1297806 九、發明說明： 【發明所屬之技術領域】 本發明係關於一種投影系統，特別是關於一種液晶投 影系統。 【先前技術】 近年來，液晶顯示元件已經漸漸地廣泛應用於日常生 活上，如最常見的液晶螢幕、筆記型電腦、數位液晶電視 等直視型（Direct View)之顯示器，以及液晶投影機、背 投影電視等顯示器所使用的非直視型顯示面板，例如單晶 石夕液晶面板（Liquid Crystal on Silicon Panel，LCoS Panel)、高溫多晶矽液晶面板（HTPS-LCD)等等。由於直 視型顯示器在大尺寸顯示上仍有諸多限制，因此，藉由具 有高解析度之非直視型顯示面板來搭配光學引擎，以達到 大尺寸顯示之液晶投影機與背投影電視已經逐漸成為主 流趨勢。 % 習知的液晶投影裝置可分成穿透式以及反射式兩種 型式。穿透式液晶顯示裝置和反射式液晶投影裝置，其基 本原理相似，只是穿透式液晶顯示裝置是利用光源穿過液 晶顯示面板（LCD Panel)來作調變；反射式液晶投影裝 置疋利用LCoS面板來調變光源所發射出來的光信號再反 射至螢幕。其中，LCoS面板是以CMOS晶片為電路基板 及反射層，然後再塗佈液晶層後，以玻璃平板封裝。因此， 光源發射出來的光會被LCoS面板反射至螢幕上。 1297806 首先，請參照圖1，以三片型穿透式液晶投影裝置10 為例，其係主要包含一光源11、分色鏡（Dichroic Mirror ) 121,122、反射鏡 131，132，133、液晶面板（Liquid Crystal Panel) 141，142，143、一分光稜鏡15、以及一投影鏡頭16。 由光源11所發出的光線，經過分色鏡121,122後分成紅藍 綠三色光，並具有不同的光路徑。之後，三色光分別穿透 對應之液晶面板141，142，143並進入分光稜鏡15，進行合 光並將影像投射至投影鏡頭16。 接著，請參照圖2，反射式液晶投影裝置20係包含一 光源21、分色鏡221,222、反射鏡231,232,233、偏極化 分光稜鏡241，242,243、穿透式液晶面板（Liquid Crystal on Silicon Panel，LCoS Panel) 251，252,253、一合光稜鏡 26、 以及一投影鏡頭27。由光源21所發出的光線，經過分色 鏡221，222後分成紅藍綠三色光，並具有不同的光路徑。 經過反射鏡231，232,233分別改變三色光之路徑後，三色 光分別進入偏極化分光稜鏡241,242,243，然後再分別反 射至液晶面板251,252,253，經過反射後，三色光再分別 進入合光稜鏡26以進行合光，並將影像投射至投影鏡頭 27 〇 然而’不論是穿透式液晶投影裝置1〇還是反射式液 晶投影裝置20,由於色光進行反射及折射時，各色光之光 路徑上各點為不等長，導致各光束照射至穿透式或反射式 液晶面板之平面面積增加，故於液晶面板表面形成邊緣亮 度降低且亮度不均勻之現象。 1297806 而且，為了使影像的亮度重新變得均勻，穿透式或反 射式液晶面板，會浪費部份的能量對於亮度進行預補償， 以提昇邊緣區域的亮度。如此一來，則會造成液晶投影裝 置整體表現的灰階數目降低，進而影響了最終影像晝質的 表現。 有鑑於上述問題，本案發明人爰因於此，亟思一種可 以解決上述影像亮度不均勻，甚至造成灰階數目降低等問 題之「液晶投影系統」。 【發明内容】 有鑑於上述課題，本發明'之目的為提供一種液晶投影 系統，可使影像之亮度均勻。 緣是，為達上述目的，依本發明之液晶投影系統，其 係包含一合光單元、一第一顯像單元、一第二顯像單元、 一第三顯像單元、至少一光源、一第一分色鏡、以及第二 分色鏡。其中，第一顯像單元、第二顯像單元、及第三顯 像單元係分別設置於合光單元之一第一側、一第二侧及一 第三側。第一顯像單元係具有一第一梯度變化濾光元件， 第二顯像單元係具有一第二梯度變化濾光元件，第三顯像 單元係具有一第三梯度變化濾光元件。光源係發出一光 線，以形成一光路徑。第一分色鏡係設置於光路徑並鄰設 於光源。第二分色鏡係設置於該光路徑，光線之至少一部 份係先投射至第一分色鏡，再射至第二分色鏡。複數梯度 變化濾光元件之中央區域之穿透率係小於邊緣區域之穿 1297806 透率。 承上所述，因依本發明之液晶投影系統中之梯度變化 濾光元件的中央區域穿透率係小於邊緣區域之穿透率，因 此，由光源所發出的光，分別經過顯像單元内之梯度變化 濾光元件時，造成中央區域之亮度較低，而邊緣區域之亮 度較高，故能形成亮度不均勻之照明光束。如此一來，可 使得顯像單元原本因為投影距離不等長而造成的影像亮 度不均勻現象獲得改善，進而獲得均勻亮度的影像。再 者，顯像單元内之液晶面板也不需再浪費能量去進行亮度 預補償，故能提高液晶投影系統之灰階數目，使得最終影 像之晝質更佳。 【實施方式】 以下將參照相關圖式，說明依本發明之液晶投影系統 之數個實施例。 第一實施例 請參考圖3，液晶投影系統30，其係包含至少一光源 31、一第一分色鏡（Dichroic Mirror )321、第二分色鏡 322、 一第一顯像單元（Imager Unit) 33、一第二顯像單元34、 一第三顯像單元35、以及一合光單元（Prism Unit) 36。 本實施例中，液晶投影系統30係應用於一穿透式液晶投 影器中。 光源31係發射出一光線，以形成一光路徑。本實施 例中，光源31係可以選自一燈泡、一有機發光二極體(Light 1297806 emitting Diode，LED)、一有機發光二極體陣歹丨J (LED array)、一雷射、以及一雷射陣列（Laser array)。另外，一 紫外/紅光截止濾鏡311，係鄰設於光源31旁，以過濾光 線中的紫外線及紅外線。 本實施例中，液晶投影系統30更包含一第一偏極分 光單元（First Polarization Beam Splitter Unit) 37，其係設 置於光源31之一侧，光源31所發出之光線係通過第一偏 極分光單元37，再射至第一分色鏡321。本實施例中，第 一偏極分光單元37係具有一透鏡陣列371以及一偏振轉 換元件（Polarization Beam Splitter，PBS) 372，光源 31 所 發出之光線係先通過透鏡陣列371，以達到均勻化的效 果’再經過偏振轉換元件372 ’用以改變光線之偏振狀態， 使得光線以S偏振型態的光線Rs、Gs、Bs射出，並射至 第一分色鏡321。 第一分色鏡321及第二分色鏡322係用以將光線分 光，第一分色鏡321及第二分色鏡322係設置於光路徑 上。其中，第一分色鏡321係鄰設於光源31，光線之至少 一部份係先投射至第一分色鏡321，再射至第二分色鏡 322。本實施例中，第一分色鏡321係允許光線Rs、Gs通 過，而將光線Bs反射；第二分色鏡322則允許光線Rs通 過，而將光線Gs反射至第三顯像單元35。 本實施例中，液晶投影系統30更包含一第一反射鏡 381設置於光路徑。光線Bs係被第一分色鏡321反射後， 經第一反射鏡381反射以射至第一顯像單元33。 11 1297806 本實施例中，液晶投影系統30更包含一第二反射鏡 382設置於光路徑。光線Rs係穿過第一分色鏡321及第二 分光鏡322後，經第二反射鏡382反射以射至第二顯像單 元34。其中，第一反射鏡381及第二反射鏡382設置之數 量係可隨實際製程需要而定。 第一顯像單元33係設置於合光單元36之一第一侧 361，第一顯像單元33係具有一第一梯度變化滤光元件 (First Gradient Filter) 331。第二顯像單元34係設置於合 光單元36之一第二側362，第二顯像單元34係具有一第 二梯度變化濾光元件341。第三顯像單元35係設置於合光 單元36之一第三側363，第三顯像單元35係具有一第三 梯度變化濾光元件351。其中，第一梯度變化濾光元件 331、第二梯度變化濾光元件341、以及第三梯度變化濾光 元件351之中央區域之穿透率係小於邊緣區域之穿透率。 而合光單元36可為一合光稜鏡，例如是一 X-稜鏡。 再請參照圖3及圖4，梯度變化濾光元件331,341,351 係分別具有一透明基板以及一梯度變化濾光層。以梯度變 化濾光元件331為例，其梯度變化濾光層L1係可設置於 透明基板S上。而設置的方式可為錢錢、塗佈、黏置等等 方式，使得梯度變化濾光層L1與透明基板s結合。 如圖4及圖5所示，梯度變化濾光層L1之中央區域 之穿透率係小於邊緣區域之穿透率。於圖5中，X軸係為 梯度變化濾光層L1上任一點離中心點的距離，而y轴代 表其穿透率（Transmission Rate，T%)，梯度變化濾光層q 12 1297806 中央至邊緣區域係具有不同的穿透率。中央區域之穿透率 較低，而邊緣區域之穿透率較高。穿透率較高則表示光通 量較高，反之，穿透率較低則表示光通量較低。再者，梯 度變化滤光層之面積大小’則可視產品之實際情形來製 作。當然，各個設置於不同透明基板上之梯度變化濾、光層 可具有不同之光線穿透率’依實際製程需要而製作不同穿 透率之梯度變化濾光層。 本實施例中，梯度變化濾光層之材質可為一金屬反射 層（例如為鉻、銀）、或是一介電質，可利用材料的厚度 或密度不同等方式，來使得梯度變化濾光元件331，341，351 之中央區域之穿透率係小於邊緣區域之穿透率。 本實施例中，第一顯像單元33更具有一第一液晶面 板332，第二顯像單元34更包含一第二液晶面板342，第 三顯像單元35更包含一第三液晶面板352,光線Bs、rs、 Gs係先分別射至梯度變化濾光元件331,341,351，再入射 至對應之液晶面板332,342,352。其中，液晶面板 332,342,352係分別為一穿透式液晶面板。 射至梯度變化濾光元件331,341,351之光線，經過不 同穿透率之梯度變化濾光層後，即可將光行進過程中光路 不等長所造成之亮度不均勻現象改善，進而形成均勻亮度 之光束以射至液晶面板332,342,352。故，液晶面板 332,342,352不需浪費能量去作亮度之預補償，故能提昇液 晶面板332,342,352之灰階數目。 再請參照圖3，本實施例中，液晶投影系統30更可包 13 1297806 含複數偏光片（Polarizers) 333,343,353，以及複數檢偏器 (Analizers) 334,344,354。複數偏光片 333,343,353 係設 置於梯度變化濾光元件331，341，351與液晶面板 332,342,352之間，而檢偏器334,344,354係設置於液晶面 板332,342,352與合光單元36之間。其中，綠光之檢偏器 354通常不具有偏振光延遲（retar(jer)的效果，因此已被 偏光片353改變偏振狀態成p偏振型態之光線經過檢 偏器354之後，仍為p偏振型態，而直接通過合光單元36。 由於合光單元36中係具有波長選擇性之光學鍍膜，因此 可將光線Rs及B s反射出來。 本實施例中，液晶投影系統30更包含一投影透鏡39, 光線由合光單元36射出後，即投射至投影透鏡39。光線 Rs、Gp、Bs經由合光單元36的合光之後，即可將各色光 的影像疊加，並藉由投影透鏡39投影出亮度均勻彩色的 晝面。 第二實施例 請參照圖6，液晶投影系統40係包含一光源41、一 第一分色鏡421、一第二分色鏡422、一第一顯像單元 (Imager Unit) 43、一第二顯像單元44、一第三顯像單元 45、以及一合光單元（PrismUnit)牝。本實施例中，液晶 投影系統40係應用於一反射式液晶投影器（LCoS Projector)中。 光源41係發射出一光線，以形成一光路徑，一紫外/ 紅光截止濾鏡411，係鄰設於光源41旁，以過濾光線中的 1297806 糸外線及紅外線。本實施例中，光源41、紫外/紅光截止 濾鏡411、以及合光單元46係分別與第—實施例中之光源 31、糸外/紅光戴止濾鏡311、合光單元36以及具有相同 之特徵及功效，故於此不再贅述。 本貫施例中，液晶投影系統40更包含一第一偏極分 光單元47，其係設置於光源41之一侧，用以改變光線之 偏振狀態’使得光線以S偏振型態的光線Rs、gs、Bs射 出，並射至第一分色鏡421。其中，第—偏極分光單元47 與第一實施例中之第一偏極分光單元37具有相同之特徵 及功效，故於此不再贅述。 第一分色鏡421及第二分色鏡422係設置於光路徑 上。其中，第一分色鏡421係鄰設於光源41，光線之至少 一部份係先投射至第一分色鏡421，再射至第二分色鏡 422 〇 本實施例中，液晶投影系統40更包含一第一反射鏡 481設置於光路徑。光線Rs穿過第一分色鏡421後，經第 一反射鏡481反射並射至第一顯像單元43。 本實施例中，液晶投影系統40更包含一第二反射鏡 482設置於光路徑。光線Gs被第一分色鏡421、第二反射 鏡482、及第二分色鏡422反射後，射至第二顯像單元44。 光線Bs係被第一分色鏡421及第二反射鏡482反射後， 穿過第二分色鏡422，並射至第三顯像單元45。其中，第 一反射鏡481及第二反射鏡482設置之數量係可隨實際製 程需要而定。 15 1297806 第一顯像單元43係設置於合光單元46之一第一側 461，第一顯像單元43係具有一第一梯度變化濾光元件 (Gradient Filter ) 431。第二顯像單元44係設置於合光單 元46之一第二侧462，第二顯像單元44係具有一第二梯 度變化濾光元件441。第三顯像單元45係設置於合光單元 46之一第三側463，第三顯像單元45係具有一第三梯度 變化濾光元件451。其中，第一梯度變化濾光元件431、 第二梯度變化濾光元件441、第三梯度變化濾光元件451、 以及合光單元46之功能及特徵係與第一實施例中之第一 梯度變化濾光元件331、第二梯度變化濾光元件341、第 三梯度變化濾光元件351、以及合光單元36相同，故不再 贅述。 本實施例中，第一顯像單元43更具有一第一液晶面 板432，第二顯像單元44更包含一第二液晶面板442，第 三顯像單元45更包含一第三液晶面板452,光線係先分別 射至梯度變化濾光元件431，441，451，再入射至對應之液晶 面板432,442,452。其中，液晶面板432,442,452係分別為 一反射式液晶面板（LCoS Panel)。反射式液晶面板是以 CMOS晶片為基板及反射層，然後再塗佈液晶層後，以玻 璃平板封裝，使得光源41發射出來的光被反射式液晶面 板反射出來。 射至梯度變化濾光元件431,441,451之光線，經過不 同穿透率之梯度變化濾光層後，即可將光行進過程中光路 不等長所造成之亮度不均勻現象改善，進而形成均勻亮度 1297806 之光束以射至液晶面板432,442,452。故，液晶面板 432,442,452不需浪費能量去作亮度之預補償，故能提昇液 晶面板332,342,352之灰階數目。 再請參照圖6，本實施例中，液晶投影系統40更包含 複數第二偏極分光單元433,443,453以及複數偏振延遲元 件（Retarder) 434,454。光線係先通過梯度變化濾光元件 431，441，451再分別經過第二偏極分光單元433,443,453， 以進入液晶面板432,442,452,經過調變後才穿過第二偏極 分光單元433,443,453及偏振延遲元件434,454。其中，第 二偏極分光單元433,443,453係可分別為一偏極分光稜鏡。 由於第二偏極分光單元433,443,453内係分別具有光 學鍵膜，而光學鍵膜具有偏振選擇的特性，故能將通過梯 度變化濾光元件431，441，451之入射光線反射至面板1297806 IX. Description of the Invention: [Technical Field] The present invention relates to a projection system, and more particularly to a liquid crystal projection system. [Prior Art] In recent years, liquid crystal display elements have been widely used in daily life, such as the most common direct-view display such as LCD screen, notebook computer, digital LCD TV, and LCD projector, back. A non-direct-view type display panel used for a display such as a projection television, such as a liquid crystal on silicon panel (LCoS Panel), a high temperature polycrystalline liquid crystal panel (HTPS-LCD), or the like. Since the direct-view display still has many limitations on the large-size display, the liquid crystal projector and the rear-projection television have been gradually becoming mainstream by the high-resolution non-direct-view display panel to match the optical engine to achieve large-size display. trend. % Conventional liquid crystal projection devices can be divided into two types, transmissive and reflective. The basic principle of the transmissive liquid crystal display device and the reflective liquid crystal projection device is similar, except that the transmissive liquid crystal display device uses a light source to pass through a liquid crystal display panel (LCD Panel) for modulation; the reflective liquid crystal projection device uses LCoS. The panel modulates the light signal emitted by the light source and reflects it to the screen. Among them, the LCoS panel is a CMOS wafer as a circuit substrate and a reflective layer, and then coated with a liquid crystal layer, and then packaged in a glass plate. Therefore, the light emitted by the light source is reflected by the LCoS panel onto the screen. 1297806 First, please refer to FIG. 1 , taking a three-piece transmissive liquid crystal projection device 10 as an example, which mainly includes a light source 11 , a dichroic mirror 121 , 122 , a mirror 131 , 132 , 133 , a liquid crystal panel ( Liquid Crystal Panel) 141, 142, 143, a splitter 15, and a projection lens 16. The light emitted by the light source 11 passes through the dichroic mirrors 121, 122 and is split into three colors of red, blue and green, and has different light paths. Thereafter, the three color lights respectively penetrate the corresponding liquid crystal panels 141, 142, 143 and enter the beam splitter 15, perform the combined light and project the image onto the projection lens 16. Next, referring to FIG. 2, the reflective liquid crystal projector 20 includes a light source 21, dichroic mirrors 221, 222, mirrors 231, 232, 233, polarized beamsplitters 241, 242, 243, and a liquid crystal on silicon panel (Liquid Crystal on Silicon Panel, LCoS Panel) 251, 252, 253, a combined aperture 26, and a projection lens 27. The light emitted by the light source 21 passes through the dichroic mirrors 221, 222 and is split into three colors of red, blue and green, and has different light paths. After the mirrors 231, 232, and 233 respectively change the path of the three color lights, the three color lights enter the polarization splitting beams 241, 242, and 243, respectively, and then are respectively reflected to the liquid crystal panels 251, 252, and 253. After being reflected, the three color lights respectively enter the light combining plate 26 to Combine the light and project the image onto the projection lens 27. However, whether it is the transmissive liquid crystal projection device 1 or the reflective liquid crystal projection device 20, when the color light is reflected and refracted, the points on the light path of each color light are The unequal length causes the plane area of each of the light beams to be transmitted to the transmissive or reflective liquid crystal panel to increase, so that the edge of the liquid crystal panel is reduced in brightness and uneven in brightness. 1297806 Moreover, in order to make the brightness of the image uniform again, the transmissive or reflective LCD panel wastes part of the energy to pre-compensate the brightness to improve the brightness of the edge area. As a result, the overall number of gray scales of the liquid crystal projector is reduced, which in turn affects the performance of the final image. In view of the above problems, the inventor of the present invention has a "liquid crystal projection system" which can solve the problem of uneven brightness of the above-mentioned image and even cause a decrease in the number of gray scales. SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide a liquid crystal projection system that can make the brightness of an image uniform. In order to achieve the above object, a liquid crystal projection system according to the present invention comprises a light combining unit, a first developing unit, a second developing unit, a third developing unit, at least one light source, and a The first dichroic mirror and the second dichroic mirror. The first image forming unit, the second image forming unit, and the third image forming unit are respectively disposed on the first side, the second side, and the third side of the light combining unit. The first developing unit has a first gradient varying filter element, the second developing unit has a second gradient varying filter element, and the third developing unit has a third gradient varying filter element. The light source emits a line of light to form a light path. The first dichroic mirror is disposed in the light path and adjacent to the light source. A second dichroic mirror is disposed in the optical path, and at least a portion of the light is first projected to the first dichroic mirror and then to the second dichroic mirror. The transmittance of the central region of the complex gradient filter element is less than the penetration of the edge region 1297806. As described above, since the central region transmittance of the gradient change filter element in the liquid crystal projection system according to the present invention is smaller than the transmittance of the edge region, the light emitted by the light source passes through the developing unit respectively. When the gradient changes the filter element, the brightness of the central region is low, and the brightness of the edge region is high, so that an illumination beam with uneven brightness can be formed. In this way, the image unit can be improved in that the image brightness is uneven due to the unequal projection distance, thereby obtaining an image of uniform brightness. Moreover, the liquid crystal panel in the developing unit does not need to waste energy to perform brightness pre-compensation, so the number of gray scales of the liquid crystal projection system can be increased, so that the final image is better. [Embodiment] Several embodiments of a liquid crystal projection system according to the present invention will be described below with reference to the related drawings. First Embodiment Referring to FIG. 3, a liquid crystal projection system 30 includes at least one light source 31, a first dichroic mirror 321, a second dichroic mirror 322, and a first image forming unit (Imager Unit). 33. A second developing unit 34, a third developing unit 35, and a Prism Unit 36. In this embodiment, the liquid crystal projection system 30 is applied to a transmissive liquid crystal projector. Light source 31 emits a light to form a light path. In this embodiment, the light source 31 can be selected from a light bulb, an organic light emitting diode (LED 1297806 emitting diode), an organic light emitting diode array (LED array), a laser, and a light source. Laser array. In addition, an ultraviolet/red light cut filter 311 is disposed adjacent to the light source 31 to filter ultraviolet rays and infrared rays in the light. In this embodiment, the liquid crystal projection system 30 further includes a first polarization beam splitter unit (37) disposed on one side of the light source 31, and the light emitted by the light source 31 passes through the first polarized light splitting. The unit 37 is again incident on the first dichroic mirror 321. In this embodiment, the first polarizing beam splitting unit 37 has a lens array 371 and a polarization conversion component (PBS) 372. The light emitted by the light source 31 passes through the lens array 371 to achieve uniformity. The effect 're-polarization conversion element 372' is used to change the polarization state of the light such that the light is emitted by the S-polarized light rays Rs, Gs, Bs and is incident on the first dichroic mirror 321. The first dichroic mirror 321 and the second dichroic mirror 322 are used to split the light, and the first dichroic mirror 321 and the second dichroic mirror 322 are disposed on the optical path. The first dichroic mirror 321 is disposed adjacent to the light source 31, and at least a portion of the light is first projected onto the first dichroic mirror 321 and then incident on the second dichroic mirror 322. In the present embodiment, the first dichroic mirror 321 allows the light rays Rs, Gs to pass, and reflects the light Bs; the second dichroic mirror 322 allows the light rays Rs to pass, and reflects the light rays Gs to the third developing unit 35. In this embodiment, the liquid crystal projection system 30 further includes a first mirror 381 disposed on the optical path. The light Bs is reflected by the first dichroic mirror 321 and then reflected by the first mirror 381 to be incident on the first developing unit 33. 11 1297806 In this embodiment, the liquid crystal projection system 30 further includes a second mirror 382 disposed on the optical path. The light rays Rs pass through the first dichroic mirror 321 and the second dichroic mirror 322, and are reflected by the second reflecting mirror 382 to be incident on the second developing unit 34. The number of the first mirror 381 and the second mirror 382 can be set according to the actual process requirements. The first developing unit 33 is disposed on the first side 361 of the light combining unit 36. The first developing unit 33 has a first gradient filter 331. The second developing unit 34 is disposed on one of the second sides 362 of the light combining unit 36, and the second developing unit 34 has a second gradient changing filter element 341. The third developing unit 35 is disposed on one of the third sides 363 of the light combining unit 36, and the third developing unit 35 has a third gradient changing filter element 351. The transmittance of the central region of the first gradient change filter element 331, the second gradient change filter element 341, and the third gradient change filter element 351 is smaller than the transmittance of the edge region. The light combining unit 36 can be a combined aperture, such as an X-turn. Referring to FIG. 3 and FIG. 4, the gradient change filter elements 331, 341, 351 respectively have a transparent substrate and a gradient change filter layer. Taking the gradient change filter element 331 as an example, the gradient change filter layer L1 may be disposed on the transparent substrate S. The manner of setting may be money, coating, sticking, etc., so that the gradient change filter layer L1 is combined with the transparent substrate s. As shown in Figs. 4 and 5, the transmittance of the central region of the gradient change filter layer L1 is smaller than the transmittance of the edge region. In FIG. 5, the X-axis is the distance from any point on the gradient change filter layer L1, and the y-axis represents the transmittance (T%), the gradient change filter layer q 12 1297806 from center to edge The regional system has different penetration rates. The penetration rate in the central region is lower and the penetration rate in the edge region is higher. A higher penetration rate indicates a higher luminous flux, whereas a lower transmittance indicates a lower luminous flux. Further, the size of the gradient change filter layer can be made depending on the actual situation of the product. Of course, the gradient change filters and the optical layers respectively disposed on different transparent substrates may have different light transmittances. The gradient change filter layers of different transmittances are prepared according to actual process requirements. In this embodiment, the material of the gradient change filter layer may be a metal reflective layer (for example, chrome or silver) or a dielectric material, and the thickness or density of the material may be used to make the gradient change filter. The transmittance of the central region of the elements 331, 341, 351 is less than the penetration of the edge regions. In this embodiment, the first image forming unit 33 further includes a first liquid crystal panel 332, the second image forming unit 34 further includes a second liquid crystal panel 342, and the third image forming unit 35 further includes a third liquid crystal panel 352. The light rays Bs, rs, and Gs are first incident on the gradient change filter elements 331, 341, and 351, respectively, and are incident on the corresponding liquid crystal panels 332, 342, and 352. The liquid crystal panels 332, 342, and 352 are respectively a transmissive liquid crystal panel. The light that is incident on the gradient change filter elements 331, 341, 351, after varying the filter layer of different transmittances, can improve the brightness unevenness caused by the unequal optical paths during the light travel, thereby forming a beam of uniform brightness. The liquid crystal panels 332, 342, 352 are incident. Therefore, the liquid crystal panels 332, 342, 352 do not need to waste energy for pre-compensation of brightness, so the number of gray levels of the liquid crystal panels 332, 342, 352 can be increased. Referring to FIG. 3 again, in the embodiment, the liquid crystal projection system 30 further includes 13 1297806 including a plurality of Polarizers 333, 343, 353, and an Aalizers 334, 344, 354. The plurality of polarizers 333, 343, 353 are disposed between the gradient change filter elements 331, 341, 351 and the liquid crystal panels 332, 342, 352, and the analyzers 334, 344, 354 are disposed between the liquid crystal panels 332, 342, 352 and the light combining unit 36. Wherein, the green light analyzer 354 generally does not have the effect of polarization retardation (rear (jer), so the light that has been polarized by the polarizer 353 to become a p-polarized mode passes through the analyzer 354, and is still p-polarized. The liquid crystal projection system 30 further includes a projection. In this embodiment, the liquid crystal projection system 30 further includes a projection. Since the light combining unit 36 has a wavelength selective optical coating, the light rays Rs and B s can be reflected. The lens 39, after being emitted by the light combining unit 36, is projected onto the projection lens 39. After the light rays Rs, Gp, and Bs are combined by the light combining unit 36, the images of the respective color lights can be superimposed and projected by the projection lens 39. The second embodiment is shown in FIG. 6. The liquid crystal projection system 40 includes a light source 41, a first dichroic mirror 421, a second dichroic mirror 422, and a first image forming unit. (Imager Unit) 43, a second developing unit 44, a third developing unit 45, and a light combining unit (PrismUnit). In the embodiment, the liquid crystal projection system 40 is applied to a reflective liquid crystal projector. (LCoS Projector). Light source The 41 system emits a light to form a light path, and an ultraviolet/red light cut filter 411 is disposed adjacent to the light source 41 to filter the 1297806 outer line and the infrared light in the light. In this embodiment, the light source 41, The ultraviolet/red light cut filter 411 and the light combining unit 46 respectively have the same characteristics and functions as the light source 31, the outer/red light wear filter 311, and the light combining unit 36 in the first embodiment. In the present embodiment, the liquid crystal projection system 40 further includes a first polarizing beam splitting unit 47 disposed on one side of the light source 41 for changing the polarization state of the light 'so that the light is S-polarized. The light rays Rs, gs, and Bs of the type are emitted and are incident on the first dichroic mirror 421. Among them, the first-polarizing beam splitting unit 47 has the same characteristics and functions as the first polarizing beam splitting unit 37 in the first embodiment. Therefore, the first dichroic mirror 421 and the second dichroic mirror 422 are disposed on the light path. The first dichroic mirror 421 is adjacent to the light source 41, and at least a portion of the light is First projected to the first dichroic mirror 421, and then to the second dichroic mirror 422 〇 In the embodiment, the liquid crystal projection system 40 further includes a first mirror 481 disposed on the light path. After the light ray Rs passes through the first dichroic mirror 421, it is reflected by the first mirror 481 and is incident on the first developing unit 43. In this embodiment, the liquid crystal projection system 40 further includes a second mirror 482 disposed on the light path. The light Gs is reflected by the first dichroic mirror 421, the second mirror 482, and the second dichroic mirror 422, and then The second developing unit 44. The light Bs is reflected by the first dichroic mirror 421 and the second reflecting mirror 482, passes through the second dichroic mirror 422, and is incident on the third developing unit 45. The number of the first mirror 481 and the second mirror 482 can be set according to actual process requirements. 15 1297806 The first developing unit 43 is disposed on the first side 461 of the light combining unit 46, and the first developing unit 43 has a first gradient changing filter element 431. The second developing unit 44 is disposed on one of the second sides 462 of the light combining unit 46, and the second developing unit 44 has a second gradient changing filter element 441. The third developing unit 45 is disposed on one of the third sides 463 of the light combining unit 46, and the third developing unit 45 has a third gradient changing filter element 451. The functions and features of the first gradient change filter element 431, the second gradient change filter element 441, the third gradient change filter element 451, and the light combining unit 46 are the same as the first gradient change in the first embodiment. The filter element 331, the second gradient change filter element 341, the third gradient change filter element 351, and the light combining unit 36 are the same, and therefore will not be described again. In this embodiment, the first image forming unit 43 further includes a first liquid crystal panel 432, the second image forming unit 44 further includes a second liquid crystal panel 442, and the third image forming unit 45 further includes a third liquid crystal panel 452. The light rays are first incident on the gradient change filter elements 431, 441, 451 and then incident on the corresponding liquid crystal panels 432, 442, 452. The liquid crystal panels 432, 442, and 452 are respectively a reflective liquid crystal panel (LCoS Panel). The reflective liquid crystal panel is a CMOS wafer as a substrate and a reflective layer, and then coated with a liquid crystal layer, and then packaged in a glass plate, so that the light emitted from the light source 41 is reflected by the reflective liquid crystal panel. The light incident on the gradient change filter elements 431, 441, 451, after varying the filter layer of different transmittances, can improve the brightness unevenness caused by the unequal optical path during the light travel, thereby forming a beam of uniform brightness 1297806 To the liquid crystal panels 432, 442, 452. Therefore, the liquid crystal panels 432, 442, 452 do not need to waste energy for pre-compensation of brightness, so the number of gray levels of the liquid crystal panels 332, 342, 352 can be increased. Referring to FIG. 6, in the embodiment, the liquid crystal projection system 40 further includes a plurality of second polarized light splitting units 433, 443, 453 and a plurality of polarization delay elements (Retarder) 434, 454. The light passes through the gradient changing filter elements 431, 441, 451 and then passes through the second polarizing beam splitting units 433, 443, 453, respectively, to enter the liquid crystal panels 432, 442, 452, and then passes through the second polarizing beam splitting units 433, 443, 453 and the polarization delay elements 434, 454. . The second polarizing beam splitting units 433, 443, and 453 are respectively a polarizing splitter. Since the second polarized light splitting units 433, 443, and 453 respectively have optical key films, and the optical key films have polarization selective characteristics, incident light rays passing through the gradient varying filter elements 431, 441, and 451 can be reflected to the panel.
光線會轉變成p偏振光線Rp，再從第一液晶面板432 入射至第二偏極分光單元433中，且光線Rp會穿透第二 偏極为光單兀433之光學鍍膜，並經由偏振延遲元件434 轉換為S偏振光線RS入射至合光單元#。同樣地，入射The light is converted into the p-polarized light Rp, and then incident from the first liquid crystal panel 432 to the second polarizing beam splitting unit 433, and the light Rp penetrates the optical coating of the second polarizing light unit 433, and is delayed by the polarization. Element 434 is converted to S-polarized light RS and incident on light combining unit #. Similarly, incident
17 1297806 延遲元件454轉換為S偏振光線Bs入射至合光單元46。 本貫施例中’液晶投影糸統40更包含一投影透鏡49 ^ 光線Rs、Bs、Gp由合光單元46射出後，即投射至投影透 鏡49。光線Rs、Gp、Bs經由合光單元46的合光之後， 即可將各色光的影像疊加，並藉由投影透鏡49投影出彩 色的晝面。 綜上所述，本發明之液晶投影系統中之梯度變化濾光 元件的中央區域穿透率係小於邊緣區域之穿透率，因此， 由光源所發出的光，分別經過顯像單元内之梯度變化濾光 元件時，可使原來因為光路徑長度不同所造成之影像不均 勻現象，獲得改善。使得照射至液晶面板上之光束具有均 勻亮度，如此一來，可使得液晶面板即不需再浪費能量去 進行亮度預補償，故能提高液晶投影系統之灰階數目，使 得最終影像之晝質更佳。 以上所述僅為舉例性，而非為限制性者。任何未脫離 本發明之精神與範疇，而對其進行之等效修改或變更，均 應包含於後附之申請專利範圍中。 【圖式簡單說明】 圖1係為習知穿透式液晶投影裝置之一示意圖； 圖2係為習知反射式液晶投影裝置之一示意圖； 圖3係為本發明第一實施例之液晶投影系統之一示意 圖； 圖4係本發明之液晶投影糸統之梯度變化渡光元件之 18 1297806 一示意圖； 圖5係為本發明之液晶投影系統之梯度變化濾光元件 之穿透率變化示意圖；以及 圖6係為本發明第二實施例之液晶投影系統之一示意 圖。 元件符號說明： 10 穿透式液晶投影裝置 11 光源 121 分色鏡 122 分色鏡 131 反射鏡 132 反射鏡 133 反射鏡 141 液晶面板 142 液晶面板 143 液晶面板 15 分光稜鏡 16 投影鏡頭 20 反射式液晶投影裝置 21 光源 221 分色鏡 222 分色鏡 231 反射鏡 反射鏡 反射鏡 偏極化分光棱鏡 偏極化分光稜鏡 偏極化分光稜鏡 穿透式液晶面板 穿透式液晶面板 穿透式液晶面板 合光稜鏡 投影鏡頭 液晶投影糸統 光源 紫外/紅光截止濾鏡 第一分色鏡 第二分色鏡 第一顯像單元 第一梯度變化濾光元件 第一液晶面板 偏光片 檢偏器 第二顯像單元 第二梯度變化濾光元件 第二液晶面板 偏光片 20 檢偏器 第三顯像單元 第三梯度變化濾光元件 弟二液晶面板 偏光片 檢偏器 合光單元 第一侧 第二侧 第三侧 第一偏極分光單元 透鏡陣列 偏振轉換元件 第一反射鏡 第二反射鏡 投影透鏡 液晶投影糸統 光源 紫外/紅光截止濾鏡 第一分色鏡 第二分色鏡 第一顯像單元 第一梯度變化濾光元件 弟一液晶面板 21 1297806 433 第二偏極分光單元 434 偏振延遲元件 44 第二顯像單元 441 第二梯度變化濾光元件 442 第二液晶面板 443 第二偏極分光單元 45 第三顯像單元 451 第三梯度變化濾光元件 452 第三液晶面板 453 第二偏極分光單元 454 偏振延遲元件 46 合光單元 461 第一侧 462 第二侧 463 第三側 47 第一^爲極分光單元 471 透鏡陣列 472 偏振轉換元件 481 第一反射鏡 482 第二反射鏡 49 投影透鏡 LI 梯度變化濾光層 S 透明基板 R，Rs，Rp 光線 22 1297806 G，Gs，Gp 光線 B，Bs，Bp 光線17 1297806 The delay element 454 is converted into the S-polarized light Bs and incident on the light combining unit 46. In the present embodiment, the liquid crystal projector system 40 further includes a projection lens 49. The light rays Rs, Bs, and Gp are emitted from the light combining unit 46, and are projected to the projection lens 49. After the light rays Rs, Gp, and Bs are combined by the light combining unit 46, the images of the respective color lights can be superimposed, and the pupil plane of the color can be projected by the projection lens 49. In summary, the transmittance of the central region of the gradient change filter element in the liquid crystal projection system of the present invention is smaller than the transmittance of the edge region. Therefore, the light emitted by the light source passes through the gradient in the imaging unit. When the filter element is changed, the image unevenness caused by the difference in the length of the light path can be improved. The light beam irradiated onto the liquid crystal panel has uniform brightness, so that the liquid crystal panel can be used to perform brightness pre-compensation without any waste of energy, so that the number of gray scales of the liquid crystal projection system can be improved, and the quality of the final image is further improved. good. The above is intended to be illustrative only and not limiting. Any equivalent modifications or alterations to the spirit and scope of the present invention are intended to be included in the scope of the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram of a conventional transmissive liquid crystal projection device; FIG. 2 is a schematic diagram of a conventional reflective liquid crystal projection device; FIG. 3 is a liquid crystal projection according to a first embodiment of the present invention. FIG. 4 is a schematic diagram of a gradient change light-emitting element of the liquid crystal projection system of the present invention; FIG. 5 is a schematic diagram showing a change in transmittance of a gradient change filter element of the liquid crystal projection system of the present invention; And FIG. 6 is a schematic diagram of a liquid crystal projection system according to a second embodiment of the present invention. Component symbol description: 10 Transmissive liquid crystal projection device 11 Light source 121 Dichroic mirror 122 Dichroic mirror 131 Mirror 132 Mirror 133 Mirror 141 Liquid crystal panel 142 LCD panel 143 Liquid crystal panel 15 Splitter 16 Projection lens 20 Reflective LCD Projection device 21 light source 221 dichroic mirror 222 dichroic mirror 231 mirror mirror mirror polarized beam splitting prism polarized beam splitting polarized beam splitting penetrating liquid crystal panel penetrating liquid crystal panel penetrating liquid crystal Panel 合 稜鏡 projection lens LCD projection system light source UV / red light cut filter first dichroic mirror second dichroic mirror first imaging unit first gradient change filter element first liquid crystal panel polarizer analyzer Second developing unit second gradient changing filter element second liquid crystal panel polarizer 20 analyzer third developing unit third gradient changing filter element second liquid crystal panel polarizing plate analyzer light combining unit first side Two-side third side first polarization splitting unit lens array polarization conversion element first mirror second mirror projection lens liquid crystal projection system light UV/red light cut filter first dichroic mirror second dichroic mirror first image developing unit first gradient change filter element brother liquid crystal panel 21 1297806 433 second polarized light splitting unit 434 polarization delay element 44 second display Image unit 441 Second gradient change filter element 442 Second liquid crystal panel 443 Second polarization splitting unit 45 Third development unit 451 Third gradient change filter element 452 Third liquid crystal panel 453 Second polarization splitting unit 454 Polarization Delay element 46 light combining unit 461 first side 462 second side 463 third side 47 first ^ pole splitting unit 471 lens array 472 polarization conversion element 481 first mirror 482 second mirror 49 projection lens LI gradient change filter Light layer S transparent substrate R, Rs, Rp light 22 1297806 G, Gs, Gp light B, Bs, Bp light