JP2009134089A - Image display device and head mount display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To attain reduction in size and weight of a housing 30 and consequently of a device as a whole, while circumventing deterioration of the image quality by reducing adhesion of foreign matter in the air to a display surface of a display element 13, at assembling of a device, or the like. <P>SOLUTION: A permeable cover 14 is disposed on an ocular prism 21 side extending from the display surface of the display element 13 through an air layer. According to this, foreign matter in the air is adhered to the permeable cover 14, for example, when the housing 30 is installed or removed during assembling of the device or the like, without adhering directly to the display surface of the display element 13. Since the housing 30, covering a display means 10, is adapted to be supported by the ocular prism 21 which constitutes a part of an ocular optical system 20, the housing 30 can be reduced in size and weight, as compared with the structure adapted to cover the display means 10 and the body of the ocular optical system 20 as a whole. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image display device that provides an observer with an image displayed on a display element as a virtual image, and a head mounted display (hereinafter also referred to as an HMD) including the image display device.

  Conventionally, various video display apparatuses that guide video light from a display element to an observer's pupil via an eyepiece optical system have been proposed. In particular, the video display devices of Patent Documents 1 and 2 are configured so that the display element and the eyepiece optical system are collectively covered with a single case, and the HMD is configured by supporting the case in front of the observer's eyes. Has been. Thus, by covering the entire display element and the eyepiece optical system with one casing, during normal use (when observing an image), foreign substances such as dust existing in the air outside the casing are displayed on the display element (particularly, Adhering to the display surface can be avoided.

JP 2001-281593 A JP 2005-202060 A

  However, in the configuration in which the entire display element and the eyepiece optical system are covered with a single casing, for example, foreign substances in the air are likely to adhere to the display element when the casing is attached or removed during assembly or disassembly of the apparatus. Become. When foreign matter adheres to the display surface, the quality of the observation image is degraded. Further, in the configuration in which the entire display element and the eyepiece optical system are covered with the casing, the casing becomes large, so that the entire apparatus becomes large and heavy.

  The present invention has been made to solve the above-described problems, and its purpose is to adhere foreign matter to the display surface of the display element even when the housing is attached or detached during assembly of the device. And a video display device capable of reducing the size and weight of the entire device by reducing the size and weight of the device, and the video display device. To provide HMD.

  An image display apparatus of the present invention includes a virtual image eyepiece optical system having a transparent substrate, a display unit disposed on one end side of the transparent substrate, having a display element, and a casing covering the display unit, and an image from the display unit An image display device that reflects light inside a transparent substrate and guides it to an optical pupil, wherein the casing is supported by the transparent substrate, and the display means forms an air layer from the display surface of the display element to the transparent substrate side. It is characterized by having a permeable cover arranged through.

  According to said structure, the image light from the display element of a display means injects into the transparent substrate of a virtual image eyepiece optical system through a transparent cover, is reflected in the inside, and is guide | induced to the optical pupil. Therefore, at the position of the optical pupil, the observer can observe the virtual image of the video displayed on the display surface of the display element. At this time, since the housing that covers the display unit is supported by a transparent substrate that forms part of the virtual image eyepiece optical system, the display unit and the entire virtual image eyepiece optical system are covered with the housing. Compared to the configuration, the housing is small and lightweight. This makes it possible to realize a small and lightweight video display device.

  In addition, since a transparent cover is arranged through the air layer from the display surface of the display element to the transparent substrate side, for example, when the device is assembled or disassembled, the housing is in the air Even if foreign matter such as dust or dirt is present on the surface, the foreign matter adheres to the transmissive cover and is less likely to adhere directly to the display surface of the display element.

  Therefore, according to the above configuration, it is possible to reduce the adhesion of foreign matters to the display surface during assembly of the device while reducing the size and weight of the image display device without covering the entire virtual image eyepiece optical system with a housing. It is possible to make the observer observe a quality image.

  In the video display device of the present invention, it is desirable that the distance between the transmissive cover and the display surface is a distance at which the difference in diopter between virtual images by the virtual image eyepiece optical system is 5 diopters or more. If the diopter difference is, for example, 1 diopter, the foreign object can be observed instantaneously when the foreign object adheres to the transparent cover, but if the diopter difference is 5 diopter, the transparency Even if foreign matter adheres to the cover, the foreign matter becomes difficult to be observed, and a high-quality image can be surely observed by the observer.

  In the video display device of the present invention, the display means further includes a light source and an illumination optical system that guides light from the light source to the display element, and the light source, the illumination optical system, the display element, and the transmissive cover are unitized. Display unit.

  When the display means is constituted by the display unit, the assembling property when assembling the video display device using the display means can be improved (the assembly becomes easy and the cost is reduced).

  In the video display device of the present invention, it is desirable that the display unit is formed without an opening between the display surface and the transmissive cover. In this case, it is possible to reliably prevent external foreign matter from adhering to the display surface when the apparatus is assembled.

  In the video display device of the present invention, the virtual image eyepiece optical system may include an axially asymmetric optical system. In this case, the degree of freedom of arrangement of each optical member including the display element is increased, and the apparatus can be reduced in size while ensuring good optical performance.

  In the image display apparatus of the present invention, the virtual image eyepiece optical system includes a volume phase type reflection hologram optical element, and the hologram optical element diffracts and reflects image light from the display element and guides it to the optical pupil. At the same time, it may be configured to transmit outside light and guide it to the optical pupil.

  Since the volume phase type reflection type hologram optical element has a narrow reflection wavelength range and a high transmittance of external light, it is possible to observe an external image while seeing through a display image (virtual image). Further, in the present invention, since the entire virtual image eyepiece optical system is not covered with the casing, it is possible to secure a wide external field of view (area that can be viewed through see-through).

  In the video display device of the present invention, it is desirable that the distance between the transmissive cover and the display surface is a distance at which the difference in diopter between virtual images by the virtual image eyepiece optical system is 10 diopters or more. In this case, even if foreign matter from the outside adheres to the transmissive cover, it is possible for the observer to reliably prevent the foreign matter from being out of focus and reducing the quality of the observed image (virtual image). .

  In the video display device of the present invention, it is desirable that the display means and the transparent substrate are positioned in the housing. As described above, the display unit and the transparent substrate are positioned by the common member (housing), so that the positioning can be performed with high accuracy.

  In the video display device of the present invention, the transmissive cover is preferably inclined with respect to a plane perpendicular to the optical axis. Note that the optical axis refers to an axis that optically connects the center of the display area of the display element and the center of the optical pupil. In this case, it is possible to suppress the occurrence of flare and ghost by superimposing the surface reflected light (returned light) on the transparent cover of the image light emitted from the display surface of the display element with other image light.

  In the video display device of the present invention, the transmissive cover may be an optical film having an optical function. In addition, as said optical film, a polarizing plate and a half-wave plate can be considered, for example. Since the transmissive cover also serves as an optical function of such an optical film, the cost is lower than a configuration in which such an optical film is separately provided.

  In the video display device of the present invention, the transmissive cover may be a polarizing plate that transmits S-polarized light when reflected by the hologram optical element. In this case, since the transmissive cover also functions as a polarizing plate, the cost is lower than a configuration in which such a polarizing plate is separately provided. In addition, since the light incident on the hologram optical element is S-polarized light, the diffraction efficiency of the hologram optical element is high, and it is possible for the observer to observe a bright image.

  In the video display device of the present invention, the transmissive cover may be a half-wave plate that converts incident linearly polarized light into S-polarized light and emits it. In this case, even if the light emitted from the display surface of the display element is linearly polarized light other than S-polarized light, it is converted to S-polarized light by passing through a transmissive cover made of a half-wave plate, and is transmitted to the hologram optical element. Incident. Thereby, the diffraction efficiency in a hologram optical element is high, and it becomes possible to make an observer observe a bright image. Note that the optical axis of the half-wave plate may be set according to the polarization direction of the incident linearly polarized light.

  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.

  According to the present invention, while being a small and lightweight video display device that does not cover the entire virtual image eyepiece optical system with a housing, it reduces the adhesion of foreign matter to the display surface of the display element during assembly of the device, It is possible to make the observer observe a high-quality image.

[Embodiment 1]
An embodiment of the present invention will be described below with reference to the drawings.

(1. Configuration of HMD)
2A is a plan view showing a schematic configuration of the HMD according to the present embodiment, FIG. 2B is a side view of the HMD, and FIG. 2C is a front view of the HMD. is there. The HMD has an image display device 1 and a support means 2 that supports the image display device 1, and as a whole has an appearance in which one lens (for example, for the left eye) is removed from general glasses.

  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. In the video display device 1 shown in FIG. 2C, a portion corresponding to the right eye lens of the glasses is configured by bonding an eyepiece prism 21 and a deflection prism 22. Details of the video display device 1 will be described later.

  The support means 2 is a support member that supports the image display device 1 in front of the observer's eyes (for example, in front of the right eye). The bridge 3, the frame 4, the temple 5, the nose pad 6, the cable 7, and the outside And light transmittance control means 8. The frame 4, the temple 5 and the nose pad 6 are provided as a pair on the left and right sides. However, when these are distinguished from each other, the right frame 4R, the left frame 4L, the right temple 5R, the left temple 5L, and the right nose pad 6R. The left nose pad 6L is expressed.

  One end of the video display device 1 is supported by the bridge 3. In addition to the image display device 1, the bridge 3 supports the left frame 4 </ b> L, the nose pad 6, and the external light transmittance control means 8. The left frame 4L supports the left temple 5L so as to be rotatable. On the other hand, the other end of the video display device 1 is supported by the right frame 4R. An end of the right frame 4R opposite to the support side of the video display device 1 supports the right temple 5R so as to be rotatable. The cable 7 is a wiring for supplying an external signal (for example, a video signal, a control signal) and power to the video display device 1, and is provided along the right frame 4R and the right temple 5R. The external light transmittance control means 8 is provided in the bridge 3 in order to control the transmittance of external light (light of an external image), and is positioned in front of the video display device 1 (on the side opposite to the observer). is doing.

  When the observer uses the HMD, the right temple 5R and the left temple 5L are brought into contact with the right and left heads of the observer, and the nose pad 6 is put on the nose of the observer so as to wear general glasses. The HMD is attached to the observer's head. When an image is displayed on the image display device 1 in this state, the observer can observe the image of the image display device 1 as a virtual image, and observe the outside world image through the image display device 1 in a see-through manner. Can do.

  At this time, if the external light transmittance control unit 8 sets the external light transmittance to be low, for example, 50% or less, the observer can easily observe the image on the video display device 1. If the rate is set as high as, for example, 50% or more, the observer can easily observe the external image. Therefore, the external light transmittance in the external light transmittance control means 8 may be set as appropriate in consideration of the ease of observation of the video and external image of the video display device 1. The external light transmittance control means 8 may be provided as necessary.

  Note that the HMD is not limited to a configuration including only one video display device 1, but may be configured to include two video display devices 1 corresponding to the eyes of the observer. That is, the support means 2 may be configured to support the two video display devices 1 in front of the observer's eyes.

(2. Details of video display device)
Next, a detailed configuration of the video display device 1 will be described with reference to FIG. FIG. 1 is a cross-sectional view schematically showing the configuration of the video display device 1 described above. The video display device 1 includes a display unit 10 and an eyepiece optical system 20.

(2-1. Display means)
The display means 10 includes a light source 11, an illumination optical system 12, a display element 13, and a transmissive cover 14, and is configured by a display unit in which these are unitized. The display means 10 is disposed on one end side of the eyepiece prism 21 of the eyepiece optical system 20 and is covered with a housing 30 supported by one end portion of the eyepiece prism 21.

  The display means 10 is positioned on the housing 30 via a positioning member (not shown). At this time, since the housing 30 is supported by the eyepiece prism 21, the display means 10 and the eyepiece prism 21 are eventually positioned in the same housing 30. Hereinafter, each structure of the display means 10 is demonstrated.

  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 13 and the center of the optical pupil E formed by the eyepiece optical system 20 is defined as 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 an optical axis incident surface of a hologram optical element 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 hologram optical element 23 refers to a plane including the optical axis of incident light and the optical axis of reflected light in the hologram optical element 23, that is, the YZ plane.

  The light source 11 is composed of an RGB-integrated LED having three light emitting units that emit light having wavelengths corresponding to the three primary colors of RGB. The light source 11 is arranged so as to have a positional relationship conjugate with the optical pupil E.

  The illumination optical system 12 includes a condenser lens 15 and a diffusing unit 16. The condensing lens 15 is a condensing unit that condenses the light from the light source 11 in the Y direction and guides it to the display element 13, and is configured by a cylinder lens, for example. The diffusing means 16 diffuses the light emitted from the light source 11. In this embodiment, the diffusion means 16 diffuses incident light by 40 degrees in the X direction and diffuses 0.5 degrees in the Y direction. It consists of direction diffusion plates 16a and 16b.

  The diffusing unit 16 may be composed of a single unidirectional diffuser. In the present embodiment, the diffusing unit 16 is disposed on the side opposite to the light source 11 with respect to the condenser lens 15, but may be disposed on the light source 11 side. Incidentally, FIG. 3 is a cross-sectional view of the video display device 1 in which the diffusing means 16 is disposed on the light source 11 side with respect to the condenser lens 15, and FIG. FIG.

  The display element 13 shown in FIG. 1 modulates the light emitted from the light source 11 in accordance with image data and displays an image. For example, the display element 13 has a matrix of pixels that are areas through which light is transmitted. Type LCD. The display element 13 is arranged such that the long side direction of the rectangular display region is the X direction and the short side direction is the Y direction. In addition, when the display element 13 is comprised by LCD, the surface by the side of the liquid crystal layer of the cover glass arrange | positioned on the outermost side shall be called the display surface where an image | video is displayed.

  The transmissive cover 14 transmits image light from the display element 13 and guides it to the eyepiece optical system 20. In the present embodiment, the transmissive cover 14 is constituted by a lens, for example. Details of the arrangement position of the transmissive cover 14 will be described later. By configuring the transmissive cover 14 with a lens, the transmissive cover 14 can have a part of optical power of an eyepiece optical system 20 to be described later. That is, the optical power can be dispersed in the transmissive cover 14 and the eyepiece optical system 20. As a result, the observer can observe a high-quality image in which aberrations are favorably reduced. The transmissive cover 14 may be formed of a transparent substrate or film that does not have optical power.

  As described above, in the present embodiment, the housing 30 that covers the display unit 10 is supported by one end of the eyepiece prism 21 that constitutes a part of the eyepiece optical system 20. Since only one end is covered with the housing 30, the housing 30 is smaller and lighter than the configuration in which the entire display unit 10 and the eyepiece optical system 20 are covered with the housing 30. It can be realized. Further, since the housing 30 is downsized, foreign matter such as dust in the air is less likely to remain in the housing 30 when the apparatus is assembled, and image quality is prevented from being deteriorated due to the foreign matter. Can do.

  Moreover, since the display means 10 and the eyepiece prism 21 are positioned by the same housing | casing 30, the accuracy of mutual positioning can be improved. In the video display device 1, the positional relationship between the display surface of the display element 13 of the display unit 10 and the eyepiece prism 21 is severe. If the positional relationship is deviated, a large amount of aberration occurs, and good video observation cannot be performed. . However, if the display means 10 and the eyepiece prism 21 can be accurately positioned, the image light can be guided to the optical pupil E by using a portion that can satisfactorily suppress the occurrence of aberration in the eyepiece optical system 20. Good video observation is possible. Further, the housing 30 can be made smaller than the case where the display unit 10 and the eyepiece prism 21 are directly positioned and fixed in advance.

  Further, since the display means 10 is unitized, the video display device 1 can be easily assembled and the manufacturing cost of the device can be reduced. Here, in this embodiment, the display means 10 is unitized so that an opening is not formed at least between the display surface and the transmissive cover 14. If an opening is formed between the two, foreign matter in the air enters between the display surface and the transmissive cover 14 through the opening when the apparatus is assembled, and the foreign matter enters the display surface. Although there is a possibility of adhering, since there is no opening between at least the two, occurrence of such a situation can be avoided.

  The display unit 10 may have a slight opening (gap) on the light source 11 side from the display surface. In the case where an opening is formed at a position on the light source 11 side from the display surface, even if a foreign object enters the inside of the display means 10 through the opening, the foreign material reaches other members before reaching the display surface. This is because it is considered that it hardly adheres and finally adheres to the display surface. Further, since the virtual image is generally set at a position of −3 to 0 diopter (distance from the observer's pupil position is 30 cm to ∞) so that it can be easily observed with a normal eye, it is closer to the light source 11 than the display surface. This foreign object becomes + diopter and is difficult to focus with a normal eye and is difficult to observe. The diopter is a unit representing the diopter, that is, the power (refractive power) of the optical system, represented by the reciprocal (−1 / m) of the value of the focal length of the optical system (for example, a lens) expressed in meters. Is commonly used.

(2-2. Eyepiece optical system)
Next, details of the eyepiece optical system 20 will be described. The eyepiece optical system 20 is a virtual image eyepiece optical system that provides an observer with an enlarged virtual image of an image displayed on the display element 13, and includes an eyepiece prism 21, a deflection prism 22, and a hologram optical element 23. Has been.

  The eyepiece prism 21 totally reflects image light incident from the display element 13 via the transmissive cover 14 and guides it to the optical pupil E via the hologram optical element 23, while transmitting external light to the optical pupil E. A transparent substrate that leads to the light source, and is made of, for example, an acrylic resin together with the deflecting prism 22. The eyepiece prism 21 is formed in a shape in which the lower end portion of the parallel plate is thinned toward the lower end so as to be wedge-shaped, and the upper end portion thereof is thickened toward the upper end. Further, the eyepiece prism 21 is joined to the deflection prism 22 with an adhesive so as to sandwich the hologram optical element 23 disposed at the lower end thereof.

  The deflection prism 22 is formed of a substantially U-shaped parallel plate in plan view (see FIG. 2C), and is bonded 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 integrated into a substantially parallel flat plate. By joining the deflecting prism 22 to the eyepiece prism 21, it is possible to prevent distortion of the external image observed by the observer through the eyepiece prism 21.

  The hologram optical element 23 diffracts and reflects the image light from the display element 13 and guides it to the optical pupil E. At the same time, the hologram optical element 23 transmits most of the external light and guides it to the optical pupil E. It is composed of a volume phase type reflection hologram having a diffraction efficiency peak at a wavelength corresponding to the wavelength. Volume phase reflection holograms have a narrow reflection wavelength range (half-value wavelength width of diffraction efficiency peak) and high external light transmittance, so the observer sees through the external image while observing the display image (virtual image). It becomes possible to observe. In particular, in the present embodiment, as described above, since the entire eyepiece optical system 20 is not covered with the housing 30, a wide see-through region is secured.

  Further, the hologram optical element 23 has an axially asymmetric positive optical power, and has the same function as an aspherical concave mirror having a positive power. As described above, since the eyepiece optical system 20 includes the axially asymmetric optical system, 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 can be improved. An aberration-corrected image can be provided to the observer.

(2-3. Operation)
Next, the operation of the video display device 1 having the above configuration will be described. The light emitted from the light source 11 is condensed by the condenser lens 15 and then diffused only in the X direction by the diffusing unit 16 and enters the display element 13 as uniform illumination light in which RGB color mixing is sufficiently performed. To do. The light incident on the display element 13 is modulated for each pixel based on the image data and is emitted as video light. That is, a color image is displayed on the display element 13.

  The image light from the display element 13 is transmitted through the transmissive cover 14, enters the eyepiece prism 21 of the eyepiece optical system 20 from its upper end surface (surface 21 a), and multiple times on the two opposing surfaces 21 b and 21 c. The light is totally reflected and enters the hologram optical element 23. The light incident on the hologram optical element 23 is 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 video displayed on the display element 13.

  On the other hand, the eyepiece prism 21, the deflecting prism 22, and the hologram optical element 23 transmit almost all of the external light, so that the observer can observe the external image. Therefore, the virtual image of the image displayed on the display element 13 is observed while overlapping a part of the external image.

(3. About the position of the permeable cover)
Next, details of the arrangement position of the transparent cover 14 of the display means 10 will be described with reference to FIG.

  The transparent cover 14 is disposed on the eyepiece prism 21 side from the display surface of the display element 13 via an air layer. The distance between the transmissive cover 14 and the display surface is set such that the difference in the diopter of the virtual images by the eyepiece optical system 20 is 5 diopters or more. Further, the transmissive cover 14 is provided to be inclined with respect to a plane perpendicular to the optical axis.

  As described above, since the permeable cover 14 is disposed through the display surface and the air layer, for example, foreign matter exists in the air when the housing 30 is attached or removed during assembly of the device or the like. However, these foreign substances adhere to the transmissive cover 14 and are difficult to adhere directly to the display surface. Therefore, as described above, the small and lightweight video display device 1 that does not cover the entire eyepiece optical system 20 with the housing 30 can reduce the adhesion of foreign matter to the display surface when the device is assembled. It is possible to make the observer observe a quality image. In addition, since the adhesion of foreign matter to the display surface can be reduced, it is not necessary to seal the entire housing 30.

  Further, when an LCD is used as the display element 13, the cover glass serves to prevent foreign matter from adhering to the display surface, but the cover glass is generally as thin as about 0.5 mm, for example. Therefore, in the image display device 1, when the focal length of the eyepiece optical system 20 is set to, for example, about 20 mm to 40 mm, when a foreign object adheres to the surface of the cover glass, the foreign object and the display surface are separated from the eyepiece optical system. The difference in diopter between virtual images by the system 20 is a distance difference of about 1 diopter. In this case, foreign matter is observed simultaneously with the video, and the video quality is impaired. Although it is possible to avoid a reduction in image quality by increasing the thickness of the cover glass, in that case, a special cover glass having a large thickness is required, and the cost of the display element 13 is increased. And the display element 13 and thus the entire apparatus become heavy.

  However, in this embodiment, the simple configuration of disposing the transmissive cover 14 can reduce the adhesion of foreign matter to the display surface and allow the observer to observe a high-quality image. It is not necessary to use a thick special display element 13, and an inexpensive and lightweight video display device 1 can be realized.

  If the distance between the transmissive cover 14 and the display surface is such that the difference in the diopter of the virtual images of the eyepiece optical system 20 is 1 diopter, as described above, the transmissive cover 14 is transmissive when the apparatus is assembled. When foreign matter adheres to the cover 14, the foreign matter can be observed instantaneously. However, in this embodiment, the difference in diopter between the two virtual images is 5 diopters or more, and is larger than the 1 diopter. In other words, the transmissive cover 14 is arranged at a distance from the display surface from the position where the foreign object is observed instantaneously. Therefore, for example, even when a foreign object adheres to the transmissive cover 14 when the apparatus is assembled, the foreign object is hardly observed, and a high-quality image can be surely observed by the observer.

  In addition, since 5 diopters correspond to a distance difference between 20 cm and infinity, for example, even when the display image is focused at the time of observation, the foreign matter adhering to the transmissive cover 14 is sufficiently out of focus and difficult to observe. . Therefore, in this respect as well, it can be said that the observer can surely observe a high-quality image.

  By the way, it is desirable that the distance between the transmissive cover 14 and the display surface is a distance at which the difference in the diopter of the virtual images by the eyepiece optical system 20 is 10 diopters or more. 10 diopters indicate the maximum adjustment range of the focus of a human (adult) eye. In other words, an image in which the difference in diopter from the virtual image of the display image is 10 diopters or more is not observed by an adult. Therefore, by setting the distance between the transmissive cover 14 and the display surface as described above, even if the foreign matter adheres to the transmissive cover 14, the foreign matter is surely out of focus for the observer, and the observed image It is possible to reliably prevent the quality of the (virtual image) from deteriorating.

  In the present embodiment, since the transmissive cover 14 is disposed to be inclined with respect to a plane perpendicular to the optical axis, video light emitted from a pixel having a display surface of the display element 13 is transmissive cover. Even if it is surface-reflected at 14, the reflected light (return light) can be prevented from being superimposed on the video light emitted from another pixel on the display surface. As a result, the occurrence of flare and ghost can be suppressed.

(4. Other)
In the present embodiment, the housing 30 is supported by one end of the eyepiece prism 21, so that a part of the eyepiece prism 21 is covered (hidden) by the housing 30. Therefore, identification information (for example, a serial number) of the eyepiece prism 21 may be written on a portion of the eyepiece prism 21 that is covered with the housing 30 so that it cannot be visually recognized from the outside. Further, a groove (so-called adhesive residue) for collecting the adhesive on the joint surface between the eyepiece prism 21 and the deflecting prism 22 may be provided in the joint portion hidden by the housing 30. In this case, since the joint ends in the other joints can be made small, the observer can observe the outside world satisfactorily through the eyepiece prism 21 and the deflection prism 22.

  Further, a field frame may be provided in the vicinity of the display element 13 of the display unit 10 so that unnecessary light in the area other than the display portion of the display element 13 is shielded by the field frame. Further, the display element 13 may be positioned by supporting a part of the display element 13 with a field frame. In this case, since the field frame also serves as a positioning member, the field frame is close to the display element 13 at a low cost, so that the display element 13 can be positioned accurately and accurately.

[Embodiment 2]
The following will describe another embodiment of the present invention with reference to the drawings. For convenience of explanation, the same components as those in the first embodiment are denoted by the same member numbers, and the description thereof is omitted.

  FIG. 5 is a cross-sectional view showing a schematic configuration of the video display device 1 of the present embodiment, and FIG. 6 is a cross-sectional view of a portion of the video display device 1 shown in FIG. These are explanatory drawings schematically showing a schematic configuration of the display means 10 of the video display device 1 of the present embodiment. In the present embodiment, a reflective display element 13 ′ is used instead of the display element 13, and the configurations of the illumination optical system 12 and the transmissive cover 14 are slightly different. . That is, other configurations such as the point that the transmissive cover 14 is disposed through the display surface of the display element 13 ′ and the air layer, and the point that the display unit 10 is unitized are the same as those in the first embodiment. It is exactly the same.

  The display element 13 'is a reflective display element. As such a display element 13 ′, for example, a reflective LCD or a DMD (Digital Micromirror Device; manufactured by Texas Instruments Inc., USA) can be considered.

  The illumination optical system 12 includes a reflection mirror 17 and a polarizing plate 18. The illumination optical system 12 may have a diffusing unit similar to the diffusing unit 16 (see FIG. 1) of the first embodiment between the reflecting mirror 17 and the polarizing plate 18.

  The reflection mirror 17 reflects the light emitted from the light source 11 and guides it to the display element 13 ′, and reflects and condenses the incident light on the display area of the display element 13 ′. In the present embodiment, the reflection mirror 17 is constituted by a concave mirror, for example, but may be a spherical mirror or a cylindrical concave mirror.

  The polarizing plate 18 transmits light of a predetermined polarization direction (here, P-polarized light) out of the light emitted from the light source 11 and guides it to the reflection mirror 17, and the light whose optical path is bent by the reflection mirror 17. Then, light having the same polarization direction as the predetermined polarization direction (here, P-polarized light) is transmitted and guided to the display element 13 ′.

  By making light incident on the display element 13 ′ into P-polarized light by disposing the polarizing plate 18, surface reflection (Fresnel loss) on the display element 13 ′ can be suppressed as compared with the case where incident light is made S-polarized light. . That is, in the case of P-polarized light, unlike S-polarized light, there is an incident angle (Brewster angle) at which the reflectance at the surface becomes zero, and thus it is possible to suppress the light amount loss. As a result, it is possible to avoid a reduction in video quality due to light loss.

  In this embodiment, the transmissive cover 14 is made of an optical film having an optical function. More specifically, the transmissive cover 14 is composed of a polarizing plate that transmits predetermined linearly polarized light. This polarizing plate is disposed so as to transmit S-polarized light when reflected by the hologram optical element 23. That is, the polarizing direction of the polarizing plate 18 and the transmissive cover 14 are orthogonal to each other.

  According to the above configuration, of the light emitted from the light source 11, for example, P-polarized light passes through the polarizing plate 18, is reflected by the reflection mirror 17, and then passes through the polarizing plate 18 again to display the display element 13. 'Is incident. In the display element 13 ′, incident light is modulated and emitted as image light (S-polarized light). This image light passes through the transmissive cover 14 formed of a polarizing plate and is guided to the optical pupil E through the eyepiece optical system 20.

  As described above, in this embodiment, the transmissive cover 14 is composed of an optical film called a polarizing plate, which not only has a function of preventing foreign matter from adhering to the display surface during assembly of the apparatus, but also a predetermined linearly polarized light. Therefore, the apparatus can be configured at a lower cost than the case where such a polarizing plate is provided separately from the transmissive cover 14, and the configuration of the apparatus can be reduced. It can also be simplified.

  In particular, since the transmissive cover 14 is composed of a polarizing plate that transmits S-polarized light when reflected by the hologram optical element 23, the light incident on the hologram optical element 23 is converted to S-polarized light and is highly diffracted by the hologram optical element 23. Efficiency can be obtained and a bright image can be observed by the observer.

[Embodiment 3]
The following will describe still another embodiment of the present invention with reference to the drawings. For convenience of explanation, the same components as those in the first and second embodiments are denoted by the same member numbers, and the description thereof is omitted.

  FIG. 8 is a cross-sectional view showing a schematic configuration of the video display device 1 of the present embodiment. The video display apparatus 1 of the present embodiment is the same as that of the first embodiment in that the transmissive display element 13 is used, but the configurations of the illumination optical system 12, the transmissive cover 14, and the eyepiece optical system 20 are slightly different. This is different from the first embodiment in the changed point.

  The illumination optical system 12 has two reflection mirrors 17 and 19, and sequentially reflects the light from the light source 11 by the reflection mirrors 17 and 19 and guides it to the display element 13. The reflection mirror 17 is composed of, for example, a cylindrical concave mirror, and the reflection mirror 19 is composed of, for example, a plane mirror. In this embodiment, the transmissive cover 14 is formed of a half-wave plate that converts incident linearly polarized light into S-polarized light and emits it. That is, the transmissive cover 14 is the same as that of the second embodiment in that it is made of an optical film having an optical function.

  The eyepiece optical system 20 is configured by bonding a first prism 24 having positive optical power that is axisymmetric and a second prism 25. The first prism 24 has a light incident surface 24a from the display element 13, a reflection surface 24b, and a transmission / reflection surface 24c. The first prism 24 is a free-form surface prism having a free-form surface. The transmission / reflection surface 24c may be a hologram surface on which a hologram optical element is formed. The second prism 25 is bonded to the transmission / reflection surface 24 c of the first prism 24. The first prism 24 and the second prism 25 correspond to the eyepiece prism 21 and the deflection prism 22 of the first embodiment, respectively.

  The light emitted from the light source 11 is sequentially reflected by the reflection mirrors 17 and 19 of the illumination optical system 12, and then enters the display element 13, where it is modulated and emitted as image light. The image light enters the first prism 24 of the eyepiece optical system 20 from the incident surface 24a through the transmissive cover 14, is totally reflected by the reflective surface 24b, and then is reflected by the transmissive reflective surface 24c. , Guided to the optical pupil E. The observer can observe the display image of the display element 13 as a virtual image by the combined power of each surface of the first prism 24 by causing the light reaching the optical pupil E to enter the pupil.

  As in the present embodiment, the transmissive cover 14 is formed of a half-wave plate that converts incident linearly polarized light into S-polarized light and emits the light, so that light emitted from the display surface of the display element 13 is emitted. Is linearly polarized light other than S-polarized light, the light can be converted to S-polarized light by the transmissive cover 14 and guided to the transmissive reflecting surface 24c. As a result, when the transmission / reflection surface 24c is a hologram surface, the S-polarized light is incident on the hologram optical element, so that the diffraction efficiency is increased and the observer can observe a bright image.

  Note that the optical axis of the half-wave plate may be set according to the polarization direction (vibration direction) of linearly polarized light incident thereon. That is, as shown in FIG. 9, when the linearly polarized light emitted from the polarizing plate on the light emitting side of the display element 13 is incident on the half-wave plate, the vibration direction of the linearly polarized light is that of the half-wave plate. When incident at an angle of θ with respect to the optical axis, the linearly polarized light is emitted from the half-wave plate as linearly polarized light whose vibration direction is rotated by 2θ. Therefore, S-polarized light can be emitted from the half-wave plate by appropriately setting the angle formed by the vibration direction of the incident linearly polarized light and the optical axis of the half-wave plate.

  Needless to say, the video display device 1 and thus the HMD can be realized by appropriately combining the configurations described in the embodiments.

  The present invention is applicable to HMD.

It is sectional drawing which shows typically the structure of the video display apparatus applied to HMD which concerns on one Embodiment of this invention. (A) is a top view which shows the outline structure of HMD, (b) is a side view of HMD, (c) is a front view of HMD. It is sectional drawing which shows the other structure of the said video display apparatus. It is a perspective view which shows the external appearance of the principal part of the video display apparatus of the said other structure. It is sectional drawing which shows the structure of the outline of the video display apparatus concerning other embodiment of this invention. It is sectional drawing of the part which removed the housing | casing of the said video display apparatus. It is explanatory drawing which shows typically the structure of the outline of the display means of the said video display apparatus. It is sectional drawing which shows the structure of the outline of the video display apparatus based on further another embodiment of this invention. It is explanatory drawing which shows typically the vibration direction of the linearly polarized light which permeate | transmitted the polarizing plate of the display element, the optical axis of a 1/2 wavelength plate, and the vibration direction of the image light after permeate | transmitting a 1/2 wavelength plate.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image display apparatus 2 Support means 10 Display means 11 Light source 12 Illumination optical system 13 Display element 13 'Display element 14 Transmissive cover 20 Eyepiece optical system (virtual image eyepiece optical system)
21 Eyepiece prism (transparent substrate)
23 Hologram optical element 30 Case E Optical pupil

Claims (13)

A virtual image eyepiece optical system having a transparent substrate;
A display means disposed on one end of the transparent substrate and having a display element;
A video display device comprising: a housing that covers the display means, and reflecting video light from the display means inside the transparent substrate to guide the optical pupil;
The housing is supported by a transparent substrate,
The video display apparatus, wherein the display means includes a transmissive cover disposed on the transparent substrate side from the display surface of the display element via an air layer.   The video display device according to claim 1, wherein the distance between the transmissive cover and the display surface is a distance at which a difference in diopter between virtual images by the virtual image eyepiece optical system is 5 diopters or more.   The display means further includes a light source and an illumination optical system that guides light from the light source to the display element, and the display unit is a display unit in which the light source, the illumination optical system, the display element, and the transmissive cover are unitized. The video display apparatus according to claim 1 or 2, characterized in that   The video display device according to claim 3, wherein the display unit is formed without an opening between the display surface and the transmissive cover.   The video display apparatus according to claim 1, wherein the virtual image eyepiece optical system includes an axially asymmetric optical system. The virtual image eyepiece optical system includes a volume phase type reflection hologram optical element,
6. The hologram optical element according to claim 1, wherein the hologram optical element diffracts and reflects the image light from the display element and guides it to the optical pupil, and simultaneously transmits external light and guides it to the optical pupil. Video display device.   The image according to any one of claims 1 to 6, wherein the distance between the transparent cover and the display surface is a distance at which a difference in diopter between virtual images by the virtual image eyepiece optical system is 10 diopters or more. Display device.   The video display device according to claim 1, wherein the display unit and the transparent substrate are positioned in the housing.   The video display device according to claim 1, wherein the transmissive cover is inclined with respect to a plane perpendicular to the optical axis.   The image display device according to claim 1, wherein the transmissive cover is an optical film having an optical function.   The image display device according to claim 6, wherein the transmissive cover is a polarizing plate that transmits S-polarized light when reflected by the hologram optical element.   The image display device according to claim 10, wherein the transmissive cover is a half-wave plate that converts incident linearly polarized light into S-polarized light and emits the converted light. A video display device according to any one of claims 1 to 12,
A head-mounted display comprising support means for supporting the video display device in front of an observer's eyes.

Images