JP2003035881A - Image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compact image display device where axially asymmetric aberration caused in a beam splitter is compensated. SOLUTION: This image display device is equipped with a reflection type liquid crystal display element (1) for displaying a picture on a display surface (1a), an illumination optical system (4) for illuminating the display surface (1a), an eyepiece optical system (3) by which the image on the display surface (1a) is enlarged and observed, and a PBS sheet (2) separating an illumination optical path from the optical system (4) to the display surface (1a) and an eyepiece optical path from the display surface (1a) to the optical system (3a), and the optical system (3) has a toric surface (S5#) in order to compensate the axially asymmetric aberration caused in the sheet (2).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image display device, for example, a reflective liquid crystal display element (LC).
The present invention relates to an image display device such as an electronic viewfinder (so-called EVF) for a digital camera and an HMD (Head Mounted Display) that projects and displays a two-dimensional image of D: Liquid Crystal Display on an observation eye.

[0002]

2. Description of the Related Art The number of pixels, the cost and the size of reflective liquid crystal display elements used in EVFs and HMDs have been increasing. For example, an ultra-small (about 5 mm diagonal screen) reflective liquid crystal display element in which a circuit portion and a display portion are integrated by sealing a liquid crystal between a silicon substrate and a sealing glass is produced. Is starting to appear. When such a reflective liquid crystal display element is used, it is necessary to illuminate the eyepiece optical system side. Therefore, a low-cost sheet-shaped beam splitter (for example, Sumitomo 3M Co., Ltd. product name: DBEF) that separates the illumination optical path and the eyepiece optical path is generally used, and is disclosed in JP-A-2000-98918. The publication proposes an image display device that separates the illumination optical path and the eyepiece optical path with a sheet-shaped reflector.

[0003]

If a sheet-like beam splitter is used for optical path separation, the following problems will occur. FIG. 9A shows an eyepiece optical path in which a parallel plate (FP) corresponding to a sheet-like beam splitter is arranged. Further, FIG. 9B shows the eyepiece optical path before the parallel plate (FP) is arranged. As shown in FIG. 9 (A), a parallel plate
When (FP) is put in the optical path of the condensed light flux, an axially asymmetric lens back shift (δ), that is, an astigmatic difference on the axis occurs. Since this astigmatic difference is an axially asymmetric aberration that causes a diopter error of the eyepiece optical system, it deteriorates the appearance of the observed image.

Here, the refractive index of the parallel plate (FP) is 1.5
2. When the plate thickness is 0.5 mm and the parallel plate (FP) is arranged at an angle with respect to the optical axis of the eyepiece optical system, the paraxial lens back shift (δ: The astigmatic difference on the axis is shown in Table 1 (however, the tilt angle in the case of vertical incidence is 0 degree). As can be seen from Table 1, the astigmatic difference (δ) becomes a non-negligible amount when the inclination angle is close to 45 degrees. This astigmatic difference (δ) is proportional to the thickness of the parallel plate (FP). The astigmatic difference in diopter as a finder is proportional to the square of the magnification of the eyepiece optical system. Therefore,
This problem becomes more serious as the screen of the reflective liquid crystal display device becomes smaller.

[0005]

[Table 1]

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a compact image display device in which axially asymmetric aberration generated in the beam splitter is corrected.

[0007]

In order to achieve the above object, an image display device of a first invention is a reflection type liquid crystal display element for displaying an image on a display surface, and an illumination optical device for illuminating the display surface. A system, an eyepiece optical system for magnifying and observing an image on the display surface, and a beam splitter for separating an illumination optical path from the illumination optical system to the display surface and an eyepiece optical path from the display surface to the eyepiece optical system. In the image display device, the eyepiece optical system has at least one axially asymmetric optical surface in order to correct the axially asymmetric aberration generated in the beam splitter.

In the image display device of the second invention, in the configuration of the first invention, the direction of the line of intersection between the plane orthogonal to the optical axis of the eyepiece optical system and the declination surface of the beam splitter is the first direction. Direction, and a direction orthogonal to the first direction on a plane orthogonal to the optical axis of the eyepiece optical system is a second direction, the first of the axially asymmetric optical surfaces on the optical axis of the eyepiece optical system. It is characterized in that the power in one direction is weaker positive or stronger negative than the power in the second direction.

In the image display device of the third invention, in the structure of the second invention, the axially asymmetric optical surface has power only in one of the first and second directions. And

In the image display device of the fourth invention, in the constitution of the second invention, the focal length of the eyepiece optical system is 18
It is characterized by being mm or less.

In the image display device of the fifth invention, in the structure of the second invention, the liquid crystal display element is provided in order to correct the vertical / horizontal difference of the distortion generated in the beam splitter and the axially asymmetric optical surface. It is characterized in that the input image information is corrected.

An image display apparatus according to a sixth aspect of the present invention is a reflection type liquid crystal display element for displaying an image on a display surface, an illumination optical system for illuminating the display surface, and eyepiece optics for magnifying and observing the image on the display surface. An image display device comprising: a system; and a beam splitter for separating an illumination optical path from the illumination optical system to the display surface and an eyepiece optical path from the display surface to the eyepiece optical system, the beam splitter In order to correct the vertical / horizontal difference of the distortion that occurs in (1), the pixel pitch of the display surface is different in the vertical direction and the horizontal direction.

[0013]

DETAILED DESCRIPTION OF THE INVENTION An image display device embodying the present invention will be described below with reference to the drawings. Each of the embodiments described below can of course be used as an image display device such as an EVF or HMD, but a liquid crystal display element (1) described later is also used.
If an observation object that replaces the above is prepared, it can be used as an image observation device for illuminating and observing a display image of a predetermined size. In addition, the same reference numerals are given to the same or corresponding portions in the embodiments and the like, and the duplicate description will be appropriately omitted.

<< First Embodiment (FIGS. 1 and 2) >> FIG. 1 shows a first embodiment of the image display device, and an enlarged view of a portion where the illumination optical path and the eyepiece optical path are separated. 2 shows. This image display device includes a reflective liquid crystal display element (1) and a PBS (Po
larizing Beam Splitter sheet (2) and eyepiece optical system (3)
And an illumination optical system (4), which is an EVF for a digital still camera. Liquid crystal display element (1) has a screen size:
An image is displayed on the display surface (1a) of 2.88 (short side) × 3.84 (long side) mm. And the display surface (1a) of the liquid crystal display element (1)
Are illuminated by the illumination optics (4). Illumination optics (4)
Is composed of a collimator lens (4a) and a diffuser plate (4b) {AX0: optical axis of the illumination optical system (4)}, and its collimator lens
(4a) establishes a conjugate relationship between the surface of the diffuser plate (4b) and the pupil (EP).

The illumination light emitted from the diffuser plate (4b) is a parallel plate PBS sheet (2) arranged at an inclination angle of about 45 degrees with respect to the optical axis (AX1) of the eyepiece optical system (3). Incident on.
The PBS sheet (2) is a polarized beam that separates the illumination optical path from the illumination optical system (4) to the display surface (1a) and the eyepiece optical path from the display surface (1a) to the eyepiece optical system (3). Is a splitter,
Specific examples thereof include D manufactured by Sumitomo 3M Limited.
BEF (trade name) is mentioned. Of the incident light on the PBS sheet (2), S-polarized light is reflected and enters the display surface (1a), and among the reflected light from the display surface (1a), P-polarized light is transmitted through the PBS sheet (2). Become.

A linear polarizing plate (2p) is attached to the surface of the PBS sheet (2) on the side of the eyepiece optical system (3). Linear polarizing plate
The transmission axis direction of (2p) is made to coincide with the direction in which the P-polarized light transmitted through the PBS sheet (2) is transmitted. Therefore, PB
The P-polarized light transmitted through the S sheet (2) passes through the linear polarizing plate (2p) and then enters the eyepiece optical system (3) as image light. PB
The thickness of the parallel plate composed of the S sheet (2) and the linear polarizing plate (2p) is 0.4 mm. When such a sheet-like beam splitter is used for optical path separation, astigmatism difference in size proportional to the plate thickness occurs as described above. Therefore,
When P-polarized light passes through the PBS sheet (2) and the linear polarizing plate (2p), an astigmatic difference corresponding to the plate thickness of 0.4 mm occurs.

As shown in FIG. 2, the optical axis (AX1) of the eyepiece optical system (3) is parallel-shifted by the PBS sheet (2) and the linear polarizing plate (2p), but the liquid crystal display element (1) is also the same. Since it is arranged at the shift position in the direction, the parallel-shifted optical axis (AX1) passes through the screen center (CP) of the display surface (1a). In other words, the eyepiece optical system (3) is decentered with respect to the display surface (1a) of the liquid crystal display element (1) by the amount of light beam shift due to the PBS sheet (2) or the like.

The image light (P-polarized light) transmitted through the PBS sheet (2) and the linear polarizing plate (2p) enters the eyepiece optical system (3) having a focal length of about 10.5 mm. Eyepiece optical system (3) is the first lens
(G1), second lens (G2), third lens (G3) and protective glass
It consists of (3a) and guides the image light to the pupil (EP) to display screen (1a) 2.
Magnify and observe a three-dimensional image. Table 2 shows the construction data of this eyepiece optical system (3).

As construction data of the eyepiece optical system (3), the radius of curvature (mm) of the surface Si (i = 1,2,3, ...), the axial distance (mm), and the refractive index (nd for the d line ), Abbe number (νd)
Etc. Further, the direction parallel to the optical axis (AX1) of the eyepiece optical system (3) is defined as the X direction, and the direction of the line of intersection between the plane orthogonal to the optical axis (AX1) and the declination surface of the PBS sheet (2) is Z. And the optical axis (AX
The focal length (mm) of the eyepiece optical system (3) on the XY plane and the XZ plane is shown together with other data, where the Y direction is the direction orthogonal to the Z direction on the plane orthogonal to 1). The Z direction is the long side of the screen of the display surface (1a), and the Y direction is the display surface (1a).
Is the direction of the short side of the screen. The difference between the focal length on the XY plane and the focal length on the XZ plane is due to the toric surface described later, and the astigmatic difference is corrected by the difference in the focal length.

In the construction data, the surface marked with * (Si) is an axisymmetric aspherical surface defined by the following expression (AS). Aspherical data is shown together with other data.

[0021]

[Equation 1]

However, X: the amount of displacement in the optical axis (AX1) direction (that is, the X direction) at the position of height H (reference to the surface apex), H: height in the direction perpendicular to the optical axis (AX1) (H ² = Y ² + Z ² ), C0: paraxial curvature (= 1 / radius of curvature), ε: quadric surface parameter, Ai: i-th order aspheric coefficient (data for Ai = 0 is omitted. .),

In the construction data, the surface marked with # (Si) is a toric surface. The toric surface is a curved surface having a rotational symmetry axis in the direction orthogonal to the optical axis (AX1). Among them, the one having a rotational symmetry axis parallel to the Y axis is the Y toric surface, which is rotational symmetry parallel to the Z axis. The Z-toric surface has an axis. The Y toric surface is expressed by the following equations (YT1) and (YT2), and the Z toric surface is the following equation.
It is represented by the equations (ZT1) and (ZT2). In other words, the Y toric surface is the surface formed by rotating the curve X = f (Y) around the rotational symmetry axis parallel to the Y axis, passing through the point that is CRy on the X axis from the coordinate origin (surface vertex). Yes, the Z toric surface is the curve X = f
It is a surface formed by rotating (Z) around a rotational symmetry axis parallel to the Z axis, passing through a point separated from the coordinate origin (surface apex) by CRz on the X axis. The toric surface data is shown together with other data.

[0024]

[Equation 2]

However, in the C0: Y toric surface, the surface vertex curvature in the XY section,
On the Z toric surface, the surface vertex curvature (= 1 /
Radius of curvature), ε: quadric surface parameter, CRy: Y toric radius of curvature (the radius of curvature in the Z direction,
The sign is + when the axis of rotational symmetry is on the right side of the coordinate origin. ), CRz: Z toric radius of curvature (the radius of curvature in the Y direction,
The sign is + when the axis of rotational symmetry is on the right side of the coordinate origin. ), Ai: i-th order aspherical coefficient (data is omitted when Ai = 0),

[0026]

[Table 2]

The beam splitter for optical path separation is
Like the PBS sheet (2) used in this image display device, it needs to be arranged at an angle with respect to the optical axis (AX1) of the eyepiece optical system (3). However, as described above, when the PBS sheet (2) having a finite thickness is arranged so as to be inclined with respect to the optical axis (AX1), an astigmatic difference is always generated in the light flux that has passed through it. Astigmatism can be corrected by arranging a parallel plate tilted in the opposite direction to the PBS sheet (2) in the vicinity, but in practice there is a restriction on the focal length of the eyepiece optical system (3). It becomes impossible to secure sufficient space. In this image display device, a toric surface (S5 #) is attached to the eyepiece optical system (3) in order to correct the astigmatic difference generated in the PBS sheet (2).
Is used. If at least one axially asymmetric optical surface such as a toric surface (S5 #) is provided in the eyepiece optical system (3), there is no special space for the axially asymmetric aberration (here, astigmatic difference) generated by the beam splitter. Can be corrected to.

The toric surface (S5 #) used in the eyepiece optical system (3) has a Y-direction power of Y on the optical axis (AX1).
It is more negative than the directional power. In this way, the direction of the line of intersection between the plane (YZ plane) orthogonal to the optical axis (AX1) of the eyepiece optical system (3) and the declination surface of the beam splitter is the first direction.
(Z direction) and when the direction orthogonal to the first direction on the plane orthogonal to the optical axis (AX1) of the eyepiece optical system (3) is the second direction (Y direction), the eyepiece optical system (3) On the optical axis (AX1), it is desirable that the power in the first direction of the axially asymmetric optical surface (toric surface or the like) to be used is positive or strong negative, which is weaker than the power in the second direction. When the illumination optical path and the eyepiece optical path are separated using a sheet-like beam splitter as in this embodiment, by using a toric surface (S5 #) as an axially asymmetric optical surface that satisfies this condition, Astigmatic difference can be effectively corrected.

The third lens (G5) having a toric surface (S5 #)
3) consists of resin molded products. Although it is difficult to polish the optical surface so as to be axially asymmetric, it is possible to easily form an axially asymmetric optical surface by resin molding. Therefore, it is desirable that the axially asymmetric optical surface such as the toric surface (S5 #) is made of a resin molded product.
The focal length of the eyepiece optical system (3) is preferably 18 mm or less. Considering that the astigmatic difference increases in proportion to the square of the magnification of the eyepiece optical system (3),
This is an effective condition for balancing the entire optical configuration.
In the present embodiment, the focal length satisfying this condition: about 10.
By using the 5 mm eyepiece optical system (3), EV
The optical configuration is suitable for F.

<< Second Embodiment (FIGS. 3 to 6) >> FIG. 3 shows a second embodiment of the image display device, and an enlarged view of the separated portion of the illumination optical path and the eyepiece optical path. 4 shows. One of the features of this image display device is the illumination optical system (4), and the PBS sheet (2) having the function of the collimator lens (4a, FIG. 1) is provided.
The construction is the same as that of the first embodiment except that (A) is used (see Table 2 for construction data of the eyepiece optical system (3)). }.

The illumination light emitted from the diffusion plate (4b) is incident on the cylindrical PBS sheet (2A) which is curved along the XZ plane. The PBS sheet (2A) is a display surface from the illumination optical system (4).
Illumination optical path to (1a) and eyepiece optical system from its display surface (1a)
It is a polarizing beam splitter that separates the eyepiece optical path to (3) and is made of the same material as the PBS sheet (2). Therefore, similar to the first embodiment, S-polarized light of the incident light on the PBS sheet (2A) is reflected and enters the display surface (1a), and P-polarized light of the reflected light from the display surface (1a) is reflected. PBS
It will pass through the sheet (2A).

No linear polarizing plate is attached to the PBS sheet (2A) (it may be attached if necessary), and the thickness of the PBS sheet (2A) is 0.33 mm. This PB
Also in the S sheet (2A), the astigmatic difference having a size proportional to the plate thickness occurs as described above. However, the astigmatic difference is corrected by the toric surface (S5 #) of the eyepiece optical system (3) as in the first embodiment. PBS sheet (2A)
Has a collimating effect due to a cylindrical shape that is curved in one direction, so that the illumination optical system (4) can be reduced in weight, size, and cost because there is no collimator lens (4a, FIG. 1).

As for the positional relationship between the eyepiece optical system (3) and the display surface (1a), the optical axis (AX1) is the same as in the first embodiment.
The parallel shift of is considered. That is, as shown in FIG. 4, the optical axis (AX1) parallel-shifted by the PBS sheet (2A) passes through the screen center (CP) of the display surface (1a). But P
Since the BS sheet (2A) has an inclined curved surface that transmits image light, the curved surface causes distortion. In other words, the larger the incident angle with respect to the PBS sheet (2A) (that is, the inclination angle due to the curved surface), the greater the parallel shift, and as a result, the image elongated in the Z direction (the long side of the screen) is observed. . No distortion occurs in the Y direction (direction of the short side of the screen) because the curvature is zero, and as a result, a vertical and horizontal difference in distortion occurs.

Distortion occurs not only on the PBS sheet (2A) but also on the toric surface (S5 #) of the eyepiece optical system (3). Since the distortion generated on the toric surface (S5 #) is in the opposite direction to that generated on the PBS sheet (2A), it can be offset to some extent. However, it cannot be completely corrected. Distortion correction is possible in principle by arranging multiple axially asymmetric optical surfaces such as a toric surface (S5 #), but optical design and manufacturing become difficult.
(It is difficult to process axially asymmetric lenses, etc.). In this way, considering the distortion that also occurs in the eyepiece optical system (3), the PBS sheet (2A) and the eyepiece optical system (3) are included,
For the entire observation system from the display surface (1a) to the pupil (EP), it is necessary to correct the vertical / lateral difference of distortion. For that purpose, it is desirable that the correction has already been completed at the stage of image display by the liquid crystal display element (1), and image processing or image display level correction is effective rather than optical correction. A configuration for performing such distortion correction will be described below.

As shown in FIG. 3, the image information input to the liquid crystal display device (1) includes CCD (Charge Coupled Device, 1).
Output data from (0) is A / D converted, and then the CPU (Central
It is obtained by image processing in the Processing Unit, 11). Two types of independent image data are output from the CCD (10), and one of the image data is input to the CPU (11). One is all pixel data, which is sampled vertically and horizontally by the CPU (11) and then recorded in the memory (12).
The other is vertically thinned pixel data vertically sampled for EVF (that is, thinned in the Y direction). The vertically thinned pixel data is horizontally sampled by the CPU (11) and then input to the liquid crystal display element (1).

Here, the configuration for distortion correction will be described by dividing it into two types. In the first type, the image information input to the liquid crystal display element (1) is corrected in order to correct the vertical and horizontal difference of distortion. The image information is corrected by horizontal sampling in the CPU (11). Figure 5 shows the distortion correction (3.1 in the Z direction).
An example of data sampling when performing 25% reduction) is shown, and FIG. 6 shows an example of data sampling when distortion correction is not performed. 5 and 6, Y = 7,1
Rows 2, 23, and 28 are vertical thinned-out pixel data, and the sub-pixels in the hatched portion are pixel data that are horizontally sampled and input to the liquid crystal display element (1). CCD (1
The image data obtained in (0) has three types of sub-pixels: R (red)
It is composed of G (green) and B (blue), and one recording pixel at the time of shooting is composed of GB of an odd row and RG of an even row immediately below it. E
In the display for VF (to reduce the number of pixels), the range surrounded by a thick solid line is set as a virtual one pixel, and four sub-pixels (hatched part) representing the virtual one pixel are displayed in the color of the liquid crystal display element (1). One pixel is displayed. The pixel pitches of the CCD (10) and the liquid crystal display element (1) are equally spaced vertically and horizontally.

As can be seen by comparing FIG. 5 with FIG.
The sampling pitch in the (vertical) direction is the same (Y =
(7, 12, 23, 28 rows), the sampling pitch in the Z (horizontal) direction alternately increases by one sub-pixel for each row every time one virtual pixel advances to the right. This is shown as a shift in the position of the sub-pixel (hatched portion) that is laterally sampled. For example, shifting from B and G at 7 rows, 24 columns and 25 columns in FIG. 6 to G and B at 7 rows, 25 columns and 26 columns in FIG. 5, 12 in FIG.
Row 40 column, column 41 G, R to 12 row 41 column in FIG. 5,
It appears as a shift to RG in the 42nd row. When the ratio of the horizontal sampling pitch to the vertical sampling pitch becomes large, it means that the data is sampled from a wider range in the horizontal direction, so the distortion correction that compresses the image in the horizontal direction has been performed. .
By changing the ratio of the horizontal sampling pitch to the vertical sampling pitch in this way, it is possible to correct the vertical and horizontal difference of distortion in the entire observation system. Moreover, since this is a soft correction that does not affect the optical system, it becomes possible to easily design and manufacture the eyepiece optical system (3) and the like.

The second type uses a liquid crystal display element (1) in which the pixel pitch of the display surface (1a) is different in the vertical direction and the horizontal direction in order to correct the vertical / horizontal difference of distortion. For example, the sampling pitch of the CCD (10) is equal to the vertical and horizontal intervals.
As shown in FIG. 6, the ratio of the horizontal pixel pitch to the vertical pixel pitch of the liquid crystal display element (1) is reduced (for example, 12 μm in the vertical direction).
X 11.6 μm) and the pixel pitch is equal to the vertical and horizontal intervals (for example, 12 μm in length × 12 μm in width), so that a wider range of images is displayed in the horizontal direction.
This means that the distortion correction for compressing the image in the horizontal direction has been performed. By changing the ratio of the horizontal pixel pitch to the vertical pixel pitch in this way, it is possible to correct the vertical and horizontal difference of distortion in the entire observation system. Moreover, since this is a hardware correction that does not affect the optical system, it is possible to easily design and manufacture the eyepiece optical system (3) and the like.

<< Third Embodiment (FIG. 7) >> FIG. 7 shows an image display apparatus according to a third embodiment. This image display device has an optical configuration suitable for an HMD, and is characterized in that polarization-selective catadioptric refraction is used in an observation system. The basic configuration of the liquid crystal display element (1) and the illumination optical system (4) is the same as that of the second embodiment, and the configuration of correcting the vertical / lateral difference of the distortion can also be adopted.
(Not shown). The liquid crystal display element (1) has a screen diagonal length of 4.8.
An image is displayed on the mm display surface (1a), and the display surface (1a) is illuminated by the illumination optical system (4). The collimating effect of the illumination optical system (4) is obtained by the cylindrical PBS sheet (2A) curved along the XZ plane, as in the second embodiment.

Illumination light emitted from the diffuser plate (4b) enters the PBS sheet (2A), and S-polarized light of the incident light is reflected and enters the display surface (1a), and from the display surface (1a). P out of reflected light
The polarized light passes through the PBS sheet (2A). PBS sheet (2A)
On the surface of the eyepiece optical system (3) side, a linear polarizing plate (2p) is attached, and on the linear polarizing plate (2p), a quarter wavelength plate (2p) is attached.
q) is attached. The transmission axis direction of the linear polarizing plate (2p) is made to coincide with the transmission direction of the P-polarized light transmitted through the PBS sheet (2A), and the phase difference direction is shifted by 45 degrees with respect to the transmission axis, and a quarter wavelength. The plate (2q) is located. Therefore, the light transmitted through the PBS sheet (2A), the linear polarizing plate (2p), and the quarter wavelength plate (2q) is used as image light in the eyepiece optical system (3).
Will be incident on. The thickness of the parallel plate composed of the PBS sheet (2A), the linear polarizing plate (2p) and the quarter wavelength plate (2q) is 0.33 mm. As described above, an astigmatic difference having a size proportional to the plate thickness occurs, and the astigmatic difference is corrected by the toric surface (S1 #) of the eyepiece optical system (3).

PBS sheet (2A), linear polarizing plate (2p) and 1
Image light transmitted through / 4 wavelength plate (2q) has a focal length of about 1
It is incident on the eyepiece optical system (3) of 1.5 mm. Eyepiece optical system (3)
Consists of a catadioptric lens (GL) and a protective glass (3a),
The image light is guided to the pupil (EP) to magnify and observe the two-dimensional image on the display surface (1a). Construction data of this eyepiece optical system (3) are shown in Table 3 (display format is the same as in Table 2).

[0042]

[Table 3]

The surface of the catadioptric lens (GL) on the liquid crystal display element (1) side is a positive toric surface (S1 #) on the optical axis (AX1) in which the power in the Z direction is weaker than the power in the Y direction. ing. As described above, by using a positive axis asymmetric optical surface in which the power in the Z direction is weaker than the power in the Y direction,
Astigmatism can be effectively corrected. The surface of the catadioptric lens (GL) on the pupil (EP) side is a semi-transparent mirror surface in which metal evaporation (or dielectric multilayer film coating) is applied to an axisymmetric aspherical surface (S2 *).
It is (HM). This semi-transparent mirror surface (HM) allows the catadioptric lens (GL) to be used as a concave mirror, so the eyepiece optical system
The thinning of (3) is achieved. In addition, a PBS sheet (3r) is attached to the surface (S5) of the protective glass (3a) on the catadioptric lens (GL) side, and a quarter wave plate (3q) is attached on the PBS sheet (3r). ) Is attached. This PBS sheet (3r)
Is a polarization selection optical element made of the same material as the PBS sheet (2, 2A) for optical path separation, reflects linearly polarized light in the first polarization direction, and transmits linearly polarized light in the second polarization direction orthogonal thereto.

Next, the flow of light in the observation system of this image display device will be described. The light emitted from the liquid crystal display element (1) is linearly polarized by the PBS sheet (2A) and the linear polarizing plate (2p), and further circularly polarized by the quarter wavelength plate (2q). The circularly polarized light passes through the catadioptric lens (GL) and then through the semi-transparent mirror surface (HM). At this time, the polarization state of circularly polarized light is not affected by the semi-transparent mirror surface (HM), and the light reflected by the semi-transparent mirror surface (HM) is not used. The circularly polarized light transmitted through the semi-transparent mirror surface (HM) is linearly polarized in the first polarization direction by the quarter wave plate (3q) attached on the protective glass (3a), and then PBS.
It is reflected by the sheet (3r).

The linearly polarized light of the first polarization direction reflected by the PBS sheet (3r) again enters the quarter wavelength plate (3q) and is circularly polarized. The circularly polarized light is reflected by the semi-transmissive mirror surface (HM) and is converted into the reverse circularly polarized light. After that, it is incident on the quarter-wave plate (3q) again and linearly polarized, and then the PBS sheet (3r)
Incident again. Since the linearly polarized light in the first polarization direction is changed to the linearly polarized light in the second polarization direction by passing through the quarter wavelength plate (3q) twice (that is, the polarization direction is rotated by 90 degrees), the PBS here is used. It will pass through the sheet (3r).
Then, the light passes through the protective glass (3a) and enters the pupil (EP). In this image display device, in order to prevent screen vignetting due to the movement of the eyeball when used as an HMD, a wide pupil (EP) is secured as compared with EVF.

<< Fourth Embodiment (FIG. 8) >> FIG. 8 shows a fourth embodiment of the image display device. This image display device also has an optical configuration suitable as an HMD, and a protective glass
The structure is the same as that of the third embodiment except that a cylindrical lens (GC) is used instead of (3a). Screen size of liquid crystal display element (1), eyepiece optical system (3)
The focal length and the thickness of the parallel plate composed of the PBS sheet (2A) are the same as those in the third embodiment. Construction data of this eyepiece optical system (3) is shown in Table 4 (display format is the same as in Tables 2 and 3).

[0047]

[Table 4]

The surface of the cylindrical lens (GC) on the pupil (EP) side is a toric surface (S6 #) that has power in only one direction, and the astigmatic difference described above is corrected by this toric surface (S6 #). To be done. The toric surface used here (S6 #)
As described above, it is desirable to use an optical surface having power in only one of the Y direction and the Z direction as an axially asymmetric optical surface for astigmatic difference correction. If an axially asymmetric optical surface having power on only one side is used, the lens becomes a simple cylindrical lens, which has the advantage of improving workability.

Similar to the third embodiment, the catadioptric lens
The surface of the (GL) pupil (EP) side is metal-deposited on an axisymmetric aspherical surface (S2 *)
It is a semi-transparent mirror surface (HM) to which (or a dielectric multilayer coating) is applied. This semi-transparent mirror surface (HM) allows catadioptric lenses
Since (GL) is used as a concave mirror, the eyepiece optical system (3) can be made thin. Also, a cylindrical lens (GC)
PBS sheet (3r) on the surface (S5) of the catadioptric lens (GL) side
Is affixed, and 1 / on the PBS sheet (3r)
A four-wave plate (3q) is attached. This PBS sheet
(3r) is a polarization-selecting optical element made of the same material as the PBS sheet (2,2A) for optical path separation, reflects linearly polarized light in the first polarization direction, and converts linearly polarized light in the second polarization direction orthogonal thereto. To Penetrate.

Next, the flow of light in the observation system of this image display device will be described. The light emitted from the liquid crystal display element (1) is linearly polarized by the PBS sheet (2A) and the linear polarizing plate (2p), and further circularly polarized by the quarter wavelength plate (2q). The circularly polarized light passes through the catadioptric lens (GL) and then through the semi-transparent mirror surface (HM). At this time, the polarization state of circularly polarized light is not affected by the semi-transparent mirror surface (HM), and the light reflected by the semi-transparent mirror surface (HM) is not used. The circularly polarized light transmitted through the semi-transparent mirror surface (HM) is linearly polarized in the first polarization direction by the quarter-wave plate (3q) attached on the cylindrical lens (GC), and then the PBS sheet (3r ) Is reflected.

The linearly polarized light in the first polarization direction reflected by the PBS sheet (3r) again enters the quarter wavelength plate (3q) and is circularly polarized. The circularly polarized light is reflected by the semi-transmissive mirror surface (HM) and is converted into the reverse circularly polarized light. After that, it is incident on the quarter-wave plate (3q) again and linearly polarized, and then the PBS sheet (3r)
Incident again. Since the linearly polarized light in the first polarization direction is changed to the linearly polarized light in the second polarization direction by passing through the quarter wavelength plate (3q) twice (that is, the polarization direction is rotated by 90 degrees), the PBS here is used. It will pass through the sheet (3r).
Then, it passes through the cylindrical lens (GC) and enters the pupil (EP). In this image display device, in order to prevent screen vignetting due to movement of the eyeball when used as an HMD,
It has a wider pupil (EP) than F.

[0052]

As described above, according to the present invention, it is possible to correct the axially asymmetric aberration generated in the beam splitter while maintaining the compactness of the image display device.

[Brief description of drawings]

FIG. 1 is an optical cross-sectional view showing a first embodiment of an image display device.

FIG. 2 is an enlarged view showing an optical path separation portion of FIG.

FIG. 3 is an optical sectional view showing a second embodiment of the image display device.

FIG. 4 is an enlarged view showing an optical path separation portion of FIG.

FIG. 5 is a diagram for explaining data sampling when performing distortion correction.

FIG. 6 is a diagram for explaining data sampling when distortion correction is not performed.

FIG. 7 is an optical cross-sectional view showing a third embodiment of the image display device.

FIG. 8 is an optical cross-sectional view showing a fourth embodiment of the image display device.

FIG. 9 is a schematic diagram for explaining the influence of a parallel plate on the eyepiece optical path.

[Explanation of symbols]

1 ... Reflective liquid crystal display element 1a… Display surface 2,2A ... PBS sheet (beam splitter) 3… Eyepiece optical system G1 ... 1st lens G2 ... Second lens G3 ... Third lens GL ... Catadioptric lens GC: Cylindrical lens *… Axisymmetric aspherical surface # ... toric surface (axis-asymmetrical optical surface) 3a… Protective glass 4… Illumination optics 4a… Collimator lens 4b ... Diffuser AX1… Optical axis of eyepiece optical system AX0… Optical axis of illumination optical system EP ... Hitomi

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H04N 5/225 H04N 5/225 B 5/64 511 5/64 511A F term (reference) 2H052 BA02 BA07 BA09 BA11 2H087 KA00 LA11 NA01 PA03 PA17 PB03 QA02 QA07 QA14 QA22 QA25 QA32 QA42 QA45 RA05 RA08 RA13 RA42 RA45 2H088 EA02 HA20 HA21 HA24 HA28 KA30 MA04 2H091 FA10X FA26X FA41X FD06 GA11 C022 AC10 LA30 MA09

Claims (6)

[Claims] 1. A reflective liquid crystal display device for displaying an image on a display surface, an illumination optical system for illuminating the display surface, an eyepiece optical system for magnifying and observing an image on the display surface, and the illumination optical system. An image display device comprising a beam splitter that separates an illumination optical path to the display surface and an eyepiece optical path from the display surface to the eyepiece optical system, wherein an axially asymmetric aberration generated in the beam splitter is generated. An image display device, wherein the eyepiece optical system has at least one axially asymmetric optical surface for correction. 2. A direction of a line of intersection between a plane orthogonal to an optical axis of the eyepiece optical system and a declination surface of the beam splitter is a first direction.
Direction, and a direction orthogonal to the first direction on a plane orthogonal to the optical axis of the eyepiece optical system is a second direction, the first of the axially asymmetric optical surfaces on the optical axis of the eyepiece optical system. 2. The image display device according to claim 1, wherein the power in one direction is positive or strong and weaker than the power in the second direction. 3. The image display device according to claim 2, wherein the axially asymmetric optical surface has power only in one of the first and second directions. 4. The image display device according to claim 2, wherein the focal length of the eyepiece optical system is 18 mm or less. 5. The image information input to the liquid crystal display device is corrected in order to correct the vertical / lateral difference of distortion generated on the beam splitter and the axially asymmetric optical surface. 2. The image display device according to 2. 6. A reflective liquid crystal display element for displaying an image on a display surface, an illumination optical system for illuminating the display surface, an eyepiece optical system for magnifying and observing an image on the display surface, and an illumination optical system. An image display device comprising a beam splitter that separates an illumination optical path to the display surface and an eyepiece optical path from the display surface to the eyepiece optical system, wherein a vertical and horizontal difference of distortion generated in the beam splitter is provided. An image display device, wherein the pixel pitch of the display surface is different in the vertical direction and the horizontal direction for correction.