Hologram screen and a method of producing the same

• US 20020154348A1
• Filed: 03/26/2002
• Published: 10/24/2002
• Est. Priority Date: 07/07/1998
• Status: Active Grant

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: Takada, Kenichiro, Shiozawa, Masahiro
• Granted Patent: US 6,597,477 B2
• Time in Patent Office: Days
• US Class Current: 359/15
• CPC Class Codes: G02B 2027/0118 comprising devices for improving the contrast of the display / brillance control visibility
• CPC Class Codes: G02B 27/0103 comprising holographic elements
• CPC Class Codes: G02B 5/32 Holograms used as optical elements

Abstract

In a hologram screen for reproducing an image based on an output light obtained by scattering and diffusing an image light from an image projector, when a white light (image light) is projected on the hologram screen; and when a distance between two points at optional two points A and B on a surface of the hologram screen is given by 20 cm or less, and a value of the CIE 1976 chromaticity coordinate (u′, v′) at the point A is given by (u′_A, v′_A) and the value of the CIE 1976 chromaticity coordinate (u′, v′) at the point B is given by (u′_B, v′_B); the output light perpendicularly from the surface of the hologram screen has a color distribution in which a color difference Δu′v′ between two points A and B is derived from the following formula (1) and given by 0.06 or less, where, the formula (1) is expressed by,

Δu′v′=[(u′_A-u′_B)²+(v′_A-v′_B)²]^½  (1)

Further, the output light, which is output to a viewpoint defined by the following formula (2) from the surface of the hologram screen, has the color distribution in which a color difference Δu′v′ between two points A and B is derived from the above formula (1) and given by 0.01 or less, where, the formula (2) is expressed by,

H/2L=0.1   (2)

in the formula (2), L is a distance between the viewpoint and a center of the hologram screen, and H is a length of the hologram screen in the direction of the height.

Claims

1. A hologram screen for reproducing an image based on an output light obtained by scattering and diffusing an image light from an image projector, characterized in that;

when a white light is used as the image light and projected on the hologram screen; and

when a distance between two points at optional two points A and B on a surface of the hologram screen is given by 20 cm or less, and a value of the CIE 1976 chromaticity coordinate (u′

, v′

) at the point A is given by (u′

_A, v′

_A) and the value of the CIE 1976 chromaticity coordinate (u′

, v′

) at the point B is given by (u′

_B, v′

_B);

the output light, which is output perpendicularly from the surface of the hologram screen, has a color distribution in which a color difference Δ

u′

v ′

between two points A and B is derived from the following formula (1) and given by 0.06 or less, where, the formula (1) is expressed by,

Δ

u′

v′

=[(u′

_A-u′

_B)²+(v′

_A-v′

_B)²]^½

 

 

(1)

3. A hologram screen as claimed in claim 1, wherein a spectral characteristic of the output light, which is output perpendicularly from the surface of the hologram screen, has a characteristic in which either a difference between peak wavelengths at the whole of the surface of the hologram screen is given by 120 nm or less, or a difference between half bandwidth is given by 100 nm or less.

4. A method for producing a hologram screen in an exposure optical system in which a diffusion light obtained by a light diffusion body is used as an object light, and a non-diffusion light is used as a reference light, characterized in that, when producing the hologram screen defined in claim 1 or 2 by irradiating the object light and the reference light onto a photosensitive material and by exposing the photosensitive material, the photosensitive material has a thickness distribution which is inclined to an incident direction of the reference light.

5. A method for producing a hologram screen as claimed in claim 4, wherein when an incident angle of the reference light to the photosensitive material becomes large, the thickness distribution of the photosensitive material becomes thick.

6. A method for producing a hologram screen as claimed in claim 4, wherein when the thickness at a center of the photosensitive material is T₀, and when thickness difference of both ends of the photosensitive material is Δ

T, the following relationship, i.e., Δ

T≦

0.5T_{0 1}, is defined.

7. A method for producing a hologram screen as claimed in claim 4, wherein the thickness distribution of the photosensitive material is defined by the following formula (3), i.e.,

T=a(R_O-R)+T₀, and a=b·

θ

₀<sup>−

0.9</sup>  

 

(3)

where, T is a thickness at an optional point on the photosensitive material, T₀ is a thickness at the center of the photosensitive material, R is an incident distance of the reference light at the optional point on the photosensitive material, R₀ is the incident distance of the reference light at the center on the photosensitive material, θ

₀ is an incident angle of the reference light at the center of the photosensitive material, and “

b”

is a coefficient determined by the thickness of the photosensitive material and given by 0<

b<

1.

8. A method for producing a hologram screen in an exposure optical system in which a diffusion light obtained by a light diffusion body is used as an object light, and a non-diffusion light is used as a reference light, characterized in that, when producing the hologram screen defined in claim 1 or 2 by irradiating the object light and the reference light onto a photosensitive material and by exposing the photosensitive material, an ultraviolet is previously irradiated onto the photosensitive material so as to have an energy distribution which is inclined to an incident direction of the reference light.

9. A method for producing a hologram screen as claimed in claim 8, wherein the energy distribution of the ultraviolet is given by the following formula (4), i.e.,

0.8E≦

Euv≦

1.2E, and E=0.01·

(R-R₀)+E₀  

 

(4)

where, R is the incident distance of the reference light at the optional point on the photosensitive material, Euv is an amount of energy of the ultraviolet irradiated to the optional point on the photosensitive material, R₀ is the incident distance of the reference light at the center of the photosensitive material, and E₀ is the amount of energy of the ultraviolet irradiated to the center of the photosensitive material.

10. A method for producing a hologram screen in an exposure optical system in which a diffusion light obtained by a light diffusion body is used as an object light, and a non-diffusion light is used as a reference light, characterized in that, when producing the hologram screen defined in claim 1 or 2 by irradiating the object light and the reference light onto a photosensitive material and by exposing the photosensitive material, an incident distance of the reference light at an optional point of the reference light is shorter than an incident distance of an image light which is irradiated from an image projector when reproducing the image on the hologram screen.

11. A method for producing a hologram screen in an exposure optical system in which a diffusion light obtained by a light diffusion body is used as an object light, and a non-diffusion light is used as a reference light, characterized in that, when producing the hologram screen defined in claim 1 or 2 by irradiating the object light and the reference light onto a photosensitive material and by exposing the photosensitive material, an intensity ratio of the reference light and the object light is defined by a relationship of I_R/I_O≦

10, on the whole of the surface of the photosensitive material, where, I_R is the intensity of the reference light, and I_O is the intensity of the object light.

12. A method for producing a hologram screen in an exposure optical system in which a diffusion light obtained by a light diffusion body is used as an object light, and a non-diffusion light is used as a reference light, characterized in that, when producing the hologram screen defined in claim 1 or 2 by irradiating the object light and the reference light onto a photosensitive material and by exposing the photosensitive material, at least two sets of the following steps a) to d) are combined when producing the hologram screen, i.e.,

a) step of using the photosensitive material having the thickness distribution which is inclined to an incident direction of the reference light;

b) step of using the photosensitive material previously irradiated by an ultraviolet so as to have an energy distribution which is inclined to the incident direction of the reference light;

c) step of shortening an incident distance of the reference light at an optional point on the photosensitive material than the incident distance of the image light which is irradiated from an image projector when reproducing the image on the hologram screen; and

d) step of defining an intensity ratio of the reference light and the object light by the relationship of I_R/I_O≦

10, on the whole of the surface of the photosensitive material, where, I_R is the intensity of the reference light, and I_O is the intensity of the object light.

15. A hologram screen as claimed in claim 14, wherein the light diffusion angle of the hologram screen is defined by an angle in which the light diffusion angle of the hologram screen is 10°

or more.

18. A hologram screen as claimed in claim 17, wherein the diffusion light which is obtained by the light diffusion body is used as the object light;

the non-diffusion light is used as the reference light;

the object light and the reference light are irradiated on the photosensitive material in order to form the interference fringe; and

a heat treatment is performed for the photosensitive material in the range of 80°

to 150°

C. so that a hologram element is produced.

19. A hologram screen as claimed in claim 17, wherein the diffusion light which is obtained by the light diffusion body is used as the object light;

the non-diffusion light is used as the reference light;

a sum of an exposure intensity of the object light and the exposure intensity of the reference light is defined in the extent of 0.02 to 50 mW/cm²;

the object light and the reference light are irradiated on the photosensitive material in order to form the interference fringe so that a hologram element is produced.

20. A hologram screen as claimed in claim 17, wherein the diffusion light which is obtained by the light diffusion body is used as the object light;

the non-diffusion light is used as the reference light;

an intensity ratio (R/O) of the intensity (O) of the object light and the intensity (R) of the reference right is defined by 0.1 to 30; and

the object light and the reference light are irradiated on the photosensitive material in order to form the interference fringe so that a hologram element is produced.

2. A hologram screen for reproducing an image based on an output light obtained by scattering and diffusing an image light from an image projector, characterized in that;

when a white light is used as the image light and projected on the hologram screen; and

when a distance between two points at optional two points A and B on a surface of the hologram screen is given by 20 cm or less, and a value of the CIE 1976 chromaticity coordinate (u′

, v′

) at the point A is given by (u′

_A, v′

_A) and the value of the CIE 1976 chromaticity coordinate (u′

, v′

) at the point B is given by (u′

_B, v′

_B);

the output light, which is output to a viewpoint defined by the following formula (2) from the surface of the hologram screen, has a color distribution in which a color difference Δ

u′

v′

between two points A and B is derived from the following formula (1) and given by 0.01 or less, where, the formula (1) is expressed by,

Δ

u′

v′

=[(u′

_A-u′

_B)²+(v′

_A-v′

_B)²]^½

 

 

(1)

and, where, the formula (2) is expressed by,

H/2L=0.1  

 

(2)

in the formula (2), L is a distance between the viewpoint and a center of the hologram screen, and H is a length of the hologram screen at the direction of the height.

13. A method for producing a hologram screen formed by interfering of a reference light and an object light transmitted through a light diffusion body, and by recording the light diffusion body on a photosensitive material, characterized in that;

a mirror is arranged approximately perpendicular to the light diffusion body;

the photosensitive material and the light diffusion body are rotated by the same angle θ

around an axis which is intersected perpendicularly to a center of the photosensitive material and used as a rotational center; and

a polarized direction of a laser light is defined by either P-polarization or S-polarization which is inclined by the angle in the range of θ

−

5 to θ

+5.

14. A hologram screen for reproducing an image based on an output light obtained by scattering and diffusing an image light from an image projector, characterized in that;

a half bandwidth of a spectral characteristic of the hologram screen is given by 100 nm or more;

a diffusion light which is obtained by a light diffusion body having a large light diffusion angle is used as an object light;

a non-diffusion light is used as a reference light; and

the object light and the reference light are irradiated on a photosensitive material in order to form an interference fringe so that a hologram element is produced.

16. A hologram screen for reproducing an image based on an output light obtained by scattering and diffusing an image light from an image projector, characterized in that;

a half bandwidth of a spectral characteristic of the hologram screen is given by 100 nm or more;

a diffusion light which is obtained by a light diffusion body is used as an object light;

a non-diffusion light is used as a reference light; and

the object light and the reference light are irradiated on a photosensitive material having thickness of 1 to 20 μ

m in order to form an interference fringe so that a hologram element is produced.

17. A hologram screen for reproducing an image based on an output light obtained by scattering and diffusing an image light from an image projector, characterized in that;

a peak wavelength of the hologram screen is either 525 nm or less, or 585 nm or more;

a half bandwidth of a spectral characteristic of the hologram screen is 100 nm or more;

a diffusion light which is obtained by a light diffusion body is used as an object light;

a non-diffusion light is used as a reference light;

the object light and the reference light are irradiated on a photosensitive material in order to form an interference fringe; and

a refractive index of the photosensitive material is adjusted so that a hologram element is produced.

21. A hologram screen for reproducing an image based on an output light obtained by scattering and diffusing an image light from an image projector, characterized in that;

a peak wavelength of the hologram screen is either 525 nm or less, or 585 nm or more;

a diffusion light which is obtained by a light diffusion body is used as an object light;

a non-diffusion light is used as a reference light;

the object light and the reference light are irradiated on a photosensitive material in order to form an interference fringe; and

a thickness of of the photosensitive material is adjusted so that a hologram element is produced.

22. A hologram screen for reproducing an image based on an output light obtained by scattering and diffusing an image light from an image projector, characterized in that;

a peak wavelength of the hologram screen is either 525 nm or less, or 585 nm or more;

a diffusion light which is obtained by a light diffusion body is used as an object light;

a non-diffusion light is used as a reference light;

an incident angle θ

_r of the reference light to a photosensitive material is different from an incident angle θ

e of the image light to the hologram screen; and

the object light and the reference light each having the above different angle are irradiated on the photosensitive material in order to form an interference fringe so that a hologram element is produced.

23. A hologram screen as claimed in claim 22, wherein an amount of angle correction which indicates a difference between the incident angle θ

_r and the incident angle θ

e is defined by the extent of −

5°

to +5°

.

27. A hologram screen as claimed in claim 26, wherein a screen gain of the hologram screen is given by 0.3 or more.

29. A method for producing a hologram screen as claimed in claim 28 wherein, when the scattering angle of the light diffusion body is set to a large angle, the intensity ratio E_R/E_O is set to a small value.

24. A hologram screen for reproducing an image based on an output light obtained by scattering and diffusing an image light from an image projector, characterized in that;

a half bandwidth of a spectral characteristic of the hologram screen is given by 100 nm or more;

a diffusion light which is obtained by a light diffusion body is used as an object light;

a non-diffusion light is used as a reference light; and

a plurality of object lights each having different angle are irradiated on a photosensitive material in order to form an interference fringe so that a hologram element is produced.

25. A hologram screen for reproducing an image based on an output light obtained by scattering and diffusing an image light from an image projector, characterized in that;

when producing the hologram screen based on the conditions in which a half bandwidth of a spectral characteristic of the hologram screen is given by 100 nm or more, and a peak wavelength of the hologram screen is either 525 nm or less, or 585 nm or more;

any one or more of the following steps (A) to (H) is used when producing the hologram screen, i.e.,

(A) step of forming the interference fringe on a photosensitive material in such a way that a diffusion light which is obtained by a light diffusion body having a large diffusion angle is used as an object light, a non-diffusion light is used as a reference light, and the object light and the reference light are irradiated on the photosensitive material;

(B) step of forming the interference fringe on the photosensitive material in such a way that the diffusion light which is obtained by the light diffusion body is used as the object light, the non-diffusion light is used as the reference light, and the object light and the reference light are irradiated on the photosensitive material having a thickness of 1 to 20 μ

m;

(C) step of forming the interference fringe on the photosensitive material in such a way that the diffusion light which is obtained by the light diffusion body is used as the object light, the non-diffusion light is used as the reference light, an intensity ratio (R/O) of an intensity (O) of the object light and the intensity (R) of the reference light is given by 0.1 to 30; and

the object light and the reference light are irradiated on the photosensitive material;

(D) step of forming the interference fringe on the photosensitive material in such a way that the diffusion light which is obtained by the light diffusion body is used as the object light, the non-diffusion light is used as the reference light, an incident angle θ

_r of the reference light to the photosensitive material is different from an incident angle θ

e of the image light to the hologram screen; and

the object light and the reference light each having the above different angle are irradiated on the photosensitive material in order to form the interference;

(E) step of forming the interference fringe on the photosensitive material in such a way that the diffusion light which is obtained by the light diffusion body is used as the object light, the non-diffusion light is used as the reference light, and a plurality of object lights each having different angle are irradiated on the photosensitive material in order to form the interference fringe thereon;

(F) step of forming the interference fringe on the photosensitive material in such a way that the diffusion light which is obtained by the light diffusion body is used as the object light, the non-diffusion light is used as the reference light, the object light and the reference light are irradiated on the photosensitive material in order to form the interference fringe, and a heat treatment is performed in the extent of 80°

to 150°

C.;

(G) step of forming the interference fringe on the photosensitive material in such a way that the diffusion light which is obtained by the light diffusion body is used as the object light, the non-diffusion light is used as the reference light, a sum of an exposure intensity of the exposure intensity of the object light and the exposure intensity of the reference light is given by the extent of 0.02 to 50 mW/cm², and the object light and the reference light are irradiated on the photosensitive material in order to form the interference fringe; and

(H) step of forming the interference fringe on the photosensitive material in such a way that the diffusion light which is obtained by the light diffusion body is used as the object light, the non-diffusion light is used as the reference light, the object light and the reference light are irradiated on the photosensitive material in order to form the interference fringe, and the thickness of the photosensitive material is adjusted.

26. A hologram screen for reproducing an image based on an output light obtained by scattering and diffusing an image light from an image projector, characterized in that, a haze ratio is given by 5 to 60%.

28. A method for producing a hologram screen in which an object light which is obtained by transmitting a light diffusion body or by reflecting on the light diffusion body, and a reference light obtained by a non-diffusion light, are irradiated on a photosensitive material to form an interference fringe;

and the interference fringe is recorded on the photosensitive material;

an intensity ratio E_R/E_O of the intensity E_O of the object light and the intensity E_R of the reference light is changed in accordance with a scattering angle of the light diffusion body.