JP4325042B2 - Optical pickup device and optical disk device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical pickup apparatus and an optical disk apparatus that reproduce or record a plurality of optical disks that are used differently, and more particularly to an optical pickup apparatus and an optical disk apparatus that use different wavelengths of light.
[0002]
[Prior art]
In recent years, with the widespread use of optical disk devices, there are increasing demands for cost reduction and high reliability of the devices. For this reason, it is necessary to reduce the number of parts of the optical pickup unit, suppress the part cost, simplify the adjustment process at the time of manufacturing, and reduce the defect occurrence rate in the process and the market. In particular, an integrated optical element in which a light emitting element and a light receiving element are integrated in a single package does not require the light emitting point and the light receiving point to be independently adjusted. There are many advantages.
[0003]
For example, several types of integrated optical elements including a laser coupler have been developed and put into practical use for the most popular CD (Compact Disc). Also, DVD (Digital Versatile Disc) with higher recording capacity has been put into practical use, and the prevalence of video discs (DVD-video) and computer storage devices (DVD-ROM) is increasing. As with CDs, the number of parts has been reduced.
[0004]
By the way, since a high-end model DVD has just been put into practical use with respect to a widespread CD, a reproducing apparatus capable of reproducing both a CD and a DVD is required. A laser light source with a wavelength of 650 nm is necessary for DVD reproduction, but a light source with a wavelength of 780 nm is used for CD reproduction. Particularly, write-once CD (CD-R) uses an organic dye having a high wavelength dependency for a recording film. Therefore, reproduction is not possible unless the wavelength is 780 nm. For this reason, the CD / DVD compatible reproducing apparatus requires an optical pickup using a light source of two wavelengths.
[0005]
In this CD / DVD compatible two-wavelength optical pickup, there is a request to reduce the number of parts in order to achieve low cost and high reliability, and part of the optical path is shared and objective lenses are shared. ing. Similarly to CD laser couplers, an integrated optical element that includes two laser diodes with wavelengths of 780 nm and 650 nm and is packaged including a light receiving element has been developed for the purpose of integrating an optical system.
[0006]
FIG. 6 is a diagram showing a configuration example of an optical system of a two-wavelength optical pickup device using such an integrated optical element. In the two-wavelength pickup device 20 of FIG. 6, the two-wavelength laser coupler 21 is integrally provided with two different wavelength laser light sources and corresponding light receiving elements. The objective lens 25 is driven in a direction perpendicular to the disk surface (Z direction) and a radial direction of the disk (Y direction) for focusing and tracking adjustment. The light emitted from the two-wavelength laser coupler 21 passes through the window glass 22, is collimated by the collimator lens 23, is reflected by the prism 24, and is collected on the signal recording surface 26 a of the optical disk 26 by the objective lens 25. The light reflected by the signal recording surface 26a is incident on the light receiving element provided in the two-wavelength laser coupler 21 through the objective lens 25, the prism 24, the collimator lens 23, and the window glass 22 again.
[0007]
Next, details of the two-wavelength laser coupler 21 will be described. FIG. 7 is an enlarged view of the two-wavelength laser coupler of FIG. The light emitted from the first light source 212a (for DVD: wavelength 650 nm here) and the second light source 212b (here for CD: wavelength 780 nm) is reflected by the beam splitter 211a provided in the microprism 211, Head toward the disc. The light reflected and returned from the disk passes through the beam splitter 211a and is split into transmitted light and reflected light by the half mirror 211b formed on the lower surface of the microprism 211. The transmitted light is received by the respective light receiving portions 213a and 214a on the front side. The reflected light is again reflected by the high reflection film 211c formed on the upper surface of the microprism 211, and is received by the respective rear light receiving portions 213b and 214b.
[0008]
When an integrated optical element such as the above-mentioned two-wavelength laser coupler is used, all optical parts from the light emitting and receiving elements to the objective lens can be shared, so the number of parts is single format optical such as CD. It becomes almost the same as the system, and the number of parts can be drastically reduced as compared with the conventional CD / DVD shared optical system.
[0009]
[Problems to be solved by the invention]
However, in the optical system using the two-wavelength laser coupler of FIG. 7, since two laser light sources are arranged in parallel, one or both light sources do not coincide with the optical axis with reference to the center of the objective lens. The reflected light reflected on the disk in a state where the optical axes do not match does not accurately enter the light receiving portion. In this case, reproduction signal deterioration due to off-axis aberrations in the optical system, tracking error signal offset, movement of the objective lens in the disk parallel direction, and unbalanced changes in RF (Radio Frequency) signal level due to tilt in the disk radial direction, etc. Therefore, stable recording or reproduction of CD and DVD discs under various environments becomes difficult, which causes a problem in reliability of the apparatus.
[0010]
As a method for solving this problem, there is a method in which a diffraction element such as a hologram is provided between the light source and the objective lens so that one virtual light emitting point of the plurality of light sources viewed from the objective lens side is set to one point. FIG. 8 is a diagram showing the relationship between the laser optical axis and the hologram in the two-wavelength optical pickup device. The hologram 80 is a diffractive element having wavelength selectivity, and is disposed in the optical path between the laser light source and the objective lens. As shown in FIG. 8, when the first light source 81 is aligned with the optical axis 83 of the objective lens, the light from the first light source 81 passes through the hologram 80 and passes through the 0th-order optical path 81L. The light from the second light source 82 is diffracted by the hologram 80 and passes through the primary light path 82L. Thereby, the light from the second light source 82 can also coincide with the optical axis 83 of the objective lens, and the optical axis shift due to the position of the light source can be eliminated. However, in this method, the number of optical components is increased due to the arrangement of the hologram and the like, and a process for adjusting the position of the hologram is newly required. Therefore, the initial purpose of integrating the optical system is difficult to achieve because it leads to an increase in cost, a complicated manufacturing adjustment process, and a decrease in reliability.
[0011]
The present invention has been made in view of these points, and an object thereof is to provide an optical pickup device capable of recording or reproducing optical discs having different specifications with a simple device configuration.
[0012]
Another object of the present invention is to provide an optical disc apparatus capable of recording or reproducing optical discs having different specifications with a simple apparatus configuration.
[0013]
[Means for Solving the Problems]
The present invention proposed in order to achieve the above-described object includes an optical pickup device that records or reproduces a plurality of optical discs having different specifications, a first light emitting element that emits light of a first wavelength, and the first light emitting device. A second light emitting element that is arranged in parallel with the light emitting element in the radial direction of the optical disc and emits light having a second wavelength different from the first wavelength, and the first or second wavelength. A light receiving element that receives the light of the first wavelength, an objective lens that condenses the light of the first and second wavelengths, a drive unit that drives the objective lens, and the objective on the optical axis of the light of the first wavelength. lens to match the optical axis of, the when using light of a second wavelength, said driving means compensation instruction to compensate the distance between the optical axis of the optical axis and the second wavelength of the objective lens optical And an optical axis distance compensation means for providing That.
[0014]
In such an optical pickup device, when using the light of the second wavelength to the recording or reproduction of the disc, compensation instruction to compensate the distance between the optical axis and the optical axis of the objective lens of the second wavelength light Therefore, the optical axis coincides with the center of the objective lens, and recording or reproduction of optical discs having different specifications can be performed with high accuracy.
[0015]
According to another aspect of the present invention, there is provided an optical pickup device for recording or reproducing a plurality of optical discs having different specifications, a first light emitting element that emits light of a first wavelength, and the optical disc of the optical disc with respect to the first light emitting element. A second light emitting element that is arranged in parallel in the radial direction and emits light of a second wavelength different from the first wavelength; and a light receiving element that receives light of the first or second wavelength; The first and second wavelengths of light, which are arranged without matching the optical axis to either the optical axis of the light of the first wavelength or the optical axis of the light of the second wavelength, are collected. An objective lens and a driving means for driving the objective lens, and when using the light of the first wavelength, the distance between the optical axis of the objective lens and the optical axis of the light of the first wavelength is A compensation command for compensation is given to the driving means, and the light of the second wavelength is When use is characterized by having an optical axis distance compensating means for applying a compensation instruction to said drive means to compensate for the distance between the optical axis and the optical axis of the second wavelength light of the objective lens.
[0016]
In such an optical pickup device, a compensation command for compensating for the distance between the optical axis of the light to be used and the optical axis of the objective lens is given every time recording or reproduction of the disc is performed, so that the optical axis is placed at the center of the objective lens. It is possible to record or play back optical discs that match and are used differently.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram showing a configuration of a main part of an optical disc apparatus according to the present invention.
[0018]
The two-wavelength optical pickup device 10 includes laser light sources 112a and 112b having two different wavelengths, and light receiving units 113 and 114 that receive the reflected lights from the optical disc 1, respectively. The two laser light sources 112 a and 112 b are arranged so as to be parallel to the radial direction of the optical disc 1. The objective lens 15 is driven in the direction perpendicular to the disk surface and the disk radial direction by the driving means 15a, and performs focus error correction and tracking error correction.
[0019]
The light emitted from the first light source 112 a is reflected by the beam splitter 111 a, becomes parallel light by the collimator lens 13, is reflected by the prism 14, and is condensed on the signal recording surface 1 a on the optical disk 1 by the objective lens 15. The The light reflected by the signal recording surface 1 a passes through the beam splitter 111 a through the objective lens 15, the prism 14, and the collimator lens 13 and is received by the light receiving unit 113. The light emitted from the second light source 112b passes through a similar optical path and is received by the light receiving unit 114.
[0020]
In this optical disk apparatus, since the two laser light sources 112a and 112b are arranged in parallel, when the optical axis of the light from the first light source 112a is aligned with the center of the objective lens 15, the second light source 112b Light enters the objective lens 15 in a state where the optical axes do not match. For this reason, when the light from the second light source 112b is used, the objective lens 15 is moved in the disc radial direction by the driving means 15a so as to compensate the distance between the optical axes according to the compensation command from the optical axis distance compensating means 16. To drive.
[0021]
If the center of the objective lens 15 is arranged in the middle of the optical axes of the light from the two light sources 112a and 112b, the distance between the optical axes is instructed by a command from the compensation means each time each light is used. The objective lens 15 is driven in the disk radial direction by the driving means so as to compensate for the above.
[0022]
Next, the control system of the optical disk apparatus of the present invention will be described.
FIG. 2 is a block diagram of a control system of the optical disc apparatus of the present invention. The optical disc apparatus 100 includes an optical disc 1 that is rotationally driven by a spindle motor 2, a two-wavelength optical pickup device 10, and a feed motor 3 that drives the two-length optical pickup device 10. As the optical disc 1, a plurality of types of optical discs can be selected and recorded and played back, or only played back. The system controller 7 sends a command to select one of a plurality of laser light sources of the two-wavelength optical pickup device 10 to the two-wavelength optical pickup device 10 via the signal modulator / demodulator 6 and the preamplifier 4 according to the type of the disk. At the same time, a compensation command is sent to the servo control circuit 5 so as to compensate the distance between the optical axis of the laser beam and the objective lens.
[0023]
The two-wavelength optical pickup device 10 irradiates the signal recording surface of the rotating optical disc 1 according to the command of the signal modulator / demodulator 6 to record information. The two-wavelength optical pickup device 10 detects a light beam as will be described later based on the reflected light beam from the signal recording surface of the optical disc 1 and supplies a signal corresponding to each light beam to the preamplifier 4.
[0024]
The preamplifier 4 generates a focus error signal, a tracking error signal, an RF signal, and the like based on signals corresponding to each beam. Depending on the type of recording medium to be reproduced, the servo control circuit 5 and the signal modulator / demodulator 6 perform predetermined processing such as demodulation and error correction based on these signals.
[0025]
FIG. 3 is a diagram showing a configuration example of an optical system of the optical pickup device of the present invention. FIG. 4 is an enlarged view of the two-wavelength laser coupler 11 shown in FIG.
In the two-wavelength pickup device 10, the two-wavelength laser coupler 11 is integrally provided with laser light sources 112a and 112b having two different wavelengths, and light receiving elements 113a and 113b and 114a and 114b corresponding to the laser light sources 112a and 112b, respectively. The two laser light sources are arranged so as to be parallel to the radial direction of the optical disc 1. That is, the spots formed by the two laser beams on the signal recording surface 1a of the disk are aligned in the radial direction of the disk, that is, in the direction perpendicular to the track of the disk. The objective lens 15 has the same optical axis as the light from the first light source 112a of the two laser beams. The objective lens 15 is driven in a direction perpendicular to the disk surface (Z direction) and a radial direction of the disk (Y direction) for focusing and tracking adjustment.
[0026]
The light emitted from the first light source 112 a is reflected by the beam splitter 111 a provided in the microprism 111, passes through the window glass 12, is collimated by the collimator lens 13, is reflected by the prism 14, and is reflected by the objective lens 15. It enters accurately and is focused on the signal recording surface 1 a of the optical disc 1. The light reflected by the signal recording surface 1 a is transmitted again through the beam splitter 111 a through the objective lens 15, the prism 14, the collimator lens 13, and the window glass 12, and is transmitted by the half mirror 111 b formed on the lower surface of the microprism 111. Branched into light and reflected light. The transmitted light is correctly received by the front light receiving unit 113a. The reflected light is reflected again by the high reflection film 111c formed on the upper surface of the microprism 111, and is correctly received by the rear light receiving portion 113b.
[0027]
Thus, when using the 1st light source 112a, the special control with respect to the objective lens 15 for the agreement of an optical axis is not required.
On the other hand, the light emitted from the second light source 112 b is reflected by the beam splitter 111 a, enters the objective lens 15 through the window glass 12, the collimator lens 13, and the prism 14 in a state where the optical axes do not coincide with each other. It is condensed on the recording surface 1a. The light reflected by the signal recording surface 1 a is transmitted again through the beam splitter 111 a through the objective lens 15, the prism 14, the collimator lens 13, and the window glass 12, and is transmitted by the half mirror 111 b formed on the lower surface of the microprism 111. Branched into light and reflected light. The transmitted light is incident on the front light receiving portion 114a, and the reflected light is reflected by the highly reflective film 111c and is incident on the rear light receiving portion 114b. However, at this time, the light does not enter the correct positions on the light receiving portions 114a and 114b.
[0028]
For this reason, the detected tracking error signal includes an offset due to optical axis mismatch. Therefore, when the second light source 112b is used, an error correction signal, that is, a command for generating a drive voltage for the objective lens 15 is sent to the drive mechanism of the objective lens 15 based on the detected tracking error signal. Thereby, the objective lens 15 is controlled so as to coincide with the optical axis of the light from the second light source 112b, and a correct detection signal can be obtained in the light receiving unit.
[0029]
In addition, when a drive command for the objective lens 15 that compensates for such a distance between the optical axes is measured in advance and the second light source 112b is used, the drive voltage based on this drive command is always applied to the objective lens drive mechanism. It may be added to. In this case, the relationship between the tracking driving voltage of the objective lens and the tracking displacement is measured in the manufacturing process of the apparatus. From this result, a drive voltage when the tracking displacement is the distance between the two laser optical axes is obtained, and this is used as the compensation voltage. When the second light source 112b is selected, a command to add the compensation voltage is given to the objective lens driving mechanism at the same time. As a result, when the second light source 112b is used, the objective lens 15 is driven based on the position displaced so that the lens optical axis coincides with the laser optical axis, and the laser light is correctly incident on the light receiving element.
[0030]
Further, as a method for obtaining the driving voltage when the optical axes coincide with each other, a relationship between the tracking driving voltage of the objective lens and the tracking error signal of the light from the second light source 112b is obtained by using the push-pull method of the tracking error detection method. You may obtain | require from the measured value of.
[0031]
The push-pull method utilizes the fact that the intensity distribution of the light that is diffracted and reflected by the pits on the recording surface of the optical disc and then re-enters the objective lens changes due to the relative position change between the pits and the laser beam spot, By using a light receiving element divided in a direction parallel to the track and taking the difference between them, a bipolar tracking error signal can be obtained. That is, if tracking is in a good state, the difference in light intensity detected by the divided light receiving elements is zero.
[0032]
Therefore, here, in the manufacturing process, the mirror disk on which no signal is recorded is reproduced using the second light source 112b, and the objective lens 15 is driven when the push-pull tracking error signal synthesized from the received light signal becomes zero. The voltage is measured and used as a compensation voltage. When the second light source 112b is selected, a command to add the compensation voltage is given to the objective lens driving mechanism at the same time. As a result, when the second light source 112b is used, the objective lens 15 is driven based on the position displaced so that the lens optical axis coincides with the laser optical axis, and the laser light is correctly incident on the light receiving element.
[0033]
In the above description, an example in which the laser optical axis and the objective lens optical axis are made to coincide with one of the lights has been described. However, there is a case where neither of the lights coincides with the optical axis of the objective lens. FIG. 5 shows an enlarged view of the two light sources 112a and 112b in the direction of arrow A in FIG. 5A shows an example in which one light coincides with the objective lens optical axis B, and FIG. 5B shows an example in which the objective lens optical axis B is at the center of two light sources. 5A and 5B, the light emitted from the light sources 112a and 112b is reflected toward the objective lens by the beam splitter 111a provided in the microprism 111.
[0034]
In the case of FIG. 5A, as described above, when the first light source 112a is used, it is not necessary to perform special objective lens control, and only when the second light source 112b is used, the light of the objective lens. A compensation signal was applied to the drive mechanism to match the axis B. In the case of FIG. 5B, a compensation signal for making the laser optical axis coincide with the objective lens optical axis B may be given to the drive mechanism when using either light source.
[0035]
For example, when this compensation signal is obtained from a tracking error signal during disk reproduction or recording, when the first light source 112a is used, an error signal is generated from the detection signals of the light receiving portions 113a and 113b, and the second light source 112b In the same manner, the light receiving portions 114a and 114b may receive light. Since the optical axis B of the objective lens is the center of the two light sources 112a and 112b, the compensation signal when the second light source 112b is used has the polarity of the compensation signal when the first light source 112a is used reversed. Signal.
[0036]
Similarly, when the compensation signal is obtained in advance, the relationship between the tracking driving voltage of the objective lens and the tracking displacement or push-pull tracking error signal is measured for each light source, and the compensation signal is obtained from this value. Good. Since the optical axis B of the objective lens is the center of the two light sources 112a and 112b, the compensation signal when one light source is used is the reverse of the polarity of the compensation signal when the other light source is used. By supplying the compensation signal thus obtained to the objective lens driving mechanism every time each light source is selected, the laser optical axis and the objective lens optical axis coincide with each other, and can be correctly incident on the light receiving unit.
[0037]
In the above description, the position of the optical axis of the objective lens is the center of the optical axes of the two lights. However, it is not always necessary to select a position close to the frequently used light.
[0038]
【The invention's effect】
As described above, in the present invention, in the optical pickup device using two light sources having different wavelengths, the compensation signal for compensating the distance between the optical axis of the laser beam and the objective lens is supplied to the objective lens driving means. Thus, an optical system free from optical axis deviation can be realized, and recording or reproduction with high accuracy can be performed on optical discs having different specifications with a simple apparatus configuration.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of a main part of an optical disc apparatus according to the present invention.
FIG. 2 is a block diagram of a control system of the optical disc apparatus of the present invention.
FIG. 3 is a diagram illustrating a configuration example of an optical system of a two-wavelength optical pickup device of the present invention.
4 is a diagram showing details of the two-wavelength laser coupler in FIG. 3. FIG.
FIG. 5 is an enlarged view of two light sources and a microprism according to the arrow A in FIG. 4;
FIG. 6 is a diagram illustrating a configuration example of an optical system of a conventional two-wavelength optical pickup device.
7 is a diagram showing details of the two-wavelength laser coupler in FIG. 6. FIG.
FIG. 8 is a diagram showing a relationship between a laser optical axis and a hologram in a two-wavelength optical pickup device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Optical disk, 1a ... Signal recording surface, 10 ... 2 wavelength optical pick-up apparatus, 13 ... Collimator lens, 14 ... Prism, 15 ... Objective lens, 15a ... Driving means, 16 ... Between optical axes Distance compensation means, 111a... Beam splitter, 112a... Laser light source, 112b... Laser light source, 113.

Claims (6)

In an optical pickup device for recording or reproducing a plurality of optical discs having different specifications,
A first light emitting element that emits light of a first wavelength;
A second light emitting element that is arranged in parallel with the first light emitting element in a radial direction of the optical disc and emits light having a second wavelength different from the first wavelength;
A light receiving element that receives light of the first or second wavelength;
An objective lens for condensing the light of the first and second wavelengths;
Driving means for driving the objective lens;
When the optical axis of the objective lens is aligned with the optical axis of the light of the first wavelength and the light of the second wavelength is used, the optical axis of the objective lens and the optical axis of the light of the second wavelength And an optical axis distance compensation means for giving a compensation command for compensating the distance to the drive means.   2. The optical pickup device according to claim 1, wherein the compensation command is a compensation signal measured in advance when the objective lens is driven so that the optical axis of the objective lens coincides with the optical axis of the light of the other wavelength. . In an optical disc apparatus having an optical pickup device for recording or reproducing a plurality of optical discs having different specifications,
The optical pickup device is
A first light emitting element that emits light of a first wavelength;
A second light emitting element that is arranged in parallel with the first light emitting element in a radial direction of the optical disc and emits light having a second wavelength different from the first wavelength;
A light receiving element that receives light of the first or second wavelength;
An objective lens for condensing the light of the first and second wavelengths;
Driving means for driving the objective lens;
When the optical axis of the objective lens is aligned with the optical axis of the light of the first wavelength and the light of the second wavelength is used, the optical axis of the objective lens and the optical axis of the light of the second wavelength An optical axis distance compensation means for giving a compensation command for compensating the distance to the drive means to the drive means. In an optical pickup device for recording or reproducing a plurality of optical discs having different specifications,
A first light emitting element that emits light of a first wavelength;
A second light emitting element that is arranged in parallel with the first light emitting element in a radial direction of the optical disc and emits light having a second wavelength different from the first wavelength;
A light receiving element that receives light of the first or second wavelength;
The first and second wavelengths of light, which are arranged without matching the optical axis to either the optical axis of the light of the first wavelength or the optical axis of the light of the second wavelength, are collected. An objective lens;
Driving means for driving the objective lens;
When using the light of the first wavelength, a compensation command for compensating the distance between the optical axis of the objective lens and the optical axis of the light of the first wavelength is given to the driving means, and the light of the second wavelength is applied. An optical axis distance compensation unit that provides a compensation command to the driving unit to compensate the distance between the optical axis of the objective lens and the optical axis of the second wavelength light when using light; An optical pickup device. 5. The optical pickup device according to claim 4 , wherein the compensation command is a compensation signal measured in advance when the objective lens is driven so that the optical axis of the objective lens and the optical axis of the other wavelength light coincide with each other. . In an optical disc apparatus having an optical pickup device for recording or reproducing a plurality of optical discs having different specifications,
The optical pickup device is
A first light emitting element that emits light of a first wavelength;
A second light emitting element that is arranged in parallel with the first light emitting element in a radial direction of the optical disc and emits light having a second wavelength different from the first wavelength;
A light receiving element that receives light of the first or second wavelength;
The first and second wavelengths of light, which are arranged without matching the optical axis to either the optical axis of the light of the first wavelength or the optical axis of the light of the second wavelength, are collected. An objective lens;
Driving means for driving the objective lens;
When using the light of the first wavelength, a compensation command for compensating the distance between the optical axis of the objective lens and the optical axis of the light of the first wavelength is given to the driving means, and the light of the second wavelength is applied. An optical axis distance compensation unit that provides a compensation command to the driving unit to compensate the distance between the optical axis of the objective lens and the optical axis of the second wavelength light when using light; Optical disk device to perform.

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