JPH0289232A - Optical pickup - Google Patents

Abstract

PURPOSE:To make it possible to read out data even from a recording medium having a wide track width by arranging a 1st dividing line of a photodetector approximately along a straight line connecting the spots of two subbeams, converging the spots of the subbeams upon the 1st and 2nd beam detecting parts and converging a main beam upon a 3rd beam detecting part. CONSTITUTION:The photodetector 29 consists of the 1st and 2nd beam detecting parts 30, 31 for converging the spots of subbeams s1, s2 and the 3rd beam detecting parts 32 arranged between the 1st and 2nd beam detecting parts 30, 31 to converge the spot of a main beam (m). The photodetector 29 is arranged so that the 1st dividing line 32a of the photodetector 29 is arranged approximately along the straight line L connecting the spots of the two subbeams s1, s2. Thereby, at least an information reproducing signal and a focus error signal are formed from the 3rd beam detecting part 32 by forming track error signals from the 1st and 2nd beam detecting parts 30, 31. Consequently, data can be read out from a recording medium having a wide track width by using an ordinarily used photodetector.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention provides a laser light source that emits a laser beam f a first optical system that divides the beam into two sub-beams that are irradiated so as to cover both sides of the track of the recording medium when on-track;
the second beam detection section and the first beam detection section; The second beam detector is disposed between the first and second beam detectors. A third beam having a light-receiving surface divided into four by a first dividing line parallel to the straight line connecting the second beam detector and a second dividing line perpendicular to the first dividing line J It has a photodetector consisting of a detection section and a second optical system that separates three reflected beams from the recording medium,
Said 1st. The present invention relates to an optical information reading device that generates a track error signal from a second beam detection section, and generates at least an information reproduction signal and a focus error signal from the third beam detection section.

(Prior Art) Next, a conventional example will be explained using the drawings. FIG. 6 is a block diagram of a conventional optical information reading device, FIG. 7 is a diagram explaining the beam spot on the recording medium in FIG. 6, and FIG.
A diagram illustrating the beam spot on the photodetector in the figure,
FIG. 9 is a diagram illustrating a method of generating various signals in the photodetector in FIG. 6.

First, the overall configuration of a conventional optical information reading device will be explained using FIG. 6. In the figure, 1 is a laser light source that emits a laser beam. 2 is a collimator lens that converts the laser beam emitted from the laser light source into a parallel beam; 3 is a collimator lens that converts the parallel laser beam into a main beam m and two sub beams s1.
．． This is a diffraction grating that separates s2. A beam splitter 4 transmits the three beams from the diffraction grating 3 and reflects the return beam from the recording medium 5.

6 is an objective lens that focuses the laser beam emitted from the beam splitter 4. 7 is a collimator lens that focuses the parallel beam reflected by the beam splitter 4;
8 is a toric lens that receives the laser beam emitted from the collimator lens 7 and functions as a lens in only one direction.

Furthermore, 9 is a photodetector on which the laser beam from the toric lens 8 is focused.

Next, the beam spot on the recording medium 5 will be explained using FIG. Of the three beams separated by the diffraction grating 3, the main beam m is irradiated so as to be located approximately at the center of the track T of the recording medium 5 when on-track, and the two sub beams S1 and 82 are irradiated onto the recording medium 5. The light is irradiated so as to cover both sides of the recording track T. In addition, two sub beams 81.8
2 is shifted back and forth in order to prevent detection signals from leaking in and to avoid crosstalk from adjacent tracks.

Next, the beam spot on the photodetector 9 will be explained using FIG. 8. In the figure, the photodetector 9 has sub-beams 81 .
The main beam detection section 10 and the second beam detection section 11 are arranged between the first beam detection section 10 and the second beam detection section 11 on which 82 spots are focused. It consists of a third beam detection section 12 that emits light.

The third beam detection section 12 has a first dividing line 12 parallel to the straight line connecting the first beam detection section 10 and the second beam detection section 11.
a, and a second dividing line 12b perpendicular to this first dividing line.
The light-receiving surfaces 12c, 12d, which are divided into four by
12e and 12f.

The photodetector 9 is arranged along the tangential direction of the track T of the recording medium 5.

Next, a method of generating various signals in the photodetector 9 will be explained using FIG. 9. In the figure, the output of the first beam detection section 10 is A1, and the output of the second beam detection section 11 is B1.
The outputs of the light receiving surfaces 12c to 12f of the third beam detection unit 12 are C and D, respectively.

Let them be E and F. 13.17 is a differential amplifier, 14°15.
16 is an adder. The spot shape of the main beam m is circular as shown by a solid line in the figure when in just focus, but becomes an ellipse as shown by a chain double-dashed line when out of focus.

These differential amplifiers 13, 17 and adders 14, 15.
16, the following performance was performed, and a track error signal, a focus error signal, and an information reproduction signal (
HF signal) is generated.

Track error signal - A-8 Focus error signal = (C + E) - (D -> -F) Information reproduction signal - (C + E) + (D + F) (Problem to be solved by the invention) The above conventional configuration When reading information on a recording medium with a wide track width, such as an optical card, using an optical information reading device, the diffraction grating 3 is rotated and adjusted in the circumferential direction of the laser beam, and two sub-beams S1 and B2 are read. Increase the distance between
These two sub-beams s1. The s2 spot must cover both sides of the track.

However, as in the above conventional example, the photodetector 9 is connected to the recording medium 5.
are arranged along the tangential direction of the track T of the sub-beams s1. There is a problem in that the light beam s2 is not focused on the first beam detection section 10 and the second beam detection section 11, so that a tracking error signal cannot be obtained.

The present invention has been made in view of the above problems, and its purpose is to provide an optical information reading device capable of reading a recording medium with a wide track width using a conventionally used photodetector. It is in.

(Means for Solving the Problems) The present invention for solving the above problems includes a laser light source that emits a laser beam, a main beam that irradiates the laser beam onto a substantially central portion of a track of a recording medium when on-track, and a first optical system that divides the recording medium into two sub-beams that are applied to both sides of the track during tracking; a first and second beam detector; The second beam detector is disposed between the first and second beam detectors. From a third beam detector having a light receiving surface divided into four by a first dividing line parallel to the straight line connecting the second beam detectors and a second dividing line perpendicular to the first dividing line. and a second optical system that separates the three reflected beams from the recording medium, and a second optical system that separates the three reflected beams from the recording medium. In an optical information reading device that generates a track error signal from the second beam detection section and generates at least an information reproduction signal and a focus error signal from the third beam detection section, a straight line connecting the spots of the two sub-beams. The first dividing line of the photodetector is placed approximately along the line Qt-', and the spot of the sub beam is placed approximately along the first dividing line Qt-'. The main beam is focused on the second beam detection section, and the main beam is focused on the third beam detection section.

(Function) In the optical information reading device of the present invention, the laser beam emitted from the laser light source is a main beam that is irradiated to the approximate center of the track of the recording medium when on-track in the first optical system; It is divided into two sub-beams that irradiate both sides of the recording medium track,
The recording medium is irradiated. Next, the three reflected beams from the recording medium are separated by a second optical system. The 1st and 2nd beam detectors and the 1st and 2nd beam detectors and the first and second beam detectors. The second beam detector is disposed between the first and second beam detectors. It consists of a third beam detection section having a light receiving surface divided into four by a first division line parallel to the straight line connecting the second beam detection section and a second division line perpendicular to the first division line. , a spot of the sub-beam is placed on the first and second beam detection portions of the photodetector in which the first dividing line of the photodetector is arranged approximately along a straight line connecting the spots of the two sub-beams, The main beams are each focused on the third beam detection section. Here, the first. A track error signal is generated from the second beam detection section, and at least an information reproduction signal and a focus error signal are generated from the third beam detection section.

(Example) Next, one embodiment of the present invention will be described using the drawings.

FIG. 1 is a configuration diagram of a photodetector of an optical information reading device illustrating an embodiment of the present invention, FIG. 2 is a configuration diagram of the optical information reading device shown in FIG. 1, and FIG. A configuration diagram explaining the beam spot 1 on the recording medium of the optical information reading device shown in the figure, FIG. 4 is a diagram explaining the method of generating various signals in the photodetector in FIG. It is an explanatory diagram showing an example of.

First, the overall configuration of the optical information reading device of this embodiment will be explained using FIG. In the figure, 21 is a laser light source that emits a laser beam. 22 is a collimator lens that converts the laser beam emitted from the laser light source into a parallel beam, and 23 is a diffraction grating that separates the laser beam into a main beam m and two sub beams 81 and 82. 24 is the third part of the diffraction grating 23
It is a beam splitter that transmits two beams and reflects the return beam from the recording medium (in this embodiment, an optical card with a wide track width) 25. 26 is an objective lens that focuses the laser beam emitted from the beam splitter 24.

27 is a collimator lens that focuses the parallel beam reflected by the beam splitter 24, and 28 is a toric lens that receives the laser beam emitted from the collimator lens 27 and functions as a lens in only one direction. Furthermore,
29 is a photodetector on which the laser beam from the toric lens 28 is focused.

Next, the beam spot on the recording medium 25 will be explained using FIG. Of the three beams separated by the diffraction grating 23, the main beam m is illuminated so as to be positioned approximately at the center of the track T of the recording medium 25 when on-track, and the two sub beams 81. s2 is irradiated so as to cover both sides of the recording track T of the recording medium 25. In addition, two D1 beams sl.

The reason why the straight line connecting S2 is inclined by θ with respect to track 1 (shifted in the forward direction) is to prevent leakage of the detection signal and to avoid crosstalk from adjacent tracks.

Next, the configuration of the photodetector 29 will be explained using FIG. 1. In the figure, the photodetector 29 includes a first beam detection section 3C'' and a second beam detection section 31 where the spots of the sub beams 81 and 82 are focused, a first beam detection section 30 and a second beam detection section 31. A third beam detection section 32 is disposed between the two and converges the spot of the main beam m, and has the same size as the conventional photodetector 9 shown in FIG. The third beam detection section 32 is the first beam detection section 30
A first dividing line 32a parallel to the straight line connecting
The light receiving surface 3 is divided into four parts by the dividing line 32b.
2c, 32d, 32e, and 32f. and,
The first dividing line 32a of the photodetector 29 separates the two sub beams s.
1. The photodetector 29 is arranged substantially along the straight line connecting the spots s2. In addition, the third beam detector 32
When the upper main beam m is out of focus, it forms an elliptical spot shape at the position shown in Fig. 4.
The toric lens 28 is adjusted in the generatrix direction.

Next, a method for generating various signals in the photodetector 29 will be explained using FIG. 4. In the figure, the output of the first beam detector 30 is A, and the output of the second beam detector 31 is B.
, the outputs of the light receiving surfaces 32c to 32f of the third beam detector 32 are C and D, respectively.

Let them be E and F. 33.37 is a differential amplifier, 34°35.
36 is an adder. The spot shape of the main beam m is circular as shown by the solid line in the figure when in just focus, but becomes elliptical as shown by the two-dot chain line when out of focus.

And, these differential amplifiers 33, 37 and the tamperer 34
．． The following calculations are performed using 35 and 36, and a track error signal, a focus error signal, and an information reproduction signal @ (HF signal) are generated.

Track error signal - A-8 Focus error signal = (C + E) - (D + F) Information reproduction signal = (C + E) + (D + F) According to the above configuration, the photodetector 29 of the same size and configuration as the conventional one is used. Even when reading information on a recording medium with a wide track width, the photodetector 29 can be mounted by changing the direction, adjusting the diffraction grating 23, and adjusting the toric lens 28 without changing the basic structure. Secondary beam 51. Since the spot S2 is focused on the first beam detection section 3o and the second beam detection section 31, a tracking error signal can be generated.

Note that the present invention is not limited to the above embodiments.

For example, as shown in FIG. 5, if a collimator lens 41 is disposed between the beam splitter 24 and the objective lens 26, only one collimator lens is required. Furthermore, if a finite specification objective lens is used, a collimator lens is not required. Further, in the above embodiment, an optical pickup for reading has been described, but the present invention can also be applied to an optical pickup for writing and reading.

(Effects of the Invention) As described above, according to the present invention, the first dividing line of the photodetector is disposed approximately along the straight line connecting the spots of two sub-beams, and the spot of the sub-beams is 1. By focusing the light on the second beam detection section and the main beam on the third beam detection section, even recording media with wide track widths can be read using a conventional photodetector. It is possible to realize an optical information reading device that is capable of

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a photodetector of an optical information reading device illustrating an embodiment of the present invention, FIG. 2 is a configuration diagram of the optical information reading device shown in FIG. 1, and FIG. A configuration diagram explaining the beam spot on the recording medium of the optical information reading 1iff shown in the figure, FIG. 4 is a diagram explaining the method of generating various signals in the photodetector in FIG. An explanatory diagram showing an embodiment, FIG. 6 is a configuration diagram of a conventional optical information reading device, FIG. 7 is a diagram explaining a beam spot on a recording medium in FIG. 6, and FIG. 8 is a diagram explaining a beam spot on a recording medium in FIG. 6. FIG. 9 is a diagram illustrating a beam spot on a detector, FIG. 9 is a diagram illustrating a method of generating each ladder bow in the photodetector in FIG. 6, and FIG. 10 is a diagram illustrating a problem. In these figures, 1.21... Laser light source Fig. 1 Fig. 2 2.22... Collimator lens 3.23... Diffraction grating 4.24... Beam splitter 5.25... Recording Medium 6.26... Objective lens 7.27... Collimator lens 8.28... Toric lens 9.29... Photodetector 0.30... First beam detection section 1.31... -Second beam detection section 2.32...Third beam detection section 2a, 32a...First division line 2b, 32b...Second division line

Claims (1)

[Claims] a laser light source that emits a laser beam; a main beam that irradiates the laser beam to approximately the center of the track of the recording medium when on-track; and two beams that irradiate the laser beam to cover both sides of the track of the recording medium when on-track. A straight line arranged between a first optical system that divides into sub-beams, first and second beam detection sections, and the first and second beam detection sections, and connecting the first and second beam detection sections. a photodetector comprising a third beam detection section having a light-receiving surface divided into four by a first dividing line parallel to the first dividing line and a second dividing line perpendicular to the first dividing line; and the recording medium. a second optical system that separates three reflected beams from the beam, generates a tracking error signal from the first and second beam detection sections, and generates at least an information reproduction signal and a focus signal from the third beam detection section. In an optical information reading device that generates an error signal, a first dividing line of the photodetector is disposed approximately along a straight line connecting the spots of the two sub-beams, and the spot of the sub-beams is separated from the spot of the sub-beams by the 1. An optical information reading device characterized in that the main beam is focused on the second beam detection section, and the main beam is focused on the third beam detection section.