TW563109B - Objective lens device capable of correcting chromatic aberration and optical pickup employing the same - Google Patents

Abstract

An objective lens device is formed of three lenses including a lens having a negative power and formed of material having an Abbe number which is 45 or less in line d. At least one of surfaces of the three lenses is formed to be aspherical. Thus, in the objective lens device, a high numerical aperture 0.70 or more can be realized and chromatic aberration can be corrected with respect to blue light. Also, an optical pickup employing the objective lens device and using blue light can perform superior recording and/or reproduction.

Description

563109 «^? 〇Dif.doc / 008 A7 B7 Printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs. 5. Description of the Invention (() Invention Field) The present invention relates to an objective lens with a high numerical aperture and the use of the same. Optical reader, and in particular, an objective lens capable of correcting chromatic aberration, the chromatic aberration is changed by the wavelength, and / or emitted from a light source when a high number chirped aperture implements high-density light concentration Caused by the increase of the line width of the light wavelength. The recording capacity of the conventional optical recording / reproducing device is determined by the size of the light spot formed by the objective lens on the optical disc. The size of the light spot is a function of the wavelength It is directly proportional to the numerical aperture NA of the objective lens. Therefore, the next-generation DVD, which is currently being developed, is the so-called HD-DVD optical reader (hereinafter referred to as a high-density optical reading device), It is possible to use a light source that emits blue light and an objective lens with an aperture of more than 0.6. By reducing the size of the light spot formed on the disc, you can get more information than a conventional CD or DVD disc. The recording density is a high recording density. When an optical medium such as glass or plastic is used as the material for the objective lens, as shown in Table 1, the refractive index will be less than 650 nm in the wavelength range. There have been drastic changes.

[Table 1] Wavelength change Refractive index change of Hoya's M-BaCD5N glass 650 nm-651 nm 0.000038 405 nm-406 nm 0.000154 Paperless use of China National Standard (CNS) A4 Specification (⑵χχ 297 mm) Ministry of Economic Affairs Printed by the Intellectual Property Bureau employee consumer cooperative 563109 A7 8320pif.doc / 008 B7 V. Description of the invention (π) As shown in Table 1, for a small wavelength change of about 1 nm, the optical media at 405 nm The change in the refractive index in the blue wavelength range exhibits a change that is four times larger than the wavelength of 650 nm used in optical reading devices in DVDs. Defocus in a recordable high-density optical recording / reproducing device that can be repeatedly recorded and reproduced using a blue wavelength light source, resulting in a dramatic change in the refractive index of the optical medium against blue light, is One of the main reasons for poor performance. That is, in the recordable optical recording / reproducing apparatus, different optical powers are used for recording and reproduction. When recording / reproducing, the wavelength change caused by the change in optical output power is, for a blue light source, between 0.5-1 nm. Generally, if the output of a light source increases, the wavelength of the light emitted from the light source will become longer. Therefore, in the example of a high-density optical reading device using a blue light source, a large amount of chromatic aberration is generated, and defocus is relatively generated. Chromatic aberration is caused by the wavelength change caused by switching the optical output between recording and reproduction for an objective lens with a reference wavelength. For example, from Figures 1 to 3, it can be seen that the objective lens designed for a wavelength of 405 nm with an aperture of 0.65 chirp shows a large wavelength change of about 1 nm. Wavefront aberration and defocus. Fig. 1 illustrates the influence of various defocuses generated during recording / reproducing due to changes in optical output power on the intensity of the light spot formed on the recording medium. Figures 2 and 3 This paper size applies to China National Standard (CNS) A4 (210 X 297 mm) (Please read the precautions on the back before filling this page) -I ------- •, Order ---------- line------------------------- 563109 A7 ^ _ 832〇pif.doc / 0 0 8 B7 i. Description of the Invention (,) The figure shows an objective lens with an aperture of 0.65 値, according to the change in wavelength, the respective wavefront aberrations (optical path difference (ODD) and female focal length the amount. Although the defocus caused by the wavelength change can be corrected by adjusting the objective lens, it takes a long time to track the change of the wavelength by driving the objective lens through an actuator. Therefore, the quality of the reproduced and recorded signals is deteriorated in the above-mentioned time period. Defocusing during an increase in recording output can cause insufficient recording optical power. The defocus during the reduction of the reproduction output is an increase in jitter. That is, when the output of the light source is increased to record information on the optical disc, the wavelength of the light emitted from the light source will increase, for example, to 406 nm, and defocus will generate a light spot formed on the optical disc. Therefore, before the actuator can track this defocus, the recording cannot be done properly. When the output of the light source is reduced for rework, the wavelength of the light source will be shortened, for example, to 405 nm. In this example, because the actuator performs the tracking well to increase the wavelength, defocus is generated again. Due to defocus, jitter also increases in the reproduced signal. When the light source is driven by a high frequency (HF) to reduce the feedback of the light source caused by the light returning from the disc to the light source, the line width of the light source wavelength will increase, for example by about 1 nm, and the resulting chromatic aberration Will worsen the remake signal. Therefore, 'a readable and high-density optical reader needs to have an optical system that can also limit or compensate for the chromatic aberration that occurs when the recording and reproduction output is changed and the wavelength of the light emitted by the light source is changed' . (Please read the notes on the back before filling out this page) -1 ------- iri ^ ------- line 丨 · Printed by the Intellectual Property Bureau of the Ministry of Economic Affairs, Consumer Cooperatives Paper size applicable to China Standard (CNS) A4 Specification _ (21〇X 297) 563109 Printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs A7 8 32Qpif.doc / Q08__B7_ V. Description of the Invention (0) The disclosed conventional objective lens has two lenses that can correct chromatic aberration. Referring to FIG. 4, the conventional objective lens includes a first lens 1 and a second lens 4. The two lenses are made of low-dispersion glass with an Abbe number over 40, so that the surface of at least one lens is aspherical. Therefore, it can provide a high numerical chirp, and correct the chromatic aberration for the light of 635 nm wavelength. The first lens 1 interposed between the magnetic disk 6 and the second lens 4 for concentrating light, and an objective lens having an aperture of more than 0.7 to correct this chromatic aberration. Reference numeral 2 represents a diaphragm (diaphragm) for limiting the light input area. However, since the conventional objective lens is composed of two lenses in two groups, and uses a low dispersion with an Abbe number exceeding 40 glass. Therefore, for light with a wavelength of 635 nm, it can be used to correct chromatic aberration and provide a high numerical aperture. However, for blue light, it cannot be used to correct chromatic aberrations and provide a high numerical aperture. SUMMARY OF THE INVENTION In order to solve the above problems, an object of the present invention is to provide an objective lens that can be used to correct chromatic aberration for blue light, provide a high numerical aperture, and provide an optical reader using the objective lens. To achieve this, the present invention provides an objective lens device composed of three lenses, including a lens having a negative power and composed of a material having an Abbe number 値 of 45 or less than 45. At least one of the surfaces of these three lenses is aspherical. Preferably, at least one of the three lenses of the present invention is positive power, and the paper size is applicable to the Chinese National Standard (CNS) A4 specification (210 X 297 Public Love " 3 ------ (Please read the note on the back first) Please fill in this page again) Lu line A7 Printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs 563109 8320pif.doc / 008 B7 V. Description of the invention (K) A lens with negative power and a lens with positive power are combined to form a lens Doublet. Therefore, two groups can be used to form a three-lens structure. The two lenses of the present invention are preferably a first lens with positive power and a second lens with negative power. The lens and a third lens with positive power are arranged in order from the direction of light input. According to the present invention, it is assumed that the focal length of a lens with negative power is / 77, and the overall focal length lens of the objective lens satisfies the following formula: To this end, the present invention provides an optical reader. The optical reader includes: a light source, an objective lens, an optical path converter, and a photodetector. The source generates and emits light. The objective lens focuses the light radiated from the light source to form a light spot on the recording medium. An optical path converter arranged between the light source and the objective lens changes the traveling path of the incident light. The photodetector receives and inputs the light reflected by the recording medium via the objective lens and the optical path converter. The objective lens is composed of three lenses, including one with negative power and an Abbe number with online d It is a lens made of 45 or smaller materials. At least one of the three lens surfaces is aspherical. According to the present invention, the light source for emitting light preferably has a substantially between 400- The wavelength between 420 nm and the objective lens must have a numerical aperture larger than 0.7 or larger than 0.7. In order to make the above and other objects, features, and advantages of the present invention obvious and easy to understand, one of them is given below. The preferred embodiment, with the accompanying drawings, for details (please read the precautions on the back before filling this page)

This paper size applies to China National Standard (CNS) A4 specifications (210 X 297 issued) 563109 A7 8320pif.doc / 008 B7 Printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs 5. Description of the invention (l) The description below. Brief description of the drawing _ · Figure 1 shows the effect of various defocus generated by the optical output power during recording / reproduction on the intensity of the light spot formed on the recording medium; Figures 2 and 3 show the objective lens with an aperture of 0.65 値, according to the change of the wavelength, the respective wavefront aberration and defocus amount; Figure 4 shows an example of a conventional objective lens Figure 5 shows a diagrammatic view of an objective lens according to a preferred embodiment of the present invention; Figure 6 shows a diagram of an optical reader using an objective lens according to a preferred embodiment of the present invention View; FIG. 7 shows a structural view of the objective lens according to the first optical design of the present invention as shown in the second table; FIG. 8 shows a design based on the optical data in the second table. The aberration of the objective lens of the present invention is shown in FIG. 9; FIG. 9 shows a structural view of the objective lens according to the second optical design of the present invention as shown in the third table; Optical data in the table, designed by the invention Aberrations of the objective lens; FIG. 11 shows a structural view of an objective lens according to the third optical design of the present invention as shown in the fourth table; FIG. 12 shows an optical data according to the fourth table , Designed the aberration of the objective lens of the present invention; (Please read the precautions on the back before filling out this page) 0 Order -L ------- line — i ^ w. F — III — — — — — — — — This paper size applies the Chinese National Standard (CNS) A4 specification (210 X 297 mm) 563109 〇Oif.doc / Q08 A7 B7 Printed by the Consumers ’Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs 5. Description of the invention (?) FIG. 13 is a structural view of an objective lens according to the fourth optical design of the present invention as shown in Table 5. FIG. 14 is a schematic view of a designed lens based on the optical data in Table 5. The aberrations of the invention's objective lens; a brief description marked in the picture: 1 first lens 2 diaphragm 4 first * lens 6 magnetic disk 10 objective lens 11 first lens 13 second lens 15 third lens 15a surface 30 record Media 51 Light source 53 Scope 55 Beam shaping 稜鏡 57 Polarization Beam splitter 59 Quarter wave plate 71 Condenser 73 Photodetector S14 Aspheric surface S24 Aspheric surface 10 This paper size applies to China National Standard (CNS) A: 丨 Specifications (210 X 297 mm) (Please read first Note on the back, please fill out this page again) ------- • Order i. Printed by the Intellectual Property Bureau of the Ministry of Online Economics, printed by the Consumer Cooperatives 563109 A7 _R ?? Oni f.doc / QQ8_B7 V. Description of Invention (J) S34 Aspheric surface S44 For a preferred embodiment of an aspherical surface, please refer to FIG. 5. The objective lens 10 according to the present invention is composed of a first lens 11, a second lens Π, and a third lens 15 in a direction from which light rays enter. Make up. Among the first lens 11, the second lens 13, and the third lens 15, at least one lens has negative power and is made of glass or plastic material having an Abbe number be of 45 or less than 45. . It is best to use glass or plastic materials with an Abbe number of 35 or less. Among the first lens 11, the second lens 13, and the third lens 15, the surface of at least one lens, for example, the surface 15a of the third lens 15 where light is incident is formed by an aspherical surface Make up. For example, assuming that the focusing distance of the second lens Π with negative power is // 7 and the overall focusing distance of the objective lens 10 is /, then the objective lens satisfies the following formula 1: [Formula 1] In Figure 5, The objective lens 10 of the present invention is composed of two units. Among these three lenses, the second lens 13 has negative power, and the first lens 11 and the third lens 15 have positive power. The first lens 11 and the third lens 15 are combined to form a dual pair structure. Among them, reference numeral 30 represents a recording medium like the next-generation DVD series. As can be seen from the following description, according to the present invention, the objective lens 10 having the above-mentioned structure can provide a high numerical aperture of 0.7 or higher, and the paper size is applicable to the Chinese National Standard (CNS) A4 specification (210 X 297). Mm) • -------------------- ^ Order · I -------- I-(Please read the precautions on the back before wk this page ) F --------------------- 563109 A7 f.doc / QQ8__B7 Five inventions printed by the Consumers ’Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs (can modify the blue light wavelength range. Chromatic aberration. Please read the “Notes on the back side” and fill in FIG. 6 to draw an optical reader using an objective lens according to a preferred embodiment of the present invention. Please refer to FIG. 6. The optical reader of the preferred embodiment includes a light source 51, an optical path converter, an objective lens 10, and a photodetector 73. The optical path converter is used to change the traveling path of incident light. The objective lens 10 focuses light emitted from the light source 51 to form a light spot on the recording medium 30. The photodetector 73 receives The light reflected by the medium 30 and passed through the optical path converter. The light source 51 uses a blue semiconductor laser with a wavelength of about 400 to 420 nm (preferably about 405 nm) to emit light. Because it is a semiconductor laser, It has an edge emitting laser and a vertical cavity surface emitting laser. The optical path converter is arranged in the optical path between the light source 51 and the objective lens 10. Used to change the path of incident light. As shown in Figure 6, the optical path converter preferably includes a polarization beam splitter 57 and a quarter wave plate (1/4 wave plate) 59. The polarizing beam splitter is used to selectively transmit or reflect the incident light according to the polarization. The quarter wave plate 59 is used to change the phase of the incident light. Among them, it has a predetermined coefficient for transmission and reflection. The beam splitter (not shown) of the incident light may be included and used as an optical path converter. The objective lens 10 having a structure as shown in FIG. 5 has 0 .7 (preferably 12 paper sizes are applicable to the Chinese National Standard (CNS) A'4 specification (210x297)) 563109 Printed by the Consumers ’Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs A7 5. Description of the invention ((b) 〇 85) A numerical aperture is used to form a light spot on a high-density recording medium 30, preferably a next-generation DVD series storage medium 30, for recording / reproducing purposes. Among them, the recording medium 30 is preferably a next-generation DVD series recording medium, and the thickness of such a recording medium may be 0.1 mm. The photodetector 73 receives the light reflected by the recording medium 30 and detects an information signal and an error signal. In a better case, the sight 53 is more provided with an optical path between the light source 51 and the optical path converter. The scope 53 focuses the scattered light emitted by the light source 51 to generate a parallel light beam. As shown in FIG. 7, when the scope 53 is placed in the optical path between the light source 51 and the optical path converter, a condenser 71 is further provided between the optical path converter and the photodetector 73. . When an edge-emitting laser is used as the light source 51, a beam-shaping beam 55 is further provided between the optical path between the sight 53 and the optical path converter. This allows information to be recorded with a fairly low output. The beam shaping unit 55 shapes an elliptical beam emitted from an edge emitting laser, and shapes it into a circular beam. The beam shaping 稜鏡 55 may be disposed between the light source 51 and the sight 53. Here, when a vertical cavity surface radiating laser for radiating an almost circular light beam is adopted as the light source 51, the optical system 'in Fig. 7 does not require the use of a beam shaper 55. Among them, the reference number 73 represents a sensor lens, and an astigmatism method is used to detect a focus error signal. For example, 'a astigmatism mirror may be used as the sensing mirror 73, causing the astigmatism of the incident light -------------------- ITi · ^ ---- --- Line— ^ wi (Please read the notes on the back before filling out this page) This paper size is applicable to China National Standard (CNS) A4 (210 X 297 public love) Printed by the Intellectual Property Bureau of the Ministry of Economic Affairs Consumer Cooperatives 563109 A / Q ^ 7〇pi f.dor / nn «B7 V. Description of the invention (π) Light. Because the optical reader of the present invention includes an objective lens 10, this objective lens 10 has a high number chirped aperture for blue light and has the ability to correct chromatic aberration. Therefore, reproduction information can be recorded on a next-generation DVD series recording medium. Therefore, since the objective lens 10 can correct the generated chromatic aberration, according to the present invention, the optical reader of the objective lens 10 can be used to perform recording and / or reproduction on the next-generation DVD series recording medium. This chromatic aberration is due to the change in the wavelength of the light emitted from the light source 51 when the light output is changed when switching between the reproduction mode and the recording mode, and the line width of the wavelength increases when the light source is driven by a high frequency Caused. Fig. 6 shows an optical reader using an objective lens 10 according to a preferred embodiment of the present invention. However, the optical reader according to the present invention is not limited to the optical architecture shown in FIG. In order to determine the influence of the chromatic aberration of the objective lens 10 according to the present invention against blue light, the first to fourth optical design examples of the objective lens 10 according to the present invention will be described below. In the first to fourth optical design examples, the objective lens 10 according to the present invention is composed of a first lens 11 having a positive power, a second lens 13 having a negative power, and a third lens 15 having a positive power. . The surface 15a of the third lens 15 to which the light is incident is made aspherical. For a recording medium having a thickness of 0.1 mm, the reference wavelength is 405 nm and the overall focal length is 1.765 mm. Also, a parallel beam having a pupil entrance diameter of 3.0 mm is input, and the aperture of the chirp is 0 70 or larger than 0.7. Tables 2 and 7 show the first setting 1 & scale of the objective lens 10 according to the present invention applicable to the Chinese National Standard (CNS) A4 specification m0x (Please read the precautions on the back before filling out this page)

-II ϋ II —ϋ 口 t · ϋ · ϋ * ^ 1 βΜ / —ϋ ϋ ^^ 1 I ϋ I 563109 A7 8 2? 〇 if _, d π c / 〇〇8 B7 V. Description of the invention (丨 ~) Please read the back gauge example first. FIG. 8 illustrates aberrations of the objective lens 10 according to the present invention having the optical data in the second table. Tables 3 and 9 show a second design example of the objective lens 10 according to the present invention. Fig. 10 shows aberrations of the objective lens 10 according to the present invention having the optical data in the third table. Figures 4A and 11 show a third design example of the objective lens 10 according to the present invention. Fig. 12 illustrates aberrations of the objective lens 10 according to the present invention having the optical data in the fourth table. Ministry of Economic Affairs, Intellectual Property Bureau, Employee Consumer Cooperatives, printed matters, and then surface 511 512 curvature radius (mm) thickness / interval (mm) material (glass) refractive index online d 甶 Abbe number fi ι !, 〆! 3.003070 1.2000000 E-BaF8_H0YA 1.64673 4 47.1 3.003070 0.500000 E-FD4_H〇YA 1.80629 5 27.5 S13 〇〇1.707467 514 (aspheric surface) 515 ———_ 0.911822 1.250000 M-Lacl30_H〇YA 1.71556 6 53.2 K: -0.696940 Α: 0.917676E-01 Β: 0 · 462801E-01 C: 0.317180E- (D: 0.114090E + 00 E: -.182547E + 00 F:-. 198125E-09 G:-. 406463E-10 1 〇〇0.100000 S16 --- ^ oo 0.100000 ' CG '1.62146 2 31.0 S17 oo 〇〇〇〇〇〇〇〇〇 Alignment book' s Zhang scale translation 'national standard (CNSM4 specifications ⑽ X 297 public love) 563109 A7 _f.doc / QQ8_B7 V. Description of the invention (0) Ministry of Economic Affairs Printed by the Intellectual Property Bureau's Consumer Cooperatives [Table 3] Surface curvature radius (mm) Thickness / interval (mm) Material (glass) Refraction coefficient online d 甶 Abbe number 値 η Γί7 S21 2.823244 1.3500000 E-BaF8—H〇YA 1.64673 4 47.1 u S 22 -2.798572 0.500000 E-FD4_H〇YA 1.80629 5 27.5 h machine% Ben 11 S23 148.5261 58 1.020972 S24 (aspherical surface) 0.903599 1.300000 M- BaCD5N_H〇YA 1.60518 3 61.3 K: -0.596430 A: 0.807580E-01 B:- .827319E-02 C: 0.165423E + 00 D: '912224E-01 S25 oo 0.150000 S26 oo 0.100000' CG '1.62146 2 31.0 S27 oo 〇.〇〇〇〇〇〇〇 IJ Order II it # 16 This paper size applies to China Standard (CNS) A4 specification (210 X 297 mm) 563109 Printed by the Consumers ’Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs A7 ο ^ 9 () pi r .aoc / uuo 5. Description of the invention ((W) [Table 4] Surface Curvature Radius (mm) Thickness / Separation (mm) Material (Glass) Abbe Number of Refraction Coefficient on Line d S31 2.591625 1.5000000 E-BaF8_H〇YA 1.64673 4 47.1 S32 -2.636949 0.500000 E-FD4-HYAYA 1.80629 5 27.5 S33 13.93241 6 1.649604 S34 (aspherical surface) 0.795351 1.000000 M-Lacl30—H〇YA 1.71556 6 53.2 K: -0.350912 Α: 0.333620E-01 Β:-· 767010E-01 C: 0.337696E + 00 D:-. 546842E + 00 S35 oo 0.150000 S36 oo 0.100000 TG '1.62146 2 31.0 S37 ———- oo 〇〇〇〇〇〇〇〇〇 As shown in Tables 2 to 4, in the first to third design examples of the objective lens 10 according to the present invention Each of the second lenses 13 ′ having a negative power is made of glass having an Abbe number of 27.5. And the focus distances of the second lens 13 in these examples are -3.725 mm and -3.420 mm, respectively. 17 Η R3 I ύι 1 u I term I then I fill in τ Ben's scale ^ Home Standard (CNS) A4 specification (21 〇χ7mm)-it

I 563109 A7 B7 P ^? 〇pif.doc / QQ ^ V. Description of the invention) and -2.713 mm 〇 Figures 8, 10 and 12 are shown, with the optics in Tables 2 to 4 The aberrations of the objective lens 10 in the data. When the wavelength of the light emitted from the light source 51 changes to 406 nm and exceeds the range of 405 nm of the reference wavelength, it is difficult for the objective lens 10 to produce aberrations. Table 5 and Figure π show a fourth optical design example of the objective lens 10 according to the present invention. FIG. 14 illustrates aberrations of the objective lens 10 according to the present invention having the optical data in Table 5. ------------- Tired · (Please read ★ Read the precautions on the back before filling

S41 3.017331 Thickness / room separation (mm) 1.2000000, material (glass) Abbe number of line d 値

E- BaCD12 HOYA 1.59958 59.5 S42 -2.869224 0.500000

E-FD8 H〇YA 1.72948 31.2 S43 Printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs 1.872786 S44 0.888542 1.250000 M-Lacl30 HOYA 1.71556 53.2 surface) K: -0.6540 (A: 0.89521 D: 0.93034 Ε: '18254Ί 50 6E -01 7E-01 1E + 00 F:-. L Β: 0.422347E-01 [93469E-09 C: 0.5 59695E-C 1 S45 oo 0.100000 S46 οο 0.100000 'CG' 1.62146 2 31.0 S47 οο 〇.〇〇〇〇〇 〇〇18 This paper size applies Chinese National Standard (CNS) A4 specification (210x297 mm) A7 563109 f.doc / 008 B7 _ 5. Description of the invention (^) As shown in Table 5, the objective lens according to the present invention is shown in Table 5. In the fourth optical design example of i0, the second lens 13 with negative power is made of glass with an Abbe number of 31.2. And the focusing distance of the second lens 13 is designed to be -3.333 mm. By the 14th It can be seen in the figure that when the wavelength of the light emitted from the light source 51 changes to 406 nm and exceeds the range of 405 nm of the reference wavelength, the objective lens 10 according to the present invention and having the optical data in Table 5 is very It is difficult to produce aberrations. Degree is Z, the aspheric surfaces S14, S24, S34, and S44 can be expressed by Equation 2: [Equation 2] ^ -p- + Ah4 + Bh6 ^ ChKDhlKEhl2 + Fh] 4 ^ Gh] 6 ^ Hh] Kjh20

Uyll-il-hK ^ h2 In Tables 2 to 5 and Formula 2, K is the conic constant of the aspherical surfaces S14, S24, S34, and S44 of the third lens 15, and A to ] Is the coefficient of the aspheric surface. h represents the height from the optical axis, and c represents the curvature. From the above optical design example, we can see that 'the objective lens 10 according to the present invention has a function of correcting chromatic aberration for blue light. Therefore, when a blue light source is used, the optical reading of the next-generation DVD series recording media Take the device and use the objective lens 10 according to the present invention (please read the precautions on the back before filling out this page)% Printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs IIIIII | Order i · ------- line I ----------------------- m (cns) a4 ^ ^ 563109 A / P ^? QDif. (ioc / 00R B7 V. Description of the invention (〇) In this way, excellent recording and / or reproduction signals can be obtained. As mentioned above, because the objective lens 10 according to the present invention is composed of three lenses. These two lenses include one with negative power and The Abbe number of d is a lens made of a material smaller than or equal to 45, and at least one of the three lens surfaces is an aspherical surface. Therefore, it can provide a high number of apertures and have chromatic aberration correction functions for blue light. So 'by using an optical reader with an objective lens according to the present invention, In order to obtain an excellent record and / or reproduction. Although the present invention has been disclosed as above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art will not depart from the spirit and scope of the present invention. As it can be slightly changed and retouched, the scope of protection of the present invention shall be determined by the scope of the attached patent application. ---- 1 —.-------------: Order i .------- line— (Please read the notes on the back before filling out this page) Printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs

Claims (1)

563109 Α8 Β8 C8 D8 The consumer property cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs prints clothing /, and applies for patent scope hi objective lens device, consisting of lenses, these three lenses = tongue one with a negative power 'and by the An Abbe ^ is a lens made of 45 or smaller materials, at least one of the surfaces of the two lenses is aspherical. $ 2. The device as described in item 1 of the scope of patent application, wherein the three McKinseys see at least one of which has ~ positive power, and the lens which has a negative power and has a positive power The lenses are combined to form an even pair, so that the three lenses are formed in two groups. 3. The device according to item 1 of the scope of patent application, wherein the numerical aperture of the device is 0.7 or more. 4. The device according to item 1 of the scope of patent application, wherein the lens having a negative power is composed of a glass or plastic material having an Abbe number 値 of 45 or less on the line d. 5. The device as described in any one of items 1 to 4 of the patent scope of claim g, wherein the three lenses are: a first lens with a positive power, and a first lens with a negative power. A lens and a third lens with positive power are arranged in order from the direction of light input. 6. The device according to item 5 of the scope of patent application, wherein assuming that the focusing distance of the second lens having a negative power is /; 7 and the overall focusing distance of the objective lens is /, the objective lens satisfies The following formula: -2 · 4 <, < -1α 7 · The device according to any one of claims 1 to 4 of the scope of patent application, wherein the focus distance of the lens which has a negative power of false 3 is (Please read the notes on the back before filling out this page) Order; -line 丨 #! This paper size applies to China National Standard (CNS) A4 (210 X 297 mm) 563109 A8 B8 po 8320pif.doc / 008 d8 6. The scope of patent application and the overall focusing distance of the objective lens is /, then the objective lens satisfies the following formula: 8.-an optical reader, including a light source, an objective lens, an optical path converter, and an A photodetector in which the light source generates and emits light, the objective lens focuses the light emitted from the light source to form a light spot on a recording medium, and the optical path converter is arranged between the light source and the interface An optical path between the mirrors is used to change a traveling path of incident light. The photodetector receives and inputs the light reflected by the recording medium and passing through the objective lens and the optical path converter. The mated optical reader includes three lenses including a lens having a negative power and composed of a material having an Abbe number 在线 of 45 or less on the line d, and the At least one of these three lenses is aspherical. 9. The optical reader according to item 8 of the scope of patent application, wherein at least one of the three lenses has a positive power, and the lens with a negative power is combined with a lens with a positive power, Become a pair. 10. The optical reader according to item 8 of the scope of patent application, wherein the light emitted by the light source has a wavelength substantially between 400-420 nm, and the objective lens has a wavelength of 0.7 or greater. A numerical aperture. 11. The optical reader described in item 8 of the scope of patent application, wherein the lens with a negative power is an Abbe number with an online d (please read the precautions on the back before filling this page) Ministry of Economic Affairs Printed by the Intellectual Property Bureau's Consumer Cooperatives-I · ϋ n I ϋ ί I 一 δ, »—Μ« ϋ n ϋ ϋ ϋ I ϋ n H ϋ · ϋ I ϋ ϋ ϋ ϋ nn I nnnnn-This paper is for China National Standard (CNS) A4 Specification (2) 0 X 297 mm) 563109 8320pif.doc / 008 A8 B8 C8 D8 6. The scope of patent application is made of glass or plastic material of 45 or less than 45. 12. The optical reader according to any one of claims 8 to 11, wherein the objective lens comprises a first lens having a positive power and a second lens having a negative power, and A third lens with a positive power is formed by arranging in order from the direction of light input. 13. The optical reader as described in item 12 of the scope of patent application, wherein, assuming that the focusing distance of the second lens with a negative power is ，, and the overall focusing distance of the objective lens is 则, the objective lens satisfies the following Formula: -2Α < Δ ^ <-\ Λ / 14. The optical reader as described in any one of claims 8 to 11 of the scope of patent application, wherein the lens is assumed to have a focusing distance of the lens with a negative power Yes // 7, and the overall focusing distance of the objective lens is /, then the objective lens meets the following formula:-2.4 < ^ »< -1.4 (Please read the precautions on the back before filling this page) Wisdom of the Ministry of Economic Affairs Property bureau employee consumer cooperatives seal?衣 23 1-mouth, 1 L— 1. ^ 1 ϋ ϋ »1 II nn ϋ nn / I nn ϋ n I ϋ ϋ ϋ n ϋ ϋ n ϋ ϋ ϋ I This paper size applies to China National Standard (CNS) A4 (2) 0 X 297 mm)