JP2010243786A - Video display and head-mounted display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a video display for accurately matching an exit pupil of an optical system with then entrance pupil of an eye of a user, while having a simple and low-cost constitution. <P>SOLUTION: The video display is constituted of a display element for displaying images; a light guide plate for making the images displayed on the display element incident; a propagation means for totally reflecting the incident images in the inside of the light guide plate, to be propagated toward the pupil of the user; and an optical member for totally reflecting the images incident, by passing a part and making the images incident on the light guide plate again so that the images are re-reflected totally in the inside of the light guide plate and propagate toward the pupil of the user, concerning a plurality of kinds of the optical members being selectively bonded on the part on the light guide plate which totally reflects the images at the interface of the light guide plate and air, and having differences in shape or refractive indices. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention is a video display device worn on a user's head, and an image of the display element is applied to a user's pupil using a holographic optical element (hereinafter referred to as “HOE”). It relates to a head mounted display (hereinafter referred to as “HMD”) and a video display device that constitutes the head mounted display, and more specifically, adjustment of the optical system in accordance with the eye width of the user. The present invention relates to a video display device that can be used and an HMD.

  In recent years, an HMD that is a video display device mounted on a user's head is generally known. The HMD is configured to optically enlarge an image displayed on a display element and allow a user to observe it as an enlarged virtual image.

  By the way, in this type of HMD, when the user's pupil position deviates from the center of the exit pupil of the optical system of the HMD, color misregistration or contrast decreases depending on the misregistration amount, and the image Problems such as distortion are pointed out. In order to prevent the occurrence of such a problem and allow the user to observe the image of the display element satisfactorily, it is necessary to make the exit pupil of the optical system coincide with the entrance pupil of the user's eye. However, there are individual differences in the human eye width (the distance between the left and right eyes), and it is said that they are distributed in a range of approximately 58 to 72 mm. Therefore, unless the user has a pupil width that is substantially the same as the value adopted in the design, the entrance pupil does not coincide with the exit pupil of the optical system, and thus the image on the display element cannot be observed well with both eyes.

  Therefore, a general HMD is designed so that the exit pupil position of the optical system of the HMD can be changed according to the eye width of the user, as exemplified in Patent Documents 1 and 2. Specifically, the HMDs described in Patent Documents 1 and 2 are configured so that a pair of left and right display elements can be directly attached to an appropriate position that the user thinks fits the eye width.

Japanese Patent No. 4018677 International Publication No. 04/017122 Pamphlet

  However, in the HMDs described in Patent Documents 1 and 2, since it is necessary to rely on the user's sense when positioning the display element, the eye width adjustment with high accuracy (that is, the exit pupil of the optical system of the HMD 1) It is actually difficult to match the entrance pupil of the user's eyes with high accuracy. In addition, since the bonding area to the spectacle body is small relative to the total weight of the various components such as the fixing parts and display elements that fix the display element to the spectacle body, sufficient adhesion is sufficient to securely fix the various parts to the spectacle body There is a possibility that power cannot be obtained. Since various parts are not securely fixed, when some external stress is applied to the fixed parts (for example, the user moves the head), the display element vibrates slightly with respect to the spectacle body. Defects that cause image blurring or that cause the display element to fall out of the spectacle body are pointed out. Further, in the HMD described in Patent Document 1, since the projection (shaft body connecting the intermediate member for fixing the display element to the spectacle main body and the display apparatus main body) has a small diameter, the display element is easily damaged. There is also a concern that will drop out.

  As another method for providing an HMD suitable for the user's eye width, for example, a plurality of types of optical units having different intervals between the exit pupil positions of the left and right optical systems are prepared in advance, and the interval is determined by the user. A method of assembling the HMD by selecting the optical unit closest to the eye width can be considered. However, since it is necessary to manufacture a plurality of types of optical units, problems such as an increase in mold costs for optical components and complicated production management are pointed out. In order to provide an HMD that accurately matches the exit pupil of the optical system with the entrance pupil of the user's eye, there is a disadvantage that an even wider lineup of optical units with slightly different eye widths must be prepared. . In order to reduce the number of types of optical units, it is necessary to determine which eye width should be prepared in consideration of consistency with demand. There is a negative effect of increasing the load. In addition, in order to solve these problems, many manufacturers have arranged a display element on both the left and right sides of the eyeglass part so that image information dedicated to the left eye from the left side and dedicated to the right eye from the right side is provided. Adopted. However, in this method, since it is necessary to equip two sets of parts related to the display element (for example, a liquid crystal plate, a backlight, an optical part, a liquid crystal controller, etc.), the cost is high and the weight is high. It was a thing.

  Therefore, the present invention has been made in view of the above circumstances, and the object of the present invention is to accurately set the exit pupil of the optical system and the entrance pupil of the user's eye with a simple and inexpensive configuration. An object is to provide an image display device and an HMD that can be matched.

  A video display device according to an embodiment of the present invention that solves the above problems includes a display element that displays an image, a light guide plate on which an image displayed on the display element is incident, and an incident image that is displayed inside the light guide plate. Propagation means that totally reflects and propagates toward the user's pupil, and a shape or refraction that is selectively pasted at a location on the light guide plate that is an interface between the light guide plate and air and where the image is totally reflected A plurality of types of optical members having different rates, which totally reflect the image incident through the portion, and the image is totally reflected again inside the light guide plate and propagates toward the pupil of the user. And an optical member for re-entering the light guide plate on the light guide plate.

  According to the video display device of the present invention, the position of the exit pupil that is emitted from the light guide plate toward the user's eyes is displaced outwardly due to the extension of the optical path length of the image due to the application of the optical member. . The amount of displacement of the exit pupil position depends on the shape or refractive index of the optical member attached to the light guide plate. Therefore, the user can affix any one of a plurality of types of optical members to the light guide plate and adjust the position of the exit pupil from the light guide plate so as to match his or her own eye width. The resolution when adjusting the eye width can be easily increased by the number and types of optical members to be prepared. Thus, in the video display device, the exit pupil of the optical system of the video display device and the entrance pupil of the user's eye can be made to coincide with each other with a simple and inexpensive configuration.

  Here, it is desirable that the refractive index of the optical member is substantially the same as that of the light guide plate in consideration of the occurrence of a critical angle and color shift at the interface with the light guide plate. Further, for the same reason, the light guide plate and the optical member are preferably bonded with an adhesive having substantially the same refractive index as that of the light guide plate and the optical member. However, the film thickness of the adhesive layer made of adhesive is much thinner than the refractive index and the thickness of the light guide plate. Therefore, if the difference between the refractive index and the refractive index of the light guide plate is not extremely large, color misregistration should be considered. There is no need. For the sake of explanation, here, an adhesive having high transparency with respect to the wavelength of the image is used.

  The plurality of types of optical members may be, for example, a plurality of types of parallel flat plates with different dimensions in the plane (length, width) direction orthogonal to the plate thickness or the plate thickness so as to correspond to various eye widths.

  The light guide plate is provided with a predetermined marking at a position on the light guide plate where the image is totally reflected at the interface between the light guide plate and air so that the user can easily attach the optical member to an appropriate position. May be.

  The propagation means includes, for example, a first HOE or a first DOE (Diffractive Optics Element) that diffracts the image incident on the light guide plate so that the image is totally reflected inside the light guide plate and propagates to the predetermined position, and a predetermined position. It is good also as a structure which has 2nd HOE or 2nd DOE which diffracts the image propagated to the user's pupil. Furthermore, the second HOE or the second DOE is disposed, for example, in front of the left and right eyes of the user, and the first HOE or the first DOE has two images incident on the light guide member. It is good also as a structure which diffracts so that it may divide | segment and each divided image may inject into a pair of each.

  An HMD according to an embodiment of the present invention that solves the above-described problems is provided with the video display device according to any one of the above, in front of the user's eyes so that the user can observe the image propagated by the propagation unit as a virtual image. It has the support means to support by.

  According to the video display device and the HMD according to the present invention, the exit pupil of the optical system and the entrance pupil of the user's eye can be made to coincide with each other with high accuracy while having a simple and inexpensive configuration.

It is a perspective view which shows the structure of HMD of embodiment of this invention. It is a side view which shows typically the structure of HMD of embodiment of this invention. It is a side view which shows typically the structure of HMD of embodiment of this invention.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1A and FIG. 1B are a front perspective view and a rear perspective view, respectively, showing the configuration of the HMD 1 of this embodiment. As shown in FIGS. 1 (a) and 1 (b), a spectacle lens 3 is attached to the front portion of the spectacle-type frame 2 attached to the user's head. A backlight 4 for illuminating an image is attached to the attachment portion 2 a of the eyeglass-type frame 2. A signal processing device 5 for projecting an image and a speaker 6 for reproducing sound are provided at the temple portion of the eyeglass frame 2. The light guide plate 10 is made of an optical member (for example, EFD 15, SF 11, SF 15, etc.), and FPC (Flexible Printed Circuits) 7 constituting the wiring drawn out from the circuit of the signal processing device 5 is wired along the eyeglass frame 2. Is done. The display element unit (for example, a liquid crystal display element) 20 is wired by the FPC 7 to the center position of both eyes of the user, and is held so that the substantially central portion of the display element unit 20 is disposed on the optical axis of the backlight 4. . The display element unit 20 is fixed relative to the light guide plate 10 so as to be positioned at a substantially central portion of the light guide plate 10. HOEs 32R and 32L are fixed in close contact with the first surface 10a of the light guide plate 10 by bonding or the like at locations located in front of the user's eyes. HOEs 52R and 52L are stacked on the second surface 10b of the light guide plate 10 at positions facing the display element unit 20 with the light guide plate 10 interposed therebetween. The parallel flat plate 60 performs the eye width adjustment described later (that is, the exit pupil of the optical system of the HMD 1 and the entrance pupil of the user's eye are accurately matched). The two surfaces 10b) are selectively attached. In this description, the parallel plate 60 is affixed to the opposite side of the user's pupil position so that the user does not feel uncomfortable.

  FIG. 2 is a side view schematically showing the configuration of the HMD 1 of the present embodiment. In FIG. 2, for the sake of clarity, only the main part of the invention is shown, and the spectacle frame 2 and the like are not shown. As shown in FIG. 2, the HMD 1 has a substantially left-right symmetric structure across a center line X that connects the center of the display element 24 and the light guide plate 10. Further, light of each wavelength incident on the light guide plate 10 from the display element 24 is divided into two parts as will be described later, and is guided to the right eye and the left eye of the user. The optical path of each wavelength of light guided to each eye is also symmetrical with respect to the center line X.

  As shown in FIG. 2, the backlight 4 includes a laser light source 21, a diffusion optical system 22, and a microlens array 23. The display element unit 20 is an image generation unit including the display element 24, and is driven by, for example, a field sequential method. The laser light source 21 has a laser light source corresponding to each wavelength of R (HeNe laser), G (Hd: YAG laser), and B (He-Cd laser), and sequentially emits light of each wavelength at a high speed (for example, 180 Hz). Irradiate. The light of each wavelength is incident on the diffusion optical system 22 and the microlens array 23, converted into a uniform light beam with no unevenness in the amount of light, and incident perpendicularly on the display panel surface of the display element 24.

  The display element 24 is, for example, a transmissive liquid crystal (LCD T-LCOS) panel that is driven by a field sequential method. The display element 24 modulates light of each wavelength according to an image signal generated by an image engine (not shown) of the signal processing device 5. The light of each wavelength modulated by the pixels in the effective area of the display element 24 is incident on the light guide plate 10 with a predetermined light beam cross section (substantially the same shape as the effective area). The display element 24 is a display element of another form such as a DMD (Digital Mirror Device), a reflective liquid crystal (LCOS) panel, a MEMS (Micro Electro Mechanical Systems), an organic EL (Electro-Luminescence), an inorganic EL, or the like. Substitution is also possible.

  The display element unit 20 is not limited to a field sequential display element, and may be an image generation unit of a simultaneous display element (a display element having a predetermined arrangement of RGB color filters on the front surface of the emission surface). In this case, for example, a white light source is used as the light source.

  As shown in FIG. 2, the light of each wavelength modulated by the display element 24 is sequentially incident on the inside of the light guide plate 10 from the first surface 10a. On the second surface 10b of the light guide plate 10, HOEs 52R and 52L are stacked. The HOEs 52R and 52L are, for example, reflection type volume phase type HOEs having a rectangular shape, and are configured by laminating three photopolymers each recording interference fringes corresponding to light of each wavelength of R, G, B Have That is, the HOEs 52R and 52L are configured to have a wavelength selection function of diffracting light of R, G, and B wavelengths and transmitting light of other wavelengths.

  Further, the HOEs 52R and 52L may be a single-layer photopolymer in which interference fringes corresponding to light of each wavelength of R, G, and B are recorded. In addition, when there are n types of wavelengths used (n is a natural number), the layer structure of the HOEs 52R and 52L includes n photopolymers each recording interference fringes corresponding to light of each wavelength. Or a single photopolymer on which interference fringes corresponding to light of each wavelength are recorded.

  It is also possible to form the HOEs 52R and 52L with two layers of photopolymers and to provide a wavelength selection function corresponding to light of each wavelength of R, G, and B. As an example, the HOE52R is composed of a total of two layers of a photopolymer in which interference fringes corresponding to light of R and G wavelengths are recorded and a photopolymer in which interference fringes corresponding to light of B wavelengths are recorded. And 52L can be configured. HOEs 32R and 32L are also reflective volume phase HOEs and have the same layer structure as HOEs 32R and 32L. For example, the pitches of the interference fringe patterns may be substantially the same in the HOEs 32R and 32L and 52R and 52L.

  The HOEs 52R and 52L are stacked in a state where their centers coincide with each other and the interference fringe pattern is inverted by 180 (deg). Then, in the laminated state, it is firmly fixed by adhesion or the like on the second surface 10b of the light guide plate 10 so that the center thereof coincides with the center line X. Light of each wavelength modulated by the display element 24 is sequentially incident on the HOEs 52R and 52L via the light guide plate 10.

Each of the HOEs 52R and 52L diffracts by giving a predetermined angle in order to guide sequentially incident light of each wavelength to the right eye and the left eye. The light of each wavelength diffracted by the HOEs 52R and 52L repeats total reflection at the interface between the light guide plate 10 and air, propagates through the light guide plate 10, and is separated from the center line X by distances L _R and L _L. It is incident on 32L. In FIG. 2, reference signs “X _R ” and “X _L ” are attached to the normals of the HOE 32 _R and HOE 32 _L that pass through the centers of the right eye and the left eye of the user. In FIG. 2, the normal lines X _R and X _L are separated from the center line X by distances L _R and L _L , respectively, and the center of the display image of the display element 24 matches the center of the entrance pupil of the user's eye ( According to another expression, it shows that the exit pupil of the optical system of the HMD 1 and the entrance pupil of the user's eye coincide).

  Here, the HOEs 52R and 52L give the same diffraction angle to the light of each wavelength. Therefore, light of all wavelengths having substantially the same incident position with respect to the light guide plate 10 (or, according to another expression, emitted from substantially the same coordinates within the effective area of the display element 24) The light propagates through the same optical path and enters substantially the same position on the HOEs 32R and 32L. According to another aspect, the HOEs 52R and 52L are arranged so that the pixel positional relationship in the effective area of the image displayed in the effective area of the display element 24 is faithfully reproduced on the HOEs 32R and 32L. Diffracts light.

  As described above, in the present embodiment, the HOEs 52R and 52L each diffract light so that light of all wavelengths emitted from substantially the same coordinates in the effective area of the display element 24 is incident on substantially the same positions on the HOEs 32R and 32L. On the other hand, in another embodiment, the HOEs 52R and 52L make light of all wavelengths originally forming the same pixel relatively shifted within the effective area of the display element 24 incident at substantially the same positions on the HOEs 32R and 32L. It may be configured to diffract.

  The light of each wavelength incident on the HOEs 32R and 32L is diffracted by the HOEs 32R and 32L and sequentially emitted from the second surface 10b of the light guide plate 10 to the outside substantially vertically. Thus, the light of each wavelength emitted as substantially parallel light forms an image on the right eye retina and left eye retina of the user as a virtual image of the image generated by the display element 24. In order to allow the user to observe a virtual image of the enlarged image, the HOEs 52R and 52L are arranged so that the pixel positional relationship on the HOEs 32R and 32L is the pixel positional relationship in the effective region of the image displayed in the effective region of the display element 24. The light of each wavelength of RGB may be diffracted so as to form an enlarged similar shape. Moreover, you may provide a capacitor | condenser effect | action to HOE52R and 52L so that a user can observe the virtual image of an enlarged image. That is, the light incident on the peripheral area of the HOEs 52R and 52L is emitted with an angle so as to be closer to the center of the pupil, and is imaged on the retina of the user with the angle through the HOEs 32R and 32L. Also good.

  At least one of the HOEs 32R, 32L, 52R, and 52L can be replaced with a DOE. For example, all HOEs may be replaced with DOE, or both HOE32R and 32L, or HOE52R and 52L may be replaced with DOE, or either HOE32R or 32L, or either HOE52R or 52L It may be replaced with DOE. That is, various patterns are assumed for replacement of HOE and DOE. Since the HOE and the DOE are shown in the same diagram in FIG. 1 or FIG. 2, the configuration drawing of the HMD 1 having the DOE is omitted here.

  Since the light of each wavelength is sequentially formed on the retina of the user at high speed, the user recognizes the generated image by the display element 24 as a color image. The actual distance between the user's eyes and the display element 24 is only about several tens of millimeters. However, since light of each wavelength is incident on the eyeball as substantially parallel light, the user can clearly see the generated image by the display element 24 when viewed at infinity. Further, the volume phase type reflective HOEs HOE32R and 32L have a narrow half-value width of diffraction efficiency and a high light transmittance of an external image. Therefore, the user can clearly observe the external image together with the display image of the display element 24.

  In the present embodiment, a configuration in which a single-plate display element 24 is provided without separately providing right-eye and left-eye display elements is employed. For this reason, effects such as manufacturing cost reduction can be obtained. In addition, light from a common object point (that is, an image of the single-panel display element 24) is guided to the eyes of the user through the same optical path length on the left and right. For this reason, a synchronized image can be made incident on each eye of the user.

By the way, the distances L _R and L _L (unit: mm) between the left and right exit pupil centers of the optical system of the HMD 1 and the center line X both define the thickness of the light guide plate 10 as t (unit: mm), The diffraction angle of light propagating through the light guide plate 10 (more precisely, the refraction angle of light reflected and diffracted by the HOE and incident on the light guide plate 10) is defined as θ1 (unit: deg), and the light guide plate 10 When the number of reflections of the image light of the display element 24 propagating through the inside toward each eye is defined as N (N is a natural number, and in the case of FIG. 2, the right eye and the left eye are 3 times) Is represented by the following equation (1).
L _R = L _L = Nt × tan θ1 (1)
Eye width of the user distance L (a distance between in FIG normal X _R and X _L, the distance L _R and sum of the L _L) when in the projection of the optical system of HMD1 for each eye The pupil coincides with the entrance pupil of each eye. In this case, the user can observe the display image of the display element 24 satisfactorily.

  The HMD 1 is designed assuming a user whose distance L is narrow (for example, a little over 50 mm). Therefore, a user whose eye width is wider than the interval L cannot observe the display image of the display element 24 with good binocular vision because the exit pupil of the optical system of the HMD 1 for each eye and the entrance pupil of each eye do not match. . In order for such a user to observe the display image of the display element 24 with good binocular vision, it is necessary to change the eye width of the HMD 1. Here, as already described, there have been problems such as cost and accuracy in changing the eye width of the HMD. Therefore, the HMD 1 of the present embodiment is configured so that the exit pupil of the optical system of the HMD 1 for each eye and the entrance pupil of each eye coincide with each other with a simple and inexpensive configuration described below. The problems pointed out in the past have been resolved.

  FIG. 3 is a side view schematically showing the configuration of the HMD 1 of the present embodiment, as in FIG. 2, and an optical path from the display element 24 to the left eye of the user in order to explain the change of the eye width of the HMD 1. Is shown enlarged.

  In order to change the eye width of the HMD 1, as shown in FIG. 3, the parallel flat plate 60 is attached to the reflection point on the first surface 10 a where the image light of the display element 24 is reflected by adhesion or the like. In FIG. 3, the broken line indicates the optical path of the image light when the parallel flat plate 60 is pasted. The image light enters the parallel flat plate 60 from the light guide plate 10 and is totally reflected by the surface 60a, and then reenters the light guide plate 10 toward the user's pupil. The parallel flat plate 60 has a configuration in which another reflection point on the first surface 10a (not shown in FIG. 3, but the number of reflections of image light inside the light guide plate 10 is larger in order to change the eye width of the HMD1. If there is, another reflection point exists on the first surface 10a.) Or a reflection point on the second surface 10b.

The parallel flat plate 60 is a widely distributed inexpensive glass plate made of a material having the same or substantially the same refractive index as that of the light guide plate 10, for example. The parallel plate 60 can be easily provided with a wide variety of plate thicknesses because of its availability, and also in this embodiment, a plurality of types with different plate thicknesses t ′ (unit: mm) are prepared. A distance L ′ _L (unit: mm) between the center line X and the center of the exit pupil of the optical system when the parallel plate 60 is pasted is expressed by the following equation (2).
L ′ _L = L _L + (2 × t ′ × tan θ1) = (Nt + 2t ′) × tan θ1 (2)
As shown in Expression (2), the interval L ′ _L varies depending on the plate thickness t ′ of the parallel flat plate 60 attached to the reflection point. Note that the adhesive layer between the light guide plate 10 and the parallel plate 60 is much thinner than the thickness of the light guide plate 10 or the parallel plate 60 and can be ignored, so it is considered in the equation (2). Not. However, as the adhesive used here, the light guide plate 10 and the parallel plate 60 are considered in consideration of the occurrence of critical angles and color misregistration at each interface as well as high transparency to light in the visible light range. And those whose refractive index difference is not extremely large are selected. The refractive index of the adhesive is desirably substantially the same as that of the light guide plate 10 and the parallel plate 60.

  Thus, according to the HMD 1 of the present embodiment, for example, a simple and inexpensive method of simply attaching the parallel plate 60 to the light guide plate 10 without preparing a plurality of types of optical units composed of the light guide plate 10 and various HOEs. The eye width of the HMD 1 can be changed by the configuration. In addition, since a plurality of types of parallel plates 60 having slightly different plate thicknesses are prepared to increase the resolution when adjusting the eye width, high accuracy between the exit pupil of the optical system of the HMD 1 and the entrance pupil of the user's eye. Match is easily achieved.

  For example, a plurality of types of the parallel plate 60 in a state where an adhesive is applied are packaged in the HMD 1 main body and sold. The parallel plate 60 need only be attached to the parallel plate 60 as long as the parallel plate 60 can totally reflect the image light corresponding to the effective area of the display element 24 and re-enter the light guide plate 10 without high accuracy. Therefore, the user can easily change the eye width of the HMD 1 to the eye width optimum for the user by attaching the parallel plate 60 to the light guide plate 10 by himself / herself. As an aid to the work of attaching the parallel plate 60 to the light guide plate 10, a predetermined marking may be attached to a position corresponding to the reflection point of the light guide plate 10. Note that when the parallel flat plate 60 is bonded across a part of adjacent reflection points, a part of the image light corresponding to the effective area of the display element 24 is not normally guided to the user's pupil. By setting the diffraction angle θ1 to be larger and widening the pitch at which the reflection point appears, it may be designed so that the parallel flat plate 60 does not easily straddle a part of the adjacent reflection points during bonding.

  As in this embodiment, an attempt to change the eye width of the HMD using the shift of the exit pupil position caused by the change in the optical path length is, for example, preparing a plurality of types of light guide plates having different plate thicknesses and using them from among them It is also achieved by assembling the HMD by selecting a light guide plate that matches the eye width of the person. However, in this case, it is added that a problem of the same quality as that of the prior art that a plurality of types of molds are required to form light guide plates having different thicknesses.

ｎ１＞ｎ２であるとき、式（３）の（ｎ１ｃｏｓθ１／ｎ２ｃｏｓθ２）は１より大きい。この場合の間隔Ｌ’_Ｌは、式（２）との比較から明らかなように、導光板１０と平行平板６０の屈折率が同一である場合よりも長くなる。別の側面によれば、ｎ２＞ｎ１であるときには式（３）の（ｎ１ｃｏｓθ１／ｎ２ｃｏｓθ２）は１より小さくなるため、間隔Ｌ’_Ｌは式（２）の場合と比べて短くなる。このように、間隔Ｌ’_Ｌは、平行平板６０の板厚だけでなく屈折率によっても変えることができる。なお、かかる場合の平行平板６０の材料（屈折率）も接着剤と同じく、各界面における臨界角や色ズレの発生を考慮した上で選定される。 The parallel plate 60 may be made of a material having a refractive index different from that of the light guide plate 10. The distance L ′ _L (unit: mm) when the parallel flat plate 60 is pasted is defined such that the refractive index of the light guide plate 10 is defined as n1, the refractive index of the parallel flat plate 60 is defined as n2, and is incident on the parallel flat plate 60. When the refraction angle of the emitted light is defined as θ2 (unit: deg), it is expressed by the following equation (3).

When n1> n2, (n1 cos θ1 / n2 cos θ2) in the formula (3) is larger than 1. Distance L _'L in this case, as is apparent from a comparison between Equation (2) is longer than the refractive index of the light guide plate 10 and parallel plate 60 are identical. According to another aspect, since (n1 cos θ1 / n2 cos θ2) in equation (3) is smaller than 1 when n2> n1, the interval L ′ _L is shorter than in the case of equation (2). Thus, the distance L ′ _L can be changed not only by the plate thickness of the parallel plate 60 but also by the refractive index. In this case, the material (refractive index) of the parallel flat plate 60 is also selected in consideration of the occurrence of critical angles and color shifts at each interface, like the adhesive.

As described above, the interval L ′ _L becomes longer as the plate thickness of the parallel plate 60 is thicker or as the refractive index of the parallel plate 60 is smaller than the refractive index of the light guide plate 10. The HOEs 32R and 32L are designed to be large in advance so that the image light can be diffracted toward the user's pupil without omission even when the distance L′ _L is extended. However, when the size of the HOE 32R, 32L is designed to be dark, the image light at the reflection point that is originally desired to be diffracted as well as the image light at the reflection point adjacent thereto is diffracted by the HOE 32R, 32L to form a double image. There is a risk of becoming. That is, the sizes of the HOEs 32R and 32L are defined in consideration of the position where the next reflection point appears, while corresponding to a user with a wide eye width.

Next, specific numerical examples of the HMD 1 described so far will be described. The numerical configuration (design value) of the HMD 1 of this embodiment is as follows.
λ _B : 457
λ _G : 532
λ _R : 633
n _B : 1.72750
n _G : 1.70442
n _R: 1.69426
L _R : 26.6
L _L : 26.6
t: 3.0
θ ' _IB : 0
θ ' _IG : 0
θ ' _IR : 0
θ ′ _DB , θ ″ _IB : 77.0
θ ′ _DG , θ ″ _IG : 77.0
θ ′ _DR , θ ″ _IR : 77.0
θ ” _DB : 0
θ ” _DG : 0
θ ” _DR : 0
“Λ _B ”, “λ _G ”, and “λ _R ” are wavelengths (unit: nm) of B, G, and R light emitted from the laser light source 21 and guided to the user's eyes, “n _B ”,“ N _G ”, and“ n _R ”are refractive indexes of the light guide plate 10 with respect to light of B, G, and R wavelengths, and“ θ ′ _IB ”,“ θ ′ _IG ”, and“ θ ′ _IR ”are The incident angles (unit: deg) of light of B, G, and R wavelengths to the HOEs 52R and 52L, “θ ′ _DB ”, “θ ′ _DG ”, and “θ ′ _DR ” are B, G, diffraction angle of light of each wavelength of the R (unit: deg), _{"theta" IB} "," theta _{"IG", "theta" IR} "refers HOE32R, B to 32L, G, incidence of light of each wavelength of R angle (unit: deg), _{"theta" DB} "," theta _{"DG", "theta" DR} "is HOE32R, by 32L B, G, the diffraction angle of light of each wavelength of the R (unit: de ) Are shown, respectively. Eye width L of HMD1 in this embodiment 'is in a state which does not paste the parallel plate 60 the sum of _{L R} and _{L L,} that is, 53.2Mm.

The refractive index n of the material constituting the HOEs 52R and 52L is, for example, 1.52 (equivalent to BK7). The following formula n1sin θ1 = n2sin θ2
When the value of the wavelength λ _G corresponding to the approximate center of the used wavelength is substituted for the right side of, the diffraction angle (θ1 described above) of the light actually propagating through the light guide plate 10 is approximately 60.6 deg. Since the diffraction angles of light of each wavelength by the HOEs 52R and 52L are large, for example, even when the light guide plate 10 is thinned (lightened according to another aspect), the first surface 10a of the light guide plate 10 or A design is realized in which the reflection points of the image light of the display element 24 reflected on the two surfaces 10b do not overlap. Further, the number of reflections of the image light of the display element 24 propagating through the light guide plate 10 is reduced (for example, in the present embodiment, five times for both the right eye and the left eye), and the light is propagated through the light guide plate 10. Since the optical path of the image light is shortened, light quantity loss due to internal diffusion is suppressed.

Same refractive index, for example, thickness 0.5mm and the light guide plate 10 in HMD1 of this embodiment, 1.0 mm, when pasted parallel plate 60 of 2.0mm as shown in FIG. 3, the interval L _'L respectively, It changes to approximately 28.40 mm, 30.17 mm, and 33.72 mm. When the parallel flat plate 60 is similarly attached to the right side of the light guide member 10, the eye width L ′ of the HMD 1 is approximately 56.79 mm, 60.34 mm, and 67.44 mm. As shown from these numerical data, when a plurality of types of parallel flat plates 60 having a further slight difference in plate thickness are used, the eye width of the HMD 1 can be finely adjusted according to the eye widths of various users. It is obvious. Note that the parallel plate 60 is not necessarily attached to the reflection points corresponding to the left and right optical paths because the eye width of the HMD 1 extends as long as the parallel plate 60 is attached to any one of the reflection points.

  The above is the description of the embodiment of the present invention. The present invention is not limited to the configurations of the embodiments and the specific numerical configurations, and various modifications are possible within the scope of the technical idea of the present invention. For example, the HOEs 32R, 32L, 52R, and 52L may be, for example, transmissive HOEs. In such a case, the HOEs 52R and 52L are closely fixed in a state where they are stacked on the first surface 10a of the light guide plate 10 facing the display element unit 20, for example, and light of each wavelength from the display element unit 20 is transmitted to the inside of the light guide plate 10. And diffracted so as to be propagated to the HOE 32R or 32L. For example, the HOEs 32R and 32L are closely fixed on the second surface 10 of the light guide plate 10 facing the user's pupil, and diffract light of each wavelength propagated through the light guide plate 10 toward the user's pupil.

  A plurality of types of parallel flat plates 60 may be prepared in which not only the plate thickness but also the dimensions in the plane (length, width) direction orthogonal to the plate thickness are different. The dimension in the surface direction is larger than that of the parallel flat plate 60 of the present embodiment. For example, the parallel flat plate 60 attached to the light guide plate 10 so as to cover the entire two reflection points without omission is considered as an example. In this case, the parallel flat plate 60 can make the image light corresponding to the effective area of the display element 24 be totally reflected twice without being leaked and re-enter the light guide plate 10. The amount of extension of the optical path length of the image due to the application of the parallel plate 60 is doubled compared to the case where the image light is totally reflected once. Therefore, for example, even if the parallel flat plate 60 is thin, the optical path length of the image can be further extended compared to the present embodiment, and the exit pupil position of the image light can be displaced further outward. Since the parallel flat plate 60 is thinned, the partial and extreme protruding shape (that is, the shape of the parallel flat plate 60) becomes inconspicuous, so that a product with an emphasis on design can be provided.

  The light source 21 included in the display element unit 20 may be, for example, an LED or an LD (semiconductor laser) backlight that sequentially emits light of each wavelength of R, G, and B at high speed.

1 HMD
2 glasses-type frame 4 backlight 10 light guide plate 20 display element units 32R, 32L, 52R, 52L HOE
60 parallel plates

Claims (8)

A display element for displaying an image;
A light guide plate on which an image displayed on the display element is incident;
Propagating means for totally reflecting the incident image inside the light guide plate and propagating toward the user's pupil;
A plurality of types of optical members having different shapes or refractive indexes, which are selectively attached to a location on the light guide plate where the image is totally reflected at the interface between the light guide plate and air, An optical member that totally reflects the image incident thereon and re-enters the light guide plate so that the image is totally reflected again inside the light guide plate and propagates toward the pupil of the user. When,
A video display device comprising:   The image display apparatus according to claim 1, wherein the optical member has a refractive index substantially the same as that of the light guide plate.   The light guide plate and the optical member are highly transmissive with respect to the wavelength of the image, and are bonded by an adhesive having substantially the same refractive index as that of the light guide plate and the optical member. The video display device described in 1.   4. The image according to claim 1, wherein the plurality of types of optical members are plate types or a plurality of types of parallel flat plates having different dimensions in a plane direction orthogonal to the plate thickness. 5. Display device.   The image display device according to claim 1, wherein the light guide plate is provided with a predetermined marking at the location. The propagation means includes
A first HOE (Holographic Optical Element) or a first DOE (Diffractive Optics Element) that diffracts the image incident on the light guide plate so that the image is totally reflected inside the light guide plate and propagates to a predetermined position;
A second HOE or second DOE that diffracts the image propagated to the predetermined position toward the pupil of the user;
The video display device according to claim 1, further comprising: A pair of the second HOE or the second DOE is disposed in front of the left and right eyes of the user,
The first HOE or the first DOE divides an image incident on the light guide member into two parts and diffracts each of the divided images so as to enter each of the pair. The video display device according to claim 6.   The image display apparatus according to any one of claims 1 to 7, further comprising support means for supporting the video display device according to any one of claims 1 to 7 in front of the user's eyes so that the user can observe the image propagated by the propagation means as a virtual image. Head-mounted display featuring

Images