JPH04113381A - Hologram exposing method - Google Patents

Abstract

PURPOSE:To correct image distortion, generated at the time of reproduction of a hologram of a curved surface, by exposure in the state of a flat plate hologram photosensitive material by arranging a cylindrical lens in the optical path of one of laser light beams which are body light and reference light. CONSTITUTION:Laser light 2 from a laser device 1 is made incident on objective lenses 5 and 5' through mirrors 3 and 3' and a beam splitter 4 to become diverged light beams 6 and 6'. The light 6' irradiates the hologram photosensitive material 8 as it is. The cylindrical lens 7 is newly installed between the objectives and photosensitive material 8 so as to deform the wave front of the diffused light 6. The lens 7 deforms the light 6 as shown by 7', the light becomes elliptic on the photosensitive material 8, and the ellipticity of the transmitted light 7' can freely be selected by varying the distance between the lens 7 and lens 5. When a hologram exposed elliptically to the photosensitive material 8 is reproduced in the curved state, circular reproduction light cancels the exposed state even if distorted owing to the curvature and operates equivalently to irradiate a plane hologram with circular reproduction light.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a hologram exposure method for correcting distortion of a hologram image due to curved surface.

[Prior Art] Head-up displays have recently come into use as a method of displaying information to drivers and the like in automobiles. This is a system that incorporates optical information projected from an information projection means such as a liquid crystal display device into the windshield of a car.
The information is displayed on a half-mirror, which is a combined combiner, so that the driver can read the information without having to move his/her viewpoint while driving.

Recently, holograms have been attracting attention as the above-mentioned combiner due to their simplicity as optical elements and the richness of added functions. The holographic combiner has not only a reflection function but also a diffraction function, a lens function, etc., so it can diffract optical information in the direction of the driver's field of vision or form an image at any position. becomes possible.

When using a hologram as such a holographic combiner, the hologram is attached to the windshield of an automobile, so it is used in a curved state. If such a hologram is manufactured by exposing it to light in a flat state, distortion will occur in the image due to the difference in shape between the time of exposure and the time of reproduction. Therefore, in the past, a lens (for correction) was designed and manufactured to match the curved surface of the hologram plate each time it was used, and was installed between the light source and the hologram to correct the distorted image. It is proposed that.

[Problems to be Solved by the Invention] In the case of the conventional technology, a correction lens for each hologram is required, which is expensive, and lenses corresponding to each hologram are required depending on the curvature. In addition, if the lens is complex, such as having two curvatures (vertical and horizontal), it is extremely difficult to manufacture the lens.

[Means for Solving the Problems] The present invention has been made to solve the above-mentioned problems, and is an exposure method for producing a hologram, in which at least one laser beam forming an object beam and a reference beam is used. The present invention provides a hologram exposure method characterized by arranging a cylindrical lens in the optical path of one of the laser beams.

FIG. 1 is a schematic diagram of a new exposure method related to the present invention. Laser light 2 from laser device 1 passes through mirror 3,
3° and the objective lens 5, 5 through the beam splitter 4.
The light enters at 6.6° and spreads out at 6.6°. The hologram photosensitive material 8 is irradiated with the 6° angle as it is. In the present invention,
In order to modify the wavefront of the diffused light 6, a cylindrical lens 7 is newly installed between the objective lens and the photosensitive material 8.

The curvature of the cylindrical lens should be determined taking into consideration the bending of the hologram 8 during reproduction.

[Function] The cylindrical lens 7 introduced in the present invention is shown in FIG.
), the light 6 that has passed through the objective lens 5 is deformed by 7°, and on the holographic photosensitive material it becomes an ellipse, deviating from the circular irradiation surface when there is no 7.

In other words, when the objective lens 5 is located closer to the cylindrical lens 7 than the focal point of the cylindrical lens 7, the hologram itself can have the function of stretching the original reproduced image in the vertical direction.

By changing the distance between the cylindrical lens 7 and the objective lens 5, it is possible to freely select the ellipticity of the transmitted light 7'.

When a hologram exposed as shown in FIG. 2(a) is reproduced in a curved state as shown in FIG. 2(b), even if the circular reproduced light is distorted due to the curvature, it is canceled out by the exposed state. This works in the same way as if circular reproduction light were irradiated onto a flat hologram.

[Example] FIG. 3 shows one example. The first lens is located behind the objective lens 5.
Cylindrical lens 7-1, and then 7-
Another cylindrical lens 7-2 is installed in a direction perpendicular to cylindrical lens 1. This makes it possible not only to change the ellipticity freely, but also to change the size of the ellipse.

If 7-1 and 7-2 are rotated by the same angle at the same time, the directions of the major and minor axes of the ellipse can be changed, and even more complex deformations can be made by rotating 7-1 and 7-2 independently. .

As another embodiment, the cylindrical lens 7 can be tilted as shown in FIG. 4 to cause expansion and contraction in the upper and lower parts of the ellipse. Of course, two cylindrical lenses may be combined.

All of these may be done in such a way that the distortion effect due to the shape of the hologram is canceled out, taking into account the usage condition of the hologram during reproduction.

[Effects of the Invention] The present invention makes it possible to correct the image distortion that occurs when reproducing a curved hologram by exposing the flat hologram photosensitive material, and corrects the image distortion that occurs when the hologram photosensitive material is curved and exposed. It has the advantage of avoiding problems such as difficulty in fixing and the generation of unnecessary diffraction gratings, but an even greater effect is that it can be applied to tilted glass plates with different vertical and horizontal curvature radii, such as automobile windshields. The object of the present invention is to make it possible to correct image distortion reproduced with a laminated hologram in an extremely simple manner. For this purpose, exposure may be performed by combining the methods shown in FIGS. 3 and 4.

In addition, these exposure methods can be used not only for distortion correction (on the contrary, they can also be used to create artistic holograms that cause distortion, and can be used to create unique holograms based on the ideas of individual artists). We can expect great works.

[Brief explanation of the drawing]

FIG. 1 is a conceptual diagram of the exposure method according to the present invention, FIG. 2 is an explanatory diagram showing the role played by the cylindrical lens in the present invention, and FIGS. 3 and 4 are diagrams showing the arrangement of other cylindrical lenses in the present invention. FIG. 1...Laser device 2...Laser beam 33°...Mirror 4...Beam splitter 5,5'...Objective lens 6.6°...Diffused light 7...Cylindrical lens・・Light after correction・Hologram photosensitive material・・Hologram after exposure

Claims (1)

[Claims] (1) A hologram exposure method for producing a hologram, which is characterized in that a cylindrical lens is placed in the optical path of at least one of laser beams forming an object beam and a reference beam.