JPH0949979A - Display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a display device capable of separating a position, on which a virtual image to be observed is clearly formed, far apart from an observer, being miniaturized and being arranged in a limited space by providing the device with a reflection surface composed of an off-axis rotary symmetric aspherical surface except a paraboloid in an optical system. SOLUTION: The display device 1 constituting, for example, a vehicle head up display is provided with a picture display device 2 and an optical system, and the optical system is composed of a first optical element 3 and a second optical element 4 opposed to the first optical element 3. At least one of the reflection surface 8 of the first optical element 3 and the reflection surface 12 of the second optical element 4 is made to be an off-axis rotary symmetric aspherical surface except a paraboloid. By this constitution, since the optical path of picture display light is changed by the reflection surface composed of the off-axis rotary symmetric aspherical surface except a paraboloid, parameters for determining the position, on which a virtual image is clearly formed, are increased compared with a planar mirror, a toric mirror, a concave mirror of off-axis paraboloid of revolution and a spherical concave mirror.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display device suitable for use as a head-up display mounted on vehicles such as vehicles and ships.

[0002]

2. Description of the Related Art For example, it has been proposed to use a head-up display as a display device for providing navigation information to a vehicle driver. That is, a driver for displaying an image corresponding to the navigation information and an optical system having a combiner arranged in front of the driver are provided, and the optical path of the image display light emitted from the display is changed by the optical system. By leading to the pupil, the virtual image formed in front of the combiner is made visible to the driver.

As an optical element constituting the optical system,
A plane mirror, a trick mirror, an off-axis rotating parabolic concave mirror, a spherical concave mirror, or a diffraction grating having the same optical characteristics as a spherical concave mirror is used alone or in combination, and the optical path of the image display light is changed by the reflecting surface or diffracting surface of the optical element. Have changed.

[0004]

When the image forming position of the virtual image of the observation object is close to the driver, it takes time to recognize the virtual image from the state of gazing at the actual scenery in front of the vehicle. It is not preferable for driving. Therefore, in order to quickly recognize the actual scenery and the virtual image in front of the vehicle, it is necessary to set the image formation position of the virtual image to the front of the driver.

The optical elements constituting the reflecting surface and the diffracting surface of the optical system in the conventional display device are plane mirrors, trick mirrors, off-axis rotation parabolic concave mirrors, spherical concave mirrors, and diffraction gratings having the same optical characteristics as spherical concave mirrors. Therefore, in order to clearly form the virtual image in front of the driver, the optical distance between the exit surface of the image display light and the optical element, the optical distance between the optical elements, the combiner and the pupil of the driver. It is necessary to lengthen the optical distance between and and the optical path length of the image display light.

However, since the space in front of the driver in the vehicle is limited, if the optical distance is increased, the display device becomes large and it becomes difficult to mount it on the vehicle.

It is an object of the present invention to provide a display device which can solve the above problems.

[0008]

SUMMARY OF THE INVENTION The present invention comprises an image display light emitting means and an optical system having a semitransparent optical path changing surface arranged in front of an observer, and is provided in front of the optical path changing surface. In a display device in which the optical system changes the optical path of image display light so as to form a virtual image of an observation target, the optical system has a reflecting surface composed of an off-axis rotationally symmetric aspheric surface excluding a paraboloid. It is characterized by Furthermore, the present invention is characterized by having a diffractive surface having optical characteristics equivalent to that of a reflecting surface formed by an off-axis rotationally symmetric aspherical surface other than a parabolic surface instead of or together with the reflecting surface. And The rotationally symmetric aspherical surface has ρ ² = x ² + y ² , c = 1 / R, K is a quadric surface coefficient and αi is an aspherical surface coefficient in xyz coordinate space.

[Equation 2] R is the radius of the spherical surface when the quadric surface coefficient K and the aspherical surface coefficient αi are zero, and at least one aspherical surface coefficient is not zero.

According to the structure of the present invention, the optical path of the image display light is formed by the reflecting surface constituted by the off-axis rotationally symmetric aspherical surface excluding the parabolic surface or the diffractive surface having the same optical characteristics as the reflecting surface. Therefore, compared to a plane mirror, a trick mirror, an off-axis rotation parabolic concave mirror, and a spherical concave mirror, there are more parameters that determine the position where the virtual image can be clearly formed. That is, the position at which the virtual image is clearly formed can be determined according to the quadratic surface coefficient or the aspherical surface coefficient that defines the off-axis rotationally symmetric aspherical surface other than the parabolic surface. As a result, the position where the virtual image can be clearly formed can be separated to the front and far without increasing the optical path length of the image display light, and the display device can be miniaturized and installed in a limited space. Become.

It has an optical path changing surface facing a semitransparent optical path changing surface arranged in front of the observer, and at least one of the both optical path changing surfaces is constituted by an off-axis rotationally symmetric aspheric surface excluding a parabolic surface. It is preferable that the reflecting surface is a diffractive surface having the same optical characteristics as that of the reflecting surface or a reflecting surface formed by an off-axis rotationally symmetric aspherical surface other than a parabolic surface. As a result, the relative arrangement of both optical path changing surfaces can be used as a parameter for determining the position where the virtual image is clearly formed, and the aberration can be further reduced to reduce the distortion of the display virtual image. it can. Furthermore, by making the both optical path changing surfaces be off-axis rotationally symmetric aspheric surfaces excluding a parabolic surface, it is possible to further reduce aberrations and reduce distortion of the display virtual image.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a display device 1 of a first embodiment constituting a vehicle head-up display,
The image display 2 and the optical system are provided, and the optical system is the first
It is composed of an optical element 3 and a second optical element 4 facing the first optical element 3.

The image display 2 is built in the dashboard 7 and is composed of, for example, a transmissive liquid crystal display, and the display light L of an image corresponding to navigation information or the like is emitted from the image display surface 6.

The first optical element 3 is composed of a total reflection mirror built in the dashboard 7 and has a reflection surface 8 as an optical path changing surface of the image display light L. The first optical element 3
The image display light L reflected by the reflecting surface 8 of the second light is transmitted through the transparent plate 9 that covers the opening formed in the dashboard 7 to the second light.
It reaches the optical element 4.

The second optical element 4 is a dashboard 7
The combiner is arranged in front of the driver (observer) by being arranged above, and has the reflecting surface 12 as an optical path changing surface of the image display light L. The image display light L reflected by the reflecting surface 12 of the second optical element 4 is combined with the light from the front of the second optical element 4 and the pupil 13 of the driver.
Be led to. As a result, the driver visually recognizes the virtual image at the front position P of the reflecting surface 12 of the second optical element 4.

In the first embodiment, at least one of the reflecting surface 8 of the first optical element 3 and the reflecting surface 12 of the second optical element 4 is an off-axis rotationally symmetric aspheric surface excluding a parabolic surface. For example, the reflecting surface 8 of the first optical element 3 is a plane other than an off-axis rotationally symmetric aspherical surface other than a paraboloid, a concave spherical surface, a trick surface, etc., and the reflecting surface 12 of the second optical element 4 is a parabolic surface. Excluding the off-axis rotationally symmetric aspherical surface, or the reflecting surface 8 of the first optical element 3 is the off-axis rotationally symmetric aspherical surface excluding the parabolic surface, and the reflecting surface 12 of the second optical element 4 is a flat surface.
It may be a concave spherical surface, a trick surface, or the like, or both reflection surfaces 8 and 12 may be off-axis rotationally symmetric aspherical surfaces other than paraboloids.

The off-axis rotationally symmetric aspherical surface other than the paraboloid is a surface having an eccentric center from the rotationally symmetric axis of the aspherical surface in the aspherical surface specified by the following mathematical formula in the xyz coordinate space. In the equation, ρ
² = x ² + y ² and c = 1 / R. The mathematical expression represents a spherical surface when the quadratic surface coefficient K and the aspherical surface coefficient αi are set to zero, the radius of the spherical surface is R, and at least one aspherical surface coefficient is not zero.

[0017]

(Equation 3)

For example, as shown in FIG. 2, in the xz plane of the coordinate system of the mathematical formula, when the aspherical surface has a shape as shown by the broken line in the figure, x is from the z axis which is the rotational symmetry axis of the aspherical surface. A surface shown by a solid line in the drawing having a center eccentric by e in the axial direction is an off-axis rotationally symmetric aspheric surface excluding a parabolic surface. A curvature 1 / R, a quadric surface coefficient K, and an aspherical surface coefficient αi that define an off-axis rotationally symmetric aspherical surface excluding the paraboloid
Is the magnification of the virtual image of the observation target with respect to the real image on the display 2, the optical path length from the display 2 to the driver's pupil 13, the image display surface 6 with respect to the driver's pupil 13, and the reflecting surfaces 8 and 12 of the optical elements 3 and 4. The virtual image is determined so that it can be clearly formed at the far front position of the driver according to the relative angle of. Note that the order of ρ is not limited as long as the virtual image of the observation target can be clearly formed at the far front position of the driver. When both reflecting surfaces 8 and 12 are off-axis rotationally symmetric aspheric surfaces excluding a parabolic surface, the aspherical surface coefficient α _i of one reflecting surface may be zero.

FIG. 3 shows a display device 1'of a second embodiment which constitutes a vehicle head-up display. The difference from the first embodiment is that instead of the reflecting surface 12 of the combiner forming the second optical element 4, a part of the semi-transparent windshield 11 having a reflectance is used as the reflecting surface 12 ', This is at the point where the reflecting surface 8 of the element 3 is a rotationally symmetric aspherical surface excluding the parabolic surface. Since the windshield 11 generally has a horizontal cross section having different curvatures at each point, its reflecting surface 12 'is an aspheric trick surface. Other parts are the same as those of the first embodiment, and the same parts are denoted by the same reference numerals.

4 shows a display device 1 "of a third embodiment constituting a vehicle head-up display. The difference from the first embodiment is that the first optical element 3 is eliminated and the second optical element is omitted.
The reflecting surface 12 of the optical element 4 is an off-axis rotationally symmetric aspherical surface excluding a parabolic surface, and in the off-axis rotationally symmetric aspherical surface,
The point is that the image display light L emitted from the image display surface 6 is directly reflected. Other parts are the same as those of the first embodiment, and the same parts are denoted by the same reference numerals.

In each of the above-mentioned embodiments, the optical path of the image display light L is changed by the reflecting surface constituted by the off-axis rotationally symmetric aspherical surface excluding the parabolic surface. However, instead of the reflecting surface, the parabolic surface is changed. The optical path may be changed by using a diffractive surface having optical characteristics equivalent to that of a reflecting surface formed by an off-axis rotationally symmetric aspheric surface other than.

The image display 2 and the first optical element 3 may be arranged on the dashboard 7 or at other positions.

Further, the present invention can be applied to a display device such as a ship other than an automobile, and the content of the display image is not limited to the navigation information.

[0024]

First Example FIGS. 5 to 7 show that in the first embodiment, the reflecting surface 8 of the first optical element 3 is constituted by a plane mirror,
2 shows the optical path of the first embodiment when the reflecting surface 12 of the second optical element 4 is constituted by an off-axis rotationally symmetric aspheric surface excluding a parabolic surface. In the first embodiment, the position P of the virtual image of the observation target is 2 m forward from the center of the driver's pupil 13.
The eccentric amount e from the axis of rotational symmetry of the off-axis rotationally symmetric aspherical surface excluding the paraboloid is about 100 mm. Further, the display field of view corresponding to the size of the virtual image of the observation target has a vertical angle of view of 2.26 ° and a horizontal angle of view of 3.0 °. The size of each pupil is 40 mm in the vertical direction and 11 in the horizontal direction.
It is 0 mm, and if the pupil is in this pupil size range, the virtual image in the display field can be observed without being missing. The quadratic surface coefficient of the off-axis rotationally symmetric aspheric surface excluding the paraboloid is K =
-0.41573, aspheric coefficients α _{i (i} = 1~10) is ^{_{α 1 = 0.394997546 × 10 -3,}} α 2 = -0.
107837985 × 10 ⁻⁸ , α ₃ = −0.29226
1795 × 10 ⁻¹³ , α ₄ = −0.2194421651
× 10 ^-19 , α ₅ = 0.386929154 × 1
0 ^-22 , α ₆ = 0.631947195 × 10 ^-27 , α
^{_{7 = -0.136442866 × 10 -31, α}} 8 = -
0.179278111 × 10 ⁻³⁵ , α ₉ = −0.58
1806977 × 10 ^-40 , α ₁₀ = 0.3449245
It is 54 × 10 ⁻⁴⁴ . In addition, in Table 1 below, the image display surface 6, the reflective surfaces 8 and 12, and the pupil 13 of the driver are shown.
Shows the radius of curvature, the vertex position, and the normal angle of. The vertex position is the intersection of the optical axis in the image display surface 6 and the reflecting surface 8 of the first optical element 3, and the intersection with the rotation target axis in the reflecting surface 12 of the second optical element 4. It is the intersection. Each vertex position is indicated by positive and backward directions with the center of the driver's pupil 13 as the origin, the Z axis in the front-back direction, the X axis in the up-down direction, and positive directions in the backward and upward directions. Also, the normal direction is
The direction of the normal line at each apex position is shown with the backward direction being zero.

[0025]

[Table 1]

FIG. 8 is a spot diagram in which the light rays are traced backward from the 15 point coordinate position in the pupil 13 toward the image display surface 6 and the obtained results are plotted. This spot diagram shows the aberration of each point virtual image when forming the 15 point virtual images distributed in the display field and moving the pupil within the pupil size range to view each point virtual image. From this FIG. 9, it can be confirmed that the aberration is small and a clear virtual image can be formed in the distance in front of the driver.

[0027]

Second Embodiment FIGS. 9 to 11 show that in the first embodiment, the reflecting surface 8 of the first optical element 3 is constituted by an off-axis rotationally symmetric aspheric surface excluding a paraboloid, and the second optical element 4 is formed. 2 shows the optical path of the second embodiment when the reflecting surface 12 is formed of a concave spherical surface. In the second embodiment, the position P of the virtual image of the observation target is 2 m forward from the center of the pupil 13 of the driver. The eccentricity e from the rotationally symmetric axis of the off-axis rotationally symmetric aspherical surface excluding the paraboloid is about 75 mm. Further, the display field of view corresponding to the size of the virtual image of the observation target has a vertical angle of view of 1.5 ° and a horizontal angle of view of 3.0 °. Also,
Each pupil size is 50mm vertically and 110m horizontally
m. The quadratic surface coefficient of an off-axis rotationally symmetric aspheric surface excluding the parabolic surface is K = -28.95829, and the aspheric surface coefficient α
_i (i = 1 to 10) is α ₁ = −0.443721733
× 10 ^-4 , α ₂ = -0.194440792 × 10 ^-8 ,
α ₃ = 0.21068246 × 10 ^-12 , α ₄ = 0.2
14657198 × 10 ^-16 , α ₅ = 0.143220
739 × 10 ^-20 , α ₆ = 0.787114632 × 1
0 ^-25 , α ₇ = 0.337524496 × 10 ^-29 , α
₈ = −0.50071688 × 10 ⁻³⁴ , α ₉ = −0.
439027707 × 10 ⁻³⁷ , α ₁₀ = −0.8672
It is 17421 × 10 ⁻⁴¹ . Further, Table 2 below shows the radius of curvature, the vertex position, and the normal angle of the image display surface 6, the reflecting surfaces 8 and 12, and the pupil 13 of the driver.
The vertex position is the intersection of the optical axis in the image display surface 6 and the reflection surface 12 of the second optical element 4, and the intersection with the rotation target axis in the reflection surface 8 of the first optical element 3. It is the intersection.

[0028]

[Table 2]

FIG. 12 is a spot diagram in which the light rays are traced backward from the position of 15 point coordinates on the pupil 13 toward the image display surface 6 and the obtained results are plotted. This spot diagram shows the aberration of each point virtual image when forming the 15 point virtual images distributed in the display field and moving the pupil within the pupil size range to view each point virtual image. From this FIG. 13, it can be confirmed that the aberration is small and a clear virtual image can be formed in the distance in front of the driver.

[0030]

According to the display device of the present invention, the position at which the virtual image of the observation object is clearly formed can be located far away in front of the observer, and the device is downsized and placed in a limited space. can do.

[Brief description of drawings]

FIG. 1 is a configuration explanatory diagram of a display device according to a first embodiment of the present invention.

FIG. 2 is an explanatory view of an off-axis rotationally symmetric aspheric surface excluding a paraboloid of the present invention.

FIG. 3 is a structural explanatory view of a display device according to a second embodiment of the present invention.

FIG. 4 is a structural explanatory view of a display device according to a third embodiment of the present invention.

FIG. 5 is a side view showing the optical path of the first embodiment of the present invention.

FIG. 6 is a plan view showing the optical path of the first embodiment of the present invention.

FIG. 7 is an enlarged side view of the optical path according to the first embodiment of the present invention.

FIG. 8 is a spot diagram of the first embodiment of the present invention.

FIG. 9 is a side view showing the optical path of the second embodiment of the present invention.

FIG. 10 is a plan view showing an optical path of a second embodiment of the present invention.

FIG. 11 is an enlarged side view of the optical path according to the second embodiment of the present invention.

FIG. 12 is a spot diagram of a second embodiment of the present invention.

[Explanation of symbols]

 1 Display Device 2 Image Display 8 Reflective Surface 12 Reflective Surface 13 Pupil L Image Display Light P Virtual Image Forming Position

Claims (4)

[Claims] 1. An image display light emitting means, and an optical system having a semitransparent optical path changing surface arranged in front of an observer, wherein a virtual image of an observation object is formed in front of the optical path changing surface. In the display device for changing the optical path of the image display light by the optical system, the optical system has a reflection surface constituted by an off-axis rotationally symmetric aspheric surface excluding a parabolic surface. 2. An image display light emitting means and an optical system having a semi-transparent optical path changing surface arranged in front of an observer, wherein a virtual image of an observation object is formed in front of the optical path changing surface. In addition, in the display device that changes the optical path of the image display light by the optical system, the optical system has a diffractive surface having the same optical characteristics as the reflective surface configured by the off-axis rotationally symmetric aspherical surface excluding the parabolic surface. Display device having. 3. A non-axial rotationally symmetric aspherical surface having an optical path changing surface facing a semitransparent optical path changing surface arranged in front of the observer, at least one of the optical path changing surfaces excluding a parabolic surface. Or a diffractive surface having an optical characteristic equivalent to that of the reflecting surface formed by an off-axis rotationally symmetric aspheric surface excluding a parabolic surface.
The display device according to claim 1. 4. The rotationally symmetric aspherical surface in the xyz coordinate space has ρ ² = x ² + y ² , c = 1 / R, K is a quadric surface coefficient, and αi is an aspherical surface coefficient. 4. The R is a radius of a spherical surface when the quadratic surface coefficient K and the aspherical surface coefficient αi are zero, and at least one aspherical surface coefficient is not zero. Display device.