TW293121B

TW293121B - Optical pick-up head of CD-ROM drive

Info

Publication number: TW293121B
Application number: TW85102902A
Authority: TW
Inventors: chao-ju Zhu; Tsong-Ming Yang; Jong-Kae Jang
Original assignee: Ind Tech Res Inst
Priority date: 1996-03-08
Filing date: 1996-03-08
Publication date: 1996-12-11

Abstract

An optical pick-up head of CD-ROM drive comprises of: (1) one first part with one first aspherical used to make one beam with predetermined wavelength passed through the first part focus on one first focus; (2) one second part with one second aspherical used to make one beam with predetermined wavelength passed through the second part focus on one second focus; (3) one third part with one third aspherical, the first part decides numerical aperture of the third part, i.e. numerical aperture is decided by the most convergent angle of beam, used to make one beam with predetermined wavelength passed through the third part focus on the first focus; (4) one fourth part with one fourth aspherical, the second part decides numerical aperture of the fourth part, used to make one beam with predetermined wavelength passed through the fourth part focus on the second focus.

Description

經濟部中央標準局員工消費合作社印製 A7 B7 五、發明説明（1 ) 本發明是有關於一種光碟機之光學讀取頭（Optical Pick-up Head)，且特別是有關於一種應用在高密度數位影音光碟機（DVD)之光學讀取頭中，既能讀取SD (Super Density Compact Disc也簡稱SDCD)光碟片，又能和傳統 CD(C〇mpaCt Disc)光碟片相容，且具有雙焦點(Dual Focus) 特性的物鏡(Objective Lens)。光碟片由於具有儲存容量大，易保存，資料不易損害… 等優點，已逐漸成爲現代人不可或缺的媒體之一，例如：播放音樂的CD_Audio光碟片，可同時播放影像及音樂的 Video CD、CD-I、CD-R光碟片，以及存放電腦檔案資料的CD-ROM光碟片等，尤其使用在電腦周邊設備中更是普遍。再由於雷射光電產品之生產製造技術以及多媒體影音壓縮技術日愈成熟，更高密度的光碟片已成爲必然的趨勢。要製作更高密度的光碟片意味著須有超高的光學解析度，而解析度與光波的長短以及物鏡的數値孔徑(Numerical Aperture簡稱ΝΑ)有關係，也就是愈短的波長及愈大的數値孔徑，其解析度愈好。但是愈大的數値孔徑，容易因光碟片輕微傾斜而造成讀取的像差，解決的辦法就是光碟片基底（Substrate)的厚度必須盡量的薄。在新一代的高密度數位影音光碟機中，其光碟片的規格有 MMCD(Multi-Media Compact Disk)光碟片和 SD 光碟片兩種，目前初步整合規格的結果，光碟片的物理規格將採用SD光碟片的規格，亦即光碟片基底的厚度爲〇.6mm，使 3 本紙張尺度適用中國國家標準（CNS ) A4規格（210X297公釐） ~~~ I I I 裝 —II 訂 c-viv (請先閲讀背面之注意事項再填寫本頁) 經濟部中央標準局貝工消費合作社印裝顺Μ a7 B7 五、發明説明（2 ) 用物鏡的數値孔徑爲0.6，使用雷射光的波長爲65〇nm或 635nm。但是傳統CD光碟片，其光碟片基底的厚度爲 1.2mm，使用物鏡的數値孔徑爲0.45，使用雷射光的波長爲780nm，故必須發展出一種既能讀取SD光碟片，又能讀取CD光碟片的雙焦點光學讀取頭，才能使高密度數位影音光碟機也能和已佔有廣大市場之CD光碟片相容。由於高密度數位影音光碟機的規格才剛確立不久，目前在幾次國內外相關展覽及發表會中，歸納有關雙焦點光學讀取頭習知的技藝有三：雙物鏡切換法、H〇E(H〇l〇graphiC Optical Element)分焦法、以及物鏡HOE分焦法，其優缺點簡述如下= 第1圖是習知的一種依照雙物鏡切換法之雙焦點光學讀取頭之示意圖。請參照第1圖，該光學讀取頭具有兩個不同焦點之物鏡，即適用於SD光碟片之大數値孔徑、短焦距物鏡12和適用於CD光碟片之小數値孔徑、長焦距物鏡 14，其主要動作原理乃是依靠機械動作來切換’亦即根據使用的光碟片種類，適當地切換所使用的物鏡’來達到具有雙焦點的功能。因爲使用兩個單一焦點物鏡，其光路能量的使用效率最高，但是有如下的缺點： a. 需配合物鏡致動器做切換，機構非常複雜’也增加組裝的困難度。 b. 需再加上切換的感知控制設備’以及須有兩個物鏡’ 成本較高。第2a和2b圖是習知的一種HOE分焦法之光學聚焦示 4 本紙張尺度適用中國國家標準（CNS ) A4规格（210X297公釐） --------^^-- (請先閲讀背面之注意事項再填寫本頁) 、tr 乂經濟部中央橾準局員工消費合作社印製 203121 at __B7____ 7、發明説明（3 ) 意圖。請參照第2a圖，所謂HOE分焦法，主要是在傳統的物鏡24前，加上一紋刻過的HOE元件22 ’通過HOE元件 22的零階光26，不會改變其方向，再通過物鏡24後，聚焦在薄基底的SD光碟片28上，其焦點較近。請參照第2b _，通過HOE元件22的一階光產生繞射現象’其方向向外發散，再通過物鏡24後，聚焦在厚基底的CD光碟片29上，其焦點較遠，因此零階光和一階光會有不同的焦點，達到雙焦點的目的。第2c圖是習知之一種HOE表面刻紋的切面圖。HOE 表面的紋刻主要目的是讓一階光發散而改變方向，零階光通過不變方向，理論上HOE表面的紋刻應使用多階梯形，光路效率較好，但製作上一般只使用四階。 HOE分焦法不須使用雙物鏡來切換，機構較簡單，且在零階光下，其解析度相當高，但是有如下的缺點： a. 爲了提昇光路效率，以及簡化製作的複雜度，雙重考量下，使用4階梯形，但HOE製程仍然相當複雜。 b. 4階梯形，仍然有大約24%的部份能量損失。第3a圖是習知的一種物鏡HOE分焦法之光學聚焦示意圖。請參照第3a圖，其和上述HOE分焦法之不同處’只是將HOE刻紋直接做在物鏡30上，其動作原理完全相同，也是利用零階光和一階光會有不同的焦點，達到雙焦點的目的。A7 B7 printed by the Staff Cooperative of the Central Bureau of Standards of the Ministry of Economic Affairs 5. Description of the invention (1) The present invention relates to an optical pick-up head of an optical disc drive, and in particular to an application in high density The optical pick-up head of the digital audio-visual disc drive (DVD) can not only read SD (Super Density Compact Disc, also referred to as SDCD) discs, but also compatible with traditional CD (C〇mpaCt Disc) discs, and has dual Objective lens with dual focus characteristics. Optical discs have gradually become one of the indispensable media for modern people due to their advantages of large storage capacity, easy storage, and easy damage to data. For example: CD_Audio discs for playing music, Video CDs that can play video and music at the same time, CD-I, CD-R discs, and CD-ROM discs that store computer file data, etc., are especially common in computer peripherals. Furthermore, as the manufacturing technology of laser photoelectric products and multimedia audio-visual compression technology become more mature, higher-density optical discs have become an inevitable trend. To make a higher-density optical disc means that it needs ultra-high optical resolution, and the resolution is related to the length of the light wave and the numerical aperture of the objective lens (Numerical Aperture referred to as NA), that is, the shorter the wavelength and the larger The resolution of the numerical aperture is better. However, the larger the numerical aperture, the easier the aberration of reading due to the slight tilt of the disc. The solution is to make the substrate thickness of the disc (Substrate) as thin as possible. In the new generation of high-density digital audio and video drives, the specifications of the optical discs are MMCD (Multi-Media Compact Disk) discs and SD optical discs. At present, the result of preliminary integration of the specifications, the physical specifications of the optical discs will use SD The specification of the optical disc, that is, the thickness of the optical disc substrate is 0.6mm, so that the three paper standards are applicable to the Chinese National Standard (CNS) A4 specification (210X297mm) ~~~ III Pack—II order c-viv (please first Read the precautions on the back and then fill out this page) Printed by the Beigong Consumer Cooperative of the Central Bureau of Standards of the Ministry of Economic Affairs M a7 B7 V. Description of the invention (2) The numerical aperture of the objective lens is 0.6, and the wavelength of the laser light is 65〇nm Or 635nm. However, for traditional CD discs, the thickness of the disc substrate is 1.2mm, the numerical aperture of the objective lens is 0.45, and the wavelength of the laser light is 780nm, so it is necessary to develop a method that can read both SD discs and The dual-focus optical pickup head of the CD disc can make the high-density digital audio-visual drive compatible with the CD discs that have occupied the broad market. Since the specifications of high-density digital audio and video disc players have just been established, at present, in several domestic and foreign related exhibitions and conferences, there are three techniques that are known about the dual-focus optical pickup head: dual objective lens switching method, H〇E (H 〇l〇graphiC Optical Element) defocusing method, and objective lens HOE defocusing method, its advantages and disadvantages are briefly described as follows = Figure 1 is a schematic diagram of a conventional dual-focus optical pickup head according to the dual-objective lens switching method. Please refer to Fig. 1, the optical pickup has two objective lenses with different focal points, that is, the large numerical aperture, short focal length objective lens 12 suitable for SD discs and the small numerical aperture, long focal length objective lens 14 suitable for CD discs The main action principle is to rely on mechanical action to switch 'that is, according to the type of optical disc used, switch the objective lens used appropriately' to achieve the function of dual focus. Because of the use of two single-focus objectives, the efficiency of the optical path energy is the highest, but it has the following disadvantages: a. Need to cooperate with the objective lens actuator to switch, the mechanism is very complicated 'also increases the difficulty of assembly. b. The need to add a switched sensing control device and two objective lenses are more expensive. Figures 2a and 2b are the optical focusing of a conventional HOE defocusing method. 4 The paper scale is applicable to the Chinese National Standard (CNS) A4 specification (210X297mm) -------- ^^-(please Read the precautions on the back before filling out this page), printed by the Employee Consumer Cooperative of the Central Central Bureau of Economics of the Ministry of Economy 203121 at __B7____ 7. Invention description (3) Intent. Please refer to Fig. 2a. The so-called HOE defocusing method is mainly to add a patterned HOE element 22 'in front of the traditional objective lens 24' through the zero-order light 26 of the HOE element 22, without changing its direction, and then pass After the objective lens 24, it is focused on the SD optical disc 28 with a thin substrate, and its focus is relatively close. Please refer to section 2b_, the first-order light passing through the HOE element 22 produces a diffractive phenomenon whose direction diverges outwards, and then passes through the objective lens 24, focusing on the thick substrate CD disc 29, the focus of which is far, so the zero order Light and first-order light will have different focal points to achieve the purpose of bifocal. Figure 2c is a cross-sectional view of a conventional HOE surface engraving. The main purpose of the embossing on the HOE surface is to diverge the first-order light and change the direction. The zero-order light passes through the same direction. In theory, the embossing on the HOE surface should use a multi-step shape, and the optical path efficiency is better, but generally only four Level. HOE defocusing method does not need to use double objective lens to switch, the mechanism is relatively simple, and its resolution is very high under zero-order light, but has the following disadvantages: a. In order to improve the efficiency of the optical path and simplify the complexity of production, double In consideration, the 4-step shape is used, but the HOE process is still quite complicated. b. 4 stepped, there is still some 24% energy loss. Figure 3a is a schematic diagram of optical focusing of a conventional objective lens HOE defocusing method. Please refer to Figure 3a, which is different from the HOE defocusing method described above, except that the HOE engraving is directly made on the objective lens 30, and the action principle is exactly the same. Also, the zero-order light and the first-order light will have different focal points. To achieve the purpose of dual focus.

第3b圖是習知的一種依照物鏡HOE分焦法之雙焦點光學讀取頭之示意圖。首先光由雷射二極體32發出’經過BS 5 本紙張尺度適用中國國家標準（CNS ) A4规格（2丨0X297公釐） ---------{政— (請先閎讀背面之注意事項再填寫本頁) 訂經濟部中央標準局員工消費合作社印製 A7 B7 五、發明説明（4 ) 分光鏡34反射後，通過有HOE刻紋的物鏡36，因爲繞射現象，一階光聚焦在厚基底的CD光碟片39上，其焦點較遠，而零階光聚焦在薄基底的SD光碟片38上，其焦點較短，反射回來的光，經過有HOE刻紋的物鏡36，直接通過 BS分光鏡34，將光碟片上〇與1資料忠實反映在光感應器 35上。第3b圖和第3a圖所舉之例子，不同之處在於射入物鏡的光’第3a圖是平行光，而第3b圖是由點光源所發出。物鏡HOE分焦法整合HOE元件以及物鏡，機構更爲簡單，甚至可使用原先用在CD光碟片的機構，零階光下，其解析度相當高，但是有如下的缺點： a.將HOE刻紋直接做在物鏡上，製程更爲複雜且困難度更高。 b_只要是使用HOE分焦的原理，仍然有大約24%的部份能量損失。因此本發明的主要目的就是在提供一種光碟機光學讀取頭之物鏡，使新一代數位影音光碟機，具有雙焦點的功能，能讀取SD光碟片也能和現存之CD光碟片相容。本發明的另一主要目的就是在提供一種光碟機光學讀取頭之物鏡，能夠簡化數位影音光碟機之雙焦點光學讀取頭的機械結構，以利實際組裝，並提高組裝容許誤差。本發明的再另一主要目的就是在提供一種光碟機光學讀取頭之物鏡，能夠簡化數位影音光碟機之雙焦點光學讀取頭內的元件設計，使之生產容易，並降低成本。本發明的再另一主要目的就是在提供一種光碟機光學 6 本紙張尺度逋用中國國家;^準（CNS )八4规格（2丨0乂297公釐） '~~' (請先閲讀背面之注意事項再填寫本頁) 裝· 經濟部中央櫺準局員工消费合作社印製 A7 _ B7 五、發明説明（5 ) 讀取頭之物鏡，能夠避免習知HOE分焦法之能量損失問題，使光路之能量效率充分發揮。爲達成本發明之上述和其他目的，一種光碟機光學讀取頭之物鏡包括：一第一部份，具有一第一非球面，用以使通過該第一部份之一預定波長之光，聚焦在一第一焦點上；一第二部份，具有一第二非球面，用以使通過該第二部份之該預定波長之光，聚焦在一第二焦點上；一第三部份，具有一第三非球面，該第三非球面和該第一非球面具有相同之非球面特性係數及中心厚度，且該第一部份決定該第三部份之數値孔徑，即數値孔徑爲光束最大收斂角所決定，用以使通過該第三部份之該預定波長之光’聚焦在該第一焦點上；以及一第四部份’具有一第四非球面，該第四非球面和該第二非球面具有相同之非球面特性係數及中心厚度，且該第二部份決定該第四部份之數値孔徑’用以使通過該第四部份之該預定波長之光’聚焦在該第二焦點上。爲達成本發明之上述和其他目的’另一種光碟機光學讀取頭之物鏡包括一凸透鏡以及一區域發散透鏡’該區域發散透鏡包括：一第一部份，具有—第一非球面，用以使通過該第一部份和該凸透鏡之一預定波長之光，聚焦在一第一焦點上；以及一第二部份，具有一第二非球面，用以使通過該第二部份和該凸透鏡之該預定波長之光’聚焦在一第二焦點上；一第三部份，具有一第三非球面，該第二非球面和該第一非球面具有相同之非球面特性係數及中心厚 7 本紙張尺度適财關家鮮（CNS)A4· (210x297公^ " I 1^11111^ —II 訂 II II 人冰 (請先閲讀背面之注意事項再填寫本頁)Figure 3b is a schematic diagram of a conventional bifocal optical pickup head according to the objective lens HOE defocusing method. First of all, the light is emitted by the laser diode 32 'After passing BS 5 The paper standard is applicable to the Chinese National Standard (CNS) A4 specification (2 丨 0X297mm) --------- {政 — (please read first (Notes on the back and then fill out this page) Order A7 B7 printed by the Employee Consumer Cooperative of the Central Bureau of Standards of the Ministry of Economic Affairs 5. Description of the invention (4) After the beam splitter 34 is reflected, it passes through the objective lens 36 with HOE engraving. The first-order light is focused on a thick-based CD disc 39 with a relatively far focus, while the zero-order light is focused on a thin-based SD disc 38 with a short focus and the reflected light passes through an HOE-scored objective lens 36. Directly pass the BS beam splitter 34 to faithfully reflect the data of 0 and 1 on the optical disc on the light sensor 35. The example shown in Figure 3b and Figure 3a differs in that the light entering the objective lens' Figure 3a is parallel light, and Figure 3b is emitted by a point light source. The objective lens HOE defocusing method integrates the HOE element and objective lens, the mechanism is simpler, and even the mechanism originally used on CD discs can be used. Under zero-order light, its resolution is quite high, but it has the following disadvantages: a. The pattern is made directly on the objective lens, the process is more complicated and more difficult. b_ As long as the principle of HOE defocusing is used, there is still about 24% energy loss. Therefore, the main purpose of the present invention is to provide an objective lens for an optical pickup of an optical disc drive, so that a new generation of digital audio-visual optical disc drive has a dual focus function, can read SD optical discs and is compatible with existing CD optical discs. Another main object of the present invention is to provide an objective lens for an optical pickup head of an optical disc drive, which can simplify the mechanical structure of the bifocal optical pickup head of the digital audio-visual optical disc drive, so as to facilitate actual assembly and improve assembly tolerance. Still another main object of the present invention is to provide an objective lens for an optical pickup head of an optical disc drive, which can simplify the design of components in a bifocal optical pickup head of a digital audio-visual optical disc drive, making it easy to produce, and reducing costs. Yet another main purpose of the present invention is to provide an optical disk drive for optical 6-sheet paper using the Chinese national standard; ^ quasi (CNS) 84 specifications (2 丨 0 侂 297mm) '~~' (please read the back first Please pay attention to this page and then fill out this page) Outfit · A7 _ B7 printed by the Employee Consumer Cooperative of the Central Bureau of Economic Development of the Ministry of Economic Affairs 5. Invention Description (5) The objective lens of the reading head can avoid the energy loss problem of the conventional HOE defocusing method, Make full use of the energy efficiency of the light path. To achieve the above and other objects of the invention, an objective lens of an optical pickup head of an optical disc drive includes: a first part having a first aspheric surface for passing light of a predetermined wavelength passing through the first part, Focusing on a first focal point; a second part with a second aspheric surface for focusing the light of the predetermined wavelength passing through the second part on a second focal point; a third part With a third aspherical surface, the third aspherical surface and the first aspherical surface have the same aspherical surface characteristic coefficient and center thickness, and the first part determines the numerical aperture of the third part, ie the numerical value The aperture is determined by the maximum convergence angle of the light beam, used to focus the light of the predetermined wavelength passing through the third part on the first focal point; and a fourth part has a fourth aspheric surface, the fourth The aspherical surface and the second aspherical surface have the same aspherical surface characteristic coefficient and center thickness, and the second portion determines the numerical aperture of the fourth portion to allow the predetermined wavelength to pass through the fourth portion The light 'is focused on this second focus. In order to achieve the above and other objects of the invention, the objective lens of another optical pickup head of an optical disc drive includes a convex lens and a regional divergent lens. The regional divergent lens includes: a first part having a first aspheric surface for Causing a predetermined wavelength of light passing through the first part and the convex lens to focus on a first focal point; and a second part having a second aspheric surface for passing the second part and the The light of the predetermined wavelength of the convex lens is focused on a second focal point; a third part has a third aspherical surface, the second aspherical surface and the first aspherical surface have the same aspherical surface characteristic coefficient and center thickness 7 This paper is suitable for CNS A4 · (210x297 public ^ " I 1 ^ 11111 ^ —II Order II II Renbing (please read the precautions on the back before filling this page)

經濟部中央標準局貝工消費合作社印製五、發明説明（6 ) 度，且該第一部份決定該第三部份之數値孔徑’即數値孔徑爲光束最大收斂角所決定，該第一部份和第三部份典型的例子就是一平面，用以使通過該第三部份和該凸透鏡之該預定波長之光，聚焦在該第一焦點上；以及一第四部份’ 具有一第四非球面，該第四非球面和該第二非球面具有相同之非球面特性係數及中心厚度’且該第二部份決定該第四部份之數値孔徑，用以使通過該第四部份和該凸透鏡之該預定波長之光，聚焦在該第二焦點上。爲讓本發明之上述和其他目的、特徵、和優點能更明顯易懂，下文特舉一較佳實施例，並配合所附圖式’作詳細說明如下1 圖式之簡單說明：第1圖是習知的一種依照雙物鏡切換法之雙焦點光學讀取頭之示意圖。第2a和2b圖是習知的一種HOE分焦法之光學聚焦示意圖。第2c圖是習知之一種HOE表面刻紋的切面圖。第3a圖是習知的一種物鏡HOE分焦法之光學聚焦示意圖。第3b圖是習知的一種依照物鏡HOE分焦法之雙焦點光學讀取頭之示意圖。第4圖是一種具有凸透鏡及平凹透鏡的雙焦點物鏡之光學聚焦示意圖。第5圖是一種具有二非球面的雙焦點物鏡之光學聚焦 8 本紙張尺度適用中國國家標準（CNS)A4規格（210X297公釐） --------{ 袭— (請先閲讀背面之注意事項再填寫本頁)Printed by the Beigong Consumer Cooperative of the Central Bureau of Standards of the Ministry of Economic Affairs 5. The invention description (6) degrees, and the first part determines the numerical aperture of the third part. That is, the numerical aperture is determined by the maximum beam convergence angle. A typical example of the first part and the third part is a plane for focusing the light of the predetermined wavelength passing through the third part and the convex lens at the first focal point; and a fourth part ' Has a fourth aspherical surface, the fourth aspherical surface and the second aspherical surface have the same aspherical surface characteristic coefficient and central thickness' and the second part determines the numerical aperture of the fourth part for passing The light of the predetermined wavelength of the fourth part and the convex lens is focused on the second focal point. In order to make the above-mentioned and other objects, features, and advantages of the present invention more obvious and understandable, a preferred embodiment is described below in conjunction with the attached drawings, which are described in detail as follows: 1 Brief description of the drawings: It is a schematic diagram of a conventional dual-focus optical pickup head according to the dual-objective lens switching method. Figures 2a and 2b are schematic diagrams of optical focusing of a conventional HOE defocusing method. Figure 2c is a cross-sectional view of a conventional HOE surface engraving. Figure 3a is a schematic diagram of optical focusing of a conventional objective lens HOE defocusing method. Figure 3b is a schematic diagram of a conventional bifocal optical pickup head according to the objective lens HOE defocusing method. Fig. 4 is a schematic diagram of optical focusing of a bifocal objective lens having a convex lens and a plano-concave lens. Figure 5 is an optical focus of a bifocal objective lens with two aspherical surfaces. The size of this paper is applicable to the Chinese National Standard (CNS) A4 specification (210X297 mm) -------- {袭 — (please read the back first (Notes to fill out this page)

•«I A7 B7 經濟部中央榡準局員工消費合作社印製五、發明説明（7 ) 示意圖。第6a圖是一種單一焦點非球面物鏡之正視圖。第6b圖是一種具有二非球面的雙焦點物鏡之正視圖。第6c圖是依照本發明之一種雙焦點非球面物鏡之正視圖。一第7圖是分析光通過第6a至6c圖之物_ ’ 份光的能量和光點大小的關係曲線圖° w 第8a圖是分析光通過第6b圖之物鏡’其的能量和光點大小的關係曲線圖。 /w 第8b圖是分析光通過第6c圖之物鏡’其長的能量和光點大小的關係曲線圖。 w ^ 第9a圖是分析依照本發明之第6c圖中物鏡上的分佈圖。 \/ 第9b圖是分析依照本發明之第6c圖中長焦、距光& 物鏡上的分佈圖。 t @ 第1〇圖是脚本額—較佳飾_ —種光碟機〜讀取頭之示意圖。第π圖是數種不同形式物鏡之像高與波面像、’、圖。 Μ* 。彳ΐ 一非球面透首先闡明本發明物鏡之理論及推論依擇1 鏡表面可以如下的數學式來表示： Ζ ： + Ah* +Bh6 +Chs +Dhi0 1+V1 - o+ + Eh12 + Fhu + Ghx6 + Hhn + Jh20 (1)• «I A7 B7 Printed by the Employee Consumer Cooperative of the Central Bureau of Economics of the Ministry of Economy V. Illustration of the invention (7). Figure 6a is a front view of a single-focus aspheric objective lens. Figure 6b is a front view of a bifocal objective with two aspheric surfaces. Figure 6c is a front view of a bifocal aspheric objective lens according to the present invention. Figure 7 is the analysis of the light passing through the objects in Figures 6a to 6c _ 'The relationship between the energy of the light and the size of the light spot ° w Figure 8a is the analysis of the energy and the size of the light spot passing through the objective in Figure 6b' Relationship graph. / w Figure 8b is a graph showing the relationship between the energy of the light passing through the objective lens of Figure 6c and its spot size. w ^ Figure 9a is an analysis of the distribution on the objective lens in Figure 6c according to the present invention. \ / FIG. 9b is an analysis of the distribution on the telephoto, objective & objective lens in FIG. 6c according to the present invention. t @ 第 10 图 is a schematic diagram of the script amount-better decoration--kind of optical disc drive ~ reading head. Figure π is the image height and wavefront image of several different forms of objective lens. Μ *. Firstly, the theory and inference of the objective lens of the present invention are first explained by the aspheric surface. The surface of the mirror can be expressed by the following mathematical formula: Z: + Ah * + Bh6 + Chs + Dhi0 1 + V1-o + + Eh12 + Fhu + Ghx6 + Hhn + Jh20 (1)

---------ί ·裝-- (請先閲讀背面之注意事項再填寫本頁) -訂本紙張尺度適用中國國家揉準（CNS ) A4规格（21 OX297公釐）經濟部中央標準局負工消費合作社印製 A7 ____B7 五、發明説明（8 ) 式中 Z爲在z軸方向的座標値 c爲非球面表面之曲率(curvature) k爲圓錐曲線係數(conic coefficient) k=0 表示爲球面（sphere)--------- ί · Installation-- (Please read the precautions on the back before filling in this page) -The size of this paper is applicable to China National Standard (CNS) A4 (21 OX297mm) Ministry of Economic Affairs Printed by the Central Standards Bureau Negative Workers Cooperative A7 ____B7 V. Description of the invention (8) where Z is the coordinate in the z-axis direction and c is the curvature of the aspheric surface k is the conic coefficient k = 0 means sphere

-l<k<0表示爲橢圓面（ellipsoid) k=-l 表示爲拋物面（paraboloid) k<-l 表示爲雙曲面(hyperboloid) A，B,C，D，E，F,G,H，J 爲第4階、6階、8階、10階、12階、 14階、16階、18、20階變形係數 (deformation coefficient) h爲在xy平面和原點之距離，即h2=X2+Y2 故曲率、圓錐曲線係數、第4到20階偶數階之變形係數就唯一決定了一非球面透鏡的表面，在此簡稱上述係數爲非球面特性係數。而一非球面透鏡對某一特定波長的光之焦點可由該透鏡之材料特性、數値孔徑、表面的非球面特性係數、厚度…等來唯一決定。請參照第4圖，其繪示一種具有凸透鏡及平凹透鏡的雙焦點物鏡之光學聚焦示意圖。該物鏡由一凸透鏡40以及一平凹透鏡42組成，凸透鏡40之表面乃是一非球面，其依照上述原理設計成，當一預定波長的光射入時，會有較短的焦距，聚焦在只有厚的SD光碟片表面。當該預定波長的光束通過平凹透鏡42的平面部份44時，光束將循原方向前進，經過凸透鏡40聚焦後，仍然聚焦在SD光碟片表 10 本度適^中國®家標準（CNs7a4規格（210X297公釐1 —— (請先閲讀背面之注意事項再填寫本頁) •裝· 訂經濟部中央標準局員工消費合作社印聚 A7 B7 五、發明説明（9 ) 面；當該預定波長的光束通過平凹透鏡42的凹下部份46 時，光束將略爲發散，再經過凸透鏡4〇聚焦後’焦距會略爲拉長，適當地設計凹下部份46表面之非球面’可改變其焦距，使其聚焦在1.2mm厚的CD光碟片表面。請參照第5圖，其繪示一種具有二非球面的雙焦點物鏡之光學聚焦示意圖。該物鏡50在光入射之表面由一非球面部份52以及另一非球面部份54組成’非球面部份52乃是依照前述原理來設計，當一預定波長的光射入時，會聚焦在只有0.6mm厚的SD光碟片表面；當該預定波長的光束通過非球面部份54時，依照前述原理適當地設計非球面部份 54，使焦距略爲拉長，而聚焦在1.2mm厚的CD光碟片表面上。第4圖和第5圖說明了二種簡單的雙焦點物鏡之原理，其與本發明所使用之雙焦點物鏡的原理相同。要注意的是，由於本發明只使用同一光源，考慮SD和CD光碟片兩種規格，並要求光點的品質，光波波長就必須以較短波長 650nm或635nm，作爲設計時的依據。以下說明通過物鏡聚焦後，光點的大小及能量關係，並進一步介紹依照此原理，本發明之效果更佳的物鏡：一個有不同程度截斷面之局斯光束（Gauss Beam with Different Degrees of Truncation)，經過單一焦點物鏡聚焦後，其光點的大小（Spot Size) ’可以如下的式子表示： 2 SP0T_SIZE = 2xr = 2xCx— ⑵ 本紙張又度適用中國國家標準（CNS ) A4規格（210X297公釐） J -裝------訂------UV咏 (請先閲讀背面之注意事項再填寫本頁)-l < k < 0 means ellipsoid k = -l means paraboloid k < -l means hyperboloid A, B, C, D, E, F, G, H, J is the 4th, 6th, 8th, 10th, 12th, 14th, 16th, 18th, and 20th order deformation coefficients. H is the distance between the xy plane and the origin, that is, h2 = X2 + Y2 Therefore, the curvature, the conic curve coefficient, and the deformation coefficients of the 4th to 20th even-numbered orders uniquely determine the surface of an aspherical lens. The above-mentioned coefficients are referred to herein as aspherical characteristic coefficients. The focus of an aspheric lens on light of a specific wavelength can be uniquely determined by the material characteristics, numerical aperture, aspheric surface characteristic coefficient, thickness, etc. of the lens. Please refer to FIG. 4, which shows a schematic diagram of optical focusing of a bifocal objective lens having a convex lens and a plano-concave lens. The objective lens is composed of a convex lens 40 and a plano-concave lens 42. The surface of the convex lens 40 is an aspherical surface, which is designed according to the above principle, when a predetermined wavelength of light enters, there will be a shorter focal length, focusing on only thick SD disc surface. When the light beam of the predetermined wavelength passes through the flat portion 44 of the plano-concave lens 42, the light beam will proceed in the original direction, after being focused by the convex lens 40, it is still focused on the SD optical disc table. 210X297mm1-(please read the precautions on the back before filling in this page) • Binding · Order A7 B7 printed by the Consumer Cooperative of the Central Standards Bureau of the Ministry of Economic Affairs 5. Invention description (9); when the beam of the predetermined wavelength When passing through the concave portion 46 of the plano-concave lens 42, the light beam will diverge slightly, and after focusing by the convex lens 40, the focal length will be slightly elongated, and the aspheric surface of the concave portion 46 surface can be appropriately designed to change its focal length To focus on the surface of a 1.2mm thick CD disc. Please refer to Figure 5 which shows a schematic diagram of the optical focusing of a bifocal objective lens with two aspherical surfaces. The objective lens 50 consists of an aspherical surface on the surface where light is incident The part 52 and another aspherical part 54 form the 'aspherical part 52 is designed according to the aforementioned principle, when a predetermined wavelength of light enters, it will focus on the surface of the SD optical disc with a thickness of only 0.6mm; when the Pre When a light beam with a wavelength passes through the aspherical portion 54, the aspherical portion 54 is appropriately designed according to the aforementioned principle so that the focal length is slightly elongated and focused on the surface of the 1.2-mm-thick CD disc. Figures 4 and 5 The principles of two simple bifocal objectives are described, which are the same as the bifocal objectives used in the present invention. It should be noted that since the present invention only uses the same light source, two specifications of SD and CD discs are considered, and If the quality of the light spot is required, the wavelength of the light wave must be 650nm or 635nm with a shorter wavelength as the basis for design. The following describes the relationship between the size and energy of the spot after focusing through the objective lens, and further introduces the effect of the present invention according to this principle Better objective lens: A Gauss Beam with Different Degrees of Truncation, which is focused by a single focus objective, its spot size (Spot Size) can be expressed as follows: 2 SP0T_SIZE = 2xr = 2xCx— ⑵ This paper is again applicable to the Chinese National Standard (CNS) A4 specification (210X297mm) J -installed ------ ordered ------ UV chant (please read first Note the surface to fill out this page)

7 7 A B 經濟部中央橾準局員工消費合作社印製五、發明説明（10 ) 式中：NA=nSine ，是數値孔徑，也代表光束經透鏡聚焦之最大的聚焦收斂角度θ，η爲折射率 λ是光波波長 C是一個係數，與不同程度截斷面之高斯光束及在該大小之光點能量有關，C愈大代表光點大小愈大，其可由表1查得：表1 h2 0. 0.693 1. 1.2 1.5 2.0 3.0 4.5 8. FWHM 0.258 0.266 0.270 0.273 0.277 0.283 0.298 0.323 0.387 1/e2 0.409 0.424 0.431 0.435 0.442 0.455 0.482 0.526 0.643 第一繞射環 0.610 0.641 0.656 0.664 0.680 0.710 0.780 0.925 4r\f. m 表中：h是通過物鏡前高斯光束之截斷面參數 h2=0表示均勻光束，h2=0.693表示截斷面之高斯光束能量爲0.5 FWHM是通過物鏡聚焦後，光點能量爲1/2時 Ι/e2是通過物鏡聚焦後，光點能量爲l/e2(14%)時第一繞射環是通過物鏡後，產生第一個繞射光環時由第(2)式和表1可知，光點的大小與該大小光點之強度及能量有關。對光碟機之光學讀取頭這種應用來說，同一光點能量其光點大小當然是愈小愈好。本紙張尺度適用中國國家標準（CNS ) A4规格（210X297公釐） --------{•裝------訂------{紙 (請先閲讀背面之注意事項再填寫本頁) 經濟部中央標準局貝工消費合作社印製 A7 B7 五、發明説明（11 ) 第6a圖是單一焦點非球面物鏡之正視圖，其焦點設計在短焦距SD光碟片表面；第6b圖是一種具有二非球面的雙焦點物鏡之正視圖；第6c圖是依照本發明之一種雙焦點非球面物鏡之正視圖。第6b圖其動作原理已以第5圖說明，而第6c圖之雙焦點非球面物鏡比第6b圖增加了兩個部份，亦即該物鏡表面具有4個非球面部份，且由該物鏡正視圖來看，以近似同心圓的分佈形狀’由外至內依序爲第一部份6〇、第二部份62、第三部份64、以及第四部份66。適當地設計各部份之非球面特性係數、中心厚度及數値孔徑等，使第一部份60和第三部份64、第二部份62和第四部份66之非球面特性係數及中心厚度相同’且該第一部份決定該第三部份之數値孔徑，即數値孔徑爲光束最大收斂角所決定，該第二部份決定該第四部份之數値孔徑，則該物鏡內之各部份焦點就只有兩種，且由外至內依序變換焦點，亦即第一部份60和第三部份64之焦點相同，其數値孔徑皆爲0.6，焦距較短，會聚焦在只有〇.6mm厚的SD光碟片表面；而第二部份62和第四部份66之焦點相同，其數値孔徑皆爲0.35到0.43之間擇一，焦距較長，會聚焦在1.2mm 厚的CD光碟片表面，本實施例所選用的數値孔徑較 ΝΑ=0.45小的原因乃是使用了較短波長的光，其效果較好的緣故。光通過第6a至6c圖物鏡之短焦距部份，亦即通過第6a 圖透鏡的全部，或通過第6b圖物鏡的外圍部份61，或通過第6c圖物鏡的第一部份60和第三部份64後，其光的能量本紙張尺度適用中國國家標準（CNS > A4規格（210X297公釐） ^n·# «HI nn n . n^i - (請先閲讀背面之注意事項再填寫本頁) 訂 A7 ____B7 五、發明説明（12 ) 和大小的關係，可參看表2以及第7圖，表2是同上述第(2) 式光大小的係數表，第7圖詳細繪出各點光的能量和光點大小的關係曲線。表2 第6a圖第6b圖第6c圖 FWHM 0.544 0.432 0.470 1/e2 0.870 0 670 0.736 第一 0.8% 13% 6.22% 繞射環 (請先閱讀背面之注意事項再填寫本頁) .裝· 請參照表2以及第7圖，通過單一焦距物鏡的光關係曲線70，其幾乎完全沒有第一繞射環，但是在同能量的光點其光點最大；通過如第6b圖物鏡的外圍部份61的光關係曲線72，在同能量的光點其光點最小，但是有非常大的繞射環，大到幾乎不能接受；通過第6c圖物鏡的第一部份60 和第三部份64的光關係曲線74，其繞射環影響較小，且在同能量時，其光點大小也比一般的單一焦距透鏡小。表3是改變第6a至6c圖長焦距以及短焦距部份區域的大小比例，所得出光通過物鏡之短焦距部份的光點大小係數表。由表中可知，長焦距部份的直徑範圍，做些微的變化，亦即改變長焦距以及短焦距部份區域的大小比例，其對通過短焦距部份的光能量及大小影響並不大，最主要的本紙張尺度適用中國國家揉準（CNS > A4规格（210X297公釐）訂經濟部中央標準局員工消費合作社印裝 A7 五、發明説明（13 ) 決定性影響因素在於：如第6b圖提供2部份，或如6c圖提供4部份，而提供4部份或以上，其結果愈讓人滿意。 3 夷第6a圖第6b圖第6c圖 Shading region 4nt m 0.0- 2.62mm 0.0-3.0mm 2.62-2.〇mm 0.0-1.5mm 3 0-2.〇mm FWHM 0.544 0.432 0.412 0.470 0.460 1/e2 0.870 0.670 0.636 0.736 0.722 第一繞射環 0.8% 13% 14.6% 6.22% 5.04% Shading region:代表長焦距部份的直徑範圍，其對通過短焦距部份的光等效於遮蔽 ---------f ·裝-- (請先閲讀背面之注意事項再填寫本頁} 訂經濟部中央橾準局貝工消费合作社印製光通過第6b至6c圖物鏡之長焦距部份，亦即通過第6b 圖物鏡的圓心部份63，或通過第6c圖物鏡的第二部份62 和第四部份66後’其光的能量和光點大小的關係，可參看表4以及第8a和8b圖，表4是光通過第6b至6c圖物鏡之長焦距部份的光點大小係數表，第8a圖詳細繪出光通過第 6b圖之物鏡，其長焦距部份光的能量和光點大小的關係曲線圖，第8b圖詳細繪出光通過第&圖之物鏡，其長焦距部份光的能量和光點大小的關係曲線圖。由圖及表的結果可知，對長焦距部份光的能量和光點大小，幾乎沒有影響，本紙張尺度適用中國國家榡準（CNS ) A4规格（210X297公釐） A7 _ B7五、發明説明（14 ) 也幾乎看不到第一繞射環。表4 第6b圖第6c圖 Shading ΛττΤ Μ 1.5-2. 0mm region 物鏡 ΝΑ=0.38 NA=0.43 NA=0.38 NA=0.43 參數 D=2.62mm D=2.89mm D=2.62mm D-2.89mm FWHM 0.264 0.265 0.263 0.258 1/e2 0.419 0.422 0.422 0.412 第一 1.34% 1.26% 0.1% 0.4% 繞射環 {請先閲讀背面之注意ί項再填寫本頁) 裝- 經濟部中央橾準局員工消費合作社印策7 7 AB Printed by the Employee Consumer Cooperative of the Central Ministry of Economic Affairs of the Ministry of Economy V. Invention description (10) where: NA = nSine, which is a numerical aperture, and also represents the maximum focusing convergence angle θ of the beam focused by the lens, η is the refraction The rate λ is the wavelength of the light wave C is a coefficient, which is related to the Gaussian beams with different degrees of cross section and the energy of the spot at this size. The larger C represents the larger the spot size, which can be found in Table 1: Table 1 h2 0. 0.693 1. 1.2 1.5 2.0 3.0 4.5 8. FWHM 0.258 0.266 0.270 0.273 0.277 0.283 0.298 0.323 0.387 1 / e2 0.409 0.424 0.431 0.435 0.442 0.455 0.482 0.526 0.643 First diffraction ring 0.610 0.641 0.656 0.664 0.680 0.710 0.780 0.925 4r \ f.m In the table: h is the cut surface parameter of the Gaussian beam before the objective lens h2 = 0 indicates a uniform beam, h2 = 0.693 indicates that the energy of the Gaussian beam of the cut surface is 0.5 FWHM is after focusing through the objective lens, and the spot energy is 1/2 when Ι / After e2 is focused by the objective lens, and the spot energy is l / e2 (14%), the first diffraction ring is after the objective lens, and the first diffraction ring is generated. According to equation (2) and Table 1, the light spot The size of the light spot Degree and energy. For applications such as optical pickups for optical drives, the spot size of the same spot energy is of course the smaller the better. This paper scale is applicable to the Chinese National Standard (CNS) A4 specification (210X297mm) -------- {• installed ------ ordered ------ {paper (please read the note on the back first Please fill in this page again) A7 B7 printed by the Beigong Consumer Cooperative of the Central Bureau of Standards of the Ministry of Economic Affairs 5. Description of the invention (11) Figure 6a is a front view of a single-focus aspherical objective lens, the focus of which is designed on the surface of a short-focus SD disc; Figure 6b is a front view of a bifocal objective with two aspheric surfaces; Figure 6c is a front view of a bifocal aspheric objective according to the present invention. The operation principle of Fig. 6b has been explained with Fig. 5, and the bifocal aspherical objective lens of Fig. 6c has two additional parts compared to Fig. 6b, that is, the surface of the objective lens has 4 aspherical parts, and the From the front view of the objective lens, the approximately concentric circle distribution shape is the first part 60, the second part 62, the third part 64, and the fourth part 66 in order from the outside to the inside. Appropriately design the aspheric characteristic coefficients, center thickness and numerical aperture of each part, so that the aspheric characteristic coefficients of the first part 60 and the third part 64, the second part 62 and the fourth part 66 are The center thickness is the same 'and the first part determines the numerical aperture of the third part, that is, the numerical aperture is determined by the maximum beam convergence angle, and the second part determines the numerical aperture of the fourth part, then There are only two kinds of focal points in the objective lens, and the focal points are sequentially changed from the outside to the inside, that is, the focal points of the first part 60 and the third part 64 are the same, and their numerical apertures are all 0.6, and the focal length is relatively If it is short, it will focus on the surface of the SD optical disc with a thickness of only 0.6mm; and the focus of the second part 62 and the fourth part 66 are the same, and its numerical aperture is between 0.35 and 0.43, and the focal length is longer. It will focus on the surface of the 1.2mm thick CD disc. The reason why the numerical aperture selected in this embodiment is smaller than NA = 0.45 is because a shorter wavelength of light is used and its effect is better. The light passes through the short focal length part of the objective lens in Figs. 6a to 6c, that is, through the entire lens in Fig. 6a, or through the peripheral part 61 of the objective lens in Fig. 6b, or through the first part 60 and the first part of the objective lens in Fig. 6c. After the three parts are 64, the light energy of this paper is in accordance with Chinese National Standards (CNS & A4 specifications (210X297 mm) ^ n · # «HI nn n. N ^ i-(Please read the notes on the back first (Fill in this page) Order A7 ____B7 5. The relationship between the description of the invention (12) and the size, please refer to Table 2 and Figure 7, Table 2 is the coefficient table of the light size of the above formula (2), Figure 7 is drawn in detail The relationship between the energy of each point of light and the size of the spot. Table 2 Figure 6a Figure 6b Figure 6c Figure FWHM 0.544 0.432 0.470 1 / e2 0.870 0 670 0.736 First 0.8% 13% 6.22% Diffraction ring (please read the back side first Please pay attention to this page and then fill out this page.) · Install · Please refer to Table 2 and Figure 7, the light relationship curve 70 through a single focal length objective lens, it almost does not have the first diffraction ring, but the light spot at the same energy point Maximum; through the light relation curve 72 of the peripheral part 61 of the objective lens as shown in Fig. 6b, at the spot of the same energy The light spot is the smallest, but it has a very large diffraction ring, which is too large to be acceptable; through the light relationship curve 74 of the first part 60 and the third part 64 of the objective lens in Figure 6c, the influence of the diffraction ring is small , And at the same energy, its spot size is also smaller than that of a general single focal length lens. Table 3 is the ratio of the size of the parts of the long focal length and short focal length in Figures 6a to 6c, and the resulting light passes through the short focal length of the objective lens The light spot size coefficient table. It can be seen from the table that the diameter range of the long focal length part is slightly changed, that is, the size ratio of the long focal length and the short focal length part area is changed, and its effect on the light energy passing through the short focal length part The size of the paper is not significant, and the most important paper size is applicable to the Chinese National Standard (CNS > A4 specification (210X297 mm). Printed by the Ministry of Economic Affairs Central Standards Bureau Employee Consumer Cooperative A7 V. Invention description (13) Decisive impact The factors are: as shown in Figure 6b provides 2 parts, or as Figure 6c provides 4 parts, and provides 4 parts or more, the results are more satisfactory. 3 Yi 6a Figure 6b Figure 6c Figure Shading region 4nt m 0.0- 2.62 mm 0.0-3.0mm 2.62-2.〇mm 0.0-1.5mm 3 0-2.〇mm FWHM 0.544 0.432 0.412 0.470 0.460 1 / e2 0.870 0.670 0.636 0.736 0.722 First diffraction ring 0.8% 13% 14.6% 6.22% 5.04 % Shading region: represents the diameter range of the long focal length part, which is equivalent to the shielding of the light passing through the short focal length part --------- f · installation-(please read the precautions on the back before filling in This page} Order the Ministry of Economic Affairs Central Bureau of Precision Industry Beigong Consumer Cooperative to print light through the long focal length of the objective lens in Figures 6b to 6c, that is, through the central part 63 of the objective lens in Figure 6b, or through the objective lens in Figure 6c After the second part 62 and the fourth part 66, the relationship between the light energy and the spot size can be seen in Table 4 and Figures 8a and 8b. Table 4 is the long focal length part of the light passing through the objective lens in Figures 6b to 6c The spot size coefficient table of Fig. 8a details the light passing through the objective lens of Fig. 6b, the relationship between the energy of the long focal length of the light and the spot size, and Fig. 8b details the light passing through the objective of the & The graph of the relationship between the energy of the long focal length part of the light and the size of the light spot. It can be seen from the results of the graph and table that there is almost no effect on the energy and spot size of the light at the long focal length. The paper size is applicable to the Chinese National Standard (CNS) A4 specification (210X297 mm) A7 _ B7 V. Invention description ( 14) The first diffraction ring is hardly visible. Table 4 Figure 6b Figure 6c Shading ΛττΤΜ 1.5-2. 0mm region Objective ΝΑ = 0.38 NA = 0.43 NA = 0.38 NA = 0.43 Parameter D = 2.62mm D = 2.89mm D = 2.62mm D-2.89mm FWHM 0.264 0.265 0.263 0.258 1 / e2 0.419 0.422 0.422 0.412 First 1.34% 1.26% 0.1% 0.4% Diffraction ring (please read the notes on the back first and then fill out this page)

Shading region:代表短焦距部份的直徑範圍，其對通過長焦距部份的光等效於遮蔽 D:長焦距部份之直徑第9a圖是分析第6c圖中短焦距光能量的分佈圖，第9b 圖是分析第6c圖中長焦距光能量的分佈圖。歸納通過如第 6c圖所示之依照本發明之一種雙焦點非球面物鏡的光，其能量恰好完全應用，長焦距部份和短焦距部份互補，絲毫沒有損失，這與使用HOE分焦的原理’總是有大約24%的部份能量損失截然不同。如熟習此藝者可瞭解的，以上分析皆以單一雙焦點非球本紙張尺度適用中國國家榡準（CNS ) A4規格（210X297公釐）訂 -人經濟部中央標準局員工消費合作社印製 A 7 B7 五、發明説明（15 ) 面物鏡爲之，其實對本發明之另一種包括一凸透鏡以及一區域發散透鏡之物鏡，其效果相同，只要適當地設計該區域發散透鏡中之非球面各部份即可。事實上爲簡化設計，只要該凸透鏡的焦距設計成與短焦距相同，該區域發散透鏡中和凸透鏡形成短焦距的非球面部份，使用平面即可。請參照第10圖，其繪示依照本發明一較佳實施例的一種光碟機光學讀取頭之示意圖。首先光由雷射二極體100 發出，經過光柵101產生三光束，預備作爲尋軌訊號用，再經BS分光鏡102分光反射後，通過準CL直透鏡103產生平行光，再經FM轉折稜鏡104，進入具有4非球面部份的雙焦點物鏡105，經長焦距非球面部份的光聚焦在厚基底的CD光碟片上，經短焦距非球面部份的光聚焦在薄基底的SD光碟片上，然後光循原路徑反射回來，當再度通過 BS分光鏡102時，直接將光碟片上0與1資料忠實反映在光感應器106，由系統接收。表5列出一經光學軟體演算，如第6c圖所示之具有4 非球面部份的雙焦點物鏡的實際例子，其非球面特性係數、厚度…等數據。該物鏡可應用在如第10圖之光碟機光學讀取頭中。由於不同的4非球面部份是在光進入物鏡的入射面上，故在出射面上，僅有一種非球面特性係數數據。表5中也列出長焦距部份選用不同之數値孔徑的數據。本紙張尺度適用中國國家榡準（CNS ) Α4规格（210Χ297公釐） 11— f -裝訂 ί 脉 (請先閲讀背面之注意事項再填寫本五、發明説明（）表5 A7 _B7 第一部份與第第二部份與第第二部份與第三部份四部份四部份數値孔徑 0.6 0.38 0.43 焦距 3,37mm 3,44mm 3,36mm 直徑 4.04mm 2.62mm 2.89mm 厚度 2.6mm 2.5mm 2.35mm 1/曲率 2.17 2.24668 2.19390 圓錐曲線係數 -1.041422 -1.009525 -0.986959 入第4階變形係數 0.682912E-2 0.654792E-2 0.676608E-2 射第6階變形係數 0.185375E-3 0.125891E-3 0.135219E-3 面第8階變形係數 0.123534E-4 0.255350E-4 0.300778E-4 第10階變形係數 -0.198067E-5 -0.292505E-5 -0.371438E-5 1/曲率 -6.73803 圓錐曲線係數 -47.796398 出第4階變形係數 0.344686E-2 射第6階變形係數 -0.109217E-2 面第8階變形係數 0.180174E-3 第10階變形係數 -0.109326E-4 I _J -裝訂人銀 (請先閱讀背面之注意事項再填寫本頁) 經濟部中央標準局員工消費合作社印製請參照第11圖，其繪示數種不同形式物鏡之像高與波面像差的關係圖。圖中之水平軸爲像高，垂直軸爲波面像差。單一焦距之物鏡的曲線110，其組裝容忍度最大，亦即同一組裝誤差時，其波面像差最小；依照本發明表5之數據所製作之物鏡的曲線116，顯示其組裝容忍度次之；依照HOE分焦法如第2b圖所製作之物鏡的曲線114，顯示其組裝容忍度再次之；組裝容忍度最差的是以一具有2部本紙張尺度適用中國國家標準（CNS ) A4規格（210X297公釐） A7 B7 經濟部中央橾準局員工消費合作社印策五、發明説明（17 ) 份之平凹透鏡加一凸透鏡所組成的物鏡，其特性如曲線112 所示。水平線118代表一預射之能容許的波面像差，可知依照本發明之物鏡和單一焦距物鏡一樣效果優異，容許之組裝誤差都大於〇.12mm以上。如熟習此技藝者可瞭解的，本發明並非限定只用於上述較佳實施例之一種表面具有4個非球面部份的物鏡，或是限定於由該物鏡正視圖來看，以近似同心圓的形狀分佈，其他具有更多非球面部份，或是不依照同心圓形狀來分佈，只要所有組成的非球面部份，其焦點只有兩種，就都不脫離本發明之精神。如熟習此技藝者可瞭解的，上述較佳實施例之物鏡可使用本發明另一由凸透鏡及區域發散透鏡組成的雙焦點物鏡，該區域發散透鏡具有4非球面部份，其分佈形狀如同上述較佳實施例，只要適當地設計該區域發散透鏡中之非球面各部份，即可得到相同的效果。事實上爲簡化設計，只要該凸透鏡的焦距設計成與短焦距相同，該區域發散透鏡中和凸透鏡形成短焦距的非球面部份，使用平面即可。綜合以上所述，本發明之一種光碟機光學讀取頭之物鏡，除了基本之提供雙焦點的功能外，具有以下顯而易見的優點： a. 避免使用雙物鏡切換，因此可使物鏡致動器之結構單純化，且組裝容許誤差大，實際組裝容易。 b. 不用HOE的原理，避免了能量的損失。 c. 光學透鏡使用非球面曲面，比HOE法使用表面4階梯 (請先閱讀背面之注意事項再填寫本頁) - ί 裝- ，^τ 妹本紙張尺度適用中國國家標準（CNS ) Α4規格（210X297公釐） A7 _B7 _ 五、發明説明（18 ) 形結構刻紋，製作物鏡更簡單容易，成本低。 d.數値孔徑大時，具有縮小光點的效果，增加系統性能。雖然本發明已以一較佳實施例揭露如上，然其並非用以限定本發明，任何熟習此技藝者，在不脫離本發明之精神和範圍內，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爲準。 ---------ί ,裝------訂-----線 (請先閱讀背面之注意事項再填寫本頁) 經濟部中央標準局員工消費合作社印製 20 本紙張尺度逋用中國國家橾準（CNS ) Α4規格（210X 297公釐）Shading region: represents the diameter range of the short focal length part, which is equivalent to the shielding of the light passing through the long focal length part. D: the diameter of the long focal length part. Figure 9a is an analysis of the distribution of short focal length light energy in Figure 6c. Figure 9b is an analysis of the distribution of long focal length light energy in Figure 6c. Summarizing the light passing through a bifocal aspherical objective lens according to the present invention as shown in Fig. 6c, the energy is exactly fully applied, the long focal length part and the short focal length part are complementary, and there is no loss, which is the same as that using HOE The principle is that there is always a difference of about 24% in partial energy loss. As those familiar with this artist can understand, the above analysis is based on the single bifocal aspherical paper standard and is applicable to the Chinese National Standard (CNS) A4 specification (210X297 mm).-Printed by the Staff Consumer Cooperative of the Central Standards Bureau of the Ministry of Human Economy A 7 B7 Fifth, the description of the invention (15) is based on the objective lens. In fact, it has the same effect on another objective lens of the present invention including a convex lens and a regional divergent lens, as long as the aspheric parts in the regional divergent lens are properly designed Copies. In fact, in order to simplify the design, as long as the focal length of the convex lens is designed to be the same as the short focal length, the aspherical portion of the area-diverging lens and the convex lens forming the short focal length can be flat. Please refer to FIG. 10, which illustrates a schematic diagram of an optical pickup head of an optical disc drive according to a preferred embodiment of the present invention. First, the light is emitted by the laser diode 100, and the three beams are generated by the grating 101, which is ready for the tracking signal, and then split and reflected by the BS beam splitter 102, then the parallel light is generated by the collimated CL collimator lens 103, and then the corner is converted by FM Mirror 104, enters a bifocal objective lens 105 with 4 aspherical parts, the light through the long focal length aspherical part is focused on a thick base CD disc, and the light through the short focal length aspherical part is focused on a thin base SD disc On the chip, the light is reflected back along the original path, and when it passes through the BS beam splitter 102 again, the data 0 and 1 on the disc are directly reflected in the light sensor 106 and received by the system. Table 5 lists the actual example of a bifocal objective lens with 4 aspherical parts as shown in Fig. 6c after calculation by optical software, and its aspherical characteristic coefficients, thickness, etc. data. The objective lens can be applied to the optical pickup head of the optical disc drive as shown in Fig. 10. Since the different 4 aspherical portions are on the incident surface where light enters the objective lens, there is only one kind of aspherical characteristic coefficient data on the exit surface. Table 5 also lists the data of different numerical apertures for the long focal length part. This paper scale is applicable to the Chinese National Standard (CNS) Α4 specification (210Χ297mm) 11— f-binding (please read the precautions on the back before filling in this V. Invention description) Table 5 A7 _B7 Part 1 With the second part and the second part and the third part, the four parts, the four parts, the four parts, the numerical aperture, aperture 0.6 0.38 0.43, the focal length 3,37mm 3,44mm 3,36mm, the diameter 4.04mm 2.62mm 2.89mm, the thickness 2.6mm 2.5 mm 2.35mm 1 / curvature 2.17 2.24668 2.19390 conic curve coefficient -1.041422 -1.009525 -0.986959 into the fourth-order deformation coefficient 0.682912E-2 0.654792E-2 0.676608E-2 the sixth-order deformation coefficient 0.185375E-3 0.125891E-3 0.135219E-3 8th order deformation coefficient 0.123534E-4 0.255350E-4 0.300778E-4 10th order deformation coefficient -0.198067E-5 -0.292505E-5 -0.371438E-5 1 / curvature -6.73803 conic coefficient -47.796398 out the fourth-order deformation coefficient 0.344686E-2 shot sixth-order deformation coefficient -0.109217E-2 surface eighth-order deformation coefficient 0.180174E-3 tenth-order deformation coefficient -0.109326E-4 I _J-binding silver ( Please read the notes on the back first Write this page) Printed by the Staff Consumer Cooperative of the Central Bureau of Standards of the Ministry of Economic Affairs, please refer to Figure 11, which shows the relationship between the image height and wavefront aberration of several different types of objective lenses. The horizontal axis in the figure is the image height and the vertical axis It is the wavefront aberration. The curve 110 of the single focal length objective lens has the highest assembly tolerance, that is, the wavefront aberration is the smallest when the same assembly error occurs; the curve 116 of the objective lens produced according to the data of Table 5 of the present invention shows its assembly Tolerance is second; the curve 114 of the objective lens produced according to the HOE defocusing method as shown in Figure 2b shows that its assembly tolerance is again; the worst assembly tolerance is that one with 2 copies of this paper standard is applicable to Chinese national standards ( CNS) A4 specification (210X297 mm) A7 B7 Printed by the Central Consumers ’Bureau of the Ministry of Economic Affairs Employee Consumer Cooperative V. Description of the Invention (17) An objective lens composed of a plano-concave lens and a convex lens is shown in curve 112. Horizontal line 118 represents a wavefront aberration that can be tolerated by pre-shooting. It can be seen that the objective lens according to the present invention is as effective as a single focal length objective lens, and the allowable assembly error is greater than 0.12 mm. As can be understood by those skilled in the art, the present invention is not limited to an objective lens having four aspherical surfaces on the surface of the preferred embodiment described above, or is limited to a concentric circle viewed from the front view of the objective lens Other shapes have more aspheric parts, or are not distributed according to concentric circles. As long as all the aspheric parts are composed of only two types of focus, they will not deviate from the spirit of the present invention. As can be understood by those skilled in the art, the objective lens of the above preferred embodiment can use another bifocal objective lens composed of a convex lens and a regional divergent lens according to the present invention. The regional divergent lens has 4 aspherical parts, and its distribution shape is as described above In the preferred embodiment, the same effect can be obtained as long as the aspheric surfaces of the divergent lens in the area are properly designed. In fact, in order to simplify the design, as long as the focal length of the convex lens is designed to be the same as the short focal length, the aspherical portion of the area-diverging lens and the convex lens forming the short focal length can be flat. In summary, the objective lens of the optical pickup head of the optical disc drive of the present invention has the following obvious advantages in addition to the function of providing dual focus: a. Avoid the use of dual objective lens switching, so the objective lens actuator can be used The structure is simple, and the assembly tolerance is large, and the actual assembly is easy. b. Without the HOE principle, energy loss is avoided. c. The optical lens uses aspherical curved surface and 4 steps of surface than HOE method (please read the precautions on the back before filling in this page)-ί 装-, ^ τ The size of the sister paper is in accordance with China National Standard (CNS) Α4 specifications ( 210X297mm) A7 _B7 _ 5. Description of the invention (18) The engraving of the shape structure makes it easier and easier to produce the objective lens, and the cost is low. d. When the numerical aperture is large, it has the effect of reducing the light spot and increasing the system performance. Although the present invention has been disclosed as above in a preferred embodiment, it is not intended to limit the present invention. Anyone who is familiar with this skill can make some changes and retouching without departing from the spirit and scope of the present invention. The scope of protection of an invention shall be deemed as defined by the scope of the attached patent application. --------- ί, installed ------ ordered ----- line (please read the notes on the back before filling in this page) 20 copies printed by the Employee Consumer Cooperative of the Central Bureau of Standards The paper scale adopts China National Standard (CNS) Α4 specification (210X 297mm)

Claims

A8 Β8 C8 D8 printed by the Employees ’Cooperative of the Central Bureau of Standards of the Ministry of Economic Affairs VI. Patent application I. An objective lens for an optical pickup head of an optical disc drive, including:-The first part, which has a first aspheric surface for passing through the The light of a predetermined wavelength in the first part is focused on-the first focal point;-the second part has a second aspheric surface for focusing the light of the predetermined wavelength passing through the second part at A second focal point; a third part with a third aspherical surface, the first part determines the numerical aperture of the second part 'that is, the numerical aperture is determined by the maximum beam convergence angle' Causing the light of the predetermined wavelength passing through the third part to focus on the first focal point; and a fourth part 'having a fourth aspherical surface, the second part determines the value of the fourth part The aperture 'uses to focus the light of the predetermined wavelength passing through the fourth part' on the second focal point. 2. The objective lens as described in item 1 of the patent application scope, wherein the third aspherical surface and the first aspherical surface have the same aspherical surface characteristic coefficient and center thickness, the fourth aspherical surface and the second aspherical surface have the same Coefficient of aspherical surface characteristics and center thickness. 3. The objective lens as described in item 2 of the patent application scope, wherein the aspherical surface characteristic coefficients include: curvature, conic curve coefficients, fourth-order deformation coefficients, sixth-order deformation coefficients, eighth-order deformation coefficients, and tenth-order deformation coefficients . 4. The objective lens as described in item 1 of the patent application scope, in which the parts in the objective lens are in the form of approximately concentric circles, from the outside to the inside in order of the first part, the second part, the first Three parts, and the fourth part. 5_ The objective lens described in item 1 of the patent application scope, wherein the light of the predetermined wavelength refers to light having a wavelength of 65 nm. This paper standard applies to China National Standards (CNS) Μgambling (21〇 > < 297mm) (please read the notes on the back before filling out this page) i Ding Printed by Employee Consumer Cooperative of Central Standards Bureau of Ministry of Economy A8 B8 C8 D8 6. Scope of patent application 6. The objective lens as described in item 1 of the scope of patent application, wherein the light of the predetermined wavelength refers to light with a wavelength of 635 nm. 7. The objective lens described in item 1 of the patent application scope, wherein the numerical aperture of the first aspherical surface and the third aspherical surface is 0.6. 8. The objective lens as described in item 1 of the patent application range, wherein the numerical aperture of the second aspherical surface and the fourth aspherical surface is one of 0.35 to 0.43. 9. An objective lens of an optical pickup head of an optical disc drive, including a convex lens and a regional divergent lens, the regional divergent lens includes:-a first part having a first aspheric surface for passing the first part and A light of a predetermined wavelength of the convex lens is focused on a first focal point; a second part has a second aspheric surface for focusing the light of the predetermined wavelength passing through the second part and the convex lens At a second focal point; a third part with a third aspherical surface, the third aspherical surface and the first aspherical surface have the same aspherical surface characteristic coefficient and center thickness, and the first part determines the The numerical aperture of the third part 'that is, the numerical aperture is determined by the maximum convergence angle of the light beam' is used to focus the light of the predetermined wavelength passing through the third part and the convex lens at the first focal point; and a The fourth part has a fourth aspherical surface, the fourth aspherical surface and the second aspherical surface have the same aspherical surface characteristic coefficient and center thickness, and the second part determines the numerical aperture of the fourth part 'Used to pass And fourth parts of the light of the predetermined wavelength of the lens' focus on the second focal point. 10. The objective lens as described in item 9 of the patent application scope, where the parts in the area divergent lens are distributed in the shape of approximately concentric circles from outside to inside are the first part and the second part , Part three, and part four. 22 This paper scale is applicable to the Chinese National Standard (CNS) A4 specification (210X297mm) "Binding I (please read the precautions on the back and then fill out this page) A8 Βδ C8 D8 6. Scope of patent application 11. If the scope of patent application The objective lens according to item 9, wherein the aspherical characteristic coefficients include: curvature, conic curve coefficients, fourth-order deformation coefficients, sixth-order deformation coefficients, eighth-order deformation coefficients, and tenth-order deformation coefficients. 12. The objective lens as described in item 9 of the patent application range, wherein the light of the predetermined wavelength refers to light having a wavelength of 650 nm. 13. The objective lens as described in item 9 of the patent application range, wherein the light of the predetermined wavelength refers to light having a wavelength of 635 nm. 14. The objective lens as described in item 9 of the patent application scope, wherein the first aspherical surface and the third aspherical surface are flat surfaces. ----- ί__ 装 ------ 訂 ---- Γ ^ ^ (Please read the notes on the back before filling in this I) 23 copies of the paper standard printed by the Staff Consumer Cooperative of the Central Standards Bureau of the Ministry of Economic Affairs Applicable to China National Standard (CNS) A4 specification (210X297mm)