200909862 九、發明說明： 【發明所屬之技術領域】 本發明涉及投影技術，特別涉及一種投影鏡頭。 【先前技術】 當鈾’數位光處理(Digital Light Processing，DLP)投影 儀及採用液晶光閥(Light valve)之液晶顯示(Liquid Crystal Display，LCD)投影儀、石夕晶(Liquid Crystal on Silicon，LCoS) 投影儀已取代陰極射管(Cathode Ray Tube，CRT)投影儀成 為市場主流產品。以往，CRT投影儀可通過電性補償 (Electrically compensation)修正投影鏡頭之像差，而 DLP， LCD及LCoS投影儀並不具備電性補償能力，因此，要求 應用於DLP，LCD或LCoS投影儀之投影鏡頭具有光學修正 像差之能力，以獲得高品質投影晝面。 另一方面，隨著半導體技術之發展，DLP，LCD及LCoS 投影儀採用之空間光調製器（Spatial light m〇dulat〇r， SLM) ’ 包括數也微鏡晶片（Digital micro_mirror device)、液 晶顯示面板(LCD panel)及矽晶晶片（LCoS chip)，在提高像 素之同時，朝小型化方向發展，以此滿足消費者對投影晝 面σσ貝之要求及便攜性之要求。對應地，投影鏡頭需提高 解析度、縮小尺寸，以配合SLM組成高投影品質、小尺寸 之投影儀。 再有，投影鏡頭還需具有足夠之視場角(Wide angle)， 以在較狹小之場合（短投影距離）獲得較大晝幅（Large screen) ° 200909862 然而，投影鏡頭之設計存在如下矛盾：提高解析度， 意味需採用更多之鏡片或高成本之非球面玻璃鏡片消^各 種像差(Aberration)，投影鏡頭全長(投影鏡頭第一個光學面 到SLM表面之距離)變長，成本增加。增大視場角，往往 需要縮短投影鏡頭放大端(近螢幕端)之鏡群（負光焦度)之 有效，距’提高負光焦度。然而，鏡群之有效焦距較短將 產生嚴重之單色像差，特別係畸變(Dist〇rti〇n),投影鏡頭 解析度綠響。另外，制非球面鏡片（制係非球面玻璃 鏡片）可有效修正像差，減少投影鏡頭所制鏡#之數量， 然而’成本增加。 【發明内容】 有鑒於此，有必要提供一種高解析度、小尺寸之投影 鏡頭。 -種投影鏡頭，其從放大端至縮小職次包括：具有 負光焦度之第-鏡群及财正光域之第二鏡群。該投影 鏡頭滿足條件式 -2.5<F1/F<-1.5 ; 1.3<F2/F<1.5。 /、中F1’F2及F分別為該第一鏡群、該第二鏡群及 該投影鏡頭之有效焦距。 條件式：-2.5<F1/F<-1.5用於限制該第一鏡群之光焦度 (1/F1)，以獲得足夠之視場角，並控解色像差。條件式： 1加2/兄5用於限制該第二鏡群之光焦度，以有效平衡 該第-鏡群產生之單色像差，並_投影鏡頭全長。 200909862 【實施方式】 請參閱圖ι(示意圖，鏡片參數請參具體實施例），本發 明實施例之投影鏡頭100從放大端至縮小端(近SLM端)依 次包括具有負光焦度之第一鏡群10及具有正光焦度之第 二鏡群20。 作為範例，本實施例之投影鏡頭100應用於LCoS投 衫儀，4又衫時，SLM(發晶晶片，圖未不)調製之投影訊號光 自SLM表面99投射入投影鏡頭1〇〇，依次經第二鏡群2〇 及第一鏡群10，投射於螢幕（圖未示）上便可得到投影書 面。具體地’ LCoS投影儀投影時’ SLM表面99投射出之 才又衫訊5虎光依次經過偏振片98(Polarizer)、半波片 97(Retarder)及偏振分光(P〇iarizing Beam Splito，pBS)棱鏡 組合96後進入投影鏡頭loo。 為得到高解析度、小尺寸之投影鏡頭1〇〇，投影鏡頭 100滿足條件式： (1) -2.5<F1/F<-1.5 ； (2) 1.3<F2/F<1.5。 其中，Fl，F2及F分別為第—鏡群1〇、第二鏡群2〇 及投影鏡頭100之有效焦距。 ' 條件式(1)給出第一鏡群10之光焦度(1/F1)與投影鏡頭 ， 100之光焦度(1/F)之關係，以獲得理想之視場角，並控制 單色像差(在第二鏡群20修正之範圍内）。F1/F較大，有利 於增大視場角及縮小投影鏡頭全長，故限定Fl/p^-25，考 慮到F1/F過大，導致第一鏡群1〇負光焦度過大，將產生 200909862 * 嚴重之單色像差’特別係畸變’為將畸變控制在可修正之 範圍内，故另限定Fl/F<-1.5。 條件式(2)給出第二鏡群20之光焦度(1/F2)與投影鏡頭 100之光焦度(1/F)之關係’以有效平衡第一鏡群1〇產生之 單色像差，並控制投影鏡頭全長。一方面，F2/F較大，利 於滿足投影鏡頭縮小端遠心(Telecentric)成像要求(如此，營 幕可在一段距離範圍内接收到清晰投影晝面），而F2/F較 小，利於縮短投影鏡頭全長；另一方面，為有效平衡第— 鏡群10產生之單色像差，避免修正過度或修正不及，需限 定F2/F範圍，故限定1.3<F2/F<1.5。 優選地’投影鏡頭100滿足條件式： (3) Lb/F>1.6。 其中，Lb為投影鏡頭後焦距，即第二鏡群2〇最後一 個光學面到SLM表面99之距離。 關係式(3)限定後焦距Lb，以獲得足夠之空間設置偏振 片98、半波片97·及PBS棱鏡組合96等LCoS投影儀組件。 更加優選地，投影鏡頭1〇〇還滿足關係式： (4) 0.24<D12/F<0.5。 其中’ D12為第一鏡群1〇與第二鏡群2〇之轴上間距(第 鏡群10與第二鏡群2〇相對兩個表面截得之光軸長度）。 條件式(4)限定第一鏡群1〇與第二鏡群之間空氣隙 之寬度’以縮短投影鏡頭全長，並提供足夠之調焦空間（第 -鏡頭10與第二鏡頭2〇之相對移動量）。具體地，較小之 D12/F有利於縮短投影鏡頭全長，故限定5，為 200909862 預留空間調焦，限定D12/F>0.24。 具體地，第一鏡群10從放大端至縮小端依次包括具有 負光焦度之第一鏡片11、具有正光焦度之第二鏡片12、具 有負光焦度之第二鏡片13及具有正光焦度之第四鏡片 14，以合理分配第一鏡群1〇之光焦度。 為有效修正單色像差，優選地，第一鏡群1〇包括至少 -個非球面鏡片（至少-個表面採用非球面鏡)。考慮到球面 鏡片具有價格優勢，可降低投影鏡頭1〇〇之成本，本實施 例之第一鏡群10採用一個非球面鏡片。更優選地，在工作 溫度允許之情況下，如採用發光二極體(Light emitting diode) 作為LCgS投影儀光源’本實施例之第—鏡群1G採用一個 塑踢材料製成之非球面鏡片，以進—步降低投影鏡頭ι〇〇 之成本。 類似地’第二鏡群20從放大端至縮小端依次包括呈有 正光焦度之第五鏡片21、具有負光焦度之第六鏡片22、具 有正光焦度之第;fc鏡片23及具有正光焦度之第八鏡片2心 優選地，第二鏡群2〇包括至少一個非球面鏡，更偵 地，弟二鏡群2Q包括—個非球面鏡。同樣，在工作溫度为 許之情況下’第二鏡群2Q採用—個轉非球面鏡片。 更加’、體地’投影鏡頭勘還包括一個設置於第五顧 片21與第六鏡片22之間之光闌95(apen職_)，以限帝 軸外光線由第六透鏡22進人紅透鏡21喊生較嚴重戈 ，及場曲。料，光闌95使得經過第六透鏡22之制 更加對稱’利於修正篆差(c_)。 200909862 另方面’為修正色差(chr〇matic aberration)，還限定 第-鏡群10之至少—個鏡片滿足關係式： (5) vdl>55; (6) nd>1.5; 其中’vdl及nd分別為d光(波長為587.6奈米，下同) 在第一鏡群10之至少—個鏡片之阿貝數^北以number)及折 射率 第二鏡群20之至少一鏡片滿足關係式： (7) vd2>60。 其中，vd2為d光在第二鏡群20之至少一個鏡片之阿 貝數。 以下結合圖2至圖1〇，以具體實施例進一步說明投影 鏡頭100。 以鏡片表面中心為原點，光軸為x軸，鏡片表面之非 球面面型運算式為： _ ch2 ' 其中’ C為鏡面表面中心之曲率，k係二次曲面係數， hVFTF為從光轴到鏡片表面之高度，[从表示對 累加，i為自然數’ Ai為第i階之非球面面型係數。 另外，約定FN。為投影鏡頭100之光圈數，2ω為投影 鏡頭100之視場角，R為對應表面之曲率半徑，D為對應 表面到後一個表面(像側)之軸上距離(兩個表面截得光轴之 長度），Nd為對應鏡片（濾光片）對d光之折射率，vd為d 10 200909862 光在對應鏡片（濾光片）之阿貝數，En表示10n(n為整數）。 實施例1 實施例1之投影鏡頭100滿足表1及表2所列之條件， 且 F=21.58 毫米（millimeter, mm) ， Fl=-38.85mm， F2=30.425mm，FNo=2.45，2ω=54·7°，第二鏡片 12 及第七 鏡片23採用塑膠非球面鏡片。 表1 表面 R (mm) D (mm) Nd vd 第一鏡片放大端表 面 56.088 1.5 1.589 61.135 第一鏡片縮小端表 面 23.041 2.111 - - 第二鏡片放大端表 面 66.179 4.045 1.6073 26.65 第二鏡片縮小端表 面 - -39.229 2.771 - - 第三鏡片放大端表 面 -79.672 1.5 1.571 50.8 第三鏡片縮小端表 面 13.178 3.771 - - 第四鏡片放大端表 面 -35.77 3.156 1.744 44.786 第四鏡片縮小端表 面 -24.669 5.28 - - 11 200909862 第五鏡片放大端表 面 43.254 3.481 1.589 61.135 第五鏡片縮小端表 面 -19.618 0.15 - - 光闌表面 無窮大 9.834 - - 第六鏡片放大端表 面 -25.202 1.5 1.8467 23.78 第六鏡片縮小端表 面 32.223 3.46 - - 第七鏡片放大端表 面 -49.8 7.1 1.5247 56.26 第七鏡片縮小端表 面 -16.129 0.246 - - 第八鏡片放大端表 面 72.513 7.946 1.6968 55.53 第八鏡片縮小端表 面 -29.765 2.15 - - 偏振片放大端表面 無窮大 22 1.6477 33.848 偏振片細小端表面 無窮大 2 - - 半波片放大端表面 無窮大 0.7 1.5184 61.7 表2 表面 表面非球面面型參數 第二鏡 片放大 k=-10.97392; A4=1.82963E-5; A6=-9.26848E-8; A8=5.59189E-10; 12 200909862 端表面 A10=-1.98742E-12 第二鏡 片縮小 端表面 k=-22.43766; A4=3.49E-6; A6=2.72E-8; A8=7.02E-11； A10=-7.80E-13 第七鏡 片放大 端表面 k=-79.16789; A4=-l.08162 E-4; A6=9.00E-07; A8=-9.89E-9; A10=3.47E-11 第七鏡 片縮小 端表面 k=0.4065924; A4=l.〇7E-5; A6=8.96E-9; A8=2.79E-10； A10=-2.67E-12 實施例1之投影鏡頭100之球差特性曲線、場曲特性 曲線及畸變之特性曲線分別如圖2、圖3及圖4所示。圖2 中，曲線f，d及c分別為f光(波長為486.1奈米，下同）、 d光及c光(波長為656.3奈米，下同)經投影鏡頭1〇〇之球 差特性曲線(下同）。可見，實施例1之投影鏡頭1〇〇對可見 光(400-700奈米·)產生之球差被控制在-〇.lmm~0.1mm間。 圖3中’曲線t及s為子午場曲(Tangential field curvature) 特性曲線及弧矢場曲(Sagittal field curvature )特性曲線(下 同）。可見’子午場曲值及弧矢場曲值被控制在 -0.1mm〜0.1mm間。圖4中，曲線為畸變特性曲線(下同）。 可見，畸變量被控制在-2%〜2%間。綜前，儘管投影鏡頭 1〇〇具有較大之視場角及較小尺寸，其產生之球差、場曲 及崎變卻被控制(修正)在較小之範圍内。 實施例2 13 200909862 實施例2之投影鏡頭100滿足表3及表4所列之條件， 且 F=20.57mm，Fl=-43.378mm，F2=29.585mm，FNo=2.44， 2ω=56.98°，第二鏡片12及第七鏡片23採用塑膠非球面 鏡片。 表3 表面 R (mm) D (mm) Nd vd 第一鏡片放大 端表面 56.37951 1.5 1.5163 64.142 第一鏡片縮小 端表面 19.45174 2.784273 - - 第二鏡片放大 端表面 67.52031 4.063589 1.6073 26.65 第二鏡片縮小 端表面 -35.39937 1.838138 - - 第三鏡片放大 端表面 -115.634 1.5 1.5225 59.8354 第三鏡片縮小 端表面 12.79318 4.061006 - - 第四鏡片放大 端表面 -33.31014 3.632139 1.6204 60.2896 第四鏡片縮小 端表面 -22.97251 5.274921 - - 第五鏡片放大 端表面 47.65653 3.315928 1.589 61.135 14 200909862 第五鏡片縮小 端表面 -19.51972 0.15 - - 光闌表面 無窮大 8.758488 - - 第六鏡片放大 端表面 -24.89886 1.5 1.8467 23.78 第六鏡片縮小 端表面 30.70857 3.418172 - — 第七鏡片放大 端表面 -50.35514 7.1 1.5247 56.26 第七鏡片縮小 端表面 -15.63497 1.041066 - - 第八鏡片放大 端表面 84.05907 7.926621 1.6968 55.53 第八鏡片縮小 端表面 -28.60263 2.135659 - - 偏振片放大端 表面 無窮大 22 1.6477 33.848 偏振片縮小端 表面 無窮大 2 - - 半波片放大端 表面 無窮大 0.7 1.5184 61.7 表4 表面 表面非球面面型參數 第二鏡 k=-10.17326; A4=1.74E-5; A6=-1.02E-7; 15 200909862 片放大 端表面 A8=6.22E-10； A10=-2.15E-12 弟一鏡 片縮小 端表面 k=-19.16988; A4=1.81E-6; A6=3.9E-8; A8=3.7E-11； A10=-6.46E-13 第七鏡 片放大 端表面 k=-91.33926; A4=-1.21802E-4; A6=1.14E-6; A8=-1.34E-8; A10=5.7E-11 第七鏡 片縮小 端表面 k=0.3093345; A4=8.74E-6; A6=-4.76E-9; A8=3.04E-10； A10=-3.85E-12 實施例2之投影鏡頭100之球差特性曲線、場曲特性 曲線及靖變之特性曲線分別如圖5、圖6及圖7所示。可 見，實施例2之投影鏡頭1〇〇對可見光產生之球差被控制 在〜0.1mm間’子午場曲值及孤矢場曲值被控制在 -0.1mm〜0.1mm間，畸變量被控制在〜2%間。綜前，儘 管投影鏡頭1〇〇視場角，尺寸縮小，其產生之球差、場曲 及畸變卻被控制在較小之範圍内。 實施例3 實施例3之投影鏡頭100滿足表5及表6所列之條件， 且 F=21.2mm，Fl=-47mm，F2=31.〇2mm，Fn〇=2 46，％ =55.57，第一鏡片11及第七鏡片23採用塑膠非球面鏡 表5 表面 | R (mm) D (mm) ~ 16 200909862 第一鏡片放大端 表面 58.051 2.41 1.5247 56.26 第一鏡片縮小端 表面 11.667 2.202 第二鏡片放大端 表面 21.439 3.004 1.806 33.2694 第二鏡片縮小端 表面 103.82 2.701 - - 第三鏡片放大端 表面 -21.595 1.501 1.6175 48.0786 第三鏡片縮小端 表面 20.408 2.524 - - 第四鏡片放大端 表面 30.179 3.302 1.6742 51.7521 第四鏡片縮小端 表面 - -51.502 6.5 - - 第五鏡片放大端 表面 41.495 2.383 1.6987 48.9334 第五鏡片縮小端 表面 -40.266 0.918 - - 光闌表面 無窮大 11.36 - - 第六鏡片放大端 表面 -19.698 1.5 1.8467 23.78 第六鏡片縮小端 73.743 1.214 - - 17 200909862 表面 第七鏡片放大端 表面 153.785 10 1.5247 56.26 第七鏡片縮小端 表面 -20.171 0.2 - - 第八鏡片放大端 表面 47.879 7.871 1.6178 60.4578 第八鏡片縮小端 表面 -34.109 2 - - 偏振片放大端表 面 無窮大 22 1.6477 33.8482 偏振片縮小端表 面 無窮大 1 - - 半波片放大端表 面 無窮大 0.7 1.5184 61.7 表6 表面 表面非球面面型參數 第一鏡 片放大 端表面 k=2.9896; A4=1.42E-5; A6=-8.47E-8; A8=3.87E-10; A10=7.12E-13 第一鏡 片縮小 端表面 k=-0.8105889; A4=2.33E-5; A6=~5.69E~9; A8=-1.99E-9; A10=2.06E-11 第七鏡 k=-748.1059; A4=2.68E-5; A6=-1.04E-7; 18 200909862 片放大 端表面 A8=1.76E-09; A10=-4.39E-12 第七鏡 片縮小 端表面 k=-0.4196788; A4=1.26E-5; A6=9.62E-8; A8=-1.61E-10； A10=3.23E-12 實施例3之投影鏡頭loo之球差特性曲線、場曲特性 曲線及畸變之特性曲線分別如圖8、圖9及圖10所示。可 見，實施例3之投影鏡頭100對可見光產生之球差被控制 在-O.lirnn〜O.lmm間’子午場曲值及弧矢場曲值被控制在 -0.1mm〜0.1mm間，畸變量被控制在_2%〜2%間。綜前，儘 管投影鏡頭100視場角，尺寸縮小，其產生之球差、場曲 及畸變卻被控制(修正)在較小之範圍内。 條件式：-2.5<F1/F<-1.5用於限制該第一鏡群之光焦度 (1/F1) ’以獲得足夠之視場角，並控制單色像差。條件式： 1.3<F2/F<1.5用於限制該第二鏡群之光焦度，以有效平衡 該第一鏡群產生之單色像差，並限制投影鏡頭全長。 綜上所述，本發明確已符合發明專利要件，爰依法提 出專利巾請。惟，以上所述者僅為本發明之較佳實施方式， 舉凡熟悉柄技藝之人士，於援依本案伽精神所作之等 效修飾或變化’皆應包含於以下之申請專利範圍内。 【圖式簡單說明】 圖1為本㈣實施狀郷_之紐構成示意圖。 圖2為切i之投韻社球差如 aberration)特性曲線圖。 19 200909862 * 圖3為本發明實施例1之投影鏡頭之場曲(Field curvature) 特性曲線圖。 圖4為本發明實施例1之投影鏡頭之畸變特性曲線圖。 圖5為本發明實施例2之投影鏡頭之球差特性曲線圖。 圖6為本發明實施例2之投影鏡頭之場曲特性曲線圖。 圖7為本發明實施例2之投影鏡頭之畸變特性曲線圖。 圖8為本發明實施例3之投影鏡頭之球差特性曲線圖。 圖9為本發明實施例3之投影鏡頭之場曲特性曲線圖。 圖10為本發明實施例3之投影鏡頭之畸變特性曲線圖。 【主要組件符號說明】 成像鏡頭 100 第六鏡片 22 第一鏡群 10 第七鏡片 23 第一鏡片 11 第八鏡片 24 第二鏡片 12 SLM表面 99 第三鏡片 13 偏振片 98 第四鏡片 14 半波片 97 弟二鏡群 20 PBS棱鏡組合96 第五鏡片 21 光闌 95 20200909862 IX. Description of the Invention: [Technical Field] The present invention relates to projection technology, and in particular to a projection lens. [Prior Art] When uranium 'Digital Light Processing (DLP) projectors and liquid crystal display (LCD) projectors using liquid crystal light valves, Liquid Crystal on Silicon (Liquid Crystal on Silicon, LCoS) projectors have replaced cathode ray tube (CRT) projectors as the mainstream product. In the past, CRT projectors can correct the aberration of the projection lens by electrical compensation. DLP, LCD and LCoS projectors do not have electrical compensation capability. Therefore, they are required to be applied to DLP, LCD or LCoS projectors. The projection lens has the ability to optically correct aberrations to achieve a high quality projection surface. On the other hand, with the development of semiconductor technology, spatial light modulators (SLM) used in DLP, LCD and LCoS projectors include digital micro-mirror devices and liquid crystal displays. The LCD panel and the LCoS chip are developed in the direction of miniaturization while increasing the number of pixels, thereby satisfying the requirements of consumers for the requirements and portability of the projection surface. Correspondingly, the projection lens needs to be improved in resolution and downsized to match the SLM to form a projector with high projection quality and small size. Furthermore, the projection lens needs to have a sufficient angle of view to obtain a larger screen in a narrower case (short projection distance). 0909862 However, the design of the projection lens has the following contradictions: Increasing the resolution means that more lenses or high-cost aspherical glass lenses are needed to eliminate various aberrations (Aberration), and the total length of the projection lens (the distance from the first optical surface of the projection lens to the SLM surface) becomes longer and the cost increases. . Increasing the angle of view often requires shortening the effective effect of the mirror group (negative power) of the projection end of the projection lens (near screen end), and increasing the negative power. However, the effective focal length of the mirror group will produce severe monochromatic aberrations, especially distortion (Dist〇rti〇n), and the projection lens resolution will be green. In addition, the aspherical lens (systematic aspherical glass lens) can effectively correct the aberration and reduce the number of mirrors made by the projection lens, but the cost increases. SUMMARY OF THE INVENTION In view of the above, it is necessary to provide a high resolution, small size projection lens. A projection lens, which includes a first-mirror group having a negative power and a second lens group having a negative optical power. The projection lens satisfies the conditional expression -2.5 < F1/F <-1.5; 1.3 < F2 / F < 1.5. /, middle F1'F2 and F are the effective focal lengths of the first mirror group, the second mirror group, and the projection lens, respectively. The conditional expression: -2.5 <F1/F<-1.5 is used to limit the power of the first mirror group (1/F1) to obtain a sufficient angle of view and to control chromatic aberration. Conditional formula: 1 plus 2/brother 5 is used to limit the power of the second mirror group to effectively balance the monochromatic aberration generated by the first mirror group, and to project the full length of the lens. 200909862 [Embodiment] Please refer to FIG. 1 (schematic diagram, lens parameters are referred to as specific embodiments). The projection lens 100 of the embodiment of the present invention includes the first one with negative optical power from the amplification end to the reduction end (near SLM end). The mirror group 10 and the second mirror group 20 having positive power. As an example, the projection lens 100 of the embodiment is applied to the LCoS shirting device. When the shirt is in the 4th, the projection signal modulated by the SLM (the crystal chip, the picture is not) is projected from the SLM surface 99 into the projection lens 1 . The second mirror group 2 and the first mirror group 10 are projected onto a screen (not shown) to obtain a projection. Specifically, when the LCoS projector is projected, the SLM surface 99 is projected and then passed through a polarizer 98 (Polarizer), a half-wave plate 97 (Retarder), and a polarization splitting (PBS). After the prism combination 96 enters the projection lens loo. In order to obtain a high-resolution, small-sized projection lens, the projection lens 100 satisfies the conditional expression: (1) -2.5 <F1/F<-1.5; (2) 1.3 < F2/F < 1.5. Among them, Fl, F2 and F are the effective focal lengths of the first mirror group 1〇, the second mirror group 2〇 and the projection lens 100, respectively. 'Conditional formula (1) gives the relationship between the power of the first mirror group 10 (1/F1) and the projection lens, the power of 100 (1/F) to obtain the ideal angle of view, and control the single Chromatic aberration (within the range corrected by the second mirror group 20). Large F1/F is beneficial to increase the angle of view and reduce the total length of the projection lens. Therefore, Fl/p^-25 is limited. Considering that the F1/F is too large, the first mirror group 1 has too much negative power, which will result in 200909862 * Severe monochromatic aberration 'special distortion' is to limit the distortion to a correctable range, so Fl/F<-1.5 is also defined. The conditional expression (2) gives the relationship between the power (1/F2) of the second mirror group 20 and the power (1/F) of the projection lens 100 to effectively balance the monochrome generated by the first mirror group 1 Aberration and control the full length of the projection lens. On the one hand, the F2/F is larger, which is suitable for meeting the Telecentric imaging requirements of the projection lens (so that the screen can receive a clear projection surface over a distance), while the F2/F is smaller, which helps to shorten the projection. The full length of the lens; on the other hand, in order to effectively balance the monochromatic aberration generated by the first lens group 10, to avoid overcorrection or correction, it is necessary to limit the F2/F range, so it is limited to 1.3 < F2 / F < 1.5. Preferably, the projection lens 100 satisfies the conditional expression: (3) Lb/F > 1.6. Where Lb is the focal length of the projection lens, that is, the distance from the last optical surface of the second mirror group 2 to the SLM surface 99. The relation (3) defines the back focal length Lb to obtain sufficient space for the LCoS projector assembly such as the polarizer 98, the half wave plate 97, and the PBS prism assembly 96. More preferably, the projection lens 1〇〇 also satisfies the relationship: (4) 0.24 < D12/F < 0.5. Wherein ' D12 is the on-axis spacing of the first mirror group 1 〇 and the second mirror group 2 ( (the optical axis lengths of the first mirror group 10 and the second mirror group 2 〇 opposite the two surfaces). The conditional expression (4) defines the width of the air gap between the first mirror group 1〇 and the second mirror group to shorten the total length of the projection lens and provide sufficient focusing space (the opposite of the first lens 10 and the second lens 2) The amount of movement). Specifically, the smaller D12/F is advantageous for shortening the total length of the projection lens, so it is limited to 5, and the space is adjusted for 200909862, and D12/F>0.24 is limited. Specifically, the first mirror group 10 includes, in order from the enlarged end to the reduced end, a first lens 11 having a negative power, a second lens 12 having a positive power, a second lens 13 having a negative power, and a positive light. The fourth lens 14 of the power is used to reasonably distribute the power of the first mirror group 1〇. In order to effectively correct the monochromatic aberration, preferably, the first mirror group 1 includes at least one aspherical lens (at least one surface is an aspherical mirror). Considering that the spherical lens has a price advantage, the cost of the projection lens can be reduced. The first mirror group 10 of this embodiment employs an aspherical lens. More preferably, if the operating temperature permits, such as using a light emitting diode as the LCgS projector light source, the first embodiment of the mirror group 1G uses an aspherical lens made of a plastic kick material. To further reduce the cost of the projection lens. Similarly, the second mirror group 20 includes, in order from the enlarged end to the reduced end, a fifth lens 21 having a positive power, a sixth lens 22 having a negative power, and a portion having a positive power; the fc lens 23 has Preferably, the second lens group 2 includes at least one aspherical mirror, and the second mirror group 2Q includes an aspherical mirror. Similarly, in the case where the operating temperature is allowed, the second mirror group 2Q employs a rotating aspherical lens. The more ', body' projection lens survey also includes a diaphragm 95 (apen job _) disposed between the fifth film 21 and the sixth lens 22 to limit the off-axis light from the sixth lens 22 into the red Lens 21 shouts more serious Ge, and field music. It is expected that the diaphragm 95 is made more symmetrical by the sixth lens 22 to facilitate correction of the coma (c_). 200909862 In other respects, for the correction of chrominance (chr〇matic aberration), at least one lens of the first-mirror group 10 is also defined to satisfy the relationship: (5) vdl>55; (6) nd>1.5; wherein 'vdl and nd respectively The d-light (wavelength is 587.6 nm, the same below) at least one of the lenses of the first mirror group 10 and the number of lenses of the second mirror group 20 satisfy the relationship: 7) vd2>60. Wherein vd2 is the Abbe number of at least one lens of the d-light in the second mirror group 20. The projection lens 100 will be further described with reference to the specific embodiments in conjunction with Figs. 2 to 1B. Taking the center of the lens surface as the origin and the optical axis as the x-axis, the aspherical surface of the lens surface is: _ ch2 ' where 'C is the curvature of the center of the mirror surface, k is the quadric coefficient, hVFTF is the optical axis To the height of the lens surface, [from the pair of representations, i is the natural number 'Ai is the aspherical surface coefficient of the i-th order. In addition, the agreement FN. For the number of apertures of the projection lens 100, 2ω is the angle of view of the projection lens 100, R is the radius of curvature of the corresponding surface, and D is the on-axis distance from the corresponding surface to the latter surface (image side) (the two surfaces are intercepted by the optical axis) The length), Nd is the refractive index of the corresponding lens (filter) to d light, vd is the Abbe number of the light of the corresponding lens (filter), and En is 10n (n is an integer). Embodiment 1 The projection lens 100 of Embodiment 1 satisfies the conditions listed in Tables 1 and 2, and F = 21.58 mm (millimeter, mm), Fl = -38.85 mm, F2 = 30.425 mm, FNo = 2.45, 2ω = 54 7°, the second lens 12 and the seventh lens 23 are made of a plastic aspherical lens. Table 1 Surface R (mm) D (mm) Nd vd First lens enlarged end surface 56.088 1.5 1.589 61.135 First lens reduced end surface 23.041 2.111 - - Second lens enlarged end surface 66.179 4.045 1.6073 26.65 Second lens reduced end surface - -39.229 2.771 - - Third lens magnification end surface - 79.672 1.5 1.571 50.8 Third lens reduction end surface 13.178 3.771 - - Fourth lens magnification end surface - 35.77 3.156 1.744 44.786 Fourth lens reduction end surface - 24.669 5.28 - - 11 200909862 Fifth lens enlarged end surface 43.254 3.481 1.589 61.135 Fifth lens reduced end surface - 19.618 0.15 - - Matte surface infinity 9.834 - - Sixth lens enlarged end surface - 25.202 1.5 1.8467 23.78 Sixth lens reduced end surface 32.223 3.46 - - Seven-lens enlarged end surface -49.8 7.1 1.5247 56.26 Seventh lens reduced end surface - 16.129 0.246 - - Eighth lens enlarged end surface 72.513 7.946 1.6968 55.53 Eighth lens reduced end surface - 29.765 2.15 - - Polarizing plate magnification end surface infinity 22 1.6477 33.848 Polaroid fine end surface infinity 2 - - Half wave Magnification end surface infinity 0.7 1.5184 61.7 Table 2 Surface surface aspherical surface parameters Second lens magnification k=-10.97392; A4=1.82963E-5; A6=-9.26848E-8; A8=5.59189E-10; 12 200909862 Surface A10=-1.98742E-12 Second lens reduced end surface k=-22.43766; A4=3.49E-6; A6=2.72E-8; A8=7.02E-11; A10=-7.80E-13 seventh lens Amplified end surface k=-79.16789; A4=-l.08162 E-4; A6=9.00E-07; A8=-9.89E-9; A10=3.47E-11 seventh lens reduced end surface k=0.4065924; A4 =1.〇7E-5; A6=8.96E-9; A8=2.79E-10; A10=-2.67E-12 The spherical aberration characteristic curve, field curvature characteristic curve and distortion characteristic of the projection lens 100 of Embodiment 1 The curves are shown in Figures 2, 3 and 4, respectively. In Fig. 2, the curves f, d and c are the spherical aberration characteristics of the projection lens 1 after f light (wavelength 486.1 nm, the same below), d light and c light (wavelength 656.3 nm, the same below). Curve (the same below). It can be seen that the spherical aberration generated by the projection lens 1 of Example 1 against visible light (400-700 nm·) is controlled between -〇.lmm and 0.1 mm. In Fig. 3, the curves t and s are the Tangential field curvature characteristic curve and the Sagittal field curvature characteristic curve (the same applies hereinafter). It can be seen that the meridional field curvature value and the sagittal field curvature value are controlled between -0.1 mm and 0.1 mm. In Fig. 4, the curve is a distortion characteristic curve (the same applies hereinafter). It can be seen that the distortion variable is controlled between -2% and 2%. In the meantime, although the projection lens 1 has a large angle of view and a small size, the spherical aberration, curvature of field and roughness caused by it are controlled (corrected) to a small extent. Embodiment 2 13 200909862 The projection lens 100 of Embodiment 2 satisfies the conditions listed in Tables 3 and 4, and F=20.57 mm, Fl=-43.378 mm, F2=29.585 mm, FNo=2.44, 2ω=56.98°, The second lens 12 and the seventh lens 23 are made of a plastic aspherical lens. Table 3 Surface R (mm) D (mm) Nd vd First lens magnification end surface 56.37951 1.5 1.5163 64.142 First lens reduction end surface 19.45174 2.784273 - - Second lens magnification end surface 67.52031 4.063589 1.6073 26.65 Second lens reduction end surface - 35.39937 1.838138 - - Third lens magnification end surface -115.634 1.5 1.5225 59.8354 Third lens reduction end surface 12.79318 4.061006 - - Fourth lens magnification end surface -33.31014 3.632139 1.6204 60.2896 Fourth lens reduction end surface -22.72951 5.274921 - - Fifth lens Magnifying end surface 47.65653 3.315928 1.589 61.135 14 200909862 Fifth lens narrowing end surface -19.51972 0.15 - - Matte surface infinity 8.758488 - - Sixth lens magnifying end surface - 24.89886 1.5 1.8467 23.78 Sixth lens reducing end surface 30.70857 3.418172 - - Seventh Lens enlarged end surface -50.35514 7.1 1.5247 56.26 Seventh lens reduced end surface - 15.63497 1.041066 - - Eighth lens enlarged end surface 84.05907 7.926621 1.6968 55.53 Eighth lens reduced end surface - 28.60263 2.135659 - - Polarizer magnification end table Infinity 22 1.6477 33.848 Polarizing plate reduced end surface infinity 2 - - Half wave plate amplifying end surface infinity 0.7 1.5184 61.7 Table 4 Surface surface aspherical surface parameters Second mirror k=-10.17326; A4=1.74E-5; A6=- 1.02E-7; 15 200909862 Amplified end surface A8=6.22E-10; A10=-2.15E-12 Younger lens reduced end surface k=-19.16988; A4=1.81E-6; A6=3.9E-8; A8=3.7E-11; A10=-6.46E-13 7th lens magnification end surface k=-91.33926; A4=-1.21802E-4; A6=1.14E-6; A8=-1.34E-8; A10= 5.7E-11 seventh lens reduced end surface k=0.3093345; A4=8.74E-6; A6=-4.76E-9; A8=3.04E-10; A10=-3.85E-12 Projection lens 100 of Example 2 The spherical aberration characteristic curve, the field curvature characteristic curve, and the characteristic curve of the Jingcheng are shown in FIG. 5, FIG. 6, and FIG. 7, respectively. It can be seen that the projection lens of Embodiment 2 has a spherical aberration for visible light controlled between ~0.1 mm, and the meridional field curvature value and the orbital field curvature value are controlled between -0.1 mm and 0.1 mm, and the distortion variable is controlled. ~2% between. In the meantime, although the projection lens 1 has a field of view and the size is reduced, the spherical aberration, curvature of field and distortion generated by the projection lens are controlled to a small extent. Embodiment 3 The projection lens 100 of Embodiment 3 satisfies the conditions listed in Tables 5 and 6, and F = 21.2 mm, Fl = -47 mm, F2 = 31. 〇 2 mm, Fn 〇 = 2 46, % = 55.57, A lens 11 and a seventh lens 23 are made of a plastic aspherical mirror. Surface 5 | R (mm) D (mm) ~ 16 200909862 First lens magnification end surface 58.051 2.41 1.5247 56.26 First lens reduction end surface 11.667 2.202 Second lens amplification end Surface 21.439 3.004 1.806 33.2694 Second lens reduced end surface 103.82 2.701 - - Third lens enlarged end surface - 21.595 1.501 1.6175 48.0786 Third lens reduced end surface 20.408 2.524 - - Fourth lens enlarged end surface 30.179 3.302 1.6742 51.7521 Fourth lens reduction End surface - -51.502 6.5 - - Fifth lens enlarged end surface 41.495 2.383 1.6987 48.9334 Fifth lens reduced end surface -40.266 0.918 - - Matte surface infinity 11.36 - - Sixth lens enlarged end surface - 19.698 1.5 1.8467 23.78 Sixth lens Reduction end 73.743 1.214 - - 17 200909862 Surface 7th lens magnification end surface 153.785 10 1.5247 56.26 7th lens reduction end surface - 20.171 0.2 - - Eighth lens magnification end surface 47.879 7.871 1.6178 60.4578 Eighth lens reduction end surface -34.109 2 - - Polarizer magnification end surface infinity 22 1.6477 33.8482 Polarizer reduction end surface infinity 1 - - Half wave plate magnification end surface infinity 0.7 1.5184 61.7 Table 6 Surface surface aspherical surface parameters First lens magnification end surface k=2.9896; A4=1.42E-5; A6=-8.47E-8; A8=3.87E-10; A10=7.12E-13 The first lens has a reduced end surface k=-0.8105889; A4=2.33E-5; A6=~5.69E~9; A8=-1.99E-9; A10=2.06E-11 seventh mirror k=-748.1059; A4= 2.68E-5; A6=-1.04E-7; 18 200909862 Amplified end surface A8=1.76E-09; A10=-4.39E-12 Seventh lens reduced end surface k=-0.4196788; A4=1.26E-5 A6=9.62E-8; A8=-1.61E-10; A10=3.23E-12 The spherical aberration characteristic curve, field curvature characteristic curve and distortion characteristic curve of the projection lens loo of Embodiment 3 are as shown in FIG. 8 and FIG. 9 and Figure 10. It can be seen that the spherical aberration generated by the projection lens 100 of Embodiment 3 on the visible light is controlled between -O.lirnn~O.lmm' the meridional field curvature value and the sagittal field curvature value are controlled between -0.1 mm and 0.1 mm, and the distortion variable It is controlled between _2% and 2%. In the meantime, although the projection lens 100 has a field of view and the size is reduced, the resulting spherical aberration, field curvature and distortion are controlled (corrected) to a small extent. The conditional expression: -2.5 <F1/F<-1.5 is used to limit the power of the first mirror group (1/F1)' to obtain a sufficient angle of view and to control monochromatic aberration. Conditional Formula: 1.3 < F2/F < 1.5 is used to limit the power of the second mirror group to effectively balance the monochromatic aberration generated by the first mirror group and limit the total length of the projection lens. In summary, the present invention has indeed met the requirements of the invention patent, and the patent towel is required in accordance with the law. However, the above description is only a preferred embodiment of the present invention, and those who are familiar with the skill of the handle, and the equivalent modifications or changes made by the aid of the spirit of the case shall be included in the following patent application. [Simple description of the figure] Fig. 1 is a schematic diagram showing the structure of the 郷__ of the implementation of (4). Fig. 2 is a characteristic curve of the spherical aberration such as aberration of the cut rhyme. 19 200909862 * FIG. 3 is a graph showing a field curvature characteristic of a projection lens according to Embodiment 1 of the present invention. 4 is a graph showing distortion characteristics of a projection lens according to Embodiment 1 of the present invention. Fig. 5 is a graph showing spherical aberration characteristics of a projection lens according to Embodiment 2 of the present invention. Fig. 6 is a graph showing the field curvature characteristics of the projection lens of the second embodiment of the present invention. Fig. 7 is a graph showing distortion characteristics of a projection lens according to Embodiment 2 of the present invention. Fig. 8 is a graph showing spherical aberration characteristics of a projection lens according to Embodiment 3 of the present invention. Fig. 9 is a graph showing the field curvature characteristics of the projection lens of Embodiment 3 of the present invention. Figure 10 is a graph showing distortion characteristics of a projection lens according to Embodiment 3 of the present invention. [Major component symbol description] Imaging lens 100 Sixth lens 22 First mirror group 10 Seventh lens 23 First lens 11 Eighth lens 24 Second lens 12 SLM surface 99 Third lens 13 Polarizing plate 98 Fourth lens 14 Half wave Piece 97 brother two mirror group 20 PBS prism combination 96 fifth lens 21 diaphragm 95 20