JPH02141787A - Reflection type hologram and its manufacture - Google Patents

Abstract

PURPOSE:To enable reproduction by a light source which differs in wavelength from a light source for exposure without varying the thickness of a hologram by performing the exposure during the reproduction so that the angle between laser light beams in two directions in a photosensitive material is different from the angle between incident light and diffracted light in the photosensitive material. CONSTITUTION:The reflection type hologram 3 where the wavelength of the laser light source for the exposure and the wavelength of the light source for the reproduction are different is exposed so that the angle 2thetae between the laser light beams in two directions in the photosensitive material is different from the angle 2thetar between the incident light and diffracted light which is the sum of an incidence angle thetar1 and a diffraction angle thetar2 in the reproduction. Consequently, when the light sources for the reproduction and exposure are different in wavelength, the hologram thickness need not be varied by a heat treatment, etc., and the reproduction is performed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a reflection hologram in which diffracted light is emitted on the same side as a reproduction light source with the hologram surface as a boundary, and particularly relates to a reflection type hologram in which diffracted light is emitted on the same side as a reproduction light source with the hologram surface as a boundary. This invention relates to a reflection hologram reproduced by a light source.

[Conventional technology]

Since a laser light source is used as a light source to create a reflection hologram, the wavelength of exposure is limited and usually does not match the wavelength of the light source during reproduction.
In such cases, conventional methods such as heat treatment and chemical treatment are used to expand or contract the thickness of the hologram.
The method used was to change the grid spacing.

[Problem that the invention seeks to solve]

However, in such a conventional method, especially when the hologram has a large area, it is difficult to uniformly change the thickness, and therefore the reflected image is optically distorted.

The present invention has been made in view of these points, and allows the wavelength λ of the light source during exposure to be adjusted without changing the hologram thickness.
It is an object of the present invention to provide a reflection hologram that can be reproduced with a light source having a wavelength λr different from e.

[Means for solving problems]

The present invention has a wavelength λe of a light source during exposure and a wavelength λe of a light source during reproduction.
A reflection type hologram with different r is characterized in that during reproduction, the angle 2θr formed by the incident light and the diffracted light in the sensitive material is different from the angle 2θe formed by laser beams from two directions in the sensitive material. do.

Furthermore, in the case of a reflection hologram placed on a laminated glass made by bonding two sheets of glass with a polyvinyl butyral film, the manufacturing method involves predicting the change in the thickness of the reflection hologram during playback, and then predicting the change in the thickness of the reflection hologram during playback. The photosensitive material is characterized in that the angle 2θe formed by the laser beams from two directions in the sensitive material is exposed to be different from the angle 2θr formed by the incident light and the diffracted light in the material.

[Effect]

Wavelength λe of the laser light source during exposure and λr of the light source during reproduction
For reflection holograms with different angles, the incident angle θ during reproduction is
FIG. 3 shows a partial longitudinal cross-sectional view of the photosensitive material, where r1, the diffraction angle θr2, and the refractive index of the photosensitive material are n (the refractive index of air is 1).
a), (b), (The action will be explained in a two-dimensional manner based on C1.

■ Incident light and diffracted light in the photosensitive material are si according to Snell's law.
nθr'+=(1/n)sinθrlSsinθr'
It is refracted to satisfy z□ (1/n) sin θr2 and intersects at the lattice plane AB.

(2) If the angle formed by the incident light and the diffracted light in the photosensitive material is 2θr, then 2θr=θr”1+θr12.

The normal to the lattice plane is created by the incident light and the diffracted light.

If the angle between the surface of the photosensitive material and the lattice plane is φ, then the direction of the lattice plane is determined.

■ The spacing between lattice planes is 2n cos according to Bragg's condition.
θr is determined.

■ When dichromate gelatin is used as a sensitive material, the thickness shrinks by 2 to 6% due to the heat during the bonding process, and the hologram thickness is predicted to change from Tb to Ta as shown in Figure 3 (bl). Or, if a photopolymer is used as the sensitive material and a reflective hologram is placed on laminated glass in contact with the polyvinyl butyral film, it may depend on the type of polyvinyl butyral film, especially the type of plasticizer mixed in. If the thickness of the hologram with interference fringes is expected to change from Tb to Ta, the lattice plane will change from the solid line AJ 1Azo, A, E--- to the dotted line A, 'B
, A, "D18 IE ---, so Tb/l CB l = tanφb (IcBI is C
8) Ta/CB = tanφa Tb,', tanφb=(-tanφa)Ta, and if the lattice spacing db becomes da, then DE l sinφb=db DE sinφa”da, so sin φa and Become.

■ As shown in Figure 3 (C), the wavelength λe of the light source during exposure
The incident angles of the two incident lights in the photosensitive material are θe′ and θ
If e+8 is the angle between the normal to the lattice plane and the incident light, then the Bragg's line ndb is obtained, and the angle between the two incident lights in the photosensitive material is 2θe.

Hereinafter, the incident angles θe and θe of the laser light source from two directions outside the photosensitive material are determined by the procedure in reverse of the procedure (2).

are respectively sin θe, = n sin θe.

sinθe2=nsinθe′! The input should be as follows. In other words, in a reflection type hologram that is different from the wavelength λe of the light source during exposure and the wavelength λr of the light source during reproduction, the angle 2θr between the incident light and the diffracted light in the sensitive material during reproduction, and the laser beam from two directions in the sensitive material. It is only necessary to perform exposure with different angles 2θe formed by the light. Also,
When dichromate gelatin is used as the sensitive material, the thickness becomes 2-6% thinner through lamination processing, and a photopolymer is used as the sensitive material, and a reflective hologram is placed on the laminated glass so that it is in contact with the polyvinyl butyral film. In this case, the present inventors have obtained the knowledge that the hologram thickness increases by 15% and changes during processing when the plasticizer is blended with tetraethylene glycol diN-heptanoate. This further makes the present invention useful. Note that if there is almost no change in the thickness of the hologram, it is sufficient to delete the operation (■).

〔Example〕

Hereinafter, the present invention will be described in detail with reference to the drawings.

Figure 1 shows a schematic exploded view of the main parts of the reflection hologram of the present invention applied to the front laminated window glass of an automobile as a combiner for a head-up display, and Figure 2 shows the optical system for producing the reflection hologram. Figure 3 (al
, (bl, (C1 is a partial vertical cross-sectional view of a photosensitive material for explaining the present invention in detail, and shows the times of reproduction, change in thickness of the photosensitive material, and exposure, respectively).

As shown in FIG. 1, an application example will be explained in which the reflection hologram of the present invention is attached to the front window glass of an automobile as a combiner for a head-up display.

Two sheets of glass 1.1° are bonded together with polyvinyl butyral as an interlayer film 2.2°, and between the interlayer film 2.2°,
A reflection hologram 3 produced by a method described later is enclosed as a combiner, and display information projected from a display device 4 such as a fluorescent display tube is reflected by the reflection hologram 3 to be visually recognized by the driver's eyes 5. .

Electroluminescence with λr = 585 nm (yellow) is used as a light source for reproduction, and the incident angle θr is set to 30
degree, diffraction angle θr2 was reproduced at 35°, dichromate gelatin (refractive index 1.55
), if the exposure incident angles of the laser beam in two directions during exposure are determined by the method described above, φa =
1.45°, da=201.2om, thickness change 95
%, φb = 1.5°, db = 207.4 om, and θe = 35.3°, θez = 38.3°. At this time, the angle 2θr formed by the incident light and the diffracted light during reproduction in the sensitive material is 4°, 5°, and the angle 2θe formed by the laser beams from two directions during exposure is 73.7°.

(Hologram production) A hologram thick plate made by coating dichromate gelatin with a refractive index n=1.55 as the sensitive material 7, for example, 15 μm on a polyester film 6 and drying it, is exposed to light using an optical system as shown in Fig. 2. let A laser beam with a wavelength λe of 514.5 om emitted from an argon laser oscillator 8 is split into two by a beam splinter 9, and one is converted into a spherical wave through a reflecting mirror 10 and a convex lens 11 at an angle of θe+=36.9°. The other side was irradiated as a plane wave at an angle of θez=38.3° via the reflecting mirror 12, convex lens 13, and convex lens 14, and then developed by a conventional method to produce a reflection hologram.

(Reproduction) The reflection type hologram obtained in this way was attached to the front windshield of an automobile as shown in Fig. 1, and a display 4 made of electroluminescence with a wavelength λr of 585 om (yellow) was used as a light source for reproduction. When display information was projected onto a reflection hologram with an incident angle θr1 of 30”, it was diffracted at an angle of 35° with a diffraction angle θr2 and was clearly visible to the driver's eyes 5 without causing any optical distortion.

Although the present invention has been described above using preferred embodiments, it is not limited thereto and can be applied in various ways.

For exposure, one of the laser beams was made into a spherical wave,
As in the embodiment, the light at the center of the spherical wave may be used in calculations as the light representing the spherical wave.

In this case, the angle of the light outside the center of the spherical wave with respect to the photosensitive material is shifted, but there is no practical problem as long as the focal length of the spherical wave is 200 u or more, preferably 400 u or more.
It is also possible to make the laser beam from the direction a spherical wave. However, if both are plane waves, such errors will not occur at all, which is most preferable.

As for the light-sensitive material, in addition to dichromate gelatin, polyvinyl carbazole, silver halide light-sensitive materials, various photopolymers, etc. may be selected as appropriate.

The light source for reproduction is various light emitting diodes (λr: 470n
m, 550nm, 635nm, 660nm, etc.)
, fluorescent display tube (λr: 550-580rv), electroluminex (λr: 530nm, 585nm, etc.), CRT, white light source, etc. can be used.
On the other hand, exposure can be performed using various laser light sources with wavelengths λe ranging from λr150rm to λr+150nm.

In addition, the reflection hologram of the present invention can be applied not only to combiners for head-up displays but also to display devices for recognizing information to be transmitted.
Therefore, it can be installed in vehicles such as automobiles, constructions such as architectural windows, and in that case, it goes without saying that it can be installed not only in laminated glass but also in single glass.

[Effects of the present invention]

The reflection hologram of the present invention eliminates the need to change the hologram thickness by heat treatment or other methods when the wavelengths of the light sources differ during reproduction and exposure, and the incident light and diffracted light are separated in the sensitive material during reproduction. The angle 2θe formed by the laser light from two directions in the photosensitive material is exposed differently to the angle 2θr formed by the reflection hologram, and even if the thickness of the reflection hologram is large, it is uniform and the optical properties are maintained. Excellent.

Furthermore, when the reflection hologram of the present invention is applied to laminated glass, since even thickness changes are predicted and exposed, both the incident angle and diffraction angle can be reproduced as designed values using a predetermined light source. be.

[Brief explanation of the drawing]

Fig. 1 is an exploded schematic diagram of the main parts of the reflection hologram of the present invention applied to a front laminated window glass for a car as a combiner for a head-up display, and Fig. 2 shows an optical system for producing the reflection hologram. Figure 3(a)
, ridges) and (C) are partial vertical cross-sectional views of a photosensitive material for explaining the present invention in detail, showing the times of reproduction, change in thickness of the photosensitive material, and exposure, respectively. Figure 2

Claims (2)

[Claims] (1) In a reflection hologram where the wavelength λe of the light source during exposure and the wavelength λr of the light source during reproduction are different, in the photosensitive material during reproduction,
A reflection type hologram characterized in that the angle 2θe formed by laser beams from two directions in a sensitive material is exposed differently to the angle 2θr formed between incident light and diffracted light. (2) In a method for manufacturing a reflection hologram placed on a laminated glass made by bonding two sheets of glass with a polyvinyl butyral film, the change in thickness of the reflection hologram during playback is predicted and A method for producing a reflection hologram, characterized in that the angle 2θe formed by laser beams from two directions in a sensitive material is exposed differently to the angle 2θr formed between incident light and diffracted light.