Image forming apparatus and method of operating same

Abstract

To provide an image forming apparatus that can prevent disturbance of an image, and a method for actuating the same.SOLUTION: An image forming apparatus comprises: a light-emitting device that emits light; a movable mirror that reflects the light emitted from the light-emitting device; a first actuator that causes the movable mirror to oscillate around a first axis; a first reference signal output unit that estimates the time when the deflection angle around the first axis of the movable mirror becomes a first reference angle and outputs a first reference signal; a light emission control unit that causes the light-emitting device to emit light based on the first reference signal output from the first reference signal output unit; an imaging apparatus that picks up an image of the light reflected by the movable mirror; and a correction unit that, based on imaging information acquired by the imaging apparatus, corrects the timing of the first reference signal output by the first reference signal output unit.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The disclosed techniques relate to image forming devices and methods of operation thereof. [Background technology]

[0002] There is known an image forming apparatus that draws an image on a screen or the like by irradiating light to an optical scanning device configured by MEMS (Micro Electro Mechanical Systems). The optical scanning device includes a movable mirror that oscillates around two orthogonal axes. For example, the optical scanning device performs Lissajous scanning with light that has been intensity-modulated according to an input image. The movable mirror is resonantly driven by two sine waves with different frequencies. In Lissajous scanning, the movable mirror is resonantly driven around two axes, which has the advantage that the deflection angle is large and the light scanning range can be enlarged.

[0003] To draw an image using this optical scanning device, it is necessary to accurately estimate the deflection angle of the movable mirror when it is oscillating, and to irradiate the movable mirror with light of a predetermined intensity according to the estimated deflection angle. If the estimation accuracy of the deflection angle of the movable mirror is low, the image drawn by the optical scanning device will be distorted. For example, the image drawn by the optical scanning device will be distorted due to a difference in irradiation timing between the forward and backward swings of the movable mirror.

[0004] Patent Document 1 discloses a configuration in which a distortion sensor is provided within an optical scanning device, and the deflection angle of a movable mirror is estimated based on a sensor signal from the distortion sensor.

[0005] Furthermore, Patent Document 2 discloses a method for measuring the projection distance by projecting and capturing a measurement image, and correcting the position of the image for calibration by projecting a calibration image based on the measured projection distance. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] U.S. Patent No. 8,559,086 [Patent Document 2] JP 2020-39082 A Summary of the Invention [Problem to be solved by the invention]

[0007] The deflection angle of the movable mirror can be estimated by the strain sensor described in Patent Document 1, as well as by a drive signal for driving the movable mirror, or an angle sensor formed of a piezoelectric element.

[0008] However, since a time delay occurs in the drive signal or the sensor signal due to noise or the like, it is difficult to accurately estimate the deflection angle of the movable mirror.

[0009] Furthermore, Patent Document 2 describes a method of performing calibration by projecting a calibration image to match positions on an image displayed on a display surface with positions on a captured image, but this does not correct the projection timing by the projection unit.

[0010] An object of the technique disclosed herein is to provide an image forming apparatus capable of suppressing image distortion, and an operating method thereof. [Means for solving the problem]

[0011] In order to achieve the above-mentioned object, the image forming apparatus of the present disclosure includes a light-emitting device that emits light, a movable mirror that reflects the light emitted from the light-emitting device, a first actuator that oscillates the movable mirror around a first axis, a first reference signal output unit that estimates the point in time when the deflection angle of the movable mirror around the first axis becomes a first reference angle and outputs a first reference signal, a light-emitting control unit that causes the light-emitting device to emit light based on the first reference signal output from the first reference signal output unit, an imaging device that captures the light reflected by the movable mirror, and a correction unit that corrects the timing of the first reference signal output by the first reference signal output unit based on imaging information acquired by the imaging device.

[0012] It is preferable that the imaging device further comprises a second actuator which swings the movable mirror around the second axis, and a second reference signal output unit which estimates the time when the deflection angle of the movable mirror around the second axis becomes the second reference angle and outputs a second reference signal, and the correction unit corrects the timing of the first reference signal output by the first reference signal output unit and the timing of the second reference signal output by the second reference signal output unit based on imaging information captured by the imaging device.

[0013] It is preferable that the first reference angle is an angle at which the deflection angle of the movable mirror about the first axis is zero, and the second reference angle is an angle at which the deflection angle of the movable mirror about the second axis is zero.

[0014] It is preferable that the first reference angle is the angle at which the deflection angle of the movable mirror about the first axis is maximum or minimum, and the second reference angle is the angle at which the deflection angle of the movable mirror about the second axis is maximum or minimum.

[0015] It is preferable that the first reference signal output unit estimates the point in time when the deflection angle of the movable mirror about the first axis becomes the first reference angle based on the first drive signal applied to the first actuator, and the second reference signal output unit estimates the point in time when the deflection angle of the movable mirror about the second axis becomes the second reference angle based on the second drive signal applied to the second actuator.

[0016] It is preferable to provide an optical element on the optical path of the light reflected by the movable mirror for directing a part of the light to the imaging device.

[0017] The operating method of the image forming apparatus disclosed herein is a method for operating an optical scanning device including a light-emitting device that emits light, a movable mirror that reflects the light emitted from the light-emitting device, a first actuator that swings the movable mirror around a first axis, a first reference signal output unit that estimates the point in time when the deflection angle of the movable mirror around the first axis becomes a first reference angle and outputs a first reference signal, an emission control unit that causes the light-emitting device to emit light based on the first reference signal output from the first reference signal output unit, and an imaging device that images the light reflected by the movable mirror, and includes correcting the timing of the first reference signal output by the first reference signal output unit based on imaging information acquired by the imaging device. Effect of the Invention

[0018] According to the technique of the present disclosure, it is possible to provide an image forming apparatus capable of suppressing image distortion, and an operating method thereof. [Brief description of the drawings]

[0019] [Figure 1] FIG. 1 is a schematic diagram illustrating an example of a configuration of an image forming apparatus. [Diagram 2] FIG. 1 is a schematic perspective view showing an example of the configuration of a MEMS mirror. [Diagram 3] 5A and 5B are diagrams for explaining the deflection angle when the mirror portion swings, in which (A) shows a first deflection angle and (B) shows a second deflection angle. [Figure 4] FIG. 2 is a block diagram showing an example of a functional configuration of a control device. [Diagram 5] 4A to 4C are diagrams illustrating an example of a first drive signal, a first zero-cross signal, and a first reference signal. [Figure 6] 5A to 5C are diagrams illustrating an example of a second drive signal, a second zero-cross signal, and a second reference signal. [Figure 7] FIG. 13 is a diagram illustrating an example of an LUT. [Figure 8] 13A and 13B are diagrams illustrating an example of a pattern drawn on a projection surface in a calibration mode. [Figure 9]13 is a diagram showing an example of a pattern drawn on a projection surface when a timing difference occurs between the oscillation of a mirror section and the timing of a first reference signal and a second reference signal. FIG. [Figure 10] FIG. 4 illustrates an example of a functional configuration of a correction unit. [Figure 11] 5A and 5B are diagrams showing an example of timing correction by a signal correction unit, in which (A) shows an example of correcting the timing of a first reference signal, and (B) shows an example of correcting the timing of a second reference signal. [Figure 12] FIG. 11 is a diagram showing a first modified example relating to the position setting of the first reference line and the second reference line. [Figure 13] FIG. 11 is a diagram showing a second modified example relating to the setting of the positions of the first reference line and the second reference line. [Figure 14] FIG. 13 is a diagram showing an example in which laser light is irradiated only once within one scanning period of Lissajous scanning. [Figure 15] FIG. 13 is a diagram illustrating a first modified example of an image forming apparatus. [Figure 16] FIG. 13 is a diagram illustrating a second modified example of the image forming apparatus. [Figure 17] 13 is a diagram showing an example in which the first reference angle is set to the angle at which the first deflection angle is maximum or minimum, and the second reference angle is set to the angle at which the second deflection angle is maximum or minimum. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Hereinafter, an embodiment of the technology of the present disclosure will be described in detail with reference to the drawings. As an example, in the following embodiment, a form in which the technology of the present disclosure is applied to an image forming apparatus that forms an image on a projection surface by scanning a laser beam using the Lissajous method will be described.

[0021] Fig. 1 shows an example of the configuration of an image forming apparatus 10 of this embodiment. As shown in Fig. 1, the image forming apparatus 10 of this embodiment includes a control device 20, a MEMS driver 22, a light emitting device 24, a beam combining optical system 26, a collimator 28, a MEMS mirror 30, and an imaging device 32. The MEMS mirror 30 is an example of an "optical scanning device" according to the technology of the present disclosure.

[0022] The light emitting device 24 has a laser driver 25 and a laser light source 27. The laser driver 25 of this embodiment drives the laser light source 27 based on an intensity modulation signal supplied from the control device 20, and causes the laser light source 27 to output laser light for forming an image. The laser light source 27 outputs laser light of three colors, for example, R (Red), G (Green), and B (B: Blue). Note that the laser light is an example of "light" according to the technology of the present disclosure.

[0023] The laser light output from the laser light source 27 is multiplexed by the multiplexing optical system 26, and then irradiated onto the MEMS mirror 30 via the collimator 28. The laser light focused on the MEMS mirror 30 is reflected by the MEMS mirror 30 toward a projection surface 34. The projection surface 34 is, for example, a screen for projecting an image, or the retina of a human eye. That is, the image forming apparatus 10 of this embodiment is used in a projector, AR (Augmented Reality) glasses, or the like.

[0024] In this embodiment, the projection surface 34 is not limited to the surface of an actual object such as a screen, but also includes a virtual surface in space.

[0025] The MEMS driver 22 drives the MEMS mirror 30 based on the control from the control device 20. In the MEMS mirror 30, a mirror section 40 (see FIG. 2) that reflects the laser light L oscillates independently around two mutually orthogonal axes as central axes. In this embodiment, the mirror section 40 oscillates based on a drive signal, so that the laser light L scans the projection surface 34 in a state in which it draws a Lissajous curve. The Lissajous curve is a curve determined by the oscillation frequency around the first axis, the oscillation frequency around the second axis, and the phase difference between them. The mirror section 40 is an example of a "movable mirror" according to the technology disclosed herein.

[0026] The control device 20 of this embodiment includes an FPGA (Field Programmable Gate Array) 20A and a memory 20B. The memory 20B is, for example, a volatile memory, and stores various information such as an image signal representing an image to be projected onto the projection surface 34. The memory 20B stores, for example, an image signal input from outside the image forming apparatus 10.

[0027] The imaging device 32 captures an image of the projection surface 34 irradiated with the laser light L by the MEMS mirror 30, thereby generating a captured image IP, and outputs the generated captured image IP to the control device 20. The imaging device 32 is composed of an image sensor such as a CCD (Charge Coupled Device) type image sensor or a CMOS (Complementary Metal Oxide Semiconductor) type image sensor. The imaging device 32 may also be composed of a PSD (Position Sensitive Detector). The captured image IP is used to correct the timing of a first reference signal and a second reference signal, which will be described later. The captured image IP is an example of "imaging information" according to the technology of the present disclosure.

[0028] 2 shows an example of the configuration of the MEMS mirror 30. The MEMS mirror 30 has a mirror section 40, a first supporting section 41, a first movable frame 42, a second supporting section 43, a second movable frame 44, a connecting section 45, and a fixed frame 46.

[0029] The mirror section 40 has a reflecting surface 40A that reflects incident light. The reflecting surface 40A is formed of a metal thin film such as gold (Au), aluminum (Al), silver (Ag), a silver alloy, etc. The shape of the reflecting surface 40A is, for example, a circular shape.

[0030] The first support parts 41 are disposed on the outer sides of the mirror part 40 at positions facing each other across the second axis a2. The first support parts 41 are connected to the mirror part 40 on the first axis a1, and support the mirror part 40 so that it can swing around the first axis a1.

[0031] The first movable frame 42 is a rectangular frame surrounding the mirror section 40, and is connected to the mirror section 40 on the first axis a1 via a first support section 41. Piezoelectric elements 50 are formed on the first movable frame 42 at positions facing each other across the first axis a1. In this manner, the two piezoelectric elements 50 are formed on the first movable frame 42, thereby constituting a pair of first actuators 51.

[0032] The pair of first actuators 51 are disposed at positions facing each other across the first axis a1. The first actuators 51 apply a rotational torque about the first axis a1 to the mirror section 40, thereby causing the mirror section 40 to swing about the first axis a1.

[0033] The second support parts 43 are disposed on the outer side of the first movable frame 42 at positions facing each other across the first axis a1. The second support parts 43 are connected to the first movable frame 42 on the second axis a2, and support the first movable frame 42 and the mirror part 40 so that they can swing around the second axis a2. In this embodiment, the second support parts 43 are torsion bars extending along the second axis a2.

[0034] The second movable frame 44 is a rectangular frame surrounding the first movable frame 42, and is connected to the first movable frame 42 on the second axis a2 via the second support portion 43. Piezoelectric elements 50 are formed on the second movable frame 44 at positions facing each other across the second axis a2. In this manner, the two piezoelectric elements 50 are formed on the second movable frame 44, thereby constituting a pair of second actuators 52.

[0035] The pair of second actuators 52 are disposed at positions facing each other across the second axis a2. The second actuators 52 apply a rotational torque about the second axis a2 to the mirror section 40 and the first movable frame 42, thereby causing the mirror section 40 to swing about the second axis a2.

[0036] The connection portions 45 are disposed on the outer side of the second movable frame 44 at positions facing each other across the first axis a1. The connection portions 45 are connected to the second movable frame 44 on the second axis a2.

[0037] The fixed frame 46 is a rectangular frame body that surrounds the second movable frame 44, and is connected to the second movable frame 44 via a connection portion 45 on the second axis a2.

[0038] In this embodiment, the first axis a1 and the second axis a2 are perpendicular to each other. In the following description, the direction parallel to the first axis a1 is the X direction, the direction parallel to the second axis a2 is the Y direction, and the direction perpendicular to the first axis a1 and the second axis a2 is the Z direction.

[0039] Fig. 3 explains the deflection angle when the mirror section 40 swings. Fig. 3(A) shows the deflection angle θ1 around the first axis a1 of the mirror section 40 (hereinafter referred to as the first deflection angle). Fig. 3(B) shows the deflection angle θ2 around the second axis a2 of the mirror section 40 (hereinafter referred to as the second deflection angle).

[0040] The first deflection angle θ1 is an angle at which the normal to the reflecting surface 40A is inclined with respect to the Z direction in the YZ plane. The second deflection angle θ2 is an angle at which the normal to the reflecting surface 40A is inclined with respect to the Z direction in the XZ plane.

[0041] Fig. 4 shows an example of the functional configuration of the control device 20. As shown in Fig. 4, the control device 20 includes an image input unit 60, an information generation unit 61, an information storage unit 62, a first reference signal output unit 63A, a second reference signal output unit 63B, a light emission control unit 64, a correction unit 65, a table holding unit 66, and a humidity and temperature sensor 67. The image input unit 60, the information generation unit 61, the information storage unit 62, the first reference signal output unit 63A, the second reference signal output unit 63B, the light emission control unit 64, the correction unit 65, and the table holding unit 66 are functional units realized by the cooperation of the FPGA 20A and the memory 20B.

[0042] Image data DT representing an image to be formed is input from the outside to the image input unit 60. Hereinafter, an image corresponding to the image data DT input to the image input unit 60 may be referred to as an input image. As an example, in this embodiment, color image data DT represented by RGB signals is input to the image input unit 60. The image data DT input to the image input unit 60 is output to the information generating unit 61. Note that the image data DT input to the image input unit 60 is not limited to this embodiment, and may be any data corresponding to the image to be formed. For example, it may be binarized data representing whether or not to output laser light L. Also, for example, it may be data representing multiple values ​​of the output amount.

[0043] The information generating unit 61 generates intensity information SI representing the correspondence between the scanning position of the laser light L by the MEMS mirror 30 and the signal intensity of the input image. If the input image is a color image, the signal intensity represents the intensity of each of the RGB signals. The information storage unit 62 stores the intensity information SI generated by the information generating unit 61.

[0044] 5 to the pair of first actuators 51 of the MEMS mirror 30, and generates a first zero-cross signal ZC1 and outputs it to the first reference signal output section 63A. The first drive signal V1A and the first drive signal V1B are sine waves with a phase difference of 180°.

[0045] The first zero-cross signal ZC1 is a pulse-shaped signal that indicates the points at which the first drive signals V1A and V1B become zero. Note that the signal output from the MEMS driver 22 to the first reference signal output unit 63A is not limited to a zero-cross signal, and may be any signal having the same period as the first drive signals V1A and V1B.

[0046] 6 to the pair of second actuators 52 of the MEMS mirror 30, and generates a second zero-cross signal ZC2 and outputs it to the second reference signal output section 63B. The second drive signal V2A and the second drive signal V2B are sine waves with a phase difference of 180°.

[0047] The second zero-cross signal ZC2 is a pulse-shaped signal that indicates the points at which the second drive signals V2A and V2B become zero. Note that the signal output from the MEMS driver 22 to the second reference signal output unit 63B is not limited to a zero-cross signal, and may be any signal having the same period as the second drive signals V2A and V2B.

[0048] The frequency ratio between the frequency of the first drive signals V1A and V1B (hereinafter referred to as the first drive frequency) and the frequency of the second drive signals V2A and V2B (hereinafter referred to as the second drive frequency) is different. The frequency ratio between the first drive frequency and the second drive frequency is determined based on the shape of the Lissajous curve of the optical scanning performed by the MEMS mirror 30.

[0049] The first reference signal output section 63A estimates the time when the first deflection angle θ1 of the mirror section 40 becomes the first reference angle, and outputs the first reference signal PS1 to the light emission control section 64. In this embodiment, the first reference angle is set to 0°. The first reference signal output section 63A estimates the time when the first deflection angle θ1 becomes the first reference angle based on the first drive signals V1A and V1B, and generates the first reference signal PS1.

[0050] Specifically, as shown in Fig. 5, the first reference signal output unit 63A outputs a signal obtained by delaying the first zero cross signal ZC1 input from the MEMS driver 22 by a delay time D1 as the first reference signal PS1. When the mirror unit 40 resonates around the first axis a1, the delay time D1 is ideally a time equivalent to ¼ times the period of the first zero cross signal ZC1, but a deviation occurs depending on the environmental conditions (temperature, humidity, etc.). For this reason, in this embodiment, the first reference signal output unit 63A obtains the delay time D1 based on the temperature and humidity detected by the humidity and temperature sensor 67 and a lookup table (hereinafter referred to as LUT) 66A held in the table holding unit 66, and generates the first reference signal PS1 based on the obtained delay time D1.

[0051] The second reference signal output section 63B estimates the time when the second deflection angle θ2 of the mirror section 40 becomes the second reference angle, and outputs the second reference signal PS2 to the light emission control section 64. In this embodiment, the second reference angle is set to 0°. The second reference signal output section 63B estimates the time when the second deflection angle θ2 becomes the second reference angle based on the second drive signals V2A and V2B, and generates the second reference signal PS2.

[0052] Specifically, as shown in Fig. 6, the second reference signal output unit 63B outputs a signal obtained by delaying the second zero cross signal ZC2 input from the MEMS driver 22 by a delay time D2 as the second reference signal PS2. When the mirror unit 40 resonates around the second axis a2, the delay time D2 is ideally a time equivalent to 1 / 4 times the period of the second zero cross signal ZC2, but a deviation occurs depending on the environmental conditions (temperature, humidity, etc.). For this reason, in this embodiment, the second reference signal output unit 63B obtains the delay time D2 based on the temperature and humidity detected by the humidity and temperature sensor 67 and the LUT 66A held in the table holding unit 66, and generates the second reference signal PS2 based on the obtained delay time D2.

[0053] 7, the relationship between the delay time D1, temperature, and humidity, and the relationship between the delay time D2, temperature, and humidity are recorded in advance in the LUT 66A. These relationships are determined, for example, based on past history.

[0054] The light emission control unit 64 causes the light emitting device 24 to emit laser light L based on the first reference signal PS1 and the second reference signal PS2. In a drawing mode in which an image based on the image data DT is drawn on the projection surface 34, the light emission control unit 64 reads out the intensity information SI from the information storage unit 62, and causes the light emitting device 24 to emit laser light L of an intensity determined based on the first reference signal PS1 and the second reference signal PS2 at regular time intervals (e.g., every clock period).

[0055] In this embodiment, a calibration mode is performed to correct the timing of the first reference signal PS1 and the second reference signal PS2 output by the first reference signal output unit 63A and the second reference signal output unit 63B, respectively. In the calibration mode, the light emission control unit 64 causes the light emitting device 24 to emit the laser light L in accordance with the timing at which the first reference signal PS1 is output from the first reference signal output unit 63A and the timing at which the second reference signal PS2 is output from the second reference signal output unit 63B. That is, in the calibration mode, the light emission control unit 64 causes the light emitting device 24 to emit the laser light L at a time when the first deflection angle θ1 is estimated to be the first reference angle (0° in this embodiment) and a time when the second deflection angle θ2 is estimated to be the second reference angle (0° in this embodiment).

[0056] In the calibration mode, the imaging device 32 captures an image of a pattern drawn on the projection surface 34 by the laser light L emitted from the light emitting device 24 being reflected by the MEMS mirror 30. The imaging device 32 outputs a captured image IP generated by capturing an image of the projection surface 34 to the correction unit 65.

[0057] The correction section 65 corrects the timing of the first reference signal PS1 and the second reference signal PS2 outputted by the first reference signal output section 63A and the second reference signal output section 63B, respectively, based on the amount of deviation of the pattern captured in the captured image IP from a specified shape.

[0058] 8 shows an example of a pattern drawn on the projection surface 34 in the calibration mode. In this example, for simplicity of explanation, the frequency ratio between the first drive frequency and the second drive frequency is set to 3:2. In this example, a Lissajous curve 70 is drawn on the projection surface 34 by the optical scanning performed by the MEMS mirror 30.

[0059] 8 shows a case where there is no misalignment between the oscillation of the mirror section 40 and the timing of the first and second reference signals PS1 and PS2. In this way, when there is no misalignment, the light emitting device 24 emits the laser light L at the time when θ1=0 and at the time when θ2=0, so that the laser light L is irradiated onto the first and second reference lines L1 and L2 on the projection surface 34. In this embodiment, the first reference line L1 is a straight line that passes through the center of the Lissajous curve 70 and is parallel to the X direction, and the second reference line L2 is a straight line that passes through the center of the Lissajous curve 70 and is parallel to the Y direction. The symbol P indicates a point (i.e., a bright point) on the projection surface 34 where the laser light L is irradiated.

[0060] When the frequency ratio between the first drive frequency and the second drive frequency is set so as to make the Lissajous curve 70 more precise, the bright points P form a linear pattern along the first reference line L1 and the second reference line L2.

[0061] 9 shows a case where there is a shift between the oscillation of the mirror section 40 and the timing of the first reference signal PS1 and the second reference signal PS2. In this way, when there is a shift, the light emitting device 24 emits the laser light L at a time shifted from the time when θ1=0 and the time when θ2=0, so that the laser light L is irradiated at a position shifted from the first reference line L1 and the second reference line L2 on the projection plane 34. In this example, the laser light L is irradiated on straight lines L1A and L1B shifted from the first reference line L1, and on straight lines L2A and L2B shifted from the second reference line L2.

[0062] The straight line L1A is a line along which the laser light L is irradiated in the outward path of the Lissajous scan. The straight line L1B is a line along which the laser light L is irradiated in the return path of the Lissajous scan. The straight line L2A is a line along which the laser light L is irradiated in the outward path of the Lissajous scan. The straight line L2B is a line along which the laser light L is irradiated in the return path of the Lissajous scan. The outward path refers to a path along which the first deflection angle θ1 increases in the Y direction, and a path along which the second deflection angle θ2 increases in the X direction. The return path refers to a path along which the first deflection angle θ1 decreases in the Y direction, and a path along which the second deflection angle θ2 decreases in the X direction.

[0063] In this way, when there is a misalignment between the oscillation of the mirror portion 40 and the timing of the first reference signal PS1 and the second reference signal PS2, the first reference line L1 is separated into straight lines L1A and L1B, and the second reference line L2 is separated into straight lines L2A and L2B.

[0064] When the frequency ratio between the first drive frequency and the second drive frequency is set so as to make the Lissajous curve 70 more precise, the bright spots P form a linear pattern along the lines L1A, L1B, L2A, and L2B.

[0065] 10 shows an example of the functional configuration of the correction unit 65. The correction unit 65 includes a correction amount calculation unit 72 and a signal correction unit 73. The correction unit 65 receives an input of a captured image IP from the imaging device 32.

[0066] The correction amount calculation unit 72 derives the deviation amount ΔY between the straight lines L1A and L1B in the Y direction and the deviation amount ΔX between the straight lines L2A and L2B in the X direction based on the captured image IP. The correction amount calculation unit 72 also derives the correction amount δ1 of the timing of the first reference signal PS1 to make ΔX=0 and the correction amount δ2 of the timing of the second reference signal PS2 to make ΔY=0, and outputs the derived correction amounts δ1 and δ2 to the signal correction unit 73. The correction amount calculation unit 72 derives the correction amounts δ1 and δ2 based on, for example, the relationship between the deviation amount ΔX and the correction amount δ1 and the relationship between the deviation amount ΔY and the correction amount δ2 stored in advance. Note that the relationship between the deviation amount ΔX and the correction amount δ1 and the relationship between the deviation amount ΔY and the correction amount δ2 are approximately proportional to each other.

[0067] The correction amount calculation unit 72 derives the shift amounts ΔX and ΔY based on the captured image IP obtained without correcting the timing of the first reference signal PS1 and the second reference signal PS2 (i.e., a state in which δ1=0 and δ2=0), and derives the correction amounts δ1 and δ2 based on the derived shift amounts ΔX and ΔY.

[0068] The signal correction unit 73 corrects the timing of the first reference signal PS1 output from the first reference signal output unit 63A based on the correction amount δ1 input from the correction amount calculation unit 72, and corrects the timing of the second reference signal PS2 output from the second reference signal output unit 63B based on the correction amount δ2 input from the correction amount calculation unit 72.

[0069] Fig. 11 shows an example of timing correction by the signal correction unit 73. Fig. 11(A) shows an example of correcting the timing of the first reference signal PS1 based on a correction amount δ1. Fig. 11(B) shows an example of correcting the timing of the second reference signal PS2 based on a correction amount δ2. By correcting the timing of the first reference signal PS1 and the second reference signal PS2, ΔX=0 and ΔY=0. As a result, the straight lines L1A and L1B coincide with each other, and the straight lines L2A and L2B coincide with each other.

[0070] The signal correction unit 73 may be provided inside each of the first reference signal output unit 63A and the second reference signal output unit 63B. In this case, the first reference signal output unit 63A corrects the timing of the first reference signal PS1 based on the correction amount δ1 input from the correction amount calculation unit 72. Similarly, the second reference signal output unit 63B corrects the timing of the second reference signal PS2 based on the correction amount δ2 input from the correction amount calculation unit 72.

[0071] The above-mentioned calibration mode is executed for a predetermined period of time, for example, when the image forming apparatus 10 is started. After the calibration mode ends, in the drawing mode, the first reference signal output section 63A and the second reference signal output section 63B continue the timing correction based on the above-mentioned correction amounts δ1 and δ2. Note that the calibration mode may be executed periodically while the drawing mode is being executed.

[0072] As described above, the image forming device 10 can suppress distortion of the image drawn on the projection surface 34 by correcting the timing of the first reference signal PS1 and the second reference signal PS2 based on the imaging information acquired by the imaging device 32.

[0073] Various modifications of the above embodiment will be described below.

[0074] In the above embodiment, as shown in FIG. 8, the first reference line L1 and the second reference line L2 are set to pass through the center of the Lissajous curve 70, but the setting positions of the first reference line L1 and the second reference line L2 are not limited to this and can be changed as appropriate.

[0075] As an example, as shown in FIG. 12, the positions of the first reference line L1 and the second reference line L2 may be set at the ends of the drawing area of ​​the laser light L. In this example, when there is no deviation between the oscillation of the mirror unit 40 and the timing of the first reference signal PS1 and the second reference signal PS2, the laser light L is irradiated onto the first reference line L1 and the second reference line L2. On the other hand, when there is a deviation, the laser light L is irradiated onto the straight lines L1A and L1B deviated from the first reference line L1, and onto the straight lines L2A and L2B deviated from the second reference line L2. As in the above embodiment, the correction unit 65 corrects the timing of the first reference signal PS1 and the second reference signal PS2 so that the straight lines L1A and L1B coincide with each other and the straight lines L2A and L2B coincide with each other.

[0076] In this way, by setting the positions of the first reference line L1 and the second reference line L2 at the ends of the drawing area, it becomes difficult for the user to recognize the first reference line L1 and the second reference line L2, so it is possible to perform calibration while displaying an image on the projection surface 34 without causing the user any discomfort.

[0077] In the above embodiment, the laser light L is irradiated in the outward and return passes of the Lissajous scan in the calibration mode. As a result, when the above-mentioned deviation occurs, the first reference line L1 is separated into a straight line L1A and a straight line L1B, and the second reference line L2 is separated into a straight line L2A and a straight line L2B. Alternatively, the laser light L may be irradiated only in either the outward or return pass of the Lissajous scan.

[0078] 13 shows an example in which the laser light L is irradiated only on the forward path when the positions of the first reference line L1 and the second reference line L2 are set at the ends of the drawing area of ​​the laser light L. In this example, when a deviation occurs between the oscillation of the mirror unit 40 and the timing of the first reference signal PS1 and the second reference signal PS2, the laser light L is irradiated on a straight line L1A shifted from the first reference line L1 and a straight line L2A shifted from the second reference line L2. In this example, the correction unit 65 only needs to correct the timing of the first reference signal PS1 and the second reference signal PS2 so that the straight line L1A coincides with the first reference line L1 and the straight line L2A coincides with the second reference line L2.

[0079] In the above embodiment, in the calibration mode, the laser light L is irradiated multiple times within one scanning period of the Lissajous scan. One scanning period of the Lissajous scan corresponds to the frame period of the image projected on the projection surface 34. In the calibration mode, the laser light L may be irradiated once (i.e., one pulse) within one scanning period of the Lissajous scan.

[0080] 14 shows an example in which the laser light L is irradiated only once within one scanning period of the Lissajous scan. In this example, when the above-mentioned deviation does not occur, the laser light L is irradiated to the reference point P0. On the other hand, when the above-mentioned deviation occurs, the laser light L is irradiated to a point P1 that is shifted from the reference point P0. In this example, the correction unit 65 only needs to correct the timing of the first reference signal PS1 and the second reference signal PS2 so that the point P1 coincides with the reference point P0.

[0081] In the example shown in FIG. 14, the reference point P0 is set at the end of the drawing area, but the reference point P0 may be the center position of the drawing area (i.e., the position where θ1=0 and θ2=0). The reference point P0 may also be a point where the Lissajous curve 70 intersects. In this case, it is also preferable to irradiate the laser light L every time the Lissajous scan passes the reference point P0 (i.e., irradiate the laser light L twice within one scanning period of the Lissajous scan). In this case, if the above-mentioned deviation occurs, the reference point P0 is separated into two points, and the correction unit 65 may correct the timing of the first reference signal PS1 and the second reference signal PS2 so that the two separated points coincide with each other.

[0082] In the above embodiment, the laser light L is irradiated from the MEMS mirror 30 to a projection surface 34 such as a screen, but the laser light L may be irradiated from the MEMS mirror 30 to a human eyeball or the like. In this case, as shown in Fig. 15 as an example, a first optical element 80 having a light diffusion function is provided on the optical path of the laser light L reflected by the MEMS mirror 30. The first optical element 80 has a function of expanding the so-called eyebox (the range in which an image can be viewed by moving the eyes).

[0083] Laser light L emitted from the light emitting device 24 is incident on the MEMS mirror 30. The reflection direction of the laser light L incident on the MEMS mirror 30 is modulated by the oscillating mirror portion 40, and the laser light L is emitted toward the first optical element 80.

[0084] The first optical element 80 transmits and diffuses the laser light L incident from the MEMS mirror 30. The first optical element 80 is, for example, a microlens array. The first optical element 80 is not limited to a microlens array, and may be an optical element such as ground glass, a grating, a hologram, or a combination of these.

[0085] On the optical path of the laser light L transmitted through the first optical element 80, a second optical element 81 for guiding the laser light L to the eyeball E is provided.

[0086] Further, a third optical element 82 for guiding a portion of the laser light L to the imaging device 32 is provided on the optical path of the laser light L transmitted through the first optical element 80. The third optical element 82 collects a portion of the laser light L transmitted through the first optical element 80 and forms an image on the imaging surface of the imaging device 32. In this example, since the laser light L is diffused by the first optical element 80, it is preferable to provide the third optical element 82 for collecting the laser light L. Note that the third optical element 82 is an example of an "optical element for guiding a portion of light to the imaging device" according to the technology of the present disclosure.

[0087] The second optical element 81 and the third optical element 82 are, for example, lenses made of glass or resin. The second optical element 81 and the third optical element 82 are not limited to lenses, and may be optical elements such as holograms and concave mirrors, or may be a combination of these. Compiling the third optical element 82 from a hologram is preferable from the viewpoint of miniaturization, compared to the case where it is composed of liquid crystal or the like.

[0088] Moreover, the MEMS mirror 30 is housed in, for example, a package 90. The inside of the package 90 is depressurized or evacuated in order to reduce the air resistance of the oscillating mirror portion 40. The package 90 is formed of, for example, glass. At least a part of the package 90 is translucent. The laser light L emitted from the light emitting device 24 enters the MEMS mirror 30 through a translucent portion 91 of the package 90, and the laser light L reflected by the mirror portion 40 is emitted to the outside through the translucent portion 91.

[0089] As an example, as shown in FIG. 16, the imaging device 32 may be provided inside the package 90. In FIG. 16, the imaging device 32 is provided on the optical path of the laser light L reflected by the surface of the light-transmitting portion 91 among the laser light L reflected by the mirror portion 40. In this case, the imaging device 32 receives the laser light L before it is diffused, so there is no need to provide an optical element (the third optical element 82 shown in FIG. 15) for concentrating the laser light L. The captured image IP generated by the imaging device 32 performing the imaging operation is output to the outside via the lead terminal 35. In this way, by accommodating the imaging device 32 inside the package 90, the image forming apparatus 10 can be made smaller. In this example, the light-transmitting portion 91 is an example of an "optical element that guides a part of light to the imaging device" according to the technology of the present disclosure.

[0090] In the above embodiment, the first reference angle and the second reference angle are both set to 0°, but the first reference angle and the second reference angle may be angles other than 0°. For example, the first reference angle may be set to an angle at which the first deflection angle θ1 is maximum or minimum, and the second reference angle may be set to an angle at which the second deflection angle θ2 is maximum or minimum. In this case, as shown in FIG. 17 as an example, the laser light L is irradiated on four reference lines L1 to L4 on the projection surface 34. The reference lines L1 to L4 are straight lines tangent to the outer shape of the Lissajous curve 70. When a deviation occurs between the timing of the first reference signal PS1 and the timing of the second reference signal PS2, the bright point P of the laser light L is displaced inward from the reference lines L1 to L4. The correction unit 65 may correct the timing of the first reference signal PS1 and the second reference signal PS2 based on the amount of displacement of the bright point P from the reference lines L1 to L4 derived using the captured image IP.

[0091] In the above embodiment, the first reference signal output section 63A estimates the time when the first deflection angle θ1 becomes the first reference angle using the temperature and humidity detected by the hygroscopic sensor 67 and the LUT 66A, and outputs the first reference signal PS1. Alternatively, the first reference signal output section 63A may estimate the time when the first deflection angle θ1 becomes the first reference angle based on an angle sensor (not shown) that detects the first deflection angle θ1, and output the first reference signal PS1. Similarly, the second reference signal output section 63B may estimate the time when the second deflection angle θ2 becomes the second reference angle based on an angle sensor (not shown) that detects the second deflection angle θ2, and output the second reference signal PS2.

[0092] In addition, in the above embodiment, the two-axis MEMS mirror 30 is used as the optical scanning device, but a one-axis MEMS mirror may be used as the optical scanning device. Therefore, the technology disclosed herein can be applied to an image forming apparatus including a one-axis optical scanning device that oscillates a movable mirror around a first axis.

[0093] The above-described embodiment and each modified example can be appropriately combined as long as no contradiction occurs.

[0094] In the above embodiment, the following various processors can be used as the hardware structure of the processing units that execute various processes, such as the image input unit 60, the information generating unit 61, the information storing unit 62, the first reference signal output unit 63A, the second reference signal output unit 63B, the light emission control unit 64, the correction unit 65, and the table holding unit 66. The above various processors include a CPU (Central Processing Unit), which is a general-purpose processor that executes software (programs) and functions as various processing units, as well as a programmable logic device (PLD), which is a processor whose circuit configuration can be changed after the manufacture of the above-mentioned FPGA, and a dedicated electric circuit, which is a processor having a circuit configuration designed specifically for executing specific processes, such as an ASIC (Application Specific Integrated Circuit).

[0095] A single processing unit may be configured with one of these various processors, or may be configured with a combination of two or more processors of the same or different types (e.g., a combination of multiple FPGAs and / or a combination of a CPU and an FPGA). Also, multiple processing units may be configured with a single processor.

[0096] As an example of configuring multiple processing units with one processor, first, there is a form in which one processor is configured with a combination of one or more CPUs and software, as typified by computers such as client and server, and this processor functions as multiple processing units. Second, there is a form in which a processor is used that realizes the functions of the entire system including multiple processing units with one IC (Integrated Circuit) chip, as typified by System On Chip (SoC), etc. In this way, the various processing units are configured using one or more of the above various processors as a hardware structure.

[0097] Furthermore, more specifically, the hardware structure of these various processors can be an electric circuit that combines circuit elements such as semiconductor elements.

[0098] All publications, patent applications, and standards mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication, patent application, and standard was specifically and individually indicated to be incorporated by reference. [Explanation of symbols]

[0099] 10 Image forming device 20 Control device 20A FPGA 20B Memory 22 Drivers 24 Light emitting device 25 Laser driver 26 Combined optical system 27 Laser light source 28 Collimator 30 MEMS mirror 32 Imaging device 34 Projection plane 35 Lead terminal 40 Mirror section 40A reflective surface 41 1st support part 42 First movable frame 43 Second support part 44 2nd movable frame 45 Connection 46 Fixed Frame 50 Piezoelectric element 51 First Actuator 52 Second Actuator 60 Image input unit 61 Information generation section 62 Information storage section 63A First reference signal output section 63B Second reference signal output section 64 Light Emission Control Unit 65 Correction section 66 Table holder 66A LUT 67 Humidity and temperature sensor 70 Lissajous curve 72 Correction amount calculation section 73 Signal correction section 80 First optical element 81 Second optical element 82 Third Optical Element 90 Packages 91 Translucent part ΔX, ΔY deviation amount δ1, δ2 correction amount θ1 First deflection angle θ2 Second deflection angle D1,D2 Delay Time DT image data E Eyeball IP Captured Images L Laser light L1 1st reference line L1A,L1B straight line L2 Second Reference Line L2A,L2B straight line P bright spot P0 reference point P1 point PS1 First reference signal PS2 Second reference signal SI Strength Information V1A, V1B First drive signal V2A, V2B Second drive signal ZC1 1st zero cross signal ZC2 Second zero cross signal a1 First axis a2 2nd axis

Claims

1. A light emitting device that emits light; a movable mirror that reflects the light emitted from the light emitting device; A first actuator that oscillates the movable mirror about a first axis; a package that houses the movable mirror and has a light-transmitting portion, wherein the light emitted from the light-emitting device is incident on the movable mirror via the light-transmitting portion, and the light reflected by the movable mirror is emitted to the outside via the light-transmitting portion; a first reference signal output unit that estimates a time when the deflection angle of the movable mirror about the first axis becomes a first reference angle and outputs a first reference signal; a light emission control unit that causes the light emitting device to emit the light based on the first reference signal output from the first reference signal output unit; an imaging device accommodated in the package and provided on an optical path of light reflected by a surface of the light-transmitting portion out of the light reflected by the movable mirror; a correction unit that corrects a timing of the first reference signal output by the first reference signal output unit based on an image captured by the imaging device; An image forming apparatus comprising: the imaging device receives the reflected light, thereby imaging the drawing pattern of the light reflected by the movable mirror; The correction unit corrects a timing of the first reference signal based on an amount of deviation of the drawing pattern shown in the captured image from a specified shape. Image forming device.

2. A second actuator that oscillates the movable mirror about a second axis; a second reference signal output unit that estimates a time when the deflection angle of the movable mirror about the second axis becomes a second reference angle and outputs a second reference signal, the correction unit corrects a timing of the first reference signal output by the first reference signal output unit and a timing of the second reference signal output by the second reference signal output unit based on the captured image. The image forming apparatus according to claim 1 .

3. the first reference angle is an angle at which a deflection angle of the movable mirror about the first axis is zero, and the second reference angle is an angle at which a deflection angle of the movable mirror about the second axis is zero. The image forming apparatus according to claim 2 .

4. the first reference angle is an angle at which a deflection angle of the movable mirror about the first axis is maximum or minimum, and the second reference angle is an angle at which a deflection angle of the movable mirror about the second axis is maximum or minimum. The image forming apparatus according to claim 2 .

5. the first reference signal output unit estimates a time point at which a deflection angle of the movable mirror about the first axis becomes a first reference angle, based on a first drive signal provided to the first actuator; the second reference signal output unit estimates a time point at which a deflection angle of the movable mirror about the second axis becomes a second reference angle, based on a second drive signal provided to the second actuator; The image forming apparatus according to claim 2 .

6. an optical element that guides a part of the light reflected by the movable mirror to the imaging device on an optical path of the light reflected by the movable mirror; The image forming apparatus according to claim 1 .

7. A light emitting device that emits light; a movable mirror that reflects the light emitted from the light emitting device; A first actuator that oscillates the movable mirror about a first axis; a package that houses the movable mirror and has a light-transmitting portion, wherein the light emitted from the light-emitting device is incident on the movable mirror via the light-transmitting portion, and the light reflected by the movable mirror is emitted to the outside via the light-transmitting portion; a first reference signal output unit that estimates a time when the deflection angle of the movable mirror about the first axis becomes a first reference angle and outputs a first reference signal; a light emission control unit that causes the light emitting device to emit the light based on the first reference signal output from the first reference signal output unit; an imaging device accommodated in the package and provided on an optical path of light reflected by a surface of the light-transmitting portion out of the light reflected by the movable mirror; a correction unit that corrects a timing of the first reference signal output by the first reference signal output unit based on an image captured by the imaging device; A method for operating an optical scanning device comprising: the imaging device receives the reflected light, thereby imaging the drawing pattern of the light reflected by the movable mirror; The correction unit corrects the timing of the first reference signal based on an amount of deviation of the drawing pattern shown in the captured image from a specified shape. A method for operating an image forming device.

Images