JPH02240679A - Formation of reflective hologram - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Summary] Regarding a method for creating a reflection hologram, the purpose of this invention is to realize a diffracted light wavelength in a range that has not been previously possible. When creating a reflection hologram by irradiating creation light from both sides, a prism is arranged on the hologram photosensitive material and the creation light from the photosensitive material side is made to enter through the prism at a large incident angle. .

[Industrial application field]

The present invention relates to a method for creating a reflection hologram.

Head-up displays (hereinafter abbreviated as HUD), which were developed as display devices in aircraft, have recently been
It is being applied to automobiles and other vehicles from the standpoint of safety and simplification of driving operations, and research and development toward practical use is actively progressing.

A HUD displays instrument displays superimposed on the background, and is an excellent display system in that it allows the driver to read the information necessary for driving without moving his/her line of sight.

[Conventional technology]

FIG. 7 shows an example of an automobile HUD, in which the driver can superimpose information on a display device 11 such as a CRT using a holographic combiner IO while looking at the scenery in front of the vehicle.

A reflection hologram is usually used as a holographic combiner that displays the HUD background and information in an overlapping manner. As shown in FIG. 8, the reflection type hologram includes a hologram dry plate 16 (a glass substrate 15 and a hologram photosensitive material 17).
Rade light (reference wave W2, object wave W2) is irradiated from the front and back sides of the object (having a 100-degree angle) to record interference fringes 18 formed substantially parallel to the surface. As shown in FIG. 9, the reproduction light (diffraction light) is reflected and diffracted on the same side as the incident light.

[Problem to be solved by the invention]

FIG. 6 shows problems with the conventional method of creating a reflection hologram. According to this method, even if the incident light is incident on the glass substrate 15 at an almost parallel angle θ1, the refractive index n of the emulsion 17 is
, is 1.6 (ne !4.6), the angle of incidence θ within the emulsion cannot exceed 39°. This is because the difference between the refractive index of the emulsion and the refractive index of the emulsion is too large when the refractive index of air is defined as n. Therefore, the wavelength of the created light is 488nm.
Therefore, when white light is used as a light source during reproduction, the wavelength of the diffracted light is limited to around 500 nm. Note that n is the refractive index of glass (-1, 5).

An object of the present invention is to provide a method for creating a reflection hologram that allows the user to freely select the color of an image that appears to the human eye by freely obtaining the wavelength of diffracted light.

[Means to solve the problem]

In order to achieve the above object, according to the present invention, when creating a reflection hologram by irradiating creation light from both sides of a hologram photosensitive material formed on one surface of a transparent substrate,
The structure is characterized in that a prism is arranged on the photosensitive material for holograms, and the creating light from the photosensitive material side is made to enter through the prism at a large angle of incidence.

[For production]

The refractive index of the prism (glass) is almost the same as that of the emulsion, so even if it is incident on the emulsion at a fairly close angle of incidence θi, it will not be totally reflected, and as a result, the wavelength of light created within the emulsion will be The angle of incidence can be made as close to 90° as possible. Since the pitch (interval) of the interference fringes of a hologram increases as the incident angle increases, the pitch of the interference fringes can be widened, and diffracted light with a longer wavelength than the conventional diffracted light wavelength can be obtained.

The principle of creating a reflection hologram according to the present invention is shown in FIG. A prism 30 is placed on the emulsion side of the hologram dry plate 16.
is placed, the incident light enters the prism 30, and then the emulsion 17
Inject it into the the angle of incidence of light on the prism 30;
Angle α of the surface 30A of the prism on which light enters with respect to the substrate
By appropriately designing the angle of incidence θ within the emulsion 17, it is possible to control the interval (pitch) d of the interference fringes. Therefore, the reproduction light wavelength that depends on the pitch of the interference fringes can be freely selected.

〔Example〕

An embodiment of the present invention is shown in FIG. The incident surface 30A of the prism 30 is at an angle of 45° with respect to the glass substrate 15. Light is made incident on the surface of the prism at an incident angle of 45°. The refractive index n9 of the prism (glass) is 1.5, and the refractive index n of the emulsion
Assuming that 1 is 1.6, the incident angle of light within the emulsion 17 is 64°. On the other hand, if the angle of incidence on the substrate is 30°, the light will be incident on the emulsion 17 at an angle of 18°. In this case, the stripe spacing d is 0.2021-. When this is reproduced with white light at an incident angle of 21° to the glass substrate, the selected wavelength is 630r++
n light is diffracted in a direction of 70° with respect to the glass substrate (FIG. 3).

Another embodiment of the invention is shown in FIG. A prism 30 is placed on the surface of the emulsion 17, and light is incident thereon as shown in the figure. Interference fringes 18 are created by interfering the incident light with the reflected light on the back surface of the glass substrate 15 (back surface reflection method). In this way, interference fringes with a fringe inclination angle of 0° are created.

FIG. 5 shows yet another embodiment, in which in addition to the prism 30A on the emulsion 17 side, the glass substrate 15
A prism 30B is also arranged on the back side of the . Prisms 30A and 30B have the same shape. This makes it possible to control the angle of incidence of the incident created light from both sides.

The angle of incidence within the emulsion can be arbitrarily controlled by controlling the angle α of the incident surface of the prism and the angle of incidence of the created light onto the prism.

〔Effect of the invention〕

As described above, when creating a reflection hologram according to the present invention, a prism having a small difference in refractive index from the emulsion is placed on the hologram dry plate, and the light is incident on the hologram emulsion through this prism. As a result, a wider range of diffracted light wavelengths can be obtained.

[Brief explanation of drawings]

Figure 1 is a diagram explaining the basic principle of the present invention, Figure 2 is a diagram explaining the method for creating a reflection hologram according to the invention, and Figure 3 is a diagram explaining the reproduction state of the reflection hologram shown in Figure 2. FIG. 4 is a diagram explaining a method for creating a reflection hologram according to another embodiment of the present invention, FIG. 5 is a diagram showing still another embodiment of FIG. 4, and FIG. A diagram explaining a method for creating a reflection hologram, FIG. 7 is a diagram showing a conventional head-up display for a car, FIG. 8 is a diagram showing a general method for creating a reflection hologram, and FIG. A diagram showing a method for reproducing a hologram. 15... Transparent substrate, 17... Photosensitive material, 18...
... Hologram (interference fringe), 30... Prism.

Claims (1)

[Claims] When creating a reflective hologram (18) by irradiating creation light from both sides of the hologram photosensitive material (17) formed on one surface of the transparent substrate (15), a prism (30) is placed on the hologram photosensitive material. A method for producing a reflection hologram, characterized in that the production light from the photosensitive material side can be made incident at a large angle of incidence through the prism.