JP2746973B2 - 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 toward a disk-shaped recording medium, that is, an optical disk to record or reproduce information. That is, at the time of recording, the irradiation of the light beam causes a change in the state of the recording medium on the recording surface, and as a result, information is recorded on the optical disk as, for example, pits. During reproduction, a light beam is normally irradiated onto the information recording medium, and the light beam is intensity-modulated by pits in accordance with 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. In the conventional multi-beam optical head, a recording light beam L1 and a reproduction light beam L2 are emitted from regions provided adjacent to each other on the semiconductor laser array 1. The recording and reproducing light beams L1 and L2 are superimposed on each other and transmitted through the beam splitter. The light beam transmitted through the beam splitter is focused on the recording film surface of the optical disk via the objective lens. At this time, the light beams L1 and L2 condensed on the recording surface are set so that the converging points are adjacent to each other and condensed on the same track. Thus, adjacent recording and reproducing beam spots are formed 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 In this way, the reproducing operation is performed immediately after the recording operation. The light beams L1 and L2 irradiated on the recording film surface are reflected and returned to the beam splitter again through the objective lens. The recording and reproducing light beams L1 and L2 returned to the beam splitter are reflected by the joint surface and enter the beam splitter. Incident light beam
Part of L1 and L2 is transmitted, and each has a predetermined recording area, that is,
The light beam is incident on a tracking control photodetector for irradiating a predetermined track with a light beam. Further, the remaining light beams L1 and L2 are reflected on the joint surface and transmitted through the convex lens provided on the exit surface. The light beam transmitted through the convex lens is separated into a recording light beam and a reproduction light beam, and one of the reproduction light beams is subjected to light detection through a focus control device for detecting a focus control signal of the objective lens. Incident on the vessel. On the basis of the signal detected by the photodetector, a defocus detection signal is supplied to a drive circuit of the objective lens as a response means, and the objective lens is maintained at the in-focus position. This focus control operation, as shown in FIGS. 7A to 7C,
This is performed by utilizing the intensity balance of the beam spot on the two light detection areas irradiated with the light beam. More specifically, a defocus detection signal is generated based on the balance between the light intensity of the beam spot irradiated on the light detection area 20A of the light detector 20 and the light intensity of the beam spot irradiated on the light detection area 20B. Is done.

(Problems to be Solved by the Invention) In a conventional focus control device provided in a multi-beam optical head, one of two light beams emitted from two light sources is irradiated onto a recording medium when a response unit is started. The focus position at which the intensity balance of the beam spot in each light detection area is detected is controlled. Therefore, for example, when the initial position of the light-collecting unit is very far from the in-focus position at the start of defocus detection of the response unit, that is,
If the information recording medium is not arranged within the depth of focus of the objective lens, an image as shown in FIG. 7A or 7C is formed on the photodetector. That is, for example, when the initial position of the light collecting unit with respect to the recording medium is away from the in-focus position, the light detector 20
On the upper detection area 20A, a half-moon shaped beam spot Sr is formed by the reproducing light beam Lr, while the initial position of the light condensing unit with respect to the recording medium is closer than the in-focus position by exactly the same amount. In addition, a half-moon-shaped beam spot is formed on the detection area 20B on the photodetector 20, and a half-moon-shaped beam spot Sw is formed on the photodetector 20A by the recording light beam Lw. Therefore, the defocus detection signal generated for the same defocus amount is the eighth defocus signal when the objective lens is closer to the recording medium than when the objective lens is farther from the recording medium.
As shown in the figure, the image becomes asymmetric with respect to the in-focus state. Therefore, an erroneous signal is generated in the focus control signal corresponding to the defocus amount, and precise focus control of the objective lens is not performed.

The present invention provides an optical information processing apparatus provided with a multi-beam optical head that performs stable information reproduction and focus control by detecting one of light beams for recording and reproduction reflected from a recording medium. The purpose is to:

[Structure of the Invention] (Means for Solving the Problems) The present invention has been made based on the above-mentioned problems, and is a first method used for reproducing information from a recording medium.
And a second used for recording information on the recording medium.
Means for emitting a first light beam, the first and second light beams
Focusing means for focusing the light beam on a recording medium,
Condensing / separating means for converging and separating the first and second light beams from the recording medium, and a second light detecting means for detecting the first light beam separated by the light condensing / separating means. A first responding means for adjusting a position of the focusing means in the optical axis direction with respect to the recording medium in response to an output of the first detecting means; Second detecting means for detecting the second light beam, and a position of the focusing means in a plane direction perpendicular to the optical axis direction with respect to the recording medium in response to an output of the second detecting means. An optical information processing apparatus, comprising: a second response unit that adjusts the focal length of the optical information. The first response unit detects the out-of-focus state, which is a movement within a depth of focus that moves the light-collecting unit in the optical axis direction. Initiation is initiated in response to the first light beam only. The focusing means, when in the focused state, separates the first and second light beams by a predetermined distance d1, and focuses the first and second light beams respectively on the minimum beam spot. And condensed on the recording medium,
Detecting means, when the focusing means is in focus,
When the second beam spot of the second light beam is formed with a magnification of m times at a distance indicated by d3 with respect to the focal position where the beam spot of the first beam is formed, An outer edge portion is provided at a distance of d2 from the second beam spot of the second light beam, and
Is to provide an optical information processing apparatus having a light receiving surface having a size satisfying the expressions of d3 <d2 and d2 <md1.

(Operation) In the optical information processing apparatus of the present invention, when the detection of defocus from the initial position of the objective lens is started, the magnitude of the defocus detection signal indicates that the objective lens is located at a position different from the original position. As a result, it is possible to prevent the occurrence of such an erroneous signal, and to accurately detect the defocus amount even when the objective lens is not located within the depth of focus.

Further, according to the optical information processing apparatus of the present invention, crosstalk due to the recording light beam on the reproduction signal is reduced.

(Embodiment) FIG. 1 shows 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. Tracks 16 defining a tracking guide area are formed concentrically on the substrate of the optical disc. 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.

In 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. The light beams Lr and Lw emitted from the laser diode array 10A are superposed on each other and radiated onto the same colleter lens 12 while gradually diverging. The light beams Lr and Lw incident on the collimator lens 12 are substantially superimposed on each other and converted into a parallel combined light beam, and are converted into a beam splitter.
It is incident on 18. The combined light beam that has entered the beam splitter 18 passes through the combined light beam and irradiates the objective lens 14. The light beam applied to the objective lens 14
When the light beam is transmitted through and focused, the light beam is again separated into the recording light beam Lw and the reproduction light beam Lr, and is focused on the recording area of the optical disk 16, that is, on the track 16A. Preferably, the respective focal points of the recording and reproducing light beams Lw and Lr are irradiated on the same track adjacent to each other. Thus, adjacent recording and reproducing beam spots are simultaneously formed on a predetermined track. The optical disc is rotated at a constant linear velocity while the recording and reproducing beam spots are simultaneously formed. In accordance with the rotation of the optical disk, a predetermined 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 the information reproduction signal, the reproduction light beam must be maintained in a focused state and a focused 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. When the objective lens 14 is located at the optimum position on the optical axis, that is, at the focal 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 disc 16. Thereby, the minimum beam spot is formed on the surface of the recording film of the optical disc 16. On the other hand, when the objective lens 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, a beam spot formed on the optical disc 16 is defined as a recording area. Formed precisely on the track so that the track is tracked by the laser beam. These two states (focused state
The information can be reproduced by keeping the in-focus track state). That is, the intensity-modulated recording light beam Lw
A state change of pits or the like is caused in the recording film to record information, and the light beam is intensity-modulated by irradiating a laser beam Lr of a constant intensity to a recording area formed by pits or the like in the track. The 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 reproduction light beam Lr and the recording light beam Lw is gradually focused, and at the same time, each light beam Lr,
The central axes lr and lw of 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 into light beams LA and LB having substantially the same light intensity at the joint surface.

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 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 show the beam cross section. Is reduced, and at the same time, the central axes lr and lw expand. Therefore, the combined light beam LA is
As Lr and Lw are respectively focused, they are gradually separated into individual reproduction light beams Lr and recording light beams Lw. 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. still,
The other recording light beam Lw is, for example, a knife edge 29
The light is transmitted without being irradiated onto the photodetector 20 in a state where a part thereof is shielded.

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 is gradually separated into individual reproduction light beams Lr and recording light beams Lw as the constituent light beams Lr and Lw are respectively focused. A photodetector 45 for detecting a tracking guide signal for maintaining the light beam on a predetermined track on the optical disk and an information reproduction signal is arranged on the optical path of the separated light beam for reproduction. In addition, photo detector
45 is set in advance so that the detection area is irradiated with a circular beam spot having a predetermined area, and at the same time, the size of the detection area is set to the reproduction light beam Lr on the surface including the detector surface. Is set in accordance with the distance between the center axis lr of the recording light beam Lw and the center axis lw of the recording light beam Lw. In other words, the photodetector 45 is set so that its size is within a range where only the reproduction light beam is irradiated, that is, within a range where the recording light beam is not irradiated, and at the same time, its position in the optical axis direction is It is set within a range where accurate tracking control is possible using the beam spot of the reproduction light beam irradiated on the photodetector.

The light beam converted to an electric signal by the tracking photodetector 45 is processed by a predetermined method, and a driving circuit 44 generates a tracking error signal. 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. Further, 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.

Note that the other separated recording light beam Lw passes through the focused photodetector 45 without being irradiated.

FIGS. 2 and 3 show the structures of the photodetector 20 for focus control and the photodetector 45 for tracking control provided in the multi-beam optical head of the optical information processing apparatus of the present invention.

2A to 2C show changes in the beam spot shape on the photodetector 20 during focusing and when not focused.

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 a focused state 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 position where the focusing error signal (FE signal) becomes equal to zero at the time of focusing, that is, FE = ｛-｝
= 0.

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. 2C 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 diverged slightly more than at the time of focusing. Therefore knife edge
The condensing point of the light beam Lr, which is partially illuminated at 29 and illuminates the photodetector, is moved rearward of the detector. Therefore, a beam spot as shown in FIG. 2A is formed on the photodetector 20. That is, the linear portion contacts the non-detection region 22 on the light detection region 20A, 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 Lw formed on the same track
When the distance between the respective beam spots is d1, the focal length of the objective lens 14 for irradiating a light beam onto the optical disk is f _O , and the focal length of the lens 6 is f _D , the detection area of the photodetector 20 is on the same plane. in the interval d3 between the focal point of the focal point and the reproduction light beam Lr of the recording light beam Lw _{is, d3 = (f D / f} O) × d1 = md1 ... in it expressed. (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 light 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 beam and the focusing point of the reproduction 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 a 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 100 μm from each other on a plane where the photodetector is to be arranged in order to avoid crosstalk.
Must be separated.

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 the minimum value determined by the numerical aperture NA and magnification m of the optical diameter to be used and the wavelength λ of the light source.

That is, the numerical aperture of the lens system with respect to the recording medium side is set to NA
_{If o} , the beam spot diameter W1 on the recording medium is W
1 ≒ 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 48 as a light non-detection area. And two light detection areas 45A and 45B provided on both sides thereof. When the objective lens 14 is accurately formed on the track that defines the recording area of the optical disk, that is, in the combined track state, the light non-detection area 48 is formed on the photodetector 45 as shown in FIG. 3B. A substantially circular beam spot Sr having a predetermined beam diameter is formed at the center, and at the same time, a band-shaped shadow portion generated by diffraction at the track is formed around the non-detection region 48. In other words, assuming that the output of the light detection area 45A is the output of the light detection area 45B,
The position 8 is a position where the tracking error signal (TE) is equal to zero at the time of tracking, that is, TE =
It is set so as to satisfy the condition of ｛−｝ = 0.

On the other hand, for example, when the objective lens 14 moves away from the combined track position with respect to the optical disk, a circular beam spot is formed on the photodetector as shown in FIG. 3A or 3C. That is, the band-shaped dark part diffracted by the track is
It appears asymmetrically with respect to the dividing line 48 as a non-detection area. At this time, the focusing 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, in order to obtain the above-described tracking control signal, the position of the photodetector 45 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 size of the photodetector 45 is set so that only the reproduction light beam Lr is irradiated.

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 the beam spots of the reproduction light beam Lr and the recording light beam Lw formed on the same track is d1, the focal length of the objective lens for irradiating the optical beam on the optical disk is f _O , and the focal length of the lens 6 F _D , the detection surface of the photodetector 45 and the lens 6
The distance along the optical axis between the image point and Z of the distance Z is a negligibly small with respect to the focal length f _D, on the detection area and the same plane of the optical detector 20, the recording light beam
Distance d3 between Lw focal point and the focal point of the reproducing light beam Lr 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 6, phi, represented by _{W = Z / f D × φ} . In the formulas and formulas, d3> W must be satisfied in order to irradiate only the reproducing light beam onto the detection area of the photodetector 45. That is, when substituting the above expression, to expression, 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.

When substituting the relationship of φ = 2f _O · NA in the equation, 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 reproduction and recording are performed. The application light beam is irradiated on the photodetector 45 in a separated state. Therefore, crosstalk between the reproducing and recording light beams Lr and Lw is prevented, and an accurate tracking control signal is detected.

When tracking control and focus control are performed in the present invention, a desired light beam, for example, only a reproduction light beam is emitted from the light source at the start of the defocusing.
4A to 4C show light beam spot images on the focus control photodetector which may appear at the start of defocus detection in the focus control operation. FIG. 4B shows a beam spot image at the time of focusing, FIG. 4A shows a case where the objective lens is extremely far from the information recording medium, and FIG. The beam spot image in the case where the beam spot is turned on is shown. The relationship between the defocus detection signal detected by these photodetectors and the defocus amount is the fifth.
It is shown in the figure.

As shown in FIG. 5, the defocus detection signal detected by the focus control device is symmetrical with respect to the defocus amount regardless of when the defocus detection is started and when the control operation is performed. Appear. In other words, when the same defocus amount is compared between when the objective lens approaches and goes away from the recording medium, the defocus detection signal appears symmetrically with respect to the in-focus state. Therefore, when the objective lens is not generally within the focus controllable range, that is, even when not positioned within the depth of focus, the defocus detection of the focus control operation is performed in response to the defocus amount of one light beam. Starts, that is, an initial operation is performed. After the detection of the defocus in the focus control operation starts, the objective lens is positioned within a certain focus controllable range, that is, within the depth of focus, and then the recording light beam is generated from the light source member 10 to record information and Playback takes place simultaneously. More specifically, by using the reproducing light beam at the start of the focus control operation, the objective lens is controlled in focus from its initial position to a depth of focus, that is, a range in which the two light beams are not influenced by each other,
Thereafter, a normal focus control operation as shown in FIGS. 2A to 2C is performed.

FIG. 6 shows a processing circuit for processing all signals detected by the focus control photodetector 20 and the tracking control photodetector. The signal detected by the tracking control photodetector shown in FIG. 3 is used as a servo signal for tracking control, and is also used as a reproduction signal of information formed on an information recording medium. .

In FIG. 6, 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. The output of the light detection area 45B is supplied to the amplifier circuit 31D.
The output of the amplifier circuit 31C and 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 is supplied to the inverting input terminal of the differential amplifier 42, and the output of the amplifier circuit 31D is supplied to the non-inverting input terminal of the differential amplifier 42. Differential amplifier 42
In the above, the detection output of the light detection area 45A and the light detection area 4
5B is compared with the detected output, and the 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 31D, that is, all output signals of the photodetector 45 are processed by the signal processing circuit 43 and used for reproducing information.

In the above-described focus control photodetector according to one embodiment of the present invention, a detection method using a knife edge is described. However, other methods of focus detection may be used. When using other detection methods, the crosstalk between the two light beams is reduced by arranging the photodetector at the image point of the light beam and setting its size to a specific value.
A stable focus control signal can be obtained.

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
, The photodetectors 20 and 45 are provided, but in principle, the photodetector 20 may be provided for the other recording light beam Lw. Furthermore, the shape of the photodetector may be changed as long as a similar effect is obtained.

(Effect of the Invention) In the optical information processing apparatus according to the present invention, when the detection of the defocus is started from the initial position of the objective lens, the magnitude of the defocus detection signal is different from the original position of the objective lens. As a result, it is possible to prevent the occurrence of an erroneous signal and to accurately detect the amount of defocus even when the objective lens is not located within the depth of focus.

Further, according to the optical information processing apparatus of the present invention, crosstalk due to the recording light beam on the reproduction signal is reduced.

[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 FIGS. 2A to 2C.
FIGS. 3A to 3C 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 focused state and a non-focused state of the light beam. FIGS. FIGS. 4A to 4C are front views of a photodetector provided in the optical information processing apparatus of the present invention, showing a change of a beam spot in a state and a non-matching track state. FIGS. FIG. 5 is a diagram showing a change in the shape of a beam spot on a focus control photodetector which may sometimes appear, and FIG. 5 is a defocus detection signal (tracking) detected by the focus control photodetector provided in the optical information processing apparatus of the present invention. A diagram showing a relationship between an error signal) and a defocus amount;
FIG. 6 is an electric circuit diagram showing a method of processing all signals detected by the photodetectors shown in FIGS. 2 and 3, and FIGS. 7A to 7C can appear at the start of a conventional focus control operation. FIG. 8 shows a change in the shape of a beam spot on a focus control photodetector. FIG. 8 shows a defocus detection signal (tracking error signal) detected by a focus control photodetector provided in a conventional optical information processing apparatus. FIG. 4 is a diagram illustrating a relationship between defocus amounts. 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, 48… Detection area (dividing line), Lr: light beam for reproduction, Lw: beam for recording,
lr: central axis of the reproducing light beam, lw: central axis of the recording light beam.

Claims (1)

(57) [Claims] 1. A means for emitting a first light beam used for reproducing information from a recording medium, and a second light beam used for recording information on the recording medium; Converging means for converging the first and second light beams on a recording medium; condensing and separating means for condensing and separating the first and second light beams from the recording medium. First detecting means for detecting the first light beam separated by the light condensing / separating means; and light of the focusing means with respect to the recording medium in response to an output of the first detecting means. First responding means for adjusting the position in the axial direction; second detecting means for detecting the second light beam separated by the light condensing / separating means; and an output of the second detecting means. In response to the optical axis of the focusing means with respect to the recording medium. An optical information processing apparatus comprising: a second response unit that adjusts a position in a straight plane direction; wherein the first response unit moves the light-collecting unit in a depth of focus that moves in the optical axis direction. The start of detection of a certain defocus is started in response to only the first light beam, and the condensing means shifts the first and second light beams by a predetermined distance d1 when in a focused state. And focused on the recording medium as first and second beam spots respectively focused on the minimum beam spot, wherein the first detecting means is in a focused state. Sometimes, the second beam spot of the second light beam is formed at a magnification of m times at a distance indicated by d3 with respect to the focal position where the beam spot of the first beam is formed. The second beam of the second light beam An outer edge portion is provided at a distance of d2 from the beam spot, and the first detecting means has a light receiving surface having a size satisfying the expressions of d3 <d2 and d2 <md1. Processing equipment.