JPH11326823A - Virtual image observation optical system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress noise and ghost resulted from the reflected light by an optical element by making the image on the background of the optical element visible together with the virtual image of the display video by an LCD as a natural background image without aberrations and without a change in the distance and size of the image. SOLUTION: This optical system comprises the optical element 12 which has refractive power to form the virtual image of the display image of the LCD 6 and a curved translucent mirror 13 which reflects the light through this optical element 12, introduces the light to the observer's pupils 11, allows the transmission of the back light and introduces the light to the pupils 11. This curved translucent mirror 13 is formed to a surface shape varying in a first surface and a second surface and the refractive power thereof to the transmitted light is made zero.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a virtual image observation optical system for observing a virtual image of a display image of an image display device.

[0002]

2. Description of the Related Art A conventional so-called see-through type virtual image observation optical system has been proposed. This virtual image optical system is an LCD
(Liquid crystal display) and an optical element such as a concave mirror or a Lippman volume hologram that forms a virtual image of a display image by the image display device and guides the virtual image to an observer's pupil. The optical element has at least one semi-transmissive surface, and reflects the light emitted from the image display device to guide the light to the pupil of the observer on the semi-transmissive surface. The light from the background is transmitted to reach the pupil.

In this virtual image observation optical system, an observer
The virtual image of the display image by the image display device and the background behind the optical element can be superimposed and observed.

[0004]

By the way, two surfaces of a substrate for supporting a concave mirror and a Lippmann volume hologram which are optical elements constituting the virtual image observation optical system as described above are:
Are formed with exactly the same radius of curvature, or
The radius of curvature of the surface with the larger radius of curvature is a value obtained by adding the substrate thickness to the radius of curvature of the surface with the smaller radius of curvature so that the substrate thickness is constant, and the refractive power for transmitted light is strictly It is not 0.

For this reason, the background image which passes through the substrate of these optical elements and enters the pupil has an aberration or the distance and size of the image are changed, so that the background image is viewed as a natural background image. Can not do.

The substrate of the Lippman volume hologram is often a flat plate. In this case, the refractive power of the substrate with respect to the transmitted light is 0, but the light reflected on the surface of the substrate is incident on the pupil and often causes noise.

Further, when the radius of curvature of the concave mirror or the substrate of the Lippman volume hologram is close to twice the value of the distance between the substrate and the exit pupil of the virtual image observation optical system, the light from the periphery of the pupil on the substrate surface is reduced. The reflected light forms an image on the retina to form a ghost image.

When a film-shaped photopolymer is used as the Lippman volume hologram,
If the substrate has a two-dimensional curvature, it is difficult to mount the hologram on the substrate.

Accordingly, the present invention has been proposed in view of the above-mentioned circumstances, and in addition to a virtual image of a display image by an image display device, an image of a background of an optical element has no aberration and a distance of an image. It is an object of the present invention to provide a virtual image observation optical system which can be viewed as a natural background image without a change in size and further suppresses noise and ghost caused by light reflected by the optical element.

Another object of the present invention is to provide a virtual image observation optical system in which a hologram is easily mounted on a substrate when a hologram is used as an optical element.

[0011]

In order to solve the above-mentioned problems, a virtual image observation optical system according to the present invention comprises at least one optical element having a refractive power for forming a virtual image of a display image of an image display device; A curved translucent mirror that reflects the light passing through the optical element and guides the light behind to guide the pupil of the observer, and guides the light behind to the observer's pupil. Since the second surface has a surface shape different from that of the second surface, the refractive power for transmitted light is set to zero. In this virtual image optical system, a Lippman volume hologram can be used in place of the curved translucent mirror.

Since these curved translucent mirrors and Lippmann volume holograms have a refracting power of 0 for transmitted light, they see a natural background image with no aberration and no change in image distance or size. To make things possible.

In this virtual image observation optical system, the refractive power for forming a virtual image of the display image of the image display device may be assigned only to an optical element different from a curved semitransparent mirror or a Lippman volume hologram. Also, the curved semi-transparent mirror and the optical element, or the Lippmann volume hologram and the optical element may be used, or only the Lippman volume hologram may be used.

The reflecting surface of the curved semi-transparent mirror or Lippmann volume hologram can be concave. In this case, if the radius of curvature of the curved semitransparent mirror or the substrate of the Lippman volume hologram has a difference of 3 mm or more with respect to a value twice as large as the distance between the substrate and the exit pupil, occurrence of ghost is prevented. be able to. Further, in the curved semi-transparent mirror or the Lippman volume hologram, the reflection surface can be a concave aspheric surface. By making the Lippman volume hologram substrate holding the Lippman volume hologram into a meniscus shape with a curvature in only one direction,
The film-shaped hologram photosensitive material can be easily mounted on the Lippmann volume hologram substrate.

In this virtual image observation optical system, when a curved translucent mirror or a Lippman volume hologram and an optical element different from the curved semitransparent mirror or the Lippmann volume hologram are used, the curved translucent mirror or the Lippman volume hologram is used. A light beam splitting element can be provided between the optical element and the optical element.

[0016]

Embodiments of the present invention will be described below with reference to the drawings.

As shown in FIG. 1, the virtual image observation optical system according to the present invention has an LCD (Liquid Crystal Display) 6 serving as an image display device and a refractive power for forming a virtual image of the display image of the LCD 6 in cooperation with each other. Free-form surface (non-rotationally symmetric) reflecting mirror 12 and concave semi-transparent mirror (half mirror) 1 serving as an optical element having
3 are provided.

In this virtual image observation optical system, first, a video signal 1 is input to an LCD driver 2 which is a circuit for driving an LCD 6. A backlight voltage 3 and an LCD drive signal 4 are output from the LCD driver 2 and input corresponding to the backlight 5 and the LCD 6.

The backlight 5 has a cold cathode tube 5a as a light source. On the LCD 6 side of the cold-cathode tube 5a, a diffusion plate 5b is arranged to make the luminance of the light emitted from the cold-cathode tube 5a uniform and to control the diffusion angle.
The diffusion angle from the cold cathode tube 5a is a half-value angle of about 10 °.

As the LCD 6, for example, a 0.55-inch transmissive liquid crystal display can be used. In the LCD 6, an image signal, which is an electric signal, is converted into an image, and light emitted from the backlight 5 passing through the LCD 6 is modulated according to the image. The light beam transmitted through the LCD 6 enters the free-form surface reflection mirror 12. This L
The incident angle from the CD 6 to the free-form surface reflection mirror 12 is about 50 °
It has become.

The light beam transmitted through the LCD 6 and incident on the free-form surface reflection mirror 12 is reflected by being given a part of the refractive power for forming a virtual image. In the free-form surface reflection mirror 12, the free-form surface reflection mirror 12 which is an optical element having a refractive power is used.
And a non-rotationally symmetric phase is added to the reflected wavefront so as to reduce aberrations caused by the decentering of the concave semi-transparent mirror 13 with respect to the principal ray.

The luminous flux given the wavefront change in this manner is subsequently applied to the semi-transparent film 13b on the concave semi-transparent mirror substrate 13a.
Is incident on the concave semi-transparent mirror 13 formed and adhered, and a part thereof is given a refracting power by the semi-permeable film 13b and is reflected, and is guided to the pupil 11 of the observer. Thereby, the observer can see a virtual image of the display image on the LCD 6.

On the other hand, the luminous flux from the background traveling from the back side of the concave semi-transparent mirror substrate 13a is
3a, a part of the light is reflected by the semi-permeable membrane 13b, and the rest is guided to the pupil 11. In this way, the observer has L
The virtual image of the display image of the CD 6 can be seen in fusion with the background image.

However, here, the concave semi-transparent mirror substrate 13a
Has refractive power to transmitted light, the background image is enlarged or reduced, the image position moves, or aberration is added, and in some cases, visibility is extremely deteriorated,
You will not be able to see the natural background. Therefore, in this virtual image observation optical system, the concave semi-transparent mirror substrate 13a has no refractive power for transmitted light. If the thickness of the concave semi-transparent mirror substrate 13a is so thin that the thin-wall approximation can be applied ignoring the thickness, the radius of curvature of the surface of the concave semi-transparent mirror substrate 13a is made equal to that of the rear surface. , The refracting power to transmitted light can be made zero.

However, in reality, the radius of curvature of the convex surface of the concave semitransparent mirror substrate 13a is r1, and the radius of curvature of the concave surface is r1.
2. Assuming that the center thickness is t and the refractive index is n, the refractive power p of the concave semitransparent mirror substrate 13a is p = (n-1) {(1 / r1)-(1 / r2)} + {t (n-1) 2 / (nr1r2)} (Equation 1) The radius of curvature r2 of the curved surface is given by f = r2 / 2, where f is the focal length of the concave semi-transparent mirror, and is uniquely determined when a given refractive power is determined. Therefore, in order for the concave semitransparent mirror substrate 13a to have no refracting power, it is assumed that p = 0 in Equation (1), and r1 = (nr2 + nt-t) / n = r2 + (nt-t) /
It is sufficient that r1, which is n, is the radius of curvature of the convex surface of the concave semitransparent mirror substrate 13a.

For example, n = 1.53, t = 5 mm, r
If 2 = 30 mm, r1 ≒ 32 mm. Temporarily
Is equal to r2 and r1 = 30 mm, p ≒ 0.00102, and the focal length f has a convex lens action of f = 1 / p = 980 mm, has a refractive power of about +1 diopter, and is a background for most observers. Will be difficult to see. Further, r1 is calculated by adding thickness t to r2.
If it is 5 mm, then p ≒ 0.00165, and the focal length f has a concave lens action of f = 1 / p = −606 mm and has a refractive power of about −1.65 diopters.

As described above, in order to eliminate the refractive power of the concave semi-transparent mirror substrate 13a with respect to the transmitted light, the radius of curvature of the convex surface of the concave semi-transparent mirror substrate 13a is larger than the radius of curvature of the concave surface of 30 mm, and the radius of curvature of the concave surface is Radius of curvature 3 with thickness t added
It can be realized by setting the value smaller than 5 mm, about 32 mm.

As shown in FIG. 2, the virtual image observation optical system according to the present invention comprises an LCD 6 and a free-form surface (non-rotationally symmetric) half having a refractive power for forming a virtual image of an image displayed on the LCD 6. It can be constituted by the transparent mirror 14. L
The operation until the image is displayed on the CD 6 is the same as in the above-described embodiment.

The light beam emitted from the LCD 6 is incident on a free-form surface semi-transparent mirror 14 which is formed by covering a semi-transparent film 14b on a free-form surface semi-transparent mirror substrate 14a. In the free-form semi-transparent mirror 14, a part of the incident light is given a refractive power for forming a virtual image of a display image on the LCD 6, and a non-rotationally symmetric curved surface is added with a non-rotationally symmetric phase. The light is reflected by the semi-permeable film 14b in a state where the aberration due to the eccentricity is reduced. The light beam reflected by the semi-permeable film 14b enters the pupil 11, and the observer can see a virtual image of the display image on the LCD 6.

On the other hand, a light beam entering from the back side of the free-form surface semi-transparent mirror substrate 14a from the background enters the pupil 11 via the free-form surface semi-transparent mirror substrate 14a and the semi-permeable film 14b. Here, if the free-form semi-transparent mirror substrate 14a has a refractive power to transmitted light, the background image is enlarged or reduced,
In some cases, the image position moves or aberration is added, and in some cases, the visibility is extremely deteriorated, and a natural background cannot be seen. Therefore, in this virtual image observation optical system, the free-form surface translucent mirror substrate 14a is configured so as not to have a refractive power for transmitted light.

The semi-permeable membrane 14 in the free-form surface semi-transparent mirror 14
The surface shape of the surface s1 on the side where b is formed is restricted in order to generate refracting power for forming a virtual image and to correct eccentric aberration. Therefore, this free-form semi-transparent mirror substrate 14a
In, the refractive power for transmitted light is set to 0 by devising the shape of the other surface s2. When the surface s1 is a free-form surface, it is difficult to uniquely determine the shape of the surface s2. In an actual design, optimization is performed by automatic design or the like using computer software for performing an optical design evaluation simulation. It will be.

As shown in FIG. 3, the virtual image observation optical system according to the present invention includes an LCD 6, a beam splitter 7 serving as a light beam splitting element, and a non-light source having a refracting power for forming a virtual image of a display image on the LCD 6. And a spherical concave semi-transparent mirror 15. The operation until the image is displayed on the LCD 6 is the same as in the above-described embodiment.

The light emitted from the LCD 6 enters the beam splitter 7. In this beam splitter 7, a part of the incident light is reflected, and the aspherical concave semi-transparent mirror substrate 15a
The light impinges on an aspherical concave translucent mirror 15 having a semi-permeable film 15b formed thereon. At the semi-permeable film 15b of the aspherical concave semi-transparent mirror 15, a part of the incident light is given a refracting power for forming a virtual image of a display image on the LCD 6 and is reflected. The light beam reflected by the semi-permeable film 15b passes through the beam splitter 7 again, and a part of the light beam enters the pupil 11. In this way, the observer can see a virtual image of the display image on the LCD 6.

On the other hand, the aspherical concave translucent mirror substrate 15a
It is designed not to have a refracting power for transmitted light.
In this aspherical concave semitransparent mirror substrate 15a, a surface s on the side of the aspherical concave semitransparent mirror 15 on which the semipermeable membrane 15b is disposed.
In No. 1, the surface shape is restricted for generating refracting power and correcting aberration. Therefore, this aspheric concave semi-transparent mirror substrate 1
In 5a, the refractive power for transmitted light is set to 0 by devising the shape of the other surface s2. When one surface s1 is an aspheric concave surface, the other surface s2
Is difficult to determine uniquely, and in actual design, optimization is performed by automatic design or the like using computer software that performs optical design evaluation simulation.

For example, as shown in FIG. 4, when the other surface s2 is formed in the same shape as the surface s1 on which the semi-permeable film 15b of the aspherical concave semi-transparent mirror substrate 15a is deposited, the light is incident at various angles. The aspheric concave semi-transparent mirror substrate 15a has a refractive index or an aberration with respect to the incoming light beam, and the incident parallel light beam is deformed. As a result, the observer cannot naturally see the background image through the aspherical concave semi-transparent mirror substrate 15b. Table 1 below shows a lens list of this optical system. The STO (aperture stop surface) and the second surface correspond to the surface s2 and the surface s1, respectively, and the curvature (R
DY), aspherical phase coefficient (K, A, B, C, D)
It can be seen that both are equal. Where K,
A, B, C, and D are conic coefficients, fourth-order aspheric phase coefficients,
A sixth-order aspherical phase coefficient, an eighth-order aspherical phase coefficient, and a tenth-order aspherical phase coefficient are represented by the following equations.

Z = h2 / [RDY ｛1 + SQRT [1-
(1 + K) h2 / RDY2]｝] + Ah4 + Bh6 + C
h8 + Dh10 Here, Z represents a sag of a plane parallel to the Z axis, and h represents a distance from the optical axis.

[0037]

[Table 1]

On the other hand, as shown in FIG. 5, the aspherical concave semi-transparent mirror substrate 15a has a refractive index with respect to a light beam incident on the surface s2 of the aspherical concave semi-transparent mirror substrate 15a at various angles.
Alternatively, if the semi-permeable film 15b of the aspherical concave semi-transparent mirror substrate 15a is formed on a surface different from the surface s1 on which the semi-permeable film 15b is deposited so as not to have aberration, the incident parallel light beam is not deformed.
You can see a natural background image. Table 2 below shows a lens list of this optical system. The surface s1 and the surface s2 are
It can be seen that the surface shapes are different from each other.

[0039]

[Table 2]

The virtual image observation optical system according to the present invention
LCD as an image display device as shown in FIGS.
6, a polarizing beam splitter 7 serving as a light beam splitting element,
It can be constituted by a Lippman volume hologram 10 having a refractive power for forming a virtual image of the display image on the LCD 6.

Here, the structure and function of the Lippmann volume hologram will be described. The Lippman volume hologram is formed with a plurality of interference fringes in the cross-sectional structure as shown in FIG. In FIG. 8, the interference fringes are indicated by stripes, but in reality, the refractive index is modulated. Examples of the hologram material include photopolymer and dichromated gelatin. For a typical photopolymer,
The central refractive index n and the refractive index modulation Δn after the heat treatment are n = 1.52 and Δn = 0.06, respectively. As shown in FIG. 8, it can be seen that the interference fringes in the Lippmann volume hologram 10 substantially enter along the thickness direction of the material. This can be realized by causing two light beams, the reference light and the object light, to enter from the front and back of the hologram surface when printing the hologram.

When reproducing the Lippmann volume hologram, the behavior of the diffracted light of the light incident on the Lippmann volume hologram depends on the angle of incidence on the interference fringes when the incident angle to the interference fringes is θ1. What kind of reflection angle θ2 the scattered light from the layer reinforces each other should be considered.

There are two conditions for this. One is FIG.
As shown in (1), it is necessary that scattering components at two different points on a certain layer reinforce each other. The condition is Lsinθ1−Lsinθ2 = mλ, where L is the distance between the two points. In order for this to be true for any L, it is only necessary that this equation be an identity for L. That is, θ1 = θ2 (Equation 1) Next, in order for the scattering components in the two different layers to reinforce each other, as shown in FIG.
Then, dcosθ1 + dcosθ2 = mλ (Equation 2) From (Equation 1) and (Equation 2), 2dcosθ1 = mλ ... Bragg diffraction condition Here, when m = 1 (first order), 2dcosθ1 = Λ. In other words, it can be said that Bragg diffraction is specular reflection having wavelength selectivity or angle selectivity. By recording the appropriate interference fringes on the hologram, it is possible to deflect the light beam of a certain wavelength λ incident on the hologram in an arbitrary direction and reflect it, and use it as a reflecting mirror having a lens function. Can be.

In this virtual image observation optical system,
As shown in FIG. 7, a video signal 1 is input to an LCD driver 2 which is a circuit for driving an LCD 6. From the LCD driver 2, an LED current 3 for lighting an LED (light emitting diode) and a drive signal 4 for driving the LCD 6 are output and input to the backlight 5 and the LCD 6.

The backlight 5 has, as a light source, an LED array 5a in which a so-called chip-size LED having a light emission center wavelength of 525 nm is mounted in a total of eight rows of two rows and four columns. On the LCD 6 side of the LED array 5a,
A diffusion plate 5b is provided to make the luminance of the irradiation light from the LED array 5a uniform and to control the diffusion angle.
The diffusion angle from the LED array 5a is about 10 ° at a half-value angle.

As the LCD 6, for example, a 0.55-inch transmissive liquid crystal display can be used. In the LCD 6, an image signal, which is an electric signal, is converted into an image, and light emitted from the backlight 5 passing through the LCD 6 is modulated according to the image. The light beam transmitted through the LCD 6 enters the polarization beam splitter 7. In the polarization beam splitter 7, a part of the incident light amount passes through the polarization beam splitter 7, and the remainder is reflected by the polarizing beam splitting film 8 on the polarization beam splitter 7, and enters the Lippmann volume hologram substrate 9.
The light beam that has passed through the Lippman volume hologram substrate 9 has a full width at half maximum around a specific wavelength range, here 525 nm, which is the wavelength of the light source, by the Lippman volume hologram 10 formed on the back side of the Lippman volume hologram substrate 9. Only a light beam of about 10 nm is selectively given a refractive power and reflected, passes through the Lippman volume hologram substrate 9 again, and enters the polarization beam splitter 7.
Then, in the polarization beam splitter 7, a part of the light flux returned from the Lippman volume hologram 10 is transmitted,
The light enters the pupil 11 of the observer.

On the other hand, the background light beam traveling from behind the Lippman volume hologram 10 passes through the Lippman volume hologram 10, the Lippman volume hologram substrate 9 and the polarization beam splitter 7, and enters the pupil 11.
At this time, the intensity of the spectrum of the light beam reaching the pupil 11 from the background at around 525 nm is the same as that of the Lippman volume hologram
Since the light is reflected at 0, it becomes smaller in substantially inverse proportion to the diffraction efficiency.

Here, the Lippmann volume hologram substrate 9
Has refractive power, the background image is enlarged or reduced, the image position moves, aberration is added, and in some cases, visibility is extremely deteriorated, and it is impossible to see the natural background . Therefore, in this virtual image observation optical system, the Lippmann volume hologram substrate 9 is configured not to have a refractive power with respect to transmitted light. In the Lippmann volume hologram substrate 9, the surface s2 on which the Lippmann volume hologram 10 is attached is
The surface shape is restricted to some extent. Therefore, in this Lippman volume hologram substrate 9, the other surface s
By devising the shape of 1, the refractive power for transmitted light is set to 0. When the surface s2 is concave, the shape of the surface s1 can be determined by calculation as in the embodiment shown in FIG. When the surface s2 is an aspherical concave surface or the like, optimization can be performed by automatic design using optical design evaluation simulation software as in the embodiment shown in FIG.

In the case of this embodiment, as shown in FIGS. 6 and 7, the Lippmann volume hologram substrate 9 has a meniscus shape having a curvature in only one direction. This is approximately 20 μm as Lippman volume hologram 10.
Because a 70-μm-thick film-like photopolymer consisting of a hologram photosensitive material layer with a thickness of approximately 50 μm and a polyester cover film with a thickness of approximately 50 μm is used, it must be laid on a surface with a two-dimensional curvature. Is difficult. Also, for the purpose of reducing aberration due to eccentricity, the configuration is such that the direction of curvature matches the eccentric direction of the optical system.

In this embodiment, since the Lippmann volume hologram substrate 9 is not flat but has a concave surface or an aspherical concave surface, stray light due to surface reflection of the Lippman volume hologram substrate 9 enters the pupil 11. Can be prevented. Further, the radius of curvature of the Lippman volume hologram substrate 9 is a value sufficiently different from a value twice as large as the distance between the Lippman volume hologram substrate 9 and the pupil 11, for example, a value having a difference of 3 mm or more. I have. This is related to the fact that the focal length of the concave mirror becomes の of the radius of curvature, and the light flux from the periphery of the pupil 11 becomes parallel light due to reflection by the surface of the Lippman volume hologram substrate 9, and This is to prevent the light from entering and forming an image on the retina to form a ghost image.

In each of the above embodiments,
Although it is configured to display green in a single color, the Lippman volume hologram is represented by R (red), G (green), B
Full-color display is also possible by using a light source that includes R, G, and B spectra as the backlight light source.
By coloring the Lippman volume hologram in this way, when light from the background passes through the Lippman volume hologram, the R, G, and B spectrums are equally missing and reach the pupil 11, so that the background color Can be seen as more natural.

Further, the virtual image observation optical system according to the present invention can be configured in full color using a reflection type liquid crystal display device. That is, in this virtual image observation optical system, a video signal 1 is input to an LCD driver (liquid crystal display driving circuit) 2 as shown in FIG. LC
From the D driver 2, an LED (light emit
An ing diode (light emitting element) lighting current 3 and a drive signal 4 for driving an LCD (liquid crystal display) 6 serving as an image display device are output and input to the light 5 and the LCD 6.

The light 5 is an LED array 5 having a so-called chip-size LED having a central emission wavelength of 470 nm, 525 nm, and 640 nm mounted thereon as a light source.
a. Further, as the LCD (liquid crystal display) 6 serving as an image display device, for example, a 0.55-inch reflective liquid crystal display can be used. In the LCD 6, an image signal, which is an electric signal, is converted into an image, and a light beam incident on the LCD 6 from the light 5 by the light guide plate 6a is modulated according to the image and reflected. L
The light beam reflected by the CD 6 enters a wedge-shaped polarizing beam splitter 7 serving as a light beam splitting device. In the wedge-shaped polarizing beam splitter 7, a part of the total amount of incident light passes through the wedge-shaped polarizing beam splitter 7,
The rest is reflected by the polarizing beam splitting film 8 formed on the wedge-shaped polarizing beam splitter 7 and enters the HOE (holographic optical element) substrate 9. The HOE substrate 9 is formed in a concave cylindrical shape with respect to the incident light from the wedge-shaped polarizing beam splitter 7. The light beam transmitted through the HOE substrate 9 has a specific wavelength range, that is, the interference fringes in the Lipman volume hologram 10 satisfy the Bragg condition by the Lippman volume hologram 10 formed on the back surface of the HOE substrate 9. Only light rays of a wavelength are selectively reflected. Here, only light rays in a range of about 10 nm in a full width at half maximum centering on the wavelengths of the light sources, 470 nm, 525 nm, and 640 nm, are reflected.

The light beam reflected by the Lippmann volume hologram 10 passes through the HOE substrate 9 again, enters the wedge-shaped polarizing beam splitter 7, and partially transmits through the wedge-shaped polarizing beam splitter 7 for observation. Incident on the pupil 11 of the person.
On the other hand, the background light beam traveling from the back side of the HOE substrate 9 passes through the Lippman volume hologram 10, the HOE substrate 9 and the wedge-shaped polarizing beam splitter 7, and the pupil 11
Incident on.

At this time, in the spectrum of the light beam reaching the pupil 11 from the background, the wavelength is 470 nm, 525 n
Since the light near m and 640 nm is reflected by the Lippman volume hologram 10, the intensity of this band decreases substantially in inverse proportion to the diffraction efficiency.

Here, the Lippmann volume hologram substrate 9
Has refractive power, the background image is enlarged or reduced, the image position moves, aberration is added, and in some cases, visibility is extremely deteriorated, and it is impossible to see the natural background . Therefore, in this virtual image observation optical system, the Lippmann volume hologram substrate 9 is configured not to have a refractive power with respect to transmitted light. In the Lippmann volume hologram substrate 9, the surface s2 on which the Lippmann volume hologram 10 is attached is
The surface shape is restricted to some extent. Therefore, in this Lippman volume hologram substrate 9, the other surface s
By devising the shape of 1, the refractive power for transmitted light is set to 0. When the surface s2 is concave, the shape of the surface s1 can be determined by calculation as in the embodiment shown in FIG. When the surface s2 is an aspherical concave surface or the like, optimization can be performed by automatic design using optical design evaluation simulation software as in the embodiment shown in FIG.

In the case of this embodiment, as shown in FIGS. 6 and 7, the Lippmann volume hologram substrate 9 has a meniscus shape having a curvature in only one direction. This is approximately 20 μm as Lippman volume hologram 10.
Because a 70-μm-thick film-like photopolymer consisting of a hologram photosensitive material layer with a thickness of approximately 50 μm and a polyester cover film with a thickness of approximately 50 μm is used, lay it on a surface with a two-dimensional curvature. Is difficult. Also, for the purpose of reducing aberration due to eccentricity, the configuration is such that the direction of curvature matches the eccentric direction of the optical system.

In this embodiment, since the Lippmann volume hologram substrate 9 is not flat but has a concave surface or an aspherical concave surface, stray light due to surface reflection of the Lippman volume hologram substrate 9 enters the pupil 11. Can be prevented. Further, the radius of curvature of the Lippman volume hologram substrate 9 is a value sufficiently different from a value twice as large as the distance between the Lippman volume hologram substrate 9 and the pupil 11, for example, a value having a difference of 3 mm or more. I have. This is related to the fact that the focal length of the concave mirror becomes の of the radius of curvature, and the light flux from the periphery of the pupil 11 becomes parallel light due to reflection by the surface of the Lippman volume hologram substrate 9, and This is to prevent the light from entering and forming an image on the retina to form a ghost image.

As shown in FIG. 11, the virtual image observation optical system according to the present invention can be composed of an image display device such as an LCD 6, a free-form surface reflection mirror 12, and a Lippmann volume hologram 10. This optical system is obtained by replacing the concave semi-transparent mirror 13 with the Lippmann volume hologram 10 in the optical system shown in FIG. further,
The virtual image observation optical system according to the present invention, as shown in FIG.
It can be constituted by an image display device such as the LCD 6 and the Lippman volume hologram 10. This optical system is obtained by replacing the free-form surface translucent mirror 14 with the Lippmann volume hologram 10 in the optical system shown in FIG.

In these optical systems, a natural background image can be seen by determining the shape of each of the surfaces s1 and s2 so that the refractive power of the Lippman volume hologram substrate 9 with respect to the transmitted light becomes zero. Also in these optical systems, the surface of the Lippmann volume hologram substrate 9 is not a plane but a curved surface, so that stray light due to surface reflection of the Lippman volume hologram substrate 9 is prevented from entering the pupil 11.

In each of the above embodiments, a transmissive LCD (liquid crystal image display device) is used as the image display device.
Is replaced with other image display devices such as a reflective LCD (liquid crystal image display device), a self-luminous element, an electroluminescence image display device, or a field emission display. Is also good.

As described above, in the virtual image observation optical system according to the present invention, the refractive power of the concave mirror substrate or the Lippmann volume hologram substrate used in the so-called see-through type virtual image observation optical system with respect to the transmitted light is measured. Completely 0
By doing so, a natural background image can be seen.

By providing a curvature on the Lippmann volume hologram substrate, it is possible to prevent the occurrence of noise caused by the surface reflected light of the Lippman volume hologram substrate entering the pupil of the observer. Further, by making the radius of curvature of the Lippmann volume hologram substrate sufficiently different from twice the value of the distance between the Lippman volume hologram substrate and the exit pupil of the virtual image observation optical system, The generation of stray light entering the pupil due to surface reflection can be effectively prevented.

Further, by forming the Lippman volume hologram substrate into a meniscus shape having a curvature in only one direction, the film-like Lippman volume hologram can be easily mounted on the Lippman volume hologram substrate.

[0065]

As described above, in the virtual image observation optical system according to the present invention, since the curved semi-transparent mirror and the Lippmann volume hologram have no refractive power for transmitted light, they have no aberration. , It is possible to see a natural background image with no change in image distance and size.

When the reflecting surface of the curved semi-transparent mirror or Lippman volume hologram is concave, the radius of curvature of the substrate of the curved semi-transparent mirror or Lippmann volume hologram is twice the distance between the substrate and the exit pupil. 3 for the value
Ghosts can be prevented from occurring by setting a value having a difference of at least mm.

That is, according to the present invention, the background image of the optical element is viewed as a natural background image with no aberration and no change in image distance and size, together with the virtual image of the display image by the image display device. Further, it is possible to provide a virtual image observation optical system in which noise and ghost caused by light reflected by the optical element are suppressed.

Further, according to the present invention, when a hologram is used as an optical element, the hologram substrate is formed into a meniscus shape having a curvature in only one direction, thereby facilitating the mounting of the hologram on the substrate. An observation optical system can be provided.

[Brief description of the drawings]

FIG. 1 is a plan view showing a configuration of a first embodiment of a virtual image observation optical system according to the present invention.

FIG. 2 is a plan view showing a configuration of a virtual image observation optical system according to a second embodiment of the present invention.

FIG. 3 is a plan view showing a configuration of a virtual image observation optical system according to a third embodiment of the present invention.

FIG. 4 is a side view showing a shape of an aspherical concave semi-transmissive mirror substrate constituting the virtual image observation optical system.

FIG. 5 is a side view showing another example of the shape of the aspherical concave semi-transmissive mirror substrate constituting the virtual image observation optical system.

FIG. 6 is a perspective view showing a configuration of a fourth embodiment of the virtual image observation optical system according to the present invention.

FIG. 7 is a plan view showing a configuration of the virtual image observation optical system.

FIG. 8 is an enlarged sectional view showing a configuration of a Lippmann volume hologram constituting the virtual image observation optical system.

FIG. 9 is a sectional view for explaining a phenomenon (reflection on the surface) in the Lippman volume hologram.

FIG. 10 is a cross-sectional view for explaining a phenomenon (reflection on a surface other than the surface) in the Lippman volume hologram.

FIG. 11 is a plan view showing a configuration of a fifth embodiment of the virtual image observation optical system according to the present invention.

FIG. 12 is a plan view showing a configuration of a virtual image observation optical system according to a sixth embodiment of the present invention.

FIG. 13 is a plan view showing a configuration of a virtual image observation optical system according to a seventh embodiment of the present invention.

[Explanation of symbols]

6 LCD, 7 polarizing beam splitter, 10 Lippman volume hologram, 11 pupil, 12 free-form reflecting mirror, 13 concave semi-transmissive mirror, 14 free-form semi-transmissive mirror, 1
5 Aspherical concave semi-transmissive mirror

Claims (27)

[Claims] An image display device, at least one optical element having a refractive power for forming a virtual image of a display image of the image display device, and reflecting light passing through the optical element to guide the light to an observer's pupil. And a curved semi-transparent mirror that transmits light behind and guides the light to the pupil of the observer. The curved semi-transparent mirror has a first surface and a second surface having different surface shapes, thereby transmitting transmitted light. A virtual image observation optical system, wherein the refracting power with respect to is set to 0. 2. The virtual image observation optical system according to claim 1, wherein the curved semi-transparent mirror has a concave reflecting surface. 3. The curvature radius of the substrate of the curved semitransparent mirror is a value having a difference of 3 mm or more with respect to a value twice as large as a distance between the substrate and the exit pupil. Virtual image observation optical system. 4. The virtual image observation optical system according to claim 1, wherein the reflecting surface of the curved semi-transparent mirror is a concave aspheric surface. 5. The virtual image observation optical system according to claim 1, wherein the image display device is a reflection type liquid crystal image display device. 6. An image display device, having a refractive power to form a virtual image of a display image of the image display device by reflecting light emitted from the image display device, and emitted from the image display device. A curved semi-transparent mirror that reflects light and guides it to the observer's pupil, and transmits light behind to guide the observer's pupil, wherein the curved semi-transparent mirror has a first surface and a second surface. Has a different surface shape so that the refractive power for transmitted light is zero. 7. The virtual image observation optical system according to claim 6, wherein the curved surface translucent mirror has a concave reflecting surface. 8. The method according to claim 6, wherein the radius of curvature of the substrate of the curved semi-transparent mirror has a difference of 3 mm or more with respect to a value twice as large as a distance between the substrate and the exit pupil. Virtual image observation optical system. 9. The virtual image observation optical system according to claim 6, wherein the curved semi-transparent mirror has a reflecting surface formed as a concave aspheric surface. 10. The virtual image observation optical system according to claim 6, wherein the image display device is a reflection type liquid crystal image display device. 11. The virtual image observation optical system according to claim 6, wherein a light beam splitting element is provided between the image display device and the curved translucent mirror. 12. The virtual image observation optical system according to claim 10, wherein the curved semi-transparent mirror has a concave reflecting surface. 13. The radius of curvature of the substrate of the substrate of the curved semitransparent mirror is 3 m for a value twice the distance between the substrate and the exit pupil.
11. A value having a difference of not less than m.
The virtual image observation optical system according to the above. 14. The virtual image observation optical system according to claim 10, wherein the curved translucent mirror has a reflecting surface formed as a concave aspheric surface. 15. An image display device, at least one optical element having a refractive power for forming a virtual image of a display image of the image display device, and reflecting light passing through the optical element to guide the light to an observer's pupil. And a Lippman volume hologram that transmits light behind and guides the light to the pupil of the observer. The Lippman volume hologram substrate that holds the Lippmann volume hologram has a first surface and a second surface having different surface shapes. Thus, the virtual image observation optical system is characterized in that the refractive power for transmitted light is set to 0. 16. The Lippmann volume hologram substrate has a concave surface on the Lippmann volume hologram holding surface, and the other surface of the Lippman volume hologram substrate has a thickness of 3 mm or more with respect to a value twice the distance between this surface and the exit pupil. The virtual image observation optical system according to claim 15, wherein the concave surface has a difference in curvature radius. 17. The virtual image observation optical system according to claim 15, wherein the Lippman volume hologram substrate has a meniscus shape having a curvature in only one direction. 18. The virtual image observation optical system according to claim 15, wherein the image display device is a reflection type liquid crystal image display device. 19. An image display device, and cooperates with at least one optical element to form a virtual image of a display image of the image display device, and reflects light emitted from the image display device to form an observer's pupil. And a Lippman volume hologram substrate for transmitting the light behind and guiding the light to the pupil of the observer. The Lippman volume hologram substrate holding the Lippmann volume hologram has a first surface and a second surface having different surface shapes. A virtual image observation optical system characterized by having a refractive power of 0 for transmitted light. 20. The Lippmann volume hologram substrate has a concave surface on the Lippmann volume hologram holding surface, and the other surface of the Lippman volume hologram substrate has a thickness of 3 mm or more with respect to a value twice the distance between this surface and the exit pupil. 20. The virtual image observation optical system according to claim 19, wherein the concave surface has a difference in curvature radius. 21. A substrate for a Lippmann volume hologram,
20. The virtual image observation optical system according to claim 19, wherein the virtual image observation optical system has a meniscus shape having a curvature in only one direction. 22. An image display device, having a refractive power to form a virtual image of a display image of the image display device by reflecting light emitted from the image display device, and emitted from the image display device. A Lippmann volume hologram substrate that reflects the light and guides the light to the observer's pupil while transmitting light behind and guides the light to the observer's pupil; A virtual image observation optical system, characterized in that the refracting power for transmitted light is made zero by having different surface shapes of the first and second surfaces. 23. The Lippmann volume hologram substrate has a concave surface on the Lippmann volume hologram holding surface, and the other surface of the Lippman volume hologram substrate has a thickness of 3 mm or more with respect to a value twice the distance between this surface and the exit pupil. 23. The virtual image observation optical system according to claim 22, wherein the concave surface has a difference in curvature radius. 24. The virtual image observation optical system according to claim 22, wherein the Lippman volume hologram substrate has a meniscus shape having a curvature in only one direction. 25. The virtual image observation optical system according to claim 22, further comprising a light beam splitting element between the image display device and the Lippman volume hologram. 26. The Lippmann volume hologram substrate has a concave surface on the Lippmann volume hologram holding surface, and the other surface of the Lippman volume hologram substrate has a thickness of 3 mm or more with respect to a value twice the distance between this surface and the exit pupil. 26. The virtual image observation optical system according to claim 25, wherein the concave surface has a difference in curvature radius. 27. The substrate of the Lippmann volume hologram comprises:
26. The virtual image observation optical system according to claim 25, wherein the virtual image observation optical system has a meniscus shape having a curvature in only one direction.