JP3324705B2 - Achromatized hologram - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an achromatic hologram, and more particularly to a hologram suitable for a combiner for a head-up display.

[0002]

2. Description of the Related Art A head-up display provides an information image of various instruments in front of a window glass in front of a cockpit or a driver's seat and allows the user to view the instrument information without looking away from an external field of view. Thus, there is an advantage that the safety of aircraft, ships, and vehicles is increased.

At present, several automobile companies have released automobiles equipped with a head-up display. However, mirrors provided in or on a window glass called a combiner are all vapor-deposited,
A non-holographic mirror formed by coating or the like is used.

When using a non-holographic mirror,
Since the combiner cannot have a lens function, the size of the projector unit for providing display information cannot be increased, and the distance from the mirror at the position where the display image is formed cannot be too large. There is also a problem that a ghost image is generated due to reflection on the back surface.

In order to improve the problem of the non-holographic mirror, research on a head-up display using a holographic mirror as a combiner has been advanced in recent years.

[0006]

Since the holographic mirror can have a lens function and can separate the angle between the reflected light and the diffracted light, all of the above problems can be solved. However, since the holographic mirror has wavelength selectivity, light of a specific wavelength among light incident from an external field of view is diffracted out of the field of view and does not reach a part of the observer. Have the disadvantage that they appear colored. This is problematic in terms of safety and design, and it is necessary to make the holographic mirror visually colorless.

The present invention has been made in view of such a situation, and an object of the present invention is to provide an achromatic hologram which is colored and invisible, and is particularly suitable for a holographic combiner for a head-up display. To provide an achromatized hologram.

[0008]

The achromatized hologram of the present invention, which achieves the above object, is used for reproduction in a hologram which is multiplex-recorded on a single-layer recording material and can be reproduced by two wavelengths having a complementary color relationship to each other. The position of the image formed by one wavelength is different from the position of the image formed by the other wavelength that is not used in the reproduction. is there.

Another achromatized hologram of the present invention is a hologram which is multiplex-recorded on a single layer of recording material and can be reproduced with three or more wavelengths at which a mixed color becomes white. The position of the image formed by the wavelength is different from the position of the image formed by other wavelengths not used in the reproduction, and it is characterized in that even if white light is transmitted, the image looks white or a color close thereto, and is not colored.

[0010]

These achromatized holograms are suitable for use in holographic combiners for head-up displays of aircraft, ships, vehicles and the like.

[0012]

In the present invention, holograms multiplex-recorded on a single layer of recording material are reproduced by two wavelengths having a complementary color relationship with each other or by three or more wavelengths at which a mixed color becomes white. Even if it passes through white light, it looks white or close to it, does not look colored, and is suitable for a holographic combiner for a head-up display or the like, which requires an apparently colorless appearance. In this case, since the position of the image formed by one wavelength or one wavelength used in the reproduction is different from the position of the image formed by the other wavelength not used in the reproduction, a crosstalk image (ghost image) based on the multiplex recording is obtained. Call blur can be reduced or prevented.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A holographic mirror is provided with diffraction characteristics for a plurality of wavelengths, and if the mixture of colors represented by those wavelengths is white (or a color close to white), light enters the interior through the holographic mirror from the outside. Light appears white (or a color close to it). This is the basic principle of the achromatic hologram of the present invention.

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing the principle of a holographic mirror. Light of a specific wavelength emitted from a light source 2 is diffracted by a holographic mirror 1 and a point 3
A virtual image of the light source 2 is observed at the position. In the conventional holographic mirror 10, as shown in FIG. 2, only the light of a specific wavelength corresponding to the specific wavelength of the light source 2 is diffracted from the white light 4 incident from the outside, And is observed as light having a color complementary to that wavelength. FIG. 2 also shows the wavelength intensity distribution of the incident light 4, the diffracted light 5, and the transmitted light 6, and the intensity of the incident light 4 is normalized.

Therefore, as one embodiment of the present invention,
By creating a hologram that diffracts the light from the light source 2 with the same angular relationship at the two wavelengths a and b that have a complementary color relationship to each other, the incident light 4 is prevented from being colored. That is, such a holographic mirror 1
As shown in FIG. 3, two wavelengths a,
Only the light b is diffracted, and these wavelength components are reduced or eliminated in the transmitted light 6. Since the wavelengths a and b are complementary colors, the transmitted light 6 is white (or close to white). Color).

As a specific example, a holographic mirror 1 was prepared as follows. As a recording material, a 10 wt% gelatin aqueous solution is applied to glass and dried,
A gelatin dry plate having a gelatin film thickness of about 15 μm was prepared, and this gelatin dry plate was treated with an aqueous solution of ammonium bichromate / methylene blue (concentration: 2 wt% of ammonium bichromate).
%, Methylene blue 0.03 wt%) for several minutes,
It was made by drying. Using the recording material 7 thus prepared, the positional relationship between the two diverging points A and B shown in FIG.
That is, the distance of the divergence point A from the recording material 7 is 30 cm,
The incident angle 45 °, the distance 6 of the divergence point B from the recording material 7
Double photographing was performed using a Kr laser (647 nm) and an Ar laser (488 nm) in this order at 0 cm and an incident angle of 60 °. The exposure amount for each wavelength is 200 μJ /
cm ² . Thereafter, as a development treatment, an alum solution (solution composition: 1 liter of water, 120 g of alum, 10 g of glacial acetic acid)
(0 ml, 60 g of anhydrous sodium sulfite) to perform hardening treatment, then dipping in 70% isopropyl alcohol aqueous solution, further immersing in 100% isopropyl alcohol aqueous solution, washing with water, drying, and clearing Holographic mirror 1 is completed. This mirror 1
When I saw the outside world through it, I could not see it colored. In addition,
The fact that the light of the above two wavelengths (647 nm and 488 nm) has a complementary color relationship to each other and that the mirror 1 is colorless and transparent is plotted on the chromaticity coordinates in FIG. A point 8 at a wavelength of 488 nm and a wavelength 64 on the spectral color locus of FIG.
Since the straight line connecting the point 9 of 7 nm passes very close to the white point, it can be said that the two have a substantially complementary color relationship.

In a holographic mirror according to another embodiment of the present invention, the same positional relationship between the object light and the reference light is provided, and two separate single wavelengths are provided by another light whose wavelength is complementary. Create a recording hologram and attach it to one
It is a holographic mirror. The operation is the same as in FIG. As a specific example, SP672 manufactured by Ilford for an Ar laser (488 nm) and a Kr laser (647 nm) are used as recording materials.
Using SP673 Ilford Ltd. as, 2 with an exposure amount of each 200μJ / cm ² by an optical arrangement of FIG. 4
Expose the single-record holographic mirror and develop it as recommended by Ilford to create a 488 nm wavelength holographic mirror and a 647 nm wavelength holographic mirror, and bond them together When I made one holographic mirror, when I looked at the outside world through it, it was not colored.

Further, another embodiment of the colorless holographic mirror of the present invention will be described. In this example, three or more wavelengths that become white (or a color close to it) by mixing colors in one hologram are multiplexed and recorded so as to be diffracted in the same direction. In this case, the wavelength shown in FIG. Although different in that a and b are three or more, even if the external world is viewed through such a hologram as in the first embodiment, it does not look colored. To create such a hologram,
At the time of recording, multiple recording may be performed with the same optical configuration using light sources of different wavelengths that diffract, but using a single light source, changing the degree of swelling during exposure of the recording material, and changing the optical configuration It is realistic to make the interference fringes recorded at the same angle diffract at predetermined three or more wavelengths.

The following three wavelengths are 488 μm and 545 μm.
A specific example of the creation of a holographic mirror that prevents external light from diffracting in the same direction and preventing coloring at m and 633 μm will be described. A single light source (H
Multiple recording was performed using an e-Ne laser (633 nm) and SP-673 manufactured by Ilford Corporation as a recording material.

(1) First recording with the following optical system.

Distance of divergence point A: 30 cm Incident angle: 45 ° Distance of divergent point B: 60 cm Incident angle: 60 ° Exposure amount: 200 μJ / cm ² (2) Immersion in D-sorbitol solution (concentration 10%) for 1 minute , Drying (swelling treatment).

(3) Second recording by the following optical system.

Distance of divergence point A: 26 cm Incident angle: 32 ° Distance of divergent point B: 52 cm Incident angle: 55 ° Exposure amount: 200 μJ / cm ² (4) Immersion in D-sorbitol solution (concentration: 20%) for 1 minute , Drying (swelling treatment).

(5) Third recording by the following optical system.

Distance at divergence point A: 23 cm Incident angle: 25 ° Distance at divergence point B: 46 cm Incident angle: 39 ° Exposure amount: 200 μJ / cm ² (6) Development treatment This was carried out by a method recommended by Ilford Corporation.

According to the above method, 488 μm, 545 μm
A transparent holographic mirror that diffracts light of m and 633 μm was obtained. The points 8, 11, and 12 corresponding to these three wavelengths are plotted on the spectrum color locus on the chromaticity coordinates in FIG. 6, but since the white point is located within the triangle connecting these points, It can be seen that the light of these three wavelengths makes the diffracted light white or a color close thereto, and the transmitted light also looks white or a color close thereto.

In the above achromatized hologram,
Not all recording wavelengths are used,
It is conceivable that the hologram of the third embodiment reproduces a single color, and the hologram of the third embodiment reproduces a single color or two colors.
A hologram formed at the same position with light of different wavelengths causes blur called a crosstalk image (ghost image). Therefore, the position of the image formed by the recording wavelength not used in reproduction is different from the position of the used one. This can reduce or prevent this blurring.

Although the achromatic hologram of the present invention has been described based on the embodiments, the present invention is not limited to these embodiments, and various modifications are possible. For example, the second embodiment can be applied to the case of three or more wavelengths, and the third embodiment can be applied to the case of complementary colors.

[0029]

As is apparent from the above description, according to the achromatic hologram of the present invention, two holograms multiplex-recorded on one layer of recording material have complementary colors to each other.
Reproduced by three wavelengths or by three or more wavelengths in which the mixed color becomes white, it looks white or close to it even through white light, does not look colored, and has a headless color that is apparently colorless It is suitable for a holographic combiner for a display. In that case,
Since the position of the image formed by one wavelength or one wavelength used in the reproduction is different from the position of the image formed by the other wavelength not used in the reproduction, a blur called a crosstalk image (ghost image) based on the multiplex recording is generated. Can be reduced or prevented.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating the principle of a holographic mirror.

FIG. 2 is a diagram for explaining the reason why a conventional holographic mirror is colored.

FIG. 3 is a diagram for explaining the operation of the first embodiment of the present invention.

FIG. 4 is a diagram showing a relationship between a recording material and a light beam when recording according to the first embodiment.

FIG. 5 is a diagram showing chromaticity coordinates in which positions of diffraction wavelengths in the second embodiment are plotted.

FIG. 6 is a diagram showing chromaticity coordinates obtained by plotting the positions of the diffraction wavelengths in the third embodiment.

[Explanation of symbols]

 O: observer 1: holographic mirror 2: light source 3: virtual image of light source 4: incident light 5: diffracted light 6: transmitted light 7: recording material 10: holographic mirror

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-103816 (JP, A) JP-A-5-124456 (JP, A) JP-A-3-148687 (JP, A) JP-A-2- 235085 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03H 1/02 G02B 5 / 08,5 / 32,27 / 02

Claims (3)

(57) [Claims] 1. A hologram which is multiplex-recorded on one layer of recording material and can be reproduced by two wavelengths having a complementary color relationship with each other, wherein the position of an image formed by one wavelength used in the reproduction is not used in the other wavelengths. It is different from the position of the imaging by a white or even through white light
An achromatized hologram characterized by a color that looks similar to it and is invisible . 2. A hologram which is multiplex-recorded on a single layer of recording material and which can be reproduced by three or more wavelengths at which a mixed color becomes white, the position of an image formed by one wavelength used in reproduction. Is different from the position of the image formed by other wavelengths not used in the reproduction, and the white light is not white.
Is an achromatized hologram characterized by the fact that it looks similar to that color but does not look colored . 3. The achromatic hologram according to claim 1, wherein the holographic combiner is used for a holographic combiner for a head-up display of an aircraft, a ship, a vehicle, or the like.