JP2011081869A - Optical pickup device and method of manufacturing optical pickup device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To properly suppress the comatic aberration of an objective lens in both of the two kinds of laser lights radiated from a laser light source which radiates two-wavelength-based laser beams. <P>SOLUTION: An optical pickup device includes: the laser light source which has a first light-emitting element which radiates a first laser light to be applied on a first optical recording medium 5 and a second light-emitting element which radiates a second laser light to be applied on a second optical recording medium 5; and the objective lens 18 which condenses the first laser light on the first optical recording medium 5 and condenses the second laser light on the second optical recording medium 5. The image height characteristics of the comatic aberration of the objective lens 18 in each of the first laser light and the second laser light are matched. The laser light source is disposed so that the light axis of the objective lens 18 is orthogonal with a line segment which connects the light-emitting point 111 of the first light-emitting element with the light-emitting point 112 of the second light-emitting element and so that the light axis of the objective lens 18 passes through the midpoint of the line segment. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an optical pickup device and a method for manufacturing the optical pickup device, and more particularly to appropriately set coma aberration of an objective lens for each of two types of laser light emitted from a laser light source that emits laser light corresponding to two wavelengths. It relates to the technology to suppress.

  In an optical pickup device corresponding to a plurality of optical recording media, various contrivances have been made for the purpose of miniaturization / lightening and the like. For example, a two-wavelength compatible objective lens is adopted, and a two-wavelength laser diode 1 or the like is used. Some packages employ a laser light source that emits two wavelengths. Here, in the optical pickup device having such a configuration, both of the light emitting points of the respective light emitting elements cannot be arranged on the optical axis of the objective lens at the same time, and the objective lens for both the laser beams of the respective wavelengths. The problem is how to suppress the coma aberration (see, for example, Patent Document 1).

JP 2009-170091 A

  In an optical pickup device that employs a two-wavelength laser light source, the emission point of each laser beam is different, and it is generally designed by focusing on the optical characteristics of one predetermined optical recording medium, usually a high-density optical recording medium. Two-wavelength compatible objective lenses have different image height characteristics for each wavelength. FIG. 13A is an example of image height characteristics of coma aberration of an objective lens with respect to a laser beam (hereinafter referred to as a first laser beam) used for recording / reproduction of the DVD (Digital Versatile Disk) standard, and FIG. (Compact Disk) is an example of an image height characteristic of coma aberration of the objective lens with respect to laser light (hereinafter referred to as second laser light) used for recording / reproduction of a standard optical recording medium. As shown in these figures, this two-wavelength compatible objective lens has a higher image height characteristic of the first laser beam used for recording / reproduction of a DVD standard optical recording medium having a short wavelength and a high density. It is designed to be better than the image height characteristic of the second laser beam used for recording / reproducing of the image.

  FIG. 14 shows a principle diagram of an optical system of a general optical pickup device. In the figure, reference numeral 111 denotes a light emitting point (hereinafter referred to as a first laser light) of a laser light source 11 (not shown) composed of a two-wavelength laser diode for DVD recording / reproducing laser light (hereinafter referred to as a first laser light). Reference numeral 112 denotes a light emitting point of a light emitting element (hereinafter referred to as a second laser light) of a laser beam for recording / reproducing a CD of the laser light source 11 (hereinafter referred to as a second laser light). (Referred to as second light emitting point 112). As shown in the figure, this optical system includes a collimating lens 16, a two-wavelength compatible objective lens 18, a diffraction grating 12, and a quarter-wave plate 13. Reference numeral 5 denotes an optical recording medium (DVD standard or CD standard optical recording medium).

In the optical system shown in FIG. 14, for example, it is assumed that the focal length of the collimating lens 16 is 14 mm and the distance between the first light emitting point 111 and the second light emitting point 112 is 110 μm. In this case, the angle between the traveling direction of the first laser beam or the second laser beam and the optical axis of the objective lens 18 is tan ⁻¹ {(0.11 / 2) / 14} = 0.2 °. . 13A and 13B, the coma aberration amount of the objective lens 18 with respect to the first laser light is 2 mλrms, and the coma aberration amount of the objective lens 18 with respect to the second laser light is 10 mλrms, both of which are practically used. This is a particularly safe range.

  Here, it is assumed that the first light emission point 111 and the second light emission point 112 are displaced by 110 μm in the −Z direction due to a manufacturing error or the like. In this case, the angle formed by the traveling direction of the second laser light and the optical axis of the objective lens 18 is 0.4 °. Referring to FIG. 13B, the coma aberration amount of the objective lens 18 with respect to the second laser light in this case It can be seen that the value becomes as large as 20 mλrms.

  Thus, in an optical pickup device that employs a laser light source that emits two wavelengths in one package, there is a problem in that coma aberration of both types of laser light cannot always be properly suppressed. .

  The present invention has been made in view of such problems, and appropriately suppresses the coma aberration of the objective lens for each of the two types of laser light emitted from a laser light source that emits laser light corresponding to two wavelengths. It is an object of the present invention to provide an optical pickup device that can be used, and a method for manufacturing the optical pickup device.

One of the present invention for achieving the above object is an optical pickup device for irradiating an optical recording medium or an optical recording medium with a light beam and detecting the light beam reflected from the optical recording medium,
A laser light source comprising: a first light emitting element that emits a first laser beam irradiated on the first optical recording medium; and a second light emitting element that emits a second laser light irradiated on the second optical recording medium. When,
An objective lens for condensing the first laser light on the first optical recording medium and condensing the second laser light on the second optical recording medium;
With
The objective lens has matching image height characteristics of coma aberration for each of the first laser light and the second laser light,
In the laser light source, an optical axis of the objective lens is orthogonal to a line segment connecting a light emitting point of the first light emitting element and a light emitting point of the second light emitting element, and the optical axis is a midpoint of the line segment. It shall be arranged to pass through.

  In this way, the image height characteristics of the coma aberration for the first laser light and the second laser light of the objective lens are made to coincide with each other, the laser light source, the optical axis of the objective lens is the light emitting point of the first light emitting element, and the second light emission. 2 is emitted from a laser light source that emits laser light corresponding to two wavelengths by arranging the optical axis of the objective lens so as to pass through the midpoint of the line segment while being orthogonal to the line segment connecting the light emitting point of the element. The coma aberration of the objective lens can be appropriately suppressed for both types of laser light.

  For example, it is assumed that the first optical recording medium is a DVD standard optical recording medium, the second optical recording medium is a CD standard optical recording medium, and the laser radiator is shifted to the second light emitting element side. In this case, since the light emitting point of the first light emitting element approaches the optical axis of the objective lens, the amount of coma aberration for the first laser light is reduced. On the other hand, the light emitting point of the second light emitting element moves away from the optical axis of the objective lens, but the image height characteristics of the coma aberration for each of the first laser light and the second laser light are the same. The image height characteristic of the objective lens is gentler than that of a conventional objective lens, and the amount of coma caused by the shift is reduced as compared with the conventional one.

  Further, for example, it is assumed that the laser radiator is displaced toward the first light emitting element. In this case, since the light emitting point of the second light emitting element approaches the optical axis of the objective lens, the amount of coma aberration for the second laser light is reduced. On the other hand, the light emitting point of the first light emitting element is moved away from the optical axis of the objective lens. However, since the coma aberration amount is slightly larger than that of the conventional one, the influence on the performance of the optical pickup device is small.

  The coma aberration image of the first laser light and the second laser light is set by appropriately setting the aspheric coefficient of the lens surface on the collimator lens side of the objective lens and the aspheric coefficient of the lens surface on the optical recording medium side. High characteristics can be matched as described above.

  In addition, the subject which this application discloses, and its solution method are clarified by the column of the form for inventing, and drawing.

  ADVANTAGE OF THE INVENTION According to this invention, the coma aberration of the objective lens about each of two types of laser beams radiated | emitted from the laser light source which radiates | emits the laser beam for two wavelengths can be suppressed appropriately.

2 is a diagram showing a configuration of an optical system of the optical pickup device 1. FIG. 2 is a diagram illustrating a configuration of a first optical system of the optical pickup device 1. FIG. It is a figure explaining the structure of the 2nd optical system of the optical pick-up apparatus. It is a perspective view which shows the mode of the housing 50 and the optical system mounted in this. 2 is a block diagram showing an example of an optical disc device 500. FIG. FIG. 3 is a view showing a structure of a first laser light source 11. It is a principle figure of a 1st optical system. 2 is a side view of a first objective lens 18. FIG. FIG. 4 is a diagram showing specifications of the first objective lens 18. When the shape of the first objective lens 18 is represented by the phase function formula Φ (r) shown in FIG. 11, the radius radius and the aspherical coefficient of the lens surface of the first objective lens 18 on the first collimator lens 16 side are shown. FIG. The figure which shows the radial radius and aspherical coefficient of the lens surface by the side of the optical recording medium 5 of the 1st objective lens 18 in the case of expressing the shape of the 1st objective lens 18 by the phase function formula Φ (r) shown in FIG. It is. It is a figure which shows phase function type | formula (PHI) (r). It is a figure which shows the image height characteristic of the coma aberration about the 1st laser beam of the 1st objective lens 18 shown as embodiment. It is a figure which shows the image height characteristic of the coma aberration about the 2nd laser beam of the 1st objective lens 18 shown as embodiment. It is a figure which shows the image height characteristic of the coma aberration about the 1st laser beam of the 1st objective lens. It is a figure which shows the image height characteristic of the coma aberration about the 2nd laser beam of the 1st objective lens. It is a principle figure of the optical system of an optical pick-up apparatus.

  The best mode for carrying out the invention will be described below.

  The optical pickup device 1 described in the present embodiment is a device that irradiates a rotating optical recording medium 5 with a light beam and detects a light beam reflected from the optical recording medium 5. The optical pickup device 1 is mounted on an information recording / reproducing apparatus such as an optical recording medium recording / reproducing apparatus 500 described later. The optical recording medium 5 on which information is recorded or reproduced by the optical pickup device 1 is, for example, a DVD (Digital Versatile Disk) standard optical recording medium 5 (hereinafter referred to as a first optical recording medium 5), a CD. (Compact Disk) standard optical recording medium 5 (hereinafter referred to as second optical recording medium 5) and BD (Blu-ray Disk) standard (or HD-DVD (High Definition Digital Versatile Disk) standard) optical recording The medium 5 (hereinafter referred to as the third optical recording medium 5).

  FIGS. 1 to 3 show the configuration of the optical system of the optical pickup device 1 used for recording / reproducing of the optical recording medium 5 described as the present embodiment. The optical pickup device 1 performs recording / reproducing of the first optical system, which is an optical system for recording / reproducing the first optical recording medium 5 and the second optical recording medium 5, and the third optical recording medium 5. A second optical system which is an optical system of 1 coincides with the radial direction (radial direction) of the optical recording medium 5, and the rotation center of the optical recording medium 5 exists in the + X direction.

  First, the first optical system will be described. The first optical system includes a first laser light source 11, a first diffraction grating 12, a first quarter wavelength plate 13, a first beam splitter 14, a second quarter wavelength plate 15, a first collimating lens 16, A first raising mirror 17, a first objective lens 18, a first sensor lens 19 (detection lens), and a first photodetector 20 are included.

  The first laser light source 11 is a two-wavelength laser diode, a first light emitting element that emits a first laser light having a first wavelength (for example, red light of 660 nm) in a red wavelength band of 645 nm to 675 nm, and an infrared wavelength band of 765 nm to 765 nm. A second light emitting element that emits a second laser beam having a second wavelength of 805 nm (for example, infrared light of 785 nm) is provided.

  The first laser beam or the second laser beam emitted from the first laser light source 11 is incident on the first diffraction grating 12. The first diffraction grating 12 separates incident laser light into 0th order light, + 1st order diffracted light, and −1st order diffracted light.

  The half-wave plate 13 is incident with the first laser light or the second laser light that has passed through the first diffraction grating 12. The half-wave plate 13 converts the polarization direction of the first laser light or the second laser light incident as linearly polarized light into a predetermined direction.

  The first beam splitter 14 reflects the first laser light or the second laser light incident from the half-wave plate 13, while the return light incident from the first quarter-wave plate 15 is transmitted.

  The first laser beam or the second laser beam reflected by the first beam splitter 14 is incident on the first quarter-wave plate 15. The first quarter-wave plate 15 converts incident laser light from linearly polarized light to circularly polarized light. The first quarter-wave plate 15 may be provided integrally with the first collimating lens 16 on the lens surface on one side of the first collimating lens 16, or separate from the first collimating lens 16. It may be provided on the body.

  The first collimating lens 16 converts the first laser light or the second laser light incident after passing through the first quarter-wave plate 15 after being reflected by the first beam splitter 14 into parallel light. 1 The light enters the rising mirror 17.

  The first rising mirror 17 reflects the incident first laser beam or second laser beam in a direction perpendicular to the signal recording surface of the first optical recording medium 5 or the second optical recording medium. As shown in FIG. 3, the first laser light or the second laser light reflected by the first raising mirror 17 enters the first objective lens 18. The first objective lens 18 focuses the incident first laser beam or second laser beam on the signal recording surface of the first optical recording medium 5 or the second optical recording medium 5.

  In the first optical system configured as described above, the first laser light or the second laser light focused by the second objective lens 38 and incident on the signal recording surface of the first optical recording medium 5 or the second optical recording medium 5. Is returned to parallel light by the first objective lens 18, and then passes through the first rise-up mirror 17, the first collimator lens 16, and the first quarter-wave plate 15, and then the first beam splitter 14. Is incident on. The return light incident on the first beam splitter 14 passes through the first beam splitter 14, passes through the first sensor lens 19, and finally enters the first photodetector 20.

  The first sensor lens 19 converges the return light of the first laser light or the second laser light on the second photodetector 40 and generates astigmatism in the return light to generate a focus error signal. The first sensor lens 19 is constituted by, for example, a cylindrical lens, a toric lens, an anamorphic lens, or a parallel plate inclined in a predetermined direction with respect to the optical axis.

  The first photodetector 20 has a light detection region that is divided into a plurality of portions (for example, each light receiving region of each laser beam divided into three by the first diffraction grating 12 is divided into four). The first photodetector 20 is configured using a light receiving element such as a photodiode, for example. It should be noted that a signal reproduction operation and a signal recording operation based on the signal detected by the first photodetector 20, a processing method of the signal detected by the first photodetector 20, a tracking error detection method by DPP (Differential Push Pull), etc. Since the focus error detection method by the astigmatism method is well known, the details are omitted.

  Next, the second optical system will be described. The second optical system includes a second laser light source 31, a second diffraction grating 32, a second beam splitter 33, a second reflecting mirror 34, a second collimating lens 35, a second rising mirror 36, and a second quarter wavelength. A plate 37, a second objective lens 38, a second sensor lens 39 (detection lens), and a second photodetector 40 are included.

  The second laser light source 31 emits third laser light having a third wavelength (for example, 405 nm blue light) in a blue-violet wavelength band of 400 nm to 420 nm. The second laser light source 31 is configured using a light emitting element such as a semiconductor laser.

  The third laser light emitted from the second laser light source 31 is incident on the second diffraction grating 32. The second diffraction grating 32 separates the third laser light into 0th-order light, + 1st-order diffracted light, and −1st-order diffracted light, and the polarization direction of the third laser light that is linearly polarized light in a predetermined direction. A half-wave plate to be converted is a component.

  The second beam splitter 33 reflects the third laser light incident from the second diffraction grating 32, while the return light of the third laser light incident from the second reflecting mirror 34 is transmitted. The second reflecting mirror 34 reflects the third laser light incident from the second beam splitter 33 in the direction of the second collimating lens 35.

  The second collimating lens 35 converts the third laser light incident from the second reflecting mirror 34 into parallel light. The third laser light (parallel light) converted by the second collimating lens 35 enters the second rising mirror 36. The second raising mirror 36 reflects the third laser light incident from the second collimating lens 35 in a direction perpendicular to the recording surface of the third optical recording medium 5.

  As shown in FIG. 2, the third laser light reflected by the second rising mirror 36 in the direction perpendicular to the recording surface of the third optical recording medium 5 is incident on the second quarter-wave plate 37. The third laser light is converted from linearly polarized light into circularly polarized light by the second quarter-wave plate 37.

  The third laser light (circularly polarized light) transmitted through the second quarter wavelength plate 37 enters the second objective lens 38. The second objective lens 38 focuses the incident third laser light (circularly polarized light) on the signal recording surface of the third optical recording medium 5.

  In the second optical system configured as described above, the return light of the third laser light focused by the second objective lens 38 and incident on the signal recording surface of the third optical recording medium 5 is collimated by the second objective lens 38. It is converted into light and incident on the second quarter-wave plate 37, and the second quarter-wave plate 37 converts the circularly-polarized light into linearly-polarized light (the direction opposite to the direction incident from the second rising mirror 36). Is converted to The return light that has become linearly polarized light is incident on the second beam splitter 33 via the second rising mirror 36, the second collimating lens 35, and the second reflecting mirror 34.

  The return light that has entered the second beam splitter 33 passes through the second beam splitter 33, passes through the second sensor lens 39, and enters the second photodetector 40. The second sensor lens 39 converges the return light of the third laser light on the second photodetector 40 and generates astigmatism in the return light to generate a focus error signal. The second sensor lens 39 is constituted by, for example, a cylindrical lens, a toric lens, an anamorphic lens, or a parallel plate inclined in a predetermined direction with respect to the optical axis.

  The second photodetector 40 has a light detection area divided into a plurality of parts (for example, each light receiving area of each laser beam divided into three by the second diffraction grating 32 is divided into four). The second photodetector 40 is configured using a light receiving element such as a photodiode, for example. A signal reproduction operation and a signal recording operation based on the signal detected by the second photodetector 40, a processing method of the signal detected by the second photodetector 40, a tracking error detection method by DPP (Differential Push Pull), etc. Since the focus error detection method by the astigmatism method is well known, the details are omitted.

  FIG. 4 is a perspective view showing a state in which the optical system having the above configuration is mounted on a housing 50 made of a material such as metal or resin. In the figure, an arrow X indicates the radial direction (radial direction) of the optical recording medium 5. The rotation center of the optical recording medium 5 exists in the + X direction.

  As shown in the figure, each component of the optical system of the optical pickup device 1 is provided at a predetermined position of the housing 50 so that these are in the positional relationship shown in FIGS. Each component of the optical system is provided in the housing 50 by being bonded or fitted to a convex portion or a partition plate provided in the housing 50.

  FIG. 5 is a block diagram showing an example of an optical recording medium recording / reproducing apparatus 500 configured using the optical pickup apparatus 1 described above. As shown in the figure, the optical recording medium recording / reproducing apparatus 500 has the configuration of the optical pickup apparatus 1 described above, and also includes a spindle motor 502, a motor driving circuit 503, a laser driver 504, an access mechanism 505, a modulation circuit 506, It further includes an amplifier circuit 507, a demodulation circuit 508, a focus control circuit 509, a tracking control circuit 510, a tilt control circuit 511, an optical characteristic correction circuit 512, a system control device 513, and an external device 514.

  In the figure, a spindle motor 502 rotates the optical recording medium 5. The motor drive circuit 503 controls the rotation of the spindle motor 502 in accordance with a control signal sent from the system control device 513.

  The access mechanism 505 moves the optical pickup device 1 in the radial direction (radial direction) of the optical recording medium 5 in accordance with a control signal sent from the system control device 513.

  The laser driver 504 controls the output of the first to third laser beams emitted from the first laser light source 11 and the second laser light source 31 in accordance with the signal input from the modulation circuit 506.

  The modulation circuit 506 modulates data to be recorded on the optical recording medium 5 input from the system control device 513 into a recording pulse signal. The data to be recorded on the optical recording medium 5 is supplied as needed from an external device 514 such as a personal computer via the system control device 513, for example.

  The amplification circuit 507 amplifies an RF signal (RF: Radio Frequency) included in the electrical signal output from the photodetector 22 of the optical pickup device 1 and outputs the amplified RF signal to the demodulation circuit 508. The demodulation circuit 508 demodulates the RF signal input from the amplification circuit 507 and outputs it to the system control device 513. The system control device 513 outputs a data signal based on the demodulated signal input from the demodulation circuit 508 to the external device 514.

  A focus control circuit 509, a tracking control circuit 510, and a tilt control circuit 511 perform drive control of the first objective lens 18 and the second objective lens 38. Among these, the focus control circuit 509 detects a focus error signal included in the electrical signal output from the first photodetector 20 or the second photodetector 40 of the optical pickup device 1, and based on the detected focus error signal, Focus control of the first objective lens 18 and the second objective lens 38 is performed. The tracking control circuit 510 detects a tracking error signal included in the electrical signal output from the first photodetector 20 or the second photodetector 40 of the optical pickup device 1, and based on the detected tracking error signal, the first objective. Tracking control of the lens 18 and the second objective lens 38 is performed. The tilt control circuit 511 detects a tilt error signal included in the electrical signal output from the first photodetector 20 or the second photodetector 40 of the optical pickup device 1, and based on the detected tilt error signal, the first objective. Tilt control of the lens 18 and the second objective lens 38 is performed.

  The optical characteristic correction circuit 515 corrects deterioration of the optical characteristics of the first objective lens 18 and the second objective lens 38 based on the temperature change. The optical characteristic correction circuit 515 corrects spherical aberration caused by a difference in cover thickness for each optical recording medium 5 or a difference in cover thickness for each layer in an optical recording medium having a multilayer structure. This correction method includes, for example, a magnification characteristic method that uses a degree of divergence / focusing with respect to a design value of a light beam incident on the first objective lens 18 and the second objective lens 38, and a spherical aberration having a reverse polarity using a liquid crystal element. There is a spherical aberration method in which spherical aberration is corrected by generating it. The optical characteristic correction circuit 515 corrects the optical characteristic by moving, for example, the collimating lens 16 in the optical axis direction (see, for example, JP 2008-234803 A).

= Light emitting element =
FIG. 6 shows the structure of the first laser light source 11. The first laser light source 11 includes a first light emitting element and a second light emitting element. As shown in the figure, the light emitting point of the first light emitting element (hereinafter referred to as the first light emitting point 111) and the light emitting point of the second light emitting element (hereinafter referred to as the second light emitting point 112) are predetermined. They are separated by a distance d.

  FIG. 7 shows a principle diagram of the first optical system. As shown in the figure, the first laser light source 11 has an optical axis of the first objective lens 18 orthogonal to a line segment connecting the light emitting point 111 of the first light emitting element and the light emitting point 112 of the second light emitting element. The optical axis of the first objective lens 18 is disposed in the housing 50 in such a positional relationship that it passes through the midpoint of the line segment. For this reason, the shortest distance from the first light emitting point 111 to the optical axis of the first objective lens 18 (the length of the perpendicular line extending from the first light emitting point 111 to the optical axis) and the second light emitting point 112 to the first objective lens. The shortest distance to the 18 optical axes (the length of the perpendicular line extending from the second light emitting point 112 to the optical axis) is equal.

= Objective lens =
FIG. 8 is a side view of the first objective lens 18. In the figure, the thick line denoted by reference numeral 81 is the first optical recording medium 5, and the thin line denoted by reference numeral 82 is the second optical recording medium 5. The outer diameter of the first objective lens 18 is 5.00 mm. As shown in the figure, in the first objective lens 18, the curvature of the lens surface on the first collimating lens 16 side is larger than the curvature of the lens surface on the optical recording medium 5 side.

  The specifications of the first objective lens 18 are shown in FIG. As shown in the drawing, the design wavelength of the first objective lens 18 for the first optical recording medium 5 is 660 nm, the focal length is 2.33 mm, and the numerical aperture (hereinafter referred to as NA (Numerical Aperture)) is 0. 60. The design wavelength of the first objective lens 18 for the second optical recording medium 5 is 785 mm, the focal length is 2.35 mm, and the NA is 0.47.

  FIG. 10A is an aspherical coefficient of the lens surface of the first objective lens 18 on the first collimating lens 16 side when the shape of the first objective lens 18 is represented by the phase function equation Φ (r) shown in FIG. . FIG. 10B is an aspheric coefficient of the lens surface of the first objective lens 18 on the optical recording medium 5 side when the shape of the first objective lens 18 is represented by the phase function equation Φ (r) shown in FIG. . In these figures, r is a radial radius and cc is a conic coefficient.

  12A is an actual measurement value of image height characteristics of coma aberration for the first laser light of the first objective lens 18 of the present embodiment, and FIG. 12B is coma aberration for the second laser light of the first objective lens 18. This is an actual measurement value of image height characteristics. As shown in these figures, the image height characteristic of the coma aberration of the first objective lens 18 with respect to the first laser light and the image height characteristic of the coma aberration with respect to the second laser light substantially coincide (the occurrence of wavefront aberration with respect to the incident light angle). The angle of the straight line indicating the degree is substantially the same). Note that the term “match” here means design match and not necessarily complete match.

= Coma aberration =
In the first optical system shown in FIG. 7, when the focal length of the collimating lens 16 is 14 mm and the distance between the first light emitting point 111 and the second light emitting point 112 is 110 μm, the first objective lens from the first light emitting point 111 is used. The shortest distance to the optical axis 18 is equal to the shortest distance from the second light emitting point 112 to the optical axis of the first objective lens 18, that is, the center of the first light emitting point 111 and the second light emitting point 112 is the first objective. Since it is arranged on the optical axis of the lens 18, the angle formed by the angle of the incident light of the first laser light emitted from the first light emitting point 111 to the first objective lens 18 and the optical axis of the objective lens 18 is tan ⁻¹ {(0.11 / 2) / 14} = 0.2 °. Further, the angle between the angle of the incident light of the second laser light emitted from the second light emitting point 112 to the first objective lens 18 and the optical axis of the objective lens 18 is also tan ⁻¹ {(0.11 / 2) / 14} = 0.2 °. 12A and 12B, the coma aberration amount of the objective lens 18 with respect to the first laser beam corresponding to 0.2 ° is 5 mλrms, and the coma aberration amount of the objective lens 18 with respect to the second laser beam is also 5 mλrms. Yes, the skew characteristics for the first optical recording medium 5 (DVD) and the second optical recording medium 5 (CD) can be made equal.

  Here, in FIG. 7, for example, it is assumed that the first laser radiator 11 is displaced by 110 μm in the −Z direction (second light emitting element side). In this case, since the first emission point 111 approaches the optical axis of the first objective lens 18, the amount of coma aberration for the first laser light is reduced. The second light emitting point 112 moves away from the optical axis of the first objective lens 18, but as shown in FIGS. 12A and 12B, the image height characteristics of coma aberration for the first laser light and the second laser light coincide with each other. Therefore, the image height characteristic of the first objective lens 18 with respect to the second laser light is gentler than that of the objective lens of the conventional configuration, and the amount of coma caused by the above-described deviation is smaller than that of the conventional one.

  In FIG. 7, it is assumed that the first laser radiator 11 is displaced in the + Z direction (the first light emitting element side). In this case, since the second emission point 112 approaches the optical axis of the first objective lens 18, the amount of coma aberration for the second laser light decreases. Further, the first light emitting point 111 moves away from the optical axis of the first objective lens 18, but when comparing FIG. 12A and FIG. 13A, the increase in the amount of coma aberration is slightly larger than the conventional one, so that the performance of the optical pickup device 1 is improved. The effect is small.

  As described above, in the optical pickup device 1 of the present embodiment, even when the first laser radiator 11 is displaced in either the −Z or + Z direction, the first laser beam about the first laser beam is used. Both the coma aberration of the first objective lens 18 and the coma aberration of the first objective lens 18 for the second laser light can be appropriately suppressed. For this reason, according to the optical pickup device 1 of the present embodiment, the optical performance in a well-balanced manner for both the first optical recording medium 5 and the second optical recording medium 5 without extremely degrading the performance of either one. Can keep.

  Although the embodiment has been described above, the above description is intended to facilitate understanding of the present invention and is not intended to limit the present invention. The present invention can be changed and improved without departing from the gist thereof, and the present invention includes the equivalents thereof.

DESCRIPTION OF SYMBOLS 1 Optical pick-up apparatus 5 Optical recording medium 11 1st laser light source 111 1st light emission point 112 2nd light emission point 12 1st diffraction grating 13 1/2 wavelength plate 14 1st beam splitter 15 1st 1/4 wavelength plate 16 1st 1 collimating lens 17 first raising mirror 18 first objective lens 19 first sensor lens 20 first photodetector 31 second laser light source 32 second diffraction grating 33 second beam splitter 34 second reflecting mirror 35 second collimating lens 36 Second rising mirror 37 Second quarter wave plate 38 Second objective lens 39 Second sensor lens 40 Second photodetector 50 Housing

Claims (4)

An optical pickup device that irradiates an optical recording medium or an optical recording medium with a light beam and detects a light beam reflected from the optical recording medium,
A laser light source comprising: a first light emitting element that emits a first laser beam irradiated on the first optical recording medium; and a second light emitting element that emits a second laser light irradiated on the second optical recording medium. When,
An objective lens for condensing the first laser light on the first optical recording medium and condensing the second laser light on the second optical recording medium;
With
The objective lens has matching image height characteristics of coma aberration for each of the first laser light and the second laser light,
In the laser light source, an optical axis of the objective lens is orthogonal to a line segment connecting a light emitting point of the first light emitting element and a light emitting point of the second light emitting element, and the optical axis is a midpoint of the line segment. An optical pickup device arranged to pass through. The optical pickup device according to claim 1,
The objective lens includes an aspherical coefficient of a lens surface on the collimator lens side and a lens on the optical recording medium side so that image height characteristics of coma aberration for the first laser beam and the second laser beam coincide with each other. An optical pickup device characterized in that a surface aspheric coefficient is set. The optical pickup device according to claim 1,
The first optical recording medium is a DVD (Digital Versatile Disk) standard optical recording medium,
The second optical recording medium is a CD (Compact Disk) standard optical recording medium,
The first laser light has a red wavelength band of 645 nm to 675 nm,
The second laser light has an infrared wavelength band of 765 nm to 805 nm.
An optical pickup device characterized by that. An optical pickup device for irradiating an optical recording medium or an optical recording medium with a light beam and detecting the light beam reflected from the optical recording medium,
A laser light source comprising: a first light emitting element that emits a first laser beam irradiated on the first optical recording medium; and a second light emitting element that emits a second laser light irradiated on the second optical recording medium. When,
The first laser beam is focused on the first optical recording medium, the second laser beam is focused on the second optical recording medium, and a coma for each of the first laser beam and the second laser beam is collected. An objective lens having the same image height characteristics of aberration, and
In the laser light source, the optical axis of the objective lens is orthogonal to a line segment connecting the light emitting point of the first light emitting element and the light emitting point of the second light emitting element, and the optical axis is a midpoint of the line segment. An optical pickup device manufacturing method, wherein the optical pickup device is disposed so as to pass through.

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