JP6455724B2 - Image display device - Google Patents

Description

  The present invention relates to an image display device, and is suitable for mounting on a moving body such as a passenger car, for example.

  In recent years, an image display device called a head-up display has been developed, and is mounted on a moving body such as a passenger car. For example, in a head-up display mounted on a passenger car, light modulated by image information is projected toward a windshield (front glass), and the reflected light is irradiated to the eyes of the driver. As a result, the driver can see a virtual image of the image in front of the windshield. For example, the vehicle speed, the outside temperature, etc. are displayed as a virtual image. Recently, displaying navigation images and images that call attention to passers-by are also considered as virtual images.

  In the head-up display, a laser light source such as a semiconductor laser can be used as a light source. In this configuration, the screen is scanned while the laser light is modulated in accordance with the video signal. The laser light is diffused by the screen, and the area of the light irradiated to the driver's eyes is expanded. As a result, even if the driver moves his head to some extent, the eyes do not come out of the irradiation area, and the driver can see the image (virtual image) well and stably.

  In such a head-up display, an image spread in the depth direction can be displayed by moving the screen in parallel with the traveling direction of the laser beam. Patent Document 1 below describes a configuration in which a screen is moved in parallel with the traveling direction of laser light.

JP 2009-150947 A

  In the image display apparatus having the above configuration, the screen is reciprocated in the optical axis direction with a predetermined movement stroke. In this case, the image spread in the depth direction is displayed by scanning the screen with laser light while the screen is moving. On the other hand, an image that does not spread in the depth direction is displayed by scanning the screen with laser light while the screen is stopped. For this reason, in order to display an image that does not spread in the depth direction, it is necessary to temporarily stop the screen during the movement stroke. In this case, it is necessary to smoothly stop the moving screen at high speed without causing oscillation.

  In view of such a problem, an object of the present invention is to provide an image display device capable of smoothly displaying a non-expanding image in the depth direction by smoothly stopping a reciprocating screen.

  An image display device according to a main aspect of the present invention includes a light source that emits light, a screen on which an image is formed by scanning the light, and the screen that scans the light emitted from the light source. A scanning unit; an optical system that generates a virtual image by the light transmitted through the screen; a driving unit that moves the screen in parallel with at least the traveling direction of the light; and a screen driving circuit that drives the driving unit. Prepare. Here, the screen driving circuit superimposes an acceleration / deceleration signal for stopping the screen on a periodic signal that causes the screen to reciprocate monotonously at a predetermined period according to the stop timing of the screen. A drive signal for moving the is generated.

  According to the image display apparatus according to this aspect, since the drive signal is generated as described above, the screen that is moving at high speed can be smoothly positioned at the stop position without being oscillated.

  For example, when the drive signal is adjusted so that the screen is stopped at a predetermined position by feeding back the moving position of the screen, a drive signal is generated that gradually converges to the stop position after the screen overruns the stop position. The In this case, the screen vibrates near the stop position before stopping. Such vibration reduces the quality of an image that does not spread in the depth direction. In addition, when trying to converge the vibration of the screen in a short time in order to suppress degradation of the image quality, the screen resonates and converges to the stop position when the screen is elastically supported by a spring or the like. It can happen that the message is transmitted without much. In this case, an image that does not spread in the depth direction can no longer be displayed.

  On the other hand, according to the image display apparatus according to this aspect, the acceleration / deceleration signal for stopping the screen is superimposed on the periodic signal for reciprocally moving the screen in a predetermined cycle according to the stop timing of the screen. Since the drive signal for moving the screen is generated, the screen does not vibrate greatly in the vicinity of the stop position. Therefore, the screen moving at high speed can be smoothly positioned at the stop position without oscillating, and an image that does not spread in the depth direction can be displayed favorably.

  As described above, according to the present invention, it is possible to provide an image display device capable of smoothly displaying a non-expanding image in the depth direction by smoothly pausing the reciprocating screen.

  The effects and significance of the present invention will become more apparent from the following description of embodiments. However, the embodiment described below is merely an example when the present invention is implemented, and the present invention is not limited to what is described in the following embodiment.

FIGS. 1A and 1B are diagrams schematically illustrating a usage pattern of the image display device according to the embodiment, and FIG. 1C is a schematic diagram of the configuration of the image display device according to the embodiment. FIG. FIG. 2 is a diagram illustrating a configuration of an irradiation light generation unit and a circuit used for the irradiation light generation unit of the image display device according to the embodiment. FIG. 3A is a perspective view showing the configuration of the drive unit according to the embodiment, and FIG. 3B is a cross-sectional view of a part of the drive unit according to the embodiment. FIG. 4A is a perspective view schematically showing the configuration of the screen according to the embodiment, and FIG. 4B is a diagram schematically showing a laser beam scanning method for the screen. FIGS. 5A and 5B are diagrams illustrating images obtained by imaging the microlens array and the bead assembly according to the embodiment, respectively. FIG. 6A is a plan view of a part of the mask according to the embodiment as viewed from the front, and FIG. 6B is a part of the mask before the wrinkles according to the embodiment are formed from the back. FIG. 6C is a perspective view of a part of the mask after the eyelids according to the embodiment are formed, as viewed from the back (Z-axis positive side). FIG. 7 is a diagram schematically illustrating the operation of the screen according to the embodiment. FIG. 8A is a diagram illustrating an example of a screen moving process according to the embodiment, and FIG. 8B is a diagram illustrating an example of an image displayed by moving the screen. FIG. 9A is a diagram illustrating a configuration of a screen driving circuit according to a comparative example, and FIG. 9B is a diagram illustrating a configuration of the screen driving circuit according to the embodiment. FIG. 10A is a diagram illustrating a waveform of a periodic signal supplied to the screen drive unit when the screen according to the embodiment is monotonously reciprocated, and a driving state of the screen based on the periodic signal. FIG.10 (b) is a figure which shows the waveform of the acceleration / deceleration signal superimposed when stopping the screen which concerns on embodiment. FIG. 10C is a diagram showing the waveform of the drive signal obtained by superimposing the acceleration / deceleration signal of FIG. 10B on the periodic signal of FIG. 10A, and the screen drive state by this drive signal. is there. FIG. 11A is a diagram illustrating a screen driving state when the end point position of the return path is deviated from the normal position due to the disturbance according to the embodiment. FIG. 11B is a diagram illustrating a correction operation when the end point position of the return path is deviated from the normal position due to the disturbance according to the embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. For convenience, X, Y, and Z axes that are orthogonal to each other are appended to each drawing as appropriate.

  FIGS. 1A and 1B are diagrams schematically illustrating how the image display device 20 is used. FIG. 1A is a schematic view of the inside of the passenger car 1 seen through from the side of the passenger car 1, and FIG. 1B is a view of the passenger car 1 as viewed from the front in the running direction.

  In the present embodiment, the present invention is applied to an in-vehicle head-up display. As shown in FIG. 1A, the image display device 20 is installed inside the dashboard 11 of the passenger car 1.

  As shown in FIGS. 1A and 1B, the image display device 20 projects the laser light modulated by the video signal onto the projection area 13 near the driver seat below the windshield 12. The laser light is reflected by the projection region 13 and is irradiated to a horizontally long region (eye box region) around the eye position of the driver 2. Thus, the predetermined image 30 is displayed as a virtual image in the field of view ahead of the driver 2. The driver 2 can superimpose an image 30 that is a virtual image on the scenery in front of the windshield 12. That is, the image display device 20 forms an image 30 that is a virtual image in a space in front of the projection region 13 of the windshield 12.

  FIG. 1C is a diagram schematically illustrating the configuration of the image display device 20.

  The image display device 20 includes an irradiation light generation unit 21 and a mirror 22. The irradiation light generation unit 21 emits laser light modulated by the video signal. The mirror 22 has a curved reflecting surface, and reflects the laser light emitted from the irradiation light generation unit 21 toward the windshield 12. The laser beam reflected by the windshield 12 is applied to the eyes 2a of the driver 2. The optical system and the mirror 22 of the irradiation light generation unit 21 are designed so that a virtual image 30 is displayed in a predetermined size in front of the windshield 12.

  FIG. 2 is a diagram illustrating a configuration of the irradiation light generation unit 21 of the image display device 20 and a configuration of a circuit used for the irradiation light generation unit 21.

  The irradiation light generation unit 21 includes a light source 101, collimator lenses 102 a to 102 c, a mirror 103, dichroic mirrors 104 and 105, a scanning unit 106, a correction lens 107, a screen 108, and a driving unit 109.

  The light source 101 includes three laser light sources 101a to 101c. The laser light sources 101a to 101c emit laser beams in a red wavelength band, a green wavelength band, and a blue wavelength band, respectively. In the present embodiment, in order to display a color image as the image 30, the light source 101 includes three laser light sources 101a to 101c. When displaying a monochromatic image as the image 30, the light source 101 may include only one laser light source corresponding to the color of the image. The laser light sources 101a to 101c are made of semiconductor lasers, for example.

  Laser light emitted from the laser light sources 101a to 101c is converted into parallel light by the collimator lenses 102a to 102c, respectively. At this time, the laser beams emitted from the laser light sources 101a to 101c are each shaped into a circular beam shape by an aperture (not shown). Instead of the collimator lenses 102a to 102c, a shaping lens that shapes the laser beam into a circular beam shape and converts it into parallel light may be used. In this case, the aperture can be omitted.

  Thereafter, the optical axes of the laser beams of the respective colors emitted from the laser light sources 101a to 101c are aligned by the mirror 103 and the two dichroic mirrors 104 and 105. The mirror 103 substantially totally reflects the red laser light transmitted through the collimator lens 102a. The dichroic mirror 104 reflects the green laser light transmitted through the collimator lens 102 b and transmits the red laser light reflected by the mirror 103. The dichroic mirror 105 reflects the blue laser light transmitted through the collimator lens 102 c and transmits the red laser light and the green laser light transmitted through the dichroic mirror 104. The mirror 103 and the two dichroic mirrors 104 and 105 are arranged so that the optical axes of the laser beams of the respective colors emitted from the laser light sources 101a to 101c are aligned.

  The scanning unit 106 reflects the laser light of each color that passes through the dichroic mirror 105. The scanning unit 106 includes, for example, a micro electro mechanical system (MEMS) mirror, and a mirror 106a on which laser light of each color that has passed through the dichroic mirror 105 enters an axis parallel to the Y axis according to a drive signal. And a configuration for rotating around an axis parallel to the X axis. By rotating the mirror 106a in this way, the reflection direction of the laser light changes in the in-plane direction of the XZ plane and the in-plane direction of the YZ plane. Thereby, as will be described later, the screen 108 is scanned by the laser light of each color.

  Here, the scanning unit 106 is configured by a biaxially driven MEMS mirror, but the scanning unit 106 may have other configurations. For example, the scanning unit 106 may be configured by combining a mirror that is rotationally driven around an axis parallel to the Y axis and a mirror that is rotationally driven around an axis parallel to the X axis.

  The correction lens 107 is designed to direct the laser light of each color in the positive direction of the Z axis regardless of the swing angle of the laser light by the scanning unit 106. The screen 108 scans the laser beam to form an image, and has an action of diffusing the incident laser beam to a region around the position of the eyes 2a of the driver 2 (eye box region). The configuration of the screen 108 will be described later with reference to FIGS. 4 (a) to 6 (c).

  The drive unit 109 reciprocates the screen 108 in a direction (Z-axis direction) parallel to the traveling direction of the laser light. The configuration of the drive unit 109 will be described later with reference to FIGS. 3 (a) and 3 (b).

  The image processing circuit 201 includes an arithmetic processing unit such as a CPU (Central Processing Unit) and a memory, and processes an input video signal to control the laser driving circuit 202, the mirror driving circuit 203, and the screen driving circuit 204. The laser drive circuit 202 changes the emission intensity of the laser light sources 101a to 101c in accordance with a control signal from the image processing circuit 201. The mirror driving circuit 203 drives the mirror 106 a of the scanning unit 106 in accordance with a control signal from the image processing circuit 201. The screen drive circuit 204 drives the screen 108 according to the control signal from the image processing circuit 201. The control in the image processing circuit 201 during the image display operation will be described later with reference to FIG.

  3A is a perspective view showing the configuration of the drive unit 109, and FIG. 3B is a plane parallel to the XZ plane of the drive unit 109 shown in FIG. 3A at the center position in the Y-axis direction. It is sectional drawing of the holder 303 vicinity at the time of cut | disconnecting by.

  The drive unit 109 has a symmetric configuration in the Y-axis direction and the X-axis direction. The drive unit 109 includes a rectangular housing 301 whose Z-axis negative side is open, a support plate 302 attached to the Z-axis negative side of the housing 301, a holder 303, two leaf springs 304, and a coil 305. And magnets 306 and 307 and a yoke 308.

  The support plate 302 includes a T-shaped support portion 302a that protrudes inward on the X-axis positive side and the X-axis negative side. Two leaf springs 304 are attached to these support portions 302a. The upper leaf spring 304 is fixed to the support portion 302a at the positions P1 and P2, and the lower leaf spring 304 is fixed to the support portion 302a at the positions P3 and P4. The two leaf springs 304 are respectively installed in parallel to the X axis.

  A holder 303 is fixed to an intermediate position in the longitudinal direction of the two leaf springs 304. The holder 303 includes two protrusions 303 a that protrude in the Y-axis positive direction and the Y-axis negative direction from an intermediate position in the X-axis direction, and these protrusions 303 a are fixed to the leaf spring 304. The holder 303 has a rectangular shape with rounded corners in plan view, and is formed with leg portions 303b extending from the four corners in the Z-axis positive direction. A coil 305 is mounted on the holder 303 so as to be wound around these four leg portions 303b. The holder 303 is made of a nonmagnetic material such as a resin material.

  The holder 303 is provided with a rectangular opening 303c, and the screen 108 is attached to the opening 303c. A step 303d is provided on the upper side of the opening 303c, and the screen 108 is fitted and fixed to the step 303d. An opening 301 a is provided on the bottom surface of the housing 301 at a position facing the screen 108. The light transmitted through the screen 108 in the positive Z-axis direction passes through the opening 301a and reaches the mirror 22 (see FIG. 1C).

  As shown in FIG. 3B, magnets 306 and 307 are arranged so as to sandwich a coil 305 wound and fixed in a rectangular shape on the four leg portions 303 b of the holder 303. A U-shaped yoke 308 is installed on the bottom surface of the housing 301, and magnets 306 and 307 are mounted on the inner surface of the yoke 308.

  3B shows the magnets 306 and 307 sandwiching the two sides of the coil 305 wound in a rectangular shape, but the remaining two sides of the coil 305 have the same configuration. It is sandwiched between two magnets. The magnets 306 and 307 and the remaining magnets have their magnetic poles adjusted so that a driving force in the Z-axis positive direction or the Z-axis negative direction is generated by passing a current through the coil 305. By switching the direction of the current flowing through the coil 305, the driving direction of the holder 303 is switched. By driving the holder 303 in this way, the screen 108 is driven in the Z-axis direction integrally with the holder 303.

  The drive unit 109 is provided with an encoder (not shown) that detects the position of the holder 303 in the Z-axis direction, that is, the position of the screen 108 in the Z-axis direction and outputs a signal related to the position. For example, the encoder may be configured to include a gauge that is installed in the holder 303 and moves together with the holder 303, and a sensor that is installed in the housing 301 and optically detects the gauge. As long as the position of the holder 303 in the Z-axis direction can be detected, an encoder having another configuration may be used.

  FIG. 4A is a perspective view schematically showing the configuration of the screen 108.

  In the present embodiment, the screen 108 includes a base material 401, a microlens array 402, a bead aggregate 403, and a mask 500. The screen 108 is configured by integrating a base material 401 having a microlens array 402 and a bead assembly 403 on both sides and a mask 500 via spacers (not shown).

  The base material 401 has a rectangular shape in a plan view and is made of a transparent material. For example, the base material 401 is made of a transparent resin such as PET (polyethylene terephthalate).

  The microlens array 402 is disposed on the surface of the substrate 401 on the laser light emission side. The microlens array 402 is formed, for example, by applying a resin material to the emission surface of the base material 401 and then roll-shaping the resin material.

  The bead aggregate 403 is disposed on the laser light incident side surface of the base material 401. The bead aggregate 403 is formed by applying beads containing a resin to the incident surface of the substrate 401.

  The materials and forming methods of the microlens array 402 and the bead aggregate 403 are not limited to the above, and other materials and forming methods may be used. For example, the beads 403a are not limited to resin and may be glass.

  FIG. 5A is an image obtained by capturing a part of the microlens array 402 from the Z axis positive side.

  As shown in FIG. 5A, the microlens array 402 has a configuration in which a predetermined number of rectangular lens portions 402a are arranged in a horizontal direction parallel to the X axis and a vertical direction parallel to the Y axis in plan view. ing. The width Wx in the horizontal direction of each lens unit 402a is the same as each other, and the width Wy in the vertical direction of each lens unit 402a is also the same. The widths Wx and Wy are about several tens of μm. In the example of FIG. 5A, the width Wx and the width Wy are set to the same dimension, but the width Wx and the width Wy may be different.

  Each lens unit 402a has a different curvature radius Rx in the X-axis direction and a curvature radius Ry in the Y-axis direction. Here, the radius of curvature Rx is smaller than the radius of curvature Ry, for example, Rx: Ry = 1: 2. Therefore, in the lens portion 402a, the curvature in the X-axis direction is larger than the curvature in the Y-axis direction. By setting the curvature of the lens portion 402a in this manner, the laser light transmitted through each lens portion 402a can be efficiently guided to a horizontally long region (eye box region) around the position of the eyes 2a of the driver 2. it can. The curvature of the lens unit 402a is determined according to the shape of the eye box region.

  FIG. 5B is an image obtained by imaging a part of the bead assembly 403 from the negative side of the Z axis.

  As shown in FIG. 5B, the bead aggregate 403 has a configuration in which the beads 403a are spread almost without gaps in plan view. The beads 403a are made of spherical particles. Here, the beads 403a have non-uniform particle sizes. If the particle size of the beads 403a is uniform, the beads 403a are likely to be regularly arranged in the bead aggregate 403. For this reason, there is a problem in that the laser beam penetrates the beads 403a as they are and a bright spot is generated on the image 30. Can happen. On the other hand, if the particle size of the beads 403a is set non-uniformly, the beads 403a are irregularly distributed as shown in FIG. 5B, so that the laser light does not penetrate the beads 403a as they are, and as a result, Generation of bright spots on the image 30 can be suppressed.

  FIG. 4B is a diagram schematically showing a laser beam scanning method for the screen 108.

  The surface of the screen 108 having the above configuration on the side of the bead assembly 403 is scanned in the positive direction of the X axis by the beam B1 on which the laser beams of the respective colors are superimposed. Scan lines L1 to Ln through which the beam B1 passes are set in advance in the Y-axis direction at regular intervals with respect to the surface of the screen 108 on the bead assembly 403 side. The start position and the end position of the scanning lines L1 to Ln coincide with each other in the X-axis direction. Therefore, the area surrounding the scanning lines L1 to Ln is a rectangle. The diameter of the beam B1 is set to about 100 μm, for example.

  The scanning lines L1 to Ln are scanned at a high frequency by the beam B1 in which the laser light of each color is modulated by the video signal, thereby forming an image. The image thus configured is projected onto an area (eye box) around the position of the eye 2a of the driver 2 via the screen 108, the mirror 22 and the windshield 12 (see FIG. 1C). As a result, the driver 2 visually recognizes the image 30 as a virtual image in the space in front of the windshield 12.

  6A is a plan view of a part of the mask 500 as viewed from the front (Z-axis negative side), and FIG. 6B is a back view of the part of the mask 500 before the ridge 502 is formed (Z FIG. 6C is a perspective view of a part of the mask 500 after the ridge 502 is formed, as viewed from the back (Z-axis positive side). For convenience, in FIG. 6A, the uppermost lens portion 402a of the microlens array 402 is indicated by a broken line.

  As shown in FIG. 6B, the mask 500 before the ridge 502 is formed has a plurality of grooves 500a extending in the X-axis direction on the light incident side (Z-axis negative side) surface in the Y-axis direction. Are formed at a constant pitch. The groove 500a extends from the X-axis positive side surface of the mask 500 to the X-axis negative side surface. The cross section of the groove 500a cut along a plane parallel to the YZ plane is an isosceles triangle. The mask 500 is made of a transparent resin material such as PET. The mask 500 may be made of other transparent materials such as glass.

  As shown in FIG. 6C, a ridge 502 is formed by embedding a black pigment that absorbs light in each groove 500a. The cross-sectional shape of the flange 502 is an isosceles triangle like the groove 500a. In addition, a horizontally long opening 501 that transmits light is formed between two ridges 502 adjacent in the Y-axis direction. The light that has entered the opening 501 from the Z-axis negative side passes through the opening 501a and is emitted from the surface on the Z-axis positive side. Further, light incident on the ridge 502 from the Z-axis negative side is absorbed by the ridge 502.

  As shown in FIG. 6A, in the mask 500 having the above-described configuration, horizontally long rectangular openings 501 are arranged at regular intervals in the vertical direction in plan view. The width of the opening 501 in the horizontal direction is set wider than the range of all the lens portions 402a arranged in the horizontal direction. That is, the opening 501 covers the range in the horizontal direction of the group of lens units 402a arranged in the horizontal direction.

  Further, the vertical width of the opening 501 is set to be narrower than the width Wy of the lens portion 402a. Further, the vertical width of the opening 501 is set to a dimension that does not cause diffraction in the laser light passing through the opening 501. For example, in the laser light sources 101a to 101c in the wavelength band, diffraction occurs in the laser light when the vertical width of the opening 501 is 10 μm or less. For this reason, the vertical width of the opening 501 may be set to 10 μm or more. The length of the flange 502 in the X-axis direction is the same as the length of the opening 501 in the X-axis direction.

  FIG. 7 is a diagram schematically showing the operation of the screen 108.

  The laser light (beam B 1 in FIG. 4B) incident on the screen 108 is diffused by the bead assembly 403 and then enters the microlens array 402. Here, the laser light diffused by the bead assembly 403 enters the plurality of lens portions 402a of the microlens array 402 and receives an optical action from the lens portions 402a. The lens unit 402a imparts a converging action to the laser light to guide the transmitted laser light to an area (eye box) around the position of the eyes 2a of the driver 2. The convergence action of the lens unit 402a is set in consideration of the optical action of the mirror 22 and the windshield 12 (see FIG. 1C).

  Thereafter, the laser light is guided to the mirror 22 through the opening 501 of the mask 500. At this time, most of the laser light passing through the opening 501 is guided to the mirror 22 without entering the ridge 502. However, as shown in FIG. 7, a part of the laser light that passes through the opening 501 enters the ridge 502 and receives an optical action from the ridge 502. That is, the laser light incident on the ridge 502 at a shallow angle is reflected at the interface of the groove 500a (see FIG. 6B) before the ridge 502 and guided to the mirror 22. Further, the laser light incident on the ridge 502 at a deep angle passes through the interface of the groove 500a (see FIG. 6B) before the ridge 502, reaches the ridge 502, and is absorbed by the ridge 502.

  As described above, the ridge 502 excludes a part of the laser beam for image display transmitted through the microlens array 402 from the image display. On the other hand, however, the ridge 502 reverses the optical path from the screen 108 toward the mirror 22 and the windshield 12, and incident light (stray light) such as natural light that enters the screen 108 from the outside enters the bead assembly 403. Demonstrate the effect of light shielding.

  For example, when the mask 500 is not provided, stray light that enters the screen 108 from the outside as described above passes through the microlens array 402 and enters the bead assembly 403. Here, since the bead aggregate 403 is composed of beads 403a having various particle diameters, a part of the stray light incident on the bead aggregate 403 is reflected by the beads 403a in the bead aggregate 403, and the microlens. Head towards the array 402. Thus, the stray light directed to the microlens array 402 passes through the microlens array 402 and is guided to the mirror 22. As a result, the driver 2 visually recognizes an image in which a white blurred image due to stray light is superimposed on an image based on the video signal. In this case, the driver 2 sees an unnatural image in which a white blurred region is superimposed on the scenery in front of the windshield 12, resulting in the driver 2 feeling uncomfortable.

  In contrast, when the mask 500 is arranged on the positive side of the Z-axis of the microlens array 402 as in the present embodiment, stray light from the outside is blocked by the ridge 502 of the mask 500. Therefore, it is possible to suppress a white blurred image due to stray light from being superimposed on an image based on the video signal, and to provide the driver 2 with a natural image.

  From the viewpoint of blocking stray light, it can be said that the height of the ridge 502 in the Z-axis direction is desirable. However, when the height of the ridge 502 is increased, the amount of the laser light based on the video signal transmitted through the microlens array 402 is increased by the ridge 502, and the brightness of the image 30 provided to the driver 2 decreases. . Therefore, it is necessary to set the height of the ridge 502 to an appropriate value in consideration of suppression of stray light superimposition on the image 30 and securing the luminance of the image 30. For example, as shown in FIG. 6C, when the cross-sectional shape of the flange 502 is an isosceles triangle, the height of the flange 502 is 3 to 5 times the width of the opening 501 in the Y-axis direction. desirable.

  In the present embodiment, the cross-sectional shape of the ridge 502 is an isosceles triangle as described above, and this is due to the following reason.

  That is, in order to form the ridge 502 with high accuracy while maintaining the mechanical strength, it is necessary to secure the width of the bottom side portion of the ridge 502 to a predetermined dimension or more. Here, if the ridge 502 protrudes in the positive direction of the Z-axis with the width of the bottom portion, the ratio of the laser light incident on the ridge 502 out of the laser light based on the video signal transmitted through the lens portion 402a increases. The brightness of the image 30 provided to the driver 2 is reduced. On the other hand, if the cross-sectional shape of the heel 502 is made to be a shape whose width decreases toward the tip, the amount of laser light based on the video signal incident on the heel 502 can be reduced, and the image 30 provided to the driver 2 Can increase the brightness.

  As described above, the ridge 502 is directed to the tip from the viewpoint of forming the ridge 502 with high accuracy while maintaining the mechanical strength, and from the viewpoint of reducing the amount of laser light based on the video signal shielded by the ridge 502. Accordingly, the cross-sectional shape becomes narrower in width, that is, the cross-sectional shape of an isosceles triangle.

  Note that the cross-sectional shape of the ridge 502 is not limited to an isosceles triangle as long as the width becomes narrower toward the tip, and may be another shape. For example, the cross-sectional shape of the ridge 502 may be a shape in which two sides of an isosceles triangle are slightly recessed in an arc shape inward, or may be a trapezoid. In addition, as long as the ridge 502 can be formed with high accuracy while maintaining mechanical strength, the cross-sectional shape of the ridge 502 may be a rectangle in which the width of the bottom portion on the Z-axis negative side is further reduced.

  As described above, the mask 500 exerts an action of shielding stray light incident on the screen 108 from the outside. Thereby, the effect that the image quality fall of the image 30 by stray light injecting into the bead aggregate 403 can be suppressed is show | played.

  FIG. 8A is a diagram illustrating an example of the moving process of the screen 108, and FIG. 8B is a diagram illustrating an example of an image displayed by moving the screen 108. The moving process of FIG. 8A is a moving process of the screen 108 when displaying an image as shown in FIG.

  As shown in FIG. 8A, the movement of the screen 108 is repeated with time t0 to t4 as one cycle. Between times t0 and t1, the screen 108 is moved from the initial position Ps0 to the farthest position Ps1, and between times t1 and t4, the screen 108 is returned from the farthest position Ps1 to the initial position Ps0. The moving period of the screen 108, that is, the time from time t0 to t4 is, for example, 1/60 seconds. The screen 108 is moved as shown in FIG. 8A by changing the current applied to the coil 305 shown in FIG.

  Time t0 to t1 is a period for displaying the depth image M1 spreading in the depth direction in FIG. 8B, and time t1 to t4 is the vertical image M2 spreading in the vertical direction in FIG. 8B. This is the period for display. In the example of FIG. 8B, the depth image M1 is an arrow for suggesting to the driver 2 the direction in which the passenger car 1 should turn on the road R1 by the navigation function, and the vertical image M2 includes the pedestrian H1. This is a marking for alerting the driver 2. For example, the depth image M1 and the vertical image M2 are displayed in different colors.

  At time t0 to t1, the screen 108 is linearly moved from the initial position Ps0 to the farthest position Ps1. As the screen 108 moves, the position where the virtual image in front of the windshield 12 is formed moves in the depth direction. Therefore, when the screen 108 exists at each position in the depth direction of the depth image M1, the laser light sources 101a to 101c are caused to emit light at the timing corresponding to the depth image M1 on the scanning line corresponding to the depth image M1. A depth image M1 as shown in FIG. 8B can be displayed as a virtual image in front of the projection area 13 of the windshield 12.

  On the other hand, since the vertical image M2 does not change in the depth direction and spreads only in the vertical direction, it is necessary to generate a virtual image with the screen 108 fixed at a position corresponding to the vertical image M2. The stop position Ps2 in FIG. 8A is the position of the screen 108 corresponding to the depth position of the vertical image M2. While the screen 108 returns from the farthest position Ps1 to the initial position Ps0, the screen 108 is stopped at the stop position Ps2 from time t2 to time t3. In the meantime, the laser light sources 101a to 101c emit light at the timing corresponding to the vertical image M2 on the scanning line corresponding to the vertical image M2, so that the front of the projection area 13 of the windshield 12 is shown in FIG. It is possible to display a vertical image M2 as shown in FIG.

  The above control is performed by the image processing circuit 201 shown in FIG. By this control, the depth image M1 and the vertical image M2 are displayed as virtual images between time t0 and time t4. In the above control, there is a difference between the display timing of the depth image M1 and the display timing of the vertical image M2, but since this shift is extremely short, the driver 2 is an image obtained by superimposing the depth image M1 and the vertical image M2. Recognize In this way, the driver 2 can view the image (depth image M1 and vertical image M2) based on the video signal in front of the projection area 13 over the landscape including the road R1 and the pedestrian H1.

  In FIG. 8B, since there is one vertical image M2, the stop position Ps2 of the screen 108 is set to one in the process of FIG. 8A, but if there are a plurality of vertical images M2. Accordingly, a plurality of stop positions are set in the process of FIG. However, in the process of FIG. 8A, the time from time t0 to t4 is constant, and time t4 is unchanged, so the moving speed of the screen 108 before and after the stop position ( The slope of the waveform in FIG. 8A is changed.

  Next, the circuit configuration of the screen driving circuit 204 will be described.

  First, FIG. 9A shows a circuit configuration of a screen driving circuit 204 according to a comparative example.

  The screen drive circuit 204 according to the comparative example includes a counter 211, a comparison circuit 212, and a current control circuit 213. A pulse signal Pt having the number of pulses corresponding to the moving position of the screen 108 is input from the image processing circuit 201 to the counter 211. The comparison circuit 212 compares the signal input from the counter 211 (target position of the screen 108) with the signal input from the encoder of the drive unit 109 (current position of the screen 108), and according to the difference between the two signals. The signal is output to the current control circuit 213. Based on the signal input from the comparison circuit 212, the current control circuit 213 drives the drive signal Sd to be applied to the coil 305 of the drive unit 109 so that the position of the drive unit 109 converges to a position corresponding to the count value of the counter 211. Adjust. As a result, the screen 108 moves while following the position designated by the image processing circuit 201.

  At this time, the image processing circuit 201 outputs, for example, a pulse signal Pt that moves the screen 108 to the counter 211 in accordance with the waveform shown in FIG. In this case, the screen driving circuit 204 according to the comparative example performs control to rapidly stop the screen 108 that moves between times t1 and t2 at time t2, and then maintain the screen 108 in a stopped state until time t3.

  However, in this control, after the screen 108 overruns the stop position Ps2, the drive unit 109 that drives the screen 108 returns the screen 108 to the stop position Ps2, and then gradually converges the screen 108 to the stop position Ps2. A drive signal Sd is supplied. Therefore, in this control, the screen 108 vibrates in the vicinity of the stop position from the time t2 until the screen 108 stops at the stop position Ps2. Such vibration reduces the image quality of the vertical image M2 (see FIG. 8B) that does not spread in the depth direction. Specifically, the outline of the image is blurred, resulting in a video lacking visibility. Further, if it is attempted to converge the vibration of the screen 108 in a short time in order to suppress the deterioration of the image quality, the screen 108 is elastically supported by the leaf spring 304 as shown in FIG. 108 may resonate and the screen 108 may oscillate greatly without converging to the stop position. In this case, the vertical image M2 that does not spread in the depth direction can no longer be properly displayed.

  In order to solve such a problem, the screen driving circuit 204 according to the present embodiment has a configuration shown in FIG.

  The screen drive circuit 204 according to the present embodiment includes a periodic signal generation circuit 221, an acceleration / deceleration signal generation circuit 222, an adder 223, and a current control circuit 224. The periodic signal generation circuit 221 outputs a signal for moving the screen 108 back and forth monotonously at a predetermined period. The acceleration / deceleration signal generation circuit 222 outputs a signal for moving the screen 108 again after being stopped for a certain period in accordance with the control signal Cs from the image processing circuit 201. The adder 223 supplies the current control circuit 224 with a signal obtained by superimposing the signal input from the acceleration / deceleration signal generation circuit 222 on the signal input from the periodic signal generation circuit 221. The current control circuit 224 changes the drive signal Sd applied to the coil 305 of the drive unit 109 according to the signal input from the adder 223.

  FIG. 10A shows a waveform of a drive signal (periodic signal) supplied to the drive unit 109 of the screen 108 when the screen 108 is monotonously moved back and forth, and the screen 108 driven by this drive signal (periodic signal). It is a figure which shows the simulation result of this movement position.

  In FIG. 10A, “current value” indicates a drive signal supplied to the coil 305 of the drive unit 109. In FIG. 10A, “target value” indicates the movement target position of the screen 108, and “actual value” indicates the case where the drive signal of “current value” is supplied to the coil 305 of the drive unit 109. The actual moving position of the screen 108 is shown. The horizontal axis represents time, the left vertical axis represents the position of the screen 108, and the right vertical axis represents the current value.

  When the screen 108 is not stopped on the return path, a drive signal (periodic signal) having a current value shown in FIG. 10A is applied to the coil 305 of the drive unit 109. In this case, a signal having the same waveform as the current value in FIG. 10A is output from the periodic signal generation circuit 221 in FIG. No signal is output from the acceleration / deceleration signal generation circuit 222 of FIG. By applying such a drive signal (current value) to the coil 305 of the drive unit 109, the screen 108 can be moved while following the position of the substantially target value, as shown in FIG.

  In FIG. 10A, the forward movement of the screen 108 is activated by the positive amplitude waveform signal A11, and the screen 108 is moved at a constant speed by the positive amplitude waveform signal A12. Further, the moving direction of the screen 108 is reversed in the backward direction by the waveform signal A13 having a negative amplitude, and the screen 108 is driven at a constant speed by the waveform signal A14 having a negative amplitude.

  FIG. 10B is a diagram illustrating a waveform of a signal (acceleration / deceleration signal) superimposed on the drive signal (periodic signal) in FIG. 10A when the screen 108 is stopped for a predetermined period.

  FIG. 10B shows a signal output from the current control circuit 224 of FIG. 9B. In this case, the acceleration / deceleration signal generation circuit 222 in FIG. 9B outputs a signal having the same waveform as that in FIG.

  In FIG. 10B, a braking force is applied to the movement of the screen 108 by the positive amplitude waveform signal A21, and the backward movement of the screen 108 is activated again by the negative amplitude waveform signal A22. Further, a propulsive force that increases the moving speed of the return path is applied to the screen 108 by a waveform signal A23 having a negative amplitude following the waveform signal A22. In the example of FIG. 10B, since the stop period of the screen 108 is short, the waveform signal A21 and the waveform signal A22 are substantially continuous. However, when the stop period of the screen 108 is long, the waveform signal A21 and the waveform Between the signal A22, a waveform signal having a positive amplitude that cancels the drive signal (periodic signal) in FIG. 10A during that period is set.

  FIG. 10C shows the waveform of the drive signal (current value) obtained by superimposing the signal (acceleration / deceleration signal) of FIG. 10B on the drive signal (periodic signal) of FIG. It is a figure which shows the simulation result of the movement position of the screen driven by the signal.

  In this case, a signal having a waveform corresponding to the current value in FIG. 10A is output from the periodic signal generation circuit 221 in FIG. Also, a signal having a waveform corresponding to the current value in FIG. 10B is output from the acceleration / deceleration signal generation circuit 222 in FIG. 9B. These two signals are superimposed on each other by the adder 223 in FIG. 9B and input to the current control circuit 224. As a result, a drive signal indicated by the current value in FIG.

  By applying the drive signal (current value) thus generated to the coil 305 of the drive unit 109, the screen 108 can be moved while following the position of the substantially target value, as shown in FIG. 10C. . In the stop period T1, the screen 108 can be substantially stopped at the target position of 2.0 mm.

  In the signal shown in FIG. 10B, a propulsive force that increases the moving speed of the return path is applied to the screen 108 by the waveform signal A23 having a negative amplitude following the waveform signal A22. For this reason, as shown in FIG. 10C, in the return path following the stop period T1, the moving speed of the screen 108 is increased as compared with the case of FIG. 10A, and the end time of the drive signal is shown in FIG. It coincides with the end time of the drive signal in a). Thereby, the periodicity of the drive signal is maintained. The negative amplitude of the waveform signal A23 in FIG. 10B is set larger as the stop period T1 becomes longer so that the periodicity of the drive signal is ensured in this way.

  According to the screen drive circuit 204 according to the present embodiment, as described above, the acceleration / deceleration signal for stopping the screen 108 is used as the periodic signal for causing the screen 108 to reciprocate monotonously in a predetermined cycle, and the stop timing of the screen 108 is used. Accordingly, a drive signal for moving the screen 108 is generated in accordance with the above, so that the screen 108 does not vibrate excessively near the stop position as in the comparative example, and the screen 108 is smoothly moved to the stop position. Can be positioned. Therefore, even when the screen 108 is elastically supported by the leaf spring 304 as shown in FIG. 3A, the screen 108 does not resonate when stopped, and the screen 108 transmits a large amount at the stop position. There is nothing. Therefore, it is possible to satisfactorily display the vertical image M2 that does not spread in the depth direction during the stop period of the screen 108.

  FIG. 10C shows an example in which there is one stop position of the screen 108. However, when there are a plurality of stop positions of the screen 108, the waveform shown in FIG. The deceleration signal is superimposed on the drive signal (periodic signal) shown in FIG. 10A at a timing corresponding to each stop position. The superimposition timing of the acceleration / deceleration signal is instructed by the control signal Cs from the image processing circuit 201 in FIG. However, the number of stop positions that can be set is limited to the number that can superimpose the waveform signal of FIG. 10B in the falling period of the periodic signal of FIG.

  Further, in the screen driving circuit 204 according to the present embodiment, the actual movement position of the screen 108 is not fed back to the generation of the driving signal in one cycle period of the driving signal. It can be assumed that a deviation occurs in the end point position or the end point position of the return path. As described above, when a shift occurs in the end position of the forward path or the end position of the return path of the screen 108, the screen 108 is not moved within the normal stroke range.

  For example, as shown in FIG. 11A, it is assumed that the end point position of the return path of the screen 108 is displaced from the initial position Ps0 to the farthest position Ps1 side by ΔP during the return period of the screen 108 due to the disturbance Ds. In this case, the movement of the screen 108 in the next cycle is started from a position Ps0 ′ that is shifted by ΔP from the normal initial position Ps0. For this reason, the end point position of the forward path and the end position of the return path in the next cycle are positions that are separated by ΔP from the regular farthest position Ps1 and the initial position Ps0, respectively, and the stop position is also ΔP from the regular stop position Ps2. It will be a position far away. These positional shifts are inherited in the subsequent drive signal cycle. This problem also occurs when the end position of the forward path of the screen 108 is shifted due to disturbance during the forward path period.

  In order to solve such a problem, in this embodiment, as shown in FIG. 9B, the position signal output from the encoder of the drive unit 109 is input to the periodic signal generation circuit 221 to generate the periodic signal. In the circuit 221, the end position of the forward path and the end position of the return path of the screen 108 are monitored. If the end position of the forward path or the end position of the return path of the screen 108 deviates from the normal farthest position Ps1 or the initial position Ps0, the forward path output from the periodic signal generation circuit 221 so as to correct the deviation. The period signal is adjusted. In other words, the periodic signal generation circuit 221 determines whether the peak value (the end position of the forward path) and the bottom value (the end position of the return path) of the position signal acquired from the drive unit 109 match the boundary of the stroke range of the reciprocating movement of the screen 108. Based on whether or not, the waveform of the periodic signal is adjusted.

  For example, as shown in FIG. 11A, when the end point position of the return path is shifted by ΔP from the normal initial position Ps0 due to the disturbance Ds, the periodic signal generation circuit 221 eliminates this shift in the forward period of the next period. The output signal is adjusted so as to reduce the moving speed of the screen 108 by a necessary amount. Specifically, the periodic signal generation circuit 221 reduces the amplitude of the waveform signal A11 in the normal current value signal shown in FIG. The amplitude of A12 is reduced to lower the moving speed of the screen 108 than usual. As a result, as shown in FIG. 11B, the end position of the forward path of the screen 108 in the next cycle is aligned with the regular farthest position Ps1. In the subsequent return period, the periodic signal generation circuit 221 outputs a signal having the same waveform as that in the normal case. Thereby, the end point position of the return path of the screen 108 is aligned with the regular initial position Ps0, and the stop position of the screen 108 is aligned with the regular stop position Ps2.

  After the deviation is thus eliminated, the periodic signal generation circuit 221 outputs a signal similar to that in the normal case in both the forward pass period and the return pass period. Thereafter, the periodic signal generation circuit 221 continues to monitor the position signal output from the encoder of the drive unit 109, and each time it detects that a deviation has occurred in the end position of the forward path or the end position of the return path of the screen 108, A correction operation similar to the above is executed.

  Even when a disturbance or the like occurs in the forward path, and the end position of the forward path deviates from the farthest position Ps1, the periodic signal generation circuit 221 eliminates this shift in the forward period of the next cycle as described above. The output signal is adjusted so as to reduce the moving speed of the screen 108 by a necessary amount. Thereby, as described above, the end point position of the forward path and the end point position of the return path are matched with the regular farthest position Ps1 and the initial position, respectively.

<Effect of embodiment>
As described above, according to the present embodiment, the following effects are exhibited.

  The acceleration / deceleration signal (see FIG. 10B) for stopping the screen 108 is set in accordance with the stop timing of the screen 108 in response to a periodic signal (see FIG. 10A) for reciprocating the screen 108 monotonously in a predetermined cycle. Thus, a drive signal (see FIG. 10C) for moving the screen 108 is generated, so that the screen 108 does not vibrate excessively near the stop position. Therefore, the screen 108 moving at high speed can be smoothly positioned at the stop position without oscillating, and the vertical image M2 that does not spread in the depth direction can be displayed favorably.

  Further, the forward period from time t0 to t1 in FIG. 8A is set to a period in which the screen 108 is monotonously moved to display the depth image M1, and the screen 108 is stopped at any time during the return period from time t0 to t1. Therefore, since the vertical image M2 is set to be displayed, the depth image M1 and the vertical image M2 can be displayed smoothly by a simple process.

  Further, as shown in FIG. 8A, the return pass period in which the screen 108 is stopped is set longer than the forward pass period in which the screen 108 is not stopped. For this reason, more stop periods for stopping the screen 108 can be set with respect to the return path period, and the vertical image M2 can be arranged more effectively in the display image.

  As shown in FIG. 11B, when the screen 108 is displaced due to the influence of disturbance Ds or the like, the signal output from the periodic signal generation circuit 221 is adjusted according to the positional displacement of the screen 108, Misalignment is eliminated. Thereby, the depth image M1 and the vertical image M2 can always be displayed at appropriate positions.

  The embodiment of the present invention has been described above, but the present invention is not limited to the above embodiment, and the application example of the present invention can be modified in various ways in addition to the above embodiment. Is possible.

  For example, in the above-described embodiment, the depth image M1 is displayed in the forward path when the screen 108 is reciprocated, and the vertical image M2 is displayed by pausing the screen 108 in the return path. However, the screen 108 is temporarily stopped in the forward path. The vertical image M2 may be displayed, and the depth image M1 may be displayed while moving the screen 108 monotonously on the return path. In this case, the acceleration / deceleration signal shown in FIG. 10B is superimposed on the drive signal at the movement timing of the screen 108 in the forward path period. In this case, it is preferable that the forward period is longer than the return period so that more stop periods can be set as the forward period.

  In the above embodiment, the screen 108 is configured to include the microlens array 402 and the bead assembly 403, the opening 501 and the ridge 502. However, the screen 108 is scanned with laser light. Any other configuration may be used as long as an image is generated and the generated image can be formed as a virtual image. For example, the screen 108 may include only the microlens array 402 or may be configured by combining a plurality of microlens arrays 402.

  However, when the screen 108 is configured as in the above embodiment, the laser light from the light source 101 is randomly diffused by the bead assembly 403 and then enters the microlens array 402. For this reason, the laser light after passing through the microlens array 402 is separated from the optical path, and it is difficult to align the phases of each other. Therefore, the generation of speckle noise due to interference can be more effectively suppressed. In addition, since the laser light is diffused by the bead aggregate 403, it is not necessary to strictly adjust the positional relationship between the bead aggregate 403 and the microlens array 402. Therefore, the work at the time of assembly can be simplified. Note that speckle noise can be more effectively suppressed as the particle size of the beads 403a is reduced. As described above, it is desirable that the beads 403a have a non-uniform particle size.

  Moreover, in the said embodiment, although the example which applied this invention to the head-up display mounted in the passenger car 1 was shown, this invention is applicable not only to vehicle-mounted but another kind of image display apparatus. It is.

  The configurations of the image display device 20 and the irradiation light generation unit 21 are not limited to the configurations described in FIG. 1C and FIG. 2, and can be changed as appropriate. Further, the configuration of the drive unit 109 that moves the screen 108 is not limited to the configuration illustrated in FIGS. 3A and 3B, and can be changed as appropriate.

  In the above-described embodiment, the image processing circuit 201 and the screen driving circuit 204 are shown separately, but these may be composed of one control unit.

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

20 ... Image display device 22 ... Mirror (optical system)
DESCRIPTION OF SYMBOLS 101 ... Light source 106 ... Scanning part 108 ... Screen 109 ... Drive part 202 ... Laser drive circuit (light source drive circuit)
203 ... Mirror drive circuit (scanning unit drive circuit)
204 ... Screen drive circuit 205 ... Image processing circuit (control circuit)
302a ... support part 303 ... holder 304 ... leaf spring (support part)
305 ... Coil 306, 307 ... Magnet

Claims (6)

A light source that emits light;
A screen on which an image is formed by scanning the light;
A scanning unit that scans the screen with the light emitted from the light source;
An optical system that generates a virtual image by the light transmitted through the screen;
A drive unit that moves the screen parallel to at least the traveling direction of the light;
A screen drive circuit for driving the drive unit,
The screen drive circuit moves the screen by superimposing an acceleration / deceleration signal for stopping the screen on a periodic signal that causes the screen to reciprocate monotonously at a predetermined period according to the stop timing of the screen. Generating a drive signal for,
An image display device characterized by that. The image display device according to claim 1,
The screen driving circuit does not stop the movement of the screen in a first movement stroke in which the screen moves in a first direction, and the screen moves in a second direction opposite to the first direction. Stop the movement of the screen in two movement strokes;
An image display device characterized by that. The image display device according to claim 2,
A light source driving circuit for driving the light source;
A scanning unit driving circuit for driving the scanning unit;
A control circuit for controlling the screen driving circuit, the light source driving circuit and the scanning unit driving circuit,
The control circuit generates a virtual image of a depth image spreading in the depth direction in the first movement stroke, and does not spread in the depth direction in a period for stopping the movement of the screen in the second movement stroke. Execute control to generate a virtual image of the vertical image,
An image display device characterized by that. The image display device according to claim 2 or 3,
The period signal has a period for moving the screen in the second direction longer than a period for moving the screen in the first direction.
An image display device characterized by that. The image display device according to any one of claims 1 to 4,
The drive unit outputs a position signal indicating the position of the screen to the screen drive circuit;
The screen drive circuit adjusts the waveform of the periodic signal based on whether the peak value and the bottom value of the position signal acquired from the drive unit match the boundary of the reciprocating range of the screen.
An image display device characterized by that. In the image display device according to any one of claims 1 to 5,
The drive unit is
A holder for holding the screen;
A support portion for supporting the holder in an elastically displaceable manner;
A coil and a magnet for applying a driving force to the holder,
An image display device characterized by that.