JP4742575B2 - Image display optical system and image display apparatus - Google Patents

Description

  The present invention relates to an image display optical system that is mounted on a see-through image display device such as an eyeglass display and displays a virtual image of an image display element superimposed on an external image, and the image display device.

In recent years, an eyeglass-type / see-through type image display device (eyeglass display) has been proposed (FIG. 14 of Patent Document 1).
In this eyeglass display, an image display element such as an LCD and an image display optical system are fixed to a spectacle frame.
The image display optical system is provided with a combiner such as a thin-film holographic optical element (holographic optical film) or a beam splitter in a transparent substrate having the same appearance as a spectacle lens.

The display light beam emitted from the image display element propagates through the substrate while being internally reflected, and is then deflected by the combiner and is incident on the observation eye at an appropriate angle (FIGS. 7 to 13, 15, and 15 of Patent Document 1). 17 etc.).
Further, the external light flux emitted from the external environment passes through the substrate and enters the observation eye.
Therefore, an observer who wears this eyeglass display on his / her head can simultaneously observe an external image and a virtual image (hereinafter referred to as “display image”) superimposed on the image display element.
JP 2001-264682 A

By the way, when this eyeglass display is used in an extremely bright place (such as outdoors), the external image looks extremely bright with respect to the brightness of the display image. At this time, the pupil of the observation eye shrinks in response to the brightness of the external image.
On the other hand, it is difficult in terms of size and cost to improve the intensity of the display light beam emitted from an image display element such as a small LCD or to adjust it over a wide range.

For this reason, the eyeglass display has a problem that the visibility of the display image when the outside is bright is poor.
Therefore, an object of the present invention is to provide an image display optical system and an image display apparatus that can reliably improve the visibility of a display image when the outside is bright.

The image display optical system of the present invention is disposed in front of the observation eye and deflects the display light beam for image display on a substrate transparent to visible light and the display light beam on the observation eye side of the substrate. An introduction mirror that propagates toward the observation eye while alternately reflecting the inner surface between the surface and the surface on the outside, and the display light flux that has propagated through the substrate is provided in the substrate at a position immediately before the observation eye. A deflection unit that guides the display light beam to the observation eye by deflecting, and a dimming unit is formed in close contact with the entire surface of the substrate on the outside side, and at least the dimming unit The layer closest to the substrate reflects the display light beam propagating through the substrate with a reflectance of approximately 100%, and reduces the external light beam incident from the outside at an incident angle near 0 ° by a predetermined amount. and characterized in that it comprises an optical multilayer film dimming a light rate That.

In addition, the said light reduction part may be comprised from the said optical multilayer film provided in the surface by the side of the external field of the said board | substrate.
The optical multilayer film may be made of a metal and / or a dielectric.

Moreover, the said light reduction part may be comprised from the said optical multilayer film provided in the surface by the side of the external field of the said board | substrate, and the 2nd board | substrate provided in the surface of the optical multilayer film.
The optical multilayer film may be made of a metal and / or a dielectric.

Also, the second substrate may have an absorbent for the visible light.

Further, a second optical film different from the optical multilayer film may be provided on the surface of the second substrate.
The second optical film may be made of a metal and / or a dielectric.

Further, the second optical film may be composed of a holographic optical film.
Further, the second optical film may be composed of the electrochromic film.
Further, the second optical film may be composed of photochromic film.

The deflecting unit may be a combiner that is transparent to the external light flux.

Further, the light reducing portion, the external light beam incident on the combiner, may be dimmed at a high extinction ratio than other external light beam.
The image display device of the present invention includes an image display element that emits a display light beam for image display, and the image display optical system of the present invention that guides the display light beam to the observation eye. To do.

The image display device of the present invention may comprise a mounting means for mounting the image display optical system to the head of the observer.

  ADVANTAGE OF THE INVENTION According to this invention, the image display optical system and image display apparatus which can improve the visibility of the display image when the external field is bright are implement | achieved reliably.

[First Embodiment]
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. 1, 2, 3, 4, 5, and 6.
This embodiment is an embodiment of an eyeglass display.
FIG. 1 is an external view of the present eyeglass display.

As shown in FIG. 1, the present eyeglass display is a monocular eyeglass display that displays an image only on the right eye of the observer. The present invention is also applicable to a monocular eyeglass display that displays an image only on the left eye of the observer, a binocular eyeglass display that displays an image on both eyes of the observer, and the like.
The coordinate system in FIG. 1 is a right-handed XYZ orthogonal coordinate system in which the downward direction is the X direction and the right direction is the Y direction when viewed from the observer wearing the eyeglass display. In the following, the direction expression by the XYZ coordinate system or the left / right / up / down direction expression as viewed from the observer is used as necessary.

As shown in FIG. 1, the present eyeglass display has a substrate 1 and an image display unit 2 fixed to a spectacle frame 3.
The substrate 1 is made of optical glass that is transparent to visible light. The external shape of the substrate 1 is the same as that of a spectacle lens. The fixing location of the substrate 1 is the right front of the spectacle frame 3.
The image display unit 2 is a unit in which an optical system (described later) is arranged. The fixing point of the image display unit 2 is the vicinity of the right front of the spectacle frame 3 (the right temple of the spectacle frame 3 in FIG. 1).

The image display unit 2 is connected to an external device via a cable 4. Power and signals are supplied from the external device to the image display unit 2 via the cable 4.
The substrate 1 is provided with a dimming function for dimming the external light flux from the external environment toward the observer's right eye.
Also, to balance the amount of external light flux from the outside world toward the observer's right eye and the amount of external light flux from the outside world to the left eye of the observer, and to balance the left and right appearance of the eyeglass display Therefore, a board 5 having the same dimming function as that of the board 1 and having the same appearance as that of the board 1 is mounted on the left front of the spectacle frame 3. Note that this is not necessary unless it is necessary to balance the external light flux and the external appearance.

Incidentally, if the left-side configuration of the present eyeglass display is the same as the right-side configuration, a binocular eyeglass display can be realized. Also, if the left and right configurations of the present eyeglass display are reversed, a monocular eyeglass display that displays an image only on the left eye of the observer is realized.
FIG. 2 is a detailed view of the optical system of the present eyeglass display, and is a schematic sectional view formed by cutting the optical system portion of the present eyeglass display along a plane parallel to the YZ plane.

As shown in FIG. 2, the image display unit 2 projects a display light beam L <b> 1 toward the right end portion of the substrate 11.
In the image display unit 2, an LED light source 2a, an illumination optical system 2b, an LCD 2c, an objective lens 2d, a drive circuit (not shown), and the like are arranged. The LED light source 2a, LCD 2c, and drive circuit (not shown) are connected to the cable 4 (see FIG. 1).

An introduction mirror 1A is provided at the right end portion in the substrate 1, and a combiner 1B is provided in the substrate 1 at a position corresponding to immediately before the observer's right eye. The combiner 1B is a deflecting optical film that is transparent to the external light beam L2 made of visible light, such as a half mirror, a polarizing beam splitter, or a holographic optical film.
A dimming film 20 for dimming the external light flux L2 at a predetermined dimming rate is formed on the external surface 1b of the substrate 1.

Among these, the substrate 1 including the introduction mirror 1A and the combiner 1B corresponds to the image display optical system in the claims. The introduction mirror 1A and the combiner 1B correspond to the optical path forming means in the claims. The light reducing film 20 corresponds to the light reducing means in the claims.
Next, the behavior of the display light beam L1 and the external light beam L2 in this eyeglass display will be described in order.

The LED light source 2a and the illumination optical system 2b illuminate the LCD 2c under appropriate illumination conditions. The LCD 2c displays a moving image or a still image. From each position of the LCD 2c, a display light beam L1 of each angle of view is emitted.
Here, the moving image or the still image displayed on the LCD 2c is a color image, and the display light beam L1 includes each wavelength component in the visible light region (wavelength 400 to 700 nm).

The display light beam L1 is converted into a parallel light beam by the objective lens 2d, and then enters the right end portion of the surface 1a on the viewer side of the substrate 1.
In FIG. 2, the display light beam L1 is drawn like a single light beam, but the actual display light beam includes display light beams at various angles of view. The display light flux at each angle of view enters the substrate 1 at different incidence angles near 0 °.

The display light beam L1 incident on the substrate 1 is incident on an introduction mirror 1A provided in the substrate 1. The display light beam L1 incident on the introduction mirror 1A is deflected.
The deflected display light beam L1 propagates in the left direction while alternately reflecting on the surface 1a on the viewer side of the substrate 1 and the surface 1b on the outside world side of the substrate 1 and then the combiner 1B provided in the substrate 1 Is incident on.

The incident angle of the display light beam L1 on the surfaces 1a and 1b is larger than the critical angle θc of the substrate 1 (the minimum value of the incident angle of light that can be reflected from the inner surface), for example, around 50 °.
The display light beam L1 incident on the combiner 1B is deflected in the direction of the observer's right eye. Note that the optical system from the objective lens 2d to the combiner 1B forms an exit pupil (a region where light beams of various angles of view are superimposed and incident) near the pupil position of the right eye.

Incidentally, the display light beam L1 depicted in FIG. 2 is a principal light beam (light beam passing through the center of the exit pupil) of the display light beam (display light beam with a central angle of view) emitted from the center of the LCD 2c among the actual display light beams. is there.
On the other hand, the external light beam L2 is light that is emitted from a sufficiently long distance as viewed from the observer and travels in the direction of the observer.

The external light flux L2 is incident on the dimming film 20 provided on the substrate 1 at an incident angle near 0 °, is attenuated at a predetermined dimming rate, and is then incident on the substrate 1 at an incident angle near 0 °. Incident light passes through the substrate 1 and reaches the right eye of the observer.
With the display light beam L1 and the external light beam L2, the observer can observe the virtual image (display image) of the LCD 2c superimposed on the external image together with the external image. Since the display light beam L1 is converted into a parallel light beam by the objective lens 2d, the position where the display image is formed is sufficiently far from the observer. Further, the brightness of the external image is reduced at a predetermined rate by the function of the light reducing film 20 provided on the substrate 1.

Next, a specific example of the light reducing film 20 will be described.
As a material for a general light-reducing film, a single metal such as aluminum (Al), chromium (Cr), tungsten (W), rhodium (Ro), or an alloy such as Inconel is used.
However, since these materials have a property of absorbing light (absorbability), if a light reducing film 20 is provided on the surface of the substrate 1 unnecessarily, a certain amount of the display light beam L1 that reflects the inside of the substrate 1 internally. Is absorbed by the light-reducing film 20. That is, the light amount loss in the optical path of the display light beam L1 becomes significant.

In the present embodiment, in order to prevent this light loss, a two-layer film in which a silver (Ag) film and a dielectric film are stacked is used as the light reducing film 20. The basic configuration of the dimming film 20 is as follows.
Substrate / Ag / 0.25L / air
Ag: Silver (Ag layer),
L: low refractive index dielectric (L layer),
Numerical value on the left side of the L layer: optical thickness of the L layer (at the center wavelength of the used wavelength)
In this basic configuration, the L layer plays a role of protecting the surface of the Ag layer that easily changes in air and improving the reflectance with respect to incident light having a large incident angle.

The details (specifications) of the dimming film 20 are as follows.
Set transmittance: 30% (at 0 degree incidence),
Center wavelength λc: 500 nm,
Substrate refractive index: 1.56
Ag layer thickness: 30 nm,
Refractive index of L layer: 1.46
Incidentally, the single optical constant of the Ag layer is as shown in FIGS. FIG. 3 shows the wavelength characteristics of the refractive index of the single Ag layer, and FIG. 4 shows the wavelength characteristics of the extinction coefficient of the single Ag layer.

The wavelength characteristics of the reflectance and transmittance (incident angles 0 °, 45 °) on the substrate 1 side of the dimming film 20 are as shown in FIG. Further, the reflectance and transmittance angle characteristics (wavelength 550 nm) of the light-reducing film 20 on the substrate 1 side are as shown in FIG.
5 and 6, “R” indicates the reflectance, and “T” indicates the transmittance. Also, the reflectance or transmittance index “p” indicates the characteristic for the p-polarized light component, and the reflectance or transmittance index “s” indicates the characteristic for the s-polarized light component (the same applies to other figures). .)

As is apparent from FIGS. 5 and 6, the dimming film 20 exhibits a reflectivity of approximately 100% for visible light having an s-polarized component with an incident angle of 40 ° or more. Further, the light reducing film 20 exhibits a transmittance of about 30% with respect to visible light having an incident angle of 0 °.
Therefore, the light reduction film 20 reduces the light amount loss in the optical path of the display light beam L1, and reduces only the external light beam L2 in the visible light region with a light attenuation rate of about 70%.

At this time, the brightness of the display image is maintained and the brightness of the external image is reduced to about 30%. Therefore, the visibility of the display image when the outside is bright is surely increased. Thus, by selecting a preferable film type from the reflection-transmittance characteristics with respect to the incident angle of the dimming film 20, a desired effect can be obtained with a minimum configuration.
The basic configuration of the light reduction film 20 of the present embodiment is a two-layer configuration of an Ag layer and a dielectric layer. However, instead of the Ag layer, another metal layer is used, or two dielectric layers are used. A three-layer structure with a metal layer interposed may be employed. However, the two-layer configuration of the Ag layer and the dielectric layer can easily obtain better characteristics (characteristic that dimmes only the external light beam L2 without increasing the light amount loss of the display light beam L1).

[First Modification of First Embodiment]
Hereinafter, a first modification of the first embodiment will be described with reference to FIG.
This modification is a modification of the light reduction film 20.
The light-reducing film 20 of this modification is made only of a dielectric. The light-reducing film 20 has a film thickness of each layer so that the phase of reflected light at each layer interface has a desired relationship, and various characteristics can be set depending on the phase relationship of the reflected light. Therefore, the degree of freedom of the set transmittance is higher than that of the light reducing film 20 of the first embodiment. There are three basic configurations of the light-reducing film 20 as follows.

Substrate / (0.25H0.25L) ^p 0.25H / air,
Substrate / (0.125H0.25L0.125H) ^p / air,
Substrate / (0.125L0.25H0.125L) ^p / air where
H: High refractive index dielectric (H layer),
L: low refractive index dielectric (L layer),
Numerical value on the left side of each layer: optical film thickness of each layer (at the center wavelength of the used wavelength),
p: Number of stacks of layer groups enclosed in parentheses According to these basic configurations, it is possible to improve the reflectance for specific light and to suppress the transmittance for specific light.

However, in order to surely reduce the brightness of the external image, the design of the light-reducing film 20 arranges a plurality of types of periodic layer groups having different center wavelengths, so that the wavelength range of light with which transmittance can be suppressed is visible. It is necessary to expand to the entire light range.
Furthermore, in order to suppress variation in transmittance due to color, it is necessary to optimize the film thickness of all layers by a computer.

Details (specifications) of the dimming film 20 after optimization are as follows.
Set transmittance: 5%,
Center wavelength λc: 480 nm,
Refractive index of substrate: 1.583,
Refractive index of H layer: 2.3
Refractive index of L layer: 1.46
Total number of layers: 22
The configuration of the light reducing film 20 is as shown in Table 1.

この減光膜２０の透過率の波長特性は、図７に示すとおりである。
図７に明らかなとおり、この減光膜２０は、可視光線に対し約５％の透過率を示す。したがって、本変形例によると、外界像の明るさは、約５％に低減される。

The wavelength characteristic of the transmittance of the light reducing film 20 is as shown in FIG.
As apparent from FIG. 7, the light reducing film 20 exhibits a transmittance of about 5% with respect to visible light. Therefore, according to this modification, the brightness of the external image is reduced to about 5%.

[Second Modification of First Embodiment]
Hereinafter, a second modification of the first embodiment will be described with reference to FIG.
This modification is a modification of the light reduction film 20.
The set transmittance of the light reducing film 20 of this modification is 15%. The dimming film 20 is also made of only a dielectric, and its basic configuration is the same as that of the first modification.

Details (specifications) of the light reduction film 20 are as follows.
Set transmittance: 15%,
Center wavelength λc: 480 nm,
Refractive index of substrate 1.583,
Refractive index of H layer 2.3
Refractive index of L layer 1.46
Total number of layers: 18
The configuration of the light reduction film 20 is as shown in Table 2.

この減光膜２０の透過率の波長特性は、図８に示すとおりである。
図８に明らかなとおり、この減光膜２０は、可視光線に対し約１５％の透過率を示す。したがって、本変形例によると、外界像の明るさは、約１５％に低減される。

The wavelength characteristic of the transmittance of the light reducing film 20 is as shown in FIG.
As apparent from FIG. 8, the light reducing film 20 exhibits a transmittance of about 15% with respect to visible light. Therefore, according to the present modification, the brightness of the external image is reduced to about 15%.

[Supplement of modification]
In the light-reducing film 20 of the first and second modified examples, the condition that the brightness of the display image is reliably maintained, that is, the condition that the display light beam L1 is internally reflected in the substrate 1 with a reflectance of about 100%. Considering from the condition of internal reflection of the substrate 1.
First, as shown in FIG. 9A, a state where the light reducing film 20 is not provided on the substrate 1 is considered.

When the refractive index of air, which is a medium on which the substrate 1 exists, is n ₀ , the refractive index of glass, which is the material of the substrate 1, is _ng , and the incident angles of light on the substrate 1 and the medium are θ ₀ and θ _g respectively. The following formula (1) is established from Snell's law.
n ₀ sin θ ₀ = n _g sin θ _g (1)
Therefore, the critical angle θc of the substrate 1 in this state (the minimum value of the incident angle of light that can be reflected from the inner surface) is expressed by Expression (2).

θc = arcsin (n ₀ / _ng ) (2)
Next, as shown in FIG. 9B, a state in which the substrate 1 is provided with a dimming film 20 made of a dielectric multilayer film is considered. If each layer of the multilayer film is non-absorbing (absorbance zero), the refractive index of each layer of the multilayer film is n ₁ , n ₂ ,..., N _k , and the incident angle of light of each layer is θ ₁ , If θ ₂ ,..., θ _k are set, the following equation (3) is established from Snell's law.

n ₀ sin θ ₀ = n ₁ sin θ ₁
= N ₂ sin θ ₂ ,
...
= N _k sin θ _{k
= N g sinθ g ··· (3} )
Therefore, if each layer of the multilayer film is non-absorbing, the critical angle θc of the substrate 1 is expressed by the expression (2), as in the state where the dimming film 20 is not provided.

Therefore, a non-absorbing dielectric is used for the light-reducing film 20 of the first modification and the second modification.
Incidentally, the angle characteristics of the reflectance on the substrate 1 side (the reflectance of the internal reflection of the substrate 1) of the light-reducing film 20 of the first and second modified examples using the non-absorbing dielectric are shown in FIG. As shown in
As is apparent from FIG. 10, the dimming film 20 exhibits a reflectance of about 100% for light having an incident angle of 45 ° or more.

[Third Modification of First Embodiment]
Hereinafter, a third modification of the first embodiment will be described with reference to FIGS. 11, 12, 13, and 14.
This modification is a modification of the light reduction film 20.
The light-reducing film 20 of this modification is given a function of cutting ultraviolet rays and infrared rays.

The dimming film 20 is also made of only a dielectric, and its basic configuration is the same as that of the first modification or the second modification.
In this modification, in order to provide the function of cutting ultraviolet rays and infrared rays, an absorptive dielectric is positively used for the H layer. Titanium dioxide (TiO ₂ ) is used as an absorptive dielectric.

Incidentally, the optical constants of titanium dioxide (TiO ₂ ) are as shown in FIGS. FIG. 11 shows the wavelength characteristic of the refractive index of titanium dioxide (TiO ₂ ), and FIG. 12 shows the wavelength characteristic of the titanium dioxide (TiO ₂ ) extinction coefficient.
Details (specifications) of the light reduction film 20 are as follows.
Set transmittance: 30%,
Center wavelength λc: 800 nm,
Refractive index of substrate: 1.583,
Refractive index of L layer 1.46
Total number of layers: 48
The configuration of the light reducing film 20 is as shown in Table 3.

この減光膜２０の透過率の波長特性は、図１３に示すとおりである。また、本変形例の減光膜２０の基板１側の反射率（基板１の内面反射の反射率）の波長特性は、図１４に示すとおりである。

The wavelength characteristic of the transmittance of the dimming film 20 is as shown in FIG. Further, the wavelength characteristic of the reflectance on the substrate 1 side of the light-reducing film 20 of this modification (the reflectance of the internal reflection of the substrate 1) is as shown in FIG.

As is apparent from FIG. 14, the wavelength characteristic curve of the reflectance has a dent (reflectance valley).
On the other hand, in the curve of the emission wavelength characteristic of the LCD 2c of the eyeglass display, peaks are generally generated at the wavelengths of R color, G color, and B color.
Therefore, the configuration of the dimming film 20 of this modification is finely adjusted so that the valley of the reflectance wavelength characteristic curve deviates from the peak of the emission wavelength characteristic curve.

As a result, each wavelength component contained in the display light beam L1 is reliably internally reflected with a high reflectance in the substrate 1. Therefore, the brightness of the display image is reliably maintained.
By the way, referring to FIG. 14, the way in which the valley is generated differs between the curve of the s-polarized component and the curve of the p-polarized component. In particular, the number of valleys generated in the p-polarized component curve is smaller.

Therefore, when the dimming film 20 is applied to an eyeglass display, if the display light beam L1 is limited to only the p-polarized light component, the valley of the wavelength characteristic curve of the reflectance can be assured from the peak of the emission wavelength characteristic curve. Can be removed.
Incidentally, since the display light beam L1 is polarized in accordance with the principle of the LCD 2c, the positional relationship between the LCD 2c and the substrate 1 is optimized so that the polarization direction is the p-polarization direction with respect to the dimming film 20, or the LCD 2c If a phase plate is inserted in the subsequent stage, the display light beam L1 can be limited to only the p-polarized component.

[Second Embodiment]
Hereinafter, a second embodiment of the present invention will be described with reference to FIG. 15, FIG. 16, and FIG.
This embodiment is an embodiment of an eyeglass display. Here, only differences from the first embodiment will be described.
FIG. 15 is an external view of the present eyeglass display.

The coordinate system in FIG. 15 is a right-handed XYZ orthogonal coordinate system in which the downward direction when viewed from the observer is the X direction and the right direction is the Y direction. In the following, the direction expression by the XYZ coordinate system or the left / right / up / down direction expression as viewed from the observer is used as necessary.
As shown in FIG. 15, the difference from the first embodiment of the present eyeglass display is that the light attenuation rate of the central region in the vicinity of the combiner 1 </ b> B in the substrate 1 is different from that in the peripheral region in the substrate 1. It is in a point set higher than the dimming rate.

  In addition, to balance the light quantity of the external light flux from the outside world toward the observer's right eye and the light quantity of the external light flux from the outside world to the left eye of the observer, it also balances the left and right appearances of the eyeglass display. Therefore, a board 5 having the same dimming function as that of the board 1 and having the same appearance as that of the board 1 is mounted on the left front of the spectacle frame 3. Note that this does not apply if it is not necessary to balance the external light flux and the external environment.

FIG. 16 is a detailed view of the optical system of the present eyeglass display, and is a schematic sectional view formed by cutting the optical system portion of the present eyeglass display along a plane parallel to the YZ plane.
As shown in FIG. 16, the behavior of the display light beam L1 and the external light beam L2 in the present eyeglass display is the same as that of the first embodiment (see FIG. 2).
A dimming film 20 similar to that of the first embodiment or a modification thereof is provided on the surface 1 b on the outside world side of the substrate 1.

However, in the central region of the surface of the light reducing film 20, a light reducing film 40 made of a metal or dielectric multilayer film is provided in an overlapping manner.
Thereby, the light attenuation rate of the central region of the substrate 1 becomes higher than the light attenuation rate of the peripheral region of the substrate 1.
Note that the position of the central region viewed from the observer is substantially the same as the position of the combiner 1B viewed from the observer. Further, the size of the central region viewed from the observer is slightly larger than the size of the combiner 1B viewed from the observer.

In such an eyeglass display, the brightness of the external image in the portion serving as the background of the display image is particularly strongly suppressed, so that the visibility of the display image is further enhanced.
Next, specific examples of the light reducing films 20 and 40 will be described.
As in the modification of the first embodiment, the dimming film 20 is composed of a dielectric multilayer film. The dimming film 40 is also composed of a dielectric multilayer film.

Details (specifications) of the dimming films 20 and 40 are as follows.
Set transmittance of the light-reducing film 20: 50%,
The set transmittance of the light reducing film 40: 50%,
Center wavelength λc: 800 nm,
Refractive index of substrate 1.583,
Refractive index of H layer 2.3
Refractive index of L layer 1.46
Total number of light-reducing films 20: 11,
Total number of light-reducing films 40: 16
The configuration of the light-reducing films 20 and 40 is as shown in Table 4.

減光膜２０，４０の中央領域の透過率の波長特性、減光膜２０の周辺領域の透過率の波長特性は、図１７に示すとおりである。
図１７に明らかなとおり、中央領域の可視光に対する透過率は約２５％、周辺領域の可視光に対する透過率は約５０％である。

The wavelength characteristics of the transmittance in the central region of the light reducing films 20 and 40 and the wavelength characteristics of the transmittance in the peripheral region of the light reducing film 20 are as shown in FIG.
As apparent from FIG. 17, the transmittance for visible light in the central region is about 25%, and the transmittance for visible light in the peripheral region is about 50%.

Therefore, according to the present eyeglass display, the overall brightness of the outside world image is reduced to about 50%, and the brightness of the outside world image in the portion serving as the background of the display image is reduced to about 25%.
In the present embodiment, the dimming film 20 and the dimming film 40 are superposed, but they may not be superposed. In that case, the light-reducing film 20 having an opening in the central region is provided on the substrate 1, and the light-reducing film 40 having a light attenuation rate higher than that of the light-reducing film 20 is provided in the opening. However, in this case, since it is necessary to perform masking both when the light-reducing film 20 is formed and when the light-reducing film 40 is formed, the light-reducing film 20 and the light-reducing film 40 are overlapped. However, it is desirable in that the manufacturing cost can be reduced.

[First Modification of Second Embodiment]
Hereinafter, a first modification of the second embodiment will be described with reference to FIGS. 18 and 19.
This modification is a modification of the light reduction film 20 and the light reduction film 40.
The light-reducing film 40 of this modification is composed of a metal film.
The configuration of the light-reducing film 20 of this modification is the same as that shown in Table 2. The single characteristics of the light-reducing film 20 are as shown in FIG.

The dimming film 40 has a single layer of chromium (Cr) with a thickness of 5 mm. At this time, the wavelength characteristic of the transmittance in the central region of the light-reducing films 20 and 40 is as shown in FIG.
Further, the angle characteristic (however, the characteristic in the central region) of the reflectance of the light reducing film 20 on the substrate 1 side (the reflectance of the internal reflection of the substrate 1) is as shown in FIG.
As apparent from FIG. 19, the reflectance of the light having an incident angle of 40 ° or more with respect to the s-polarized component is a high numerical value. However, the reflectance of the light with respect to the p-polarized component is low. Therefore, when the dimming films 20 and 40 of this modification are applied to an eyeglass display, it is desirable to limit the display light beam L1 to only the s-polarized component.

Incidentally, because the display light beam L1 is polarized in accordance with the principle of the LCD 2c, the positional relationship between the LCD 2c and the substrate 1 is optimized so that the polarization direction is the s-polarization direction, or a phase plate is inserted after the LCD 2c. Then, the display light beam L1 can be limited to only the s-polarized component.
[Second Modification of Second Embodiment]
Hereinafter, a second modification of the second embodiment will be described with reference to FIGS.

This modification is a modification of the light reduction film 20. The light-reducing film 20 of this modification is made of a holographic optical film.
In the production of the holographic optical film, exposure is performed twice.
The first exposure is exposure for imparting the holographic optical film with such a characteristic that light having an incident angle of about 0 ° is transmitted with a predetermined transmittance. This exposure is performed, for example, with an optical system as shown in FIG.

  That is, two light beams are incident on the hologram photosensitive material 56 vertically. An optical attenuator 52 is inserted into one light beam. The transmittance value can be set by the attenuation amount of the optical attenuator 52. In FIG. 20, 51 is a laser light source (can emit laser light of each wavelength of R color, G color, and B color), BS is a beam splitter, M is a mirror, 53 is a beam expander, and 55 is a beam splitter. It is.

The second exposure is exposure for ensuring the reflectivity of the display light beam L1 that is internally reflected in the substrate 1. This exposure is performed, for example, with an optical system as shown in FIG.
That is, two light beams are incident on the hologram photosensitive material 56 at the same angle as the display light beam L 1 that is internally reflected in the substrate 1. In FIG. 21, 51 is a laser light source (can emit laser light of each wavelength of R color, G color, and B color), BS is a beam splitter, M is a mirror, 53 is a beam expander, and 57 is an auxiliary prism. It is.

After the completion of the two exposures, the hologram photosensitive material 56 is developed to complete a holographic optical film.
The completed holographic optical film is provided with a function required for the dimming film 20.
In this modification, the dimming film 20 is a holographic optical film. However, the dimming film 20 and the dimming film 40 may be formed of a single holographic optical film.

In the manufacture of the holographic optical film, the first exposure is performed in two steps.
One of them is exposure of the central region of the holographic optical film (peripheral region is masked), and the other one is exposure of the peripheral region (the central region is masked). )
In these two exposures, the attenuation amount of the optical attenuator 52 is set to a different value. Thereby, the transmittance of the central region of the holographic optical film and the transmittance of the peripheral region are set to different values.

[Third Embodiment]
Hereinafter, a third embodiment of the present invention will be described with reference to FIGS. 22, 23, 24, and 25.
This embodiment is an embodiment of an eyeglass display. Here, only differences from the first embodiment will be described.
FIG. 22 is an external view of the present eyeglass display.

The coordinate system in FIG. 22 is a right-handed XYZ orthogonal coordinate system in which the downward direction when viewed from the observer is the X direction and the right direction is the Y direction. In the following, the direction expression by the XYZ coordinate system or the left / right / up / down direction expression as viewed from the observer is used as necessary.
As shown in FIG. 22, the appearance of the present eyeglass display is substantially the same as that of the first embodiment (see FIG. 1).

FIG. 23 is a detailed view of the optical system of the present eyeglass display, and is a schematic sectional view formed by cutting the optical system portion of the present eyeglass display along a plane parallel to the YZ plane.
As shown in FIG. 23, the behavior of the display light beam L1 and the external light beam L2 in the eyeglass display is the same as that of the first embodiment (see FIG. 2).
A first optical film 60 is provided on the surface 1 b on the outside world side of the substrate 1. A second substrate 70 made of optical glass is attached to the surface of the first optical film 60. A second optical film 80 is provided on the surface of the second substrate 70.

The first optical film 60 has the same function as the air gap with respect to the substrate 1. That is, the interface on the substrate 1 side of the first optical film 60 reflects the display light beam L1 with a reflectance of approximately 100%. The first optical film 60 transmits the external light beam L2. The first optical film 60 may be provided with a visible light dimming function or an ultraviolet ray or infrared ray cutting function.
The second substrate 70 and the second optical film 80 have a function of dimming the external light flux L2. It should be noted that the second substrate 70 and the second optical film 80 may also be provided with a visible light attenuation function or an ultraviolet ray or infrared ray cut function.

In the present eyeglass display, the function of the first optical film 60 ensures the reflectivity of the display light beam L1 that is internally reflected in the substrate 1, so that the second substrate 70 and the second optical film 80 are There is no need to provide a function for increasing the reflectance of the display light beam L1.
Therefore, the degree of freedom in designing the second substrate 70 and the second optical film 80 is high. For example, various existing optical filter glasses can be applied to the second substrate 70.

Therefore, a higher dimming function can be imparted to the second substrate 70 and the second optical film 80.
In addition, a high light reduction function refers to, for example, that there is little variation in the light attenuation rate due to the incident angle, and that there is little variation in the light attenuation rate due to the wavelength.
Next, a specific example of the first optical film 60 will be described. Here, a case where the display light beam L1 is limited to only the s-polarized component will be described.

The configuration of the first optical film 60 is as follows.
Substrate / (0.125L0.28H0.15L) (0.125L0.25H0.125L) ⁴ (0.15L0.28H0.125L) / Second substrate However,
H: High refractive index dielectric (H layer),
L: low refractive index dielectric (L layer),
Numerical value on the left side of each layer: optical film thickness of each layer (at the center wavelength of the used wavelength),
Superscript number: number of stacking of layer group enclosed in parentheses Details (specifications) of the first optical film 60 are as follows.

Center wavelength λc = 850 nm,
Substrate refractive index: 1.56
Refractive index of H layer: 2.30,
Refractive index of L layer: 1.48,
Refractive index of the second substrate: 1.507,
Second substrate extinction coefficient k = 0.01
Incidentally, the reason why the extinction coefficient k of the second substrate 70 is set to a large value such as 0.01 is that various optical filter glasses are applied to the second substrate 70, so This is because it is assumed that a good dimming characteristic and a wavelength cut function are given.

  Table 5 shows the relationship between the extinction coefficient k and the transmittance of a glass substrate having a refractive index of 1.50 and a thickness of 1 mm.

この表５から、消衰係数ｋの実質的な最大値は、０．０１であることがわかる。
よって、第２の基板７０の消衰係数ｋを０．０１に設定しておけば、第２の基板７０に如何なる光学フィルタガラスを適用した場合にも有効な、第１の光学膜６０を設計することができる。

From Table 5, it can be seen that the substantial maximum value of the extinction coefficient k is 0.01.
Therefore, if the extinction coefficient k of the second substrate 70 is set to 0.01, the first optical film 60 that is effective when any optical filter glass is applied to the second substrate 70 is designed. can do.

The wavelength characteristic (incidence angle 0 °, 60 °) of the reflectance on the substrate 1 side of the first optical film 60 is as shown in FIG.
Further, the angle characteristic of the reflectance of the first optical film 60 on the second substrate 70 side is as shown in FIG.
As is apparent from FIGS. 24 and 25, the first optical film 60 exhibits an average reflectance of 10% or less with respect to the s-polarized light component of visible light having an incident angle of 0 °, and visible light having an incident angle of 60 °. The reflectivity is approximately 100% with respect to the s-polarized component.

As described above, any optical filter glass can be used as the second substrate 70. In other words, any commercially available optical filter glass such as an infrared cut, an ultraviolet cut, a color filter, a neutral intensity filter (a filter that uniformly attenuates all wavelengths in the visible light region), and the like can be applied to the second substrate 70.
Further, any film suitable for protecting the surface of the second substrate 70, such as an antireflection film, can be applied to the second optical film 80. Preferably, a film that achieves desired performance in combination with the second substrate 70 is applied to the second optical film 80.

For example, a neutral intensity filter may be applied to the second substrate 70, and an infrared cut film may be applied to the second optical film 80. Further, an ultraviolet cut glass may be applied to the second substrate 70, and a light reducing film and an infrared cut film may be applied to the second optical film 80.
That is, the combination of the second substrate 70 and the second optical film 80 can be appropriately selected according to the performance required for the eyeglass display, the manufacturing cost of the eyeglass display, and the like.

Incidentally, various filters, various types and functions of the multi-layer film of, for example, since it is described in detail in books such as HAMacleod al., "Thin-Film optical Filters 3 ^rd .Edition", is omitted here.
In the configuration of the first optical film 60 described above, the reason why the one-cycle layer group is arranged on both sides of the multiple-cycle layer group is that the refractive index of the first optical film 60 and the substrate 1 is This is for mismatch adjustment and for refractive index mismatch adjustment between the first optical film 60 and the second substrate 70 (that is, a layer group of one period is a matching layer). The matching layer plays a role of finely correcting the characteristics of the first optical film 60, such as reducing ripples in a wavelength band where the transmittance should be suppressed.

[Modification of Third Embodiment]
Note that the first optical film 60 may have a configuration different from the above-described configuration. Each configuration includes an appropriate periodic layer group. In addition, it is desirable that any configuration be optimized by a computer.
Further, as a combination of the second optical film 80 and the second substrate 70, a combination of a metal film such as chromium (Cr) and an optical glass substrate having a small extinction coefficient k is also applicable.

Various functional thin films such as an electrochromic film (EC film) and a photochromic film (PC film) may be applied to the second optical film 80.
If an electrochromic film (EC film) is applied, the presence or absence of dimming can be selected according to the usage status of the eyeglass display by the energization operation by the user. For example, when a user uses an eyeglass display outdoors during the day, the light is dimmed when the external image is extremely bright, and when the eyeglass display is used indoors, the light is dimmed. You can choose not to.

According to the operation, both the visibility of the external image and the visibility of the display image are maintained regardless of the usage state of the eyeglass display.
If a photochromic film (PC film) is applied, the external light beam L2 is automatically dimmed only when the light amount of the external light beam L2 is high. Both the visibility and the visibility of the display image are automatically maintained.

The application of the functional thin film described above significantly improves the performance of the eyeglass display.
In the present eyeglass display, as in the second embodiment, it is easy to set the light attenuation rate of the central region of the substrate 1 higher than the light attenuation rate of the peripheral region of the substrate 1.
For example, the second substrate 70 may be configured with a neutral intensity filter, the second optical film 80 may be configured with a dimming film, and the formation region of the second optical film 80 may be limited to only the central region. .

  Further, in the present eyeglass display, the first optical film 60 can also be composed of a holographic optical film. The optical system shown in FIG. 21 can be used for manufacturing the holographic optical film. However, since the first optical film 60 is sandwiched between the substrate 1 and the second substrate 70 in use, auxiliary prisms of the same type as those substrates are arranged in the optical paths of the two light beams in FIG. The

  Further, in the present eyeglass display, the second optical film 80 can be constituted by a holographic optical film.

It is an external view of the eyeglass display of 1st Embodiment. It is detail drawing of the optical system of the eyeglass display of 1st Embodiment. It is a wavelength characteristic of the refractive index of an Ag layer. It is a wavelength characteristic of the extinction coefficient of an Ag layer. It is the wavelength characteristic of the reflectance by the side of the board | substrate 1 of the light attenuation film 20 of 1st Embodiment, and the transmittance | permeability. It is the angle characteristic of the reflectance by the side of the board | substrate 1 of the light attenuation film 20 of 1st Embodiment, and the transmittance | permeability. It is the wavelength characteristic of the transmittance | permeability of the light reduction film | membrane 20 of the 1st modification of 1st Embodiment. It is the wavelength characteristic of the transmittance | permeability of the light reduction film | membrane 20 of the 2nd modification of 1st Embodiment. FIG. 9A is a diagram for explaining reflection at the interface on the air side of the substrate 1, and FIG. 9B is a diagram for explaining reflection at the interface on the dimming film 20 side of the substrate 1. It is an angle characteristic of the reflectance by the side of the board | substrate 1 of the light attenuation film 20 of a 1st modification and a 2nd modification. It is a wavelength characteristic of the refractive index of titanium dioxide (TiO ₂ ). It is a wavelength characteristic of the extinction coefficient of titanium dioxide (TiO ₂ ). It is the wavelength characteristic of the transmittance | permeability of the light reduction film | membrane 20 of the 3rd modification of 1st Embodiment. It is a wavelength characteristic of the reflectance by the side of the board | substrate 1 of the light attenuation film 20 of the 3rd modification of 1st Embodiment. It is an external view of the eyeglass display of 2nd Embodiment. It is detail drawing of the optical system of the eyeglass display of 2nd Embodiment. These are the wavelength characteristics of the transmittance in the central region of the light reducing films 20 and 40 and the wavelength characteristics of the transmittance in the peripheral region of the light reducing film 20. It is a wavelength characteristic of the transmittance | permeability of the center area | region of the light attenuation films 20 and 40 of the 1st modification of 2nd Embodiment. It is an angle characteristic (characteristic in a center area | region) of the reflectance by the side of the board | substrate 1 of the light attenuation film 20 of the 1st modification of 2nd Embodiment. It is a figure explaining the 1st exposure in manufacture of a holographic optical film. It is a figure explaining the 2nd exposure in manufacture of a holographic optical film. It is embodiment of the eyeglass display of 3rd Embodiment. It is detail drawing of the optical system of an eyeglass display. This is a wavelength characteristic of the reflectance of the first optical film 60 on the substrate 1 side. This is an angle characteristic of the reflectance of the first optical film 60 on the second substrate 70 side.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Board | substrate 2 Image display unit 3 Eyeglass frame 4 Cable 2a LED light source 2b Illumination optical system 2c LCD
2d Objective lens 1A Introduction mirror 1B Combiner 20, 40 Dimming film L1 Display light beam L2 External light beam 51 Laser light source BS, 55 Beam splitter M Mirror 53 Beam expander 56 Hologram photosensitive material 57 Auxiliary prism 60 First optical film 70 Second Substrate 80 Second optical film

Claims (15)

A substrate placed in front of the observation eye and transparent to visible light;
An introduction mirror for deflecting the display light beam for image display and propagating the display light beam toward the observation eye while alternately reflecting the inner surface of the substrate on the observation eye side surface and the external surface side surface;
A deflection unit that is provided in the substrate immediately before the observation eye and deflects the display light beam that has propagated through the substrate to guide the display light beam to the observation eye;
A dimming portion is formed in close contact with the entire area of the outer surface of the substrate,
At least the layer on the most substrate side of the dimming part is
An optical multilayer film that reflects the display light beam propagating through the substrate with a reflectivity of approximately 100% and attenuates the external light beam incident from the outside at an incident angle near 0 ° with a predetermined attenuation rate. image display optical system, characterized by comprising. The image display optical system according to claim 1,
The dimming part is
An image display optical system comprising the optical multilayer film provided on a surface of the substrate on the outside world side. The image display optical system according to claim 2,
The optical multilayer film is
An image display optical system comprising a metal and / or a dielectric. The image display optical system according to claim 1,
The dimming part is
An image display optical system comprising: the optical multilayer film provided on a surface of the substrate on the outside world side; and a second substrate provided on a surface of the optical multilayer film. The image display optical system according to claim 4 ,
The optical multilayer film is
An image display optical system comprising a metal layer and a dielectric. In the image display optical system according to claim 4 or 5 ,
The second substrate is
An image display optical system characterized by having an absorbability with respect to the visible light. The image display optical system according to any one of claims 4 to 6 ,
On the surface of the second substrate,
An image display optical system, wherein a second optical film different from the optical multilayer film is provided. The image display optical system according to claim 7 ,
The second optical film includes:
An image display optical system comprising a metal and / or a dielectric. The image display optical system according to claim 7 ,
The second optical film includes:
An image display optical system comprising a holographic optical film. The image display optical system according to claim 7 ,
The second optical film includes:
An image display optical system comprising an electrochromic film. The image display optical system according to claim 7 ,
The second optical film includes:
An image display optical system comprising a photochromic film. In the image display optical system according to any one of claims 1 to 11 ,
The image display optical system, wherein the deflection unit is a combiner that is transparent to the external light flux. The image display optical system according to claim 12 , wherein
The dimming part is
An image display optical system, wherein the external light beam incident on the combiner is attenuated with a higher attenuation rate than other external light beams. An image display element for emitting a display light beam for image display;
An image display apparatus comprising: the image display optical system according to any one of claims 1 to 13 , which guides the display light beam to the observation eye. The image display device according to claim 14 ,
An image display device comprising: mounting means for mounting the image display optical system on the head of the observer.

Images