TWI227471B - Optical member and optical device which uses the same - Google Patents

Abstract

To avoid problems that a conventional diffraction grating shows large fluctuation in the wavelength by the changes in the temperature and causes a large shift of the light-accepting position in the light-accepting part for laser light. Projections 11a as a first grating are formed on a transparent resin substrate and steps 11b as a second grating are formed as superposed on the inclined faces of the projections 11a. The depth dimension h of each step in the steps 11b is determined in such a manner that (n-1)h, wherein n is the refractive index, is equal to an positive integral multiple of the wavelength. The optimum number of steps is determined by the depth h and the period p. When the wavelength is 658 nm or 785 nm, the optimum number of steps is 6.

Description

V. Description of the invention (u [Technical Field] Printed by the Consumer Cooperative of the Intellectual Property Office of the Ministry of Economics The present invention relates to an optical component of laser light incident with two kinds of different wavelengths, and more particularly to a light receiving unit that receives the optical axes of each other Staggered laser optical components and optical devices using the optical components. [Preceding technology] In order to simplify the structure, an optical pickup mounted in an optical disc device that can be used by both CDs and DVDs is equipped with two Laser light sources of different wavelengths are provided as an integrated light emitting section. In the light emitting section, the light sources are arranged at minute intervals, so that the optical path is formed in a state where the optical axes of the lasers are staggered. The optical axes are staggered Since the light receiving position of the light receiving unit is deviated in the state, it is necessary to make the light receiving positions of both lasers coincide in the light receiving unit. FIG. 7 is a plan view showing a conventional optical member 30 provided to eliminate the deviation. The optical member 30 has a concave and convex diffraction grating 30a formed on one surface of a plate-shaped transparent member, and is provided at a position facing the light receiving portion. The optical member 30 is mounted on an optical disc device for both CD and DVD, and the optical disc device is provided with a laser emitting a wavelength of 7 8 5 nm (CD 1) for CD and 65 8 nm for DVD The light emitting part of the laser with a wavelength of (2). As shown in FIG. 7, the optical axis of the returned light reflected on the disc is staggered and returned to the optical member 30, and the diffraction grating of the optical member 30 is used. 30a makes the laser diffraction of both sides reach the position of the light receiving part 31, so that the light receiving positions are consistent with each other. In addition, according to the length of the wavelength (please read the precautions on the back before filling this page) This paper size is applicable to China National Standard (CNS) A4 Specification (210X297 mm)-4- 1227471 More if ·, ea 1 π | B7 V. Description of the Invention (2) The angle of diffraction is different. In the case shown in Figure 7, λ 1 The diffraction angle (0 1) is larger than the diffraction angle (0 2) of λ 2. [Problems to be Solved by the Invention] However, the light emitting part emitting the laser has a wavelength that changes with temperature. Due to the changing characteristics, in the conventional optical member 30 described above, As the temperature changes and the diffraction angle changes, the light receiving positions of the laser light receiving section become inconsistent with each other, which causes a problem of shifting. For example, if the light receiving position of the light receiving section is greatly shifted, it is higher than the first winding. The high-order diffracted light of the emitted light leaks into the light-receiving part and is shifted. In view of the above-mentioned problems, an object of the present invention is to provide a light-receiving part whose laser light axes can be aligned with each other and can be reduced. Optical member affected by wavelength variation caused by temperature change and optical device using the optical member. [Means to Solve the Problem] In order to achieve the above-mentioned object, the optical member of the present invention is incident at different wavelengths λ 1 and λ 2 The laser is characterized in that: a diffraction grating is provided to diffract the laser of the first wavelength λ 1 and make the second wavelength; the laser of I 2 transmits without diffraction. In this case, the structure of the diffraction grating can be such that: for a laser of the first wavelength λ 1, it is selective for a single diffraction light, and for a laser of the second wavelength λ 2, It has selectivity to zero diffraction light. The diffraction grating has a first grating portion forming a concave and convex shape, and the Chinese National Standard (CNS) A4 specification (210X297 mm) is applied to the paper size (please read the precautions on the back before filling this page). Printed by the Ministry of Intellectual Property Bureau's Consumer Cooperative -5- 1227471 Factory A7 B7 V. Description of the invention (3) The second grating portion formed in a step shape on the inclined surface of the first grating portion, and the first grating portion formed in the step shape. The depth (h) of each step of the two grating portions with respect to the second wavelength λ 2 is (n-1) h = m λ 2 (but 'η is a refractive index and m is a positive integer), Preferably, the number of step-like steps of the second grating portion is set to enable the second wavelength; the laser of I 2 is transmitted without diffraction, and the laser of the first wavelength λ 1 is given to Diffraction at a fixed angle. In addition, it is preferable that the respective stages of the second grating portion are formed at equal distances in the width direction and the depth direction. In the present invention, since the laser beam of one wavelength is not diffracted, the diffraction angle of the other laser beam can be made smaller, thereby reducing the influence of wavelength variation due to temperature changes and reducing the light receiving portion. Deviation of the light receiving position. In addition, by setting the first wavelength λ 1 to 785 nm and the first wavelength λ 2 to 65 8 nm, the present invention can be applied to an optical pickup for both CD and DVD. In addition, in this case, by setting the number of step-like steps of the second grating portion to six steps, it is possible to design the laser beams of both sides with high efficiency while maintaining their light receiving positions. In addition, it is preferable that a concave-convex third grating portion is formed on a surface of the second grating portion, and the concave-convex is formed so that a period of the third grating portion formed on one step of the second grating portion is at The laser wavelength is below. Since the effect of preventing the reflection is obtained by using the unevenness, the loss caused by the reflection of light can be reduced. This paper size is applicable to China National Standard (CNS) A4 specification (210X297 mm) (Read the precautions on the back before filling this page)

'1T Printed by the Consumer Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs -6-

5. Description of the Invention (4) In addition, since the first grating portion and the second grating portion are both formed of resin, the manufacturing cost can be reduced. In addition, the optical device of the present invention is characterized in that the light emitting point of the laser emitting the first wavelength λ 1 and the second wavelength are provided; the light emitting point of the laser emitting I 2 is staggered in a direction orthogonal to the optical axis. And the optical member that transmits the light from the light emitting portion so that the optical axis of the laser having the first wavelength of 1 and the optical axis of the laser having the second wavelength λ 2 are at predetermined positions. Consistent. In the present invention, since a light emitting unit in which two-wavelength laser light sources are integrated and a single optical member capable of independently diffracting two-wavelength lasers is provided, the number of parts can be reduced. , Simplifying the structure, which can reduce costs. [Best Embodiment of the Present Invention] FIG. 1 is a schematic diagram showing an example of an optical device equipped with the optical member of the present invention, and FIG. 2 is a schematic diagram showing the optical member and its optical axis. FIG. 4 is a plan view showing a part of the optical member, FIG. 4 is a line graph showing the efficiency of light with respect to a grating depth of 6 steps, and FIG. 5 is a graph showing the efficiency of light with respect to a grating depth of 5 steps Line illustration. The optical pickup 10 shown in FIG. 1 as an optical device includes: a light emitting section 12 in which a semiconductor laser diode is built in; and a collimating lens for converting the laser emitted by the light emitting section 12 into parallel light. 13; Beamsplitters that transmit incident light from the direction of reflection while reflecting incident lasers 1 4; This paper size applies Chinese National Standard (CNS) A4 specifications (210X297 mm) —-(Please Read the notes on the back before filling out this page), printed by the Consumer Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs 1227471 Α7 Β7 V. Description of the invention (-5 objective lens 15; light receiving unit 16; arranged in the light receiving unit 16 The optical member 1 1 of the present invention between the dichroic mirror i 4 and the beam splitter i 4. (Please read the precautions on the back before filling this page.) In the light emitting section 12, a wavelength 7 8 5 nm (λ 1 for CD) is formed. The light emitting element 1 2 a of the laser light emitting point) and the light emitting element 12 b formed with a laser light emitting point having a wavelength of 65 8 nm (also 2) for a DVD are in a state of being separated by a minute interval (S) in a single frame. Configuration: if the wavelength emitted from the light emitting part 12; the laser of I1, λ2 When it hits the beam splitter 14, the beam splitter 14 reflects in the direction of the disc D1, changes from collimating lens 13 to parallel light, and then enters the objective lens 15. The laser beam condensed by the objective lens 15 forms light on the disc D1. Point, the return light reflected on the disk D1 passes through the objective lens 15, the collimator lens 13, and the transmission beam splitter 14 to the optical member in a state where the optical axes of the disks are staggered from each other. As shown in FIG. 2, the optical member 11 is a plate-shaped member made of a light-transmitting resin member, a glass member, or a composite material of resin and glass. In this optical member 11, a wavelength for DVD is used. The laser of λ 2 is transmitted directly without being diffracted, and is introduced into the light receiving unit 16. After the laser of wavelength λ 1 is diffracted to the CD, the laser is introduced into the light receiving unit 16. In addition, as shown in FIG. A concave lens 17 is arranged between the light receiving part 16 and the shape of the laser beam formed on the light receiving part 16 to enlarge the light receiving part 16 formed of a photodiode and having a sensor divided into four parts. A, B, C, D combined photosensitive element and on both sides of the photosensitive element The side photosensitive elements constituted by sensors E and F. For example, as the tracking servo mechanism for CD and DVD, the three-beam method and the phase difference method are applicable, and the astigmatism method is used as the focusing servo mechanism. In this paper The standard is applicable to the Chinese National Standard (CNS) A4 specification (2) 0X 297 mm. -8- 1227471 A7 B7 ----- 5. Description of the invention (6) In the focus servo mechanism of CD and DVD, the photosensitive element is used as Common components. (Please read the precautions on the back before filling in this page.) In the light receiving unit 16, 'the wavelength of the laser varies with the temperature, and the light point of the laser is between sensor E and sensor F. The connected EF directions are shifted in a direction orthogonal to each other, and as a result, higher-order diffracted light leaks into the photosensitive element, causing a problem of shift. Herein, "the optical member 1 1 after the deviation is improved is shown below. On the side of the exit surface of the optical member 11", a first grating portion in which a plurality of convex portions 1 1a are continuously formed is formed. A stepped step portion 1 1 b (a second grating portion) is formed on the inclined surface of the portion 1 1 a. The convex portion 1 1 a and the step portion 1 1 b constitute a diffraction grating 11 A. The first grating portion is almost sawtooth-shaped, and each of the convex portions 11a has the same shape, and is a right-angled triangle formed by a vertical surface and an inclined surface. In addition, in the stepped portion lib, the flat surfaces S1 to S6 gradually change in height, and the number of steps formed is six. The width dimension w in each direction in the X direction and the depth dimension h in the y direction are equally spaced (h = d / 5, w = p / 6). However, p is a period, and this period is a width dimension of the convex portion 1 1 a. The diffraction grating 1! A formed on the optical member 11 shown in Figure 3 by the Consumer Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs, if the depth dimension of each stage is h, the refractive index of the resin is n, and the laser The wavelength of λ is λ, then the relationship (n -1) h = m λ holds. However, m is a positive integer. By determining h from the relational expression so that (η -1) h is a positive integer multiple of the wavelength, a laser of the wavelength λ can be transmitted directly without diffraction. From the relationship, set h for a laser of λ 2 (658 nm) so that the paper size applies the Chinese National Standard (CNS) A4 specification (2 丨 OX297 mm) -9-

Printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs. 5. Description of the Invention (7) (m) h is a positive integer multiple of λ 2. When a laser of λ 2 is incident on the diffracted light W 1 1 Α, it can be undiffracted. Instead, it is directly transmitted with 0 times of diffracted light. According to the above, the grating depth dimension d (= 5h) of the convex portion 1 1 a is determined, and the period P is also set in advance, for example, in a range from 30 to 50 // m @ 'to determine the number of steps of the remaining step portion, according to This can determine the shape of the optical member 11. Here, by changing the number of steps one step at a time, it has been proved that the shape with the number of steps indicated by 3 β being 6 steps is optimal. The reason will be described below with reference to FIG. 4. Fig. 4 is a graph showing the relationship between the grating depth and the efficiency of each diffracted light with respect to the wavelength? 1 and the wavelength? 2. However, the period (ρ) was 20 V m and the refractive index was 1.54. In addition, the efficiency of the vertical axis in FIG. 4 indicates that when the laser passes through the diffraction grating 1 1 A, the amount of laser light before passing is 1 ', and the diffraction light is 0 times (0T) after passing and ± 1 time. (: B 1T) and the ratio of the light quantity of ± 2nd-order diffracted light (soil 2T). As shown in Fig. 4 (a), by setting the grating depth dimension d of the diffraction grating to around 6 // m, it is possible to obtain highly efficient 0x diffraction light of 65 8nm (2) and 7 85 nm (λ 1 ) 1st diffracted light. As described above, by forming the optical member 1 1, for the laser of λ 1, there is a selectivity of selecting the first diffraction light, and for the laser of λ 2, it has the selectivity of selecting the 0 diffraction light. In addition, it is possible to obtain the first diffraction light of λ 1 and the zero diffraction light of λ 2 with high efficiency. In addition, at the grating depth dimensions shown in Figs. 4 (b) and (c), high-efficiency 1st diffracted light of 7 85nm (λ 1) and 0th diffracted light of 65 8nm (λ 2) cannot be obtained. If the depth dimension d becomes larger, the corresponding wavelength This paper size applies the Chinese National Standard (CNS) A4 specification (210X297 mm) (Please read the precautions on the back before filling this page)

-10- 1227471

V. Description of the invention (8) The change becomes larger, so it is not good. In addition, although the second-order diffracted light of 7 8 5 n m can be obtained at the depth of (b), the efficiency is deteriorated, which is not good. Therefore, the grating depth dimension d is around 6 // m (more precisely, it should be around 6 · 1 // m). By forming the width and depth dimensions of the steps 丨 丨 b at equal distances, It is possible to obtain a diffraction grating 1 1 A which maintains a high efficiency. In addition, the line diagram shown in FIG. 5 is a step number of the diffraction grating 1 1 A shown in FIG. 3 changed from 6 steps to 5 steps. However, in this case, as described above, the width and depth dimensions of each stage are formed at equal distances. In the diffraction grating 1 1 A shown in FIG. 5, by setting the grating depth dimension d of the diffraction grating to the vicinity of 5 · 8 // m (e), the quotient efficiency of 6 5 8 nm can be obtained. -1 diffraction light and 0 8 diffraction light at 7 8 5 nm. In this case, it is also possible to reverse λ 1 and λ 2 so that 65 8 nm is λ 1 and 7 85 nm is λ 2. As described above, by adopting the shape of the grating depth dimension d of the diffraction grating determined by (a) in FIG. 4 or (e) in FIG. 5, only the 0th order diffraction light of the 65 8 nm laser is transmitted, and Diffracting only 1 diffraction light of a laser of 7 8 5 nm, or -1 diffraction light of a 65 8 nm laser, and transmitting only 0 diffraction light of a 785 nm laser, can make 7 The optical axis of 8 5 nm and the optical axis of 65 8 nm are aligned on the light receiving portion 16. Therefore, since one laser is not diffracted, it is not affected by the wavelength variation, and although the other laser is diffracted, the diffraction angle is smaller than in the past, so the effect of wavelength variation can be reduced as a whole. And 'The Chinese standard (CNS) A4 size (210x297 mm) applies to this paper size (Please read the precautions on the back before filling this page) Order printed by the Intellectual Property Bureau Staff Consumer Cooperatives of the Ministry of Economic Affairs -11-: 227471 5. Invention Description (9) In the optical member 11 according to (9), the shape of the 6th step in the number of steps of 6th and 5th steps is better in terms of light efficiency. In addition, in this embodiment, although the combination of the wavelengths of 65 8 nm and 7 8 5 nm is described, a combination of other wavelengths may be used. Depending on the combination of wavelengths, the number of steps and depth dimensions of the optimal stepped portion will vary. In addition, by integrally forming the convex portion 11a constituting the first grating portion and the step portion 1lb constituting the second grating portion with resin, the cost can be reduced. The diffraction grating 1 1 B shown in FIG. 6 is a plan view showing a part of a modification of the diffraction grating 1 i a. This diffraction grating 1 1 B is superposed on each of the flat surfaces S 1 to S 6 of the stepped portion 1 1 b of the diffraction grating 1 1 A to form a minute diffraction grating (a third grating) composed of jagged irregularities. Part) 1 1 c. In the micro grating portion 1 1 c, when one period is taken from the convex portion to the adjacent convex portion, the one period is preferably shorter than the wavelengths λ 1 and λ 2 of the laser. This makes it possible to prevent reflection in the same manner as when forming an expensive antireflection film. To sum up, the present invention can make the staggered optical axes consistent at a given position, and can only diffract the laser of one wavelength, and make the diffraction angle of the other laser more than the conventional diffraction angle. It is smaller, and therefore, it is possible to reduce the influence of the wavelength variation due to the temperature change more than in the case where both the lasers are diffracted. In addition, since the optical device of the present invention has a light emitting portion that emits lasers of two wavelengths and a single optical member that aligns the optical axes of the lasers, the number of parts can be reduced, the structure can be simplified, and the cost can be reduced. This paper size applies the Chinese National Standard (CNS) Α4 specification (2Ι0 × 297 mm) (Please read the precautions on the back before filling this page) Order printed by the Intellectual Property Bureau of the Ministry of Economic Affairs and Consumer Cooperatives-12- 1227471 Printed by employee consumer cooperative f VP '> a 7I dHr B7 V. Description of the invention (id [Simplified description of drawing] Figure 1 is a schematic diagram showing an example of an optical device equipped with the optical member of the present invention. Fig. 2 is a schematic view showing an optical member and its optical axis. Fig. 3 is a plan view showing a part of the optical member. Fig. 4 is a line chart showing the efficiency of light with respect to a grating depth of 6 steps. Fig. 5 is a line diagram showing the efficiency of light with respect to a grating depth of 5 steps. Fig. 6 is a plan view showing a part of a modification of the optical member of the present invention. Fig. 7 is a view showing a conventional optical member and its Schematic diagram of the optical axis. [Description of symbols] 10—optical pickup; 11—optical component; 11a—convex (first grating portion); Π b—step portion (second grating portion); 11c—micro Grid section (third grating section); 12—light emitting section; 12a, 12b—light emitting element; 1 3—collimator lens; 1 4—beamsplitter lens; 15—objective lens; (please read the precautions on the back before filling this page ) This paper size applies to China National Standard (CNS) A4 (210X 297 mm) -13- 1227471

V. Description of the invention (J 1 6-Light receiving section. (Please read the precautions on the back before filling this page)

Printed by 8T Consumer Cooperatives, Bureau of Intellectual Property, Ministry of Economic Affairs, 1T This paper is sized to the Chinese National Standard (CNS) A4 (210 × 297 mm) -14-

Claims (1)

1227471 -if- A8 B8 C8 D8 Patent application scope. An optical structure of an optical component, which is provided to prevent the first wave of light from being diffracted. For example, the diffraction grating is applied for the application. For example, for the patented laser light set 2 of the laser 2 all pair 1 light, the stage has a step shape of 3, and relative to m λ 2 the diffraction of the second λ 1 is formed in the step shape in the ( η is the predetermined wavelength of the second wavelength λ laser light grating with the second component of the second wavelength refractive index two gratings, which is a feature whose length is 1 and the range of transmission. For the selectivity, the selection range of light The first part has a concave grating part, aU. Tint, especially W length; I 2, m is a part of the table light does not angle around the incident on: the laser diffraction light for the selectivity. 2 convex shape of the inclined part Each of the lasers is diffracted in a positive order and diffracts light of different wavelengths λ 1 and λ 2 to make the second wavelength λ grid. The optical component according to item 1, wherein: the first wavelength λ Laser light of 1 with laser body of the second wavelength λ 2 The optical component described above, wherein: the first grating portion formed and the second grating portion on the table, the depth of the first step (h) is -1 h number); the number of steps is set to: The first wavelength (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: Yes: 2: Zhongdu Zhong λ Zhong Qi Zhong Chang Long, Fang, Wave, Pieces The two parts of the structure are the deep structure of the structure and the theory of the light. The description of the light, the light, the light, the light, the light, the light, the light, the light, the light, the light, the light, the light, the light, the light, the light, the light, the light or the light, the light, the light, the light, the light, the light, the light, the light, the light, the light, the light, the light, the light, the light, the light, the light, the light, the light, the light, the light, the light, the light, the light, the light, the light, the light, the light, the light, the light, the light, the light, light Each circle is the Fan 1 Fan Li Department of the Fan. Lee's expertise Please apply for two-form application, 1T1 application as the first item, such as item η, such as • distance, description 8 · 4 between 5 places 5 6 etc. 6 The Chinese paper standard (CNS) Α4 specification (210X297 mm) applies to this paper size- 15-1227471 (revised ABCD page VI '4 1B instead of Φ VI. Patent application scope 2 The number of steps of the second grating portion of the second grating portion is six. 7 · The optical member according to item 3 of the patent application scope , Wherein: a concave-convex third grating portion is formed on a surface of the second grating portion, and the concave-convex is formed so that a third grating portion formed on a step of the second grating portion The period is below the wavelength of the laser light. 8 · The optical member according to item 7 of the patent application scope, wherein: the first grating portion and the second grating portion are both integrally formed of resin. 9 · An optical The device is characterized in that: a light-emitting portion is provided in which the light-emitting point emitting laser light of a first wavelength λ 1 and the light-emitting point emitting laser light of a second wavelength λ 2 are staggered in a direction orthogonal to the optical axis, and Transmitting light from the light-emitting part The optical member according to any one of the items 1 to 8 of the patent scope, please make the optical axis of the laser light of the first wavelength λ 1 and the optical axis of the laser light of the second wavelength λ 2 coincide at a predetermined position. (Please read the precautions on the back before filling out this page), 11 Printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs -16- This paper size applies to China National Standard (CNS) Α4 specification (2Ι0 × 297 mm)