JPH02185730A - Optical information processor - Google Patents

Abstract

PURPOSE:To reduce the crosstalk between a light beam for reproduction and a light beam for recording and to reduce the cost of the optical information processor by arranging a photodetector at the image point of a light beam and setting its size to a specific value. CONSTITUTION:The interval between 1st and 2nd light beams Lr and Lw which are converged on a recording medium 16 is denoted as d1, the magnification of an optical system provided between the recording medium 16 and a detecting means 20 is as (m), and the interval between the position on the detecting means 20 irradiated with the light beam and the end part of the detecting means 20 close to the 2nd light beam Lw is as d2. Then the detecting means 20 is set so that d2<md1 holds. Therefore, any special optical system for separating and detecting the light beam Lr for reproduction and light beam Lw for recording is not required. Further, the crosstalk between the light beam Lr for reproduction and the light beam Lw for recording is reduced. Consequently, a low- cost, high-accuracy multi-beam optical head is obtained.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to an optical information processing device, and more specifically, to an optical information processing device that records, reproduces, or erases information using a plurality of light beams. The present invention relates to an optical information processing device equipped with simultaneous multi-beam optical input.

(Prior Art) In recent years, optical information processing devices such as optical disk devices that can record image information such as documents, retrieve the image information as needed, and reproduce it as a single copy or soft copy have become popular. is being developed. In an optical disk storage device, a condensing light beam is irradiated toward a disc-shaped recording medium, that is, an optical disc, to record or reproduce information. That is, during recording, a state change is caused on the recording surface of the recording medium by being irradiated with a light beam, and as a result, information is recorded on the optical disc as, for example, pits. Further, during reproduction, a steady light beam is irradiated onto the information recording medium, and the intensity of the light beam is modulated by the pits according to the recorded information. Information is recovered by processing the modulated light beam intensity. 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 a light beam to the optical disk.

As these optical disk devices, optical information processing devices have recently been developed that include a multi-beam optical head that simultaneously records and reproduces information using a plurality of light beams. FIG. 5 shows an example of a conventional multi-beam optical head.

As shown in FIG. 5, a recording light beam L1 and a reproducing light beam L2 are emitted from regions 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 2. Beam splitter 2
The light is transmitted through the optical disc 5, and is again focused on the recording film surface 5A of the optical disc 5. At this time, the respective light beams L1 and L2 focused on the recording surface 5A are set so that their focusing points are preferably adjacent to each other and focused on the same track. As a result, adjacent recording and reproducing beam spots are formed on predetermined tracks on the recording film surface. With the recording and reproduction beam spots formed in this way, the optical disk is rotated at a constant linear velocity, whereby a predetermined recording area is irradiated with the recording light beam, and then the reproduction light beam is immediately irradiated. irradiated by. In this way, the playback operation is performed immediately after the recording operation.

The light beams L1 and L2 irradiated onto the recording film surface 5A are reflected and returned to the beam splitter 2 via the objective lens 4 and the reflection prism 3 again. The recording and reproducing light beams L1 and L2 returned to the beam splitter 2 are reflected by the joint surface and enter the beam splitter 6. Parts of the incident light beams L1 and L2 are transmitted and are respectively incident on a tracking control photodetector for irradiating the light beam onto a predetermined recording area, that is, a predetermined track. The remaining light beams L1 and L2 are reflected by the cemented surface and transmitted through the convex lens 12 provided on the exit surface. The light beam transmitted through the convex lens 12 is separated into a recording light beam and a reproduction light beam, reimaged, and incident on the spatial filter 8. Among the light beams incident on the spatial filter 8 , one of the light beams corresponding to the recording signal is reflected there and focused on the photodetector 9 . The other reproduction light beam is transmitted through a pinhole 8A made in a spatial filter according to its beam cross section in order to control the focus of the objective lens 4 and obtain an information reproduction signal. An information reproduction signal and a focus control signal are detected by detecting the transmitted reproduction light beam.

As another method, an optical information processing apparatus is known that includes a multi-beam optical head that emits two light beams with different wavelengths as a reproduction light beam and a recording light beam. In this method, two light beams Ll and L2 with different wavelengths are emitted from each light source for reproduction and recording.
are substantially combined using a combining dichroic mirror or the like, and focused onto a predetermined area on the optical disk by an objective lens. Preferably, the condensed light beams L1 and L2 are set so that their condensing points are adjacent to each other and condensed onto the same track. 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. Using the irradiated beam spot, a reproducing operation is performed immediately after a recording operation, similar to the apparatus shown in FIG. A light beam focused on a track of an optical disk is reflected and incident on a dichroic mirror. The light beams incident on the dichroic mirror and substantially combined are separated for each wavelength, that is, into a recording light beam and a reproduction light beam. The separated light beams are used for information reproduction signals and focus control signals.

(Problem to be Solved by the Invention) In a method in which a reproducing light beam and a recording light beam are separated by a pinhole, the light beam irradiated onto a photodetector through the pinhole is used for information reproduction and focus control. It is used for. Therefore, the position of the pinhole must be set accurately and with high precision both when in focus and when out of focus. Furthermore, since an optical system for re-imaging after passing through the pinhole is required, it becomes difficult to miniaturize the entire optical head. Furthermore, since crosstalk occurs between the recording light beam and the reproduction light beam, it becomes impossible to accurately detect the reproduction signal and the focus control signal.

On the other hand, in a multi-beam optical head that uses two light beams with different wavelengths as recording and reproducing light beams, it is difficult to manufacture a laser diode as a light source on the same chip. Therefore, two L-D
When placing the chips next to each other, a high degree of mounting precision is required.

Furthermore, since light beams of different wavelengths are used, it is necessary to correct the chromatic aberration of the lens caused by the difference in dispersion power of the optical system.

The present invention provides an optical information processing device equipped with a multi-beam optical head that stably detects a reproduction light beam from recording and reproduction light beams reflected by a recording medium to reproduce information and control focus. The purpose is to

[Structure of the Invention] (Means for Solving the Problems) The present invention includes means for emitting first and second light beams, and means for converging the first and second light beams onto a recording medium. a focusing means for separating the first and second light beams emitted from the recording medium; and a detection means for detecting the first light beam separated by the separating means. In an optical information recording and reproducing apparatus, the optical information recording and reproducing apparatus includes a response means for adjusting the position of the condensing means in the optical axis direction with respect to the recording medium in response to the first light beam detected by the detection means. The distance between the first and second focused light beams on the recording medium is dl, and the magnification of the optical system provided between the recording medium and the detection means is m1 The position where the light beam of the detection means is irradiated When the distance between the end of the detection means on the side approaching the second light beam is d2, the detection means
<mdi.

(Function) In the present invention, an optical information processing device equipped with a multi-beam optical head that is lower cost and more accurate because of special optics for separating and detecting a reproduction light beam and a recording light beam. is provided.

(Embodiment) FIG. 1 shows 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 disk substrate made of glass or plastic with a metal film such as tellurium or bismuth as an information recording film.

Tracks 16 defining tracking guide areas are formed concentrically on the substrate of the optical disk. A multi-beam optical head 100 is provided facing the optical disc 1, and during recording, reproduction, and erasing, the optical disc 16 is rotated relative to the multi-beam optical head 100 at a constant linear velocity. In FIG. 1, a track 16m defining a recording area extends in the Z direction.

A light source member 10C serving as a light source is provided inside the multi-beam optical head 100. A laser diode array 10A that emits two light beams for recording and reproduction is arranged within the light source member 10. The emission apertures of the laser diode array 10A are oriented in one direction when opening and are set apart from each other in the Z direction on the same chip, and from the emission apertures, for example, a reproduction light beam Lr and a recording light beam Lw of the same wavelength are emitted. is emitted. Laser diode array 10
The light beams Lr and Lw emitted from A are gradually diverged, overlapped, and irradiated onto the same collimator lens 12. The light beams LrsLw incident on the collimator lens 12 are substantially overlapped with each other and converted into a parallel combined light beam, which is then incident on the beam splitter 18 . The combined light beam incident on the beam splitter 18 is transmitted and irradiated onto the objective lens 14. When the light beam irradiated to the objective lens 14 passes through the objective lens 14 and is condensed, it is separated again into a recording light beam Lw and a reproduction light beam Lr, and is then separated onto the recording area of the optical disc 16, that is, the track. The light is focused on.

Note that the recording and reproducing light beams Lw are preferably used.

Each focal point of Lr is preferably adjacent to each other and irradiated onto the same track. As a result, adjacent recording and reproducing beam spots are simultaneously formed on a predetermined track. In this manner, the optical disk is rotated at a constant linear velocity while recording and reproducing beam spots are simultaneously formed. As the optical disc rotates, a predetermined recording area on the optical disc is first irradiated with, for example, a recording light beam Lw to record information. The area on the track where information is recorded is moved in accordance with the rotation of the optical disc, and is immediately irradiated with the reproducing light beam Lr. Information is reproduced by detecting the reflected light of the light beam Lr irradiated onto the recording area. Note that when obtaining an information reproduction signal, the reproduction light beam must be maintained in a focused state and on-track state with respect to a desired recording area. More specifically, the objective lens 14 is supported so as to be movable in the direction of its optical axis and in the in-plane direction orthogonal to the optical axis. When the objective lens 14 is placed at the optimum position on the optical axis, that is, at the in-focus position, this objective lens 1
The beam waist of the focused laser beam emitted from the optical disc 16 is projected onto the surface of the recording film of the optical disc 16, thereby forming a minimum beam spot on the surface of the recording film of the optical disc 16. On the other hand, when the objective lens 14 is placed at the optimum position in a plane perpendicular to the optical axis (in a plane parallel to the recording film surface), that is, at the alignment track position, the beam spot formed on the optical disc 16 is determined as a recording area. The laser beam is then tracked by the laser beam. These two states (focus state/
Information can be reproduced by maintaining the focused track state). That is, the intensity-modulated recording light beam L
The w causes a change in the state of bits, etc. on the recording film, and information is recorded.The recording area formed by pits, etc. in the track is irradiated with a laser beam L' of a constant intensity, which modulates the intensity of the light beam. The information is reproduced by detecting a change in the intensity of the reflected light beam Lr.

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

The light beam LA reflected by the cemented surface is used to obtain a focus control signal. The transmitted light beam is also used to obtain a trucking jig control signal and an information reproduction signal.

To describe the light beam reflected by the beam splitter 27 in more detail, the reproduction light beam Lr included in the light beam LA reflected by the joint surface of the beam splitter 27
The beam cross section of the recording light beam Lw is gradually made smaller, and at the same time, the central axes lr and 1w thereof become wider. Therefore, as the constituent light beams Lr and Lw are respectively focused, the combined light beam LA is gradually separated into individual reproduction light beams L and recording light beams Lw. A knife 29 is disposed on the optical path of the light beam Lr, which is approximately half of the optical path with respect to the central axis 1!r as a border, and thereby blocks approximately half of the optical path of the light beam. Only the light beam Lr is gradually focused onto a photodetector 20 placed on the optical path.At this time, the photodetector 20 detects the beam spot of the light beam irradiated onto the detection area. is set in advance so that it is the smallest during focusing, and at the same time, its size depends on the distance between the central axis of the reproducing light beam Lr and the central axis of the recording light beam Lw in the plane including the detector surface. The light beam irradiated onto the photodetector 20 is converted into an electrical signal in each photodetection area and processed in a predetermined manner.In other words, the beam spot irradiated onto the photodetector 20 is A focusing error signal, that is, a signal corresponding to the amount of defocus is generated by detecting a change in the position of The other recording light beam Lw is partially blocked by, for example, a knife edge 29 and is not irradiated onto the photodetector 20. is transmitted to.

On the other hand, to explain in detail the combined light beam LB transmitted through the beam splitter 27, the transmitted combined light beam LB, like the reflected light beam LA, contains the reproduction light beam Lr and the recording light beam Lr. As the beam cross section of the light beam Lw is gradually reduced, its central axes Lr and Zw become wider. Therefore, as the light beams LrSLw constituting the combined light beam LA are focused, the individual reproduction light beams L
r and a recording light beam Lw. On the optical path of the separated reproduction light beam, there is a photodetector 4 for detecting a tracking guide signal for maintaining the light beam on a predetermined track on the optical disk and an information reproduction signal.
5 is provided. The photodetector 45 is set in advance so that its detection area is irradiated with a circular beam spot having a predetermined area. It is set according to the distance between the central axis Qr of the recording light beam Lr and the central axis Jw of the recording light beam Lw. In other words, the size of the photodetector 45 is set within the range where only the reproduction light beam is irradiated, that is, within the range where the recording light beam is not irradiated, and at the same time, its position in the optical axis direction is set within the range where only the reproduction light beam is irradiated. It is set within a range that allows accurate tracking control using the beam spot of the reproduction light beam irradiated onto the photodetector.

The light beam converted into an electrical signal by the tracking photodetector 45 is processed by a predetermined method, and a tracking error signal is generated from the drive circuit 44. In response to the generated tracking error signal, current is supplied to the voice coil motor 50 to move the objective lens 14 in a plane perpendicular to its optical axis, so that 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.

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

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

FIGS. 2A to 2C show changes in the shape of the beam spot on the photodetector 20 when the beam is in focus and when it is out of focus.

The photodetector 20 for focus control is arranged on the optical path of the reproduction light beam Lr of the light beam LA reflected by the beam splitter 27, and divides the light beam in the vertical direction (X direction) as a light non-exposed region. It is composed of two photodetection areas 2OA and 20B formed on both sides of the line 22. When the objective lens 14 is in focus on the optical disc 16, the minimum beam spot Sr is irradiated onto the front non-detection area 22 of the photodetector. In other words, the photodetection area 2OA
Assuming that the output of 20B is ■ and the output of 20B is ■, the position of the dividing line 22 as a non-detection area is the position where the focus lens error signal (FE signal) is equal to zero at the time of focusing, that is, FφE- It is set to a position that satisfies the conditions of (■-■)-〇.

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 when it is in focus. Therefore, the focal point of the light beam Lr, which is partially blocked by the knife 29 and irradiated onto the photodetector, is moved to the front of the detector. Therefore, a beam spot as shown in FIG. 2C is formed on the photodetector 20. That is, a half-moon-shaped beam spot is formed on the photodetection area 20B, the straight portion of which is in contact with the non-detection area 22, and which has a larger diameter than when focused. At this time, the forcing error signal becomes 0 (FE-(■-■)).

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 becomes slightly more divergent than when it is in focus.

Therefore, the focal point of the light beam Lr, which is partially blocked by the knife 29 and irradiated onto the photodetector, is moved to the rear of the detector. Therefore, a beam spot as shown in FIG. 2A is formed on the photodetector 20.

That is, a half-moon-shaped beam spot is formed on the photodetection area 2OA, the straight portion of which is in contact with the non-detection area 22, and having a larger diameter than when focused. At this time, the forcing error signal is F・E−(■−■
) 〉0.

The size of the photodetector configured in this way is set based on the conditions described below. That is, the interval between the respective beam spots of the reproduction light beam Lr and the recording light beam Lw formed on the same track is d11, and the focal length of the objective lens 14 that irradiates the light beam onto the optical disk is f,%.
When the focal length of the lens is fD, the distance d3 between the focal point of the recording light beam Lw and the focal point of the reproduction light beam Lr on the same plane as the detection area of the photodetector 20 is da = (fo / fo )Xdl = mdl −
■It makes me feel sad. (Note that m indicates the magnification of the optical system.) Therefore, in order to irradiate only the reproduced signal onto the photodetector, it is necessary to The following relationship must always hold between the distance d2 between the end of the photodetector on the side approaching the virtual focal point of the beam and the focal point of the reproduction light beam.

da > d2...■
From the formulas ■ and ■, d2 < (fp/fo) Xdl -mdi -■
There is a relationship between

As shown in this equation, the distance d between the end of the photodetector on the side approaching the virtual focal point and the virtual focal point of the recording light beam
2 is roughly set to satisfy d2<mdi. By arranging a photodetector that satisfies these conditions, d2 < mdi, crosstalk between the recording light beam and the reproduction light beam is prevented, and information is efficiently read or reproduced.

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

In the embodiment of the present invention, the Knifezi method is used as a method for obtaining the focus control signal. Compared to focus control methods such as the astigmatism method, the Naifetsu method allows the size of the beam spot formed on the photodetector to be smaller when focused, making it easier to manufacture the photodetector 20. It becomes easier. That is, when controlling the focus using the conventional astigmatism method, a beam spot with a beam diameter of 50 μm or more must be formed on the photodetector during focusing. Accordingly, the central axes LrSEw of the recording and reproducing light beams must be separated from each other by 100 μm or more on the plane in which the photodetector is arranged in order to avoid crosstalk.

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

That is, if the numerical aperture of the lens system with reference to the recording medium side is NAo, the beam spot diameter W on the recording medium is
l becomes W1ζλ/N A o.

If the magnification of the lens system is m, the numerical aperture NAp of the lens system with respect to the photodetector side is NAD#NA□/m.

At this time, the beam spot diameter W2 of the light beam irradiated onto the photodetector is W2-λ/NAD-m rho number NA: 0,
4-0.6, λ: 600-900nm, m: 2-1C1
For example, NAo-0.5, λ-830nm.

When m-7, the beam spot diameter W2 on the photodetector becomes W2-mλ/NA □ 'i 10 p m.

When the photodetector is placed at the image point of the light beam in this manner, the size of the beam spot is formed to be very small.

Therefore, recording and reproducing light beams separated by minute intervals can be detected separately for each container.

On the other hand, FIGS. 3A to 3C show beam spots on the photodetector at the time of the valve stand track and the time of the combination track. A 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 is located on the horizontal (Y direction) dividing line 48 as a non-detection area. It is composed of two I-light detection areas 45A and 45B provided on both sides of the I-light detection area. When the objective lens 14 is accurately formed on the track that defines the recording area of the optical disk, that is, in the aligned track state, there is a non-detection area 48 on the photodetector 45 beyond which, as shown in FIG. 3B. A substantially circular beam spot Sr having a predetermined beam diameter is formed centered on the beam spot Sr, and at the same time, a band-shaped shadow portion generated by being diffracted by the track is formed centered on the non-detection area 48 . In other words, the output of the photodetection area 45A is
Assuming that the output of It is set to meet the requirements.

On the other hand, for example, when the objective lens 14 moves away from the on-track position with respect to the optical disk, a circular beam spot as shown in FIG. 3A or 3C is formed on the photodetector. In other words, the band-shaped dark area generated by diffraction by the track is asymmetrical with respect to the dividing line 48 serving as a non-detection area.

At this time, the 9g\g large → = Guerra signal is T-E
0 or TφE>0.

The set position of the photodetector 45 configured in this way is set based on the conditions described below.

In other words, in order to obtain the tracking control signal mentioned above,
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 photodetector 45 is
Its size 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 reproducing light beam Lr formed on the same track
And the focal length of the objective lens that emits each beam of the recording light beam Lw is f O% The focal length of the lens is fDs
Assuming that the distance in the optical axis direction between the detection surface of the photodetector 45 and the image point of the lens S V is Z, and that the distance Z is negligibly small with respect to the focal length M f o , then the distance of the photodetector 20 is On the same plane as the detection area, the distance d3 between the focal point of the recording light beam Lw and the focal point of the reproduction light beam Lr is d3#(fo/fo)Xdl-mdl
−■ to make it rain.

On the other hand, the diameter W of the beam formed on the detection area of the photodetector 45 at this time is given by W-Z/foXφ, where φ is the diameter of the light beam incident on the lens. ...■Formula■
In the equation (2), in order to irradiate only the reproduction light beam onto the detection area of the photodetector 45, d3 > W...■ must be satisfied. In other words, the formulas ■ and ■ mentioned above can be transformed into the formula ■
By substituting into
X (dl/φ)...Must be installed within a range that satisfies ■.

When substituting the relationship φ-2fo-NA into the formula (■), the formula (2) is generally rewritten as Zku(m2dl)/(2·NA)...■. (Note that m is the magnification of the optical system based on the recording medium side, and NA is the numerical aperture of the objective lens.) By installing the photodetector 45 within the range described in formula The optical beams are irradiated onto the photodetector 45 in a separated state.

Therefore, crosstalk between the reproducing and recording light beams Lr%Lw is prevented and accurate tracking control signals are detected. Focus control photodetector 2 configured in this way
A processing circuit for all signals detected by the zero and tracking control photodetectors is shown in FIG. As shown in FIG. 4, while the signal is used as a servo signal for control, it is also used as a reproduction signal for information formed on an information recording medium.

In FIG. 4, the output of the photodetection area 2OA is the output of the amplifier circuit 3.
1A. The output of the photodetection region 20B is supplied to an amplifier circuit 31B. Amplification circuit 31A and amplification circuit 31
The output signal from B is utilized to provide forcing control signals 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 addition result of the detection signal of the photodetection area 2OA and the detection signal of the photodetection area 20B is compared, and an output corresponding to the difference signal, that is, a focus control signal is supplied to the drive circuit 44. In accordance with the focus shift detection signal supplied to the drive circuit 44, a current is fed back to a coil (not shown) that drives the objective lens 1& in the direction of its optical axis. Objective lens 1e depending on the current with varied feed! is driven in the optical axis direction to correct defocus.

On the other hand, the output of the photodetection region 45A is supplied to the amplifier circuit 31C. The output of the photodetection region 45B is supplied to the amplifier circuit 31D. The output of this amplifier circuit 31C and the amplifier circuit 31
The output of D is utilized to provide 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. In the differential amplifier 42, the detection output of the photodetection area 45A and the detection output of the photodetection area 45B are compared, and an output corresponding to the difference, that is, a tracking deviation detection signal, is supplied to the drive circuit 44. In response to a tracking control signal supplied to the drive circuit 44, a coil is used to drive the objective lens 18 in a plane perpendicular to its optical axis (as shown in the figure, tracking deviation is corrected).

Furthermore, the outputs of the amplifier circuits 31C to 31D, that is, the entire output signal of the photodetector 45, are processed by a signal processing circuit 43 and used for information reproduction.

In the focus control photodetector according to one embodiment of the invention described above, a detection method using a knife is described.

However, other methods of focus detection may be used. When using other detection methods, by placing a photodetector at the image point of the light beam and setting its dimensions to a specific value, the crosstalk between the two light beams is reduced and a stable focus control signal is obtained. 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 onto the same track of the information recording medium, and a reproduction operation is performed immediately after the recording operation. However, the light beam may be irradiated so as to simultaneously record or reproduce information on two parallel tracks, for example.

It may also be used to continuously erase and record information.

Furthermore, in this invention, the front beam Lr for reproduction
Although a photodetector 20.45 is provided for the recording light beam Lw, in principle a photodetector may be provided for other recording light beams Lw. Furthermore, the shape of the photodetector may also be varied within a range that produces similar effects.

(Effects of the Invention) According to the present invention, the reproduction light beam and the recording light beam are separated without using a special optical system, and the size of the photodetector is adjusted according to the beam spot shape of the reproduction light beam. is set. Therefore, crosstalk between the reproducing light beam and the recording light beam is reduced, and an optical information processing device equipped with a highly accurate multi-beam optical head at lower cost is provided.

[Brief explanation of the drawing]

FIG. 1 is a front view of a multi-beam optical head provided in an optical information processing device according to an embodiment of the present invention, and FIGS. 2A to 2C show changes in the beam spot when the light beam is in a focused state and in an unfocused state. FIGS. 3A to 3C are front views of the photodetector included in the optical information processing apparatus of FIG. -Front view of a photodetector provided in an optical information processing device,
FIG. 4 is an electrical circuit diagram showing a method for processing all signals detected by the photodetectors shown in FIGS. 2 and 3, and FIG. FIG. 10... Light source member, IOA... Laser diode array 12... Collimator lens, 14... Objective lens, 16... Optical disk, 16A... Track,
18... Beam splitter, 20... Focus control photodetector, 2OA, 20B... Photo detection area, 22...
Tip non-detection area (dividing line) 25... Plano-convex lens, 27
...beam splitter, 29...naifetsuji, 3
1A to 31D...Amplification circuit, 41.42...Differential amplifier, 43...Signal processing circuit, 44...Drive circuit, 45...Tracking photodetector, 45A, 45B
...Light detection area, 48...Target non-detection area (dividing line)
, Lr... Light beam for reproduction, Lw... Beam for recording, Rr... Central axis of the optical beam for reproduction, -tw... Central axis of the optical beam for recording. Applicant's agent Patent attorney Takehiko Suzue Figure 7

Claims (1)

[Scope of Claims] Means for emitting first and second light beams, condensing means for condensing the first and second light beams onto a recording medium, and the recording medium. separation means for separating the first and second light beams emitted from the medium; detection means for detecting the first light beam separated by the separation means; and detection means for detecting the first light beam separated by the separation means; in response to the first light beam;
In an optical information processing device comprising a response means for adjusting the position of the light condensing means in the optical axis direction with respect to the recording medium, the recording medium of the first and second light beams condensed onto the recording medium. the distance above is d1, the magnification of the optical system provided between the recording medium and the detection means is m, the position where the light beam of the detection means is irradiated and the second position of the detection means
An optical information processing device characterized in that the detection means is set to satisfy d2<md1, where d2 is a distance from the end of the light beam approaching the light beam.