WO2019244419A1

WO2019244419A1 - Image display device and wearable display

Info

Publication number: WO2019244419A1
Application number: PCT/JP2019/008895
Authority: WO
Inventors: 敬太丸井
Original assignee: コニカミノルタ株式会社
Priority date: 2018-06-19
Filing date: 2019-03-06
Publication date: 2019-12-26

Abstract

This optical see-through image display device includes a combiner capable of simultaneously guiding video light from a display element and external light from external scenery into an observer's eye. The combiner is a notch filter comprising a dielectric multilayer film having properties for selectively reflecting only light of at least one specific wavelength, and the following conditional expression is satisfied: 0.01 < Δλdeg × 106 / fy < 0.35 where Δλdeg represents a wavelength shift amount [mm/deg] of the longest wavelength peak with respect to a change in the incident angle of a beam from the center of a screen presenting video to the notch filter, and given a local rectangular coordinate system represented by (x, y, z) where the screen center in the display video is the origin, the line normal to the screen in the display video is the z-axis, the line normal to the plane including a principal beam at the center of the screen that is incident onto and reflected by the combiner is the x-axis, and the line normal to the z-x plane is the y-axis, fy represents the focal length [mm] of the principal beam at the center of the screen in the y-direction and satisfies fy = tan(ΔΘ)／Δy, wherein Δy represents the difference on the screen of the display video between the principal beam at the center of the screen and a principal beam with an angle of view different from the principal beam at the center of the screen by a minute angle of ΔΘ in the y-direction.

Description

Image display and wearable display

The present invention relates to an image display device and a wearable display, for example, an optical see-through type image display device that projects and displays a two-dimensional image of a liquid crystal display device (LCD) on an observer's eye with a combiner, The present invention relates to a wearable display (such as a head-mounted display) provided with an image display device.

(2) An optical see-through type image display device equipped with a combiner for performing see-through display of an image has been conventionally known. For example, Patent Literature 1 proposes an image display device that reflects light of a predetermined wavelength using a notch filter coated on a lattice surface of a relief hologram as a combiner. Patent Document 2 discloses an image in which a double image is prevented from occurring even when the reflection wavelength range of the notch filter is narrow by changing the light source wavelength according to the change in the incident angle to the notch filter used in the combiner. Display devices have been proposed.

JP 2013-127489 A JP 2012-78619 A

In the image display devices described in

Patent Literatures

1 and 2, the combiner is formed of a notch filter, but the change in screen brightness when the combiner surface is a curved surface is not considered. In a wearable image display device, when work or walking is performed in the mounted state, the user's pupil position is vertically displaced from the designed pupil position of the device, and the observed screen becomes dark. Or the color may change. This is because, when the combiner surface is a curved surface, if the pupil position shifts, the incident angle of the image light to the notch filter changes. That is, since the image light whose incident angle with respect to the notch filter has changed enters the eyes, a luminance change occurs on the screen.

For example, in the image display device described in Patent Literature 1, no consideration is given to the fact that the screen is darkened due to the deviation of the pupil position. In the device of Patent Document 2, the output wavelength of the light source is changed by changing the light source temperature in order to prevent the occurrence of a double image due to the wavelength shift of the notch filter. However, this method consumes a large amount of power. I will.

The present invention has been made in view of such a situation, and an object of the present invention is to provide an image display device in which a screen is hardly darkened even when a pupil position is relatively shifted, and a wearable display including the same. It is in.

In order to achieve the above object, the image display device of the present invention is an optical see-through image display device that projects an image onto an observer's eye by superimposing an image on an external scene,
A display element that displays the image, a combiner that simultaneously guides image light from the display element and external light from the external scene to the observer's eye, and joins to act as a plane-parallel plate with respect to the external light. And two prisms that support the combiner at the joint surface thereof,
The joining surface includes a prism convex surface and a prism concave surface,
The combiner is a notch filter made of a dielectric multilayer film having a characteristic of selectively reflecting only at least one light of a specific wavelength,
It is characterized by satisfying the following conditional expression (1).
0.01 <Δλ _deg × 10 ⁶ /fy<0.35 (1)
However,
Δλ _deg : the wavelength shift amount [mm / deg.] Of the longest wavelength peak with respect to the change of the incident angle of the light beam from the center of the screen of the displayed image to the notch filter,
[] Indicates the unit, deg. Is the degree of the angle,
The center of the screen in the display image is the origin, the normal of the screen in the display image is the z-axis, the normal of the plane containing the screen central chief ray incident and reflected on the combiner is the x-axis, and the normal of the zx plane is the y-axis. Let (x, y, z) be the local Cartesian coordinate system
fy: focal length [mm] of the central ray of the screen in the y direction,
fy = tan (ΔΘ) / Δy,
Δy: difference between a central ray of the screen and a principal ray having a small angle ΔΘ in the y direction from the central ray of the screen on the screen of the display image,
It is.

The wearable display according to the present invention is characterized in that the image display device according to the present invention is mounted, and the combiner has a function of projecting and displaying the image to the observer's eye in a see-through manner.

According to the present invention, it is possible to realize an image display device which is lightweight and compact, and whose screen is hardly darkened even when the pupil position is relatively shifted, and a wearable display including the image display device. For example, by performing work or walking while wearing a head-mounted display, even if the relative position of the pupil in the design of the image display device with respect to the user's pupil shifts in the vertical direction, the luminance change in the center of the screen is not changed. It is possible to observe a screen with a small and stable brightness.

FIG. 1 is a schematic configuration diagram showing one embodiment (Examples 1 and 2) of an image display device. FIG. 2 is a front view showing a glasses-type head mounted display including the image display device of FIG. 1. FIG. 5 is a sectional view taken along line V-V ′ of FIG. 3. FIG. 2 is an optical path diagram showing fy = tan (ΔΘ) / Δy in the image display device in FIG. 1. FIG. 2 is an optical path diagram showing Δλ _deg of a notch filter in the image display device of FIG. FIG. 2 is a conceptual diagram of a spectrum showing a relationship between an output wavelength region of a light source and a reflection wavelength region of a notch filter in the image display device of FIG. 1. 4 is a graph showing the reflection characteristics (incident angle: 26 °) of the notch filter of Example 1 in terms of spectral reflectance (wavelength: 380 to 780 nm). 5 is a graph showing the reflection characteristics (incident angle: 26 °) of the notch filter of Example 1 in terms of spectral reflectance (wavelength: 620 to 650 nm). 5 is a graph showing the reflection characteristics (incident angle: 21 °) of the notch filter of Example 1 in terms of spectral reflectance (wavelength: 620 to 650 nm). 9 is a graph showing the reflection characteristics (incident angle: 26 °) of the notch filter of Example 2 in terms of spectral reflectance (wavelength: 380 to 780 nm). 9 is a graph showing the reflection characteristics (incident angle: 26 °) of the notch filter of Example 2 in terms of spectral reflectance (wavelength: 620 to 660 nm). 11 is a graph showing the reflection characteristics (incident angle: 21 °) of the notch filter of Example 2 in terms of spectral reflectance (wavelength: 620 to 660 nm).

Hereinafter, an image display device, a wearable display, and the like according to an embodiment of the present invention will be described with reference to the drawings. The same reference numerals are given to the same or corresponding parts in the embodiments, examples, and the like, and the description thereof will not be repeated.

FIG. 1 shows a schematic cross section of an image display device 9 according to an embodiment of the present invention. FIG. 2 shows an external configuration of a glasses-type head mounted display 10 provided with an image display device 9, and FIG. 3 shows a schematic structure of a cross section taken along line V-V '. The image display device 9 shown in FIG. 1 projects the image of the display element 6 (FIG. 1) on the external scenery to the observer's eye EY, as can be seen from the optical paths of the image light La and the external light Lb shown in FIG. This is an optical see-through type image display device for displaying, and has an optical device 5, a display element 6, a polarizing beam splitter 7, and the like. In FIG. 1, the surface numbers i (i = 1, 2,..., 11) are assigned in the order of the optical paths from the pupil EP to the display image IM, so the first surface S1 of the i-th surface Si Is a reference surface, the second surface S2 at the same position as the reference surface is the pupil EP corresponding to the stop, the tenth surface S10 is the final surface, and the eleventh surface S11 at the same position as the image display is the image surface. This is a surface 6a (for example, a liquid crystal screen displaying an image IM).

The display element 6 is an optical device that displays an image IM by emitting image light La composed of visible light, and specific examples thereof include, for example, a reflective LCD represented by LCOS (liquid crystal on silicon), and a transmissive LCD. -Type LCD, digital micromirror device, organic electro-luminescence (EL) display represented by organic light-emitting diode (OLED), micro LED (light-emitting diode) panel Etc. or those containing them. The ninth surface S9 is a cover glass surface of the display element 6.

照明 Furthermore, an illumination device for illuminating the display element 6 may be provided. Examples of the illuminating device include an illuminating device including an illuminating optical system including a light source such as an LED and a condensing optical element (a lens, a mirror, and the like). Examples of the light source for illumination include an LED light source, a laser light source, and an organic EL light source, and correspond to, for example, three primary colors RGB that emit light in three wavelength bands (emission peak wavelengths are, for example, 450 nm, 532 nm, and 640 nm). LED light source.

(4) By collimating the illumination light from the light source with the illumination optical system, the illumination light emitted from the light source can be efficiently delivered to the observer's eye EY. It is preferable to use a reflection-type liquid crystal display element as the display element 6 in order to not only spatially modulate the illumination light but also reduce the size by folding back the light. The image display device 9 uses a plane-type polarization beam splitter 7 in a small space to define the polarization to be incident on the reflection type liquid crystal display element and to selectively transmit the modulated light. By utilizing two polarization separation functions of generating polarized light by reflection and selecting polarized light by transmission, it is possible to reduce the size of the optical configuration. The seventh surface S7 is the lower surface of the polarization beam splitter 7, and the eighth surface S8 is the upper surface of the polarization beam splitter 7.

The optical device 5 is joined to the combiner 3 for simultaneously guiding the image light La from the display element 6 and the external light Lb from the external scene to the observer's eye EY so as to act as a plane parallel plate to the external light Lb. And the

prisms

1 and 2 that support the combiner 3 at the joint surface. The joining surface between the prism 1 and the prism 2 is formed by joining the prism convex surface 1a of the prism 1 and the prism concave surface 2a of the prism 2, and the combiner 3 is positioned so as to be sandwiched between the prism convex surface 1a and the prism concave surface 2a. are doing.

The two

transparent prisms

1 and 2 are transparent optical members made of a resin material such as acrylic resin, polycarbonate (PC), and cycloolefin resin. In the prism 1, two reflections are performed between the incident and the exit. By configuring the light guide optical system that reflects twice with the prism 1, a large-sized reflective liquid crystal display element can be arranged on the opposite side of the observer's eye. As a result, it is possible to avoid interference between the liquid crystal display element and the observer's forehead and glasses. Note that the third surface S3 and the fifth surface S5 are prism surfaces on the eye EY side, and the sixth surface S6 is a prism surface on the side where the image light La is incident.

The combiner 3 is a notch filter (a band stop filter having a narrow stop band) made of a dielectric multilayer film having a characteristic of selectively reflecting only at least one specific wavelength of light (narrow band reflection characteristic). This dielectric multilayer film is composed of alternating layers of a high-refractive-index layer (for example, TiO ₂ ) and a low-refractive-index layer (for example, SiO ₂ ), and the total number of film layers is 40 or more. The method of forming the dielectric multilayer film includes electron beam evaporation, resistance heating evaporation, ion plating, sputtering, and the like. The fourth surface S4 is a notch surface (polynomial surface).

Compared with the hologram optical element, the dielectric multilayer film can make the refractive index difference larger, so that the wavelength variation (that is, angle dependency) due to the incident angle can be reduced, and the dielectric multilayer film can be made thinner. Ridge line becomes thin, and high see-through property is obtained. Further, since the dielectric multilayer film has a larger wavelength width than the hologram optical element, the reflectance (display efficiency) is increased. When the wavelength width is small, the see-through property increases, but when the wavelength width is too small, the display efficiency is reduced. Conversely, if the display efficiency is to be improved, the see-through property (how to see or see) is reduced as in the case of the half mirror.

The optical device 5 has a non-axially symmetric (non-rotationally symmetric) positive optical power in the combiner 3, and thereby an observation optical system for guiding the image light La from the display element 6 to the observer's eye EY. Function as As a result, the display image is projected and displayed on the observer's eye EY as an enlarged virtual image so that the image of the display element 6 overlaps the external image via the combiner 3. The optical power of the combiner 3 can be realized by depositing a dielectric multilayer film on the prism convex surface 1a of the prism 1 or depositing a dielectric multilayer film on the prism concave surface 2a of the prism 2. By configuring the optical power of the combiner 3 with a curved surface, it is not necessary to separately arrange an optical element such as a lens, so that the size of the image display device 9 can be reduced. In addition, as a specific example of the prism convex surface 1a and the prism concave surface 2a which form the joining surface, a curved surface such as a conical surface is exemplified.

The two

prisms

1 and 2 are joined with an adhesive 4 such that a combiner 3 made of a dielectric multilayer film deposited on one of the

prisms

1 and 2 is sandwiched between a prism convex surface 1a and a prism concave surface 2a. Has formed. Therefore, the prism convex surface 1a and the prism concave surface 2a preferably have the same shape or substantially the same shape, and preferably have a shape in which the thickness of the layer of the adhesive 4 is uniform. The prism 1 acts to guide the image light La coming from the display element 6 internally by total internal reflection while transmitting light of an external image (external light Lb). At this time, since the combiner 3 is provided on the joint surface between the

prisms

1 and 2, the see-through property (combiner function) of the external image via the joint surface is ensured.

Since the prism 2 is joined to the prism 1 so as to act as a plane-parallel plate with respect to the external light Lb, the external light Lb is formed at the lower end portion of the prism 1 (a portion forming a curved surface inclined substantially in a wedge shape). Can be prevented from being canceled out by the prism 2 when refracting light through the prism 2 and the observed external image is distorted (improvement in see-through performance). Further, since the dielectric multilayer film forming the combiner 3 is not in direct contact with air by being sandwiched between the prism convex surface 1a and the prism concave surface 2a, even if the humidity fluctuates rapidly, the influence is not affected. Is greatly reduced by the

prisms

1 and 2. As a result, film cracking due to humidity fluctuation is reduced or prevented.

The dielectric multilayer film forming the combiner 3 is a notch filter having reflection bands at three wavelengths of three primary colors RGB for colorization. Therefore, the image light La in the RGB reflection band is reflected as a part of the image light La incident on the combiner 3. The image light La reflected by the combiner 3 enters the observer's eye EY together with the external light Lb transmitted through the combiner 3, so that the observer observes the displayed image as well as the external image (high transmittance). be able to. Further, since the prism 1 as a transparent base is configured to totally reflect the image light La from the display element 6 and guide the image light La to the combiner 3, the image light La emitted from the display element 6 is wasted. Without using it, a bright image can be provided to the observer.

The notch filter is an optical filter that reflects only a single wavelength of light at a predetermined reflectance and transmits the rest of the light. Therefore, compared with a half mirror, the notch filter has compatibility with light sources such as LEDs, wavelength width, and wavelength variation. Efficiency is high with respect to the above. Therefore, as described above, the dielectric multilayer film is preferably a notch filter having reflection bands at three wavelengths corresponding to the three primary colors RGB. Also, in designing a dielectric multilayer film, a certain number of layers is required to design a notch filter having reflection bands at three wavelengths corresponding to the three primary colors RGB. If the number of layers is small, the transmittance of the transmission part decreases (see-through property), the band of the reflection part narrows (see-through property), and the reflectance (brightness) of the reflection part decreases. The dielectric multilayer film is preferably composed of alternating layers of a high refractive index layer and a low refractive index layer, and the total number of film layers is preferably 40 or more.

As described above, by forming a dielectric multilayer film on the prism convex surface 1a or the prism concave surface 2a, it is possible to obtain the combiner 3 constituting the concave surface of positive power. If a combiner having the same shape is formed by a half mirror, the luminous transmittance decreases, and it becomes difficult to obtain a good see-through property. Therefore, when a dielectric multilayer film is used as compared with a half mirror, it is possible to achieve a good balance between the high luminous transmittance of the external light Lb and the brightness of the image light La (display image).

In a conventional wearable display, when work or walking is performed in the mounted state, the pupil position of the user is vertically displaced from the pupil position in the device design, and the screen to be observed becomes dark or has a color. May change. This is because, when the combiner surface is formed of a curved surface, if the pupil position shifts, the incident angle of the image light to the notch filter changes. That is, the image light whose incident angle with respect to the notch filter has changed enters the observer's eyes, so that the luminance changes on the screen. In order to solve this problem, the image display device 9 has a configuration satisfying the following conditional expression (1).
0.01 <Δλ _deg × 10 ⁶ /fy<0.35 (1)
However,
Δλ _deg : the wavelength shift amount [mm / deg.] Of the longest wavelength peak with respect to the change of the incident angle of the light beam from the center of the screen of the displayed image to the notch filter,
[] Indicates the unit, deg. Is the degree of the angle,
The center of the screen in the displayed image is the origin, the normal of the screen in the displayed image is the z-axis, the normal of the plane including the central ray of the screen incident and reflected on the combiner is the x-axis, and the normal of the zx plane is the y-axis. Let (x, y, z) be the local Cartesian coordinate system
fy: focal length [mm] of the central ray of the screen in the y direction,
fy = tan (ΔΘ) / Δy,
Δy: difference between a central ray of the screen and a principal ray having a small angle ΔΘ in the y direction from the central ray of the screen on the screen of the display image,
It is.

FIG. 4 is a conceptual diagram of fy = tan (ΔΘ) / Δy. On the screen of the display image IM, a central ray Lc (solid line) at the center of the screen, and a principal ray Ld (dashed line) having a field angle different from the central ray Lc by a small angle ΔΘ (for example, ΔΘ = 0.01 °) in the y direction. From the difference Δy, the focal length fy of the observation optical system can be regarded as a local focal length in the central ray Lc at the center of the screen. The principal ray Ld is drawn as an optical path of the observation optical system from the pupil EP to the image plane (display image) IM.

FIG. 5 is a conceptual diagram of the wavelength shift amount Δλ _{deg with} respect to the change of the incident angle to the notch filter (NL: surface normal of the combiner 3). The wavelength shift amount Δλ _deg depends on the difference between the incident angle of the light beam L1 (solid line) and the light beam L2 (dashed line), ie, the peak wavelength does not change, that is, the incident angle of the image light La to the notch filter changes by 1 °. The figure shows the wavelength shift amount [mm / deg.] At this time.

FIG. 6 is a conceptual diagram showing the relationship between the spectrum of the light source and the spectrum of the notch filter by the relationship between the light source wavelength region A0 and the reflection wavelength regions B0 and B1. In FIG. 6, the horizontal axis represents wavelength, and the vertical axis represents intensity (light source luminance or normalized reflectance). When the head mount display 10 is displaced from the position to be mounted, the light source wavelength region A0 does not change, but the reflection wavelength region B0 (broken line) of the notch filter is reflected by the change in the incident angle of the image light La to the notch filter. The wavelength shifts to the wavelength region B1 (solid line). For example, when the head-mounted display 10 shifts upward in the vertical direction, the peak wavelength shifts to the longer wavelength side and the screen becomes darker. Conversely, when the head-mount display 10 shifts downward in the vertical direction, the peak shifts. The wavelength shifts to the shorter wavelength side and the screen becomes darker.

The threshold value: 0.01 that defines the lower limit of conditional expression (1) is calculated as Δλ _deg × 10 ⁶ = 0.5 [nm / deg.] And fy = 50 [mm]. At a threshold value of fy = 50 [mm], the eye point is about 50 [mm]. In glasses, the distance between the corneal vertices (the distance from the glasses to the eyes) is generally 12 [mm]. Considering this, the eye point of the head mounted display 10 is preferably about 20 to 30 [mm]. At the eye point of 50 [mm], the mounting position of the head mounted display 10 is far from the observer's eye EY and becomes large. Therefore, it is preferable to set the value so as to exceed the lower limit of the conditional expression (1).

In the case of an observation optical system having power in the combiner 3 such as the optical device 5, the thicknesses of the

prisms

1 and 2 increase in proportion to the eye point. If the eye point is 50 [mm], considering that the general eye point of the head mounted display 10 is about 20 to 30 [mm], the thickness of the

prisms

1 and 2 becomes approximately double, and It is not preferable as a terminal to be attached. Although not strict, the angle of view is reduced as a function of tangent by increasing fy from the relational expression (size of liquid crystal) = fy × tan (angle of view). This is not preferable for presenting information as a see-through image.

The threshold value: 0.35 that defines the upper limit of conditional expression (1) is calculated as Δλ _deg × 10 ⁶ = 6.0 [nm / deg.] And fy = 17 [mm]. This is a condition for preventing the screen center principal ray Lc from becoming dark when the head-mounted display 10 deviates from a position (designed) where the head-mounted display 10 is to be mounted. Therefore, by satisfying this condition, it is possible to display an image with a small change in luminance at the center of the screen with respect to the vertical displacement of the head mounted display 10.

It is preferable that the image display device 9 satisfies the following conditional expression (1a).
0.013 <Δλ _deg × 10 ⁶ /fy<0.21 (1a)
The conditional expression (1a) defines a more preferable condition range based on the viewpoints and the like, among the conditional ranges defined by the conditional expression (1). Therefore, preferably, by satisfying conditional expression (1a), the above effect can be further enhanced.

The threshold value defining the lower limit of conditional expression (1a): 0.013 is calculated as Δλ _deg × 10 ⁶ = 0.5 [nm / deg.], Fy = 40 [mm], and the upper limit of conditional expression (1a) Is calculated as Δλ _deg × 10 ⁶ = 4.0 [nm / deg.] And fy = 19 [mm]. By satisfying conditional expression (1a), when the head-mounted display 10 deviates from the position where it is to be mounted (designed), the central ray of light Lc is prevented from becoming darker than in conditional expression (1). Can be.

It is preferable that the image display device 9 does not form an intermediate image of the display video IM. Since conditional expression (1) presupposes that the focal length and the eye point substantially match, the configuration in which the display image IM is not re-imaged like the optical device 5 is reduced in size of the image display device 9 and the screen brightness. It is effective for stabilization of etc.

According to the image display device 9 described above, it is possible to perform image display in which the screen is hardly darkened even when the pupil position is relatively shifted, while achieving weight reduction and compactness. For example, by performing work or walking with the head mounted display 10 mounted, the relative position of the designed pupil EP of the image display device 9 with respect to the pupil of the observer eye EY of the user is shifted in the vertical direction. Also, it is possible to observe a screen with stable brightness with little change in luminance at the center of the screen.

As described above, since the combiner 3 simultaneously guides the image displayed on the display element 6 and the external image to the observer's eye EY, the observer can view the image provided from the display element 6 via the combiner 3 and the external image. Can be observed simultaneously. Therefore, by mounting the above-described image display device 9, a wearable display (such as the head-mounted display 10) having a function of projecting and displaying an image on the observer's eye EY by the optical device 5 in a see-through manner can be configured.

As described above, it is preferable that the image display device 9 is mounted on the wearable display to provide the combiner 3 with a function of projecting and displaying an image on the observer's eye EY in a see-through manner. Further, the wearable display is a head-mounted display including a support member that supports the image display device 9 so that the combiner 3 is positioned in front of the observer's eye EY (that is, supports the image display device 9 in front of the observer's eyes). Is desirable. Since the image display device 9 has a high see-through property, a high image display effect can be obtained by disposing the image display device 9 in front of the observer's eyes.

As the wearable display, a head-mounted display (HMD), a head-up display (HUD) and the like can be mentioned. Examples of the form of the head-mounted display include an eyeglass type and a helmet type, and examples of the use of the head-up display include driving of an automobile, control of an airplane, and the like. Since the

prisms

1 and 2 made of resin are lighter in weight than glass prisms, they are suitable for wearable displays such as the head mounted display 10.

A head-mounted display 10 (FIGS. 2 and 3) is a head-mounted wearable display including the above-described image display device 9, a frame (supporting member) 11,

lenses

12a and 12b, and a housing 13. This is an example. The

lenses

12 a and 12 b and the housing 13 are supported by the frame 11. The display element 6 and the illumination device (not shown) of the image display device 9 are housed in the housing 13, and the upper end of the optical device 5 serving as an observation optical system is also located in the housing 13. Therefore, by supporting the housing 13 with the frame 11, the main body of the optical device 5 is located in front (outside of the outside) of the lens 12a for the right eye (FIG. 3). Note that the

lenses

12a and 12b may be spectacle lenses, or may be dummy lenses made of parallel plane plates.

The display element 6, the light source (not shown), and the like in the housing 13 are connected to a circuit board (not shown) via a cable (not shown) provided through the housing 13, and Driving power and video signals are supplied to the display element 6, the light source, and the like. The image display device 9 further includes an imaging device for photographing a still image or a moving image, a microphone, a speaker, an earphone, and the like. The information of the captured image and the display image is transmitted via an external server or terminal to a communication line such as the Internet. Or a configuration for exchanging (transmitting and receiving) audio information.

When the head mounted display 10 is mounted on the observer's head and an image is displayed on the display element 6 (FIG. 1), the image light La (FIG. 3) is guided to the observer's eye EY via the optical device 5. The observer can observe an enlarged virtual image of the display image on the image display device 9. At the same time, the observer can observe the external image through the optical device 5 in a see-through manner. Since the image display device 9 is supported by the frame 11, the observer can simultaneously and stably observe the display image and the external image provided from the image display device 9 in a hands-free manner for a long time. Can perform a desired operation. Note that two image display devices 9 may be used so that images can be observed with both eyes.

分かる As can be understood from the above description, the above-described embodiments and examples described below include the following characteristic configurations (# 1) to (# 5).

(# 1): An optical see-through image display device that superimposes an image on an external scene and displays the image on an observer's eye,
A display element that displays the image, a combiner that simultaneously guides image light from the display element and external light from the external scene to the observer's eye, and joins to act as a plane-parallel plate with respect to the external light. And two prisms that support the combiner at the joint surface thereof,
The joining surface includes a prism convex surface and a prism concave surface,
The combiner is a notch filter made of a dielectric multilayer film having a characteristic of selectively reflecting only at least one light of a specific wavelength,
An image display device satisfying the following conditional expression (1);
0.01 <Δλ _deg × 10 ⁶ /fy<0.35 (1)
However,
Δλ _deg : the wavelength shift amount [mm / deg.] Of the longest wavelength peak with respect to the change of the incident angle of the light beam from the center of the screen of the displayed image to the notch filter,
[] Indicates the unit, deg. Is the degree of the angle,
The center of the screen in the display image is the origin, the normal of the screen in the display image is the z-axis, the normal of the plane containing the screen central chief ray incident and reflected on the combiner is the x-axis, and the normal of the zx plane is the y-axis. Let (x, y, z) be the local Cartesian coordinate system
fy: focal length [mm] of the central ray of the screen in the y direction,
fy = tan (ΔΘ) / Δy,
Δy: difference between a central ray of the screen and a principal ray having a small angle ΔΘ in the y direction from the central ray of the screen on the screen of the display image,
It is.

(# 2): The image display device according to (# 1), wherein the following conditional expression (1a) is satisfied.
0.013 <Δλ _deg × 10 ⁶ /fy<0.21 (1a)

(# 3): The image display device according to (# 1) or (# 2), wherein an intermediate image of the display image is not formed.

(# 4): By mounting the image display device according to any one of (# 1) to (# 3), a function of projecting and displaying the video image to the observer's eyes with the combiner is provided. A wearable display characterized by the above.

(# 5): The wearable display according to (# 4), further including a support member that supports the image display device so that the combiner is located in front of an observer's eye.

Hereinafter, the configuration and the like of the image display device embodying the present invention will be described more specifically with reference to the construction data and the like of the embodiments. Examples 1 and 2 (EX1 and EX2) mentioned here are common except for the film configuration of the dielectric multilayer film (notch filter), and are numerical examples corresponding to the above-described embodiments of the image display device. The schematic cross-sectional view (FIG. 1) shows the optical arrangement, optical paths, and the like of the first and second embodiments.

Table 1 shows the construction data and the like of Examples 1 and 2. In the construction data, the surface number i (i = 0, 1, 2,..., 11; OB: object surface, ST: aperture, IM: image surface), surface shape, curvature in the Y direction are arranged in order from the left column. The radius (mm), the radius of curvature (mm) in the X direction, the optical action (reflection and refraction), the refractive index and the Abbe number for a wavelength of 532 nm are shown. The i-th surface Si (surface number i = 0, 1, 2,..., 11) is the i-th surface counted from the object surface OB side in the optical path from the object surface OB (S0) to the image surface IM (S11). Is shown. Therefore, the aperture ST corresponds to the pupil EP, and the image plane IM corresponds to the image display surface 6a (for example, a liquid crystal screen for displaying an image). The radii of curvature in the Y direction and the X direction are defined by coordinate axes in an orthogonal coordinate system (X, Y, Z) with the origin at the surface vertex of each optical surface Si and the normal at the surface vertex as the Z axis. is there.

Table 2 shows the arrangement data of the surface Si in Examples 1 and 2. The arrangement of each surface Si is specified by the surface vertex coordinates (X, Y, Z) and the rotation angle around the X axis in the eccentricity data based on the first surface S1. The surface vertex coordinates of the optical surface Si are determined by using the surface vertex as the origin of the local rectangular coordinate system (X, Y, Z), and using the local rectangular coordinates (X, Y, Z) of the global first surface S1. It is represented by the coordinates of the origin of the coordinate system (X, Y, Z) (unit: mm), and the inclination of each optical surface Si is represented by the rotation angle about the X axis about the surface vertex ( Unit: °; counterclockwise with respect to the positive direction of the X, Y, Z axes is the positive direction of the rotation angle of the X, Y, Z rotation.)

However, all the coordinate systems are defined by the right-handed system, and the global orthogonal coordinate system (X, Y, Z) of the first surface S1 is not limited to the first surface S1 but also to the local surface of the second surface S2 (aperture ST). It is an absolute coordinate system that also matches the simple rectangular coordinate system (X, Y, Z). The reference direction of the rotation angle around the coordinate axis (that is, the coordinate axis direction before rotation) is the coordinate axis direction in the orthogonal coordinate system (X, Y, Z) of the first surface S1. Therefore, on the first surface S1, the X direction is the direction perpendicular to the paper surface (the horizontal direction of the angle of view), the Y direction is the vertical direction of the paper surface (the vertical direction of the angle of view), the depth direction of the paper is the + X direction, The upward direction is the + Y direction, and the right direction on the paper is the + Z direction.

Tables 3 and 4 show the coefficients Cj of the fourth surface S4 and the sixth surface S6 in Examples 1 and 2. The fourth surface S4 and the sixth surface S6 are XY polynomial surfaces, and their surface shapes are defined by the following expression (FS) using a local rectangular coordinate system (X, Y, Z) with the origin at the surface vertex. You. Note that the coefficient of the term without the notation is 0, and ^En = × 10 ⁻ⁿ for all data.
^{Z = (C0 · h 2)} / [1 + √ {1- (1 + K) · C0 2 · h 2}] + Σ (Cj · X m · Y n) ... (FS)
However, in the formula (FS),
h: height in the direction perpendicular to the Z axis (h ² = X ² + Y ² ),
Z: Amount of displacement in the Z-axis direction at the position of height h (based on surface vertex),
C0: curvature at surface vertex (= 1 / radius of curvature),
K: conic constant,
Cj: coefficients of the monomials X ^m Y ^n,
j = [{(m + n) ² + m + 3n} / 2] +1,
Σ: sum of j = 2 to 66,
It is.

The film configurations of the dielectric multilayer films (notch filters) of Examples 1 and ₂ and the refractive indexes of the film materials TiO ₂ , H4 (trade name of Merck Ltd.) and SiO ₂ for each wavelength are as follows. Shown in The dielectric multilayer film of Example 1 is composed of alternating layers (TiO2 / H4) of a high refractive index layer made of TiO ₂ and a low refractive index layer made of H4. The film is composed of alternating layers (TiO2 / SiO2) of a high refractive index layer made of TiO ₂ and a low refractive index layer made of SiO ₂ , and the layer numbers are assigned in order from the prism 1 side.

7 to 9 show the spectral reflectance characteristics of the dielectric multilayer film (notch filter) of Example 1, and the graphs of FIGS. 10 to 12 show the spectral reflectance of the dielectric multilayer film (notch filter) of Example 2. The reflectance characteristics are shown (vertical axis: reflectance [%], horizontal axis: wavelength [nm]).

FIG. 7 shows the reflection characteristics (incidence angle: 26 °) of the notch filter of Example 1 in terms of spectral reflectance (wavelength: 380 to 780 nm), and FIG. 8 shows the reflection characteristics (of the notch filter of Example 1). Incident angle: 26 °) is shown by spectral reflectance (wavelength: 620 to 650 nm). FIG. 9 shows the reflection characteristics (incident angle: 21 °) of the notch filter of Example 1 in terms of spectral reflectance (wavelength: 620 to 650 nm). In the first embodiment, since Δλ _deg × 10 ⁶ = (643-633) / (26-21) = 2.0 and fy = 26.2, Δλ _deg × 10 ⁶ /fy=0.076, and the conditional expression (1) , (1a).

FIG. 10 shows the reflection characteristics (incidence angle: 26 °) of the notch filter of Example 2 in terms of spectral reflectance (wavelength: 380 to 780 nm), and FIG. 11 shows the reflection characteristics of the notch filter (Example 2). Incident angle: 26 °) is shown by spectral reflectance (wavelength: 620 to 660 nm). FIG. 12 shows the reflection characteristics (incident angle: 21 °) of the notch filter of Example 2 in terms of spectral reflectance (wavelength: 620 to 660 nm). In the second embodiment, since Δλ _deg × 10 ⁶ = (652-635) / (26-21) = 3.4 and fy = 26.2, Δλ _deg × 10 ⁶ /fy=0.130, and the conditional expression (1) , (1a).

Dielectric multilayer film of Example 1 (notch filter)
Layer number Material Thickness (nm)
1 TiO2 90.97
2 H4 80.46
3 TiO2 21.48
4 H4 15.75
5 TiO2 72.96
6 H4 105.54
7 TiO2 104.55
8 H4 15.00
9 TiO2 10.00
10 H4 114.28
11 TiO2 87.41
12 H4 76.74
13 TiO2 78.87
14 H4 137.63
15 TiO2 75.08
16 H4 79.75
17 TiO2 134.95
18 H4 15.00
19 TiO2 27.98
20 H4 37.63
21 TiO2 112.69
22 H4 93.53
23 TiO2 99.87
24 H4 20.25
25 TiO2 10.01
26 H4 75.43
27 TiO2 67.70
28 H4 69.91
29 TiO2 176.53
30 H4 21.43
31 TiO2 199.39
32 H4 15.00
33 TiO2 151.36
34 H4 15.00
35 TiO2 78.92
36 H4 77.50
37 TiO2 86.90
38 H4 53.37
39 TiO2 10.40
40 H4 62.06
41 TiO2 74.14
42 H4 74.14
43 TiO2 96.50
44 H4 139.17
45 TiO2 108.66
46 H4 89.52
47 TiO2 83.31
48 H4 15.00
49 TiO2 15.40
50 H4 81.31
51 TiO2 87.91

Relationship between wavelength and refractive index of TiO2 Wavelength (nm) Refractive index
450 2.365302
550 2.284830
650 2.238846

Relationship between H4 wavelength and refractive index Wavelength (nm) Refractive index
450 1.9825524
550 1.9512684
650 1.9285164

Dielectric multilayer film of Example 2 (notch filter)
Layer number Material Thickness (nm)
1 TiO2 90.23
2 SiO2 188.96
3 TiO2 93.33
4 SiO2 192.20
5 TiO2 96.70
6 SiO2 20.00
7 TiO2 10.00
8 SiO2 76.16
9 TiO2 17.81
10 SiO2 27.83
11 TiO2 58.64
12 SiO2 65.95
13 TiO2 17.33
14 SiO2 42.45
15 TiO2 96.13
16 SiO2 167.97
17 TiO2 120.05
18 SiO2 52.09
19 TiO2 21.81
20 SiO2 29.13
21 TiO2 82.56
22 SiO2 57.22
23 TiO2 10.24
24 SiO2 72.13
25 TiO2 85.77
26 SiO2 34.51
27 TiO2 15.61
28 SiO2 93.12
29 TiO2 100.13
30 SiO2 79.69
31 TiO2 10.00
32 SiO2 91.76
33 TiO2 100.27
34 SiO2 68.96
35 TiO2 10.00
36 SiO2 76.06
37 TiO2 103.49
38 SiO2 196.66
39 TiO2 110.63
40 SiO2 161.61
41 TiO2 101.97
42 SiO2 29.22
43 TiO2 33.71
44 SiO2 30.00
45 TiO2 66.64
46 SiO2 58.53
47 TiO2 10.25
48 SiO2 81.72
49 TiO2 109.88
50 SiO2 188.83
51 TiO2 87.33
52 SiO2 72.18
53 TiO2 10.78
54 SiO2 59.23
55 TiO2 104.12

Relationship between wavelength and refractive index of TiO2 Wavelength (nm) Refractive index
450 2.518380
550 2.432700
650 2.383740

Relationship between SiO2 wavelength and refractive index Wavelength (nm) Refractive index
450 1.439592
550 1.431720
660 1.428768

1,2 prism 1a prism convex surface (joint surface)
2a Prism concave surface (joint surface)
3 Combiner (dielectric multilayer film, notch filter)
Reference Signs List 4 adhesive 5 optical device 6 display element 7 polarizing beam splitter 9 image display device 10 head mounted display (wearable display)
11 frame (supporting member)
12a, 12b Lens 13 Housing EP Pupil IM Display image (image plane)
L1, L2 Ray La Image light Lb External light Lc Center chief ray Ld Chief ray EY Observer's eye

Claims

An optical see-through type image display device for projecting and displaying an image on an observer's eye by superimposing an image on an external scene,
A display element that displays the image, a combiner that simultaneously guides image light from the display element and external light from the external scene to the observer's eye, and joins to act as a plane-parallel plate with respect to the external light. And two prisms that support the combiner at the joint surface thereof,
The joining surface includes a prism convex surface and a prism concave surface,
The combiner is a notch filter made of a dielectric multilayer film having a characteristic of selectively reflecting only at least one light of a specific wavelength,
An image display device satisfying the following conditional expression (1);
0.01 <Δλ deg × 10 6 /fy<0.35 (1)
However,
Δλ deg : the wavelength shift amount [mm / deg.] Of the longest wavelength peak with respect to the change of the incident angle of the light beam from the center of the screen of the displayed image to the notch filter,
[] Indicates the unit, deg. Is the degree of the angle,
The center of the screen in the display image is the origin, the normal of the screen in the display image is the z-axis, the normal of the plane containing the screen central chief ray incident and reflected on the combiner is the x-axis, and the normal of the zx plane is the y-axis. Let (x, y, z) be the local Cartesian coordinate system
fy: focal length [mm] of the central ray of the screen in the y direction,
fy = tan (ΔΘ) / Δy,
Δy: difference between a central ray of the screen and a principal ray having a small angle ΔΘ in the y direction from the central ray of the screen on the screen of the display image,
It is.
The image display device according to claim 1, wherein the following conditional expression (1a) is satisfied.
0.013 <Δλ deg × 10 6 /fy<0.21 (1a)
3. The image display device according to claim 1, wherein an intermediate image of the display image is not formed.
(4) A wearable display having a function of projecting and displaying the video image to an observer's eye in a see-through manner by the combiner by mounting the image display device according to any one of (1) to (3).
5. The wearable display according to claim 4, further comprising a support member that supports the image display device so that the combiner is located in front of an observer's eye.