JP4359189B2 - Optical pickup device - Google Patents

Description

  The present invention relates to an optical pickup device, and more particularly to means for suppressing deterioration of reproduction characteristics caused by intrinsic noise of a semiconductor laser in a recording type optical pickup device, and the above means are applied to be formed on a signal recording layer of an optical disc. The present invention relates to an optical pickup device that can correct spherical aberration caused by deviation of the thickness of a cover layer from a reference value.

  In recent years, optical discs have been widely used as media for recording data such as video data, audio data, and computer data, and the demand for higher recording density (higher capacity) and high-speed recording for optical discs is increasing. Recently, large-capacity optical disk devices using blue-violet semiconductor lasers have begun to be commercialized.

In an optical disk apparatus using a semiconductor laser as a light source, there is a phenomenon that reproduction characteristics deteriorate due to laser noise. Laser noise can be classified into two types, one is inherent noise that occurs when there is no return light, and the other is return light noise that is added when return light is returned. Usually, the noise evaluation uses the following RIN (Relative Intensity Noise) values. Here, P is the laser output and Δf is the measurement bandwidth.
RIN = {(noise intensity) ² / P ² } / Δf [dB / Hz]
In the case of an optical pickup device, the laser beam output from the semiconductor laser is inevitably returned to the semiconductor laser after being reflected by the optical disk. Return light noise is generated by the amount of return light. This return light noise tends to become the largest when the semiconductor laser is oscillated in a single mode. Therefore, normally, high-frequency superimposition is applied to the laser light during reproduction to make it multimode to minimize this return light noise. It is suppressed.

  In addition, the intrinsic noise corresponds to fluctuations in the light intensity of the laser light. An example of intrinsic noise characteristics of a blue-violet semiconductor laser is shown in FIG. As shown in the figure, the intrinsic noise has a tendency that the RIN, that is, the noise is higher as the emission power of the semiconductor laser is lower.

  Therefore, considering the inherent noise, it is preferable to use the laser beam emission power as high as possible. Of course, the reproduction power of the disc is generally defined by the media, and the power of the light spot output from the objective lens of the optical pickup device must be used at the specified value. Therefore, the optical efficiency of the optical system (light spot power / (Laser light emission power) is preferably set. Specifically, by reducing the optical efficiency and setting the output power of the objective lens to the specified value, the optical system is configured so that the output power from the semiconductor laser is as large as possible, thereby suppressing the intrinsic noise of the semiconductor laser. Playback performance is improved.

  Such an optical disc has a cover layer that transmits light on the signal recording layer, and data is recorded / reproduced by condensing the light onto the signal recording layer through the cover layer. The objective lens that focuses light on the signal recording layer is designed so that spherical aberration is minimized on the signal recording layer when the thickness of the cover layer is a reference value (standard value of the standard value of the optical disc). . For this reason, spherical aberration occurs when the thickness of the cover layer deviates from the reference value, such as when there are multiple signal recording layers on one side of the optical disk, or when the thickness of the cover layer varies in manufacturing. Recording / reproduction characteristics deteriorate.

  In Patent Document 1, a collimator lens is provided with two convex lenses or a beam expander composed of one convex lens and one concave lens in order to correct spherical aberration that occurs when the thickness of the cover layer deviates from a reference value. An optical pickup device is disclosed that is arranged in parallel light between the lens and the objective lens, and adjusts the parallelism of the light by adjusting the distance between the two lenses.

In this optical pickup device, when the thickness of the cover layer deviates from the reference value, the beam expander converts incident light to the objective lens from parallel light into diffused light or convergent light. Then, the spherical aberration that occurs when the thickness of the cover layer deviates from the reference value is canceled by the spherical aberration that occurs in the objective lens, and the spherical aberration on the signal recording layer is reduced to an extent that does not substantially affect recording / reproduction. To do.
JP 2002-170276 A

In order to reduce the intrinsic noise of the semiconductor laser, the optical efficiency of the optical pickup device is designed to be low, and the output power of the semiconductor laser should be as large as possible when the output light power of the objective lens is a specified value. It is possible to configure such an optical system as long as it is a read-only optical pickup device. However, in the case of a recording optical pickup device, the optical efficiency may be reduced unnecessarily in order to secure recording power during recording. Can not.

  The present invention is an optical pickup capable of performing reproduction while reducing the intrinsic noise of such a semiconductor laser as much as possible, and varying optical efficiency during reproduction and recording so as to ensure as much recording power as possible during recording. An object is to provide an apparatus. Another object of the present invention is to correct spherical aberration that occurs when the thickness of the cover layer of the optical disc has manufacturing variations or when there are multiple signal recording layers on one side of the optical disc. It is providing the optical pick-up apparatus which is.

1st invention is the optical pick-up apparatus which records and reproduces the optical disk in which the cover layer is formed on the signal recording layer, Comprising: The light from the said light source permeate | transmits the said cover layer, and the said signal An objective lens for focusing on the recording layer; a collimator lens for causing the light from the light source to enter the objective lens; a divergent lens and a correction lens sequentially arranged from the light source toward the collimator lens; and the light source; A divergent lens moving means for moving the divergent lens along an optical axis in order to change a distance from the divergent lens; and an optical axis for changing the distance between the correction lens and the collimator lens. Correction lens moving means for moving along the distance between the light source and the divergent lens And optical efficiency is set to a first state at the time of recording by changing the distance between the correction lens and the collimator lens, and characterized in that when setting the first second state lower optical efficiency than state playback This is an optical pickup device.

According to a second invention, in the optical pickup device of the first invention, after the optical efficiency is set, the distance between the correction lens and the collimator lens is further finely adjusted so as to correct the spherical aberration in the signal recording layer . The incident light to the objective lens is any one of parallel light, diffused light, and convergent light.

  After the optical efficiency is set to either the first state or the second state, only the correction lens is moved along the optical axis by the correction lens moving means, thereby reducing the distance between the correction lens and the collimator lens. The light emitted from the collimator lens is adjusted to one of parallel light, diffused light, and convergent light. Light emitted from the collimator lens is condensed on the signal recording layer through the cover layer of the optical disk by the objective lens. Therefore, when the thickness of the cover layer deviates from the reference value, the correction lens is moved along the optical axis, and the incident light to the objective lens is changed from parallel light to diffused light or convergent light. As a result, the spherical aberration caused by the deviation of the thickness of the cover layer from the reference value is canceled out by the reverse spherical aberration generated in the light emitted from the objective lens. For this reason, spherical aberration on the signal recording layer can be suppressed.

  According to a third invention, in the optical pickup device of the first or second invention, the correction lens is a single concave lens. For this reason, an optical pick-up apparatus can be reduced in size.

According to a fourth invention, in the optical pickup device according to any one of the first to third inventions, the divergent lens and the correction lens are moved along the optical axis in accordance with the type of the optical disk. Since the divergent lens and correction lens can be moved along the optical axis according to the type of optical disk such as ROM disk, R / RW disk, single-layer disk, double-layer disk, etc., the optical efficiency of each optical disk can be changed. And spherical aberration correction.

  According to the present invention, reproduction can be performed with the intrinsic noise of the semiconductor laser reduced as much as possible, and the optical efficiency can be varied between reproduction and recording so as to ensure recording power as much as possible during recording. . In addition, it is possible to correct spherical aberration that occurs when the thickness of the cover layer of the optical disc has manufacturing variations or when there are a plurality of signal recording layers on one side of the optical disc.

The above object, other objects, features, and advantages of the present invention will become more apparent from the following detailed description of embodiments with reference to the drawings.

  With reference to FIGS. 1A to 1C, an optical pickup device 10 capable of recording / reproducing a high density optical disc (hereinafter referred to as an optical disc in this embodiment) 19 of this embodiment will be described. 1A to 1C are a perspective view, a plan view, and a side view of the optical pickup device 10, respectively.

  First, an optical path (outward path) from the light source blue-violet semiconductor laser 11 (hereinafter referred to as a semiconductor laser) to condensing on the optical disk 19 will be described. The linearly polarized laser beam emitted from the semiconductor laser 11 enters the polarization beam splitter 12. The light emitted from the semiconductor laser 11 is diffused light having a spread of about ± 5.4 degrees. The polarizing beam splitter 12 substantially transmits linearly polarized light incident from the semiconductor laser side. The laser beam that has passed through the polarizing beam splitter 12 enters the quarter-wave plate 13 and is converted from linearly polarized light to circularly polarized light. The spread angle of the laser light converted into circularly polarized light is moderated by the divergent lens 14, and then the spread angle is widened by the correction lens 15. Although a convex lens can be used as the correction lens, a concave lens is preferable because the optical pickup device can be downsized. The divergent lens 14 and the correction lens 15 can be moved along the optical axis direction (X direction) according to the adjustment of the optical efficiency and the degree of spherical aberration. Details of the positional relationship will be described later. The light that has passed through the correction lens 15 is reflected by the rising mirror 16 in the direction in which the objective lens 18 is arranged (+ Z direction) after being reflected by the rising mirror 16, and becomes parallel light by the collimator lens 17. The light is incident on the lens 18, and the collimated light is focused by the objective lens 18 and condensed on the signal recording layer of the optical disk 19. A part of the light incident on the rising mirror 16 is transmitted and incident on the front monitor diode 23 disposed behind the rising mirror. The front monitor diode 23 is a photodetector that outputs an electrical signal corresponding to incident light and is used for APC (Automatic Power Control) control for controlling the output power of the semiconductor laser 11.

  Next, the optical path (return path) of the reflected light from the signal recording layer of the optical disc 19 will be described. The circularly polarized laser beam reflected by the signal recording layer of the optical disk 19 is transmitted again through the objective lens 18 and the collimator lens 17 and then reflected by the rising mirror 16 in the direction (−X direction) in which the correction lens 15 is disposed. The Next, the reflected circularly polarized laser light passes through the correction lens 15, the divergent lens 14, and the ¼ wavelength plate 13, and is converted from circularly polarized light to linearly polarized light by the ¼ wavelength plate 13. In the return path, the direction of circularly polarized light is opposite to that of the forward path due to reflection on the optical disk. Therefore, the polarization direction of the laser light that is linearly polarized by the quarter wavelength plate 13 is emitted from the forward path, that is, the semiconductor laser 11. The rotation direction is 90 degrees with respect to the polarization direction of the linearly polarized light. Therefore, the laser light converted into linearly polarized light is reflected by the polarization beam splitter 12 in a direction (plus Y direction) that forms an angle of 90 degrees with the incident direction. The light reflected by the polarization beam splitter 12 passes through the detection lens 20 that causes astigmatism so that focus servo can be performed, and then enters the photodetector 21. The photodetector 21 is composed of a photodiode and outputs a signal corresponding to the intensity of incident light. The photodetector 21 includes a well-known four-divided sensor that is divided into four detectors like a square shape. . A servo error signal such as a focus error signal and a tracking error signal is calculated and generated by a control device (not shown) based on the outputs (a to d) of the respective division detection units. Further, the sum of the outputs (a to d) of the division detection unit becomes an RF signal representing the information of the signal recording layer on the optical disc.

  Next, a method for changing the optical efficiency will be described with reference to FIG. In the figure, the focus is on changing the optical efficiency, and optical components, photodetectors, and the like that do not affect the optical efficiency are omitted. Reference numeral 11 denotes a semiconductor laser, 14 denotes a divergent lens, 15 denotes a correction lens, 17 denotes a collimator lens, and 18 denotes an objective lens. FIG. 5A shows an optical arrangement (first state) with high optical efficiency, which is an effective configuration during recording that requires high recording power. FIG. 2B shows an optical arrangement (second state) with low optical efficiency. Compared with the arrangement of (a) described above, the divergent lens 14 moves away from the semiconductor laser 11 and approaches the optical disk. The correction lens 15 moves along the optical axis in the direction of approaching the semiconductor laser 11 and away from the optical disk. Since the optical arrangement in FIG. 2B has low optical efficiency, when the output power of the objective lens 18 is the same as that in the case where the optical efficiency in FIG. 2A is high, the output power of the semiconductor laser 11 is set large. As a result, the intrinsic noise of the semiconductor laser 11 becomes low. Therefore, when reproducing a read-only disc (ROM) or a recorded R / RW disc, the optical arrangement in FIG. 2B, that is, the optical efficiency is set to the second state lower than the first state. Reproduction characteristics are improved.

  The spherical aberration correction will be described with reference to FIG. In the figure, an optical disk 19 is a two-layer disk, and has a first signal recording layer 19b nearer to the disk surface 19a and a second signal recording layer 19c farther away.

  Referring to FIG. 3A, when laser light is incident on the objective lens 18 as parallel light, the laser light passes through the first cover layer 30b and the second cover layer 30a from the disk surface 19a, and the first cover layer 30a passes through the first cover layer 30a. When the objective lens 18 is designed to focus on the second signal recording layer 19c, the spherical aberration of the laser light focused on the second signal recording layer 19c is minimized.

  When the objective lens 18 is used to focus the light on the first signal recording layer 19b, the first signal recording layer 19b has a spherical surface because the first cover layer 30b is the only cover layer through which the laser light is transmitted. Aberration occurs. Therefore, as shown in FIG. 3B, when the laser light incident on the objective lens 18 is converged light, the spherical aberration that substantially cancels the spherical aberration due to the reduced thickness of the cover layer is the laser light. It is possible to suppress the spherical aberration of the laser beam that occurs in the first signal recording layer 19b.

  Contrary to the above, when laser light is incident on the objective lens 18 as parallel light, the laser light is transmitted from the disk surface 19a through the first cover layer 30b, and the first signal close to the disk surface 19a. When the objective lens 18 is designed to focus on the recording layer 19b, the spherical aberration of the laser light focused on the first signal recording layer 19b is minimized.

  When the objective lens 18 is used to focus the laser beam on the second signal recording layer 19c located deeper than the first signal recording layer 19b, the laser beam is emitted from the first cover layer 30b and the second cover layer 30b. The second signal recording layer 19c generates spherical aberration. Therefore, when the laser light incident on the objective lens 18 is diffused light, spherical aberration that substantially cancels the spherical aberration due to the increased thickness of the cover layer is generated in the laser light, and the second signal recording layer 19c. It is possible to suppress spherical aberration of the laser light focused on the light.

  In addition, since the thickness of the cover layer varies even in a single-layer optical disc, the configuration in which the incident light to the objective lens can be adjusted from a parallel light state to a convergent light or a diffused light has a reproduction and recording quality. It is effective for improving the characteristics of

  Next, with reference to FIG. 4, it will be described that the laser light incident on the objective lens 18 becomes one of parallel light, diffused light, and convergent light by changing the position of the correction lens 15. This optical system has an optical arrangement (second state) in which the optical efficiency effective at the time of reproduction shown in FIG. 2B described above is set as a reference position, and includes a semiconductor laser 11, a divergent lens 14, The positions of the collimator lens 17 and the objective lens 18 are fixed, and spherical aberration correction is performed by moving only the correction lens 15 in the optical axis direction from the reference position.

  FIG. 4B shows a case where the thickness of the cover layer of the optical disc 19 is a reference value. At this time, the position of the correction lens 15 is such that the laser light emitted from the collimator lens 17 becomes parallel light. Therefore, the incident light to the objective lens 18 becomes parallel light.

  FIG. 4A shows a case where the cover layer is thicker than the reference value. At this time, since the position of the correction lens 15 has moved to the collimator lens 17 side as compared with the case of FIG. 5B, the laser light emitted from the collimator lens 17 becomes diffused light. Therefore, the incident light to the objective lens 18 becomes diffuse light.

  FIG. 3C shows the case where the cover layer is thinner than the reference value. At this time, since the position of the correction lens 15 has moved to the divergent lens 14 side as compared with the case of FIG. 5B, the laser light emitted from the collimator lens 17 becomes convergent light. Therefore, the incident light to the objective lens 18 becomes convergent light.

  Although the above description is based on the second state with low optical efficiency that is effective at the time of reproduction shown in FIG. 2B, the optical efficiency that is effective at the time of recording shown in FIG. Even when the optical arrangement in the first state higher than the second state is used, spherical aberration correction can be performed by adjusting only the correction lens 15 in the same manner.

  Next, with reference to FIG. 5, the spherical aberration that occurs when the thickness of the cover layer of the optical disc 19 is in the range of 70 μm to 130 μm, and the simulation results when the above correction is performed for this spherical aberration will be described. . Here, the reference value of the thickness of the cover layer was 100 μm, and the numerical aperture NA of the objective lens was 0.85.

  For example, when the thickness of the cover layer is deviated from the reference value 100 μm by ± 10 μm, that is, when the thickness of the cover layer is 110 μm or 90 μm, as shown in FIG. (Λ is the wavelength of light). In general, in order to obtain good recording / reproducing characteristics, the amount of spherical aberration generated must be suppressed to 0.07λ or less in the entire optical pickup device 10. For this reason, when the generation amount of spherical aberration is 0.1λ, good recording / reproducing characteristics cannot be obtained.

  Therefore, by moving the correction lens 15 provided between the divergent lens 14 and the collimator lens 17 back and forth along the optical axis, the laser light incident on the objective lens 18 is corrected to diffused light or convergent light. As can be seen from FIG. 5, the amount of generation of spherical aberration is 0.01λ or less, which can be significantly suppressed as compared with the case where correction is not performed. As described above, if the generation amount of spherical aberration can be suppressed to 0.01λ or less, it is considered that there is almost no influence on the recording / reproducing characteristics.

  Note that the method of moving the divergent lens 14 and the correction lens 15 in the optical axis direction for changing the optical efficiency and correcting the spherical aberration can be performed by using a driving device using a general stepping motor or voice coil. It is.

  In this embodiment, the optical pickup device for a high-density optical disk using a blue-violet laser has been described. However, the optical pickup device for a DVD using a red laser can also be used. In a recordable DVD optical pickup device, it is desirable to increase the optical efficiency by mounting a high-power laser in order to cope with the high-speed recording, but there is a concern about laser-specific noise due to low output during reproduction. . In addition, there are two-layer discs for DVD discs, and spherical aberration is not as high as that for high-density discs using a blue-violet laser, but the recording / reproducing performance is improved by correcting it.

  Next, the optical disc recording / reproducing apparatus 60 will be described with reference to FIG. The optical disk recording / reproducing device 60 includes an optical pickup device 10 that includes a laser drive circuit 41, a temperature sensor 42, and an objective lens actuator in addition to the optical components and photodetectors shown in FIG. 43, a divergent lens moving means 44, a correction lens moving means 45, and the like. Reference numeral 50 denotes a control device for controlling the pickup device 10.

  The laser drive circuit 41 drives the semiconductor laser 11, and the front monitor diode 23 measures the output of the semiconductor laser 11 and gives the measured value to the control device 50. Based on this value, the control device 50 controls the laser drive current so that the target laser power is emitted from the objective lens 18. The laser drive circuit 41 also has a function of applying high-frequency superposition to the laser for the purpose of reducing return light noise during reproduction. During recording, pulsed emission of recording power is controlled based on a recording signal given from the control device 50. The temperature sensor 42 is attached in the vicinity of the semiconductor laser 11 of the optical pickup device 10, detects the ambient temperature of the semiconductor laser 11, and gives the information to the control device 50. In the blue-violet laser, the oscillation wavelength of the laser tends to increase slightly as the temperature rises. When the wavelength changes, the degree of spherical aberration also changes, so the ambient temperature is detected and the spherical aberration correction amount is controlled. The divergent lens moving means 44 and the correction lens moving means 45 are for controlling the movement of the divergent lens 14 and the correction lens 15 along the optical axis, respectively, and are constituted by a pulse motor or the like.

  The actuator 43 controls the movement of the objective lens 18 in the focus direction and the tracking direction. Based on the output signal of the light detector 21, the control device 50 causes servo error signals such as a focus error signal and a tracking error signal. Is generated and the actuator 43 is controlled based on this signal. Here, for example, when the optical disk 19 is warped, if the objective lens 18 is moved in a direction perpendicular to the main surface of the optical disk to adjust the focus, the distance between the objective lens 18 and the correction lens 15 changes, and spherical aberration is reduced. Affects the outbreak. Therefore, the distance between the objective lens 18 and the optical disk 19 is estimated by referring to the focus drive voltage of the actuator 43 in a state where the focus servo control is performed, and the spherical aberration correction amount is finely adjusted.

  In the present embodiment, an example in which the spherical aberration correction amount is finely adjusted based on the ambient temperature of the semiconductor laser 11 and the position information of the objective lens 18 in the focus direction is shown. However, the target disk is a ROM or a recorded R / RW disk. If so, it is also possible to determine the optimum correction amount based on the jitter and error rate of the reproduction signal.

  Next, a processing flow in movement control of the divergent lens 14 and the correction lens 15 will be described with reference to FIG.

  First, in step S1, the divergent lens 14 and the correction lens 15 are moved to the initial positions. In this embodiment, the initial value is set to a position where the optical efficiency is low, that is, the intrinsic noise of the laser is low, and the reproduction characteristic is good (second state). The position of the correction lens 15 is a position where the spherical aberration is reduced in the L0 layer of the single layer disc (single layer SL) and the double layer disc (dual layer DL). The optical disk in this example is a double-layer disk, the L0 layer has the same cover layer thickness as the single-layer disk, and the L1 layer has a structure closer to the disk surface than the L0 layer. Next, in step S2, adjustment is performed so that the laser is turned on and the reproduction power is obtained when the objective lens is emitted. Here, after the divergent lens 14 and the correction lens 15 are moved to predetermined positions, the laser is turned on to adjust the power because the optical efficiency changes with the movement of both the lenses.

  Next, in step S3, the disc is discriminated. If the disc is a read-only disc (ROM) or a recorded R / RW disc, the lens position initially adjusted in step S1, that is, the second optical efficiency is low. Since this state is preferable, the process proceeds to step S7 without changing the positions of both lenses. In the case of an unrecorded disc, in order to change the optical efficiency to a high state, the laser is turned off once in step S4, and correction is performed with the divergent lens 14 so that the first state where the optical efficiency is high in step S5. The lens 15 is moved, and then, in step S6, the laser is turned on and adjustment is performed so that the reproduction power is obtained. Also in step S5, the position of the correction lens 15 has an initial value at which the spherical aberration is reduced in the L0 layer of the single-layer disc and the double-layer disc.

  The process of changing the optical efficiency is completed by the process so far, and the subsequent process is an aberration correction process.

  Next, in step S7, the layer structure of the disc is discriminated. If it is the L0 layer of a single layer disc or a dual layer disc, the process proceeds to step S9, and if it is the L1 layer of a dual layer disc, step S1 is performed. Alternatively, since the correction lens position initially set in step S5 is not preferable, the correction lens 15 is moved to a position where the spherical aberration is reduced in the L1 layer. However, the position of the correction lens so far uses a set value prepared in advance by the optical disc recording / reproducing apparatus for rough adjustment of spherical aberration correction.

    Next, in step S9, reproduction is performed in the signal area, and the position of the correction lens 15 is finely adjusted so that the reproduction characteristics are the best. As this indicator, the reproduction jitter, error rate, etc. of the reproduction signal are measured by the control device and judged. At the same time, the ambient temperature of the semiconductor laser and the objective lens position at this time are stored and used for spherical aberration correction at the time of recording to be described later.

  Next, in step S10, it is determined whether the reproduction operation or the recording operation. In the case of reproduction, in step S11, the target track is reproduced, and the jitter and error rate are optimized based on the reproduction signal. The position of the correction lens 15 is always finely adjusted.

  At the time of recording, spherical aberration correction is performed by finely adjusting the correction lens 15 according to the temperature at the optimum position of the correction lens 15 obtained in step S9 and the amount of change from the objective lens position (step S12). Make a record.

  As described above, the positions of the divergent lens and the correction lens are changed in the optical axis direction during reproduction and recording, and the optical efficiency of the optical pickup device is high during recording, that is, the first state, and first during reproduction. By setting the second state lower than the above state, the reproduction characteristics are good during reproduction, and high recording power can be emitted during recording. After determining the optical efficiency of either the first or second state, it is possible to correct spherical aberration by finely adjusting only the correction lens in the optical axis direction.

  Although the embodiment of the present invention has been specifically described by way of examples, the present invention is not limited to these examples. For example, in the present embodiment, the optical pickup apparatus having one light source has been described. However, it is needless to say that the present invention can also be applied to an optical pickup apparatus having a plurality of light sources.

It is an illustration figure which shows the Example of the optical pick-up apparatus of this invention. It is an illustration figure which shows the change method of optical efficiency. It is an illustration figure which shows the relationship between spherical aberration and the incident light of an objective lens. It is an illustration figure which shows the relationship between the position of a correction lens, and the incident light of an objective lens. It is a spherical aberration characteristic figure which shows the effect of the correction by an Example. 1 is a block diagram illustrating an optical disc recording / reproducing apparatus including an optical pickup device according to an embodiment. It is a flowchart which shows operation | movement of an Example. It is a characteristic view which shows an example of the intrinsic noise characteristic of a blue-violet semiconductor laser.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Optical pick-up apparatus 11 ... Semiconductor laser 14 ... Divergent lens 15 ... Correction lens 17 ... Collimator lens 18 ... Objective lens 19 ... Optical disk 21 ... Optical detector 44 ... Divergent lens moving means 45 ... Correction lens moving means 50 ... Control Apparatus 60 ... Optical disk recording / reproducing apparatus

Claims (4)

An optical pickup device for recording / reproducing an optical disc in which a cover layer is formed on a signal recording layer,
A light source;
An objective lens for condensing light from the light source through the cover layer and condensing on the signal recording layer;
A collimator lens that makes the light from the light source incident on the objective lens;
A divergent lens and a correction lens sequentially arranged from the light source toward the collimator lens;
Divergent lens moving means for moving the divergent lens along an optical axis in order to change the distance between the light source and the divergent lens;
Correction lens moving means for moving the correction lens along the optical axis in order to change the distance between the correction lens and the collimator lens;
With
The optical efficiency is set to the first state during recording by changing the distance between the light source and the divergent lens and the distance between the correction lens and the collimator lens, and the optical efficiency is lower than that in the first state during reproduction. the optical pickup apparatus characterized by setting the second state. After setting the optical efficiency, the distance between the correction lens and the collimator lens is finely adjusted so as to correct the spherical aberration in the signal recording layer. The optical pickup device according to claim 1, wherein the optical pickup device is any one of the above.   3. The optical pickup device according to claim 1, wherein the correction lens is a single concave lens. The correction lens and the divergent lens, the optical pickup device according to any one of claims 1 to 3, characterized in that moving along the optical axis in accordance with the type of the optical disc.

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