JP2644110B2 - Optical recording / reproducing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording apparatus,
More specifically, the information recording medium is irradiated with a plurality of beams,
The present invention relates to an optical recording / reproducing apparatus for recording, reproducing, or erasing information by using a plurality of beams.

[0002]

2. Description of the Related Art A conventional optical recording / reproducing apparatus irradiates an information recording medium with a single beam, and performs recording, reproduction, or erasing of information with this beam. However, an optical recording / reproducing apparatus that irradiates an information recording medium with a plurality of beams has been considered for the purpose of further enhancing the functionality thereof.
The specific functions are as follows. Real-time monitor, b. Overwriting, c. It is roughly divided into parallel recording and playback. I.
Irradiates at least two beams on the same track of the information recording medium, and records information with the preceding beam,
The information immediately after recording is reproduced by the succeeding beam. As a result, there is an advantage in that recording can be performed all at once by performing recording with a single beam, reproducing information recorded after one rotation, and determining whether or not recording has been performed correctly. Also, b. Is a. In the same manner as described above, the information already recorded on the information recording medium is erased by the preceding beam, and new information is recorded by the succeeding beam. As a result, there is an advantage that the information can be recorded all at once by using a single beam and recording information after one rotation. Also, c. Irradiates a plurality of tracks of an information recording medium with respective beams to perform recording, reproduction, and erasure. This has the advantage that a large amount of information can be processed at one time.

A conventional optical recording / reproducing apparatus will be described with reference to FIGS. FIG. 13 is a perspective view showing a two-beam semiconductor laser of a conventional optical recording / reproducing apparatus, and FIG. 10 is a perspective view showing an optical recording / reproducing apparatus having a conventional configuration. FIG.
Is an optical recording / reproducing apparatus disclosed in, for example, Japanese Patent Application Laid-Open No. 2-161624. As shown in FIG. 13, a two-beam semiconductor laser 1 irradiates two recording beams 2 (shown by broken lines) and a reproducing beam 3 (shown by solid lines) parallel to each other, as shown in FIG. . Although an array type two-beam semiconductor laser device having two active regions in one device is shown here, each of the beams 2 and 3 is used.
May be arranged in parallel, as long as they can be independently driven. Reference numeral 4 denotes a collimator lens disposed on the beam exit side of the two-beam semiconductor laser device 1, 5 denotes a polarization beam splitter, and 6 denotes a quarter wavelength that polarizes the beam transmitted through the collimator lens 4 and guides the beam to the objective lens 7. It is a board. Numeral 8 denotes an information recording medium arranged close to the objective lens 7, and the quarter-wave plate 6 and the objective lens 7 are arranged between the polarizing beam splitter 5 and the information recording medium 8. 9 is an information recording medium 8
Guide grooves formed along the information recording direction of
Reference numeral 1 denotes a recording spot and a reproduction spot formed by the beams 2 and 3 irradiated along the guide groove 9. Reference numeral 12 denotes a convex lens for converging the reflected beam from the information recording medium 8 reflected by the polarization beam splitter 5, and reference numeral 13 denotes a half prism for dividing the converged beam from the convex lens 12 into reflected light and transmitted light. Reference numeral 14 denotes a roof-shaped wedge prism having two refraction surfaces 14a and 14b and a ridge line 14c. Are located. Although the wedge prism 14 is attached to the half prism 13 here, the wedge prism 14 may be disposed separately. 1
5a and 15b indicate that the recording beam 2 is the wedge prism 14
The recording beams 16a and 16b respectively refracted and emitted by the refraction surfaces 14a and 14b are the reproduction beam similarly emitted from the wedge prism 14 by the reproduction beam 3.
17 is a recording beam 15a, 15b and a reproducing beam 1
A quadrant photodetector that receives the four beams 6a and 16b and is disposed at a substantially condensing position of the beams, and receives the recording beams 15a and 15b at the light receiving surfaces 17a and 17b, respectively. The reproducing beams 16a and 16b are received by the light receiving surfaces 17c and 17d, respectively. The quadrant photodetector 17 is divided into light receiving surfaces 17a, 17c and light receiving surfaces 17b, 17d by dividing lines parallel to the ridge line 14c.
Further, it is divided into four by a dividing line orthogonal to the dividing line. Reference numeral 18 denotes an adder to which output signals from the light receiving surface 17a and light receiving surface 17b of the four-split photodetector 17 are input. The adder 18 outputs a monitor signal E of a recording beam. The non-inverting output terminal is connected to the light receiving surface 17a of the split photodetector 17,
7b, which is a differential amplifier for detecting a tracking error TE of the recording beam 2. Reference numeral 20 denotes an adder to which output signals from the light receiving surfaces 17c and 17d of the four-split photodetector 17 are input, and which outputs a reproduction output C of the reproducing beam 3, and 28 denotes a reproduction output C from the adder 20. A reproduction signal detection circuit 21 for obtaining a reproduction signal D from the light-receiving surface 1 of the quadrant photodetector 17
7c, the non-inverting output terminal of which is connected to the light receiving surface 17d of the quadrant photodetector 17,
Is a differential amplifier that detects the tracking error TE. Reference numeral 22 denotes a roof-shaped wedge prism having two refraction surfaces 22a, 22b and a ridge line 22c of the boundary line, and the ridge line 22c is optically orthogonal to the convergent beam emitted from the convex lens 12, that is, information recording. The half prism 13 is disposed in the optical path of the transmitted light so as to be in a direction orthogonal to the guide groove 9 of the medium 8. 23a, 2
Reference numeral 3b denotes a recording beam emitted when the recording beam 2 is refracted by the refraction surfaces 22a and 22b of the wedge prism 22, 24a and 24b similarly denote a reproducing beam from which the reproducing beam 3 is emitted from the wedge prism 22, and 25 denotes a reproducing beam. Recording beams 23a and 23b and reproducing beams 24a and 24
b is an eight-segment photodetector that receives the four beams b and is arranged at the beam condensing position and has eight light receiving surfaces 25a to 25h arranged in order. The light receiving surfaces 25c, 25
d and the dividing lines of the light receiving surfaces 25g and 25h are parallel to the ridge line 22c of the wedge prism 22, and the light receiving surfaces 25a and 25h
b and the respective dividing lines of the light receiving surfaces 25e and 25f are inclined at the same angle in the same direction. Then, the recording beams 24a, 2
4b is received with the dividing lines of the light receiving surfaces 25a and 25b and the dividing lines of the light receiving surfaces 25e and 25f as the centers, respectively.
The reproducing beams 24a and 24b are respectively received by light receiving surfaces 25c and 25c.
Light is received with the division line of 25d and the division lines of the light receiving surfaces 25g and 25h being the respective centers. Reference numeral 26 denotes a differential amplifier for receiving output signals from the light receiving surfaces 25a and 25f and light receiving surfaces 25b and 25e of the 8-split photodetector 25, and for detecting a focusing error FE of the recording beam.
Light receiving surfaces 25c, 25h and light receiving surface 25 of split photodetector 25
d, a differential amplifier that detects a focusing error FE from 25g. For example, the differential amplifiers 26 and 27 have inverting input terminals whose light receiving surfaces 25a and 25f and the light receiving surface 25
c and 25h, respectively, and their non-inverting input terminals are connected to the light receiving surfaces 25b and 25e and the light receiving surfaces 25d and 25g, respectively. The output terminals of the two differential amplifiers 26 and 27 are connected to a switch 33 for focusing error FE.
Connected to the stator side. Reference numeral 31 denotes an error signal switching circuit for switching and controlling a switch 32 for switching the tracking error TE between the recording beam and the reproducing beam and a switch 33 for switching the focusing error FE between the recording beam and the reproducing beam. The light receiving surfaces 25a, 2 of the split photodetector 25
5b, 25e, 25f and the differential amplifier 26, and similarly, the light receiving surfaces 25c, 25d, 25g, 25 of the eight-segment photodetector 25.
The h and the differential amplifier 27 constitute an optical system for executing a well-known focusing error detection method called the Foucault method.

Next, the operation of the conventional example will be described with reference to FIGS.
This will be described with reference to FIGS. FIG. 9 is a perspective view showing a wedge prism of a focusing error detecting optical system of a conventional optical recording / reproducing apparatus, FIG. 11 is a plan view showing a focusing error detecting system of a conventional optical recording / reproducing apparatus, and FIG. 12 is a conventional optical recording / reproducing apparatus. FIG. 14 is a perspective view showing a focusing error detecting optical system of the apparatus, FIG. 14 is an explanatory view showing an irradiation position of each spot of the conventional optical recording and reproducing apparatus, and FIG. 15 is an explanatory view of a recording and reproducing operation of the conventional optical recording and reproducing apparatus. . First, FIG.
When a recording signal A as shown in FIG. 1A is generated, the two-beam semiconductor laser 1 is driven based on the recording signal A. In FIG. 10, a recording beam 2 and a reproducing beam 3 emitted from a two-beam semiconductor laser 1 are converted into parallel beams of a parallel light beam by a collimator lens 4, and are divided into a polarizing beam splitter 5, a quarter-wave plate 6, and an objective lens 7. Information recording spot 10 and reproduction spot 11
Becomes The recording spot 10 includes recording information (for example, pulse width) of the recording / reproducing signal A as shown in FIG. 15A, and a pit having a shape B corresponding thereto as shown in FIGS. 15B and 14. 34 are sequentially formed on the information recording medium 8. On the other hand, the reproduction spot 11 following the recording spot 10 by a distance l is driven at a constant light intensity, and reproduces the written pit 34 after a time tl (several μ seconds) corresponding to the distance l. I will do it. That is, the recording spot 10 is reflected on the surface of the information recording medium 8 and forms a pit 34, and the reproduction spot 11 is reflected on the surface of the information recording medium 8 immediately after the pit 34 is formed.
The recording beam 2 and the reproducing beam 3 reflected by the information recording medium 8 pass through the objective lens 7 and the quarter-wave plate 6 again, but reciprocate through the quarter-wave plate 6 to change the polarization direction. Is rotated by 90 °, so that it is reflected by the polarization beam splitter 5. The reflected recording beam 2 and reproducing beam 3 are respectively converged by the convex lens 12, partially reflected by the half prism 13, and transmitted through the rest. These reflected lights are further split via a wedge prism 14 to become recording beams 15a and 15b and reproduction beams 16a and 16b, which are incident on a four-split photodetector 17 and are input to a tracking error detection system, where information is recorded. It is used for tracking correction of the beam irradiated on the medium 8. The light beam transmitted through the half prism 13 is shown in FIG.
As shown in FIG. 9 which is an enlarged view of the wedge prism 2 and the wedge prism 22, the recording beam 2
The light beam asymmetrically incident on c and incident on the split surface 22a is split into a recording beam 23a, and the light beam incident on the split surface 22b is split into a recording beam 23b. The reproduction beam 3 is also asymmetrically incident on the division line 22c, and the light beam incident on the division surface 22a becomes the reproduction beam 24a, and the light beam incident on the division surface 22b is divided into the reproduction beam 24b after the division. The laser beam is incident on the split photodetector 25 and is used for correcting a focusing error of a beam which is input to a focusing error detection system to be described later and irradiated on the information recording medium 8. The recording beam 2 reflected by the half mirror 13 is
The light is received by the photodetector and detected as a monitor signal E corresponding to the recording signal A, and is used to determine the presence or absence of a failure such as the information recording medium 8 and the optical path. On the other hand, the half prism 13
The reproduction beam 3 reflected by the detector is received by the photodetector and detected as a reproduction output C as shown in FIG. 15C corresponding to the pit shape B, and further subjected to waveform processing in a reproduction signal detection circuit 28. It is detected as a pulse-shaped reproduced signal D as shown in FIG. The reproduction signal D thus obtained is compared with the recording signal A, and is used for determining the presence or absence of a defect in information recording. Here, the case where the reflectivity of the information recording medium 8 is reduced due to the formation of the pits 34 is shown, but the information recording state is similarly determined for the information recording medium 8 whose reflectivity is increased by the pits. You can do it. The reproduction signal D is different from the recording signal A by the time tl.
It is considered that the presence or absence of a recording defect can be determined almost in real time because the time tl is on the order of several microseconds. When reproducing the information recorded on the information recording medium 8, the reproducing beam 3 is output from the two-beam semiconductor laser 1.
Out, and the reproduced signal may be detected by the reproduction signal detection circuit 28.

Next, a recording beam 2 and a reproducing beam 3
Is performed with reference to FIG. FIG. 11 shows an optically equivalent state when the configuration of FIG. 10 is viewed from above in plan view (however,
The front of the light-receiving surface of the eight-segment photodetector 25 is also shown for easy understanding of the state of the structure. ), The parts necessary for detecting a focusing error are shown.

FIG. 1A shows a state in which the information recording medium 8 is at a focal point F with respect to the objective lens 7, the recording beam 2 is incident on the wedge prism 22, and is divided by a dividing line 22c. Is the recording beam 23a
The beam incident on the division surface 22b is a recording beam 23.
b, the light receiving surface 2 of each of the eight divided photodetectors 25
Light is condensed on the division line between 5a, 25b and light receiving surfaces 25e, 25f. The reproduction beam 3 is incident on the wedge prism 22, and a beam incident on the division surface 22a at the division line 22c is divided into a reproduction beam 24a, and a beam incident on the division surface 22b is divided into a reproduction beam 24b. The light receiving surfaces 25c and 25d of the split photodetector 25 and the light receiving surface 25g,
The light is condensed on the division line of 25h. In this case, the output signal (of the recording beam) FE of the differential amplifier 26 and the output signal (of the reproducing beam) FE of the differential amplifier 27 are both zero (FE = 0).

FIG. 1B shows a state in which the information recording medium 8 is farther from the objective lens 7 than the focal point F, and the recording beam 2 is incident on the wedge prism 22 and is divided by a dividing line 22c.
The beam incident on the dividing surface 22a at the boundary of
3a, the beam incident on the split surface 22b is split into a recording beam 23b, which is incident on the light receiving surface 25a and the light receiving surface 25f of the 8-split photodetector 25, respectively.
Is incident on the wedge prism 22, the beam incident on the dividing surface 22a at the dividing line 22c is converted into a reproducing beam 24a,
The beam incident on the split surface 22b is split into a reproducing beam 24b, and each of the light receiving surfaces 25c of the eight-split photodetector 25 is split.
Is incident on the light receiving surface 25h. In this case, the differential amplifier 26
Output signal (of recording beam) FE and differential amplifier 27
FE (of the reproducing beam) is negative (FE
<0).

FIG. 1C shows a state in which the information recording medium 8 is closer to the objective lens 7 than the focal point F, and the recording beam 2 is incident on the wedge prism 22 and is divided by a dividing line 22c.
The beam incident on the dividing surface 22a at the boundary of
3a, the beam incident on the split surface 22b is split into a recording beam 23b, which is incident on the light receiving surface 25b and the light receiving surface 25e of the 8-split photodetector 25, respectively.
Is incident on the wedge prism 22, the beam incident on the dividing surface 22a at the dividing line 22c is converted into a reproducing beam 24a,
The beam incident on the splitting surface 22b is split into a reproducing beam 24b, and the light receiving surface 25d of the eight-split photodetector 22 is received.
Is incident on the light receiving surface 25g. In this case, the differential amplifier 26
Output signal (of recording beam) FE and differential amplifier 27
Output signals (of the reproducing beam) FE are positive (FE
> 0). Although the conventional example shows an example of a two-beam recording / reproducing apparatus, the same configuration can be applied to a multi-beam optical recording / reproducing apparatus having two or more beams. Further, in the focusing error detection device according to the conventional example, a method in which a focusing error detection beam is divided and separated in the track direction by a wedge prism having a dividing line in a direction perpendicular to the track has been described. There is also a conventional example in which the beams are separated in a direction perpendicular to the track in order to avoid interference of the beams.

[0009]

In the conventional multi-beam optical recording / reproducing apparatus having the above-mentioned structure, in detecting a focusing error of a recording / reproducing light beam, a wedge having a dividing line perpendicular to a track is used. In order to use a prism, a plurality of recording / reproducing light beams which are also arranged in a direction perpendicular to the track are incident on each of the dividing lines in an asymmetrical manner with respect to each beam, are divided, and light beams having different light intensity ratios are incident on the photodetectors, respectively. . A focus error detection signal is obtained from the difference signal of each detector output, but this signal becomes asymmetric,
The linear zone of the focus error detection signal is narrowed, the servo is unstable due to external disturbance, and a focus offset is generated, which adversely affects reproduction signal detection. In particular, in an optical head having a large number of beams, this effect becomes large, and there is a case where the beam is hardly split at the end beam, and there is a problem that the focus error signal cannot be detected by the Foucault method.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and divides a plurality of recording / reproducing light beams into two symmetrically in a direction perpendicular to the track as focusing error detecting light beams. It is an object of the present invention to provide an optical recording / reproducing apparatus which can obtain a focus error detection signal which is stable and free from offset.

[0011]

Means for Solving the Problems An optical recording reproducing apparatus according to the present invention, out of the plurality of light sources to the track of the information recording medium
Optical storage for recording and reproducing information by condensing the emitted light beam
In the recording / reproducing apparatus, a plurality of
It is located where the interval between reflected light beams is large ,
The reflected light of the light beam from the information recording medium is connected to the center of each circular light beam at a position passing through the center of each circular light beam.
Along two directions perpendicular to the line
A beam splitting means for splitting the bundle have a dividing line into the light receiving surface
And the light beam splitting means splits the light beam into two light beams.
Number of reflected luminous fluxes independently, and the dividing line of each light receiving surface is set
And a plurality of four-division photodetector for receiving in the central, the
Focus independent from multiple quadrant photodetectors
It is obtained to detect the Nguera signal.

Further, as a light beam separating means, one triangle
Rhythm, Noso two reflected light beam from said information recording medium
The respective centers are arranged so as to be located on both side surfaces of the triangular prism , respectively .

[0013] The light beam separating means may have a predetermined interval.
The two triangular prisms spaced apart from each other are divided into two triangular prisms.
Each side of the prism is 2
Substantially perpendicular to the line connecting the centers of the reflected light beam of the present, opposing side side surface of the two triangular prisms, each of the above
It is arranged so as to be located at the center of two reflected light beams from the information recording medium .

Further, two triangles are used as a light beam separating means.
With the prism upside down, part of it overlaps,
The side surfaces of the two triangular prisms are orthogonal to the line connecting the centers of the two reflected light beams from the information recording medium, and
The two reflected light beams from the medium are arranged so that the centers of the two reflected light beams are located on the respective side surfaces on the overlapping side of the two triangular prisms.

[0015] Further, as a light beam separating means, the three triangular prisms, side by side as normal next contact the triangular prisms have included angles, the three sheets of triangular prisms
The side of the system is in the two reflected light beams from the information recording medium.
At right angles to the line connecting the hearts, two counters from the information recording medium
The center of the emitted light beam is next to the above three triangular prisms
They are arranged so as to be located on the contact surface .

[0016]

According to the present invention, since a plurality of recording / reproducing light beams are split at the center of a circular light beam, the split light beams are correctly formed into a semicircular shape.

[0017]

Embodiment 1 One embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a perspective view showing an optical recording / reproducing apparatus according to Embodiment 1 of the present invention. FIG. 2 is an explanatory diagram of a focusing error detection system of the optical recording / reproducing apparatus according to the first embodiment of the present invention. FIG. 3 is a perspective view showing a focusing error detecting optical system of the optical recording / reproducing apparatus according to Embodiment 1 of the present invention. FIG. 4 is a perspective view showing a triangular prism of a focusing error detecting optical system of the optical recording / reproducing apparatus according to Embodiment 1 of the present invention. In FIG. 1, reference numerals 1 to 21 are the same as in the conventional example, and the description is omitted. Reference numeral 35 denotes a triangular prism. As shown in FIG. 4, the distance d between the optical axes of the recording beam 2 and the reproducing beam 3 is larger than the light beam radius r of each light beam. Is located inside. The width of the triangular prism 35 is given equal to the distance d between the optical axes of the recording beam 2 and the reproducing beam 3. 23a is a recording beam transmitted through a space beside the triangular prism 35, 23b is a recording beam emitted by refracting the recording beam 2 by the triangular prism 35, and 24b is a reproducing beam transmitted through a space beside the triangular prism 35. Beam, 2
Reference numeral 4a denotes a reproducing beam emitted from the reproducing beam 3 after being refracted by the triangular prism 35, and 25 denotes recording beams 23a and 2a.
An eight-segment light detector that receives four beams 3b and reproduction beams 24a and 24b, and is disposed at a beam condensing position and has eight light receiving surfaces 25a to 25h in which four light receiving surfaces are arranged in two rows. It is a vessel. The light receiving surfaces 25e, 25f
And the light receiving surfaces 25g and 25h are each divided by a triangular prism 35.
Are parallel to the side surfaces 35a and 35b of the
a, 25b and the dividing lines of the light receiving surfaces 25c, 25d are inclined at the same angle in the same direction , and the side surfaces 35a,
Parallel to 35b. Then, the recording beams 23a, 2
3b is received with the dividing lines of the light receiving surfaces 25a and 25b and the dividing lines of the light receiving surfaces 25c and 25d at the center, respectively.
The reproduction beams 24a and 24b are respectively received by light receiving surfaces 25e and 25e.
Light is received with the division line of 25f and the division lines of the light receiving surfaces 25g and 25h being the respective centers. Reference numeral 26 denotes a differential amplifier for receiving output signals from the light receiving surfaces 25a and 25b and light receiving surfaces 25c and 25d of the 8-split photodetector 25, and detecting a focusing error FE of the recording beam.
The light receiving surfaces 25e and 25f of the split photodetector 25 and the light receiving surface 25
g, a differential amplifier that detects FE from 25h. For example, the differential amplifiers 26 and 27 have their non-inverting input terminals connected to the light receiving surfaces 25b and 25c and the light receiving surfaces 25e and 25h, respectively, and their inverting input terminals connected to the light receiving surfaces 25a and 25d and the light receiving surfaces 25f and 25g, respectively. Have been. The output terminals of the two differential amplifiers 26 and 27 have a focusing error F
The switch E is connected to the stator side of the switch 33. Reference numeral 31 denotes an error signal switching circuit for switching and controlling a switch 31 for switching a tracking error TE between the recording beam 2 and the reproducing beam 3 and a switch for switching a focusing error FE between the recording beam 2 and the reproducing beam 3. The triangular prism 35, the light receiving surfaces 25 a, 25 b, 25 c, 25 d of the eight-divided photodetector 25 and the differential amplifier 26, similarly to the light-receiving surface 2 of the eight-divided photodetector 25.
The reference numerals 5e, 25f, 25g, 25h and the differential amplifier 27 constitute an optical system for executing a well-known focusing error detection method called the Foucault method.

Next, the operation of the present invention shown in FIGS. 1 to 4 will be described. The operation of recording and reproducing information on and from the information recording medium 8 using the recording beam 2 and the reproducing beam 3 from the two-beam semiconductor laser element 1 is the same as the operation of the above-described conventional optical recording and reproducing apparatus. Here, a focusing error detection optical system and detection which are features of the present embodiment will be described. First, the focusing error detection optical system will be described. In FIG. 3, the recording beam 2 transmitted through the half prism 13 is transmitted symmetrically to the side surface 35a of the triangular prism 35, half of the recording beam 2a passes through the space beside the triangular prism as it is, and the half is converted to the triangular prism. It is incident and split into recording beams 23b. Similarly, the reproducing beam 3 is also divided symmetrically on the side surface 35b, and the reproducing beams 24a, 24b
Get. The recording beams 23a and 23b and the reproducing beams 24a and 24b are incident on the eight-divided photodetector 25 and are used for correcting a focusing error of the beam irradiated on the information recording medium 8.

Next, detection of a focusing error of a recording beam and a reproducing beam will be described with reference to FIG. FIG. 2 shows an optically equivalent state when the configuration of FIG. 1 is viewed from above in a plan view (however, in order to easily understand the state of the structure of the eight-segment photodetector 25, FIG. The front of the light receiving surface is also shown.
Each dividing line of the light receiving surface 25c and the light receiving surface 25c is parallel to the side surfaces 35a and 35b of the triangular prism. ), The parts necessary for detecting a focusing error are shown.

FIG. 3A shows a state in which the information recording medium 8 is at the focal point F with respect to the objective lens 7, and the recording beam 2 and the recording beam 23 a are bordered on the side surface 35 a of the triangular prism 35. Beam 23b, each of which is 8
Light receiving surfaces 25a, 25b and light receiving surface 25 of split photodetector 25
Light is condensed on the dividing lines of c and 25d. Similarly, the reproducing beam 3 is divided into the reproducing beam 24a and the reproducing beam 24b at the side surface 35b, and is condensed on the dividing lines of the light receiving surfaces 25g and 25h and the light receiving surfaces 25e and 25f of the 8-split photodetector 25, respectively. You. In this case, the output signal (of the recording beam) FE of the differential amplifier 26 and the output signal (of the reproducing beam) FE of the differential amplifier 27 are both zero (FE = 0).

FIG. 3B shows a state in which the information recording medium 8 is farther than the focal point F with respect to the objective lens 7, and the recording beam 2 is separated from the recording beam 23 a by the side surface 35 a of the triangular prism 35. The light is split into recording beams 23b and condensed on the light receiving surfaces 25b and 25c of the 8-split photodetector 25, respectively. Similarly, the reproducing beam 3 is divided into a reproducing beam 24a and a reproducing beam 24b on the side surface 35b, and the light receiving surface 25h and the light receiving surface 2 of the 8-split photodetector 25 are respectively divided.
The light is focused on 5e. In this case, the output signal (of the recording beam) FE of the differential amplifier 26 and the output signal (of the reproduction beam) FE of the differential amplifier 27 are each positive (FE> 0).
Becomes

FIG. 3C shows a state in which the information recording medium 8 is closer to the objective lens 7 than the focal point F. The recording beam 2 is separated from the recording beam 23 a by the side surface 35 a of the triangular prism 35. The beam is split into recording beams 23b and condensed on the light receiving surfaces 25a and 25d of the 8-split photodetector 25, respectively. Similarly, the reproducing beam 3 is divided into a reproducing beam 24a and a reproducing beam 24b at a side surface 35b , and the light receiving surface 25g and the light receiving surface 2 of the 8-split photodetector 25 are respectively divided.
It is focused on 5f. In this case, the output signal (of the recording beam) FE of the differential amplifier 26 and the output signal (of the reproducing beam) FE of the differential amplifier 27 are each negative (FE <0).
Becomes

Embodiment 2 FIG. 5 is a view showing a beam separating means of a focusing error detection system according to another embodiment of the present invention. In Embodiment 1, the recording beam 2 and the reproducing beam 3 are located in the region between the optical axes. Although one triangular prism is arranged to divide the beam, two triangular prisms 35c and 35d are used to define the space between the optical axes of the recording beam 2 and the reproducing beam 3 as a space, Even if the triangular prisms 35c and 35d are respectively arranged at the positions of the half light flux of each beam outside the beam, the beam can be divided similarly. Further, in this configuration, the interval 35a between the opposing side surfaces of the triangular prisms 35c and 35d,
There is an advantage that the distance between the beams 2 and 3 can be adjusted by adjusting 35b.

Embodiment 3 FIG. 6 shows another embodiment of the present invention.
Similarly to the above, a configuration is obtained in which beam splitting and adjustment of the interval between the dividing lines can be performed using the two triangular prisms 35c and 35d. This embodiment is characterized in that the triangular prisms 35c and 35d are used upside down so as to be divided by the side surfaces 35a and 35b.

Embodiment 4 FIGS. 7 and 8 show another embodiment of the present invention.
If the normal line of the triangular prism adjacent to the boundary between 5a and 35b has an angle, it is separated and divided with respect to the side surface. The angle between the normals can be adjusted to the arrangement of the detectors and optical components. For example, FIG. 7 shows an example in which the same triangular prism as the triangular prism 35d is used upside down for the triangular prisms 35c and 35e of the first embodiment. As shown in FIG. 8, the triangular prism 35d may be a plane perpendicular to the recording / reproducing light beam.

[0026]

As described above, according to the present invention, in a focusing error detection system, a plurality of reflected light beams from an information recording medium are converted into semicircular light beams by a triangular prism symmetrically in a direction perpendicular to a track. Since the light is divided and received by the photodetector, there is an effect that a focusing error detection signal obtained by the Foucault method is stable.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an optical recording / reproducing apparatus according to Embodiment 1 of the present invention.

FIG. 2 is an explanatory diagram of a focusing error detection system of the optical recording / reproducing apparatus according to the first embodiment of the present invention.

FIG. 3 is a perspective view showing a focusing error detecting optical system of the optical recording / reproducing apparatus according to Embodiment 1 of the present invention.

FIG. 4 is a perspective view showing a triangular prism of a focusing error detecting optical system of the optical recording / reproducing apparatus according to Embodiment 1 of the present invention.

FIG. 5 is a perspective view showing a triangular prism of a focusing error detection system of an optical recording / reproducing apparatus according to Embodiment 2 of the present invention.

FIG. 6 is a perspective view showing a triangular prism of a focusing error detection system of an optical recording / reproducing apparatus according to Embodiment 3 of the present invention.

FIG. 7 is a perspective view showing a triangular prism of a focusing error detection system of an optical recording / reproducing apparatus according to Embodiment 4 of the present invention.

FIG. 8 is a perspective view showing a triangular prism of a focusing error detection system of an optical recording / reproducing apparatus according to Embodiment 4 of the present invention.

FIG. 9 is a perspective view showing a wedge prism of a focusing error detection system of a conventional optical recording / reproducing apparatus.

FIG. 10 is a perspective view showing a conventional optical recording / reproducing apparatus.

FIG. 11 is a plan view showing a focusing error detection system of a conventional optical recording / reproducing apparatus.

FIG. 12 is a perspective view showing a focusing error detecting optical system of a conventional optical recording / reproducing apparatus.

FIG. 13 is a perspective view showing a two-beam semiconductor laser device of a conventional optical recording / reproducing apparatus.

FIG. 14 is an explanatory diagram showing the irradiation position of each spot of the conventional optical recording / reproducing apparatus.

FIG. 15 is an explanatory diagram of an operation of a conventional optical recording / reproducing device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 2-beam semiconductor laser 2 Recording beam 3 Reproduction beam 7 Focusing means 8 Information recording medium 9 Information track 25 Photodetector 35 Triangular prism

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Naoyuki Egusa 1 Baba Zujo Station, Nagaokakyo City, Kyoto Prefecture Mitsubishi Electric Corporation Electronic Product Development Laboratory (56) References JP-A-51-150303 (JP, A)

Claims (5)

(57) [Claims] An information recording medium includes a plurality of light sources on a track .
In the optical recording and reproducing apparatus for recording and reproducing information by converging the al emitted light beams, are arranged at intervals of a plurality of reflected light beam from said information recording medium is large, the plurality of light beams the reflected light from the information recording medium, position passing through the center of each circular light flux
Orthogonal to the line connecting the centers of each circular beam
Along the direction, and beam splitting means for splitting each of the two light beams have a dividing line into the light receiving surface, two by the beam splitting means
The reflected light beams divided into light beams of
And a plurality of four-division photodetector for receiving the dividing line of the light receiving surface in the central, independent Four from the plurality of four-divided light detector
An optical recording / reproducing apparatus for detecting a caching error signal . 2. The optical recording / reproducing apparatus according to claim 1, wherein the light beam separating means comprises: one triangular prism; and two light beams reflected from the information recording medium , each having a center.
An optical recording / reproducing apparatus, which is disposed so as to be located on both side surfaces of a square prism . 3. The optical recording / reproducing apparatus according to claim 1 , wherein said light beam separating means is arranged at a predetermined interval.
Each of the two triangular prisms
Central sides of the two reflected light beam from said information recording medium
Substantially perpendicular to the line connecting the mutually of the two triangular prisms
The opposing side surfaces are respectively from the information recording medium.
An optical recording / reproducing apparatus, which is arranged so as to be located at the center of two reflected light beams . 4. The optical recording / reproducing apparatus according to claim 1 , wherein the light beam separating means turns the two triangular prisms upside down.
The two triangular prisms are partially overlapped.
Is the center of two reflected light beams from the information recording medium.
Perpendicular to the line connecting the morphism anti two from said information recording medium
An optical recording / reproducing apparatus, wherein a center of a light beam is disposed on each side of an overlapping side of the two triangular prisms. 5. The optical recording / reproducing apparatus according to claim 1 , wherein the light beam separating means includes three triangular prisms adjacent to each other.
Adjacent so that the normals of the triangular prism are at an angle to each other
And the side surfaces of the three triangular prisms are
Perpendicular to the line connecting the centers of the two reflected light beams from the body, the center of the reflected light beam of the two from the information recording medium, respectively
An optical recording / reproducing apparatus, wherein the three triangular prisms are arranged so as to be positioned adjacent to each other.