JP2007188587A - Optical pickup, manufacturing method thereof, and information processor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize an improved optical axis adjustment processing configuration for an optical pickup having an aberration correction element. <P>SOLUTION: In the optical pickup having an aberration correction element, an adjustment is made so that the center of the optical axis of an objective lens coincides with that of the aberration correction element. With this configuration, signal quality at a permissible level can be obtained nearly in a fixed range regardless of, for example, the inclination direction of an optical disk, thus maintaining a disk inclination margin and performing recording/reproducing processing by a high-quality recording/reproducing signal. And the center axis of the aberration correction element can be matched to that of the objective lens without requiring any additional space for adjusting the position of the aberration correction element, thus preventing skew deviation based on the disagreement between the aberration correction element and the objective lens and advantageously miniaturizing the optical pickup and an optical disk device. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical pickup, an information processing apparatus, and an optical pickup manufacturing method. More specifically, the present invention relates to an optical pickup having an optical pickup configuration including an aberration correction element, an information processing apparatus, and an optical pickup manufacturing method.

  In recent years, optical discs (including magneto-optical discs) are often used as digital data recording / reproducing media. For example, CD (Compact Disk), MD (Mini-Disk), DVD (Digital Versatile Disk), and the like.

  In an optical pickup for an optical disc, an aberration caused by variations in characteristics of optical elements (optical components) constituting an optical system including a light source and an objective lens, an aberration caused by uneven thickness of the optical disc, or an optical disc In the case of the two-layer configuration, aberration due to the difference in position of each recording layer occurs.

  For example, the optical disc has thickness unevenness and warpage, and these cannot be completely eliminated. As a result, the optical disk surface of the opposing portion of the optical pickup is not a uniform flat surface, and a certain degree of inclination occurs. As a result, a deviation (tilt angle) occurs between the vertical axis with respect to the optical disk surface and the optical axis of the optical pickup. This shift becomes a factor such as coma aberration of the optical system, and causes the adjacent track data and crosstalk to occur, thereby causing degradation of signal quality, so-called jitter.

  Since such aberrations have a large effect on the characteristics of the recording signal with respect to the optical disc or the characteristics of the reproduction signal reproduced from the optical disc, an aberration correction element made of, for example, a liquid crystal element is provided in the optical system of the optical pickup to correct the aberration. A configuration in which aberration is corrected by an element has been proposed. As the aberration correction element, for example, a liquid crystal aberration correction element using a liquid crystal panel can be used. The liquid crystal aberration correction element is composed of a liquid crystal element in which liquid crystal molecules having refractive index anisotropy are aligned in a predetermined direction, and corrects aberration of light passing through the optical pickup by the liquid crystal element.

  The configuration of the liquid crystal aberration correction element will be described with reference to FIG. The liquid crystal aberration correction element 100 includes concentric electrodes 101 to 105 as shown in FIG. These electrodes are transparent electrodes and allow laser light to pass through. FIG. 1B shows drive levels for wavefront aberration correction for the electrodes 101 to 105 shown in FIG.

  In the liquid crystal aberration correction element 100, liquid crystal molecules having refractive index anisotropy are aligned in a predetermined direction on a glass substrate. And the other electrode which opposes the concentric electrodes 101-105 comprised by the upper (or lower) transparent electrode is formed.

  When a driving voltage is applied to each of the electrodes 101 to 105 of the liquid crystal aberration correcting element 100 having such a configuration, the orientation of liquid crystal molecules is deviated according to the electric field generated by the applied voltage. Thereby, the refractive index distribution in the cross section perpendicular to the traveling direction of the light beam transmitted through the liquid crystal aberration correction element 100 can be arbitrarily set, and the wavefront phase of the light beam can be controlled for each divided region.

  For example, as shown in FIG. 1A, the electrode 101 is a circular electrode region A1 having a radius r0, the electrode 102 is an outer radius r1 and a hollow circular electrode region A2 is an inner radius r0, and the electrode 103 is an outer radius r2. And a hollow circular electrode region A3 having an inner radius r1, an electrode 104 having an outer radius r3 and an inner radius r2 having a hollow circular electrode region A4, and an electrode 105 having a circular shape having an inner radius r3 and having an electrode region A5. A case where the liquid crystal aberration correcting element 100 using a pattern is used will be described.

  As shown in FIG. 1B for each of the electrodes 101 to 105 of the liquid crystal aberration correction element 100, 0 is applied to the electrodes 101 and 105, d1, d3 are applied to the electrodes 102 and 104, and d3 are applied to the electrodes 103, respectively. Applies a voltage corresponding to the level indicated by d2. There is an electrode separation gap (not shown) between the electrodes. Here, d1 and d3 are set at the same level so that the center of the light beam and the center of the concentric circle of each electrode coincide with each other, and the values corresponding to the amount of wavefront aberration in the radial direction of the light beam are selected for each radius r0 to r3. Thus, in this example, the drive levels of the electrodes 101 to 105 can be selected and switched with a simple drive circuit as a digital signal with three values of 0, d1, and d3, and the wavefront is obtained by giving a phase difference to the transmitted light flux. Aberration can be corrected. The details of the liquid crystal aberration correction element to which the liquid crystal panel is applied are described in Patent Document 1, for example.

  The optical pickup is composed of a plurality of optical elements (optical components) that constitute an optical system including a light source and an objective lens, and it is desirable that the center axes of these optical elements coincide with each other. The optical axis adjustment of the pickup component is described in, for example, Patent Document 2 and Patent Document 3.

  Even when an aberration correction element is incorporated in an optical pickup, it is desirable to arrange it so that the central axis coincides with the other optical elements constituting the optical pickup. However, an aberration correction element such as a liquid crystal aberration correction element has a certain positional accuracy in advance. Is often supplied as an aberration correction element component fixed to the slide base, and when this aberration correction element component is incorporated into an optical pickup comprising an optical system including a light source and an objective lens, the optical axis of other pickup components There is a problem that it is difficult to make them completely coincide.

  When the center of the optical axis of the liquid crystal aberration correcting element and the center of the optical axis of the optical pickup coincide with each other, accurate aberration correction is performed, but the optical axis center of the liquid crystal aberration correcting element and the optical axis center of the optical pickup are If they do not match, accurate aberration correction cannot be performed. The difference between the case where the optical axis center of the liquid crystal aberration correction element coincides with the optical axis center of the optical pickup and the case where they do not coincide will be described with reference to FIGS.

  FIG. 2 is a diagram for explaining a case where the optical axis center of the liquid crystal aberration correcting element and the optical axis center of the optical pickup coincide with each other, and the horizontal axis indicates the radial distance from the optical axis center. The vertical axis is the wavefront indicating the aberration generation amount / aberration correction amount. The solid line shown as a graph shows the relationship between the normalized radius of the objective lens in the optical pickup and the wavefront corresponding to the aberration generation amount, and the dotted line shows the normalized radius and aberration correction amount of the liquid crystal aberration correction element configured in the optical pickup. The wavefront relationship corresponding to is shown. The locus of the dotted line and the solid line shown in FIG. 2 is symmetrical with respect to the optical axis center (normalized radius = 0), and the optical axis center of the liquid crystal aberration correction element and the optical axis center of the optical pickup are This shows that the aberration of the light passing through the objective lens is accurately corrected by the aberration correction element.

  On the other hand, FIG. 3 is a diagram for explaining a case where the optical axis center of the liquid crystal aberration correcting element and the optical axis center of the optical pickup do not coincide with each other, and the horizontal axis is the radial direction from the optical axis center as in FIG. , And the vertical axis represents the wavefront indicating the aberration generation amount / aberration correction amount. The solid line shown as a graph shows the relationship between the normalized radius of the objective lens in the optical pickup and the wavefront corresponding to the aberration generation amount, and the dotted line shows the normalized radius and aberration correction amount of the liquid crystal aberration correction element configured in the optical pickup. The wavefront relationship corresponding to is shown. The solid line shown in FIG. 3, that is, the locus indicating the relationship between the normalized radius of the objective lens and the wavefront corresponding to the amount of aberration, is symmetric about the optical axis center (normalized radius = 0). 3, that is, the locus indicating the relationship between the normalized radius of the liquid crystal aberration correcting element configured in the optical pickup and the wavefront corresponding to the aberration correction amount is compared with the locus shown in FIG. The locus is shifted to the right. This indicates that the optical axis center of the liquid crystal aberration correction element and the optical axis center of the optical pickup do not coincide with each other. In this case, the amount of aberration of the light passing through the objective lens and the aberration correction element Aberration correction amount does not correspond, and correct aberration correction is not performed.

  With reference to FIG. 4, a description will be given of signal quality degradation, that is, a so-called jitter generation amount when the optical axis center of the liquid crystal aberration correction element and the optical axis center of the optical pickup coincide with each other. FIG. 4 shows (tilt angle (deg)) corresponding to the amount of deviation between the vertical axis with respect to the optical disc surface and the optical axis of the optical pickup, and the vertical axis shows jitter, ie, jitter (%) indicating the degree of signal quality degradation. ). The lower the numerical value, the higher the quality of the signal, and the higher the numerical value, the more the noise component is judged as a degraded signal. Here, as an example, a signal having a jitter of 15% or less is set as an allowable value. That is, a signal whose recording signal or reproducing signal with respect to the optical disc has a jitter of 15% or less is set as a recording / reproducing allowable signal level.

  FIG. 4 shows three lines. The solid line (a) indicates that the center of the optical axis of the liquid crystal aberration correction element is coincident with the center of the optical axis of the optical pickup, and the dotted line (b) indicates that the optical axis center of the liquid crystal aberration correction element and the optical axis center of the optical pickup are aligned. When they do not match, the dotted line (c) also shows the case where the optical axis center of the liquid crystal aberration correction element and the optical axis center of the optical pickup do not match, and shows the case where the deviation direction is opposite to the case of (b). Yes.

  For example, when the optical axis center of the liquid crystal aberration correcting element and the optical axis center of the optical pickup coincide with each other, that is, in the solid line (a), the tilt range in which a signal having a jitter of 15% or less is obtained is P = It is in the range of about −0.62 to +0.62 (deg). On the other hand, when the center of the optical axis of the liquid crystal aberration correcting element and the center of the optical axis of the optical pickup do not coincide, that is, with respect to the dotted line (b), the tilt range in which a signal having a jitter of 15% or less is obtained is Q = It is in the range of about −0.18 to +1.10 (deg).

  As shown by the dotted line (b), when the tilt range in which a signal having a jitter of 15% or less is obtained is Q = about −0.18 to +1.10 (deg), the tilt is in the + direction. In this case, the allowable range is -0.18 to 0 in the negative direction, and the allowable tilt amount is significantly reduced. This means that, for example, when the tilt of the optical disk occurs in a certain direction, that is, in the direction in which the tilt shown in the graph is-, an acceptable level of signal quality is hardly obtained. That is, since the optical axis centers of the objective lens and the aberration correction element are deviated, the aberration correction is not properly performed, and a signal with deteriorated quality is recorded or reproduced.

  On the other hand, when the optical axis center of the liquid crystal aberration correction element and the optical axis center of the optical pickup coincide with each other, that is, in the solid line (a), the tilt range in which a signal having a jitter of 15% or less is obtained is P = It is in the range of about −0.62 to +0.62 (deg), and an acceptable level of signal quality can be obtained in an almost constant range regardless of the direction of the tilt of the optical disk.

  As described above, when the optical axis center of the liquid crystal aberration correction element and the optical axis center of the optical pickup coincide with each other, a sufficient disk tilt margin can be obtained. If the center of the optical axis does not match, the disc tilt margin will decrease.

However, as described above, an aberration correction element such as a liquid crystal aberration correction element is often supplied as an aberration correction element component fixed in advance to the slide base with a certain positional accuracy. When incorporated in an optical pickup comprising an optical system including an objective lens, there is a problem that it is difficult to completely match the optical axis center of the liquid crystal aberration correction element with the optical axis center of other components of the optical pickup. .
Japanese Patent Laid-Open No. 10-269611 JP 2005-129100 A JP 2005-71457 A

  The present invention has been made in view of such circumstances, and in an optical pickup provided with an aberration correction element, it is possible to reduce signal deterioration due to an optical axis shift between the aberration correction element and the objective lens. It is an object to provide a pickup, an information processing apparatus, and an optical pickup manufacturing method.

The first aspect of the present invention is:
An optical pickup applied to information recording on an optical disc or information reproduction from an optical disc,
A light source that emits irradiation light to the optical disc;
An objective lens that focuses the light emitted from the light source onto the optical disc;
A collimator lens disposed between the light source and the objective lens, which guides the light beam emitted from the light source to parallel light as the collimator lens;
An aberration correction element that is disposed in an optical path connecting the light source and the optical disc and corrects an aberration;
In the optical pickup, the optical axis center of the objective lens is configured to coincide with the optical axis center of the aberration correction element as a reference.

  Furthermore, in one embodiment of the optical pickup of the present invention, the optical axis center of the objective lens is deviated from the optical axis center of the collimator lens.

  Furthermore, in one embodiment of the optical pickup of the present invention, the objective lens is held by an actuator, and the optical axis center of the objective lens is based on the optical axis center of the aberration correction element by the control of the actuator. It is characterized by having a matched configuration.

  Furthermore, in one embodiment of the optical pickup of the present invention, the aberration correction element is a spherical aberration correction element configured by a liquid crystal element, and the liquid crystal element has a spherical surface whose refractive index is generated in the light passing through the optical pickup. It is an aberration correction element having a configuration controlled by a control unit so that a wavefront change opposite to the aberration occurs.

Furthermore, the second aspect of the present invention provides
An information processing apparatus for performing information recording on an optical disc or information reproduction from an optical disc,
It has an optical pickup that is used for recording or reproducing information,
The optical pickup is
A light source that emits irradiation light to the optical disc;
An objective lens that focuses the light emitted from the light source onto the optical disc;
A collimator lens disposed between the light source and the objective lens, which guides the light beam emitted from the light source to parallel light as the collimator lens;
An aberration correction element that is disposed in an optical path connecting the light source and the optical disc and corrects an aberration;
In the information processing apparatus, the optical axis center of the objective lens is configured to coincide with the optical axis center of the aberration correction element as a reference.

Furthermore, the third aspect of the present invention provides
An optical pickup manufacturing method for adjusting an optical pickup applied to information recording on an optical disc or information reproduction from an optical disc,
The optical pickup is
A light source that emits irradiation light to the optical disc;
An objective lens that focuses the light emitted from the light source onto the optical disc;
A collimator lens disposed between the light source and the objective lens, which guides the light beam emitted from the light source to parallel light as the collimator lens;
An aberration correction element that is disposed in an optical path connecting the light source and the optical disc and corrects an aberration;
The optical pickup manufacturing method includes an optical axis adjustment processing step of executing a process of matching the optical axis center of the objective lens with the optical axis center of the aberration correction element as a reference.

  Furthermore, in one embodiment of the optical pickup manufacturing method of the present invention, the optical axis adjustment processing step applies a voltage to the aberration correction element, causes the light source to emit light in a state where a concentric aberration pattern is generated, and The method has a step of measuring the center of the aberration pattern and the optical axis shift, and a step of moving the objective lens in accordance with the shift amount of the aberration pattern.

  Furthermore, in an embodiment of the optical pickup manufacturing method of the present invention, the objective lens is held by an actuator, and the optical axis adjustment processing step is performed by controlling the actuator with the optical axis center of the objective lens being controlled by the actuator. This is a processing step for matching with the optical axis center of the correction element as a reference.

  Other objects, features, and advantages of the present invention will become apparent from a more detailed description based on embodiments of the present invention described later and the accompanying drawings. In this specification, the system is a logical set configuration of a plurality of devices, and is not limited to one in which the devices of each configuration are in the same casing.

  According to the configuration of the embodiment of the present invention, in the optical pickup having the aberration correction element, the optical axis center of the objective lens is adjusted to coincide with the optical axis center of the aberration correction element. However, no matter what direction it occurs, an information processing device that achieves an acceptable level of signal quality in a substantially constant range, maintains disc tilt margin, and performs recording and playback processing using high-quality recording and playback signals is realized. The

  In particular, an optical pickup in which an aberration correction element is inserted in the convergent light between the light source and the collimator lens can reduce the size of the aberration correction element, but increases the discrepancy with the aberration of the objective lens and further increases the skew deviation. However, according to the configuration of the present invention, the central axis of the aberration correction element and the objective lens can be matched without requiring an extra space for adjusting the position of the aberration correction element. Therefore, it is possible to prevent the skew deviation based on the mismatch between the aberration correction element and the objective lens, which is advantageous in reducing the size of the optical pickup and the optical disc apparatus.

  Hereinafter, the details of an optical pickup, an information processing apparatus, and an optical pickup manufacturing method of the present invention will be described with reference to the drawings.

  First, the configuration of an optical pickup applied to data recording on an optical disc or data reproduction from an optical disc will be described with reference to FIG. FIG. 5 shows a configuration of the optical pickup 200 including the aberration correction element 214.

  As shown in FIG. 5, the optical system of the optical pickup 200 includes an integrated optical element (laser coupler) 212, an aberration correction element 214, a quarter wavelength plate 216, a collimator lens 218, a mirror 220, an objective lens 222, and an actuator 224. Contains.

  In front of the integrated optical element 212, an aberration correction element 214, a quarter-wave plate 216, a collimator lens 218, and a mirror 220 are arranged on a straight line in this order, and an objective lens 222 is arranged on the optical disk 202 side of the mirror 220. Has been.

  Although not shown, the integrated optical element 212 includes a light source composed of a laser diode, a grating element, a light receiving element for signal reproduction, a light receiving element for light source monitoring, a prism, a beam splitter, and the like. These components are mounted on one substrate. Various types of conventionally known configurations can be employed.

  The light beam emitted from the light source in the integrated optical element 212 is emitted toward the aberration correction element 214 via the prism, beam splitter, and grating element in the integrated optical element 212, and also through the aberration correction element 214. The incident reflected light beam is guided to a signal reproducing light receiving element in the integrated optical element 212 via a prism and a beam splitter in the integrated optical element 212, and a focus error signal, tracking error signal, RF A signal or the like is detected.

  A part of the light beam emitted from the light source in the integrated optical element 212 is directly guided to the light receiving element for light source monitoring in the integrated optical element 212 via the prism in the integrated optical element 212, and this light receiving for light source monitoring. A monitor signal of the output power of the light source is detected by the element. The grating element in the integrated optical element 212 separates the light beam emitted from the light source into three beams.

  For detection of tracking error and focus error, various conventionally known methods can be used. For example, a tracking error signal is detected by a three-beam method, and a focus error signal is detected by an astigmatism (Astigma) method. Can be detected.

  The collimator lens 218 receives a light beam as a divergent light emitted from the light source in the integrated optical element 212 via the aberration correction element 214 and the quarter wavelength plate 216, and this light beam is incident on the mirror 220 as parallel light. The collimator lens 218 is arranged so that the distance from the light source in the integrated optical element 212 matches the focal length of the collimator lens 218.

  The cross section of the light beam emitted from the collimator lens 218 toward the mirror 220 is uniform along the traveling direction of the light beam. The mirror 220 is arranged such that its reflection surface forms 45 degrees with respect to the optical axis of the collimator lens 218, and the optical beam as parallel light guided from the collimator lens 218 is bent by 90 degrees by the reflection surface, and the optical disk. It is configured to be reflected toward the 202 side.

  The objective lens 222 is arranged so that its optical axis forms 45 degrees with respect to the reflection surface of the mirror 220, and collects a light beam as parallel light reflected by the reflection surface to collect the recording layer of the optical disk 202. It is comprised so that it may irradiate.

  The actuator 224 is configured to move the objective lens 222 in the focusing direction and the tracking direction by a drive signal supplied from a servo control unit (not shown), and various conventionally known actuators can be employed.

  The reflected light beam reflected by the recording layer of the optical disk 202 is incident on the objective lens 222, becomes parallel light again, is reflected by the reflecting surface of the mirror 220, is collected by the collimator lens 218, and is ¼ wavelength as convergent light. The light is guided to the integrated optical element 212 through the plate 216 and the aberration correction element 214, and is received by the light receiving element for signal reproduction in the integrated optical element 212 through the prism in the integrated optical element 212.

  The quarter-wave plate 216 converts the linearly polarized light beam emitted from the light source in the integrated optical element 212 into circularly polarized light and guides it to the optical disc 202 and guides it from the optical disc 202. It has a function of converting the reflected light beam, which is circularly polarized light, into linearly polarized light that oscillates in the Y-axis direction.

  The quarter-wave plate 216 converts the direction of linearly polarized light by 90 degrees, so that the light beam emitted from the light source of the integrated optical element 212 passes through the beam splitter and is reflected from the optical disk 202. Is reflected by the beam splitter of the integrated optical element 212 and guided to the light receiving element for signal reproduction.

  The aberration correction element 214 is disposed in the optical path connecting the integrated optical element 212 and the collimator lens 218, that is, in the optical path connecting the light source in the integrated optical element 212 and the collimator lens 218. It is arranged. The optical path connecting the light source in the integrated optical element 212 and the collimator lens 218 is an optical path through which divergent light whose cross section expands as the light beam emitted from the light source travels in the traveling direction, and the collimator lens. The reflected light beam converged by 218 is an optical path through which convergent light whose cross section is reduced as it travels in the traveling direction, in other words, an optical path through which divergent light and convergent light pass.

  The configuration of the aberration correction element 214 will be described with reference to FIG. The aberration correction element is, for example, a spherical aberration correction element composed of a liquid crystal element, and the liquid crystal element has a control unit so that the refractive index has a wavefront change opposite to the spherical aberration generated in the light passing through the optical pickup. Is an aberration correction element having a configuration controlled by.

  In this embodiment, as shown in FIG. 6, the aberration correction element 214 is formed between the first and second transparent substrates 301 and 302 that are overlapped with each other and the first and second transparent substrates 301 and 302. The liquid crystal layer sealed in the space having the uniform thickness and the first and second transparent substrates 301 and 302 have transparent electrodes formed on the respective surfaces facing the liquid crystal layer.

  The aberration correction element 214 is arranged such that the first transparent substrate 301 faces the light source in the integrated optical element 212 shown in FIG. 5 and the second transparent substrate 302 faces the collimator lens 218. On the surface where 302 faces the collimator lens 218, a quarter-wave plate 216 is overlaid and attached.

  The transparent electrodes 301 and 302 are composed of, for example, one circular electrode and a plurality of annular electrodes provided on the outer periphery thereof concentrically with the circle. This configuration is the electrode configuration described above with reference to FIG. A flexible substrate is connected to each of these electrodes, and a drive signal from an aberration control unit (not shown) is supplied through the flexible substrate.

  As described above with reference to FIG. 1, the driving signals having different voltages are supplied to the respective electrodes, so that the orientation of the liquid crystal molecules in the liquid crystal layer is changed corresponding to each electrode. The refractive index changes corresponding to each electrode. Specifically, control is performed to change the refractive index of the liquid crystal layer so that a wavefront change opposite to the aberration (spherical aberration) occurs.

  By this control, aberration caused by variations in characteristics of optical elements (optical components) constituting an optical system including a light source and an objective lens, aberration caused by uneven thickness of an optical recording medium, or two-layer recording It is possible to correct an aberration caused by a difference in position of each recording layer in an optical disc having a layer.

  In an optical pickup using a liquid crystal aberration correction element, it is ideal to arrange each element such as a light source, a collimator lens, and an objective lens so that their optical axes coincide. However, as described above, along with the downsizing of optical pickups, the liquid crystal elements that are additionally arranged for aberration correction have little space between other optical elements such as collimator lenses and beam splitters, and their positions are adjusted. In order to do this, a jig pin cannot be inserted or bonded after position adjustment. As a result, the aberration correcting element is arranged at a position where the center thereof is deviated from the optical axis of the other element.

  The optical axis shift will be described with reference to a diagram in which elements constituting the pickup shown in FIG. 7 are linearly arranged. As shown in FIG. 7, as the elements constituting the pickup, as described above with reference to FIG. 5, the integrated optical element 401 including the light source, the light receiving element, etc., the aberration correcting element 402, the collimator lens 403, the objective A lens 404 is provided, and data recording or reproduction with respect to the optical disc 410 is performed. Note that a quarter wave plate is integrated with the aberration correction element 402.

  In the configuration shown in the drawing, the integrated optical element 401, the collimator lens 403, and the objective lens 404 are adjusted so that their optical axis centers coincide with each other, and finally the aberration correction element 402 is mounted as an additional component. The miniaturized pickup has a configuration in which the mounting space for the aberration correction element 402 is scarce, and a jig pin cannot be inserted to adjust the position or cannot be bonded after the position adjustment. As a result, a situation occurs in which the center of the aberration correction element is shifted from the optical axis of other elements.

  That is, as shown in FIG. 7, the result is that the optical axis center 501 of the aberration correction element does not coincide with the optical axis center 502 of the other optical element that is the optical axis center of the optical pickup component other than the aberration correction element 402. become.

  In the optical pickup of the present invention, the objective lens moving process is executed for such a deviation of the optical axis, and the optical axis of the objective lens and the aberration correcting element is matched. Hereinafter, this process will be described with reference to FIG.

  FIG. 8 shows an integrated optical element 701 including a light source, a light receiving element and the like, an aberration correction element 702, a collimator lens 703, and an objective lens 704 as elements constituting the pickup, as in FIG. Data recording or reproduction with respect to the optical disk 710 is performed by an optical pickup composed of these components. Note that a quarter-wave plate is integrated with the aberration correction element 702.

  The aberration correction element 702 is mounted after setting up other optical pickup components. As a result, the optical axis shift described above with reference to FIG. 7 occurs. Immediately after the aberration correction element 702 is attached, the objective lens 704 is in the position (P1). At this point, there is a deviation between the optical axis center 801 of the aberration correction element 702 and the optical axis center 802 of the objective lens 704.

  The optical axis adjustment process will be described. First, in a state where no voltage is applied to the transparent electrode of the aberration correction element 702, or in a state before the aberration correction element 702 is inserted, that is, in a state where no aberration pattern is generated by the aberration correction element 702, the light source in the integrated optical element 701 is used. And the optical axes of the light source, collimator lens 703 and objective lens 704 are aligned. This procedure can be performed by a conventionally known method, for example, a spatial position adjusting device disclosed in Japanese Patent Laid-Open No. 2003-59095.

  Next, a voltage is applied to the transparent electrode of the aberration correction element 702 to cause the light source in the integrated optical element 701 to emit light in a state where a concentric aberration pattern is generated. At this time, by observing the center of the concentric aberration pattern with a CCD camera or the like, the deviation between the center of the aberration pattern and the optical axis can be measured. The objective lens 704 is moved to the position (P2) as shown in FIG. 8 by moving the objective lens 704 in the direction of the arrow (Q) shown in FIG. The center of the optical axis 702 and the center of the optical axis of the objective lens 704 can be matched. That is, the objective lens 704 is held by an actuator (not shown), and the optical axis center of the objective lens 704 is made to coincide with the optical axis center of the aberration correction element 702 as a reference by controlling the actuator.

  As a result of the above optical axis adjustment processing, the aberration correction element and the adjusted objective lens optical axis center 801 are displaced from the collimator lens optical axis center 802 as shown in FIG. It arrange | positions so that a center axis may correspond. As a result, it is possible to prevent the occurrence of coma due to the misalignment between the central axes of the objective lens 704 and the aberration correction element 701. As a result, it is possible to ensure a sufficient margin with respect to the tilt of the disk.

  That is, as shown in FIG. 9, there is a relationship between the amount of deviation (tilt angle (deg)) between the vertical axis with respect to the optical disc surface and the optical axis of the optical pickup, and jitter (%) indicating the degree of signal quality degradation. In the graph showing the correspondence, by aligning the optical axis center of the liquid crystal aberration correction element with the optical axis center of the optical pickup, for example, a signal with an acceptable level of signal quality, a jitter of 15% or less can be obtained. The range (R) is substantially the same for both the tilts of − and +, and an acceptable level of signal quality can be obtained within a substantially constant range regardless of the direction of the tilt of the optical disc. In this way, by making the optical axis center of the liquid crystal aberration correction element coincide with the optical axis center of the objective lens, it becomes possible to perform recording / reproduction processing with a high-quality recording / reproduction signal while maintaining a disc tilt margin. .

  The present invention has been described in detail above with reference to specific embodiments. However, it is obvious that those skilled in the art can make modifications and substitutions of the embodiments without departing from the gist of the present invention. In other words, the present invention has been disclosed in the form of exemplification, and should not be interpreted in a limited manner. In order to determine the gist of the present invention, the claims should be taken into consideration.

  As described above, according to the configuration of the embodiment of the present invention, in the optical pickup having the aberration correction element, the configuration is adjusted so that the optical axis center of the objective lens coincides with the optical axis center of the aberration correction element. Therefore, no matter what direction the tilt of the optical disc occurs, an acceptable level of signal quality can be obtained within a certain range, and the disc tilt margin can be maintained, and recording / playback processing with high-quality recording / playback signals can be performed. An information processing apparatus to perform is realized.

  In particular, an optical pickup in which an aberration correction element is inserted in the convergent light between the light source and the collimator lens can reduce the size of the aberration correction element, but increases the discrepancy with the aberration of the objective lens and further increases the skew deviation. However, according to the configuration of the present invention, the central axis of the aberration correction element and the objective lens can be matched without requiring an extra space for adjusting the position of the aberration correction element. Therefore, it is possible to prevent the skew deviation based on the mismatch between the aberration correction element and the objective lens, which is advantageous in reducing the size of the optical pickup and the optical disc apparatus.

It is a figure explaining the structural example of an aberration correction element. It is a figure explaining the example in case the optical axis center of an aberration correction element corresponds with the optical axis center of an optical pick-up. It is a figure explaining the example in case the optical axis center of an aberration correction element and the optical axis center of an optical pick-up do not correspond. It is a figure explaining deterioration of signal quality, the so-called jitter generation amount, when the optical axis center of the aberration correction element and the optical axis center of the optical pickup coincide with each other. It is a figure explaining the structure of an optical pick-up. It is a figure explaining the structural example of an aberration correction element. It is a figure explaining the example of a pick-up structure in which the optical axis center of an aberration correction element and the optical axis center of the other optical element of an optical pickup do not correspond. It is a figure explaining the process example which makes the optical axis center of an aberration correction element correspond with the optical axis center of an objective lens. It is a figure explaining the amount of jitter generation when the optical axis center of the aberration correction element and the optical axis center of the optical pickup are matched.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Liquid crystal aberration correction element 101-105 Electrode 200 Optical pick-up 202 Optical disk 212 Integrated optical element 214 Aberration correction element 216 1/4 wavelength plate 218 Collimator lens 220 Mirror 222 Objective lens 224 Actuator 301,302 Transparent electrode 401 Integrated optical element 402 Aberration correction Element 403 Collimator lens 404 Objective lens 410 Optical disk 501 Aberration correction element optical axis center 502 Other optical element optical axis center 701 Integrated optical element 702 Aberration correction element 703 Collimator lens 704 Objective lens 710 Optical disk 801 Aberration correction element and adjusted objective lens optical axis Center 802 Collimator lens and optical axis center before adjustment

Claims (8)

An optical pickup applied to information recording on an optical disc or information reproduction from an optical disc,
A light source that emits irradiation light to the optical disc;
An objective lens that focuses the light emitted from the light source onto the optical disc;
A collimator lens disposed between the light source and the objective lens, which guides the light beam emitted from the light source to parallel light as the collimator lens;
An aberration correction element that is disposed in an optical path connecting the light source and the optical disc and corrects an aberration;
An optical pickup having a configuration in which an optical axis center of the objective lens is matched with an optical axis center of the aberration correction element as a reference.   The optical pickup according to claim 1, wherein an optical axis center of the objective lens is deviated from an optical axis center of the collimator lens. The objective lens is held by an actuator,
2. The optical pickup according to claim 1, wherein the optical axis center of the objective lens is configured to coincide with the optical axis center of the aberration correction element as a reference by the control of the actuator.   The aberration correction element is a spherical aberration correction element configured by a liquid crystal element, and the liquid crystal element has a control unit so that the refractive index has a wavefront change opposite to the spherical aberration generated in the light passing through the optical pickup. The optical pickup according to claim 1, wherein the optical correction element is an aberration correction element having a configuration controlled by. An information processing apparatus for performing information recording on an optical disc or information reproduction from an optical disc,
It has an optical pickup that is used for recording or reproducing information,
The optical pickup is
A light source that emits irradiation light to the optical disc;
An objective lens that focuses the light emitted from the light source onto the optical disc;
A collimator lens disposed between the light source and the objective lens, which guides the light beam emitted from the light source to parallel light as the collimator lens;
An aberration correction element that is disposed in an optical path connecting the light source and the optical disc and corrects an aberration;
An information processing apparatus having a configuration in which an optical axis center of the objective lens is matched with an optical axis center of the aberration correction element as a reference. An optical pickup manufacturing method for adjusting an optical pickup applied to information recording on an optical disc or information reproduction from an optical disc,
The optical pickup is
A light source that emits irradiation light to the optical disc;
An objective lens that focuses the light emitted from the light source onto the optical disc;
A collimator lens disposed between the light source and the objective lens, which guides the light beam emitted from the light source to parallel light as the collimator lens;
An aberration correction element that is disposed in an optical path connecting the light source and the optical disc and corrects an aberration;
An optical pickup manufacturing method comprising: an optical axis adjustment processing step of executing a process of matching an optical axis center of the objective lens with reference to an optical axis center of the aberration correction element. The optical axis adjustment processing step includes
Applying a voltage to the aberration correction element, causing the light source to emit light in a state where a concentric aberration pattern is generated, and measuring a center of the aberration pattern and an optical axis deviation;
The method of manufacturing an optical pickup according to claim 6, further comprising a step of moving the objective lens in accordance with a shift amount of the aberration pattern. The objective lens is held by an actuator,
The optical axis adjustment processing step includes
The optical pickup manufacturing method according to claim 6, wherein the optical axis center of the objective lens is matched with the optical axis center of the aberration correction element as a reference by controlling the actuator.

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