JP2002107656A - 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 head-mounted display which enables excellent observation of picture information displayed by a reflection type liquid crystal display element while realizing the miniaturization of the entire 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 eccentric curvature reflection surfaces to guide the light from the display means to a pupil for observation, and only one optical surface A having both transmitting and reflecting actions exists which is held in common by the illumination optical system and the display optical system, and an angle formed by an incident reference light beam obtained when making 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 incident on the optical surface A from the illumination means and a reflected reference light beam obtained when reflecting the reference light beam is appropriately set to α (degrees).

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 reflection type 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-11-1
In the embodiment disclosed in the HMD proposed in Japanese Patent No. 25791, there is no illumination optical system, and light from an illumination light source directly illuminates a reflective liquid crystal. In this case, there is no shared surface between the illumination optical system and the display optical system. However, in other known examples, a common plane is provided between the illumination optical system and the display optical system. If there is a shared surface, there is naturally a place where the optical path overlaps between the illumination optical system and the display optical system, and the more this shared surface is, the more complicated the optical system becomes. On the other hand, the present inventors have proposed a compact display optical system of the HMD in Japanese Patent Application Laid-Open No. 7-333551. The present inventor has disclosed an HMD in which a free-form surface prism and a reflective display element are combined, as disclosed in Japanese Patent Application Laid-Open Nos.
No. 337863 and Japanese Patent Application Laid-Open No. 2000-10041.

[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 light from an illumination light source illuminates a reflective liquid crystal, the light arrives at the reflective liquid crystal if it passes through many reflective or transmissive surfaces or passes through a prism having a long optical path. Before the operation, the light amount from the illumination light source is inevitably lost. In addition to the transmission type liquid crystal and the reflection type liquid crystal, as a characteristic of a general liquid crystal (TN liquid crystal or the like), light emitted almost perpendicular to the liquid crystal surface has a sufficient contrast and good image quality. When the emitted light is inclined away from the vertical, the contrast is lowered and the image quality is deteriorated. Therefore, it is desirable that the light from the illumination light source be designed so that the light emitted from the liquid crystal is emitted as vertically as possible. Needless to say, compact illumination optical systems and display optical systems are desired.

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. There is only one surface A, and a reference ray emitted from the illumination light source means and passing through the image center and the eyeball center of the display means enters the optical surface A from the illumination light source means, and is reflected by the optical surface A. Angle α between the incident reference ray and the reflected reference ray
(Degree) is reflected under the following conditions, is substantially perpendicularly incident on the display means, is transmitted through the optical surface A, is reflected by a plurality of eccentric curvature reflecting surfaces, is guided to the eyeball, and the display optical system is the optical system. Surface A
And another optical member having an optical refracting power is disposed with an air gap therebetween.

20 <α <80 (1) In the first aspect of the present invention, the optical surface A in the illumination optical system may have a local meridional section (the reference light beam). (A surface including the incident light and the outgoing light) has a curvature reflecting surface having a positive refractive power.

According to a third aspect of the present invention, in the first aspect of the present invention, the illuminating light source means is an RGB time-division light source, and the display means is an RGB time-division light source in accordance with the emission of RGB color light. The image is displayed in a time-division manner.

According to a fourth aspect of the present invention, in the first aspect of the present invention, the incident angle β (degree) of the reference light beam emitted from the illumination light source means to the reflective display means is -10 <β. <10 ... (2)

According to a fifth aspect of the present invention, in the second aspect of the present invention, the local optical line cross-sectional focal length of only the optical surface A in the illumination optical system is defined as local_fy, Where <local_fyA> / <local_fyA / local_fy <0.6 (3)

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

According to a seventh aspect of the present invention, in the sixth aspect of the present invention, the most peripheral image on the local meridional section of the display means (the plane including the incident light and the emitted light of the reference light) A ray passing through the outermost peripheral image on the far side from the eyeball and the center of the eyeball is defined as an F3 eyeball center ray, and the focal length of the entire system local bus cross section of the display optical system on the F3 eyeball center ray is defined as
local_fy (F3) is the local focal plane cross-sectional focal length at the point where the F3 eyeball center ray hits on the transmission surface B having the refractive power closest to the eyeball.
When (F3), -0.6 <local_fy (F3) / local_fyB (F3) <-0.1 (4)

An eighth aspect of the present invention provides a head mounted display having the image display device according to any one of the first to seventh aspects.

[0017]

1 to 5 show a first embodiment of the present invention.
It is principal part sectional drawing of No.-5. 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 reflective 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. 5, a boomerang-type lens (first optical member), 8 and 9 are polarizing plates, 10 is an illumination prism (first optical member) 11, an illumination correction lens, and 12 is an illumination junction prism (first optical member). The illumination prism 10 and the illumination system correction prism 11 are joined together.

Reference numerals 4, 5 or 4, 5, 10 constitute one element of the illumination optical system.
7,2 or number 3,10,5,11,2 or number 3,1
Elements indicated by 0, 5, and 2 constitute 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. A free-form surface prism 2 is used for a display optical system, and a member constituting an illumination optical system is provided between the free-form surface prism and the reflective liquid crystal 3. Further, the contrast of the image quality is increased by making the light emitted from the liquid crystal 3 as vertical as possible.

Prior to the description of each embodiment of the present invention, a cross section of a meridional line, a cross section of a sagittal line, a cross section of a local meridional line used in the present invention,
The definition of the local sagittal section 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. At the hit point (incident point) between the image center of the display means (the center of the external image in the case of see-through for observing the outside world and the center of the eyeball) and the center of the eyeball (hereinafter referred to as the reference ray), the reference ray is incident. A plane containing light and emitted light is defined as a local meridional section, and a plane perpendicular to the local meridional section including the hit point and parallel to a sagittal section (normal sagittal section) of each surface vertex coordinate system is defined as a local sagittal section. Define.

When the display means is of a reflection type, the reference light beam is extended to the illumination optical system and the illumination light source, and a local meridional section and a local sagittal section are defined on each hit point in the same manner as described above. I do. 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, embodiments of the present invention will be described.
1 to 5 are optical path cross-sectional views (local bus cross-sectional views) of Examples 1 to 5 of the present invention.

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. The light beam is reflected by the (half mirror) 5, and the principal ray of the light beam is incident on the reflective LCD 3 almost perpendicularly (± 10 °). The light reflected by the reflective LCD 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, the polarization direction of the light linearly polarized by the polarizing plate 8 rotates inside the liquid crystal (liquid crystal driving voltage OFF or O
N), it is necessary to set the polarizing plate 9 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 becomes: Although there is light (ghost light) that is transmitted without being reflected by the optical surface 5 (half mirror), the ghost light can be cut by the polarizing plate 9, so that an added value for preventing ghost light from entering the eyeball E is also created. . In addition, reflective LCD3
However, in the type in which a single polarizing plate (not shown) is used to display near the display surface, the polarizing plates 8 and 9 become unnecessary. Polarizing plate 9
Is incident on the entrance surface 14 of the free-form surface prism 2, and is totally reflected by the total reflection surface (transmission surface B) 6 in order, and the concave mirror 1
The light is reflected at 3, and then transmitted through the total reflection surface (transmission surface B) 6 and guided to the pupil 1 where the eyeball of the observer is located. Thus, image information based on the reflective LCD 3 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 facing the reflective LCD 3. Is used as the optical surface (half mirror) 5 so that the reflective LCD 3 and the free-form prism 2 on the lowermost peripheral image (F3) side on the local meridional section of the reflective LCD 3 can be used. Display system (members 3, 7, 2)
However, the lighting system (members 4 and 5) is also compact. In the first embodiment shown in FIG. 1, both surfaces 5, 5a of the boomerang type lens 7 are cylindrical surfaces (free-form surfaces) having power only in the meridional section, and the occurrence of aberrations on the local sagittal section (perpendicular to the paper) is minimized. Less
In addition, since there is no power in the sagittal section or local sagittal section direction and the surface shape does not curve in this section direction, the reflective LC
D3 and the optical surface 5 can be made close to each other, and compactness is also possible. 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 the cylindrical surface of the boomerang type lens 7 is one of free-form surfaces because the refractive power varies depending on the azimuth angle. However, in the present invention, when either the sagittal section or the generatrix section has no refractive power, the cylindrical surface is hereinafter referred to. And the other surfaces are hereinafter referred to as free-form surfaces. Of course, if a free-form surface having more degrees of freedom is used for both surfaces 5, 5a of the boomerang lens 7, better optical system performance can be obtained. In the second embodiment shown in FIG. 2, a rotationally symmetric aspheric surface is used for both surfaces 5, 5a of the boomerang lens 7.
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. 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. In addition, both sides 5,
Although a 5a rotationally symmetric spherical surface is possible, a two-sided rotationally symmetric aspheric surface has better optical system performance.

The free-form surface prism included in the display system of the present invention (common to the first to fifth embodiments) employs a free-form surface for the concave mirror 13 having the main power (positive refractive 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. The total reflection surface (transmission surface B) 6 is designed such that the 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. Illumination prism 1
0 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 case, the illumination system junction prism 12 in the display system (3, 10, 11, 12)
The optical performance of the display system can be improved because there is almost no occurrence of aberrations. As the optical path, the 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 and reflected on the reflection type LCD 3, and re-enters the illumination system prism 10. Incident, 5 optical surfaces 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 reflection type 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 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 prism 11 of the third and fourth embodiments is not required, the distance between the free-form surface prism 2 and the reflection liquid crystal 3 can be shortened, and the size can be reduced. As the optical surface 5, a cylindrical surface having no power on the sagittal section is used to suppress the occurrence of aberration on the local sagittal section.

In the image display apparatus of the present invention, the illumination optical system and the display optical system have only one optical surface A having both transmission and reflection functions, which are shared by the illumination optical system and the display optical system. The reference ray passing through the image center and the pupil center is
The angle between the incident reference light beam and the reflected reference light beam when reflected from the illumination means when the light is incident on the optical surface A is α.
(Degree) 20 ° <α <80 ° (1) is satisfied.

In the present invention, only one optical surface A (half mirror) having both functions of transmission and reflection shared by the illumination optical system and the display optical system is used, and the loss of light quantity from the illumination light source to the reflective liquid crystal is reduced. According to the conditional expression (1), the contrast of image quality is improved, and a compact illumination optical system is achieved. If the lower limit of conditional expression (1) is not reached, the emitted light from the liquid crystal is almost vertical, so that the liquid crystal collides with the illumination light source, making the configuration of the optical system difficult. If the upper limit is exceeded, the illumination optical system protrudes toward the eyeball and becomes thick.
As for the display optical system, the light from the reflection type liquid crystal passes through the optical surface 5 which is a half mirror, and the light beam is folded by a plurality of eccentric curvature reflection surfaces, thereby making the display optical system thin. It is more preferable that the numerical range of the conditional expression (1) satisfy the following condition: 40 <α <70 (1a). Within the lower limit, a sufficient space where the liquid crystal does not collide with the illumination light source can be secured, and within the upper limit, the thickness of the illumination optical system can be further reduced.

Further, air is provided between an optical member (first optical member) including the optical surface 5 in the display optical system and another optical member (second optical member) having optical refracting power, 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 between the reflective liquid crystal and the polarizing plate in the display optical system has an optically parallel two-cold relationship. It is not preferable because it is visually observed. 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 5 is short, glass having no birefringence or a mold 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 apparatus 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 apparatus.

(A-1) The optical surface 5 in the illumination optical system is
The curvature reflecting surface has a positive refractive power on the local meridional section. In this way, the illumination light source can be enlarged by the curvature reflection surface having a positive refractive power to illuminate the reflective liquid crystal. Therefore, a small illumination light source can be used, and the illumination optical system itself can be made compact.

(A-2) It is desirable that the illumination light source and the eyeball (pupil position) have a substantially image-forming relationship (Keiler illumination). In this case, the light use efficiency becomes the best.

(A-3) The illumination light source is an RGB time-division light source which emits polychromatic light such as red, green and blue in a time-division manner, and the display means is adapted to emit RGB color light of the RGB time-division light source. This is to display RGB images in hours and minutes. In general, in color display in the color 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, in the above-described system of the combination of the reflection type liquid crystal of the time division display and the LED of three colors (RGB), the total number of pixels is １ ／ of that of the liquid crystal in the color filter system.
No problem. For this reason, if the number of color display pixels is the same, the size of the liquid crystal becomes smaller, and accordingly, both the illumination optical system and the display optical system can be made smaller.

(A-4) The incident angle β (degree) of the reference light beam emitted from the illumination light source to the reflective display means is preferably −10 <β <10 (2) .

Outside this range, the contrast of the liquid crystal image is reduced, and it is difficult to obtain good image quality. Still more preferably, when the numerical range of conditional expression (2) is within the following range, it is better to satisfy the following condition: -5 <β <5 (2a). According to this, a high-quality image of one rank with almost no contrast drop can be obtained.

(A-5) The focal length in the local meridional section of the display optical system is local_fy, and the focal length in the local meridional section of only the optical surface 5 in the illumination optical system is local_fyA.
0.1 <local_fyA / local_fy <0.6 (3) Here, the display optical system is from the reflective liquid crystal as the display means to the surface immediately before the eyeball. The illumination optical system extends from the illumination light source to the surface immediately before the display means (reflection type liquid crystal). The description of the local meridional section focal length will be described in the item of the embodiment. When the lower limit value of the conditional expression (3) is exceeded, the power of the optical surface 5 in the illumination optical system becomes strong, and the concave portion of the optical surface 5 of the concave mirror becomes deeper. The distance between the optical surface A and the optical surface A must be long, and the size of the apparatus in this direction increases. If the value exceeds the upper limit, the power of the optical surface A becomes weak.
A relatively large illumination light source is required, which also increases the size. As for the upper limit, if the following conditional expression is satisfied, 0.1 <local_fyA / local_fy <0.45 (3a) A smaller illumination light source can be used, and the size can be further reduced.

(A-6) In an optical system having an eccentric curvature reflecting surface, rotationally asymmetric eccentric aberration occurs in a screen.
Therefore, the display optical system of the present invention preferably includes two or more surfaces having different refractive powers depending on the azimuth angle, and the display optical system as a whole preferably 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 system having a positive refractive power 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-7) Of the most peripheral images on the local meridional section of the display means, a ray passing through the most peripheral image farther from the eyeball and the center of the eyeball is defined as an F3 eyeball center ray,
The focal length of the display optical system in the system local generatrix section on the F3 eyeball center ray is local_fy (F3), and the F3 eyeball center ray hits on the transmission surface B having the closest refractive power to the eyeball. Assuming that the focal length in the local meridional section on the point is local_fyB (F3), -0.6 <local_fy (F3) / local_fyB (F3) <-0.1 (4) is satisfied. If the lower limit is exceeded, the negative power on the hit point between the F3 eyeball center ray and the transmission surface B becomes too strong, and the surface shape of the transmission surface B is greatly curved toward the eyeball, so that the display optical system is thick. Become. Conversely, exceeding the upper limit weakens the negative power on the hit point. The power arrangement of each surface on the central ray of the F3 eyeball is such that the negative power of the transmission surface B on the hit point is increased, and a retro-type power arrangement is adopted. With this power arrangement, the liquid crystal is made as far as possible on the central ray of the F3 eyeball, and the optical surface A of the illumination optical system can be arranged. Therefore, above the upper limit, the negative power at this point is insufficient, and there is no space for inserting the optical surface A of the illumination optical system. It is more preferable that the upper limit value satisfies the following value. −0.6 <local_fy (F3) / local_fyB (F3) <− 0.25 (4a) According to this, a sufficient space for inserting the optical surface 5 of the illumination optical system can be secured.

Next, the local paraxial axis used in each embodiment of the present invention will be described. 1 to 5 are cross-sectional views of main parts (local bus cross-sectional view, suffix y) of Numerical Examples 1 to 5 to be described later of the present invention, and show the surface vertex coordinate system of the first surface (eyeball 7). As shown in FIG. In the present invention, the surface vertex of each surface is
Since only shift eccentricity in the y-axis direction and tilt eccentricity around the x-axis are performed, the conventional generatrix section and local generatrix section are the same, but the conventional sagittal section and 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 pupil 1 is defined as a reference light ray La, and a conventional radius of curvature / surface interval based on the surface vertex of each surface is used. 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 (the radius of curvature on the local meridional section and the radius of curvature on the 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 conventional radius of curvature, surface spacing, eccentricity, refractive index, Abbe number and local radius of curvature, surface refractive index, local surface spacing, local focal length are shown. .

In the present invention, five embodiments have been described. Numerical data of Examples 1 to 5 are shown in Tables 1 to 5, and optical path sectional views are shown in FIGS. In the conventional paraxial of Tables 1 to 5, (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. Further, the one with M is a reflection surface, and the refractive index nd of the d-line has the opposite sign. Tables 1 to 5 show pupil plane 1 (eyeball).
Is the numerical data of the reverse trace from the 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 travels from left to right.

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)

[0048]

(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).

[0051]

(Equation 2)

H ² = x ² + y ² , r = rx = ry.

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.

Furthermore, the local paraxial (local-p
Next to the reference ray and the hit points on each surface, the LCD outermost peripheral image F3 (lower side, farther from the eyeball, FOV: Wy = -10.
59deg Wx = 0deg) and the local curvature radius local-ry, local-r on the hit point between each ray and the ray passing through the center of the eyeball
x-Local surface spacing local-d (reflection surface has opposite sign)-Local focal length local-fy, local-fx-Refractive index nd (reflection surface has opposite sign)-Hit point coordinates on each surface (surface vertex) To
0,0) ・ Display optical system whole system local focal length is also local para
Added xial ray <FOV: Wy = -10.59deg Wx = 0deg> at the end. Numerical data and calculated values at this time were calculated by replacing the local paraxial reference light beam with a light beam passing through the LCD outermost peripheral image F3 (lower side) and the center of the eyeball.

[0055]

[Table 1]

[0056]

[Table 2]

[0057]

[Table 3]

[0058]

[Table 4]

[0059]

[Table 5]

[0060]

[Table 6]

[0061]

[Table 7]

[0062]

[Table 8]

[0063]

[Table 9]

[0064]

[Table 10]

[0065]

[Table 11]

[0066]

[Table 12]

[0067]

[Table 13]

[0068]

[Table 14]

[0069]

[Table 15]

[0070]

[Table 16]

[0071]

[Table 17]

[0072]

[Table 18]

FIG. 6 is an explanatory view showing a case where 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-and-head mount display. It is.

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.

[0076]

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-to-head mounted display using the same can be achieved.

In particular, according to the present invention, there is little loss of light amount from the illumination light source, an image with sufficient contrast is provided, and an HMD using a reflective LCD in which a compact illumination optical system and a display optical system are realized is 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 schematic diagram of a main part when the image display device of the present invention is applied to an HMD.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Eyeball (pupil) 2 Free-form surface prism 3 Reflection type LCD (The figure shows the protection plate of 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 joint prism surface 1 16 Illumination system joint prism surface 2

────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission Date] April 13, 2001 (2001.4.1
3)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claim 1

[Correction method] Change

[Correction contents]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] Claim 4

[Correction method] Change

[Correction contents]

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0010

[Correction method] Change

[Correction contents]

20 (degrees) <α <80 (degrees) (1) In the first aspect of the present invention, the optical surface A in the illumination optical system is a local light source. It is characterized in that it is a curvature reflection surface having a positive refractive power on a cross section of the generatrix (a surface including the incident light and the emitted light of the reference light).

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0012

[Correction method] Change

[Correction contents]

According to a fourth aspect of the present invention, in the first aspect of the present invention, an incident angle β (degree) of the reference light beam emitted from the illumination light source means to the reflection type display means is -10 (degrees). ) <Β <10 (degrees) (2)

[Procedure amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0031

[Correction method] Change

[Correction contents]

In the present invention, only one optical surface A (half mirror) having both functions of transmission and reflection shared by the illumination optical system and the display optical system is used, and the loss of light quantity from the illumination light source to the reflective liquid crystal is reduced. According to the conditional expression (1), the contrast of image quality is improved, and a compact illumination optical system is achieved. If the lower limit of conditional expression (1) is not reached, the emitted light from the liquid crystal is almost vertical, so that the liquid crystal collides with the illumination light source, making the configuration of the optical system difficult. If the upper limit is exceeded, the illumination optical system protrudes toward the eyeball and becomes thick.
As for the display optical system, the light from the reflection type liquid crystal passes through the optical surface 5 which is a half mirror, and the light beam is folded by a plurality of eccentric curvature reflection surfaces, thereby making the display optical system thin. It is more preferable that the numerical range of Conditional Expression (1) satisfies the following condition: 40 (degrees) <α <70 (degrees) (1a). Within the lower limit, a sufficient space where the liquid crystal does not collide with the illumination light source can be secured, and within the upper limit, the thickness of the illumination optical system can be further reduced.

[Procedure amendment 6]

[Document name to be amended] Statement

[Correction target item name] 0037

[Correction method] Change

[Correction contents]

(A-4) The incident angle β (degree) of the reference light beam emitted from the illumination light source to the reflective display means is −10 (degree) <β <10 (degree) (2) )

[Procedure amendment 7]

[Document name to be amended] Statement

[Correction target item name] 0038

[Correction method] Change

[Correction contents]

Outside this range, the contrast of the liquid crystal image is reduced, and it is difficult to obtain good image quality. Still more preferably, when the numerical range of conditional expression (2) is within the following range, it is better to satisfy −5 (degree) <β <5 (degree) (2a). According to this, a high-quality image of one rank with almost no contrast drop can be obtained.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G02F 1/13 505 G02F 1/13 505 1/1335 520 1/1335 520 H04N 5/64 511 H04N 5/64 511A 9/12 9/12 A F-term (reference) 2H042 CA01 CA12 CA17 DA12 DB14 DD10 DE00 2H087 KA24 RA41 RA45 TA01 TA03 2H088 EA10 HA18 HA21 HA22 HA24 HA28 KA05 MA02 2H091 FA08X FA14Y FA15X FA17X FA21X FA26 LA11A17X FA26X BA03 BA08 BB13 BC05 DB13 HC09 HC19 HD07 JB00

Claims (8)

[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 the image display apparatus having a display optical system for guiding to the eyeball, there is only one optical surface A having both transmission and reflection functions shared by the illumination optical system and the display optical system, and the illumination light source means A reference ray emitted from the display means and passing through the center of the image of the display means and the center of the eyeball enters the optical surface A from the illumination light source means, and the angle α (degrees) between the incident reference light ray and the reflected reference light ray on the optical face A forms ) Is reflected under the following conditions, is substantially perpendicularly incident on the display means, is transmitted through the optical surface A, is reflected by a plurality of eccentric curvature reflecting surfaces, is guided to the eyeball, and the display optical system includes the optical surface A. And another optical member having an optical refractive power, the air gap The image display apparatus characterized by being spaced. 20 <α <80 (1) 2. The optical system according to claim 1, wherein the optical surface A in the illumination optical system has a curvature reflection having a positive refractive power on a local meridional section (a plane including incident light and emission light of the reference light beam). An image display device characterized by being a surface. 3. The method according to claim 1, wherein the illumination light source means is RG.
An image display device, which is a B-time-division light source, wherein the display means displays an RGB image in a time-division manner in accordance with the emission of RGB color light from the RGB time-division light source. 4. An incident angle β of said reference light beam emitted from said illumination light source means to said reflection type display means according to claim 1.
The image display device is characterized in that (degree) is −10 <β <10 (2). 5. The local optical system according to claim 2, wherein a local meridional section focal length of the display optical system is local_fy, and a local meridional section focal length of only the optical surface A in the illumination optical system is local_fyA.
Where 0.1 <local_fyA / local_fy <0.6 (3). 6. The image according to claim 2, wherein the display optical system includes two or more surfaces having different refractive powers depending on the azimuth angle, and the display optical system has a positive refractive power as a whole. Display device. 7. The method according to claim 6, wherein, among the most peripheral images on the local meridional cross section of the display means (the plane including the incident light and the emitted light of the reference light beam), the most peripheral image farthest from the eyeball is included. A ray passing through the center of the eyeball is defined as an F3 center ray of the eyeball.
The local focal line cross-sectional focal length of the display optical system on the three-eyeball center ray is local_fy (F3), and on the transmission surface B having the closest refractive power to the eyeball, on the point where the F3 eyeball hits. Where the local meridional section focal length is local_fyB (F3), −0.6 <local_fy (F3) / local_fyB (F3) <− 0.1 (4) . 8. A head mounted display comprising the image display device according to claim 1.