JP3161607B2 - Hologram exposure method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure method and an exposure apparatus for various holograms, such as a combiner for a head-up display for an automobile, a high-mount stop lamp, and a display of a show window.

[0002]

2. Description of the Related Art Usually, a hologram is exposed by laminating an expensive non-reflective glass called AR glass on a photosensitive material in order to prevent the formation of unnecessary interference fringes due to reflection on the surface of the photosensitive material. For example, when exposing a hologram with a relatively large incident angle or reproduction angle during reproduction, the exposure light source used a laser with a wavelength close to the wavelength of the reproduction light source. However, since the incident angle increases and the amount of unnecessary reflection increases, it is inevitable that unnecessary interference fringes are formed.

The present invention has been made in view of the above points, and does not require a non-reflective glass. Even if the hologram has at least one of an incident angle and a reproduction angle of 40 ° or more at the time of reproduction, unnecessary interference is obtained. It is an object of the present invention to provide an apparatus for exposing a hologram having high display quality without generating stripes.

[0004]

Means for Solving the problems] The present invention is Kohi - irradiated from a laser light source which rents length is C a laser beam sensitive material, a method <br/> of exposing a reflection hologram by one beam, The refractive index is close to the refractive index of the light-sensitive material, and when the refraction angle of the laser light on the light-sensitive material is θ ′, C · cos θ ′ / 2
This is an exposure method in which a transparent plate having the above-described plate thickness is laminated on the incident side of the photosensitive material . In addition, using a laser light source with a coherent length of C , the distance from the laser light source to the photosensitive material
Two beams with optical paths of M and N are set under the condition | M−N | ≦ C.
Transmission type photo-detector, which is incident on the same side of
In the exposure method of the program , when the refraction angle of the laser beam whose optical path of the two beams is M at the photosensitive material is θ ′ and the refraction angle of the laser beam whose optical path is N at the photosensitive material is φ ′, M
If ≧ N, C · cos θ ′ / 2 or more, and cos φ ′
[C- (NM)] / 2 or more, and if M <N, C
・ Cos φ '/ 2 or more and cos θ' ・ [C- (M-
N)] / 2 is an exposure method in which a transparent plate having a thickness not less than / 2 and having a refractive index close to that of the photosensitive material is laminated on the side opposite to the incident side of the photosensitive material. Further, a laser light source having a coherent length of C and irradiating the light-sensitive material with light having a light path to the light-sensitive material and a light path having a light path to the light-sensitive material satisfying | M−N | ≦ C. In the method of exposing a reflection type hologram with two beams, the refractive index approximates the refractive index of the photosensitive material, the laser beam having an optical path of M has a refraction angle θ ′ at the photosensitive material, and the laser beam has an optical path of N. In the light-sensitive material
When the refraction angle is φ ′ and the thickness is M ≧ N, C
・ Cos θ '/ 2 or more and cos φ' ・ [C- (NM)]
/ 2 or more and if M <N, cos θ ′ · [C− (M−N)
] / 2 or more and C · cos φ ′ / 2 or more, a transparent plate having a plate thickness on the side opposite to the incident side of the light- sensitive material is laminated.

[0005]

The light source for hologram exposure is a laser with good coherence, but the coherence distance, ie, the coherence length is 4 to 5 cm for an argon laser, krypton laser, etc. Therefore, in actual exposure, an etalon plate is attached and the coherence length is set to, for example, 500 cm or more.

The present inventors have made the present invention focusing on the fact that increasing the coherence length causes unnecessary formation of interference fringes. That is, two beams
When exposing with 2 beams , two beams from laser light source to photosensitive material
The optical path difference of the light becomes light and N light path is M of Kohi - exposure to lower than the rent lengths. In this case, to interfere with the light light transmitted through the photosensitive material is reflected at the interface between air and the transparent plate for the second time is transmitted through the photosensitive material for the first time, that may arise from unwanted interference fringes.
This unnecessary interference fringe is caused by the light transmitted through the photosensitive material for the first time and the sky.
Light reflected at the interface between the air and the transparent plate and transmitted through the photosensitive material for the second time
If the optical path difference is longer than the coherent length of the laser beam,
good. Assuming that the optical paths to the photosensitive material are M and N, the incident angles of the laser beams in the optical paths M and N to the photosensitive material are θ and φ, respectively, the refraction angles are θ ′ and φ ′, and the thickness of the transparent plate is t. Is transmitted through the light-sensitive material and reflected at the interface between the air and the light-sensitive material, and the total optical path to the interface between the light-sensitive material and the transparent plate is M + 2t / cos θ '(1). 2t / cos θ 'or M + 2t from the optical path M to the light-sensitive material to the light-sensitive material or the optical path N from the other laser light to the light-sensitive material for the first time.
/ Cos θ'-N is greater than the coherence length C of the laser light source, that is, the thickness t of the transparent plate is t> C ・ cos θ '... (2) t> cos θ'. (M−N)] If all of (3) are satisfied, no interference fringes are generated.

Satisfaction of both (2) and (3) means that if M−N ≧ 0, then C ≧ [C− (M−N)].
Equation (2) should be satisfied, and if M−N <0, equation (3) should be satisfied.

Similarly, with respect to the laser beam on the optical path N,
If N−M ≧ 0, then C ≧ [C− (N−M)], and t
> C · cos φ ′, and if N−M <0, a transparent plate having a thickness satisfying t> [C− (N−M)] · cos φ ′ is used as the light path of the photosensitive material. May be laminated on the opposite side.

In the case of one-beam exposure, since M = N, it is sufficient to satisfy t> C · cos θ ′ when the refraction angle of the laser light on the photosensitive material is θ ′. I just need.
Actually, when an etalon plate such as an argon laser or a krypton laser is attached, the coherent length is shortened by removing the etalon plate, and the coherent length at that time is denoted by C. Then, cos θ ′ · [C− (M−
N)] / 2 or more, that is, the absolute value of MN is almost 0 and cos θ ′ is 1 or less, so that a transparent plate having a plate thickness of about C / 2 or more can be laminated on the photosensitive material. I just need.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the drawings. FIGS. 1, 3, and 5 are schematic views of a main part of a hologram exposure apparatus according to preferred embodiments 1, 2, and 3, respectively, of the present invention. FIGS. 2, 4 are embodiments 1 and 2, respectively. FIG. 3 is a schematic diagram of a main part showing an optical system at the time of reproduction of FIG.

Embodiment 1 The conditions at the time of reproduction, the incident angle, the reproduction angle, and the reproduction wavelength are each η.
An example will be described in which 1 = 65 °, η2 = 65 °, and 520 nm (green), and one-beam exposure is performed using a reflecting mirror.

As shown in FIG. 1, a photosensitive material 1 such as dichromated gelatin is put together with a reflecting mirror 2 and a transparent plate 3 having a thickness of 25 mm such as soda lime glass (refractive index 1.52) through an index matching liquid (not shown). An argon laser having an oscillation wavelength of 514.5 nm or an oscillation wavelength of 528.7 nm is incident on the transparent plate 3 as the laser light source 4.
As well as the convex lens 5 and the concave mirror 6.

From the conditions at the time of reproduction, the incident angle θ at the time of exposure is 67.4 when the oscillation wavelength is 514.5 nm according to the Bragg condition.
° and the oscillation wavelength is 528.7 nm, it is 61.4 °, and the refraction angles θ 'are 37.4 ° and 35.3 °, respectively.

514. Oscillation from such a laser light source.
The light of 5 nm or 528.7 nm is converted into parallel light m1, m2,... Mn by the convex lens 5 and the concave mirror 6, and when irradiated on the transparent plate 3, is refracted by the transparent plate 3 and transmitted to the photosensitive material 1 as it is. The light is reflected by the reflecting mirror 2, passes through the light-sensitive material and the transparent plate, is refracted at the transparent plate-air interface, and is emitted. At this time, the reflected light of the light beam m1 by the reflecting mirror 2 (the light transmitted through the light-sensitive material for the second time) m1 '' and the incident light of the light beam m2 to the light-sensitive material (light transmitted through the light-sensitive material for the first time)
An interference fringe is formed in the light-sensitive material due to the interference of m2 '.
Light reflected by m3 reflector (light transmitted through photosensitive material for the second time)
m3 optical path difference between '''' light m1 transmitted through the photosensitive material and the third time is re-reflected at the interface between air and the transparent plate 'is second transparent and air light transparent plate in which has passed through the photosensitive material distance 2 × 25 / cos θ 'becomes reciprocating being reflected by the interface of the plate, in the case of 514.5nm is 62.8Mm, in the case of 528.7nm is ing and 61.2Mm. Both laser light sources have a coherent length C of 40 to 50 mm, and the optical path difference is longer than the coherent length C.
Thus, a hologram with high display quality was obtained without forming unnecessary interference fringes. In this example, since the minimum thickness of the transparent plate is C · cos θ ′ / 2, the thickness may be 19.9 mm or more for 514.5 nm and 20.5 mm or more for 528.7 nm.

The hologram 1 'thus obtained is
Reproduction light source 7 such as a fluorescent display tube or a CRT as shown in FIG.
When the hologram is irradiated with various kinds of information, the hologram reflects light of 520 nm and can be visually recognized by human eyes 8, and thus is suitable as a combiner for a head-up display or the like.

[0016] As shown in Comparative Example 1 FIG. 1, the reproduction condition was replaced by non-reflective glass 3 'having a thickness of 3mm transparent plate, Ru der which the exposure conditions were the same as in Example 1. The incident angle θ to the non-reflective glass is
At 40 ° or less, the reflectance is 0.5% or less, and is non-reflective to air
Light reflected at the interface with glass can be ignored . But this example
Since it is much larger than 40 °, unnecessary reflection at the interface between air and non-reflective glass cannot be ignored . And ray m3
Of light reflected by the mirror (light transmitted through the photosensitive material for the second time) m
The optical path difference between 3 ″ and the light m1 ″ ′ which is re-reflected at the interface between the air and the non-reflective glass and transmitted through the photosensitive material for the third time is 2 × 3 / cos θ ′
Therefore, it becomes 7.6 mm at 514.5 nm and 7.3 mm at 528.7 nm, which is less than the coherent length (40-50 mm) of the laser light source, causing unnecessary interference and generating stripe noise. did.

Example 2 The conditions for reproduction, the incident angle, the reproduction angle, and the reproduction wavelength were each set to η.
An example will be described in which 1 = 30 °, η2 = 60 °, and 620 nm (red), and a transmission hologram is exposed by two beams.

As shown in FIG. 3, an argon laser having an oscillation wavelength of 514.5 nm is used as a laser light source 4 on a laminate of a photosensitive material 1 such as gelatin dichromate and a transparent plate 3 via an index matching solution (not shown). Transparent plate 3
Θ and φ are incident angles to the optical components,
The laser light oscillated from the laser light source 4 is split into two by a beam splitter 9, one of which is converted into parallel light through a reflecting mirror 14, a microscope objective lens 15 and a convex lens 16, and the other light is turned into a reflecting mirror 10. Each of the light-sensitive materials is irradiated as parallel light through a reflecting mirror 11, a microscope objective lens 12, and a convex lens 13 to form interference fringes, and a hologram is recorded.

The incident angles θ and φ at the time of exposure are θ = 22.1 ° and φ = 49.2 ° from the conditions at the time of reproduction according to the Bragg's condition, and the refraction angles θ ′ and φ ′ to the photosensitive material are θ ′ = 14.3. °, φ '=
29.9 °.

The oscillation wavelength as the laser light source is 514.5 nm, Kohi - rent length C is to use an argon laser of 40 to 50 mm. Reflector 14, microscope objective lens 15, convex lens
One of the lights m1, m2, etc. irradiated as parallel light via 16
-Optical path M, reflector 10 and reflector until mn reaches photosensitive material 1
11, the optical paths N of the other lights n1, n2,... Nn irradiated as parallel light through the microscope objective lens 12 and the convex lens 13 to the photosensitive material 1 are arranged to be substantially equal . The thickness of the transparent plate is C · cos θ ′ / 2 or more, that is, argon
When the coherent length C of the laser is 40 mm, 19.4 mm or more,
When the coherent length C is 50 mm, the length is 24.2 mm or more . Light rays refracted by the light-sensitive material 1 at refraction angles θ ′ and φ ′ (light transmitted through the light-sensitive material for the first time), for example, m2 ′ and n2 ′ interfere in the light-sensitive material to form desired interference fringes. However, light reflected at the interface between the air and the transparent plate forming unnecessary interference fringes and transmitted through the photosensitive material for the second time, for example, m1 ″ and n3 ″ and light transmitted through the photosensitive material for the first time, for example, m2 ′ , N2 'are larger than the coherent length, so that interference fringes based on these are not formed, and a hologram with high display quality can be obtained.

The light reflected by the interface between the air and the transparent plate and transmitted through the light-sensitive material for the second time, for example, the interference due to m1 ″ and n3 ″ is a light having a low intensity, and may be ignored. .
As shown in FIG. 4, the hologram 1 'thus obtained is suitably applied to a high-mount stop lamp or the like which is visible to the eyes 8 of a driver or the like of a rear vehicle when light is emitted from the reproduction light source 7. be able to.

The non-reflective glass 3 was replaced 'the reproduction condition of a thickness of 3mm transparent plate 3 shown in Comparative Example 2 FIG. 3, Ru der which the exposure conditions were the same as in Example 2. The reflected light at the interface between air and non-reflective glass is
The angle of incidence θ or φ reflectance becomes 0.5% or less at 40 ° or less relative to nonreflective glass, but can be ignored, that such can not be ignored when it exceeds 40 °. Unnecessary reflection at the interface between air and non-reflective glass avoids et <br/> is not so φ is larger in this example, moreover light transmitted through the photosensitive material a second time is reflected at the interface between air and non-reflective glass For example, the optical path difference between the light transmitted by the light-sensitive material for the first time, for example, m1 ″ and n3 ″, for example, m2 ′ and n2 ′ is 2 × 3 / cos θ ′ = 6.2 mm, respectively. 2 × 3 / cos φ '= 6.9
mm and the coherent length of the laser light source (40-50 m
m) becomes less, creating unnecessary interference, noise striped it occurs.

Example 3 The conditions for reproduction, the incident angle, the reproduction angle, and the reproduction wavelength were respectively η
An example in which 1 = 40 °, η2 = 65 °, and 520 nm (green) are used to expose a reflection hologram with two beams will be described.

As shown in FIG. 5, a light-sensitive material 1 such as dichromated gelatin is laminated on transparent plates 31 and 32 via an index matching solution (not shown), and argon laser having an oscillation wavelength of 514.5 nm is used as a laser light source 4. The laser is disposed together with the optical components with incident angles θ and φ on the transparent plates 31 and 32, and the laser light oscillated from the laser light source 4 is split into two by a beam splitter 9.
A parallel light passes through a microscope objective lens 12 and a convex lens 13, and the other light passes through a reflector 14, a microscope objective lens 15, and a convex lens 16. Record.

The incident angles θ and φ at the time of exposure are, from the conditions at the time of reproduction, θ = 41.8 ° and φ = 68.1 ° according to the Bragg condition, and the refraction angles θ ′ and φ ′ to the photosensitive material are θ ′ = 26.0 °. , Φ '= 37.6 °
Becomes

Reflecting mirror 11, microscope objective lens 12, convex lens
One of the lights m1, m2,... Illuminated as parallel light via 13
.. Nn of the other light n1, n2,... Nn irradiated as parallel light through the optical path M until the mn reaches the photosensitive material 1 and the reflecting mirror 14, the microscope objective lens 15, and the convex lens 16 And the thickness of the transparent plate 31 is not less than C · cos θ ′ / 2, that is, the coherent length is 50 mm.
In the case of 22.5 mm or more, the thickness of the transparent plate 32 is C · cos φ '/ 2
If the coherent length is 19.8 mm or more when the coherent length is 50 mm , the light-sensitive material is reflected at the interface between air and the transparent plate for the second time.
Light m1 '' which transmits through the first time and light n2 ', m which transmits through the light-sensitive material for the first time
Optical path difference from 2 'or reflected at the interface between air and transparent plate
The light n1 ″ that passes through the photosensitive material the second time and the light passes through the photosensitive material the first time
The optical path difference from the light m3 'and n3' is the coherent length.
Since C is larger than C, unnecessary interference fringes based on these lights were not formed, and a hologram with high display quality was obtained.

The light reflected by the interface between the air and the transparent plate and transmitted through the light-sensitive material for the second time, for example, interference by n1 ″ and m1 ″ is a light having a low light intensity and can be ignored. . Comparative Example 3 The transparent plates shown in FIG.
The reproduction condition was replaced, Ru der which the exposure conditions were the same as in Example 3. Reflect at the interface between air and non-reflective glass
That light is incident angle θ reflectance at 40 ° or less relative to nonreflective glass is negligible becomes 0.5% or less, that such can not be ignored when it exceeds 40 °. In this example, since it is larger than 40 degrees , unnecessary reflection at the interface between air and non-reflective glass is unavoidable, and light m1 '' reflected at the interface between air and non-reflective glass and transmitted through the photosensitive material for the second time Light transmitted through the photosensitive material for the first time
The optical path difference between n2 'and m2' , or the difference between light n1 '' reflected at the interface between air and non-reflective glass and transmitted through the photosensitive material for the second time and light m3 'and n3' transmitted through the photosensitive material for the first time Since each of the optical path differences is smaller than the coherent length, unnecessary interference was caused, and striped noise was generated.

Although the preferred embodiments have been described above, the present invention is not limited to these, and various applications are possible. Regarding the light source for exposure, argon lasers having various oscillation wavelengths are preferable because they have high output, but krypton lasers and ruby lasers are also used since coherent lengths are 40 to 50 mm and several mm, respectively, if the etalon plate is removed. Can be. In each of the embodiments, the laser light incident on the photosensitive material at the time of exposure is described as an example of parallel light.
Exposure may be performed using divergent light and divergent light, or divergent light and parallel light. In the case of diverging light, exposure may be performed by an optical system excluding the concave mirror in FIG. 1 and the convex lens in FIG.

The transparent plate is preferably a glass plate having a refractive index close to that of the light-sensitive material, but a transparent resin plate such as acrylic or polycarbonate may be used. As for the photosensitive material, a silver halide photosensitive material, various photopolymers, a photoresist and the like may be appropriately selected and used in addition to the dichromated gelatin.

The hologram obtained by the apparatus of the present invention can be applied as a decorative display to a turn signal of an automobile, a window for a building, a partition, etc. in addition to a head-up display and a high-mount stop lamp.

[0031]

According to the hologram exposure apparatus of the present invention,
Exposure of holograms with high display quality can be performed without the need for expensive non-reflective glass, and even for holograms in which at least one of the incident angle and reproduction angle during reproduction is 40 ° or more, without generating unnecessary interference fringes. You can do it.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a main part of a hologram exposure apparatus according to a first embodiment of the present invention.

FIG. 2 is a main part schematic diagram showing an optical system at the time of reproduction according to the first embodiment.

FIG. 3 is a schematic diagram illustrating a main part of a hologram exposure apparatus according to a second embodiment.

FIG. 4 is a schematic diagram illustrating a main part of an optical system during reproduction according to a second embodiment.

FIG. 5 is a schematic diagram illustrating a main part of a hologram exposure apparatus according to a third embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Sensitive material 3, 31, 32 Transparent plate 3 ', 31', 32 'Non-reflective plate 4 Laser light source 7 Light source for reproduction

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G03H 1/04

Claims (3)

(57) [Claims] 1. A method of irradiating a light-sensitive material with a laser beam from a laser light source having a coherent length of C to expose a reflection hologram with one beam, wherein the refractive index is close to the refractive index of the light-sensitive material. the exposure method of the hologram, which comprises laminating a transparent plate having a thickness of a / 2 or more 'C · cos [theta] is taken as' the refraction angle in the photosensitive material of the light θ to the incident side of the photosensitive material. 2. A laser light source having a coherent length of C.
The optical path from the laser light source to the photosensitive material is M and N
Under the condition of | M−N | ≦ C, two beams are
Exposure method for transmission hologram, which is incident from the side and exposed
In the method, when the refraction angle of the laser beam whose optical path of M is M with the light-sensitive material is θ ′ and the refraction angle of the laser light whose optical path is N with the light-sensitive material is φ ′, M ≧ N Then C
cos θ '/ 2 or more, and cos φ' · [C- (NM)
] / 2 or more, and if M <N, C · cos φ '/ 2
A transparent plate having a plate thickness such that cos θ ′ · [C− (M−N)] / 2 or more and having a refractive index close to that of the photosensitive material is provided on the incident side of the photosensitive material. Hologram exposure method characterized by being laminated on the side opposite to
Law . 3. A light-sensitive material from a laser light source having a coherent length of C, the light having a light path to the light-sensitive material and the light path to the light-sensitive material satisfying | M−N | ≦ C. by irradiating a method <br/> of exposing a reflection hologram by 2-beam, the refractive index is close to the refractive index of the photosensitive material, the optical path is the angle of refraction at the sensitive material of the laser light is M theta ' , The optical path is N
When the refraction angle of the laser beam on the photosensitive material is φ ',
If the thickness is M ≧ N, C · cos θ ′ / 2 or more and cos
φ '· [C- (NM)] / 2 or more, if M <N, co
s θ '· [C- (MN)] / 2 or more, and C · cos
A hologram exposure method, wherein a transparent plate having a thickness of φ '/ 2 or more is laminated on the side opposite to the incident side of the photosensitive material.