JPH04298710A - Display device - Google Patents

Abstract

PURPOSE:To realize a display device which is transparent and whose display surface agrees with a device surface in substance as the headup type display device. CONSTITUTION:This device is constituted of a display unit which projects a specified video, an image-formation optical system 2 which forms the real image of the video by the display unit at a specified position, and a transparent hologram screen which is arranged at the image forming position of the image- formation optical system and which diffracts the real image with directivity in a specified direction.

Description

[Detailed description of the invention]

0001

FIELD OF INDUSTRIAL APPLICATION The present invention relates to a display device that images an image displayed on a display device onto a transparent screen using an imaging optical system, and in particular, a display device that displays an image in a field of view by superimposing it on a background. The present invention relates to a so-called head-up display type display device.

[0002]Head-up displays, which allow displays of various devices to be seen superimposed on the forward field of view (background), have been used in aircraft, especially fighter jets, and in recent years have been applied to automobiles, etc. from the perspective of improving safety. is also popular.

By the way, if such a head-up display type display device could be used at counter operations in banks or other service industries, at speech stands for speeches and lectures, or at commentary seats at sports games, etc., it would reduce fatigue and improve efficiency. It is useful and convenient from the viewpoint of etc. In other words, since the display image (second information) can be superimposed on the front field of view (first information), counter staff, lecturers, commentators, etc. can see the front view without moving their eyes. 1
It is possible to simultaneously view necessary secondary information (account information, lecture materials, individual player data, etc.) while keeping information (customers, audience, match site, etc.) within the field of view.

[0004] The present invention was developed in response to such a need, but the present invention is not limited to the above-mentioned applications, and can be applied to, for example, personal computers, word processors, or other OA applications.
The present invention can be applied to all display devices including displays of devices and the like.

[0005]

2. Description of the Related Art Conventionally, CRTs, liquid crystal display devices, plasma display devices, etc. have been used as display devices for personal computers and word processors. However, all conventional display devices are plate-shaped or box-shaped opaque objects, and while using the display device, the eyes are focused on the display surface and cannot see anything else. Or, while looking at something, in order to refer to the information displayed on the display device, it is necessary to move the line of sight to the display device, and during that time, the user has to take his eyes off the object he was looking at. Must be. Therefore, if there is a transparent display device through which the background can be seen, it is possible to see both the background and the display without having to shift your line of sight.

[0006] A head-up display (HUD) is a method for superimposing a background and a display. This eliminates not only the need to move the line of sight but also the focus of the eyes by superimposing the image (virtual image) of the display device within the field of view and displaying it at a distance (FIG. 29). In FIG. 29, a background image and an image from a display 105 are sent to an image combiner 10 via a transmission hologram 103.
1 to reflect and superimpose.

A reflection hologram is generally used as an image combiner. This is because the wavelength selectivity of the reflection hologram increases the light utilization efficiency for both display light and background light. Note that since the head-up display itself is a known technology, detailed explanation will be omitted.

[0008]

[Problems to be Solved by the Invention] It goes without saying that the head-up display technology can be used in the transparent display device mentioned above, but if it is applied as is, it will cause a virtual image (
Because the position of the display (display) does not match the device surface (image combiner surface), it cannot be used in the same way as conventional display devices (CRT, liquid crystal display, etc.), and there are problems such as a sense of discomfort, or problems with clear viewing distance. (about 30 cm), there was a problem in that the image combiner surface was too close to the eyes.

This will be explained in detail with reference to FIG. 29 mentioned above. The HUD includes a display 105, a transmission hologram 103,
It is composed of a reflection hologram (image combiner) 101. The image displayed on the display 105 is formed by two holograms 103 and 101 as a virtual image IV on the opposite side of the image combiner as viewed from the eye position. This makes it possible to superimpose the background B and the display image (virtual image) IV.

The direction of diffraction and reflection of light by the hologram depends on the wavelength of the light (wavelength dispersion). When using light with a wide wavelength band rather than monochromatic light like a laser, usually
Compensate for wavelength dispersion using two holograms. Originally, it is meaningful to use a hologram in the image combiner part, but in order to correct chromatic aberration, a pair (101, 10
3) It is used as. When configuring an imaging system with two holograms, it is difficult to obtain a system with a large screen and short focal length (the distance between the virtual image and the image combiner is short) (the numerical aperture becomes large, making it difficult to correct chromatic aberration) .

[0011] Therefore, when a head-up display is used, the position of the device (display surface) and the position of the display cannot be aligned, unlike conventional display devices (light-emitting type). When viewing the display at a clear viewing distance (approximately 30 cm), the image combiner will be close to the face, and the display device cannot be said to be suitable for practical use.

An object of the present invention is to realize a display device that is transparent and whose display surface substantially coincides with the surface of the device.

[0013]

[Means for Solving the Problems] In order to achieve the above object, according to the present invention, an image displayed on a small display device is
An image is formed on a hologram surface by an imaging system, and the hologram is created to have the function of deflecting spherical wave light diverging from the position of the imaging system toward the position of the user's eyes of the display device. In addition, in order to expand the field of view in which the display can be seen, holograms that deflect the spherical wave light diverging from the pupil position of the imaging system in different directions near the eye position are layered or recorded in multiple layers. can be used.

That is, according to the present invention, there is provided a display device for projecting a predetermined image, an imaging optical system for forming a real image of the image by the display device at a predetermined position, and an image forming position of the imaging optical system. A display device is provided that includes a transparent hologram screen that is disposed in a transparent hologram screen and that diffracts the real image in a predetermined direction with directionality.

The hologram constituting the transparent hologram screen can be realized by either a reflection hologram or a transmission hologram. This hologram transmits spherical wave light that propagates while diverging from the position of the imaging optical system for one wavelength in the display light spectrum to the eye of an observer located on the same side of the hologram surface as the imaging optical system or on the opposite side of the space. It has the function of converting into spherical wave light that propagates while converging toward the position of .

According to another embodiment, the hologram transmits spherical wave light that propagates while diverging from the position of the imaging optical system for one wavelength in the display light spectrum, on the same side of the hologram surface as the imaging optical system. Alternatively, the hologram may be configured as a multilayer stack of multiple holograms that are diffracted toward multiple points near the observer's eye position located in the opposite space, or as a hologram that is multiplexed in the same photosensitive medium. Ru.

Preferably, the hologram transmits spherical wave light that propagates while diverging from the position of the imaging optical system for one wavelength in the display light spectrum, to a position on the same side or on the opposite side of the imaging optical system with respect to the hologram surface. a first hologram that converts into spherical wave light that converges and propagates toward a first point;
A second hologram that converts into spherical wave light that converges and propagates toward a second point located on the same side of the space as the imaging optical system with respect to the hologram surface, or a photosensitive medium layer that is superimposed in multiple layers, or that is the same photosensitive medium layer. This is a hologram recorded multiple times within the image, and these two points, the first and second, are selected at the positions of the observer's left and right eyes.

A wavelength bandpass filter that selectively transmits light within the selective reflection wavelength width of the reflection hologram or an optical path folding mirror having wavelength selectivity is inserted in the optical path between the reflection hologram and the display. It is also possible to do so. A variable aperture stop may be attached to the imaging optical system.

According to another embodiment, the transparent hologram screen is formed by a transparent curved substrate on which a hologram is formed, and in this case, the imaging optical system focuses a planar image of the display onto the curved hologram screen. It has field curvature aberration that causes the image to be imaged. Other features will become apparent from the following description of the embodiments. In the present invention, "one wavelength" means a wavelength band having a certain width.

[0020]

[Operation] Due to the transparency of the hologram, the background and display can be superimposed, and the image combiner surface works as an image emitting surface like the display surface of a conventional display device, so the display surface of the display device and the actual display It is possible to realize a display device in which the positions of the two coincide with each other.

[0021] In addition, a hologram transmits spherical wave light that propagates while diverging from the position of the imaging optical system for one wavelength in the display light spectrum, to a space located on the same side or on the opposite side of the imaging optical system with respect to the hologram surface. Since it has the function of converting into spherical wave light that converges and propagates toward the observer's eye position, the observer sees the real image of the image displayed on the display on the display surface of the image combiner (reflection hologram or transmission hologram). I can do it.

[0022] By setting the image formation positions of the hologram at a plurality of positions near the eye, even if the eye moves within a certain range, it can be reliably captured within the visual field. The imaging positions are preferably selected for the left and right eyes of the observer.

A wavelength bandpass filter or an optical path folding mirror having wavelength selectivity disposed in the optical path between the reflection hologram and the display selectively reflects light within the selective reflection wavelength range of the reflection hologram. Since the light is transmitted, the display light can be set to a desired color, for example. In addition, by making the wavelength band of the light incident on the reflection hologram the same as or smaller than the wavelength selection width of the reflection hologram itself, the light that passes through the reflection hologram is weakened, and leakage light from the surroundings of the display device is prevented. You can make it invisible.

The visible range of the displayed image can be easily controlled by controlling the size of the variable aperture stop provided in the imaging optical system. Furthermore, the present invention can be applied to a curved hologram screen, and in that case, it is only necessary to provide the imaging optical system with field curvature aberration that causes a flat image of the display to be imaged onto the curved hologram screen. .

[0025]

[Embodiment] According to an embodiment of the present invention, in the display device 5 shown in FIG.
is imaged on the medium surface of a transparent reflective hologram (image combiner) 4 by an imaging means (lens etc.) 3,
By directing the reflected diffracted light 21 from the reflective hologram 4 toward the user's eye position 6, a transparent display device is constructed.

The reflection hologram 4 emits spherical wave light diverging from the pupil (or approximately central position) position 22 of the imaging means 3 to the eye position 6 with respect to the center wavelength λc (FIG. 2) of the display light wavelength band. (The converging light beam is shown by the thick line 23 in FIG. 1). Note that since the method for creating a reflection hologram is well known, its explanation will be omitted.

Light emitted from a point P on the display surface 2 forms a real image Q on the medium surface of the reflection hologram 4 by the imaging means 3. Although Q behaves like a point light source, the solid angle Ω of light divergence is approximately equal to the solid angle Ω0 of light convergence when point Q is formed by the imaging means 3. Therefore, if it is desired to widen the range of the eye position 6 where the display can be seen, the aperture of the imaging system is increased accordingly (described later).

The lights emitted from all points on the display surface 2 overlap at the eye position 6, so the entire display can be seen. If we consider the case where the reflection hologram 4 is replaced with a half mirror 7, as shown in FIG. 28, the entire display (indicated by the arrow figure in FIG. 1) cannot be viewed at the same time due to mere specular reflection. That is, since the direction of reflection at each point of the real image does not necessarily match the position 6 of the user's eyes of the display device, a wide-field display device cannot be realized with a planar optical element (mirror, etc.) having a specular reflection function.

FIG. 3 shows variations in the relative positional relationship among the display surface 2, imaging means 3, reflection hologram 4, and eye position 6 in the present invention. FIG. 2A shows a case where the display surface 2 and the reflection hologram 4 are installed perpendicularly to the direction 24 connecting the centers of the display surface 2 and the reflection hologram 4, and the user of the display device can: Oblique (angle θ) to the normal to the reflection hologram 4 (image combiner)
This is a configuration in which the display is viewed from the direction (direction forming the direction o).

In this configuration, the apparent vertical dimension of the display is cosθo times that of the real image, but θo = 3
Since it is about 0.8 times at 7 degrees, it can be used practically without any problem.

FIG. 3(b) shows the reflection hologram 4,
This is a case where the beam is tilted by θi with respect to the direction 24, and the reflection direction is θo. This is advantageous in that θo can be made smaller than in the case of FIG. It must be noted that if the wavelength selection range of the reflection hologram 4 is wider than the wavelength selection range of the reflection hologram 4, the display color and brightness will be partially changed.

FIG. 3(c) shows the case where the user of the display device views the reflection hologram 4 vertically. Although it is preferable that the display surface 2 is perpendicular to the line of sight, the reflective hologram 4 is tilted significantly (angle θi) with respect to the direction 24.
), which places a burden on the imaging system. 3 mentioned above
The positional relationship between the two is determined depending on the shape conditions, usage, etc. of the display device.

FIG. 4 shows an example of the configuration of the imaging system according to the present invention. Figure (a) is the most common one,
The display surface 2 and the reflection hologram 4 (image surface) are perpendicular to the optical axis 25 of the imaging means 3, corresponding to FIG. 3(a). FIGS. 4(b) and 4(c) correspond to the configurations of FIGS. 3(b) and (c).

Similar to FIG. 4(a), FIG. 4(b) shows a case where the display surface 2 and the reflection hologram 4 (image surface) are perpendicular to the optical axis 25 of the imaging means (lens system) 3. However, this configuration uses a portion with a large image height. For implementation, a lens system with a wide field of view is required.

FIG. 4(c) shows a case where the reflection hologram 4 (image plane) is tilted with respect to the optical axis 25 of the imaging means 3, and the display surface 2 must also be tilted. As a result, trapezoidal distortion occurs in the image. The above three configurations are selected depending on the amount of distortion allowed for display, the cost of the display device, and the intended use.

FIG. 5 is an explanatory diagram of an embodiment that allows viewing a display with both eyes or expands the range of eye positions that can view a display. As mentioned in the explanation of FIG. 1, the point P on the display surface 2 forms an image on the point Q on the reflection hologram 4 and diverges toward the eye position 6 at a solid angle Ω. When viewing a display (when the distance between the eyes and the image combiner is short, for example 30 cm), the aperture of the imaging means 3 must be made large in order for both eyes to fit inside the cone 26 formed by the diverging light. However, in order to achieve both a wide field of view and a wide field of view, an expensive imaging means is required. In order to use a relatively simple and inexpensive lens system as the imaging means 3, it is necessary to allow display light to reach both eyes 6a and 6b even with a small aperture.

This includes a reflection hologram 4a that converges the spherical wave light diverging from the pupil position 22 of the image forming means 3 toward the right eye position 6a of the user of the display device, and This can be easily achieved by superposing a reflection hologram 4b that converges the spherical wave light emitted from the display device user's left eye position 6b, or by using a multiplexed hologram 4'. The method of creating multiplex holograms is also well known. In this text, "multiplex" means when a plurality of holograms are formed in the same recording medium layer, and "multilayer" means when recording medium layers each having a desired hologram formed thereon are stacked.

FIG. 6 shows another embodiment of the present invention. The image displayed on the display surface 2 of the display device 1 passes through the imaging means 3 (for example, a lens system) and is reflected by the specular reflection mirror 8.
The image is formed on a vertically placed reflection hologram 4 (image combiner), and is reflected and diffracted toward the user's eye 6 in the normal direction of the reflection hologram 4.

The reason why the optical path is folded by the regular reflection mirror 8 is as follows.
This is because the display device 1 and the imaging means 3 are arranged horizontally. The display surface 2 is inclined with respect to the optical axis 25 of the imaging means 3. Tilting causes trapezoidal distortion in the real image on the image combiner, but this is done by distorting the display into an inverted trapezoid.
Can be offset.

The reflection hologram 4 transmits a spherical wave diverging from the virtual image 22' at the pupil position 22 of the lens system 3 to the eye position 6.
An off-axis reflection hologram is used, which has the function of converging towards. The method for creating the hologram 4 is as shown in FIG. That is, a hologram is created in the photosensitive material layer (recording medium) 51 formed on the substrate 50 by causing coherent spherical waves that diverge from point 6 and spherical waves that converge at point 22' to interfere with each other. The above is a creation method when the hologram creation wavelength is the same as the peak wavelength used for display, but if the wavelength used for display and the hologram creation wavelength are different, two light beams are made to interfere, taking into account the difference in wavelength. It is necessary to design the wavefront of , but since the method is well known, the explanation will be omitted. Regarding the hologram processing, the conventional volume hologram creation procedure may be used as is.

In FIG. 6, the light reflected and diffracted by the reflection hologram 4 behaves as if the hologram surface were a light-emitting surface, but it is different from conventional light-emitting displays in that it has strong directivity. different. All of the reflected light propagates toward the vicinity of the user's eyes 6 of the display device. Therefore, bright display is possible.

Specularly reflected light 2 on the surface of the reflection hologram 4
7 (dotted line in FIG. 6) can be removed from the field of view by creating a hologram off-axis. Since the reflection hologram has wavelength selectivity, what is actually used for display is limited to the wavelength band selected by the hologram within the emission spectrum of the display 1.

Generally, the emission spectrum of a display is wider than the wavelength selection range of a hologram, so wavelengths outside the wavelength selection range are transmitted through the combiner (transmitted light 28). In a transparent display device, if the user does not want a third party on the opposite side of the combiner to know the displayed content, the transmitted light 2
We need to get rid of the 8. One way to achieve this is to replace the optical path folding mirror 8 with a mirror having the same wavelength selectivity as the combiner hologram, such as a specular reflection hologram, a multilayer mirror, etc., instead of a simple aluminum vapor-deposited mirror. As a result, light in a wavelength band that is not reflected by the combiner is removed in advance.

Since FIG. 6 is a side view of the device, only one eye is shown, but in order to guide the display light to both the left and right eyes, the holograms must be multilayered or multiplexed as described above (FIG. 5). All you have to do is record it. Regarding the restriction on the position of the eye 6, the larger the aperture of the imaging means 3, the more relaxed it becomes. Therefore, the imaging means 3
By providing an adjustable aperture stop 9 near the pupil position 22 of the eye, the spatial constraint range of the eye position 6 can be changed somewhat.

FIG. 8 shows an example of the appearance of a display device according to the present invention. A transparent plate 10 (image combiner) on which a reflection hologram 4 is formed is installed perpendicularly to a unit 11 (FIG. 6) containing a display 1, an image forming means 3, and a mirror 8. When not in use, the structure is such that it can be rotated 90 degrees by a rotation mechanism (for example, the image combiner may be rotatably supported by a pin 53) and stored in a position parallel to the unit surface. Note that 56 is a projection window, and 57 is a power cord.

The embodiment shown in FIG. 8 is based on the configuration shown in FIG. 3(c), but it goes without saying that the configurations shown in FIGS. 3(a) and 3(b) may also be adopted. .

FIG. 9 shows yet another embodiment of the present invention. If the image combiner 10 is preferably not a flat plate but a curved surface 10', the image forming means 3 is provided with field curvature characteristics, that is, field curvature aberration. This allows the real image on the display surface 2 to substantially match the surface of the reflection hologram 4 formed on the curved substrate 10'.

FIG. 10 shows a case where a transmission hologram 4' is used as the image combiner 10 instead of a reflection hologram. The configuration up to the point where the real image of the display surface 2 is formed onto the surface of the transmission hologram 4' is the same as that shown in FIG. It is diffracted toward eye position 6. Since multiple recording is also possible in the transmission hologram 4', images can be incident on both the left and right eyes.

Specular reflection light 27 on the image combiner surface
If you want to prevent this, you can attach a transparent plate coated with an anti-reflection film. Further, the light 28 that is not diffracted by the transmission hologram 4' does not enter the eye if the deflection angle β of the hologram is set large. Since the transmission hologram 4' has weak wavelength selectivity, the color of the displayed light changes depending on the position of the eye.

In FIG. 10, when the eye moves from top to bottom, the display light changes in the order of blue → green → yellow → red (when the display displays white). As described above, even when a transmission hologram is used, the configurations of FIGS. 1 to 9 can be realized in exactly the same manner according to the present invention.

By the way, since a reflection hologram selectively reflects light in a narrow wavelength band (20 to 30 nm), when a single reflection hologram is used as an image combiner, a one-color display is obtained. Display of two or more colors is achieved by creating a structure in which reflection holograms that reflect light in different wavelength bands are recorded in multiple layers or in multiple layers.

For example, in order to realize a transparent display device that can display two colors, yellow and red, with the configuration shown in FIG. A hologram can be used. However, the multiple recorded reflection holograms are 585 nm and 66 nm, respectively.
It is made to have a function of converting spherical wave light diverging from the pupil position 22 of the imaging means 3 into spherical wave light converging toward the eye position 6 of the display device user for a wavelength of 0 nm. Instead of multiplexing the two reflection holograms,
The same function can be achieved even if they are made separately and then glued together face-to-face.

In the case of three-color display, the number of holograms to be multiplexed or multilayered should be three. For example, if a multi-recording reflective hologram having wavelength selective reflection characteristics as shown in FIG. 12 is used. good. However, the multiple recorded reflection holograms are 445 nm (blue) and 53 nm, respectively.
For wavelengths of 0 nm (green) and 680 nm (red),
It is created to have a function of converting the spherical wave light that diverges from the pupil position 22 of the image forming means 3 into the spherical wave light that converges toward the eye position 6 of the display device user.

Instead of multiplexing all three reflection holograms, they may be created separately and then bonded together. For example, it is possible to integrate two holograms by multiple-recording and bonding a single-recorded hologram with the media surfaces aligned. However, if all three holograms are created separately and then bonded together, at least one substrate will be sandwiched between the hologram layers, resulting in a large positional shift (on the order of mm) corresponding to the thickness of the substrate. This results in
It should be noted that it is no longer possible to form a real image of the display surface simultaneously on the three-layer hologram surface, and that the clarity may deteriorate.

In the display device described with reference to FIG. 5 above, the reflection holograms 4' (4a, 4b) are shown in FIGS.
As can be seen, the reflection wavelength band is generally 20 to 30 nm.
Because of the relatively narrow emission wavelength band, when combined with a normal display device with an emission wavelength band of about 70 nm or more, the light utilization efficiency becomes low. In such a case, a display with high brightness may be used, but a display with high brightness and a narrow emission wavelength band using a special phosphor is expensive. The following examples (Figs. 13 to 19) do not require such a special display with high brightness, but instead use a display with existing spectra and brightness to increase the brightness of the display. This realizes a display device.

This display device basically includes a reflection hologram 13 corresponding to the reflection hologram 4' shown in FIG.
reflects light in a wavelength band centered on wavelength λ1 toward the position of one eye 6a of the user of the display device, and
It is created so that light in a wavelength band centered on a wavelength λ2 different from λ2 is reflected toward the position of the other eye 6b of the user of the display device, It is characterized by the ability to view images in different wavelength bands.

By providing a reflection hologram 13 in which reflection holograms that reflect light in two or more different wavelength bands are multiplexed or layered, the wavelength band reflected by the reflection hologram 13 can be changed. Since the area is enlarged, the utilization rate of display light is improved and a bright display becomes possible. This makes it easier to visually recognize the superimposed display image even in a bright background. Furthermore, stereoscopic display is also possible by making two reflection wavelength bands significantly different and performing display including parallax information in accordance with each wavelength band.

In the embodiment shown in FIG. 13, which is intended for a display device that performs monochrome display, 1 is a display device, 3 is an image forming means using a lens, etc., and 13 is a device for forming an image 14 displayed on the display device 1. It is a reflection hologram provided at a position where it is imaged as a real image 15 by the imaging means 3, and has a reflection wavelength band having a peak at wavelength λ1 (hereinafter simply referred to as λ1).
A first reflection hologram 13a having a wavelength of It is something.

As shown in FIG. 14, the wavelengths λ1 and λ2 are set so that they differ by approximately the half width of the reflection wavelength band of the reflection hologram within the emission spectrum of the display (shown by curve C). For example, if the full width at half maximum is about 30 nm, λ1 = 515 nm, λ2 = 54
Set to 5nm. Note that curves A and B indicate the spectra of reflection holograms 13a and 13b, respectively. As shown in FIG. 13, the first reflection hologram 13a is created so as to focus the spherical wave light diverging from the pupil position 22 of the imaging means 3 onto the left eye 6a. Further, the reflection hologram 13b is created so as to focus the spherical wave light diverging from the pupil position 22 of the imaging means 3 at the position of the right eye 6b.

In this embodiment configured as described above, the image 14 displayed on the display 1 is formed as a real image 15 on the surface of the reflection hologram 13 by the imaging means 3. Of the display light reflected by the reflection hologram 13, λ
1 is mainly reflected toward the position of the left eye 6a of the display device user, and λ2 is mainly reflected toward the position of the right eye 6b, allowing the displayed image to be viewed.

According to the present embodiment described above, compared to the conventional method in which light of one wavelength band is distributed to both the left and right eyes, in this embodiment, light of one wavelength band is allocated to each of the left and right eyes. , the brightness increases. Note that here, a difference occurs in the displayed color between the left and right eyes. For example, a difference in wavelength of 30 nm can be identified as a color. For example, 515 nm (yellow green) and 54
5nm (yellow green close to yellow) can be identified. However, in binocular viewing, a slight difference in color between the left and right eyes is not a substantial problem in monochrome display. Light with a wavelength near the middle between λ1 and λ2 is reflected by both reflection holograms 13a and 13b, but since the real image is on the hologram surface, no double image is generated.

In the first embodiment described above, the holograms for λ1 and λ2 were created separately and bonded together, but one hologram includes the first reflection hologram 13a and the second reflection hologram 13a. It goes without saying that the same function can be achieved by multiple recording the reflection holograms 13b. FIG. 15 is a diagram showing another embodiment of the present invention. In the figure, the same parts as in FIG. 13 are designated by the same reference numerals.

The difference between this embodiment and the previous embodiment is that the first and second reflection holograms 13a and 13b constituting the reflection hologram 13 are respectively multiplexed recording holograms 1.
3c and 13d. That is, a reflection hologram 13 is formed by bonding a multiple (double) recording reflection hologram 13c that acts on the wavelength λ1 and a multiple (double) recording reflection hologram 13d that acts on the wavelength λ2 so that their hologram surfaces face each other. It was created. The method of selecting λ1 and λ2 is the same as in the first embodiment described above.

In the case of this embodiment, since the mixed color of λ1 and λ2 is seen with both the left and right eyes, there is no difference in color between the left and right eyes, and the brightness is the same as in the first embodiment. improves. In this embodiment, the reflection holograms 13 are 13c, 13
Although it is composed of two reflective holograms in d, it is possible to use three or more holograms and direct light in three or more wavelength bands to the user's left eye and right eye for each wavelength, or to holograms near the eye position. It is also possible to make it possible to view images in a mixed color of three or more wavelength bands depending on the direction.

FIG. 16 is a diagram showing still another embodiment. In the figure, the same parts as those in FIG. 13 are designated by the same reference numerals. The difference between this embodiment and the first embodiment described with reference to FIG.
was changed as follows. That is, the wavelength λ1 is significantly different from the reflection wavelength bandwidth of the reflection hologram 13.
The first and second reflection holograms 13e and 13f, which selectively reflect λ2' and An image (λ1) that is reflected only by the first reflection hologram 13e and an image (λ2') that is reflected only by the second reflection hologram 13f can be generated.

This embodiment configured as described above enables stereoscopic display using parallax. That is, when left-eye and right-eye images containing parallax information are displayed at λ1 and λ2', respectively, the left eye 6a can only see λ1, and the right eye 6b can only see λ2', resulting in parallax and stereoscopic vision. can. FIG. 17 shows an example of selection of λ1 and λ2'. As shown in the figure, if λ1 is set to the blue region and λ2' is set to the red region, it looks the same as stereoscopic vision using conventional red-blue glasses, but in this embodiment, the red-blue glasses are not required and the background is You can see it straight through.

In each of the above embodiments, when a plurality of holograms are bonded in multiple layers, the smaller the interval between the holograms, the better. This is because if the distance between the holograms is large, a difference will occur in the position of the real image plane, leading to the generation of double images. In the case of a two-layer hologram, the specific bonding method is as shown in FIG. 18(a). b) They may be bonded together using an optical adhesive 19 or the like as shown in FIG. The thickness of the adhesive layer is usually several tens of microns.
It is possible to suppress it to less than m, and it does not affect double image generation.

When the hologram has three or more layers, the method shown in FIG. 19 (
As shown in a), the holograms at both ends are formed by using a glass plate with a thickness of several mm as the substrate 18, and the hologram 17 is formed thereon, and the hologram sandwiched in the middle is formed by a thin transparent sheet 2.
0 on which the hologram 17 is formed, and adhere them with an optical adhesive 19 or the like as shown in FIG. 19(b). This allows the thickness of the entire hologram including the substrate to be kept small.

As described above, the viewing zone can be expanded by the method shown in FIG. When you move left/right or front/back (direction of display light propagation),
A situation arises where the display can only be seen with one eye. In this case, by enlarging the aperture of the imaging lens 3, it is possible to eliminate the spatial separation of the display light beams directed toward the left and right eyes, and to reduce the degree to which a situation in which the display is visible only with one eye occurs. However, in this case, the brightness of the display may change.

FIG. 27(a) shows the range (visual zone) in which the display can be seen. When the eye is located in the shaded area S, the brightness of the display is approximately twice as bright as in other areas. Increase. Therefore, if you move your head from side to side while looking at the display, the brightness of the display changes and flickers. Displays whose display brightness changes depending on the position of the eye cause fatigue and are not easy to use. This problem of uneven brightness can be solved by providing a rectangular mask in the imaging lens system and connecting the viewing zones as shown in Figure 27(b), but eliminating the boundary line L (discontinuous line) is not possible. Can not.

The embodiments shown below (FIGS. 20 to 26) realize expansion of the viewing zone without producing discontinuous lines. The holographic screen 61 that diffracts a real image is configured by forming a two-dimensional array of hologram elements that have the function of converting the diverging solid angle or converging solid angle of an incident light wave, and diffracting the light in a predetermined wavelength band. Each of the hologram elements satisfying the Bragg condition is created so that its light incident direction and light output direction pass through predetermined points A and B or two narrow sections including the respective points.

According to this, when a point on the displayed image forms a real image by the imaging lens system, the solid angle of the focused beam determined by the focal length and aperture of the lens system increases due to diffraction at the hologram element. be able to. As a result, the viewing area can be expanded without creating discontinuous boundaries.

FIGS. 20(a) and 20(b) show an example of the structure and function of the holographic screen of the present invention. FIG. 6A is an overall view of the holographic screen 61, showing that hologram elements that convert the solid angle of a diverging wave or a convergent wave and reflect the same are formed in a two-dimensional array. However, since this is a schematic diagram, grid lines are shown, but the hologram (screen 61) is actually transparent.

An enlarged view of one reflective hologram element 63 is shown in FIG. 20(b). This reflection hologram reflects diverging light with a solid angle of Ω for light in a predetermined wavelength band,
Convert the solid angle to Ω′. If Ω′>Ω, the divergence angle of light increases. The optical axis l1 of the incident light to each hologram element 63 and the optical axis l2 of the emitted light are created so as to pass through point A and point B, respectively, as shown in FIG. 20(a). All hologram elements 63 are created so that the incident optical axis and the output optical axis pass through point A and point B, respectively. In the above, even if the path does not strictly pass through point A and point B, there is often no substantial problem even if the path is near point A or point B.

FIG. 20(a) shows the case where the diverging wave is reflected, but FIGS. 21(a), (b), and (c)
As shown in Figure 20(a), the configuration in Figure 20(a) also holds true for (a) when a diverging wave converges after reflection, (b) when a convergent wave diverges after reflection, and (c) when a convergent wave is reflected. . Although the hologram element 63 is shown as a rectangular area in FIG. 20(a), the shape is not limited to a rectangle. Furthermore, the boundaries between hologram elements do not necessarily have to be clear.

FIGS. 22(a) and 22(b), and FIG. 20(a)
2 shows an optical system of a display device constructed using the holographic screen 61 shown in FIG. (a) is the overall view, (
b) is an enlarged view of the holographic screen. However, each reflection hologram 63 has a small circular shape. In FIG. 22(a), image 1 displayed on display 1
4 is imaged onto the holographic screen 61 by the imaging lens 3 to form a real image 15. Each point of the real image propagates while diverging toward the midpoint between the left and right eyes 6a and 6b of the person using the display device.

[0077] Here, points A and B shown in Fig. 20(a)
The points are the center of the exit pupil of the imaging lens 3, the left and right eyes 6a, respectively.
, 6b, respectively. If we pay attention to the point P of the displayed image 14, the envelope surface of the light beam will be as shown by the shaded area in FIGS. 22(a) and 22(b). The convergence solid angle Ω by the imaging lens 3 becomes Ω'(>Ω) after reflection by the holographic screen 61, and the viewing area in FIG. 5 (FIG. 22(a)
) can be extended to the area shown by 60.

FIG. 23 shows an example of a method for producing the holographic screen 61 shown in FIGS. 22(a) and 22(b). A dry plate 70 with a hologram recording medium 73 formed on one side of a transparent substrate 71 is prepared, and coherent light L is emitted from both sides.
A reflection hologram is formed by irradiating with 1, L2 and developing the same dry plate. One of the coherent lights L1 irradiated onto the dry plate 70 is a divergent spherical wave, and the other is a convergent spherical wave L2, and these coherent lights L1, L2
is a gradient index lens array plate 7 placed near the dry plate.
Irradiate through 5. Gradient index lens array plate 75
It is preferable to form a mask 77 on the surface of the photoreceptor for cutting unnecessary noise light. By controlling the relative positions of the two gradient index lens array plates 75, it is also possible to create a two-dimensional array of reflective hologram lenses formed by irradiating divergent waves from both sides of the dry plate. The size of the reflective hologram lens (hologram element) is designed to be approximately several hundred μm, for example, in order to correspond to the display pixels.

FIG. 24 shows the holographic screen 61
This shows how the creation system is viewed as a macro. The position of the divergent point of the divergent wave is determined by considering the center of the exit pupil of the imaging lens 3 of the display device that will be constructed later. Further, the focal position of the convergent wave L2 is determined in consideration of the position of the eyes of the user of the display device. The angle of incidence of the two light beams L1 and L2 on the dry plate 70 is set in accordance with the direction of projection onto the holographic screen and the viewing direction of the display.

The wavelength of the coherent light is selected depending on the sensitivity of the hologram recording medium, but does not necessarily match the display wavelength band. In such a case, the installation position of the gradient index lens array plate 75 and the position of the two coherent beams L should be adjusted in consideration of the difference in wavelength between when creating and using the hologram.
1, determine the irradiation direction of L2.

FIG. 25 shows the gradient index lens array plate 7.
An example of 5 is shown below. It is created by forming substantially spherical regions 83 having different refractive indexes on a transparent substrate 81 by a proton exchange method or the like. Since this is a known technique, the explanation will be omitted. When the direction of incidence of light on the gradient index lens changes, aberrations occur, but this does not pose a problem as long as the aberrations are within the dimensions of the pixel.

Although the above description has focused on the reflective holographic screen 61, it goes without saying that the display device can also be realized using a transmissive holographic screen. (FIG. 26) However, since it is difficult to create an array of minute transmission hologram lenses using a gradient index lens array plate, it is necessary to use other methods such as mask exposure and EB drawing.

[0083]Although the above description of the reflective holographic screen is based on a single selective reflection wavelength, it is also possible to use a structure in which a plurality of holographic screens that selectively reflect light in different wavelength bands are stacked in multiple layers. This allows multi-color display. Alternatively, similar multi-coloring is also possible by using a structure in which multiple recordings are made within a single layer of media instead of using multiple layers.

[0084]

[Effects of the Invention] As described above, the real image of the image on the display device is formed on the hologram surface of the image combiner, and the real image is diffracted by the hologram toward the eyes of the user of the display device, thereby creating a transparent image. Moreover, it becomes possible to realize a non-virtual image (real image) type display device similar to conventional display devices. By using a transparent display device according to the invention, it is possible to view the display and the background simultaneously.

Furthermore, by recording multiple holograms or making them multilayered, it becomes possible to expand the range of eye positions where the display can be seen and to display multiple colors. Since the hologram element has wavelength dispersion, it is usually used in combination with a hologram for canceling chromatic aberration. In the configuration of the present invention, since the real image exists on the hologram surface, there is also the advantage that no aberration occurs even if there is a difference in the deflection direction due to a difference in wavelength.

According to the embodiments shown in FIGS. 13 to 19, the image displayed on the display device is imaged on the reflective hologram surface using the imaging system, and the reflected light is directed to the user of the display device. A structure in which holograms that reflect light in two different wavelength bands are double recorded or layered in a display device that allows the displayed image and background to be viewed at the same time by focusing on the eye position. The brightness of the display can be increased by creating two reflection holograms so as to focus light on different positions of the left and right eyes of the user of the display.

Furthermore, stereoscopic display is also possible by making two reflection wavelength bands significantly different and performing display including parallax information in accordance with each wavelength band. In addition, the brightness of the display can be improved by multiple recording or multilayer structure of reflection holograms, which have different reflection wavelength bands and focus the display light on multiple points near the eye position of the user of the display device. can be done.

Furthermore, according to the present invention, the viewing range of the display can be expanded, and even if the position of the head of the user of the display device moves somewhat, the display can be viewed stably.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a display device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing the emission spectrum form of a display built into the display device of the present invention.

FIG. 3 is a diagram showing three examples of the positional relationship of the imaging system of the present invention.

FIG. 4 is a diagram showing an example of the positional relationship of the imaging system according to the present invention.

FIG. 5 is a diagram for explaining means for expanding the viewing area of the display device according to the present invention.

FIG. 6 is a diagram showing the structure of a display device according to the present invention.

FIG. 7 is a diagram showing a method for creating a reflection hologram used in the present invention.

FIG. 8 is a diagram showing the appearance of a display device according to the present invention.

FIG. 9 is a diagram showing a modification of the imaging system of the present invention.

FIG. 10 is a diagram showing a configuration using a transmission hologram in an embodiment of the present invention.

FIG. 11 is a characteristic diagram of a hologram used when performing two-color display in an embodiment of the present invention.

FIG. 12 is a characteristic diagram of a hologram used when performing three-color display in an embodiment of the present invention.

FIG. 13 is a diagram showing another embodiment of the present invention.

14 is a diagram showing an example of selection of a reflection wavelength band of a reflection hologram in the embodiment of FIG. 13; FIG.

FIG. 15 is a diagram showing another embodiment of the present invention.

FIG. 16 is a diagram showing still another embodiment of the present invention.

17 is a diagram illustrating an example of selecting a reflection wavelength band of a reflection hologram in the embodiment of FIG. 16. FIG.

FIG. 18 is a diagram showing a method of bonding two holograms according to the present invention.

FIG. 19 is a diagram showing a method of bonding three or more holograms according to the present invention.

FIG. 20 is a diagram showing still another embodiment of the present invention.

FIG. 21 is a diagram showing three examples of reflection forms of an incident light beam in the present invention.

22 is a diagram showing an example of a display device using the hologram screen shown in FIG. 20. FIG.

23 is a diagram showing a method for creating the hologram screen shown in FIG. 20. FIG.

FIG. 24 is a diagram showing an overall outline of the creation system in FIG. 20;

25 is a diagram showing a lens eye of the creation system shown in FIG. 24. FIG.

FIG. 26 is a diagram showing a transmission hologram screen in the present invention.

FIG. 27 is a diagram illustrating a display area.

FIG. 28 is a diagram for explaining problems when a half mirror is used as an image combiner.

FIG. 29 is a diagram showing an example of a conventional head-up display.

[Explanation of symbols]

1...Indicator 2...Display surface 3...Imaging means 4...Hologram 5...Display device 6...Eye position 7…Half mirror 8...Mirror 9...Aperture diaphragm 10...Image combiner (board) 11...Unit 21...Light flux converging toward the eye 22... Pupil position of imaging means

Claims (19)

[Claims] 1. A display device (1) for projecting a predetermined image, an imaging optical system (3) for forming a real image of the image by the display device at a predetermined position, and an imaging position of the imaging optical system. placed in
A display device comprising a transparent hologram screen (10) that diffracts the real image in a predetermined direction with directionality. Claim 2: The transparent hologram screen (10
) is composed of a reflection hologram (4), which transmits spherical wave light that propagates while diverging from the position of the imaging optical system for one wavelength in the display light spectrum to a hologram on the same side as the imaging optical system with respect to the hologram surface. The display device according to claim 1, having a function of converting the light into spherical wave light that propagates while converging toward the position of the observer's eyes located in space. Claim 3: The transparent hologram screen (10
) is composed of a reflection hologram (4), which transmits spherical wave light that propagates while diverging from the position of the imaging optical system for one wavelength in the display light spectrum to a hologram on the same side as the imaging optical system with respect to the hologram surface. 2. The display device according to claim 1, wherein the display device is a plurality of holograms that are diffracted toward a plurality of points near the position of an observer's eyes located in space. Claim 4: The transparent hologram screen (10
) is composed of a reflection hologram (4), which transmits spherical wave light that propagates while diverging from the position of the imaging optical system for one wavelength in the display light spectrum, to the same side of the hologram surface as the imaging optical system. A first hologram (4a) that converts into spherical wave light that converges and propagates toward a first point located in the space of The second hologram (4b) converts the spherical wave light that propagates while converging toward a second point located in the same side of the space as the imaging optical system with respect to the hologram surface, and the second hologram (4b) The two different points 1 and 2 are the left and right eyes of the observer (6
The display device according to claim 1, wherein the display device is selected from a and 6b). [Claim 5] A reflection hologram (4) and a display device (1).
) is a wavelength bandpass filter that selectively transmits light within the selective reflection wavelength width of the reflection hologram (
8). The display device according to claim 2, wherein the display device includes: 8). [Claim 6] A reflection hologram (4) and a display device (1).
) An optical path folding mirror (8) having wavelength selectivity for selectively reflecting light within a selective reflection wavelength width of the reflection hologram is inserted in the optical path between the reflection hologram and the reflection hologram. The display device according to any one of the above. Claim 7: The transparent hologram screen (10
) is constituted by a transmission hologram (4'), which transmits spherical wave light that propagates while diverging from the position of the imaging optical system for one wavelength in the display light spectrum, and transmits the spherical wave light that propagates while divergent from the position of the imaging optical system with respect to the hologram surface. 2. The display device according to claim 1, having a function of converting the light into spherical wave light that propagates while converging toward the eye position of an observer located in a side space. Claim 8: The transparent hologram screen (10
) is constituted by a transmission hologram (4'), which transmits spherical wave light that propagates while diverging from the position of the imaging optical system for one wavelength in the display light spectrum, and transmits the spherical wave light that propagates while divergent from the position of the imaging optical system with respect to the hologram surface. 2. The display device according to claim 1, wherein the display device is a plurality of holograms that are diffracted toward a plurality of points near the position of an observer's eyes located in a side space. 9. The transparent hologram screen (10
) is constituted by a transmission hologram (4'), which transmits spherical wave light that propagates while diverging from the position of the imaging optical system for one wavelength in the display light spectrum, and transmits the spherical wave light that propagates while divergent from the position of the imaging optical system with respect to the hologram surface. The first one located in the side space
A first hologram (4a) converts the spherical wave light into a spherical wave light that propagates while converging toward a point, and a spherical wave light that similarly propagates while diverging from the position of the imaging optical system for one wavelength in the display light spectrum. A second hologram (4b) that converts into spherical wave light that propagates while converging toward a second point located in a space on the opposite side of the imaging optical system with respect to the hologram surface.
The first and second different points above are the left and right eyes of the observer (
6a, 6b). The display device according to claim 1. 10. The imaging optical system includes a variable aperture diaphragm (9
), and the visible range of the displayed image is controlled by changing the aperture diaphragm. 11. The transparent hologram screen is formed by a transparent curved substrate (10') on which a hologram is formed, and the imaging optical system has a curvature of field that images a flat image of the display on the curved hologram screen. The display device according to any one of claims 1 to 10, having an aberration. 12. The hologram screen (10)
reflects light in a wavelength band centered on wavelength λ1 toward the position of one eye (16a) of the user of the display device, and reflects light in a wavelength band centered on wavelength λ2, which is different from wavelength λ1, for the display. It has a reflection hologram (13) that reflects toward the position of the other eye (16a) of the user of the display device, and the user of the display device can view images in different wavelength bands with the left and right eyes. 2. The display device according to claim 1, wherein the display device is configured to be able to display images. [Claim 13] The difference between the wavelengths λ1 and λ2 is
By selecting the same wavelength bandwidth as the reflection wavelength bandwidth of the first and second reflection holograms (13a, 13b),
13. The display device according to claim 12, wherein the overlap of the reflection spectra of the reflection holograms (13a, 13b) is reduced, and the difference between wavelength λ1 and wavelength λ2 is selected to be small. 14. The first reflection hologram (13
a) and is reflected by the second reflection hologram (13b
), and a display that is reflected by the second reflection hologram (13b) and hardly reflected by the first reflection hologram (13a). 13. The display device according to claim 12, wherein λ2 and λ2 are selected. 15. A display device (11) that generates a display generates a left eye image and a right eye image in consideration of the parallax caused by the left eye (16a) and right eye (16b), respectively, at the wavelength λ1.
, λ2, and enables stereoscopic viewing. 16. The hologram screen has N wavelengths centered at N different wavelengths λ1 ...λ2 (N≧2).
a reflection hologram (13) that reflects light in different wavelength bands toward the left eye position, right eye position of the user of the display device, or in multiple directions near the eye position for each wavelength; 2. The display device according to claim 1, wherein the display device allows a user of the display device to view images in a mixed color of a plurality of wavelength bands. 17. Reflective or transmissive holographic lenses are formed in an array in the same medium layer, and the directions of the incident axis and output axis of each holographic lens are gradually changed. holographic screen. 18. A holographic screen, a display device, and a projection lens system according to claim 17, each of which is used to project a real image of the image displayed on the display device onto the holographic screen surface by the projection lens system. 1. A display device characterized in that the display device is arranged so as to be formed at or in the vicinity thereof. 19. The display device according to claim 2, wherein the incident axis and the exit axis of the holographic lens constituting the holographic screen pass through the principal point of the projection lens system and the eye position of the display device user, respectively. The display device according to claim 18, wherein the display device is set as follows.