JP3905648B2 - Rear projection display - Google Patents

Description

【表２】

【００２７】
表１に示すように、レンチキュラーレンズシートへの光線の入射角が５°の条件では、ｔ／ｆが０．７から１．２の範囲であるときに全光線透過率が７０％以上となる。また、表２に示すように、レンチキュラーレンズシートへの光線の入射角が２０°の条件では、ｔ／ｆが０．９以上であるときに全光線透過率が５０％以下となる。
【００２８】
すなわち、レンチキュラーレンズシートにある入射側レンズの主焦点距離（ｍｍ）をｆで、入射側レンズのレンズ面頂部と光遮蔽部材の頂部との距離（ｍｍ）をｔでそれぞれ表すとき、ｔ／ｆが０．７以上１．２以下の範囲にある場合に、レンチキュラーレンズシートへの光線の入射角度θ（ｄｅｇ）、レンチキュラーレンズシートの全光線透過率Ｔｔ（θ）（％）およびレンチキュラーレンズシートに含有された光吸収剤による光透過損失αが、｜θ｜＝５（ｄｅｇ）のときに式Ｔｔ（θ）＞７０×（１−α）を満足し、かつ、｜θ｜＝２０（ｄｅｇ）のときに式Ｔｔ（θ）＜５０×（１−α）（％）を達成することが可能である。このようなレンチキュラーレンズシートによって、フレネルレンズシートから発生する迷光、不要反射光などのゴースト光を大幅に低減することが可能となる。
【００２９】
以上、説明したように、フレネルレンズシート等からのゴースト光を低減させるためには、レンチキュラーレンズシートへの入射角が２０°の光線に対する全光線透過率が低いことが好ましく、５０×（１−α）％以下の透過率であればゴースト光を大幅に低減することが可能である。透過率が３０×（１−α）％以下であることがより望ましい。しかし、単に入射角が２０°の光線に対する透過率を低減させるのみでは、レンチキュラーレンズシートの明るさを低下させてしまうため、レンチキュラーレンズシートへの入射角が５°の光線に対する全光線透過率を７０％以上とする必要がある。入射角５°の光線に対する全光線透過率は８０％以上であることがより望ましい。
【００３０】
本発明において、ブラックストライプの比率を高めることにより、明るい室内での外光反射を低減させ、スクリーンのコントラストを向上させることもできる。 ＣＲＴ３管式の映像表示装置では、３管それぞれからの光線がレンチキュラーレンズシートへ入射する角度が異なるため、レンチキュラーレンズシートの出射側レンズの異なる位置に３管それぞれからの光線が集光することに起因するカラーシフトを補正する必要がある。一方、ＬＣＤ等を用い、単一の投射レンズを備えた映像表示装置では、レンチキュラーレンズの出射側レンズのほぼ一定の位置に光を収束させることが可能であり、カラーシフトを補正する必要がないので、ブラックストライプの比率を高めることが可能である。
【００３１】
フレネルレンズシートとして拡散性を有するシートが用いられることがあるが、そのようなシートの光線拡散特性の一例を図９に示す。図９に示すようにフレネルレンズシートから出射される光線の大部分は出射角が±１０°以内である。本発明におけるレンチキュラーレンズシートでは、入射角が２０°以下であるときに全光線透過率が５０％以上であるため、拡散性を有するフレネルレンズシートと組み合わせて用いても全く問題はない。
【００３２】
【実施例】
以下、実施例によって本発明の背面投写型映像表示装置をより具体的に説明する。なお、以下の実施例において、全光線透過率の測定には村上色彩研究所製ＧＰ―１Ｒゴニオメータを用い、コントラストの評価にはソニー(株)製ＫＬ−３７ＨＷ１ ＬＣＤ式背面投写型プロジェクションテレビを用い、輝度等の測定にはミノルタ（株）製色彩色差計ＣＳ−１００を用いた。
【００３３】
（実施例１）
レンチキュラーレンズのレンズピッチが０．５３ｍｍであり、シートの厚さが０．６２ｍｍであり、ブラックストライプの比率が６７％であるレンチキュラーレンズシートを、東芝機械（株）製押し出し成型機を用いたロール成形法により作製する。このレンチキュラーレンズシートの表面には、黒色インクを用い、スクリーン印刷法によりブラックストライプを形成する。上記レンチキュラーレンズの形状を式で表すと以下の通りである。なお、ｔ／ｆは、０．９である。
レンズ形状：ＣＲ²／〔１＋｛１−（Ｋ＋１）Ｃ²Ｒ²｝^1/2〕＋ＤＲ⁴＋ＥＲ⁶＋ＦＲ⁸＋ＧＲ¹⁰
入射側レンズ：Ｃ＝４．５、Ｋ＝−０．４４８６、Ｄ＝Ｅ＝Ｆ＝Ｇ＝０
出射側レンズ：Ｃ＝−４．５、Ｋ＝−０．４４８６、Ｄ＝Ｅ＝Ｆ＝Ｇ＝０
また、 Ｒはレンチキュラーレンズ中心からの半径である。
【００３４】
上記のレンチキュラーレンズシートと組み合わせて背面投写型映像表示装置を構成するフレネルレンズシートは、微粒子拡散材が配合された樹脂板からなり、このフレネルレンズの拡散特性は図９で示すものである。
【００３５】
本実施例のレンチキュラーレンズシートの全光線透過率Ｔｔ（θ）（％）を測定した結果を表３に示す。全光線透過率とは、レンチキュラーレンズシートの入射面より入射した光線の量に対する出射面より出射される全光線の量の比率を表したものである（なお、表３には、後述する実施例２についての測定結果をあわせて示してある。）。
【００３６】
【表３】

【００３７】
上記したプロジェクションテレビに、本実施例のレンチキュラーレンズシートおよび上記のフレネルレンズシートを取り付け、外光コントラストの指標となる投射映像および外光反射の輝度を測定した結果を表４に示す。ここで、表４中の水平視野角αＨ、βＨ、γＨは、ピークの輝度に対して、それぞれ１／２、１／３、１／１０となる水平視野角を示す。実施例１のものは、後述する実施例２とともに実用上問題ない水平視野角を有している。
【００３８】
【表４】

【００３９】
投射映像の輝度測定は、プロジェクションテレビに白黒模様の規準信号を入力し、プロジェクションテレビから１ｍの距離で、上記測定器を用いて白色部分を測定することにより行った。また、外光反射輝度の測定は、プロジェクションテレビのスクリーン面の照度が３６０Ｌｘとなるように、スクリーンに対して上方から約４５°の角度でハロゲンランプを調光して照らした状態で、白黒模様の黒色部分の輝度を測定することにより行った。表４において、外光コントラスト は投射映像の白色輝度を黒色輝度で割った値で示した。外光コントラストは投射映像光に対する外光の影響を示し、この値が大きいほど外光によるコントラストの低下が少ないことを意味する。
【００４０】
次に、評価室内の照明を消し、プロジェクションテレビに白黒の基準信号を入力し、白色部輝度および黒色部輝度をそれぞれ測定した。白色輝度を黒色輝度で割った値を迷光コントラストとした。この値が大きいほど、迷光によるコントラストの低下が少ないことを意味する。
【００４１】
（実施例２）
上記のレンチキュラーレンズシートのレンズ形状を表す式において、
入射側レンズ：Ｃ＝４．５ 、Ｋ＝−０．４４８６、Ｄ＝Ｅ＝Ｆ＝Ｇ＝０
出射側レンズ：Ｃ＝−４．５ 、Ｋ＝−０．４４８６、Ｄ＝Ｅ＝Ｆ＝Ｇ＝０
とし、レンズピッチを０．５３ｍｍ、シートの厚さを０．６２ｍｍとし、また、ｔ／ｆを０．９とし、ブラックストライプの比率を６０％としたものを実施例１で説明したと同様にして作製する。
【００４２】
このレンチキュラーレンズシートを用いて、実施例１におけると同様に全光線透過率およびコントラストの測定を行った結果を上記の表３および表４にあわせて示す。
【００４３】
（比較例１）
上記のレンチキュラーレンズシートのレンズ形状を表す式において、
入射側レンズ：Ｃ＝４．５、Ｋ＝−１．０、Ｄ＝Ｅ＝Ｆ＝Ｇ＝０
出射側レンズ：Ｃ＝−６．３、Ｋ＝−１．０、Ｄ＝Ｅ＝Ｆ＝Ｇ＝０
とし、レンズピッチを０．５５ｍｍ、シートの厚さを０．６７ｍｍとし、また、ｔ／ｆを１．０とし、ブラックストライプの比率を４４％としたものを実施例１で説明したと同様にして作製する。
【００４４】
このレンチキュラーレンズシートを用いて、実施例１におけると同様に全光線透過率およびコントラストの測定を行った結果を上記の表３および表４にあわせて示す。表３に示すように、比較例のレンチキュラーレンズシートは入射角２０°に対する透過率が高いものである。この比較例では表４に示すように、コントラストが実施例のものに比べて劣ってる。
【００４５】
【発明の効果】
本発明によれば、外光が無い状態でも発生する投射光学系内における迷光、不要反射光などのゴースト光が低減され、かつ、明るい室内における外光反射をも低減されたコントラストの優れた背面投写型映像装置を提供することができる。
【図面の簡単な説明】
【図１】フレネルレンズシートから出射されるゴースト光を説明する図である。
【図２】フレネルレンズシートから出射されるゴースト光を説明する他の図である。
【図３】フレネルレンズシートから出射されるゴースト光の位置を表す図である。
【図４】レンチキュラーレンズシートへの入射角と全光線透過率との関係を求めた図である。
【図５】従来のレンチキュラーレンズシートにおける光線の透過経路を説明する図である。
【図６】本発明におけるレンチキュラーレンズシートの断面図である。
【図７】本発明のレンチキュラーレンズシートにおいて不要な入射光がカットされる様子を説明する図である。
【図８】レンチキュラーレンズシートへの入射角と全光線透過率との関係を異なるＢＳ比率のものについて求めた結果を示す図である。
【図９】フレネルレンズシートから出射される光線拡散特性の一例を説明する図である。
【図１０】透過型スクリーンの構成例を示す図である。
【図１１】透過型スクリーンの断面を示す図である。
【符号の説明】
１・・・フレネルレンズシート
４・・・レンチキュラーレンズシート
４ａ・・・入射側レンズ
７・・・ブラックストライプ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a rear projection type image display device including a projection device using a single lens using a liquid crystal panel and the like, and a screen on which an image from the projection device is projected from the rear surface.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, for example, a transmission screen of a rear projection type image display device provided with a single lens projection device using one or a plurality of liquid crystal panels has a configuration as shown in FIG. It was. In this transmissive screen, a divergent light beam from a projection device (not shown) is projected from one surface of a Fresnel lens sheet 11 having a Fresnel lens formed on the surface of a transparent resin plate, and the divergent light beam is parallel by the Fresnel lens sheet 11. It is changed into a light beam or a convergent light beam and is transmitted from the other surface, and then this parallel light beam or the convergent light beam is transmitted through the lenticular lens sheet 12 in which the kamaboko type convex lenses are repeatedly formed in the horizontal direction on both surfaces. This enlarges the horizontal viewing angle on the viewing side and creates a desired projected image. Here, the front plate 13 shown in FIG. 10 is used for the purpose of protecting the lenticular lens sheet.
[0003]
In the transmission screen shown in FIG. 10, the lenticular lens sheet 12 has a diffusion made of fine particles such as quartz, glass, and a crosslinked polymer resin so as to increase not only the horizontal viewing angle but also the vertical viewing angle. An agent is blended. Further, the diffusing agent may be dispersed in the Fresnel lens sheet 11 in the same manner for the same purpose.
[0004]
[Problems to be solved by the invention]
However, such a conventional transmissive screen has a problem in viewability, particularly in terms of image clarity and contrast. One cause of the decrease in the sharpness and contrast of the image is stray light generated from members constituting the projection optical system such as a projection light source, a magnifying lens, and a Fresnel lens sheet, and so-called ghost light such as unnecessary reflected light. I know it can be mentioned. Conventionally, in order to reduce such stray light and unnecessary reflected light, the members constituting the projection optical system are painted black, and the non-lens surface of the Fresnel lens sheet (for example, the side opposite to the lens surface of the Fresnel lens sheet) However, the effect was not satisfactory.
[0005]
Another cause of a decrease in the sharpness and contrast of the image is that external light such as room lighting is reflected on the inside or the surface of the lenticular lens sheet. As shown in FIG. 11, since the external light 14 incident from the observation surface side (the side opposite to the projection device) is diffusely reflected by the fine particle diffusing agent 15, and the diffuse reflection light 16 returns to the viewer side, the entire screen is displayed. Becomes white and the contrast of the projected image from the video source decreases.
[0006]
In order to solve the problem of low image sharpness and low image contrast, JP-A-49-12943, JP-A-58-59436, JP-A-58-134627, etc. Thus, conventionally, a black stripe 17 has been provided on the observation surface side surface of the lenticular lens sheet 12 as a light shielding member (see FIG. 11).
[0007]
Here, it is clear that if the area ratio of the black stripe is high, the degree of contrast reduction due to external light is reduced. However, in the CRT 3-tube image display device, since the incident angles from the three tubes to the lenticular lens sheet are different, the light from each projection tube is condensed at different positions of the exit lens of the lenticular lens sheet. It is necessary to correct the color shift caused by this. Therefore, the black stripe ratio (ratio of the black stripe width to the lenticular lens pitch) is generally 50% or less.
[0008]
The present invention has been made to solve the above problems, stray light and unnecessary reflected light in the projection optical system has been reduced, and light generated by reflecting external light has been reduced. An object of the present invention is to provide a rear projection type video apparatus having a projection type screen having an excellent contrast.
[0009]
[Means for Solving the Problems]
The rear projection type video apparatus of the present invention that solves the above problems includes a single projection lens, a Fresnel lens sheet, and a region through which light does not pass when incident light is emitted through the Fresnel lens sheet. And a lenticular lens sheet provided with a light shielding member such as a black stripe, the incident angle (deg) to the lenticular lens sheet is θ, and the total light transmittance of the lenticular lens sheet with respect to light having the incident angle θ ( %) Is Tt (θ), and light transmission loss due to the light absorber contained in the lenticular lens sheet is represented by α, respectively, Tt (θ) and α are represented by the following formulas in the center of the lenticular lens sheet: 1) and formula (2),
Formula (1): When | θ | = 5 Tt (θ)> 70 × (1-α)
Formula (2): When | θ | = 20 Tt (θ) <50 × (1-α)
Satisfied.
[0010]
In the lenticular lens sheet according to the present invention, the main focal length (mm) of the incident side lens in the lenticular lens sheet is represented by f, and the distance (mm) between the top of the lens surface of the incident side lens and the top of the light shielding member is represented by t. When f and t are the following formulas (3),
Formula (3): 0.7 ≦ t / f ≦ 1.2
Satisfying the above is preferable because a brighter screen can be obtained.
[0011]
Further, when the width of the light shielding member with respect to the pitch of the incident side lens in the lenticular lens sheet is 60% or more, stray light and unnecessary light are more effectively reduced, and reflection of outside light is greatly reduced. Preferred for reasons.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the configuration of the rear projection type image display apparatus of the present invention will be specifically described with reference to the drawings.
[0013]
The reason why ghost light (stray light / unnecessary reflected light) is generated on a conventional screen combining a Fresnel lens sheet and a lenticular lens sheet will be described. FIG. 1 and FIG. 2 show optical paths of so-called ghost light (stray light, unnecessary reflected light, etc.) generated from a Fresnel lens or the like that causes deterioration of the screen contrast in a dark room. As shown in FIG. 1, the light 2a incident on the Fresnel lens sheet 1 is refracted and reaches the surface of the Fresnel lens 1a, and the reflected light 2c on the surface of the Fresnel lens 1a is reflected from the back surface of the Fresnel lens sheet. Total reflection occurs at 1b (2d), and light 2e is emitted from the rise surface 1c to the observation side, and this light 2e becomes ghost light. Alternatively, as shown in FIG. 2, the light 3a incident on the Fresnel lens sheet 1 is refracted (3b) and reaches the Fresnel lens surface 1a, and the reflected light 3c on the Fresnel lens surface 1a is reflected from the rise surface 1c. The emitted light 3d is incident on the Fresnel lens sheet 1 again from the Fresnel lens surface 1a (3e), undergoes total reflection on the back surface 1b of the Fresnel lens sheet (3f), and is transmitted from the Fresnel lens surface 1a to the observation side. 3g is emitted, and this light 3g becomes ghost light.
[0014]
Here, ghost light appears strong from the observation side under conditions that cause total reflection on the back surface of the Fresnel lens sheet. Ghost light is generated when the incident angle of light incident on the Fresnel lens sheet (θ1 shown in FIGS. 1 and 2) and the Fresnel lens's Fresnel angle (θ2 shown in FIGS. 1 and 2) meet certain conditions. Strongly observed.
[0015]
As a result of studying this condition by calculation, as an example, when the screen size on which the image is projected is 60 inches and the distance from the pupil of the projection lens to the Fresnel lens sheet is 1078 mm, the Fresnel angle θ2 of the Fresnel lens is reduced. It was found that ghost light is strongly observed when the following equation is satisfied.
θ2 = tan ⁻¹ (CR / [1+ {1− (K + 1) C ² R ² } ^1/2 ] + 4DR ³ + 6ER ⁵ + 8FR ⁷ + 10GR ⁹
However, C = 1.98E-3, K = −1.05, D = E = F = G = 0. R is the radius from the center of the Fresnel. Here, the state in which ghost light is generated will be described with reference to FIG. 3. The horizontal axis represents the distance (mm) from the mechanical center of the screen, and the vertical axis represents the emission angle of the ghost light with respect to the normal of the screen ( deg). The ghost light emitted from the Fresnel lens sheet when the above conditions are satisfied is generated only at the outer periphery of the Fresnel lens sheet as can be seen from FIG. 3, and the emission angle is directed toward the center of the Fresnel lens sheet. is there. In FIG. 3, a curve a represents ghost light (2e) traced as shown in FIG. 1, and a curve b represents ghost light (3g) traced as shown in FIG.
[0016]
By the way, as described above, ghost light to be observed only at a specific position on the outer periphery of the screen is actually observed in a wider range. This is greatly influenced by the characteristics of the lenticular lens sheet used together with the Fresnel lens sheet. In the lenticular lens sheet, since the light emitted from the Fresnel lens sheet is greatly diffused in the horizontal direction, even light emitted from the Fresnel lens sheet only at a specific angle passes through the lenticular lens sheet. After that, since it is diffused in the horizontal direction, ghost light is observed at a wider angle than shown in FIG.
[0017]
The calculation result of the light transmittance with respect to the incident angle of the conventional lenticular lens is shown in graph a of FIG. In FIG. 4, the vertical axis represents the total light transmittance Tt (%) of the lenticular lens sheet, and the horizontal axis represents the incident angle θ (deg) of the light beam to the lenticular lens sheet. As shown in graph a of FIG. 4, in the conventional lenticular lens sheet, the total light transmittance Tt is about 90% when the incident angle is in the range of 0 ° to 20 °, and the ghost light shown in FIG. It is easily transmitted. On the other hand, ghost light emitted from the Fresnel lens sheet at a larger emission angle (30 ° or more) does not come out to the observation side. This phenomenon will be described with reference to FIG. Referring to FIG. 5, a light beam 5 (solid line) represents an incident light beam having an incident angle of 20 °, and a light beam 6 (broken line) represents an incident light beam having an incident angle of 30 °. As shown in the result of ray tracing in FIG. 5, the light incident on the incident side lens 4 a of the lenticular lens sheet 4 at a certain angle (more than 30 °) is black stripes formed on the emission side of the lenticular lens sheet 3. It hits 7 and does not come out to the observation side.
[0018]
Therefore, in a conventional screen that combines a Fresnel lens sheet and a lenticular lens sheet, ghost light (stray light and unnecessary reflected light) generated by reflection inside the Fresnel lens sheet is observed only at a specific position of the screen. In addition, although there is a change in intensity, even if the observation position is changed, the position on the screen does not change.
[0019]
Hereinafter, the generation state of ghost light in the rear projection display apparatus of the present invention will be described.
[0020]
In the rear projection type image display device of the present invention, the generation state of ghost light in the Fresnel lens sheet is the same as the conventional one, but in the lenticular lens sheet of the present invention, the transmittance of the emitted light with respect to the angle of the incident light The characteristics are very different from the conventional ones. In the conventional lenticular lens sheet, light is transmitted to the observation side even when the incident angle is 20 ° or more. However, the lenticular lens sheet in the present invention has a transmittance of approximately 50% or less.
[0021]
When such a lenticular lens sheet according to the present invention is combined with the same Fresnel lens sheet as in the prior art, the area observed as ghost light is significantly narrowed. In the outer periphery of the screen, the incident angle of the ghost light to the lenticular lens sheet is large, and the lenticular lens sheet according to the present invention has a particularly great effect of reducing the ghost light. In order to further reduce ghost light, the transmittance at an incident angle of 20 ° or less is preferably lower, and the transmittance is preferably 30% or less.
[0022]
FIG. 6 shows the configuration of the lenticular lens sheet according to the present invention. The shapes of the entrance side lens 4a and the exit side lens 4b of the lenticular lens sheet 4 in the present invention have an elliptical or circular cross-sectional shape as in the conventional lenticular lens sheet. Here, as described above, in the conventional lenticular lens sheet, a light beam incident at a large angle is partially (light beam 6) as shown by light beam 5 (solid line) and light beam 6 (broken line) in FIG. Only) is cut by the black stripe 7. FIG. 7 shows a state where light rays are transmitted through the lenticular lens sheet according to the present invention. Referring to FIG. 7, the light beam 8 (solid line) represents the path when the incident angle is 0 °, and the light beam 9 (broken line) represents the path when the incident angle is 20 °. As shown by the light beam 9 (broken line) in FIG. 7, according to the lenticular lens sheet of the present invention, the light beam having an incident angle of 20 ° is also cut by the black stripe 7, and unnecessary incident light causing ghost is greatly reduced. The
[0023]
FIG. 4 shows the result of calculating the total light transmittance of one example of the lenticular lens sheet in the present invention. In FIG. 4, graphs (b) and (c) are the results of calculating the total light transmittance of one example of the lenticular lens sheet in the present invention. As shown in graphs (b) and (c) of FIG. 4, it can be seen that stray light of 20 ° or more emitted from the Fresnel lens sheet is hardly transmitted.
[0024]
By the way, the light transmittance of the unnecessary reflected light from the Fresnel lens sheet is greatly influenced by the position of the exit side lens with respect to the main focal position of the entrance side lens. This will be described with reference to FIG. The vertical axis in FIG. 8 represents the total light transmittance Tt (%) of the lenticular lens sheet, and the horizontal axis represents the incident angle θ (deg) of the light beam to the lenticular lens sheet. In FIG. 8, when the principal focal length (mm) of the incident side lens in the lenticular lens sheet is represented by f and the distance (mm) between the top surface of the incident side lens and the top of the light shielding member is represented by t, t 8 is a calculation result when / f is 1.6, and graphs (a), (b), and (c) of FIG. 8 are ratios of the width of the light shielding member to the pitch of the incident side lens (hereinafter referred to as this). "BS ratio") is 45%, 60% and 70% (however, the light transmission loss due to the light absorber contained in the lenticular lens sheet was calculated as 0%). Here, when the position of the exit side lens is far from the main focus position of the entrance side lens designed to maintain a practical horizontal viewing angle, the light transmittance for a light beam having a large incident angle to the lenticular lens sheet is set. It can be greatly reduced. However, the light transmittance required for displaying an image having an incident angle near 0 ° is also lowered, and desirable characteristics as a lenticular lens sheet cannot be obtained. Further, when the position of the exit side lens with respect to the main focal position of the entrance side lens is far, the horizontal diffusion characteristic which is important as the characteristic of the lenticular lens is deteriorated, which is not preferable. On the other hand, even when the position of the exit side lens with respect to the main focus position of the entrance side lens is too close, the transmittance of the light beam necessary for displaying an image is similarly reduced, and desirable characteristics as a lenticular lens sheet are obtained. I can't get it.
[0025]
When the principal focal length (mm) of the incident side lens on the lenticular lens sheet is represented by f and the distance (mm) between the top surface of the incident side lens and the top of the light shielding member is represented by t, the value of t / f Tables 1 and 2 show the results of calculating the relationship of the total light transmittance (Tt) of the lenticular lens sheet by changing the ratio of the width of the light shielding member to the pitch of the incident side lens. In Table 1, the incident angle of the light beam to the lenticular lens sheet is 5 °, and in Table 2, the incident angle of the light beam to the lenticular lens sheet is 20 °.
[0026]
[Table 1]

[Table 2]

[0027]
As shown in Table 1, the total light transmittance is 70% or more when t / f is in the range of 0.7 to 1.2 under the condition that the incident angle of the light beam to the lenticular lens sheet is 5 °. . Further, as shown in Table 2, under the condition that the incident angle of the light beam to the lenticular lens sheet is 20 °, the total light transmittance is 50% or less when t / f is 0.9 or more.
[0028]
That is, when the principal focal length (mm) of the incident side lens in the lenticular lens sheet is represented by f and the distance (mm) between the top surface of the incident side lens and the top of the light shielding member is represented by t, t / f Is in the range of 0.7 to 1.2, the incident angle θ (deg) of the light beam to the lenticular lens sheet, the total light transmittance Tt (θ) (%) of the lenticular lens sheet, and the lenticular lens sheet The light transmission loss α due to the contained light absorber satisfies the expression Tt (θ)> 70 × (1−α) when | θ | = 5 (deg), and | θ | = 20 (deg) ) It is possible to achieve the expression Tt (θ) <50 × (1−α) (%). With such a lenticular lens sheet, ghost light such as stray light and unnecessary reflected light generated from the Fresnel lens sheet can be greatly reduced.
[0029]
As described above, in order to reduce ghost light from a Fresnel lens sheet or the like, it is preferable that the total light transmittance with respect to a light beam having an incident angle of 20 ° to the lenticular lens sheet is low, and 50 × (1− If the transmittance is less than α)%, it is possible to significantly reduce ghost light. The transmittance is more desirably 30 × (1-α)% or less. However, simply reducing the transmittance with respect to a light beam having an incident angle of 20 ° reduces the brightness of the lenticular lens sheet. Therefore, the total light transmittance with respect to a light beam having an incident angle of 5 ° with respect to the lenticular lens sheet is reduced. It is necessary to make it 70% or more. It is more desirable that the total light transmittance for a light beam having an incident angle of 5 ° is 80% or more.
[0030]
In the present invention, by increasing the ratio of black stripes, reflection of external light in a bright room can be reduced, and the contrast of the screen can be improved. In the CRT 3-tube type image display device, the light beams from each of the three tubes are condensed at different positions on the exit side lens of the lenticular lens sheet because the angles at which the light beams from the three tubes enter the lenticular lens sheet are different. It is necessary to correct the resulting color shift. On the other hand, in an image display device using an LCD or the like and having a single projection lens, light can be converged to a substantially constant position of the exit side lens of the lenticular lens, and there is no need to correct the color shift. Therefore, it is possible to increase the ratio of black stripes.
[0031]
A diffusive sheet may be used as the Fresnel lens sheet. FIG. 9 shows an example of the light diffusing characteristic of such a sheet. As shown in FIG. 9, most of the light rays emitted from the Fresnel lens sheet have an emission angle within ± 10 °. In the lenticular lens sheet according to the present invention, since the total light transmittance is 50% or more when the incident angle is 20 ° or less, there is no problem even if it is used in combination with a Fresnel lens sheet having diffusibility.
[0032]
【Example】
Hereinafter, the rear projection type image display apparatus of the present invention will be described more specifically with reference to examples. In the following examples, the GP-1R goniometer manufactured by Murakami Color Research Laboratory was used for measuring the total light transmittance, and the KL-37HW1 LCD rear projection type projection television manufactured by Sony Corporation was used for evaluating the contrast. The color difference meter CS-100 manufactured by Minolta Co., Ltd. was used for measurement of luminance and the like.
[0033]
Example 1
A lenticular lens sheet having a lenticular lens pitch of 0.53 mm, a sheet thickness of 0.62 mm, and a black stripe ratio of 67% is rolled into a roll using an extrusion molding machine manufactured by Toshiba Machine Co., Ltd. It is produced by a molding method. On the surface of this lenticular lens sheet, black stripes are formed by screen printing using black ink. The shape of the lenticular lens is expressed as follows. Note that t / f is 0.9.
Lens shape: CR ² / [1+ {1− (K + 1) C ² R ² } ^1/2 ] + DR ⁴ + ER ⁶ + FR ⁸ + GR ¹⁰
Incident side lens: C = 4.5, K = −0.4486, D = E = F = G = 0
Output side lens: C = −4.5, K = −0.4486, D = E = F = G = 0
R is the radius from the center of the lenticular lens.
[0034]
The Fresnel lens sheet constituting the rear projection type image display device in combination with the above lenticular lens sheet is made of a resin plate mixed with a fine particle diffusion material, and the diffusion characteristics of this Fresnel lens are shown in FIG.
[0035]
Table 3 shows the results of measuring the total light transmittance Tt (θ) (%) of the lenticular lens sheet of this example. The total light transmittance is a ratio of the total amount of light emitted from the exit surface to the amount of light incident from the entrance surface of the lenticular lens sheet (in Table 3, examples described later) The measurement results for 2 are also shown.)
[0036]
[Table 3]

[0037]
Table 4 shows the results obtained by attaching the lenticular lens sheet of the present example and the above Fresnel lens sheet to the above-described projection television, and measuring the brightness of the projected image and the external light reflection as an index of the external light contrast. Here, horizontal viewing angles αH, βH, and γH in Table 4 indicate horizontal viewing angles that are 1/2, 1/3, and 1/10, respectively, with respect to the peak luminance. The thing of Example 1 has a horizontal viewing angle which is satisfactory practically with Example 2 mentioned later.
[0038]
[Table 4]

[0039]
The luminance of the projected image was measured by inputting a black and white pattern reference signal to the projection television and measuring the white portion using the measuring device at a distance of 1 m from the projection television. In addition, the external light reflection luminance is measured in a state in which a halogen lamp is dimmed and illuminated at an angle of approximately 45 ° from above with respect to the screen so that the illuminance on the screen surface of the projection television is 360 Lx. This was done by measuring the luminance of the black part. In Table 4, the external light contrast is shown as a value obtained by dividing the white luminance of the projected image by the black luminance. The external light contrast indicates the influence of external light on the projected image light. The larger this value, the less the contrast is reduced by the external light.
[0040]
Next, the illumination in the evaluation room was turned off, a black and white reference signal was input to the projection television, and the white portion luminance and the black portion luminance were measured. A value obtained by dividing white luminance by black luminance was defined as stray light contrast. A larger value means that there is less decrease in contrast due to stray light.
[0041]
(Example 2)
In the formula representing the lens shape of the lenticular lens sheet,
Incident side lens: C = 4.5, K = −0.4486, D = E = F = G = 0
Output side lens: C = −4.5, K = −0.4486, D = E = F = G = 0
The lens pitch was 0.53 mm, the sheet thickness was 0.62 mm, t / f was 0.9, and the black stripe ratio was 60%, as described in Example 1. To make.
[0042]
The results of measuring the total light transmittance and contrast using this lenticular lens sheet in the same manner as in Example 1 are shown in Tables 3 and 4 above.
[0043]
(Comparative Example 1)
In the formula representing the lens shape of the lenticular lens sheet,
Incident side lens: C = 4.5, K = −1.0, D = E = F = G = 0
Outgoing lens: C = −6.3, K = −1.0, D = E = F = G = 0
The lens pitch is 0.55 mm, the sheet thickness is 0.67 mm, t / f is 1.0, and the black stripe ratio is 44% as described in the first embodiment. To make.
[0044]
The results of measuring the total light transmittance and contrast using this lenticular lens sheet in the same manner as in Example 1 are shown in Tables 3 and 4 above. As shown in Table 3, the lenticular lens sheet of the comparative example has a high transmittance for an incident angle of 20 °. In this comparative example, as shown in Table 4, the contrast is inferior to that of the example.
[0045]
【The invention's effect】
According to the present invention, ghost light such as stray light and unnecessary reflected light generated in a projection optical system that is generated even in the absence of external light is reduced, and reflection of external light in a bright room is also reduced. A projection type video apparatus can be provided.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating ghost light emitted from a Fresnel lens sheet.
FIG. 2 is another view for explaining ghost light emitted from a Fresnel lens sheet.
FIG. 3 is a diagram illustrating a position of ghost light emitted from a Fresnel lens sheet.
FIG. 4 is a diagram showing a relationship between an incident angle to a lenticular lens sheet and a total light transmittance.
FIG. 5 is a diagram illustrating a light transmission path in a conventional lenticular lens sheet.
FIG. 6 is a cross-sectional view of a lenticular lens sheet according to the present invention.
FIG. 7 is a diagram for explaining how unnecessary incident light is cut in the lenticular lens sheet of the present invention.
FIG. 8 is a diagram showing the results of obtaining the relationship between the incident angle to the lenticular lens sheet and the total light transmittance with different BS ratios.
FIG. 9 is a diagram for explaining an example of a diffusion characteristic of light emitted from a Fresnel lens sheet.
FIG. 10 is a diagram illustrating a configuration example of a transmission screen.
FIG. 11 is a view showing a cross section of a transmissive screen.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Fresnel lens sheet 4 ... Lenticular lens sheet 4a ... Incident side lens 7 ... Black stripe

Claims (3)

A lenticular lens comprising: a single projection lens; a Fresnel lens sheet; and a lenticular lens sheet provided with a light shielding member in a region where the light that has passed through the Fresnel lens sheet is not transmitted when the light is emitted. The incident angle (deg) to the lens sheet is θ, the total light transmittance (%) of the lenticular lens sheet with respect to the light having the incident angle θ is Tt (θ), and the light is transmitted by the light absorbent contained in the lenticular lens sheet. When the loss is represented by α, at the center of the lenticular lens sheet, Tt (θ) and α are the following formulas (1) and (2),
Formula (1): When | θ | = 5 Tt (θ)> 70 × (1-α)
Formula (2): When | θ | = 20 Tt (θ) <50 × (1-α)
A rear projection type image display device satisfying the above requirements. When the principal focal length (mm) of the incident side lens in the lenticular lens sheet is represented by f and the distance (mm) between the top surface of the incident side lens and the top of the light shielding member is represented by t, f and t are as follows. Equation (3)
Formula (3): 0.7 ≦ t / f ≦ 1.2
The rear projection type image display apparatus according to claim 1, wherein: The rear projection type image display device according to claim 1, wherein the width of the light shielding member with respect to the pitch of the incident side lens in the lenticular lens sheet is 60% or more.

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