JP2746972B2 - Optical information processing device - Google Patents

Description

The present invention relates to an optical information processing apparatus, and more particularly, to recording, reproducing, or erasing information using a plurality of light beams. The present invention relates to an optical information processing apparatus including a multi-beam optical head formed simultaneously.

(Prior Art) In recent years, an optical information processing device such as an optical disk device capable of recording image information of a document or the like, retrieving the image information as necessary, and reproducing as a hard copy or a soft copy has been developed. . In an optical disk device, a condensing light beam is irradiated onto a recording medium on a disk, that is, an optical disk to record or reproduce information. That is, at the time of recording, a state change is caused in the recording medium on the recording surface by irradiating the light beam, and as a result, information is recorded on the optical disk as, for example, pits. At the time of reproduction, a light beam is normally irradiated onto the information recording medium, and the light beam is intensity-modulated by pits according to the recorded information. The modulated light beam is processed to reproduce information. During recording and reproduction, the optical disk is rotated at a constant linear velocity and linearly moved in the radial direction on the optical disk to direct the light beam to the optical disk.

As these optical disk devices, recently, an optical information processing device including a multi-beam optical head for simultaneously recording and reproducing information using a plurality of light beams has been developed.

For example, an optical information processing apparatus including a multi-beam optical head for simultaneously recording and reproducing information by using two light beams having different wavelengths is used. In this method, two light beams L1 and L2 having different wavelengths for reproduction and recording emitted from the respective light sources are substantially synthesized by a dichroic mirror or the like for synthesis, and directed toward a predetermined area on the optical disc by an objective lens. Is collected. Each of the light beams L1 and L2 to be collected is set so that the light-condensing points are adjacent to each other and condensed on the same track. In other words, in order to irradiate a reproduction light beam and a recording light beam on the same track of the information recording medium, reproduction and recording light sources are previously mounted parallel to the track extending direction. As a result, minute beam spots for recording and reproduction are formed adjacent to each other on a predetermined track on the recording film surface. The optical disc is rotated at a constant linear velocity with the recording and reproducing beam spots formed in this way, whereby a predetermined recording area is irradiated with the recording light beam, and immediately thereafter, the reproducing light beam is irradiated. Irradiated by

The light beam condensed on the track of the optical disk is reflected and enters the dichroic mirror. The light beam that is incident on the dichroic mirror and substantially synthesized is separated for each wavelength, that is, a recording light beam and a reproduction light beam. The separated light beams are respectively incident on photodetectors arranged on the optical path. The light beam incident on the photodetector is converted into an information reproduction signal, a tracking control signal, and a focus control signal.

(Problems to be Solved by the Invention) In a conventional multi-beam optical head, in order to irradiate a reproducing light beam and a recording light beam onto the same track of an information recording medium, a reproducing and recording light source is previously provided. It must be mounted with high precision parallel to the track extension direction. For example, if the mounting error in manufacturing is large,
Accurate reproduction or recording of information from a predetermined recording area on the optical disk is not performed, and the performance of the apparatus is significantly reduced.

In an apparatus using a dichroic mirror, it is difficult to manufacture laser diodes having different oscillation wavelengths as light sources on the same chip. Therefore, when installing two laser diode chips, high mounting accuracy is required adjacent to each other. Furthermore, since light beams having different wavelengths are used, it is necessary to correct chromatic aberration of a lens caused by a difference in dispersive power of an optical system. Furthermore, a dichroic mirror for synthesizing or separating two light beams having different wavelengths is coated in order to obtain unique characteristics. This complicates the manufacturing and increases the cost.

The present invention relates to an optical information processing apparatus provided with an inexpensive multi-beam optical head for stably detecting a reproduction light beam from a recording and reproduction light beam reflected by a recording medium and performing information reproduction and tracking control. The purpose is to provide.

[Configuration of the Invention] (Means for Solving the Problems) The present invention has been made based on the above-mentioned problems, and includes light source means for emitting first and second light beams, and the first and second light beams. Focusing means for focusing the second light beam toward the same track on the medium; and focusing means for focusing and separating the first and second light beams reflected by the recording medium. Light collecting and separating means, detecting means for detecting the first and second light beams separated and collected by the light collecting and separating means, and the first and second light beams detected by the detecting means. Optical information processing means for rotating the light source means so as to irradiate the first and second light beams on the same track of the recording medium using the light beam of An apparatus is provided.

Also, the present invention provides a laser array for emitting first and second light beams, and a condensing device for converging the first and second light beams toward the same track on a recording medium. Means, condensing and separating means for condensing and separating the first and second light beams reflected by the recording medium, and the first and second light beams separated and condensed by the condensing and separating means. Detecting means for detecting a second light beam, and using the phase difference between the first and second light beams detected by the detecting means, the first and second light beams on the same track of the recording medium. It is an object of the present invention to provide an optical information processing apparatus, comprising: a rotation drive unit that rotates the laser array so that a second light beam is emitted.

Further, the present invention provides a laser array for emitting the first and second light beams, and a condensing device for converging the first and second light beams toward the same track on a recording medium. Means, and first and second reflected by the recording medium.
Condensing and separating means for condensing and separating the light beam of
Detecting means for detecting the first and second light beams separated and condensed by the light condensing / separating means; and light intensities of the first and second light beams detected by the detecting means An optical information processing apparatus comprising: a rotation drive unit that rotates the laser array so that the first and second light beams are irradiated on the same track of the recording medium by utilizing a difference between the two. Is provided.

(Operation) In the optical information processing apparatus of the present invention, the light source means
The first and second light beams emitted by the light source means are located on the same track based on the detection result of the light beams, the first and second light beams reflected by the recording medium, detected by the detection means. Thus, the light source means is rotated by the rotation driving means. Thereby, accurate information reproduction from the track and accurate information recording on the track are performed.

Further, when the light source means is rotated by a predetermined amount by the rotation driving means, for example, a first light beam used for recording information and a second light beam used for reproducing information, for example, are on the same track. , The crosstalk between the reproducing light beam and the recording light beam is minimized.

As a result, an optical information processing apparatus capable of recording and reproducing high-density information at a lower cost is provided.

(Embodiment) FIG. 1 is a front view of a multi-beam optical head 100 provided in an optical information processing apparatus according to an embodiment of the present invention.

In FIG. 1, an optical disk (recording medium) 16 is formed by coating a disc substrate such as glass or plastic with a metal film such as tellurium or bismuth as an information recording film. On the substrate of the optical disc, tracks 16A that define a tracking guide area where information is to be recorded are formed concentrically. A multi-beam optical head 100 is provided so as to face the optical disc 1, and the optical disc 16 is driven to rotate at a constant linear velocity with respect to the multi-beam optical head 100 during recording, reproduction and erasing. In FIG. 1, a track 16A defining a recording area extends in the Z direction.

Inside the multi-beam optical head 100, a light source member 10 as a light source is provided. In the light source member 10, a laser diode array 10A that emits two light beams for recording and reproduction is arranged. The emission ports of the laser diode array 10A are oriented in substantially the same direction, and are set apart from each other in the Z direction on the same chip.From the emission ports, for example, a reproduction light beam Lr and a recording light beam Lw having the same wavelength are emitted. Is emitted. A light source driving circuit 70 for rotating the light source member about an axis provided along the optical path of the emitted light beam is provided substantially in the middle of each emission port on the laser diode array of the light source member 10. ing.

Light beam L emitted from laser diode array 10A
r and Lw are radiated on the same collimator lens 12 while being gradually diverged and superimposed on each other. Collimator lens
The light beams Lr and Lw incident on the light source 12 are substantially superimposed on each other, converted into a parallel combined light beam, and incident on the beam splitter 18. The combined light beam that has entered the beam splitter 18 is transmitted and radiated to the objective lens 14. Objective lens
When the light beam applied to the light source 14 passes through the objective lens 14 and is condensed, the light beam is again separated into the recording light beam Lw and the reproduction light beam Lr, and is recorded on the recording area of the optical disc 16, that is, on the same track. Is collected. Light beam L for recording and reproduction
Each of the focus points w and Lr is preferably irradiated on the same track adjacent to each other. Thus, adjacent recording and reproducing beam spots are simultaneously formed on the same track. The optical disk is rotated at a constant linear velocity while the recording and reproducing beam spots are formed on the same track. In accordance with the rotation of the optical disk, the track 16A that defines a recording area on the optical disk is first irradiated with, for example, a recording light beam Lw to record information. The area on the track where the information is recorded is moved in accordance with the rotation of the optical disk, and immediately thereafter, is irradiated with the reproducing light beam Lr. Information is reproduced by detecting reflected light of the light beam Lr applied to the recording area. When obtaining an information reproduction signal,
The reproducing light beam must be maintained in a focused state and a focused track state with respect to a desired recording area. More specifically, the objective lens 14 is movably supported in its optical axis direction and in an in-plane direction orthogonal to the optical axis. Objective lens
When 14 is located at the optimum position on the optical axis, that is, the focusing position,
The beam waist of the converging laser beam emitted from the objective lens 14 is projected on the surface of the recording film of the optical disk 16, whereby a minimum beam spot is formed on the surface of the recording film of the optical disk 16. Meanwhile, the objective lens
When the optical disk 14 is arranged at an optimum position in a plane perpendicular to the optical axis (in a plane parallel to the recording film surface), that is, at a combined track position, the optical disk
The beam spot formed in 16 is accurately formed on the track defined as the recording area, and the track is tracked by the laser beam. By maintaining these two states (the in-focus state and the in-focus track state), information can be reproduced. That is, a state change of pits or the like is caused in the recording film by the intensity-modulated recording light beam Lw, information is recorded, and a recording area formed by pits or the like in the track is irradiated with a laser beam Lr of a constant intensity. As a result, the light beam is intensity-modulated and reflected, and information is reproduced by detecting a change in the intensity of the reflected light beam Lr.

The divergent recording and reproducing light beams Lr and Lw reflected by the recording film of the optical disk 16 are combined with each other and are incident on the objective lens 16. The combined light beam incident on the objective lens 16 is converted into a parallel light beam at the time of focusing, and is returned to the beam splitter 18 again. The light beam incident on the beam splitter is reflected by the joint surface 18 and transmitted through a plano-convex lens 25 for condensing the combined light beam. The beam of the combined light beam transmitted through the plano-convex lens 25, that is, the beam of the light beam including the reproducing light beam Lr and the recording light beam Lw is gradually focused, and at the same time, the central axis lr of each light beam Lr, Lw , Lw gradually diverge from each other. This combined light beam is transmitted through the plano-convex lens 25 and is incident on a beam splitter 27 integrally attached to the exit surface. The combined light beam incident on the beam splitter 27 is split at the joint surface into light beams LA and LB having substantially equal light intensity.

The light beam LA reflected from the bonding surface is used to obtain a focus control signal. The transmitted light beam is used to obtain a tracking control signal, a light source position adjustment signal, and an information reproduction signal.

The light beam reflected by the beam splitter 27 will be described in further detail.The reproducing light beam Lr and the recording light beam Lw included in the light beam LA reflected at the joint surface of the beam splitter 27 gradually become the beam. At the same time as the cross section is reduced, their central axes lr, lw expand with each other. Therefore, the combined light beam LA is gradually separated into individual reproduction light beams Lr and recording light beams Lw as the constituent light beams Lr and Lw are focused. A knife edge 29 is disposed on an optical path approximately half of the center axis lr of the reproduction light beam Lr as a boundary, thereby blocking approximately half the optical path of the light beam. Therefore, only the reproduction light beam Lr not blocked by the Nassif edge 29 is gradually focused and condensed on the photodetector 20 arranged on the optical path. At this time, the photodetector 20 is set in advance so that the beam spot of the light beam irradiated on the detection area is minimized at the time of focusing, and at the same time, the size thereof is a surface including the detector surface. Are set in accordance with the distance between the central axis of the reproducing light beam Lr and the central axis of the recording light beam Lw. The light beam irradiated on the photodetector 20 is converted into an electric signal in each of the light detection areas and processed by a predetermined method. That is, by detecting a change in the position of the beam spot irradiated on the photodetector 20, a focusing error signal, that is, a signal corresponding to the amount of defocus is generated, and the voice coil motor 50 is driven in accordance with the tracking error signal. And the objective lens 14 is driven in the direction of its optical axis to maintain the light beam in focus.
Incidentally, the other recording light beam Lw is, for example, a knife edge.
The light is transmitted without being irradiated onto the photodetector 20 in a state where a part thereof is shielded by 29.

On the other hand, the combined light beam transmitted through the beam splitter 27
To explain LB in detail, the transmitted synthetic light beam
As with the reflected light beam LA, the center axes lr and lw of the LB expand with each other as the beam cross-sections of the reproducing light beam Lr and the recording light beam Lw are gradually reduced. Therefore, the combined light beam LA becomes individual reproduction light beam Lr and recording light beam Lw as the constituent light beams Lr and Lw are respectively focused.
Is gradually separated. A photodetector 45 is provided on the optical path of the separated reproduction light beam Lr and recording light beam Lw. The light beams Lr and Lw applied to the photodetector 45 are converted into electric signals according to the light intensity. The detected signal is a tracking control signal for maintaining each light beam on a predetermined track on the optical disc, and drives the light source means so that two light beams are irradiated on the same track of the recording medium. It is used as a light source drive signal and an information reproduction signal. The photodetector 45 is preset so that its detection area is irradiated with two circular beam spots having a predetermined area and separated from each other. In other words, the photodetector 45 is installed such that its position in the optical axis direction is within a range where the beam spots of the light beams irradiating the photodetection area do not overlap with each other, and at the same time, the light radiated on the photodetector. The distance is set within a range where tracking control can be accurately performed using the beam spot of the beam.

The light beam converted into an electric signal by the tracking light detector 45 is processed by a predetermined method, and a tracking error signal is generated from the drive circuit 44. An electric current is supplied to the voice coil motor 50 in response to the generated tracking error signal, and the objective lens 14 is moved in a plane perpendicular to the optical axis, whereby a predetermined track is tracked by the light beam. Furthermore, the signals detected in all the detection areas on the photodetector 45 are added by the signal processing circuit 43 and used as an information reproduction signal. The signal detected by the photodetector 45 is used as a light source drive signal for rotating a light source so as to accurately focus two light beams on the same track of the optical disc 16.

FIG. 2 is a perspective view of a light source member provided in the optical information processing apparatus of the present invention and a structure around the light source member.

In FIG. 2, the light source member 10 is provided with a laser diode array 10A that oscillates two light beams having the same wavelength, and the light emitting ports of the respective light beams provided on the same chip of the laser diode array 10A are the same. It is installed facing the direction. The exit ports are arranged symmetrically with respect to the optical axis m of the collimator lens 12 and the objective lens 14 provided on the optical path and are spaced apart by a predetermined width. For example, in FIG. 2, the light beam output ports are spaced apart in the Z direction parallel to the extending direction of the track 16A on the information recording medium.

The light source member 10 emits a divergent reproducing light beam Lr and a recording light beam Lw. When the emitted light beam is incident on the collimator lens 12, each light beam is converted into a parallel light partly synthesized. The partially overlapped parallel light beam enters the condenser lens 14 and is collected again, and at the same time, the reproduction light beam Lr and the recording light beam Lw
Is separated again. The separated light beams for reproduction and recording are irradiated onto the same track 16A extending in the Z direction of the information recording medium 16 at a distance D1. The light source member 10 described above has an axis m passing through the middle between one of the exit ports and the other exit port, that is, the optical axis of the collimator lens and the condenser lens.
It is rotatably mounted by a light source driving circuit 70 around an axis m passing through the 14 optical axes.

The light source drive circuit 70 is provided for accurately irradiating the recording light beam and the reproduction light beam onto the same track of the information recording medium. The driving of the light source member, that is, the axis k
Is performed based on the intensity balance between the light beams Lr and Lw reflected by the information recording medium. Third
The figure shows a beam spot image when a light beam for reproduction and a light beam for recording are irradiated onto a track of an information recording medium while being shifted from the same track. As shown in FIG. 3, when the beam spots Sr and Sw by the reproducing beam and the recording beam are not irradiated on the same track of the optical disc 16, for example, the beam spot of the recording light beam is accurately formed on the track 16A. When the beam spot of the other reproduction light beam is applied to a position slightly shifted from the same track 16A, the light beam reflected by the recording medium is detected on the tracking control light detector 45. For example, a beam spot as shown in FIG. 4 is formed.

As shown in FIG. 4, the tracking control light detector 45 is a light detection area for detecting the light beam Lr for reproduction.
It comprises four light detection areas 45A and 45B and light detection areas 45C and 45D for detecting the recording light beam Lw. The light detection area 45A and the light detection area 45B are separated by a dividing line 48 as a non-detection area parallel to the Y direction, that is, the direction in which the belt-shaped dark portion extends when the light beam is diffracted at the track. And the light detection region 45D are also similarly separated by a dividing line 48A. Light beam for reproduction
Light detection area 45A, 45B irradiated with Lr and recording light beam Lr
The light detection areas 45C and 45D irradiated by
It is separated by a dividing line 48B that passes through substantially the middle of Sr and the beam spot Sw and is orthogonal to the dividing line 48A. The dividing line 48A is provided so as to pass through the center of the beam spot of each incident light beam. As shown in FIG. 3 on the photodetector 45 set in this way, when the beam spots Sr and Sw by the reproducing beam and the recording beam are not irradiated on the same track of the optical disc 16, that is,
For example, the beam spot Sw of the recording light beam is
If the beam spot Sr of the other reproduction light beam is accurately formed on A and irradiates a position slightly deviated from the same track on the same track, a band-like shadow due to the track appearing in the beam spot on the light detection area. The positions also do not match. If the track's band shadows do not match,
Accurate information reproduction and information recording in the predetermined recording area become impossible. Therefore, before the tracking control operation of each light beam is performed, it must be adjusted so that the reproducing and recording light beams are accurately formed on the same track. For example, FIG. 5 shows a method of detecting a light source drive signal for driving a light source member so that light beams for reproduction and recording are accurately formed on the same track.

In the present invention, the light source member is driven based on a signal detected by the light detector 45. That is, when the light source member outputs the light of the light detection area 45A, the output of the light detection area 45B, the output of the light detection area 45C, and the output of the light detection area 45D, the intensity difference signal Ir = ｛-｝ Is compared with the recording light beam intensity difference signal Iw = の-｝, and the driving is performed so that the difference signal becomes zero. More specifically, for example, as shown in FIG. 3, in a state where the beam spots Sr and Sw by the reproducing beam and the recording beam are not accurately irradiated on the same track of the optical disc 16, When the irradiation position of the beam spot is moved in the X direction perpendicular to the extending direction, as shown in FIG. 5, the intensity difference signal Ir of the reproducing light beam Lr detected on the photodetector 45 and , The intensity difference signal of the recording light beam Lw
Iw is oscillated at the same cycle each time it traverses a track, and at the same time, its signal varies depending on the position irradiated by each light beam. Therefore, when the reproducing light beam and the recording light beam are not irradiated on the same track,
A phase difference δ occurs between the intensity difference signal Ir of the reproducing light beam and the intensity difference signal Iw of the recording light beam in accordance with the amount of displacement of the position in the direction orthogonal to the track 16A. The intensity difference signal Ir and the intensity difference signal Iw are supplied to a phase comparator 65, where the phase difference δ is detected, and a light source drive signal for rotating a light source member according to the phase difference δ is transmitted to a light source drive circuit 70. Is supplied. The light source member is driven to rotate about its central axis m in response to the light source drive signal supplied to the light source drive circuit 70.
Thereby, the reproducing light beam and the recording light beam are accurately formed on the same track 16A. In this operation, the light source drive signal corresponding to the phase difference δ between the intensity difference signal Ir and the intensity difference signal Iw is supplied until the phase difference δ = 0, and is stopped when the phases match. In this manner, focus control, tracking control, and information reproduction are performed in a state where the reproduction light beam and the recording light beam are irradiated on the same track.

In order to accurately form the reproducing light beam and the recording light beam on the same track 16A, the intensity difference signals Ir, Iw
Instead of the method of measuring the phase difference δ to drive the light source, another method as shown in FIG. 6 may be used.

As shown in FIG. 6, for example, a reproduction intensity difference signal at a position irradiated with a recording light beam and a reproduction light beam.
Ir and the recording intensity difference signal Iw are similarly detected, and a difference signal between the two intensity difference signals, that is, a light source driving signal corresponding to Iδ = {Ir−Iw} is supplied to the light source driving circuit 70, thereby The light source member is driven to a position where the difference signal becomes zero. By such a method, adjustment is performed so that the reproducing light beam and the recording light beam are accurately formed on the same track 16A.

FIGS. 7A to 7C and FIGS. 8A to 8C show a photodetector 20 for focus control and a photodetector 45 for tracking control provided in the multi-beam optical head of the optical information processing apparatus of the present invention. Is shown. Here, FIGS.
FIG. 7C shows a change in the beam spot shape on the photodetector 20 at the time of focusing and at the time of out-of-focus.

The focus control photodetector 20 is disposed on the optical path of the reproduction light beam Lr of the light beam LA reflected by the beam splitter 27, and serves as a vertical (X-direction) dividing line as a light non-detection area. It comprises two light detection areas 20A and 20B formed on both sides of the light detection area 22. When the objective lens 14 is in focus with respect to the optical disc 16, the minimum beam spot Sr is irradiated on the light non-detection area 22 of the photodetector.
In other words, assuming that the output of the light detection area 20A is the output of 20B, the position of the dividing line 22 as the non-detection area is the focusing error signal (FE signal) at the time of focusing.
Is equal to zero, that is, FE = ｛−｝ = 0
Is set to a position that satisfies the condition

On the other hand, for example, when the objective lens 14 moves away from the in-focus position with respect to the optical disc, the light beam reflected by the optical disc is focused slightly more than at the time of focusing. Therefore, the focal point of the light beam Lr that is partially irradiated by the knife edge 29 and irradiated onto the photodetector is moved forward of the detector. Therefore, a beam spot as shown in FIG. 7C is formed on the photodetector 20. That is, the linear portion contacts the non-detection region 22 on the light detection region 20B,
A half-moon-shaped beam spot having a larger diameter than that at the time of focusing is formed. At this time, the focusing error signal is FE = ｛−｝ <0.

Conversely, when the objective lens 14 is closer to the optical disc than the in-focus position, the light beam reflected by the optical disc is slightly diverged from that at the time of focusing. Therefore knife edge 29
Then, the focal point of the light beam Lr, which is partially shielded and is irradiated on the photodetector, is moved rearward of the detector. Therefore, a beam spot as shown in FIG. 7A is formed on the photodetector 20. That is, on the light detection area 20A, the linear portion contacts the non-detection area 22, and a half-moon-shaped beam spot having a diameter larger than that at the time of focusing is formed. At this time, the focusing error signal is
F · E = ｛−｝> 0.

The size of the photodetector thus configured is set based on the conditions described below. That is, the reproduction light beam Lr and the recording light beam formed on the same track
The distance between the Lw beam spots is d1, the focal length of the objective lens 14 for irradiating a light beam onto the optical disk is f _O , the lens 6
When the focal length of the between f _D, on the detection area and the same plane of the optical detector 20, the interval d3 of the focal point of the recording light beam Lw and the converging point of the reproducing light beam Lr is, d3 = (f _D / f _O) represented by × d1 = md1 .... (Note that m indicates the magnification of the optical system.) Therefore, in order to irradiate only the reproduction signal onto the photodetector on the photodetector, the end of the photodetector extending in the vertical direction, ie, the recording end The following relationship must always be established between the distance d2 between the end of the photodetector on the side approaching the virtual focusing point of the light beam and the focusing point of the reproducing light beam.

d3> d2 ... formula, from _{d2 <(f D / f O} ) × d1 = md1 ... a relationship of.

As shown in this equation, the distance between the end of the photodetector on the side approaching the virtual focal point and the virtual focal point of the recording light beam
d2 is roughly set to satisfy d2 <md1. By arranging a photodetector that satisfies these conditions, that is, d2 <md1, crosstalk between the recording light beam and the reproducing light beam is prevented, and efficient reading or reproducing of information is performed.

 The size of the photodetector will be described in more detail.

In the embodiment of the present invention, a knife edge method is used as a method for obtaining a focus control signal. The knife edge method can reduce the size of the beam spot formed on the photodetector at the time of focusing as compared with a focus control method such as the astigmatism method. It will be easier. That is, when focus control is performed by using the conventionally used astigmatism method, a beam spot having a beam diameter of 50 μm or more must be formed on the photodetector at the time of focusing. Accordingly, the central axes 1r and 1w of the recording and reproducing light beams are set at 100 μm from each other on a plane where the photodetector is to be arranged in order to avoid crosstalk.
m or more.

On the other hand, in the focus detection method such as the knife edge method used in the present invention, since the photodetector is arranged on the focal point of the lens 25, the beam of the light beam irradiated on the photodetector is used. The spot diameter is set to a minimum value determined by the numerical aperture NA and magnification m of the optical system to be used and the wavelength λ of the light source.

That is, the numerical aperture of the lens system based on the recording medium side is
If NA _o , the beam spot diameter W1 on the recording medium
Is W1 ≒ λ / NA _O.

When the magnification of the lens system is m, the numerical aperture NA _D of the lens system relative to the optical detector side, the NA _D = NA _O / m.

At this time, the beam spot diameter W2 of the light beam irradiated on the photodetector is W2 = λ / NA _D = mλ / NA _O.

For practical optical diameters, generally the numerical aperture N
A: 0.4 to 0.6, λ: 600 to 900 nm, and m: 2 to 10. For example, when NA _O = 0.5, λ = 830 nm, and m = 7, the beam spot diameter W2 on the photodetector is W2 = Mλ / NA _O ≒ 10
μm.

When the photodetector is arranged at the image point of the light beam as described above, the size of the beam spot is formed very small. Therefore, the recording and reproducing light beams separated at minute intervals can be easily separated and detected.

On the other hand, FIGS. 3A to 3C show beam spots on the photodetector at the time of non-matching track and at the time of matching track. The tracking control photodetector 45 is disposed on the optical path of the reproduction light beam Lr of the light beam LB transmitted through the beam splitter, and serves as a horizontal (Y-direction) dividing line 48A as a light non-detection area. And two light detection areas 45A and 45B provided on both sides of the recording light beam Lw.
In the horizontal direction (Y
), And two light detection areas 45C and 45D provided on both sides of the dividing line 48A of (direction). Furthermore, the light detection regions 45C and 45D irradiated with the reproduction light beam Lr are separated by a division line 48B passing substantially between the beam spot Sr and the beam spot Sw and orthogonal to the division line 48A. When the recording light beam is accurately formed on the track that defines the recording area on the optical disk, that is, in the combined track state, the light non-detection area is displayed on the photodetector 45 as shown in FIG. 8B. Two substantially circular beam spots Sr having a predetermined beam diameter with the center at 48 are formed, and at the same time, band-shaped shadows generated by being diffracted by tracks are formed around the non-detection region 48A. In other words, when the output of the light detection area 45A, the output of the light detection area 45B, the output of the light detection area 45C, and the output of the light detection area 45D, the light non-detection area 4
The position of 8A is a position where the tracking error signal (TE) is equal to zero at the time of tracking, that is, TE.
= {(+) − (+)} = 0.

On the other hand, for example, when the objective lens 14 is separated from the combined track position with respect to the optical disc, the 8A to 8th
Two circular beam spots are formed as shown in FIG. 8C. That is, the band-shaped dark portion generated by diffraction on the track appears asymmetrically about the dividing line 48A as a non-detection region. At this time, the tracking error signal is T ·
E <0 or T · E> 0.

The setting position of the photodetector 45 configured as described above is set based on the conditions described below. That is, to obtain the tracking control signal described above, the photodetector 45
The position in the optical axis direction is set so that the beam spot diameter of the irradiated light beam is formed within a specific range. In other words, the position of the photodetector 45 is set so that the reproduction light beam Lr and the recording light beam Lw are irradiated separately from each other.

More specifically, the position of the photodetector in the optical axis direction is set based on the conditions described below. That is,
The interval between each beam spot of the reproducing light beam Lr and the recording light beam Lw formed on the same track is d1, the focal length of the objective lens irradiating the optical beam on the optical disk is f _O ,
If the focal length of the lens 6 is f _D , the distance between the detection surface of the photodetector 45 and the image point of the lens 6 in the optical axis direction is Z, and the distance Z is so small as to be negligible with respect to the focal length f _D. Then, on the same plane as the detection area of the photodetector 20, the distance between the focal point of the recording light beam Lw and the focal point of the reproduction light beam Lr is d3.
Is represented by _{d3 ≒ (f D / f O} ) × d1 = md1 ....

On the other hand, the beam diameter W which is formed on the detection area of the photodetector 45 at this time, when the diameter of the light beam incident on the lens 25 and phi, is expressed by _{W = Z / f D × φ} . In the formulas and formulas, d3> W must be satisfied in order to irradiate only the light beam for reproduction onto the detection area of the photodetector 45. That mentioned equations above, the substituted into the formula, the distance Z along the optical axis between the image point of the detection surface and the lens 6 of the optical detector ^{_{45, Z <(f D) 2}} / f O × ( d1 / φ)… must be installed within the range that satisfies.

In the equation, when substituting the relationship of φ = 2f _O · NA, it is generally rewritten as Z <(m ² d1) / (2 · NA). (Note that m is the magnification of the optical system with reference to the recording medium side, and NA is the numerical aperture of the objective lens.) By installing the photodetector 45 within the range described in the expression, the beam of each light beam is set. The spot diameter is formed within a specific range. Therefore, crosstalk between the reproducing and recording light beams Lr and Lw is prevented, and an accurate tracking control signal is detected. FIG. 9 shows a circuit for processing all signals detected by the focus control photodetector 20 and tracking control photodetector 45 configured as described above.

In FIG. 9, the output of the light detection area 20A is an amplifier circuit 31A.
Supplied to The output of the light detection area 20B is supplied to the amplifier circuit 31B. Output signals from the amplifier circuits 31A and 31B are used to supply a focusing control signal to the voice coil. That is, the output of the amplifier circuit 31A is supplied to the inverting input terminal of the differential amplifier 41, and the output of the amplifier circuit 31B is supplied to the non-inverting input terminal of the differential amplifier 41. In the differential amplifier 41, the detection signal of the light detection area 20A and the light detection area 20B
Is compared with the result of addition of the detection signal, and an output corresponding to the difference signal, that is, a focus control signal is supplied to the drive circuit 44. In response to the focus shift detection signal supplied to the drive circuit 44, current is fed back to a coil (not shown) that drives the objective lens 16 in the optical axis direction. The objective lens 16 is driven in the direction of the optical axis in accordance with the fed back current, and the defocus is corrected.

On the other hand, the output of the light detection area 45A is supplied to the amplifier circuit 31C, and the output of the light detection area 45B is supplied to the amplifier circuit 31D.
The output of the light detection area 45C is supplied to the amplifier circuit 31E, and the output of the light detection area 45D is supplied to the amplifier circuit 31F. The output of the amplifier circuit 31C to the output of the amplifier circuit 31D are used to supply a tracking control signal to the voice coil. That is, the output of the amplifier circuit 31C and the output of the amplifier circuit 31D are added by the adder circuit 46 and supplied to the inverting input terminal of the differential amplifier 42. The output of the amplifier circuit 31E and the amplifier circuit 31F
Are added by an adder circuit 47 and supplied to the non-inverting input terminal of the differential amplifier 42. In the differential amplifier 42, the addition result of the detection output of the light detection area 45A and the light detection area 45C is compared with the addition result of the detection output of the light detection area 45B and the light detection area 45D, and an output corresponding to the difference, that is, The tracking shift detection signal is supplied to the drive circuit 44. In response to a tracking control signal supplied to the drive circuit 44, a current (not shown) is fed back to a coil that drives the objective lens 16 in a plane perpendicular to the optical axis. Thereby, the objective lens 16 is driven in a direction perpendicular to the optical axis, and the tracking deviation is corrected.

Further, outputs of the amplifier circuits 31C to 31F, that is, all output signals of the photodetector 45 are processed by the signal processing circuit 43 and used for reproducing information.

Furthermore, in the present invention, the light detection areas 45A to 4A
The signal detected in 5D is used as a light source driving signal for accurately irradiating a reproduction and recording light beam onto the same track on a recording medium.

That is, the output of the amplifier circuit 31C is supplied to the inverting input terminal of the differential amplifier 55, and the output of the amplifier circuit 31D is supplied to the non-inverting input terminal of the differential amplifier 55. In the differential amplifier 55, the detection output of the light detection area 45A and the detection output of the light detection area 45B are compared, and an output corresponding to the difference, that is, a reproduction light intensity difference signal is supplied to the phase comparator 65. On the other hand, the other amplifier circuit 31E
Is supplied to the inverting input terminal of the differential amplifier 60, and the output of the amplifier circuit 31F is supplied to the non-inverting input terminal of the differential amplifier 60. In the differential amplifier 60, the detection output of the light detection area 45C and the detection output of the light detection area 45D are compared, and an output according to the difference, that is, a recording light intensity difference signal is also compared with the phase comparator 65.
Supplied to The recording light intensity difference signal and the reproduction light intensity difference signal supplied to the phase comparator 65 are compared in phase,
A light source drive signal is output according to the phase difference and supplied to the light source drive circuit 70. The light source member is rotationally driven by the light source drive signal supplied to the light source drive circuit 70, and the positions of the reproducing and recording light beams on the same track of the information recording medium are adjusted.

In the embodiment of the present invention described above, the adjustment for irradiating the recording light beam and the reproduction light beam on the same track is performed by adjusting the intensity of the reproduction light beam irradiated on the tracking control photodetector. This is achieved by feeding back a light source drive signal corresponding to a phase difference signal or an intensity difference signal between the difference signal and the intensity difference signal of the recording light beam to the light source member drive circuit. However, within the range described in the present invention, the deviation of the tracks of the recording and reproducing light beams may be detected by other methods.

In the present invention, the two light beams emitted from the light source member 10 are set so that they are irradiated on the same track of the information recording medium, and the reproducing operation is performed immediately after the recording operation. However, for example, a light beam may be irradiated so as to record or reproduce information on two parallel tracks at the same time. Further, it may be used to continuously erase and record information.

Furthermore, in the present invention, the light beam Lr for reproduction is
Although the photodetector 20 is provided for the recording light beam Lw, a photodetector may be provided for the recording light beam Lw in principle. Furthermore, the shape of the photodetector may be changed as long as a similar effect is obtained.

(Effects of the Invention) According to the present invention, since the reproducing and recording light beams emitted from the light source are accurately irradiated on the same track, the recording, reproducing and erasing of information from the information recording medium can be accurately performed. You.

Furthermore, the reproducing light beam and the recording light beam are separated without using a special optical system, and the position of the photodetector is set according to the beam spot diameter of the reproducing light beam. Therefore, crosstalk between the reproducing light beam and the recording light beam is reduced, and an optical information processing apparatus having a multi-beam optical head with lower cost and higher accuracy is provided.

[Brief description of the drawings]

FIG. 1 is a front view of a multi-beam optical head provided in an optical information processing apparatus according to one embodiment of the present invention, and FIG. 2 shows the structure of a light source member and its peripheral members provided in the optical information processing apparatus of the present invention. FIG. 3 is a schematic perspective view, FIG. 3 is a diagram showing recording and reproducing beam spots applied to a track on the information recording medium of the present invention, and FIG. 4 is a diagram in which recording and reproducing beam spot images are exactly on the same track. FIG. 5 is a diagram showing a beam spot on a photodetector when the light is not irradiated on a light source. FIG. 5 is a graph showing one embodiment of a light source drive signal detecting method for adjusting the position of the light source according to the present invention. FIG. 5 is a graph showing another embodiment of the method of detecting a light source drive signal shown in FIG. 5, and FIGS. 7A to 7C are diagrams showing changes in a beam spot in a focused state and a non-focused state of a light beam. Optical inspection provided in information processing equipment FIGS. 8A to 8C are front views of a photodetector provided in the optical information processing apparatus according to the present invention, showing a change of a beam spot in a combined track state and a non-matched track state of a light beam. FIG. 9 is an electric circuit diagram showing a method of processing all signals detected by the focus control photodetector and the tracking control photodetector. 10… Light source member, 10A …… Laser diode array, 12
…… Collimator lens, 14… Objective lens, 16 …… Optical disk, 16A …… Track, 18 …… Beam splitter, 2
0: Focus control photodetector, 20A, 20B ... Light detection area, 2
2 ... Light non-detection area (dividing line), 25 ... Plano-convex lens, 27
…… Beam splitter, 29 …… Knife edge, 31A ~ 31D
…… Amplifier circuits, 41,42 …… Differential amplifiers, 43 …… Signal processing circuits, 44 …… Drive circuits, 45… Tracking photodetectors, 45A, 45B …… Light detection areas, 46, 47… Adder circuit, 48
A, 48B: light non-detection area (divided line), 55, 60: differential amplifier, 65: phase comparator, 70: light source driving circuit, 100
... Optical head, Lr... Reproduction light beam, Lw... Recording beam, lr... Reproduction light beam central axis, lw... Recording light beam central axis, k.

Continuation of front page (56) References JP-A-62-60139 (JP, A) JP-A-59-14148 (JP, A) JP-A-60-195744 (JP, A) JP-A-62-256236 (JP, A) , A) JP-A-55-25853 (JP, A)

Claims (3)

(57) [Claims] 1. Light source means for emitting first and second light beams, and light condensing means for condensing the first and second light beams toward the same track on a recording medium When,
Condensing and separating means for condensing and separating the first and second light beams reflected by the recording medium; and the first and second light beams separated and condensed by the condensing and separating means. Utilizing detection means for detecting a light beam and the first and second light beams detected by the detection means, the first and second light beams are located on the same track of the recording medium. An optical information processing apparatus comprising: a rotation driving unit that rotates the light source unit so that the light is emitted. 2. A laser array for emitting first and second light beams, and a light condensing means for converging the first and second light beams toward the same track on a recording medium. Converging and separating means for condensing and separating the first and second light beams reflected by the recording medium; and the first and second light beams separated and condensed by the condensing and separating means. Detecting means for detecting the first and second light beams, and utilizing the phase difference between the first and second light beams detected by the detecting means to detect the first and second light beams on the same track of the recording medium. 2
An optical information processing apparatus, comprising: a rotation driving unit that rotates the laser array so that the laser beam is emitted. 3. A laser array for emitting first and second light beams, and a light condensing means for converging the first and second light beams toward the same track on a recording medium. Converging and separating means for condensing and separating the first and second light beams reflected by the recording medium; and the first and second light beams separated and condensed by the condensing and separating means. Detecting means for detecting the second light beam, and utilizing the difference between the light intensities of the first and second light beams detected by the detecting means to form the first light beam on the same track of the recording medium. An optical information processing apparatus comprising: a rotation drive unit configured to rotate the laser array so as to be irradiated with a second light beam.