JP3197350B2 - Head or face-mounted display device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a portable display device, and more particularly, to a display device which is mounted on an observer's head or face to observe an electronic image or the like.

[0002]

2. Description of the Related Art Conventionally, as a display device which is mounted on an observer's head or face to view an electronic image displayed on an image display device such as a liquid crystal display device, a half mirror and a concave surface are provided on the front surface of an eyeball. It is known that a reflection mirror or a half mirror is arranged, and an electronic image is reflected on these mirror surfaces and guided to an eyeball (Japanese Patent Application Laid-Open No. 3-188777). That is, as shown in FIG. 4A, a half mirror 2 is arranged obliquely with respect to the optical axis on the front surface of the eyeball 1 of the observer, and a concave mirror 3 is arranged in front of the half mirror 2 and arranged outside the optical axis. The electron image from the image display element 4 such as a liquid crystal display element
Is reflected to the concave mirror 3 side, the image is enlarged and reflected by the concave mirror 3 as an enlarged image in the air, and the enlarged image is transmitted through the half mirror 2 and guided to the eyeball 1. In the case of FIG. 2B, a concave half mirror 5 is used instead of the concave mirror 3 of FIG.
A liquid crystal shutter 6 is arranged in front of the concave half mirror 5 and selectively introduced into the eyeball 1 in order to enable enlarged observation similarly to FIG. This makes it possible to selectively observe one or one of a combination of an external image and an electronic image.

According to such an arrangement, the image display element 4
Is reflected by the half mirror 2 and is reflected by the concave mirror 3 or the concave half mirror 5, and then passes through the half mirror 2 to form an image on the retina of the eyeball 1. Therefore, the concave mirror 3
Alternatively, the distance to the concave half mirror 5 and the distance from the image display element 4 to the concave mirror 3 or the concave half mirror 5 can be made equal and short, and image distortion is reduced. Also, by using the concave half mirror 5 instead of the concave mirror 3,
When the electronic image of the image display element 4 and the external image are viewed in a superimposed manner, a see-through function can be provided.

[0004]

However, in the case of FIG. 4A, since the light from the image display element 4 is reflected or transmitted twice in total by the half mirror 2, the amount of light that can be seen by the observer is small. When the concave half mirror 5 is used in place of the concave mirror 3 as shown in FIG. 4B, the reflection of the concave half mirror 5 is added to this, so that the light amount is reduced to 1/8. As a result, the observation efficiency is poor and only a dark electronic image can be seen. In order to further increase the brightness of the electronic image, the image display element 4 may have a large size and a large output, but this is not desirable because the weight and size of the display device increase.

When the concave half mirror 5 is used,
Since external light always enters when viewing an image from the image display element 4, it is necessary to provide a shutter in front of the concave half mirror 5 to block external light. A mechanical shutter may be used as the shutter, but it is practical to use a light and small liquid crystal shutter for a head or face-mounted shutter. Fig. 4
The liquid crystal shutter 6 restricts incident light to linearly polarized light and switches between passing and blocking by rotating the plane of polarization of the liquid crystal shutter 6. The intensity of the arriving external light is attenuated by half, and furthermore, the concave half mirror 5 and the half mirror 2
, The brightness of the external image is also reduced to ８, and only a dark external image can be seen.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a small and lightweight head or face-mounted display device that reduces light loss and improves light use efficiency. The purpose is to make a bright image observable.

[0007]

According to the present invention, there is provided a head-mounted or face-mounted display device for displaying an image to be observed, and partially transmitting and partially reflecting light from the image display device. For transmitting light reflected by the partial transmission / reflection surface to an eyeball of an observer, and a light amount control unit provided in front of the concave half mirror. In the head or face-mounted display device, the partial transmission / reflection surface is formed by a polarizing beam splitter, and a first quarter-wave plate is provided between the polarizing beam splitter and the concave half mirror,
A polarizing plate and a second quarter-wave plate are provided as the light amount control means.

[0008]

In this case, the direction of the polarization axis of the polarizing plate can be relatively rotated with respect to the second quarter-wave plate, so that the amount of external light can be arbitrarily controlled. .

[0010]

According to the present invention, a polarizing beam splitter is used as a partially transmitting partial reflecting surface for guiding light from an image display device to a concave mirror or a concave half mirror as an eyepiece optical system, and the concave mirror or the concave half mirror side is used. Since the quarter-wave plate is disposed, all linearly polarized light components in a predetermined direction from the image display device reach the observer's eyes without attenuation. Therefore, a bright electronic image from the image display device can be observed.

Further, by arranging a quarter-wave plate and a polarizing plate in front of the concave half mirror, an external image can be observed brightly, and at the same time, the amount of external light can be controlled and switched.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a head or face-mounted display device according to the present invention will be described below with reference to the drawings.
The basic principle of the present invention is that an image display device such as a liquid crystal display device, a half mirror for partially transmitting and partially reflecting light from the image display device, and a light reflected by the half mirror for an observer. In a head or face-mounted display device including a concave mirror or a concave half mirror that reflects light to be guided to the eyeball, a polarizing beam splitter is used instead of the half mirror, and between the polarizing beam splitter and the concave mirror or the concave half mirror. 1/4
A wave plate is provided, and the light from the image display device is first totally reflected by a polarizing beam splitter, and the direction of polarization of the light reflected by the concave mirror or the concave half mirror via the quarter-wave plate is changed by 90 °, and the polarization is changed. The objective of the present invention is to allow the beam splitter to pass through the entire beam splitter and guide the beam splitter onto the eyeball, eliminate the loss of light amount at the half mirror, and increase the efficiency of using display light from the image display device. Further, a quarter-wave plate and a polarizing plate are provided outside the concave half mirror, and the brightness of an external image is controlled by changing the direction of the polarization axis of the polarizing plate.

First, a first embodiment of the present invention will be described with reference to the schematic diagram of FIG. Observer's eyeball 1
A liquid crystal display in which a polarizing beam splitter 8 is disposed obliquely with respect to the optical axis, a quarter-wave plate 9 is disposed in front of the polarizing beam splitter 8, and a concave mirror 3 is disposed in front of the polarizing beam splitter 8, and is disposed outside the optical axis. An electron image from an image display element 4 such as an element is reflected by the polarizing beam splitter 8 to the concave mirror 3 side, and the image is reflected by the concave mirror 3.
As a result, the reflected light is enlarged and reflected as an enlarged image in the air, and the enlarged image is transmitted to the eyeball 1 through the polarizing beam splitter 8.

Here, the light emitted from the liquid crystal display element 4 is usually linearly polarized in a specific direction. One example of a liquid crystal display device is shown in FIG. This is an example of the configuration of a high-resolution active matrix type liquid crystal display device. In brief, a liquid crystal 10 is sealed between two glass substrates 11 and 12, and one of the substrates 11 A color filter layer 13 and a common electrode 14 are arranged on the inner surface of the substrate, and data lines 15 and scanning lines 16 are arranged on the inner surface of the other substrate 12 in a matrix.
17 and the transparent drive electrode 18 are connected to each other.
Polarizing plates 19 and 20 which are orthogonal to each other are arranged outside of 1 and 12. When no voltage is applied between the driving electrode 18 and the common electrode 14, the polarization direction of the linearly polarized light that has passed through the polarizing plate 20 is rotated by 90 ° by the TN mode liquid crystal 10 at that portion, and the other polarizing plate 1 is rotated.
9, when a voltage is applied between the electrodes 18 and 14, the liquid crystal 10 loses optical rotation, the polarization plane does not rotate, and the liquid crystal 10 is blocked by the other polarizing plate 19 and cannot pass. Therefore, the display image of such a liquid crystal display element 4 is linearly polarized in a specific direction. This polarization direction is arranged to be, for example, S-polarized light perpendicular to the paper surface.

As the polarization beam splitter 8, for example, a polarization interference filter is used. This is a kind of polarizer comprising an oblique incidence interference filter composed of a dielectric multilayer film. For example, S-polarized light reflects almost 100% and P-polarized light transmits almost 100%. When such a combination of the liquid crystal display element 4 and the polarization beam splitter 8 is used, most of the light emitted from the liquid crystal display element 4 is reflected by the polarization beam splitter 8. And
When the optical axis of the quarter-wave plate 9 is set at an angle of 45 ° with respect to the S-polarized light, the S-polarized light reflected by the polarization beam splitter 8 passes through the quarter-wave plate 9 and becomes circularly polarized light. After entering the concave mirror 3 and reflected there, it passes through the quarter-wave plate 9 again, changes to P-polarized light after transmission, and then passes through the polarization beam splitter 8 without reflection, thereby obtaining the eyeball 1 of the observer. To reach. Therefore, light emitted from the liquid crystal display element 4 reaches the observer's eyeball 1 with little loss, and a bright electronic image can be observed.

In the above description, even when an image display element 4 that emits unpolarized light, such as an LED array, is used instead of a liquid crystal display element in which emitted light is linearly polarized in a specific direction, a polarized beam is used. Since the amount of light is only attenuated by half when the light first enters the splitter 8, there is no attenuation after that as in the above case. Can be observed.

In FIG. 1, the concave mirror 3 may be a concave half mirror to have a see-through function. Even in this case, although there is a loss in the concave half mirror, the use efficiency of the light from the liquid crystal display element 4 is quadrupled as compared with the conventional example.

In the second embodiment, when the see-through function is provided as described above, the brightness of the external image can be changed. That is, in FIG. 2 in which the concave mirror 3 of FIG. 1 is replaced by a concave half mirror 5, a second quarter of the front of the concave half mirror 5 from the concave half mirror 5 side.
The wave plate 21 and the polarizing plate 22 are arranged. The optical axis of the second quarter-wave plate 21 is oriented in the same direction as the first quarter-wave plate 9. When the direction of the polarization axis of the polarizing plate 22 is set to the S direction, that is, perpendicular to the plane of the drawing, the external light 7 passes through the polarizing plate 22 and becomes S-polarized light, and the second quarter-wave plate 21 becomes circularly polarized light. . After passing through the concave half mirror 5, it is converted into P-polarized light by the first 波長 wavelength plate 9, passes through the polarization beam splitter 8, and reaches the eyeball 1 of the observer. At this time, the amount of the external light 7 becomes maximum. When the direction of the axis of the polarizing plate 22 is rotated, the light transmitted through the two quarter-wave plates 21 and 9 gradually increases in the S-polarized component, and is reflected by the polarizing beam splitter 8. When the direction of the polarization axis of the polarizing plate 22 is the P direction, the external light 7 is almost reflected by the polarizing beam splitter 8 and does not reach the eyeball 1. As described above, by changing the direction of the polarization axis of the polarizing plate 22, the brightness of the external image can be changed and its switching can be performed. In this embodiment, a case where a liquid crystal shutter is simply used (FIG. 4)
The use efficiency of the external light is doubled as compared with (b)).

As a method for changing the direction of the polarization axis of the polarizing plate 22, the polarizing plate 22 may be mechanically rotated, or a liquid crystal element for rotating the polarizing plane is provided after the polarizing plate 22, May be changed.

Although the head or face-mounted display device of the present invention has been described based on several embodiments, the present invention is not limited to these embodiments, and various modifications are possible. For example, as the polarizing beam splitter, in each of the above embodiments, a polarizing interference filter is used. However, a known polarizing beam splitter, such as a prism made of a birefringent crystal, may be used. .

[0021]

As is apparent from the above description, according to the head or face-mounted display device of the present invention, a portion for guiding light from an image display device to a concave mirror or a concave half mirror as an eyepiece optical system. Since a polarizing beam splitter is used as the transmitting partial reflecting surface and a quarter-wave plate is arranged on the concave mirror or concave half mirror side, all linearly polarized light components in a predetermined direction from the image display device are not attenuated by the observer. To reach. Therefore, a bright electronic image from the image display device can be observed.

Further, by arranging a quarter-wave plate and a polarizing plate in front of the concave half mirror, an external image can be observed brightly, and at the same time, the amount of external light can be controlled and switched.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of a first embodiment of a head or face-mounted display device of the present invention.

FIG. 2 is a diagram showing a schematic configuration of a second embodiment.

FIG. 3 is a perspective view illustrating a configuration of an example of a liquid crystal display element.

FIG. 4 is a diagram showing a configuration of a conventional head or face-mounted display device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Eyeball of an observer 3 ... Concave mirror 4 ... Image display element (liquid crystal display element) 5 ... Concave half mirror 7 ... External light 8 ... Polarization beam splitter 9 ... (1st) 1/4 wavelength plate 21 ... 2nd 1/4 wavelength plate 22 ... Polarizing plate

Continued on the front page (72) Inventor Toshiro Okamura 2-43-2 Hatagaya, Shibuya-ku, Tokyo Inside Olympus Optical Co., Ltd. (56) References JP-A-6-43397 (JP, A) 97378 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) G02B 27/28 H04N 5/64 511

Claims (1)

(57) [Claims] An image display device for displaying an observation image, a partial transmission reflection surface for partially transmitting and partially reflecting light from the image display device, and a light reflected by the partial transmission reflection surface for an observer. In a head or face-mounted display device having a concave half mirror that reflects light to be guided to an eyeball and a light amount control unit provided in front of the concave half mirror, the partially transmitting / reflecting surface is formed by a polarizing beam splitter. A first quarter of the distance between the polarizing beam splitter and the concave half mirror.
A head-mounted or face-mounted display device comprising a wavelength plate and a polarizing plate and a second quarter-wave plate as the light amount control means.