JP2020071475A - Display unit, display system, and movable body - Google Patents

Abstract

To provide a display unit that displays a virtual image having an appropriate brightness.SOLUTION: A display unit comprises: a light source that radiates light; a light deflection unit that deflects the radiated light to be incident in a main scanning direction and a sub scanning direction; a divergent optical system that diverges deflected light to be incident, and the display unit forms a virtual image to be visually recognized by an observer with divergent light diverged by the divergent optical system. The display unit has a dioptric system refracting the deflected light to be incident on a light path between the light deflection unit and the divergent optical system, and the refractive power in the main scanning direction and the refractive power in the sub scanning direction are different in the dioptric system.SELECTED DRAWING: Figure 13

Description

  The present invention relates to a display device, a display system and a moving body.

In a moving body such as a vehicle, various information (vehicle information,
A display device such as a HUD (Head Up Display) is used as an application for visually recognizing warning information, navigation information, and the like.

  For example, in Patent Document 1, image light emitted from a light source is two-dimensionally scanned in a main scanning direction and a sub scanning direction by an optical scanning unit to form an intermediate image on a light diverging portion, and the intermediate image is formed on a windshield of a vehicle. A display device that displays a virtual image by superimposing and projecting it on a projection target member such as the above is displayed.

  Further, in Patent Document 2, a light source that generates a light flux having coherence, and an optical plate that has a plurality of microlenses arranged at a cycle larger than the diameter of the light flux and controls the divergence angle of the light flux, There is described a display device comprising:

  An object of the present invention is to provide a display device that displays a virtual image having appropriate brightness.

  In order to solve the above-mentioned problems, the invention according to claim 1 provides a light source that emits light, and a light deflector that deflects the incident light that is incident in the main scanning direction and the sub-scanning direction. A divergence optical system for diverging the deflected deflected light, and a display device for forming a virtual image to be visually recognized by an observer by the divergent light diverged by the divergent optical system. A display having a refraction optical system for refracting the incident deflected light on an optical path between the refraction optical system and the refraction power in the main scanning direction and the refraction power in the sub scanning direction of the refraction optical system. It is a device.

  According to the present invention, it is possible to provide a display device that displays a virtual image having appropriate brightness.

It is a figure which shows an example of the system configuration of the display system which concerns on 1st Embodiment. It is a figure which shows an example of the hardware constitutions of the display apparatus which concerns on 1st Embodiment. It is a figure showing an example of functional composition of a display concerning a 1st embodiment. It is a figure which shows an example of the specific structure of the light source device which concerns on 1st Embodiment. It is a figure which shows an example of the specific structure of the optical deflection apparatus which concerns on 1st Embodiment. It is a figure which shows an example of the specific structure of the screen which concerns on 1st Embodiment. It is a figure for demonstrating the difference in an operation | movement by the difference in the magnitude relationship of an incident light beam diameter and a lens diameter in a micro lens array. It is a figure for demonstrating the correspondence of the mirror of a light deflection device, and a scanning range. It is a figure which shows an example of the scanning line locus at the time of two-dimensional scanning. It is a figure which shows the intensity distribution of the light beam diverged by the screen. It is the figure which showed the outline of the optical path length in the display system which concerns on 1st Embodiment. It is a figure for explaining roughly an example of the relative physical relationship of each component in the display system concerning a comparative example. It is a figure for explaining roughly an example of the relative physical relationship of each component in the display system concerning this embodiment. It is a figure which shows the 1st modification of the system configuration of a display system. It is a figure which shows the 2nd modification of the system configuration of a display system. It is a first example of an optical element that constitutes the refractive optical system according to the present embodiment. It is a second example of an optical element forming the refractive optical system according to the present embodiment. It is the 3rd example of the optical element which constitutes the refraction optical system concerning this embodiment. It is the 4th example of the optical element which constitutes the refraction optical system concerning this embodiment. It is a figure for demonstrating the astigmatic difference produced by the optical element which comprises a refractive optical system. It is a figure for demonstrating the relationship between the focus position of a refraction optical system, and the beam diameter of the light beam which injects into a light deflection part.

  Hereinafter, embodiments for carrying out the invention will be described with reference to the drawings. In the description of the drawings, the same elements will be denoted by the same reference symbols, without redundant description.

System Configuration FIG. 1 is a diagram showing an example of the system configuration of the display system according to the first embodiment. The display system 1 causes the observer 3 to visually recognize the display image by projecting the projection light projected from the display device 10 onto the transmissive / reflecting member. The display image is an image displayed as a virtual image 45 superimposed on the field of view of the observer 3. The display system 1 is provided, for example, in a moving body such as a vehicle, an aircraft or a ship, or a non-moving body such as an operation simulation system or a home theater system. In the present embodiment, a case will be described in which the display system 1 is provided in an automobile, which is an example of a moving body. Note that the usage pattern of the display system 1 is not limited to this.

  The display system 1 uses, for example, navigation information (for example, vehicle speed, route information, distance to a destination, current location name, presence / absence of an object (object) in front of the vehicle) necessary for steering the vehicle through the windshield 50. The observer 3 (pilot) visually recognizes a position, a speed limit, and other signs, traffic jam information, and the like). In this case, the windshield 50 functions as a transflective member that transmits a part of the incident light and reflects at least a part of the remaining light. The distance from the viewpoint of the observer 3 to the windshield 50 is about several tens of cm to 1 m.

  The display system 1 includes a display device 10, a free-form curved mirror 30, and a windshield 50. The display device 10 is, for example, a head-up display device (HUD device) mounted on an automobile, which is an example of a moving body. The display device 10 is arranged at an arbitrary position according to the interior design of the automobile. The display device 10 may be arranged, for example, below a dashboard of an automobile, or may be embedded in the dashboard.

  The display device 10 includes a light source device 11, a light deflection device 13, and a screen 15. The light source device 11 is a device that irradiates the laser light emitted from the light source to the outside of the device. The light source device 11 may irradiate, for example, laser light obtained by combining laser light of three colors of R, G, and B. The laser light emitted from the light source device 11 is guided to the reflecting surface of the light deflecting device 13. The light source device 11 has a semiconductor light emitting element such as an LD (Laser Diode) as a light source. The light source is not limited to this, and may have a semiconductor light emitting element such as an LED (light emitting diode).

  The light deflector 13 is a device that changes the traveling direction of the laser light by using a MEMS (Micro Electro Mechanical Systems) or the like. The optical deflecting device 13 includes, for example, a scanning unit such as a single minute MEMS mirror that swings about two orthogonal axes, or a mirror system that includes two MEMS mirrors that swing or rotate about one axis. It is configured by using. The laser light emitted from the light deflector 13 is scanned on the screen 15. The light deflection device 13 is not limited to the MEMS mirror, and may be configured using a polygon mirror or the like.

  The screen 15 is a diverging member having a function of diverging the laser light at a predetermined divergence angle. The screen 15 is formed of a transmission type optical element having a light diffusion effect, such as a microlens array (MLA) or a diffusion plate, in the form of, for example, EPE (Exit Pupil Expander). The screen 15 may be composed of a reflective optical element having a light diffusion effect, such as a micromirror array. The screen 15 forms an intermediate image 40, which is a two-dimensional image, on the screen 15 by scanning the laser light emitted from the optical deflector 13 onto the screen 15.

  Here, the projection system of the display device 10 is a “panel system” in which the intermediate image 40 is formed by an imaging device such as a liquid crystal panel, a DMD panel (digital mirror device panel) or a fluorescent display tube (VFD), and the light source device 11 emits light. There is a "laser scanning method" in which the scanning means scans the generated laser light to form an intermediate image 40.

  The display device 10 according to the first embodiment employs the latter “laser scanning method”. In the “laser scanning method”, light emission or non-light emission can be assigned to each pixel, and thus an image with high contrast can generally be formed. The display device 10 may use the “panel method” as the projection method.

  The virtual image 45 projected on the free-form curved mirror 30 and the windshield 50 by the laser light (light flux) emitted from the screen 15 is enlarged and displayed from the intermediate image 40. The free-form surface mirror 30 is designed and arranged so as to cancel the inclination, distortion, positional deviation, etc. of the image due to the curved shape of the windshield 50. The free-form surface mirror 30 may be installed rotatably around a predetermined rotation axis. Thereby, the free-form surface mirror 30 can adjust the reflection direction of the laser light (light flux) emitted from the screen 15 and change the display position of the virtual image 45.

  Here, the free-form curved surface mirror 30 is designed by using existing optical design simulation software so that the image forming position of the virtual image 45 becomes a desired position and has a constant condensing power. The display device 10 sets the condensing power of the free-form surface mirror 30 so that the virtual image 45 is displayed at a position (depth position) of, for example, 1 m or more and 30 m or less (preferably 10 m or less) from the viewpoint position of the observer 3. To be done. The free-form curved mirror 30 may be a concave mirror or a curved mirror. The free-form surface mirror 30 is an example of an imaging optical system.

  The windshield 50 is a transflective member having a function (partial reflection function) of transmitting a part of laser light (light flux) and reflecting at least a part of the rest. The windshield 50 functions as a semi-transparent mirror that allows the observer 3 to visually recognize the front scene and the virtual image 45. The virtual image 45 is image information for allowing the observer 3 to visually recognize vehicle information (speed, mileage, etc.), navigation information (route guidance, traffic information, etc.), warning information (collision warning, etc.), for example. The transflective member may be a windshield or the like provided separately from the windshield 50. The windshield 50 is an example of a reflecting member.

  The virtual image 45 may be displayed so as to overlap with the scenery in front of the windshield 50. Further, the windshield 50 is not flat but curved. Therefore, the image forming position of the virtual image 45 is determined by the curved surfaces of the free-form surface mirror 30 and the windshield 50. The windshield 50 may use a semi-transmissive mirror (combiner) as an individual transmission / reflection member having a partial reflection function.

  With such a configuration, the laser light (light flux) emitted from the screen 15 is projected toward the free-form surface mirror 30 and reflected by the windshield 50. The observer 3 can visually recognize the virtual image 45 in which the intermediate image 40 formed on the screen 15 is enlarged by the light reflected by the windshield 50.

Hardware Configuration FIG. 2 is a diagram showing an example of the hardware configuration of the display device according to the first embodiment. The hardware configuration shown in FIG. 2 may have the same configuration in each embodiment, and constituent elements may be added or deleted as necessary.

  The display device 10 has a control device 17 for controlling the operation of the display device 10. The control device 17 is a controller such as a board or an IC chip mounted inside the display device 10. The control device 17 includes an FPGA (Field-Programmable Gate Array) 1001, a CPU (Central Processing Unit) 1002, a ROM (Read Only Memory) 1003, a RAM (Random Access Memory) 1004, and an I / F 1006 I / F (Inf) 100f. , LD driver 1008, MEMS controller 1010 and motor driver 1012.

  The FPGA 1001 is an integrated circuit whose setting can be changed by the designer of the display device 10. The LD driver 1008, the MEMS controller 1010, and the motor driver 1012 generate a drive signal according to the control signal from the FPGA 1001. The CPU 1002 is an integrated circuit that performs processing for controlling the entire display device 10. The ROM 1003 is a storage device that stores a program that controls the CPU 1002. The RAM 1004 is a storage device that functions as a work area for the CPU 1002. The I / F 1005 is an interface for communicating with an external device. The I / F 1005 is connected to, for example, a CAN (Controller Area Network) of an automobile.

  The LD 1007 is, for example, a semiconductor light emitting element that forms a part of the light source device 11. The LD driver 1008 is a circuit that generates a drive signal that drives the LD 1007. The MEMS 1009 is a device that constitutes a part of the optical deflector 13 and displaces the scanning mirror. The MEMS controller 1010 is a circuit that generates a drive signal that drives the MEMS 1009. The motor 1011 is an electric motor that rotates the rotating shaft of the free-form surface mirror 30. The motor driver 1012 is a circuit that generates a drive signal that drives the motor 1011.

Functional Configuration FIG. 3 is a diagram showing an example of the functional configuration of the display device according to the first embodiment. The functions implemented by the display device 10 include a vehicle information reception unit 171, an external information reception unit 172, an image generation unit 173, and an image display unit 174.

  The vehicle information receiving unit 171 has a function of receiving vehicle information (information such as speed and mileage) from a CAN or the like. The vehicle information receiving unit 171 is realized by the processing of the I / F 1005 and the CPU 1002 shown in FIG. 2, the program stored in the ROM 1003, and the like.

  The external information receiving unit 172 has a function of receiving information on the outside of the vehicle (position information from GPS, route information or traffic information from the navigation system, etc.) from the external network. The external information receiving unit 172 is realized by the processing of the I / F 1005 and the CPU 1002 shown in FIG. 2, the program stored in the ROM 1003, and the like.

  The image generation unit 173 has a function of generating image information for displaying the intermediate image 40 and the virtual image 45 based on the information input by the vehicle information reception unit 171 and the external information reception unit 172. The image generation unit 173 is realized by the processing of the CPU 1002 illustrated in FIG. 2, the program stored in the ROM 1003, and the like.

  The image display unit 174 forms the intermediate image 40 on the screen 15 based on the display information generated by the image generation unit 173, and projects the laser light (light flux) forming the intermediate image 40 toward the windshield 50. Function to display the virtual image 45. The image display unit 174 is realized by the processing of the CPU 1002, the FPGA 1001, the LD driver 1008, the MEMS controller 1010 and the motor driver 1012 shown in FIG. 2, the program stored in the ROM 1003, and the like.

  The image display unit 174 includes a control unit 175, an intermediate image forming unit 176, and a projection unit 177. The control unit 175 generates a control signal for controlling the operations of the light source device 11 and the light deflection device 13 in order to form the intermediate image 40. Further, the control unit 175 generates a control signal for controlling the operation of the free-form curved surface mirror 30 in order to display the virtual image 45 at a predetermined position.

  The intermediate image forming unit 176 forms the intermediate image 40 on the screen 15 based on the control signal generated by the control unit 175. The projection unit 177 projects the laser light forming the intermediate image 40 onto the transmissive / reflecting member (the windshield 50 or the like) in order to form the virtual image 45 visually recognized by the observer 3.

Light Source Device FIG. 4 is a diagram showing an example of a specific configuration of the light source device according to the first embodiment. The light source device 11 includes light source elements 111R, 111G, and 111B (hereinafter, referred to as light source element 111 when there is no need to distinguish them), coupling lenses 112R, 112G, and 112B, apertures 113R, 113G and 113B, and a combining element 114. , 115, 116, and lens 117.

  The three color (R, G, B) light source elements 111R, 111G, 111B are, for example, LDs (Laser Diodes) each having a single or a plurality of light emitting points. The light source elements 111R, 111G, and 111B emit laser beams (light fluxes) having different wavelengths λR, λG, and λB (for example, λR = 640 nm, λG = 530 nm, λB = 445 nm).

  The emitted laser beams (light fluxes) are coupled by coupling lenses 112R, 112G, and 112B, respectively. The coupled lasers (light fluxes) are shaped by the apertures 113R, 113G, 113B, respectively. The apertures 113R, 113G, 113B have a shape (for example, a circle, an ellipse, a rectangle, a square, etc.) according to a predetermined condition such as a divergence angle of the laser light (light flux).

  The laser beams (light fluxes) shaped by the apertures 113R, 113G, 113B are combined by the three combining elements 114, 115, 116. The combining elements 114, 115, and 116 are plate-shaped or prism-shaped dichroic mirrors, which reflect or transmit the laser light (light flux) according to the wavelength and combine them into one light flux. The combined light flux passes through the lens 117 and is guided to the light deflector 13.

Optical Deflection Device FIG. 5 is a diagram showing an example of a specific configuration of the optical deflection device according to the first embodiment. The light deflection device 13 is a MEMS mirror manufactured by a semiconductor process, and includes a mirror 130, a meandering beam portion 132, a frame member 134, and a piezoelectric member 136. The light deflection device 13 is an example of a scanning unit.

  The mirror 130 has a reflective surface that reflects the laser light emitted from the light source device 11 toward the screen 15 side. The light deflecting device 13 forms a pair of meandering beam portions 132 with the mirror 130 interposed therebetween. The meandering beam portion 132 has a plurality of folded portions. The folded portion is composed of first beam portions 132a and second beam portions 132b which are alternately arranged. The meandering beam portion 132 is supported by the frame member 134. The piezoelectric member 136 is arranged so as to connect the adjacent first beam portion 132a and second beam portion 132b. The piezoelectric member 136 applies different voltages to the first beam portion 132a and the second beam portion 132b and causes the beam portions 132a and 132b to warp.

  As a result, the adjacent beam portions 132a and 132b bend in different directions. The mirror 130 rotates in the vertical direction about the axis in the left-right direction by accumulating the bending. With such a configuration, the optical deflecting device 13 can perform optical scanning in the vertical direction at a low voltage. Optical scanning in the horizontal direction about the vertical axis is performed by resonance using a torsion bar or the like connected to the mirror 130.

Screen FIG. 6 is a diagram showing an example of a specific configuration of the screen according to the first embodiment. The screen 15 is a diverging member that diverges at a predetermined divergence angle. The screen 15 shown in FIG. 6 has a microlens array structure in which a plurality of hexagonal microlenses 150 are arranged without gaps. The width of the microlens 150 (distance between two opposite sides) is about 200 μm. The screen 15 can arrange a plurality of microlenses 150 at high density by making the shape of the microlenses 150 hexagonal.

  The shape of the microlens 150 is not limited to the hexagon, and may be, for example, a quadrangle or a triangle. Further, although the structure in which the plurality of microlenses 150 are regularly arranged is illustrated, the arrangement of the microlenses 150 is not limited to this, and for example, the centers of the respective microlenses 150 are eccentric to each other and irregular. It may be an arbitrary array. When adopting such an eccentric arrangement, the respective microlenses 150 have different shapes.

  FIG. 7 is a diagram for explaining a difference in action due to a difference in the magnitude relationship between the incident light beam diameter and the lens diameter in the microlens array. In FIG. 7A, the screen 15 is composed of an optical plate 151 on which microlenses 150 are aligned. When the incident light 152 is scanned on the optical plate 151, the incident light 152 is diverged by the microlens 150 and becomes divergent light 153. Due to the structure of the microlens 150, the screen 15 can diverge the incident light 152 at a desired divergence angle 154. The period 155 of the microlens 150 is designed to be larger than the diameter 156a of the incident light 152. As a result, the screen 15 does not cause speckle (speckle noise) without causing interference between the lenses.

  FIG. 7B shows an optical path of divergent light when the diameter 156b of the incident light 152 is twice as large as the cycle 155 of the microlens 150. Incident light 152 is incident on the two microlenses 150a and 150b and produces divergent lights 157 and 158, respectively. At this time, since two divergent lights exist in the region 159, light interference may occur. When this interference light enters the eyes of the observer, it is visually recognized as speckle.

  In consideration of the above, in order to reduce the speckle, the period 155 of the microlens 150 is designed to be larger than the diameter 156 of the incident light. Although FIG. 7 has been described in the form of the convex lens, the same effect can be obtained in the form of the concave lens.

  FIG. 8 is a diagram for explaining the correspondence between the mirrors of the optical deflector and the scanning range. The light emission intensity, the lighting timing, and the light waveform of each light source element of the light source device 11 are controlled by the FPGA 1001. Each light source element of the light source device 11 is driven by the LD driver 1008 and emits a laser beam. As shown in FIG. 8, the laser light emitted from each light source element and combined in the optical path is two-dimensionally deflected around the α axis and the β axis by the mirror 130 of the optical deflecting device 13 and scanned through the mirror 130. The screen 15 is irradiated with light. That is, the screen 15 is two-dimensionally scanned by the main scanning and the sub-scanning by the light deflecting device 13.

  The scanning range is the entire range that can be scanned by the optical deflector 13. The scanning light oscillates (reciprocally scans) in the main scanning direction (X-axis direction) in the scanning range of the screen 15 at a high frequency of about 20 to 40,000 Hz, and at a slow frequency of about tens of Hz in the sub-scanning direction. One-way scanning is performed in the (Y-axis direction). That is, the light deflecting device 13 performs raster scanning on the screen 15. In this case, the display device 10 can perform drawing or virtual image display for each pixel by controlling the light emission of each light source element according to the scanning position (scanning light position).

  The time for drawing one screen, that is, the scanning time for one frame (one cycle of two-dimensional scanning) is several tens msec because the sub-scanning cycle is several tens Hz as described above. For example, when the main scanning cycle is 20000 Hz and the sub scanning cycle is 50 Hz, the scanning time for one frame is 20 msec.

  FIG. 9 is a diagram showing an example of a scanning line locus during two-dimensional scanning. As shown in FIG. 9, the screen 15 has an image region 61 (effective scanning region) in which the intermediate image 40 is drawn (light modulated according to image data is irradiated) and a frame region surrounding the image region 61. 62 is included.

  The scanning range is a range in which the image area 61 on the screen 15 and a part of the frame area 62 (a part near the outer edge of the image area 61) are combined. In FIG. 9, the loci of scanning lines in the scanning range are indicated by zigzag lines. In FIG. 9, the number of scanning lines is smaller than the actual number for convenience.

  As described above, the screen 15 is composed of a transmission type optical element having a light diffusion effect such as a microlens array. The image area 61 does not need to be rectangular or flat, but may be polygonal or curved. Further, the screen 15 may be a flat plate or a curved plate having no light diffusion effect. Further, the image area 61 may be a reflective element having a light diffusion effect, such as a micromirror array, depending on the device layout.

  The screen 15 is provided with a synchronous detection system 60 including a light receiving element in a peripheral area (a part of the frame area 62) of the image area 61 in the scanning range. In FIG. 9, the synchronization detection system 60 is arranged at the −X side and + Y side corners of the image area 61. The synchronization detection system 60 detects the operation of the optical deflector 13 and outputs a synchronization signal for determining the scan start timing and the scan end timing to the FPGA 1001.

-Details Next, the optical design of the display system 1 according to the first embodiment will be described. The relationship between the divergence angle and the intensity of the divergent light emitted from the screen 15 will be described with reference to FIG.

  FIG. 10A is a diagram showing the intensity distribution of the light flux diverging on the screen. The horizontal axis of FIG. 10A is the divergence angle Δθ of the divergent light on the screen 15 when the luminous flux incident on the screen 15 is used as a reference. As shown in FIG. 10 (a), it has an intensity profile in which the intensity decreases as the divergence angle Δθ increases. Here, the divergence angle Δθ is an angle difference between the incident angle of the light incident on the screen 15 and the center of the divergence angle of the divergent light which is diverged by the screen 15 and reaches the viewpoint of the observer 3. is there.

  Further, as shown in FIG. 10B, the intensity of the divergent light decreases as the divergence angle Δθ with respect to the luminous flux incident on both ends of the intermediate image 40 formed on the screen 15 increases. When the intensity of the divergent light at both ends of the intermediate image 40 decreases, the brightness near the ends of the virtual image 45 decreases. As a result, in-plane deterioration of the virtual image 45 visually recognized by the observer 3 occurs.

  In the present embodiment, in order to allow the observer 3 to visually recognize the virtual image 45 having a good luminance distribution while suppressing the decrease in luminance at the end of the virtual image 45 visually recognized by the observer 3, the optimum optical of the display device 10 is displayed. It is a design proposal.

  FIG. 11 is a diagram showing an outline of the optical path length in the display system according to the first embodiment. Here, each optical path length is measured using the optical path through which the image center when observed from the eye lip center (reference eye point) in each component of the display system 1. The image center is assumed to be substantially coincident with the geometric center of each component. The eye lip center (reference eye point) is the viewpoint position that is the reference of the observer 3, and is the center of the eye box.

  The observer 3 (for example, a driver who drives a car) visually recognizes the virtual image 45 from an eye box (a region near the eyes of the observer 3) on the optical path of the light reflected by the windshield 50. Here, the eye box means a range in which the observer 3 can visually recognize the virtual image 45 without adjusting the position of the viewpoint. Specifically, the eye box is equal to or less than the driver's eye range (JIS D0021) of the automobile. The eye box is set as an area in which the driver can visually recognize the virtual image 45, based on the eye lip, which is a spatial area in which the eye point of the driver seated in the seat can exist.

  In the display system 1, the optical path length Ta from the light deflecting device 13 to the image center of the intermediate image 40 formed on the screen 15 and the center position of the region where the light flux diverged from the intermediate image 40 passes through the free-form surface mirror 30. The optical path length is defined as Tb, and the optical path length from the center of the free-form surface mirror 30 to the center of the virtual image 45 is defined as Tc.

  The light beam emitted by the light source device 11 enters the light deflecting device 13 and is two-dimensionally scanned on the screen 15. As a result, the intermediate image 40 shown in FIG. 11 is formed on the screen 15. The screen 15 is provided with a light diverging member such as a microlens array as described above, and the light beam scanned by the screen 15 is diverged at a predetermined divergence angle by passing through the screen 15. In FIG. 12, the light ray emitted from the screen 15 is the central ray of the divergent light. The light flux emitted from the screen 15 enters the free-form curved mirror 30.

  The free-form surface mirror 30 has a surface shape designed to reduce the optical distortion generated in the windshield 50 shown in FIG. The light beam incident on the free-form surface mirror 30 follows the surface shape of the free-form surface mirror, and the light flux reflected by the free-form surface mirror 30 subsequently enters the windshield 50, and at least the eyelip region including at least the eyelip center (reference eyepoint). Reach a point of view. The light flux incident on the windshield 50 is reflected according to the surface shape of the windshield 50.

  FIG. 12 is a diagram for schematically explaining the optical paths between the respective components of the display system 1. FIG. 12 shows the optical path length Ta and the optical path length Tb defined in FIG. 11, and further shows the optical path length from the center of the free-form surface mirror 30 to the center of the virtual image 45 as Tc. FIG. 12A shows a cross section perpendicular to the sub-scanning direction (Y direction) by the optical deflector 13 and parallel to the main scanning direction (X direction). That is, the horizontal direction of the paper surface of FIG. 12A is the main scanning direction. FIG. 12B shows a cross section that is perpendicular to the main scanning direction (X direction) and parallel to the sub scanning direction (Y direction). That is, the horizontal direction of the paper surface of FIG. 12B is the sub-scanning direction.

  In the description of FIG. 12, among the luminous fluxes of the deflected light by the optical deflector 13 for forming the intermediate image 40, the deflected light corresponding to the image end is a straight line Li + and a straight line Li−. The straight line Lix + and the straight line Lix− in FIG. 12A are the incident lights on the screen 15 corresponding to both ends of the image in the main scanning direction, and the straight line Liy + and the straight line Liy− in FIG. The incident light on the screen 15 corresponding to both ends in the direction is shown.

  Further, in the description of FIG. 12, a straight line Lo + and a straight line Lo− connecting the screen 15 and the image end of the virtual image 45 are optical paths in which light rays at the image end of the intermediate image 40 are directed to the center of the eyelips (reference eye point). The straight line Lox + and the straight line Lox− in FIG. 12A indicate the optical paths from the screen 15 corresponding to both ends in the main scanning direction of the image, and the straight line Loy + and the straight line Loy− in FIG. The optical paths from the screen 15 corresponding to both ends in the direction are shown.

  As described with reference to FIG. 10, the intensity of the divergent light decreases as the divergence angle Δθ with respect to the luminous flux incident on both ends of the intermediate image 40 formed on the screen 15 increases. When the intensity of the divergent light at both ends of the intermediate image 40 decreases, the brightness near the ends of the virtual image 45 decreases. Therefore, in order for the viewer 3 to visually recognize the virtual image without unevenness in brightness in the eye-lips area, the divergence angle Δθ with respect to the light beams incident on both ends of the intermediate image 40 formed on the screen 15 is such that the light beam is present in the eye box. It is desirable to be as small as possible within the reachable range. Further, in order to suppress the decrease in the luminance of the image end portion of the virtual image 45, the angle difference Δθ + formed by the straight line Li + and the straight line Lo + and the angle difference Δθ− formed by the straight line Li− and the straight line Lo− shown in FIG. 12 are small. Preferably.

  When the width of the eye box in the main scanning direction is wider than the width in the sub scanning direction, the brightness of the virtual image 45 seen from the eye box end in the main scanning direction is seen from the eye box end in the sub scanning direction. The brightness is smaller than the brightness of the virtual image 45. In particular, the image end portion of the virtual image 45 in the main scanning direction has a larger decrease in luminance than the image end portion of the virtual image 45 in the sub scanning direction.

  Here, the fact that the width of the virtual image 45 is constant and the width of the eye box is large means that the width of the virtual image 45 per unit length of the eye box is small. Therefore, virtually, the width of the eye box is constant and the virtual image is constant. If the width of 45 becomes smaller (the angle formed by the straight line Lo + and the straight line Lo− becomes smaller), it can be replaced.

  That is, when the width of the eye box in the main scanning direction is wider than the width in the sub scanning direction, the angular differences Δθx + and Δθx− in the main scanning direction are the angular differences Δθy + in the sub scanning direction. Each becomes larger than Δθy−. For example, Ta = 100, Tb = 300, Tc = 3100, the distance from the eye box to the virtual image 45 (virtual image distance) Td = 3600, the eye box width Ex = 130 in the main scanning direction, and the eye box width in the sub scanning direction. When Ey = 40, Δθx + is 11.2 °, whereas Δθy + is 4.1 °. As a result, the image end portion of the virtual image 45 in the main scanning direction has a larger decrease in luminance than the image end portion in the sub scanning direction.

  FIGS. 13A and 13B show an optical system in which, in addition to the constituent elements shown in FIGS. 12A and 12B, a refractive optical system 80 having a refractive power for refracting light is further arranged. The refracting optical system 80 is arranged on the optical path between the deflecting device 13 and the screen 15, as shown in FIG. That is, the refracting optical system 80 refracts the deflected light emitted from the deflecting device 13, and the refracted deflected light enters the screen 15. The refractive optical system 80 is an optical system having different refractive powers in the main scanning direction and the sub scanning direction. Therefore, the incidence angle of the deflected light incident on the screen 15 can be changed to suppress the decrease in the luminance of the image end portion of the virtual image 45.

  In the present embodiment, as an example in which the main scanning direction and the sub-scanning direction have different refracting powers, a case will be described in which the main scanning direction has refracting power and the sub-scanning direction does not have refracting power. As shown in FIG. 13A, by disposing the refracting optical system 80, the image end light indicated by Lix + and Lix− in the main scanning direction after passing through the refracting optical system 80 is directed toward the image center. Gives the refracting power to refract (sometimes referred to as positive refracting power hereinafter). At this time, in FIG. 13A, the deflected lights corresponding to the image edges incident on the screen 15 are shown as Ljx + and Ljx−. Therefore, in FIG. 13, the deflected light corresponding to the image end incident on the screen 15 and the light at the image end of the intermediate image 40 diverged by the screen 15 toward the center of the eye lip, that is, the deflected light corresponding to the image end. The angles are the angle differences Δθx + ′ and Δθx− ′ formed by the straight line Ljx + and the straight line Lox +, and the straight line Ljx− and the straight line Lox−. As a result, Δθx + ′ and Δθx− ′ are smaller than Δθx + and Δθx− in FIG. On the other hand, since the refracting optical system 80 has no refracting power in the sub-scanning direction, Δθy + and θy− are the same in both FIG. 12B and FIG. 13B.

  As an example, in FIG. 13A, when the optical path length of the optical deflecting device 13 and the refracting optical system 80 is To and the refracting optical system 80 is a cylindrical mirror curved by a radius of curvature Rx, Rx = −200, To. = 40, Ta = 100, Tb = 300, Tc = 3100, Td = 3600, Ex = 130, Ey = 40, Δθx ′ = 6.5 °, and the angle difference Δθx = 11 in FIG. Can be made narrower than 2 °. Therefore, by arranging the refracting optical system 80 such as a cylinder mirror, it is possible to confirm the effect that the luminous flux is efficiently diverged in the eye box region and the luminance of the image end portion of the virtual image 45, particularly, the image end portion of the main scanning is improved. ..

  On the other hand, since the refracting optical system 80 has no refractive power in the sub-scanning direction, the scanning lines for Li + and Li− are the same as in FIG. 12 (b), as shown in FIG. 13 (b). That is, Δθy + and θy− are 4.1 ° in both FIG. 12 (b) and FIG. 13 (b).

  As described above, in the refraction optical system 80, among the deflected light incident on the screen 15, the deflected light corresponding to the image end, which is the deflected light corresponding to the image end of the virtual image, and the deflected light corresponding to the incident image end are screened. 15 has a refracting power that reduces the angle formed by the deflected light corresponding to the image end, which is the divergent light that is diverged by 15 and reaches the observer's viewpoint, and the refracting power in the main scanning direction is refracting in the sub scanning direction. Since the force is larger than the force, the refraction optical system 80 is provided between the light deflection unit 13 and the screen 15 to bring the magnitudes of the angles of the main scanning and the sub-scanning close to each other, and as a result, the brightness in the plane of the virtual image 45. The deviation can be reduced.

  In the above description, the case where the refractive power is positive has been described, but the layout of the display system 1 and the nature of each optical system, the refractive power is negative, that is, the light beam corresponding to the edge of the image entering the diverging optical system By refracting in the direction opposite to the center, the angle difference between the incident angle of the incident light and the outgoing angle of the emitted light to the divergence optical system may be reduced. In that case, the refracting power in the negative scanning direction may be compared to make the refracting power in the main scanning direction larger than the refracting power in the sub scanning direction.

  FIG. 14 shows an example of a display system 1A in which a reflecting mirror having a positive refractive power in the main scanning direction is used as the refracting optical system 80. In this case, as shown in FIG. 16, the deflected light emitted from the optical deflector 13 and deflected is reflected by the refraction optical system 80, and the reflected light is incident on the screen 15. By adopting the reflection mirror as the refraction optical system 80 in this manner, since there is no chromatic aberration, it is possible to provide a high-quality image in which no color shift occurs even if a plurality of light sources having different wavelengths are included. ..

  FIG. 15 shows an example of the display system 1B when a lens having a positive refractive power in the main scanning direction is used as the refraction optical system 80. In this case, as shown in FIG. 16, the deflected light emitted from the optical deflector 13 and deflected is transmitted through the refraction optical system 80, and the transmitted light is incident on the screen 15. By adopting a transmissive lens as the refraction optical system 80 in this way, it is not necessary to turn back the light rays, and when the display device is mounted in a vehicle or the like, it may be advantageous in layout considering the display system 1 and the entire vehicle. is there.

  FIG. 16 shows a first example of the optical element that constitutes the refractive optical system. FIG. 16 shows an example of the shape of a mirror having a positive refractive power in the main scanning direction. By using a reflection mirror as the refraction optical system 80, since there is no chromatic aberration, it is possible to provide a high-quality image in which no color shift occurs even if a plurality of light sources having different wavelengths are included.

  FIG. 17 shows a second example of the optical element that constitutes the refractive optical system. FIG. 17 shows an example of the shape of a lens having a positive refractive power in the main scanning direction. By adopting a transmissive lens as the refraction optical system 80, it is not necessary to turn back the light beam, which may be advantageous in vehicle layout.

  FIG. 18 shows a third example of the optical element that constitutes the refracting optical system. The reflecting mirror shown in FIG. 18 has a reflecting surface as the refracting optical system 80 and a diverging surface of the screen 15 as the diverging optical system on the same reflecting surface. That is, the refracting optical surface of the refracting optical system 80 and the diverging optical surface of the screen 15 as the diverging optical system are the same optical surface. For example, it has a configuration in which micromirror arrays are arranged on a reflecting mirror surface. With such a configuration, Δθ can be suitably narrowed while diverging the light beams incident on the same optical element at a predetermined divergence angle, so that the number of parts of the device can be reduced.

  FIG. 19 shows a fourth example of the optical element that constitutes the refracting optical system. The transmission lens shown in FIG. 19 has a refractive optical surface and a divergent optical surface. For example, as shown in FIG. 19, a refracting surface that functions as the refracting optical system 80 is provided on the incident surface side, and a microlens array that functions as a diverging optical system is arranged on the exit surface side to provide a diverging surface. With such a configuration, it is possible to complete the function of diffusing the incident light flux at a predetermined diffusion angle with the same optical element while appropriately reducing Δθ. Not limited to the configuration of FIG. 19, a configuration in which a microlens array is provided on the incident surface side and a refracting surface is disposed on the exit surface side, or an incident surface as a refracting optical system 80 and a diverging optical system as an incident surface are provided. The same effect can be obtained even if the screen 15 has a divergent surface or if the exit surface has an exit surface as the refraction optical system 80 and a divergent surface of the screen 15 as the divergence optical system.

  FIG. 20 is a conceptual diagram of the astigmatic difference generated by the refractive optical system 80. FIG. 20 shows a case where the refracting optical system 80 has a positive refracting power only in the main scanning direction. 20A is a sectional view in the main scanning direction, and FIG. 20B is a sectional view in the sub scanning direction. The focal length in the sub-scanning direction is the focal length f of the optical element including the refractive optical system 80 as shown in FIG. 20 (a), while the focal position fi in the main scanning direction as shown in FIG. 20 (b). Is displaced from the screen 15 which is the surface to be scanned by δF. At this time, the focus position shift amount δF is obtained as follows using Snell's law.

  Note that So is the distance between the laser emission point of the light source element 111 and the lens 112 arranged between the light source element 111 and the light deflector 13, f1 is the focal length of the lens 112, f2 is the focal length of the refractive optical system 80, and d is the distance between the lens 112 and the refractive optical system 80.

  FIG. 21 shows the position dependence of the beam diameter when the focal length of the lens 112 is 8 mm and the diameter of the aperture 113 is 1.2 mm.

  Here, the beam diameter means the diameter of the peripheral portion where the intensity is reduced to 13.5% of the intensity on the central axis. The focal position is 0 on the screen 15. As shown in the graph of FIG. 21, it can be confirmed that the beam diameter tends to be steeply thick at a position displaced from the focus position by more than ± 20 mm. Therefore, in order to reduce the speckle, in order to make the diameter 156a of the incident light beam sufficiently small with respect to the period 155 of the microlens array shown in FIG. 7, the focus position shift δF of the refracting optical system 80 such as a cylinder mirror is required. Should be designed to be ± 20 mm or less.

  That is, according to (Equation 1), as an example, by setting the focal length, surface spacing, etc. of the refracting optical system 80, which is a cylinder mirror, within the relational expression of (Equation 2), it is possible to reduce luminance and deteriorate speckle noise. It is possible to reduce the size of the display device while suppressing it.

  Although the image forming apparatus according to the exemplary embodiment has been described above, the present invention is not limited to the above exemplary embodiment, and various modifications and improvements can be made within the scope of the present invention.

1A, 1B Display system 10 Display device 11 Light source device (an example of a light source)
13 Light Deflection Device (Example of Light Deflection Unit)
15 screen (an example of divergence optical system)
30 Free-form surface mirror (an example of imaging optical system)
45 Virtual image 50 Windshield (an example of a reflection member)
80 Refractive optics

JP, 2013-61554, A JP, 2009-128659, A

Claims (9)

A light source that emits light,
A light deflector for deflecting the incident light in the main scanning direction and the sub scanning direction,
A divergence optical system that diverges the deflected light that is the incident deflected light,
Have
A display device for forming a virtual image to be visually recognized by an observer by divergent light diverged by the divergent optical system,
A refraction optical system for refracting the deflected light incident on the divergence optical system on an optical path between the light deflector and the divergence optical system,
A display device in which the refracting power of the refracting optical system in the main scanning direction is different from the refracting power in the sub-scanning direction. Of the deflected light incident on the diverging optical system, the refracting power corresponds to the deflected light corresponding to the image end of the virtual image, and the incident deflected light is diverged by the divergent optical system to make a viewpoint of the observer. Is a refracting power that reduces the angle formed by the divergent light reaching
The display device according to claim 1, wherein the refractive power in the main scanning direction is larger than the refractive power in the sub-scanning direction.   The display device according to claim 1, wherein the refraction optical system includes a reflection mirror.   The display device according to claim 1, wherein the refraction optical system includes a transmission lens.   The display device according to claim 1, wherein the refraction optical system and the divergence optical system have the same optical element.   The display device according to claim 5, wherein the refracting optical surface of the refracting optical system and the diverging optical surface of the diverging optical system are the same optical surface. 7. The display device according to claim 1, which satisfies the following (formula 1) and (formula 2).
(So is a distance between the light source and a lens disposed between the light source and the light deflection unit, f1 is a focal length of the lens, f2 is a focal length of the refracting optical system, and d is the lens and the refraction. The distance of the optical system.) A display device according to any one of claims 1 to 7,
An image forming optical system for forming the virtual image by the divergent light diverged by the divergent optical system,
A reflecting member that reflects the light emitted from the imaging optical system,
Display system having. The display system according to claim 8,
The movable body is a windshield that reflects the divergent light.