JP2002139800A - Transmission type screen and video display device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase a light transmittance by reducing a surface reflection, and also, to prevent focus deterioration and moire by suppressing the deformation of a sheet due to the moisture adsorption, etc., as for a transmission type screen. SOLUTION: A light transmissive member having a refractive index lower than that of a Fresnel lens sheet and that of a lenticular lens sheet, but, higher than that of an air is arranged in between both sheets, and then, both sheets are fixed. The Fresnel lens sheet is constituted by laminating a plurality of Fresnel lens sheets.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission screen constituted by using a Fresnel lens and a lenticular lens.

[0002]

2. Description of the Related Art FIG. 5 shows the basic structure of a conventional transmission screen. As shown in FIG. 5A, the conventional transmissive screen includes two Fresnel lens sheets 11 and a lenticular lens sheet 12. For example, in a three-tube type rear projection device, as shown in FIG.
RT, G CRT and B CRT are arranged horizontally.
An RT image is projected on the rear surface of the transmission screen 10 by a projection lens corresponding to each color. The Fresnel lens sheet 11 includes a Fresnel lens on the surface on the emission side, and converts video light projected from the projection lens onto the screen into substantially parallel emission light. Lenticular lens sheet 1
2 spreads the parallel incident light from the Fresnel lens sheet 11 microscopically to widen the viewing angle of the screen. FIG.
2 shows an enlarged sectional view of the Fresnel lens sheet 11 and the lenticular lens sheet 12. FIG. In FIG. 6, 16
Is an air layer formed when the Fresnel lens sheet 11 and the lenticular lens sheet 12 are overlapped. FIG. 7 shows a conventional assembly example of the Fresnel lens sheet 11 and the lenticular lens sheet 12. Normally, the Fresnel lens sheet 11 and the lenticular lens sheet 12 have different amounts of warp, and the sheet 12 has a larger warp. The two sheets having different warpages are overlapped, and the inside of the sheet end face is fixed with a double-sided adhesive tape or the like (not shown).
After the lamination, the end face is inserted into the groove of the U-shaped channel frame 20 and adhered and fixed. Further, Japanese Patent Application Laid-Open No. 10-3942
No. 0 describes a configuration in which silicon gel is filled between a Fresnel lens sheet and a lenticular lens sheet or between a lenticular lens sheet and a flat sheet in order to reduce reflection of projection light on the screen surface. ing.

[0003]

Among the above-mentioned conventional transmission screens, those shown in FIGS. 5, 6 and 7 are as follows.
(1) Between two sheets, that is, Fresnel lens sheet 1
1 and air layer 16 between lenticular lens sheet 12
However, this causes focus deterioration and a decrease in light transmittance due to reflection occurring at the interface between each sheet and the air layer. In general,
When light passes through an interface having a different refractive index, a part of the light is reflected, and the reflectance depends on the refractive index and the incident angle. The higher the difference in the refractive index between the light and the exit side medium, and the larger the angle of incidence, the higher the difference. For example, the reflectance at the interface between air having a refractive index of about 1 and resin for a lens having a refractive index of about 1.5 is about 4%. In a conventional transmission screen composed of two sheets, since this interface portion exists at four places on the optical axis, about 15% of the entire screen is reflected and lost. (2) Both the Fresnel lens sheet 11 and the lenticular lens sheet 12 expand due to moisture absorption. In each of the two sheets, there is a difference in the amount of moisture absorption between the incident side surface and the outgoing side surface, so that there is also a difference in the amount of expansion in the surface portion, and the gap 21 between the two sheets expands as shown in FIG. Deform like a warp. As a result, the optical path length varies depending on the position in the sheet plane, and focus deterioration and moiré occur. Further, Japanese Patent Application Laid-Open No. H10-39
In the technique described in Japanese Patent Publication No. 420, there is a possibility that the refractive power on the exit surface of the Fresnel lens sheet is reduced. It is an object of the present invention to (1) reduce the amount of interfacial reflection and increase the light transmittance, and (2) reduce the amount of change in the inter-sheet distance due to moisture absorption to suppress focus deterioration and moire generation in a transmissive screen. ,It is in. An object of the present invention is to provide a technique capable of solving the above problems.

[0004]

According to the present invention, there is provided a transmission screen including a Fresnel lens sheet and a lenticular lens sheet, wherein the Fresnel lens sheet and the lenticular lens are provided. A light transmissive member having a lower refractive index than the two sheets and a higher refractive index than the air is provided between the sheets and the two sheets are fixed, and the Fresnel lens sheet is laminated with a plurality of Fresnel lens sheets. It is configured as follows. (2) A transmissive screen including a Fresnel lens sheet and a lenticular lens sheet, wherein light having a lower refractive index than the two sheets and a higher refractive index than air is provided between the Fresnel lens sheet and the lenticular lens sheet. A transparent resin is provided to fix the two sheets, and the lenticular lens sheet has a configuration in which the exit lens surface is shifted from the focal position of the entrance lens. (3) A transmission screen including a Fresnel lens sheet and a lenticular lens sheet, wherein the Fresnel lens sheet is formed by laminating a plurality of Fresnel lens sheets, between the plurality of Fresnel lens sheets, and the Fresnel lens sheet. Between the lenticular lens sheet and the lenticular lens sheet, a light transmissive resin having a lower refractive index than the Fresnel lens sheet or a higher refractive index than air than the lenticular lens sheet is provided to fix the respective sheets, and the lenticular lens sheet is provided. The lens sheet is configured such that its emission-side lens surface is located at a position shifted from the focal position of the incidence-side lens. (4) A transmission screen including a Fresnel lens sheet and a lenticular lens sheet, wherein the Fresnel lens sheet has a configuration in which a plurality of Fresnel lens sheets are stacked. (5) A video display device is configured using the transmission screen of any of the above (1) to (4). In the above configuration, the light-transmitting member or the light-transmitting resin improves the adhesion between the Fresnel lens sheet and the lenticular lens sheet, suppresses sheet deformation due to moisture absorption, and suppresses a change in optical path length. Further, the light-transmitting member or the light-transmitting resin reduces the difference in refractive index between the Fresnel lens sheet and the lenticular lens sheet to reduce the amount of interface reflection. For example, assuming that the refractive index of the light transmitting member or the light transmitting resin is approximately 1.3, the reflectance of one interface on the optical axis is approximately 0.5%, and the reflection in the case of an air layer. It is significantly lower than the rate of about 4%. The plurality of Fresnel lens sheets improve a reduction in refractive power at the exit surface of the Fresnel lens sheet due to the provision of the light transmitting member or the intermediate layer of the light transmitting resin. Further, the configuration in which the exit-side lens surface of the lenticular lens sheet is located at a position deviated from the focal position of the entrance-side lens is provided by providing the light-transmitting member or the intermediate layer made of the light-transmitting resin. Improves the refractive power reduction at the entrance surface of the sheet.

[0005]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 4 show an embodiment of a transmission screen according to the present invention. This embodiment is an example of a configuration using two Fresnel lens sheets. FIG. 1 is a perspective view, FIG. 2 is a cross-sectional view, FIG. 3 is an optical path diagram of image light, and FIG. 4 is an explanatory diagram of light incidence and emission in a lenticular lens unit. 1 and 2, 1 is a base substrate, and 2 is a first substrate.
Reference numeral 4 denotes a second Fresnel lens, 6 denotes an incident side lenticular lens, 7 denotes an output side lenticular lens, 3 denotes a first intermediate layer, 5 denotes a second intermediate layer, and 8 denotes a black stripe. A first Fresnel lens 2 is fixed on a base substrate 1, and the first Fresnel lens 2
A first intermediate layer 3 made of a light transmitting resin is formed on the first intermediate layer 3, and a second Fresnel lens 4 is fixed on the first intermediate layer 3. The first intermediate layer 3 has a lower refractive index of light than the first and second Fresnel lenses and higher than air. On the second Fresnel lens 4, a second intermediate layer 5 made of a light transmitting resin is formed.
A lenticular lens 6 on the input side and a lenticular lens 7 on the output side are fixed on the upper side. The second intermediate layer 5 includes:
The refractive index of light is lower than that of the second Fresnel lens 4 and the incident side lenticular lens 6, and higher than air.

In FIG. 3, light incident through a base substrate 1 is incident on a first Fresnel lens 2 at an incident angle α1, and exits at an exit angle β1. Next, through the intermediate layer 3, the second
Incident on the Fresnel lens 4 at an incidence angle α2 and exit at an emission angle β2. The light emitted from these Fresnel lens groups basically becomes substantially parallel light, and enters the incident-side lenticular lens 6 and the emission-side lenticular lens 7. In the lenticular lens, the light is condensed by the incident-side lenticular lens 6 so as to reduce the aberration, and the incident-side lenticular lens 6 and the exit-side lenticular lens 7 satisfy a predetermined horizontal viewing angle. Hereinafter, an example of the refractive power distribution and the refractive index of the high refractive resin and the low refractive resin will be described with reference to FIG. Prism angle θ, which is the lens curvature of each Fresnel lens
1, it is considered that there is a limit in the processing of θ2. The following is an example of a case where the processing limit value is set to, for example, approximately 63 ° and the refractive power is distributed as the maximum prism angle of the first Fresnel lens. For example, in the case of a 52-inch projection television, the incident conjugate distance (the conjugate distance: the distance from the principal point to the object point and the image point) a is 723 mm, the output conjugate distance b is 13225 mm, and the maximum Fresnel radius r is 666.8 m.
m, the angle of incidence α0 on the base substrate 1 is 42.7 °, and the angle of emergence β0 from the second Fresnel lens is 2.9 °, the first Fresnel lens 2 and the second Fresnel which are the refractive power of the lens. The respective prism angles θ1 and θ2 of the lens 4 can be obtained. α0, β0 are the base substrate 1, the first
Lens 2, low-refractive resin intermediate layer 3, and second
The incident angle and the outgoing angle when the composite sheet group including the Fresnel lens 4 is regarded as one equivalent Fresnel lens sheet. N1 is the refractive index of the base substrate 1, N2 is the refractive index of the first Fresnel lens 2, N3
Is the refractive index of the first intermediate layer 3, N4 is the refractive index of the second Fresnel lens 4, N5 is the refractive index of the second intermediate layer 5, and N6 is the refractive index of the incident-side lenticular lens 6. The prism angle θ1 of the first Fresnel lens 2 is calculated from equation (1) shown in FIG. The refractive index of each of the above parts,
N1 = 1.53, N2 = 1.591, N3 = 1.37
8, N4 = 1.593, N5 = 1.378, N6 = 1.
In the case of 591, the prism angle θ1 at the position of the maximum Fresnel radius r = 666.8 mm is approximately 62.9 °. The prism angle maximizes the value of θ1, and becomes smaller toward the center of the screen. The prism angle of the second Fresnel lens is also calculated by equation (2) shown in FIG. The maximum angle θ2 of the second Fresnel lens 4 at the maximum Fresnel radius r = 666.8 mm is also equal to or less than 63 ° when the refractive indices N1 to N6 have the same values as above. As described above, in the combination configuration of the Fresnel lens and the lenticular lens having a high refractive index and the resin having a lower refractive index than that provided as the intermediate layer, the Fresnel lens prism angle at each Fresnel radius position is obtained, and the refraction of the Fresnel lens is determined. The power distribution is decided.

[0007] The interface reflection loss can be obtained by dividing the polarization state of incident light into reflection of P-polarized light and reflection of S-polarized light. The reflectance Rp of the P-polarized light and the reflectance Rs of the S-polarized light are obtained by the equation (3) shown in FIG. 3, an average value R is obtained based on the reflectance, and the average value R is calculated as the reflectance of the interface. I do. In the equation (3), α is an incident angle, β is an outgoing angle, N
Is the refractive index on the incident side, and N 'is the refractive index on the outgoing side. As a result of the calculation, the reflectance R is approximately 1 in the case of the conventional screen.
It is 4.1%, and in the case of the screen of the two-layer laminated Fresnel lens of the present invention, it is about 7.5%.

In the lenticular lens, the directional characteristics in the horizontal direction are determined by cylindrical cylindrical lenses provided on the entrance side and the exit side. As in the case of the Fresnel lens, a resin material having a lower refractive index than the lens is used. The refractive power distribution based on the intermediate layer is performed. Generally, for a light beam emitted almost in parallel from a Fresnel lens, the refractive power can be increased by reducing the radius of curvature of the lenticular lens on the incident side. However, the angle of incidence increases toward the periphery of the lens, the refractive power increases, and interface reflection increases. Therefore, there is a limit to the correction of refractive power using only the incident-side lenticular lens. In the present invention, a predetermined refractive power is achieved as a whole including the incident-side lenticular lens and the exit-side lenticular lens. Specifically, as shown in FIG. 4, the emission-side lenticular lens surface is moved with respect to the focal position of the incidence-side lenticular lens.
It is arranged to be shifted to the light incident side or the emission side (FIG.
(This is a case where the surface of the emission-side lenticular lens 31 is shifted toward the near side (incident side) from the focal position of the incidence-side lenticular lens 30). FIG. 4 shows the optical path of the G light of the lenticular lens. When the surface of the exit-side lenticular lens 31 is located at the focal position 32 of the entrance-side lenticular lens 30, the refractive power is determined only by the curvature of the entrance-side lenticular lens 30, but the surface of the exit-side lenticular lens 31 is When the focal point 32 of the lenticular lens 30 is shifted to the near side (incident side) or the rear side (outgoing side) from the focal point 32, a predetermined refractive power is obtained by combining the curvature of the incident side lenticular lens 30 and the curvature of the exit side lenticular lens. An emission angle can be obtained. In FIG. 4, the light on the optical axis goes straight, but the other light going to the focal point 32 is refracted by the exit side lenticular lens 31 before crossing the optical axis, and the surface of the exit side lenticular lens is located at the focal position 32. In this case, an emission angle φ2 larger than the emission angle φ1 can be obtained. The amount of deviation of the entrance-side lenticular lens from the focal position 32 is set in accordance with a predetermined exit angle, lens shape, refractive index of a lens material, and the like. As described above, in the lenticular lens, the refractive power of the lens obtained by combining the curvature of the incident-side lenticular lens and the curvature of the exit-side lenticular lens can be obtained.

According to the present embodiment, it is possible to reduce the amount of interfacial reflection, suppress a decrease in light transmittance, and improve the brightness. Further, sheet deformation due to moisture absorption can be prevented or greatly reduced, and focus deterioration and moire can be suppressed. In addition,
In the above embodiment, the Fresnel lens sheet is composed of two Fresnel lens sheets, but the present invention is not limited to this, and a plurality of Fresnel lens sheets is composed of three or more Fresnel lens sheets. You may. Further, in the above embodiment, the configuration in which an intermediate layer having a lower refractive index is provided between the Fresnel lens sheet and the lenticular lens sheet and the configuration in which the Fresnel lens sheet is formed by a plurality of Fresnel lens sheets are combined. However, the present invention is not limited to this. For example, a configuration in which a plurality of Fresnel lens sheets are provided without providing the intermediate layer having the above-described refractive index may be employed.

[0010]

According to the present invention, it is possible to provide a transmissive screen technology having a small interface reflection and a high light transmittance. Also,
Changes in the distance between sheets due to moisture absorption and the like are suppressed, and focus deterioration and moire generation in the image display device are also suppressed. It is also possible to suppress a decrease in the refractive index on the exit surface of the Fresnel lens sheet.

[Brief description of the drawings]

FIG. 1 is a diagram showing one embodiment of the present invention.

FIG. 2 is a sectional view showing one embodiment of the present invention.

FIG. 3 is an optical path diagram in the embodiment of the present invention.

FIG. 4 is an optical path diagram of an exit-side lenticular lens according to an embodiment of the present invention.

FIG. 5 is a diagram showing a conventional example.

FIG. 6 is a sectional view of a conventional example.

FIG. 7 is a diagram showing an assembling method in a conventional example.

FIG. 8 is an explanatory diagram of sheet deformation in a conventional example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Base board 2 ... 1st Fresnel lens 3 ...
1st intermediate layer, 4 ... second Fresnel lens, 5 ... second intermediate layer, 6 ... incident side lenticular lens, 7
... Lenticular lens on the emission side, 8 ... Black stripe.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Kazunari Nakagawa 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Inside Digital Media Systems Division, Hitachi, Ltd. (72) Inventor Yukio Maeda Yoshida, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture No. 292, Hitachi, Ltd. Production Technology Research Laboratory, Hitachi, Ltd. (72) Inventor Keiji Takasu 292, Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture F-term in Hitachi, Ltd. Production Technology Laboratory 2H021 BA24 BA25 BA28

Claims (5)

[Claims] 1. A transmissive screen comprising a Fresnel lens sheet and a lenticular lens sheet, wherein a refractive index between the Fresnel lens sheet and the lenticular lens sheet is lower than that of both sheets and higher than air. A transmissive screen characterized in that a light transmissive member having a high transmittance is provided to fix the two sheets, and the Fresnel lens sheet has a configuration in which a plurality of Fresnel lens sheets are laminated. 2. A transmission screen comprising a Fresnel lens sheet and a lenticular lens sheet, wherein a refractive index between the Fresnel lens sheet and the lenticular lens sheet is lower than that of both sheets and higher than that of air. A light transmitting resin is provided to fix the two sheets,
Further, the lenticular lens sheet has a configuration in which the exit lens surface is shifted from the focal position of the entrance lens. 3. A transmission screen having a Fresnel lens sheet and a lenticular lens sheet, wherein the Fresnel lens sheet is formed by laminating a plurality of Fresnel lens sheets, between the plurality of Fresnel lens sheets, and between the Fresnel lens sheets. A light-transmitting resin having a lower refractive index than the Fresnel lens sheet or a higher refractive index than air is provided between the lens sheet and the lenticular lens sheet, and the respective sheets are fixed; and The lenticular lens sheet has a configuration in which the exit side lens surface is located at a position shifted from the focal position of the entrance side lens. 4. A transmission screen including a Fresnel lens sheet and a lenticular lens sheet, wherein the Fresnel lens sheet has a configuration in which a plurality of Fresnel lens sheets are stacked. 5. An image display device which performs image display using the transmission screen according to claim 1.