JP2000221899A - Display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a display device small in size, light in weight, thin in thickness, high in quality and having stable visual field characteristic. SOLUTION: This device is provided with an optical system which effectively bends a light beam including picture information from a picture display module by using a composite prism 33, and curvature of field aberration formed on the module 31 is effectively compensated by using a compensator 32. Thus, the display device thin in thickness and high in design potential is constituted without increasing the thickness of the entire optical system.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display device having a function of displaying an enlarged image by a virtual image for monitoring a moving image or a still image.

[0002]

2. Description of the Related Art Various information devices, especially devices capable of handling visual information by means of liquid crystal or photoelectric image display means, have made remarkable progress.
In addition, information processing machines for personal use, which are so-called mobile devices that can be used anywhere and at any time, have been remarkably developed. The performance required of this mobile device is a compact package with good portable performance, high information processing speed, a large number of processing functions, etc., and more accurate information in a limited space of a small device. There is a need for a means for displaying the information in an easily understandable manner. At present, liquid crystal display means and the like that fill the entire surface of the device are mainstream, but there is no possibility of following the miniaturization of the device.

As one of the effective display methods, a head-mounted display, a finder (check) display, and the like have attracted attention in recent years, and much research and development of devices have been advanced.

[0004] It is a method of enlarging an image such as a moving image or a still image on a display device by a photoelectric device such as a substantially small liquid crystal or plasma as a virtual image, and visually projecting it as an apparently larger screen than an actual display screen. , Device. Enlarging a small display device as a virtual image has the advantages of reducing the size of equipment, reducing the power consumption of the device, and reducing the price, and presenting an apparent display screen as a large virtual image regardless of the size of the display element. Can be. Today, with the improvement of resolution, contrast, brightness, performance of magnifying optics, and image processing technology of small display devices, high-performance magnified display devices are being used in various devices and scenes. Was.

FIGS. 6 to 11 show an optical system used in a conventional head mount.

FIG. 6 is an explanatory view of a conventional refracting lens type eyepiece optical system. Similar to the monitoring finder optical system of many video camcorders, one or a plurality of lenses are combined to project a virtual image visually with positive refracting power. Although the structure is simple, and it is lightweight as an optical system having a relatively small angle of view, it is widely used in general. However, the structure is slightly larger in the optical axis direction of the optical system. In the figure, a lens group 2 having a positive refractive power and comprising a plurality of lenses for correcting various aberrations on a display image (not shown) drawn on a display module 1 made of a small liquid crystal or the like.
The virtual image enlarged as a whole is projected on the visual sense of the eye 4 in the direction of the optical axis 3 of the lens group.

FIG. 7 is an explanatory view of a conventional reflection type eyepiece optical system. FIG. 7 shows a reflective display device that projects an enlarged virtual image by a concave mirror. A display image (not shown) drawn on the display module 1 is first reflected by the half mirror unit 5 and converged by the concave mirror 7 arranged on the optical axis 6, and again transmits through the half mirror unit 5 again, A virtual image (not shown) of the enlarged display image is projected to the eyes 4. By using the concave mirror 7, the configuration of the optical system can be folded, and the entire configuration can be realized compactly.
There is also an advantage that coma and chromatic aberration of magnification can be suppressed due to the principle of the optical system. Therefore, in general, the observation angle of view is 4
It can be as large as about 0 degrees, and a relatively wide screen can be observed.

FIG. 8 is an explanatory diagram of an eyepiece optical system using a conventional concave mirror. In the figure, the half mirror shown in FIG. 6 has a structure in which the half mirror faces the concave mirror. The optical path reciprocates in the optical axis, and the optical system can be made more compact. A display image (not shown) drawn on the display module 1 in FIG.
Is transmitted through a concave mirror 8 made of an optically rotating glass material having a translucent polarizing film provided on an incident surface, and then is a half made of a polarizing film having a polarization axis perpendicular to the polarization axis of the incident polarized light facing the concave mirror 8. While being reflected by the mirror 9 and again reflected and converged by the concave mirror 8, a virtual image of the enlarged display image can be projected to the eye 4. Further, by disposing the polarizing element in this manner, a direct display image (light ray) from the display module 1 can be removed. According to this method, a wide angle of view of 40 degrees or more can be obtained, and the generation of aberration can be suppressed to a relatively small value.

FIG. 9 is an explanatory view of an eyepiece optical system using a conventional decentered concave mirror. In FIG. 1, a virtual image of a display image (not shown) of the display module 1 can be projected to the eye 4 by a concave mirror 10 having an optical axis decentered from the line of sight disposed in front of the eyes. Further, since a light beam with a wide angle of view can be sent to the eyeball and the optical path can be taken out without using a half mirror unlike the prior art, almost 100% of the light quantity from the display module 1 can be used. Since the display module 1 is simple in configuration and can be arranged on the side of the axis of the line of sight, a compact display device as a whole can be realized.

[0010] An optical system based on this concept and having a prism having an eccentric concave mirror has been disclosed. FIG.
FIG. 2 is an explanatory diagram of an eyepiece optical system using a conventional prism.
As shown in FIG. 10, the display module 1 is disposed diagonally above the eye, and as a light path, light of a display image (not shown) of the display module 1 enters the prism 11 and is further totally reflected. The light is reflected by the first internal reflection surface 12 that satisfies the conditions, and is reflected from the emission surface 12 having the same curved surface as the first internal reflection surface 12 while converging the reflection from the first internal reflection surface 13. An enlarged virtual image of the display image is projected to the eye 4. As described above, since there is no half mirror or blocking member in the middle of the optical path, the display image can be observed with high efficiency, that is, a bright image. Although a chromatic aberration does not occur in principle because a virtual image is created by reflection, the reflecting surface, especially the inner reflecting surface 2, is largely decentered, and thus an eccentric aberration occurs. In order to improve this, a three-dimensional aspherical surface (hereinafter, a free-form surface) which is a non-rotation object is adopted.

Here, the free-form surface will be described a little more. Assuming that the drawing sheet is a generatrix section and a plane perpendicular to the drawing sheet is a sagittal section, the rotationally symmetric spherical and aspherical surfaces have a radius of curvature in the generatrix section and the sagittal section. Are equal, and the focal lengths of both sections are the same. However, in a non-rotationally symmetric free-form surface, the radii of curvature of the generatrix section and the sagittal section are different, and naturally the focal lengths of both sections are also different. By employing a free-form surface having such a property for a plurality of prism surfaces, eccentric aberration can be favorably corrected. In order to match the aspect ratio between the display module 1 and its virtual image, the focal lengths of the meridional section and the sagittal section of each prism surface are appropriately set, and the focal lengths of the whole system and the sagittal section of the free-form surface prism are set. The focal lengths are set to be the same.

FIG. 11 is an explanatory view of an eyepiece optical system using a conventional roof prism. The structure and operation of an enlarged display device using an optical path bending optical system using a roof prism will be described. Referring to FIG. 1, the display device includes a small image display unit 13 such as an LCD, a roof prism 14 for bending an optical path, and a magnifying optical system 1.
Consists of five. The light having the image information indicated by, propagates from the entrance surface 16 of the roof prism 14 to the inside of the prism from the small image display unit 13 and is reflected by the internal reflection surfaces 17, 18, and 19, and is shown in FIG. As described above, the light enters the magnifying optical system 15 (eyepiece) from the surface 16 that is the same as the incident surface, and the image on the small image display unit 13 is visually enlarged and projected as a virtual image. The reflecting surfaces 1 and 3 are coated with a reflecting film of silver or the like in order to increase the reflectance, and the reflecting surface 2 is totally reflected since the incident angle with respect to the reflecting surface exceeds a critical angle, so that total reflection is caused. There is no reflective film to increase the reflectance.

By using such an optical prism, the optical system can be made relatively thin in the line of sight, and the small image display unit 13 and the magnifying optical system 15 can be connected to the entrance / exit surface 1.
6, the head portion as a whole has less protruding portions and can be made relatively thin.

[0014]

However, problems to be solved in the above-described virtual image projection type display device will be described.

First, in the case of a straight-axis refracting lens type, the distance in the optical axis direction directly determines the size of the display device, so that it is difficult to make the display device compact. Contrary to this, if the size is to be reduced, performance such as the viewing angle and the size of the pupil will be reduced. Further, since the virtual image is projected only by the refraction system, the viewing angle is relatively small and the size of the pupil is also small. This is because coma aberration and chromatic aberration of magnification occur, and the reason why the angle of view is about 20 degrees or more is that the occurrence of these aberrations degrades the peripheral image quality.

Next, in a concave mirror type in which a display module is arranged on a side portion, the same type can reduce the entire configuration as compared with the above-mentioned refractive lens type because the optical path is folded. Although it is possible to realize a small size and light weight and a good mounting balance, it is necessary to provide a half mirror for extracting a light beam from the reciprocating optical path since the optical path reciprocates. It will be as follows. In order to further widen the angle of view, there is a problem in correcting the curvature of field generated by the concave reflecting mirror, and it is difficult to obtain an observation angle of view of about 40 degrees or more. Further, there is a disadvantage that the entire configuration is suddenly increased in size when the angle of view is widened due to the presence of a half mirror arranged in an inclined manner.

In the type having the same concave mirror and facing the half mirror, although it has a potential to widen the angle of view, an isolator system using a polarizing element is provided in order to cut off a light beam from the image display module directly entering the eyes. The optical system must be assembled, and the optical system becomes complicated, which affects adjustment man-hours and costs. Further, it is difficult to obtain a polarizer having good polarization characteristics and efficiency over the entire use wavelength range, and there is a problem that image quality is reduced and luminance is insufficient.

Next, for the concave mirror type, including the type using a prism, a compact and efficient optical system capable of obtaining a light amount of almost 100% can be realized.
In order to form a decentered optical system, it is necessary to correct axial astigmatism, coma aberration, and image plane inclination. Further, if an aspherical optical system is used for these corrections, there is a problem in that design and mirror finishing are difficult.

The present invention solves the above-mentioned problems, and realizes a smaller, lighter, and especially thinner display device as a whole to enhance mounting stability and design potential, and has a high quality and stable visual field characteristic. It is an object to provide a display device.

Finally, with regard to the folding optical system type using a roof prism, a thin optical system can be realized as a whole, but the magnifying optical system (eyepiece lens system) can be made thin. Doing so indicates that it is difficult to correct various optical aberrations,
By dividing into two groups as in the conventional technique, spherical aberration, coma aberration and the like are relatively alleviated, but it cannot be said that it is extremely difficult to correct field curvature aberration. The effect increases exponentially as the viewing angle increases.

[0021]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a small-sized image display section made of a liquid crystal or a photoelectric element, and an optically magnified image of the small-sized image display section as a visual image. And an optical prism member having a function of bending the optical path from the small image display unit to the image enlargement unit, and the optical prism member is substantially flat with the display screen of the small image display device. After facing the non-contact at the incident surface, and further bending the optical path incident from the small image display device into the optical prism on the plane inside the prism, or the first internal reflection surface composed of a curved surface, the second optical path is formed substantially flat. After being bent on the inner reflection surface, and further bent on the third inner reflection surface formed of a flat surface or a curved surface, and then passed through the exit surface formed in the same plane as the incident surface. Said emitted from the optical prism member, a display apparatus for projecting an enlarged as virtual images visually more by the image enlargement portion by,
A correction plate including an aspherical surface for correcting field curvature aberration of the enlarged virtual image generated on the small image display device is provided between the small image display device and the optical prism member.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the first aspect of the present invention, a small-sized image display section made of a liquid crystal or a photoelectric element and an image formed by the small-sized image display section are optically magnified visually as a virtual image. An image magnifying portion, and an optical prism member having a function of bending an optical path from the small image display portion to the image magnifying portion, wherein the optical prism member is non-contact with the display screen of the small image display device on an almost flat entrance surface. After bending the optical path from the small image display device into the optical prism from the plane inside the prism, or the first internal reflection surface formed of a curved surface, and then bending the second internal reflection surface formed of a substantially flat surface, After being bent at the third internal reflection surface formed of a flat surface or a curved surface, the light is emitted from the optical prism member by passing through the emission surface formed in the same plane as the incidence surface. And a display device for visually enlarging and projecting as a virtual image by an image magnifying unit, wherein a field curvature aberration of an enlarged virtual image generated on the small image display device between the small image display device and the optical prism member is corrected. The display device is characterized in that a correction plate including an aspherical surface is provided. By adopting such a configuration, an image plane of an enlarged virtual image generated by a comparatively thin magnifying optical system The curvature aberration can be easily corrected, and the entire optical system of the display device can be configured to be small and light, particularly without greatly increasing the human gaze direction.

According to a second aspect of the present invention, the correction plate is provided in a non-contact manner with the optical prism. With this configuration, the correction plate is provided in the optical prism. Thus, stable and efficient internal light propagation can be realized without affecting the total reflection at the second reflection surface.

According to a third aspect of the present invention, the correction plate comprises a substantially flat optical member having a refractive power, such as a Fresnel lens having an aspherical transmission optical effect or a hologram lens. By taking such a configuration, it is possible to make the thickness of the action portion for correcting the field curvature extremely thin,
This can greatly contribute to a reduction in the thickness of the optical system as a whole in the viewing direction.

According to a fourth aspect of the present invention, the third internal reflection surface inside the optical prism is provided on a free-form surface, and has an action of correcting a field curvature aberration of an enlarged virtual image. By adopting such a configuration, a small-sized image display unit formed by a liquid crystal or a photoelectric mechanism can be installed as close as possible to an optical prism, which further contributes to a reduction in the thickness of the optical system as a whole in the line of sight. You can do it.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1) FIG. 1 is an external view of a display apparatus according to Embodiment 1 of the present invention. In FIG. In addition, the head unit 21 is attached to one of the left and right eyes (the left eye in the present embodiment), or the peripheral unit is brought into contact with the head unit 21 to read the enlarged image display by the output virtual image. The head unit 21 includes a liquid crystal having a function of forming a display image or a display module 22 made of photoelectric means, and an image magnifying lens 23 for optically enlarging the image of the display module 22 as a virtual image. Prism 24 having a function to bend the optical path to form a compact head section
And a small circuit section 25 for driving the display module 22 and the like.

The head holder 26 and the head holder 2 for stably fixing the head to the head are provided.
Signal cable lead-out part 27 provided along 6
Is provided. The signal cable lead-out portion 27 is installed so as to be guided to the rear part of the ear hook so that the signal line at the time of mounting does not become troublesome on the face.

The head holder 26 is mainly composed of a nose bridge,
It is held by the pinna and the occipital region, so that the eyepiece of the display device can be stably held at the pupil position. However, the present invention is not limited to this embodiment, and can take various forms such as a pair of spectacles to be worn on both ears, a suction type, and a head mount type.

Further, there are provided an adjustment mechanism (not shown) capable of adjusting a fine inclination of the head portion and an eccentricity of the eyepiece portion which occur at the time of mounting due to individual differences, and a mounting strength adjusting mechanism (not shown). Will be omitted.

Next, the structure and operation of the peripheral portion of the main optical system will be described with reference to FIG. FIG. 2 shows a main part view of the display device of FIG. 1. In FIG. 2, light required for projecting a virtual image is received from a backlight device 29 which receives power from a backlight power supply 28 provided outside. Be emitted. Further, an image is formed by an image display module 31 having an operation of reproducing an image information signal from an external image processing module 30 as an image. The light beam emitted from the backlight 29 passes through the image display module 31 to form a light beam containing image information. After passing through the compensator 32, this light ray enters the prism from an incident surface 34 which is a part of the side surface of the compound prism 33 having a substantially triangular pyramid shape, is reflected by the first internal reflection surface 35, and is reflected by the first internal reflection surface 35. The light reaches the second inner reflection surface 34 formed of the same surface as that of the first inner reflection surface 34. This second internal reflection surface 34
The light ray reflected again at the third inner reflection surface 36 is further reflected and exits from the exit surface 34, which is the same as the incident surface 34 and the second inner reflection surface 34, to the outside of the composite prism 33. . The emitted light is mainly transmitted to the image display module 3 by an image magnifying lens group 37 including two groups of convex lenses.
1 is projected as a visually enlarged virtual image. Further, the above-described first internal reflection surface 35 and third internal reflection surface 36
In order to increase the internal reflectance of light rays, a coating of a metal such as silver or aluminum is deposited, or a coating treatment with a dielectric multilayer film is performed. In addition, the above-described incident surface 34, second internal reflection surface 34, and exit surface 3
No. 4 is not particularly subjected to the above-mentioned coating treatment for increasing the reflectance. This is because not only is there no need for reflection processing at the time of incidence and emission, but also at the second internal reflection surface 3.
The incident angle of the light beam reaching the surface 4 is as large as about 60 degrees, and all the light beams incident to satisfy the total reflection condition defined by Snell's law without leaking to the outside of the composite prism 33. Is reflected inside the composite prism 33. Therefore, a coating process for increasing the reflectance becomes unnecessary. The angle of incidence of light rays incident on the first internal reflection surface 35 and the third internal reflection surface 36 is 30.
Because of its small size, it is not possible to satisfy the condition for total reflection, so that a coating treatment for increasing the reflectance is required.

The configuration and operation of the main part of the display device according to the present invention have been outlined, but a thinner image magnifying lens group is realized, and the field curvature aberration caused by the thin magnifying lens group is corrected. The configuration and operation of the compensator 32 installed to perform the operation will be described in more detail.

As shown in FIG.
Is disposed between the image display module 31 and the prism 33 and in a non-contact manner with the prism 33, and the opposing surface is substantially flat, and the surface on the image display module 31 side has a field curvature correction effect. Aspherical surface. This aspheric surface is composed of an on-axis hyperboloid reference surface, and generally,

[0034]

(Equation 1)

In the following, each parameter is defined as follows: K = −227.387389 A = 3.66894E-3 B = −2.05524E-4 C = 2.92782E−6 Become like

When the compensator 32 is provided, the field curvature aberration on the image display module 31 can be effectively corrected when viewed from the image magnifying lens group 37, so that a portion having a large angle of view (high image height) can be obtained. In this case, it is possible to suppress a decrease in the resolution and contrast of the image.

Further, the fact that the first inner reflection surface 35 and the third inner reflection surface 36 are coated with different functions will be described in more detail with reference to FIG.

In the drawing, the first inner reflection surface 35 is mainly subjected to the above-described metal film coating treatment with silver, aluminum, or the like in order to obtain a reflectance as high as possible close to 100%. However, the third inner reflection surface 36 is set so that the reflectance is in the range of about 30% to 70%, and the remaining light rays are transmitted to the outside of the compound prism 33. This is a counterproductive action to reduce the amount of light reaching the image display module 31 and to make the observed image look bright. However, this is for installing a see-through mechanism capable of directly observing an important external environment as a display device, and is necessary for improving safety and work efficiency of a wearer. Without the see-through mechanism, the user would visually lose stereoscopic vision and sense of distance, and would not be able to cope with changes in the external environment or the like, making it impossible to ensure safety. Further, when it is necessary to recognize the external environment at the time of switching work, the display device must be removed each time, which is a problem in terms of work efficiency. For this reason, the third inner reflection surface 36 is not a perfect reflection surface but a half mirror that transmits some light rays to the outside.

Further, the see-through mechanism will be described with reference to FIG. FIG. 3 is an enlarged view of the see-through configuration of FIG. In the figure, a light beam from a display module (not shown) propagates through the inside of the compound prism 33 and is reflected by the third internal reflection surface 36 to reach the image magnifying lens group 37.
Further, as described above, the third internal reflection surface 36 is formed of a half mirror surface and has a function of reflecting a part of an incident light beam and transmitting the remaining light beam, so that a part of an external light beam can be transmitted. As shown in the figure, a light ray 38 from the outside passes through a liquid crystal shutter portion 39, a wavefront compensation prism 40, and a third internal reflection surface 36 which is a half mirror, passes through the inside of the composite prism 33, and passes through the image magnifying lens group. It reaches the eye (not shown) via 37. Here, the structure and operation of the liquid crystal shutter 39 and the wavefront compensation prism 40 will be described. This liquid crystal shutter 39 simply controls the amount of transmitted light. By closing the liquid crystal shutter 39, a screen from a 100% display module (not shown) is projected visually, and as the liquid crystal shutter 39 is opened. By increasing the number of light rays from the outside, it is possible to present the external situation more clearly. In addition, the wavefront compensation prism 40 having a substantially triangular pyramid shape close to the third internal reflection surface 36 is such that the third internal reflection surface 36 has a normal of approximately 30 with respect to the line of sight.
If the light rays are directly introduced due to the inclination, the external scene apparently shifts to the right side, which is inconvenient for recognition or work. It has the effect of compensating the line of sight,
A concave surface 41 having a negative refractive power is provided at the front end to compensate for a wavefront transmitted through the image magnifying lens group 37 having a positive refractive power, and the refractive power of the image magnifying lens group 37 is canceled to generate a natural light beam. Comes to the line of sight.

In the first embodiment of the present invention, an eyeglass is used. That is, an enlarged virtual image is projected by both the left and right eyes, but a form having a high design potential can be realized even when worn with one eye due to its small size and light weight without necessarily corresponding to both eyes.

(Embodiment 2) Embodiment 2 of the present invention will be described with reference to FIG. FIG. 4 is a main partial view of a display device according to a second embodiment of the present invention. This figure shows a top view of the optical prism 42, which is a main part of the display device, and its peripheral portion. In order to make the optical system thinner and lighter, the optical system according to the first embodiment described above is used. The spherical compensator and a part of the image magnifying lens group are replaced with the flat plate optical system shown in FIG.

The aspherical optical system must have an optical member having a certain thickness, and the optical system becomes thicker in the line of sight, which affects the thickness of the display head. This is for realizing a head having higher design potential and mounting performance. There are two main types of flat optical systems, depending on how they are given refractive power.

One is that a gradient of a refraction surface of a lens called a Fresnel lens is gradually transferred to a plane, and is formed as a concentric refraction gradient pattern.

The other is a grating lens or Horoka, also called a lens, which forms a necessary wavefront by using light diffraction and forms a concentric pattern around the optical axis like a Fresnel lens. I do. However, the arrangement pitch of the concentric patterns is extremely small in order to increase the diffraction efficiency as compared with the Fresnel lens.
In any case, the effect for correcting the optical aberration can be apparently formed almost in a planar shape.

The flat plate optical system in the present embodiment is based on a Fresnel lens 43 as shown in FIG. 1 and corrects the curvature of field on the image display module viewed from the observer side. At the position, the surface gradient is substantially the same as the surface gradient in the aspherical shape in the first embodiment, and a similar aberration correction effect can be obtained.

Third Embodiment A third embodiment of the present invention will be described with reference to FIG. FIG. 5 is a main partial view of a display device according to a third embodiment of the present invention. This figure shows a top view of the compound prism 44, which is a main part of the display device, and its surroundings, as viewed from the observer side by the correction plate described in the first and second embodiments. In this case, the function of correcting the field curvature on the display module is given to the inner reflecting surface of the compound prism, and by adopting such a configuration, the optical system can be made thinner and lighter, The present invention can improve the mounting performance of the display device and realize a high design potential.

In the figure, the aberration is corrected by changing the first inner reflection surface 45 of the compound prism from a substantially flat surface to an off-axis reflection aspheric surface. This reflecting aspherical surface is formed by a curved surface having a slight bulge with the hyperboloid as a reference surface, which is difficult to understand in the figure, and the value of K among the aspherical surface coefficients is larger than 10.

Further, by using the aspherical surface, it is possible to effectively correct the curvature of field caused by a relatively thin magnifying optical system without increasing the number of optical components, and to reduce the overall thickness. Optical system can be formed without enlargement,
Significant effects can be expected in terms of mounting performance and freedom of design as described above.

[0049]

As is apparent from the above embodiments, according to the present invention, the image display module is mounted on the image display module when viewed from an observer who is likely to be generated by the magnifying optical system formed relatively thin in the optical axis direction. By effectively suppressing the generated curvature of field, thin and compact optics can be realized, and the head portion of the display device can be configured to be small and light, particularly thin.
The feeling of wearing and balance on the face is remarkably improved due to the reduction in thickness, and the simplification of the mechanism can be realized for the assist of wearing, and the degree of freedom in design can be increased.

[Brief description of the drawings]

FIG. 1 is an external view of a display device according to a first embodiment of the present invention.

FIG. 2 is a main partial view of the display device of FIG. 1;

FIG. 3 is an enlarged view of the see-through configuration of FIG. 2;

FIG. 4 is a main partial view of a display device according to a second embodiment of the present invention;

FIG. 5 is a main partial view of a display device according to a third embodiment of the present invention;

FIG. 6 is an explanatory view of a conventional refraction lens type eyepiece optical system.

FIG. 7 is an explanatory diagram of a conventional reflective eyepiece optical system.

FIG. 8 is an explanatory diagram of an eyepiece optical system using a conventional concave mirror.

FIG. 9 is an explanatory diagram of an eyepiece optical system using a conventional decentered concave mirror.

FIG. 10 is an explanatory diagram of an eyepiece optical system using a conventional prism.

FIG. 11 is an explanatory diagram of an eyepiece optical system using a conventional roof prism.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 21 Head part 22 Display module 23 Image magnifying lens 24 Composite prism 25 Small circuit part 26 Head holder part 27 Signal cable lead-out part 28 Backlight power supply 29 Backlight device 30 Image processing module 31 Image display module 32 Compensator 33 Composite prism 34 Incident surface (Second internal reflection surface, exit surface) 35 First internal reflection surface 36 Third internal reflection surface 37 Image magnifying lens group

Claims (4)

[Claims] 1. A small image display section comprising a liquid crystal or a photoelectric element, an image enlargement section for optically enlarging an image on the small image display section as a virtual image visually, and the image from the small image display section. An optical prism member having a function of bending an optical path to an enlarged portion, wherein the optical prism member faces the display screen of the small-sized image display device in a non-contact manner on a substantially flat incident surface, and further from the small-sized image display device. After bending the optical path incident into the optical prism on the first internal reflection surface formed of a flat surface or a curved surface inside the prism, then bending the optical path on the second internal reflection surface formed of a substantially flat surface, further flat or formed of a curved surface After being bent at the third internal reflection surface, the light is emitted from the optical prism member by passing through an exit surface formed in the same plane as the incident surface, and Wherein the image enlargement unit to a display apparatus for projecting an enlarged as virtual images to the visual sense,
A display, wherein a correction plate including an aspheric surface for correcting a field curvature aberration of the enlarged virtual image generated on the small image display device is provided between the small image display device and the optical prism member. apparatus. 2. The display device according to claim 1, wherein the correction plate is provided in non-contact with the optical prism. 3. The display device according to claim 1, wherein the correction plate is made of a substantially flat optical member having a refractive power, such as a Fresnel lens having an aspherical transmission optical function or a hologram lens. 4. The display according to claim 1, wherein the third internal reflection surface inside the optical prism is provided on a free-form surface, and corrects a field curvature aberration of the enlarged virtual image. apparatus.