1243958 九、發明說明： 【發明所屬之技術領域】 本發明係關於一種背投螢幕及其光學單元，尤其是指 一種可改善干涉紋效應（moir6 effect)之背投螢幕及其光學 單兀。 【先前技術】 按隨著科技進步，背投式電視機也愈來愈受到消費 者的青睞。背投式電視機係以其大螢幕、圖像清晰爲特 色’與傳統利用映像管之電視機相比，背投式電視機除了 具有無輻射、晝面尺寸大等優點外，更可直接接上電腦或 是其他影音設備，達到最大的娛樂效果。因此，在可預見 的未來’背投式電視機將在娛樂顯示設備(Entertainrnent Display)市場中，扮演舉足輕重的角色。背投式電視機， 係由背面（Rear Side)投射影像，使在前面（Front Side)觀看 的使用者此由背投式螢幕(Rear Projection Screen)看到影 像。故在設計背投式螢幕時，必須考慮到觀看者的視角、 影像的對比、解析度、以及亮度等等問題。 請參照圖1，習知背投式螢幕χ係為一穿透型螢幕 (Transmissive Screen)，而背投式螢幕1主要係由一菲涅耳 透鏡（Fresnel Lens) 11 及一柱狀透鏡（LanticularLens) 12所構成。菲 >圼耳透鏡u主要係用以提昇影像的亮度與 均勻度，以使得視域内的光線能做良好的運用，而柱狀透 鏡12則用以提供影像之成像。柱狀透鏡12係具有複數個 1243958 柱狀凸部m設置於人光面，以及複數個黑帶條紋(Biack 二:一face)122設置於出光面。由光源來之入射光，係 錢1絲平行光。鮮行光再入射至 係以涉二進而被♦光。位於出光面之黑帶條紋122 材料，分別精顧蓋相對於柱狀凸部m之非 具有黑帶條紋122之出光面，除可用以散射光線， 才冋守可降低外部光線之影響。 條紋’當業者界欲在柱狀透鏡12形成複數個黑帶 紋122 2時，首先會在柱狀透鏡12欲形成複數個黑帶條 狀凸|之一面’塗佈一光阻，再利用一光源照射複數個柱 投射部、U1，藉由柱狀凸部121使得光源之光規則性聚焦 ^，丨於光阻上，再進行正顯影（或是負顯影）等之製程步 ，而產生複數個黑帶條紋 122，由於柱狀凸部121為規 則排列，曰古由 巧度曲率大致相同，因此形成規則排列且等寬 广之黑Τ條故122。但是規則之黑帶條紋122以及黑帶條 紋122 > ρ“曰 g Ί規則的透鏡，容易在視覺上形成干涉現象，亦 生仏稱的干涉紋(Moir6)現象，因而降低了整個晝面的 品質。 一 '，鐘於上述問題，本案發明人爰因於此，亟思一種可 u解決習知背投式螢幕具有干涉紋現象之「背投螢幕及盆 光學單元」。 ，、 【發明内容】 有鐘於上述課題，本發明之目的為提供一種背投螢幕 1243958 及其光學單元’用以改善干涉紋效應（moir6 effect)。 緣是，為達上述目的，依本發明之光學單元，包括有 一光學元件、一折射層、和一遮光層。其中光學元件具有 一第一表面與一第二表面，第一表面與第二表面相對設 置，且第/表面具有袓數個柱狀凸部。折射層鄰接第二表 面且具有複數個光線折射物質。遮光層鄰接折射層且具有 複數個光線吸收物質。 承上所述，因依本發明之背投螢幕，包括有一第一光 學單元與/第二光學單元，第一光學單元與第二光學單元 相對設置，真第二光學單元具有一光學元件、一折射層、 以及一遮光層，其中光學元件具有一第一表面與一第2表 面，且第/表面與該第二表面相對設置，第一表面具有複 數個柱狀凸部，折射層鄰接該第二表面且具有複數個光^ 折射物質，遮光層鄰接該折射層且具有複數個光線吸收物 質。 承上所述，因依本發明之背投螢幕及其光學單元，係 利用折射層之複數個光線折射物質改變光線行徑路線，用 以形成不同寬度之條狀光線吸收物質，以達到改善干涉紋 效應之功妹。 【實施方式】 以下將參照相關圖式，說明依本發明較佳實施例之背 投螢幕及其光學單元。 、 請參閲圖2A所示，為本發明之光學單元之較佳實施 l243958 例。光學單元2包括有一光學元件21、一折射層23、和 〜遮光層25。 光學元件21具有一第一表面211與一第二表面212， 第一表面211與第二表面212相對設置，第一表面211具 有複數個柱狀凸部213。在此較佳實施例中，光學元件21 為一柱狀透鏡，當一平行光線入射光學元件21時，柱狀 凸部213用以匯聚光線，且條狀光線吸收物質251用以吸 收光線，可降低外部光線之影響。此外，光學元件21可 為一透光材質製作而成’例如聚乙稀(polyethylene)，且光 學元件21具有一第一折射率。 折射層23接合於第二表面212，並且折射層23具有 複數個不同折射率之光線折射物質231。其中複數個光線 折射物質231其係排列設置於折射層23内，且複數個光 線折射物質231呈現不規則分佈。在此實施例中，光線折 射物質231為一共聚合物，其係由不同的物質聚合而成， 例如一曱基丙烯酸曱酯（MMA)、一苯乙稀（styene)、一聚苯 乙烯(Polystyrene)、或是一丙烯(Acryl〇nitrile)等聚合而 成，可形成具有不同折射率之共聚合物。舉例說明，一曱 基丙烯酸曱酯（MMA)其折射率為丨·49與一苯乙烯(styene) 其折射率為1.59，兩者可聚合而成折射率介於up〜1 59 之間的共聚合物，使用者可依據需求選用。 為了方便說明，在此複數個光線折射物質231選用三 種不同折射率之光線折射物質231，分別具有一第二折射 率N2、一第三折射率Ns、一第四折射率n4。其中複數個 1243958 光線折射物質231排列設置於折射層23内。在此複數個 光線折射物質231呈現不規則排列，但是在實際實施時， 也可為依序排列。此外，更假設第二折射率n2大於第三 折射率Ns，且第三折射率％大於第四折射率n4。按習知 之光學原理，可得知一光線經過不同折射率之物質會產生 折射現象，並且經過不同折射率之物質會產生不同折射角 度，藉由此種現象改變光線行徑路線，使得投射至遮光層 25之光線係為不規則分佈，以利形成不同寬度之條狀光線 吸收物質251。 遮光層25接合於折射層23且具有複數個不同寬度之 條狀光線吸收物質251。在此較佳實施例中，條狀光線吸 收物貝251可為一味色油墨，用以吸收光線。 當欲在遮光層25形成複數個不同寬度之條狀光線吸 收物質251，先在折射層23上塗佈—光阻，利用一光源照 射於第一表面211之複數個柱狀凸部213，使光源之光線 規則性匯聚投射折射層23，再藉由複數個光線折射物質 231改變光線行徑路線，使得光線不規則照射於光阻上， 再進行正顯影（或是負顯影）之等製程步驟(此為熟悉此項 技術者所熟知，在此不加以贅述），用以在遮光層％形成 複數個不同寬度之條狀光線吸收物質251。曰 請參閱圖2B赫，舉魏明，糾 線折射物質2M，其中複數個光線折射物質23ι = 弟二折射率N2、第三折射率％、第四折射率用以改 變光線行徑路線，以利形成不同寬度之條狀光線吸收物質 1243958 251。二光線100A、100B平行進入各柱狀凸部2i3後， 線100A、100B藉由柱狀凸部213匯聚後，投射至折射屛 23，且由於折射層23具有複數個光線折射物質231且八9 別具有第二折射率N2、第三折射率&、第四折射率N刀。 光線100A、100B從光學元件21(具有第一折射率4私 至折射層23(分別具有第二折射率％、第三折射率 四折射率n4)後，光線100A、100B穿過不同折射率弟 質會產生折射現象，且經過不同的折射率之物質， 同之折射角度。依據光線折射原理可藉由不同折射^1243958 IX. Description of the invention: [Technical field to which the invention belongs] The present invention relates to a rear projection screen and its optical unit, and particularly to a rear projection screen and its optical unit that can improve the moir6 effect. [Previous technology] As technology advances, rear projection TVs are becoming more and more popular with consumers. The rear projection TV is characterized by its large screen and clear images. Compared with the traditional TV using televisions, the rear projection TV has the advantages of no radiation, large daytime size, etc. Go to a computer or other audio and video equipment for maximum entertainment. Therefore, in the foreseeable future, the 'rear projection TV' will play an important role in the entertainment display device (Entertainrnent Display) market. Rear-projection TV sets project images from the rear side, so that users viewing from the front side can see the images from the rear-projection screen. Therefore, when designing a rear-projection screen, consideration must be given to the viewer's perspective, image contrast, resolution, and brightness. Please refer to FIG. 1. The conventional rear projection screen χ is a transmissive screen, and the rear projection screen 1 is mainly composed of a Fresnel Lens 11 and a lenticular lens (LanticularLens). ). The Philip > ear lens u is mainly used to enhance the brightness and uniformity of the image, so that the light in the field of view can be used well, and the cylindrical lens 12 is used to provide the image of the image. The lenticular lens 12 has a plurality of 1243958 cylindrical convex portions m provided on the human light surface, and a plurality of black band stripes (Biack 2: one face) 122 provided on the light emitting surface. The incident light from the light source is a piece of parallel light. The fresh light is incident on the system to be involved and is then lighted. The material of the black stripe 122 on the light-emitting surface carefully considers the light-exiting surface of the cover that is not provided with the black stripe 122 with respect to the columnar convex portion m, and can be used to scatter light to reduce the effect of external light. Stripe 'When the professional industry wants to form a plurality of black stripe patterns 122 2 on the lenticular lens 12, first, a photoresist is coated on the lenticular lens 12 to form a plurality of black stripe projections | The light source irradiates a plurality of column projection parts, U1, and the light of the light source is regularly focused by the columnar convex part 121. On the photoresist, a process step such as positive development (or negative development) is performed to generate a plurality of The black stripe stripes 122 have a regular arrangement, and the curvatures of the arcs are almost the same, so they form a regular arrangement and a wide black T strip 122. However, the regular black stripe 122 and the black stripe 122 > ρ "said g Ί regular lens, it is easy to form interference phenomenon visually, also known as the interference pattern (Moir6) phenomenon, thus reducing the entire daytime surface Quality. First, the above-mentioned problem, the inventor of this case, because of this, eagerly thought of a "back-projection screen and basin optical unit" that can solve the conventional rear-projection screen with interference fringes. [Summary of the Invention] With the above problems in mind, the object of the present invention is to provide a rear projection screen 1243958 and its optical unit 'for improving the moir6 effect. The reason is that, in order to achieve the above object, the optical unit according to the present invention includes an optical element, a refractive layer, and a light-shielding layer. The optical element has a first surface and a second surface, the first surface and the second surface are opposite to each other, and the / surface has a plurality of columnar convex portions. The refractive layer is adjacent to the second surface and has a plurality of light-refracting substances. The light shielding layer is adjacent to the refractive layer and has a plurality of light absorbing substances. As mentioned above, the rear projection screen according to the present invention includes a first optical unit and / or a second optical unit. The first optical unit is opposite to the second optical unit. The true second optical unit has an optical element, a A refractive layer, and a light-shielding layer, wherein the optical element has a first surface and a second surface, and the third surface is opposite to the second surface; the first surface has a plurality of columnar convex portions; the refractive layer is adjacent to the first surface; The two surfaces have a plurality of light diffracting materials, and the light shielding layer is adjacent to the refracting layer and has a plurality of light absorbing materials. As mentioned above, the rear projection screen and its optical unit according to the present invention use a plurality of light-refracting substances in the refractive layer to change the course of light rays, so as to form strip-shaped light-absorbing substances with different widths, so as to improve the interference pattern. Effect of the girl. [Embodiment] A rear projection screen and its optical unit according to a preferred embodiment of the present invention will be described below with reference to related drawings. Please refer to FIG. 2A, which is a preferred embodiment of the optical unit of the present invention. The optical unit 2 includes an optical element 21, a refractive layer 23, and a light-shielding layer 25. The optical element 21 has a first surface 211 and a second surface 212, the first surface 211 is opposite to the second surface 212, and the first surface 211 has a plurality of columnar convex portions 213. In this preferred embodiment, the optical element 21 is a lenticular lens. When a parallel light beam enters the optical element 21, the cylindrical convex portion 213 is used to collect light, and the strip-shaped light absorbing substance 251 is used to absorb light. Reduce the effect of external light. In addition, the optical element 21 may be made of a light-transmitting material, such as polyethylene, and the optical element 21 has a first refractive index. The refractive layer 23 is bonded to the second surface 212, and the refractive layer 23 has a plurality of light-refracting substances 231 having different refractive indices. The plurality of light-refracting substances 231 are arranged in the refractive layer 23 in an array, and the plurality of light-refracting substances 231 are irregularly distributed. In this embodiment, the light-refracting substance 231 is a copolymer, which is polymerized from different substances, such as monomethyl acrylate (MMA), styene, and polystyrene. ), Or acrylonitrile, etc., can form copolymers with different refractive indices. For example, monomethyl acrylate (MMA) has a refractive index of ty · 49 and monostyrene (styene) has a refractive index of 1.59. The two can be polymerized to form a common refractive index between up to 1 59. Polymer, users can choose according to their needs. For the convenience of explanation, the plurality of light-refracting materials 231 are selected from three types of light-refracting materials 231 having a second refractive index N2, a third refractive index Ns, and a fourth refractive index n4. A plurality of 1243958 light-refracting substances 231 are arranged in the refractive layer 23. Here, the plurality of light-refracting substances 231 are irregularly arranged, but in actual implementation, they may be arranged sequentially. In addition, it is further assumed that the second refractive index n2 is larger than the third refractive index Ns, and the third refractive index% is larger than the fourth refractive index n4. According to the conventional optical principle, it can be known that a light passing through a substance with different refractive index will produce a refraction phenomenon, and a material passing through a different refractive index will produce different refractive angles. This phenomenon changes the course of the light so that it is projected onto the light-shielding layer. The light rays of 25 are irregularly distributed so as to form strip-shaped light-absorbing substances 251 of different widths. The light shielding layer 25 is bonded to the refractive layer 23 and has a plurality of strip-shaped light absorbing substances 251 having different widths. In this preferred embodiment, the strip-shaped light absorbing shell 251 can be a monochromatic ink for absorbing light. When it is desired to form a plurality of strip-shaped light absorbing substances 251 with different widths on the light-shielding layer 25, first apply a photoresist on the refractive layer 23, and irradiate the plurality of columnar convex portions 213 of the first surface 211 with a light source, so that The light rays of the light source regularly converge the projection refracting layer 23, and then a plurality of light refracting substances 231 are used to change the course of the light path, so that the light is irregularly irradiated on the photoresist, and then process steps such as positive development (or negative development) are performed This is well known to those skilled in the art, and will not be repeated here), and is used to form a plurality of strip-shaped light absorbing materials 251 with different widths in the light shielding layer%. Please refer to FIG. 2B. For example, Wei Ming, line-refractive material 2M, where a plurality of light-refracting materials 23 ι = the second refractive index N2, the third refractive index%, and the fourth refractive index are used to change the course of the light, in order Form strip-shaped light-absorbing substances of different widths 1243958 251. After the two rays 100A and 100B enter the columnar convex portions 2i3 in parallel, the lines 100A and 100B are converged by the columnar convex portions 213 and projected to the refracting ridge 23, and because the refractive layer 23 has a plurality of light refracting substances 231 and 8-9 Do not have a second refractive index N2, a third refractive index &, a fourth refractive index N knife. After the light rays 100A and 100B pass from the optical element 21 (having a first refractive index 4 to a refractive layer 23 (having a second refractive index% and a third refractive index four refractive index n4, respectively)), the light rays 100A and 100B pass through different refractive indices. Refraction occurs in matter, and substances with different refractive indices have the same refraction angle. According to the principle of light refraction, different refractions can be used ^
質改變光線之行進路徑。如圖2B所示，光線驅藉 狀凸部加匯聚投射於第四折射率乂之光線折射物質 231，且光線麵藉由柱狀凸部213 g聚投射於第二折射 率仏之光線折射物質231，由於第二折射率仏與第 射率n4為不同折射率之光線折射物質231，且第二折射率 n2又大於第四折射率N4，因此當光線舰、誦穿過光 學元件T折射層23後，使得光線1〇〇a之寬度大於光線 之見度由上述可知光線1〇〇A、l〇〇B經過光學元件 折射層23後，會產生不_折射路徑，使得光線 !〇〇A、麵具有㈣寬度。因此可在折射層23上塗佈一 =且=行正顯影(或是負顯影)之等製程步驟時，即可 = =25以及不同寬度之條狀光線吸收物質251。依 ===光線驅、_經由光學以㈣、折射層… Ζ彳^ ’使得遮光層25可形成複數個不同寬 度嫩光線吸收物質251，用以破壞光線之規律性，以 1243958 建到避免干涉紋效應之功效。 此外，請參閱圖2C所示，為本發明之光學單元之另 車父佳貫施例。其中與圖2 A中相同的元件將以相同的參 照符號加以說明。 光學單元2’包括有一光學元件21、一折射層23,、和 —遮光層25。其中折射層23,為一透光材質（在此較佳實施 例中，為一 UV膠），且折射層23,内填有複數個光線折射 物質231。其中，複數個光線折射物質231可選用數種不 同折射率之光線折射物質231，使其不均勻分佈於折射層 23’内。在實際實施過程，先將複數個光線折射物質231 苓雜於UV膠内，並且UV膠内之複數個光線折射物質231 不撥拌均勻，而使複數個光線折射物質231亂數分佈於UV 膠内，再照射UV光，使UV膠硬化，即可形成具有不均 勻光線折射物質231之折射層23,。當欲在遮光層25形成 複數個條狀光線吸收物質251，先在折射層23,上塗佈一光 阻，利用一光源照射於第一表面211之複數個柱狀凸部 213，使光源之光線規則性匯聚投射折射層23，，再藉由折 射層23 |L數分佈之複數個光線折射物質231用以改變光 線行徑路線，使得光線不規則照射於光阻上，再進行正顯 影（或是負顯影）之等製程步驟（此為熟悉此項技術者所熟 知，在此不加以贅述），即可在遮光層25形成複數個不同 寬度之條狀光線吸收物質251。 請參閱圖3所示，為本發明之背投螢幕之較佳實施 例。背投螢幕利用上述之光學單元2用以成像。背投螢幕 11 1243958 3,包括有一第一光學單7031和—第二光學單元2(第二光 學單元2如_2A料之光學單元2，在此給予相同符號 且不加以贅述）。 在此較佳貫施例中，第一光學單元31為一菲涅耳透 鏡（Fresnel Lens),且第一光學單元31與第二光學單元2 相鄰設置（分離接合），且第一光學單元31其係用以收集光 線’使原本發散的光線可以收集進人觀眾的視線内。如此Quality changes the path of light. As shown in FIG. 2B, the light-repellent convex portion converges the light-refracting material 231 projected on the fourth refractive index 乂, and the light surface condenses the light-refracting material projected on the second refractive index 藉 by the columnar convex portion 213 g. 231, because the second refractive index 仏 and the first refractive index n4 are different refractive refractive materials 231, and the second refractive index n2 is greater than the fourth refractive index N4, so when the light beam passes through the T refractive layer of the optical element After 23, the width of the light 100a is greater than the visibility of the light. From the above, it can be known that after the light 100A and 100B pass through the optical element refractive layer 23, a non-refractive path will be generated, making the light! 00A The surface has a width of ㈣. Therefore, when the process steps such as positive development (or negative development) are applied on the refractive layer 23, the strip-shaped light absorbing materials 251 with different widths can be applied. According to === light drive, _ through optical fiber, refracting layer ... Z 彳 ^ 'makes the light shielding layer 25 can form a plurality of tender light absorbing materials 251 of different widths to destroy the regularity of light, built to avoid interference with 1243958 The effect of the grain effect. In addition, please refer to FIG. 2C, which is another embodiment of the driver of the optical unit of the present invention. The same components as those in Fig. 2A will be described with the same reference symbols. The optical unit 2 'includes an optical element 21, a refractive layer 23, and a light-shielding layer 25. The refractive layer 23 is a light-transmitting material (in this preferred embodiment, it is a UV glue), and the refractive layer 23 is filled with a plurality of light-refracting substances 231. Among them, the plurality of light-refracting substances 231 may be selected from a plurality of light-refracting substances 231 having different refractive indices so that they are unevenly distributed in the refractive layer 23 '. In the actual implementation process, a plurality of light refracting substances 231 are mixed in the UV glue, and the plurality of light refracting substances 231 in the UV glue are not uniformly mixed, so that the plurality of light refracting substances 231 are randomly distributed in the UV glue. Then, the UV light is irradiated to harden the UV glue to form a refractive layer 23 with a non-uniform light refracting substance 231. When a plurality of strip-shaped light absorbing substances 251 are to be formed on the light-shielding layer 25, a photoresist is first coated on the refractive layer 23, and a plurality of columnar protrusions 213 on the first surface 211 are irradiated with a light source, so that The light rays regularly converge the projection refracting layer 23, and then a plurality of light refracting substances 231 distributed by the refracting layer 23 | L number are used to change the course of light rays, so that the light rays are irregularly irradiated on the photoresist, and then positive development (or Is negative development) and other process steps (this is well known to those skilled in the art, and will not be repeated here), a plurality of strip-shaped light absorbing materials 251 with different widths can be formed on the light shielding layer 25. Please refer to FIG. 3, which is a preferred embodiment of the rear projection screen of the present invention. The rear projection screen uses the above-mentioned optical unit 2 for imaging. The rear projection screen 11 1243958 3 includes a first optical unit 7031 and a second optical unit 2 (the second optical unit 2 is an optical unit 2 of _2A material, the same symbols are given here and will not be repeated). In this preferred embodiment, the first optical unit 31 is a Fresnel lens, and the first optical unit 31 and the second optical unit 2 are disposed adjacent to each other (separated and bonded), and the first optical unit 31 31 It is used to collect light, so that the originally divergent light can be collected into the sight of people. in this way
-來，各光線便可以被匯聚，並以互相平行的方式離開菲 涅耳透鏡’導入第二光學單元2中。 由於第二光學單元2之折射層23,利用光線經過不同 光線折射率物質231會產生折射之現象，用以改變光線行 徑路線’使其呈現亂數分佈且投射域光層25，用以形成 不同寬度之條狀光線吸收物質251 ’使得光線不規律分佈 用以破壞規律性’因此可改善背投螢幕之干涉紋效應 (moir6 effect)。 綜上所述，本發明之背投榮幕及其光學單元與習知技-Then, the respective rays of light can be converged and leave the Fresnel lens' in parallel to each other and introduced into the second optical unit 2. Due to the refractive layer 23 of the second optical unit 2, the phenomenon of refraction occurs when light passes through different light refractive substances 231, which is used to change the course of the light path so that it has a random number distribution and the projection domain light layer 25 is used to form different The width of the strip-shaped light absorbing substance 251 'makes the light irregularly distributed to destroy the regularity', thereby improving the moir6 effect of the rear projection screen. To sum up, the rear projection glory of the present invention, its optical unit and know-how
術比較’係藉由複數個折射層23之複數個光線折射物質 =，改變光線之行進路徑1以形成不同寬度之條狀光 線吸收早元251 ’以避免因為規狀條狀光線吸收物質， 而產生M〇ir6的現象。 本僅為舉例性’而非為限制性者。任何未颜 舍月之精神與料，而對其進行^效修改或變更，^ 應包含於後附之申請專利範圍中。 12 1243958 【圖式簡單說明】 圖1為習知背投式螢幕之一立體示意圖。 圖2A為本發明之光學單元之較佳實施例。 圖2B為本發明之光學單元之作動示意圖。 圖2C為本發明之光學單元之另一較佳實施例。 圖3為本發明之背投螢幕之較佳實施例。 元件符號說明 • 1 背投式螢幕 11 菲涅耳透鏡 12 柱狀透鏡 121 柱狀凸部 122 黑帶條紋 2、2， 光學單元 21 光學元件 211 第一表面 212 弟·一表面 213 柱狀凸部 23、23” 折射層 231 光線折射物質 Nx 第一折射率 n2 第二折射率 n3 第三折射率 n4 第四折射率 13 1243958 25 遮光層 251 條狀光線吸收物質 3 31 背投螢幕 第一光學單元 100A、100B 光線 14The technical comparison is to refract the substances by the plurality of light rays of the plurality of refractive layers 23, and change the path 1 of the light rays to form strip-shaped light-absorbing early elements 251 of different widths. The phenomenon of Moir6 was produced. The text is exemplary only and not limiting. Any modification or change that does not have the spirit and materials of the month shall be included in the scope of the attached patent application. 12 1243958 [Schematic description] Figure 1 is a three-dimensional schematic diagram of a conventional rear projection screen. FIG. 2A is a preferred embodiment of the optical unit of the present invention. FIG. 2B is a schematic diagram of the operation of the optical unit of the present invention. FIG. 2C is another preferred embodiment of the optical unit of the present invention. FIG. 3 is a preferred embodiment of the rear projection screen of the present invention. Explanation of component symbols • 1 rear-projection screen 11 Fresnel lens 12 cylindrical lens 121 cylindrical convex portion 122 black band stripes 2, 2 optical unit 21 optical element 211 first surface 212 brother one surface 213 cylindrical convex portion 23, 23 ”refractive layer 231 light-refracting substance Nx first refractive index n2 second refractive index n3 third refractive index n4 fourth refractive index 13 1243958 25 light-shielding layer 251 strip-shaped light absorbing substance 3 31 rear projection screen first optical unit 100A, 100B light 14