JPH0682625A - Transmission type projecting screen and production of hologram element for transmission type projecting screen - Google Patents

Abstract

PURPOSE:To provide the transmission type projecting screen having a smooth surface and high durability. CONSTITUTION:This transmission type projecting screen 16 is constituted of a Fresnel lens 2 which allows the transmission of the light projected from a projector in the direction from a rear surface to a front surface and changes the light to collimated beams of light and a hologram element 14 which is disposed on the front surface side of the Fresnel lens 2 and allows the transmission and diffusion of the collimated beams of light transmitted through the Fresnel lens 2. The thickness of the transmission type projecting screen 16 is reduced and its surface is smoothed by using the hologram element 14 having the function substitutive for the function of the conventional lenticular lenses as compared to such lenticular lenses, thereby, the durability is enhanced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmissive projection screen used in a video conference apparatus, an overhead projector, a slide projector, etc., and a method for producing a hologram element for the transmissive projection screen.

[0002]

2. Description of the Related Art In order to give a realistic image, it is desirable to have a high definition and a high viewing area. For large screen displays, HDTV for CRT direct view type
Although 36 inches is mass-produced for the purpose, the thickness of 50 inches or more is heavy because the glass needs to be thick to counter the atmospheric pressure, and its practical application is difficult. On the contrary,
The projector is also called a projection type display, and is divided into a rear type using a transmission type projection screen and a front type using a reflection type projection screen. Further, there are a method using a CRT and a method using a liquid crystal display.

Front type (reflective type), rear type (transmissive type)
In addition, the image quality of the projection screen is determined by the light source, CRT, liquid crystal display, optical system, performance of the screen, etc., but the performance is greatly affected especially by the last screen.
This screen is required to diffuse the projection light projected from the projector in order to expand the field of view, and in many cases as a substitute for the CRT, a horizontal viewing area of ± 30 degrees or more and a horizontal viewing area of ± 10 degrees or more. Vertical viewing zone is required.

Regarding this type of projection screen, there is a combination of a Fresnel lens and a lenticular lens as disclosed in Japanese Patent Laid-Open No. 3-60104, and a complex type of this type has three or more sheets. There is also. In addition, as disclosed in Japanese Utility Model Publication No. 3-42432, 2
One that uses two lenticular lenses arranged orthogonally,
Some use a diffuse transmission plate. On the other hand, as a typical reflection type projection screen, there is one that uses a diffuse reflection plate, but in addition to this, reflection with a directivity is performed,
There is one that increases the gain around 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.
Shows a plan view of a transmissive projection screen. This transmissive projection screen 1 is arranged such that the lens concave and convex surfaces of a projector-side Fresnel lens 2 and an observer 3-side lenticular lens 4 described later face each other. Is configured. On the surface of the lenticular lens 4 on the observer 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 the black stripes 4a is an opening portion 4b through which light is transmitted.

When the transmission type projection screen 1 is used, it is arranged, for example, as shown in FIG. That is, the projector 5 is arranged on the left side of 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 arranged near the rear of the metal halide lamp 6, and a liquid crystal display 8 arranged 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 structure, as shown in FIG. 16, the projection light 11 projected from the left side of the paper on the transmissive projection screen 1 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 that is collimated 11 ₂ by the Fresnel lens 2 and then diffused by the lenticular lens 4 to widen the field of view.
Next, the observer 3 on the right side of the transmissive projection screen 1
It is observed as image information in a wide viewing area.

More specifically, as shown in an enlarged view of a part of the lenticular lens 4 in FIG. 17, the projection light 11 ₁ from the projector 5 is collimated by the Fresnel lens 2 into parallel light 11 1.
_{2a to} 11 _2e , and these parallel lights 11 _{2a to} 11 _2e
Enters the one lens 4c constituting the lenticular lens 4 from the left side of the paper, is transmitted through this lens 4c and is diffused to become transmitted diffused light 11 _{3a to} 11 _3e . At this time, FIG.
As indicated 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.

When the lenticular lens 4 is a perfect diffusing plate, the luminous intensity of the transmitted diffused light 11 _{3c in} the normal direction of the transmitting surface of the lens 4c is Ic, for example, the transmitted diffused light 11
Let Ib be the luminous intensity of the transmitted diffused light 11 _{3b in} the direction that forms θb with _3c.
Then, there is a relation of Ib = Ic · cos (θb) (1). The expression (1) shows that the luminous intensity decreases as it deviates from the normal line, but the luminance is constant.
Generally, in the case of the transmissive projection screen 1, since it is not necessary to diffuse the parallel light 11 ₂ in the vertical direction by the lenticular lens 4 so much, fine particles are mixed in the lenticular lens 4 and the parallel light 11 ₂ is made vertical by scattering. The method of diffusing in the direction is used. Further, the horizontal viewing area 13 is ± 30 to
It is limited to 45 degrees and the brightness is increased around the normal direction.

[0010]

By the way, the lenticular lens 4 used in the transmission type projection screen 1 generally becomes complicated from the integrated type of the Fresnel lens 2 to the lenticular lens separated type and the front and back double lenticular lens type. Performance improves. Further, by providing the black stripe 4a on the surface of the lenticular lens 4 on the viewer 3 side, the lenticular lens 4 for the illumination light in the room is provided.
The surface reflection is suppressed and the contrast is increased. For this reason, the shape of the lenticular lens 4 becomes complicated, the molding method is difficult, and the cost becomes high.

Specifically, the lenticular lens 4 is composed of a plurality of minute lenses 4c, and is made of plastic with a pitch between the lenses 4c of about 0.5 to 1.0 mm. The thickness of the lenticular lens 4 is 3 to 7
Since it is about mm, the manufacturing method is complicated due to the unevenness on the surface, and the larger the in-plane variation at the time of molding, the easier the occurrence. The lenticular lens 4 diffuses parallel light largely in the horizontal direction and does not need to diffuse much in the vertical direction. Therefore, as a method of diffusing the parallel light 11 ₂ in the vertical direction, fine particles are mixed into the lenticular lens 4. It is necessary to install another lens in the vertical direction. Further, a relatively thick lens is required to form a planar shape with a gradient index lens, and it is difficult to increase the viewing area. As described above, the shape of the lenticular lens 4 is complicated, and the method of molding the lenticular lens 4 is extremely difficult and the cost is high.

Further, since the lens surface of the lenticular lens 4 is uneven, it is vulnerable to mechanical contact with the surface, and when scratching dust or dirt, the surface is scratched, and the image quality is gradually deteriorated. However, there is a problem of poor durability.

[0013]

According to a first aspect of the present invention, a Fresnel lens that transmits projection light projected from a projector from the rear surface to the front surface to convert the light into parallel light is provided, and the Fresnel lens is disposed on the front surface side of the Fresnel lens. A transmission type projection screen is constituted by an optical element having a hologram element for transmitting and diffusing the parallel light transmitted through the Fresnel lens to the observer side.

According to a second aspect of the present invention, a Fresnel lens for converting the projection light spatially divided into three colors of red, green, and blue from the projector and projecting the light into parallel light by transmitting the light from the back surface to the front surface direction. A transmission type projection screen is formed by an optical element having a hologram element having a different wavelength characteristic for each pixel of the parallel light of red, green and blue transmitted through the Fresnel lens and transmitted through the Fresnel lens. did.

According to a third aspect of the present invention, an optical element having a hologram element for transmitting and diffusing the projection light projected from the projector from the back surface to the front surface, and the hologram element provided on the back surface side of the optical element. A transmission type projection screen is constituted by a deflection optical element for deflecting the traveling direction of the projection light incident on the optical system to the peripheral direction of the visual field outside the visual field of the observer.

According to a fourth aspect of the present invention, as a method for producing a hologram element for these transmission type projection screens,
A sheet-shaped hologram recording material is divided into a plurality of stripe-shaped recording areas, and one of these recording areas is irradiated with signal light composed of a spherical wave or cylindrical surface wave and reference light composed of a plane wave to cause interference. To record a hologram with
A hologram is recorded in sequence in each of a predetermined number of recording areas connected to the recording area in which the hologram is recorded, so that a planar hologram element for a transmission projection screen is manufactured.

In a fifth aspect of the present invention, as a method for producing a hologram element for these transmission type projection screens,
The sheet-shaped hologram recording material is divided into a plurality of stripe-shaped recording areas, and the hologram is transferred and recorded based on a mask having a desired hologram pattern formed in advance in one of these recording areas. A flat hologram element for a transmissive projection screen is manufactured by sequentially transferring and recording a hologram for each of a predetermined number of the recording areas connected to the transferred and recorded recording areas.

[0018]

According to the first aspect of the present invention, the transmissive projection screen is constructed by using a hologram element in place of the conventional lenticular lens, thereby making the transmissive projection screen thin and smoothing its surface. This makes it possible to strengthen the mechanical contact at the time of wiping off dust and dirt and enhance the durability.

According to the second aspect of the invention, red, green,
By providing an optical element that has a hologram element with different wavelength characteristics for each pixel of blue parallel light, it is possible to reduce the color dispersion due to the hologram element compared to one hologram element with the same wavelength characteristics. Therefore, it can be applied to a color projector.

In the third aspect of the invention, the traveling direction of the projection light incident on the hologram element of the optical element is deflected by the deflecting optical element in the peripheral direction of the visual area outside the visual area of the observer. Can observe an image with little variation in brightness without observing the 0th order light from the hologram element.

In a fourth aspect of the present invention, the sheet-shaped hologram recording material is divided into a plurality of stripe-shaped recording areas, and a predetermined number of these recording areas are connected to each other, that is, a number corresponding to the size of the transmissive projection screen. By recording the hologram by sequentially irradiating the interference wave of the signal light and the reference light for each recording area, compared to the conventional lenticular lens, which is difficult to mold, it is a large screen for a transmission type projection screen with the same function. A hologram element having an area and a plane shape can be easily manufactured.

In the fifth aspect of the invention, the sheet-shaped hologram recording material is divided into a plurality of stripe-shaped recording areas, and the hologram pattern of the mask is sequentially transferred to each of a predetermined number of recording areas that are connected to each other. By recording, it becomes possible to easily manufacture a large-area and flat hologram element for a transmission type projection screen having a function similar to that of a conventional lenticular lens which is difficult to form.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the invention described in claim 1 will be described with reference to FIGS. Note that FIGS.
The same parts as those described in 1 are indicated by the same reference numerals, and the description will be omitted. In this embodiment, instead of the lenticular lens 4 of the transmission type projection screen 1 shown in FIGS. 15 to 17, an optical element having a hologram element 14 on the front side of the Fresnel lens 2 as shown in FIGS. 1 and 2. The transmission type projection screen 16 is formed by disposing the element 15. The optical element 15 is formed by the hologram element 16 and a supporting substrate 17, and the hologram element 14 is supported by the supporting substrate 17 that is in close contact with the front surface thereof.

In such a structure, as shown in FIG. 3 (the Fresnel lens 2 is omitted for simplicity), the projection lights 11 _{1a to} 11 _1e collimated by the Fresnel lens 2 are incident on the optical element 15. Then, first, the hologram element 14 diffuses each minute portion to become diffused light 11 _{2a to} 11 _2e . Then, at a distance where the widths of the projection lights 11 _{1a to} 11 _1e are sufficiently small, the projection light 11 is divided into light rays (actually, a very large number of light rays) 11 ₄ that give a surface 11 ₃ with equal luminous intensity as a result. It becomes possible to diffuse ₁ . 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). Therefore, the transmissive projection screen 16 can be made thinner and smoother, and it is more resistant to mechanical contact when wiping dust and dirt, and durability can be improved.

As a modification of the optical element 15 shown in FIG. 3, as shown in FIG. 4, a plurality of black stripes 17a are provided on the front surface of the supporting substrate 17 in the vertical direction, and the black stripes 17a are provided between the black stripes 17a. If the aperture 17b through which light is transmitted and the respective light rays of the projection lights 11 _{1a to} 11 _1e are deflected in different directions by the hologram element 14 in correspondence with the conventional lenticular lens 4, as a result, equal luminosity is obtained. It becomes possible to divide the light beam that gives the surface 11 ₂ (actually a very large number of light beams) 11 _{3a to} 11 _3e and diffuse it. This is the same as when the projection lights 11 _{1a to} 11 _1e are made incident on one hologram lens. Further, the black stripe 17a can be easily provided as in the case of the conventional lenticular lens 4.

Here, the optical element 1 shown in FIG. 3 and FIG.
5, the hologram element 14 is configured by using a silver salt photosensitizer or a polymer film as the hologram recording material and using polycarbonate as the supporting substrate 17, and using a laser optical system in advance as the hologram recording material. To record. At this time, the exposure pattern (hologram pattern) may be optically produced, but may be directly written using a laser or an electron beam in accordance with the CGH data, or a mask may be produced based on the CGH data. You may make it expose according to the hologram pattern of this mask. Details of a method of manufacturing such a hologram element 14 will be described later.

As for the design of the hologram element 14, the same hologram may be designed so as to be diffused horizontally in all places, but the transmission type projection screen 16 is used.
You may change the diffusion state of the center part and an edge part so that it may become symmetrical at right and left. Further, the diffusion state may be changed so as to be asymmetrical above and below the screen 16.
This is because when the large screen 16 is observed and the distance between the screen 16 and the observer 3 is small with respect to the size of the screen 16, the central portion and the peripheral portion of the screen 16 are compared with each other. 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 becomes large, and the required diffusion state varies 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 supporting substrate 17 and diffused in the vertical direction. Further, if the hologram element 14 is designed in advance so as to be diffused in both horizontal and vertical directions, the restriction of the support substrate 17 is small 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 made different in both the vertical and horizontal directions.

If, for example, the hologram element 14 is manufactured as a volume hologram and also as a phase hologram, the utilization efficiency thereof will theoretically be 100%, but in reality, the utilization efficiency of the hologram element 14 is 95% or more. Is difficult to manufacture, and the remaining part is emitted as the 0th 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 a surface 11 _{2 of} equal luminous intensity, the projection light 1 1
The luminous intensity of the 0th order light 11 ₃ increases in the direction that coincides with the incident direction of 1 ₁ . This is the same for both types of optical element 15 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 It is important to fabricate the hologram element 14 so that the 0th-order light 11 ₃ is made as small as possible, for example, by designing so as to be small in advance.

Therefore, in the case of the hologram element 14 in which the intensity of the 0th-order light 11 ₃ is high, for example, as a modification of the optical element 15 having the configuration shown in FIG. 4, as shown in FIG. 6, an opening between the black stripes 17a is formed. By providing the dimming means 18 near the center of the portion 17b, it becomes possible to prevent the intensity from increasing in the direction of the 0th order light. The light reducing means 18 may be a simple ND (Neutral Density) filter, which absorbs a large amount of light that gives diffused light in the vicinity of the 0th-order light to the projection light 11 ₁ , and this direction is different from other parts. By supplementing with the 0th-order light, it is possible to obtain a surface 11 ₂ having an equal luminous intensity as a result. 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
It may be provided on the entire surface of 7b. In this case, an element designed with a dichroic dye and capable of largely absorbing light in directions other than the designed direction may be used.

Subsequently, modifications of the transmission type projection screen 16 shown in FIG. 1 are shown in FIGS. First, as shown in FIG. 7A, the hologram element 14 includes a support substrate 17
7 may be provided on both the front and back sides, or two may be provided on the back surface of the support substrate 17, as shown in FIG. 7B. In the case of the method shown in FIGS. 7A and 7B, by increasing the number of hologram elements 14 to two, it becomes easy to correct the optical aberration as in the case where the number of lenses is increased.

Further, as shown in FIG. 8, the hologram element 14 may be used together with the lenticular lens 4, and in this case, the aberration which cannot be eliminated by the lenticular lens 4 is greatly reduced or the shape of the lenticular lens 4 is changed. It can be made 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 is closely attached to form the optical element 15. In this case, the support substrate 17 supporting the hologram element 14 can be omitted. Moreover, since the hologram element 14 can be provided with the function of the black stripe 4a, one surface 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 by the support substrate 17 is arranged 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 supporting substrate 1 are removed.
The transmission type projection screen 16 may be formed only by the optical element 15 composed of 7. That is, the hologram element 14 does not diffuse parallel light (parallel light parallelized by the Fresnel lens 2) in the traveling direction perpendicular to the surface of the screen 16, but the projection light 1 from the projector 5
The 1 _{1a to} 11 _1e may be designed to be diffused directly, for example, centering on the light rays 11 _{2a to} 11 _2e in the normal direction of the screen 16. In this case, the projection light 11 _1a to 1 _1a radiated to the screen 16 directly through the liquid crystal display 8 and the magnifying projection lens 9 by the light irradiation of the metal halide lamp 6.
The direction between the 1 _1e and the screen 16 is the screen 1
Since it depends on the position on 6, it is necessary to prepare the optimum hologram for each position. Also, the 0th order light 1
Since the traveling directions of 1 _3a , 11 _3b , 11 _3c (11 _2c ), 11 _3d , and 11 _3e are different depending on the position on the screen 16, as a result, isoluminous surfaces 11 _{4a to} 11 _4e are obtained. In particular, it is necessary to pay attention so that the 0th-order lights 11 _{3a to} 11 _3e decrease.

By the way, when the transmission type projection screen 16 composed of 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), Projected light 11 ₁ of three colors of R (red), G (green), and B (blue), which is projected from the left side of the paper according to an image signal and is made into parallel light by the Fresnel lens 2, is incident on the optical element 15. To do. Here, the hologram element 1 supported by the support substrate 17 of the optical element 15
In general, 4 has a large wavelength dependency, and for example, when the hologram element 14 is designed for light having a short wavelength of B, it is assumed that a surface 11 _2b having a desired _isoluminance is obtained for the B projection light 11 ₁ . Also, with respect to the G and R projection lights 11 ₁ , respectively, the surfaces 11 _2g and 11 _{2r having the same} luminosity different from B become R,
Surfaces of equal intensity in three colors G and B 11 _2r , 11 _2g , 11 _2b
Therefore, the angle at which the screen 16 is viewed is very limited while maintaining good color reproducibility, and the color dispersion referred to by a normal lens occurs.

Therefore, as a transmission type projection screen in which the color dispersion is reduced, an embodiment of the invention described in claim 2 will be described with reference to FIG. The same parts as those described in FIG. 10 are designated by the same reference numerals, and the description thereof will be omitted. In this example, instead of the hologram element 14 shown in FIG. 10, as shown in FIG. 11, the Fresnel lens 2 (see FIG.
(Not shown in FIG. 1), a hologram area 19 having different wavelength characteristics for each pixel of the R, G, B projection lights 11 _1r , 11 _1g , 11 _1b transmitted through the Fresnel lens 2 is provided.
The hologram element 19 having r, 19g, and 19b is provided. A transmission projection screen 21 is formed by the Fresnel lens 2 and the optical element 20 in which the hologram element 19 is supported by the support substrate 17.

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

Here, in a liquid crystal projector using one panel, it is general to spatially divide R, G, B by using color filters for color display, and the projection light is also used. Although it is spatially divided into R, G, and B and enters the screen, as in this embodiment,
Providing separate hologram areas 19r, 19g, and 19b for the R, G, and B projection lights 11 _1r , 11 _1g , and 11 _1b can be performed relatively easily by only performing alignment. Is.

Further, since the blue color of B itself is generally not a single wavelength except for the case of using a laser, it will be dispersed. Therefore, laser light is preferable as a backlight for liquid crystal display, but as in this embodiment. In addition, by matching the bright line of the metal halide lamp 6 that is often used and the optimum wavelength for the hologram element 19, it is possible to obtain the transmission type projection screen 21 in which B itself is less dispersed.

Next, an embodiment of the invention described in claim 3 will be described with reference to FIG. The same parts as those described in FIG. 9 are designated by the same reference numerals, and the description thereof will be omitted. In the present embodiment, the variation in the brightness of the image due to the 0th-order light is reduced, and in addition to the configuration of the transmissive projection screen 16 shown in FIG. 9, as shown in FIG. A deflection optical element 23 for deflecting the traveling directions of the projection lights 11 _{1a to} 11 _1e incident on the hologram element 14 from the projector 5 to 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 15. Has been. 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 by the support substrate 17.

In such a structure, the transmissive 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 the light irradiation of the metal halide lamp 6.
The projection lights 11 _{1a to} 11 _1e projected onto the light beam _{No. 4} are deflected by the deflection optical element 23 in directions other than the visual field 22 of the observer 3 to become parallel lights 11 _{2a to} 11 _2e.
2a to _112e are incident on the hologram element 14. Then, the light is diffused by the hologram element 14 and further transmitted through the support substrate 17 to form equal-intensity surfaces 11 _{3a to} 11 _3e to be observed by the observer 3. At this time, since the traveling directions of the 0th-order lights 11 _{4a to} 11 _4e of the hologram element 14 are deflected by the deflection optical element 23 in the peripheral direction of the visual field 22 of the observer 3, the 0th-order light is directed in the direction of the observer 3. 11 _{4a to} 11 _4e disappear. As a result, the observer 3 can observe an image with little variation in brightness without observing the 0th-order lights 11 _{4a to} 11 _4e in any direction within the predetermined viewing area 22.

Here, as the deflecting optical element 23, a micro prism, a Fresnel lens or a hologram element can be used. When the deflecting optical element 23 including a hologram element is used, even if there is a little 0th-order light, the effect of the 0th-order light generated in the first sheet is very small in the second sheet if two hologram elements are used. Therefore, this 0th-order light rarely poses a problem. In addition, as in this embodiment, the observer 3
Of the 0th-order light 11 _{4a to} 11 _4e in the direction corresponding to the periphery of the viewing zone 22
Projection light 11 _1a onto the hologram element 14 so that
By the to 11 _1e be incident, it is possible to increase the luminous intensity near viewing zone 22. Further, if the characteristics of the hologram element 14 are changed, the projection lights 11 _{1a to} 11 _1e to the hologram element 14 at this time do not have to be parallel, so the Fresnel lens is omitted in this embodiment. It will be possible.

Next, an embodiment of the invention described in claim 4 will be described with reference to FIG. The present embodiment relates to a method of manufacturing a hologram element used in the transmission type projection screen of each of the above-described embodiments. FIG. 13 shows the arrangement of the optical system at the time of manufacturing the hologram element, and a hologram recording material roll 26 around which a sheet-shaped hologram recording material 25 is wound is provided. The hologram recording material 25 that is sequentially fed out from the hologram recording material roll 26 in the arrow Y direction is divided into a plurality of slit-shaped recording areas 25a along the width direction. A recording optical system 27 for recording a hologram on the hologram recording material 25 is disposed below the hologram recording material 25. The recording optical system 27 includes a laser light source 28 located at the lowermost position, a small diameter spherical lens 29a, a large diameter spherical lens 29b, and a cylindrical lens arranged between the laser light source 28 and the hologram recording material 25. It is composed of 30 and a reflection mirror 31.

In such a configuration, the laser light source 28
The laser light emitted from the laser beam is made into a plane wave light 32a through the spherical lenses 29a and 29b, a part of the plane wave light 32a is changed to a cylindrical wave light by the cylindrical lens 30, and the signal light 32b is obtained as the hologram recording material 25. The same recording area 25a of the hologram recording material 25 is irradiated with one slit-shaped recording area 25a of the hologram recording material 25 at the same time by reflecting a part of the light 32a composed of the plane wave by the reflection mirror 31 and irradiating it as the reference light 32c. The signal light 32b and the reference light 32c are interfered with each other to record a hologram in the recording area 25a of the hologram recording material 25. After recording the hologram with a predetermined exposure amount in this way,
The hologram recording material 25 is moved in the direction of the arrow Y, and a hologram is recorded in a newly adjoining 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 transmissive projection screen, and then the whole is developed to form a large area and flat hologram element for the transmissive projection screen. Are formed. However, the development may be continuously performed for each recording area 25a in which the hologram is recorded.

According to this manufacturing method, when the hologram element for the transmission type projection screen may have the same diffusion characteristics in the vertical direction, the light composed of the cylindrical wave can be simply used as the signal light 32b, and further, the pixel light can be used. If the pitch is
The fact that the hologram element may be divided into stripes is used. Therefore, according to this embodiment, it is possible to easily manufacture a hologram element having a function to replace the lenticular lens, which is difficult to form in the related art.

Depending on the required characteristics of the hologram element, a plurality of spherical lenses may be used instead of the cylindrical lens 30, or a spatial modulator may be arranged in the middle. Further, the spherical lens does not have to be the spherical lens 29b having a large diameter as shown in FIG. 13, and the area of the required plane wave is sufficient. On the other hand, when the coherency of the two light fluxes of the signal light 32b and the reference light 32c is insufficient, the reference light 32c may be extracted using a beam splitter.

Next, an embodiment of the invention described in claim 5 will be described with reference to FIG. The same parts as those described in FIG. 13 are designated by the same reference numerals. This embodiment also relates to a method of manufacturing a hologram element for a transmission type projection screen, like the embodiment shown in FIG.
FIG. 14 shows the arrangement of the optical system at the time of manufacturing the hologram element, and a hologram is recorded on the hologram recording material 25 below the hologram recording material 25 fed from the hologram recording material roll 26 in the arrow Y direction. A recording optical system 33 is provided. This recording optical system 33 is
The light source 34 is located at the lowest position, and the lens 35 and the mask 36 are arranged between the light source 34 and the hologram recording material 25. However, it is assumed that a desired hologram pattern is previously recorded on the mask 36 based on CGH data or the like.

In such a structure, the light emitted from the light source 34 is made incident on the mask 36 through the lens 35, and the hologram pattern of the mask 36 is transferred to one slit-shaped recording area 25a of the hologram recording material 25. By doing so, the hologram is recorded. After recording the hologram with a predetermined exposure amount in this way, the hologram recording material 25 is moved in the direction of the arrow Y, and the hologram is similarly recorded in the newly adjacent slit-shaped recording area 25a. After repeating the above scanning a plurality of times for the recording area 25a corresponding to the size of the transmissive projection screen,
By developing the whole, a large-area and flat hologram element for a transmission type projection screen is formed. Therefore, according to the present embodiment as well, it is possible to easily fabricate a hologram element having a function in place of the conventional lenticular lens, as compared with the conventional lenticular lens.

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

[0049]

According to the first aspect of the present invention, the Fresnel lens for converting the projection light projected from the projector from the rear surface to the front surface to convert it into parallel light is provided, and the Fresnel lens is disposed on the front surface side of the Fresnel lens. Since a transmissive projection screen is configured with an optical element that has a hologram element that transmits and diffuses the parallel light that has passed through this Fresnel lens to the observer side, compared to a transmissive projection screen that uses a conventional lenticular lens, The mold projection screen can be made thin and its surface can be made smooth, which makes it more resistant to mechanical contact when wiping dust and dirt and improving durability.

According to the second aspect of the present invention, the Fresnel lens for converting the projection light spatially divided into three colors of red, green and blue from the projector and transmitting the projection light from the rear surface to the front surface to convert it into parallel light. And a optical element having a hologram element having a different wavelength characteristic for each pixel of the parallel light of red, green and blue which is disposed on the front side of the Fresnel lens and transmitted through the Fresnel lens. Since it is configured, it is possible to reduce the color dispersibility of the hologram element as compared with one hologram element having the same wavelength characteristic, and the present invention can be applied to a color projector.

According to the third aspect of the invention, an optical element having a hologram element for transmitting and diffusing the projection light projected from the projector from the back surface to the front surface, and the optical element provided on the back surface side of the optical element, Since the transmission type projection screen is constituted by the deflection optical element which deflects the traveling direction of the projection light incident on the hologram element to the peripheral direction of the visual field outside the visual field of the observer, the observer observes the 0th order light by the hologram element. It is possible to observe an image with little variation in brightness without observing.

As a method of manufacturing these transmission type projection screens, according to the invention described in claim 4, a sheet-like hologram recording material is divided into a plurality of stripe-shaped recording areas, and one of these recording areas is formed. A hologram is recorded by irradiating and interfering with a signal light composed of a spherical wave or a cylindrical surface wave and a reference light composed of a plane wave, and a hologram is recorded by sequentially recording each of a predetermined number of the recording areas connected to the recording area in which the hologram is recorded. Since a flat hologram element is produced by recording a hologram, a large area and flat hologram element for a transmission type projection screen having the same function as that of a conventional lenticular lens, which is difficult to mold, is produced. Can be easily manufactured.

According to the invention of claim 5, the sheet-shaped hologram recording material is divided into a plurality of stripe-shaped recording areas, and a desired hologram pattern formed in advance in one of these recording areas is formed. A hologram is produced by transferring and recording a hologram based on a mask having the same, and sequentially transferring and recording the hologram for each of a predetermined number of the recording areas connected to the recording area where the hologram is transferred and recorded. As a result, as compared with the conventional lenticular lens which is difficult to form, it is possible to easily manufacture a large-area and flat hologram element for a transmission projection screen having the same function as this.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of the invention described in claim 1.

FIG. 2 is a plan view thereof.

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

FIG. 4 is an enlarged plan view showing a modified example of the optical element of FIG.

FIG. 5 is an enlarged plan view showing a generation state of zero-order light.

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

FIG. 7 is a plan view showing two modified examples of FIG.

8 is a plan view showing another two modified examples of FIG. 1. FIG.

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

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

FIG. 11 is a plan view showing an embodiment of the invention described in claim 2;

FIG. 12 is a plan view showing an embodiment of the invention according to claim 3;

FIG. 13 is a perspective view showing an embodiment of the invention described in claim 4.

FIG. 14 is a front view showing an embodiment of the invention as set forth in claim 5;

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

FIG. 16 is a plan view showing the arrangement of a transmissive projection screen during 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 25 Hologram recording material 25a Recording area 32b Signal light 32c Reference light 36 Mask

Claims (5)

[Claims] 1. A Fresnel lens for converting the projection light projected from a projector from the back surface to the front surface to convert the light into parallel light, and the parallel light which is disposed on the front surface side of the Fresnel lens and transmitted through the Fresnel lens. A transmission type projection screen comprising an optical element having a hologram element for transmitting and diffusing to an observer side. 2. A Fresnel lens for converting projection light, which is spatially divided into three colors of red, green, and blue from a projector and projected from the back surface to a parallel light, and a front side of the Fresnel lens. A transmission type projection screen comprising a hologram element having a wavelength characteristic different for each pixel of the red, green and blue parallel light transmitted through the Fresnel lens. 3. An optical element having a hologram element for transmitting and diffusing projection light projected from a projector from a back surface to a front surface, and the projection light arranged on the back surface side of the optical element to enter the hologram element. A transmission type projection screen comprising: a deflection optical element for deflecting the traveling direction of the image in the peripheral direction of the viewing zone outside the viewing zone of the observer. 4. A sheet-shaped hologram recording material is divided into a plurality of stripe-shaped recording areas, and one of these recording areas is irradiated with signal light composed of spherical waves or cylindrical surface waves and reference light composed of plane waves. Then, a hologram is recorded by causing the interference, and a flat hologram element is produced by sequentially recording the hologram in each of a predetermined number of the recording areas connected to the recording area in which the hologram is recorded. A method for producing a hologram element for a transmission projection screen, which is characterized. 5. A sheet-shaped hologram recording material is divided into a plurality of stripe-shaped recording areas, and a hologram is transferred / recorded based on a mask having a desired hologram pattern formed in advance in one of these recording areas. And a flat hologram element is produced by sequentially transferring and recording holograms for each of a predetermined number of the recording areas connected to the transferred and recorded recording areas. For manufacturing hologram element for computer.