generate the detection signal.

[0080] However, in this structure, it takes a certain amount of time until the integration value of the integrator stabilizes. On the other hand, as in the present embodiment, in the feedback control for making the drawing position of the image follow the user's line of sight, it is preferable that a detection signal representing the scanning position in the vertical direction of light can be generated within a short period such as the frame period, that is, 1 / 60 second. Thereby, the drawing position of the image can quickly and accurately follow the change of the user's line of sight.

[0081] Therefore, as described above, if only the integrator is used to integrate the voltage after I / V conversion, it takes time until the integration value stabilizes, so a detection signal suitable for the feedback control for line-of-sight following cannot be obtained.

[0082] Therefore, in the present embodiment, the structure of the mirror position detection circuit 45 is improved so that a detection signal can be generated quickly and accurately.

[0083] Figure 7 FIG. shows the structure of the mirror position detection circuit 45 according to the embodiment. For comparison, in Figure 8 the structure of the mirror position detection circuit 45 according to the comparative example is shown.

[0084] First, refer to Figure 8 to describe the mirror position detection circuit 45a according to the comparative example.

[0085] The mirror position detection circuit 45a according to the comparative example includes an I / V converter 210 and an integrator 220.

[0086] The I / V converter 210 includes an operational amplifier 211, a capacitor 212, and a resistor 213. The monitoring current of the piezoelectric element 112 is input to the negative input terminal of the operational amplifier 211. A capacitor 212 and a resistor 213 are connected in parallel between this input terminal and the output terminal of the operational amplifier 211, and the output of the operational amplifier 211 is fed back to the input. Thus, a voltage corresponding to the magnitude of the input monitoring current is output from the operational amplifier 211.

[0087] The integrator 220 includes an operational amplifier 221, a capacitor 222, and resistors 223, 224. The output voltage of the I / V converter 210 is input to the negative input terminal of the operational amplifier 221 via the resistor 224. A capacitor 222 and a resistor 223 are connected in parallel between this input terminal and the output terminal of the operational amplifier 221, and the output of the operational amplifier 221 is fed back to the input. Charge accumulates in the capacitor 222 to be integrated. The gain of the integrator 220 is determined by the two resistors 223, 224. In this way, the voltage obtained by integrating the output voltage from the I / V converter 210 is output from the operational amplifier 221 as a detection signal.

[0088] Next, with reference to Figure 7 the mirror position detection circuit 45 involved in the embodiment will be described.

[0089] The mirror position detection circuit 45 involved in the embodiment, in addition to having Figure 8 the structure of the comparative example shown (I / V converter 210, integrator 220), further includes a first switch 231, a second switch 232, and an inverter 233.

[0090] The first switch 231 and the second switch 232 are connected in parallel between the output and the input of the operational amplifier 221. By applying a high-level reset pulse to the terminal T1, the first switch 231 and the second switch 232 are switched from the open state to the closed state. The reset pulse is output from Figure 3 the control unit 41 to the terminal T1. When the first switch 231 and the second switch 232 are closed, the output and the input of the operational amplifier 221 are short-circuited, and the output and the input become the same potential. Thereby, the charge of the capacitor 222 is discharged to the ground via the operational amplifier 221, and the integrator 220 is reset.

[0091] The first switch 231 and the second switch 232 are composed of complementary elements. For example, the first switch 231 is composed of an N-type transistor, and the second switch 232 is composed of a P-type transistor.

[0092] Preferably, the resistance values of the first switch 231 and the second switch 232 when closed are low. Thereby, the influence of the resistance values of these switches on the gain of the integrator 220 can be suppressed. In addition, preferably, the first switch 231 and the second switch 232 are elements with excellent cut-off characteristics when open. Thereby, the error of the integral value due to the leakage in these switches can be suppressed.

[0093] The first switch 231 is switched to the closed state by a high-level voltage signal. Therefore, the reset pulse input to the terminal T1 is directly applied to the first switch 231. The second switch 232 is switched to the closed state by a low-level voltage signal. Therefore, the reset pulse input to the terminal T1 is applied to the second switch 232 via the inverter 233. Thereby, when a high-level reset pulse is applied to the terminal T1, both the first switch 231 and the second switch 232 are simultaneously switched to the closed state. If no reset pulse is applied to the terminal T1, both the first switch 231 and the second switch 232 are in the open state.

[0094] In FigureIn the mirror position detection circuit 45 according to the comparative example shown above, as described above, it takes time until the integration value of the integrator 220 stabilizes. Therefore, in this mirror position detection circuit 45a, a detection signal suitable for rapid feedback control such as making the drawing area follow the user's line of sight as described above cannot be obtained.

[0095] On the other hand, in the mirror position detection circuit 45 according to the embodiment, the integrator 220 can be reset by a reset pulse, so there is no need to wait for the integration value of the integrator 220 to stabilize. Therefore, by using this mirror position detection circuit 45 for detecting the vertical scanning position of light in the image generation device 3, a detection signal suitable for rapid feedback control for making the drawing area follow the user's line of sight can be obtained.

[0096] ​ (a) of is a diagram showing an analog waveform of a detection signal in the case of using the mirror position detection circuit 45a ( ​ ) according to the comparative example.

[0097] ​ The detection signal in (a) of shows the detection signal output from the mirror position detection circuit 45a (operational amplifier 221) as the mirror position detection circuit 45a is started. That is, in ​ (a) of, an analog waveform of the detection signal output from the operational amplifier 221 at the start of the mirror position detection circuit 45a according to the comparative example is shown. Here, at the time Ts in ​ (a) of, a monitoring voltage is started to be applied to the negative terminal of the operational amplifier 221. The waveform of the monitoring voltage after 0 seconds is the same as the waveform of the monitoring voltage after 0.04 seconds in ​ . In the simulation, it is assumed that the monitoring voltage after the time Ts is input to the integrator 220 during this period.

[0098] As ​ (a) of shows, when the mirror position detection circuit 45a is started, the monitoring voltage has not been applied from the I / V converter 210 to the negative terminal of the operational amplifier 221. Therefore, immediately after the mirror position detection circuit 45a is started, a detection signal of the power supply voltage (here 8V) as the operating voltage of the operational amplifier 221 is output from the operational amplifier 221. After that, when the monitoring voltage is input to the operational amplifier 221 at the time Ts, the accumulated charge amount (integration value) of the capacitor 222 changes according to the input monitoring voltage, and the output of the operational amplifier 221 gradually approaches the waveform obtained by integrating the monitoring voltage. In ​ (a) of the example, it takes approximately 5 frames for the output of the operational amplifier 221 to stabilize at the waveform obtained by integrating the monitoring voltage.

[0099] In this way, in the mirror position detection circuit 45a according to the comparative example, it takes a certain amount of time until the output of the integrator 220, that is, the detection signal, stabilizes.

[0100] In addition, ​ (a) in shows the change in the waveform of the detection signal immediately after startup. However, similarly, in the case where the drawing area is shifted vertically according to the change in the line of sight, it also takes a certain amount of time until the integration value (detection signal) of the integrator 220 before the shift stabilizes to a normal value after the shift. Therefore, in the mirror position detection circuit 45a according to the comparative example, it is difficult to quickly output a detection signal suitable for making the drawing area follow the change in the user's line of sight.

[0101] In addition, in the mirror position detection circuit 45a according to the comparative example, in the case where the waveform of the monitoring voltage is different for each frame as shown in ​ , the influence of the monitoring voltage in the immediately previous frame affects the detection signal in this frame. Therefore, in the mirror position detection circuit 45a according to the comparative example, in the case where the waveform of the drive signal changes between frames, it is difficult to obtain an accurate detection signal for each frame.

[0102] ​ (b) is a diagram showing the waveform of the detection signal in the case of using the mirror position detection circuit 45 ( ​ ) according to the embodiment.

[0103] ​ The detection signal in (b) of ​ shows the detection signal output from the mirror position detection circuit 45 (operational amplifier 221) as the mirror position detection circuit 45 starts. That is, in

[0104] In ​ , at the time Ts1 in (b), a monitoring voltage is started to be applied to the negative terminal of the operational amplifier 221. Similar to the case of ​ (a), the waveform of the monitoring voltage after 0 seconds is the same as the waveform of the monitoring voltage after 0.04 seconds in ​ . In the simulation, it is assumed that the monitoring voltage after the time Ts1 is input to the integrator 220 during this period.

[0105] After that, at the time Ts2, to ​A reset pulse is applied to the terminal T1. By applying the reset pulse, as described above, the capacitor 222 of the integrator 220 is discharged and the integrator 220 is reset. As a result, the detection signal output from the integrator 220 (operational amplifier 221) rapidly drops to 0V, and then, starting from 0V, a detection signal corresponding to the integrated value of the monitoring voltage is output from the integrator 220 (operational amplifier 221).

[0106] As described above, according to the mirror position detection circuit 45 according to the embodiment, a detection signal corresponding to the integrated value of the monitoring voltage can be rapidly output in response to the application of the reset pulse. In addition, since the integrator 220 is reset by the reset pulse, the integrated value after reset is not affected by the integrated value before reset. Therefore, in the mirror position detection circuit 45 according to the embodiment, a detection signal suitable for causing the drawing area to follow the change of the user's line of sight can be rapidly and accurately output.

[0107] In addition, in ​ the simulation of (b), a reset pulse is also applied at the timing indicated by the arrow. That is, a reset pulse is applied to the mirror position detection circuit 45 for each frame. Thereby, the influence of the integrated value in the previous frame on the integrated value in the current frame can be suppressed.

[0108] ​ is a timing chart showing the application timing of the reset pulse according to the embodiment.

[0109] In ​ the upper part, the waveform of the drive signal for driving the second mirror M2 in the vertical direction is shown, and in ​ the lower part, the waveform of the reset pulse is shown.

[0110] As ​ shown, preferably, the reset pulse is applied to the terminal T1 of ​ during the flyback period Tfb of the drive signal. As described above, the flyback period Tfb is a period in which light returns from the scan end position to the scan start position and is a period that does not directly contribute to image drawing. Therefore, even if a reset pulse is applied during the flyback period Tfb to reset the integrator 220, the influence caused by the reset is not likely to affect image drawing.

[0111] More specifically, since the reset pulse has a prescribed time width, during this period, the monitoring voltage input to the integrator 220 is not integrated. That is, in the integrator 220, the integrated value deviates from the normal integrated value by an amount corresponding to this period. After that, the integrator 220 continues to integrate the monitoring voltage in the state where this deviation has occurred. As a result, this deviation is gradually eliminated and the integrated value gradually converges to the normal integrated value.

[0112] Therefore, when a reset pulse is applied during the drawing period Td, the influence (deviation of the integrated value) caused by the reset of the integrator 220 directly affects the drawing of the image. On the other hand, if the reset pulse is applied during the flyback period Tfb as described above, the influence caused by the reset of the integrator 220 does not directly affect the drawing of the image, and the above-mentioned deviation of the integrated value caused by the reset is substantially eliminated before the start of the drawing period Td.

[0113] Therefore, it is preferable that the reset pulse is applied to the ​ terminal T1 within the flyback period Tfb of the drive signal. From the viewpoint of eliminating the above error before the start of the drawing period Td, it is more preferable that the reset pulse is applied in the first half of the flyback period Tfb.

[0114] In addition, as described above, since the integrated value deviates due to the reset pulse, it is preferable that the pulse width (time length) of the reset pulse is limited to the minimum required length as much as possible. That is, it is preferable that the pulse width of the reset pulse is set to the minimum length capable of reliably discharging the charging charge from the capacitor 222 of the integrator 220, or a length slightly longer than that length.

[0115] In addition, it is preferable that the reset pulse is applied near the timing when the swing angle of the second mirror M2 in the vertical direction with respect to the neutral position during the flyback period Tfb becomes zero (the timing when the second mirror M2 is positioned at the neutral position). By resetting the integrator 220 near the neutral position in this way, the waveform difference of the detection signal obtained after the reset can be suppressed.

[0116] ​ is a diagram showing the simulated waveform of the detection signal when the reset pulse is applied within the flyback period Tfb.

[0117] As ​ shown, the detection signal quickly converges to 0V by the application of the reset pulse, and then, starting from 0V, changes in the same waveform as the ​ upper drive signal. That is, the integrated value immediately before the application of the reset pulse does not affect the detection signal (integrated value) after the application of the reset pulse, and the integrated value corresponding to the monitoring voltage after the application of the reset pulse is output as the detection signal.

[0118] Therefore, even when the drawing area is shifted in the vertical direction due to the change of the user's line of sight, it is possible to accurately and quickly output the detection signal corresponding to the integrated value of the monitoring voltage by applying the reset pulse within the flyback period Tfb for each frame. Therefore, according to the mirror position detection circuit 45 according to the embodiment, it is possible to quickly and accurately output the detection signal suitable for following the change of the user's line of sight of the drawing area.

[0119] In addition, in the examples of ​ and ​ , the integrator 220 is reset by applying a reset pulse during each flyback period Tfb, that is, for each frame, but the integrator 220 does not necessarily have to be reset for each frame.

[0120] For example, when the position of the drawing area in the vertical direction is fixed and the frames with the same waveform of the drive signal of the second mirror M2 in the vertical direction are consecutive, the influence of the integration value in the previous frame is not likely to affect the integration value of the current frame. Therefore, a reset pulse may not be applied during this period. On the other hand, when the position of the drawing area in the vertical direction changes and the frames with different waveforms of the drive signal of the second mirror M2 in the vertical direction are consecutive, the influence of the integration value in the previous frame is likely to affect the integration value of the current frame. Therefore, during this period, it is preferably to control to apply a reset pulse for each frame.

[0121] In this way, during the period when the frames with different waveforms of the drive signal of the second mirror M2 in the vertical direction are consecutive, it is particularly preferred to apply a reset pulse for each frame, whereby an accurate detection signal can be obtained for each frame.

[0122] <Effects of the Embodiment>

[0123] According to the above embodiment, the following effects are achieved.

[0124] As ​ shown, the mirror position detection circuit 45 (detection circuit) includes: an I / V converter 210 that converts the current flowing through the piezoelectric element 112 into a voltage; an integrator 220 that integrates the converted voltage; and a first switch 231 and a second switch 232 (switches) that reset the integrator 220 according to a reset pulse.

[0125] According to this structure, the integrator 220 can be reset by a reset pulse. Therefore, as shown in (a) and (b) of ​ , it is not necessary to wait for the integration value of the integrator 220 to stabilize as in the mirror position detection circuit 45a ( ​ ) involved in the comparative example. Therefore, by using this mirror position detection circuit 45 (detection circuit) to detect the scanning position of light in the vertical direction in the image generation device 3, the scanning position of light in the vertical direction can be detected quickly and accurately. Therefore, even when the control is performed as described above to shift the drawing area vertically according to the change of the user's line of sight, the scanning position of light in the vertical direction can also be smoothly and highly accurately controlled to a specified position based on the detection signal from the mirror position detection circuit 45 (detection circuit).

[0126] As​ As shown in ​ , the mirror position detection circuit 45 (detection circuit) includes: a first switch 231 connected in parallel between the output and the input of the operational amplifier 221 included in the integrator 220; and a second switch 232 connected in parallel between the output and the input. The first switch 231 and the second switch 232 are composed of complementary elements. According to this structure, since the ringing noises generated respectively due to the opening and closing of the first switch 231 and the second switch 232 are in antiphase with each other, these ringing noises are cancelled out. Therefore, it is possible to suppress the ringing noise from being superimposed on the detection signal, and the quality of the detection signal can be improved.

[0127] In ​ and ​ the example shown, the control unit 41 outputs a reset pulse to the mirror position detection circuit 45 (detection circuit) for each frame of the video signal. Thereby, it is possible to reliably prevent the integration value obtained by the integrator 220 in the immediately preceding frame from affecting the integration value obtained by the integrator 220 in the current frame. In addition, since the control unit 41 only needs to output a reset pulse for each frame, the processing in the control unit 41 can be simplified.

[0128] As ​ shown, the piezoelectric element 112 is arranged to detect the scanning position of light in the vertical direction. As ​ shown, during the flyback period Tfb in which the control unit 41 returns the scanning position from the scanning end position in the previous frame to the scanning start position in the current frame, the control unit 41 outputs a reset pulse to the mirror position detection circuit 45 (detection circuit). Thereby, as described above, it is possible to suppress the influence (deviation of the integration value) generated due to the reset of the integrator 220 from affecting the drawing of the image.

[0129] <Modification Example 1>

[0130] In the above-described embodiment, as ​ shown, a reset pulse is applied to the mirror position detection circuit 45 (terminal T1) during the flyback period Tfb. In contrast, in Modification Example 1, a DC period during the flyback period Tfb in which the drive signal of the second scanning unit 17 is made constant is set, and a reset pulse is output to the mirror position detection circuit 45 during this DC period.

[0131] ​ is a timing chart showing the application timing of the reset pulse according to Modification Example 1.

[0132] In ​ the upper part, the waveform of the drive signal for driving the second mirror M2 in the vertical direction is shown, and in ​ the lower part, the waveform of the reset pulse is shown. As ​As shown in the upper part, the control unit 41 generates a drive signal in such a way that a DC period Tdc is set in a part of the flyback period Tfb. Also, as ​ shown in the lower part, the control unit 41 outputs a reset pulse to the mirror position detection circuit 45 during this DC period Tdc.

[0133] ​ FIG. is a diagram showing an analog waveform of a detection signal when a reset pulse is applied during the DC period Tdc.

[0134] As ​ shown, the detection signal rapidly converges to 0V by the application of the reset pulse, and then, starting from 0V, changes in the same waveform as the ​ drive signal in the upper part. At this time, since the reset pulse is included in the DC period Tdc, the monitoring voltage is maintained at 0V during the pulse width of the reset pulse. Therefore, during the pulse width of the reset pulse, the normal integral value of the integrator 220 does not change from 0V, and even if the integrator 220 does not perform integration due to reset during the pulse width of the reset pulse, there is no deviation between the integral value of the integrator 220 after the application of the reset pulse and the normal integral value.

[0135] In this way, according to the structure of Modification Example 1, it is possible to suppress the deviation of the detection signal caused by the reset pulse (the deviation from the original detection signal) generated in the structure of the above-described embodiment. Therefore, a more accurate detection signal can be obtained, and control based on the detection signal can be performed with higher accuracy.

[0136] <Modification Example 2>

[0137] In the above-described embodiment, as ​ shown, two switches, the first switch 231 and the second switch 232, are used, but either one of the switches may be omitted. For example, as ​ shown, the second switch 232 may be omitted, and the integrator 220 is reset by the closing operation of the first switch 231.

[0138] With this structure, as in the above-described embodiment, the integrator 220 can be reset by a reset pulse.

[0139] However, in this structure, as described above, there may be a case where ringing noise generated at the opening and closing of the first switch 231 is superimposed on the detection signal. Therefore, in order to eliminate this case, preferably, as in the above-described embodiment, the first switch 231 and the second switch 232 composed of complementary elements are arranged in parallel between the output and the input of the operational amplifier 221.

[0140] <Other Modification Examples>

[0141] In the above-described embodiment, the integrator 220 includes the resistor 223, but an integrator 220 that omits the resistor 223 may be used in the mirror position detection circuit 45.

[0142] In addition, in the above-described embodiment, as ​ shown, the piezoelectric element 112 is disposed at the connecting portion of the driving unit 102 that is connected to the supporting unit 101, but the arrangement position of the piezoelectric element 112 is not limited thereto. The piezoelectric element 112 may be disposed at a position where the rotational position of the second mirror M2 (the scanning position of light) can be appropriately detected.

[0143] In addition, in the above-described embodiment and Modification Examples 1 and 2, one of the two piezoelectric elements 112 is described, but the same structure and control can also be applied to the other piezoelectric element 112.

[0144] In addition, in the above-described embodiment and Modification Examples 1 and 2, the first mirror M1 and the second mirror M2 are provided independently, but one mirror that rotates about two axes may be provided instead of the first mirror M1 and the second mirror M2. In this case, the piezoelectric element 112 for detecting the mirror position may be disposed at the driving unit that rotates the mirror in the vertical direction.

[0145] In addition, in the above-described embodiment, the detection circuit of the present invention is used to detect the scanning position of light in the vertical direction, but the detection circuit of the present invention may also be used to detect the scanning position of light in the horizontal direction. In this case, the piezoelectric element 112 is disposed in the first scanning unit 15, and the energization current output from the piezoelectric element 112 during the driving of the first scanning unit 15 is input to ​ the I / V converter 210.

[0146] In addition, in the above-described embodiment, an example in which the present invention is applied to the image generation device 3 mounted on the AR glasses 1 is shown, but the image generation device to which the present invention is applied is not limited thereto. The detection circuit according to the present invention can also be used in various devices as long as it uses the current output from the piezoelectric element based on the piezoelectric effect.

[0147] The embodiments of the present invention can be appropriately modified within the scope of the technical idea shown in the claims.

[0148] (Supplementary Note)

[0149] Through the description of the above embodiments, the following techniques are disclosed.

[0150] (Technique 1)

[0151] A detection circuit, characterized by comprising:

[0152] An I / V converter that converts the current flowing through a piezoelectric element into a voltage;

[0153] An integrator that integrates the voltage; and

[0154] A switch that resets the integrator according to a reset pulse.

[0155] According to this technique, the integrator can be reset by a reset pulse, so there is no need to wait for the integration value of the integrator to stabilize. Therefore, by using this detection circuit for detecting the scanning position of light in an image generation device, the scanning position of light can be detected quickly and accurately.

[0156] (Technique 2)

[0157] The detection circuit described in Technique 1 is characterized in that

[0158] The switch includes:

[0159] A first switch that is connected in parallel between the output and the input of the operational amplifier included in the integrator; and

[0160] A second switch that is connected in parallel between the output and the input,

[0161] The first switch and the second switch are composed of complementary elements.

[0162] According to this technique, since the ringing noises generated respectively due to the opening and closing of the first switch and the second switch are in opposite phases to each other, these ringing noises are cancelled out. Therefore, it is possible to suppress the ringing noise from being superimposed on the detection signal and improve the quality of the detection signal.

[0163] (Technique 3)

[0164] An image generation device, characterized by comprising:

[0165] A light source;

[0166] A scanning unit that scans the light emitted from the light source;

[0167] A detection circuit that detects the scanning position of the light; and

[0168] A control unit that controls the light source and the scanning unit based on an image signal,

[0169] wherein the scanning unit includes a piezoelectric element for detecting the scanning position of the light,

[0170] The detection circuit includes:

[0171] An I / V converter that converts the current flowing through the piezoelectric element into a voltage;

[0172] An integrator that integrates the voltage; and

[0173] A switch that resets the integrator according to a reset pulse,

[0174] The control unit outputs the reset pulse to the detection circuit at a specified timing to operate the switch.

[0175] According to this technique, the scanning position of light is detected by a detection circuit having the same structure as that of the above Technique 1, so that the scanning position of light can be detected quickly and accurately. Therefore, for example, in the case of performing control to shift the drawing area, the scanning position of light can also be smoothly and highly accurately controlled at a specified position according to the detection signal from the detection circuit.

[0176] (Technique 4)

[0177] The image generation device according to Technique 3, characterized in that

[0178] The switch includes:

[0179] A first switch that is connected in parallel between the output and the input of the operational amplifier included in the integrator; and

[0180] A second switch that is connected in parallel between the output and the input,

[0181] The first switch and the second switch are composed of complementary elements.

[0182] According to this technique, the same effect as that of the above Technique 2 can be achieved.

[0183] (Technique 5)

[0184] The image generation device according to Technique 3 or 4, characterized in that

[0185] The control unit outputs the reset pulse to the detection circuit for each frame of the video signal.

[0186] According to this technique, it is possible to reliably prevent the integration value obtained by the integrator in the immediately preceding frame from affecting the integration value obtained by the integrator in the current frame. In addition, since the control unit only needs to output the reset pulse for each frame, the processing in the control unit can be simplified.

[0187] (Technique 6)

[0188] The image generation device according to any one of Techniques 3 to 5, characterized in that

[0189] The piezoelectric element is configured to detect the scanning position of light in the vertical direction.

[0190] During the retrace period in which the control unit returns the scanning position from the scanning end position in the previous frame to the scanning start position in the current frame, the control unit outputs the reset pulse to the detection circuit.

[0191] According to this technique, it is possible to suppress the influence of the reset of the integrator by the reset pulse from affecting the image drawing.

[0192] (Technique 7)

[0193] The image generation device according to Technique 6 is characterized in that

[0194] The control unit sets a DC period within the retrace period in which the drive signal in the vertical direction is constant, and outputs the reset pulse to the detection circuit during the DC period.

[0195] According to this technique, it is possible to suppress a deviation in the detection signal due to the reset pulse. Therefore, a more accurate detection signal can be obtained, and control based on the detection signal can be performed with higher precision.

[0196] Description of reference numerals

[0197] 3: Image generation device; 11a to 11c: Light sources; 17: Second scanning unit (scanning unit); 45: Mirror position detection circuit (detection circuit); 112: Piezoelectric element; 210: I / V converter; 220: Integrator; 221: Operational amplifier; 231: First switch; 232: Second switch; Tfb: Retrace period; Tdc: DC period.

Claims

1. A detection circuit, characterized in that, Comprising: an I / V converter that converts the current flowing through a piezoelectric element into a voltage; an integrator that integrates the voltage; and a switch that resets the integrator according to a reset pulse.

2. The detection circuit according to claim 1, wherein: the switch includes: a first switch connected in parallel between the output and the input of an operational amplifier included in the integrator; and a second switch connected in parallel between the output and the input, wherein the first switch and the second switch are formed of complementary elements.

3. An image generation device, characterized in that, Comprising: a light source; a scanning unit that scans the light emitted from the light source; a detection circuit that detects the scanning position of the light; and a control unit that controls the light source and the scanning unit based on an image signal, wherein the scanning unit includes a piezoelectric element for detecting the scanning position of the light, the detection circuit includes: an I / V converter that converts the current flowing through the piezoelectric element into a voltage; an integrator that integrates the voltage; and a switch that resets the integrator according to a reset pulse, wherein the control unit outputs the reset pulse to the detection circuit at a predetermined timing to operate the switch.

4. The image generation device according to claim 3, wherein: the switch includes: a first switch connected in parallel between the output and the input of an operational amplifier included in the integrator; and a second switch connected in parallel between the output and the input, wherein the first switch and the second switch are formed of complementary elements.

5. The image generation device according to claim 3, wherein: the control unit outputs the reset pulse to the detection circuit for each frame of the image signal.

6. The image generation device according to any one of claims 3 to 5, wherein: the piezoelectric element is arranged to detect the scanning position of the light in the vertical direction, and the control unit outputs the reset pulse to the detection circuit during a retrace period when the scanning position returns from the scanning end position in the previous frame to the scanning start position in the current frame.

7. The image generation device according to claim 6, wherein: the control unit sets a DC period during the retrace period in which the drive signal of the scanning unit is constant, and outputs the reset pulse to the detection circuit during the DC period.

Images