JP2002107657A - Picture display device and head-mounted display using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a picture display device suitable for a compact head- mounted display(HMD) or a spectacles type display enlarging and projecting a picture by using a reflection type display device. SOLUTION: This display device is provided with a reflection type display means, an illumination means illuminating the display means, an illumination optical system guiding the light from the illumination means to the display means, and a display optical system including plural reflection surfaces guiding the light from the display means to a pupil for observation, and the illumination optical system and the display optical system have an optical surface A having both transmitting and reflecting actions held in common. The optical surface A has curvature on the cross section of a local generating line (a plane including incident light and emitted light being a reference light beam emitted from the illumination means and passing through the center of the picture of the display means and the center of the pupil) and the focal distance local-fy on the cross section of the local generating line of the display optical system and the focal distance local-fyA on the cross section of the local generating line only of the optical surface A in the illumination optical system are appropriately set.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image display apparatus, for example, an optical element using a reflective liquid crystal display element as a display element for displaying image information for observation, and appropriately setting the image information displayed thereon. It is suitable for a head-mounted display (HMD), a glasses-type display, and the like, which are magnified and observed through a camera.

[0002]

2. Description of the Related Art Conventionally, a head mounted image observation apparatus (image display apparatus) for observing image information displayed on an image display element such as a liquid crystal as an enlarged virtual image, a so-called head mounted display (HMD). Are variously proposed.

[0003] Of these, an HMD using a reflective display element
However, for example, Japanese Patent Application Laid-Open No. 07-128614,
It is proposed in JP-A-1-127991, JP-A-11-337863, JP-A-2000-10041 and the like.

In the HMD proposed in these, light emitted from an illumination light source is reflected by a reflective liquid crystal, guided to an eyeball, and an enlarged image of an image displayed on the liquid crystal is observed. At this time, the light beam travels in the order of the illumination light source, the illumination optical system, the reflective liquid crystal, the display optical system, and the eyeball. JP-A-11-12
In the embodiment disclosed in the HMD proposed in Japanese Patent No. 5791, there is no illumination optical system, and light from the illumination light source directly illuminates the reflective liquid crystal. In this case, there is an example in which there is no shared surface between the illumination optical system and the display optical system. In this case, since it is necessary to prevent the light flux from the illumination light source from being shaken, a large space is required between the illumination light source and the reflective liquid crystal, and the size is easily increased. The embodiments of the other proposed publications have a common plane between the illumination optical system and the display optical system. If there is a common surface, the optical paths of the illumination optical system and the display optical system overlap with each other, so that it is easy to reduce the size. However, the greater the number of shared surfaces, the more complicated the optical system and the greater the light loss. On the other hand, HMD
The present inventor has proposed a compact display optical system of
No. 3551 proposes this. In this publication, the size of the entire apparatus is reduced by using a free-form surface prism. The present inventor has disclosed an HMD combining a free-form surface prism and a reflective display element with Japanese Patent Application Laid-Open Nos. 11-125791, 11-337863, and 2000-1004.
No. 1 proposes this.

[0005]

Conventionally, in an image observation apparatus such as an HMD, it is important to reduce the size and weight of the apparatus in order to mount the apparatus on the observer's head. I have. Another important issue is that the image information displayed on the display means can be observed well.

In order to reduce the size of the entire device when a reflection type liquid crystal display device is used as an image display device, it is necessary to appropriately incorporate a lighting device for illuminating the device in the device.

For example, when the light from the illumination light source illuminates the reflective liquid crystal, if the light passes through many reflective or transmissive surfaces or passes through a prism having a long optical path length, the light does not reach the reflective liquid crystal. Inevitably, the amount of light from the illumination light source is lost. Therefore, there is a demand for an HMD in which the loss of light amount is small and the display optical system and the illumination optical system are compact.

According to the present invention, when observing image information displayed on display means such as a liquid crystal display, an illumination optical system from a light source means to a display means and a light beam from the display means for guiding the light beam to an eyeball of an observer. By appropriately setting the configuration of the display optical system, an image observation device capable of observing the image information with good image quality while reducing the loss of light amount while reducing the size of the entire device, and a head mount using the same The purpose is to provide a display.

[0009]

An image display apparatus according to the present invention has a reflection type display means, an illumination light source means for illuminating the display means, and guides light from the illumination light source means to the display means. In an image display apparatus having an illumination optical system and a display optical system for guiding light from the display unit to an eyeball of an observer, an optical system having both transmission and reflection functions shared by the illumination optical system and the display optical system. The plane A has a curvature on a local meridional section (a plane including the incident light and the emitted light of the reference light beam emitted from the illumination light source means and passing through the center of the image and the center of the eyeball of the display means), and has a local curvature of the display optical system. Local_fy,
When the local meridional section focal length of only the optical surface A in the illumination optical system is local_fyA, 0.1 <local_fyA / local_fy <1.0 (1) is satisfied, and the light beam emitted from the illumination light source means Illuminating the display means by being reflected by the optical surface A, the reflected light from the display means being transmitted through the optical surface A this time, being reflected by a plurality of reflective surfaces, and then guided to the eyeball. Features.

A second aspect of the present invention is characterized in that, in the first aspect of the present invention, there is only one optical surface A having both transmission and reflection functions shared by the illumination optical system and the display optical system.

A third aspect of the present invention is characterized in that, in the first aspect of the present invention, the plurality of reflecting surfaces in the display optical system are eccentric curvature surfaces.

According to a fourth aspect of the present invention, in the display optical system according to the first aspect, the optical member including the optical surface A and another optical member having an optical refractive power are arranged with an air gap therebetween. It is characterized by being.

According to a fifth aspect of the present invention, in the first, second, third, or fourth aspect, the illumination light source means is an RGB time-division light source, and the display means is adapted to emit RGB color light of the RGB time-division light source. It is characterized in that RGB images are displayed in a time-division manner.

According to a sixth aspect of the present invention, in the third aspect, the display optical system includes two or more surfaces having different refractive powers depending on the azimuth angle, and the display optical system as a whole has a positive refractive power. .

[0015] The image display apparatus of the invention of claim 7 is claim 1.
6. The image display device according to any one of items 1 to 6, wherein:

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS.
It is principal part sectional drawing of FIG. In the figure, reference numeral 1 denotes a pupil position where the eyeball of the observer is located.

2 is a free-form surface prism (second optical member), 3 is a reflection type liquid crystal, 4 is an illumination light source, 5 is a transmission / reflection surface (optical surface) having a curvature composed of a half mirror, and 7 is a reflection surface. Boomerang-type lens including a 5 (first optical member)
Reference numerals 8 and 9 denote polarizing plates, 10 denotes an illumination prism, (first optical member) 11 denotes an illumination system correction prism, and 12 denotes an illumination system junction prism (first optical member), and the illumination prism 10 and the illumination system correction prism 11 And the structure which joined.

Reference numeral 17 denotes a first free-form surface mirror, and (second optical member) 18 denotes a second free-form surface mirror (second optical member).

Reference numerals 4, 5 or 4, 5, 10 constitute one element of the illumination optical system.
7, 2 or numbers 3, 10, 5, 11, 2, 17, 18 or numbers 3, 10, 5, 2 or numbers 3, 5, 7, 18, 1
Reference numeral 7 constitutes one element of the display optical system.

In this embodiment, in order to reduce the loss of the light amount from the illumination light source 4, the illumination light source 4 is brought as close as possible to the reflection type liquid crystal 3 to shorten the optical path length of the illumination optical system. When the free-form surface prism 2 is used for the display optical system, a member constituting an illumination optical system is provided between the free-form surface prism 2 and the reflective liquid crystal 3. In the case where two free-form mirrors 17 and 18 are used for the display optical system as shown in FIG. 8, a member constituting an illumination optical system between the free-form mirror system (17 and 18) and the reflective liquid crystal 3 is used. Is provided.

Prior to the description of each embodiment of the present invention, definitions of a bus bar section, a sagittal section, a local bus section, and a local sagittal section used in the present invention will be described. In the definition of the conventional system that does not correspond to the eccentric system, if the z axis is the optical axis in each surface vertex coordinate system, the yz section is the conventional meridional section (meridional section), and the xz section is the sagittal section (sagittal section). Become. Since the present invention is an eccentric system, a local meridional section and a local sagittal section corresponding to the eccentric system are newly defined. Light passing through the image center of the display means (the center of the external image when see-through for observing the external world) and the center of the eyeball (hereinafter referred to as reference light)
On the hit point (incident point) between each and the planes, the plane including the incident light and the outgoing light of the reference ray is defined as the local meridional section, and the hit line is perpendicular to the local meridional section including the hit point and is a sagittal line of each surface vertex coordinate system. A plane parallel to the cross section (normal sagittal section) is defined as a local sagittal section. When the display means is a reflection type, the reference light beam is extended to the illumination optical system and the illumination light source, and the local meridional section and the local sagittal section are defined on each hit point in the same manner as described above. The local meridional cross-sectional focal length and the local sagittal cross-sectional focal length will be described later in the examples. The features of the present invention will be described below.

Next, an embodiment of the present invention will be described. 1 to 8 are optical path cross-sectional views (local bus cross-sectional views) of Examples 1 to 8 of the present invention. Examples 1 to 5 are reflective LCDs
(Reflection type liquid crystal) 3 is of a type in which the light is illuminated with a light beam of almost normal incidence.
D3 is of a type illuminated with obliquely incident light. As a characteristic of a general liquid crystal (TN liquid crystal or the like), light emitted almost perpendicular to the liquid crystal surface has sufficient contrast and good image quality, but when the emitted light is inclined away from vertical,
It is known that the contrast is reduced and the image quality is deteriorated. In order to solve this, the former type (Examples 1 to 5) illuminates the light to the reflective LCD 3 with a vertically incident light beam. Further, ferroelectric liquid crystal (FLC) and the like have different characteristics, and the contrast does not decrease even when the light is emitted obliquely at a considerable angle, so that good image quality can be observed from almost any angle. Therefore, the latter type (Examples 6 to 8)
Supposes this liquid crystal (FLC), illuminates the reflection type LCD 3 with light obliquely incident light, thins the entire optical system, and obtains a high-quality image without a drop in contrast. In Examples 1 to 5, a ferroelectric liquid crystal (FLC) may be used.

FIGS. 1 and 2 (Examples 1 and 2) show a reflection type LC.
A boomerang-type lens 7 is disposed between D3 (the back surface is a liquid crystal surface) and the free-form surface prism 2 including an arbitrary curved surface (hereinafter, the lens 7 having the shape of FIGS. This is called a boomerang type lens). Light emitted from a planar illumination light source 4 having a plurality of RGB (red light, green light, and blue light) LEDs is linearly polarized by a polarizing plate 8 and an optical surface of a boomerang type lens 7 on the liquid crystal 3 side. 5
The light beam is reflected by the (half mirror), and the principal ray of the light beam is incident on the reflection type LCD 3 almost perpendicularly (± 10 °). Reflection L
The light reflected by the CD 3 passes through the optical surface 5 this time, exits the boomerang-type lens 7, and then enters the polarizing plate 9. At this time, the polarization direction of the light linearly polarized by the polarizing plate 8 rotates inside the liquid crystal (liquid crystal driving voltage OFF or ON).
The polarizing plate 9 needs to be set in a direction in which the light whose polarization direction is rotated passes. When the linear polarization direction of the polarizing plate 9 is shifted from the linear polarization direction of the polarizing plate 8 by about 90 degrees (the rotation of the polarization direction inside the liquid crystal is 90 degrees), the light linearly polarized by the polarizing plate 8 Although there is light (ghost light) that is transmitted without being reflected by the surface 5 (half mirror), since the ghost light can be cut by the polarizing plate 9, an added value for preventing the ghost light from entering the eyeball E is also created. In a type in which the reflective LCD 3 displays a single polarizing plate (not shown) near the display surface side,
The polarizing plates 8 and 9 become unnecessary. After emitting the polarizing plate 9,
The light enters the entrance surface 14 of the free-form surface prism 2, is totally reflected by the total reflection surface (transmission surface B) 6, is reflected by the concave mirror 13, and is transmitted by the total reflection surface (transmission surface B) 6. It is guided to the pupil 1 where the eyeball of the observer is located. Thereby, the reflection type L
The image information based on CD3 is observed as an enlarged virtual image. In the first and second embodiments, the boomerang-type lens 7 having a curvature surface facing both sides of the reflective LCD 3 on the local meridional cross section is disposed opposite to the reflective LCD 3.
By making the surface of the boomerang type lens 7 on the reflection type LCD 3 side the optical surface (half mirror) 5, the reflection type LCD 3
Lowermost peripheral image (F3) on the cross section of the local bus 3
The distance between the reflective LCD 3 on the side and the free-form surface prism 2 is made as short as possible to make the display system (members 3, 7, 2) compact and the illumination system (members 4, 5) compact. In the first embodiment shown in FIG.
Surfaces 5 and 5a are cylindrical surfaces (free-form surfaces) having power only in the generatrix section, thereby minimizing the occurrence of aberrations on the local sagittal section (section perpendicular to the paper surface), and in the sagittal section or local sagittal section. Since there is no power in the direction and the surface shape does not curve in this cross-sectional direction, the reflection type LCD 3 and the optical surface 5 can be made close to each other, and the size can be reduced. Also, the other surface 5a has a surface shape close to the optical surface 5 to cancel the occurrence of aberration in the boomerang lens 7. Of course, on both sides of boomerang type lens 7,
If a free-form surface having a weak power in the local sagittal section direction and a strong power in the local meridional section direction is used, the same effect can be obtained, and further excellent optical performance can be obtained.

In the second embodiment shown in FIG.
Rotationally symmetric aspheric surfaces are used for both surfaces 5, 5a. This is to make the light source 4 for planar illumination smaller in the local sagittal section direction by giving a positive power even on the local sagittal section of the optical surface 5. Also, the other surface 5a has a surface shape close to the optical surface 5 to cancel the occurrence of aberration in the boomerang lens 7. Note that although a two-sided rotationally symmetric spherical surface is possible, a two-sided rotationally symmetric aspherical surface has better optical performance.

The free-form surface prism included in the display system of the present invention (common to the first to seventh embodiments) employs a free-form surface for the concave mirror 13 having the main power (positive refracting power) of the free-form surface prism. The occurrence of eccentric aberration on the surface is reduced. The eccentric aberration that cannot be completely corrected by the main power surface is corrected by making the total reflection surface (transmission surface B) 6 close to the main power surface into a free-form surface so that the aberration is canceled. This alone can correct the aberration to some extent, but in order to further balance the overall aberration, the entrance surface 14 near the display means (reflection type LCD) 3 is formed into a free-form surface to achieve a good balance of the overall aberration. On the total reflection surface (transmission surface B) 6, the total reflection surface condition (critical angle condition) is such that light is totally reflected when the light is incident at an angle greater than the critical angle, and is emitted when the light is incident at an angle less than the critical angle. ) Enables a bright display optical system with no light amount loss in principle.

FIGS. 3 and 4 are sectional views of the optical paths of the third and fourth embodiments of the present invention. An illumination system prism 10 including the optical surface 5 and an illumination system correction prism 11 are joined and arranged between the reflective LCD 3 and the free-form surface prism 2. The illumination prism 10 and the illumination system correction prism 11 constitute an illumination system cemented prism 12 having almost no power on the local meridional line / local sagittal section in the display optical system. In this way, the illumination system junction prism 1 in the display system (3, 10, 11, 2)
2, the optical performance of the display system can be improved. As the optical path, light from the planar illumination light source 4 enters the illumination system prism 10, and the principal ray reflected by the optical surface 5 (half mirror) is substantially perpendicularly incident on the reflection type LCD 3 and reflected, and is reflected by the illumination system prism 10. Re-incident, optical surface 5
(Half mirror), passes through the illumination system correction prism 11, enters the entrance surface 14 of the free-form surface prism 2, is totally reflected by the surface 6, and passes through the reflection surface 13 and the transmission surface 6 to form an eyeball E. It is led to. In this embodiment, a reflection type LCD of a single polarizing plate type (not shown) is used. When two polarizing plates are used, as in the first and second embodiments, they are arranged immediately after the plane illumination light source 4 and immediately before the incident surface 14 of the free-form surface prism 2 at the angle of the polarization direction as described above. Example 3
Surface 15 of illumination system prism 10 and illumination system correction prism 1
Both surfaces of the first surface 16 are flat surfaces, and the joined optical surfaces 5 are cylindrical surfaces. Since the cylindrical surface has no power in the sagittal section or local sagittal section direction, the thickness of the illumination system junction prism 12 can be reduced. In the fourth embodiment, both the surface 15 of the illumination system prism 10 and the surface 16 of the illumination system correction prism 11 are curved surfaces to cancel aberrations generated by the free-form surface prism 2. The two joined optical surfaces 5 are rotationally symmetric aspherical surfaces, and have a positive power on the local sagittal section, thereby reducing the size of the planar illumination light source 4 in the local sagittal section direction.

FIG. 5 is an optical path sectional view of Embodiment 5 of the present invention.

FIG. 5 shows that only the illumination system prism 10 including the optical surface 5 is inserted between the reflective LCD 3 and the free-form surface prism 2. In the optical path, light from the planar illumination light source 4 enters the illumination system prism 10, is reflected by the optical surface 5 (half mirror), and the principal ray is almost perpendicularly incident and reflected on the reflection type LCD 3, and re-enters the illumination system prism 10. This time, the light passes through the optical surface 5 (half mirror), enters the entrance surface 14 of the free-form surface prism 2, is totally reflected by the surface 6, and is guided to the eyeball E via the reflection surface 13 and the transmission surface 6. In this embodiment, one polarizing plate type reflection type LCD 3 (not shown) is used. When two polarizing plates are used, as in the first and second embodiments, they are arranged immediately after the plane illumination light source 4 and immediately before the incident surface 14 of the free-form surface prism 2 at the angle of the polarization direction as described above. In this embodiment, since the illumination system correction prisms 11 of the third and fourth embodiments are not required, the interval between the free-form surface prism 2 and the reflection type liquid crystal 3 can be shortened, and the size can be reduced. The optical surface 5 uses a cylindrical surface having no power on the sagittal section to suppress the occurrence of aberration on the local sagittal section. FIGS. 6 and 7 (Examples 6 and 7) show the reflective LCD 3. A boomerang lens 7 is arranged between the free-form surface prism 2 and the free-form surface prism 2. The configuration is different from Embodiments 1 and 2 in that it is a reflective LCD.
3 is that the angle of incidence of the illumination light beam is not perpendicular but obliquely incident. Light emitted from a light source 4 for planar illumination having a plurality of RGB LEDs is a polarizing plate 8.
Is reflected by the optical surface 5 (half mirror) of the boomerang type lens 7 on the liquid crystal side, and obliquely enters the reflective LCD 3. The light reflected in the oblique direction by the reflective LCD 3 is transmitted through the optical surface 5 this time, exits the boomerang lens 7, and then enters the polarizing plate 9. At this time, since the polarization direction of the light linearly polarized by the polarizing plate 8 rotates inside the liquid crystal (liquid crystal driving voltage OFF or ON), it is necessary to set the polarizing plate 9 to a direction in which the light having the rotated polarization direction passes. . Polarizing plate 9
Is different from the linear polarization direction of the polarizing plate 8 by about 90 degrees (the rotation of the polarization direction inside the liquid crystal is 90 degrees)
There is light (ghost light) in which light linearly polarized by the polarizing plate 8 is transmitted without being reflected by the optical surface 5 (half mirror), but since the ghost light can be cut by the polarizing plate 9, There is also added value for preventing ghost light from entering the eyeball E. A reflection type LCD 3 is provided near the display surface side (not shown).
In the type in which display is performed by using two polarizing plates, the polarizing plates 8 and 9 are not required. After exiting the polarizing plate 9, the light enters the entrance surface 14 of the free-form surface prism 2, is totally reflected by the total reflection surface (transmission surface B) 6, is reflected by the concave mirror 13, and is now total reflection surface (transmission surface B) 6. And is guided to the eyeball 1. In the sixth and seventh embodiments, the boomerang-type lens 7 having a curvature surface in which the two surfaces face in the opposite direction to the reflective LCD 3 on the local meridional section.
Is placed facing the reflective LCD 3 and the surface of the boomerang lens 7 on the reflective LCD side is the optical surface 5 (half-me).
As a result, the distance between the reflective LCD 3 on the lowermost peripheral image (F3) side and the free-form surface prism 2 on the local meridional section of the reflective LCD 3 is made as short as possible, and the display system (3, 7,2) is compact and the lighting system (4,4)
5) is also compact. In addition, by illuminating the obliquely incident light beam, the amount of tilt eccentricity (clockwise rotation) on the local meridional section of the reflective LCD 3 can be increased, so that the protrusion of the reflective LCD 3 can be reduced and the entire optical system is thinned. In Embodiments 6 and 7, both surfaces 5, 5a of the boomerang type lens 7 are cylindrical surfaces having power only in the meridional section, minimizing the occurrence of aberration on the local sagittal section and reducing the sagittal section or local sagittal section. Since there is no power in the direction and the surface shape does not curve in this cross-sectional direction, the reflection type LCD 3 and the optical surface 5 can be made close to each other, and the size can be reduced. And the other side 5
Also, a has a surface shape close to the optical surface 5 so as to cancel the occurrence of aberration in the boomerang type lens 7. Of course, if a free-form surface having low power in the local sagittal section direction and strong power in the local meridional section direction is used, the same effect can be obtained, and further excellent optical system performance can be obtained. In the seventh embodiment, the curvature of the optical surface 5 (cylindrical surface) of the boomerang-type lens 7 on the local meridional section is set to be smaller than that in the sixth embodiment, and the reflection type LCD 3 and the planar illumination light source 4 are sufficient. Try not to interfere.

FIG. 8 (Embodiment 8) uses two free-form surface mirrors 17 and 18. In this embodiment, the reflection type LCD 3
The boomerang lens 7 is arranged between the optical path of the mirror and the free-form surface mirror 18. As in Embodiment 6, the reflection type L
The incident angle of the illumination light beam on the CD 3 is oblique incidence.
Light emitted from a light source 4 for planar illumination having a plurality of RGB LEDs is linearly polarized by a polarizing plate 8,
The light is reflected by the optical surface 5 (half mirror) of the boomerang type lens 7 on the liquid crystal side, obliquely enters the reflective LCD 3,
The light obliquely reflected by the CD 3 is transmitted through the optical surface 5 this time, exits the boomerang-type lens 7, and then enters the polarizing plate 9. At this time, since the polarization direction of the light linearly polarized by the polarizing plate 8 rotates inside the liquid crystal (liquid crystal driving voltage OFF or ON), it is necessary to set the polarizing plate 9 to a direction in which the light having the rotated polarization direction passes. . When the linear polarization direction of the polarizing plate 9 is shifted from the linear polarization direction of the polarizing plate 8 by about 90 degrees (the rotation of the polarization direction inside the liquid crystal is 90 degrees), the light linearly polarized by the polarizing plate 8 Although there is light (ghost light) that is transmitted without being reflected on the surface 5 (half mirror), the ghost light can be cut off by the polarizing plate 9, so that an added value for preventing ghost light from entering the eyeball is also created. In the type in which the reflective LCD 3 displays a single polarizing plate (not shown) near the display surface, the polarizing plates 8 and 9 are not required. After exiting the polarizing plate 9, the light is incident on and reflected by a free-form surface mirror 18 as a half mirror, reflected by another free-form surface mirror 17, transmitted through the free-form surface mirror 18 as a half mirror, and passes through the eyeball 1.
It is led to. In the eighth embodiment, a boomerang-type lens 7 having a curvature surface facing both sides of the reflective LCD 3 on the local meridional cross section is disposed facing the reflective LCD 3, and the boomerang lens 7 is located on the reflective LCD 3 side. Is used as the optical surface 5 (half mirror), the reflection type L
Lowermost peripheral image (F) on the local generatrix section of CD3
The distance between the reflective LCD 3 on the 3) side and the free-form surface mirrors 17 and 18 is made as short as possible, and the display system (3, 7, 17, 17
18) is compact and the illumination system (4, 5) is also compact. Also, the illumination of the obliquely incident light beam allows
Since the amount of tilt eccentricity (clockwise direction) on the local meridional section of the reflective LCD 3 can be increased, the reflective LCD 3
3 can be reduced and the entire optical system can be made thinner. In the eighth embodiment, both surfaces of the boomerang type lens 7 (5, 5
a) is a cylindrical surface having power only in the meridional section, minimizing the occurrence of aberrations in the local sagittal section, and has no power in the sagittal section or local sagittal section direction, and the surface shape is curved in this sectional direction. Therefore, the reflection type LCD 3 and the optical surface 5 can be close to each other, and the size can be reduced. Also, the other surface 5a has a surface shape close to the optical surface 5 to cancel the occurrence of aberration in the boomerang lens 7. Of course, if a free-form surface having a low power in the local sagittal section direction and a high power in the local meridional section direction is used, the same effect can be obtained, and further excellent optical system performance can be obtained.

In the image display apparatus according to the present invention, the illumination optical system and the display optical system have an optical surface A having both transmission and reflection functions shared by both, and the optical surface A has a local meridional section (the illumination means). And a focal length in the local meridional section of the display optical system is local_fy, and the illumination has a curvature on a plane including the incident light and the emitted light of the reference light beam emitted from the display means and passing through the center of the image and the center of the pupil. When the focal length of only the optical surface A in the local meridional section in the optical system is defined as local_fyA, 0.1 <local_fyA / local_fy <1.0 is satisfied, and the light beam emitted from the illuminating means is transmitted through the optical surface. The display means is illuminated through an illumination optical system using A as a reflection surface, and the reflected light from the display means is transmitted to the optical surface A, reflected by a plurality of reflection surfaces, and then guided to the eyeball. .

Here, the display optical system is from the reflection type liquid crystal 3 as the display means to the surface immediately before the eyeball E. The illumination optical system extends from the illumination light source 4 to the surface immediately before the display means (reflection type liquid crystal) 3. The description of the focal length at the local meridional cross section is described in the section of Examples.

The optical surface 5 (A) is a half mirror,
When the lower limit of conditional expression (1) is exceeded, when the light from the illumination light source illuminates the reflective liquid crystal 3 almost vertically as shown in FIG. Becomes stronger and the concave of the optical surface A of the concave mirror becomes deeper, so that the distance between the liquid crystal surface and the optical surface A on the reference light beam must be longer, and the device becomes larger in this direction. As for the upper limit, when the light from the illumination light source illuminates the reflective liquid crystal obliquely as shown in FIG. 6, the power of the optical surface A is weakened. ) Is not only required, but also the size is increased because the planar illumination light source is arranged away from the optical surface A. When the distance between the planar illumination light source and the optical surface A is left as it is,
The imaging relationship between the planar illumination light source and the eyeball (Keiler illumination) is broken, and the light use efficiency is reduced. If it exceeds the upper limit, it will be either one. Further, when the following conditional expression is further satisfied for the upper limit value, 0.1 <local_fyA / local_fy <0.85 (1a) The planar illumination light source does not separate from the optical surface A, and the connection between the planar illumination light source and the eyeball. The image relationship (Kayler illumination) is also well-balanced without breaking down. The optical surface A in the illumination optical system
Is a curvature reflecting surface having a positive refractive power on the local meridional section. Since the illumination light source can be illuminated with the reflective liquid crystal by enlarging the illumination light source with a positive curvature reflection surface, a small illumination light source can be used and the illumination optical system itself can be made compact. In addition, it is desirable that the illumination light source and the eyeball have an image-forming relationship (Keiler illumination) as much as possible to enhance the light use efficiency.

In the present invention, the optical surface A having power may have a plurality of surfaces, but by using only one surface, the optical path length from the illumination light source to the reflection type liquid crystal can be shortened, so that compactness is possible. Becomes

With respect to the display optical system, the light from the reflection type liquid crystal passes through the optical surface A which is a half mirror, and the display optical system is thinned by folding the light beam on the plurality of reflection surfaces. Further, when the plurality of reflecting surfaces are eccentric curvature surfaces, the plurality of reflecting surfaces themselves have power, so that a separate refractive lens or the like is not required, and if the amount of eccentricity of the curvature reflecting surface is appropriately set, compactness can be achieved. A simple display optical system can be obtained.

In the present invention, the distance between the optical member (first optical member) including the optical surface A in the display optical system and another optical member having optical refracting power (second optical member) is set. Air and
During this time, a polarizing plate can be inserted. The current usage of reflection type liquid crystal is often to use one polarizing plate in an illumination optical system and another polarizing plate in a display optical system. However, in the display optical system, the distance from the reflective liquid crystal to the polarizing plate in the display optical system has an optically parallel two-correlation relationship. Is undesirably observed with eyes. Further, even if the material has a weak birefringence, if the optical path length of the material is long, the photoelasticity of the material is still visually observed. Therefore, when a polarizing plate for a display optical system is placed at the position as described above, since the optical path length of only the optical member including the optical surface A is short, glass having no birefringence or a molding material having low birefringence can be used. . Another optical member having an optical refractive power can be used with any material because it has been involved in the parallel nicols.

In the image display device of the present invention, it is preferable to satisfy one or more of the following conditions in order to observe image information favorably while further reducing the size of the entire device.

(A-1) The illumination light source is an RGB time-division light source that emits polychromatic light such as red, green and blue in a time-division manner, and the display means is adapted to emit light of RGB color light of the RGB time-division light source. This is to display an RGB image in a time-division manner.
At the time of color display in the general filter system, since a three-color RGB color filter is provided in front of the liquid crystal, one-third of the total number of pixels is the actual number of color display pixels. However, when a combination of the above-mentioned reflective liquid crystal of the time-division display and three kinds of LEDs (RGB) is used, the total number of pixels is only 1/3 of the color filter type liquid crystal. And the size of both the illumination optical system and the display optical system can be reduced accordingly.

(A-2) In an optical system having an eccentric curvature reflecting surface, rotationally asymmetric eccentric aberration occurs in a screen.
Therefore, the display optical system includes two or more surfaces having different refractive powers depending on the azimuth angle, and the display optical system as a whole has a positive refractive power. By adopting a surface (free-form surface) having a different refractive power depending on the azimuth angle, it is possible to correct rotationally asymmetric eccentric aberration. By using two or more free-form surfaces, it is possible to correct the local optical axis of the display optical system. The focal length of the entire positive system on the sagittal section can be made substantially equal, and enlarged projection can be performed at the same ratio as the aspect ratio of the liquid crystal.

(A-3) The optical surface 5 is a cylindrical surface (free-form surface) having no power in the sagittal section or local sagittal section direction and having power only in the generatrix section. Since the cylindrical surface has a different refractive power depending on the azimuth angle, it is one of free-form surfaces. In the present invention, when either the sagittal section or the generatrix section has no refractive power,
Hereinafter, the surface is referred to as a cylindrical surface, and the other surfaces are hereinafter referred to as free-form surfaces. When a cylindrical surface is used, there is no power on the local sagittal cross section, so that aberration generation on this cross section can be minimized and the surface shape does not curve in the sagittal cross section or local sagittal cross section direction. The display means and the optical surface 5 can be close to each other, and the size can be reduced. Of course, if a free-form surface having a low power in the local sagittal section direction and a high power in the local meridional section direction is used, the same effect can be obtained, and further excellent optical system performance can be obtained.

Next, the local paraxial axis used in each embodiment of the present invention will be described. 1 to 8 are cross-sectional views of main parts (local meridional cross-sectional view, suffix y) of Numerical Examples 1 to 8 to be described later of the present invention. As shown in FIG. In the present invention, the surface vertex of each surface is defined as y
Since only the shift eccentricity in the axial direction and the tilt eccentricity around the x-axis are performed, the conventional generatrix section and the local generatrix section are the same, but the conventional sagittal section and the local sagittal section of each surface are different. The conventional bus section and sagittal section described above are the definitions of the conventional paraxial (general-paraxial axis), and the local bus section and local sagittal section are the definitions of the local paraxial (local-paraxial axis) to be described later. is there. In the local paraxial direction, definitions of a local radius of curvature, a local surface distance, a local focal length, and a local refractive power corresponding to an eccentric system will be described below.

In the present invention, a light ray emitted from the illumination light source means 4 and passing through the image center 3a of the display means 3 and the center 1a of the eyeball 1 is defined as a reference light ray La. Not the focal length and the refractive power, but the local curvature radius based on the hit point (incident point) on each surface of the reference light beam, the local surface distance, the local focal length, and the local refractive power are used.

Here, the local radius of curvature refers to a local radius of curvature on the hit point point of the optical surface (a radius of curvature on a local meridional section, a radius of curvature on a local sagittal section). The local plane interval refers to the value of the distance between the two hit points between the current plane and the next plane (the distance on the reference ray, a value without air conversion). The local focal length is a value calculated by a conventional focal length calculation method (paraxial tracking) from the local radius of curvature, the refractive index before and after the surface, and the local surface interval. The local refractive power is a reciprocal value of the local focal length.

In each embodiment of the present invention, the radius of curvature, the surface interval, the eccentricity, the refractive index, and the Abbe number, and the local radius of curvature, the surface refractive index, the local surface interval, and the local focal length are shown. .

In the present invention, eight embodiments have been described. Numerical data of Examples 1 to 8 are shown in Tables 1 to 8, and optical path sectional views are shown in FIGS. In the conventional paraxial of Tables 1 to 8, (genera
l-paraxial axis), meridional section curvature radius ry, sagittal section curvature radius rx, surface spacing d (parallel to the surface vertex coordinate system of the first surface), eccentricity (surface vertex coordinates of the first surface on the meridional cross section) Shift parallel eccentricity of surface vertices of each surface with respect to the system, tilt eccentricity is tilt degrees) d-line refractive index nd, Abbe number vd
Where FFS is a free-form surface, YTO is a cylindrical surface having a refractive power only in the cross section of the generatrix, and AL is an aspherical surface. Also, the one with M is a reflection surface, and the refractive index nd of the d-line is the opposite sign. Tables 1 to 8 show numerical data of the reverse trace from the eyeball to the liquid crystal and the illumination light source. The sign is positive when the chief ray travels from left to right, and negative when the principal ray is opposite.

The definition formula of FFS (free-form surface) is shown below. (In the surface vertex coordinate system of each surface) z = 1/2 * (1 / a + 1 / b) * (y ² * cos (c) ² + x ² ) / cos (c) / (1 + 1 / 2 * (1 / a
-1 / b) * y * sin (c) + (1+ (1 / a-1 / b) * y * sin (c)-(1 / a / b + 1/4 * tan (c) ² * (1 / a + 1 / b) ² ) * x ² )
^(1/2) ) + c20 * x ² + c11 * x * y + c02 * y ² + c30 * x ³ + c21 * + c03 * y ³ + c40 * x ⁴ + c31 * x ³ * y + c22 * x ² * y ² + c13 * x * y ³ + c04 * y ⁴ + c50 * x ⁵ + c41 * x ⁴ * y + c32 * x ³ * y ² + c23 * x ² * y ³ + c14 * x * y ⁴ + c05 *
y ⁵ + c60 * x ⁶ + c51 * x ⁵ * y + c42 * x ⁴ * y ² + c33 * x ³ * y ³ + c24 * x ² * y ⁴ + c15
* x * y ⁵ + c06 * y ⁶ Each of a, b, c, c20, c11, c02... is a free-form surface coefficient. (Note: In the case of this free-form surface, the coefficients of the free-form surface are related to the paraxial axis. Does not coincide with the radius of curvature of the cross section of the main line ry and the radius of the cross section of the sagittal line rx. Is defined by the following aspherical formula with the generatrix section (in the surface vertex coordinate system of each surface)

[0046]

(Equation 1)

The sagittal section is a plane (rx = ∞).

The definition formula of AL is a rotationally symmetric aspherical surface (in the surface vertex coordinate system of each surface).

[0049]

(Equation 2)

Also, a local-paraxial axis
Then, local radius of curvature local-ry, local-rx, local surface distance local-d (reflection surface has opposite sign), local focal length loc
al-fy, local-fx ・ Refractive index nd of surface (reflection surface has opposite sign)
Is shown. Also, the hit point coordinates (the surface vertex is 0,0) on each surface, the local focal length and angle of view of the entire display optical system, and the local focal length of the illumination optical system optical surface A are shown.

[0051]

[Table 1]

[0052]

[Table 2]

[0053]

[Table 3]

[0054]

[Table 4]

[0055]

[Table 5]

[0056]

[Table 6]

[0057]

[Table 7]

[0058]

[Table 8]

[0059]

[Table 9]

[0060]

[Table 10]

[0061]

[Table 11]

[0062]

[Table 12]

[0063]

[Table 13]

[0064]

[Table 14]

[0065]

[Table 15]

[0066]

[Table 16]

[0067]

[Table 17]

[0068]

[Table 18]

[0069]

[Table 19]

[0070]

[Table 20]

[0071]

[Table 21]

[0072]

[Table 22]

[0073]

[Table 23]

[0074]

[Table 24]

[0075]

[Table 25]

FIG. 9 is an explanatory view when a pair of image display devices S of the respective embodiments of the present invention are provided for the left and right eyes of the observer SA to form a binocular head mounted display. is there.

In the present invention, for example, if binocular parallax is used as an image displayed on the display device, an image observation system capable of stereoscopic viewing can be constructed.

It is needless to say that a monocular HMD in which only one unit is provided for either the left or right eye, not necessarily for both eyes, may be used.

[0079]

According to the present invention, when observing image information displayed on display means such as a liquid crystal display as described above,
By appropriately setting the configuration of the illumination optical system from the light source means to the display means and the display optical system for guiding the luminous flux from the display means to the eyeball of the observer, the amount of light can be reduced while reducing the size of the entire apparatus. An image observation device capable of reducing loss and observing the image information with good image quality and a head-mounted display using the same can be achieved.

In particular, according to the present invention, an HMD using a reflection type LCD, which has a small light quantity loss from an illumination light source, provides an image with sufficient contrast, and has a compact illumination optical system and a display optical system, can be achieved. be able to.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part according to a first embodiment of the present invention.

FIG. 2 is a sectional view of a main part according to a second embodiment of the present invention.

FIG. 3 is a sectional view of a main part of a third embodiment of the present invention.

FIG. 4 is a sectional view of a main part of a fourth embodiment of the present invention.

FIG. 5 is a sectional view of a main part according to a fifth embodiment of the present invention.

FIG. 6 is a sectional view of a main part according to a sixth embodiment of the present invention.

FIG. 7 is a sectional view of a main part of a seventh embodiment of the present invention.

FIG. 8 is a sectional view of a main part according to an eighth embodiment of the present invention.

FIG. 9 is a schematic diagram of a main part when the image display device of the present invention is applied to an HMD.

[Explanation of symbols]

1 Eyeball 2 Free-form surface prism 3 Reflection type LCD (The figure shows the protection plate of the LCD,
The liquid crystal plane exists on the focus plane. 4) Illumination light source (plane light source) 5 Optical surface A 6 Transmission surface B (total reflection surface of free-form surface prism) 7 Boomerang type lens 8 Polarizing plate 1 9 Polarizing plate 2 10 Illumination prism 11 Illumination correction prism 12 Illumination system bonding Prism 13 Concave mirror of free-form surface prism 14 Incident surface of free-form surface prism 15 Illumination system junction prism surface 1 16 Illumination system junction prism surface 2 17 Free-form surface mirror 1 18 Free-form surface mirror 2

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G02F 1/13 505 G02F 1/13 505 1/13357 H04N 5/64 511A H04N 5/64 511 G02F 1/1335 530 F term (reference) 2H042 CA01 CA12 CA17 DB14 DD10 DE00 2H087 KA24 RA41 RA45 TA01 TA03 TA04 2H088 EA10 HA21 HA22 HA23 HA24 HA28 MA02 MA06 2H091 FA14Z FA15X FA21X FA26X FA41X LA11 LA15 LA17 MA02

Claims (7)

[Claims] 1. A reflection type display means, an illumination light source means for illuminating the display means, an illumination optical system for guiding light from the illumination light source means to the display means, and an observer transmitting light from the display means to an observer. In an image display device having a display optical system for guiding the eye to the eye, an optical surface A having both transmission and reflection functions shared by the illumination optical system and the display optical system has a local meridional section (emitted from the illumination light source means). The display means has a curvature on a plane including the incident light and the emitted light of the reference light beam passing through the center of the image and the center of the eyeball, and the focal length of the local meridional section of the display optical system is loc.
al_fy, when the local meridional section focal length of only the optical surface A in the illumination optical system is local_fyA, 0.1 <local_fyA / local_fy <1.0 (1) is satisfied, and the light is emitted from the illumination light source means. Light rays are reflected by the optical surface A to illuminate the display means, and the reflected light from the display means is transmitted to the optical surface A this time, is reflected by a plurality of reflective surfaces, and is then guided to the eyeball. An image display device characterized by the above-mentioned. 2. An optical surface A according to claim 1, which has both transmission and reflection functions shared by said illumination optical system and said display optical system.
Wherein only one surface is present. 3. The image display device according to claim 1, wherein the plurality of reflection surfaces in the display optical system are eccentric curvature surfaces. 4. The display optical system according to claim 1, wherein the display optical system includes an optical member including the optical surface A and another optical member having optical refracting power, which are arranged with an air gap therebetween. Characteristic image display device. 5. The light source device according to claim 1, wherein said illumination light source means is an RGB time division light source, and said display means is an RGB light source.
An image display device for displaying an RGB image in a time-sharing manner in accordance with the emission of RGB color light from a B-time-sharing light source. 6. The image display device according to claim 3, wherein the display optical system includes two or more surfaces having different refractive powers depending on the azimuth angle, and the display optical system as a whole has a positive refractive power. 7. A head-mounted display comprising the image display device according to claim 1. Description: