JP2024007060A - Projection optics and head-up display equipment - Google Patents

Abstract

The present invention provides a projection optical device and a head-up display device capable of displaying virtual images at long distances and short distances, respectively, in which the head-up display device is miniaturized. According to the present invention, it contributes to the Sustainable Development Goal 3: Good health and well-being for all.
[Solution] A virtual image is displayed at a long distance and a short distance by refracting and reflecting image light emitted from an image forming section and projecting it onto a projection surface. The lens includes at least a first lens 51, a concave lens 53, which is a second lens, and a concave mirror 55. A first optical path P1 for displaying a virtual image at a short distance and a second optical path P2 for displaying a virtual image at a long distance are formed between the image forming section and the concave lens 53. The first lens 51 is arranged only on the first optical path P1 of the first optical path P1 and the second optical path P2.
[Selection diagram] Figure 2

Description

The present invention relates to a projection optical device and a head-up display device.

For example, a head-up display device is known that projects an image onto a windshield of a moving body such as a car or an airplane, and allows the projected image to be observed as a virtual image through the windshield. As a head-up display device, it is equipped with a transmissive liquid crystal display panel that displays an image by modulating light emitted from behind, and a projection optical device that enlarges and projects the image displayed on the liquid crystal display panel. things are known.

In the head-up display device shown in Patent Document 1, the projection optical device includes a relay lens and a projection lens, specifically an eyepiece optical section. The relay lens is configured to efficiently utilize telecentric display light by satisfying several conditions, and magnifies the image displayed on the liquid crystal display panel to form a real image. Further, the projection lens is configured to further enlarge the real image, project the image onto the windshield of a car, etc., and display the virtual image to the driver.

The head-up display device shown in Patent Document 1 displays the values of various instruments such as a speedometer, tachometer, water temperature gauge, and fuel gauge as virtual images 2 meters ahead of an observer, for example, a driver. In this case, the difference between the line-of-sight direction in which the values of various instruments are viewed as virtual images and the line-of-sight direction of the foreground viewed by the driver becomes small. Thereby, the time required to move the line of sight between these two line of sight directions can be reduced.

Furthermore, the distance to the virtual image (approximately 2 meters ahead) is closer to the distance to the foreground that the driver is looking at than the distance from which the various instruments and the like are directly viewed. As a result, the time required for focusing the eye between the state in which the eye focuses on the object in the foreground and the state in which the eye focuses on the virtual image can also be reduced. These two advantages make it possible to improve safety when driving a car or the like.

Patent Document 2 and Patent Document 3 disclose head-up display devices that project virtual images at two different distances. Patent Document 4 discloses a projection optical device including an image forming section that emits image light including image information, and an eyepiece optical section that displays a virtual image by reflecting the image light. The eyepiece optical section includes a concave lens, a free-form surface lens, and a free-form concave mirror arranged in order from the image forming section side along the emission direction of the image light.

JP2009-229552A Japanese Patent Application Publication No. 2016-173583 Japanese Patent Application Publication No. 2016-186509 International Publication No. 2018/066081

In the head-up display device shown in Patent Document 2, a first screen and a second screen are arranged at different distances from a concave mirror. Further, an imaging position adjusting mirror is provided to reflect the image light emitted from the display. The imaging position adjustment mirror changes the imaging position of a part of the incident image light, converts the incident image light into first image light and second image light having different imaging distances, and reflects the reflected image light. The first image light and the second image light are formed as real images on the first screen and the second screen, respectively.

Thereby, the real image on the first screen and the real image on the second screen are respectively displayed as virtual images at different positions as viewed from the driver via the concave mirror and the windshield of the vehicle. However, the head-up display device shown in Patent Document 2 requires a special display for projecting image light onto two different screen positions. For this reason, there was a risk that the device would become larger.

On the other hand, in the head-up display device disclosed in Patent Document 3, the first image display section and the second image display section are arranged at different distances from the concave mirror. The image on the first image display section and the image on the second image display section are respectively displayed as virtual images at different positions as viewed from the driver via the concave mirror and the windshield of the vehicle. However, the head-up display device shown in Patent Document 3 requires two image display units, for example, LCDs (Liquid Crystal Displays), and along with this, two backlight devices are also required. For this reason, there was a risk that the device would become larger and the manufacturing cost would significantly increase.

The present invention has been made in view of the above-mentioned circumstances, and one of its objects is to provide a projection optical device and a head-up display device capable of displaying virtual images at long distances and short distances, respectively. The goal is to achieve miniaturization.

The above and other objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings.

In order to solve the above problems, an embodiment of the present invention may be configured, for example, as described in the claims. The present application includes multiple means for solving the above problems, but one example is to refract and reflect the image light emitted from the image forming section and project it onto a projection surface, thereby refracting and reflecting the image light emitted from the image forming section. displays a virtual image on the image forming section, and includes at least a first lens, a second lens, and an image projecting section, which are arranged in order from the image forming section side, and the image forming section and the second lens A first optical path for displaying a virtual image at a short distance and a second optical path for displaying a virtual image at a long distance are formed between the first lens and the first lens. It is only necessary to arrange the light beam on the first optical path of the first optical path and the second optical path.

According to the embodiment, in the projection optical device and the head-up display device that can display virtual images at long distances and short distances, it is possible to realize miniaturization of the head-up display device.

FIG. 2 is an overall ray diagram of an eyepiece optical section in a YZ plane in a head-up display device according to an embodiment. FIG. 2 is an overall ray diagram of an eyepiece optical section in an XZ plane in a head-up display device according to an embodiment. FIG. 2 is a perspective view showing a configuration example of a main part of an eyepiece optical section in a head-up display device according to an embodiment. 3 is a diagram showing an example of lens data corresponding to the near distance side of the eyepiece optical section in FIG. 2. FIG. 3 is a diagram showing an example of lens data corresponding to the far side of the eyepiece optical section in FIG. 2. FIG. 3 is a diagram showing an example of free-form surface coefficients of the eyepiece optical part in FIG. 2. FIG. 3 is a diagram showing an example of an aspheric coefficient of the eyepiece optical section in FIG. 2. FIG. FIG. 3 is a diagram illustrating distortion performance of a head-up display device according to an embodiment. FIG. 2 is a spot diagram of a head-up display device according to an embodiment. FIG. 6A is a supplementary diagram of FIG. 6A. FIG. 7 is a diagram showing an angular shift of a chief ray corresponding to a virtual image plane on a far side in a head-up display device according to an embodiment. FIG. 6 is a diagram showing an angular shift of a chief ray corresponding to a virtual image plane on a short distance side in a head-up display device according to an embodiment. FIG. 7B is a supplementary figure to FIGS. 7A and 7B. 3 is a diagram illustrating details of the first lens in FIG. 2. FIG. 3 is a diagram illustrating details of the first lens in FIG. 2. FIG. 3 is a diagram illustrating details of the first lens in FIG. 2. FIG. FIG. 3 is a diagram illustrating a detailed arrangement configuration example of the first lens in FIG. 2; 9A is a diagram illustrating an example of an arrangement configuration as a comparative example of FIG. 9A. FIG. 3 is a schematic diagram illustrating the action of the first lens in FIG. 2. FIG. FIG. 10A is a schematic diagram as a comparative example of FIG. 10A. FIG. 1 is a schematic diagram showing an example of the basic configuration of a head-up display device according to an embodiment. 12 is a diagram showing a more detailed configuration example of the head-up display device in FIG. 11. FIG. FIG. 2 is a plan view of an automobile, which is a moving object, seen from the front.

Hereinafter, one embodiment and various examples of the present invention will be described using drawings and the like. The following explanations show specific examples of the contents of the present invention, and the present invention is not limited to these explanations. Changes and modifications are possible. Further, in all the figures for explaining the present invention, parts having the same functions are given the same reference numerals, and repeated explanation thereof may be omitted.

<Overview of head-up display device>
FIG. 11 is a schematic diagram showing an example of the basic configuration of a head-up display device according to an embodiment. FIG. 12 is a diagram showing a more detailed configuration example of the head-up display device in FIG. 11. A head-up display device 20 shown in FIG. 11 includes an image forming section 10 and an eyepiece optical section 5. The image forming section 10 emits image light containing image information. The eyepiece optical section 5 projects the image light emitted from the image forming section 10 onto a projection surface, such as a windshield 6 of an automobile, and reflects the image light from the projection surface to enter the observer's eye 9. As a result, when viewed from the observer's eyes 9, it appears as if the video information is being viewed on the virtual image plane 7.

First, the image forming section 10 will be explained. As shown in FIG. 12, the image forming section 10 includes a display panel or liquid crystal display panel 2, and a light source device or backlight 1. Further, the image forming section 10 includes a control device that controls the operations of the liquid crystal display panel 2 and the backlight 1, in other words, a controller 200. On the other hand, the image forming section 10 may not include the controller 200, and the operations of the liquid crystal display panel 2 and the backlight 1 may be controlled by a control section of a moving body equipped with the head-up display device 20, for example. The image forming section 10 irradiates the liquid crystal display panel 2 with light from the backlight 1 and emits the image information displayed on the liquid crystal display panel 2 toward the eyepiece optical section 5 .

The controller 200 is connected to various external devices and receives various information from the external devices. In this example, the controller 200 includes a navigation device 208 that is a navigation device that generates and outputs information regarding the operation of a moving object equipped with the head-up display device 20, and an ECU (Electronic Control Unit) 209 that controls the operation of the moving object. is connected. The ECU 209 is connected to various sensors 210 included in the moving body, and receives information detected by the various sensors 210.

The controller 200 includes a main control unit 201 that processes various data from the external device described above, a storage device 206, and a backlight drive circuit 207 that drives the backlight 1. The main control unit 201 includes a RAM (Random Access Memory) 203, a ROM (Read Only Memory) 204, and a processor 205 such as a CPU (Central Processing Unit).

RAM 203 stores various data from external devices. The ROM 204 stores programs and parameters for the processor 205 to execute arithmetic processing. The processor 205 executes arithmetic processing based on a program stored in the ROM 204 or a program developed in the RAM 203 to generate video data that is the basis of a virtual image that is visually recognized by an observer. The storage device 206 is used, for example, as an external storage device for the main control unit 201.

The image forming section 10 displays video information on the liquid crystal display panel 2 under the control of the controller 200 as described above. Then, the image forming unit 10 emits the video information displayed on the liquid crystal display panel 2 as video light using the light flux emitted by the backlight 1. The eyepiece optical section 5 includes, for example, one or more of a concave lens 53, a folding mirror 54, and a concave mirror 55, although the details will be described later. The eyepiece optical section 5 refracts and reflects the image light from the image forming section 10 using such lenses and mirrors, and projects it onto a projection surface, for example, the windshield 6. Note that in the specification, the eyepiece optical section 5 is also referred to as a projection optical device or a projection optical device.

Return to FIG. 11. The image light formed and emitted by the image forming section 10 is projected onto a projection surface, for example, a windshield 6, by the eyepiece optical section 5. The image light projected onto the windshield 6 is reflected by the windshield 6 and reaches the position of the observer's eyes 9. As a result, when viewed from the observer's eyes 9, a relationship is established as if the video information is being viewed on the virtual image plane 7.

As shown in FIG. 11, virtual points such as point Q1, point Q2, and point Q3 are considered on the image light exit surface of the liquid crystal display panel 2. The virtual points on the virtual image plane 7 corresponding to the image light emitted from these virtual points are point V1, point V2, and point V3 shown in FIG. 11, respectively. The eye box 8 is the range in which the point V1, point V2, and point V3 on the virtual image plane 7 can be visually recognized even if the observer moves the position of the eye 9. In this way, the eyepiece optical section 5 is an optical section that displays an object image, specifically a virtual image, in front of the observer's eye 9, similar to the eyepiece of a camera finder or the eyepiece of a microscope.

Here, an example in which the head-up display device 20 is mounted on a moving object will be described using FIG. 13. FIG. 13 is a plan view of an automobile 500, which is a moving object, viewed from the front. In an automobile 500 as shown in FIG. 13, a windshield 6, which is a windshield, is arranged in front of the driver's seat.

By projecting image light onto the windshield 6, the head-up display device 20 creates a state in which an observer in the driver's seat can visually recognize various information regarding the operation of the automobile 500 as a virtual image. The position where the image light is projected is in front of the driver's seat and around it. For example, the image light is projected at a position as shown in the broken line rectangular region R1 in FIG.

Here, the above-mentioned Patent Document 4 is by the same inventor as the present invention. Paragraph [0035] of Patent Document 4 states, ``In order to satisfy this telecentricity (exit pupil distance is infinite) on the liquid crystal display panel side, a field lens with negative refractive power ( It is necessary to arrange a concave lens that has a power of The concave lens corresponds to, for example, the concave lens 53 shown in FIG. 12.

<Details of the eyepiece optical section>
The head-up display device 20 according to one embodiment is particularly characterized by the configuration of the eyepiece optical section 5, in other words, the projection optical device. First, the relationship between the windshield 6 and the eyepiece optical section 5 will be described with reference to FIGS. 1A and 1B. FIG. 1A is an overall ray diagram of the eyepiece optical section in the YZ plane in a head-up display device according to an embodiment. FIG. 1B is an overall ray diagram of the eyepiece optical section in the XZ plane in the head-up display device according to one embodiment.

In the embodiment, (X, Y, Z) is used as the spatial coordinate system and direction for vehicle 500. The Y axis and Y direction are vertical directions, in other words, vertical directions and vertical directions. The X axis and the X direction are the first horizontal direction, in other words, the left and right direction and the horizontal direction. The Z axis and the Z direction are the second horizontal direction orthogonal to the X axis, in other words, the front and rear directions.

Here, the horizontal direction of the eyebox 8 is defined as the X axis, the vertical direction as the Y axis, and the direction orthogonal to the XY axis as the Z axis. FIG. 1A shows how the viewer's eyes 9 view video information on the virtual image plane 7 in the YZ plane. FIG. 1B shows how the viewer's eyes 9 view video information on the virtual image plane 7 in the XZ plane. In the YZ plane, the right eye and left eye overlap, as shown by 9 in FIG. 1A, and in the XZ plane, the right eye and left eye overlap, as shown by 9 in FIG. 1B. I can see it.

Since the windshield 6 has a symmetrical shape with respect to the left-right direction of the automobile, the range of the windshield 6 through which the image light from the head-up display device 20 passes is symmetrical, as shown in FIG. 1B. . Further, as shown in FIGS. 1A and 1B, the eyepiece optical section 5 has a virtual image plane 7a on the near side located at a distance L1 from the eye box 8, and a virtual image plane 7a on the far side located at a distance L2 from the eye box 8. Different video information and the like are displayed on the virtual image plane 7b on the side.

FIG. 2 is a perspective view showing a configuration example of the main parts of the eyepiece optical section in a head-up display device according to an embodiment. As shown in FIG. 2, the eyepiece optical section 5 includes a first lens 51, a polarizing element 52, and a concave lens 53, which is a second lens, which are arranged in order from the image forming section side including the liquid crystal display panel 2. , a folding mirror 54 which is a third lens, and a concave mirror 55 having positive refractive power. These parts form an optical path between the liquid crystal display panel 2 and the windshield 6, which is a projection surface. Note that in the specification, the concave mirror 55 is also referred to as an image projection section.

Here, a first optical path P1 for displaying a virtual image at a short distance and a second optical path P2 for displaying a virtual image at a long distance are formed between the liquid crystal display panel 2 and the concave lens 53. Ru. The first lens 51 is arranged only on the first optical path P1 of the first optical path P1 and the second optical path P2.

The polarizing element 52 attenuates polarized light different from the image light emitted from the liquid crystal display panel 2, thereby suppressing a rise in temperature of the liquid crystal display panel 2 even when sunlight is focused on the liquid crystal display panel 2. belongs to. The concave lens 53 mainly achieves telecentricity, and together with the folding mirror 54, corrects distortion.

The folding mirror 54 reflects the image light incident from the liquid crystal display panel 2 via the concave lens 53 and the like toward the concave mirror 55 . The concave mirror 55 enlarges and reflects the image light incident from the folding mirror 54, thereby projecting the image light in an enlarged manner onto the windshield 6, which is a projection surface. The refractive power of the eyepiece optical section 5 is mainly provided by the concave mirror 55.

In this way, by arranging the folding mirror 54 at the bottom of the optical path between the windshield 6 and the concave mirror 55 or between the image forming section 10 and the concave mirror 55, the head-up display device 20 can be made smaller. realizable. However, the eyepiece optical section 5 may be configured to make the image light from the liquid crystal display panel 2 enter the concave mirror 55 without passing through the folding mirror 54, depending on the case. Furthermore, the polarizing element 52 is also not an essential component. Therefore, the eyepiece optical section 5 may include at least the first lens 51, the concave lens 53, and the concave mirror 55.

FIG. 3A is a diagram showing an example of lens data corresponding to the near distance side of the eyepiece optical section in FIG. 2. FIG. FIG. 3B is a diagram showing an example of lens data corresponding to the far side of the eyepiece optical section in FIG. 2. FIG. In FIG. 3B, only the range of surface numbers whose lens data differs from that in FIG. 3A is displayed. The virtual image distance on the near side in FIG. 3A, ie, the distance L1 in FIG. 1A, is 7 m, and the virtual image distance on the far side in FIG. 3B, ie, the distance L2 in FIG. 1A, is 15 m.

In FIG. 3A, the first lens 51 corresponds to a range of 14 to 18 surfaces, and is configured to include these five surfaces. Note that details of the five surfaces will be described later with reference to FIGS. 8 and 9. On the other hand, in FIG. 3B, all of the surfaces constituting the first lens 51 are planes with a radius of curvature of ∞, and are the same plane that overlaps the plane with surface number 13. This means that the first lens 51 is not placed on the long distance side.

In FIGS. 3A and 3B, the radius of curvature is expressed with a positive sign when the center position of the radius of curvature is in the traveling direction. The distance between surfaces represents the distance on the optical axis from the apex position of each surface to the apex position of the next surface. For example, in FIG. 3A, the distance from the 14th surface to the 15th surface of the first lens 51 is 2 mm. Note that in the reflective optical system, the sign of the radius of curvature is reversed at locations where the distance between surfaces is a negative value.

Eccentricity is represented by values in the X-axis direction, Y-axis direction, and Z-axis direction, and inclination is represented by a rotation angle around the X-axis, a rotation angle around the Y-axis, and a rotation angle around the Z-axis. Eccentricity and inclination act in the order of eccentricity and inclination on the relevant surface. "Normal eccentricity" means that the next surface is placed at the position of the distance between the surfaces on the new coordinate system where eccentricity/inclination is applied. Eccentricity and inclination of "decenter and return" act only on that surface and do not affect the next surface. Note that rotation around the X-axis is positive when viewed from the positive direction of the X-axis, clockwise when viewed from the positive direction of the Y-axis, rotation around the Y-axis is positive, and rotation around the Z-axis is positive when viewed from the positive direction of the Y-axis. Counterclockwise rotation is positive when viewed from the positive direction of the axis.

In FIG. 3A, the glass material name 490.560 represents a material with a refractive index of 1.490 and an Abbe number of 56.0. Similarly, the glass material name 520.649 represents a material with a refractive index of 1.520 and an Abbe number of 64.9, and the glass material name 583.302 represents a material with a refractive index of 1.583 and an Abbe number of 30.2. . Furthermore, "ret s13" written on the 19th side means that the 19th side, which is placed next to the 18th side, is placed on the 13th side. Therefore, the 20 planes are defined based on the 19 planes, or even the 13 planes.

As shown in FIG. 2, in the section where the first lens 51 is arranged, the optical path of the image light is separated into two optical paths P1 and P2. The 19th plane is a virtual plane that allows the separated optical path to be defined from the reference plane, that is, the 13th plane. Based on FIG. 3A, for example, plane 20 is placed at a distance of 21 mm from plane 19 and thus plane 13. Further, in one embodiment, as shown in FIG. 3A, by making the concave mirror 55 and the folding mirror 54 into free-form surfaces, telecentricity is ensured, and good distortion performance and a spot diagram, which will be described later, are achieved. has been realized.

FIG. 4A is a diagram showing an example of free-form surface coefficients of the eyepiece optical part in FIG. 2. FIG. 4B is a diagram showing an example of the aspheric coefficient of the eyepiece optical section in FIG. 2. The free-form surface coefficient Cj shown in FIG. 4A is obtained by equation (1). The fourth-order, sixth-order, eighth-order, and tenth-order aspherical coefficients shown in FIG. 4B are obtained by equation (2).

The free-form surface coefficient Cj has a shape that is rotationally asymmetric with respect to each optical axis (Z axis), and is defined by a conical term component and an XY polynomial term component. For example, if X is quadratic (m=2) and Y is cubic (n=3), the corresponding C19 coefficient is j={(2+3)2+2+3×3}/2+1=19. Further, the position of each optical axis of the free-form surface is determined by the amount of eccentricity and inclination in the lens data shown in FIG.

Below, values such as the eyebox size and viewing angle of the eyepiece optical section 5 are shown in the order of horizontal direction and vertical direction.
Eye box size 120 x 40mm
Image light size on LCD panel: 81.4 x 35.7 mm
Virtual image distance (inclination direction)
Far side 13.0m
Near distance side 7.0m
Viewing angle (full angle of view)
Full range 12.0 x 4.0 degrees
Long distance 12.0 x 2.5 degrees
Close range 12.0 x 0.9 degrees Inclination 2.5 degrees

<Optical performance verification results>
Next, the results of verifying the optical performance of the head-up display device 20 according to one embodiment will be described using FIGS. 5 to 7.

FIG. 5 is a diagram illustrating distortion performance of a head-up display device according to an embodiment. FIG. 5 shows the distortion performance on the liquid crystal display panel 2 side due to a light beam passing through the center of the eye box 8, which was obtained based on the range of the rectangular virtual image plane 7 shown in FIG. If a rectangular image is displayed on the liquid crystal display panel 2 side and the eye 9 is positioned at the center of the eye box 8, the image will change from a barrel shape to a pincushion shape, from a pincushion side to a barrel shape, etc. A distortion opposite to that in FIG. 5 is observed.

In the upper part of FIG. 5, the distortion performance corresponding to the visual field range located at the virtual image distance on the far side, that is, the range of the virtual image plane 7b shown in FIG. 1A is shown. On the other hand, in the lower part of FIG. 5, the distortion performance corresponding to the visual field range located at the near virtual image distance, that is, the range of the virtual image plane 7a shown in FIG. 1A is shown. As shown in FIG. 5, good distortion performance is obtained on both the long-distance side and the short-distance side. Further, in FIG. 5, it can be seen that on the liquid crystal display panel 2, there is an unused zone between the virtual image distance on the far side and the virtual image distance on the near side.

FIG. 6A is a spot diagram of a head-up display device according to one embodiment. FIG. 6B is a supplementary figure to FIG. 6A. FIG. 6A is a spot diagram on the liquid crystal display panel 2 obtained when 23 object points are placed within the range of the virtual image plane 7, as shown in FIG. It is a spot diagram based on a luminous flux.

The spot diagram shown in FIG. 6A is a diagram in which the spot diagram at each position on the liquid crystal display panel 2 is enlarged and emphasized five times in a reduction optical system using a virtual image as an object surface. In the upper part of FIG. 6A, a spot diagram corresponding to the visual field range of the virtual image distance on the far side is shown, and in the lower part of FIG. 6A, the spot diagram corresponding to the visual field range of the virtual image distance on the near side is shown. As shown in FIG. 6, good spot maps are obtained on both the long-distance side and the short-distance side.

Further, this spot diagram is a spot diagram for the total luminous flux on the assumption that the size of the eye box 8 is 120 mm horizontally x 40 mm vertically. On the other hand, the maximum size of the iris of a human eye is said to be, for example, φ7 mm. Therefore, when an observer actually views a virtual image, the spot map at the size of the iris of a human eye is significantly improved.

FIG. 7A is a diagram showing the angular shift of the chief ray corresponding to the virtual image plane on the far side in the head-up display device according to one embodiment. FIG. 7B is a diagram showing the angular shift of the chief ray corresponding to the virtual image plane on the short distance side in the head-up display device according to one embodiment. Figure 7C is a supplementary figure to Figures 7A and 7B.

7A and 7B, as shown in FIG. 7C, the value of the angular shift of the principal ray Ray1 with respect to the virtual ray Ray0 at each view angle position is shown. The virtual ray Ray0 is a straight line obtained by rotating the normal line of the liquid crystal display panel 2 by a predetermined angle, for example, 18 degrees, around a rotation axis parallel to the long side of the liquid crystal display panel 2. By determining the virtual ray Ray0 having an angle in this manner, it is possible to determine, for example, that the sun is located above the car 500 and sunlight that has passed through the windshield 6 is reflected by the concave mirror 55 and reaches the liquid crystal display panel 2. In this case, sunlight enters the liquid crystal display panel 2 obliquely. As a result, the reflected light goes in a direction different from that of the concave mirror 55 and does not reach the eye box 8.

FIG. 7A shows the value of the angular shift of the principal ray Ray1 with respect to the virtual ray Ray0 on the liquid crystal display panel 2 when 23 object points are placed on the virtual image plane 7b at the virtual image distance on the far side. . As shown in FIG. 7A, the values of the angular deviations are all within 9.3 degrees. FIG. 7B shows the value of the angular shift of the principal ray Ray1 with respect to the virtual ray Ray0 on the liquid crystal display panel 2 when 23 object points are arranged on the virtual image plane 7a at the virtual image distance on the short distance side. . As shown in FIG. 7B, the values of the angular deviations are all within 9.3 degrees.

<Details of the first lens>
8A, FIG. 8B, and FIG. 8C are diagrams illustrating details of the first lens in FIG. 2. 9A is a diagram illustrating a detailed arrangement and configuration example of the first lens in FIG. 2, and FIG. 9B is a diagram illustrating an arrangement and configuration example that is a comparative example of FIG. 9A. FIG. 8A shows the liquid crystal display panel 2, the first lens 51, the polarizing element 52, and the concave lens 53 in FIG. 2. A first optical path P1 for displaying a virtual image at a short distance and a second optical path P2 for displaying a virtual image at a long distance are formed between the liquid crystal display panel 2 and the polarizing element 52. . The first lens 51 is arranged only on the first optical path P1.

As shown in FIG. 9A, the first lens 51 is configured, for example, by bonding a concave lens 511 and a convex lens 512 together, and thereby has a shape similar to a rectangular parallelepiped. FIG. 8B is a plan view of the first lens 51, and only the bonding surface s16 of the two lenses is visible. FIG. 8C is a diagram of the diagram shown in FIG. 8B viewed from an oblique direction, and surfaces s14 to s18 are visible, including the bonding surface s16. Surfaces s14 to s18 correspond to surfaces 14 to 18 in the lens data shown in FIG. 3, respectively.

As shown in FIG. 3, the glass materials of the surfaces s14 and s15 of the first lens 51 are the same TAFD32_HOYA, and the glass materials of the surfaces s16 and s17 of the first lens 51 are the same FDS20W_HOYA. That is, the glass material of the concave lens 511 in FIG. 9A is TAFD32_HOYA with a refractive index of 1.871 and an Abbe number of 40.7, and the glass material of the convex lens 512 is FDS20W_HOYA with a refractive index of 1.870 and an Abbe number of 20.0. . The amount of adjustment of the optical path length varies depending on the refractive index of the glass material; when the refractive index is small, the amount of adjustment of the optical path length can be made small, and when the refractive index is large, the amount of adjustment of the optical path length can be made large. Furthermore, the embodiments are not limited to the above-mentioned combinations of glass materials, and other combinations of glass materials may be used.

In this case, since the difference in refractive index for the d-line having a wavelength of 587.562 nm is only 0.001, the bonding surface s16 of the first lens 51 has no refractive effect on the d-line. If the difference in refractive index is large, the first lens 51 will have a lens effect on the d-line, which will affect only the rays on the short distance side, and the telecentricity on the short distance side will change. Put it away. Therefore, it is desirable that the difference in refractive index between the two glass materials forming the first lens 51 be 0.01 or less.

FIG. 10A is a schematic diagram illustrating the action of the first lens in FIG. 2, and FIG. 10B is a schematic diagram as a comparative example of FIG. 10A. In principle, the optical path length from the concave mirror 55 to the liquid crystal display panel 2 in FIG. 2 becomes longer when the virtual image distance is long, and becomes shorter when the virtual image distance is short, as shown in FIG. 10B. In this way, in order to display two virtual images having different virtual image distances, it is usually necessary to provide two display panels or the like.

Therefore, in one embodiment, the first lens 51 is arranged only on the first optical path P1, which is the optical path when the virtual image distance is short. Thereby, as shown in FIG. 10A, the optical path length when the virtual image distance is short can be set to the same length as the optical path length when the virtual image distance is long. In detail, the optical path length of a rectangular parallelepiped with no refractive power in terms of air is d×N using the refractive index N and thickness d, so the optical path length is d(N-1), which is the difference from the physical length d. You can make the length longer. As a result, it becomes possible to display two virtual images at two different positions using one liquid crystal display panel 2.

Further, for example, in FIG. 8C, the concave lens 53 disposed near the first lens 51 has refractive power to achieve the telecentricity shown in FIGS. 7A and 7B, and as a result, the magnification Chromatic aberration may occur. In one embodiment, the chromatic aberration of magnification is corrected using the difference in Abbe number between TAFD32_HOYA and FDS20W_HOYA. At this time, if the difference in Abbe numbers is large, the radius of curvature at the bonding surface s16 can be increased. On the other hand, if the difference in Abbe number is small, it is necessary to reduce the radius of curvature at the bonding surface s16. Therefore, it is desirable that the difference in Abbe number between the two glass materials constituting the first lens 51 be 10 or more.

Incidentally, in the first lens 51, the surface s15 and the surface s17 are made of the same glass material on the front and rear thereof, so they can be omitted, but they are provided here for use in the explanation in FIG. 9A. In one embodiment, as shown in FIG. 9A, in the first lens 51, the optical axis AX of the bonding surface s16 corresponds to the representative ray on the short distance side, that is, the principal ray at the center of the visual field on the short distance side. It is arranged so that it almost coincides with the direction. Moreover, the optical axes of the surface s15, the surface s16, and the surface s17 coincide, and the representative ray passes through the center of the rectangular parallelepiped formed by the section from the surface s15 to the surface s17.

Here, as a first comparative example, assume that the first lens 51 is configured such that the surface s15 and the surface s17 are the incident surface and the exit surface of the image light. In this case, the sunlight transmitted through the windshield 6 is reflected by the concave mirror 55, travels the optical path of the image light in the opposite direction, and then enters the surface s15 and the surface s17 facing the air substantially perpendicularly. As a result, there is a possibility that the stray light reflected by the surfaces s15 and s17 returns along the optical path of the image light and enters the eye box 8 and, ultimately, the driver's eyes 9.

Therefore, by providing the surface s14 and the surface s18 as shown in FIG. 9A, it is possible to prevent the occurrence of stray light on the entrance/exit surface of the first lens 51. That is, the first lens 51 is configured to have an entrance surface and an exit surface that are not perpendicular to the optical axis AX of the bonding surface s16, like the surface s14 and the surface s18. The surface s14 and the surface s18 are in a parallel positional relationship, and the first lens 51 including the surface s14 and the surface s18 acts on the d-line in the same way as a rectangular parallelepiped.

Furthermore, by using the configuration example shown in FIG. 9A, the lens diameters of the concave lens 511 and the convex lens 512 that constitute the first lens 51 can be made small, and material costs can be reduced. For example, in the configuration example of FIG. 9B, which is a second comparative example, the optical axis AX of the bonded surface of the lens 51b corresponding to the first lens 51 is not parallel to the representative ray on the short distance side, but is parallel to the optical axis. In this case, the concave lens 511b and convex lens 512b constituting the lens 51b have larger lens diameters than in the case of FIG. 9A before being cut out into a substantially rectangular parallelepiped shape or rectangular parallelepiped shape.

<Main effects of the embodiment>
As described above, in one embodiment, in a projection optical device and a head-up display device that can display virtual images at a long distance and a short distance, only on the first optical path P1 for displaying a virtual image at a short distance. A first lens 51 is arranged. Thereby, the optical path length of the image light can be set equally on the far side and the near side, so it becomes possible to display virtual images at different virtual image distances using one liquid crystal display panel 2. As a result, it is typically possible to downsize the head-up display device 20.

As above, the invention made by the present inventor has been specifically explained based on the embodiments, but the present invention is not limited to the embodiments described above, and various changes can be made without departing from the gist thereof. For example, the embodiments described above have been described in detail to explain the present invention in an easy-to-understand manner, and the present invention is not necessarily limited to having all the configurations described. Further, it is possible to replace a part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. . Furthermore, it is possible to add, delete, or replace some of the configurations of each embodiment with other configurations.

For example, by using the technology according to the embodiment, it is possible to prevent sunlight from entering the driver's eyes, as described above. In addition to displaying navigation information such as destination and speed projected on the windshield, the driver can also view images of information necessary for driving, such as displaying alert information when an oncoming vehicle or pedestrian is detected. It is possible to provide a head-up display device that reduces viewpoint movement and contributes to supporting safe driving. This makes it possible to prevent traffic accidents. Furthermore, it will be possible to contribute to "3. Good health and well-being for all" in the Sustainable Development Goals (SDGs) advocated by the United Nations.

2... Liquid crystal display panel, 5... Eyepiece optical section (projection optical device), 6... Windshield, 7, 7a, 7b... Virtual image plane, 8... Eye box, 9... Eye, 10... Image forming unit, 20... Head up Display device, 51... first lens, 52... polarizing element, 53... concave lens (second lens), 54... folding mirror (third lens), 55... concave mirror (image projection unit), 511... concave lens, 512... Convex lens, P1... First optical path, P2... Second optical path

Claims (10)

A projection optical device that displays virtual images at long distances and short distances with the projection surface as a reference by reflecting image light emitted from an image forming unit and projecting it onto a projection surface, the projection optical device comprising:
At least a first lens, a second lens, and an image projection section, which are arranged in order from the image forming section side and form an optical path between the image forming section and the projection surface,
A first optical path for displaying the virtual image at the short distance and a second optical path for displaying the virtual image at the long distance are formed between the image forming unit and the second lens. ,
the first lens is disposed only on the first optical path of the first optical path and the second optical path;
Projection optical device. The projection optical device according to claim 1,
The first lens is configured by bonding a concave lens and a convex lens.
Projection optical device. The projection optical device according to claim 2,
The first lens is arranged such that the optical axis of the bonded surface of the concave lens and the convex lens constituting the first lens coincides with the direction of the light ray in the first optical path.
Projection optical device. The projection optical device according to claim 3,
The first lens has an entrance surface that is not perpendicular to the optical axis of the bonded surface, and an exit surface that is not perpendicular to the optical axis of the bonded surface.
Projection optical device. The projection optical device according to claim 4,
The concave lens and the convex lens constituting the first lens are each constructed using a glass material that provides a difference in refractive index of 0.01 or less and a difference in Abbe number of 10 or more.
Projection optical device. an image forming unit that emits image light including image information;
an eyepiece optical section that reflects the image light emitted from the image forming section and projects it onto a projection surface to display a virtual image at a long distance and a short distance with the projection surface as a reference;
A head-up display device comprising:
The eyepiece optical section includes a first lens, a second lens, and an image projection section, which are arranged in order from the image forming section side and form an optical path between the image forming section and the projection surface. At least be prepared
A first optical path for displaying the virtual image at the short distance and a second optical path for displaying the virtual image at the long distance are formed between the image forming unit and the second lens. ,
the first lens is disposed only on the first optical path of the first optical path and the second optical path;
Head-up display device. The head-up display device according to claim 6,
The first lens is configured by bonding a concave lens and a convex lens,
Head-up display device. The head-up display device according to claim 7,
The first lens is arranged such that the optical axis of the bonded surface of the concave lens and the convex lens constituting the first lens coincides with the direction of the light ray in the first optical path.
Head-up display device. The head-up display device according to claim 8,
The first lens has an entrance surface that is not perpendicular to the optical axis of the bonded surface, and an exit surface that is not perpendicular to the optical axis of the bonded surface.
Head-up display device. The head-up display device according to claim 9,
The concave lens and the convex lens constituting the first lens are each constructed using a glass material that provides a difference in refractive index of 0.01 or less and a difference in Abbe number of 10 or more.
Head-up display device.

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