JPH08146862A - Exposing method for hologram - Google Patents

Abstract

PURPOSE: To reduce aberrations and distortion of a display virtual image by performing exposure to a hologram by collimated light which has specific area in a plane direction perpendicular to the optical axis so that exposure conditions of the hologram are approximated to reproduction conditions. CONSTITUTION: A laser light source 1 emits laser light, which is halved by a beam splitter 2 into a reference light and a body light. After the both are diverged by an objective 4, one light is collimated collimator lens 5 into a parallel light. This collimated light is to irradiate the center of a movable mirror 6, thereby irradiating a hologram photosensitive material 7 with the collimated light through the rotary mirror. At this time, the hologram photosensitive material 7 is scanned with the collimated light by moving the movable mirror 6. The other light, on the other hand, is made to irradiate the hologram photosensitive material 7 while diverged by the objective 4. Thus, one of the reference light and body light is made into the collimated light having the specific area in the plane direction perpendicular to the optical axis.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hologram exposure method, and more particularly to a hologram exposure method suitable for a vehicle head-up display (hereinafter referred to as HUD).

[0002]

2. Description of the Related Art HUD has recently been used as a method of displaying information to a driver in a vehicle. This is because the optical information projected from the light emitting display means such as a liquid crystal display device is displayed on a combiner including a half mirror and a hologram provided on the windshield so that the driver hardly moves his line of sight from the driving state. The information can be read.

In particular, a hologram using a hologram as a combiner is capable of diffracting optical information toward a driver and forming an image at an arbitrary position, and it has a high brightness without impairing the foreground brightness. It is effective as a combiner of HUD because it has a characteristic that a display virtual image can be obtained.

FIG. 2 is a conceptual diagram showing an exposure method for such a hologram. As shown in this figure, in the conventional hologram exposure method, a laser light source 8 emits a laser beam, and a beam splitter 9 splits the laser beam into a reference beam and an object beam. The image is enlarged by 11 and is applied to the photosensitive material 12.

[0005]

In this case, one of the exposure conditions of the hologram is that the hologram is exposed by a laser beam emitted from a point light source. Therefore, by irradiating the hologram with the light from the point light source as the reproduction light when reproducing the hologram, a very good image without aberration or image distortion can be obtained as the reproduction image.

However, the light emitting display means used in the above HUD, for example, has a predetermined area in the plane direction perpendicular to the optical axis. That is, as the normally used light emitting display means, for example, a so-called light receiving display element such as a liquid crystal display element is emitted from a light source such as a hot cathode ray tube, a cold cathode ray tube, a fluorescent display tube, a halogen lamp, a light emitting diode, or a semiconductor laser. It emits light. In addition, since a light source itself is patterned and arranged without using the above-mentioned light-receiving display element to generate specific information as light, a light source having both of these functions is used.
The reproduced light of the hologram used for the HUD is a surface light source. Therefore, the quality of the reproduced image (displayed virtual image of the HUD) that is reproduced deteriorates, and an observer such as a driver observes an image having aberration and distortion.

An object of the present invention is to solve the above-mentioned drawbacks of the prior art, and to provide a novel hologram exposure method with reduced image distortion and aberration.

[0008]

The present invention has been made in view of the above-mentioned problems, and in a method of irradiating a hologram photosensitive material with reference light and object light to expose a hologram, At least one of the object lights is a collimated light having a predetermined area in a plane direction perpendicular to the optical axis, and the hologram photosensitive material is scanned and irradiated with the collimated light. And a method for exposing a hologram.

Furthermore, the present invention is, as a more preferable example,
It is intended to provide a hologram exposure method, characterized in that the area of a plane direction perpendicular to the optical axis of the collimated light is made equal to or larger than the area of the reproduced light when reproducing the exposed hologram.

Further, the present invention provides a method for exposing a hologram by scanning a collimated light two-dimensionally or three-dimensionally using a movable mirror, as an example of a concrete method for scanning the collimated light. Is. In this case, the movable mirror is fixed on a rotary stage that rotates both horizontally and vertically, the center of the movable mirror is made to coincide with the center of rotation of both rotary stages, and the collimator is moved to the center of the movable mirror. Irradiation with light is particularly preferable.

[0011]

The present invention will be described in detail below with reference to the drawings.

FIG. 1 is a conceptual diagram showing an example of a hologram exposure method according to the present invention. As shown in this figure, in the hologram exposure method of the present invention, a laser light source 1 emits a laser beam, and a beam splitter 2 splits the laser beam into a reference beam and an object beam.

Then, after both are spread by the objective lens 4, one of the lights is made into a collimated light (parallel light) by the collimator lens 5. This collimated light is applied to the center of the movable mirror 6, and the collimated light is applied to the hologram photosensitive material 7 via the rotary mirror. At this time, the movable mirror 6 is moved to scan the hologram photosensitive material 7 with collimated light. In this embodiment, the other light is applied to the hologram photosensitive material 7 while being spread by the objective lens.

The movable mirror 6 is fixed on a rotating stage (a combination of two rotating stages) which rotates in a plane in both horizontal and vertical directions. At this time, it is preferable that the center of rotation in both directions is coincident with the center of the movable mirror in view of light utilization efficiency.

In addition, the movable mirror can be moved in translation, and a polygonal mirror or a galvanometer mirror can be used as a rotating stage by changing the angle of the traveling direction of light. In any case, as the movable mirror, one having a mechanism capable of scanning the collimated light over the entire area of the hologram photosensitive material to be exposed is used.

In these scanning mechanisms, the rotation speed and angle can be arbitrarily set by computer control or the like.

Further, in the above embodiment, one of the lights divided in two directions is the collimated light, but both may be the collimated light. In this case, the two collimated light beams are interlocked or controlled independently to match the irradiation positions on the hologram photosensitive material. It is also possible to incorporate this control into the computer control described above.

It is preferable that the area of the collimated light in the plane direction perpendicular to the optical axis is equal to or larger than the light emitting area of the light emitting display means that emits the reproduction light, because the aberration and distortion of the display virtual image can be suitably reduced. In particular, it is preferable to set the area substantially equal to the light emitting area of the light emitting display unit because the exposure condition of the hologram matches the reproduction condition, so that the aberration and distortion of the display virtual image can be more preferably reduced.

As means for producing such collimated light, in addition to using the above collimated lens, appropriate means for making light parallel by various optical members such as concave mirrors and holograms may be used alone or in combination. Among these, it is preferable to use the above collimator lens in view of the fact that irradiation of the hologram photosensitive material as coherent light necessary for exposing the hologram can be handled as a simple optical design.

By combining the above various optical members, the area of the collimated light in the plane direction perpendicular to the construction area can be made various sizes. In this case as well, the arrangement position of the collimated lens and A desired area can be obtained by appropriately selecting the optical design.

The hologram photosensitive material is not particularly limited as long as it is a material that is usually used for holograms and that is sensitive to the above-mentioned light for exposure. Examples include photopolymers, dichromated gelatin, silver salts and the like.

The operation procedure of the light from the laser light source in the present invention is not limited to the above example. For example, after the movable mirror controls the irradiation direction of the light for scanning the light, the light may be passed through the collimator lens, or another procedure may be performed. In such a case, since control of the movable mirror becomes complicated, it is preferable to scan the collimated light by the movable mirror immediately before the hologram photosensitive material is irradiated, as in the above example.

[0023]

According to the present invention, the hologram is exposed by using the collimated light having a predetermined area in the plane direction perpendicular to the optical axis so that the hologram exposure condition approaches the reproduction condition. It is possible to reduce the aberration and distortion of the reproduced display virtual image.

By appropriately selecting the above-mentioned area at the time of exposure, it is possible to obtain holograms corresponding to light emitting display means of various sizes, and particularly when mounted on a vehicle, the size of the light emitting display means can be increased. It is possible to obtain holograms having small aberrations and image distortions corresponding to the respective light emitting and displaying means, even when the number of the holograms varies.

Further, the object light for exposure in the present invention,
Since the reference light is scanned and applied to the hologram, even a hologram having a large area can be easily obtained.
It is possible to achieve diversification, mass production and large area of display contents by hologram.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing an example of a hologram exposure method according to the present invention.

FIG. 2 is a conceptual diagram showing an example of a conventional hologram exposure method.

[Explanation of symbols]

 1, 8: Laser light source 2, 9: Beam splitter 3, 10: Mirror 4, 11: Objective lens 5: Collimator lens 6: Movable mirror 7, 12: Holographic photosensitive material

Claims (4)

[Claims] 1. A method of exposing a hologram by irradiating a hologram photosensitive material with reference light and object light, wherein at least one of the reference light and the object light is perpendicular to the optical axis. A method of exposing a hologram, characterized in that collimated light having a predetermined area in a plane direction is formed, and the collimated light is scanned and irradiated on the hologram photosensitive material. 2. The hologram exposure method according to claim 1, wherein the area is equal to or larger than the area of reproduced light for reproducing the exposed hologram. 3. The hologram exposure method according to claim 1, wherein the collimated light is scanned two-dimensionally or three-dimensionally by a movable mirror. 4. The movable mirror is fixed on a rotary stage that rotates both horizontally and vertically, and the center of the movable mirror coincides with the center of rotation of both rotary stages.
4. The hologram exposure method according to claim 3, wherein the center of the movable mirror is irradiated with the collimated light.