JP2005353169A - Optical head device, optical pickup device, manufacturing method of optical head device, and assembly method of optical head device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make it possible to correctly carry out axial alignment of an objective lens and a liquid crystal type phase correction component in an optical head device having the objective lens comprising an annular diffraction face for phase corrections, and the liquid crystal type phase correction component 5 in order to make the constitution to perform recording or/and reproducing with one optical head device in common to the light of a plurality of wavelengths from a laser light source. <P>SOLUTION: Although a positioning mark 8 which forms designated positional relationship with a designated annulus of the annular-like diffraction face of the objective lens 4, when an axial center of the liquid crystal type phase correction component 5 and an axial center of the objective lens 4 having the annular-like diffraction face for phase correction are matched, is arranged in the liquid crystal type phase correction component 5, alignment of axes can be performed with high accuracy without performing a special process or processing by forming this mark 8 simultaneously with the formation of an electrode pattern of the liquid crystal type phase correction component 5. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical head device, an optical pickup device, a manufacturing method of the optical head device, and an assembling method of the optical head device, and in particular, an objective lens having a ring-shaped diffraction surface for phase correction and a liquid crystal type phase correction element. The present invention relates to an optical head device provided, an optical pickup device provided with the engineering head device, a method for manufacturing the optical head device, and a method for assembling the optical head device.

Optical information recording media that are currently in widespread use include optical disks, magneto-optical disks, optical cards, and the like.
Writing and reading of signal information to and from these optical information media is performed by an optical head device that condenses and irradiates light from a laser light source onto the optical information medium by an objective lens.
Various types of optical head devices for recording or / and reproducing are proposed.

The signal recording density in the optical information medium is basically determined by the wavelength of the laser light source and the numerical aperture of the objective lens in the optical head device. That is, the wavelength of the laser beam used is short, and the objective lens has a large numerical aperture (NA), which can improve the signal recording density by reducing the laser beam spot diameter on the optical information medium. .
Specifically, in an optical head device for a CD (Compact Disc), N.I. A. Is an objective lens having a wavelength of 0.45 and a laser beam having a wavelength of 780 nm. In the CD, the thickness of the light transmission layer on the laser light incident side is 1.2 mm.

In an optical head device for a DVD (Digital Versatile Disc), N.I. A. Is an objective lens having a wavelength of 0.6 and a laser beam having a wavelength of 650 nm. In DVD, an optical disk having a light transmission layer on the laser beam incident side having a thickness of 0.6 mm is used.
In Blu-Ray Disc, which is the next generation optical disc standard, N.I. A. Is 0.85, the wavelength is 410 nm, and the thickness of the light transmission layer on the light incident side is 0.1 mm.

  On the other hand, in recent years, there is a tendency that a device capable of performing recording or / and reproduction on a CD, a DVD, and a Blu-Ray Disc in a common drive device. Due to demands for miniaturization and the like, it is desirable that the above-described recording or / and reproduction be performed by one optical head device in common for these CDs, DVDs, and Blu-Ray Discs. For this purpose, a semiconductor laser corresponding to each wavelength and each numerical aperture N.D. A. It is necessary to use an objective lens corresponding to the above. However, since three optical systems are mounted in this method, the cost is increased due to the increase in the number of parts and the number of assembly steps, resulting in an increase in the size of the optical head device.

In order to solve such a problem, it has been proposed to synthesize and separate laser beams having different wavelengths by a synthesis / separation mirror having wavelength selectivity, and to construct a compact optical head device using the same objective lens. .
However, in this case, as described above, the CD, DVD, and Blu-Ray Disc have different light transmission layer thicknesses and wavelengths, so that the generated spherical aberrations are different. It is necessary to design the optical system so as to be appropriately suppressed.

  As a method of sufficiently suppressing spherical aberration with respect to a plurality of wavelengths with one optical system, a method of providing an annular diffractive surface on the surface of an aspheric objective lens has been proposed. This is because the outer shape of the objective lens is first designed so that the wavefront aberration is optimized in an optical system of any wavelength λA, and the spherical aberration that occurs when using the wavelength λB is cancelled. A ring-shaped diffraction surface is provided on the surface. This is because of the use of diffraction, phase correction has wavelength selectivity and is effective for light of wavelength λB, but does not affect aberrations for light of other wavelengths λA. . By this method, spherical aberration of a plurality of optical systems can be suppressed with one optical head.

On the other hand, in the Blu-Ray Disc, the objective lens N.D. A. Therefore, the optical tolerance for the disc thickness error and the objective lens manufacturing error is extremely small, and an extremely high manufacturing technique is required to keep all the discs and objective lenses within the allowable values. For this reason, the production yield of the optical head device is poor and the cost is high, so that mass production is not realistic.
Further, in the Blu-Ray Disc, it is necessary to provide the optical system with a mechanism that variably corrects the spherical aberration according to the manufacturing error for each disk and for each objective lens, not a pickup with fixed aberration.

The spherical aberration correction mechanism is roughly classified into the following two methods.
One of them is an expander lens that cancels the spherical aberration of the entire optical path by arranging two groups of lenses with positive and negative power between the objective lens and the light source and changing the lens interval in the optical axis direction. It is a system (refer patent document 1).
However, this method originally requires that two groups of lenses that are spaced apart from each other must be disposed, and that a mechanism for physically moving these lens groups must be newly disposed. There are problems such as an increase in volume.

In another method, a phase correction element filled with an anisotropic optical medium such as liquid crystal is disposed between a pair of transparent glass substrates having electrodes on the surface between an objective lens and a light source, This is because the phase of light transmitted through the surface can be continuously controlled by applying a voltage to the electrodes (see Patent Document 2).
When the objective lens and the liquid crystal type phase correction element are combined as in this method, a laser of each wavelength for recording / reproducing all of a plurality of wavelengths, for example, CD, DVD, Blu-Ray Disc. One optical head can be configured for light, and this liquid crystal phase correction element can be reduced in size and thickness, and a new drive mechanism is not required. Since there is almost no complication of the configuration, there is an advantage that the configuration can be made compact.

  However, if there is a deviation between the central axis of the spherical aberration correcting element and the central axis of the objective lens, coma aberration occurs. Therefore, when the central axes of the objective lens and the spherical aberration correcting element are each 3 mm in effective diameter, for example. Therefore, it is necessary to position and fix with a high accuracy of ± 20 μm or less.

This axial alignment is different from the spherical aberration correction element using liquid crystal, that is, the object is different, but the objective lens and the phase correction element are used as a method for positioning the objective lens and the phase correction element relative to each other. A method has been proposed in which positioning marks are formed on each of the concaves and convexes and these are adjusted to a reference (see Patent Document 3).
However, this method physically adds unevenness to the lens or phase correction element, so that a new process is added in the manufacturing process, the productivity is lowered, the accuracy of unevenness formation, and the transmittance and aberration due to the unevenness are further reduced. There are problems such as the need to consider the effects of
JP 2000-131603 JP 2001-143303 A JP 2001-6203 A

  The present invention relates to an optical head device that handles a plurality of wavelengths, and an optical pickup device that includes the optical head device, and includes an annular diffraction surface for phase correction that corrects spherical aberration and the like with respect to light of a required wavelength. The substantial central axis of the objective lens, that is, the central axis of the annular zone, and the central axis of the liquid crystal type phase correction element can be accurately matched to avoid occurrence of the above-described coma aberration, An optical head device, an optical pickup device, a method for manufacturing the optical head device, and a method for assembling the optical head device, which can improve spherical aberration with respect to wavelength, are provided.

  An optical head device according to the present invention has an optical system in which an objective lens having an annular diffractive surface for phase correction and a liquid crystal type phase correction element are arranged on the same axis, and the optical system emits light from a light source. An optical head device for condensing on an optical information medium, wherein the axis of the liquid crystal type phase correction element and the axis of the annular zone of the annular diffraction surface of the objective lens coincide with each other. The liquid crystal type phase correction element is characterized in that a positioning mark for positioning with reference to the annular zone of the belt-like diffractive surface is formed on the liquid crystal phase correction element.

The present invention is characterized in that, in the optical head device described above, the positioning mark is formed of the same constituent material as the constituent material of the electrode of the liquid crystal type phase correction element.
According to the present invention, in the above-described optical head device, the positioning mark is composed of a plurality of mark elements arranged on the same circumference centered on the axis of the liquid crystal type phase correction element. To do.

  An optical system having an optical system in which an objective lens having an annular diffractive surface for phase correction and a liquid crystal type phase correction element are arranged on the same axis, and condensing light from a light source onto an optical information medium by the optical system An optical pickup device comprising a head device, wherein the optical head device is in a state where the axis of the liquid crystal type phase correction element coincides with the axis of the annular zone of the annular diffraction surface of the objective lens. A positioning mark that is positioned with reference to the annular zone of the annular diffraction surface of the objective lens is formed on the liquid crystal type phase correction element.

The present invention is characterized in that, in the above-described optical pickup device, the positioning mark is formed of the same constituent material as the constituent material of the electrode of the liquid crystal type phase correction element.
The present invention is characterized in that, in the above-described optical pickup device, the positioning mark is composed of a plurality of mark elements arranged on the same circumference centering on the axis of the liquid crystal type phase correction element.

  An optical head device manufacturing method according to the present invention includes an optical system in which an objective lens having an annular diffractive surface for phase correction and a liquid crystal type phase correction element are arranged on the same axis, and from the light source by the optical system. A method of manufacturing an optical head device for condensing the light on an optical information medium, in the electrode pattern formation step of the liquid crystal type phase correction element, simultaneously with the formation of the electrode pattern, the annular diffractive surface of the objective lens A positioning mark for aligning the axis of the objective lens with the axis of the liquid crystal type phase correction element is formed on the liquid crystal type phase correction element.

  According to the present invention, in the above-described method of manufacturing an optical head device, the positioning mark includes a plurality of mark elements arranged on the same circumference centered on the axis of the liquid crystal type phase correction element. And

  An assembling method of an optical head device according to the present invention includes an optical system in which an objective lens having a ring-shaped diffraction surface for phase correction and a liquid crystal type phase correction element are arranged on the same axis, and from the light source by the optical system. An optical head device assembly method for condensing the light on the optical information medium, wherein a positioning mark arranged on the same axis as the axis of the liquid crystal type phase correction element is provided on the liquid crystal type phase correction element, The alignment mark is used to align the axis of the objective lens and the axis of the liquid crystal type phase correction element with reference to a predetermined annular zone of the annular diffraction surface of the objective lens, and a common holding body It is characterized by being held against.

  In the method of assembling the optical head device according to the present invention, when the objective lens and the liquid crystal type phase correction element are held on the holding body, the holding body is either the objective lens or the liquid crystal type phase correction element. One of the objective lens and the liquid crystal type phase correction element is held, and then the other liquid crystal type phase correction element and the objective lens are placed on the axis of the axis by a positioning mark provided on the liquid crystal type phase correction element. And the other liquid crystal type phase correction element and objective lens are held by the holding body.

According to the present invention, in the above-described method of assembling the optical head device, the positioning mark is formed of the same constituent material as the constituent material of the electrode of the liquid crystal type phase correction element.
According to the present invention, in the above-described method of assembling the optical head device, the positioning mark is composed of a plurality of mark elements arranged on the same circumference centered on the axis of the liquid crystal type phase correction element. It is characterized by.

  As described above, in the optical head device according to the present invention, the axis alignment of the objective lens having the annular diffractive surface for phase correction and the liquid crystal type phase correcting element is performed, and the zonal itself constituting the diffractive surface of the objective lens is adjusted. Since it is performed as a reference, the occurrence of errors when the objective lens is provided with a mark for alignment is avoided, and this makes it possible to accurately align the axis. The correction by the phase correction of the spherical aberration or the like can be surely performed by the phase correction element.

Further, since the positioning mark for axis alignment on the liquid crystal type phase correction element side is made of the same material as the constituent material of the electrode, it is possible to avoid the addition of the material constituting the special mark, the increase of parts, and the like.
The positioning mark for the liquid crystal type phase correction element is constituted by a plurality of mark elements arranged concentrically with respect to the axis of the liquid crystal type phase correction element. In other words, it is possible to accurately align the axes with each other because they are aligned with the reference annular zone.

  Therefore, the optical pickup device according to the present invention using this optical head device is excellent in correcting coma aberration and spherical aberration. For example, liquid crystals with different wavelengths for a plurality of types of optical information recording media as described above can be used. Since a good light spot is corrected by adjusting the phase correction by the mold phase correction element, an optical pickup device having recording / reproducing characteristics can be configured.

In the method of manufacturing the optical head device according to the present invention, the objective lens is not provided with any special alignment mark, and only the liquid crystal type phase correction element is simultaneously aligned with the formation of the electrode pattern. Since the mark is formed, the relative position with respect to the electrode pattern, that is, the positional relationship with the substantial axis of the liquid crystal type phase correction element can be accurately formed at a predetermined position without error.
Further, since a separate process for forming this positioning mark is not required, the number of processes due to the formation of this mark does not increase.
In the axial alignment, the mark of the liquid crystal type phase correction element only needs to be matched with reference to the annular zone of the objective lens, that is, the ring. Therefore, the alignment can be easily performed. .

  In the assembling method of the optical head device according to the present invention, when assembling the objective lens and the liquid crystal type phase correction element on the same axis on the common holder, the objective lens or the liquid crystal type phase correction element is assembled. One of these is held by a holding body, and then the axis of the objective lens or liquid crystal type phase correction element held by this holding body is aligned to hold the other liquid crystal type phase correction element or objective lens. However, at this time, the alignment of the liquid crystal type phase correction element coincides with the annular zone of the annular diffractive surface of the objective lens, that is, with respect to the ring. Can be done accurately.

  That is, according to the optical head device, the method for manufacturing the optical head device, and the method for assembling the optical head device according to the present invention, the center axis of the objective lens, that is, the center axis of the annular zone of the annular diffraction surface for phase correction Since the central axis of the liquid crystal type phase correction element can be made coincident, aberration correction, for example, generation of spherical aberration can be avoided with high accuracy for a plurality of wavelengths without generating coma. Is.

  Embodiments of an optical head device according to the present invention, an optical pickup device using the optical head device, a method of manufacturing the optical head device, and a method of assembling the optical head device will be described. Needless to say, in this embodiment, the present invention is not limited to this embodiment.

[Embodiments of Optical Head Device and Optical Pickup Device]
FIG. 1 shows recording by irradiating laser light to an optical information medium 2 selectively exchanged and arranged, for example, three types of CD, DVD, Blu-ray Disc, using an optical head device 1 according to the present invention. 1 shows a schematic configuration diagram of an example of an optical pickup device 100 according to the present invention that performs reproduction.
In this optical pickup device 100, optical information media 2 of CD, DVD, and Blu-ray Disc are respectively exchanged and recording / reproduction is performed. That is, from a laser light source that generates, for example, 780 nm, 650 nm, and 405 nm laser beams L1, L2, and L3 for performing recording or / and reproduction on a CD, DVD, Blu-ray Disc, and the above-described optical information medium 2 of these laser beams. The first, second, and third laser light emission and detection units 21, 22, and 23 having a light detection element such as a photodiode for detecting the return light of the light, and are selected for the optical information medium. For example, collimating lenses 31, 32, and 33 arranged in the optical paths of the laser beams L1, L2, and L3, first and second wavelength selectors 34 and 35, and the optical head device 1 according to the present invention are provided. Become.

  In this configuration, for example, when the optical information medium 2 is a CD, the first laser light L1 emitted from the first laser light and the first laser light L1 from the detection unit 21 is converted into parallel light by the lens 31, and the first and second wavelengths. Through the selectors 34 and 35, the spherical aberration is corrected by the optical head device 1 through the optical head device 1 according to the present invention, and the information surface of the CD as the optical information medium 2 is condensed and irradiated to record or reproduce it. I do. For example, at the time of reproduction, the return light modulated by the recording information on the information surface of the CD follows the reverse path and enters the laser light emission and detection unit 21 to detect the amount of light and reproduce the recording. The

  Similarly, when the optical information medium 2 is a DVD, the second laser light is emitted and the first laser light L2 from the detection unit 22 is reflected by the first wavelength selector 34 as parallel light by the lens 32. Then, the light passes through the second wavelength selector 35, and the spherical aberration is corrected by the optical head device 1 through the optical head device 1 according to the present invention, and the information surface of the DVD as the optical information medium 2 is condensed and irradiated. And record or play back. For example, at the time of reproduction, the return light modulated by the recording information on the information surface of the DVD follows the reverse path and is incident on the laser light emission and detection unit 22, and the amount of light is detected to reproduce the recording. The

  Further, when the optical information medium 2 is a Blu-ray Disc (hereinafter referred to as BD), the third laser light L2 from the third laser light emission and detection unit 23 is converted into parallel light by the lens 33, and the third laser light L2 is converted into parallel light. The spherical aberration is corrected by the optical head device 1 through the optical head device 1 according to the present invention after being reflected by the wavelength selector 34 of No. 2 and condensed and irradiated on the information surface of the BD as the optical information medium 2. Record or play back. For example, at the time of reproduction, the return light modulated by the recording information on the information surface of the BD follows the reverse path and enters the laser light emission and detection unit 22 to detect the amount of light and reproduce the recording. The

  The optical head device 1 according to the present invention is shown in FIG. 2 as a schematic top view, and as shown in FIG. 3 as a schematic cross-sectional view, an objective lens 4 having an annular diffraction surface 4D for phase correction and a liquid crystal phase. The correcting element 5 is positioned on the same axial center OO so as not to be eccentric, and is held by the holding body 3 and mechanically fixed integrally.

The objective lens 4 is shown in a plan view in FIG. 4 and a longitudinal sectional view in FIG. 5, and the shape of the incident surface side of the laser light toward the optical information medium 2 shown in FIG. 4 is designed to be a lens curved surface 4a having an aspherical shape so as to be optimal for the BD optical system.
That is, an annular diffractive surface 4D for phase correction is formed on the lens curved surface 4a of the objective lens 4.
As described above, the aspheric shape of the objective lens 4 is optimally designed for the BD optical system. That is, the aspherical shape of the objective lens 4 is a shape in which spherical aberration is mainly generated in the CD and DVD optical systems.
The annular diffractive surface 4D is formed into a shape pattern designed to generate a phase difference that cancels out aberrations as an optical system of the CD and DVD generated in the above-described aspheric shape.

The annular diffraction surface 4D is designed so as not to affect the BD optical system.
In this way, an optical head device is constructed in which the wavefront aberration is below a predetermined value for any of the BD, DVD, and CD optical systems, and stable reproduction / recording is possible.

The cross-sectional shape of the annular diffractive surface 4D of the objective lens 4 described above is stepped and concentric with the optical axis OO as the center.
In the objective lens 4, the portion of the lens curved surface 4a where the annular diffractive surface 4D is formed constitutes a diffraction pattern of the annular diffractive surface 4D, as shown by the broken lines in FIGS. Since the reflectance of light differs due to diffraction by the ridges of the respective steps, a concentric pattern centered on the optical axis OO can be visually recognized. The concentric pattern of the diffractive surface 4D is determined by the spherical aberration of the optical system to be corrected, and usually the number of the annular zone 4DR is about 2 to 7.

The objective lens 4 can be formed of a glass or plastic molded body having a sufficiently high light transmittance with respect to light of each wavelength used for recording or / and reproduction for the above-described BD, DVD, CD.
That is, it can be produced by molding from a mold that has been processed into a lens outer shape in advance. The annular diffractive surface 4D of the objective lens 4 can be molded simultaneously with the molding of the lens by using a mold on which the transfer pattern is formed.
Accordingly, the annular diffractive surface 4D in the objective lens 4 can be formed concentrically with the axis of the lens with extremely high accuracy.

The liquid crystal type phase correction element 5 is formed between the first and second transparent substrates 6A and 6B arranged to face each other, as shown in FIG. 6 and FIG. In addition, the liquid crystal 9 as an anisotropic optical element is enclosed.
The first and second transparent substrates 6A and 6B are made of glass, acrylic, polycarbonate, or the like having a sufficiently high light transmittance with respect to light of each wavelength used for recording or / and reproduction for the above-described BD, DVD, CD. Consists of a plastic substrate. However, it is desirable that the transparent substrates 6A and 6B are made of highly reliable glass substrates.

First and second electrodes 7A and 7B that give a required voltage distribution to the liquid crystal 9 are formed on the opposing surfaces of the first and second transparent substrates 6A and 6B, respectively.
In the first and second electrodes 7A and 7B, a transparent electrode layer, for example, an electrode layer made of ITO (Indium Tin Oxide) is formed at least at an intervening portion of the liquid crystal 9.
The first electrode 7A is formed over the entire surface of the accommodating portion of the liquid crystal 9, and, for example, the terminal T is led out to the ground potential GND.

  On the other hand, in the second electrode 7B, a relatively low resistance ring made of, for example, an aluminum (Al) metal electrode having a relatively low resistance is formed on a relatively high resistance electrode 7BH made of, for example, ITO. In the drawing, three ring-shaped metal electrodes 7BR1, 7BR2, and 7BR3 are formed on the same axis. Then, for example, a common terminal T is derived from the central ring electrode 7BR1 and the outermost ring electrode 7BR3, and the required same voltage V1 is applied, and the terminal from the ring electrode 7B2 between these ring electrodes 7BR1 and 7BR2 T is derived and the required voltage V2 is applied,

The operation relating to the liquid crystal phase correcting element having this configuration will be described with reference to FIG. Now, as shown in FIG. 8A, in the above-described three configurations, the second electrode 7B shown in FIG. 8A has been described above with respect to the ring-shaped metal electrodes 7BR1 and 7BR3 as shown in FIG. 8A. Thus, when the voltage V1 is applied and a voltage higher than the voltage V1 is applied to the intermediate ring electrode 7BR2, the equivalent circuit in a cross section passing through the center of the ring electrode in the second electrode 7B becomes FIG.
For example, as shown in FIG. 8C, the voltage at this time has a voltage distribution having a valley at the center and a peak at the position of the intermediate ring electrode 7B2 on the outer periphery.
At this time, since the first electrode 7A side is set to the ground potential, the voltage distribution applied to the liquid crystal 9 becomes the ring-shaped voltage distribution of FIG. 8D.

  Therefore, the laser light incident on the liquid crystal type phase correction element 5 from the first transparent substrate 6A toward the optical information recording medium is incident on the incident light by the refractive index distribution by the voltage distribution shown in FIG. 8D. The wavefront of is changed. The change in the wavefront of the incident light can be corrected, for example, in spherical aberration by arbitrary phase correction by changing the voltages V1 and V2.

In the present invention, as shown in FIGS. 2 and 6, the liquid crystal type phase correction element 5 is provided with a positioning mark 8 for axial alignment with the objective lens 4.
This mark 8 is, for example, on the inner side of the ring-shaped electrode 7BR1 at the innermost peripheral position, on the same axis as the axial center of the liquid crystal type phase correcting element 5, that is, the ring-shaped electrode 7B (7BR1, 7BR2, 7BR3). For example, three mark elements 8e are arranged.
The formation position of the mark 8 is selected so as to coincide with one predetermined annular zone 4DR of the annular diffraction surface 4D of the objective lens 4 in a state where the axis center with the objective lens 4 coincides. The mark elements 8e are arranged at equiangular intervals with respect to the axis of the liquid crystal type phase correction element, for example.

  These positioning marks 8, that is, the mark elements 8e are made of the same material as the electrodes of the liquid crystal type phase correction element 5, for example, the ring-shaped electrode 7A2.

[Embodiment of Manufacturing Method of Optical Head Device]
In the embodiment of the manufacturing method of the optical head device according to the present invention, the above-described optical head device 1 according to the present invention is manufactured. As described above, the positioning mark 8 of the liquid crystal type phase correction element 5, that is, Since the mark element 8e is made of the same material as the electrode of the liquid crystal type phase correction element 5, for example, the ring electrode 7BR (7BR1, 7BR2, 7BR3), the mark element of the mark 8 is used in the manufacturing method of the present invention. 8e is formed at the same time as the electrode pattern forming step of the liquid crystal type phase correcting element 5, that is, in the same step as the formation of the ring-shaped electrode 7BR.
As described above, the mark element 8e is formed at a predetermined position of the annular diffraction surface 4D of the objective lens 3 in a state where the axis of the liquid crystal type phase correction element 5 coincides with the axis of the objective lens 3. The position is selected so that the mark element 8e overlaps the two annular zones 4DR.
That is, the diameter of the circle passing through all of the positioning mark elements 8e is selected so as to match the diameter of one predetermined annular zone 4DR.

The formation of the electrode 7A2 and the mark element 8e of the mark 8 in the manufacturing method of the present invention is performed by forming the high resistance transparent electrode 7A1 made of, for example, ITO on the first transparent substrate 6A, A metal electrode layer, for example, an Al electrode layer, for example, vapor deposition, sputtering, or the like is deposited and patterned by pattern etching using photolithography to form the ring-shaped electrode 7BR and the mark element 8e simultaneously.
Therefore, according to this method, the coaxial core has a predetermined positional relationship with the ring-shaped electrode 7A2 where the axial center position of the liquid crystal type phase correction element 5 is substantially determined, that is, with the accuracy of the exposure pattern accuracy in photolithography. Thus, the mark element 8e is formed.

This accuracy can be matched with the mask processing accuracy in photolithography, and this positioning accuracy is usually within 1 μm.
The minimum size of the positioning mark, that is, the resolution is determined by the mask and the exposure wavelength, and is usually 1 μm or less. This is smaller than the accuracy range required for positioning. Therefore, the size of the positioning mark is set to be large enough to be recognized when positioning, and small enough not to adversely affect the optical system such as aberration and transmittance, for example, about several μm to several tens μm. The shape of the positioning mark 4 may be anything as long as it satisfies the requirements of positioning accuracy and can be recognized. In FIG. 3, a circle is used as an example. As the material of the positioning mark 4, a material that can be recognized at the time of positioning, such as aluminum, is used. At this time, if the same material as that of the low-resistance film 12 for power feeding described above is used, the positioning mark 4 can be formed at an arbitrary position without newly increasing the number of processes.

[Embodiment of Assembling Method of Optical Head Device]
The above-described method of assembling the optical head device is such that the positioning mark 8 makes the axis of the objective lens 4 and the liquid crystal type phase correction element 5 coincide with each other with reference to the predetermined annular zone 4DR of the annular zone diffraction surface 4D of the objective lens 4. As shown in FIG. 2 and FIG. 3, alignment is performed and the common holding body 3 is held.

The holding body 3 is made of a light and highly rigid resin such as a liquid crystal polymer.
The holding body 3 is formed, for example, by forming a circular opening 10 at the center. The diameter of the opening 10 is the largest N.D. in the optical system handled by the optical pickup. A. In this example, the BD N.D. A. Is selected to be equal to or greater than
Then, the objective lens 4 and the liquid crystal type phase correction element 5 are assembled to the holding body 3 by being fixed at predetermined positions by, for example, a UV adhesive, that is, a UV (ultraviolet) curable resin.

In this assembly, first, the objective lens 4 is fixed in alignment with the opening 10 of the holding body 3 so that the central axis thereof substantially coincides with the central axis of the opening 10 of the holding body 3.
Here, the positioning accuracy between the central axis of the opening 10 of the holder 3 and the optical axis of the objective lens 4 is relatively loose, and the positioning accuracy determined by the machining accuracy of the holder 3 and the objective lens 4 is sufficient.

Next, the liquid crystal type phase correction element 5 is fixed to the holding body 3 in the vicinity of the objective lens 4.
For this fixation, the objective lens 4 and the holder 3 are observed, and all the mark elements 8e of the positioning mark 8 of the liquid crystal type phase correction element 5 are arranged on a circle of a predetermined one annular zone 4DR of the objective lens 3. Thus, the axial center position of the liquid crystal type phase correction element 5 is selected, and the liquid crystal type phase correction element 5 is fixed to the holding body 3 at this position.

By this assembly procedure, the optical axis of the objective lens 13 and the optical axis of the liquid crystal type phase correction element 5 are arranged on the same axis OO, and the optical head device 1 is assembled.
In this case, the axis alignment can be positioned with high accuracy. For example, when the effective diameter is 3 mm, the eccentricity can be suppressed within ± 20 μm.
Therefore, the spherical aberration of the BD can be corrected without degrading the optical performance.
The positioning accuracy is determined by the annular diffraction pattern with respect to the optical axis of the objective lens 3, that is, the accuracy of the annular zone 4DR pattern, the width of the annular zone 4DR, and the size of the positioning mark 8 of the liquid crystal type phase correction element. This is about 10 μm, which is smaller than the required positioning accuracy.

  In the above-described example, the objective lens 3 is first fixed to the holder 3 and the liquid crystal type phase correction element 5 is fixed thereto. However, the liquid crystal type phase correction element 5 is fixed to the holder. 3 and then the procedure of fixing the objective lens 3 can be performed.

The optical head device, the optical pickup device, the optical head device manufacturing method, and the optical head device assembly method according to the present invention are not limited to the above-described examples. Various changes such as shape and number can be made.
Further, arbitrary phase correction can be performed by controlling the electrode arrangement, shape, and applied voltage in the liquid crystal type phase correction element.

  As described above, according to the present invention, since the axis alignment of the objective lens 3 and the liquid crystal type phase correction element 5 is performed with reference to the annular zone 4DR that constitutes the annular diffraction surface 4D of the objective lens 3, Generation of an error when an alignment mark is provided on the objective lens is avoided, and an increase in the number of manufacturing steps and an increase in the number of parts for forming this mark can be avoided.

Further, since the alignment mark 8 for alignment is made of the same material as that of the electrode 7A, it is possible to avoid the addition of a material constituting a special mark, an increase in parts, and the like.
The positioning mark 8 for the liquid crystal type phase correcting element 5 is constituted by a plurality of mark elements arranged concentrically with respect to the axis of the liquid crystal type phase correcting element 5, and the plurality of mark elements 8 e are used as the objective lens. 3. Since the axis alignment is performed by matching with the annular zone 4DR, which is the so-called reference of the above-described axis alignment 3, the axis alignment can be performed accurately with high accuracy.

  Further, in the method of manufacturing an optical head device according to the present invention, the objective lens 4 is not provided with any special alignment mark, and only the liquid crystal type phase correction element 5 is formed simultaneously with the formation of the electrode pattern. Therefore, the number of manufacturing steps of the optical head device is not increased.

  In the method of assembling the optical head device according to the present invention, when assembling the objective lens 3 and the liquid crystal type phase correcting element on the same axis on the common holder 3, the objective lens 3 or the liquid crystal type is assembled. One of the phase correction elements 5 is held by the holding body 3, and then the axis of the objective lens 4 or the liquid crystal type phase correction element 5 held by the holding body 3 is aligned to provide the other liquid crystal type phase correction element. 5 or the objective lens 4 is held. At this time, the mark 8 of the liquid crystal type phase correction element 5 is aligned with respect to the annular zone of the annular diffraction surface 4D of the objective lens 4, ie, the ring. Therefore, the axis alignment can be performed easily and accurately.

  That is, according to the optical head device of the present invention, the optical pickup device using the optical head device, the method of manufacturing the optical head device, and the method of assembling the optical head device, the center axis of the objective lens, that is, the phase correction wheel Since the center axis of the ring zone of the band-shaped diffractive surface and the center axis of the liquid crystal type phase correction element can be made to coincide with each other with high accuracy for each of a plurality of wavelengths, for example, BD, DVD, and CD. It is possible to construct an optical head device that avoids the occurrence of aberrations, particularly coma, and further brings about significant benefits such as simplification of manufacturing and improvement of productivity.

It is a block diagram of an example of the optical pick-up apparatus to which the optical head apparatus by this invention is applied. It is a schematic plan view of an example of the optical head apparatus by this invention. It is a schematic sectional drawing of an example of the optical head apparatus by this invention. It is a schematic plan view of an example of the objective lens of the optical head device according to the present invention. It is a schematic sectional drawing of an example of the objective lens of the optical head apparatus by this invention. FIG. 3 is a schematic plan view of a part of an example of a liquid crystal type phase correction element of the optical head device according to the present invention. It is a schematic sectional drawing of an example of the liquid crystal type | mold phase correction element of the optical head apparatus by this invention. FIG. 4A is an arrangement pattern diagram of second electrodes of an example of a liquid crystal type phase correction element used in the present invention, FIG. B is an equivalent circuit diagram in the diameter direction, FIG. C is a voltage distribution diagram, and FIG. Voltage distribution.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Optical head apparatus, 2 ... Optical information medium, 3 ... Holding body, 4 ... Objective lens, 4D ... Ring-shaped diffraction surface, 4a ... Lens curved surface, 4DR ... Ring zone, 5 ... liquid crystal type phase correction element, 6A ... first transparent substrate, 6B ... second transparent substrate, 7A ... first electrode, 7B ... second electrode, 7BR (7BR1, 7BR2, 7BR3) ... ring electrode, 8 ... positioning mark, 8e ... mark element, 9 ... liquid crystal, 10 ... opening, 21 ... first laser beam , Second laser light emission and detection unit, 23 ... laser light emission and detection unit, 31-33 ... collimating lens, 34, 35 ... wavelength selection Child, L1-L3 ... Laser light

Claims (12)

An optical system having an optical system in which an objective lens having an annular diffractive surface for phase correction and a liquid crystal type phase correction element are arranged on the same axis, and condensing light from a light source onto an optical information medium by the optical system A head device,
Positioning that is performed with reference to the annular zone of the annular diffractive surface of the objective lens in a state where the axial center of the liquid crystal type phase correction element and the axial center of the annular diffractive surface of the objective lens coincide with each other. An optical head device, wherein a mark is formed on the liquid crystal type phase correcting element.   2. The optical head device according to claim 1, wherein the positioning mark is formed of the same constituent material as that of the electrode of the liquid crystal type phase correction element.   2. The optical head device according to claim 1, wherein the positioning mark comprises a plurality of mark elements arranged on the same circumference centered on the axis of the liquid crystal type phase correction element. An optical system having an optical system in which an objective lens having an annular diffractive surface for phase correction and a liquid crystal type phase correction element are arranged on the same axis and condensing light from a light source onto an optical information medium by the optical system An optical pickup device comprising a head device,
The optical head device is based on the annular zone of the annular diffractive surface of the objective lens in a state where the axial center of the liquid crystal type phase correcting element and the axial center of the annular diffractive surface of the objective lens coincide with each other. An optical pickup device comprising a positioning mark for positioning as formed on the liquid crystal phase correction element.   5. The optical pickup device according to claim 4, wherein the positioning mark is formed of the same constituent material as that of the electrode of the liquid crystal type phase correction element.   5. The optical pickup device according to claim 4, wherein the positioning mark comprises a plurality of mark elements arranged on the same circumference centering on the axis of the liquid crystal type phase correcting element. An optical system having an optical system in which an objective lens having an annular diffractive surface for phase correction and a liquid crystal type phase correction element are arranged on the same axis, and condensing light from a light source onto an optical information medium by the optical system A method of manufacturing a head device,
In the step of forming the electrode pattern of the liquid crystal type phase correction element, simultaneously with the formation of the electrode pattern, the axis of the objective lens and the liquid crystal type phase correction element of the liquid crystal type phase correction element A method of manufacturing an optical head device, comprising: forming a positioning mark on the liquid crystal type phase correction element so as to coincide with an axis.   8. The method of manufacturing an optical head device according to claim 7, wherein the positioning mark comprises a plurality of mark elements arranged on the same circumference centered on the axis of the liquid crystal type phase correcting element. . An optical system having an optical system in which an objective lens having an annular diffractive surface for phase correction and a liquid crystal type phase correction element are arranged on the same axis, and condensing light from a light source onto an optical information medium by the optical system A method of assembling the head device,
The liquid crystal type phase correction element is provided with a positioning mark arranged on the same axis as the axis of the liquid crystal type phase correction element,
With this positioning mark, the axis of the objective lens and the axis of the liquid crystal type phase correction element are aligned with respect to a predetermined annular zone of the annular diffractive surface of the objective lens, and a common holding is performed. An assembly method of an optical head device, wherein the optical head device is held against a body.   In holding the objective lens and the liquid crystal type phase correcting element with respect to the holding body, the holding body holds either the objective lens or the liquid crystal type phase correcting element, and then the objective lens and the liquid crystal type phase correcting element. The other liquid crystal type phase correcting element is aligned with the other liquid crystal type phase correcting element and the objective lens by a positioning mark provided on the liquid crystal type phase correcting element. The method of assembling the optical head device according to claim 9, wherein the holding lens is held by the holding body.   10. The method of assembling an optical head device according to claim 9, wherein the positioning mark is formed of the same constituent material as that of the electrode of the liquid crystal type phase correction element.   10. The method of assembling an optical head device according to claim 9, wherein the positioning mark comprises a plurality of mark elements arranged on the same circumference centering on the axis of the liquid crystal type phase correcting element. .

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