JP3340766B2 - Transmission projection screen - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a video conference apparatus, an overhead projector, about the transmission type projection SCREEN utilized in a slide projector or the like.

[0002]

2. Description of the Related Art In order to provide an image with a sense of realism, it is desirable to have a high definition as well as a high viewing range. For large screen displays, HDTV for CRT direct view
36 inches are mass-produced, but 50 inches or more are heavy due to the need to make the glass thicker to withstand the atmospheric pressure, and its practical use is difficult. On the contrary,
The projector is also called a projection type display, and is classified into a rear type using a transmission type projection screen and a front type using a reflection type projection screen. Further, the method is divided into a method using a CRT and a method using a liquid crystal display.

[0003] Front type (reflection type), rear type (transmission type)
In both cases, the image quality of the projection screen is determined by the light source, the CRT, the liquid crystal display, the optical system, the performance of the screen, and the like.
This screen is required to diffuse the projection light projected from the projector in order to widen the field of view. In order to substitute for a CRT, a horizontal viewing area of ± 30 ° or more and a horizontal viewing area of ± 10 ° or more are often used. A vertical viewing zone is required.

A projection screen of this type includes a combination of a Fresnel lens and a lenticular lens as disclosed in Japanese Patent Application Laid-Open No. Hei 3-60104, and a complicated screen of this type has a structure of three or more sheets. There is also. Further, as disclosed in Japanese Utility Model Laid-Open No. 3-42432,
Lenticular lenses are used in orthogonal arrangement,
Some use a diffuse transmission plate. On the other hand, as a typical reflection type projection screen, there is a type using a diffuse reflection plate, but also performs reflection with directivity,
In some cases, the gain is increased mainly in the normal direction.

Here, an example of a conventional transmission type projection screen in which a Fresnel lens and a lenticular lens are combined will be described with reference to FIGS. First, FIG.
FIG. 1 shows a plan view of a transmission type projection screen, and this transmission type projection screen 1 is arranged so that the lens concave and convex surfaces of a Fresnel lens 2 on the projector side and a lenticular lens 4 on the observer 3 side, which will be described later, face each other. It is configured. On the surface of the lenticular lens 4 on the viewer 3 side, a plurality of uneven portions are formed along the vertical direction. A black stripe 4a is provided on each convex portion of the concave and convex portion, and each concave portion between these black stripes 4a is an opening 4b through which light is transmitted.

In use, the transmissive projection screen 1 is arranged, for example, as shown in FIG. That is, a projector 5 is arranged on the left side with respect to the transmissive projection screen 1, and the position of the observer 3 is set on the right side. The projector 5 includes a metal halide lamp 6 as a light source, a condenser 7 disposed near the rear of the metal halide lamp 6, and a liquid crystal display 8 sequentially disposed in front of the metal halide lamp 6.
It is composed of a magnifying projection lens 9. The periphery of the Fresnel lens 2 excluding the lens surface and the projector 5 are covered with a housing 10.

In such a configuration, as shown in FIG. 16, the projection light 11 projected on the transmission projection screen 1 from the left side of the drawing through the liquid crystal display 8 and the magnifying projection lens 9 by the light irradiation of the metal halide lamp 6. ₁ is a transmitted diffused light 11 ₃ whose collimated light 11 ₂ is formed by the Fresnel lens 2 and then diffused by the lenticular lens 4 to expand the field of view.
And observer 3 on the right side of transmissive projection screen 1
Is observed as image information of a wide viewing area.

More specifically [0008] As shown enlarged a portion of the lenticular lens 4 in FIG. 17, the parallel light 11 by the projection light 11 ₁ from the projector 5 is a Fresnel lens 2
Changed to _2a to 11 _2e, these parallel light 11 _2a to 11 _2e
Is incident on one lens 4c constituting the lenticular lens 4 from the left side, the transmitted diffused light 11 _3a to 11 _3e are transmitted spread the lens 4c. At this time, FIG.
As shown by the one-dot chain line, the transmitted diffused light 11 _{3a to} 11 _3e
Surface 11 ₄ equal intensity are formed for, As a result, the straight line 12a shown in FIG. 17, the inside of 12b viewing zone 13 is formed.

[0009] Here, when the lenticular lens 4 is complete diffusion plate, the light intensity in the normal direction of the transmitted diffused light 11 _3c of the transmission surface of the lens 4c Ic, for example the transmitted diffused light 11
Ib the intensity of the transmitted diffused light 11 _3b of direction forming an _3c and θb of
Then, there is a relationship of Ib = Ic · cos (θb) (1) The equation (1) indicates that the luminous intensity decreases as it deviates from the normal, but the luminance is constant.
In general, in the case of the transmission type projection screen 1, since it is not much spread the lenticular lens 4 a parallel beam 11 ₂ in the vertical direction, the fine particles mixed in the lenticular lens 4, a vertical parallel light 11 ₂ by scattering A method of diffusing in the direction is used. Also, the horizontal viewing zone 13 is set to ± 30
The angle is limited to 45 degrees and the luminance is increased around the normal direction.

[0010]

By the way, the lenticular lens 4 used in the transmission type projection screen 1 generally becomes more complicated as the Fresnel lens 2 is changed from an integrated type to a lenticular lens separated type and a front and back double lenticular lens type. Performance is improved. Further, by providing a black stripe 4a on the surface of the lenticular lens 4 on the observer 3 side, the lenticular lens 4 with respect to indoor illumination light is provided.
To reduce surface reflection and increase contrast. For this reason, the shape of the lenticular lens 4 is complicated, the molding method is difficult, and the cost is high.

More specifically, the lenticular lens 4 comprises a plurality of minute lenses 4c, and the pitch between the lenses 4c is about 0.5 to 1.0 mm and is made of plastic. The thickness of the lenticular lens 4 is 3-7.
It is about mm, and the manufacturing method is complicated due to the unevenness on the surface. Further, the lenticular lens 4 is greatly diffused parallel light in the horizontal direction, since it is not much spread in the vertical direction, as a method of diffusing the collimated light 11 ₂ in the vertical direction, mixing fine particles lenticular lens 4 Or it is necessary to provide another lens in the vertical direction. Further, in order to produce a planar shape with a refractive index distribution type lens, a relatively thick lens is required, and it is difficult to enlarge the viewing zone. As described above, the shape of the lenticular lens 4 is complicated, the molding method is extremely difficult, and the cost is high.

The lenticular lens 4 has irregularities on its lens surface, so it is weak to mechanical contact with the surface and scratches the surface when wiping dust and dirt, so that the image quality gradually deteriorates. However, there is a problem that the durability is poor.

[0013]

According to the first aspect of the present invention, a Fresnel lens that transmits the projection light projected from the projector from the back to the front and converts it into parallel light, and is disposed on the front side of the Fresnel lens. An optical element having two hologram elements for transmitting and diffusing the parallel light transmitted through the Fresnel lens to the observer side was configured as a transmission type projection screen.

[0014]

[0015]

[0016]

[0017]

[0018]

According to the first aspect of the present invention, the transmission type projection screen is formed by using a hologram element instead of the conventional lenticular lens, thereby making the transmission type projection screen thinner and the surface thereof smooth. This makes it possible to increase the mechanical contact when wiping dust and dirt, thereby improving the durability. Also,
By using two hologram elements, a single
Corrects optical aberrations including zero-order light by hologram elements
The observer can use the hologram element to generate the 0th order light.
Observe images with less variation in brightness without observing
Can be done.

[0019]

[0020]

[0021]

[0022]

[0023]

It is described with reference to FIGS. 1 to 10 an embodiment of the embodiment of the present invention. 15 to 17 are denoted by the same reference numerals, and description thereof will be omitted. First, based on FIG. 1 to FIG.
explain about. This embodiment is based on the premise that FIG.
Or cash forte the lenticular lens 4 of the transmission type projection screen 1 shown in FIG. 17, as shown in FIGS. 1 and 2,
An optical element 15 having a hologram element 14 is disposed on the front side of the Fresnel lens 2 to form a transmission projection screen 16.
Is formed. The optical element 15 is formed by the hologram element 16 and a support substrate 17, and the hologram element 14 is supported by the support substrate 17 which is in close contact with the front surface.

The incidence in this configuration, as shown in FIG. 3 (Fresnel lens 2 is omitted for simplicity), the projected light 11 _1a is collimated by the Fresnel lens 2 to 11 _1e optical element 15 and, first, the diffused light 11 _2a to 11 _2e is diffused in each small part by the hologram element 14. Then, the distance that the width of the projected light 11 _1a to 11 _1e is sufficient small, resulting iso-intensity (very large number of rays actually) light giving face 11 ₃ of 11 ₄ were divided into by projected light 11 ₁ can be spread. This makes those rays 11 ₄ becomes the visual field is spread is diffused by the hologram element 14, an observer 3 who is on the right side of the transmission type projection screen 16 to be observed as the image information of a wide viewing zone. Further, by using the hologram element 14, the surface of the optical element 15 can be made smoother than the conventional lenticular lens 4 (see FIG. 15). Accordingly, the transmission type projection screen 16 can be made thinner and smoother, and can be more resistant to mechanical contact when wiping dust and dirt, thereby improving durability.

As a modification of the optical element 15 shown in FIG. 3, as shown in FIG. 4, a plurality of black stripes 17a extending in the vertical direction are provided on the front surface of the support substrate 17, and the space between these black stripes 17a is provided. and opening 17b through which light is transmitted, further, if the respective beams of the conventional lenticular lens 4 to the correspondingly projected light 11 _1a to 11 _1e to deflect in different directions by the hologram element 14, the iso-intensity resulting light providing surface 11 ₂ (actually very large number of light) can be diffused by dividing into 11 _3a to 11 _3e. This is the same as obtained by the incident projection light 11 _1a to 11 _1e into one hologram lens. The black stripe 17a can be easily provided in the same manner as in the case of the conventional lenticular lens 4.

Here, the optical element 1 shown in FIGS.
5, for example, the hologram element 14 is configured by using a silver salt photosensitive agent or a polymer film for a hologram recording material and using polycarbonate for a support substrate 17, and using a laser optical system in advance for the hologram recording material. Record. At this time, the exposure pattern (hologram pattern) may be optically produced, may be directly written using a laser or an electron beam according to the CGH data, or a mask may be produced based on the CGH data. Exposure may be performed according to the hologram pattern of the mask. Details of the method of manufacturing such a hologram element 14 will be described later.

The design of the hologram element 14 may be such that the same hologram is simply designed to be diffused in all directions in the horizontal direction.
The diffusion state between the center and the end may be changed so as to be symmetrical on the left and right sides. Further, the diffusion state may be changed so as to be asymmetrical in the vertical direction on the screen 16.
This is because, when observing the large screen 16, if the distance between the screen 16 and the viewer 3 is smaller than the size of the screen 16, the central part and the peripheral part of the screen 16 are compared, and This is because the difference in angle between the normal line and the line connecting the observation position on the screen 16 and the observer 3 increases, and the required diffusion state differs around the screen 16.

Further, the hologram element 14 may have a function of diffusing only in the horizontal direction like a lenticular lens, and the optical element 15 may be designed so that fine particles are mixed into the support substrate 17 and diffused in the vertical direction. If the hologram element 14 is designed to diffuse in both the horizontal and vertical directions in advance, the support substrate 17 is less restricted and effective. At this time, the diffusion state required in the vertical direction is significantly different from that in the horizontal direction, and accordingly, the hologram element 14 may be manufactured so as to be different in both the vertical and horizontal directions.

Here, for example, if the hologram element 14 is fabricated as a volume hologram and as a phase type hologram, the utilization efficiency is theoretically 100%, but in practice the hologram element 14 has a utilization efficiency of 95% or more. Is difficult to produce, and the remaining part is emitted as the zero-order light in the same direction as the incident direction. This state is shown in FIG.
In this case, assuming that the projection light 11 ₁ is incident on the hologram element 14 and transmitted therethrough to obtain the surface 11 ₂ having the same luminous intensity, the projection light 1 1
1 ₁ of intensity of the incident direction as the 0-order light 11 ₃ matching increases. This is the same for the optical element 15 of either of the systems shown in FIGS. If this 0 order light 11 ₃ too large, since only a specific position of the screen 16 is observed greatly changes the luminance for a particular direction of the observer 3, the luminous intensity in the vicinity of the zero-order light 11 ₃ of the hologram element 14 etc. designed to advance becomes smaller, it is important to produce the hologram element 14 so as to minimize the 0 order light 11 _3.

[0030] Therefore, 0 when the large hologram element 14 of the intensity of the primary light 11 _3, for example, as a modified example of the optical element 15 of the configuration shown in FIG. 4, as shown in FIG. 6, the opening between the black stripes 17a By providing the dimming means 18 near the center of the portion 17b, it is possible to prevent the intensity from increasing in the direction of the zero-order light. As the extinction device 18, a simple ND (Neutral Density) may be a filter, absorbs more light in the portion giving the diffused light in the vicinity of the zero-order light to the projection light 11 _1, in this direction other portions by supplementing the 0 order light, as a result, it becomes possible to obtain a surface 11 ₂ of the iso-intensity. Also, this dimming means 1
8 is not limited to the central portion of the opening 17b between the black stripes 17a, but the opening 1 between the black stripes 17a.
7b may be provided on the entire surface. In this case, an element which is designed with a dichroic dye and absorbs light largely in a direction other than the designed direction may be used.

Next, FIG. 7 shows a configuration example of the present embodiment on the premise of the transmission type projection screen 16 shown in FIG. First, the hologram element 14, as shown in FIG.
Two sheets may be provided on both front and rear surfaces of the support substrate 17, and FIG.
As shown in (b), two sheets may be provided on the back surface of the support substrate 17. FIGS. 7A and 7B show the structure of this embodiment.
In the case of the example, by increasing the number of the hologram elements 14 to two, it becomes easier to correct optical aberrations, as in the case of increasing the number of lenses.

As shown in FIG. 8, the hologram element 14 may be used in combination with the lenticular lens 4. In this case, the aberration that cannot be eliminated by the lenticular lens 4 is greatly reduced, or the shape of the lenticular lens 4 is changed. It becomes possible to make it simple. That is, in the example of FIG. 8A, the hologram element 1 is provided on the front surface of the lenticular lens 4.
4 are formed in close contact with each other to form an optical element 15. In this case, the support substrate 17 that supports the hologram element 14 can be omitted. Moreover, since the function of the black stripe 4a can be given to the hologram element 14, the surface on one side of the lenticular lens 4 can be formed flat. On the other hand, in the example of FIG. 8B, the optical element 15 in which the hologram element 14 is supported on the support substrate 17 is disposed between the Fresnel lens 2 and the lenticular lens 4. In this case, the hologram element 14 can be used without largely changing the conventional configuration shown in FIG.

Further, as another modification of the transmission type projection screen 16 shown in FIG. 1, as shown in FIG. 9, the Fresnel lens 2 is eliminated, and the hologram element 14 and the support substrate 1 are removed.
The transmissive projection screen 16 may be formed only by the optical element 15 consisting of 7. That is, the hologram element 14 does not diffuse parallel light in the traveling direction perpendicular to the surface of the screen 16 (parallel light parallelized by the Fresnel lens 2), but the projection light 1 from the projector 5.
In the 1 _1a to 11 _1e directly, for example, it may be designed to diffuse around the normal direction of the light beam 11 _2a to 11 _2e of the screen 16. In this case, the projection light 11 _1a to 1 _1a to 1 applied to the screen 16 directly by the light irradiation of the metal halide lamp 6 via the liquid crystal display 8 and the magnifying projection lens 9
11 _1e and the screen 16 make this screen 1
6, it is necessary to produce holograms optimal for each position. In addition, 0-order light 1
_{1 3a, 11 3b, 11 3c} (11 2c), depends 11 _3d, 11 _3e traveling direction position on the screen 16 of, as a result, since the surface 11 _4a to 11 _4e equal intensity will be obtained, In particular, care must be taken so that the zero-order light 11 _{3a to} 11 _3e is reduced.

When the transmission type projection screen 16 comprising the optical element 15 shown in FIG. 4 is used for a color projector, as shown in FIG. 10 (the Fresnel lens 2 is omitted for simplicity), from the left side is projected in accordance with the image signal into a parallel light by the Fresnel lens 2 R (red), G (green), B projection light 11 ₁ consisting of three colors (blue) is incident on the optical element 15 I do. Here, the hologram element 1 supported on the support substrate 17 of the optical element 15
4 is generally a large wavelength dependency, for example, as when designing the hologram element 14 for light of short wavelength B, and the projection light 11 ₁ B, the surface 11 _2b of the iso-intensity desired is obtained For the G or R projection light 11 ₁ , surfaces 11 _2g and 11 _{2r having} equal luminosity different from B are obtained, respectively.
Surfaces 11 _2r , 11 _2g , and 11 _2b of three colors G and B with equal luminosity
Do not match, the angle at which the screen 16 is viewed is very limited while maintaining good color reproducibility, and chromatic dispersion referred to with a normal lens occurs.

A reference configuration example of a transmission type projection screen with reduced chromatic dispersion will be described with reference to FIG. The same parts as those described in FIG. 10 are denoted by the same reference numerals, and description thereof will be omitted. This reference configuration example is shown in FIG.
In place of the hologram element 14 shown in FIG. 11, as shown in FIG. 11, R, G, B projection light transmitted through the Fresnel lens 2 is provided on the front surface of the Fresnel lens 2 (not shown in FIG. 11). Hologram areas 19r, 19g, 19 having different wavelength characteristics for each pixel of 111r, 111g, 111b
This is provided with a hologram element 19 having b. A transmission projection screen 21 is formed by the optical element 20 supporting the hologram element 19 on the support substrate 17 and the Fresnel lens 2.

In such a configuration, R, G, and B projection lights necessary for spatially divided color display become parallel projection lights 11 _1r , 11 _1g , and 11 _1b by the Fresnel lens 2. The light enters the hologram regions 19r, 19g, and 19b of the hologram element 19 having different wavelength characteristics and located on different screens 21. Then, each of the projected lights 11 _1r , 11 _1g , 11 _1b is _{transmitted to} each hologram area 19.
The surfaces 11 _2r , 11 _2g , and 11 _2b which are dispersed at r, 19g, and 19b, respectively, and have almost the same luminous intensity are obtained. As a result, it is possible to greatly reduce chromatic dispersion due to the difference in wavelength for each of R, G, and B colors.

Here, in a liquid crystal projector using a single panel, it is general to spatially divide R, G, and B using a color filter for color display and display the projection light. The light is spatially divided into R, G, and B and is incident on the screen. However, as in the present reference configuration example, the R, G, and B projected lights 111r, 111g, and 111b are projected.
Hologram areas 19r, 19g, and 19b
Is only required to be aligned, and can be implemented relatively easily.

[0038] Also, the blue itself B, and except for using laser generally to become to disperse it is not a single wavelength, the laser beam is desired as a backlight for a liquid crystal display, the reference configuration example of As described above, by matching the emission line of the metal halide lamp 6 which is often used with the wavelength optimal for the hologram element 19, it is possible to obtain the transmission type projection screen 21 in which the dispersion of B itself is small.

Next, another reference configuration example will be described with reference to FIG. The same parts as those described in FIG. 9 are denoted by the same reference numerals, and description thereof will be omitted. In the present configuration example, the variation in the luminance of the image due to the zero-order light described above is reduced. In addition to the configuration of the transmission type projection screen 16 shown in FIG. Fifteen
A deflecting optical element 23 for deflecting the traveling direction of the projection light 111a to 111e from the projector 5 incident on the hologram element 14 toward the periphery of the viewing zone outside the viewing zone 22 of the observer 3 is provided on the back side of the hologram element 14. . A transmission type projection screen 24 is formed by the deflection optical element 23 and the optical element 15 in which the hologram element 14 is supported on a support substrate 17.

In such a configuration, the transmission type projection screen 2 is irradiated from the left side of the drawing through the liquid crystal display 8 and the magnifying projection lens 9 by irradiating the metal halide lamp 6 with light.
Projection light 11 _1a to 11 _1e projected to 4 will become respectively deflected collimated light 11 _2a to 11 _2e in a direction other than the viewing area 22 of the viewer 3 at the optical deflector 23, these parallel light 11
_{2a to} 112e _enter the hologram element 14. Then, spread by the hologram element 14, further supporting substrate 17 to form a surface 11 _3a to 11 _3e equal intensity and transmitted it will be viewed by the viewer 3. At this time, since the traveling directions of the zero-order lights 11 _{4a to} 11 _4e of the hologram element 14 are deflected toward the periphery of the viewing area 22 of the observer 3 by the deflecting optical element 23, the zero-order lights in the direction of the observer 3 _114a to _114e disappear. Thus, if the viewer 3 is a within a predetermined viewing zone 22, without observing also the zero-order light 11 _4a to 11 _4e in any direction and be capable of observing the variation image with little brightness.

Here, a micro prism, a Fresnel lens, or a hologram element can be used as the deflection optical element 23. In the case where the deflecting optical element 23 composed of a hologram element is used, the influence of the 0th-order light generated in the first sheet is very small in the second sheet if two hologram elements are used, even if there is a little 0th-order light. Therefore, the zero-order light hardly causes a problem. Also, as in the present embodiment, the observer 3
The directions corresponding to the vicinity of the visual field 22 of the 0th order light 11 _{4a to} 11 _4e
Projection light 11 _1a to the hologram element 14 so that the direction
It is also possible to increase the luminous intensity around the viewing zone 22 by making ~ _11e incident. Further, if the characteristics of the hologram element 14 are changed, the light beams 11 _{1a to} 11 _1e projected onto the hologram element 14 need not be parallel, and the Fresnel lens is omitted in this embodiment. Can be done.

Next, a manufacturing method of a hologram element used in the transmission type projection screen, such as before you施例described above will be described with reference to FIG. 13 for. FIG. 13 shows an arrangement of an optical system when a hologram element is manufactured. A hologram recording material roll 26 around which a sheet-like hologram recording material 25 is wound is provided. The hologram recording material 25 sequentially fed in the direction of the arrow Y from the hologram recording material roll 26 is divided into a plurality of slit-shaped recording regions 25a along the width direction. Further, below the hologram recording material 25, a recording optical system 27 for recording a hologram on the hologram recording material 25 is provided. The recording optical system 27 includes a laser light source 28 positioned at the lowest position, a small-diameter spherical lens 29a, a large-diameter spherical lens 29b, and a cylindrical lens disposed between the laser light source 28 and the hologram recording material 25. 30 and a reflection mirror 31.

In such a configuration, the laser light source 28
The laser light emitted from the hologram recording material 25 is converted into light 32a composed of a plane wave through spherical lenses 29a and 29b, and a part of the light 32a composed of the plane wave is converted into light composed of a cylindrical wave by a cylindrical lens 30 to become a signal light 32b. And at the same time, a part of the light 32a composed of a plane wave is reflected by the reflection mirror 31 and irradiated as the reference light 32c to the same recording area 25a of the hologram recording material 25, and The hologram is recorded in the recording area 25a of the hologram recording material 25 by causing the signal light 32b and the reference light 32c to interfere with each other. After recording a hologram with a predetermined exposure amount in this way,
The hologram recording material 25 is moved in the direction of arrow Y, and a hologram is recorded in a newly adjacent slit-shaped recording area 25a. The above scanning is repeated a plurality of times for a predetermined number of recording areas 25a corresponding to the size of the transmission projection screen, and then the whole is developed, so that a large-area and planar hologram element for the transmission projection screen is obtained. Is formed. However, the development may be performed continuously for each recording area 25a where the hologram is recorded.

According to this manufacturing method, when a hologram element for a transmission type projection screen may have the same diffusion characteristics in the vertical direction, light composed of a cylindrical wave can be simply used as the signal light 32b. If the pitch is below,
Utilizing that the hologram element may be divided into stripes. Therefore, according to this manufacturing method , a hologram element having an alternative function can be easily manufactured as compared with a conventional lenticular lens which is difficult to mold.

A plurality of spherical lenses may be used instead of the cylindrical lens 30 depending on the required characteristics of the hologram element, or a spatial modulator may be arranged in the middle. Further, the spherical lens does not need to be the large-diameter spherical lens 29b as shown in FIG. On the other hand, when the coherence of the two light beams of the signal light 32b and the reference light 32c is insufficient, the reference light 32c may be extracted using a beam splitter.

Next, a hologram for a transmission type projection screen
Another method for fabricating the memory element will be described with reference to FIG. The same parts as those described in FIG. 13 are denoted by the same reference numerals. The manufacturing method also relates to a method for manufacturing a manufacturing method <br/> similarly to transmission type holographic optical element for the projection screen shown in FIG. 13. FIG. 14 shows the arrangement of the optical system when the hologram element is manufactured. Below the hologram recording material 25 fed out from the hologram recording material roll 26 in the arrow Y direction, this hologram recording material 25 is shown.
Is provided with a recording optical system 33 for recording a hologram. The recording optical system 33 includes the light source 3 positioned at the lowermost position.
4 and a lens 35 and a mask 36 arranged between the light source 34 and the hologram recording material 25. However, it is assumed that a desired hologram pattern is recorded in advance on the mask 36 based on CGH data or the like.

In such a configuration, light emitted from the light source 34 is incident on the mask 36 via the lens 35, and the hologram pattern of the mask 36 is transferred to one slit-like recording area 25 a of the hologram recording material 25. Then, the hologram is recorded. After recording a hologram with a predetermined exposure amount in this manner, the hologram recording material 25 is moved in the direction of arrow Y, and a hologram is similarly recorded in a newly adjacent slit-shaped recording region 25a. After repeating the above scanning a plurality of times by the recording area 25a corresponding to the size of the transmission projection screen,
By developing the whole, a large-area and planar hologram element for a transmission projection screen is formed. Therefore, according to this manufacturing method , a hologram element having an alternative function can be easily manufactured as compared with the conventional lenticular lens.

The original image (hologram pattern) of the mask 36 may be exposed using a reduction optical system. Also, by dividing the sheet-like hologram recording material 25 into stripes, it is possible to similarly transfer a concavo-convex pattern or directly form a hologram pattern by modulating an electron beam or a laser beam.

[0049]

According to the first aspect of the present invention, a Fresnel lens that transmits the projection light projected from the projector from the back to the front and converts it into parallel light, and is disposed on the front side of the Fresnel lens. An optical element having two holographic elements for transmitting and diffusing the parallel light transmitted through the Fresnel lens to the observer side constituted a transmissive projection screen, so that a conventional lenticular lens was used. Compared to the transmissive projection screen, the transmissive projection screen can be thinner and its surface can be smoothed, thereby strengthening the mechanical contact when wiping dust and dirt.
The durability can be improved. In particular, two
Since a hologram element is used, a single hologram element
Optical aberrations including zero-order light caused by
The observer observes the zero-order light by the hologram element.
It is possible to observe images with little variation in brightness
You can do it.

[0050]

[0051]

[0052]

[0053]

[Brief description of the drawings]

FIG. 1 is a perspective view showing a configuration which is a premise of an embodiment of the present invention.

FIG. 2 is a plan view thereof.

FIG. 3 is an enlarged plan view showing a light ray transmission state of the optical element.

FIG. 4 is an enlarged plan view showing a modification of the optical element of FIG. 3;

FIG. 5 is an enlarged plan view showing a state where zero-order light is generated.

FIG. 6 is an enlarged plan view showing a modification of the optical element of FIG.

FIG. 7 is a plan view showing a configuration example of one embodiment of the present invention .

8 is a plan view showing two variations of FIG.

FIG. 9 is a plan view showing still another modified example of FIG.

FIG. 10 is an enlarged plan view showing a color dispersion state of a transmission type projection screen used for a color projector.

FIG. 11 is a plan view showing a reference configuration example.

FIG. 12 is a plan view showing another reference configuration example.

FIG. 13 is a perspective view illustrating an example of a method for manufacturing a hologram element .

FIG. 14 is a front view showing another example of a method for manufacturing a hologram element .

FIG. 15 is a plan view showing a conventional example.

FIG. 16 is a plan view showing an arrangement of a transmission type projection screen at the time of projection.

FIG. 17 is an enlarged plan view showing a light transmission state of a lenticular lens.

[Explanation of symbols]

 2 Fresnel lens 3 Observer 5 Projector 14 Hologram element 15 Optical element 19 Hologram element 20 Optical element 22 Viewing area 23 Deflection optical element

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G03B 21/56 G03H 1/22

Claims (1)

(57) [Claims] 1. A Fresnel lens that transmits projection light projected from a projector from the back to the front to convert the light into parallel light, and is disposed on the front side of the Fresnel lens and transmits the parallel light transmitted through the Fresnel lens. A transmission projection screen comprising an optical element having two hologram elements for transmitting and diffusing to the observer side.