JP2009122582A - Projection optical system and head-up display apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a small type head-up display apparatus that displays a virtual image the aberrations of which are satisfactorily corrected. <P>SOLUTION: The head-up display apparatus 10 includes: a projecting optical system 22 for producing display light 21 that has image information and enlarging and projecting this; and a front glass for displaying a virtual image by reflecting the display light 21. The projecting optical system 22 has: a liquid crystal panel 24 for producing display light 21; a projecting lens group 27 having positive refractive power; a concave mirror 28 having a non-rotation-symmetrical aspherical face, that is disposed so as to be eccentric to the projecting lens group 27. Display light 21 emitted from the liquid crystal panel 24 is magnified and projected while a power is dispersed by the projecting optical lens group 27 and the concave mirror 28. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a projection optical system. More specifically, the present invention is suitable for a head-up display device that projects image display light onto a windshield or the like of an automobile or an aircraft so that the virtual image can be observed through the windshield. The present invention relates to a projection optical system.

  For example, a head-up that reflects the display light of the image displayed on the image display panel toward the driver (observer) by the windshield of an automobile so that the image of instruments such as a speedometer can be observed as a virtual image A display device is known (Patent Document 1, etc.). Such an instrument image is enlarged and displayed as a virtual image at a position 2 m or more away from the driver through the windshield. Therefore, the driver can observe the display image together with the normal front view without changing the line-of-sight direction or diopter.

  An optical system used in such a head-up display device is composed of an image display panel, an illumination light source, a projection optical system, and the like. A transmissive liquid crystal display panel is frequently used as an image display panel, and a backlight light source provided behind the transmissive liquid crystal display panel serves as an illumination light source, and image display light transmitted through the liquid crystal display panel is incident on a projection optical system. For example, a concave mirror is used in the projection optical system, and reflected light from the concave mirror is incident on the windshield as display light, and further, the display light is directed to the observer by reflection of the windshield. .

  In general, since it is difficult to secure a large space in the vicinity of a windshield in an automobile or the like, there is a demand for reducing the size of, for example, an image display panel or a concave mirror. On the other hand, since the virtual image observed as described above is at a position 2 m or more away from the observer, the image size needs to be at least about 150 mm.

  Furthermore, the head-up display device is provided so that an observer observes an image with both eyes, and the observation position is not necessarily constant. For this reason, in order to enable observation with both eyes even when the observation position is shifted by about 20 mm from side to side, it is necessary to secure a pupil size of at least 100 mm. Further, considering that the windshield that reflects the display light toward the driver is positioned approximately in the middle between the driver and the display position of the virtual image, the aperture of the projection optical system needs to be about 125 mm. is there.

When a small display image displayed on the image display panel is enlarged and projected, assuming that the optical path length (image distance) from the concave mirror to the virtual image is D3, the projection magnification is β, and the focal length of the entire projection optical system is f, D3 = (1 + β) × f (imaging formula). If the image distance D3 is 1100 mm, the image size on the image display panel is 15 mm, and this is magnified 10 times to display a virtual image of 150 mm, the focal length of the entire projection optical system is 100 mm. For the above reasons, when the aperture of the projection optical system is set to 125 mm, the brightness (focal length / aperture) of this projection optical system is as very bright as 0.8, but this also suppresses aberrations as much as possible. desired.
JP 2006-11168 A

  However, since the projection optical system of the conventional head-up display device reflects display light with a large deflection angle by the concave mirror, the influence of spherical aberration and astigmatism is remarkable. For example, in the optical system described in Patent Document 1, when the reference optical axis corresponding to the principal ray passing through the center of the image is bent by the concave mirror, the angle between the optical axes before and after bending (deflection angle α) is about 60 degrees. In order to reduce aberrations and obtain good imaging performance, the focal length must be increased to about 300 mm. For this reason, if an image is displayed in a size that allows easy observation, the size of the image display panel and its illumination system also increase, and an increase in space, cost, and power consumption cannot be avoided.

  The present invention has been made in consideration of the above-described background, and is a projection optical system that can display a virtual image with an image size that is easy to observe while reducing the size of the image display panel, and is advantageous in terms of suppressing aberrations. And a head-up display device using the same.

  The projection optical system of the present invention projects the display light from the image display panel so as to be reflected on the viewer side by the reflecting surface facing the viewer at a predetermined position, and passes through the reflecting surface to the image display panel. A projection optical system that enlarges and displays the image displayed on the image as a virtual image observed with both eyes, has a positive refractive power, and projects the display light from the image display panel; and the projection lens group And a concave mirror that reflects the display light from the projection lens group and magnifies and projects it onto the reflecting surface.

  Further, when the projection magnification is β, the optical path length from the reflection point of the concave mirror to the virtual image to be displayed is D3, and the focal length of the projection lens group is f, 1.0 <f × β / D3 <2. 0.0.

  The shape of the reflecting surface of the concave mirror is a non-rotationally symmetric aspherical surface.

  Further, the principal ray of display light incident on the concave mirror from the projection lens group is an incident reference optical axis, and the principal ray of display light reflected by the concave mirror and directed to the reflective surface is an outgoing reference optical axis, and the incident A z-axis is defined along a reference optical axis, a plane including the incident reference optical axis and the output reference optical axis is a yz plane, a plane perpendicular to the yz plane and parallel to the z axis is an xz plane, and the concave surface When the paraxial curvature in the yz plane of the mirror is CY and the paraxial curvature in the xz plane of the concave mirror is CX, 1.3 <| CY / CX | is satisfied.

  Further, the image display panel is arranged to be inclined with respect to the optical axis of the projection lens group.

  The projection lens group may include two or more refractive lenses having the same material and surface shape.

  A head-up display device according to the present invention includes the above-described projection optical system.

  According to the present invention, it is possible to favorably correct aberrations and to make the projection optical system and the head-up display device compact by dispersing power and projecting an image in an enlarged manner.

  As shown in FIG. 1, the head-up display device 10 has its projection optical system arranged on the dashboard 13 of the automobile 12 and displays the value of the speedometer and the like in front of the driver (observer) 14.

  The head-up display device 10 enlarges and projects the display light from the built-in small liquid crystal panel onto the windshield 18 and reflects the light toward the driver 14 with the windshield 18. Therefore, the image displayed by the head-up display device 10 is a virtual image 19. That is, in the head-up display device 10, an image is not formed on the windshield 18 and a real image is displayed, but the virtual image 19 is displayed on the driver 14 at a distance D1 through the windshield 18. .

  The distance D1 at which the virtual image 19 is displayed is sufficiently long so that the virtual image 19 can be viewed with little eye movement during driving and little focus adjustment of the eyes. The distance is more than 2m from the driver.

  As shown in FIG. 2, the head-up display device 10 generates a display light 21 having information of an image to be displayed and enlarges and projects the display light 21, and the display light 21 in the direction of the driver 14. It consists of a windshield (reflecting surface) 18 that reflects. The projection optical system 22 includes a liquid crystal panel (image display panel) 24, a light source 26, a projection lens group 27, a concave mirror 28, and the like.

  The liquid crystal panel 24 is a small liquid crystal panel such as a 0.8 type. The liquid crystal panel 24 displays values of various instruments such as a speedometer, a tachometer, a water temperature gauge, and a fuel gauge. The image displayed on the liquid crystal panel 24 is enlarged and projected on the windshield 18 as described above.

  Further, when the path of the principal ray at the center of the virtual image 19 to be displayed is the reference optical axis L1, and the reference optical axis L1 is traced sequentially from the driver 14 (or virtual image 19) side to the projection optical system 22 side, the liquid crystal panel 24. The display surface is inclined by a predetermined angle rather than 90 degrees with respect to the reference optical axis L1.

  The inclination of the liquid crystal panel 24 with respect to the reference optical axis L1 is an inclination angle γ such that the focus of the virtual image 19 is met in all ranges within the display range. That is, the line of sight of the driver 14 who sees the upper end of the virtual image 19 is in focus at the upper end of the display surface of the liquid crystal panel 24, and the line of sight of the driver 14 who looks at the lower end of the virtual image 19 is also at the lower end of the display surface of the liquid crystal panel 24. In order to focus, the liquid crystal panel 24 is not perpendicular to the reference optical axis L1, but is inclined at an angle γ around a horizontal axis orthogonal to the reference optical axis L1.

  The image displayed on the liquid crystal panel 24 is an image having a shape obtained by converting the shape of the image to be displayed when the liquid crystal panel 24 is directly viewed according to the above-described tilt angle γ.

  The light source 26 is made of, for example, a white LED and is disposed on the back surface of the liquid crystal panel 24. That is, the light source 26 is a so-called backlight and uniformly illuminates illumination light from behind the liquid crystal panel 24. The illumination light from the light source 26 becomes display light 21 having image information displayed on the liquid crystal panel 24 when it passes through the liquid crystal panel 24, and is emitted from the liquid crystal panel 24. In addition, although the light source 26 consists of white LED, it can be set as the light source of not only this but a desired color. For example, it may be composed of single-color LEDs such as red, green, and blue, or a combination of several of these single-color LEDs to display an image in a desired color. Furthermore, the light source 26 is not limited to an LED, and other known lamps may be used.

  The projection lens group 27 is composed of one refracting lens, and is a lens group having a positive refractive power as a whole. The projection lens group 27 is disposed in front of the liquid crystal panel 24 and projects the display light 21 emitted from the liquid crystal panel 24 onto the concave mirror 28. Further, the optical axis of the projection lens group 27 is arranged so as to coincide with the above-mentioned reference optical axis L1. The photographic lens group 27 is not limited to a single refracting lens, and may be composed of two or more refracting lenses. The photographic lens is a combination of a refracting lens and another known optical member. It is good as a group.

  The concave mirror 28 is a mirror that reflects the display light 21 incident from the projection lens group 27 toward the windshield 18, and is disposed with the concave surface that is a reflection surface facing the projection lens group 27 side. The image displayed on the liquid crystal panel 24 is enlarged and projected onto the windshield 18 by the concave mirror 28 and the projection lens group 27 described above.

  As shown in FIG. 3, the surface shape of the concave mirror 28 is not only a concave surface, but also a non-rotationally symmetric aspherical shape, a so-called free curved surface shape. Since the concave mirror 28 has such a non-rotationally symmetric aspherical shape, the concave mirror 28 enlarges and projects the display light 21, and at the same time, the entire virtual image 19 displaying the aberration generated by the concave mirror 28 and the projection lens group 27. Correct well.

  That is, the surface shape of the concave mirror 28 consists of a part of a free-form surface 31, and this free-form surface 31 is deformed so as to favorably correct aberrations based on a rotationally symmetric curved surface such as a spherical surface. Yes. If the free-form surface 31 obtained by extending the concave mirror 28 is viewed globally, a rotationally symmetric axis (hereinafter referred to as an optical axis) L2 may be determined. Even when the optical axis L2 can be determined as described above, the concave mirror 28 is formed so that the optical axis L2 of the free-form surface 31 is located outside the concave mirror 28, for example. Therefore, the concave mirror 28 itself cannot have an optical axis, and the concave mirror 28 has a free-form surface having no rotational symmetry. Furthermore, the concave mirror 28 is arranged eccentrically with respect to the optical axis of the projection lens group 27. That is, at least so that the optical axis L2 is inclined with respect to the optical axis of the projection lens group 27, or so that the optical axis L2 is shifted from the optical axis position of the projection lens group 27. The concave mirror 28 is arranged. As described above, since the projection lens group 27 is arranged so that the optical axis thereof coincides with the reference optical axis L1, the arrangement of the concave mirror 28 is the same with respect to the reference optical axis L1.

  The surface shape of the concave mirror 28 is a complete free-form surface having no symmetry, but it is not necessarily a complete free-form surface, and depending on the shape of the reflection surface that magnifies and projects the display light. There may be symmetry such as line symmetry. That is, the windshield 18 for enlarging and projecting the display light 21 is tilted forward and backward with respect to the driver 14 and has an asymmetric shape on the left and right with respect to the front of the driver 14. The concave mirror 28 also has a completely free-form surface having no symmetry. However, for example, when displaying a virtual image by magnifying and projecting display light on a plane symmetrical to the left and right for an observer such as the driver 14, the surface shape of the concave mirror is changed to display a normal virtual image. The cylindrical shape is preferably symmetrical with respect to the reference optical axis.

  The projection optical system 22 composed of the above-described parts is configured so as to satisfy the following equation (1). That is, the projection optical system 22 sets the focal length of the projection lens group 27 to f, the projection magnification (the size of the virtual image to be displayed / the image size on the liquid crystal panel) to β, and the reference point of the concave mirror 28 described later to the virtual image 19. When the optical path length is D3, the following condition 1 is satisfied.

  Since the projection optical system 22 is arranged with the non-rotationally symmetric aspherical concave mirror 28 decentered with respect to the projection lens group 27, the focal length of the entire projection optical system 22 is uniquely defined as in a conventional lens system. It is difficult to determine. The above-described conditional expression (Equation 1) is a conditional expression having a meaning corresponding to the imaging formula of the conventional lens system with respect to such a projection optical system 22.

  Specifically, the conditional expression described above determines the power distribution of the projection lens group 27 and the concave mirror 28. That is, when the value of f × β / D3 falls below the lower limit (1.0) of the above conditional expression, the projection lens group 27 bears most of the power for the projection optical system 22 to display the virtual image 19. Thus, the distance from the projection lens group 27 to the imaging position of the virtual image 19 becomes longer. Therefore, if the lower limit of the above conditional expression is not reached, the projection optical system 22 cannot be made compact, and as a result, it is difficult to reduce the size of the head-up display device 10.

  On the other hand, when the value of f × β / D3 exceeds the upper limit (2.0) of the conditional expression described above, the concave mirror 28 bears most of the power for the projection optical system 22 to display the virtual image 19. Thus, it becomes difficult to correct aberrations generated by the projection lens group 27 and the concave mirror 28. The aberration generated by the concave mirror 28 is reflected by the reference optical axis L1 (hereinafter referred to as the incident reference optical axis) of the display light 21 incident from the projection lens group 27 and the concave mirror 28 as the deflection angle of the display light 21 increases. The larger the angle between the display light 21 and the reference optical axis L1 (hereinafter referred to as the emission reference optical axis), the more pronounced it becomes. However, if the value of f × β / D3 is smaller than the upper limit (2.0) of the above conditional expression, when the deflection angle of the display light is relatively large, for example, the deflection angle is about 60 degrees. Even in this case, the aberration is corrected satisfactorily.

  As described above, the projection optical system 22 is preferably configured so that the value of f × β / D3 satisfies the conditional expression of Formula 1, and satisfies 1.0 <f × β / D3 <2.0. Is more preferable. Further, the projection optical system 22 is particularly preferably configured to satisfy 1.1 <f × β / D3 <1.8.

  Further, the head-up display device 10 is formed so as to satisfy the following conditional expression 2 regarding the surface shape of the concave mirror 28. That is, when the incident reference optical axis is the z axis, the plane including the incident reference optical axis and the outgoing reference optical axis is defined as the yz plane, and the concave mirror is defined when the xz plane is defined perpendicular to the yz plane and parallel to the z axis. 28, the paraxial curvature CY in the yz plane and the paraxial curvature CX in the xz plane are formed so as to satisfy the following conditional expression (2).

  This conditional expression (Expression 2) is a condition for most drivers (observers) to normally observe the virtual image 19 displayed by the head-up display device 10 with both eyes. That is, if the ratio of the paraxial curvature CY to the paraxial curvature CX of the concave mirror 28 is below the lower limit of Equation 2, the display light reaches only one eye instead of both eyes of the driver. The driver will have problems such as the flickering of the displayed virtual image 19.

  Thus, the concave mirror 28 is preferably made so as to satisfy the condition of the above formula 2, more preferably 1.5 <| CY / CX |. .7 <| CY / CX |

  Specific examples of the head-up display device 10 and the projection optical system 22 configured as described above are shown as Examples 1 to 4 below.

[Example 1]
As shown in FIG. 4, the projection optical system 22a of the head-up display device 10a includes a projection lens group 27a, a concave mirror 28a, a liquid crystal panel 24, and the like. The head-up display device 10a is configured to display a virtual image by projecting and reflecting display light on a windshield of an automobile. Each part of the head-up display device 10a was arranged to display a virtual image at a position 2m ahead (D1 = 2m) through the windshield for the driver. Further, the size (width h × height v) of the virtual image to be displayed is h × v = 150 mm × 50 mm so that the size of the virtual image displayed by the head-up display device 10a is sufficiently large for the driver to see. did. At this time, the observation range in which the driver displayed the virtual image displayed on both eyes, that is, the size of the entrance pupil, was set to width 100 mm × height 40 mm.

  The projection lens group 27a is composed of a single refractive lens 36a having a positive refractive power. The refractive lens 36a is a meniscus lens having a convex surface facing the concave mirror 28a, and is arranged so that the optical axis of the refractive lens 36a (projection lens group 27a) coincides with the reference optical axis L1.

  The effective size of the concave mirror 28a involved in displaying a virtual image is that the length A in the vertical direction (the vertical direction of the head-up display device 10a as viewed from the driver) is 46 mm, and the horizontal direction (as viewed from the driver). The length in the horizontal direction of the head-up display device 10a is 122 mm.

  In order to show the detailed arrangement and the like of each part of the head-up display device 10a, a coordinate system having the origin O as a point where the reference optical axis L1 is reflected by the concave mirror 28a is determined. In this coordinate system, the projection lens group 27a side from the origin O along the reference optical axis L1 is the positive direction of the z axis, and the reference optical axis L1 of the display light 21 that is perpendicular to the z axis and reflected by the concave mirror 28a is used. The y-axis is defined within the plane to include, and the direction in which the windshield is disposed is defined as the positive direction of the y-axis. Further, the x-axis is determined so that it is perpendicular to the above-described y-axis and z-axis, and the coordinate system forms a right-handed system. That is, with respect to the concave mirror 28a, the plane including the incident reference optical axis and the outgoing reference optical axis is the yz plane, and the plane perpendicular to the yz plane and parallel to the z axis is the xyz plane. Define the coordinate system.

  Thus, when the coordinate system is determined, the concave mirror 28a is S1, the surface of the refractive lens 36a on the concave mirror 28a side is S2, the surface of the refractive lens 36a (projection lens group 27a) on the liquid crystal panel 24 side is S3, and the liquid crystal panel Table 1 shows the specific positions of each surface, with 24 display surfaces designated as S4. The coordinate scales shown in Table 1 are all mm. At the same time, the lower part of Table 1 also shows various conditions of the head-up display device 10a.

  Further, Table 2 shows the curvature radius Ri, refractive index Nd, and Abbe number νd of each surface of the projection lens group 27a (refractive lens 36a) together with the concave mirror 28a and the liquid crystal panel 24. The lower part of Table 2 shows the value of the focal length f of the projection lens group 27a. The refractive index Nd and Abbe number νd shown in Table 2 are both for the d-line (wavelength 587.6 nm).

  As shown in Tables 1 and 2, the liquid crystal panel 24 has an intersection between the display surface and the reference optical axis L1, that is, the center coordinates of the display surface are (x, y, z) = (0.00, 0.00 , 143.09). Further, the liquid crystal panel 24 was arranged to rotate about the x-axis direction so that the angle formed by the normal line of the display surface S4 and the z-axis was 5.0 degrees. Therefore, the angle (inclination angle of the liquid crystal panel 24) γ formed by the normal line of the display surface S4 and the reference optical axis L1 is 5.0 degrees. Further, the liquid crystal panel 24 has a display surface S4 having a size of width h × height v = 15 mm × 5 mm. That is, the projection magnification β of the head-up display device 10a is 10 times.

  The surface S3 of the refractive lens 36a on the liquid crystal panel 24 side has a spherical shape convex to the concave mirror 28a side (curvature radius R3 = 78.9791 mm), and the position coordinates of the intersection with the reference optical axis L1 are (x, y). , Z) = (0.00, 0.00, 35.00). The surface S2 on the concave mirror 28a side has a spherical shape convex to the concave mirror 28a side (curvature radius R2 = 370.7333 mm), and the position coordinates of the intersection with the reference optical axis L1 are (x, y, z). ) = (0.00, 0.00, 59.17). Further, the optical axes of these refractive lenses 36a are parallel to the z-axis and the reference optical axis L1, and the focal length f is 165.27 mm.

  The concave mirror 28a is arranged so that the position of the optical axis L2 is (x, y, z) = (0.00, −174.85, 171.18), and the optical axis L2 and the y axis The x-axis direction was rotated and arranged so that the angle formed was 62.5 degrees. The optical path length D2 from the origin O of the coordinate system to the driver is 900 mm, and the optical path length D3 from the origin O of the coordinate system to the virtual image to be displayed is 1100 mm.

  The surface shape of the concave mirror 28a is expressed by the following formula 3. Here, CX, CY, KAX, KAY, A4, K2, A6, and K3 are non-rotationally symmetric aspheric coefficients, and specific values thereof are shown in Table 3. Among these non-rotation target aspherical coefficients, CX is a paraxial curvature in the xz plane, and CY is a paraxial curvature in the yz plane.

  As shown in Table 4, in the head-up display device 10a configured in this way, the value of fxβ / D3 is 1.50, which is a value within the range of the conditional expression (Equation 1). Regarding the surface shape of the concave mirror 28a, the ratio | CY / CX | of the ratio of the paraxial curvature CY in the yz plane to the paraxial curvature CX in the xz plane is about 39.5, Satisfy the condition of 2.

  Further, an XY coordinate system is defined in which the center of the liquid crystal panel 24 (intersection of the display surface and the reference optical axis L1) is the origin and the horizontal direction is the X axis, and the image coordinates (0.0, 2) on the liquid crystal panel 24 are defined. .5), (0.0, 0.0), (0.0, -2.5), (7.5, 2.5), (7.5, 0.0), (7.0, Spot diagrams of each point of -2.5) are shown in FIGS. The scale of the image coordinates is mm, and each spot diagram is indicated by a scale having a reference length (upper right of FIG. 5) of 250 μm.

[Example 2]
As shown in FIG. 6, the projection optical system 22b of the head-up display device 10b includes a projection lens group 27b, a concave mirror 28b, a liquid crystal panel 24, and the like. This head-up display device 10b is configured to display a virtual image at a position 2 m ahead of the driver through the windshield of the automobile, as in the first embodiment. Similarly, the size (width h × height v) of the virtual image to be displayed was h × v = 150 mm × 50 mm, and the size of the entrance pupil was 100 mm wide × 40 mm high.

  The projection lens group 27b is composed of a single refractive lens 36b having a positive refractive power. The refractive lens 36b is a meniscus lens having a convex surface facing the concave mirror 28b, and is arranged so that the optical axis of the refractive lens 36b (projection lens group 27b) coincides with the reference optical axis L1.

  The effective size of the concave mirror 28b involved in the display of the virtual image is that the length A in the vertical direction (the vertical direction of the head-up display device 10b as viewed from the driver) is 46 mm, and the horizontal direction (as viewed from the driver). The length in the horizontal direction of the head-up display device 10b) is 122 mm.

  When the xyz coordinate system is determined as in the first embodiment, the concave mirror 28b is the surface S1, the surface on the concave mirror 28b side of the refractive lens 36b is S2, the surface on the liquid crystal panel side of the refractive lens 36b is S3, and the liquid crystal panel Table 5 shows the specific positions of the 24 display surfaces, S4. The coordinate scales shown in Table 5 are all mm. At the same time, the lower part of Table 5 also shows various conditions of the head-up display device 10a.

  Further, Table 6 shows the radius of curvature Ri, the refractive index Nd, and the Abbe number νd of each surface of the projection lens group 27b (refractive lens 36b) together with the concave mirror 28b and the liquid crystal panel 24. The lower part of Table 6 shows the value of the focal length f of the projection lens group 27a. The refractive index Nd and Abbe number νd shown in Table 6 are both for the d-line (wavelength 587.6 nm).

  As shown in Tables 5 and 6, the liquid crystal panel 24 was arranged so that the center coordinates of the display surface S4 were (x, y, z) = (0.00, 0.00, 139.38). Further, the liquid crystal panel 24 was arranged to rotate about the x-axis direction so that the angle formed by the normal line of the display surface S4 and the z-axis was 5.0 degrees. Therefore, the angle (inclination angle of the liquid crystal panel 24) γ formed between the normal line of the display surface S4 and the reference optical axis L1 is 5.0 degrees. Further, the liquid crystal panel 24 has a display surface S4 having a size of width h × height v = 15 mm × 5 mm. That is, the projection magnification β of the head-up display device 10b is 10 times.

  The surface S3 of the refractive lens 36b on the liquid crystal panel 24 side has a spherical shape convex toward the concave mirror 28b (curvature radius R3 = 108.2557 mm), and the position coordinates of the intersection with the reference optical axis L1 are (x, y). , Z) = (0.00, 0.00, 35.00). Further, the surface S2 on the concave mirror 28b side has a spherical shape convex on the concave mirror 28b side (curvature radius R2 = 370.7333 mm), and the position coordinates (x, y, z) of the intersection with the reference optical axis L1. = (0.00, 0.00, 59.17). The optical axis of the refractive lens 36b is parallel to the z-axis and the reference optical axis L1, and the focal length f is 189.19 mm.

  The concave mirror 28b is disposed such that the position of the optical axis L2 is (x, y, z) = (0.00, −174.85, 171.18), and the concave mirror 28b is positioned between the optical axis L2 and the y axis. The x-axis direction was rotated and arranged so that the angle formed was 62.5 degrees. The optical path length D2 from the origin O of the coordinate system to the driver is 900 mm, and the optical path length D3 from the origin O of the coordinate system to the virtual image to be displayed is 1100 mm.

  Further, the surface shape of the concave mirror 28b is expressed by the equation (3) as in the first embodiment. Table 7 shows specific values of the non-rotation target aspheric coefficient of the concave mirror 28b.

  In the head-up display device 10b configured as described above, as shown in Table 8, the value of f × β / D3 is 1.72, which is a value within the range of the above-described conditional expression (Equation 1). . Further, the ratio of the paraxial curvature CY in the yz plane to the paraxial curvature CX in the xz plane is | CY / CX | ≈1.90, which satisfies the above-described equation (2).

  Further, an XY coordinate system is defined in which the center of the liquid crystal panel 24 (intersection of the display surface and the reference optical axis L1) is the origin and the horizontal direction is the X axis, and the image coordinates (0.0, 2) on the liquid crystal panel 24 are defined. .5), (0.0, 0.0), (0.0, -2.5), (7.5, 2.5), (7.5, 0.0), (7.0, Spot diagrams of each point of -2.5) are shown in FIGS. Note that the scale of image coordinates is mm, and each spot diagram is indicated by a scale having a reference length (upper right of FIG. 7) of 250 μm.

[Example 3]
As shown in FIG. 8, the projection optical system 22c of the head-up display device 10c includes a projection lens group 27c, a concave mirror 28c, a liquid crystal panel 24, and the like. The head-up display device 10c is configured to display a virtual image at a position 2 m ahead of the driver through the windshield of the automobile, as in the first and second embodiments. Similarly, the size (width h × height v) of the virtual image to be displayed was h × v = 150 mm × 5 mm, and the size of the entrance pupil was 100 mm wide × 40 mm high.

  The projection lens group 27c is composed of a single refractive lens 36c having a positive refractive power. The refractive lens 36c is a meniscus lens having a convex surface facing the concave mirror 28c, and is arranged so that the optical axis of the refractive lens 36c (projection lens group 27c) coincides with the reference optical axis L1.

  The effective size of the concave mirror 28c involved in the display of the virtual image is that the length A in the vertical direction (the vertical direction of the head-up display device 10c as viewed from the driver) is 46 mm and the horizontal direction (as viewed from the driver). The length in the horizontal direction of the head-up display device 10c is 122 mm.

  When the xyz coordinate system is determined as in the first and second embodiments, the concave mirror 28c is the surface S1, the surface of the refractive lens 36c on the concave mirror 28c side is S2, and the surface of the refractive lens 36c on the liquid crystal panel 24 side is S3. The display surface of the liquid crystal panel 24 is S4, and the specific positions of each surface are shown in Table 9. All scales in the coordinate system shown in Table 9 are mm. At the same time, the lower part of Table 9 also shows various conditions of the head-up display device 10c.

  Further, Table 10 shows the curvature radius Ri, the refractive index Nd, and the Abbe number νd of each surface of the projection lens group 27c (refractive lens 36c) together with the concave mirror 28c and the liquid crystal panel 24. The lower part of Table 10 shows the values of the focal lengths fv and fh of the projection lens group 27c (details will be described later) although details will be described later. The refractive index Nd and Abbe number νd shown in Table 10 are both for the d-line (wavelength 587.6 nm).

  As shown in Tables 9 and 10, the liquid crystal panel 24 was arranged so that the center coordinates of the display surface S4 were (x, y, z) = (0.00, 0.00, 134.54). Further, the liquid crystal panel 24 was arranged to rotate about the x-axis direction so that the angle formed by the normal line of the display surface S4 and the z-axis was 5.0. Therefore, the angle (inclination angle of the liquid crystal panel 24) γ formed between the normal line of the display surface S4 and the reference optical axis L1 is 5.0 degrees. Further, the liquid crystal panel 24 has a display surface S4 having a size of width h × height v = 15 mm × 5 mm. That is, the projection magnification β of the head-up display device 10c is 10 times.

  The surface S3 of the refractive lens 36c on the liquid crystal panel 24 side has a spherical shape convex to the concave mirror 28c side (curvature radius R3 = −900.6493 mm), and the position coordinates of the intersection with the reference optical axis L1 are (x, y, z) = (0.00, 0.00, 61.23).

  On the other hand, the surface S2 on the concave mirror 28c side of the refractive lens 36c has a convex shape on the concave mirror 28c side, but is not a spherical surface but a non-rotationally symmetric aspherical shape. The shape of the surface S2 of the refracting lens 36c is expressed by the above formula 3. The specific value of the non-rotationally symmetric aspheric coefficient for the refractive lens 36c is shown together with that of the concave mirror 28c described later (Table 11).

  Further, the optical axis of the refractive lens 36c composed of the surfaces S2 and S3 is arranged so as to be parallel to the z axis and the reference optical axis L1. However, unlike the first and second embodiments, the surface S2 on the concave mirror 28c side is a non-rotationally symmetric aspherical surface as described above, so that the focal length varies depending on the direction in which the display light beam is transmitted. Therefore, if the focal length in the vertical direction (intersection line between the surface S2 and the yz plane) is fv, and the focal length in the lateral direction (intersection line between the surface S2 and the xz plane) is fh, fv = 124.88 mm, fh = It is 145.74 mm.

  The surface shape of the concave mirror 28c is expressed by the above-described equation (3). Specific values of the non-rotationally symmetric aspheric coefficient of the concave mirror 28c are shown in Table 11 together with specific values of the non-rotationally symmetric aspheric coefficient of the surface S2 of the refractive lens 36c.

  As shown in Table 12, the head-up display device 10c configured as described above has fv × β / D3 = 1.14 in the vertical direction and fh × β / D3 = 1.32 in the horizontal direction. In any of the vertical and horizontal directions, the value of f × β / D3 is within the range of the conditional expression (Equation 1). Further, for the concave mirror 28c, the magnitude of the paraxial curvature CY in the yz plane with respect to the paraxial curvature CX in the xz plane is | CY / CX | ≈4.42, which satisfies the above-described equation (2). .

  Further, an XY coordinate system is defined in which the center of the liquid crystal panel 24 (intersection of the display surface S4 and the reference optical axis L1) is the origin and the horizontal direction is the X axis, and the image coordinates (0.0, 2.5), (0.0, 0.0), (0.0, -2.5), (7.5, 2.5), (7.5, 0.0), (7.0 , −2.5) spot diagrams of the respective points are shown in FIGS. Note that the scale of the image coordinates is mm, and each spot diagram is shown with a scale at which the reference length (upper right in FIG. 9) is 250 μm.

[Example 4]
As shown in FIG. 10, the projection optical system 22d of the head-up display device 10d includes a projection lens group 27d, a concave mirror 28d, a liquid crystal panel 24, and the like. The head-up display device 10d is configured to display a virtual image at a position 2 m ahead of the driver through the windshield of the automobile, as in the first and second embodiments. Similarly, the size (width h × height v) of the virtual image to be displayed was h × v = 150 mm × 5 mm, and the size of the entrance pupil was 100 mm wide × 40 mm high.

  The projection lens group 27d is composed of two refractive lenses, a first refractive lens 36d and a second refractive lens 36e. These refractive lenses are arranged in the order of the first refractive lens 36d and the second refractive lens 36e from the concave mirror 28d side. Each of the first refractive lens 36d and the second refractive lens 36e is a meniscus lens having a convex surface facing the concave mirror 28d, and the projection lens group 27d as a whole has a positive refractive power. Yes. Further, the optical axis of the projection lens group 27d is arranged so as to coincide with the reference optical axis L1.

  The effective size of the concave mirror 28c involved in the display of the virtual image is that the length A in the vertical direction (the vertical direction of the head-up display device 10d as viewed from the driver) is 46 mm and the horizontal direction (as viewed from the driver). The length in the horizontal direction of the head-up display device 10d) is 122 mm.

  When the xyz coordinate system is determined as in the first to third embodiments, the concave mirror 28d is the surface S1, the surface of the first refractive lens 36d on the concave mirror 28d side is S2, and the first refractive lens 36d is on the liquid crystal panel 24 side. The surface of the second refractive lens 36e on the concave mirror 28d side is S4, the surface of the second refractive lens 36e on the liquid crystal panel 24 side is S5, and the display surface of the liquid crystal panel 24 is S6. Table 13 shows the positions. All scales in the coordinate system shown in Table 13 are mm. At the same time, the lower part of Table 13 shows various conditions of the head-up display device 10d.

  Further, Table 14 shows the radius of curvature Ri, the refractive index Nd, and the Abbe number νd of each surface of the first refractive lens 36d and the second refractive lens 36e together with the concave mirror 28d and the liquid crystal panel 24. The lower part of Table 14 shows the values of the focal lengths fv and fh of the projection lens group 27d.

  As shown in Tables 13 and 14, the liquid crystal panel 24 was arranged so that the center coordinates of the display surface S6 were (x, y, z) = (0.00, 0.00, 147.41). Further, the liquid crystal panel 24 was arranged to rotate about the x-axis direction so that the angle formed by the normal line of the display surface S6 and the z-axis was 5.0 degrees. Therefore, the angle (inclination angle of the liquid crystal panel 24) γ formed by the normal line of the display surface S6 and the reference optical axis L1 is 5.0 yelling. In addition, the liquid crystal panel 24 has a display surface S6 having a size of width h × height v = 15 mm × 5 mm. That is, the projection magnification β of the head-up display device 10d is 10 times.

  The surface S5 of the second refractive lens 36e on the liquid crystal panel 24 side has a spherical shape convex to the concave mirror 28d side (curvature radius R5 = 4766.5493 mm), and the position coordinates of the intersection with the reference optical axis L1 are (x, y). , Z) = (0.00, 0.00, 67.05).

  On the other hand, the surface S4 on the concave mirror 28d side of the second refractive lens 36e has a convex shape toward the concave mirror 28d, but is not a spherical surface but a non-rotationally symmetric aspherical shape. The surface shape of the second refracting lens 36e is expressed by the above equation (3). The specific value of the non-rotationally symmetric aspheric coefficient for the second refractive lens 36d is shown together with that of the concave mirror 28d described later (Table 15).

  Further, the surface S3 of the first refractive lens 36d on the liquid crystal panel 24 side has a spherical shape convex on the concave mirror 28d side (curvature radius R3 = 4766.5493 mm), and the position coordinates of the intersection with the reference optical axis L1 are (x , Y, z) = (0.00, 0.00, 50.52).

  On the other hand, the surface S2 on the concave mirror 28d side of the first refractive lens 36d has a convex shape on the concave mirror 28d side, but is not a spherical surface but a non-rotationally symmetric aspherical shape. The specific surface shape of the first refracting lens 36d is expressed by the above equation (3). The value of the non-rotationally symmetric aspheric coefficient for the first refractive lens 36d is shown together with that of the concave mirror 28d described later (Table 15).

  The optical axis of the projection lens group 27d including the first refractive lens 36d and the second refractive lens 36e is arranged to be parallel to the z axis and the reference optical axis L1. However, since the non-rotationally symmetric aspherical surface is included as in the above-described third embodiment, the focal length differs depending on the direction in which the display light beam is transmitted. Therefore, when the focal length in the vertical direction (light beam transmitted through the yz plane) is fv and the focal length in the horizontal direction (light beam transmitted through the xz plane) is fh, fv = 124.88 mm and fh = 148.12 mm. It has become.

  The surface shape of the concave mirror 28d is expressed by the above equation (3). The specific value of the non-rotationally symmetric aspheric coefficient of the concave mirror 28d is combined with the specific value of the non-rotationally symmetric aspheric coefficient of the surface S2 of the first refractive lens 36d and the surface S4 of the second refractive lens 36e. Table 15 shows.

  As shown in Table 16, the head-up display device 10d configured as described above has fv × β / D3 = 1.14 in the vertical direction and fh × β / D3 = 1.35 in the horizontal direction. In any of the vertical and horizontal directions, the value of f × β / D3 is within the range of the conditional expression (Equation 1). Further, for the concave mirror 28d, the magnitude of the paraxial curvature CY in the yz plane with respect to the paraxial curvature CX in the xz plane is | CY / CX | ≈3.69, which satisfies the condition of the above equation (2). .

  Further, an XY coordinate system is defined in which the center of the liquid crystal panel 24 (intersection of the display surface S6 and the reference optical axis L1) is the origin and the horizontal direction is the X axis, and the image coordinates (0.0, 2.5), (0.0, 0.0), (0.0, -2.5), (7.5, 2.5), (7.5, 0.0), (7.0 , −2.5) spot diagrams of the respective points are shown in FIGS. Note that the scale of the image coordinates is mm, and each spot diagram is indicated by a scale having a reference length (upper right of FIG. 11) of 250 μm.

  As described above, the projection optical system of the present invention projects an image to be displayed on the liquid crystal panel on the windshield (reflecting surface) by distributing the power by the projection lens group and the concave mirror, so that the projection optical system has a short focal length. The aberration can be corrected satisfactorily. Accordingly, a small-sized projection optical system such as a liquid crystal panel, its illumination, and a concave mirror can be used, and the entire projection optical system can be made compact. Also, a head-up display device equipped with this projection optical system can display a virtual image with good aberration correction, and can be configured compactly.

  Further, since the projection optical system is configured so as to satisfy the condition of Equation 1, it is possible to easily realize the above-described favorable aberration correction and downsizing of the projection optical system and the head-up display device. it can.

  In addition, the aberration can be corrected particularly well by making the concave mirror a non-rotationally symmetric aspherical surface.

  Furthermore, the position of the observer observing the virtual image displayed by the head-up display device varies, but the non-rotationally symmetric aspherical concave mirror has a condition of Formula 2 for the vertical and horizontal paraxial curvatures. By being configured so as to satisfy the equation, normal observation with both eyes without flickering of the image can be realized.

  In addition, since the liquid crystal panel is disposed at a predetermined angle with respect to the projection lens group (and the reference optical axis), the head-up display device displays a relatively large virtual image that is easy to observe. The observer can easily focus on any of the upper, lower, left and right positions without being aware of it.

  Further, by using two or more refractive lenses in the projection lens group, it is possible to disperse the refractive power among the refractive lenses in the projection lens group, and the refractive lenses constituting these projection lens groups are made of a material. If the surface shapes are the same, the projection lens group can be configured at a lower cost.

  In the above-described embodiment, one light source is arranged for the liquid crystal panel. However, the present invention is not limited to this, and a plurality of light sources may be provided for the liquid crystal panel. For example, as shown in FIG. 12, the projection optical system 41 includes a first light source 42 a and a second light source 42 b for one liquid crystal panel 24.

  The first light source 42a irradiates the liquid crystal panel 24 from an oblique direction with illumination light that finally becomes display light that reaches the right eye of the observer. The first light source 42 a is disposed on one side of the optical axis of the projection lens group 27 while being shifted by a predetermined distance, and is inclined at a predetermined angle with respect to the optical axis of the projection lens group 27. Therefore, the arrangement of the liquid crystal panel 24 is inclined by a predetermined angle with respect to the reference optical axis L1a of the display light for the right eye emitted from the liquid crystal panel 24, as in the above-described embodiment.

  On the other hand, the second light source 42b irradiates the liquid crystal panel 24 from an oblique direction with illumination light that finally becomes display light that reaches the left eye of the observer. The second light source 42b is arranged on the other side of the projection lens group 27 by a predetermined distance so as to be symmetrical with the first light source 42a described above, and with respect to the optical axis of the projection lens group 27. And arranged at a predetermined angle. Therefore, the arrangement of the liquid crystal panel 24 is inclined at a predetermined angle with respect to the reference optical axis L1b of the display light for the left eye emitted from the liquid crystal panel 24, as in the above-described embodiment.

  In the above-described embodiment, the projection lens group is arranged so that the optical axis coincides with the reference optical axis of the display light. However, in the case of the projection lens group 41 provided with two light sources, the light beam The axes are arranged so as to coincide with the bisector of the angle formed by the reference optical axis L1a for the right eye and the reference optical axis L1b for the left eye.

  In this way, by providing light sources for the right eye and the left eye, respectively, display light with a substantially equal amount of light is more reliably incident on both eyes of the observer, and observation with both eyes is possible. It can be made easier.

  In the above-described embodiment and examples, the concave mirror is a non-rotationally symmetric aspheric surface, and in Examples 3 and 4, the surface of the refractive lens of the projection lens group is also a non-rotationally symmetric aspheric surface. However, the present invention is not limited to this, and some surfaces of the refractive lens of the projection lens group may be non-rotationally symmetric aspherical surfaces, and the concave mirror may be a rotationally symmetric aspherical surface or spherical surface. In other words, the concave mirror is preferably a non-rotationally symmetric aspherical surface, but is not limited to this as long as aberrations are sufficiently corrected by the projection lens group.

  In the above-described embodiment, an example in which the projection lens group is composed of one or two refractive lenses will be described. However, the present invention is not limited to this, and the projection lens group may be composed of three or more refractive lenses. Furthermore, the projection lens group is not limited to the refraction lens alone, and a known optical member such as a mirror or a prism may be combined with the refraction lens.

  In the above-described embodiments and examples, the head-up display device is described as an example for an automobile, but the present invention is not limited to this, and the head-up display device of the present invention is applied to other things such as an aircraft and a ship. It can be used suitably. Thus, when the head-up display device of the present invention is applied to a device other than an automobile, the surface shape of the concave mirror is non-rotationally symmetric according to the shape of the reflecting surface (windscreen in the automobile) that magnifies and projects the display light. Although it is an aspherical surface shape, it must be determined individually according to the shape of each reflecting surface. Moreover, since the state of inclination and curvature of the windshield differs depending on the vehicle type and the like, the same adjustment is necessary even when the head-up display device of the present invention is used in an automobile.

  In the above-described embodiments and examples, an example in which a transmissive liquid crystal panel is used as an image display panel will be described. However, the present invention is not limited to this, and the image display panel may be a reflective liquid crystal panel. The mode may be selected as appropriate. The image display panel is not limited to the one using liquid crystal, and other known image display panels may be used as long as they can emit display light.

  The head-up display device is preferably made of a material having durability according to the installation environment. For example, in the case of a head-up display device installed on a dashboard of an automobile, it is preferable that each part constituting the device is excellent in heat resistance.

It is explanatory drawing which shows the outline of a head-up display apparatus. It is a schematic sectional drawing which shows the structure of a head-up display apparatus. It is explanatory drawing which shows the surface shape of a concave mirror. FIG. 3 is a cross-sectional view illustrating a specific configuration of the head-up display device according to the first embodiment. 2 is a spot diagram of the projection optical system of Example 1. FIG. It is sectional drawing which shows the specific structure of the head-up display apparatus of Example 2. FIG. 6 is a spot diagram of the projection optical system of Example 2. FIG. 6 is a cross-sectional view showing a specific configuration of a head-up display device of Example 3. FIG. 10 is a spot diagram of the projection optical system of Example 3. FIG. FIG. 6 is a cross-sectional view illustrating a specific configuration of a head-up display device of Example 4. 10 is a spot diagram of the projection optical system of Example 4. FIG. It is explanatory drawing which shows the example which provides a some light source.

Explanation of symbols

10, 10a-d Head-up display device 12 Car 14 Driver (observer)
18 Windshield (reflective surface)
19 Virtual Image 21 Display Light 22, 22a to d, 41 Projection Optical System 24 Liquid Crystal Panel (Image Display Panel)
26, 42a, 42b Light source 27 Projection lens group 28 Concave mirror 31 Free-form surface 36a-e Refractive lens L1 Reference optical axis L2 Optical axis of concave mirror

Claims (7)

Projecting the display light from the image display panel to the viewer with a reflection surface facing the observer at a predetermined position, and displaying the image displayed on the image display panel over the reflection surface with both eyes In the projection optical system that enlarges and displays as a virtual image to be observed with
A projection lens group having a positive refractive power and projecting display light from the image display panel;
A concave mirror that is arranged eccentrically with respect to the optical axis of the projection lens group, reflects display light from the projection lens group, and magnifies and projects the reflected light onto the reflection surface;
A projection optical system comprising: When the projection magnification is β, the optical path length from the reflection point of the concave mirror to the virtual image to be displayed is D3, and the focal length of the projection lens group is f,
1.0 <f × β / D3 <2.0
The projection optical system according to claim 1, wherein:   The projection optical system according to claim 1, wherein the shape of the reflecting surface of the concave mirror is a non-rotationally symmetric aspherical surface. A principal ray of display light incident on the concave mirror from the projection lens group is an incident reference optical axis, and a principal ray of display light reflected by the concave mirror and directed to the reflective surface is an outgoing reference optical axis, and the incident reference light A z axis is defined along the axis, a plane including the incident reference optical axis and the outgoing reference optical axis is defined as a yz plane, a plane perpendicular to the yz plane and parallel to the z axis is defined as an xz plane, and the concave mirror When the paraxial curvature in the yz plane is CY and the paraxial curvature in the xz plane of the concave mirror is CX,
1.3 <| CY / CX |
The projection optical system according to claim 1, wherein:   The projection optical system according to claim 1, wherein the image display panel is disposed to be inclined with respect to an optical axis of the projection lens group.   6. The projection optical system according to claim 1, wherein the projection lens group includes two or more refractive lenses having the same material and surface shape.   A head-up display device comprising the projection optical system according to claim 1.

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