JPH0573953A - Optical recording and reproducing device - Google Patents

Abstract

PURPOSE:To simplify the adjustment of the position of a photodetector by decreasing the number of the photodetectors. CONSTITUTION:An emitted light from a semiconductor laser 1 is condensed on an optical disk 13 by an image forming lens 18, a reflected light 14 from the optical disk 13 is diffracted by a diffracting element 3, and received by half-divided photodetecting parts 39, 40, 41, and 42 of a photodetector 4. The emitted light from the semiconductor laser 1 is reflected by a mirror 5 on the photodetector 4, so that both the +1 order diffracted light and -1 order diffracted light can be received by one photodetector 4 without forcedly working the photodetector 4 into a shape in which the light is not shielded.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording / reproducing device used for a compact disc reproducing device or the like.

[0002]

2. Description of the Related Art A conventional optical recording / reproducing apparatus using a diffractive element has a structure as disclosed in, for example, Japanese Patent Laid-Open No. 62-137736. FIG. 6 shows an example of a conventional optical recording / reproducing apparatus. Emitting light 2 of semiconductor laser 1
Passes through the diffraction grating 17 and is focused on the optical disk 13 by the imaging lens 18. The reflected light 14 from the optical disk 13 is converged by the imaging lens 18, and the diffraction grating 17
Is diffracted by. Diffracted lights 15, 16 of the diffraction grating 17,
33 and 34 reach the two-divided photodetectors 19, 20, 31, and 32 beside the semiconductor laser 1, respectively. Here, the diffracted lights 33 and 34 are in a relationship of −1st-order diffracted light when the diffracted lights 16 and 15 are + 1st-order diffracted light, and + 1st-order diffracted light when they are −1st-order diffracted light. The two-divided photodetectors 19, 20, 31, and 32 are photodetectors 9 and 10, photodetectors 11 and 12, photodetectors 27 and 28, and photodetector 29, respectively.
And 30. The two-divided photodetectors 19, 20, 31, 32 are all on the same plane perpendicular to the optical axis of the imaging lens 18.

FIG. 7 schematically shows how the grating 17 is arranged when the diffraction grating 17 is viewed from the direction of the semiconductor laser 1. The pitch of the grid is written larger than it actually is to make the arrangement easier to understand. The diffraction grating 17 is composed of a left diffraction grating 21 and a right diffraction grating 22 having different grating directions with a line intersecting the optical axis of the imaging lens 18 as a boundary. The ± first-order diffracted lights of the left diffraction grating 21 converge on a point 25 on the division line of the two-division photodetector 19 and a point 24 on the division line of the two-division photodetector 32. On the other hand, the ± first-order diffracted lights of the right diffraction grating 22 are converged on a point 26 on the dividing line of the two-division photodetector 20 and a point 23 on the dividing line of the two-division photodetector 31.

A method of obtaining the focus error signal, the tracking error signal, and the reproduction signal will be described below.

Blurring of the upper and lower surfaces of an optical disk (defocus)
On the other hand, since the amount of light received by the photodetectors 9, 10, 11, 12, 27, 28, 29, 30 of the two-divided photodetectors 19, 20, 31, 32 varies, the photodetectors 9 and 10 have different amounts. Difference in received light amount, difference in received light amount between photodetectors 11 and 12, photodetector 2
A signal indicating the difference in the amount of received light between 7 and 28 and the difference in the amount of received light between the photodetectors 29 and 30 can be used as the focus error signal. That is, at the in-focus position, as described above, 2
Since the diffracted lights 15, 16, 33, 34 converge on the division lines of the divided photodetectors 19, 20, 31, 32, the difference signal becomes zero. When the optical disk 13 is displaced in the direction away from the imaging lens 18, the convergence points of the diffracted lights 15, 16, 33, 34 are directed from the two-divided photodetectors 19, 20, 31, 32 toward the diffraction grating 17. Shift to. At this time, since the light beam incident on the center of the diffraction grating 17, that is, the optical axis of the imaging lens 18, is immovable, the blur of the convergent point of the diffracted light is the photodetector inside each of the two-split photodetectors 19 and 20. 10 and 1
1 and on the photodetectors 27 and 30 outside the two-split photodetectors 31 and 32, respectively.
The amount of light coming to 7,30 increases. On the contrary, the optical disc 13
Is closer to the imaging lens 18, the diffracted light 15, 1
The convergence points of 6, 33, and 34 shift in the direction away from the diffraction grating 17. In this case, the light amounts of the photodetectors 9 and 12 outside the two-divided photodetectors 19 and 20 and the photodetectors 28 and 29 inside the two-divided photodetectors 31 and 32, respectively, increase.

Based on the above concept, the photodetectors 9, 10,
The output voltages of 11, 12, 27, 28, 29, 30 are V (9), V (10), V (11), V (12) and V, respectively.
If (27), V (28), V (29), and V (30), the focus error signal is (V (10) + V (11))-
(V (9) + V (12))-(V (28) + V (2
9)) + (V (27) + V (30)),
The direction and amount of defocus of the optical disk 13 can be detected.

On the other hand, the tracking error signal utilizes that the intensity distribution of the returning light is unbalanced when the narrowed spot of the emitted light 2 from the semiconductor laser 1 on the optical disk 13 deviates from the track position. If the track extends in the direction perpendicular to the plane of the drawing, the intensity ratio of the diffracted lights 15 and 16 and the intensity ratio of the diffracted lights 33 and 34 will change due to the track shift, so A difference occurs between the output signal of 20 and the output signals of the two-division photodetectors 31 and 32. Therefore, the tracking error signal is (V (9) + V (10))-(V (11) + V
(12))-(V (27) + V (28)) + (V (2
9) + V (30)), and the direction of track deviation can also be detected by the positive / negative of this difference signal.

The reproduced signal from the optical disk 13 is the sum of the light amounts of the two-divided photodetectors 19, 20, 31, 32, V
(9) + V (10) + V (11) + V (12) + V (2
7) + V (28) + V (29) + V (30) can be detected.

The focus error signal is obtained by not using both the ± 1st-order diffracted light from the diffraction grating 17 but using only the + 1st-order diffracted light or the −1st-order diffracted light, for example, only by the two-split photodetectors 19 and 20. , The tracking error signal and the reproduction signal can be detected, but the two-division photodetectors 19, 20, 3
The light utilization rate is higher when all of the signals 1 and 32 are used to detect these signals.

[0010]

The above-mentioned conventional optical recording / reproducing apparatus has the + 1st order diffracted light from the diffractive element and the -1st order diffracted light.
Since different diffracted light is received by different photodetectors,
Since the number of photodetectors required is large, it takes time to adjust the position of the photodetectors. Further, among the diffracted light of the diffractive element, a photodetector 84 as shown in FIG. 8A, which has a photodetector capable of receiving both the + 1st-order diffracted light and the −1st-order diffracted light, There is a problem that the light emitted from the means is blocked. In FIG. 8 (a), 85, 86, 8
Reference numerals 7 and 88 denote two-division photodetection units, each of which is a photodetection unit 8
9, 90, light detectors 91, 92, light detectors 93, 94,
It is composed of photodetectors 95 and 96. In order to avoid such a problem, as shown in FIG. 8B, a method of forming a hole 98 in the photodetector 97 through which light emitted from the light generating means is passed, or as shown in FIG. 8C. , U-shaped photo detector 9
Although a method of scraping 9 can be considered, there is a problem that it is difficult to perform such processing without damaging the photodetection portion.

An object of the present invention is to solve the above-mentioned problems, to utilize both + 1st-order diffracted light and -1st-order diffracted light and to adjust the position of the photodetector by reducing the number of photodetectors. An object is to provide an optical recording / reproducing device that can be simplified.

[0012]

According to the present invention, there is provided a light generating means, an image forming lens for condensing light emitted from the light generating means on a recording medium, and the light generating means and the image forming lens. In between, a diffractive element for diffracting the reflected light from the recording medium out of the optical axis of the light emitted from the light generating means,
In an optical recording / reproducing device including a photodetector having a plurality of photodetectors for receiving light diffracted by the diffractive element and converting an optical signal into an electric signal, the photodetector is diffracted by the diffractive element. A reflector that receives both the + 1st-order diffracted light and the -1st-order diffracted light of the light and reflects the light emitted from the light generating means to guide it to the diffraction element is fixed on the photodetector. It is characterized by being.

[0013]

Since both the + 1st-order diffracted light and the -1st-order diffracted light are received by the same photodetector, the position of the photodetector can be adjusted more easily than when received by separate photodetectors. ..
Further, since the light emitted from the light generating means is reflected by the mirror on the photodetector, there is no risk of the light being kicked by the photodetector.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the optical recording / reproducing apparatus of the present invention will be described below with reference to FIG.

As shown in FIG. 1, an optical recording / reproducing apparatus according to this embodiment includes a semiconductor laser 1 as a light generating means,
The mirror 5 that is a reflector that reflects the emitted light 2 from the semiconductor laser 1 and the light that has passed through the diffractive element 3 are focused on the optical disk 13 that is a recording medium, and the reflected light 14 from the optical disk 13 is reflected by the diffractive element 3. To the image forming lens 18, the diffractive element 3 that diffracts the reflected light 14 out of the optical axis of the image forming lens 18, and the diffracted lights 35, 36, 37, 38 to receive the light signals and convert the optical signals into electrical signals. It is composed of a photodetector 4. The diffractive element 3 is divided into regions 3a and 3b with a point intersecting the optical axis of the imaging lens 18 as a boundary, and the region 3a is diffracted light 3
5, 38 and the region 3b generate diffracted light 36, 37.
As shown in FIG. 2, the photodetector 4 includes two-split photodetectors 39 and 40 that receive the diffracted lights 35 and 36, and diffracted lights 37 and 38.
It is provided with two-split photodetectors 41 and 42 for receiving the light. Two
The divided light detectors 39, 40, 41, 42 include the light detectors 43, 44, the light detectors 45, 46, and the light detectors 47, 4 respectively.
8 and the photodetectors 49 and 50.

The optical recording / reproducing apparatus according to this embodiment is provided with the photodetector sections 43, 44, 45, 46, 47, 48, 49, and 5.
The output voltage of 0 is V (43), V (44), V
(45), V (46), V (47), V (48), V
(49) and V (50), V is the focus error signal.
(43) -V (44) -V (45) + V (46) -V
(47) + V (48) + V (49) -V (50) is used as a tracking error signal V (43) + V (44) -V
(45) -V (46) -V (47) -V (48) + V
(49) + V (50) and V (4
3) + V (44) + V (45) + V (46) + V (4
7) + V (48) + V (49) + V (50) is used.

A second embodiment of the optical recording / reproducing apparatus of the present invention is the same as the optical recording / reproducing apparatus of the first embodiment, except that the photodetector 6 shown in FIG. The detector 63 is arranged so as to come to the semiconductor laser 1 side. Depending on the structure, the emission angle of the emitted light of the semiconductor laser 1 may be different between the direction parallel to the joint surface and the direction perpendicular to the joint surface. Therefore, only the portion near the optical axis is used instead of the entire emitted light. Sometimes. In that case, the light detector 6
The intensity of the emitted light is detected by receiving the light that is not originally used in 3, and the intensity of the emitted light is stabilized by controlling the injection current to the semiconductor laser 1. The two-divided photodetectors 51, 52, 53, 54 of the photodetector 6 are the two-divided photodetectors 39, 40, 41, 4 of the photodetector 4 of FIG. 2, respectively.
2 corresponds to the photo detectors 55, 56, 57 of the photo detector 6,
Reference numerals 58, 59, 60, 61 and 62 denote photodetector sections 43, 44, 45, 46, 47 and 4 of the photodetector 4 of FIG. 2, respectively.
It corresponds to 8, 49, 50.

A third embodiment of the optical recording / reproducing apparatus of the present invention is the same as the optical recording / reproducing apparatus of the first embodiment, except that the diffraction element 74 shown in FIG.
A photodetector 75 shown in FIG. 4B is arranged instead of the photodetector 4. The diffractive element 74 is provided with a track error detection region 74c and a region 74d.
The diffracted light from c is condensed on the photodetector 76 and the photodetector 79, and the diffracted light from the region 74d of the diffraction element 74 is condensed on the photodetector 77 and the photodetector 78. Diffractive element 7
The regions 74a and 74b of No. 4 are used for focus error detection, and the diffracted light from the region 74a of the diffractive element 74 is focused on the division line of the two-division light detection unit 81 and the division line of the two-division light detection unit 82. Then, the diffracted light from the region 74b of the diffractive element 74 is condensed on the division line from the two-division light detection unit 80 and on the division line of the two-division light detection unit 83. The focus error signal is obtained by the same calculation as that of the optical recording / reproducing apparatus of the first embodiment, and the track error signal is obtained from the sum of the outputs of the photodetector 76 and the photodetector 79 and the photodetector 77 and the optical detector. It is obtained by subtracting the sum of the outputs of the detector 78. The reproduced signal is obtained from the sum of all outputs. Since the two regions for detecting the track error and the two regions for detecting the focus error are provided on the diffractive element at a right angle, it is difficult for the track error signal to wrap around the focus error signal.

The fourth embodiment of the optical recording / reproducing apparatus of the present invention is the same as the optical recording / reproducing apparatus of the third embodiment, except that the diffraction element 64 shown in FIG.
5 has a configuration in which a photodetector 65 shown in FIG. 5B is arranged instead of the photodetector 75. Area 64 of the diffractive element 64
a, 64b, 64c and 64d are diffraction elements 74, respectively.
74a, 74b, 74c, and 74d. Then, the two-divided photodetectors 66, 67, 68 of the photodetector 65,
Reference numeral 69 denotes a two-divided photodetector section 80 of the photodetector 75,
Corresponding to 82, 81, 83, the photodetector 7 of the photodetector 65.
Reference numerals 0, 71, 72 and 73 correspond to the photo detectors 75, 77, 78 and 79 of the photo detector 75, respectively.

[0020]

As described above, according to the present invention,
By combining the photodetector that receives the + 1st-order diffracted light and the photodetector that receives the -1st-order diffracted light into one photodetector, the number of required photodetectors can be reduced. Therefore, it is easy to adjust the position of the photodetector. Further, since the light emitted from the light generating means is reflected by the reflector on the photodetector, there is no risk of the light being kicked by the photodetector, and there is no need to process the photodetector into an unreasonable shape.

[Brief description of drawings]

FIG. 1 is a schematic perspective view showing the configuration of a first embodiment of an optical recording / reproducing apparatus of the present invention.

FIG. 2 is a plan view showing a photodetector in the embodiment of FIG.

FIG. 3 is a plan view showing a photodetector in a second embodiment of the optical recording / reproducing apparatus of the present invention.

FIG. 4 is an explanatory view showing a third embodiment of the optical recording / reproducing apparatus of the present invention, (a) is a plan view showing a diffraction element,
(B) is a plan view showing a photodetector.

FIG. 5 is an explanatory view showing a fourth embodiment of the optical recording / reproducing apparatus of the present invention, (a) is a plan view showing a diffraction element,
(B) is a plan view showing a photodetector.

FIG. 6 is a schematic diagram showing a configuration of a conventional optical recording / reproducing apparatus.

FIG. 7 is an explanatory diagram showing a diffraction grating and a photodetector that constitute a conventional optical recording / reproducing device.

FIG. 8 is an explanatory diagram showing three types of photodetectors, (a)
Is a plan view of a photodetector having a rectangular shape, (b) is a plan view of a photodetector having a hole in the center, and (c) is a plan view of a photodetector having a U-shape.

[Explanation of symbols]

 1 Semiconductor Laser 2 Emitted Light 3 Diffraction Element 3a, 3b Region 4 Photo Detector 5 Mirror 6, 9-12 Photo Detector 13 Optical Disc 14 Reflected Light 15, 16 Diffracted Light 17 Diffraction Grating 18 Imaging Lens 19, 20 2 Split Light Detector 21 Left-side diffraction grating 22 Right-side diffraction grating 23-26 Convergence point of diffracted light 27-30 Photodetector 31,32 2-split photodetector 33-38 Diffracted light 39-42 2-split photodetector 43-50 Photodetection Part 51-54 2-division photodetector 55-63 Photodetector 64 Diffraction element 64a, 64b, 64c, 64d Area 65 Photodetector 66-69 2-division photodetector 70-73 Photodetector 74 Diffraction element 74a, 74b , 74c, 74d area 75 photodetector 76-79 photodetector 80-83 2-split photodetector 84 photodetector 85-88 2-split photodetector 89-96 photodetector Parts 97 and 99 optical detector 98 holes

Claims (1)

[Claims] 1. A light generating means, an image forming lens for condensing light emitted from the light generating means onto a recording medium, and a light generating means for collecting light from the recording medium between the light generating means and the image forming lens. Photodetector having a diffractive element for diffracting the reflected light out of the optical axis of the light emitted from the light generating means, and a plurality of photodetector parts for receiving the diffracted light by the diffractive element and converting an optical signal into an electrical signal. In the optical recording / reproducing apparatus including a container, the photodetector receives both the + 1st-order diffracted light and the -1st-order diffracted light of the diffracted light of the diffractive element, and outputs the diffracted light from the light generating means. An optical recording / reproducing apparatus, wherein a reflector that reflects the reflected light and guides it to the diffraction element is fixed on the photodetector.