Optical scanning device and image forming device

Abstract

To provide an optical scanner that allows a reduction in size and manufacturing cost without making stray light incident in a drawing area, and an image forming apparatus.SOLUTION: An image forming apparatus comprises an optical scanner comprising: a mirror device that has at least a movable mirror oscillating around a first axis; and a package that has at least two or more light transmission surfaces not constituting the same plane and accommodates therein the mirror device. Among the two or more light transmission surfaces of the package, one is a light take-in surface for taking in incident light to the movable mirror from the outside, and another one is a light take-out surface for taking out light reflected by the movable mirror to the outside.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The technology disclosed herein relates to an optical scanning device and an image forming apparatus. [Background technology]

[0002] There is known an image forming apparatus that draws an image on a screen or the like by irradiating a mirror device formed by a MEMS (Micro Electro Mechanical System) with light. The mirror device has a movable mirror that swings around at least one axis.

[0003] The mirror device is housed in a package with a vacuum or negative pressure inside in order to reduce the air resistance of the oscillating movable mirror. In this case, laser light is incident on the mirror device from the outside through a glass window provided in the package.

[0004] When the mirror device is housed in a package, a part of the laser light incident on the glass window is reflected by the surface of the glass window, and this reflected light may enter the drawing area of ​​the image produced by the mirror device as stray light. In this case, if stray light enters the drawing area, unwanted bright spots will appear in the image.

[0005] Non-Patent Document 1 suggests that a method of suppressing the above-mentioned reflected light would be to provide an anti-reflective coating on the surface of the glass window. However, since it is difficult to completely suppress the reflected light with an anti-reflective coating, it is proposed to guide the reflected light outside the drawing area by tilting the glass window. [Prior art documents] [Non-patent literature]

[0006] [Non-Patent Document 1] S. Gu-Stoppel et al., Advanced Manufacturing, Electronics and Microsystems: TechConnect Briefs 2016, P.87-90,<https: / / briefs.techconnect.org / wp-content / volumes / TCB2016v4 / pdf / 364.pdf> Summary of the Invention [Problem to be solved by the invention]

[0007] However, when the glass window is inclined as described in Non-Patent Document 1, the thickness of the package increases, which causes a problem of an increase in package size. In addition, the increase in package size causes a problem of an increase in manufacturing costs.

[0008] An object of the technology disclosed herein is to provide an optical scanning device and an image forming apparatus that can be miniaturized and have reduced manufacturing costs without allowing stray light to enter a drawing area. [Means for solving the problem]

[0009] In order to achieve the above-mentioned objective, the optical scanning device disclosed herein is an optical scanning device comprising a mirror device having a movable mirror that oscillates around at least one axis, and a package having at least two or more light-transmitting surfaces that do not form the same plane and housing the mirror device therein, wherein one of the two or more light-transmitting surfaces of the package is a light intake surface that takes in incident light on the movable mirror from the outside, and the other is a light extraction surface that extracts light reflected by the movable mirror to the outside.

[0010] The interior of the package is preferably at vacuum or negative pressure.

[0011] The package is preferably provided with a signal input terminal for receiving a drive signal for driving the movable mirror from the outside.

[0012] It is preferable that an optical element be provided inside the package for deflecting light incident from the light receiving surface and directing it to the movable mirror.

[0013] The light inlet surface and the light outlet surface are preferably formed by two non-parallel light-transmitting surfaces.

[0014] An imaging device and a signal output terminal for extracting an imaging signal output from the imaging device to the outside are provided inside the package, and it is preferable that the light extraction surface reflects a portion of the light reflected by the movable mirror and guides it to the imaging device.

[0015] The image forming apparatus of the present disclosure is an image forming apparatus comprising: a mirror device having a movable mirror that oscillates around at least one axis; an optical scanning device having at least two or more light-transmitting surfaces that are not coplanar and housing the mirror device inside; and a light-emitting device that emits light, wherein of the two or more light-transmitting surfaces of the package, one is a light intake surface that takes in incident light on the movable mirror from the outside, and the other is a light extraction surface that extracts light reflected by the movable mirror to the outside, and the light emitted from the light-emitting device is incident on the movable mirror via the light intake surface. Effect of the Invention

[0016] According to the technique of the present disclosure, it is possible to provide an optical scanning device and an image forming device that can be miniaturized and have reduced manufacturing costs without allowing stray light to enter the imaging area. [Brief description of the drawings]

[0017] [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] FIG. 1 is a schematic perspective view illustrating an example of an external configuration of an optical scanning device. [Figure 4] 1 is a schematic cross-sectional view showing an example of a cross-sectional structure of an optical scanning device. [Diagram 5] 11 is a schematic cross-sectional view showing an example of a cross-sectional structure of an optical scanning device according to a second embodiment. FIG. [Figure 6] 11 is a schematic cross-sectional view showing an example of a cross-sectional structure of an optical scanning device according to a third embodiment. FIG. [Figure 7] FIG. 2 is a block diagram showing an example of a functional configuration of a control device. [Figure 8] 4A to 4C are diagrams illustrating an example of a first drive signal, a first zero-cross signal, and a first reference signal. [Figure 9] 5A to 5C are diagrams illustrating an example of a second drive signal, a second zero-cross signal, and a second reference signal. [Figure 10] 13A and 13B are diagrams illustrating an example of a pattern drawn on a projection surface in a calibration mode. [Figure 11] 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 12] FIG. 4 illustrates an example of a functional configuration of a correction unit. [Figure 13] 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. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Hereinafter, embodiments of the technology disclosed herein will be described in detail with reference to the drawings. As an example, in each of the following embodiments, a form in which the technology disclosed herein 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.

[0019] [First embodiment] 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, and an optical scanning device 30. The optical scanning device 30 includes a MEMS mirror 32 and a package 33 that houses the MEMS mirror 32. The MEMS mirror 32 is an example of a "mirror device" according to the technology of the present disclosure.

[0020] 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.

[0021] 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 32 in the package 33 via the collimator 28. The laser light focused on the MEMS mirror 32 is reflected by the MEMS mirror 32 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.

[0022] 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.

[0023] The MEMS driver 22 drives the MEMS mirror 32 based on the control from the control device 20. In the MEMS mirror 32, 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 of the present disclosure.

[0024] 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.

[0025] 2 shows an example of the configuration of the MEMS mirror 32. The MEMS mirror 32 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 3 shows an example of the external configuration of the optical scanning device 30. The package 33 has a substantially rectangular parallelepiped shape. For example, the package 33 is composed of a flat substrate 35 and a box-shaped lid member 36. For example, the substrate 35 and the lid member 36 are made of light-transmitting glass. The package 33 is constructed by joining the lid member 36 to the substrate 35. The MEMS mirror 32 is accommodated inside the package 33.

[0037] The inside of the package 33 is a vacuum or negative pressure. By making the inside of the package 33 a vacuum or negative pressure in this way, energy loss during oscillation of the mirror section 40 is reduced, and a large deflection angle can be achieved with a low drive voltage. Note that negative pressure means that the air pressure inside the package 33 is lower than the air pressure outside the package 33 (i.e., atmospheric pressure).

[0038] The cover member 36 has four light-transmitting surfaces 37. The four light-transmitting surfaces 37 are composed of one upper surface and three side surfaces. In this embodiment, the light-transmitting surface 37 as one side surface of the four light-transmitting surfaces 37 functions as a "light-intake surface" that takes in incident light to the mirror section 40 from the outside. In addition, the light-transmitting surface 37 as one upper surface of the four light-transmitting surfaces 37 functions as a "light-extraction surface" that takes out light reflected by the mirror section 40 to the outside. That is, in this embodiment, the light-intake surface and the light-extraction surface are composed of two light-transmitting surfaces 37 that are non-parallel.

[0039] The laser light L emitted from the light emitting device 24 passes through a light extraction region 38 on the light extraction surface and enters the inside of the package 33. The laser light L that enters the inside of the package 33 is incident on the mirror portion 40 of the MEMS mirror 32. The laser light L reflected by the mirror portion 40 passes through a light extraction region 39 on the light extraction surface and is extracted to the outside of the package 33. The laser light L that passes through the light extraction region 39 is incident on the projection surface 34 (see FIG. 1).

[0040] Fig. 4 shows an example of the cross-sectional structure of the optical scanning device 30. As shown in Fig. 4, the MEMS mirror 32 is fixed to the substrate 35 via a support member 60. For example, the support member 60 has a triangular prism shape and has an inclined surface 61. The MEMS mirror 32 is bonded to the inclined surface 61. That is, the surface of the mirror section 40 is not parallel to either the light entrance surface or the light exit surface in a stationary state.

[0041] The substrate 35 is provided with a signal input terminal 62 for receiving a drive signal for driving the mirror section 40 from the outside. The signal input terminal 62 is electrically connected to the MEMS mirror 32 via, for example, a bonding wire 63. The MEMS driver 22 (see FIG. 1) inputs a drive signal to the MEMS mirror 32 via the signal input terminal 62. The signal input terminal 62 is provided, for example, individually for the pair of first actuators 51 and the pair of second actuators 52. Drive signals having different frequencies are applied to the pair of first actuators 51 and the pair of second actuators 52.

[0042] 3 and 4, the laser light L emitted from the light-emitting device 24 is partially reflected at the light-introducing surface to become stray light LS. The light-introducing surface is constituted by a light-transmitting surface 37 that is not flush with the light-transmitting surface 37 that constitutes the light-introducing surface, and therefore the stray light LS does not enter the drawing area (i.e., the projection surface 34).

[0043] The optical scanning device 30 of this embodiment does not need to tilt the glass window as in the conventional case in order to guide the stray light LS out of the imaging area, and therefore the package size can be reduced without increasing the thickness of the package 33. Therefore, according to the technology of the present disclosure, an optical scanning device 30 is realized that can be miniaturized and the manufacturing costs can be reduced without allowing stray light to enter the imaging area.

[0044] In the above embodiment, the entire package 33 is made of a light-transmitting material such as glass, but the package 33 may be partially made of a light-shielding material. For example, the part of the package 33 other than the light capture region 38 and the light extraction region 39 may be made of a light-shielding material.

[0045] [Second embodiment] Next, a second embodiment will be described. In the first embodiment, the laser light is introduced into the package 33 from one side surface of the cover member 36, but in the second embodiment, the laser light is introduced into the package 33 from the substrate 35.

[0046] 5 shows an example of a cross-sectional structure of the optical scanning device 30 according to the second embodiment. The substrate 35 is translucent, and its surface is a light-transmitting surface 37. In the embodiment, the light-transmitting surface 37 of the substrate 35 functions as a "light-intake surface" that takes in incident light from the outside to the mirror section 40. The laser light L emitted from the light-emitting device 24 passes through a light-intake region 38 of the substrate 35 and enters the inside of the package 33. The laser light L that has entered the inside of the package 33 enters the inner surface side of the cover member 36.

[0047] An optical element 70 is provided on the inner surface side of the cover member 36 at a position where the laser light L is incident. The optical element 70 deflects the laser light L incident from the light capture area 38 and guides it to the mirror portion 40 of the MEMS mirror 32. In this embodiment, the optical element 70 is a reflective film formed by sputtering or deposition. The optical element 70 deflects the laser light L by mirror reflection so as to guide it to the mirror portion 40.

[0048] In this embodiment, the MEMS mirror 32 is fixed directly to the substrate 35 without using a support member 60 (see FIG. 4). That is, in this embodiment, the MEMS mirror 32 is not inclined with respect to the substrate 35. The laser light L reflected by the mirror portion 40 passes through the light extraction region 39 on the upper surface of the lid member 36, and is extracted to the outside of the package 33, similar to the above embodiment.

[0049] As described above, in the second embodiment, the laser light L is taken in from the back side of the package 33, so that stray light LS generated by partial reflection at the light taking-in surface does not enter the drawing area. Therefore, in the second embodiment, it is not necessary to tilt the glass window as in the conventional case in order to guide the stray light LS out of the drawing area, so that the optical scanning device 30 that can be made compact and has low manufacturing costs is realized. In addition, it is not necessary to tilt the MEMS mirror 32 with respect to the substrate 35, so that the thickness of the package 33 can be made thinner.

[0050] The optical element 70 is not limited to a reflective film, and may be an optical element such as a grating or a hologram. The grating or hologram can emit the laser light L at an emission angle different from the incidence angle. Therefore, by using an optical element such as a grating or a hologram as the optical element 70, the degree of freedom in designing the position where the optical element 70 is disposed is improved.

[0051] [Third embodiment] Next, a third embodiment will be described. In the third embodiment, an imaging device is provided inside the package 33. The imaging device is used to correct the emission timing of the laser light L by the light emitting device 24.

[0052] 6 shows an example of a cross-sectional structure of the optical scanning device 30 according to the third embodiment. In this embodiment, an imaging device 72 is attached to a substrate 35 inside a package 33. The imaging device 72 is provided on an optical path of the laser light L reflected by the light extraction region 39 out of the laser light L reflected by the mirror section 40. A signal output terminal 73 is provided on the substrate 35 for extracting an imaging signal output from the imaging device 72 to the outside. Other configurations of the optical scanning device 30 according to this embodiment are similar to those of the optical scanning device 30 according to the first embodiment.

[0053] The imaging device 72 captures the laser light L reflected by the light extraction region 39 to generate a captured image IP, and outputs the generated captured image IP to the control device 20 (see FIG. 1). The imaging device 72 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 72 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.

[0054] Fig. 7 shows an example of the functional configuration of the control device 20. As shown in Fig. 7, the control device 20 includes an image input unit 80, an information generation unit 81, an information storage unit 82, a first reference signal output unit 83A, a second reference signal output unit 83B, a light emission control unit 84, a correction unit 85, a table holding unit 86, and a humidity and temperature sensor 87. The image input unit 80, the information generation unit 81, the information storage unit 82, the first reference signal output unit 83A, the second reference signal output unit 83B, the light emission control unit 84, the correction unit 85, and the table holding unit 86 are functional units realized by the cooperation of the FPGA 20A and the memory 20B.

[0055] Image data DT representing an image to be formed is input from the outside to the image input unit 80. Hereinafter, an image corresponding to the image data DT input to the image input unit 80 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 80. The image data DT input to the image input unit 80 is output to the information generating unit 81. Note that the image data DT input to the image input unit 80 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.

[0056] The information generating unit 81 generates intensity information SI representing the correspondence between the scanning position of the laser light L by the MEMS mirror 32 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 82 stores the intensity information SI generated by the information generating unit 81.

[0057] 8 to the pair of first actuators 51 of the MEMS mirror 32, and generates a first zero-cross signal ZC1 and outputs it to the first reference signal output section 83A. The first drive signal V1A and the first drive signal V1B are sine waves whose phases are different by 180°.

[0058] 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 83A 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.

[0059] 9 to the pair of second actuators 52 of the MEMS mirror 32, and generates a second zero-cross signal ZC2 and outputs it to the second reference signal output section 83B. The second drive signal V2A and the second drive signal V2B are sine waves whose phases are different by 180°.

[0060] 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 83B 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.

[0061] 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 32.

[0062] The first reference signal output section 83A estimates the time when the deflection angle θ1 around the first axis a1 of the mirror section 40 (hereinafter referred to as the first deflection angle) becomes the first reference angle, and outputs a first reference signal PS1 to the light emission control section 84. In this embodiment, the first reference angle is set to 0°. The first reference signal output section 83A 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.

[0063] Specifically, as shown in Fig. 8, the first reference signal output unit 83A 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 83A obtains the delay time D1 based on the temperature and humidity detected by the humidity and temperature sensor 87 and a look-up table (hereinafter referred to as LUT) 86A held in the table holding unit 86, and generates the first reference signal PS1 based on the obtained delay time D1.

[0064] The second reference signal output section 83B estimates the time when the deflection angle θ2 around the second axis a2 of the mirror section 40 (hereinafter referred to as the second deflection angle) becomes the second reference angle, and outputs the second reference signal PS2 to the light emission control section 84. In this embodiment, the second reference angle is set to 0°. The second reference signal output section 83B 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.

[0065] Specifically, as shown in Fig. 9, the second reference signal output unit 83B 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 83B obtains the delay time D2 based on the temperature and humidity detected by the humidity and temperature sensor 87 and the LUT 86A held in the table holding unit 86, and generates the second reference signal PS2 based on the obtained delay time D2.

[0066] 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 86A. These relationships are determined based on, for example, past history.

[0067] The light emission control unit 84 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 84 reads out the intensity information SI from the information storage unit 82, 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 cycle).

[0068] 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 83A and the second reference signal output unit 83B, respectively. In the calibration mode, the light emission control unit 84 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 83A and the timing at which the second reference signal PS2 is output from the second reference signal output unit 83B. That is, in the calibration mode, the light emission control unit 84 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).

[0069] In the calibration mode, the imaging device 72 captures an image of the laser light L reflected by the light extraction region 39 out of the laser light L emitted from the light emitting device 24 and reflected by the mirror unit 40. The imaging device 72 outputs a captured image IP generated by the imaging to the correction unit 85. In the captured image IP, a pattern drawn on the projection surface 34 is captured.

[0070] The correction section 85 corrects the timing of the first reference signal PS1 and the second reference signal PS2 outputted by the first reference signal output section 83A and the second reference signal output section 83B, respectively, based on the amount of deviation of the pattern captured in the captured image IP from a specified shape.

[0071] 10 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 90 is drawn on the projection surface 34 by the optical scanning performed by the MEMS mirror 32.

[0072] 10 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 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. The first reference line L1 is a straight line that passes through the center of the Lissajous curve 90 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 90 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.

[0073] When the frequency ratio between the first drive frequency and the second drive frequency is set so as to make the Lissajous curve 90 more precise, the bright points P form a linear pattern along the first reference line L1 and the second reference line L2.

[0074] 11 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.

[0075] 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.

[0076] 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.

[0077] When the frequency ratio between the first drive frequency and the second drive frequency is set so as to make the Lissajous curve 90 more precise, the bright spots P form a linear pattern along the lines L1A, L1B, L2A, and L2B.

[0078] 12 shows an example of the functional configuration of the correction unit 85. The correction unit 85 includes a correction amount calculation unit 92 and a signal correction unit 93. To the correction unit 85, a captured image IP is input from the imaging device 72.

[0079] The correction amount calculation unit 92 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 92 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 93. The correction amount calculation unit 92 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.

[0080] The correction amount calculation unit 92 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.

[0081] The signal correction unit 93 corrects the timing of the first reference signal PS1 output from the first reference signal output unit 83A based on the correction amount δ1 input from the correction amount calculation unit 92, and corrects the timing of the second reference signal PS2 output from the second reference signal output unit 83B based on the correction amount δ2 input from the correction amount calculation unit 92.

[0082] Fig. 13 shows an example of timing correction by the signal correction unit 93. Fig. 13(A) shows an example of correcting the timing of the first reference signal PS1 based on a correction amount δ1. Fig. 13(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.

[0083] The signal correction unit 93 may be provided inside each of the first reference signal output unit 83A and the second reference signal output unit 83B. In this case, the first reference signal output unit 83A corrects the timing of the first reference signal PS1 based on the correction amount δ1 input from the correction amount calculation unit 92. Similarly, the second reference signal output unit 83B corrects the timing of the second reference signal PS2 based on the correction amount δ2 input from the correction amount calculation unit 92.

[0084] 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 unit 83A and the second reference signal output unit 83B 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.

[0085] As described above, the image forming apparatus 10 according to this embodiment 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 72.

[0086] In each of the above embodiments, the two-axis MEMS mirror 32 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.

[0087] In the third 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 80, the information generating unit 81, the information storing unit 82, the first reference signal output unit 83A, the second reference signal output unit 83B, the light emission control unit 84, the correction unit 85, and the table holding unit 86. 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).

[0088] 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.

[0089] 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.

[0090] Furthermore, more specifically, the hardware structure of these various processors can be an electric circuit that combines circuit elements such as semiconductor elements.

[0091] 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]

[0092] 10 Image forming device 20 Control device 20B Memory 22 Drivers 24 Light emitting device 25 Laser driver 26 Combined optical system 27 Laser light source 28 Collimator 30 Optical scanning device 32 MEMS mirror 33 Packages 34 Projection plane 35 Substrate 36 Lid member 37 Light transmission surface 38 Light capture area 39 Light extraction area 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 Support member 61 Slope 62 Signal input terminal 63 Bonding Wire 70 Optical Elements 72 Imaging Device 73 Signal output terminal 80 Image input unit 81 Information generation section 82 Information storage section 83A First reference signal output section 83B Second reference signal output section 84 Light Emission Control Unit 85 Correction section 86 Table holder 87 Humidity and temperature sensor 90 Lissajous curve 92 Correction amount calculation section 93 Signal Correction Unit ΔX, ΔY deviation amount δ1, δ2 correction amount θ1 First deflection angle θ2 Second deflection angle D1,D2 Delay Time DT image data 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 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 mirror device having a movable mirror that oscillates around at least one axis; An imaging device; a package having two or more light transmitting surfaces that are not flush with one another and housing the mirror device and the imaging device therein; a signal output terminal for outputting an image signal output from the image pickup device to the outside of the package; An optical scanning device comprising: one of the two or more light transmitting surfaces of the package is a light intake surface that takes in incident light onto the movable mirror from the outside, and the other is a light extraction surface that takes in light reflected by the movable mirror to the outside; The package is constructed by joining a flat substrate and a box-shaped lid member, The light inlet surface and the light outlet surface are formed by two of the light transmitting surfaces that are non-parallel to each other, the light intake surface is one side surface of the cover member, the light extraction surface is an upper surface of the lid member, the imaging device and the signal output terminal are fixed to the substrate, the movable mirror has an inclined surface inclined with respect to the light intake surface and the light extraction surface, and is joined to the inclined surface of a support member provided on the substrate, the light extraction surface reflects a portion of the light reflected by the movable mirror and guides the light to the imaging device. Optical scanning device.

2. The movable mirror is not parallel to either the light input surface or the light output surface when in a stationary state.

2. The optical scanning device according to claim 1.

3. The interior of the package is under vacuum or negative pressure.

3. The optical scanning device according to claim 1 or 2.

4. The substrate is provided with a signal input terminal for receiving a drive signal for driving the movable mirror from an external source. The optical scanning device according to claim 1 .

5. An optical scanning device according to any one of claims 1 to 4; A light emitting device that emits light; An image forming apparatus comprising: The light emitted from the light emitting device is incident on the movable mirror via the light collecting surface. Image forming device.

Images