JP2001311906A - Device and system for image display - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that an image display device which uses a reflection type image display element where the length of the optical path between a projection optical system and an image display element is greatly varied with object height and optical performance deteriorates since the image display element tilts large to the projection optical system when the illumination light from a light source is made incident directly on a reflection type image display element. SOLUTION: The device and system for image display are characterized by that Ψ1<Ψ2, when r1 and r2 are the main light beams having the largest and smallest angles of projection from a light guide optical system in image light passing through the light guide optical system 3 and Ψ1 and Ψ2 are phase function values at the passing positions of the light beams r1 and r2 on a diffracting surface of a 2nd optical system 20 constituting the projection optical system.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image display device called a head mounted display (HMD) or the like and an image display device used as a finder of a camera.

[0002]

2. Description of the Related Art In an image display apparatus as described above,
There is a demand for miniaturization of the entire apparatus, and various optical systems have been proposed to achieve this.

[0003] For example, the present applicant has disclosed in
No. 51, JP-A-8-50256, JP-A-8-
JP-A-160340 and JP-A-8-179238 disclose a liquid crystal display for displaying image information, and a small prism for projecting an image displayed on the liquid crystal display to an observer's eye for observation. We have proposed an image observation device that has been reduced in size.

In the image display devices proposed in the above publications, light emitted from a liquid crystal display displaying image information is made incident on a small prism, and a refracting surface having a curvature and a total reflection surface formed on the small prism. Then, the small prism is emitted through the reflecting surface, and is guided to the observer's eye. Thereby, a virtual image of the liquid crystal display is formed in front of the observer, and the observer observes this virtual image.

[0005] In these image display devices, a transmissive liquid crystal display is used as a liquid crystal display. However, the transmissive liquid crystal display has a high pixel aperture ratio due to the recent increase in the definition of image display elements. It has been pointed out that a low image quality leads to a reduction in image quality.

[0006]

Under such circumstances, it has been proposed to use a reflection type liquid crystal display having a high pixel aperture ratio for an image display device requiring a high definition image. As an image display device using a reflection type liquid crystal display, for example, there is an image display device proposed in Japanese Patent Application Laid-Open No. H11-125791. In this apparatus, as shown in FIG. 9 of the present application, light from a light source 112 is directly incident on a reflective liquid crystal display 108 without passing through an optical element, and is illuminated.

However, in such an image display device, since the light from the light source 112 is directly incident on the liquid crystal display 108, the light source 112 and the liquid crystal display 1
There is a problem in that the size of the lighting unit including the lighting device 08 and the entire device is increased. Further, since the liquid crystal display 108 is configured to be greatly inclined with respect to the display optical system 110, there is a problem that the optical path length from the liquid crystal display 108 to the display optical system 110 greatly differs depending on the object height, and the optical performance is reduced.

As another image display apparatus, as shown in FIG. 10, a light source 112 is provided on a side opposite to a liquid crystal display 108 with respect to a prism-shaped display optical system 110. In this device, light from a light source 112 passes through a prism-shaped display optical system 110, and then illuminates a liquid crystal display 108. Of the illumination light, light reflected by the liquid crystal display 108 (image light) is again displayed. The light enters the system 110 and reaches the observer's eye 101.

However, in such an illumination system, there is a problem that unnecessary reflection occurring inside the prism-shaped display optical system 110 generates flare light which is a major factor of image quality deterioration.

Therefore, the present invention provides an image display apparatus which has a very simple structure, is well corrected for various aberrations, has a wide angle of view, and does not generate unnecessary flare. An object of the present invention is to provide a small-sized image display device using a reflective liquid crystal display corresponding to a high-definition image.

[0011]

In order to achieve the above object, the present invention provides a light source for emitting illumination light, a reflective image display device for displaying an image by internal reflection of incident illumination light, and a reflection type image display device. Optical system for projecting the image displayed on the image display device to the observer's eyes, and guiding the illumination light incident from the light source to be incident on the image light emission side of the reflection type image display device. A light guide optical system for causing image light emitted from a display element to enter the projection optical system, wherein the projection optical system has at least one reflecting surface and an image emitted from the reflective image display element. A first optical system that emits light to the observer's eye, and at least one of image light that is disposed closer to the observer's eye than the first optical system and emitted from the first optical system. Two diffractive surfaces A second optical system having an optically active surface, a ray connecting the center of the exit pupil of the projection optical system and the center of the reflective image display element is defined as a reference axis ray, and the center of the exit pupil is defined as an origin. A reference axis ray intersecting the origin is defined as a Z axis (however, a direction from the origin toward the projection optical system is defined as positive), a direction perpendicular to the Z axis on a cross section including the reference axis ray is defined as a Y axis, and a YZ axis is defined. In the YZ plane of the absolute coordinate system having an axis perpendicular to the X axis as an axis, a principal ray of the image light passing through the light guide optical system having the maximum emission angle from the light guide optical system is denoted by r1, and an emission angle. Let r2 be the chief ray that minimizes
When the phase function values at the passing positions of the principal ray r1 and the principal ray r2 on the diffraction action surface are Ψ1 and Ψ2, respectively, Ψ1 <Ψ2 <where the phase function value Ψ (x, y) is Ψ (x , y) = K × (c1 × x + c2 × y + c3 × x 2 + c4 × xy + c5 × y 2
+ c6 × x ³ + c7 × x ² y + c8 × xy ² + c9 × y ³ ), K is a constant, x and y are x and y coordinates of the diffraction action surface in the local coordinate system, Cj Is a coefficient. When the x-coordinate of the passing point of the principal rays r1 and r2 on the diffraction action surface is 0 and the y-coordinates are y1 and y2, respectively, Ψ1 = Ψ (y1) Ψ2 = Ψ (y2) Is satisfied.

That is, in the case where chromatic aberration, which is likely to be generated on the exit surface of the light guide optical system, is slightly different (specific gravity) in the screen due to a difference in the emission angle of the image light from the light guide optical system. Considering the specific gravity of the chromatic aberration, the principal ray r1 (the exit ray at the maximum angle) and the principal ray r2 on the diffraction surface
(Phase function value at the passing position of (emitted light at minimum angle))
By providing a difference between 1 and Ψ2, chromatic aberration is satisfactorily corrected for the entire display screen, and a high-quality image can be displayed.

Further, since the above-described effect can be obtained only by adding a lens-shaped or plate-shaped second optical system to the conventionally used first optical system as a projection optical system,
It is possible to realize an image display device that can obtain a high-quality display image while being small.

In the above invention, among the light rays of the image light emitted from the reflection type image display element and passing through the light guide optical system in the YZ plane of the absolute coordinate system, the light ray having the longest optical path length is used. Is defined as r3, and the light ray having the shortest optical path length is defined as r4.
The optical path lengths of the light rays r3 and r4 in the second optical system are t3 and t4, respectively, and the optical power exerted on the light rays r3 and r4 by the second optical system is Φ
3, Φ4, t3 <t4 and Φ3> Φ4 where the optical power Φi of the ri ray is the optical power of the two optical working surfaces A and B, φi (A), φi
(B), the refractive index of the material forming the second optical system is nd, the optically active surface A is a surface on the observer's eye side, and the optically active surface B is the first optical system side. And in terms of
The sign of the curvature is positive in the direction from the observer's eye toward the first optical system, and the local radii of curvature at the intersection of the light ray ri and the optically active surfaces A and B are Ri (A) and Ri (B )
Where φi (A) = (nd−1) / Ri (A) φi (B) = (1−nd) / Ri (B) φi = φi (A) + φi (B) −φi (A) × φi
(B) × ti / nd>.

Thus, in addition to the effect of correcting the chromatic aberration, the light beam r3 having the longest optical path length among the light beams of the image light emitted from the reflection type image display element and passing through the light guide optical system is provided.
The image tilt and various aberrations caused by the optical path difference between the light ray r4 having the shortest optical path length and
It is also possible to make good correction by providing a difference in the optical path lengths t1 and t2 of the light beam r4 or by providing a difference in the optical powers Φ3 and Φ4 exerted on the light beams r3 and r4 by the second optical system. Become.

[0016]

(First Embodiment) FIG. 1 shows the configuration of an image display apparatus according to a first embodiment of the present invention. 1 is a light source that emits RGB light, and 2 is a first polarizing plate. 3 is an illumination prism (light guide optical system),
Reference numeral 4 denotes a reflection type liquid crystal display panel (reflection type image display element: hereinafter, simply referred to as a display panel).

Reference numeral 5 denotes a second polarizing plate, and reference numeral 6 denotes a prism lens (first optical system). Reference numeral 20 denotes an auxiliary lens (second optical system), and reference numeral 7 denotes an observer's eye. The prism lens 6 and the auxiliary lens 20 constitute a projection optical system described in the claims.

In the image display device configured as described above,
Illumination light emitted from the light source 1 passes through the first polarizing plate 2 to become polarized light having a predetermined polarization direction, and the illumination prism 3
Incident on the light incident surface 8.

The illumination light entering the illumination prism 3 is reflected by the reflection / transmission surface 9, passes through the transmission surface 10 disposed near the display panel 4, and enters from the image light emission side of the display panel 4. The display panel 4 is illuminated.

In the display panel 4, the polarization direction of light is modulated according to a video signal supplied from an image information output device such as a personal computer or a DVD player.
The light (image light) modulated and reflected by the display panel 4 passes through the transmission surface 10 of the illumination prism 4 again, enters the illumination prism 4, and further passes through the reflection / transmission surface 9 to form the second light. The light enters the polarizing plate 5.

Here, the illumination prism 3 is disposed between the prism lens 6 and the display panel 4.
It is configured such that the angle formed between the reflection / transmission surface 9 on the prism lens side and the transmission surface 10 on the display panel side does not increase. In this illumination prism 3, the surfaces 9, 1
Between 0, the illumination light and the image light partially pass through the same area.

In the second polarizing plate 5, a polarization component parallel to a polarization direction orthogonal to the predetermined polarization direction is transmitted,
The vertical polarization component is absorbed. As a result, the image light enters the prism lens 6 in a state where unnecessary light is cut.

The state of polarization of light so far will be described with reference to FIG. In FIG. 2, double circles on the optical axis indicate polarized light having a predetermined polarization direction (for example, S-polarized light), and arrows indicate polarized light having a polarization direction orthogonal to the predetermined polarization direction (for example, S-polarized light). , P-polarized light).

The unpolarized illumination light 14 from the light source 1
The light is aligned in a predetermined polarization direction 15 by the polarizing plate 2, is reflected by the reflection / transmission surface 9 of the illumination prism 3, passes through the transmission surface 10 of the illumination prism 3, and enters the display panel 4.

The polarized light 1 incident on the display panel 4
Reference numeral 6 denotes a panel 4 which is 90 ° with respect to the predetermined polarization direction.
Of the optical rotation. The polarized light that has undergone this optical rotation is
Polarized light that has passed through the second polarizer 5 and is not affected by the optical rotation is absorbed by the second polarizer 5.

The image light transmitted through the second polarizing plate 5 and incident on the prism lens 6 through the incident surface 11 is
After being reflected by the reflection / transmission surface 12, the light is reflected again by the concave reflection surface 13, and is emitted from the reflection / transmission surface 12 to the observer's eye 7 side.

The image light emitted from the prism lens 6 is
The light enters the auxiliary lens 20 disposed closer to the eye 7 than the prism lens 6. The image light is transmitted to the auxiliary lens 20.
Through the transmission surface B (optical operation surface B) 22 and the transmission surface A (optical operation surface A) 21 to reach the eye 7 of the observer.

Here, the illumination prism 3 of the present embodiment is
As shown in FIG. 1, when the light beam of the illumination light from the light source 1 passes through the entrance surface 8 of the illumination prism 3 and is reflected by the reflection / transmission surface 9, the incident angle φ to the reflection / transmission surface 9 is represented by the following equation ( 1)
Is satisfied, and the total reflection condition is satisfied.

Sin ^-1 φ ≧ 1 / n (1) Here, the material of the illumination prism is S-BSL7 (n =
1.52), it is sufficient that φ ≧ 41.1 is satisfied.

The incident surface 1 of the prism lens 6
1, the reflection / transmission surface 12 and the concave reflection surface 13 are constituted by non-rotationally symmetric surfaces.

Further, the auxiliary lens 20 is configured to satisfy the following conditions. That is, a ray connecting the center of the exit pupil of the projection optical system (pupil of the observer's eye 7) and the center of the display panel 4 is defined as a reference axis ray, the center of the exit pupil is defined as an origin, and a reference axis ray intersecting with the origin is defined as a reference axis ray. The Z axis (however, the direction from the origin toward the projection optical system is defined as positive), the direction perpendicular to the Z axis on the cross section including the reference axis ray is defined as the Y axis, and the axes perpendicular to the YZ axes are defined as the X axis. When the absolute coordinate system of the present apparatus is defined, the principal ray (the exit pupil) at which the exit angle when the image light from the display panel 4 exits from within the illumination prism 3 becomes maximum in the YZ plane of the absolute coordinate system. , The minimum principal ray is r2, and the principal rays r1 and r2 on the diffractive surface (hereinafter referred to as the diffractive surface) of the transmission surfaces A and B of the auxiliary lens 20 are denoted by r1. Phase function value at the passing position (diffraction Values) corresponding to the inverse of word .PSI.1, when a .psi.2, and is configured so as to satisfy the relation of Ψ1 <Ψ2 ... (2).

[0032] Here, the phase function value Ψ (x, y) is, Ψ (x, y) = K × (c1 × x + c2 × y + c3 × x 2 + c4 × xy + c5 × y 2 + c6 × x ³ + c7 × x ² y + c8 × xy ² + c9 × y ³ ) (3) K is a constant, x and y are x and y coordinates in the local coordinate system of the diffraction action surface, and Cj is a coefficient.

Then, the principal ray r on the diffraction action surface
Since the x-coordinates of the passing points of 1 and r2 are 0, when the y-coordinates are y1 and y2, respectively, Ψ1 = Ψ (y1) (4) Ψ2 = Ψ (y2) (5) .

Although chromatic aberration is likely to occur on the exit surface 9 of the illumination prism 3, the chromatic aberration has a difference (specific gravity) due to the difference in the exit angle of the principal ray from the illumination prism 3.
That is, as the exit angle of the principal ray from the illumination prism 3 increases, the generated chromatic aberration also increases.

For this reason, in the present embodiment, taking into account the specific gravity of the chromatic aberration, the phase function values Ψ1 and Ψ2 at the positions where the principal rays r1 and r2 pass on the diffractive surface of the auxiliary lens 20.
By giving a difference to (making よ り 2 larger than Ψ1),
Chromatic aberration is satisfactorily corrected for the entire display screen so that a high-quality image can be displayed.

<< Numerical Example >> Since the projection optical system of the first embodiment is constituted by an eccentric surface, an absolute coordinate system and a local coordinate system are set to represent the shape of the optical system. FIG.
3 is an explanatory diagram of an absolute coordinate system and a local coordinate system.

A ray connecting the center of the exit pupil (the desired pupil position of the observer) of the projection optical system and the center of the image display element is defined as a reference axis ray. An image display device in which the Z axis is on the line (the direction from the origin to the observation optical system is positive), the direction perpendicular to the Z axis on the section including the reference axis ray is the Y axis, and the axis perpendicular to the YZ axis is the X axis. Set the absolute coordinate system of.

Next, the origin Oi of the local coordinates is set for each surface i in absolute coordinates (Sxi, Syi, Szi). The Z axis of the local coordinates is a straight line passing through the origin Oi in the YZ plane and forming an angle Ai with the axis of the absolute coordinate system.

Here, Ai is positive when the local coordinate Z-axis makes a counterclockwise angle with respect to a straight line passing through the origin Oi and parallel to the Z-axis of the absolute coordinate system. The Y axis of the local coordinate is a straight line passing through the origin Oi and making an angle of 90 ° counterclockwise with respect to the Z axis of the local coordinate. The X axis of the local coordinate is a straight line passing through the origin Oi and orthogonal to the Y axis and the Z axis of the local coordinate.

The shape of each surface is represented by local coordinates. In each of the embodiments, the shape of the optical action surface referred to as a rotationally asymmetric surface (free-form surface) is represented by a Zernike polynomial, and is represented by the following function.

[0041] Here, where c is the curvature of each surface and r is the basic radius of curvature of each surface, the curvature c is c = 1 / r. Also, c j is the aspheric coefficient of the Zernike polynomial on each surface.

Since the optically active surface is symmetric with respect to the YZ plane, the terms are not shown except for those that are asymmetric in the X-axis direction.

Next, the diffraction action surface of the auxiliary lens 20 will be described. This diffraction surface is obtained by forming a diffraction grating represented by the following phase function on an arbitrary reference surface.

[0044] Ψ (x, y) = 2π (c1 × x + c2 × y + c3 × x 2 + c4 × xy + c5 × y 2 + c6 × x 3 + c7 × x 2 y + c8 × xy 2 + c9 × y ³ ) / λ (6) where λ is 587.6 nm, x and y are local coordinates of the diffraction surface, and ci is the i-th phase coefficient on the diffraction surface. From this phase function, the pitch of the diffraction grating at an arbitrary coordinate position can be calculated.

FIG. 3 shows the configuration of an image display device as a numerical example. In the auxiliary lens 20 of this embodiment, the transmission surface A21 is a flat surface, and the transmission surface B22 is a diffraction surface formed on a plane reference surface.

Here, the transmitting surface A21 is a surface on the observer's eye 7 side, and the transmitting surface B22 is a surface on the prism lens 6 side.

The image observation apparatus shown in this embodiment is suitable for an example of arrangement of an image display device as shown in FIG. In FIG. 6, the light source 1, the display panel 4, the first and second polarizers 2, 5, and the illumination prism 3 are laid out so as to be higher than the height of the prism lens 6 and the left and right eyes of the observer. .

Table 1 shows numerical data of each surface of the projection optical system of this embodiment, f (this will be described later), and emission angles θ1, θ of the principal rays r1, r2 from the illumination prism 3.
2 and Ψ1 and Ψ2.

Here, Si is i = 1 as shown in FIG.
From the center of the exit pupil, the auxiliary lens 20, the prism lens 6, the illumination prism 3, the cover glass of the display panel 4, and the image display surface of the display panel.

The maximum half angle of view of the apparatus in the X-axis direction is W
X, the maximum half angle of view of the apparatus in the Y-axis direction is described as WY. f is a value corresponding to the focal length of the prism lens 6,
In the reverse tracing from the observer's eye 7, the incident angle WX on XZ cross-section of the device of the incident light from an object at infinity, the image height y _m where the ray is imaged on the display panel 4, f = y _m / Tan (WX), and is simply referred to as a focal length here.

[0051]

[Table 1]

In this numerical example, Ψ1 and Ψ2 satisfy the relationship of the above equation (2).

As described above, according to the present embodiment,
It is possible to realize an image display device capable of displaying an image of good image quality in an observation field of view while reducing the size of the entire device.

In the present embodiment, since the transmission surface A21 is flat, the auxiliary lens 20 can be easily held, and even if the transmission surface A21 is touched by mistake, the wiping is easy. For this reason, the substantially flat auxiliary lens 20 can be used also as a protective cover of the image display device.

Further, both transmission surfaces A21,
By applying an anti-reflection film to B22, it is possible to prevent a decrease in the contrast of the displayed image due to the light from the observer being reflected by the transmission surfaces A21 and B22.

When the auxiliary lens 20 is formed of plastic, a lighter image display device can be provided as compared with a case where the auxiliary lens 20 is formed of glass.

Further, as shown in FIG.
Is preferably held by a member 23 holding the prism lens 6. Specifically, convex reference pins 6a, 6b are formed on both left and right sides of the prism lens 6, and convex reference pins 20a, 20b are formed on both left and right sides of the auxiliary lens 20.
To form Then, each reference pin is inserted into a reference hole formed on the front and rear surfaces on the left and right sides of the holding member 23, and is bonded or press-fitted.

By doing so, it is possible to increase the positional accuracy between the prism lens 6 and the auxiliary lens 20 when assembling the apparatus, and it is possible to display a better image.

The prism lens 6 and the auxiliary lens 20 may be directly fixed without using the holding member 23.

(Second Embodiment) FIG. 4 shows a second embodiment of the present invention.
1 illustrates a configuration of an image display device according to an embodiment. FIG.
, The auxiliary lens 3 having the transmission surfaces A31 and B32
Other than 0, the configuration is the same as that of the first embodiment.

In the auxiliary lens 30 of the present embodiment, the transmission surface A31 is a Y toric surface having a different axis from the Z-axis of the apparatus (a surface obtained by rotating a curved surface shown in the drawing with respect to the Y-axis). The surface B32 is a diffractive surface formed on the plane reference surface.

Here, the transmission surface A31 is a surface on the observer's eye 7 side, and the transmission surface B32 is a surface on the prism lens 6 side.

The image observation apparatus shown in this embodiment is suitable for an example of the arrangement of the image display apparatus as shown in FIG. 6, as in the first embodiment.

Table 2 shows numerical data of each surface of the projection optical system according to the present embodiment, f, emission angles θ1, θ2 of the principal rays r1, r2 from the illumination prism 3, and Ψ1, Ψ2. .

[0065]

[Table 2]

Also in this numerical example, since Ψ1 and Ψ2 satisfy the relationship of the above equation (2), the same effects as in the first embodiment can be obtained.

(Third Embodiment) FIG. 5 shows a third embodiment of the present invention.
1 illustrates a configuration of an image display device according to an embodiment. FIG.
, The auxiliary lens 4 having the transmission surfaces A41 and B42
Other than 0, the configuration is the same as that of the first embodiment.

In the auxiliary lens 40 of this embodiment, the transmission surface A41 is a Zernike polynomial aspherical surface,
Reference numeral 42 denotes a diffraction action surface formed on the plane reference surface.

Here, the transmitting surface A41 is a surface on the observer's eye 7 side, and the transmitting surface B42 is a surface on the prism lens 6 side.

The image observation apparatus shown in this embodiment is suitable for an example of arrangement of the image display apparatus as shown in FIG.

In FIG. 7, a light source 1, a display panel 4, first and second polarizing plates 2 and 5, and an illumination prism 3 are shown.
Are laid out at the same height as the prism lens 6 and the left and right eyes of the observer.

Table 3 shows numerical data of each surface of the projection optical system of this embodiment, f, emission angles θ1 and θ2 of the principal rays r1 and r2 from the illumination prism 3, and Ψ1 and と 2. .

[0073]

[Table 3]

Also in this numerical example, since Ψ1 and Ψ2 satisfy the relationship of the above equation (2), the same effects as in the first embodiment can be obtained.

In the present embodiment, among the light beams passing through the illumination prism 3 between the prism lens 6 and the display panel 4 in the YZ plane of the absolute coordinate system, the light beam having the longest optical path length is represented by r3. When the shortest ray is r4, the optical path lengths of the rays r3 and r4 in the auxiliary lens 40 are t3 and t4, and the optical powers exerted on the rays r3 and r4 by the auxiliary lens 40 are φ3 and φ4, respectively, t3 < (7) and Φ3> Φ4 (8) are satisfied (even if either one of the relationships is satisfied).

Here, the optical power Φ exerted on the light ray ri
i is the optical power φi of the transmission surfaces A41 and B42.
(A), φi (B), the refractive index of the material forming the auxiliary lens 40 is nd, the transmission surface A41 is disposed on the observer's eye 7 side, the transmission surface B42 is disposed on the prism lens 6 side, The sign of the curvature is changed from the observer's eye 7 side to the prism lens 6
The direction toward the side is positive, and the light ray ri and the transmission surfaces A41, B
The local radius of curvature at the point of intersection with
When i (B), φi (A) = (nd−1) / Ri (A) (4) φi (B) = (1-nd) / Ri (B) (5) φi = φi ( A) + φi (B) −φi (A) × φi (B) × ti / nd (9)

Table 3 shows that t3, t4 and light rays r3,
optical path lengths tp3 and tp4 in the illumination prism 3 of r4;
Φ1 and Φ2 are shown.

By using a projection optical system in which the auxiliary lens 20 and the prism lens 6 are combined, the first
In addition to the same effects as those of the embodiment, the image plane is tilted due to a difference in optical path length between the light beams r3 and r4 in the illumination prism 3, or a difference in the incident angle of the light beams r3 and r4 to the display panel 4. The aberration can be corrected well. Further, since the layout as shown in FIG. 7 is possible, it is possible to realize an image display device in which the size in the device Y-axis direction is further reduced.

In the above embodiment, the case where the first optical system of the projection optical system is constituted by a prism lens has been described. However, in the present invention, the first optical system is composed of a half mirror and a concave mirror. Optical system.

In each of the above embodiments, the image display device as a so-called head mounted display has been described. However, the image display device of the present invention can be applied to a view finder of a camera and the like.

[0081]

As described above, according to the present invention,
In the case where chromatic aberration that is likely to occur on the exit surface of the light guide optical system is slightly different (specific gravity) in the screen due to a difference in the emission angle of the image light from the light guide optical system, the specific gravity of the chromatic aberration is considered. Then, the principal ray r1 (the exit ray at the maximum angle) and the principal ray r2 (the exit ray at the minimum angle) on the diffraction surface
By making the phase function values Ψ1 and Ψ2 have a difference at the passing position, chromatic aberration can be favorably corrected for the entire display screen, and a high-quality image can be displayed.

Further, the above effects can be obtained only by adding a lens-shaped or plate-shaped second optical system to the conventionally used first optical system as a projection optical system.
It is possible to realize an image display device which can obtain a high quality display image while being small.

The light rays r3 having the longest light path length and the light rays r4 having the shortest light path length among the light rays of the image light emitted from the reflection type image display element and passing through the light guide optical system are generated in the second optical system. The optical path lengths t3 and t4 at
If the optical power Φ3, Φ4 exerted on the light rays r3 and r4 by the second optical system has a difference, the light rays r3,
Since image tilt and various aberrations caused by the optical path length difference of r4 can be corrected well, a higher quality image can be displayed.

[Brief description of the drawings]

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

FIG. 2 is a sectional view of an illumination prism used in the image display device according to the first embodiment.

FIG. 3 is a configuration diagram of a numerical example of the image display device of the first embodiment.

FIG. 4 is a configuration diagram of an image display device according to a second embodiment of the present invention.

FIG. 5 is a configuration diagram of an image display device according to a third embodiment of the present invention.

FIG. 6 is a mounting model diagram of the image display device according to the first and second embodiments.

FIG. 7 is a mounting model diagram of the image display device of the third embodiment.

FIG. 8 is an explanatory view (top view) of a method of holding the prism lens and the auxiliary lens in the first embodiment.

FIG. 9 is a configuration diagram of a conventional image display device.

FIG. 10 is a configuration diagram of a conventional image display device.

FIG. 11 is an explanatory diagram of a coordinate system of a projection optical system in each of the embodiments.

[Explanation of symbols]

 Reference Signs List 1 light source 2 first polarizing plate 3 illumination prism 4 liquid crystal display panel 5 second polarizing plate 6 prism lens 7 observer's eye 20, 30, 40 auxiliary lens

Continued on the front page (72) Inventor Takashi Sudo 3-30-2 Shimomaruko, Ota-ku, Tokyo F-term in Canon Inc. (reference) 2H088 EA10 HA21 HA23 HA24 HA28 MA03 MA06 5C058 AA06 AB05 BA35 DA06 DA11

Claims (23)

[Claims] 1. A light source that emits illumination light, a reflective image display element that displays an image by internal reflection of incident illumination light, and an image displayed on the reflective image display element is projected to an observer's eye. A projection optical system and guides illumination light incident from the light source to enter the image light emission side of the reflective image display element, and causes image light emitted from the reflective image display element to enter the projection optical system. An image display device having a light guide optical system, wherein the projection optical system has at least one reflective surface and emits image light emitted from the reflective image display element to the observer's eye side. An optical system, and at least one of which is arranged closer to the observer's eye than the first optical system and at least one of which is a diffraction surface for image light emitted from the first optical system.
A second optical system having two optical working surfaces, a light beam connecting the center of the exit pupil of the projection optical system and the center of the reflective image display element is defined as a reference axis light beam, The origin is the center of the exit pupil, the Z axis is on a reference axis ray intersecting the origin, and the direction from the origin toward the projection optical system is positive, and is perpendicular to the Z axis on a cross section including the reference axis ray. In the YZ plane of the absolute coordinate system in which the direction is the Y axis and the axis perpendicular to the YZ axis is the X axis, the emission angle of the image light passing through the light guide optical system from the light guide optical system is The maximum principal ray is denoted by r1, the principal ray whose exit angle is minimum is denoted by r2, and the phase function values at the passing positions of the principal ray r1 and the principal ray r2 on the diffraction action surface are {1,} 2, respectively.
When a, .PSI.1 <.psi.2 <however, the phase function value Ψ (x, y) is, Ψ (x, y) = K × (c1 × x + c2 × y + c3 × x 2 + c4 × xy + c5 × y ²
+ c6 × x ³ + c7 × x ² y + c8 × xy ² + c9 × y ³ ), K is a constant, x and y are the x and y coordinates of the diffraction action surface in the local coordinate system, Cj Is a coefficient. When the x-coordinate of the passing point of the principal rays r1 and r2 on the diffraction action surface is 0 and the y-coordinates are y1 and y2, respectively, Ψ1 = Ψ (y1)） 2 = Ψ (y2) Satisfies the following relationship: 2. The diffractive surface of the second optical system has a phase function Ψ (x, y) = K × (c1 × x + c2 × y + c3 ×) on a reference surface of the diffractive surface. x ² + c4 × xy + c5 × y ²
+ c6 × x ³ + c7 × x ² y + c8 × xy ² + c9 × y ³ ), wherein the reference surface is a flat surface. 2. The image display device according to 1. 3. The image display device according to claim 2, wherein the plane is a plane that is rotationally eccentric about the X axis. 4. The image display device according to claim 1, wherein a reference surface in a diffraction operation surface of the second optical system is an aspheric surface. 5. The image display device according to claim 1, wherein a reference surface of the diffraction action surface of the second optical system is a non-rotationally symmetric surface. 6. The apparatus according to claim 1, wherein a reference plane in a diffraction action surface of the second optical system is a plane which is plane-symmetric with respect to a YZ plane of the absolute coordinate system. The image display device as described in the above. 7. An optical operating surface of the second optical system other than a diffraction operating surface is a flat surface.
The image display device according to any one of the above. 8. The image display device according to claim 7, wherein the plane is a plane which is rotationally eccentric about the X axis. 9. The image display device according to claim 1, wherein an optically active surface of the second optical system other than the diffractionally active surface is an aspherical surface. 10. The image display device according to claim 1, wherein an optical operation surface other than the diffraction operation surface of the second optical system is a non-rotationally symmetric surface. 11. An optical operation surface other than the diffraction operation surface of the second optical system is a surface which is plane-symmetric with respect to the YZ plane of the absolute coordinate system. The image display device according to any one of claims 9 and 10. 12. The image display device according to claim 1, wherein a diffraction action surface of the second optical system is arranged on the first optical system side. 13. In the YZ plane of the absolute coordinate system,
Of the light rays of the image light emitted from the reflection type image display element and passing through the light guiding optical system, the light ray having the longest optical path length is r3, the light ray having the shortest optical path length is r4, and the second light ray is the second light ray. When the optical path lengths of the light beams r3 and r4 in the optical system are denoted by t3 and t4, and the optical powers exerted on the light beams r3 and r4 by the second optical system are denoted by Φ3 and Φ4, respectively, t3 <T4 and Φ3> Φ4 where the optical power Φi of the ri ray is the optical power of the two optical working surfaces A and B
(A), φi (B), the refractive index of the material forming the second optical system is nd, the optically active surface A is a surface on the observer's eye side, and the optically active surface B is the second optical system. 1 is a surface on the side of the optical system, the sign of the curvature is positive in the direction from the observer's eye to the first optical system, and the local radius of curvature at the intersection of the light ray ri and the optically active surfaces A and B. To Ri (A),
When Ri (B), φi (A) = (nd−1) / Ri (A) φi (B) = (1−nd) / Ri (B) φi = φi (A) + φi (B) − φi (A) × φi
13. The image display device according to claim 1, wherein at least one of (B) × ti / nd> is satisfied. 14. The optical working surfaces A and B of the second optical system.
14. The image display device according to claim 1, wherein an anti-reflection film is applied to at least one of the surfaces. 15. The image display device according to claim 1, wherein said second optical system is formed of plastic. 16. The image display device according to claim 1, wherein said second optical system is held integrally with said first optical system without interposing a separate member. . 17. The image display device according to claim 1, wherein the second optical system is held by a member that holds the first optical system. 18. The first optical system includes a prism lens formed of a transparent optical material, and at least one of the optically active surfaces of the prism lens is a rotationally asymmetric surface. 2. The method according to claim 1, wherein
8. The image display device according to any one of 7. 19. The prism lens has an incident surface on which image light from the reflective image display device is incident, a reflecting surface for reflecting image light incident from the incident surface, and an image light reflected on the reflecting surface. 19. An emission surface from which light exits, and at least one of the incidence surface, the reflection surface, and the emission surface is a rotationally asymmetric surface.
An image display device according to claim 1. 20. The image display device according to claim 1, wherein the reflection surface of the first optical system is a concave reflection surface. 21. The light guide optical system, which reflects incident illumination light toward the reflective image display element and transmits image light from the reflective image display element toward the projection optical element. The image display device according to any one of claims 1 to 20, further comprising a transmission surface. 22. An image display device according to claim 1, further comprising: an image information output device that supplies the image display device with image information to be displayed on the reflective image display element. An image display system characterized by comprising: 23. The image display system according to claim 22, wherein said image information output device is a personal computer or a DVD player.