JPH0980311A - Device and method for lighting - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make illumination light incident on a lightened body at a specific angle, to make the quantity of the illumination light uniform without wasting the energy of a light source, and to reduce the size of the lighting device by diffracting transmitted light in a specific direction and obtaining a uniform light quantity distribution. SOLUTION: This lighting device is composed the light source 4, a 1st transmission type hologram 7 which diffracts the light from the light source 4, and a 2nd transmission type hologram 8 which further diffracts the light transmitted through and diffracted by the 1st hologram 7. And, the 1st hologram 7 is so formed that the quantity of variation per pitch of a diffraction grating 7b at a part which transmits and diffracts light made incident on the 2nd hologram 8 surface at a part near the light source 4 is made larger than the quantity of variation per pitch of a diffraction grating 7a at a part which transmits and diffracts light made incident on the 2nd hologram 8 surface at a part distant from the light source 4. Consequently, the amplitude, i.e., the quantity of light on the 2nd hologram 8 surface is made uniform in consideration of unevenness of the quantity of light depending upon the light source 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention provides a hologram between a light source and an object to be illuminated to illuminate the object to be illuminated by using divergent light from a point light source or the like so that the light intensity in the object to be illuminated is uniform. The present invention relates to an illuminating method and an illuminating device that enable the illumination target to be illuminated at a predetermined angle.

[0002]

2. Description of the Related Art Conventionally, when a liquid crystal panel is illuminated by a backlight system, as shown in FIG. 8, a fluorescent diffuser 2 is provided with a transparent diffuser plate 2 having an uneven diffuser surface 2a formed on its surface as a light guide. The mainstream method is to illuminate the liquid crystal panel 3 with diffused light emitted from the transparent diffusion plate 2. However, in general, in a modulator using liquid crystal,
When the incident angle of the incident light with respect to the liquid crystal surface is tilted, the rotation angle of the polarization plane is slightly deviated. Therefore, when the liquid crystal panel 3 is illuminated with the diffused light as shown in FIG. There is a problem that the contrast of the image displayed is lowered.

To solve such a problem, the liquid crystal panel 3
It is desirable that the illumination light be incident on the liquid crystal surface at a constant angle (normally perpendicular to the liquid crystal surface) and in parallel. Therefore, as shown in FIG. 9, it is conceivable to combine a light source 4 that emits divergent light such as a point light source with a lens 5 and make a parallel light flux with a uniform wavefront enter the liquid crystal panel 3. However, it is not practical to combine the light source 4 and the lens 5 as shown in FIG. 9 because the space of the entire illumination device becomes large.

Further, as an illuminating device capable of making the illuminating light incident on the liquid crystal panel 3 at a constant angle, FIG.
As shown in 0, the light source 4 that emits divergent light and the transmissive hologram 6 are combined, the diffused light emitted from the light source 4 is transmitted and diffracted by the transmissive hologram 6, and the illumination light with respect to the liquid crystal panel 3 has a constant angle. It is known that the light is made incident on (Japanese Patent Application Laid-Open No. 4-303822). According to such a device, it is possible to reduce the size of the lighting device to some extent.

[0005]

However, as shown in FIG.
In the illuminating device shown in FIG. 2, when the light source 4 and the hologram 6 are arranged close to each other in order to reduce the size of the illuminating device, the amount of incident light increases in a portion of the hologram 6 near the light source 4, and conversely, The amount of incident light is reduced in the portion distant from the light source 4, and unevenness of light amount occurs on the surface of the hologram 6.
Therefore, it is not possible to illuminate the liquid crystal panel 3 with a uniform amount of light, and uneven brightness occurs in the liquid crystal panel. FIG. 11 is a schematic view of such a state, in which the light source 4
The intensity of the light ray L emitted from is represented by the interval between the lines indicating the light ray L. In this way, the light ray L is dense in the portion of the hologram 6 surface close to the light source 4, and conversely, the light ray L is sparse in the portion distant from the light source 4.

Here, in order to reduce the unevenness of the light quantity,
It is conceivable to intentionally reduce the diffraction efficiency in a portion on the surface of the hologram 6 which is close to the light source and has a large amount of light, so that the light amount in the portion close to the light source is equal to that in the portion far from the light source.

However, lowering the diffraction efficiency is not preferable because it wastes the energy of the light source. Further, when a light control film is provided on the back surface of the liquid crystal panel in order to define the incident angle of the light that illuminates the liquid crystal panel 3, most of the light transmitted through the hologram portion whose diffraction efficiency has been lowered is the light control film. Since it is absorbed by the film and converted into heat energy, it raises the temperature of the liquid crystal panel and its surroundings, causing a misalignment of the liquid crystal. In order to prevent such an unnecessary temperature rise, it is necessary to provide a cooling mechanism, but installation of the cooling mechanism complicates the device and increases the size, which is not preferable.

The present invention is intended to solve the problems of the prior art as described above, and when the liquid crystal panel is illuminated by a backlight system, or when any other illuminated object is illuminated, the illuminated object is applied to the illuminated object. On the other hand, it is an object of the present invention to allow the illumination light to be incident at a predetermined angle, make the light amount of the illumination light uniform without wasting the energy of the light source, and make the illumination device smaller.

[0009]

The present inventor uses a light source such as a point light source which emits divergent light and controls the incident angle of illumination light by a hologram, and further controls the light quantity distribution by a separate hologram. As a result, they have found that the above objects can be achieved, and have completed the present invention.

That is, the present invention comprises a light source that emits divergent light, a first hologram that diffracts the light from the light source, and a second hologram that further diffracts the light diffracted by the first hologram. The hologram of is composed of a hologram for equalizing the light intensity on the second hologram surface,
A second hologram provides an illuminating device characterized by comprising a hologram that diffracts light in a predetermined direction.

Further, according to the present invention, a light source which emits divergent light is used, the light emitted from the light source is diffracted by the first hologram, and the light diffracted by the first hologram is further divided by the second hologram.
Providing an illumination method for diffracting the hologram by the first hologram, wherein the first hologram makes the light intensity on the second hologram surface uniform, and the second hologram diffracts the light in a predetermined direction. To do.

When illumination is performed using such an illuminating device of the present invention or according to the method of the present invention, the divergent light emitted from the light source is diffracted by the first hologram so that the second hologram is obtained. The light is incident on the surface with a uniform amount of light (that is, a uniform light intensity), and the incident light is diffracted in a predetermined direction by the second hologram, so that the object to be illuminated is uniform at a predetermined angle and without wasting energy. It becomes possible to illuminate with a light amount distribution.

The first hologram and the second hologram used in the illumination device or the illumination method of the present invention may be transmission holograms that transmit and diffract incident light, respectively, and reflection holograms that reflect and diffract incident light. But it's okay. Regardless of which type of hologram is used, the first hologram can make the amount of light incident on the second hologram uniform, and the second hologram can adjust the angle of light illuminating the illuminated body. .

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below in detail with reference to the drawings. In each of the drawings, the same reference numerals represent the same or equivalent components.

FIG. 1A is a schematic view of a case where the lighting device of the present invention is configured as a backlight of a liquid crystal panel 3. As shown in the figure, this illuminating device includes a light source 4, a first transmissive hologram 7 that diffracts light from the light source 4, and a first hologram 7.
The second hologram 8 of the transmission type that further diffracts the light that is transmitted and diffracted by the hologram 7. In the figure, the intensity of the light ray L emitted from the light source 4 is represented by the interval between the lines indicating the light ray L. Further, FIG. 1B is an explanatory diagram of the pitch of the diffraction grating of the first hologram of the illumination device of FIG. 1A.

In this illuminating device, it is preferable to use, as the light source 4, a point light source or one that emits diffused light with a size similar to a point light source. Thereby, the light transmitted through the second hologram 8 can be diffracted in a predetermined direction and can have a uniform light amount distribution. Examples of the light source 4 include a white light source having a relatively small diameter such as a tungsten lamp, a halogen lamp, and a krypton lamp, a chromatic light source such as a light emitting diode, a semiconductor laser, a solid-state laser, a gas laser, or the like. Laser light sources of the above can be used.

Further, in this illuminating device, the first hologram 7 eliminates uneven illumination when the light diffracted through the second hologram 8 diffracts the liquid crystal panel 3.
It is provided to make the light amount distribution on the second hologram 8 surface uniform. That is, when the illuminating device including such a light source and the hologram is configured by the light source 4 and the second hologram 8 without providing the first hologram 7, the conventional illuminating device described in FIG. As described above, on the surface of the second hologram 8, the amount of incident light is large in the portion close to the light source 4, and the amount of incident light is small in the portion distant from the light source 4, resulting in uneven light amount. Therefore, in this lighting device, in order to eliminate such uneven light amount,
The light quantity distribution is corrected by the first hologram 7. More specifically, for example, as shown in FIG. 1B, in the first hologram 7, a diffraction grating of a portion that transmits and diffracts light incident on a portion of the second hologram 8 surface far from the light source 4. Amount of change in pitch of 7a per pitch (Δdf /
df)

[0018]

[Formula 1] [Δdf / df = | df + 1−df | / df] The pitch of the diffraction grating 7b in the portion that transmits and diffracts the light incident on the portion closer to the second hologram 8 surface from the light source 4 Amount of change per pitch (Δdn / dn)

[0019]

## EQU2 ## [.DELTA.dn / dn = | dn + 1-dn | / dn] is increased.

When the unevenness of the light amount on the surface of the second hologram 8 is eliminated by adjusting the pitch of the diffraction grating of the first hologram 7 in this way, the light amount on the surface of the second hologram 8 is more strictly adjusted. As a method for making uniform, as shown in FIG.
The flow iterative method as shown in FIG. That is, first,
In the case where the first hologram 7 is not present, the light source 4
The complex amplitude distribution of the light emitted from the second hologram 8 surface is obtained by Fresnel transformation (step A). Next, assuming that the amplitude component of the obtained complex amplitude distribution on the surface of the second hologram 8 is constant (step B), inverse Fresnel transform is performed to obtain the complex amplitude distribution on the first hologram 7. (Step C). Then, the amplitude component of the obtained complex amplitude distribution on the first hologram 7 is replaced with the amplitude when the first hologram 7 is actually irradiated by the light source 4 (step D), and the Fresnel transform is performed again. And the complex amplitude distribution on the second hologram 8 is obtained (step E). If the unevenness of the amplitude component of the complex amplitude distribution on the surface of the second hologram 8 obtained by this is less than or equal to the desired level,
At this time, the diffraction grating of the first hologram 7 may be designed. If the amplitude component unevenness exceeds the desired level, the steps B to B are performed until the amplitude component unevenness becomes equal to or less than the desired level. Repeat E.

According to such an iterative method, the amplitude on the second hologram 8 can be made uniform, that is, the amount of light can be made uniform in consideration of the unevenness of the light amount depending on the light source 4, so that there is no unevenness. Lighting can be obtained.

Although an on-axis hologram in which the optical axis does not change before and after diffraction is shown as the first hologram 7 in FIG. 1, the optical axis changes before and after diffraction as the first hologram 7. Off-axis holograms may be used. Also in this case, as in the first hologram 7, the amount of change per pitch of the pitch of the diffraction grating of the portion diffracting the light incident on the portion of the second hologram 8 surface far from the light source 4 ( Δdf / df)

[0023]

## EQU3 ## Relative to [Δdf / df = | df + 1−df | / df], the pitch of the pitch of the diffraction grating of the portion that transmits the light incident on the portion closer to the second hologram 8 surface from the light source 4 Change amount (Δdn / dn)

[0024]

## EQU4 ## It is sufficient to provide the one having a large .DELTA.dn / dn = | dn + 1-dn | / dn.

Further, in FIG. 1, the first hologram 7 is arranged perpendicular to the optical axis of the light source 4. However, in the present invention, the inclination of the first hologram 7 with respect to the optical axis of the light source 4 is not particularly limited.

Therefore, the first hologram 7 may be configured as an on-axis hologram arranged so as to be parallel to the optical axis of the light source 4, as shown in FIG. As shown in FIG. 4, the first hologram 7 may be configured as an off-axis hologram arranged so as to be parallel to the optical axis of the light source 4.

As a method for producing the first hologram 7,
A diffraction grating is patterned on an electron beam resist using an electron beam drawing device, and the formed pattern is hot press molded on a transparent plate (for example, a polycarbonate plate, an acrylic plate, etc.) using a known pattern duplication stamper. Or
A radiation curable resin that is cured by radiation such as ultraviolet rays and electron beams may be molded by pressing and irradiation. Also,
The first hologram 7 may be produced by a laser beam drawing device, a photograph reduction method, a two-beam interference method using a laser, or the like. Furthermore, once the first hologram 7 has been produced, the hologram may be reproduced in a large amount by an embossing method, an etching method, or the like. In the present invention, the hologram thus duplicated can also be used.

In the apparatus of the present invention shown in the above, the transmission hologram is provided as the first hologram 7, but a reflection hologram may be used.

Further, as the first hologram 7, the one in which the unevenness of the light amount on the surface of the second hologram 8 is eliminated by adjusting the pitch of the diffraction grating has been described.
The present invention is not limited to this, and as the first hologram 7, for example, a diffusion plate hologram or the like can be used.

Next, the second hologram 8 of the illumination device shown in FIG. 1 will be described. The second hologram 8 transmits and diffracts the light from the first hologram 7 so as to form a parallel light flux in the direction perpendicular to the surface of the liquid crystal panel 3.

The second hologram 8 can be produced by the two-beam interference method as shown in FIG. That is, first,
Interference fringes of the reproduction light L1 of the first hologram 7 produced as described above and the light L2 having a uniform intensity and a uniform wavefront are recorded as a hologram on the photosensitive material 9. For this purpose, for example, as shown in the figure, the light emitted from the laser light source 10 is split by the half mirror 11, and one of them is used as a light source for the reproduction light L1 of the first hologram 7 by the lens 12. Then, the other lens may be collimated by a lens 13 having a large diameter into parallel light, which may be used as the light L2.

As the photosensitive material 9, for example, a silver salt photosensitive resin, a photoresist or the like can be used.

Next, the exposed light-sensitive material 9 is developed according to a conventional method. As a result, the second hologram 8 can be obtained.

The second hologram 8 may be produced by using an electron beam drawing device, a laser beam drawing device or the like instead of the two-beam interference method. Similarly to the first hologram 7 described above, the second hologram 8 may be manufactured once and then copied in large quantities by an embossing method, an etching method, or the like, and the copied hologram may be used.

Further, the second hologram 8 is not limited to a transmission hologram, but a reflection hologram may be used.

As described above, in the illustrated illumination device, the illumination device can be suitably used as a backlight of a liquid crystal panel,
The light transmitted and diffracted by the second hologram 8 is the liquid crystal panel 3
Although the parallel light flux is vertically incident on the illumination device, the illumination device of the present invention is not limited to this. If necessary, the light that is transmitted and diffracted through the second hologram may be a parallel light beam in an arbitrary predetermined direction, or may be divergent light or convergent light.

For example, when the illumination device of the present invention is used in an OHP projector, the light diffracted by the second hologram 8 may be converged as shown in FIG. In the illuminating device of FIG. 6 as well, similar to the illuminating device shown in FIG. 1, the first hologram 7 corrects the light amount distribution of the light emitted from the light source 4, and outputs the light whose light amount distribution is corrected to the first light. It is made incident on the hologram 8 of No. 2. And the second
The hologram 8 changes the direction of the light incident on the second hologram 8 so that the light converges in the imaging lens 14. The light whose direction is changed by the second hologram 8 passes through the OHP original 15 and enters the imaging lens 14. Then, this light is reflected by the mirror 16, and the original 15 is displayed on the screen 17 by the effect of the imaging lens 14.
Image is formed.

The image on the screen 17 thus obtained is bright and has an even brightness.

A configuration similar to that of the illumination device shown in FIG. 6 can be used for an optical device of an image forming system such as a slide projector.

On the other hand, when the illumination device of the present invention is used to illuminate a hologram, as shown in FIG. 7, the light transmitted and diffracted by the second hologram 8 is transmitted to the hologram 18 to be illuminated. You may make it a parallel light beam which has a predetermined incident angle, and may inject. As described above, by using the illumination device of the present invention as the hologram illumination device, the reproduced image 19 of the hologram can be obtained with uniform brightness. Further, it is possible to downsize the lighting device.

Although FIG. 7 shows the case where the illuminating device of the present invention is used as a transmissive hologram illuminating device, the illuminating device of the present invention is also used as a reflective hologram illuminating device. be able to.

[0042]

According to the present invention, when the liquid crystal panel is illuminated by the backlight system, the illumination light is made incident on the object to be illuminated at a predetermined angle and the energy of the light source is not wasted. Further, it becomes possible to make the amount of illumination light uniform and further reduce the size of the illumination device.

[Brief description of drawings]

1A and 1B are a schematic view of an illuminating device of the present invention (FIG. 1A) and an explanatory view of a pitch of a diffraction grating of a first hologram thereof (FIG. 1B).

FIG. 2 is a flowchart of a method of determining a pitch of a diffraction grating of a first hologram.

FIG. 3 is a schematic view of another aspect of the lighting device of the present invention.

FIG. 4 is a schematic view of another aspect of the lighting device of the present invention.

FIG. 5 is an explanatory diagram of a method of manufacturing a second hologram.

FIG. 6 is a schematic view of another aspect of the lighting device of the present invention.

FIG. 7 is a schematic view of another aspect of the lighting device of the present invention.

FIG. 8 is a schematic view of a backlight of a conventional liquid crystal panel.

FIG. 9 is a schematic view of another aspect of the backlight of the conventional liquid crystal panel.

FIG. 10 is a schematic view of another aspect of the backlight of the conventional liquid crystal panel.

FIG. 11 is an explanatory diagram of a light amount distribution of a backlight of a conventional liquid crystal panel.

[Explanation of symbols]

 3 Liquid crystal panel 4 Light source 5 Lens 6 Hologram 7 First hologram 8 Second hologram 9 Photosensitive material 10 Laser light source

Claims (8)

[Claims] 1. A light source that emits divergent light, a first hologram that diffracts the light from the light source, and a second hologram that further diffracts the light diffracted by the first hologram, the first hologram comprising: An illuminating device comprising a hologram for equalizing the light intensity on a second hologram surface, the second hologram being a hologram for diffracting light in a predetermined direction. 2. The lighting device according to claim 1, wherein the light source is a point light source. 3. The second hologram surface where the amount of change in the pitch of the diffraction grating forming the first hologram per pitch is greater than that of the portion diffracting the light incident on the portion of the second hologram surface far from the light source. The illumination device according to claim 1 or 2, which is large in a portion that diffracts light incident on a portion close to the light source. 4. A second hologram is provided on a back surface of the liquid crystal panel for illuminating the liquid crystal panel by a backlight method, and light diffracted by the second hologram becomes a parallel light flux, and a predetermined angle is formed on the back surface of the liquid crystal panel. The illuminating device according to any one of claims 1 to 3, wherein the illuminating device is made to enter. 5. A light source that emits divergent light is used, and the light emitted from the light source is diffracted by a first hologram to produce a first hologram.
Is a lighting method for diffracting the light diffracted by the second hologram further by the second hologram.
The illumination method, wherein the light intensity on the hologram surface is made uniform and the light is diffracted in a predetermined direction by the second hologram. 6. The illumination method according to claim 5, wherein a point light source is used as the light source. 7. The amount of change per pitch of the pitches of the diffraction gratings constituting the hologram as the first hologram is
The illumination according to claim 5 or 6, wherein a portion for diffracting light incident on a portion closer to the second hologram surface from the light source is made larger than a portion for diffracting light incident on a portion farther from the light source on the second hologram surface. Method. 8. The second hologram is provided on the back surface of the liquid crystal panel, and the light diffracted by the second hologram is made into a parallel light beam and is made incident on the back surface of the liquid crystal panel at a predetermined angle. Illumination method described in.