JP2010243972A - Video display device and head-mounted display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To secure a large see-through area without enlarging an eyepiece optical system 15 when a mark (virtual image V) is displayed to be aligned with a pupil, to reduce the size and weight of a device, and to allow a third person to easily align the pupil with the mark by visual recognition from the outside. <P>SOLUTION: An optical path of light emitted from a light source 22 for mark and reflected on an HOE 18 is on the outside of the optical path of video light from a display element 14 to an optical pupil P. The degree of freedom in design of a mark display optical system 21 is increased, and there is no need to enlarge the eyepiece optical system 15 so as to secure the large see-through area even when the mark display optical system 21 is used. Also, the HOE 18 displays the virtual image V as the mark on the side of the optical pupil P to the HOE 18 by its own optical power by reflecting the light from the light source 22 for the mark on the side opposite to the optical pupil P. Thus, the third person can visually recognize the virtual image V from the outside. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention provides an image display device that simultaneously guides image light and external light from a display element to an optical pupil by an eyepiece optical system, and allows an observer to simultaneously observe a virtual image of the display image and the external environment at the position of the optical pupil. The present invention relates to a head mounted display (hereinafter also referred to as HMD) provided with the video display device.

  2. Description of the Related Art Conventionally, various video display devices that allow an observer to observe a video (virtual image) and the outside world at the same time have been proposed. In such an image display device, since image light from the display element is guided to the optical pupil of the eyepiece optical system, it is necessary to align the position of the observer's pupil with the position of the optical pupil when observing the image. It becomes. In particular, with recent miniaturization and weight reduction of the apparatus, the size of the optical pupil is also becoming smaller, and the alignment of the pupil is becoming difficult.

  Thus, for example, Patent Documents 1 and 2 propose video display devices that can easily perform pupil alignment by using an index. More specifically, in Patent Document 1, light representing an index displayed on a display element is reflected by a half mirror so that a third party can visually recognize the index from the outside. The third party can recognize the positional deviation between the observer's pupil and the index by positioning his / her pupil on the axis along which the light of the index travels. Therefore, the third person can perform the pupil alignment by operating the eye width adjustment mechanism of the apparatus so that the observer's pupil and the index overlap.

  On the other hand, in Patent Document 2, the observer's eyeball is illuminated, and the reflected light (light from the observer's pupil) is incident on the observer's pupil again through the semi-transmissive surface and the concave reflector. The person is made to observe the image of his eyes as a virtual image in the distance. When the position of the observer's pupil and the position of the optical pupil are shifted, the observer cannot see his / her own pupil image (virtual image) in the visual axis direction. Therefore, it is possible to align the pupils by determining the shift of the pupil position based on whether or not the observer can visually recognize his / her own pupil image and operating the eye width adjustment mechanism.

JP-A-6-276458 JP 2001-142026 A

  However, the devices of Patent Documents 1 and 2 both match the optical axes of transmitted light and reflected light with a half mirror (semi-transmissive surface) so that the optical path of the index light before image observation and the time of image observation are the same. This configuration partially overlaps the optical path of the image light. In this configuration, since there is no degree of freedom of arrangement of the constituent members of the apparatus, it is necessary to increase the size of the eyepiece optical system in order to ensure a large visible range (see-through region) in the outside world, which increases the size of the entire apparatus.

  Moreover, the apparatus of patent document 2 is the structure which aligns a pupil by an observer himself / herself, and a third party cannot visually recognize an index (virtual image) from the outside and perform alignment of the pupil. Therefore, when the observer is unfamiliar with the apparatus, it is difficult to align the pupil, and particularly when the optical pupil is small, it is more difficult to align the pupil.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to increase the size of an eyepiece optical system even in a configuration in which an index (virtual image) is displayed to align a pupil. In addition, a large see-through area can be secured, which makes it possible to reduce the size and weight of the device, and enables the third party to visually recognize the index, thereby aligning the pupil. An object of the present invention is to provide a video display device that facilitates and a head-mounted display including the video display device.

  An image display device of the present invention includes a display element for displaying an image, and an eyepiece optical system that simultaneously guides image light from the display element and external light to an optical pupil, and an observer at the position of the optical pupil. An image display device for simultaneously observing a virtual image of the display image and the outside world, further comprising an index display optical system for displaying an index when the optical pupil and the observer's pupil are aligned, and the index display optical The system includes an optical element for index having optical power and both optical characteristics of transmission and reflection, and an index light source for illuminating the index optical element, and is emitted from the index light source. The optical path of the light reflected by the index optical element is outside the optical path of the image light from the display element toward the optical pupil, and the index optical element transmits the light from the index light source to the optical pupil. By reflecting on the opposite side, It is characterized by displaying a virtual image as the index into the optical pupil side with respect to the optical element for the index by the optical power of the optical element for the indicator.

  In the image display device of the present invention, the index optical element reflects the light from the index light source on the side opposite to the optical pupil with a negative optical power, thereby causing the index optical element to reflect the index optical element. A virtual image as the index may be displayed on the optical pupil side.

  In the image display device of the present invention, the eyepiece optical system includes a volume phase type reflection hologram optical element (hereinafter also referred to as HOE) that reflects image light from the display element in the direction of the optical pupil with a positive optical power. The hologram optical element may also serve as the index optical element.

  In the image display device according to the aspect of the invention, the index optical element includes a selective transmission reflection film and an optical surface having an optical power on which the selective transmission reflection film is formed. Is reflected in the direction of the optical pupil by the concave surface of the optical surface, while the light from the index light source is reflected by the convex surface on the back surface of the optical surface having the concave shape, thereby allowing the optical surface to reflect the optical surface. A virtual image as the index may be displayed on the pupil side.

  In the image display device of the present invention, the index optical element reflects the light from the index light source on the side opposite to the optical pupil with a positive optical power, whereby the index optical element is A virtual image as the index may be displayed on the optical pupil side.

  In the image display device of the present invention, the eyepiece optical system includes a volume phase type reflection type first hologram optical element that reflects image light from the display element in a direction of the optical pupil with a positive optical power. The index optical element may be constituted by a volume phase type reflection type second hologram optical element different from the first hologram optical element.

  In the video display device according to the aspect of the invention, it is preferable that the second hologram optical element is disposed on the side opposite to the optical pupil with respect to the first hologram optical element.

  In the video display device of the present invention, the index optical element reflects the light from the index light source to the side opposite to the optical pupil, whereby the position of the optical pupil is adjusted by the optical power of the index optical element. A virtual image as the index may be displayed.

  In the video display device of the present invention, the index optical element reflects light from the index light source to the side opposite to the optical pupil, so that the optical power of the index optical element is applied to the optical pupil. Thus, a virtual image as the index may be displayed at a position opposite to the index optical element.

  In the video display device of the present invention, the eyepiece optical system guides video light from the display element to the hologram optical element by total internal reflection, and transmits the external light, and the index. The light source may include a second transparent substrate that guides light from the light source to the hologram optical element by total internal reflection and transmits external 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 the eyes of the observer.

  In the present invention, the optical path of light emitted from the index light source and reflected by the index optical element is outside the optical path of the image light from the display element toward the optical pupil, and the index optical path and the optical path of the image light are Since they are completely separated, the degree of freedom in designing the index display optical system (the degree of freedom in arrangement of the constituent members) is increased. Thereby, it is possible to provide the index display optical system without changing the design of the existing eyepiece optical system. Therefore, even in the configuration in which the index display optical system is provided, that is, the configuration in which the index is displayed and the pupil is aligned, it is not necessary to increase the size of the eyepiece optical system in order to secure a large see-through area. Further, the apparatus can be made smaller and lighter than the coaxial configuration.

  The index optical element displays a virtual image as an index on the optical pupil side with respect to the index optical element by its own optical power by reflecting light from the index light source to the side opposite to the optical pupil. Therefore, it becomes possible for a third party to visually recognize the virtual image from the outside world via the index optical element. As a result, a third party can recognize the positional deviation between the optical pupil and the observer's pupil based on the displayed virtual image and align the observer's pupil with the position of the optical pupil based on the virtual image. For example, even a small device with a small optical pupil can be easily aligned by a third party.

It is sectional drawing which shows the schematic structure of the video display apparatus of one Embodiment of this invention. (A) is a top view which shows schematic structure of HMD provided with the said video display apparatus, (b) is a side view of HMD, (c) is a front view of HMD. It is explanatory drawing which shows the light emission characteristic of the light source of the said video display apparatus. It is explanatory drawing which shows the diffraction characteristic of HOE of the said video display apparatus. (A) is a front view of the HMD when the position of the virtual image as an index is deviated from the position of the observer's pupil, and (b) is the front of the HMD when the positions of the two coincide. FIG. It is explanatory drawing which expand | deploys and shows the optical path of the light radiate | emitted from the light source for parameter | index of the said video display apparatus. It is sectional drawing which shows the schematic structure of the video display apparatus of other embodiment of this invention. It is sectional drawing which shows the other structural example of the said video display apparatus. It is sectional drawing which shows the structure of the outline of the video display apparatus of further another embodiment of this invention.

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

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

  The video display device 1 allows the observer to observe the virtual image of the display video and the outside world at the same time, and details thereof will be described later.

  The support means 2 supports the video display device 1 in front of the observer's eyes (for example, in front of the right eye), and includes a bridge 3, a frame 4, a temple 5, a nose pad 6, a cable 7, and the outside world. 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 nose pad 6 is a part that contacts the observer's nose and is movable with respect to the bridge 3. Therefore, by adjusting the position of the nose pad 6, the relative position between the optical pupil P formed by the eyepiece optical system 15 to be described later and the pupil of the observer can be adjusted. After adjusting the pupil position, the nose pad 6 is fixed to the bridge 3. Instead of making the nose pad 6 movable, a known eye width adjusting mechanism may be provided to adjust the relative position between the optical pupil P and the observer's pupil.

  The cable 7 is a wiring for supplying an external signal (for example, a video signal and 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 outside light transmittance control means 8 is provided in the bridge 3 for controlling the transmittance of outside light, and is ahead of the image display device 1 (on the side opposite to the optical pupil P with respect to the eyepiece optical system 15). Is located.

  In the above configuration, 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 placed on the nose of the observer. Wear the HMD on the observer's head as if wearing glasses. After adjusting the position of the observer's pupil at the position of the optical pupil P, the nose pad 6 is fixed. When an image is displayed on the image display device 1 in this state, the observer can observe the outside world simultaneously with a virtual image of the image displayed on the image display device 1.

  At this time, if the external light transmittance control means 8 sets the external light transmittance to a low value of, for example, 50% or less, the observer can easily observe the image on the video display device 1. If, for example, is set higher than 50%, the observer can easily observe the outside world. Therefore, the external light transmittance in the external light transmittance control means 8 may be set as appropriate in consideration of the ease of observing the video on the video display device 1 and the external environment.

  As described above, since the HMD of the present embodiment is configured such that the video display device 1 is supported by the support means 2, the observer can observe the video provided from the video display device 1 in a hands-free manner, Also, continuous mounting is facilitated.

  Note that the HMD is not limited to the one provided with only one video display device 1, and may be configured to include two video display devices 1. That is, the support means 2 may be configured to support the two video display devices 1 in front of the observer's eyes. In this case, the video display device 1 disposed in front of the left eye is supported between the bridge 3 and the left frame 4L. Further, the cable 7 is connected to both the video display apparatuses 1, and an external signal or the like is supplied to both the video display apparatuses 1 via the cable 7.

(Details of video display device)
Next, a detailed configuration of the video display device 1 will be described.
FIG. 1 is a cross-sectional view illustrating a schematic configuration of the video display device 1. The video display device 1 includes a light source 11, a unidirectional diffuser 12, a condenser lens 13, a display element 14, an eyepiece optical system 15, and an index display optical system 21. As shown in FIG. 1, the light source 11, the one-way diffusing plate 12, the condenser lens 13, and the display element 14 are accommodated in a housing 10, and a part of an eyepiece optical system 15 (an eyepiece prism 16 described later). The upper part is also located in the housing 10. Details of the index display optical system 21 will be described later.

  The light source 11 is a so-called RGB integrated LED in which, for example, three light emitting chips that emit light of each color of red (R), green (G), and blue (B) are arranged in a horizontal direction (left and right direction) and integrated. It is configured. Here, FIG. 3 shows the light emission characteristics of the light source 11. In the light source 11, the peak wavelengths of the emission intensity are, for example, 465 nm, 520 nm, and 635 nm. The emission intensity in FIG. 3 is shown as a relative value when the maximum light intensity of B light is 100. The RGB light emission intensities of the light source 11 are adjusted in consideration of the diffraction efficiency of the HOE 18 described later and the transmittance of the display element 14, thereby enabling white display.

  The unidirectional diffuser plate 12 diffuses light emitted from the light source 11, but the degree of diffusion varies depending on the direction. More specifically, the unidirectional diffuser plate 12 diffuses incident light by about 30 ° in the horizontal direction in which the RGB light emitting portions of the light source 11 are arranged, and reduces incident light in the direction perpendicular to the horizontal direction. Spread 0.5 °.

  The condensing lens 13 is composed of a cylinder lens that condenses the light diffused by the unidirectional diffusing plate 12 in a direction perpendicular to the diffusing direction so that the diffused light efficiently forms the optical pupil P. Has been placed.

  The display element 14 modulates the light emitted from the light source 11 according to image data and displays an image. For example, the display element 14 is a transmissive liquid crystal display element having pixels in a matrix in which light is transmitted. (LCD).

The eyepiece optical system 15 simultaneously transmits image light from the display element 14, that is, light corresponding to the image displayed on the display element 14, and external light to the optical pupil P (or the observer positioned at the optical pupil P). This is an optical system that leads to the pupil I ₁ ), and includes an eyepiece prism 16, a deflection prism 17, and a HOE 18.

  The eyepiece prism 16 is a transparent substrate (first transparent substrate) that guides the image light from the display element 14 to the HOE 18 by total internal reflection, and transmits external light. The eyepiece prism 16 is made of, for example, an acrylic resin together with the deflecting prism 17, and has a shape in which the lower end portion of the parallel plate is wedge-shaped and the upper end portion is thickened. Further, the eyepiece prism 16 is joined to the deflection prism 17 with an adhesive so as to sandwich the HOE 18 disposed at the lower end thereof. The upper end surface of the eyepiece prism 16 is a surface 16a as an image light incident surface, and the two surfaces positioned in the front-rear direction are surfaces 16b and 16c parallel to each other.

  The deflection prism 17 is a transparent substrate (second transparent substrate) that guides light from an index light source 21 (described later) to the HOE 18 by total internal reflection, and transmits external light, and is integrated with the eyepiece prism 16. Are attached to the lower end of the eyepiece prism 16 so as to form a substantially parallel plate. That is, the two surfaces 17b and 17c located in the front-rear direction in the deflection prism 17 are parallel to each other. Further, the surface 16b and the surface 17b, and the surface 16c and the surface 17c are smoothly connected. By forming a substantially parallel flat plate with the eyepiece prism 16 and the deflection prism 17, refraction when external light passes through the wedge-shaped lower end of the eyepiece prism 16 can be canceled by the deflection prism 17. It is possible to prevent distortion from occurring in the image of the outside world observed through the see-through.

  The HOE 18 is a volume phase type reflection type hologram optical element that diffracts and reflects the image light from the display element 14 in the direction of the optical pupil P with a positive optical power. Here, FIG. 4 shows the diffraction characteristics of the HOE 18. The HOE 18 is light incident at a specific incident angle. For example, the peak wavelength of diffraction efficiency and the half-value wavelength width of the diffraction efficiency peak are 465 ± 5 nm (B light), 520 ± 5 nm (G light), 635 ± 5 nm ( R light) is produced so as to diffract and reflect light in three wavelength regions. The diffraction efficiency in FIG. 4 is shown as a relative value when the maximum diffraction efficiency of B light is 100.

  In FIG. 1, RGB light emitted from a light source 11 is diffused by a unidirectional diffusion plate 12, condensed by a condenser lens 13, and incident on a display element 14. The light incident on the display element 14 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 14.

The image light from the display element 14 enters the eyepiece prism 16 of the eyepiece optical system 15 from the surface 16a, is totally reflected by the two opposing surfaces 16b and 16c at least once, and enters the HOE 18. The light incident on the HOE 18 is diffracted and reflected there and reaches the optical pupil P. Therefore, by locating the observer's pupil I ₁ at the position of the optical pupil P, the observer can observe an enlarged virtual image of the image displayed on the display element 14.

  On the other hand, the eyepiece prism 16 and the deflecting prism 17 transmit almost all the external light, so that the observer can observe the external environment. Therefore, the virtual image of the image displayed on the display element 14 is observed while overlapping a part of the outside world.

  As described above, the HOE 18 has the same function as an aspherical concave mirror having a positive optical power. Therefore, the degree of freedom of arrangement of each optical member constituting the device is increased and the device can be easily downsized. In addition, it is possible to provide an observer with an image that is favorably corrected for aberrations. Further, since the HOE 18 functions as a combiner that simultaneously guides the image light from the display element 14 and the external light to the optical pupil P, the observer can view the image provided from the display element 14 via the HOE 18 and the external environment. Can be observed simultaneously. Furthermore, since the diffraction efficiency peak wavelength of the HOE 18 is close to the emission intensity peak wavelength of the light source 11, light from the light source 11 (image light from the display element 14) is efficiently diffracted by the HOE 18 to display a bright image. Can do.

(About index display optical system and pupil alignment)
Next, details of the index display optical system 21 and alignment of the pupil will be described.
The index display optical system 21 shown in FIG. 1 is an optical system that displays an index when the optical pupil P and the observer's pupil I ₁ are aligned. The deflection prism 17 and the HOE 18 described above, and the index light source 22.

  The indicator light source 22 is provided on the lower surface 17a of the deflecting prism 17, and illuminates the HOE 18 from the back side thereof, that is, from the side opposite to the image light incident side. In the present embodiment, the index light source 22 is configured by, for example, an LED having a light emission characteristic equivalent to that of the light source 11 for image display, but if it includes any diffraction efficiency peak wavelength of RGB of the HOE 18, You may comprise with the light source which radiate | emits monochromatic light. The HOE 18 has optical power as described above, and has both optical characteristics of transmission and reflection, and functions as an index optical element in the index display optical system 21.

The alignment between the optical pupil P and the observer's pupil I ₁ is performed before the above-described video observation. During this alignment, the image display light source 11 is turned off and only the indicator light source 22 is lit to improve the visibility of the indicator and reduce power consumption. In the drawing, the light emission point of the indicator light source 22 is indicated by a black star mark to make the light emission point easy to understand, but this shape does not have any meaning.

The light emitted from the indicator light source 22 enters the deflecting prism 17 from the surface 17a, is totally reflected at least once by the two opposing surfaces 17b and 17c, and enters the HOE 18. The HOE 18 diffracts and reflects the image light from the display element 14 in the direction of the optical pupil P with positive optical power, but the light from the index light source 22 is incident on the HOE 18 from the back side. This is reflected with a negative optical power, and is reflected on the external side opposite to the optical pupil P. As a result, the virtual image V as an index is displayed at the center of the optical pupil P, and a third party other than the observer can observe the virtual image V from the outside through the HOE 18. In the drawing, the third person's pupil is indicated by I ₂ .

Therefore, for example, when the position of the virtual image V is deviated from the position of the observer's pupil I ₁ as shown in FIG. 5A, the third party, as shown in FIG. By operating the above-described nose pad 6 and eye width adjustment mechanism so that the position of V matches the position of the observer's pupil I ₁ , the position of the optical pupil P and the observer's pupil I ₁ are finally obtained. It becomes possible to match with the position of. Incidentally, adjusting the position of the pupil I ₁ themselves by arranging a mirror on the opposite side of the optical pupil P, the observer himself to be observed the images, while viewing the virtual image V that is reflected by the mirror relative HOE18 It is also possible.

  As described above, in the present embodiment, the indicator light source 22 is arranged so that the light representing the indicator is incident on the HOE 18 from the back side, so that the light emitted from the indicator light source 22 and reflected by the HOE 18 is reflected. Is located outside the optical path of the image light from the display element 14 toward the optical pupil P. That is, the index optical path and the image light optical path are completely separated. As a result, the degree of freedom in design of the index display optical system 21 (the degree of freedom of arrangement of the constituent members) is increased, and the index display optical system 21 can be provided without changing the design of the existing eyepiece optical system 15. . Therefore, even in the configuration in which the index display optical system 21 is provided, it is not necessary to increase the size of the eyepiece optical system 15 in order to ensure a large see-through region, and thus the apparatus can be made smaller than the conventional coaxial configuration. It is possible to reduce the weight.

Further, the HOE 18 as the index optical element reflects the light from the index light source 22 to the external side opposite to the optical pupil P, so that the index is closer to the optical pupil P side than the HOE 18 by its own optical power. The virtual image V is displayed. As a result, the third person can visually recognize the virtual image V from the outside through the HOE 18, and as described above, the optical pupil P and the observer's pupil I are based on the virtual image V displayed by the third party. ₁ is recognized, and the observer's pupil I ₁ can be adjusted to the position of the optical pupil P. Therefore, even a small apparatus having a small optical pupil P can be easily aligned by a third party.

  In particular, in the present embodiment, the HOE 18 displays the virtual image V on the optical pupil P side with respect to the HOE 18 by reflecting the light from the index light source 22 to the side opposite to the optical pupil P with negative optical power. ing. Here, FIG. 6 is an explanatory diagram showing the optical path of the light emitted from the indicator light source 22 in one direction. Since the reflection optical power of the HOE 18 in the index optical path is negative, as shown in the figure, a virtual image V as an index is formed at the position of the optical pupil P (for example, the center of the pupil) by turning on the index light source 22. be able to. In the index optical path, since the reflected optical power of the HOE 18 is negative, the HOE 18 is equivalent to a double-sided concave lens as shown in FIG.

Thereby, based on the displayed virtual image V, a third party can recognize the pupil position shift in three axial directions (the same direction as each of the vertical, horizontal, and front and rear directions). Thus, the observer's pupil I ₁ can be accurately adjusted in the three-axis directions to the position of the optical pupil P. As a result, at the time of image observation, the image light condensed on the optical pupil P can be efficiently incident on the pupil I ₁ (pupil) of the observer, and the observer can observe a bright image. Further, since the observer's pupil I ₁ can be made to coincide with the optical pupil P having good optical performance in all three axial directions, it is possible to cause the observer to observe a high-quality image.

From the above, the HOE 18 reflects the light from the index light source 22 to the side opposite to the optical pupil P, so that the index is set at the position of the optical pupil P by its own optical power (in this case, the negative reflection optical power). It can also be said that the virtual image V is displayed. In this case, since the position of the optical pupil P coincides with the display position of the virtual image V, the third party shifts the positional deviation between the optical pupil P and the observer's pupil I ₁ based on the displayed virtual image V. The three-axis directions can be accurately recognized, and the observer's pupil I ₁ can be accurately adjusted to the position of the optical pupil P based on the virtual image V.

Further, since the light from the index light source 22 is reflected by the HOE 18 to the side opposite to the optical pupil P (external side) with negative optical power, the light beam spreads from the HOE 18 to the external side, and a third party The range in which the virtual image V as an index can be visually recognized from the side becomes wider. As a result, the third person visually recognizes the virtual image V even if his / her pupil I ₂ is placed on an axis other than the axis passing through the center of the optical pupil P (on the extended line of the central ray of the light beam incident on the center of the optical pupil P). This makes it easy to search for the virtual image V. Further, since the reflection optical power of the HOE 18 in the index optical path is negative, the configuration in which the index light source 22 is disposed outside the wide see-through region can be easily realized. That is, it is possible to easily secure a wide see-through region by arranging the index light source 22 at a position far from the HOE 18 having optical power.

  In the present embodiment, since the optical path of the image light and the optical path for the index are separated, the HOE 18 that reflects the image light with the positive optical power is used as an element of the index display optical system 21 (index optical element). Can also be used. That is, the side opposite to the optical path of the image light in the HOE 18 of the eyepiece optical system 15 is used as the light incident side from the index light source 22, thereby reflecting the light from the index light source 22 with the negative optical power of the HOE 18. It can be set as the structure made to do.

  Thus, since the HOE 18 of the eyepiece optical system 15 also serves as an index optical element, the number of components can be reduced and the configuration of the index display optical system 21 and thus the video display device 1 can be simplified. And weight reduction can be further achieved. In addition, the volume phase type reflective HOE has high wavelength selectivity and high external light transmittance, so that the image viewer can see the external environment brightly and is easy to see. It becomes easy to confirm the virtual image V.

  Further, the eyepiece optical system 15 includes an eyepiece prism 16 as a first transparent substrate and a deflection prism 17 as a second transparent substrate. The image light is converted into HOE 18 by total reflection in the eyepiece prism 16. The light from the index light source 22 is guided to the HOE 18 by total reflection in the deflecting prism 17. Since the image light and the index light are respectively guided inside the eyepiece prism 16 and the deflection prism 17 in this way, the eyepiece prism 16 and the deflection prism 17 are configured to be as thin as about 3 mm, for example, as much as a normal spectacle lens. The apparatus can be reduced in size and weight. Further, since total reflection in the eyepiece prism 16 and the deflection prism 17 is used, the external light transmittance in the eyepiece prism 16 and the deflection prism 17 is increased, and the surfaces 16b and 16c and the surfaces 17b and 17c are passed through. The observer can observe the outside world brightly.

  Since the eyepiece prism 16 and the deflecting prism 17 are transparent substrates, the surfaces 16b and 16c and the surfaces 17b and 17c are transparent, and the HOE 18 diffracts only light having a specific wavelength at a specific incident angle. It has little effect on transmission. Therefore, the observer can see the outside world as usual through the eyepiece prism 16, the deflecting prism 17 and the HOE 18. Further, since the surface 16b and the surface 17b, and the surface 16c and the surface 17c are smoothly connected, the connecting portion (boundary) of the surface does not adversely affect the visual recognition of the outside world, and the observer has a wide see-through range. Can be observed well.

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

  FIG. 7 is a cross-sectional view showing a schematic configuration of the video display device 1 of the present embodiment. In the video display device 1 of the present embodiment, the eyepiece optical system 15 is configured by the HOE 18 and the transparent substrate 19, and the index display optical system 21 is configured by the index light source 22 and the HOE 23. The HOE 18 is disposed on the optical pupil P side on the transparent substrate 19.

  The HOE 23 reflects the light from the index light source 22 on the side opposite to the optical pupil P with positive optical power, thereby displaying a virtual image V as an index on the optical pupil side with respect to the HOE 23, and is a reflection type volume phase. Type hologram optical element, which is used as an index optical element. That is, in the present embodiment, unlike the first embodiment, the HOE 23 (second HOE) is used as the index optical element separately from the HOE 18 (first HOE) of the eyepiece optical system 15. The HOE 23 is disposed substantially in parallel with the HOE 18 via the air layer on the back side of the HOE 18, that is, on the side opposite to the optical pupil P with respect to the HOE 18.

  The diffraction characteristics of the HOE 23 are set according to the light emission characteristics of the index light source 22. That is, if the light emitted from the indicator light source 22 has emission intensity peak wavelengths in all RGB wavelength regions, the peak wavelength of diffraction efficiency is within the half-value wavelength width of the RGB emission intensity peaks. HOE23 as it exists can be used. For example, if the indicator light source 22 has a light emission characteristic equivalent to that of the light source 11 shown in FIG. 3, the HOE 23 has a diffraction characteristic equivalent to that of the HOE 18 shown in FIG. Can be used. Further, if the light emitted from the indicator light source 22 has a light emission intensity peak wavelength only in one of the RGB wavelength regions, at least within the half-value wavelength width of the light emission intensity peak in any one of the wavelength regions. HOE23 having a peak wavelength of diffraction efficiency can be used.

In the present embodiment, the image display light source 11 is configured by, for example, an LED that emits monochromatic light (for example, light having a wavelength of 550 nm), and the HOE 18 is manufactured to diffract light having a wavelength of 550 nm ± 10 nm. It shall be. At the time of image observation, light (G light) emitted from the light source 11 is diffused by the unidirectional diffusion plate 12, condensed by the condenser lens 13, and incident on the display element 14. The light incident on the display element 14 is modulated for each pixel based on the image data, emitted as image light, diffracted and reflected by the HOE 18, and reaches the optical pupil P. Thus, by locating the observer's pupil I ₁ at the position of the optical pupil P, the observer can observe an enlarged virtual image of the image displayed on the display element 14.

  On the other hand, the transparent substrate 19 transmits almost all external light, and the HOEs 18 and 23 only diffract and reflect light having a specific wavelength incident at a specific incident angle. You can observe the outside world as usual.

In the alignment of the pupil before image observation, when the index light source 22 is turned on, the light emitted from the index light source 22 is reflected by the HOE 23 to the side opposite to the optical pupil P with positive optical power. As a result, the virtual image V as an index is displayed on the far side opposite to the HOE 23 with respect to the optical pupil P, and a third party can observe the virtual image V via the HOE 23 from the outside. Therefore, the third party operates the nose pad 6 and the eye width adjustment mechanism so that the position of the virtual image V matches the position of the observer's pupil I ₁ based on the virtual image V. Finally, the position of the optical pupil P and the position of the observer's pupil I ₁ can be matched.

  As described above, in this embodiment, since the reflected optical power of the HOE 23 as the index optical element is positive, the index light source 22 is disposed close to the HOE 23 within a range in which a see-through area can be sufficiently secured, and the index The display optical system 21 can be downsized. Thereby, even when the small eyepiece optical system 15 in which a see-through area is sufficiently secured is used, the index display optical system 21 can be miniaturized accordingly, and the entire apparatus can be miniaturized.

  Further, the HOE 23 of the index display optical system 21 is configured by a HOE different from the HOE 18 of the eyepiece optical system 15. In this way, by using the two types of HOEs 18 and 23, the image light is guided to the optical pupil P by the positive reflection optical power of the HOE 18, and the observer observes the image (virtual image). The light from the indicator light source 22 can be reflected by the reflected optical power of the first and third parties so that the indicator (virtual image V) for position adjustment can be visually recognized. That is, it is possible to realize the video display device 1 that can observe the video and adjust the pupil position by using two types of HOEs 18 and 23 both having positive reflection optical power. In addition, the volume phase type reflection type HOE18 / 23 has high wavelength selectivity and high external light transmittance, so that the viewer of the image can see the external world brightly and easily, and the third party is located from the external side. It becomes easier to confirm the alignment index (virtual image V).

  Further, since the HOE 23 is disposed on the side opposite to the optical pupil P with respect to the HOE 18, the apparatus can be compactly integrated while completely separating the index optical path and the image light optical path.

In the present embodiment, the HOE 23 reflects the light from the index light source 22 to the side opposite to the optical pupil P, so that the optical power of the HOE 23 (here, positive reflection optical power) is applied to the optical pupil P. On the other hand, a virtual image V as an index is displayed at a position opposite to the HOE 23. This makes it easier for a third party to recognize the positional deviation between the optical pupil P and the observer's pupil I _{1 in} the vertical and horizontal directions based on the displayed virtual image V, and based on the virtual image V. Thus, the observer's pupil I ₁ can be aligned with the position of the optical pupil P.

  In the present embodiment, the display position of the virtual image V can be changed depending on the setting of the optical power of the HOE 23 by using the HOE 23 different from the HOE 18 and displaying the virtual image V using the optical power of the HOE 23. The degree of freedom in designing the device is also increased.

For example, FIG. 8 is a cross-sectional view showing another configuration example of the video display device 1. In the configuration of FIG. 8, the positive reflection optical power of the HOE 23 is set smaller than that of the configuration of FIG. Thus, by adjusting the optical power of the HOE 23, the display position of the virtual image V can be matched with the position of the optical pupil P. That is, the HOE 23 reflects the light from the index light source 22 to the side opposite to the optical pupil P, thereby displaying the virtual image V as an index at the position of the optical pupil P by the optical power of the HOE 23 (positive reflection optical power). It can be set as the structure to do. In this case, since the position of the optical pupil P coincides with the display position of the virtual image V as an index, a third party can use the optical pupil P based on the displayed virtual image V as in the first embodiment. And the observer's pupil I ₁ can be accurately recognized in the three axis directions, and the observer's pupil I ₁ is accurately aligned with the position of the optical pupil P based on the virtual image V. Can do.

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

  FIG. 9 is a cross-sectional view showing a schematic configuration of the video display device 1 of the present embodiment. In FIG. 9, the illustration of the configuration preceding the display element 14 is omitted. In the video display device 1 of the present embodiment, the eyepiece optical system 15 includes a transparent substrate 31 (first transparent substrate), a transparent substrate 32 (second transparent substrate), and a transflective film 33. The index display optical system 21 has a configuration in which an index light source 22 is further added to the eyepiece optical system 15 described above.

  The transparent substrate 31 is composed of a free-form surface prism, and the surfaces 31a, 31b, and 31c, which are optical surfaces, are all free-form surfaces. Here, the surface 31a is an incident surface for image light from the display element 14, the surface 31b is a total reflection surface, the surface 31c is opposed to the surface 31b, and the surface 32d of the transparent substrate 32 and the transflective film 33 is a surface bonded through 33. The surfaces 31a, 31b, and 31c may be flat surfaces or spherical surfaces. The semi-transmissive reflective film 33 is a film that selects transmission and reflection according to the transmittance, and is formed on the surface 31 c of the transparent substrate 31, but may be formed on the surface 32 d of the transparent substrate 32.

  The transparent substrate 32 corresponds to the deflecting prism 17 of the first embodiment, and is bonded to the transparent substrate 31 via the semi-transmissive reflective film 33 so that refraction when external light passes through the transparent substrate 31. Is canceled by the transparent substrate 32, and functions as a correction substrate that prevents distortion of the external image.

  An indicator light source 22 is provided on the lower surface 32 a of the transparent substrate 32. The indicator light source 22 is configured by an LED that illuminates the surface 31 c of the transparent substrate 31 from the side opposite to the incident side of the image light through the transflective film 33. The surface 32b of the transparent substrate 32 is smoothly connected to the surface 31b of the transparent substrate 31, and a surface 32c is provided to face the surface 32b. Further, the surface 32 d of the transparent substrate 32 faces the surface 31 c of the transparent substrate 31 with the transflective film 33 interposed therebetween.

  Here, the surface 31c of the transparent substrate 31 has a concave shape when viewed from the incident side of the image light. Therefore, in the optical path of the image light, the surface 31 as a whole is reflected positively together with the transflective film 33. It can be said that it has optical power. Further, since the surface 31c has a convex shape when viewed from the light incident side of the light source 22 for the indicator, in the optical path for the indicator, the surface 31c together with the transflective film 33 has a negative reflection optical power as a whole. It can be said that it has. Therefore, in this embodiment, it can be said that at least the surface 31c and the transflective film 33 constitute an index optical element having optical power and having both transmission and reflection optical characteristics. it can. That is, the optical power referred to here is a concept generated by the action of the surface shape of the surface 31 c and the transflective film 33. The index optical element may include the entire transparent substrate 31 having the surface 31c.

At the time of image observation, the image light from the display element 14 enters the inside of the transparent substrate 31 from the surface 31a, is totally reflected by the surface 31b, and then is formed on the optical pupil P by the concave surface of the surface 31c and the transflective film 33. Reflected and focused in the direction. Thus, by locating the observer's pupil I ₁ at the position of the optical pupil P, the observer can observe an enlarged virtual image of the image displayed on the display element 14. On the other hand, since the transparent substrates 31 and 32 transmit almost all the external light, the observer can observe the image and the external environment.

In the alignment of the pupil before the image observation, when the index light source 22 is turned on, the light emitted from the index light source 22 enters the inside of the transparent substrate 32 from the surface 32a and is totally reflected by the surface 32c. Then, the light is incident on the surface 31c from the convex surface side (the back surface side of the concave surface 31c when viewed from the image light incident side), and is reflected to the opposite side of the optical pupil P by the convex surface of the surface 31c and the transflective film 33. As a result, the virtual image V as an index is displayed at the center of the optical pupil P, and a third party can observe the virtual image V from the outside through the transflective film 33. Therefore, the third party operates the nose pad 6 and the eye width adjustment mechanism so that the position of the virtual image V matches the position of the observer's pupil I ₁ based on the virtual image V. Finally, the position of the optical pupil P and the position of the observer's pupil I ₁ can be accurately matched in the three-axis directions.

  As described above, in this embodiment, the image light from the display element 14 is reflected in the direction of the optical pupil P by the concave surface of the surface 31c by the action of the surface 31c as the index optical element and the transflective film 33. The virtual image V as an index is displayed on the optical pupil P side with respect to the surface 31c by reflecting the light from the index light source 22 by the convex surface on the back surface of the concave surface 31c. Thus, the configuration in which the reflection of the image light and the reflection of the light from the index light source 22 are performed on the front and back of the surface 31c, which is the same optical surface, as compared to a configuration in which these reflections are performed by separate elements or optical surfaces. The index display optical system 21 and thus the configuration of the apparatus can be simplified, and the apparatus can be further reduced in size and weight.

  Further, the light from the index light source 22 is reflected to the side opposite to the optical pupil P by the negative reflection optical power by the surface 31c and the semi-transmissive reflection film 33, so that the light beam spreads to the outside and the third party. Can obtain the same effects as those described in the first embodiment, such as making it easier to search for the virtual image V.

  In this embodiment, instead of the transflective film 33 formed on the surface 31c, a polarization separation film that selects transmission and reflection according to polarization characteristics, a dielectric multilayer film that selects transmission and reflection according to wavelength, or A hologram may be used. That is, it is sufficient that a selective transmission / reflection film that selectively transmits or reflects incident light is formed on the surface 31c.

  Of course, the video display device 1 and thus the HMD can be configured by appropriately combining the configurations described in the embodiments.

  The video display device of the present invention can be used for, for example, an HMD provided with a movable nose pad and an eye width adjustment mechanism.

DESCRIPTION OF SYMBOLS 1 Image display apparatus 2 Support means 14 Display element 15 Eyepiece optical system 16 Eyepiece prism (1st transparent substrate)
17 Deflection prism (second transparent substrate)
18 HOE (index optical element, first hologram optical element)
21 index display optical system 22 index light source 23 HOE (index optical element, second hologram optical element)
31c surface (optical surface, index optical element)
33 Transflective film (index optical element)
I ₁ Eye of the observer P Optical pupil V Virtual image

Claims (11)

A display element for displaying an image;
An image display device comprising an eyepiece optical system that simultaneously guides image light from the display element and external light to an optical pupil, and allows an observer to simultaneously observe a virtual image of the display image and the external environment at the position of the optical pupil. There,
An index display optical system for displaying an index when aligning the optical pupil with the observer's pupil;
The index display optical system includes:
An index optical element having optical power and having both transmission and reflection optical characteristics;
An indicator light source for illuminating the indicator optical element;
The optical path of the light emitted from the index light source and reflected by the index optical element is outside the optical path of the image light from the display element toward the optical pupil,
The index optical element reflects light from the index light source toward the side opposite to the optical pupil, so that the optical power of the index optical element is closer to the optical pupil than the index optical element. A video display device that displays a virtual image as the index.   The index optical element reflects the light from the index light source on the side opposite to the optical pupil with negative optical power, so that the index optical element serves as the index on the optical pupil side with respect to the index optical element. The video display apparatus according to claim 1, wherein a virtual image is displayed. The eyepiece optical system includes a volume phase type reflection type hologram optical element that reflects image light from the display element in the direction of the optical pupil with a positive optical power,
The video display apparatus according to claim 2, wherein the hologram optical element also serves as the index optical element.   The index optical element has a selective transmission reflection film and an optical surface having an optical power on which the selective transmission reflection film is formed, and the image light from the display element is transmitted by the concave surface of the optical surface. While reflecting in the direction of the optical pupil, the light from the indicator light source is reflected by the convex surface on the back side of the optical surface having the concave shape, so that the virtual image as the indicator on the optical pupil side with respect to the optical surface The video display device according to claim 2, wherein:   The index optical element reflects the light from the index light source on the side opposite to the optical pupil with positive optical power, so that the index optical element serves as the index on the optical pupil side with respect to the index optical element. The video display apparatus according to claim 1, wherein a virtual image is displayed. The eyepiece optical system has a volume phase type and reflection type first hologram optical element that reflects image light from the display element in the direction of the optical pupil with a positive optical power,
6. The image display device according to claim 5, wherein the index optical element is constituted by a volume phase type reflection type second hologram optical element different from the first hologram optical element. .   The video display device according to claim 6, wherein the second hologram optical element is disposed on the opposite side of the optical pupil with respect to the first hologram optical element.   The index optical element displays a virtual image as the index at the position of the optical pupil by the optical power of the index optical element by reflecting light from the index light source to the side opposite to the optical pupil. The video display device according to claim 1, wherein:   The index optical element reflects the light from the index light source to the side opposite to the optical pupil, so that the index optical element is separated from the optical pupil by the optical power of the index optical element. The video display device according to claim 5, wherein a virtual image as the index is displayed at a position on the opposite side. The eyepiece optical system is
A first transparent substrate that guides image light from the display element to the hologram optical element by total internal reflection, and transmits external light;
4. The video according to claim 3, further comprising: a second transparent substrate that guides light from the indicator light source to the hologram optical element by total internal reflection and transmits external light. 5. Display device. A video display device according to any one of claims 1 to 10,
A head-mounted display comprising support means for supporting the video display device in front of an observer's eyes.

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