JP2005189893A - Back projection display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve an improvement in a contrast ratio and reduction in speckle disturbance of a light valve type back projection display. <P>SOLUTION: In the figure, the number 67 stands for a microlenticular lens commonly used for light diffusion in a perpendicular direction and reduction in speckle disturbance, 66 a Fresnel lens, 63 a main lenticular lens, 65 a light diffusion layer, 64 a black stripe layer of 60% area ratio, 69 a light transmission layer, 71 a matte light diffusion element commonly used for reduction in the speckle disturbance and reduction in mirroring disturbance of ambient light. The microlenticular lens 67 and the matte light diffusion element 71 reduces speckle disturbance. The black stripe layer 64 and the matte light diffusion element 71 improves the contrast ratio and reduces the mirroring disturbance of the ambient light. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a rear projection display device using a light valve having a pixel structure, and to reduce moire interference caused by interference between the pixel structure of the light valve and the lenticular structure of the transmissive screen, and The present invention relates to a reduction in speckle interference caused by interference between a projected light beam and a random diffuser element in a screen.

  Japanese Patent Publication No. 7-19029 by the present inventor presents a basic form of a general black stripe (hereinafter abbreviated as BS) type screen, and Japanese Patent Application Laid-Open No. 7-034909 discloses an improved version thereof. Is presented. These are effective in improving image quality such as enlargement of the horizontal viewing angle of the screen and improvement of the contrast ratio.

  Japanese Examined Patent Publication No. 7-7179 proposes means for eliminating the moire interference between the Fresnel element and the lenticular element constituting the screen.

  In Japanese Utility Model Publication No. 7-43712, a configuration shown in FIG. 1 is presented in order to reduce the moire interference between the pixel structure of the light valve and the lenticular structure of the BS screen. In the figure, 1 is a light valve having a pixel structure, 2 is a projection imaging means such as a projection lens, 3 is a Fresnel sheet, 4 is a lenticular sheet, 5 is a main lenticular lens, 6 is a black stripe, 7 is a Fresnel lens, 8 Is a micro lenticular lens, and its arrangement direction is parallel to the main lenticular lens.

According to this configuration, the micro lenticular lens (8) can diverge light in the horizontal direction, and as a result, moiré interference can be reduced. However, the following problems remain in the above configuration.
(1) Since the light diverges in the horizontal direction by the micro lenticular lens (8), the area ratio of the black stripes must be reduced. Accordingly, the effect of improving the contrast ratio is hindered.

  This is illustrated in FIG. This figure is a horizontal section of the main lenticular sheet (4). A solid line 9 indicates parallel rays, and a dotted line 10 indicates divergent light.

In order to allow the diverging light to pass through, there remains a problem that the width of the BS must be reduced to 50% or less in practice.
(2) When the angle at which the pupil of the projection imaging means is viewed from the screen side is small, so-called speckle interference occurs. Speckle interference is a failure that typically occurs when a diffused surface is irradiated with laser light, and is an obstacle in which bright spots that shine like stars appear in an image that should originally be reproduced in a uniform white color. .

  One object of the present invention is to overcome the above-mentioned problems of the prior art and provide a rear projection display having a better contrast ratio. Another object of the present invention is to provide a rear projection display with reduced moire interference caused by interference between the pixel structure of the light valve and the main lenticular structure of the screen. It is still another object of the present invention to provide a rear projection display with reduced speckle interference.

  The basic idea of the present invention is to eliminate most of the causes of moire interference in the remaining incident side optical system (light valve, projection imaging means, and spatial filter means) excluding the screen, and to prevent speckle interference in the screen. The purpose is to reduce the efficiency and improve the contrast ratio.

  In order to achieve the above object, in each embodiment of the present invention, a ratio value TP / TBS of a horizontal arrangement period: TP of a light valve pixel projected on a screen and a BS arrangement: TBS on the screen. Is assumed to be 1.5 or more (horizontal resolution securing condition) 3.5 or less (screen manufacturing facilitation condition). Furthermore, it is formed so that the area occupation ratio of the BS portion of the screen is 60% or more.

  In some embodiments of the present invention, in the remaining incident-side optical system excluding the screen, at least one of the second and third harmonic components in the horizontal pixel array spectrum of the light valve is reduced. Harmonic reduction means is provided.

  In one embodiment of the present invention, the harmonic reduction means is formed by harmonic reduction type light valve means. The harmonic reduction type light valve means is characterized in that in the spectrum of the horizontal effective pixel array pattern, the ratio of at least one of the second and third harmonic spectra to the zero frequency spectrum is 0.1 or less. To do. Accordingly, it is possible to attenuate moiré disturbance caused by interference between the harmonic component of the horizontal pixel array of the light valve and the BS array periodic component on the screen by 20 dB or more (0.1 times or less).

  In another embodiment of the present invention, the harmonic reduction means is formed by a ¼ pixel shift means disposed between the light valve and the projection imaging means. The pixel shift means is formed of a birefringent material, and acts to generate an interval of TP (1 / 3.5 to 1 / 6.5) at least in the horizontal direction between the ordinary light polarization component output and the extraordinary light polarization component output. . As a result, at least one of the second and third harmonic components is reduced, and moire interference resulting therefrom is reduced.

  In another embodiment of the present invention, the remaining projection optical system other than the screen has a harmonic that attenuates at least one of the second and third harmonic components of the horizontal pixel array of the light valve by 20 dB or more. Attenuating means and a transmissive screen means having a BS ratio of 60% or more are provided. The transmissive screen is formed of at least a light incident side Fresnel sheet and a light emission side lenticular sheet.

  The Fresnel sheet includes a micro lenticular lens element that diverges light in the vertical direction on the incident surface and a light diffusing element, and a Fresnel lens on the output surface. The vertical light divergence half-value angle of the Fresnel sheet is limited to 10 degrees PP or more, and the horizontal light divergence half-value angle is limited to 5 degrees PP or less. The lenticular sheet includes a main lenticular lens that diverges light in a horizontal direction on an incident surface, and a light diffusion layer having a light divergence half-value angle of 10 degrees PP or more and a black stripe layer are formed on a focal plane of the main lenticular lens. Further, a light transmission layer is formed on the emission side. The contrast ratio is improved by limiting the area ratio of the black stripe layer of the lenticular sheet to 60% or more. Moreover, speckle interference can be reduced by providing the Fresnel sheet with a micro lenticular lens element and a light diffusing element. Further, by limiting the horizontal light divergence half-value angle of the Fresnel sheet to 5 degrees PP or less, it is possible to avoid light vignetting loss in the subsequent black stripe layer and improve the light transmission efficiency.

  In another embodiment of the present invention, the transmission screen is formed of at least a light incident side Fresnel sheet and a light emission side lenticular sheet. The Fresnel sheet has a Fresnel lens on its exit surface. The lenticular sheet includes a main lenticular lens that diverges light in a horizontal direction on an incident surface, and a light diffusion layer having a light divergence half-value angle of 10 degrees PP or more and a black having an area ratio of 60% or more are disposed on a focal plane of the main lenticular lens. A stripe layer is formed, a light transmission layer is further formed on the emission side, and a mat-like light diffusion element is formed on the emission surface. The light spread width θDTD given by the product of the light divergence half-value angle θD of the light diffusing element and the thickness TD of the light transmission layer is the product of the F value of the projection imaging means, the projection magnification M, and the light wavelength λ. Speckle interference can be reduced by forming the diffraction correlation distance λFM larger than a given diffraction correlation distance λFM. At the same time, the matte light diffusing element eliminates the disturbance of reflection of ambient light, and the contrast ratio is improved.

  According to the present invention, it is possible to reduce speckle interference inherent in the light valve type rear projection display. Further, since vignetting of light due to black stripes can be prevented, a high-quality image with excellent light transmission efficiency and a high contrast ratio can be provided.

  First, the moire interference reduction principle employed in the present invention will be conceptually described. FIG. 3 is a block diagram for explaining moire interference. In the figure, 11 is a light valve, 12 is a spatial filter, 13 is a projection imaging means, 14 is a light diffusion layer formed in a main lenticular sheet (4 in FIG. 2) constituting the screen, and 15 is a main lenticular. Represents a lens (5 in FIG. 2).

  In general, moiré interference is noticeably generated when white is projected on the entire screen. That is, it occurs due to interference (multiplication) between the horizontal distribution T1 (x) of the effective pixel area of the light valve and the horizontal periodic structure of the main lenticular lens. This is because, as described in Japanese Patent Publication No. 7-7179, for example, a viewer located in the normal direction of the front of the screen sees only light incident on the top of each mountain of the main lenticular lens. It is. In other words, the main lenticular lens can be regarded as a “sampler” that samples information for each array period TBS.

  FIG. 4 is a waveform diagram for explaining the principle, and FIG. 5 is a spectrum diagram for explaining the principle. x represents a horizontal position coordinate, and f represents a spatial frequency [cycle / min]. The horizontal coordinate on the light valve and the horizontal coordinate on the screen have a ratio of projection magnification, but for the sake of simplicity of explanation, the following description will be made assuming that the magnification is equal to 1. T2 (x) to T5 (x) are impulse responses of 12 to 15 respectively, and G2 (f) to G5 (f) are respective Fourier spectra. T6 (x) is the screen output distribution, and G6 (f) is the Fourier spectrum. There is a relationship of the following formulas (1) to (5) between them.

光拡散層（図２の４'）のインパルスレスポンスＴ４（ｘ）は、光拡散層の水平指向性分布Ｐ（θ）においてθをｘ／ｆ０（ここにｆ０は主レンチキュラーレンズの焦点距離）に置換することによって近似的に得られる。このことの詳細原理は、本発明者による特公平７−７１７９号公報に記されている。図４は、画素配列周期ＴＰが主レンチキュラーレンズ配列周期ＴＢＳの２倍である場合を示している。図３において、ｆＰはＴＰの逆数、ｆＢＳはＴＢＳの逆数である。従って、ｆＢＳは同図では２ｆＰに等しい。

The impulse response T4 (x) of the light diffusing layer (4 ′ in FIG. 2) indicates that θ is x / f0 (where f0 is the focal length of the main lenticular lens) in the horizontal directivity distribution P (θ) of the light diffusing layer. It is obtained approximately by replacing. The detailed principle of this is described in Japanese Patent Publication No. 7-7179 by the present inventor. FIG. 4 shows a case where the pixel array period TP is twice the main lenticular lens array period TBS. In FIG. 3, fP is the reciprocal of TP, and fBS is the reciprocal of TBS. Therefore, fBS is equal to 2fP in the figure.

  In the present invention, TP is limited to the range of (1.5 to 3.5) TBS. Therefore, fBS is in the range of (1.5 to 3.5) fP. Therefore, the main cause of moire interference is beat interference between the G5 (± fBS) component and the G14 (± 2 fP) component (second harmonic component) or G14 (± 3 fP) component (third harmonic component). . On the screen, fBS-2fP and 3fP-fBS low frequency patterns are disturbed. Since the sum of both beat frequencies is equal to fP, at least one beat frequency is 0.5 fP or less. This coincides with the upper limit frequency that can be expressed by the light valve having the sampling frequency fP. Therefore, it becomes a harmful interference pattern. Reference numeral 31 ′ in FIG. 5 indicates that the frequency region that can be expressed by the light valve is 0.5 fP. The detection limit modulation degree of moire interference is about 1.6% PP (peak to peak) for a low frequency beat, and the practical limit is about 10% PP for a high frequency beat. It is concluded from Fourier analysis that each value of 4G (2fP) and 4G (3fP) corresponds to the PP modulation degree (see Japanese Patent Publication No. 7-7179).

  In FIG. 5, 33 'indicates the out-of-band characteristic of the projection imaging means. The value of G3 (f) in this region is about 0.3 to 0.2 or less. Making this value even smaller is effective in reducing moire interference. However, this increases the cost of the projection imaging means.

  The present invention seeks to provide a novel means for reducing the values of G1 (2fP), G1 (3fP), G2 (2fP), and G2 (3fP) to 0.1 or less. FIG. 6 shows a main part of the first embodiment according to the present invention. In the figure, 41 is a harmonic spectrum reduction type light valve means, 42 is an effective pixel area, 43 is a non-effective pixel area, TP is a horizontal pixel arrangement period, d1 is a horizontal effective pixel width ratio, and the width of the effective pixel area. Equal to the value divided by the pixel array period. In general, the light valve is composed of pixels arranged in a matrix of about 500 × 500 or more, but in this example, only a 3 × 3 portion is shown.

  The configuration requirement of this example is that the TP / TBS ratio is 1.5 to 3.5 and the zero frequency of the high frequency spectrum of at least one of the second and third effective pixel array patterns of the light valve. The ratio to the spectrum is 0.1 or less. FIG. 7 shows a spectrum diagram of the pattern of FIG. The figure corresponds to a d1 value of 0.5. A dotted line 44 is a spectrum for one effective pixel, and a solid line with an arrow is a spectrum of the entire light valve. The dotted line 47 is given by F1 (f) of the following equation.

上式（７）のｆに２ｆＰを代入し、上記構成要件を代入すると、ｄ１の値の範囲は０．４５〜０．５５または、０．９〜１．０となる。また、ｆに３ｆＰを代入すると、ｄ１の値の範囲は０．６０〜０．７３または０．９〜１．０と求まる。

When 2fP is substituted for f in the above formula (7) and the above-described configuration requirements are substituted, the range of the value of d1 is 0.45 to 0.55 or 0.9 to 1.0. If 3fP is substituted for f, the range of d1 is 0.60 to 0.73 or 0.9 to 1.0.

  Accordingly, the above-described configuration requirement is that the effective pixel region has a substantially rectangular shape, and the horizontal effective pixel width ratio d1 is 0.45 to 0.55, 0.60 to 0.73, and 0.90 to 1.0. Is equivalent to limiting to at least one of the ranges. The sixth ineffective pixel region 43 is utilized for wiring of electric signals and for arrangement of electric circuit elements (for example, transistors and capacitors).

  The main part of the second embodiment of the present invention is shown in FIG. In the figure, 1 is a light valve, 2 is a projection imaging means, 50 is a transmission screen, and includes the lenticular sheet described above, and the TP / TBS ratio is configured within the range of 1.5 to 3.5. The 51 is a horizontal sectional view of the pixel shift means, and has a function of generating a horizontal interval: Δ between the ordinary ray output and the extraordinary ray output.

  The principle will be described below. As shown in the figure, the optical axis direction of the projection optical system is the Z axis, the horizontal direction is the X axis, and the normal direction of the paper surface is the Y axis. The pixel shift means is made of a material having a birefringence phenomenon, such as quartz, calcite, etc., and is formed by inclining the direction of the symmetric optical axis of the birefringent material (indicated by 0 in the figure) by an angle α from the Z axis. To do. Numerical examples are given below for the case where quartz is used as the material. The ordinary ray refractive index n0 of quartz is 1.544, and the extraordinary ray refractive index ne is 1.553.

Therefore, the ne / n0 ratio is about 1.006. In FIG. 8, a solid arrow 52 indicates an ordinary ray (a ray whose electric field direction is parallel to the Y axis), and a dotted arrow 53 indicates an extraordinary ray (a ray whose electric field direction is parallel to the X axis). The separation angle θ in the birefringent medium becomes the maximum when the tilt angle α of the symmetric optical axis of the birefringent material is about 45 °, and the θ value is a value obtained by subtracting 1 from the ratio 1.006. That is, 6 mrad. Accordingly, the pixel shift amount Δ is obtained by the following equation.

従って厚みｔを１．７ｍｍとすると、△は約１０μｍとなる。ライトバルブの画素配列周期ＴＰは約４０μｍのオーダである。上記画素シフト手段のスペクトル（フーリエ変換）Ｇ２（ｆ）は次式で与えられる。

Therefore, if the thickness t is 1.7 mm, Δ is about 10 μm. The pixel array period TP of the light valve is on the order of about 40 μm. The spectrum (Fourier transform) G2 (f) of the pixel shift means is given by the following equation.

図９に上式をグラフ化して示す。△／ＴＰ比を上記の通り１／４とすると、６２に示す特性となり、従って、第２高調波成分を低減できる。△／ＴＰ比を１／６（厚さ１．１１ｍｍに対応する）とすると、６３に示す特性となり、第３高調波成分を低減できる。

FIG. 9 is a graph showing the above equation. When the Δ / TP ratio is 1/4 as described above, the characteristic shown in 62 is obtained, and therefore the second harmonic component can be reduced. If the Δ / TP ratio is 1/6 (corresponding to a thickness of 1.11 mm), the characteristic shown in 63 is obtained, and the third harmonic component can be reduced.

  The structural requirements of the present embodiment are that the TP / TBS ratio is 1.5 to 3.5 and the pixel shift amount Δ of the pixel shift means is 1 / 3.5 to 1 / 6.5 of TP. By doing so, at least one of the second and third harmonic components can be reduced by 16 dB or more, which is effective in reducing moire interference.

  The second embodiment is based on the precondition that the incident light to the image shift means 51 includes equal amounts of ordinary rays and extraordinary rays. Examples of satisfying such preconditions include circularly polarized light and linearly polarized light in the 45 ° direction in the XY plane. The linearly polarized light in the Y-axis direction does not satisfy the above conditions. Therefore, it is necessary to put a converter in front. FIG. 10 shows a countermeasure. In the figure, 1, 2, 50 and 51 are the same as those described above.

  Reference numeral 54 denotes a quarter wavelength plate or a half wavelength plate. If a quarter wave plate is used, linearly polarized light input in the Y-axis direction can be converted to circularly polarized light output. If a half-wave plate is used, it can be converted into linearly polarized waves in the 45 ° direction. This is the end of the description of this embodiment.

  It should be noted that the harmonic reduction means in the present invention is not necessarily limited to the above-described one, and other means can be substituted. For example, as shown in PCT / JP95 / 02123, a light diffusing means that diverges light at least in the horizontal direction can be substituted by being disposed close to the light valve.

  FIG. 11 is a perspective view showing the main part of the third embodiment of the present invention. In the figure, 61 is a Fresnel sheet, 62 is a lenticular sheet, 63 is a main lenticular lens, 64 is a black stripe, 65 is a light diffusion layer, 66 is a Fresnel lens, 67 is a micro lenticular lens element that emits light in the vertical direction, 68 Is a light diffusing element, and 67 and 68 are for speckle interference reduction. 63 is a main lenticular lens, 65 is a light diffusion layer, and 64 is a black stripe layer. The Fresnel lens 66 acts to collimate outgoing light. The focal plane of the main lenticular lens is formed at the position of the black stripe layer, and projection light is emitted from the light transmitting portion between the black stripe layers having a BS ratio of 60% or more. The light divergence half-value angle of the light diffusion layer 65 is limited to 10 degrees or more.

  The vertical light divergence half-value angle of the Fresnel sheet 61 is limited to 10 degrees PP or more, and the horizontal light divergence half-value angle is limited to 5 degrees PP or less. The limitation of 10 ° PP or more is for speckle interference reduction and vertical viewing angle provision as described later, and the limitation of 5 ° PP or less is for avoiding vignetting loss of light in the black stripe layer as described later.

  Next, the principle of speckle interference generation and the principle of reduction will be described. As is well known, when the surface of the ground glass is irradiated with laser light, so-called scintillation interference occurs in which stars appear to glitter. In the optical system of the light valve, the same phenomenon occurs because the angle θ at which the pupil of the projection imaging means is viewed from the screen is small. In FIG. 12, 2 is a projection imaging means, and 65 is a diffusion layer.

  The value of the angle θ [rad] is equal to the reciprocal of the product of the F value and the magnification M of the projection imaging means. If the diffraction correlation distance that the mutual interference of the phase of the light on the image plane reaches is D, this is on the order of λ / θ. When the wavelength λ is 0.5 μm, and an actual F value of 2.4 and a magnification M: 50 times are substituted, the correlation distance D is on the order of about 60 μm. The particle diameter for forming the diffusion layer is usually sufficiently smaller than 60 μm. In this case, assuming that the diffusion layer is one random phase modulation particle layer, it is known that the ratio of the standard deviation σ of luminance fluctuation (speckle) on the image plane and the average luminance B0 is equal to 1. When the pixel size (TP) on the screen is set to 1 mm and observation is performed from an appropriate viewing distance, it is considered that an integrated average value in an area of about (1 mm) 2 is detected by human eyes. When the standard deviation of the average value is denoted as σ0, the following equation is established.

スペックル妨害の検知限界はσ０／Ｂ０比、約０．０２故、約１／３倍に低減する必要がある。１／３倍に低減するには、回折相関距離Ｄに相当する面積Ｄ２の３２倍の面積にわたって像を平均化するための空間フィルタ作用が必要とされる。

The detection limit of speckle interference needs to be reduced to about 1/3 times, since the σ0 / B0 ratio is about 0.02. In order to reduce to 1/3 times, a spatial filter action is required to average the image over an area 32 times the area D2 corresponding to the diffraction correlation distance D.

  This spatial filtering action is provided in FIG. 11 by a vertical light divergence microlens element 67 and a light diffusing element 68. The spatial filter action will be described with reference to FIGS.

  FIG. 13 is a vertical cross-sectional view illustrating the vertical averaging function. In the figure, t0 is the distance from the incident surface of the Fresnel sheet to the light diffusion layer of the lenticular sheet, and is the sum of the thickness of the Fresnel sheet (usually about 3 mm) and the focal length of the lenticular lens (usually about 0.7 mm). equal. θv is a vertical light divergence half-value angle [rad] in the medium of the Fresnel sheet. TDV is the vertical averaging interval length and is equal to the θvt0 product. The above-mentioned (in the air) “divergence half-value angle of 10 degrees pp or more” is about 6.7 degrees pp divided by a refractive index value of about 1.5 in the medium, so that the θv value is about 0.12 rad.

  When the t0 value of 3.7 mm is substituted, the TDV value is about 0.43 mm. Since this value corresponds to 7 times the aforementioned D value of 60 μm, it is a little deficient compared to the required multiple of 9 times. This deficiency is satisfied by the horizontal averaging function shown in FIG. FIG. 14 is a horizontal cross-sectional view illustrating the horizontal averaging operation. The aforementioned divergence angle of 5 degrees pp corresponds to 0.06 rad in terms of θH in the medium. Therefore, the horizontal averaging section TDH corresponds to 180 μm when the t1 value is 3 mm. Since this value is larger than the D value of 60 μm, it is effective for reducing speckle interference by the averaging action.

  On the other hand, if the light spreading width in the focal plane of the lenticular sheet 62 resulting from the divergence angle θH is W, W is equal to the product θHt2. Substituting 0.06 rad and 0.7 mm, the full width at half maximum W is 42 μm. The arrangement period TBS of the main lenticular lens is usually approximately 0.7 times t2 and is on the order of 0.5 mm. Since the expansion half width W is 10% or less of TBS, it is possible to achieve both improvement of the BS rate. The speckle ratio after being improved by the averaging function is given by the following equation.

従って検知限界以下にスペックル妨害を低減することができる。上記実施例の代表的諸元を付記する。マイクロレンズ６７のピッチは８０μｍ、フレネルレンズ６６のピッチは１００μｍ、これらは、主レンチキュラーレンズのピッチ（ＴＢＳ）５００μｍの１／３以下に限定される。これはスクリーン内部での相互間モアレ現象を回避するためである。以上で第３実施例の説明を終わる。

Therefore, speckle interference can be reduced below the detection limit. Representative specifications of the above embodiment will be added. The pitch of the microlenses 67 is 80 μm, the pitch of the Fresnel lenses 66 is 100 μm, and these are limited to 1/3 or less of the main lenticular lens pitch (TBS) of 500 μm. This is to avoid the moire phenomenon between the screens. This is the end of the description of the third embodiment.

  Next, a local improvement example of the third embodiment is shown in FIG. 15 as a fourth embodiment. This figure shows that a light-transmitting resin layer 69 is added to the emission part of the lenticular sheet 62 in FIG. That is, the black stripe layer 64 and the light diffusion layer 65 are embedded in the light transmitting resin layer 69.

  As a result of the prototype experiment, it was found that this format has a great effect of improving the texture (transparency) of the image. As a modification of the fourth embodiment, it is effective to form an antireflection film on the exit surface (70 in FIG. 15) of the light transmitting resin layer. Furthermore, it is recommended to add a color filter to the light transmitting resin layer. This is because, in general, the light source for the light bulb has an intermediate color spectrum component (for example, a 575 mm yellow component attributed to mercury) that causes parasitic color purity deterioration in addition to the desired three primary color spectrum component light. . By adding a color filter, not only the color purity can be improved, but also an improvement in contrast ratio, that is, an improvement in image quality can be achieved.

  A fifth embodiment of the present invention is shown in FIG. In the figure, 61 is a Fresnel sheet, 66 is a Fresnel lens, 62 is a lenticular sheet, 63 is a main lenticular lens, 64 is a black stripe layer with a BS ratio of 60% or more, 65 is a light diffusion layer, 69 is a light transmission layer, and 71 is It is a mat-like light diffusing element formed on the exit surface of the lenticular sheet. The light divergence half-value angle of the light diffusion layer 65 is formed to be 10 degrees pp or more.

  Assuming that the in-medium light divergence half-value angle of the mat-like light diffusion element 71 is θD and the thickness of the light transmission layer is tD, the light diffusion half-value width TD by the light diffusion element 71 is given by θDtD. This value is formed to be larger than the diffraction correlation distance D described above. This condition is expressed by the following equation.

上式において、λは光の波長で約０．５μｍ、Ｆはスクリーンの入射側に配置される投写結像手段のＦ値、Ｍは投写倍率である。本実施例によればスペックル妨害を低減できるだけでなく、スクリーン出射側の周囲照明用光源（図１６の８０）のスクリーンへの映り込みを防止できるという長所を有する。即ち、スクリーン出射面を平滑面とした構成（図１５）においては周囲照明用光源の像がスクリーン上に映りこむという欠点を有するが、図１６の構成においてはその欠点が克服されている。更に本実施例においては、フレネルシート６６の中に光拡散要素を含まないため、ＢＳ層における光のケラレ損失を最小化できるという長所を有する。

In the above equation, λ is the wavelength of light of about 0.5 μm, F is the F value of the projection imaging means arranged on the incident side of the screen, and M is the projection magnification. According to this embodiment, not only can speckle interference be reduced, but also the ambient light source (80 in FIG. 16) on the screen emission side can be prevented from being reflected on the screen. That is, the configuration in which the screen exit surface is a smooth surface (FIG. 15) has the disadvantage that the image of the ambient illumination light source is reflected on the screen, but the configuration in FIG. 16 overcomes this disadvantage. Further, in this embodiment, since the light diffusing element is not included in the Fresnel sheet 66, there is an advantage that vignetting loss of light in the BS layer can be minimized.

  As a modification of the fifth embodiment, an antireflection film is formed on the surface of the mat-like light diffusing element 71. Doing so is effective in improving the contrast ratio of the reproduced image and improving the image quality.

  FIG. 17 shows another modification. In the figure, reference numeral 67 denotes a micro lenticular lens element that diverges light in the vertical direction. Others are the same as FIG. By adding the micro lenticular lens 67, an effect that speckle interference can be further reduced is obtained.

  FIG. 18 shows another modification. In the figure, reference numeral 68 denotes a light diffusing element, which is the same as that already described in FIG. Each of the screens shown in FIGS. 11 to 18 can be used in combination with the moire disturbance reducing means described before FIG. FIG. 19 shows two examples of pixel arrays of light valves. FIG. 19A is referred to as a matrix arrangement, and FIG. 19B is referred to as a delta arrangement. In both figures, 42 is a pixel. The pixel array period TP in the present invention is defined as shown.

The perspective view which shows a prior art. The horizontal sectional view of the main lenticular sheet. The block diagram for demonstrating the moire disturbance reduction principle of this invention. FIG. 4 is a waveform diagram of FIG. 3. The spectrum figure of FIG. The top view which shows the principal part of 1st Example of this invention. The spectrum figure of FIG. The horizontal sectional view which shows the structure of 2nd Example of this invention. FIG. 5 is a graph for explaining the principle of the second embodiment of the present invention. The figure which shows the modification of 2nd Example of this invention. The perspective view which shows 3rd Example of this invention. The conceptual diagram for explaining the diffraction correlation distance of the projection imaging means. The vertical sectional view for operation explanation of the 3rd example. The horizontal sectional view for operation explanation of the 3rd example. The horizontal sectional view showing the important section of the 4th example of the present invention. The perspective view which shows 5th Example of this invention. The perspective view which shows the modification of 5th Example of this invention. The perspective view which shows the modification of 5th Example of this invention. The figure which shows the definition of a pixel arrangement period.

Explanation of symbols

1, 11, 41, 44 ... Light valve,
2, 13 ... projection imaging means,
3 ... Fresnel sheet,
4 ... Lenticular sheet,
4 ', 14 ... light diffusion layer,
6 ... Black stripe,
5,15 ... Main lenticular lens,
12 ... Spatial filter,
42 ... effective pixel area,
43 ... non-effective pixel area,
51. Pixel shift means,
50 ... Transparent screen,
61 ... Fresnel sheet,
62 ... Lenticular sheet,
63 ... Main lenticular lens,
64 ... Black stripe layer,
65 ... light diffusion layer,
66 ... Fresnel lens,
67 ... Micro lenticular lens element for vertical divergence,
68. Light diffusing element,
69 ... light transmission layer,
71: Matt-like light diffusion element.

Claims (5)

  In a rear projection display comprising a light valve having a pixel arrangement structure, a projection imaging means, and a transmission screen, the transmission screen is composed of at least a Fresnel sheet on the light incident side and a lenticular sheet on the light emission side, The Fresnel sheet has a Fresnel lens on its exit surface, the lenticular sheet has a main lenticular lens that diverges light in the horizontal direction on its entrance surface, and has a light divergence half-value angle of 10 degrees PP or more on the focal plane of the main lenticular lens. A light diffusion layer and a black stripe layer having an area ratio of 60% or more are formed, a light transmission layer is formed on the emission side of both layers, and a mat-like light diffusion element is formed on the emission surface of the light transmission layer, Light spread width: θDtD given by the product of the light divergence half-value angle θD of the mat-like light diffusing element and the thickness tD of the light transmission layer is the projected image. Product of stage F value, magnification M and light wavelength λ: horizontal array period of the pixel structure of the light valve formed to be larger than the diffraction correlation distance given by λFM and projected onto the screen surface The ratio of TP to the array period TBS of the main lenticular lens is configured within the range of 1.5 to 3.5, and at least one of the second and third harmonic components of the horizontal pixel array spectrum is A rear projection display device comprising harmonic reduction means for reducing.   2. The rear projection display device according to item 1, further comprising a micro lenticular lens element that diverges light in a vertical direction on an incident surface of the Fresnel sheet.   2. The rear projection display device according to claim 1, wherein the harmonic reduction means is formed by a pixel shift means.   2. The rear projection display device according to claim 1, wherein the harmonic reduction means is formed by light divergence means that diverges light at least in the horizontal direction. In a rear projection display comprising a light valve having a pixel arrangement structure, a projection imaging means, and a transmission screen, the transmission screen is composed of at least a Fresnel sheet on the light incident side and a lenticular sheet on the light emission side, The Fresnel sheet has a micro lenticular lens element and a light diffusing element that diverges light in the vertical direction on the incident side, a Fresnel lens on the exit surface, and the vertical light divergence half-value angle of the Fresnel sheet is 10 degrees PP or more. And the horizontal light divergence half-value angle is 5 degrees PP or less,
A main lenticular lens is formed on the incident surface of the lenticular sheet, and a light diffusion layer having a light divergence half-value angle of 10 degrees PP or more and a black stripe layer having an area ratio of 60% or more are formed on the focal plane of the main lenticular lens. Furthermore, a light transmission layer is formed on the emission side of both layers, and
The ratio between the horizontal arrangement period TP of the pixel structure of the light valve projected on the screen surface and the arrangement period of the main lenticular lens is configured in the range of 1.5 to 3.5, and the remaining amount excluding the screen A rear projection display device comprising harmonic reduction means for reducing at least one of the second and third harmonic components of the horizontal pixel array spectrum in the incident side optical system.

Images