Image generation device

Abstract

An image generation device (3) is provided with: light sources (11a-11c); a second scanning unit (17) that scans the light emitted from the light sources (11a-11c); a control unit (41) that controls the light sources (11a-11c) and the second scanning unit (17) on the basis of an image signal; a piezoelectric element (112) that is disposed in the second scanning unit (17) and that expands and contracts in accordance with light scanning; and an edge detection circuit (452) that detects an inflection point on a current waveform generated from the piezoelectric element (112). The control unit (41) corrects the drive signal for switching the scanning speed of the light on the basis of the detection timing of the inflection point detected by the edge detection circuit (452).

Description

Technical Field

[0001] The present invention relates to an image generation device that scans light to generate an image. Background Art

[0002] Conventionally, as an image generation device that scans light to generate an image, for example, head-mounted displays such as goggles and glasses that implement AR (Augmented Reality) and VR (Virtual Reality) are known. In these devices, for example, light based on an image signal is irradiated onto a semi-transparent display, and the reflected light is irradiated onto the user's eyes. Alternatively, light based on an image signal is directly irradiated onto the user's eyes.

[0003] Patent Document 1 below describes a structure in which the line density of an image is changed by controlling the scanning speed of a MEMS mirror. In this structure, the MEMS mirror is controlled such that the scanning speed in a region not corresponding to the user's line of sight is faster than the scanning speed in a region corresponding to the line of sight. As a result, the resolution of the image in the region not corresponding to the line of sight becomes lower, and the user's eyes are less likely to get tired.

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Document 1: U.S. Patent No. 9,986,215 Specification Summary of the Invention

[0007] Problems to be Solved by the Invention

[0008] In the case of performing the above-described control, it is necessary to quickly change the high-resolution region and the low-resolution region according to the change in the line of sight. Therefore, it is necessary to quickly and accurately switch the scanning speed at the boundary between the high-resolution region and the low-resolution region.

[0009] In view of this problem, an object of the present invention is to provide an image generation device that can quickly and accurately switch the scanning speed of light for image generation.

[0010] Means for Solving the Problems

[0011] The image generation device according to the main aspect of the present invention includes: a light source; a scanning unit that scans the light emitted from the light source; a control unit that controls the light source and the scanning unit based on an image signal; a piezoelectric element that is disposed in the scanning unit and expands and contracts in accordance with the scanning of the light; and an edge detection circuit that detects an inflection point on the current waveform generated from the piezoelectric element. The control unit corrects a drive signal for switching the scanning speed of the light based on the detection time of the inflection point detected in the edge detection circuit.

[0012] According to the image generation device related to this method, it is possible to detect a change point in the light scanning speed based on the detection time of the inflection point on the current waveform generated from the piezoelectric element. Therefore, it is possible to detect the actual change point in the light scanning speed during one frame, and it is possible to quickly and accurately correct the drive signal applied to the next frame based on the detection time of the inflection point. Therefore, it is possible to quickly and accurately switch the light scanning speed for image generation.

[0013] Effects of the Invention

[0014] As described above, according to the present invention, it is possible to provide an image generation device capable of quickly and accurately switching the light scanning speed for image generation.

[0015] 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 an example 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

[0016] Figure 1 It is a perspective view schematically showing the structure of the AR glasses related to the embodiment.

[0017] Figure 2 It is a diagram schematically showing the structure of the projection unit related to the embodiment.

[0018] Figure 3 It is a diagram showing the structure of the circuit unit of the image generation device related to the embodiment.

[0019] Figure 4 It is a top view showing the structure of the second scanning unit related to the embodiment.

[0020] Figure 5 It is a diagram schematically showing the method for generating a frame image related to the embodiment.

[0021] Figure 6 It is a block diagram showing the structure of the mirror position detection circuit and the surrounding circuit units related to the embodiment.

[0022] Figure 7 It is a timing chart schematically showing the drive signal, monitoring current, monitoring voltage, and pulse signal equivalent to one frame for driving the second scanning unit related to the embodiment.

[0023] Figure 8 It is a timing chart schematically showing the correction method of the drive signal applied to the second scanning unit related to the embodiment.

[0024] Figure 9 FIG. (a) is a flowchart showing a correction process of a drive signal applied to a second scanning unit according to an embodiment. Figure 9 FIG. (b) is a flowchart showing a switching control of a light emission level of a light source according to an embodiment.

[0025] Figure 10 FIGS. (a) to (c) are diagrams showing the structure of a horizontal setting table according to an embodiment.

[0026] Figure 11 is a block diagram showing the structure of a mirror position detection circuit and its peripheral circuit parts according to a modification example.

[0027] Figure 12 FIG. (a) is a diagram showing the structure of table information for setting an initial drive signal according to a modification example. Figure 12 FIG. (b) is a flowchart showing a process in the case of setting an initial drive signal using the table information according to a modification example.

[0028] However, the drawings are for illustrative purposes only and do not limit the scope of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0029] 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.

[0030] Figure 1 is a perspective view schematically showing the structure of the AR glasses 1.

[0031] In Figure 1 it, 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, the Y axis, and the Z axis correspond to the right direction, the rear direction, and the upper direction of the AR glasses 1, respectively.

[0032] 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. The AR glasses 1 are worn on the user's head in the same manner as ordinary glasses.

[0033] 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 a user, the front surface portion 2a is positioned in front of a pair of eyes E of the user. The front surface portion 2a is made of a transparent material (such as resin, etc.).

[0034] 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 half-transmissive and half-reflective mirror 5.

[0035] The half-transmissive and half-reflective mirror 5 is provided on the inner side surface of the front surface portion 2a. The half-transmissive and half-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 half-transmissive and half-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 half-transmissive and half-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.

[0036] 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 half-transmissive and half-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 .

[0037] Figure 2 FIG. is a diagram schematically showing the structure of the projection unit 4.

[0038] 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.

[0039] The light sources 11a, 11b, 11c are, for example, semiconductor laser light sources. The light source 11a emits laser light having a red wavelength in the range of 635 nm or more and 645 nm or less, the light source 11b emits laser light having a green wavelength in the range of 510 nm or more and 530 nm or less, and the light source 11c emits laser light having a blue wavelength in the range of 440 nm or more and 460 nm or less.

[0040] In the present embodiment, a color image is generated as the frame image 20 described later. Therefore, the projection unit 4 includes light sources 11a, 11b, and 11c that can emit red, green, and blue lasers. When a monochromatic image is displayed as the frame image 20, the projection unit 4 may also include only one light source corresponding to the color of the image. In addition, the projection unit 4 may be configured to include two light sources having different emission wavelengths.

[0041] 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.

[0042] The mirror 14a performs substantially total reflection on 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.

[0043] 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 around a rotation axis R11 parallel to the Z-axis direction according to a drive signal. When the first mirror M1 rotates, 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.

[0044] The relay optical system 16 directs the light reflected by the first scanning unit 15 toward 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 predetermined swing angle through the first mirror M1. The relay optical system 16 directs the light of each swing angle toward the center of the second mirror M2. The relay optical system 16 includes a plurality of mirrors, and the light reflected by the first scanning unit 15 is reflected by the plurality of mirrors so as to be directed toward the second scanning unit 17. As a result, a longer optical path length can be realized inside the relay optical system 16, and the swing angle of the light when viewed from the second mirror M2 can be suppressed.

[0045] 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 passing through the relay optical system 16 around a rotation axis R12 parallel to the X-Y plane according to a drive signal. By rotating the second mirror M2, the reflection direction of the light changes. As a result, 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).

[0046] In addition, the structure of the second scanning unit 17 will be described later with reference to Figure 4 this.

[0047] 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 forms a frame image 20 on the retina of the eye E. That is, the light (the light emitted from the light sources 11a to 11c) modulated according to the video signal is scanned in the horizontal direction (X-axis direction) and the vertical direction (Z-axis direction) by the first scanning unit 15 and the second scanning unit 17, and thus a frame image 20 of one frame is formed on the retina of the eye E.

[0048] Figure 3 FIG. is a diagram showing the structure of the circuit unit of the image generation device 3.

[0049] 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 with 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 the instruction of the control unit 41. The imaging element 62 captures an image of the user's eye E according to the instruction of the control unit 41 and outputs the captured image to the control unit 41.

[0050] 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.

[0051] 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 video 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, for example, by the dark pupil method, the bright pupil method, the corneal reflection method, etc., based on the captured image from the detection unit 6. The control unit 41 obtains the viewpoint position in the frame image 20 formed on the retina of the user based on the detected user's line of sight.

[0052] The first mirror driving circuit 42 drives the first mirror M1 of the first scanning unit 15 according to a driving signal from the control unit 41. The second mirror driving circuit 43 drives the second mirror M2 of the second scanning unit 17 according to a driving signal from the control unit 41.

[0053] The mirror position detection circuit 45 outputs a detection signal corresponding to the driving 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 this.

[0054] Based on the detection signal from the mirror position detection circuit 45, the control unit 41 outputs a driving signal to the second mirror driving circuit 43 so that the second mirror M2 rotates in the vertical direction (Z-axis direction) with a desired driving waveform. In addition, the control unit 41 controls the second mirror driving 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.

[0055] In addition, the image generation device 3 may further include a detection circuit that detects the driving 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, based on the detection signal from this detection circuit, the control unit 41 controls the first mirror driving circuit 42 so that the first mirror M1 rotates in the horizontal direction (X-axis direction) with a desired driving waveform.

[0056] Figure 4 is a top view showing the structure of the second scanning unit 17.

[0057] 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 a meander-type MEMS mirror and may be a light deflector with other structures.

[0058] The second scanning unit 17 includes a support portion 101, a pair of driving 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. When viewed from above, the support portion 101 has a rectangular outline.

[0059] The driving portion 102 includes a substrate 110 having one end connected to the support portion 101 and the other end connected to the movable portion 103, and four piezoelectric actuators 111 formed on the upper surface of the substrate 110. The substrate 110 has a meander shape that meanders in a direction perpendicular to the rotation axis R12. The thickness of the substrate 110 is constant. The substrate 110 is integrally formed with the support portion 101 from the same material as the support portion 101.

[0060] Four piezoelectric actuators 111 are respectively disposed on the upper surfaces of four regions 110a extending in a direction perpendicular to the rotation axis R12 of the substrate 110. The piezoelectric actuator 111 has a structure in which a piezoelectric body of 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 (driving signal) between the upper electrode and the lower electrode, the piezoelectric actuator 111 (piezoelectric body) expands and contracts. Thereby, the substrate 110 flexes to generate a driving force for driving the movable portion 103.

[0061] The movable portion 103 is supported by a pair of driving portions 102. The movable portion 103 is integrally formed with the substrate 110 and the support portion 101 from the same material as the substrate 110 of the driving portion 102. In a plan view, the movable portion 103 is circular. The shape of the movable portion 103 may also be other shapes such as a square. The thickness of the movable portion 103 is the same as the thickness of the substrate 110. A rib for suppressing warping of the movable portion 103 may be formed on the back surface of the movable portion 103. The second mirror M2 is formed on the upper surface of the movable portion 103. When the reflectivity of the upper surface of the movable portion 103 is high, the upper surface of the movable portion 103 may be the second mirror M2.

[0062] When a driving voltage of the same phase is applied to the odd-numbered piezoelectric actuators 111 starting from the movable portion 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 driving voltage having a phase opposite to that of the driving voltage applied to the odd-numbered piezoelectric actuators 111 is applied to the even-numbered piezoelectric actuators 111 starting from the movable portion 103 side. Thereby, the piezoelectric bodies in the piezoelectric actuators 111 are deformed, and the even-numbered substrates 110 (regions 110a) are deformed in a flexural manner. Thus, by deforming each substrate 110, the movable portion 103 rotates about the rotation axis R12.

[0063] In addition, piezoelectric elements 112 are disposed on the upper surfaces of portions of the substrates 110 of the respective driving portions 102 that are connected to the support portion 101. The piezoelectric element 112 has the same structure as the piezoelectric actuator 111, in which a piezoelectric body is sandwiched between an upper electrode and a lower electrode.

[0064] Figure 3The mirror position detection circuit 45 shown outputs detection signals corresponding to the deformations of these two piezoelectric elements 112, respectively. Here, when the movable part 103 and the second mirror M2 rotate due to the driving of the piezoelectric actuator 111 and, accordingly, the piezoelectric element 112 deforms, based on the piezoelectric effect, a current corresponding to this deformation flows through the piezoelectric element 112. It is known that, generally, the magnitude of the current flowing through 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 corresponds to the rotational position of the second mirror M2, that is, the scanning position of light in the vertical direction.

[0065] Figure 5 is a diagram schematically showing a method for generating the frame image 20 according to the embodiment.

[0066] In Figure 5 for convenience, about 5 scanning lines are shown in the first image area R1, and about 8 scanning lines in total are shown in the second image area R2, but the actual number of scanning lines is much more than this.

[0067] The control unit 41 detects the user's line of sight based on the captured image acquired by the detection unit 6, and acquires the viewpoint position P10 on the frame image 20 based on the detected line of sight. In the first image area R1 including the viewpoint position P10 on the frame image 20 and having a specified number of scanning lines, the control unit 41 causes the light to be scanned at the first scanning speed by the second scanning unit 17. In addition, in the second image area R2 of the frame image 20 other than the first image area R1, the control unit 41 causes the light to be scanned at a second scanning speed faster than the first scanning speed by the second scanning unit 17. The horizontal scanning of the light by the first scanning unit 15 is performed at a constant speed both in the first image area R1 and the second image area R2.

[0068] In addition, the control unit 41 controls the light sources 11a to 11c, the first scanning unit 15, and the second scanning unit 17 so that an image is generated by applying the input high-resolution video signal in the first image area R1. In addition, the control unit 41 controls the light sources 11a to 11c, the first scanning unit 15, and the second scanning unit 17 so that an image is generated by applying a low-resolution video signal obtained by removing scanning lines at intervals from the input high-resolution video signal in the second image area R2. When a low-resolution video signal is input to the control unit 41, scanning lines obtained by interpolating between the scanning lines can be added to generate a high-resolution video signal.

[0069] In addition, the number of scanning lines included in the first image area R1 can also be appropriately changed. In addition, in Figure 5In [the figure], the first image region R1 has the same number of scan lines above and below centered on the viewpoint position P10, but the number of scan lines corresponding to the upper range and the number of scan lines corresponding to the lower range may also be different from each other. In addition, the number of scan lines included in the upper and lower second image regions R2 may also be different from each other.

[0070] In addition, in a case where Figure 5 the scanning speed in the vertical direction is switched according to the user's line of sight as [described], it is necessary to quickly change the configuration and range of the first image region R1 and the second image region R2 according to the change in the user's line of sight. Therefore, it is necessary to quickly and accurately switch the scanning speed in the vertical direction at the boundary between the high-resolution first image region R1 and the low-resolution second image region R2.

[0071] Therefore, in the present embodiment, the mirror position detection circuit 45 is configured to be able to quickly and accurately switch the scanning speed in the vertical direction at the boundary between the first image region R1 and the second image region R2. The control unit 41 uses the signal from the mirror position detection circuit 45 to quickly and accurately set the first image region R1 and the second image region R2 at positions and ranges corresponding to the change in the line of sight, and generates an image based on the high-resolution video signal and an image based on the low-resolution video signal in these first image region R1 and second image region R2, respectively. Hereinafter, this structure and control will be described.

[0072] Figure 6 is a block diagram showing the structure of the mirror position detection circuit 45 according to the embodiment and the circuit units around it. In Figure 6 it, in addition to the mirror position detection circuit 45, the control unit 41, the laser drive circuit 44, the second mirror drive circuit 43, and the second scanning unit 17 are also shown together.

[0073] The mirror position detection circuit 45 includes an I / V converter 451, an edge detection circuit 452, and a counter 453.

[0074] The I / V converter 451 converts the current (hereinafter referred to as "monitoring current") generated by the piezoelectric element 112 of the second scanning unit 17 into a voltage (hereinafter referred to as "monitoring voltage"). The I / V converter 451 outputs the monitoring voltage to the control unit 41 and the edge detection circuit 452, respectively. The control unit 41 converts the monitoring voltage into a digital signal through a built-in A / D converter to perform the processing described later.

[0075] The edge detection circuit 452 detects the inflection points on the voltage waveform of the input monitoring voltage and outputs a pulse signal according to the detection of each inflection point. Here, since the monitoring voltage has the same waveform as the monitoring current, the edge detection circuit 452 detects the inflection points on the current waveform of the monitoring current by means of the monitoring voltage.

[0076] The counter 453 counts the reference clock during the period from the frame start time point to each inflection point. Therefore, each count value of the counter 453 corresponds to the time from the frame start time point to each inflection point. Here, the frame start time point is defined by, for example, the vertical synchronization signal (Vsync) of each frame.

[0077] Figure 7 is a timing chart schematically showing a drive signal, a monitoring current, a monitoring voltage, and a pulse signal equivalent to one frame for driving the second scanning unit 17.

[0078] In Figure 7 the periods corresponding to the first image area R1 and the second image area R2 of Figure 5 are represented as R1 and R2, and the period in which the scanning position returns from the scanning end position in the lower right to the scanning start position in the upper left in the frame image 20 of Figure 5 i.e., the retrace period, is represented as FB. In addition, Figure 7 shows a state in which the first image area R1, the second image area R2, and the retrace period FB in the drive signal are consistent with the first image area R1, the second image area R2, and the retrace period FB in the monitoring current and the monitoring voltage on the time axis.

[0079] When driving the second scanning unit 17 according to the drive signal shown in Figure 7 the piezoelectric element 112 disposed in the second scanning unit 17 expands and contracts, and a monitoring current having a waveform corresponding to the expansion and contraction speed is generated from the piezoelectric element 112. Therefore, the waveform of the monitoring current is a waveform substantially equivalent to the waveform obtained by differentiating the drive signal. In addition, the monitoring voltage is obtained by converting the monitoring current into a voltage, and thus has the same waveform as the monitoring current.

[0080] The pulse signal is output at a moment corresponding to the inflection point of the waveform of the monitoring voltage. Therefore, as shown at the lowermost part of Figure 7 each pulse signal is generated at a change point of the scanning speed in the vertical direction, i.e., at the boundary between the retrace period FB and the period of the first image area R1, and at the boundary between the period of the first image area R1 and the period of the second image area R2.

[0081] Returning to Figure 6 the control unit 41 corrects the drive signal applied to the second scanning unit 17 based on the pulse signal input from the edge detection circuit 452 and the count value (elapsed time from the vertical synchronization signal Vsync) input from the counter 453 at the time of input of the pulse signal.

[0082] Figure 8It is a timing chart schematically showing a correction method for a drive signal applied to the second scanning unit 17.

[0083] The control unit 41 sets target times t1 to t5 corresponding to the boundaries of these periods for the drive signal in order to set a retrace period FB corresponding to the line of sight, a period of the first image area R1, and periods of two second image areas R2 in the drive signal. Then, a drive signal based on these target times t1 to t5 is generated and applied to the second scanning unit 17.

[0084] In addition, Figure 8 shows the drive signal applied to one of the plurality of piezoelectric actuators 111 shown in Figure 4 and the same drive signal is applied to the other piezoelectric actuators 111. A drive signal inverted with respect to the drive signal of Figure 8 is applied to the piezoelectric actuator 111 to which an inverted drive voltage is applied.

[0085] By driving the piezoelectric actuator 111 with such a drive signal, a monitoring current shown in Figure 7 is generated from the piezoelectric element 112. Correspondingly, a monitoring voltage and a pulse signal are output from the I / V converter 451 and the edge detection circuit 452, respectively. At this time, due to factors such as the ambient temperature of the image generation device 3, the actual drive of the second scanning unit 17 may deviate from the reference drive assumed based on the drive signal.

[0086] In Figure 8 the lower part shows the pulse signal output in the case of such a deviation. The dotted pulse signal is the pulse signal output when the second scanning unit 17 performs the reference drive. Here, the actual pulse signal is output at detection times t11 to t15.

[0087] The control unit 41 calculates differences ΔT1 to ΔT5 between the target times t1 to t5 and the detection times t11 to t15, respectively. Then, the control unit 41 sets correction values for the target times t1 to t5 for suppressing these differences ΔT1 to ΔT5, and controls Figure 3 the second mirror drive circuit 43 so as to apply a drive signal corrected according to the set correction values to the second scanning unit 17 in the next frame. Through this feedback control, the differences ΔT1 to ΔT5 are quickly eliminated and the drive of the second scanning unit 17 becomes appropriate.

[0088] Figure 9 (a) of Figure 8 is a diagram showing a flowchart for executing the control of

[0089] When the user's line of sight changes and the viewpoint position P10 changes, the control unit 41 sets the first image area R1 and the second image area R2 based on the changed viewpoint position P10, and correspondingly sets the target times t1 to t5. Then, the control unit 41 sets the initial drive signal applied to the second scanning unit 17 based on the newly set target times t1 to t5, and drives the second scanning unit 17 using the set initial drive signal. Correspondingly, the control unit 41 executes Figure 9 the feedback control of (a), and corrects the drive signal for each frame.

[0090] The control unit 41 determines the detection times t11 to t15 of the respective inflection points (S11) based on the pulse signal input from the edge detection circuit 452 during the current frame scan and the count value input from the counter 453 at this time. Next, the control unit 41 compares the determined detection times t11 to t15 with the above-mentioned target times t1 to t5 (S12), and calculates the differences ΔT1 to ΔT5 between them (S13). Then, the control unit 41 sets the correction values for the target times t1 to t5 for suppressing the differences ΔT1 to ΔT5 (S14), and outputs the drive signal corrected according to the correction values to the second mirror drive circuit 43 as the drive signal for the next frame (S15).

[0091] Before the viewpoint position P10 changes (S16: "No"), the control unit 41 repeats the processing of steps S11 to S15 for each frame. After that, when the viewpoint position P10 changes (S16: "Yes"), the control unit 41 ends Figure 9 the processing of (a). Correspondingly, the control unit 41 sets the initial drive signal based on the new viewpoint position P10 as described above, drives the second scanning unit 17 with the set initial drive signal, and executes Figure 9 the processing of (a) again.

[0092] In the present embodiment, in addition to Figure 9 the correction control of the drive signal of (a), the switching control of the light emission levels of the light sources 11a to 11c is also performed based on the pulse signal output from the edge detection circuit 452.

[0093] Figure 9 (b) of

[0094] is a flowchart showing the switching control of the light emission levels of the light sources 11a to 11c. When the control unit 41 is input with a pulse signal from the edge detection circuit 452, it determines whether the pulse signal is a pulse signal indicating the start time of the period corresponding to the first image area R1 or the second image area R2 (S21). For example, the control unit 41 determines which arrival the pulse signal is from the vertical synchronization signal Vsync.

[0095] As Figure 7 shown, when the control unit 41 receives the second pulse signal from the vertical synchronization signal Vsync, the control unit 41 determines that the start time of the first second image region R2 has arrived. Similarly, when the control unit 41 receives the third and fourth pulse signals from the vertical synchronization signal Vsync respectively, the control unit 41 determines that the start times of the first image region R1 and the second second image region R2 have arrived respectively.

[0096] When the control unit 41 determines that the start time of the first image region R1 or the second image region R2 has arrived (S21: "Yes"), it switches the light emission levels of the light sources 11a to 11c to the light emission levels suitable for the arrived image region (S22). That is, the first scanning speed in the vertical direction in the first image region R1 is slower than the second scanning speed in the vertical direction in the second image region R2. Therefore, when the image is displayed with the same brightness in the first image region R1 and the second image region R2, the control unit 41 sets the light emission levels of the light sources 11a to 11c when the light is scanned in the first image region R1 to be lower than the light emission levels of the light sources 11a to 11c when the light is scanned in the second image region R2.

[0097] Here, the control unit 41 sets the light emission levels of each image region by making the light emission intensities (maximum light emission intensities) of the light sources 11a to 11c corresponding to the highest gray level of the video signal different for each image region. That is, the maximum light emission intensities of the light sources 11a to 11c when the light is scanned in the first image region R1 are set to be lower than the maximum light emission intensities of the light sources 11a to 11c when the light is scanned in the second image region R2, so that the brightness of the entire frame image 20 is equal. The maximum light emission intensities of such light sources can be held in advance by the control unit 41 corresponding to the first image region R1 and the second image region (i.e., the scanning speed in the vertical direction).

[0098] When the light emission levels are switched in this way, the control unit 41 determines whether one frame period has ended (S23). Step S23 is determined, for example, based on whether the last pulse signal (the fifth pulse signal) among the five pulse signals shown in Figure 7 is received. When the frame period has not ended (S23: "No"), the control unit 41 returns the process to step S21 and repeats the same process. Thus, whenever the start time of a newly arrived image region (the first image region R1, the second image region R2) arrives, the light emission levels of the light sources 11a to 11c are switched.

[0099] After that, when one frame period ends (S23: "Yes"), the control unit 41 ends Figure 9Processing of (b). Accordingly, the control unit 41 executes again Figure 9 the processing of (b), and sequentially switches the emission levels of the light sources 11a to 11c by the same processing as described above.

[0100] In addition, the emission levels during the scanning periods of the first image area R1 and the second image area R2 can also be set based on the voltage levels of the monitoring voltages during the scanning periods of the first image area R1 and the second image area R2 (corresponding to the current levels during the respective scanning periods of the monitoring current generated from the piezoelectric element 112).

[0101] That is, as Figure 7 shown, the voltage levels of the monitoring voltages during the scanning periods of the first image area R1 and the second image area R2 correspond to the scanning speeds in the vertical direction during the respective scanning periods. As described above, the emission levels of the light sources 11a to 11c are switched according to the differences in the scanning speeds in the vertical direction. Therefore, the emission levels of the light sources 11a to 11c can also be switched based on the voltage levels of the monitoring voltages during the scanning periods of the first image area R1 and the second image area R2.

[0102] In this case, for example, in the control unit 41, there are held Figure 10 the horizontal setting tables shown in (a) to (c) for each of the light sources 11a, 11b, and 11c (red light source, green light source, and blue light source).

[0103] In each table, the voltage levels of the monitoring voltages correspond to the emission intensities (maximum emission intensities) of the light sources 11a to 11c at the highest gray level of the image signals of each color. In one table, a set of the monitoring voltage levels and the maximum emission intensities is set such that when the light is scanned at the scanning speed in the vertical direction corresponding to each of the monitoring voltage levels, the light sources emit light at the maximum emission intensities corresponding to the monitoring voltage levels, and the same brightness (light amount per unit area) is obtained. In addition, the maximum emission intensities are adjusted between the tables so that the light amount balance between the colors is appropriate.

[0104] During the vertical scanning in the current frame period, the control unit 41 detects the voltage levels of the monitoring voltages during the scanning periods of the first image area R1 and the second image area R2. Then, the control unit 41 starts from Figure 10Extract the luminous intensity (maximum luminous intensity) of the highest gray level corresponding to the detected voltage level from the horizontal setting tables of the respective light sources (each color) shown in (a) to (c). For example, the control unit 41 determines the voltage level closest to the detected voltage level in the horizontal setting table, and extracts the maximum luminous intensity corresponding to the determined voltage level from the horizontal setting table. Then, the control unit 41 applies the extracted maximum luminous intensities to the light sources 11a to 11c respectively, and causes the laser drive circuit 44 to drive the light sources 11a to 11c.

[0105] In addition, in this control, if the scanning in the vertical direction in the first image region R1 and the second image region R2 does not start, the voltage level of the monitoring voltage cannot be detected. Therefore, it is difficult to set the luminous levels of the light sources 11a to 11c based on the voltage level of the monitoring voltage without delay during the current frame period. Therefore, in this control, it is preferable to use the voltage level of the monitoring voltage detected during the scanning period of each image region in the current frame period during the next frame period, and apply the maximum luminous intensity during the scanning period of the corresponding image region to the light sources 11a to 11c from the horizontal setting tables of (a) to (c). Figure 10 Apply the maximum luminous intensity during the scanning period of the corresponding image region to the light sources 11a to 11c from the horizontal setting tables of (a) to (c).

[0106] According to this control, the luminous levels of the light sources 11a to 11c are set according to the voltage level actually generated under the monitoring voltage, that is, the actual scanning speed in the vertical direction. Therefore, it is possible to apply a luminous level more suitable for actual operation to the light sources 11a to 11c. Therefore, it is possible to more appropriately equalize the brightness of the entire frame image 20.

[0107] <Effects of the Embodiment>

[0108] According to the above embodiment, the following effects are achieved.

[0109] As Figure 6 shown, the image generation device 3 includes: light sources 11a to 11c; a second scanning unit 17 that scans the light emitted from the light sources 11a to 11c; a control unit 41 that controls the light sources 11a to 11c and the second scanning unit 17 based on an image signal; a piezoelectric element 112 that is disposed in the second scanning unit 17 and expands and contracts in response to the scanning of the light; and an edge detection circuit 452 that detects an inflection point on the current waveform (monitoring current) generated from the piezoelectric element 112. The control unit 41 corrects the drive signal for switching the scanning speed of the light based on the detection time of the inflection point detected by the edge detection circuit 452.

[0110] According to this structure, as Figure 8As shown, the change point of the light scanning speed can be detected based on the detection times t11 to t15 of the inflection points (pulse signals) on the current waveform (monitoring current) generated from the piezoelectric element 112. Therefore, the actual change point of the light scanning speed (detection times t11 to t15) can be detected within one frame period, and the drive signal for the next frame can be corrected quickly and accurately based on the detection times t11 to t15 of the inflection points (pulse signals). Therefore, the scanning speed of the light for image generation can be switched quickly and accurately at the target times t1 to t5.

[0111] As referred to Figure 8 and Figure 9 As described in (a) of, the control unit 41 sets the correction value of the drive signal for the next frame ( Figure 9 step S15 of (a) of) based on the differences ΔT1 to ΔT5 between the detection times t11 to t15 of the inflection points (pulse signals) and the target times t1 to t5 for switching the scanning speed. Thereby, the drive signal can be corrected quickly and accurately in a manner that eliminates the differences ΔT1 to ΔT5.

[0112] As Figure 9 shown in (b) of, the control unit 41 switches the light emission levels of the light sources 11a to 11c (S22) based on the detection times t12 to t14 of the inflection points (pulse signals) (S21: "Yes"). Thereby, the light emission levels of the light sources 11a to 11c can be smoothly switched to the light emission levels suitable for the scanning speed in the vertical direction of the first image region R1 and the second image region R2.

[0113] As referred to Figure 10 As described in (a) to (c) of, the control unit 41 sets the light emission levels of the light sources 11a to 11c within each scanning period based on the current levels (voltage levels equivalent to the monitoring voltage) of the current waveform (voltage waveform equivalent to the monitoring voltage) generated from the piezoelectric element 112 corresponding to each scanning period of the first image region R1 and the second image region R2. According to this control, as described above, the light emission levels of the light sources 11a to 11c are set according to the actual current levels (voltage levels of the monitoring voltage), that is, the actual scanning speed in the vertical direction. Therefore, the light emission levels more suitable for the actual operation can be applied to the light sources 11a to 11c. Therefore, the brightness of the entire frame image 20 can be more appropriately uniformized.

[0114] As Figure 4 shown, the piezoelectric element 112 is disposed in the second scanning unit 17 to detect the scanning position of the light in the vertical direction. As referred to Figures 6 - 8As described above, the control unit 41 corrects the drive signal for switching the scanning speed of light in the vertical direction based on the detection times t11 to t15 of the inflection points (pulse signals) in the edge detection circuit 452, and applies it to the scanning for the next frame. Thus, in the next frame, the scanning for the blanking period FB, the first image area R1, and the two second image areas R2 can be appropriately performed, and the scanning speed of the light for image generation can be quickly and accurately switched at the target times t1 to t5.

[0115] <Modified Example>

[0116] In the above-described embodiment, when the user's line of sight changes, the first image area R1 and the second image area R2 are set according to the changed viewpoint position P10, and the target times t1 to t5 are set accordingly. Moreover, the initial drive signal after the line of sight changes is set based on the newly set target times t1 to t5, and then, through Figure 8 and Figure 9 the feedback control shown in (a) of, the drive signal is corrected for each frame.

[0117] In contrast, in this modified example, a temperature sensor for detecting the ambient temperature of the image generation device 3 is also provided. Moreover, the control unit 41 holds table information in which representative values of the differences ΔT1 to ΔT5 at each temperature are associated with the respective temperatures. After the line of sight changes, the control unit 41 extracts the representative value corresponding to the temperature detected by the temperature sensor from the table information, and sets the initial drive signal based on the extracted representative value and the target times.

[0118] Figure 11 is a block diagram showing the structure of the mirror position detection circuit 45 and the surrounding circuit parts according to the modified example.

[0119] As Figure 11 shown, the image generation device 3 further includes a temperature sensor 46. The temperature sensor 46 detects the ambient temperature of the image generation device 3 and outputs it to the control unit 41. The control unit 41 holds table information in which the temperature is associated with the representative value of the difference. After the line of sight changes, the control unit 41 sets the initial drive signal in the feedback control based on the temperature detected by the temperature sensor 46 and the table information.

[0120] Figure 12 (a) of is a diagram showing the structure of the table information for setting the initial drive signal according to the modified example.

[0121] The table information is configured to correspond to the representative value of the difference for each temperature. The representative value of the difference is obtained by performing Figure 9The representative value of the difference initially generated in the case of feedback control of (a). This representative value can be obtained, for example, by the following method: while setting various target times at the corresponding ambient temperature, performing the above feedback control, and performing statistical processing or learning processing on the initially generated difference at that time. In the case of statistical processing, the representative value is obtained as the average, median, or mode of these differences, etc. When the representative value is positive, a difference is generated in the forward direction of time, and when the representative value is negative, a difference is generated in the backward direction of time.

[0122] The representative value of the difference can be set uniformly for all target times. In this case, at the corresponding ambient temperature, the initially obtained differences for all target times are provided for statistical processing or learning processing, and a unified representative value is set for all target times.

[0123] Alternatively, the representative value of the difference can also be set for each sequential item of the target time. For example, in the case where five target times are set in the drive signal as Figure 8 such, representative values of the difference are set for each of the first to fifth sequential items. In this case, the above-mentioned statistical processing or learning processing is performed separately for each sequential item, and representative values are set for each sequential item. Therefore, in the control unit 41, table information of (a) is held for each sequential item. Figure 12 of (a).

[0124] Figure 12 (b) shows a flowchart of the process in the case of setting an initial drive signal using the table information.

[0125] When the viewpoint position P10 of the user changes (S31: "Yes"), the control unit 41 sets the first image area R1 and the second image area R2 according to the changed viewpoint position P10, and accordingly sets the target times t1 to t5 (S32). Next, the control unit 41 obtains the ambient temperature from the temperature sensor 46, and obtains the representative value corresponding to the obtained temperature from the table information (the representative value corresponding to the temperature closest to the obtained temperature). Then, the control unit 41 corrects the target times t1 to t5 according to the obtained representative value (S34).

[0126] In step S34, the control unit 41 subtracts the representative value from the target times t1 to t5 to obtain the corrected target times t1' to t5'. Therefore, when the representative value is negative, the absolute value of the representative value is added to the target times t1 to t5 to calculate the corrected target times t1' to t5'.

[0127] As described above, when the representative values ΔTtv are uniformly set for all target times t1 to t5, the representative value Ttv is subtracted from each of the target times t1 to t5 to calculate the corrected target times t1' to t5'. Further, when the representative values ΔTtv1 to ΔTtv5 are set for each of the target times t1 to t5, the representative values ΔTtv1 to ΔTtv5 are subtracted from the target times t1 to t5 respectively to calculate the corrected target times t1' to t5'.

[0128] The control unit 41 sets an initial drive signal using the corrected target times t1' to t5', and causes the second scanning unit 17 to perform scanning based on the set initial drive signal (S35). Thus, after the second scanning unit 17 starts scanning, the control unit 41 executes Figure 9 the feedback control of (a) of

[0129] According to the control of the modification example, feedback control is performed based on the initial drive signal suitable for the ambient temperature at that time, and thus it is possible to suppress Figure 8 the initial differences ΔT1 to ΔT5 shown in Figure 8 That is, the drive characteristics of the second scanning unit 17 can vary according to changes in the ambient temperature. Therefore, when the initial drive signal is set based on the fixed target times t1 to t5, the monitoring current and monitoring voltage obtained when driving with that drive signal may deviate in time from the ideal waveform according to changes in the ambient temperature. Thus,

[0130] In contrast, according to the control of this modification example, the target times t1 to t5 are corrected based on the above-described representative values corresponding to the ambient temperature at that time. That is, the difference (representative value) that may occur at this ambient temperature is subtracted from the target times t1 to t5 to calculate the corrected target times t1' to t5'. Therefore, the initial drive signal set based on the corrected target times t1' to t5' is likely to be suitable for the drive characteristics of the second scanning unit 17 at the ambient temperature at that time. Therefore, compared with the case where the initial drive signal is set based on the target times t1 to t5 as in the above-described embodiment, the initial differences ΔT1 to ΔT5 generated in the feedback control are suppressed a lot. As a result, in the subsequent feedback control, the differences ΔT1 to ΔT5 can be eliminated more quickly. Therefore, it is possible to display an image more stably and quickly in the first image area R1 and the second image area R2.

[0131] In addition, Figure 12The table information in (a) can also be further updated based on the differences ΔT1 to ΔT5 initially generated in the feedback control. That is, in the table information, the representative value corresponding to the ambient temperature during feedback control can also be further updated by a process using the differences ΔT1 to ΔT5 initially generated in the feedback control.

[0132] For example, when representative values ΔTtv1 to ΔTtv5 are set in the order of target times t1 to t5, new representative values ΔTtv1 to ΔTtv5 can also be set by subtracting the values obtained by multiplying the initially generated differences ΔT1 to ΔT5 by coefficients less than 1 from the representative values ΔTtv1 to ΔTtv5. Additionally, when a representative value Ttv is uniformly set for the target times t1 to t5, a new representative value ΔTtv can also be set by subtracting the value obtained by multiplying the average of the initially generated differences ΔT1 to ΔT5 by a coefficient less than 1 from the representative value ΔTtv. Thus, even when the temperature characteristics of the second scanning unit 17 change due to aging, the representative value can be set to a value corresponding to the temperature characteristics at that time.

[0133] <Other modification examples>

[0134] In the above-described embodiment, as Figure 4 shown, the piezoelectric element 112 is disposed at the connection portion of the drive unit 102 connected to the support unit 101, but the arrangement position of the piezoelectric element 112 is not limited thereto. The piezoelectric element 112 may be arranged at a position where the rotational position (light scanning position) of the second mirror M2 can be appropriately detected.

[0135] Further, in the above-described embodiment, feedback control using a pulse signal is shown for one of the two drive signals that are in antiphase, but the same control may also be performed for the other drive signal. In this case, one piezoelectric element 112 is arranged at a position where a monitoring current corresponding to one drive signal is generated, and the other piezoelectric element 112 is arranged at a position where a monitoring current corresponding to the other drive signal is generated. Alternatively, the drive signal may be corrected by feedback control based on the monitoring current corresponding to one drive signal, and the corrected drive signal may be inverted to generate the other drive signal.

[0136] Furthermore, in the above-described embodiment, 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 arranged at the drive unit that rotates the mirror in the vertical direction.

[0137] In addition, in the above-described embodiment, the control of the present invention is applied to the vertical scanning of light. However, when the scanning speed of light is switched in the horizontal direction, the control of the present invention can also be applied to the horizontal scanning of light. 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 Figure 6 the I / V converter 451.

[0138] 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. However, the image generation device to which the present invention is applied is not limited thereto. The feedback control according to the present invention can also be used for various devices as long as the current output from the piezoelectric element based on the piezoelectric effect is used.

[0139] The embodiments of the present invention can be appropriately modified in various ways within the scope of the technical idea shown in the claims.

[0140] (Supplementary Note)

[0141] Through the description of the above embodiments, the following technologies are disclosed.

[0142] (Technology 1)

[0143] An image generation device, characterized by comprising:

[0144] A light source;

[0145] A scanning unit that scans the light emitted from the light source;

[0146] A control unit that controls the light source and the scanning unit based on an image signal;

[0147] A piezoelectric element disposed in the scanning unit and expanding and contracting in response to the scanning of the light; and

[0148] An edge detection circuit that detects an inflection point on the current waveform generated from the piezoelectric element,

[0149] wherein the control unit corrects a drive signal for switching the scanning speed of the light based on the detection time of the inflection point detected in the edge detection circuit.

[0150] According to this technology, it is possible to detect the change point of the light scanning speed based on the detection time of the inflection point on the current waveform generated from the piezoelectric element. Therefore, it is possible to detect the actual change point of the light scanning speed during one frame, and it is possible to quickly and accurately correct the drive signal applied to the next frame based on the detection time of the inflection point. Therefore, it is possible to quickly and accurately switch the scanning speed of the light for image generation.

[0151] (Technology 2)

[0152] The image generation device according to Technology 1 is characterized in that

[0153] The control unit sets a correction value for the drive signal for the next frame based on the difference between the detection time of the inflection point and the target time for switching the scanning speed.

[0154] According to this technology, the drive signal can be corrected quickly and accurately in a way that eliminates the difference.

[0155] (Technology 3)

[0156] The image generation device according to Technology 2 is characterized in that

[0157] It is equipped with a temperature sensor that detects the ambient temperature of the image generation device.

[0158] The control unit performs the following processing:

[0159] Maintain table information in which representative values of the differences at each temperature are associated with the respective temperatures;

[0160] Extract the representative value corresponding to the temperature detected by the temperature sensor from the table information; and

[0161] Set the initial drive signal based on the extracted representative value and the target time.

[0162] According to this technology, an initial drive signal suitable for the ambient temperature at that time is set, so the drive signal applied to the next frame can be corrected more quickly based on the detection time of the inflection point.

[0163] (Technology 4)

[0164] The image generation device according to any one of Technologies 1 to 3 is characterized in that

[0165] The control unit switches the light emission level of the light source based on the detection time of the inflection point.

[0166] According to this technology, the light emission level of the light source can be smoothly switched to a light emission level suitable for the scanning speed.

[0167] (Technology 5)

[0168] The image generation device according to any one of Technologies 1 to 4 is characterized in that

[0169] The control unit sets the light emission level of the light source during each scanning period based on the current level within each scanning period of the current waveform generated from the piezoelectric element.

[0170] According to this technique, the light emission level of the light source is set based on the actually generated current level under the monitored current, that is, the actual scanning speed. Therefore, a light emission level more suitable for the actual operation can be applied to the light source. As a result, the brightness of the entire image can be more appropriately uniformized.

[0171] (Technique 6)

[0172] The image generation device according to any one of Techniques 1 to 5, characterized in that

[0173] The piezoelectric element is arranged to detect the scanning position of light in the vertical direction,

[0174] The control unit corrects the drive signal for switching the scanning speed of the light in the vertical direction based on the detection time of the inflection point detected in the edge detection circuit.

[0175] According to this technique, the scanning speed of light in the vertical direction can be switched quickly and accurately.

[0176] Explanation of reference numerals

[0177] 3: Image generation device; 11a to 11c: Light source; 17: Second scanning unit (scanning unit); 41: Control unit; 46: Temperature sensor; 112: Piezoelectric element; 452: Edge detection circuit; t1 to t5: Target times; t11 to t15: Detection times; ΔT1 to ΔT5: Differences.

Claims

1. An image generation device, characterized in that, Comprising: A light source; A scanning unit that scans the light emitted from the light source; A control unit that controls the light source and the scanning unit based on an image signal; A piezoelectric element disposed in the scanning unit that expands and contracts in response to the scanning of the light; And An edge detection circuit that detects an inflection point on the current waveform generated by the piezoelectric element, wherein the control unit corrects a drive signal for switching the scanning speed of the light based on the detection time of the inflection point detected in the edge detection circuit.

2. The image generation device according to claim 1, wherein the control unit sets a correction value for the drive signal for the next frame based on the difference between the detection time of the inflection point and a target time for switching the scanning speed.

3. The image generation device according to claim 2, wherein a temperature sensor is provided, the temperature sensor detects the ambient temperature of the image generation device, and the control unit performs the following processing: Maintaining table information in which representative values of the differences at each temperature are associated with the respective temperatures; Extracting the representative value corresponding to the temperature detected by the temperature sensor from the table information; And Setting the initial drive signal based on the extracted representative value and the target time.

4. The image generation device according to claim 1, wherein the control unit switches the light emission level of the light source based on the detection time of the inflection point.

5. The image generation device according to claim 1, wherein the control unit sets the light emission level of the light source during each scanning period based on the current level during each scanning period of the current waveform generated by the piezoelectric element.

6. The image generation device according to claim 1, wherein the piezoelectric element is disposed to detect the scanning position of the light in the vertical direction, and the control unit corrects a drive signal for switching the scanning speed of the light in the vertical direction based on the detection time of the inflection point detected in the edge detection circuit.

Images