JP5266525B2 - Video display device and head mounted display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a video display device 1 of a wide image angle with a small-sized and compact configuration by developing a small-sized, compact and high-NA illumination optical system 12. <P>SOLUTION: The illumination optical system 12 which guides light from a light source 11 to a display element 14 includes a first group G1 which has positive power and has a reflection surface and a second group G2 which has positive power and has a fresnel lens 18. Thus, by making the illumination optical system 12 a positive and positive two-groups constitution, a larger NA can be secured while shortening the length of the illumination optical system 12 in the proceeding direction of light as compared with the case constituting the illumination optical system 12 with one optical element. Moreover, since the first group G1 has a reflection surface, the optical path of the illumination optical system 12 is folded and the illumination optical system 12 is made small. At this time, by satisfying a prescribed conditional relation, the illumination optical system 12 can be constituted compactly while securing a space into which the reflection surface is inserted. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to an image display device that guides image light from a display element to an optical pupil via an eyepiece optical system, and a head mounted display (hereinafter also referred to as an HMD) including the image display device.

  Conventionally, light from a light source is guided to a display element via an illumination optical system, and image light from the display element is guided to an optical pupil (or an observer's pupil located on the optical pupil) via an eyepiece optical system. Various HMDs have been proposed. By illuminating the display element using the illumination optical system, it is possible to increase the utilization efficiency of light from the light source and allow the observer to observe a bright image (virtual image).

  The illumination optical system described above can be configured to include a transmissive or reflective optical element. For example, in the HMD of Patent Document 1, an illumination optical system is configured including a lens as a transmissive optical element, and the transmissive display element is illuminated via the illumination optical system. On the other hand, in the HMD of Patent Document 2, an illumination optical system is configured by a parabolic mirror as a reflective optical element, and a transmissive display element is illuminated through the illumination optical system.

JP 2006-145728 A JP 2004-61731 A

  By the way, in recent years, in addition to small size and compactness, there has been an increasing demand for wide angle of view of HMD. In order to make the HMD have a wide angle of view, for example, a method using a display element having a large size is conceivable. When using a large display element, it is necessary to increase the NA (numerical aperture) of the illumination optical system that illuminates the display element in order to efficiently guide light from the light source to the display element.

  However, in the illumination optical systems of Patent Documents 1 and 2, since there is only one optical element having optical power, in order to increase the NA of the illumination optical system, the optical element must be formed large. This makes it difficult to make the illumination optical system compact and compact. As a result, it is difficult to realize a small and compact HMD having a wide angle of view.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to realize a compact, compact and high NA illumination optical system, thereby achieving a compact and compact configuration. An object of the present invention is to provide a video display device capable of realizing a wide angle of view and an HMD provided with the video display device.

An image display apparatus according to the present invention includes a light source, a transmissive display element that modulates incident light to display an image, an illumination optical system that guides light emitted from the light source to the display element, and image light from the display element. An eyepiece optical system that guides the optical pupil to the optical pupil, wherein the illumination optical system has, in order from the light source side, at least one reflecting surface and a positive power. And a second group having at least one optical member and having a positive power, and satisfying the following conditional expression. That is,
1.5 <f2 / f1 <8.5
However,
f1: Focal length of the first group excluding the reflecting surface f2: Focal length of the second group.

  According to the above configuration, the light emitted from the light source is incident on the transmissive display element via the illumination optical system, modulated there, and then converted into image light to the optical pupil via the eyepiece optical system. Led. Therefore, at the position of the optical pupil, the observer can observe the virtual image of the image displayed on the display element.

  Here, the illumination optical system has a first group having positive power and a second group having positive power. In this way, by configuring the illumination optical system to have at least two groups of positive and positive, the length of the illumination optical system in the direction in which the light travels as compared with the case where the illumination optical system is configured by one optical element. It is possible to secure a large NA while shortening. In addition, since the first group has at least one reflecting surface, the optical path of the illumination optical system can be folded so that the illumination optical system does not jump forward and backward. That is, according to the present invention, it is possible to realize a small, compact, high NA illumination optical system. Therefore, even when a display element having a large size is used, it is possible to realize a small, compact and wide-angle video display device using the illumination optical system.

  If the lower limit of the conditional expression is not reached, the power of the second group of the illumination optical system becomes too large, and it becomes difficult to secure a space for inserting the reflecting surface. On the other hand, if the upper limit of the conditional expression is exceeded, the first group bears most of the power in the illumination optical system, so the size of the reflecting surface increases and the entire illumination optical system increases.

  Therefore, by satisfying the conditional expression, it becomes possible to configure the illumination optical system in a compact manner while ensuring the space for inserting the reflection surface, and in the configuration of the illumination optical system using the reflection surface, An effect can be obtained.

  In the video display device of the present invention, the second group of the illumination optical system may have a Fresnel lens as the optical member.

  Since the Fresnel lens is thinner than a normal lens, the use of the Fresnel lens in the second group of the illumination optical system makes it possible to reduce the size and weight of the illumination optical system compared to the case of using a normal lens. In particular, since the second group is close to the display element and has a larger effective radius than the first group, by using a thin Fresnel lens for the second group, the second group is placed close to the display element. The arrangement to be arranged can be easily adopted.

  The video display device of the present invention further includes a diffusing member that diffuses incident light, and the diffusing member may be disposed in an optical path between the second group of the illumination optical system and the display element. Good. By using the diffusing member, it becomes possible to reduce the intensity unevenness of the light source (intensity distribution unevenness) and to uniformly illuminate the entire display element.

  The image display device of the present invention further includes a diffusing member that diffuses incident light, and the diffusing member is disposed in an optical path between the second group of the illumination optical system and the display element, and the screen of the display element The diffusivity in the long side direction may be larger than the diffusivity in the screen short side direction of the display element.

  Since the display screen of the display element is usually a rectangular region, the NA of the illumination optical system used in the long side direction of the display screen is larger than the NA of the illumination optical system used in the short side direction of the display screen. On the other hand, in a configuration in which a Fresnel lens is used for the second group of the illumination optical system, the pitch (width) of the Fresnel lens becomes smaller (decreases) toward the end in the long side direction of the screen. For this reason, unevenness due to the pitch (edge) of the Fresnel lens appears significantly in the long side direction of the screen. By disposing a diffusing member between the second group of the illumination optical system and the display element, and setting the diffusing characteristics of the diffusing member as described above, the intensity unevenness of the light source is reduced, and it is caused by the Fresnel lens. It is possible to reduce unevenness in the long side direction of the screen.

  In the image display device of the present invention, the optical path of the illumination optical system is bent in a cross section parallel to the screen short side direction of the display element and perpendicular to the screen long side direction by the first group of reflecting surfaces of the illumination optical system. It is desirable to have a configuration. In this way, by bending the optical path of the illumination optical system within the cross section by the first group of reflecting surfaces, the thickness of the illumination optical system in the front-rear direction is reduced as compared with the configuration in which the optical path is folded within another cross section. be able to.

  In the video display device of the present invention, it is desirable that the positional relationship between the light source and the optical pupil is conjugate within the cross section. In this case, the light emitted from the light source can be efficiently propagated to the optical pupil within the cross section.

  In the image display device of the present invention, the eyepiece optical system includes a volume phase type reflection hologram optical element, and image light from the display element is diffracted and reflected by the hologram optical element and guided to the optical pupil. At the same time, the configuration may be such that the light of the external field image transmitted through the hologram optical element is guided to the optical pupil. Thus, by using a hologram optical element having wavelength selectivity (hereinafter also referred to as HOE) as a combiner of two types of light, an observer can superimpose a virtual image of the image displayed on the display element on an external image. And see through.

  The head-mounted display of the present invention includes the above-described video display device of the present invention and support means for supporting the video display device in front of an observer's eyes. In this configuration, since the video display device is supported by the support means, the observer can observe the video provided from the video display device in a hands-free manner. In addition, by applying the video display device of the present invention to an HMD, it is possible to realize a HMD having a wide angle of view with a compact illumination optical system and less burden on the observer during use.

  According to the present invention, an illumination optical system that is small, compact, and has a high NA can be realized. Thereby, even when a large display element is used, it is possible to realize a small, compact and wide-angle video display device using the illumination optical system. In addition, by satisfying a predetermined conditional expression, it becomes possible to configure the illumination optical system in a compact manner while securing a space for inserting the reflection surface of the first group of the illumination optical system, and illumination using the reflection surface The above-described effects can be obtained in the configuration of the optical system.

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

(1. About HMD)
FIG. 1 is a perspective view showing a schematic configuration of the HMD. The HMD includes a video display device 1 and support means 2.

  The video display device 1 allows an observer to observe an outside world image with see-through, displays an image, and provides it to the observer as a virtual image. As this video display apparatus 1, what is shown by Embodiment 1-4 mentioned later is applicable. The video display device 1 is configured by integrating an eyepiece optical system 20 with a housing 3 that houses a display element 14 (see FIG. 2) and the like. The eyepiece optical system 20 as a whole has a shape like one lens of eyeglasses (the right-eye lens in FIG. 1). The support means 2 supports the video display device 1 in front of the observer's eyes, and corresponds to, for example, a frame or temple of glasses. Details of the video display device 1 will be described below.

(2. About video display device)
2 to 5 are cross-sectional views each showing a schematic configuration of the video display device 1 according to the first to fourth embodiments. The video display device 1 includes a light source 11, an illumination optical system 12, a diffusion plate 13 (a diffusion member), a display element 14, and an eyepiece optical system 20. For convenience, the diffusion plate 13 is not shown in FIGS.

  For convenience of explanation, directions are defined as follows. First, an axis that optically connects the center of the display area of the display element 14 and the center of the optical pupil (exit pupil) E formed by the eyepiece optical system 20 is an optical axis. The optical axis direction when the optical path from the light source 11 to the optical pupil E is developed is taken as the Z direction. In addition, a direction perpendicular to the optical axis incident surface of the HOE 23 described later of the eyepiece optical system 20 is defined as an X direction, and a direction perpendicular to the ZX plane is defined as a Y direction. The optical axis incident surface of the HOE 23 refers to a plane including the optical axis of incident light and the optical axis of reflected light in the HOE 23, that is, the YZ plane.

  The light source 11 is composed of, for example, an RGB integrated LED that emits light having wavelengths corresponding to the three primary colors of RGB. This light source 11 has a conjugate positional relationship with the optical pupil E. In particular, when the diffusion characteristic of the diffusion plate 13 is, for example, one-dimensional, and the diffusion plate 13 diffuses incident light, for example, in the X direction, the light source 11 is conjugate with the optical pupil E in the YZ plane. Thereby, the light emitted from the light source 11 can be efficiently propagated to the optical pupil E in the cross section. The illumination optical system 12 collects the light emitted from the light source and guides it to the display element 14, details of which will be described later.

  The diffusing plate 13 is a diffusing member that diffuses incident light, and is disposed in an optical path between a second group G <b> 2 (described later) of the illumination optical system 12 and the display element 14. As a result, the RGB intensity unevenness of the light source 11 can be reduced, and the entire display element 14 can be illuminated uniformly.

  Further, when the diffusion characteristic of the diffusion plate 13 is, for example, one-dimensional, the distance between the diffusion plate 13 and the display element 14 is such that the difference in diopter between the virtual images by the eyepiece optical system 20 is 2 diopters (Dp) or more. It is desirable to be a distance. Here, the diopter is represented by the reciprocal (−1 / m) of the value of the focal length of the optical system (for example, lens) expressed in meters, and indicates diopter, that is, the power (refractive power) of the optical system. Generally used as a unit. By setting the positional relationship between the diffusing plate 13 and the display element 14 in this way, a virtual image by the eyepiece optical system 20 of the diffusing plate 13 (a virtual image by the eyepiece optical system 20 of the diffusing plate 13) is displayed. It is possible to reduce the appearance of overlapping images).

  The display element 14 modulates light incident from the light source 11 via the illumination optical system 12 according to image data and displays an image, and is configured by, for example, a transmissive LCD. The display element 14 is arranged such that the long side direction of the rectangular display screen is the X direction and the short side direction is the Y direction. 2 to 5, only the cover glass that is the glass substrate on the counter electrode side in the display element 14 is illustrated.

  The display element 14 has polarizing plates whose polarization directions are orthogonal to each other on the light incident side and the light emission side of the liquid crystal layer. In this case, since the polarizing plate is disposed between the diffusion plate 13 and the liquid crystal layer, even if the polarization state is changed by the illumination optical system 12 (including a lens and a reflection surface described later) and the diffusion plate 13, a predetermined value is obtained. Thus, only the linearly polarized light can be incident on the liquid crystal layer, and a decrease in contrast due to a change in polarization state can be avoided.

  The eyepiece optical system 20 is an image display optical system that guides the image light from the display element 14 to the optical pupil E, and includes an eyepiece prism 21, a deflection prism 22 (see FIG. 1), and a HOE 23. Yes.

  The eyepiece prism 21 totally reflects the image light from the display element 14 inside, and transmits light of the external image (external light). The eyepiece prism 21 is made of, for example, an acrylic resin together with the deflection prism 22. The eyepiece prism 21 is configured in a wedge shape by making the lower end of the parallel flat plate thinner toward the lower end. The upper end surface of the eyepiece prism 21 is a surface 21a as an incident surface for image light, and the two surfaces positioned in the front-rear direction are surfaces 21b and 21c parallel to each other.

  The deflecting prism 22 is configured by a substantially U-shaped parallel plate in plan view (see FIG. 1), and when attached to the lower end portion and both side surface portions (left and right end surfaces) of the eyepiece prism 21, the eyepiece prism. 21 is a substantially parallel flat plate. The deflection prism 22 is provided adjacent to or attached to the eyepiece prism 21 so as to sandwich the HOE 23. Thereby, distortion can be prevented from occurring in the external image observed by the observer through the wedge-shaped portion of the eyepiece prism 21.

  The HOE 23 diffracts and reflects the image light (wavelength corresponding to the three primary colors) from the display element 14 and guides it to the optical pupil E, thereby enlarging the image displayed on the display element 14 and the observer's pupil. 2 is a volume phase reflection hologram optical element that is guided as a virtual image on the eyepiece prism 21 and is provided on the joint surface of the eyepiece prism 21 with the deflection prism 22. In the eyepiece prism 21, the surface on which the HOE 23 is provided is hereinafter referred to as a HOE surface.

  The HOE 23 has an axially asymmetric positive optical power, and has the same function as an aspherical concave mirror having a positive optical power. Thereby, the degree of freedom of arrangement of each optical member constituting the apparatus can be increased, and the apparatus can be easily reduced in size, and an image with good aberration correction can be provided to the observer.

  In the video display device 1 having the above-described configuration, the light emitted from the light source 11 enters the display element 14 via the illumination optical system 12 and the diffusion plate 13, and is modulated there and emitted as video light. The image light from the display element 14 enters the eyepiece prism 21 of the eyepiece optical system 20 from the surface 21a, and subsequently enters the surface 21c (surface 21b in FIGS. 3 to 5) at an angle greater than the critical angle. Then, the light is totally reflected at least once by the surfaces 21 b and 21 c and enters the HOE 23. The light incident on the HOE 23 is diffracted and reflected there and reaches the optical pupil E. At the position of the optical pupil E, the observer can observe an enlarged virtual image of the image displayed on the display element 14.

  On the other hand, the eyepiece prism 21, the deflecting prism 22, and the HOE 23 transmit almost all the external light, so that the observer can observe the external image. Therefore, the virtual image of the image displayed on the display element 14 is observed while being overlapped with a part of the external image.

  As described above, in the eyepiece optical system 20, the image light from the display element 14 is guided in the eyepiece prism 21 and guided to the optical pupil E through the HOE 23, and at the same time, the external light transmitted through the HOE 23 is transmitted to the optical pupil E. Lead to. The HOE 23 composed of a volume phase type reflective holographic optical element has a narrow diffraction wavelength width and has a characteristic that acts on a specific wavelength but does not act on other wavelengths. When such a HOE 23 is used as a combiner for a so-called see-through function for simultaneously observing a display image and an external image, the HOE 23 acts only on a part of the wavelength of the external light, so that the external light is almost influenced by the HOE 23. It is possible to observe the outside world image brightly and satisfactorily without seeing. Moreover, it is possible to observe a color image by superimposing the HOE 23 acting on different wavelengths.

  Further, on the cross section passing through the center of the screen parallel to the short side direction of the display screen of the display element 14, a ray traveling on the optical axis (screen center principal ray) is bent in the direction of the optical pupil E by the HOE plane. Yes. Thus, the thickness of the eyepiece optical system 20 can be made thinner (compact) by inclining the HOE surface within a cross section passing through the center of the screen parallel to the screen short side direction.

(3. About illumination optical system)
Next, details of the illumination optical system 12 will be described. The illumination optical system 12 in each of the first to fourth embodiments includes a first group G1 and a second group G2 in order from the light source 11 side. The first group G1 has at least one reflecting surface and has positive power. On the other hand, the second group G2 has at least one optical member and has positive power.

  More specifically, in the illumination optical system 12 of the first and third embodiments, as shown in FIGS. 2 and 4, the first group G1 includes, in order from the light source 11, the lens 15, the Fresnel lens 16, and the reflection mirror. 17, and the second group G <b> 2 includes a Fresnel lens 18. The lens 15 and the Fresnel lenses 16 and 18 each have a positive power. The reflecting surface of the reflecting mirror 17 is a flat surface in the first embodiment and a spherical surface in the third embodiment.

  In the illumination optical system 12 of Embodiments 2 and 4, as shown in FIGS. 3 and 5, the first group G1 includes a lens 15 and a reflection mirror 17 in order from the light source 11 side. The second group G2 includes a Fresnel lens 18. The lens 15 and the Fresnel lens 18 each have a positive power. The reflecting surface of the reflecting mirror 17 is a spherical surface in both Embodiments 2 and 4.

  That is, in the illumination optical system 12 of Embodiments 1 and 3, the light from the light source 11 is sequentially transmitted through the lens 15 and the Fresnel lens 16 of the first group G1, and then is reflected by the reflection mirror 17 to bend its optical path. Then, the light passes through the Fresnel lens 18 of the second group G 2 and enters the diffusing member 13. On the other hand, in the illumination optical system 12 of the second and fourth embodiments, the light from the light source 11 passes through the lens 15 of the first group G1, is reflected by the reflection mirror 17, and its optical path is bent, and the second group. The light passes through the G2 Fresnel lens 18 and enters the diffusing member 13.

  As described above, the illumination optical system 12 has a positive and positive two-group configuration, so that the illumination optical system 12 in the light traveling direction can be compared with the case where the illumination optical system 12 is configured by one optical element. It is possible to secure a large NA while shortening the length. In addition, since the first group G1 includes the reflecting mirror 17 (reflecting surface), it is possible to fold the optical path of the illumination optical system 12 and prevent the illumination optical system 12 from jumping back and forth. It becomes.

  Therefore, a small, compact, high NA illumination optical system 12 can be realized, and even when a large-sized display element 14 is used, the high NA illumination optical system 12 is used to achieve a small, compact, wide area. It is possible to realize the image display device 1 having an angle of view. Further, since the illumination optical system 12 can be made compact and compact while maintaining a high NA, the center of gravity position of the illumination system when the light source 11 and the illumination optical system 12 are considered as one system, and the eyepiece optical system 15. The position of the center of gravity can be brought closer, and stability during use can also be improved.

At this time, it is desirable that the video display devices 1 of the first to fourth embodiments satisfy the following conditional expressions. That is,
1.5 <f2 / f1 <8.5
However,
f1: Focal length (mm) of the first group G1 excluding the reflecting surface
f2: Focal length (mm) of the second group G2
It is.

  If the lower limit of the conditional expression is not reached, the power of the second group G2 of the illumination optical system 12 becomes too large, and it becomes difficult to secure a space for inserting the reflection mirror 17. On the contrary, if the upper limit of the conditional expression is exceeded, the first group G1 bears most of the power in the illumination optical system 12, so that the size of the reflection mirror 17 becomes large and the illumination optical system 12 becomes large as a whole. .

  Therefore, by satisfying the conditional expression, the illumination optical system 12 can be configured in a compact manner while ensuring a space for inserting the reflection mirror 17, and the illumination optical system 12 having the reflection mirror 17 can be used in a compact size. Thus, it is possible to realize a compact and wide-angle video display device 1.

In addition, as for the video display apparatus 1 of each Embodiment 1-4, it is more desirable to satisfy the following conditional expressions. That is,
2.0 <f2 / f1 <5.0
It is.

  In each of the first to fourth embodiments, the reflection mirror 17 causes the optical path of the illumination optical system 12 to be in the YZ plane, that is, in a cross section parallel to the screen short side direction and perpendicular to the screen long side direction. It is bent by. Thereby, compared with the structure which bends an optical path in another cross section, the thickness of the front-back direction of the illumination optical system 12 can be made thin, and it is set as the structure which does not protrude the illumination optical system 12 back and forth reliably. It becomes possible.

  Further, by using the Fresnel lens 18 in the second group G2 of the illumination optical system 12, the illumination optical system 12 can be reduced in size and weight as compared with the case of using a normal lens. Furthermore, since the second group G2 is close to the display element 14 and has a larger effective radius than the first group G1, the effect of using the Fresnel lens 18 in the second group G2 is increased. That is, it becomes easy to arrange the second group G2 near the display element 14, and the use burden on the observer can be reduced by reducing the weight of the illumination optical system 12.

  By the way, in the configuration using the Fresnel lens 18 in the second group G2 of the illumination optical system 12, it is desirable to set the diffusion characteristics of the diffusion plate 13 as follows. That is, the diffusivity (for example, 40 degrees) in the screen long side direction of the display element 14 in the diffusion plate 13 is set to be larger than the diffusivity (for example, 0.5 degree) in the short screen direction of the display element 14. It is desirable. This is due to the following reason.

  Since the display screen of the display element 14 is usually a rectangular area (in this embodiment, an area that is long in the X direction and short in the Y direction), illumination optics used in the long side direction (X direction) of the display screen. The NA of the system 12 is larger than the NA of the illumination optical system 12 used in the short side direction (Y direction) of the display screen. That is, as shown in FIG. 6, the two light beams (diverging light) emitted from the light source 11 are incident on both ends of the display element 14 in the long side direction of the display screen 14 through the illumination optical system 12. The angle formed by the two light beams on the light incident side of the illumination optical system 12 is defined as a first angle α (°), and the two light beams incident on both ends in the short side direction of the display screen of the display element 14 via the illumination optical system 12. If the angle stretched on the light incident side of the illumination optical system 12 is the second angle β (°), the first angle α is larger than the second angle β.

  On the other hand, FIG. 7 shows a cross-sectional view of the Fresnel lens 18. In the configuration in which the Fresnel lens 18 is used for the second group G2 of the illumination optical system 12, as shown in the figure, the pitch (width) of the Fresnel lens 18 becomes smaller (narrower) from the center toward the end. For this reason, in the long side direction of the screen where the NA of the illumination optical system 12 to be used becomes large, unevenness due to the pitch (edge) of the Fresnel lens 18 appears more markedly than in the short side direction of the screen.

  Therefore, by arranging the diffusion plate 13 between the second group G2 of the illumination optical system 12 and the display element 14, and setting the diffusion characteristics of the diffusion plate 13 as described above, the intensity unevenness of the light source 11 is reduced. While reducing, unevenness in the long side direction of the screen due to the Fresnel lens 18 can be reduced.

  Further, when the volume phase reflection type HOE 23 is manufactured by two-beam interference of laser light, the angle selectivity of the HOE 23 is high in a cross section (YZ plane) parallel to the optical axis incident surface of the manufactured HOE 23. That is, the diffraction efficiency in the screen short side direction (Y direction) in the HOE 23 greatly depends on the incident angle of the incident light beam (image light) to the HOE 23, and even if the incident angle slightly changes, the diffraction efficiency is greatly reduced. To do. Therefore, if the angular distribution of the incident light beam is large in the short side direction of the screen, the incident light beam cannot be efficiently propagated to the optical pupil E. Therefore, also from this point, it can be said that it is preferable that the diffusion degree in the short side direction of the screen in the diffusion plate 13 is small. On the other hand, the diffraction efficiency in the screen long side direction (X direction) of the HOE 23 is less dependent on the incident angle of the light beam. Therefore, even if the angle distribution of the incident light beam is large in the long side direction of the screen, E can be efficiently guided.

(4. About Example)
Hereinafter, each example of the video display device 1 according to each of the first to fourth embodiments will be described more specifically with reference to construction data and the like as examples 1 to 4. Examples 1 to 4 are numerical examples corresponding to the first to fourth embodiments, respectively. Optical configuration diagrams (FIGS. 2 to 5) representing the first to fourth embodiments correspond to the first example. The same applies to -4.

  In the construction data shown below, Si (i = 1, 2, 3,...) Indicates the i-th surface from the optical pupil E side (the optical pupil E is the first surface). ing. In the cover glass (CG) of the display element 14, the surface on the eyepiece optical system 20 side is a CG surface, and the surface on the light source 11 side is an image surface (display surface).

  The arrangement of each surface Si is specified by each surface data of surface vertex coordinates (x, y, z) and rotation angle (ADE). The surface vertex coordinates of the surface Si are the local orthogonal coordinate system (X, Y, z) in the global orthogonal coordinate system (x, y, z) with the surface vertex as the origin of the local orthogonal coordinate system (X, Y, Z). , Z) is represented by the coordinates (x, y, z) of the origin (unit: mm). Further, the inclination of the surface Si is represented by a rotation angle around the X axis (X rotation) with the surface vertex as the center. The unit of the rotation angle is °, and the counterclockwise direction when viewed from the positive direction of the X axis is the positive direction of the rotation angle of the X rotation.

  The global orthogonal coordinate system (x, y, z) is an absolute coordinate system that matches the local orthogonal coordinate system (X, Y, Z) of the optical pupil plane (S1). In other words, the arrangement data of each surface Si is expressed in a global coordinate system with the center of the optical pupil plane as the origin. In the optical pupil plane (S1), the direction from the optical pupil E toward the eyepiece optical system 20 is the + Z direction, the upward direction with respect to the optical pupil E is the + Y direction, and the direction is perpendicular to the YZ plane. The direction from the back to the front of FIG. 2 (the direction from the left to the right when the HMD is attached) is the + X direction.

  In addition, the manufacturing wavelength (HWL; normalized wavelength) and the reproduction wavelength when producing the HOE used in each example are both 532 nm, and the use order of the diffracted light is the first order. For the HOE surface, the HOE is uniquely defined by defining the two light beams used for fabrication. The definition of the two light beams is performed by determining whether the light source position of each light beam is the convergent beam (VIA) or the divergent beam (REA). The coordinates of the first point light source (HV1) and the second point light source (HV2) are (HX1, HY1, HZ1) and (HX2, HY2, HZ2), respectively.

  In each embodiment, since the complex wavefront reproduction by HOE is performed, the HOE is also defined by the phase function φ in addition to the definition of the two light beams. The phase function φ is a generator polynomial based on the position (X, Y) of the HOE, as shown in the following formula 1, and the coefficient is expressed by a monomial in ascending order from the first order to the tenth order. In the construction data, the coefficient Cj of the phase function φ is shown.

  Note that the number j of the coefficient Cj is expressed by the following equation 2 where m and n are indices of X and Y.

In the HOE plane, the normal vectors of the emitted light are respectively p ′, q ′, and r ′, the normal vectors of the incident light are respectively p, q, and r, and the wavelength of the reproduced light beam is λ (nm), Assuming that the wavelength of the light beam for producing the HOE is λ ₀ (nm), p ′, q ′, and r ′ are expressed by the following equation (3).

  Thus, in Examples 1-6, the hologram photosensitive material is exposed using the light source which inject | emits the light of wavelength 532nm, and the phase function (phi) of HOE corresponding to wavelength 532nm is created. After the phase function φ corresponding to the wavelength is created, the eyepiece optical system 20 can be adapted to color display by multiple exposure of the hologram photosensitive material using a light source that emits light of other wavelengths.

In the construction data, the surface shape of the rotationally symmetric aspheric surface is expressed by the following equation (4). Here, Z indicates the sag amount (mm) in the Z-axis direction (optical axis direction) at the position of height h, c indicates the curvature (1 / mm) at the surface apex, and h is the height, that is, Z A distance (mm) from the axis (optical axis) is indicated, k is a conic constant, and A, B, C, D, E, F, and G are 4th order, 6th order, 8th order, 10th order, 12th, respectively. Next, 14th and 16th order coefficients (aspherical coefficients) are shown. It should be noted that for all data, the coefficients of the terms not described are all 0, and E−n = × 10 ⁻ⁿ .

  Further, the surface shape of the anamorphic aspheric surface is expressed by the following equation (5). Here, Z represents the sag amount (mm) in the Z-axis direction, CUX represents the curvature in the X direction (1 / mm), that is, the reciprocal of the curvature radius RX in the X direction, and CUY represents the curvature in the Y direction (1 / mm ), That is, the reciprocal of the radius of curvature RY in the Y direction. KX and KY denote conic constants in the X direction and the Y direction, respectively. Furthermore, AR, BR, CR, and DR indicate rotationally symmetric components of the fourth-order, sixth-order, eighth-order, and tenth-order aspheric coefficients, respectively. AP, BP, CP, and DP are fourth-order, sixth-order, The non-rotationally symmetric components of the 8th and 10th order aspheric coefficients are shown.

  In each of Examples 1 to 4, the maximum sag amount (z in FIG. 6) of each zone of the Fresnel lenses 16 and 18 was set to 0.1 mm.

Example 1
Surface number Curvature radius S1 Pupil surface INFINITY
S2 Prism exit surface INFINITY
S3 HOE surface RX; -141.533 RY; INFINITY
Definition of two luminous fluxes
HV1; REA HV2; VIR
HX1; 0 HY1; -10 HZ1; -20
HX2; 0 HY2; 100000 HZ2; 10000000
HWL; 532
Phase coefficient
C2; 0.64051758 C3; -0.018479333 C5; 0.105533963
C7; -0.005171525 C9; 0.004487547 C10; 0.000121039
C12; -0.000264254 C14; 9.26493E-05 C16; 1.82316E-05
C18; -4.75592E-06 C20; -4.23183E-07 C21; -7.75581E-10
C23; 9.53777E-07 C25; -5.3112E-09 C27; -7.08537E-08
C29; 1.32123E-09 C31; 2.14066E-08 C33; 5.77851E-10
C35; -1.445E-09 C36; 6.29843E-11 C38; 3.40788E-11
C40; 1.75889E-10 C42; 2.40048E-12 C44; -9.82606E-12
C46; 0 C48; 0 C50; 0
C52; 0 C54; 0 C55; 0
C57; 0 C59; 0 C61; 0
C63; 0 C65; 0
S4 Reflective surface INFINITY
S5 Reflective surface INFINITY
S6 Prism entrance surface 292.053051
(Aspherical)
k; 0 A; -1.55846E-04 B; 3.10103E-06
C; -3.32367E-08 D; 1.22114E-10 E; 0.00000E + 00
F; 0.00000E + 00 G; 0.00000E + 00
S7 CG side INFINITY
S8 Display screen INFINITY
S9 Fresnel lens exit surface -30
S10 Fresnel lens entrance surface INFINITY
S11 Reflective surface INFINITY
S12 Fresnel lens exit surface 15
S13 Fresnel lens entrance surface INFINITY
S14 lens exit surface 4.6721
S15 Lens entrance surface INFINITY
S16 Light source surface INFINITY

Surface number xyz ADE Nd νd
S1 0 0 0 0 Pupil diameter 3mm
S2 0 0 21.5 0 1.4914 59.93
S3 0 14.8636 41.6148 -29 1.4914 59.93
S4 0 1.5 21.5 0 1.4914 59.93
S5 0 6.5 33 0 1.4914 59.93
S6 0 2.5278 26.7626 -6.6701
S7 0 19.3043 24.6445 -35.7007 1.5168 65.26
S8 0 19.7712 23.9948 -35.7007
S9 0 21.1682 22.0507 -35.7007 1.5305 55.72
S10 0 21.7517 21.2387 -35.7007
S11 0 24.9811 16.7446 0
S12 0 34.9015 30.5499 35.7007 1.5305 55.72
S13 0 35.485 31.362 35.7007
S14 0 39.1767 33.0721 35.7007 1.5168 65.26
S15 0 41.6128 36.4622 35.7007
S16 0 42.1106 37.1549 35.7007
Angle of view
X direction; -20.7 ° to 20.7 °
Y direction; -28.5 ° to -4.5 °

(Example 2)
Surface number Curvature radius S1 Pupil surface INFINITY
S2 Prism exit surface INFINITY
S3 HOE surface INFINITY
Definition of two luminous fluxes
HV1; REA HV2; VIR
HX1; 0.000000E + 00 HY1; -9.612031E-01 HZ1; -2.276064E + 01
HX2; 0.000000E + 00 HY2; 2.485100E + 08 HZ2; -6.062901E + 09
HWL; 532
Phase coefficient
C2; 0.0000E + 00 C3; 4.2143E-03 C5; 8.8088E-03
C7; -9.1463E-05 C9; -6.6452E-06 C10; 1.6760E-05
C12; -2.3919E-05 C14; -1.1551E-05 C16; 5.5568E-06
C18; 2.8278E-06 C20; 7.9737E-06 C21; -1.2670E-06
C23; -1.5327E-08 C25; 1.9599E-06 C27; 5.2011E-08
C29; -1.6845E-07 C31; -7.6240E-08 C33; 1.6301E-08
C35; -7.8468E-07 C36; 2.7256E-08 C38; 1.2420E-08
C40; -4.8431E-08 C42; -1.4511E-07 C44; -5.1027E-10
C46; 1.8489E-09 C48; 2.4235E-10 C50; 1.0094E-09
C52; -3.9123E-09 C54; 2.2671E-08 C55; -2.1871E-10
C57; -2.5511E-10 C59; 7.0871E-10 C61; 3.3103E-10
C63; 4.8653E-09 C65; -2.7381E-10
S4 Reflective surface INFINITY
S5 Reflective surface INFINITY
S6 Reflective surface INFINITY
S7 Prism entrance surface INFINITY
S8 CG side INFINITY
S9 Display screen INFINITY
S10 Fresnel lens exit surface 24.3207
S11 Fresnel lens entrance surface INFINITY
S12 Reflective surface -40
S13 Lens exit surface -7
S14 Lens entrance surface INFINITY
S15 Light source surface INFINITY

Surface number xyz ADE Nd νd
S1 0 0 0 7.5 Pupil diameter 3mm
S2 0 -0.1555 14.1413 7.5 1.5168 65.26
S3 0 0.1512 16.4708 -23.5 1.5168 65.26
S4 0 3.3145 13.6844 7.5 1.5168 65.26
S5 0 11.3637 17.3645 7.5 1.5168 65.26
S6 0 18.6819 11.6613 7.5 1.5168 65.26
S7 0 24.8182 13.8793 85.8
S8 0 32.0346 19.6469 58.1886 1.5168 65.26
S9 0 32.7144 20.0686 58.1886
S10 0 33.3943 20.4903 58.1886 1.5305 55.72
S11 0 34.244 21.0174 58.1886
S12 0 41.6911 24.1885 25.3426
S13 0 41.999 14.369 -15.7671 1.5168 65.26
S14 0 42.8237 11.448 -15.7671
S15 0 43.1878 10.1584 -15.7671
Angle of view
X direction; -13.1 ° ~ 13.1 °
Y direction; -7.5 ° to 7.5 °

(Example 3)
Surface number Curvature radius S1 Pupil surface INFINITY
S2 Prism exit surface INFINITY
S3 HOE surface INFINITY
Definition of two luminous fluxes
HV1; REA HV2; VIR
HX1; 0.000000E + 00 HY1; -9.612031E-01 HZ1; -2.276064E + 01
HX2; 0.000000E + 00 HY2; 2.485100E + 08 HZ2; -6.062901E + 09
HWL; 532
Phase coefficient
C2; 0.0000E + 00 C3; 4.2143E-03 C5; 8.8088E-03
C7; -9.1463E-05 C9; -6.6452E-06 C10; 1.6760E-05
C12; -2.3919E-05 C14; -1.1551E-05 C16; 5.5568E-06
C18; 2.8278E-06 C20; 7.9737E-06 C21; -1.2670E-06
C23; -1.5327E-08 C25; 1.9599E-06 C27; 5.2011E-08
C29; -1.6845E-07 C31; -7.6240E-08 C33; 1.6301E-08
C35; -7.8468E-07 C36; 2.7256E-08 C38; 1.2420E-08
C40; -4.8431E-08 C42; -1.4511E-07 C44; -5.1027E-10
C46; 1.8489E-09 C48; 2.4235E-10 C50; 1.0094E-09
C52; -3.9123E-09 C54; 2.2671E-08 C55; -2.1871E-10
C57; -2.5511E-10 C59; 7.0871E-10 C61; 3.3103E-10
C63; 4.8653E-09 C65; -2.7381E-10
S4 Reflective surface INFINITY
S5 Reflective surface INFINITY
S6 Reflective surface INFINITY
S7 Prism entrance surface INFINITY
S8 CG side INFINITY
S9 Display screen INFINITY
S10 Fresnel lens exit surface 15
S11 Fresnel lens entrance surface INFINITY
S12 Reflective surface -50
S13 Fresnel lens exit surface -22.35
S14 Fresnel lens entrance surface INFINITY
S15 Lens exit surface -8.5
S16 Lens entrance surface INFINITY
S17 Light source surface INFINITY

Surface number xyz ADE Nd νd
S1 0 0 0 7.5 Pupil diameter 3mm
S2 0 -0.1555 14.1413 7.5 1.5168 65.26
S3 0 0.1512 16.4708 -23.5 1.5168 65.26
S4 0 3.3145 13.6844 7.5 1.5168 65.26
S5 0 11.3637 17.3645 7.5 1.5168 65.26
S6 0 18.6819 11.6613 7.5 1.5168 65.26
S7 0 24.8182 13.8793 85.8
S8 0 32.0346 19.6469 58.1886 1.5168 65.26
S9 0 32.7144 20.0686 58.1886
S10 0 33.3943 20.4903 58.1886 1.5305 55.72
S11 0 34.244 21.0174 58.1886
S12 0 41.2662 23.9249 22.1886
S13 0 41.4187 19.0028 -18.9211 1.5305 55.72
S14 0 41.7429 18.0569 -18.9211
S15 0 42.0672 17.1109 -18.9211 1.5168 65.26
S16 0 43.0514 14.2397 -18.9211
S17 0 43.4859 12.9721 -18.9211
Angle of view
X direction; -13.1 ° ~ 13.1 °
Y direction; -7.5 ° to 7.5 °

Example 4
Surface number Curvature radius S1 Pupil surface INFINITY
S2 Prism exit surface INFINITY
S3 HOE surface INFINITY
Definition of two luminous fluxes
HV1; REA HV2; VIR
HX1; 0.000000E + 00 HY1; -9.612031E-01 HZ1; -2.276064E + 01
HX2; 0.000000E + 00 HY2; 2.485100E + 08 HZ2; -6.062901E + 09
HWL; 532
Phase coefficient
C2; 0.0000E + 00 C3; 4.2143E-03 C5; 8.8088E-03
C7; -9.1463E-05 C9; -6.6452E-06 C10; 1.6760E-05
C12; -2.3919E-05 C14; -1.1551E-05 C16; 5.5568E-06
C18; 2.8278E-06 C20; 7.9737E-06 C21; -1.2670E-06
C23; -1.5327E-08 C25; 1.9599E-06 C27; 5.2011E-08
C29; -1.6845E-07 C31; -7.6240E-08 C33; 1.6301E-08
C35; -7.8468E-07 C36; 2.7256E-08 C38; 1.2420E-08
C40; -4.8431E-08 C42; -1.4511E-07 C44; -5.1027E-10
C46; 1.8489E-09 C48; 2.4235E-10 C50; 1.0094E-09
C52; -3.9123E-09 C54; 2.2671E-08 C55; -2.1871E-10
C57; -2.5511E-10 C59; 7.0871E-10 C61; 3.3103E-10
C63; 4.8653E-09 C65; -2.7381E-10
S4 Reflective surface INFINITY
S5 Reflective surface INFINITY
S6 Reflective surface INFINITY
S7 Prism entrance surface INFINITY
S8 CG side INFINITY
S9 Display screen INFINITY
S10 Lens exit surface 48
S11 Lens entrance surface INFINITY
S12 Reflective surface -40
S13 Lens exit surface -6
S14 Lens entrance surface INFINITY
S15 Light source surface INFINITY

Surface number xyz ADE Nd νd
S1 0 0 0 7.5 Pupil diameter 3mm
S2 0 -0.1555 14.1413 7.5 1.5168 65.26
S3 0 0.1512 16.4708 -23.5 1.5168 65.26
S4 0 3.3145 13.6844 7.5 1.5168 65.26
S5 0 11.3637 17.3645 7.5 1.5168 65.26
S6 0 18.6819 11.6613 7.5 1.5168 65.26
S7 0 24.8182 13.8793 85.8
S8 0 32.0346 19.6469 58.1886 1.5168 65.26
S9 0 32.7144 20.0686 58.1886
S10 0 33.3943 20.4903 58.1886 1.5168 65.26
S11 0 34.6689 21.281 58.1886
S12 0 42.116 24.452 25.3426
S13 0 42.4239 14.6325 -15.7671 1.5168 65.26
S14 0 43.2486 11.7115 -15.7671
S15 0 43.6127 10.422 -15.7671
Angle of view
X direction; -13.1 ° ~ 13.1 °
Y direction; -7.5 ° to 7.5 °

  In each of Examples 1 to 4, values of f2 / f1 that are targets of the conditional expression (1) described above are as shown in Table 1 below. From Table 1, it can be seen that the video display devices 1 of Examples 1 to 4 satisfy the conditional expression (1).

  In Example 1, the widest angle of view can be realized in both the X direction and the Y direction, and since two Fresnel lenses are used in the illumination optical system 12, the effect of miniaturization is great. In the second embodiment, the power of the Fresnel lens 16 on the light source 11 side of the first embodiment is given to the reflecting surface of the reflecting mirror 17. In the second embodiment, the angle of view is slightly narrower than that of the first embodiment, but it can still be said to be a wide angle of view. In addition, the illumination optical system 12 can be made compact in that the number of parts is reduced by using only one Fresnel lens. In Example 3, the angle of view is as wide as that of Example 2, and since two Fresnel lenses are used, the effect of downsizing is higher than that of Example 2. In Example 4, the angle of view is as wide as in Examples 2 and 3, and the illumination optical system 12 is made compact by using only one Fresnel lens.

  The present invention is applicable to a glasses-type HMD that can observe a virtual image of a display image.

It is a perspective view which shows the structure of the outline of HMD of this invention. It is sectional drawing which shows the structure of the outline of the video display apparatus concerning Embodiment 1 of this invention. It is sectional drawing which shows the schematic structure of the video display apparatus concerning Embodiment 2 of this invention. It is sectional drawing which shows the structure of the outline of the video display apparatus concerning Embodiment 3 of this invention. It is sectional drawing which shows the schematic structure of the video display apparatus which concerns on Embodiment 4 of this invention. It is explanatory drawing which shows the optical path of the light which injects into the display element of the video display apparatus of each embodiment in the long side direction and short side direction of a display screen. It is sectional drawing of the Fresnel lens applied to the illumination optical system of the video display apparatus of each embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image display apparatus 2 Support means 11 Light source 12 Illumination optical system 13 Diffusion plate (diffusion member)
14 Display element 17 Reflecting mirror 18 Fresnel lens (optical member)
20 Eyepiece optical system 23 HOE
E Optical pupil G1 1st group G2 2nd group

Claims (8)

A light source;
A transmissive display element that modulates incident light and displays an image;
An illumination optical system for guiding the light emitted from the light source to the display element;
An image display device comprising an eyepiece optical system for guiding image light from a display element to an optical pupil,
The illumination optical system is in order from the light source side.
A first group having at least one reflecting surface and having a positive power;
A second group having at least one optical member and having a positive power;
An image display device characterized by satisfying the following conditional expression;
1.5 <f2 / f1 <8.5
However,
f1: Focal length of the first group excluding the reflecting surface f2: Focal length of the second group.   The video display device according to claim 1, wherein the second group of the illumination optical system includes a Fresnel lens as the optical member. A diffusion member for diffusing incident light;
The video display device according to claim 1, wherein the diffusion member is disposed in an optical path between the second group of the illumination optical system and the display element. A diffusion member for diffusing incident light;
The diffusing member is disposed in the optical path between the second group of the illumination optical system and the display element, and the diffusivity in the screen long side direction of the display element is greater than the diffusivity in the screen short side direction of the display element. The video display device according to claim 2, wherein the video display device is also larger.   The optical path of the illumination optical system is bent in a cross section parallel to the screen short side direction and perpendicular to the screen long side direction of the display element by the first group of reflecting surfaces of the illumination optical system. Item 5. The video display device according to any one of Items 1 to 4.   6. The image display device according to claim 5, wherein the positional relationship between the light source and the optical pupil is conjugate within the cross section.   The eyepiece optical system has a volume phase type reflection type hologram optical element, and image light from the display element is diffracted and reflected by the hologram optical element and guided to the optical pupil. The video display device according to claim 1, wherein the transmitted light of an external image is guided to an optical pupil. A video display device according to any one of claims 1 to 7,
A head-mounted display comprising support means for supporting the video display device in front of an observer's eyes.

Images