200819781 _ n/^ 21777twf.doc/n 九、發明說明： 【發明所屬之技術領域】 本發明是有關於一種鏡頭，且特別是有關於一種定焦 鏡頭。 【先前技術】 隨著現代視訊技術的進步，諸如數位光源處理（digital light processing，DLP)投影機、數位相機（Digital Camera， 〇 DC)等影像裝置已被廣泛地使用。這些影像裝置中的核心 元件之一為鏡頭，其用以將影像清晰地成像於螢幕或是電 荷耦合元件（Charge Coupled Device, CCD)上。因此，鏡 頭的光學品質與影像的成像品質息息相關。在競爭激烈的 市場中，各廠商莫不致力於改良鏡頭的品質，減低其體積 及重量，並降低其製作成本，以提升影像裝置的競爭優勢。 請參閱圖卜美國發明專利第6,712,474號所揭示之定 焦鏡頭100係應用於投影裝置，且其包括依序排列之第一 ( 透鏡110、第二透鏡120、第三透鏡13〇、第四透鏡14〇以 及第五透鏡150，其中第三透鏡130與第四透鏡14〇組成 一屈光度為負的膠合透鏡(cemented doublet lens)，第一至 第五透鏡的屈光度(refractive power)依序為負、正、負、正、 正0 然第一透鏡110與第二透鏡120之間需維持一較長的 - 間距，才能使定焦鏡頭1〇〇有較好的成像品質。然而，由 • 於第一透鏡no與第一透鏡12〇之間的間距較大，使得整 200819781 _ PT735 21777twf.doc/n 個定焦鏡頭⑽_長度過長，如此將導祕個投影 °而由於現今投影裝置朝向輕、薄、短、^的 ΐϊΐί，故習知定焦鏡頭⑽賴無法符合投影裝置的 發展趨勢。 【發明内容】 本發明之目的是提供一種定焦鏡頭，以縮小鏡頭尺 寸，同時維持良好的成像品質。 為達上述或是其他目的，本發明提出一種定焦鏡頭， 包括一第一透鏡群以及一第二透鏡群。第一透鏡群具有正 屈光度且弟一透鏡群是由自一物侧(object side)至一像側 (image side)依序排列的一第一透鏡與一第二透鏡所組 j，其中第一透鏡是具有負屈光度且凸面朝向第二透鏡的 彎月型透鏡(meniscus lens)，而第二透鏡是具有正屈光度的 雙凸透鏡。此外，第二透鏡群具有正屈光度，且配置於第 一透鏡群與像侧之間，第二透鏡群是由自物側至像側依序 排列的一第三透鏡、一第四透鏡與一第五透鏡所組成，其 中第三透鏡是具有負屈光度的雙凹透鏡，第四透鏡是具有 正屈光度且凸面朝向第五透鏡的彎月型透鏡，而第五透鏡 疋具有正屈光度的雙凸透鏡。另外，第四透鏡與第五透鏡 的折射率平均值大於1·7，第一透鏡與第二透鏡之間的間 距小於0.5公分，且F4/F<1.2，其中ρ45是第四透鏡及第 五透鏡的組合焦距，而F是定焦鏡頭的有效焦距。 在本發明之一實施例中，上述第一透鏡與第二透鏡的 200819781 π/jD 21777twf.doc/n 組合焦距為F12，且0.5<F/F12<2。 在本發明之一實施例中，上述第四透鏡與第五透鏡的 阿貝數(Abbe number)之和大於70。 在本發明之一實施例中，上述第二透鏡與第三透鏡之 間的間距小於1公分。 在本發明之-實施例中，上述第-透鏡為非球面透鏡 (aspherical lens) 〇 Γ 在本發明之-實施例中，上述第一透鏡為塑膠透鏡。 —一在本發明之一實施例中，上述第一透鏡、第二透鏡、 第三透鏡、第四透鏡及第五透鏡為球面透鏡。 ％ 士發明之定焦鏡頭的透鏡組合可在維持良好的成像品 ^之前提下縮短第一透鏡及第二透鏡間的距離，進而減= 定焦鏡頭的總長。此外，限制F45/F<12可使定焦鏡頭^ 較佳的屈光能力，以進-步縮短定焦鏡頭的總長;;= 兩透鏡群的屈錢為正、丨的搭配可有效消 (aberration)。 私左 為讓本發明之上述和其他目的、特徵和優點能更明顯 明士，下文特舉較佳實施例，並配合所附圖式，作詳細說 【實施方式】 圖2是本發明一實施例之定焦鏡頭的結構示意圖。杜 多照圖2，定焦鏡頭包括一第—透鏡群210以及 -透鏡群220。第-透鏡群21G具有正屈光度，且第 7 200819781 一 ^1735 21777twf.doc/n 鏡群210是由自一物侧至一像側依序排列的一第一透鏡 212與一第二透鏡214所組成。其中，第一透鏡212是^ 有負屈光度且凸面朝向第二透鏡214的彎月型透鏡，而^ 二透鏡214是具有正屈光度的雙凸透鏡。此外，第二透鏡 群220具有正屈光度，且配置於第一透鏡群2丨〇與像側= 間。第二透鏡群220是由自物側至像侧依序排列的一第二 透鏡222、一第四透鏡224與一第五透鏡226所組成。^ 、三透鏡222是具有負屈光度的雙凹透鏡，第四透鏡224是 具有正屈光度且凸面朝向第五透鏡226的彎月型透鏡，^ 第五透鏡226是具有正屈光度的雙凸透鏡。 為縮短定焦鏡頭200的長度以及維持良好的成像品 質，需限制上述第四透鏡224與第五透鏡226的折射率^ 均值大於1.7，而第一透鏡212與第二透鏡214之間的間 距小於0·5公分，間距係指兩透鏡之透鏡中心之間的直^ 距離，且Fe/FCU，其中F45是第四透鏡224及第五透鏡 226的組合焦距，而ρ是定焦鏡頭2〇〇的有效焦距。兄 在本實施例中，藉由上述五片透鏡的組合可使定焦鏡 頭200在維持良好成像品質的前提下，縮短第一透鏡212 與第二透鏡214之間的間距，因此可使定焦鏡頭2〇〇的整 體長度縮短。如此，當定焦鏡頭2〇〇應用於諸如投影裝置、 數位相機及行動電話(mobileph〇ne)等影像裝置時，由於定 焦鏡頭200所佔用的空間較小，所以影像裝置的體積可以 _ 縮減。此外，限制F^/FC 1.2可使定焦鏡頭200有較佳的 屈光能力’以進一步縮短定焦鏡頭2〇〇的總長。另外，利 8 200819781 . PT735 21777twf.doc/n 用第一透鏡群210與第二透鏡群22〇的屈光度皆為正的搭 配，可有效消除像差。 為進一步消除像差，並確保定焦鏡頭2〇〇的成像品 質，在本實施例中可限定0.5<F/F12<2，其中F12為第一 透鏡212與第二透鏡214的組合焦距。此外，為消除色差 (dimmatic aberration) ’可限制第四透鏡224與第五透鏡挪 Ο200819781 _ n/^ 21777 twf.doc/n IX. Description of the Invention: [Technical Field] The present invention relates to a lens, and more particularly to a fixed focus lens. [Prior Art] With the advancement of modern video technology, image devices such as digital light processing (DLP) projectors and digital cameras (Digital Cameras, DC) have been widely used. One of the core components in these imaging devices is a lens that is used to clearly image the image onto a screen or a Charge Coupled Device (CCD). Therefore, the optical quality of the lens is closely related to the imaging quality of the image. In a highly competitive market, manufacturers are not committed to improving the quality of their lenses, reducing their size and weight, and reducing their manufacturing costs to enhance the competitive advantage of imaging devices. The fixed focus lens 100 disclosed in the U.S. Patent No. 6,712,474 is applied to a projection apparatus, and includes a first array (the lens 110, the second lens 120, the third lens 13A, and the fourth lens). 14〇 and the fifth lens 150, wherein the third lens 130 and the fourth lens 14〇 constitute a cemented doublet lens with a negative dioptric power, and the refractive power of the first to fifth lenses is negative, Positive, negative, positive, positive 0. A long-distance between the first lens 110 and the second lens 120 is required to achieve a good imaging quality of the fixed-focus lens 1 . However, by The distance between a lens no and the first lens 12〇 is large, so that the entire 200819781 _ PT735 21777twf.doc/n fixed-focus lens (10) _ length is too long, so that the projection will be guided by the current projection device Thin, short, ^ ,, so the conventional fixed focus lens (10) can not meet the development trend of the projection device. [Invention] The object of the present invention is to provide a fixed focus lens to reduce the size of the lens while maintaining good imaging In order to achieve the above or other objects, the present invention provides a fixed focus lens comprising a first lens group and a second lens group. The first lens group has positive refractive power and the first lens group is from one object side ( Object side) a first lens and a second lens group j sequentially arranged to an image side, wherein the first lens is a meniscus lens having a negative refracting power and a convex surface facing the second lens And the second lens is a lenticular lens having a positive refracting power. Further, the second lens group has a positive refracting power and is disposed between the first lens group and the image side, and the second lens group is from the object side to the image side. a third lens, a fourth lens and a fifth lens, wherein the third lens is a biconcave lens having a negative refracting power, and the fourth lens is a meniscus lens having a positive refracting power and a convex surface facing the fifth lens And the fifth lens 双 has a positive diopter lenticular lens. In addition, the fourth lens and the fifth lens have an average refractive index greater than 1.7, and the distance between the first lens and the second lens is less than 0.5 cm, and F4/ F< 1.2, where ρ45 is the combined focal length of the fourth lens and the fifth lens, and F is the effective focal length of the fixed focus lens. In one embodiment of the invention, the first lens and the second lens are 200819781 π/jD 21777 twf The combined focal length of .doc/n is F12, and 0.5 < F/F12 < 2. In one embodiment of the invention, the sum of the Abbe numbers of the fourth lens and the fifth lens is greater than 70. In an embodiment of the invention, the spacing between the second lens and the third lens is less than 1 cm. In an embodiment of the invention, the first lens is an aspherical lens. In the embodiment of the invention, the first lens is a plastic lens. In an embodiment of the invention, the first lens, the second lens, the third lens, the fourth lens and the fifth lens are spherical lenses. The lens combination of the fixed-focus lens invented by % can shorten the distance between the first lens and the second lens before maintaining a good image, and then reduce the total length of the fixed-focus lens. In addition, limiting F45/F<12 can make the fixed refractive lens better refractive power, and further shorten the total length of the fixed-focus lens;;= the two lens groups are positive and the 丨 can be effectively eliminated ( Aberration). The above and other objects, features, and advantages of the present invention will become more apparent from the embodiments of the invention. A schematic diagram of the structure of a fixed focus lens. Referring to Figure 2, the fixed focus lens includes a first lens group 210 and a lens group 220. The first lens group 21G has a positive refracting power, and the 7th 200819781 1^1735 21777 twf.doc/n mirror group 210 is a first lens 212 and a second lens 214 which are sequentially arranged from an object side to an image side. composition. The first lens 212 is a meniscus lens having a negative refracting power and having a convex surface facing the second lens 214, and the second lens 214 is a lenticular lens having a positive refracting power. Further, the second lens group 220 has a positive refractive power and is disposed between the first lens group 2丨〇 and the image side=. The second lens group 220 is composed of a second lens 222, a fourth lens 224 and a fifth lens 226 which are sequentially arranged from the object side to the image side. ^, the three lens 222 is a biconcave lens having a negative refracting power, the fourth lens 224 is a meniscus lens having a positive refracting power and the convex surface faces the fifth lens 226, and the fifth lens 226 is a lenticular lens having a positive refracting power. In order to shorten the length of the fixed-focus lens 200 and maintain good image quality, it is necessary to limit the refractive index of the fourth lens 224 and the fifth lens 226 to be greater than 1.7, and the distance between the first lens 212 and the second lens 214 is smaller than 0·5 cm, the pitch refers to the straight distance between the lens centers of the two lenses, and Fe/FCU, where F45 is the combined focal length of the fourth lens 224 and the fifth lens 226, and ρ is the fixed focus lens 2〇〇 Effective focal length. In this embodiment, by the combination of the above five lenses, the fixed focus lens 200 can shorten the spacing between the first lens 212 and the second lens 214 while maintaining good image quality, thereby enabling the fixed focus The overall length of the lens 2〇〇 is shortened. Thus, when the fixed focus lens 2 is applied to an image device such as a projection device, a digital camera, and a mobile phone, since the space occupied by the fixed focus lens 200 is small, the volume of the image device can be reduced. . In addition, limiting F^/FC 1.2 allows the fixed focus lens 200 to have a better refractive power' to further shorten the total length of the fixed focus lens 2〇〇. In addition, the PT735 21777 twf.doc/n has a positive diopter of the first lens group 210 and the second lens group 22, which can effectively eliminate aberrations. To further eliminate aberrations and ensure the imaging quality of the fixed-focus lens 2, 0.5 < F/F12 < 2 may be defined in the present embodiment, where F12 is the combined focal length of the first lens 212 and the second lens 214. In addition, the fourth lens 224 and the fifth lens may be restricted to eliminate dimmatic aberrations.
的阿貝數之和大於70。另夕卜為消除球面像差，第一透鏡 212可使用非球面透鏡。此非球面透鏡可選用較便宜的塑 膠透鏡，以降低定焦鏡頭200的生產成本。再者，為了進 :步縮短定焦鏡頭200的總長，可限制第二透鏡214盥第 二透鏡222之間的間距小於1公分。 ’、 -較佳實鏡頭2〇0應用於一投難置之第 ，例’其有效焦距為22·464毫米(贿），且 例的所有透鏡皆為球面透鏡。然而，此有效隹 ===表一及㈣所列的數據資料並^ 後’當可對其參數或設定作適當的更^ 之 發明之範疇内。 淮，、仍應屬於本The sum of the Abbe numbers is greater than 70. In addition, to eliminate spherical aberration, the first lens 212 may use an aspherical lens. This aspherical lens can be used with a less expensive plastic lens to reduce the production cost of the fixed focus lens 200. Furthermore, in order to shorten the total length of the fixed focus lens 200, the spacing between the second lens 214 and the second lens 222 may be limited to less than 1 cm. ', - The better real lens 2 〇 0 is applied to the first difficulty, for example, the effective focal length is 22·464 mm (bribe), and all the lenses of the example are spherical lenses. However, this valid 隹 === the data listed in Tables 1 and 4 is within the scope of the invention for its parameters or settings. Huai, still should belong to this
9 200819781 . PT735 21777twf.doc/n S4 -49.6643 7.5762 \ \ S5 -10.9243 0.8387 1.85 23.8 第三透鏡 S6 24.4557 1.3901 \ \ S7 -33.3566 —------- 6.3175 1.77 49.6 第四透鏡 S8 -13.4103 0.2000 \ \ S9 25.6536 4.1735 1.77 49.6 第五透鏡 S10 -50.1324 1.0000 \ \ S11 無限大 20.0000 1.65 33.8 棱鏡 S12 無限大 0.6000 \ \ S13 無限大 0.7000 1.52 81 保護罩 S14 無限大 0.5000 〈表一〉 Ο 在表一中，間距是指兩相鄰表面間於主軸上之直線距 離，舉例來說，表面S1之間距，即表面S1至表面S2間 於主軸上之直線距離。備註攔中各透鏡所對應之厚度、折 射率與阿貝數請參同列中各間距、折射率與阿貝數對應之 數值。此外，在表一中，表面si、S2為第一透鏡212的 兩表面，表面S3、S4為第二透鏡214之兩表面，表面S5、 S6為第三透鏡222之兩表面，表面S7、S8為第四透鏡224 之兩表面，而表面S9、S10為第五透鏡226之兩表面。表 面Sll、S12為稜鏡300之兩表面，而表面S13、S14為用 於保護如數位微鏡裝置(digital micro-mirror device，DMD) 等顯像元件500之保護罩400的兩表面。有關於各表面之 10 200819781 PT735 21777twf.doc/n 曲率半徑、間距等參數值，請參照表一，在此不再重述。 圖3A至圖3C是根據本發明第一較佳實施例之定焦鏡 頭的成像光學模擬數據圖。請參考圖3A至圖3C，其中圖 3A 為光學傳遞函數(m〇duiati〇n transfer functi〇n，MTF)曲 線圖，且其橫軸為每毫米的線對數(linepairper millimeter) ’ 縱轴為辨識率，圖 3B 為場曲（field curvature) 和畸變(distortion)圖，而圖3C為横向光線扇形圖(transverse9 200819781 . PT735 21777twf.doc/n S4 -49.6643 7.5762 \ \ S5 -10.9243 0.8387 1.85 23.8 Third lens S6 24.4557 1.3901 \ \ S7 -33.3566 —------- 6.3175 1.77 49.6 Fourth lens S8 -13.4103 0.2000 \ \ S9 25.6536 4.1735 1.77 49.6 Fifth lens S10 -50.1324 1.0000 \ \ S11 Infinite 20.0000 1.65 33.8 Prism S12 Infinite 0.6000 \ \ S13 Infinite 0.7000 1.52 81 Protective cover S14 Infinite 0.5000 <Table 1> Ο In Table 1 The spacing refers to the linear distance between two adjacent surfaces on the main axis. For example, the distance between the surfaces S1, that is, the linear distance between the surface S1 and the surface S2 on the main axis. For the thickness, refractive index and Abbe number of each lens in the remarks, please refer to the values corresponding to the spacing, refractive index and Abbe number in the same column. In addition, in Table 1, the surfaces si, S2 are the two surfaces of the first lens 212, the surfaces S3, S4 are the two surfaces of the second lens 214, and the surfaces S5, S6 are the two surfaces of the third lens 222, and the surfaces S7, S8 It is the two surfaces of the fourth lens 224, and the surfaces S9, S10 are the two surfaces of the fifth lens 226. The surfaces S11, S12 are the two surfaces of the crucible 300, and the surfaces S13, S14 are the surfaces of the protective cover 400 for protecting the developing element 500 such as a digital micro-mirror device (DMD). For the values of the parameters such as the radius of curvature and the spacing of each surface, please refer to Table 1, and I will not repeat them here. 3A to 3C are diagrams showing imaging optical simulation data of a fixed focus lens head according to a first preferred embodiment of the present invention. Please refer to FIG. 3A to FIG. 3C, wherein FIG. 3A is an optical transfer function (m〇duiati〇n transfer functi〇n, MTF) graph, and the horizontal axis thereof is a line pair per millimeter (linepairper millimeter) Rate, Figure 3B is the field curvature and distortion diagram, while Figure 3C is the transverse ray fan diagram (transverse)
ray fan plot)。從圖3A至圖3C的圖形可看出所測得的MTF f 曲線圖、場曲和畸變圖以及橫向光線扇形圖之圖形均在標 準的範圍内，因此第一較佳實施例的定焦鏡頭2〇〇具有良 好的成像品質。 以下内容將舉出定焦鏡頭200應用於投影裝置之第二 較佳實施例，其有效焦距為22.422毫米，且此第二較佳實 施例的第一透鏡212為非球面透鏡。此外，有關於表二中 各符號所表示的意思與表一相同，下文中將不再重述。需 注意的是，下述之實施例中列舉的數據資料並非用以限定 (J 本發明，任何熟習此項技術之人士在參照本發明之後，當 可對其參數或設定作適當的更動，惟其仍應屬於本發明之 範疇内。 表面 曲率半徑 (mm) 間距(mm) 折射率 阿貝數 備註 51 ----- 52 ----—— 二9.6479 0.9063 1.53 56 第一透鏡 ^25.4166 0.2000 200819781 (Ray fan plot). It can be seen from the graphs of FIG. 3A to FIG. 3C that the measured MTF f graph, the field curvature and the distortion map, and the pattern of the lateral ray fan graph are all within the standard range, so the fixed focus lens of the first preferred embodiment 2〇〇 has good imaging quality. In the following, a second preferred embodiment in which the fixed focus lens 200 is applied to a projection apparatus having an effective focal length of 22.422 mm is used, and the first lens 212 of this second preferred embodiment is an aspherical lens. In addition, the meanings indicated by the symbols in Table 2 are the same as those in Table 1, and will not be repeated below. It should be noted that the data listed in the following embodiments are not intended to be limiting (J. The present invention, any person skilled in the art, after referring to the present invention, may make appropriate changes to its parameters or settings, but It should still fall within the scope of the present invention. Surface Curvature Radius (mm) Spacing (mm) Refractive Index Abbe Number Remarks 51 ----- 52 ----—— Two 9.6479 0.9063 1.53 56 First Lens ^25.4166 0.2000 200819781 (
Fl 73i> 21777twf.doc/n S3 14.2047 '_ 2.6379 1.74 49.3 第二透鏡 S4 -20.3307 6.9595 S5 -7.9916 ——_ 2.2585 , 1.85 23.8 第三透鏡 S6 34.1385 ----^ 1.2797 S7 -37.2829 ----^ _ 5.1026 1.74 49.3 第四透鏡 S8 -12.1209 —____ _ 0.2000 _ S9 28.2176 *__ _ 4.8735 1.74 49.3 第五透鏡 S10 -34.7052 -----__ _ 1.8414 S11 無限大 _20.0000 1.65 33.8 稜鏡 S12 無限大 —_____ _ 0.6000 S13 無限大 —〜----- _ 0.7000 1.52 81 保護罩 S14 無限大 0.5000 〈表二〉 上述之表面Si、S2為非球面，而非球面的公式如下：Fl 73i> 21777twf.doc/n S3 14.2047 '_ 2.6379 1.74 49.3 Second lens S4 -20.3307 6.9595 S5 -7.9916 —— _ 2.2585 , 1.85 23.8 Third lens S6 34.1385 ----^ 1.2797 S7 -37.2829 ---- ^ _ 5.1026 1.74 49.3 Fourth lens S8 -12.1209 —____ _ 0.2000 _ S9 28.2176 *__ _ 4.8735 1.74 49.3 Fifth lens S10 -34.7052 -----__ _ 1.8414 S11 Infinity _20.0000 1.65 33.8 稜鏡S12 Infinite —_____ _ 0.6000 S13 Infinity—~------ _ 0.7000 1.52 81 Protective cover S14 Infinitely large 0.5000 <Table 2> The above surface Si and S2 are aspherical, and the formula of the non-spherical surface is as follows:
式中’Z為光轴方向之偏移量，c是密切球面（osculating sphere)的半徑之倒數，也就是接近光軸處的曲 表格内S卜S2的曲率半徑）的倒數。k田一 (conic)，r是非球面高度， 疋一人曲面係數 高度’而〜、a2、八3、a4、八:^鏡中心往透鏡邊緣的 coefficient)，係數八丨為〇。表三所砟壞面係數（难如 面S2的參數值。 Μ出的是表面S1與表 12 200819781 „ PT735 21777twf.doc/n 非球面 參數 二次曲面 係數k ---— 係數A: ^ --- 係數a3 係數a4 係數a5 S1 0 7.50031 E-04 -1.49704 E-05 — 6.65458E -08 2.44076 E-09 S2 0 7.4788Τ^ E-04 1.52227^ -05 ---—_ 1.27710E -07 1.79439 E-09 〈表三〉 Ο ο 圖4Α至圖4C是本發明第二較佳實施例之定焦鏡頭的 成像光學模擬數據圖。請參考圖4A至圖4C，其中圖4八 為光學傳遞函數曲線圖’圖4B為場曲和畸變圖，而圖4C 為橫向光線扇形圖。從圖4A至圖4C的圖形可看出所測得 的MTF曲線圖、場曲和畸變圖以及橫向光線扇形圖之圖 形均在標準的範圍内，因此第二較佳實施例之定焦鏡頭 2〇〇具有良好的成像品質。 綜上所述，本發明之定焦鏡頭至少具有下列優點. 1.本發明之定錄透鏡組合可在維持良好的成 像品質之前提下縮短第-透鏡及第二透鏡間的距 離，進而減少定焦鏡頭的總長。 2…限制FVFCL2可使定焦鏡頭有較佳的屈光能力， 以進一步縮短定焦鏡頭的總長。 正搭配的方式， 3·由於兩透鏡群的屈光度是採用正、 所以可有效消除像差。 4·限定〇.5<F/F12<2可有效消除像差。 5·限制第四透鏡與第五透鏡的阿貝數之和大於7 有效消除色差。 13 200819781 r i / jj 21777twf.doc/n 6·第一透鏡使用非球面鏡可消除球面像差。 雖然本發明已以較佳實施例揭露如上，然其並非用以 限定本發明，任何所屬技術領域中具有通常知識者，在不 脫離本發明之精神和範圍内，當可作些許之更動與潤飾， 因此本發明之保護範圍當視後附之申請專利範圍所界定者 為準。 【圖式簡單說明】 〇 圖1是習知一種定焦鏡頭的結構示意圖。 圖2是本發明一實施例之定焦鏡頭的結構示意圖。 圖3A至圖3C是根據本發明第一較佳實施例之定焦鏡 頭的成像光學模擬數據圖。 圖4A至圖4C是本發明第二較佳實施例之定焦鏡頭的 成像光學模擬數據圖。 【主要元件符號說明】 100 :定焦鏡頭 110 :第一透鏡 120 :第二透鏡 130 :第三透鏡 140 :第四透鏡 150 :第五透鏡 _ 200 :定焦鏡頭 210 :第一透鏡群 14 200819781 PT735 21777twf.doc/n 212 :第一透鏡 214 ·•第二透鏡 220 :第二透鏡群 222 :第三透鏡 224 :第四透鏡 226 :第五透鏡 300 ·•稜鏡 400 :保護罩 500 :顯像元件 S1〜S14 :表面Where 'Z is the offset of the optical axis direction, and c is the reciprocal of the radius of the osculating sphere, that is, the reciprocal of the radius of curvature of the Sb S2 in the curved table near the optical axis. k田一 (conic), r is the aspherical height, 疋 one person's surface coefficient height 'and ~, a2, eight 3, a4, eight: ^ the center of the mirror to the edge of the lens), the coefficient is eight. Table 3 is the coefficient of bad surface (difficult to the parameter value of surface S2. The surface is S1 and Table 12 200819781 „ PT735 21777twf.doc/n aspheric parameter quadratic coefficient k --- — coefficient A: ^ --- Coefficient a3 Coefficient a4 Coefficient a5 S1 0 7.50031 E-04 -1.49704 E-05 — 6.65458E -08 2.44076 E-09 S2 0 7.4788Τ^ E-04 1.52227^ -05 ----_ 1.27710E -07 1.79439 E-09 <Table 3> ο ο FIG. 4A to FIG. 4C are diagrams showing imaging optical simulation data of the fixed focus lens according to the second preferred embodiment of the present invention. Please refer to FIG. 4A to FIG. 4C, wherein FIG. The function graph 'Fig. 4B is the field curvature and distortion map, and Fig. 4C is the transverse ray sector diagram. From the graphs of Fig. 4A to Fig. 4C, the measured MTF graph, field curvature and distortion map, and lateral ray fan shape can be seen. The figure of the figure is within the standard range, so the fixed focus lens 2 of the second preferred embodiment has good imaging quality. In summary, the fixed focus lens of the present invention has at least the following advantages. The combination of the recording lens can reduce the distance between the first lens and the second lens before maintaining good image quality. , in turn, reduce the total length of the fixed-focus lens. 2... Limit FVFCL2 to make the fixed-focus lens have better refractive power to further shorten the total length of the fixed-focus lens. Positive matching method, 3. Because the diopter of the two lens groups is adopted Positive, so the aberration can be effectively eliminated. 4·Limited 5.5<F/F12<2 can effectively eliminate the aberration. 5. Limit the sum of the Abbe numbers of the fourth lens and the fifth lens to be greater than 7 to effectively eliminate the chromatic aberration. 200819781 ri / jj 21777twf.doc/n 6. The first lens uses an aspherical mirror to eliminate spherical aberration. Although the invention has been disclosed in the preferred embodiments as above, it is not intended to limit the invention, and is not in any art. In general, the scope of protection of the present invention is defined by the scope of the appended claims, and the scope of the invention is subject to the scope of the invention. 1 is a schematic structural view of a conventional fixed focus lens. Fig. 2 is a schematic structural view of a fixed focus lens according to an embodiment of the present invention. Figs. 3A to 3C are fixed focus mirrors according to a first preferred embodiment of the present invention. Fig. 4A to Fig. 4C are diagrams showing imaging optical simulation data of a fixed focus lens according to a second preferred embodiment of the present invention. [Main component symbol description] 100: Fixed focus lens 110: First lens 120 : second lens 130 : third lens 140 : fourth lens 150 : fifth lens _ 200 : fixed focus lens 210 : first lens group 14 200819781 PT735 21777 twf.doc / n 212 : first lens 214 · • second lens 220: second lens group 222: third lens 224: fourth lens 226: fifth lens 300 • • 稜鏡 400: protective cover 500: developing elements S1 to S14: surface