JPH0954974A - Optical pickup - Google Patents

Abstract

PROBLEM TO BE SOLVED: To monitor a recored/erased state while instantaneously reproducing information from a just recorded/erased information track by reproducing the information from a information track recorded/erased with a main beam with a subbeam. SOLUTION: The liminous flux emitted from a semiconductor laser 1 is separated into three luminous fluxes of a 0-order diffracted light 4, a plus 1-st order diffracted light 5 and a minus 1-st order diffracted light 6 by a luminous flux separating means consisting of a the diffraction grating 3 provided in a hologram unit 2. The luminous fluxes 4-6 are respectively transmitted through a grating plane 7 to be exited from the unit 2 and are transmitted through a quater-wave plate 8 to become circular polarized lights from linearly polarized lights and from optical spots (SPs) 11-13 through an objective lens 9. The SP11 performs the recording/erasing/reproducing of information and the SPs12, 13 detect tracking error signals. Moreover, the SP13 is made to be an ellipse long in a radial direction and reproduces information which are recorded/erased by the SP11. Thus, the recorded/erased state is instantaneously monitored without providing a light source for monitoring.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup for recording, reproducing and erasing information on an information recording medium such as an optical disc.

[0002]

2. Description of the Related Art Write-once optical discs such as CD-R are
Information pits are recorded by forming a light spot with laser light by an optical pickup and heating it to a high temperature to change the reflectance. In this write-once optical disc, information recording is performed at a high temperature. Therefore, the formation state of information pits can be grasped by detecting the reflectance of the light spot used for recording.

On the other hand, in an information recording medium such as a phase-change type information recording medium in which information pits are formed in the process of being heated by a laser beam by an optical pickup and then being cooled, an information pit is formed for a light beam for recording information. Even if the reflected light of the information recording medium is monitored, only the heated portion of the information recording medium is detected, and the cooled portion of the information recording medium is not detected. Therefore, the information pit is accurately detected. It is not possible. Therefore, it is necessary to monitor the information pits after the information recording medium is cooled to some extent and the information pits are formed.

Therefore, in the optical pickup, a monitor light source different from the recording light source is provided to form a monitor light spot after the recording light spot on the information recording medium, and the monitor light spot is sufficiently cooled on the information recording medium. It is conceivable that the information pits formed by monitoring the information pits are monitored to grasp the formation state of the information pits.

Further, Japanese Patent Laid-Open No. 7-6446 discloses a first light beam for recording or erasing information.
An optical pickup is provided with a light source and a second light source for providing a second beam for reproducing information, information is recorded by the first light beam, and the information recording state is reproduced and confirmed by using the second light beam as a reproduction beam. A magneto-optical recording / reproducing apparatus is described. Further, in Japanese Unexamined Patent Publication No. 6-325400, a diffraction grating that amplitude-divides a light flux from a light source is provided in an optical pickup, and a plurality of light spots are formed in series on the information recording medium in the tangential direction to form one light spot. There is described an optical information recording / reproducing apparatus that executes verification in substantially real time by detecting recorded information on an information recording medium by using one other light spot immediately after recording information by using the light spot. .

[0006]

In the above-mentioned optical pickup, since the monitor light source is provided separately from the recording light source, there is a concern that the number of parts and the assembly process may increase, resulting in cost increase and power consumption increase. . Further, the one disclosed in Japanese Patent Laid-Open No. 7-6446 requires at least two light sources for the optical pickup, and thus has a large number of parts, which results in a large number of assembly adjustment steps and a large apparatus. .

Further, in the method disclosed in Japanese Patent Laid-Open No. 6-325400, since a plurality of light spots are formed in series on the information recording medium in the tangential direction, one main beam and a main beam are used as a tracking error detecting method. In order to adopt the so-called three-beam method in which tracking error detection is performed with two sub-beams that are displaced in the radial direction, at least four recording light spots, verifying light spots, and two sub-beam light spots are used. A light spot is needed. In order to obtain these from one light source, there is no semiconductor laser diode that is a light source that can emit a sufficient amount of light, and power consumption increases.

According to the present invention, the information recording or erasing state can be monitored by immediately reproducing the information from the information track just recorded or erased on the information recording medium without adding a new light source. It is an object of the present invention to provide an optical pickup which can be put into an optimum recording or erasing state without increasing the number of parts and the assembling process, has no special cost increase, is highly reliable and consumes less power.

[0009]

In order to achieve the above object, the invention according to claim 1 is an optical pickup for recording, reproducing and erasing information on an information recording medium, and a light source which emits a light beam and a light source from the light source. A light beam separating means for dividing the emitted light beam into a main beam and two sub-beams, and a main beam and two sub-beams from the light beam separating means are condensed on the information recording medium to form three light spots. Objective lens, the main beam reflected by the information recording medium and the main beam on the information recording medium such that a part of the sub beam irradiates a portion where information is recorded or erased by the main beam. A tracking error signal is obtained from the two sub-beams, and the sub-beam is recorded from or erased by the main beam on the information recording medium at the time of recording or erasing information. It is obtained by a means for reproducing the real information in the beam.

According to a second aspect of the present invention, in the optical pickup according to the first aspect, the light spot formed by the sub beam on the information recording medium has an elliptical shape elongated in the radial direction.

According to a third aspect of the present invention, in the optical pickup according to the first aspect, a light spot formed by the sub beam on the information recording medium is large in a portion close to the main beam and long in the radial direction. It is egg-shaped.

According to a fourth aspect of the invention, a light source for emitting a light beam, a light beam separating means for dividing the light beam emitted from the light source into a main beam and a plurality of sub-beams, and a main beam from the light beam separating means and a plurality of light beams are provided. And an objective lens for forming a plurality of light spots by condensing the sub-beams of the sub-beam on the information recording medium, and performing the recording, reproducing, and erasing of information on the information recording medium. Is a diffraction grating in which the intensity distribution of diffracted light is non-uniform.

According to a fifth aspect of the present invention, in the optical pickup according to the fourth aspect, the diffraction grating distributes the diffraction efficiency by partially changing the groove depth.

According to a sixth aspect of the present invention, in the optical pickup according to the fourth aspect, the diffraction efficiency of the diffraction grating is different between the central portion and the end portion in one direction, and the diffraction efficiency in the direction orthogonal to the one direction. Is a uniform diffraction grating.

According to a seventh aspect of the present invention, in the optical pickup according to the fourth aspect, the diffraction grating lowers the diffraction efficiency at the central portion in the direction in which the divergence angle of the light flux emitted from the light source is large, and diffracts at the end portions. The efficiency is increased and the diffraction efficiency in the direction in which the divergence angle of the light flux emitted from the light source is small is made uniform.

According to an eighth aspect of the present invention, in the optical pickup according to the fourth aspect, the diffraction grating lowers the diffraction efficiency in the central portion in the direction in which the divergence angle of the light flux emitted from the light source is large and diffracts the light in the end portion. The efficiency is increased, the diffraction efficiency of the central portion is increased and the diffraction efficiency of the end portions is decreased in the direction in which the spread angle of the light flux emitted from the light source is small.

According to a ninth aspect of the present invention, there is provided an optical pickup for recording, reproducing and erasing information on an information recording medium,
A light source for emitting a light beam, a light beam separating means for dividing the light beam emitted from the light source into a main beam and two sub-beams, and a main beam and two sub-beams from the light beam separating means are collected on the information recording medium. The main lens on the information recording medium is provided with an objective lens that emits light to form three light spots, and a photoelectric conversion element that detects each of the main beam and the two sub beams reflected by the information recording medium. Information is recorded or erased by a beam so that a part of the sub beam irradiates the information track, and a part of the sub beam reflected by the information recording medium is detected by the photoelectric conversion element. The reproduction signal of the information recorded or erased by the main beam on the recording medium is obtained.

According to a tenth aspect of the invention, in the optical pickup according to the first or ninth aspect, a part of the sub-beam is detected by a photoelectric conversion element, and the main beam is used for recording or erasing. The information reproduction signal is provided with a correction unit for correcting the reproduction signal of the information with a light source drive signal for changing the light amount of the light source according to the information signal recorded on the information recording medium.

According to an eleventh aspect of the present invention, in the optical pickup according to the first or ninth aspect, a part of the sub-beam is detected by a photoelectric conversion element and recorded or erased by the main beam and left. The information reproduction signal is obtained by sampling only when the light source drive signal for changing the light amount of the light source has a maximum value in accordance with the information signal recorded on the information recording medium.

According to a twelfth aspect of the present invention, in the optical pickup according to the first or ninth aspect, a part of the sub-beam is detected by a photoelectric conversion element, and the main beam is used for recording or erasing. The reproduction signal of information is obtained by sampling only when the light source drive signal for changing the light amount of the light source has the longest and uniform value according to the information signal recorded on the information recording medium.

[0021]

1 shows an incident system from a light source to an information recording medium in a first embodiment of the present invention. The first embodiment is an embodiment of the invention described in claims 1, 2, 4 to 6, 9, and 10, and is an optical pickup for recording, reproducing, and erasing information on an information recording medium of an optical disc. Here is an example. The light beam emitted from the semiconductor laser 1 which is a light source is divided into three light beams of 0th-order diffracted light 4, + 1st-order diffracted light 5, and -1st-order diffracted light 6 by the light-flux separation means 3 formed of a diffraction grating provided in the hologram unit 2. .

About 80% of the luminous flux emitted from the semiconductor laser 1 is the 0th-order diffracted light 4, and about 10% is the + 1st-order diffracted light 5, -1.
It becomes the next diffracted light 6. These three light beams 4, 5 and 6 respectively pass through the first grating surface 7, go out of the hologram unit 2 and pass through the 1/4 λ plate 8 to be changed from linearly polarized light to circularly polarized light, and pass through the objective lens 9. The three optical spots 11, 12, which are irradiated on the optical disc 10,
13 is formed.

FIG. 2 shows a light spot 1 on the optical disk 10.
1, 12, and 13 are shown. The three light fluxes of the 0th-order diffracted light 4, the + 1st-order diffracted light 5, and the -1st-order diffracted light 6 divided by the diffraction grating 3 provided in the hologram unit 2 are the optical disc 1
The light spots 11, 12, and 13 are formed on the 0, respectively. Here, the light spot 11 formed by the 0th-order diffracted light 4 is for recording, erasing, and reproduction of information, and the light spots 12, 13 formed by the + 1st-order diffracted light 5 and the -1st-order diffracted light 6 are It is for detecting a tracking error signal for following the information track 14 on the optical disc 10. The optical disc 10 has a plurality of information tracks 14 formed concentrically or spirally, and is rotationally driven by a spindle motor.

Further, the light spot 13 formed by the -1st-order diffracted light 6 also plays a role of reproducing the information recorded or erased on the information track 14 on the optical disk 10 by the light spot 11 formed by the 0th-order diffracted light 4. is there. +1
The light spots 12 and 13 formed by the 5th-order diffracted light 5 and the -1st-order diffracted light 6 have a long elliptical shape in the direction (radial direction) orthogonal to the information track 14 on the optical disc 10, and a part thereof is the 0th-order diffracted light. An information pit 15 recorded or erased on the information track 14 on the optical disk 10 is irradiated with the light spot 11 formed by 4.

FIG. 3A is an enlarged view of the diffraction grating 3 provided on the hologram unit 2, and FIG.
The distribution of the diffraction efficiency of is shown. The diffraction grating 3 is a grating in which the groove depths are distributed so that both ends are deep and the central part is shallow. Since the groove depth of this diffraction grating 3 is proportional to the diffraction efficiency, the diffraction efficiency of the central portion is small. The distribution of the groove depth of the diffraction grating 3 is in the tangential direction, but there is no distribution of the groove depth of the diffraction grating 3 in the direction (radial direction) orthogonal to the tangential direction, and the diffraction grating 3 is radial. The depth of the groove is uniform in the direction, and the diffraction efficiency is uniform.

FIG. 4A shows the intensity distribution of the light beam before passing through the diffraction grating 3 provided in the hologram unit 2 by contour lines. The intensity distribution of the light flux before passing through the diffraction grating 3 is concentrically shaped such that the central portion is bright (strong) and the edges are dark (weak). FIG. 4B shows the intensity distribution of the + 1st-order diffracted light 5 and the -1st-order diffracted light 6 transmitted through the diffraction grating 3 provided in the hologram unit 2. Since the diffraction efficiency of the diffraction grating 3 has a large end portion and a small central portion only in the tangential direction, the intensity distribution of the + 1st order diffracted light 5 and the −1st order diffracted light 6 is a distribution in which the bright portion extends in the tangential direction. . Therefore, the light spots 12 and 13 formed by condensing the + 1st-order diffracted light 5 and the -1st-order diffracted light 6 by the objective lens 9 have an elliptical shape elongated in the radial direction.

As described above, in order to make the intensity distributions of the + 1st-order diffracted light 5 and the -1st-order diffracted light 6 nonuniform, for example, the transmittance of the hologram unit 2 may be distributed or the hologram unit 2 may be coated. Is possible,
In this method, light amount loss occurs in the portion of the hologram unit 2 where the transmittance is low. In the present embodiment, the intensity distribution of the + 1st-order diffracted light 5 and the -1st-order diffracted light 6 is obtained by providing the depth of the diffraction grating 3 provided in the hologram unit 2 with a distribution and the diffraction efficiency of the diffraction grating 3 with a distribution. Makes the diffraction efficiency of the diffraction grating 3 small (the depth of the groove is shallow).
The light quantity of the 0th-order light increases in the part, and there is no light quantity loss as a whole.

FIG. 5 shows a reflection system of this embodiment. Three light spots 11 and 1 formed on the optical disc 10.
The light beams 2 and 13 are reflected by the optical disk 10, pass through the objective lens 9, and pass through the quarter-wave plate 8 when the light flux passes through the reflection system and the incidence system shown in FIG. ° It will rotate. The first grating surface 7 and the 1/4 λ plate 8 provided on the hologram unit 2 constitute a light separating means for separating the diffracted lights 4 to 6 from the diffraction grating 3 and the reflected light from the optical disc 10. It has polarization characteristics and the first grating surface 7 is a quarter-wave plate 8
The light fluxes 20, 21, and 22 from are bent and guided to the second grating surface 16. The second grating surface 16 is shown in FIG.
It is divided into three diffraction grating portions 17, 18 and 19, as shown in FIG. Therefore, the luminous fluxes 20, 21, 22 from the first grating surface 7 are not reflected by the second grating surface 1
The light receiving element 3
Nine light spots 23 to 31 are formed on the detection surface of No. 5.

FIG. 7 shows the detection surfaces A to H of the light receiving element 35 and the calculation means. Of the nine light spots 23-31 from the second grating surface 16, seven light spots 23-
Reference numerals 26, 28, 29 and 31 denote detection surfaces A to H of the light receiving element 35.
Is detected and photoelectrically converted, that is, the light spots 27 and 30 formed from the central portions of the + 1st order diffracted light 21 and the −1st order diffracted light 22 are not detected. The photoelectric conversion signals obtained from the detection surfaces A to H of the light receiving element 35 are calculated by the calculation means 36 to.
The focus error signal, the tracking error signal, the reproduction signal, and the recording / erasing state monitor signal are obtained by calculation at 45.

First, regarding the focus error signal, 0
The light spot 23 formed from the end portion of the next-order diffracted light 20 is detected by the detection surfaces C and D of the light receiving element 35 in two divisions by the so-called knife edge method, and the photoelectric conversion signals c and d from the detection surfaces C and D are detected. The difference (c-d) is calculated by the calculating means 36 including a subtracter and output as a focus error signal.

Next, regarding the tracking error signal,
0th-order diffracted light 20, + 1st-order diffracted light 21, -1st-order diffracted light 22
Light spots 23, 25, 26, 2 created from both ends of the
8, 29 and 31 are detection surfaces A, B, C of the light receiving element 35,
D, F, G, H are detected, and the detection surfaces A, B,
Photoelectric conversion signals a, b, c from C, D, F, G, H
The d, f, g, and h are calculated by the calculating means 37 to 44 to obtain a tracking error signal (track error signal) by the so-called differential (differential) push-pull method.

That is, the sum (c + d) of the photoelectric conversion signals c and d from the detection surfaces C and D of the light receiving element 35 is calculated by the adder 37 and added with the photoelectric conversion signal f from the detection surface F of the light receiving element 35. Difference (c + d) with the output signal (c + d) of the device 37
+ D−f) is calculated by the subtractor 39, and the light receiving element 35
Of the photoelectric conversion signals g and h from the detection surfaces G and H of (g−
h) is calculated by the subtractor 41, and the difference (ab) between the photoelectric conversion signals a and b from the detection surfaces A and B of the light receiving element 35 is calculated by the subtractor 42.

The output signal (ab) of the subtractor 42 is multiplied by G ₁ by the amplifier 43 to become G ₁ (ab), and the adder 3
8, the output signal G ₁ (ab) of the amplifier 43 and the subtracter 41
With the output signal (gh) of {G ₁ (ab) + (g−
h)} is calculated. The output signal of this adder 38 {G ₁
(A−b) + (g−h)} is multiplied by G ₂ by the amplifier 44 to become G ₂ {G ₁ (a−b) + (g−h)}, and the subtractor 40 outputs the output signal of the amplifier 44. G ₂ {G ₁ (ab) +
(G−h)} and the output signal (c + d−f) of the subtractor 39 [G ₂ {G ₁ (a−b) + (g−h)} − (c + d)
-F)] is calculated and the output signal [G ₂ {G ₁
(A−b) + (g−h)} − (c + d−f)] is output as the tracking error signal. Here, G ₁ and G ₂ are 0th-order diffracted light 20, + 1st-order diffracted light 21, and −1st-order diffracted light 22.
This is a gain adjustment value for compensating for the difference in the light amount of.

Further, the reproduced signal is detected from the 0th-order diffracted light 20. That is, the photoelectric conversion signals c from the detection surfaces C, D, E, and F of the light receiving element 35 that detects the 0th-order diffracted light 20,
The sum (c + d + e + f) of d, e, and f is the adders 37 and 45.
Is calculated and output as a reproduction signal. Further, the light beam 2 from the portion of the information track 14 on which information is recorded or erased by the 0th-order diffracted light 4 on the optical disc 10 is irradiated with the -1st-order diffracted light 6 immediately after the recording or the erasure.
The photoelectric conversion signal a from the detection surface A of the light receiving element 35 that detects the light spot 29 of 2 is output as a recording / erasing state monitor signal.

FIG. 8 shows the light intensity distribution of the -1st order diffracted light.
This -1st order diffracted light is brighter as the white (the light intensity is stronger),
The darker the black, the weaker the light intensity. FIG. 8A shows the information track 14 recorded by the 0th-order diffracted light 4 on the optical disk 10.
Immediately after the recording, -1st-order diffracted light 6 was recorded in the upper information pit 15.
Shows the light intensity distribution of the -1st-order diffracted light when the light spot 13 starts to be irradiated (at the time of entry).
The secondary diffracted light 6 irradiates the edge portion of the information pit 15. It can be seen that in the light intensity distribution of the -1st-order diffracted light, the upper left portion is bright in FIG.

Further, the information pits enter the light spot 13 formed by the -1st-order diffracted light 6 on the optical disc 10, and as shown in FIG.
An information track 1 in which a light spot 13 formed by the first-order diffracted light 6 is recorded by the 0th-order diffracted light 4 on the optical disc 10.
It can be seen that the left part is almost bright when the information pit 15 above 4 is illuminated.

Then, as shown in FIG. 8C, the information pits 15 recorded by the 0th-order diffracted light 4 on the information track 14 of the optical disk 10 become the -1st-order diffracted light 6 on the optical disk 10.
It can be seen that the -1st-order diffracted light illuminates the edge portion of the information pit 15 and the lower left portion is brighter in the state in which the -1st-order diffracted light is distant from the light spot 13 formed by.

In this way, by detecting the light quantity at the end portion (the left side in FIG. 8) of the −1st order diffracted light on the detection surface A of the light receiving element 35, the 0th order diffracted light 4 on the information track 14 of the optical disk 10 is recorded. It is possible to monitor the edge portion of the information pit 15 that has been erased, and it is also possible to monitor the edge portion of the information pit 15 that has been erased by the 0th-order diffracted light 4 on the information track 14 of the optical disc 10. Become.

Next, the processing of the recording / erasing state monitor signal in this embodiment will be described with reference to FIG.
The information signal 50 to be recorded is modulated by the encoder 51, and the semiconductor laser drive pulse generator 52 receives the output signal of the encoder 51 and receives the semiconductor laser drive pulse 5
6 is generated as a light source drive signal. The semiconductor laser 1 emits pulsed light by the semiconductor laser drive pulse 56 from the semiconductor laser drive pulse generator 52. Optical disc 1
0, for example, a phase change type optical disc can be overwritten, and the semiconductor laser drive pulse 56 has values of recording power (Hi) and erasing power (Low).

Since the 0th-order diffracted light 4, the + 1st-order diffracted light 5, and the -1st-order diffracted light 6 are all pulsed, a recording / erasing state monitor signal 55 obtained from the detection surface A of the light receiving element 35 is obtained.
Is influenced by the semiconductor laser drive pulse 56. The semiconductor laser drive pulse 56 from the semiconductor laser drive pulse generator 52 is inverted through the mono multivibrator 53, the gain is corrected by the amplifier 54, and the adder 59 is added.
Is added to the recording / erasing state monitor signal 55 from the detection surface A of the light receiving element 35 to obtain a signal 58 in which the influence of the semiconductor laser drive pulse 56 is removed from the recording / erasing state monitor signal 55.

As described above, this embodiment is an embodiment of the invention described in claim 1, and emits a light beam in the optical pickup for recording, reproducing and erasing information on the information recording medium of the optical disk 10. Light source 1 consisting of a semiconductor laser
And a light beam separating means 3 formed of a diffraction grating that divides the light beam emitted from the light source 1 into a main beam 4 composed of 0th-order diffracted light and two sub-beams 5 and 6 composed of + 1st-order diffracted light and -1st-order diffracted light, The main lens 4 and the two sub-beams 5 and 6 from the light beam separating means 3 are condensed on the information recording medium to form three light spots 11, 12 and 13.
A part of the sub beam 6 irradiates a portion of the information recording medium where information is recorded or erased by the main beam 4, so that the main beam 20 and the two sub beams 21 reflected by the information recording medium, 22 is provided in the hologram unit 2 as a means for obtaining a tracking error signal from 22 and instantly reproducing information from the information track 14 recorded or erased by the main beam 4 on the information recording medium by the sub beam 6 at the time of recording or erasing information. Since the diffraction grating 3, the first grating surface 7 and the second grating surface 16, the 1/4 λ plate 8, the light receiving element 35, and the calculating means 37 to 44 are provided, information can be obtained without adding a new light source. It is possible to instantly reproduce information from the information track just recorded or erased on the recording medium and monitor the recorded or erased state of the information. It, can be the optimum recording or erasing state without increasing the number of parts and assembling process and becomes, power consumption is reduced by high special cost increase without reliability.

Further, this embodiment is an embodiment of the invention described in claim 2, and in the optical pickup described in claim 1, the light spot 13 formed by the sub beam 6 on the information recording medium is Since the elliptical shape is long in the radial direction, it is possible to easily irradiate a part of the sub beam 6 on the information track recorded or erased by the main beam 4 on the information recording medium.

Further, the present embodiment is an embodiment of the invention described in claim 4, and is a light source 1 composed of a semiconductor laser which emits a light beam, and a light beam emitted from this light source 1 with a main beam 4 and a plurality of beams. Beam splitting means 3 for splitting into the sub-beams 5 and 6, and the main beam 4 and a plurality of sub-beams 5 and 6 from this beam splitting means 3 are condensed on the information recording medium to form a plurality of light spots 11 and 12. , 13 forming an objective lens 9 for recording, reproducing and erasing information on an information recording medium, the light beam splitting means 3 diffracts the intensity distribution of diffracted light to be nonuniform in the tangential direction. Since it is a grating, the shape of the light spot formed on the information recording medium by the sub beam can be easily made into an arbitrary shape by changing the diffraction efficiency of the diffraction grating 3.

Further, the present embodiment is an embodiment of the invention described in claim 5, wherein in the optical pickup described in claim 4, the diffraction grating 3 partially diffracts the groove depth to diffract the light. Since the efficiencies are distributed, it becomes possible to easily change the diffraction efficiency of the diffraction grating so that the shape of the light spot formed on the information recording medium by the sub beam can be made into an arbitrary shape.

Further, this embodiment is an embodiment of the invention described in claim 6, and in the optical pickup described in claim 4, the diffraction grating 3 has a central portion in one direction (tangential direction). The diffraction efficiency is different from that of the edge, and the diffraction efficiency is uniform in the direction (radial direction) orthogonal to that one direction. Therefore, the light diffracted by the diffraction grating has a diffraction efficiency between the center and the edge. The light intensity distribution in different directions can be dark at the center and bright at the edges, or conversely, bright at the center and dark at the edges. The intensity distribution does not change, and the light intensity distribution of the light spot formed on the information recording medium by the diffracted light beam can be arbitrarily deformed into an elliptical shape.

Further, this embodiment is an embodiment of the invention described in claim 9, in which information is recorded on an information recording medium,
In an optical pickup for reproducing and erasing, a light beam separating means including a light source 1 including a semiconductor laser that emits a light beam, and a diffraction grating that divides the light beam emitted from the light source 1 into a main beam 4 and two sub-beams 5 and 6. 3 and the main beam 4 and the two sub-beams 5 and 6 from the light beam separating means 3 are condensed on the information recording medium to form three light spots 11, 12 and 1.
3, an objective lens 9 for forming 3 and a photoelectric conversion element 35 for detecting each of the main beam 20 and the two sub-beams 21 and 22 reflected by the information recording medium are provided. Information track 1 recorded or erased
4 so that part of the sub-beam 6 irradiates the part of the sub-beam 22 reflected by the information recording medium.
The information recorded or erased by the main beam 4 on the information recording medium and obtained by the main beam 4 on the information recording medium is obtained. Is detected by the detection surface A of the photoelectric conversion element 35 only by the monitor sub-beam 22 and not by the other sub-beam 21, so that the main beam 4 on the information recording medium having a good C / N is used for recording or erasing. It becomes possible to obtain a monitor signal (recording / erasing state monitor signal) for the remaining information.

Further, the present embodiment is an embodiment of the invention described in claim 10, and in the optical pickup described in claim 1 or 9, a part of the sub-beam 22 is detected by the photoelectric conversion element 35. A reproduction signal of information obtained by recording or erasing remaining by the main beam 4 obtained by the above is used as a light source drive signal (semiconductor laser drive pulse 56 ) Is provided with a mono-multivibrator 53, an amplifier 54, and an adder 59 as a correction means, so that a change in the light emission amount of the light source can be stably recorded by the main beam on the information recording medium without changing the monitor signal. Alternatively, a monitor signal for the erased information can be obtained.

FIG. 10 shows a part of the second embodiment of the present invention. The second embodiment is an embodiment of the invention described in claim 11, and the circuit shown in FIG. 10 is used in place of the circuit shown in FIG. 9 in the first embodiment to change the recording / erasing state monitor signal. The processing is performed as follows. That is, the information signal 60 to be recorded is modulated by the encoder 61, and the semiconductor laser drive pulse generator 62 receives the output signal of the encoder 61 and generates a semiconductor laser drive pulse as a light source drive signal. The semiconductor laser 1 emits pulsed light by the semiconductor laser drive pulse 56 from the semiconductor laser drive pulse generator 52.
The optical disk 10, for example, a phase change optical disk can be overwritten, and the semiconductor laser drive pulse has values of recording power (Hi) and erasing power (Low).

Since the 0th-order diffracted light 4, the + 1st-order diffracted light 5, and the -1st-order diffracted light 6 are all emitted as pulses, the recording / erasing state monitor signal obtained from the detection surface A of the light receiving element 35 is influenced by the semiconductor laser driving pulse. ing. Therefore, the semiconductor laser drive pulse from the semiconductor laser drive pulse generator 62 is used as a control signal for the switch section 63, and the switch section 63 supplies the recording / erasing state monitor signal from the detection surface A of the light receiving element 35 to the semiconductor laser drive pulse generator. The recording / erasing state monitor signal is sampled and output only when the semiconductor laser drive pulse has the maximum value (high level) by switching the semiconductor laser drive pulse from 62.

The second embodiment is an embodiment of the invention described in claim 11, and in the optical pickup described in claim 1 or 9, a part of the sub beam 22 is detected by the photoelectric conversion element 35. A light source drive signal (semiconductor laser drive pulse) for changing the light amount of the light source 1 according to the information reproduction signal obtained by recording or erasing the main beam 4 and remaining unerased. Is obtained by sampling only when is the maximum value, so that the monitor signal for the information recorded or erased by the main beam on the information recording medium can be stably obtained without the change in the light emission amount of the light source changing the monitor signal. it can.

FIG. 11 shows a part of the third embodiment of the present invention. The third embodiment is an embodiment of the invention according to claim 12, and the circuit shown in FIG. 11 is used in place of the circuit shown in FIG. 9 in the first embodiment to change the recording / erasing state monitor signal. The processing is performed as follows. That is, the information signal 70 to be recorded is modulated by the encoder 71, and the semiconductor laser drive pulse generator 72 receives the output signal of the encoder 71 and generates a semiconductor laser drive pulse as a light source drive signal. The semiconductor laser 1 emits pulsed light by the semiconductor laser drive pulse 56 from the semiconductor laser drive pulse generator 52.
The optical disk 10, for example, a phase change optical disk can be overwritten, and the semiconductor laser drive pulse has values of recording power (Hi) and erasing power (Low).

Since the 0th-order diffracted light 4, the + 1st-order diffracted light 5, and the -1st-order diffracted light 6 are all emitted as pulses, the recording / erasing state monitor signal obtained from the detection surface A of the light receiving element 35 is influenced by the semiconductor laser driving pulse. ing. Therefore, the output signal of the encoder 71 is used as a control signal of the switch unit 74 through the low pass filter 73,
Switches the recording / erasing state monitor signal from the detection surface A of the light receiving element 35 by the control signal from the low-pass filter 73 and samples and outputs the recording / erasing state monitor signal only when the control signal is at a high level. As a result, the recording / erasing state monitor signal can be sampled and output only when the output signal of the encoder 71 has the longest constant value.

The third embodiment is an embodiment of the invention according to claim 12, and in the optical pickup according to claim 1 or 9, a part of the sub beam 22 is detected by the photoelectric conversion element 35. The reproduction signal of the information obtained by recording or erasing with the main beam 4 and obtained, and the light source drive signal for changing the light amount of the light source 1 according to the information signal recorded on the information recording medium has the longest and uniform value. Since it is obtained by sampling only when the signal is taken, it is possible to stably obtain the monitor signal for the information recorded or erased by the main beam on the information recording medium without changing the light emission amount of the light source.

Next, a fourth embodiment of the present invention will be described. The fourth embodiment is another embodiment of the invention described in claim 7, and differs from the first embodiment in the points described below. In the first embodiment, the intensity distribution of the light flux emitted from the semiconductor laser 1 generally has different divergence angles in the horizontal direction and the vertical direction. Therefore, the light beam from the semiconductor laser 1 is passed through the objective lens 9 to the optical disc 1
When the light is focused on 0, an elliptical light spot is formed on the optical disc 10.

In order to make the light spot formed on the optical disk 10 circular, the light flux from the semiconductor laser 1 must be made to have the same spread angle in the horizontal direction and the vertical direction. As shown in FIG. 12, the light flux 101 emitted from the semiconductor laser 1 has a small divergence angle in the X-axis direction orthogonal to the optical axis and a large divergence angle in the Y-axis direction orthogonal to the optical axis. The luminous flux 101 is diffracted by the diffraction grating 3 provided in the hologram unit 2 to form a 0th-order diffracted light 4, a + 1st-order diffracted light 5, −.
It is divided into three light beams, which are first-order diffracted light 6.

The diffraction efficiency of the diffraction grating 3 is uniform in the X-axis direction, and has a distribution in which the central portion is small and both end portions are large in the Y-axis direction. That is, the diffraction grating 3 is formed by arranging grooves extending at the same depth in the X-axis direction, and the groove at the central portion in the Y-axis direction is not deep. Therefore, in the intensity distribution of the 0th-order diffracted light 4 from the diffraction grating 3 in the Y-axis direction, the central portion is brighter and both end portions are darker than before the diffraction. Therefore, the 0th-order diffracted light 4 from the diffraction grating 3 is the light beam 10 before diffraction.
The divergence angle in the Y-axis direction is smaller than that of 1. On the other hand, the 0th-order diffracted light 4 from the diffraction grating 3 is the light beam 10 before diffraction.
Since the divergence angle in the X-axis direction does not change as compared with 1, the difference between the divergence angle in the X-axis direction and the divergence angle in the Y-axis direction of the 0th-order diffracted light 4 from the diffraction grating 3 becomes small. Therefore, in the fourth embodiment, the diffraction efficiency of the diffraction grating 3 in the Y-axis direction so that the light flux 101 emitted from the semiconductor laser 1 forms a circular light spot on the optical disk 10 in the first embodiment. The distribution is set.

The fourth embodiment is an embodiment of the invention according to claim 7, and in the optical pickup according to claim 4, the diffraction grating 3 spreads the luminous flux emitted from the light source 1 made of a semiconductor laser. The diffraction efficiency of the semiconductor laser 1 is reduced because the diffraction efficiency of the central portion is decreased and the diffraction efficiency of the end portion is increased in the direction where the angle is large, and the diffraction efficiency of the emitted light flux of the light source 1 is uniform in the direction where the spread angle is small. Most of the light flux at the end of the direction with a large divergence angle is used for the sub-beam, and most of the light flux at the center is used for the main beam, so there is less light flux at the end of the main beam in the same direction, and the diffraction grating Two directions X and Y orthogonal to the optical axis of the main beam after being separated by 3
Is smaller than the difference in light intensity distribution in two directions X and Y orthogonal to the optical axis of the light beam before being separated by the diffraction grating 3, and the main beam is condensed and formed on the optical disc. It is possible to make the light spot to be formed into a circle.

A fifth embodiment of the present invention is an embodiment of the invention according to claim 8, and in the fourth embodiment, the diffraction grating 3 has a distribution in the diffraction efficiency in the X-axis direction. It is configured in. That is, in the fifth embodiment, the diffraction efficiency of the diffraction grating 3 is such that the central portion is large and the both end portions are small in the X-axis direction, and the central portion is small and both end portions are large in the Y-axis direction. . That is, in the diffraction grating 3, grooves having a deep central portion in the X-axis direction and shallow ends at both ends are lined up, and grooves extending in the X-axis direction are lined up. The groove is deep.

Therefore, the 0th-order diffracted light 4 from the diffraction grating 3
In the X-axis direction where the divergence angle was small, the center part was dark and both end parts were brightened to increase the divergence angle, and in the Y-axis direction where the divergence angle was large, the center part was bright and both end parts were darkened to the divergence angle. Is reduced. Therefore, the 0th-order diffracted light 4 from the diffraction grating 3 can have the same spread angle in the X-axis direction and the Y-axis direction. Here, the diffraction efficiency distributions in the X-axis direction and the Y-axis direction of the diffraction grating 3 are set so that the light flux 101 emitted from the semiconductor laser 1 forms a circular light spot on the optical disc 10.

The fifth embodiment is an embodiment of the invention according to claim 8, and in the optical pickup according to claim 4, the diffraction grating 3 spreads the luminous flux emitted from the light source 1 made of a semiconductor laser. The diffraction efficiency of the central portion is decreased to increase the diffraction efficiency of the end portion in the direction where the angle is large, and the diffraction efficiency of the central portion is increased to increase the diffraction efficiency of the end portion in the direction where the spread angle of the light flux emitted from the light source 1 is small. Since it is made low, the divergence angle of the main beam in the direction where the divergence angle of the emitted light beam of the semiconductor laser 1 is large becomes small, and the divergence angle of the main beam in the direction where the divergence angle of the emitted light beam of the semiconductor laser 1 is small becomes large. Therefore, the difference between the light intensity distributions in the two directions X and Y orthogonal to the optical axis of the main beam after being separated by the diffraction grating 3 is orthogonal to the optical axis of the light beam before being separated by the diffraction grating 2. It becomes smaller than the difference between the light intensity distributions in the two directions X and Y, and it becomes possible to focus the main beam and make the light spot formed on the optical disc circular.

FIG. 13 shows a light spot on the optical disc 10 in the sixth embodiment of the present invention. The sixth embodiment is an embodiment of the invention described in claim 3, and is different from the first embodiment in the following points. In the sixth embodiment, the hologram unit 2 is replaced with the diffraction grating 3 shown in FIG.
The diffraction grating 3a as shown in FIG. 4 (a) is provided, and the light flux from the semiconductor laser 1 is the 0th-order diffracted light 4, + in the diffraction grating 3a.
A light spot 110, 11 as shown in FIG.
1, 112 are formed.

Here, the light spot 110 formed by the 0th-order diffracted light 4 is for recording, erasing, and reproducing information on the optical disc 10, and the + 1st-order diffracted light 5, −.
Light spots 111 and 11 formed by the first-order diffracted light 6
2 is for detecting a tracking error signal for following the information track. Further, the light spot 112 formed by the −1st order diffracted light 6 is the optical disc 1
Light spot 110 formed by 0th-order diffracted light 4 on 0
It also plays a role of reproducing the information pit 15 recorded or erased.

The light spot 112 formed by the -1st-order diffracted light 6 is long in the direction (radial direction) orthogonal to the information track 14, and the portion close to the light spot 110 formed by the 0th-order diffracted light 4 is large. It has an egg shape, and a part of it illuminates the information pit 15 recorded or erased by the light spot 110 formed by the 0th-order diffracted light 4 on the optical disk 10.

Therefore, the amount of light that irradiates the information pit 15 recorded or erased by the light spot 110 formed by the 0th-order diffracted light 4 on the optical disk 10 increases, and the information is formed by the 0th-order diffracted light 4 on the optical disk 10. Used to monitor the recorded or erased information pit 15 in the light quantity of the optical spot 112 formed by the -1st-order diffracted light 6 which also plays a role of reproducing the recorded or erased information pit 15 in the optical spot 110. The amount of light emitted increases, and the C / N of the recording / erasing state monitor signal improves.

FIG. 14A shows the diffraction grating 3a provided on the hologram unit 2 in an enlarged manner, and FIG. 14B shows the diffraction efficiency distribution of the diffraction grating 3a. The diffraction grating 3a has a depth distribution such that the right end portion is deepest, the left end portion is slightly deeper, and the central portion is shallowest. Since the depth of this grating is proportional to the diffraction efficiency of the diffraction grating 3a,
The diffraction efficiency of the diffraction grating 3a is highest at the right end portion of the diffraction grating 3a, slightly higher at the left end portion thereof, and lowest at the center portion thereof. The diffraction grating 3a has such a distribution of diffraction efficiency in the tangential direction, but there is no such distribution in the direction orthogonal to the tangential direction (radial direction), and the diffraction efficiency is uniform in the radial direction. . The light spot 112 formed on the optical disc 10 by the −1st-order diffracted light 6 diffracted by the diffraction grating 3a having such a distribution of diffraction efficiency is long in the direction (radial direction) orthogonal to the information track 14 and is the 0th-order diffracted light. The portion near the light spot 110 formed by 4 becomes a large oval-shaped light spot.

The sixth embodiment is an embodiment of the invention according to claim 3, and in the optical pickup according to claim 1, the light spot 112 formed by the sub beam 6 on the information recording medium is Since the portion near the main beam 4 is large and has a substantially oval shape that is long in the radial direction, the end of the light spot 112 formed by the sub-beam 6 extends in the direction approaching the main beam 4 and on the information recording medium. Main beam 4
It is possible to increase the amount of light of the sub-beam irradiated on the information pit 15 recorded or erased by, and monitor the information pit 15 recorded or erased by the main beam 4 on the information recording medium in the light amount of the sub-beam. It is possible to increase the amount of light used to improve the C / N of the recording / erasing state monitor signal.

[0067]

As described above, according to the invention described in claim 1, in an optical pickup for recording, reproducing and erasing information on an information recording medium, a light source for emitting a light beam and a light beam emitted from this light source are provided. A beam splitting means for splitting the beam into a main beam and two sub beams, and an objective lens for focusing the main beam and the two sub beams from the beam splitting means on the information recording medium to form three light spots. From the main beam and the two sub-beams reflected by the information recording medium, part of the sub-beam irradiates a portion of the information recording medium where information is recorded or erased by the main beam. In addition to obtaining the tracking error signal, the information beam recorded or erased by the main beam on the information recording medium is immediately reproduced by the sub beam when the information is recorded or erased. Means for monitoring information recording or erasing status by immediately reproducing information from the information track just recorded or erased on the information recording medium without adding a new light source. It is possible to achieve the optimum recording or erasing state without increasing the number of parts and the assembling process, and the reliability is high and the power consumption is low without any special cost increase.

According to the second aspect of the invention, in the optical pickup of the first aspect, since the light spot formed by the sub beam on the information recording medium has an elliptical shape elongated in the radial direction, it is easy. It is possible to irradiate a part of the sub beam on the information track recorded or erased with the main beam on the information recording medium.

According to the invention of claim 3, in the optical pickup of claim 1, the light spot formed by the sub beam on the information recording medium has a large portion near the main beam in the radial direction. Since it is a long oval shape, the end of the light spot formed by the sub-beam extends in the direction approaching the main beam, and the sub-beam of the sub-beam irradiated to the information recorded or erased by the main beam on the information recording medium The amount of light can be increased, and the amount of light used for monitoring information recorded or erased by the main beam on the information recording medium can be increased among the amounts of light of the sub-beams to improve the C / N of the monitor signal. be able to.

According to the invention described in claim 4, a light source for emitting a light beam, a light beam separating means for dividing the light beam emitted from the light source into a main beam and a plurality of sub-beams, and a main beam from the light beam separating means. And an objective lens that collects a plurality of sub-beams on the information recording medium to form a plurality of light spots, and in the optical pickup that records, reproduces, and erases information on the information recording medium, Since the separating means is a diffraction grating in which the intensity distribution of the diffracted light is non-uniform, the shape of the light spot formed on the information recording medium by the sub beam can be easily changed to an arbitrary shape by changing the diffraction efficiency of the diffraction grating. It becomes possible to

According to the invention described in claim 5, in the optical pickup described in claim 4, since the diffraction grating partially changes the depth of the groove to distribute the diffraction efficiency, the information is recorded by the sub beam. It is possible to easily change the diffraction efficiency of the diffraction grating so that the shape of the light spot formed on the medium is arbitrary.

According to a sixth aspect of the present invention, in the optical pickup according to the fourth aspect, the diffraction efficiency of the diffraction grating is different between the central portion and the end portion in one direction, and the diffraction grating in the direction orthogonal to the one direction. As it consists of a diffraction grating with uniform diffraction efficiency, the light intensity distribution in the direction in which the diffraction efficiency of the light diffracted by the diffraction grating differs between the central part and the end part, the center part is dark and the end part is bright, or conversely the center It is possible to make the area bright and the edges dark, and the light intensity distribution in the direction of uniform diffraction efficiency orthogonal to this does not change and the light of the light spot formed on the information recording medium by the diffracted light flux The intensity distribution can be arbitrarily deformed into an elliptical shape.

According to a seventh aspect of the present invention, in the optical pickup according to the fourth aspect, the diffraction grating has a lower diffraction efficiency in the central portion in the direction in which the divergence angle of the luminous flux emitted from the light source is large, and the diffraction grating is provided in the end portion. Since the diffraction efficiency of the light source is increased and the diffraction efficiency of the light beam emitted from the light source in the direction in which the divergence angle is small is uniform, most of the light beam emitted from the light source is used as a sub-beam at the end portion in the direction in which the divergence angle is large. Since most of the light flux at the center is used for the main beam, the light flux at the end in the same direction of the main beam is reduced, and two directions orthogonal to the optical axis of the main beam after being separated by the diffraction grating are reduced. Is smaller than the difference in the light intensity distribution in two directions orthogonal to the optical axis of the light beam before being separated by the diffraction grating, and the main beam is condensed to form light on the information recording medium. The spot can be circular To become.

According to an eighth aspect of the present invention, in the optical pickup according to the fourth aspect, the diffraction grating has a lower diffraction efficiency in the central portion in the direction in which the divergence angle of the light flux emitted from the light source is large, and the end portion is reduced. The diffraction efficiency of the light source is increased, and the diffraction efficiency of the central portion is increased and the diffraction efficiency of the end portion is decreased in the direction in which the divergence angle of the light flux emitted from the light source is small. The divergence angle of the beam decreases, and the divergence angle of the main beam in the direction in which the divergence angle of the light flux emitted from the light source decreases. Therefore, the difference in the light intensity distribution in the two directions orthogonal to the optical axis of the main beam after being separated by the diffraction grating is the difference in the light intensity in the two directions orthogonal to the optical axis of the light beam before being separated by the diffraction grating. It becomes smaller than the difference in distribution, and it becomes possible to focus the main beam and form a light spot formed on the information recording medium into a circular shape.

According to the invention described in claim 9, in an optical pickup for recording, reproducing and erasing information on an information recording medium, a light source for emitting a light beam, a light beam emitted from the light source for a main beam and two sub-beams. A beam splitting means for splitting into a beam, an objective lens for focusing the main beam and two sub-beams from the beam splitting means on the information recording medium to form three light spots, and reflection by the information recording medium. And a photoelectric conversion element for detecting each of the two sub-beams, and a part of the sub-beam irradiates an information track in which information is recorded or erased by the main beam on the information recording medium. In this way, a part of the sub-beam reflected by the information recording medium is detected by the photoelectric conversion element and recorded or erased by the main beam on the information recording medium and left. Since the information reproduction signal is obtained, the information recorded or erased by the main beam on the information recording medium is detected by the photoelectric conversion element only in the monitor sub-beam, and other sub-beams are not detected. It is possible to obtain a monitor signal for information that has been recorded or erased by the main beam on the information recording medium with good quality.

According to the invention of claim 10, claim 1
Alternatively, in the optical pickup according to the item 9, the reproduction signal of the information recorded by the main beam or left unerased, which is obtained by detecting a part of the sub beam by a photoelectric conversion element, is recorded on the information recording medium. Since the correction means for correcting with the light source drive signal for changing the light amount of the light source according to the signal is provided, the change in the light emission amount of the light source is stable in the main beam on the information recording medium without changing the monitor signal. A monitor signal for recorded or erased information can be obtained.

According to the invention of claim 11, claim 1
Alternatively, in the optical pickup according to the item 9, the reproduction signal of the information recorded by the main beam or left unerased, which is obtained by detecting a part of the sub beam by a photoelectric conversion element, is recorded on the information recording medium. Since the light source drive signal for changing the light amount of the light source in accordance with the signal is sampled only when it reaches the maximum value, the change in the light emission amount of the light source is stable on the information recording medium without changing the monitor signal. A monitor signal for the information recorded or erased by the main beam can be obtained.

According to the twelfth aspect, the first aspect
Alternatively, in the optical pickup according to the item 9, the reproduction signal of the information recorded by the main beam or left unerased, which is obtained by detecting a part of the sub beam by a photoelectric conversion element, is recorded on the information recording medium. Since the light source drive signal for changing the light amount of the light source according to the signal is sampled only when the light source drive signal has the longest and uniform value, the change in the light emission amount of the light source stably records the information without changing the monitor signal. A monitor signal for the information recorded or erased by the main beam on the medium can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an incident system from a light source to an information recording medium in a first embodiment example of the present invention.

FIG. 2 is a plan view showing a light spot on an optical disc according to the first embodiment.

FIG. 3 is an enlarged schematic view of a diffraction grating provided in the hologram unit of the first embodiment and a characteristic diagram showing a distribution of diffraction efficiency of the diffraction grating.

FIG. 4 is a diagram showing the intensity distribution of the light flux before passing through the diffraction grating provided in the hologram unit of the first embodiment by contour lines, and the + 1st order diffracted light passing through the diffraction grating,
It is a figure which shows the intensity distribution of a 1st-order diffracted light.

FIG. 5 is a schematic view showing a reflection system of the first embodiment example.

FIG. 6 is a diagram showing a second grating surface provided in the hologram unit of the first embodiment and a transmitted light flux thereof.

FIG. 7 is a view showing a detection surface of a light receiving element and a calculation means in the first embodiment example.

FIG. 8 is a diagram showing a halftone image displayed on a display by measuring a light intensity distribution of −1st order diffracted light in the first embodiment.

FIG. 9 is a block diagram showing a part of the first embodiment.

FIG. 10 is a block diagram showing a part of a second exemplary embodiment of the present invention.

FIG. 11 is a block diagram showing a part of a third exemplary embodiment of the present invention.

FIG. 12 is a perspective view showing a part of a fourth embodiment of the present invention.

FIG. 13 is a plan view showing a light spot on an optical disc according to a sixth embodiment of the present invention.

FIG. 14 is an enlarged view showing a diffraction grating provided in the hologram unit of the sixth embodiment and a view showing a distribution of diffraction efficiency of the diffraction grating.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 semiconductor laser 2 hologram unit 3, 3a diffraction grating 7 1st grating surface 8 1/4 (lambda) plate 9 objective lens 10 optical disk 16 2nd grating surface 35 light receiving element 36-45 computing means 51, 61, 71 encoder 52, 62 , 72 Semiconductor laser drive pulse generator 53 Mono multivibrator 54 Amplifier 59 Adder 63, 74 Switch 73 Low pass filter

Claims (12)

[Claims] 1. An optical pickup for recording, reproducing and erasing information on an information recording medium, and a light source for emitting a light beam, and a light beam separating means for separating the light beam emitted from the light source into a main beam and two sub-beams. An objective lens for converging a main beam and two sub-beams from the light beam separating means onto the information recording medium to form three light spots; and information recording by the main beam on the information recording medium. By irradiating the erased part with a part of the sub-beam,
While obtaining a tracking error signal from the main beam and the two sub beams reflected by the information recording medium,
An optical pickup comprising: means for immediately reproducing information from the information track recorded or erased by the main beam on the information recording medium by the sub beam at the time of recording or erasing information. 2. The optical pickup according to claim 1, wherein
An optical pickup characterized in that a light spot formed by the sub-beam on the information recording medium has an elliptical shape elongated in the radial direction. 3. The optical pickup according to claim 1, wherein
An optical pickup characterized in that a light spot formed by the sub-beam on the information recording medium is a substantially oval shape in which a portion near the main beam is large and is long in a radial direction. 4. A light source for emitting a light beam, a light beam separating means for dividing the light beam emitted from this light source into a main beam and a plurality of sub-beams, and a main beam and a plurality of sub-beams from this light beam separating means. In an optical pickup that has an objective lens that converges on a recording medium to form a plurality of light spots, and that records, reproduces, and erases information on the information recording medium, the light beam separating means has an intensity distribution of diffracted light. An optical pickup having a non-uniform diffraction grating. 5. The optical pickup according to claim 4,
The diffraction grating is characterized in that the depth of the groove is partially changed to distribute the diffraction efficiency. 6. The optical pickup according to claim 4,
An optical pickup characterized in that the diffraction grating comprises a diffraction grating having different diffraction efficiencies between a central portion and an end portion in one direction, and uniform diffraction efficiency in a direction orthogonal to the one direction. 7. The optical pickup according to claim 4,
The diffraction grating lowers the diffraction efficiency of the central portion in the direction in which the divergence angle of the light flux emitted from the light source is large to increase the diffraction efficiency of the end portion, and increases the diffraction efficiency in the direction in which the divergence angle of the light flux emitted from the light source is small. An optical pickup characterized by being uniform. 8. The optical pickup according to claim 4,
The diffraction grating lowers the diffraction efficiency of the central portion in the direction in which the spread angle of the emitted light beam of the light source is large and increases the diffraction efficiency of the end portion, and the diffraction grating of the central portion in the direction in which the spread angle of the emitted light beam of the light source is small. An optical pickup characterized by having high diffraction efficiency and low diffraction efficiency at the edges. 9. An optical pickup for recording, reproducing and erasing information on an information recording medium, and a light source for emitting a light beam, and a light beam separating means for dividing the light beam emitted from the light source into a main beam and two sub-beams. An objective lens for converging the main beam and two sub-beams from the light beam separating means onto the information recording medium to form three light spots; the main beam reflected by the information recording medium; A photoelectric conversion element for detecting each of the two sub-beams, and the information recording is performed by irradiating a part of the sub-beams on an information track in which information is recorded or erased by the main beam on the information recording medium. It is characterized in that a part of the sub-beam reflected by the medium is detected by the photoelectric conversion element to obtain a reproduction signal of the information recorded or erased by the main beam on the information recording medium. The optical pick-up to be. 10. The optical pickup according to claim 1, wherein a reproduction signal of information recorded or erased by the main beam and obtained by detecting a part of the sub beam by a photoelectric conversion element, An optical pickup comprising: a correction unit that corrects a light source drive signal for changing a light amount of the light source according to an information signal recorded on the information recording medium. 11. The optical pickup according to claim 1, wherein a reproduction signal of information recorded or erased by the main beam and obtained by detecting a part of the sub-beam by a photoelectric conversion element, An optical pickup which is obtained by sampling only when a light source drive signal for changing the light quantity of the light source has a maximum value in accordance with an information signal recorded on the information recording medium. 12. The optical pickup according to claim 1, wherein a reproduced signal of information recorded or erased by the main beam and obtained by detecting a part of the sub beam by a photoelectric conversion element, An optical pickup which is obtained by sampling only when a light source drive signal for changing the light quantity of the light source has a longest and uniform value in accordance with an information signal recorded on the information recording medium.