JPH0536110A - Optical information recording and reproducing device - Google Patents

Abstract

PURPOSE:To eliminate a time waiting a rotation by providing a recording means recording information at the 1 bit period of recording information train by an overwrite system and a detecting means placing backward this recording means and detecting the information. CONSTITUTION:A recording light spot 1 and a verifying light spot 2 are positioned on the same track of a magneto-optical disk so that the recording light spot 1 is preceded. Then, a light spot spacing (l) is (l)=K.S.T, where K: an integer >=1, S: linear velocity of magneto-optical disk (m/sec), T: 1 bit period (sec) of recording data train. In such a case, the overwrite of the data is performed at respective times in accordance with the recording data. On the other hand, since the verifying light spot, as well is turned on/off a magneto- optical reproducing waveform is attained when the recorded data is irradiated with this verifying light spot 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information recording / reproducing apparatus for simultaneously performing erasing-recording-verifying.

[0002]

2. Description of the Related Art Conventionally, CAV (Constant Angler Vel) has been used as a recording system for optical disks.
, CLV (Constant linie)
ar Velocity) method. In the CAV method, since the speed of the spindle motor that rotates the optical disk is constant, there is the advantage that the rotation system circuit is simple and the seek operation can be performed at high speed. However, the storage capacity per track is the radial direction of the optical disk. Since it is constant irrespective of the above, there is a drawback that the total storage capacity per optical disk does not become so large. In the CLV system, the spindle motor is controlled so that the rotation speed is proportional to the radial direction of the optical disk, and recording and reproduction are performed at a constant linear speed. Therefore, this CLV method has an advantage that the storage capacity per track increases in proportion to the radial direction of the optical disk and the total storage capacity per optical disk is large, but on the other hand, the rotation system circuit is complicated and seek There is a drawback that the operation is delayed by the time required to change the rotation speed of the motor.

The MCAV system has been developed in order to solve the drawbacks of the CAV system and the CLV system. This MCAV system keeps the rotation speed of the optical disk constant,
In addition, it is a method of recording or reproducing while changing the bit rate so as to be substantially proportional to the radial direction of the optical disc. As a result, it is not necessary to change the rotation speed of the spindle motor during the seek operation, the high speed seek operation similar to the CAV method is possible, and the storage capacity per track is almost proportional to the optical disk in the radial direction. Since it increases, it is possible to obtain the same total storage capacity as the CLV method. In the case of the MCAV method, when the area (zone) divided into a plurality of tracks in the radial direction changes, the data recorded on the optical disk medium is demodulated unless the reference clock is switched to a frequency suitable for the zone. However, the information cannot be read. The frequency of the reference clock of the zone is different for each zone and increases from the inner zone to the outer zone.

In recent years, the CAV method and MCAV
A multi-function type device capable of recording / reproducing information, which is a single optical information recording / reproducing device having both types of functions, has also been realized.

By the way, as an apparatus for recording information on a disc-shaped magneto-optical recording medium by each of such methods, for example, as disclosed in Japanese Patent Laid-Open No. 63-37842, a magneto-optical recording medium is used. A device characterized in that the magneto-optical recording medium is irradiated with laser light according to an information signal only when a magnetic field sufficient to reverse the magnetization direction of the magneto-optical recording medium is applied. Has been done.

[0006]

Normally, the process of recording information is performed by three operations of erasing-recording-verifying. In the apparatus of the above-mentioned Japanese Patent Laid-Open No. 63-37842, a magnetic field and a light are applied. Both are methods of performing overwriting by modulating, and only two operations of erasing / recording-verifying are required. However, it takes time for the magneto-optical recording medium to make one rotation between these two operations.

Japanese Patent Laid-Open No. 2-240838 discloses
This is a simultaneous verify method that performs simultaneous recording and verification with multiple light beams.
One operation is enough. However, again, it takes time for the magneto-optical recording medium to make one rotation between these two operations. In this simultaneous verification method, the light source L
There is a drawback that two or more D's are required and the forward path for guiding the light from the plurality of light sources to the same optical path to irradiate the medium becomes complicated.

The present invention has been made in view of the above circumstances, and provides an optical information recording / reproducing apparatus which simultaneously performs erasing-recording-verifying and does not require a rotation waiting time of a recording medium at the time of recording. Is intended.

Another object of the present invention is to save space by using only one light source and simplifying the outward optical system.
An object is to provide a low-cost optical information recording / reproducing device.

[0010]

SUMMARY OF THE INVENTION An optical information recording / reproducing apparatus of the present invention is a recording means for recording information by an overwrite method at least in a 1-bit cycle of a recording information sequence to be recorded on an information recording medium, and this recording means. And a detection means located behind the means for detecting information.

Further, in the optical information recording / reproducing apparatus of the present invention, the interval l between the recording means and the detecting means is set as follows: l = k · s · T k: integer s of 1 or more: linear velocity T of recording medium : Arranged to have a 1-bit cycle of the recording information sequence.

Further, according to the present invention, a diffraction grating for separating the light beam from the light source into a plurality of light beams, an objective lens for condensing the light beam from the diffraction grating on the information recording medium, and the diffraction grating are used. Recording means for irradiating at least one light beam of the plurality of separated light beams onto the information recording medium and recording information by an overwrite method at a 1-bit cycle of a recording information sequence, and a recording means behind the recording means. In the optical information recording / reproducing device, the diffraction grating has sin θ = λ / d l = f · tan θ l = k · s · T θ: Diffraction angle λ: Light source wavelength d: Diffraction grating pitch f: Objective lens focal length l: Distance between recording means and detection means is satisfied.

[0013]

[Operation] In the above optical information recording / reproducing apparatus, the distance l between the recording means and the detection means is set as follows: l = k · s · T k: integer s of 1 or more s: linear velocity of recording medium T: recording information By controlling so as to have a 1-bit cycle of a row, the recording unit erases and records, and at the same time, the detection unit detects information recorded behind the recording unit by the interval l.

In the above optical information recording / reproducing apparatus,
The recording means erases and records, and at the same time, the detection means arranged behind the recording means at the interval l detects information recorded at the interval l behind the recording means.

Furthermore, in the above optical information recording / reproducing apparatus, the recording means erases and records, and
At the same time, by irradiating the other light beam separated by the diffraction grating behind the recording means, the detecting means for detecting the information detects the information recorded behind the recording means by the interval l.

[0016]

Embodiments of the present invention will be described below with reference to the drawings.

1 to FIG. 1 relate to a first embodiment of the present invention, FIG. 1 is an explanatory view for explaining the concept of an optical information recording / reproducing apparatus, and FIG. 2 shows a structure of a main part of the optical information recording / reproducing apparatus. FIG. 3 is an explanatory diagram for explaining a magnetic head modulation signal, FIG. 4 is an explanatory diagram for explaining separation of light spots by a diffraction grating, FIG. 5 is an explanatory view for explaining separated light spots, and FIG. 2 is a timing chart for explaining the data recording method of the optical information recording / reproducing apparatus of FIG. 2, and FIG. 7 is an explanatory diagram for explaining data recording and verification on the magneto-optical disk.

As shown in FIG. 1, in the optical information recording / reproducing apparatus of the first embodiment, a recording data string to be recorded (see FIG.
In synchronism with (A)), a light source irradiates a recording medium, for example, a magneto-optical disk with a light beam (FIG. 1C), and, for example, the time when the recording data in the recording data sequence is 1. At t1 (FIG. 1 (E)), an external magnetic field is applied in the magnetization direction of the magneto-optical disk (FIG. 1 (B)), the data recorded on the magneto-optical disk is erased, and based on the recorded data, Information is recorded on a magneto-optical disk. in this case,
At other times t2, t3, and t4, the recorded data is 0, so that the data recorded on the magneto-optical disk is only erased.

As shown in FIG. 1 (F), the light spots of the light beam form at least a recording light spot 1 and a verifying spot 2 at time t.
The verifying spot 2 is formed at a distance 1 of the optical spot from the recording optical spot 1 in the moving direction of the magneto-optical disk. That is, the recording light spot 1 and the verifying spot 2 are positioned so that the recording light spot 1 precedes them on the same track of the magneto-optical disk. The light spot interval l
Is 1 = k · s · T (1) k is an integer of 1 or more s: linear velocity of magneto-optical disk (m / sec) T: 1-bit period (sec) of recording data string, where k = 3 will be described.

With the verifying spot 2 positioned in this way, the data recorded at the time t1 by the recording light spot 1 is demodulated at the time t4 and read out as a differential reproduction waveform (FIG. 1 (D )).

For example, in the CLV type optical information recording / reproducing apparatus, as shown in FIG. 2, a magnetic head 5 for applying an external magnetic field to a magneto-optical disk 4 rotating about a rotation axis 3.
A magnetic head modulation circuit 8 for generating a magnetic head modulation signal 7 provided with a synchronizing circuit 6 for synchronizing a recording data string with a basic clock; and a light source, for example, L, in synchronization with the basic clock.
An LD modulation circuit 10 for emitting D9, and a collimator lens 11 for collimating the light emitted from the LD9.
A diffraction grating 12 for diffracting the parallel light by the collimator lens 11 and an objective lens 13 for condensing the light diffracted by the diffraction grating 12 on the magneto-optical disk 4 are provided. The magneto-optical disk 4 is provided with a protective layer 14 and a cover glass 15.

Here, the magnetic head modulation signal 7 has a waveform, for example, as shown in FIG.
The it cycle T is the shortest cycle of the magnetic head modulation signal 7, but the 1-bit cycle T of the recording data string may be the cycle of the LD modulation signal of the LD modulation circuit 10 synchronized with the basic clock.

As shown in FIG. 4, the light emitted from the LD 9 is diffracted by the diffraction grating 12 through the collimator lens 11 and at least on the magneto-optical disk 4 through the objective lens 13. The light beams are separated into two or more light spots separated by a distance l.

The diffraction angle is θ, the wavelength of light is λ, and the diffraction grating 12
Where d is the grating pitch of, and f is the focal length of the objective lens 13, the light spot interval l on the magneto-optical disk is l = f · tan θ (3) Therefore, the grating pitch d of the diffraction grating 12 is (1),
It is determined by the equations (2) and (3).

Here, the number of light beams separated by the diffraction grating 12 may be at least two or more, and for example,
As shown in FIG. 5, the verifying light spot 2,
The recording light spot 1 which precedes the verifying light spot 2 in the moving direction of the magneto-optical disk 4 by the light spot interval 1 and the tracking light spot which precedes the recording light spot 1 by a predetermined distance. The light beams may be separated so as to form 16 and.

In the optical information recording / reproducing apparatus having the above-mentioned structure, as shown in FIG.
1, 0, 0, 1, 0, 0, ...} (FIG. 6)
(A)), at each time (FIG. 6 (D)), the magnetic head modulation circuit 8 synchronizes this recording data string with the basic clock by the synchronization circuit 6 to generate the magnetic head modulation signal 7 to generate the magnetic head 5. To drive. As a result, an external magnetic field corresponding to the recording data string is applied to the magneto-optical disk 4 (FIG. 6).
(B)). At this time, the light emitted from the LD 9 from the direction facing the magnetic head 5 (FIG. 6C) is pulse-emitted in two states of high power and low power, for example, in a 1-bit cycle of recording data. The high-power pulse light emission is light emission for overwriting, and when the power is high, the power of the recording light spot 1 is high enough to raise the data recording portion of the magneto-optical disk 4 to the Curie temperature. Therefore, the light quantity of both the light spots is preset by the shape and depth of the diffraction grating 12 so that the power of the verifying light spot 2 is sufficient to reproduce the recorded data without destroying the recorded data. is doing. Further, during normal reproduction that is not overwriting, a low-power optical pulse is emitted continuously or every 1 bit, and a reproduction signal is obtained from the recording light spot 1.

As shown in FIG. 7, in the data recording portion of the magneto-optical disk 4 which is easily magnetized by the recording light spot 1, for example, at time t1 when the recording data is 1, an external magnetic field is generated by the magnetic head 5. Data is recorded by being applied as a recording magnetic field in the recording direction, and at time t2 when the recording data is 0, the magneto-optical disk 4 moves in the moving direction and the external magnetic field is applied as the erasing magnetic field in the erasing direction. Data will be erased. In this way, the data is overwritten at each time corresponding to the recording data. On the other hand, the verification spot 2 also turns ON / O at a 1-bit cycle.
Since FF is performed, a magneto-optical reproduction waveform is obtained when the recorded data is irradiated at this verifying spot 2.

The diffraction grating 12 is a collimator lens 11
It is arranged between the lens and the objective lens 13, but not limited to this,
For example, it may be arranged between the collimator lens 11 and the LD 9, and depending on the magnification of the lens system, the formula (1), that is,
The pitch of the diffraction grating 12 may be determined so as to satisfy l = k · s · T.

Although the optical information recording / reproducing apparatus is of the CLV type, the optical information recording / reproducing apparatus of the MCAV type is not limited to this.

Therefore, in the optical information recording / reproducing apparatus of the first embodiment, the three operations of data erasing, recording and verifying are all performed by one rotation of the magneto-optical disk 4, so that the optical information at the time of recording is changed. High-speed recording is possible without requiring a rotation waiting time of the magnetic disk 4.

Further, in spite of simultaneous verification being possible, only one LD which is a light source is required, and simplification of the optical system, space saving and cost reduction can be realized.

Further, two light spots are arranged on the medium so as to be an integral multiple of the distance corresponding to the 1-bit cycle of the recording data sequence, and the light source emits pulses in synchronization with the clock of the 1-bit cycle. The light does not undergo the modulation found in normal light modulation recording.

FIGS. 8 and 9 relate to the second embodiment, and FIG.
FIG. 9 is a configuration diagram showing a schematic configuration of a main part of the optical information recording / reproducing apparatus, and FIG. 9 is an explanatory diagram illustrating a swing angle of a galvano mirror.

The optical information recording / reproducing apparatus of the second embodiment is
A CAV type optical information recording / reproducing apparatus, as shown in FIG. 8, a light source LD9 ', and a collimator lens 11' for collimating the light emitted from the LD9 '.
The galvano mirror 23 having a diffraction grating for diffracting the parallel light by the collimator lens 11, and the magneto-optical disk 4 for the light reflected and diffracted by the galvano mirror 23.
The objective lens 13 'for converging the light upward, the controller 20 for setting the reflection angle of the galvano mirror 23 to an angle according to the track of the magneto-optical disk 4 to be recorded, and the galvano mirror 23 by setting the controller 20. Mirror driving circuit 21 for driving the galvano mirror 2
And a mirror position detector 22 for detecting the angular position of 3 and the detection signal of the mirror position detector 22 is fed back to the mirror drive circuit 21 and compared with the setting signal from the controller 20 to reflect the galvano mirror 23. The angle is controlled so as to be the set angle by the controller 20.

The other structure is the same as that of the first embodiment.

In the diffraction grating of the Galvano mirror 23 of the optical information recording / reproducing apparatus of the second embodiment having such a configuration, the incident angle is θ1, the diffraction angle is θ2, the grating pitch is d, and the wavelength of the incident light is λ. Then, sin θ1−sin θ2 = ± n · (λ / d) (4) Here, n is the lattice order.

Now, in equations (1), (2), and (3), k = 5, s · T = 1.5 μm, and light wavelength λ = 830.
nm, and the focal length f of the objective lens 13 ′ is f = 3.8 mm, the grating pitch is d = 420.5 μm.
If the incident angle θ1 = 45 ° and the lattice order n = 1, then (4)
From the formula, sin θ2 = sin 45 ° ± 1.97 · (1/1000) ∴θ2 = 45.16 ° (+ 1st order), 44.84 ° (−1st order).

Further, for example, in order to move the 1.5 μm light spot, from the equation (3), l = f · tan θ ∴ θ = 0.0226 °.

As shown in FIG. 9, the + 1st-order diffraction angle θ 2 = 45.16 ° and the light spot movement angle θ = 0.0 at this time.
The swing angle of the galvanometer mirror 23 required to obtain the angle difference from 226 ° is obtained.

(Θ2′−θ1 ′) − (θ2−θ1) = 0.0226 ° (5) sin θ1′−sin θ2 ′ = λ / d From (6), θ1 ′ = 51.64 °, θ2 ′ = 51.82 °, and when the galvano mirror 23 has a diffraction grating with an incident angle of 45 ° and a diffraction pitch of 420.5 μm, ISO 130 m
In the mCAV disc, the pit period at the innermost circumference and the outermost circumference is doubled, so this ISO 130 mm CAV disc has a rotation speed of 3600 rpm and a basic clock of 7.5 MH.
When recording with z, the interval between the recording beam spot, which is the preceding beam, and the verifying beam spot, which is the backward beam, between the innermost circumference and the outermost circumference is 1 bit cycle (s).
To increase T = 1.5 μm, the galvano mirror 23 is 51.64 ° −45 ° = 6.64 ° (change in incident angle) ∴ 6.64 ° / 2 between the innermost circumference and the outermost circumference. = Rotate by 3.32 °.

Other functions are the same as those in the first embodiment.

As described above, the optical information recording / reproducing apparatus of the second embodiment controls the swing angle of the galvanometer mirror 23 by controlling the swing angle of the galvano mirror 23 even in the system such as the CAV system in which the recording pit period differs in the radial direction. As in the case of the first embodiment, all three operations of data erasing, recording and verifying are performed by one rotation of the magneto-optical disk 4, so that there is no need to wait for the rotation of the magneto-optical disk 4 during recording. High-speed recording is possible.

The other effects are the same as those of the first embodiment.

The present invention is not limited to the above-mentioned optical information recording / reproducing apparatus, but may be, for example, a write-once type information recording / reproducing apparatus, and the recording medium is not limited to one utilizing the magneto-optical effect. Instead, it is also effective for media of optical type or phase change.

[0045]

As described above, the optical information recording / reproducing apparatus of the present invention is capable of simultaneously performing erasing-recording-verifying without requiring a waiting time for rotation of the recording medium during recording. There is.

Further, according to the present invention, by separating the light beam by the diffraction grating, the number of light sources can be set to one and the outward optical system can be simplified, so that a space-saving and low-cost optical information recording / reproducing apparatus can be provided. There is an effect that it can be realized.

[Brief description of drawings]

FIG. 1 is an explanatory diagram illustrating a concept of an optical information recording / reproducing device according to a first embodiment.

FIG. 2 is a configuration diagram showing a configuration of a main part of the optical information recording / reproducing apparatus in the first example.

FIG. 3 is an explanatory diagram illustrating a magnetic head modulation signal according to the first embodiment.

FIG. 4 is an explanatory diagram illustrating separation of a light spot by the diffraction grating according to the first example.

FIG. 5 is an explanatory diagram illustrating a separated light spot according to the first embodiment.

FIG. 6 is a timing diagram illustrating a data recording method of the optical information recording / reproducing apparatus of FIG. 2 according to the first embodiment.

FIG. 7 is an explanatory diagram illustrating data recording and verification on the magneto-optical disk according to the first embodiment.

FIG. 8 is a configuration diagram showing a schematic configuration of a main part of an optical information recording / reproducing apparatus in a second example.

FIG. 9 is an explanatory diagram illustrating a swing angle of the galvanometer mirror according to the second embodiment.

[Explanation of symbols]

1 ... Recording optical spot 2… Light spot for verification 4 ... Magneto-optical disk 5 ... Magnetic head 8 ... Magnetic head modulation circuit 9 ... LD 10 ... LD modulation circuit 11 ... Collimating lens 12 ... Diffraction grating 13 ... Objective lens

[Procedure amendment]

[Submission date] December 4, 1991

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0018

[Correction method] Change

[Correction content]

As shown in FIG. 1, in the optical information recording / reproducing apparatus of the first embodiment, a recording data string to be recorded (see FIG.
In synchronism with (A)), a light beam is irradiated from a light source onto a recording medium, for example, a magneto-optical disk (FIG. 1C), and, for example, at time t1 when the recording data is 1 in the recording data string In Fig. 1 (E), the external magnetic field is
The data applied on the magneto-optical disk in the recording direction (FIG. 1B) is erased, and the information is recorded on the magneto-optical disk based on the recorded data. In this case, since the recorded data is 0 at the other times t2, t3, and t4, the external magnetic field is applied in the erasing direction, and the data recorded on the magneto-optical disk is simply erased.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0020

[Correction method] Change

[Correction content]

With the verifying spot 2 thus positioned, the data recorded at the time t1 by the recording light spot 1 is read out as a differential reproduction waveform at the time t4 (FIG. 1 (D)).

[Procedure 3]

[Document name to be amended] Statement

[Name of item to be corrected] 0027

[Correction method] Change

[Correction content]

As shown in FIG. 7, the data recording portion of the magneto-optical disk 4 heated to the Curie temperature by the recording light spot 1 has, for example, a time t1 when the recording data is 1.
Then, the external magnetic field is applied as a recording magnetic field in the recording direction by the magnetic head 5 to record data, and at time t2 when the recording data is 0, the magneto-optical disk 4 moves in the moving direction and the external magnetic field is erased. Data is erased by being applied as an erasing magnetic field in the direction. In this way, the data is overwritten at each time corresponding to the recording data. On the other hand, since the verifying spot 2 is also turned on / off in a 1-bit cycle, a magneto-optical reproduction waveform can be obtained when the recorded data is irradiated by the verifying spot 2.

[Procedure amendment 4]

[Document name to be amended] Statement

[Name of item to be corrected] 0032

[Correction method] Change

[Correction content]

Further, two light spots are arranged on the medium so as to be an integral multiple of the distance corresponding to the 1-bit cycle of the recording data sequence, and the light source emits pulses in synchronization with the clock of the 1-bit cycle. The light does not undergo modulation according to the recording data pattern as found in normal light modulation recording.

[Procedure Amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0036

[Correction method] Change

[Correction content]

In the diffraction grating of the galvanometer mirror 23 of the optical information recording / reproducing apparatus of the second embodiment having such a configuration, the incident angle is θ1, the diffraction angle is θ2, the grating pitch is d,
If the wavelength of the incident light is λ, then sin θ1 −sin θ2 = ± n · (λ / d) (4) Here, n is the diffraction order .

[Procedure correction 6]

[Document name to be amended] Statement

[Name of item to be corrected] 0037

[Correction method] Change

[Correction content]

Now, in equations (1), (2), and (3), k = 5, s · T = 1.5 μm, and light wavelength λ = 830.
nm, and the focal length f of the objective lens 13 ′ is f = 3.8 mm, the grating pitch is d = 420.5 μm.
If the incident angle θ 1 = 45 ° and the diffraction order n = 1, then (4)
From the formula, sin θ 2 = sin 45 ° ± 1.97 · (1/1000) ∴θ 2 = 45.16 ° (+ 1st order), 44.84 ° (−1st order).

[Procedure Amendment 7]

[Document name to be amended] Statement

[Correction target item name] 0038

[Correction method] Change

[Correction content]

Further, for example, in order to move the light spot of 1.5 μm, from the formula (3), the primary ray obtained by giving an angle difference to the zero-order ray by l = f · tan θ ∴θ = 0.0226 ° The objective lens
Incident light on the lens.

[Procedure Amendment 8]

[Document name to be amended] Statement

[Correction target item name] 0040

[Correction method] Change

[Correction content]

(Θ2′−θ1 ′) − (θ2−θ1) = 0.0226 ° (5) sin θ1′−sin θ2 ′ = λ / d From (6), θ1 ′ = 51.64 °, θ2 ′ = 51.82 °, and when the galvano mirror 23 has a diffraction grating with an incident angle of 45 ° and a diffraction pitch of 420.5 μm, ISO 130 mmC
With AV discs, the pit cycle at the innermost and outermost circumferences is 2
Since doubled, between the innermost and the outermost, leading beam recording beam spot and 2 times the interval between the verification beam spot is a rear beam are (2l = 2 × 5 ×
1.5 = 15 μm). For example,
When k = 5 at the innermost circumference of the disc, the disk radius is the innermost circumference
With a radius that is 6/5 times larger than, l = 5 × 1.5 × 6/5 =
It must be 9 μm, and l = 5 × 1.5 = at the innermost circumference
It is sufficient to increase l by 1.5 μm from 7.5 μm. Obey
Then, the galvano mirror 23 is rotated by 51.64 ° −45 ° = 6.64 ° (incident angle change) ∴ 6.64 ° / 2 = 3.32 °.

[Procedure Amendment 9]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 1

[Correction method] Change

[Correction content]

[Figure 1]

Claims (3)

[Claims] 1. At least a recording means for recording information by an overwrite method in a 1-bit cycle of a recording information sequence to be recorded on an information recording medium, and a detecting means positioned behind the recording means for detecting information. In the provided optical information recording / reproducing apparatus, the interval l between the recording means and the detecting means is set as follows: l = k · s · T k: integer s of 1 or more s: linear velocity of recording medium T: 1 bit of recording information sequence An optical information recording / reproducing apparatus characterized in that it is controlled to have a cycle. 2. The optical information recording / reproducing apparatus according to claim 1, wherein the recording means and the detecting means are arranged such that the distance is the distance l. 3. A diffraction grating for separating a light beam from a light source into a plurality of light beams, an objective lens for condensing the plurality of light beams from the diffraction grating on an information recording medium, and a separation by the diffraction grating. Out of the multiple light beams
Recording means for irradiating at least one light beam onto the information recording medium to record information by an overwrite system at a 1-bit cycle of a recording information sequence; and a recording means located behind the recording means and separated by the diffraction grating. In the optical information recording / reproducing apparatus including a detection unit for detecting information by another light beam, the diffraction grating has sin θ = λ / d l = f · tan θ 1 = k · s · T θ: diffraction angle λ An optical information recording / reproducing apparatus characterized in that: a wavelength of a light source d: a pitch of a diffraction grating f: a focal length of an objective lens 1: a space between a recording means and a detecting means.