JPH02185731A - 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 by separating the light beam for reproduction and light beam for recording without using any special optical system and setting the position of a photodetector according to the beam spot diameter of the light beam for reproduction. CONSTITUTION:The numerical aperture of a light converging means 14 is denot ed as NA, the magnification (m) of an optical system provided between a record ing medium 16 and the detecting means 20 is as (m), and the interval on the recording medium 16 between 1st and 2nd light beams Lr and Lw converged on the recording medium 16 is denoted as d1. Then the photodetecting means 45 is provided in a position where the distance Z between the virtual light convergence point of the 1st light beam Lw converged by separative light con verging means 27 and the position where the photodetecting means 45 is pro vided is less than (m<2> d1)/(2.NA). Therefore, any special optical system for separating and detecting the light beam Lr for reproduction and light beam Lw for recording is not required and the crosstalk between the light beam Lr for reproduction and 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 a multi-beam optical head that can be used simultaneously.

(Prior Art) In recent years, image optical information processing devices such as optical disk devices have been developed that can record image information such as documents, retrieve the image information as needed, and reproduce it as a hard copy or soft copy. ing. In an optical disk device, a condensing light beam is irradiated onto a recording medium, ie, an optical disk, 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 with bits 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.

For example, optical information processing devices are used that include a multi-beam optical head that simultaneously records and reproduces information using two light beams with different wavelengths. In this method, two light beams L1 and L2 with different wavelengths for reproduction and recording emitted from each light source are roughly combined by a combining dichroic mirror, etc., and are directed to a predetermined area on the optical disk by an objective lens. The light is focused towards the target. 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.

With the recording and reproducing beam positions 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 reproducing light beam is immediately irradiated. irradiated by a beam.

The light beam focused on the track of the optical disk is reflected and incident on the dichroic mirror 7.

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 each incident on a photodetector placed on its optical path. The light beam incident on the photodetector is used as an information reproduction signal, a tracking control signal, and a focus control signal.

(Problem to be Solved by the Invention) In a multi-beam optical head that uses a dichroic mirror to separate light beams for recording and reproduction, it is necessary to manufacture laser diodes with different emission wavelengths as light sources on the same chip. is difficult. Therefore, when installing two LD chips adjacent to each other, a high degree of 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. Furthermore, a dichroic mirror for combining or separating two light beams with different wavelengths is coated to obtain specific characteristics. Its manufacturing becomes complicated and costs increase.

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

[Structure of the Invention] (Means for Solving the Problems) The optical information processing device of the present invention includes means for emitting first and second light beams, and condensing the first and second light beams. a detection means for detecting the first light beam emitted from the recording medium; and a first light beam detected by the detection means.
In the optical information processing apparatus, the optical information processing apparatus includes a response means for adjusting the position of the light condensing means in a plane direction perpendicular to the optical axis with respect to the recording medium in response to a light beam of NA, The magnification of the optical system provided between the recording medium and the detection means is m1 The distance on the recording medium between the first and second light beams focused on the recording medium is d
When i is assumed, the distance Z between the virtual convergence point of the first light beam condensed by the separation condensing means and the position where the light detection means is to be placed is z< (m2dl)/(2・NA) It is placed in a position that satisfies your needs.

(Function) According to the device of the present invention, there is no need for a special optical system for separating and detecting the reproducing light beam and the recording light beam. crosstalk between the two is reduced. Therefore, an optical information processing device equipped with a multi-beam optical head with lower cost and higher precision 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 of glass, bluff, chix, etc. with a metal wave film of tellurium, bismuth, etc. as an information recording film.

A multi-beam optical head 100 is provided, and an optical disc 16 is extended in the Z direction of the multi-beam optical head during recording, reproduction, and erasing.

Inside the multi-beam optical head 100, a light source member 10 is provided as a light source. A laser diode array 10A that emits two light beams for recording and reproduction is arranged in the light source member 101. 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 1O
The light beams Lr and Lw emitted from A are gradually diverged, overlapped, and irradiated onto the same collimator lens 12. The light beams Lr and Lw 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 beam Lw is 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
By w, the state of bits etc. in the recording film is changed and information is recorded, and the recording area formed by pits etc. in the track is irradiated with a laser beam Lr of a constant intensity, thereby modulating the intensity of the light beam. The information is reproduced by detecting changes in the intensity of the reflected light beam L'.

The combined light beam reflected by the recording film of the optical disk 16 and incident on the diverging lens 1 is converted into a parallel light beam upon focusing, and is returned to the beam splitter 8 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 #r of each light beam Lr, Lw is focused. ,
4w are gradually diverged 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 and LB of approximately equal light intensity at the junction surface.

The light beam LA reflected by the cemented surface is used to obtain a focus control signal. Further, the transmitted light beam is used to obtain a tracking 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 tr and tw thereof become wider. 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%Lw are respectively focused. A knife 29 is disposed on the optical path of the reproducing light beam Lr, which is approximately half of the optical path with respect to the central axis #r, thereby blocking approximately half of the optical path of the light beam. Therefore, only the reproduction light beam Lr that is not blocked by the knife 29 is gradually focused onto the photodetector 20 disposed on the optical path. In addition, at this time, the photodetector 20 is installed in advance so that the beam spot of the destination beam irradiated onto the detection area becomes the minimum at the time of focusing, and at the same time, the size of the photodetector 20 is set so that the beam spot of the destination beam irradiated onto the detection area becomes the minimum, and at the same time, the size of the photodetector 20 It is set according to 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 onto the photodetector 20 is converted into an electrical signal in each photodetection area and processed in a predetermined manner.

That is, by detecting a change in the position of the beam spot irradiated onto the photodetector 20, a forcing error signal, that is, a signal corresponding to the amount of defocus is generated, and the voice coil motor 50 is activated in accordance with the tracking error signal. A current is supplied to drive the objective lens 14 in the direction of its optical axis to keep the light beam in focus.

Note that the other recording light beam Lw is partially shielded by the knife 29, for example, and then passes through the photodetector 2.
0 is transmitted without being irradiated onto it.

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 gradually becomes smaller, its central axis 8r.

8w spread out from each other. Therefore, the combined light beam L
A is gradually separated into individual reproduction light beams Lr and recording light beams Lw as the constituent light beams L' and LW are respectively focused. A photodetector 45 is provided on the road for detecting a tracking guide signal for maintaining the light beam on a predetermined track on the optical disk and an information reproduction signal. It is set in advance so that a circular beam spot having a predetermined area is irradiated onto the area, and at the same time, the size of the detection area is determined by the reproduction light beam Lr on the plane including the detector surface.
It is set according to the distance between the central axis Lr of the recording light beam Lw and the central axis Ew of the recording light beam Lw. In other words, the photodetector 45
is set so that its size is 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 so that it is irradiated onto the photodetector. This is set within a range that allows accurate tracking control using the beam spot of the reproduction light beam.

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 is located on the vertical (X direction) dividing line as the first non-detection area. It is composed of two photodetection areas 2OA and 20B formed on both sides of 22. When the objective lens 14 is in focus on the optical disc 16, the smallest beam spot S' is irradiated onto the non-detection area 22 at the tip of the photodetector. In other words, the light detection area 2OA
Assuming that the output of 20B is ■, and the output of 20B 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 focal lens error signal becomes F.E-(■-■)<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 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 FE-(■-■
) 〉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 dl, the focal length of the objective lens 14 that irradiates the light beam onto the optical disk is fo,
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 2o is d8 = (fo/fo)Xdl -mdl
−■ to make it rain. (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 and the focal point of the reproduction light beam.

d3 > d2...■
From the equations (2) and (2), there is a relationship: d2<(fo/fo)Xdl-mdl...■.

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 f', ZW of the recording and reproducing light beams must be separated from each other by 100 μm or more on the plane where the photodetector is to be placed, 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 the numerical aperture NA and magnification m of the optical system used.

and the minimum value determined by 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 Wl on the recording medium is Wlζλ/NAo.

If the magnification of the lens system is m, the numerical aperture NAD of the lens/system based on the photodetector side is NAD - mNA□/m
becomes.

At this time, the beam spot diameter W2 of the light beam irradiated onto the photodetector is W2-λ/N A o -mλ/
It becomes N A o.

For practical optical diameters, the numerical aperture NA is generally
: 0.4~0.6, λ; 600~900nm, m: 2~
For example, NAo=0.5, λ-830nm.

When mm7, the beam spot diameter W2 on the photodetector is w2-mλ/NA□! : iloμm.

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, it is possible to easily separate and detect the recording and reproducing light beams that are separated by a minute interval.

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 along the horizontal (Y direction) dividing line 48 as a light non-detection area. It is composed of two forward light detection areas 45A and 45B provided on both sides of the front light detection area 45A and 45B. When the objective lens 14 is accurately formed on the track that defines the recording area of the optical disk, that is, in the alignment track state, the light non-detection area 48 is displayed on the photodetector 45 as shown in FIG. 3B. A substantially circular beam spot S'' having a predetermined beam diameter is formed with the center at the center, and at the same time, a band-shaped portion generated by being diffracted by the track is formed around the non-detection area 48.In other words, the light detection The output of the area 45A is ■, the photodetection area 45B
Assuming that the output of
The position where is equal to zero, that is, T・E−1■−■)−
It is set to satisfy the condition of 0.

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.

In this case, the error signal becomes T・Eku0 or T−E>O.

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.

In other words, the reproducing light beam L formed on the same track
The beam spot diameter distance of r and recording light beam Lw is f
D. Assuming that the distance in the optical axis direction between the detection surface of the photodetector 45 and the image point of the lens 6 is Z, and the distance Z is negligibly small with respect to the focal length fD, the detection of the photodetector 20 On the same plane as the area, the distance d3 between the focal point of the recording light beam Lw and the focal point of the reproducing light beam Lr is d3#
(fo/fo)Xdl-mdi-■.

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/fDXφ, where φ is the diameter of the light beam incident on the lens 6. ...■Form ceremony■
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
fo) 2/f5X (dl/φ) ... Must be installed within a range that satisfies ■. In formula ■, φ−
When substituting the relationship 215.NA, the formula (■) is generally rewritten as z<(m2dl)/(2.NA). (Note that m is the magnification based on the recording medium side, and NA is the numerical aperture of the objective lens.) By installing the photodetector 45 within the above range, the beam spot diameter of the light beam can be specified. formed within the range of Therefore, crosstalk between the reproducing and recording light beams Lr and Lw is prevented, and accurate tracking control signals are detected.

A processing circuit for all the signals detected by the focus control photodetector 20 and the tracking control photodetector configured in this way is shown in FIG. As shown in FIG. 4, the signal detected by the tracking control photodetector is used as a servo signal for tracking control, while it is also used as a reproduction signal for information formed on an information recording medium. be done.

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 a focus lens 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 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 response to the fuda-orcus shift detection signal supplied to the drive circuit 44, a coil (not shown) that drives the objective lens 1 second in the direction of its optical axis is driven 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 generated within a plane perpendicular to the optical axis of the drive circuit. The current is fed back to the coil (not shown) driven by the current. As a result, the objective lens 16 is driven in a direction perpendicular to the optical axis, and 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 embodiment of the present invention described above, tracking control is performed by detecting the light intensity balance of a circular beam spot of a reproduction light beam irradiated onto a photodetector for tracking control. However, within the scope of the invention, both the recording and reproducing light beams may each be provided with a tracking control photodetector. By configuring the photodetector as described above, the crosstalk between the two light beams is reduced and 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 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 4 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 reproduction light beam Lr
Although a photodetector 2S20.45 is provided for the recording light beam Lw, in principle, a photodetector may not be provided for the other recording light beam 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 photodetector is adjusted according to the beam spot diameter of the reproduction light beam. The location 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. A front view of a photodetector provided in an optical information processing device. It is a circuit diagram. 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, A1.42...Differential amplifier, 43...Signal processing circuit, 44...Drive circuit, 45...Tracking photodetector, 45A145B
...Light detection area, 48...Target non-detection area (dividing line)
, Lr... Light beam for reproduction, Lw... Beam for recording, E"... Central axis of the optical beam for reproduction, Jw... Central axis of the optical beam for recording.

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. a condensing and separating means for condensing and separating the first and second light beams emitted from the medium; and detecting the first light beam separated and condensed by the condensing and separating means. detection means; and in response to the first light beam detected by the detection means;
In an optical information processing device, the optical information processing device includes a response means for adjusting a position of the light condensing means in a surface direction perpendicular to the optical axis with respect to the recording medium, wherein the numerical aperture of the light condensing means is NA, the recording medium and the detection means If the magnification of the optical system provided between the two is m, and the distance between the first and second light beams focused on the recording medium on the recording medium is d1, then the distance between the first and second light beams focused on the recording medium is d1. The distance Z between the virtual convergence point of the first light beam and the position where the light detection means is to be placed is Z<(m^2d1)/
An optical information processing device characterized in that it can be installed in a position that satisfies (2・NA).