JPS60147940A - Skew error signal detector of optical disc - Google Patents

Abstract

PURPOSE:To detect also a skew signal by detecting a main spot reflected on a disc by a 4-split photodetector and a sub-spot with a 2-split photodetector and applying a prescribed arithmetic processing to the output of them. CONSTITUTION:The main spot reflected from the disc detected by the 4-split photodetector 8 and four detected signal A-D are inputted to an adder 21 and arithmetic amplifiers 22, 23 via amplifiers 20a-20d. The adder 24 outputs an RF signal through the arithmetic of A+B+C+D and the arithmetic amplifiers 22 gives a focus error signal through the arithmetic of (A+D)-(C+B). On the other hand, the sub-spot is detected by the 2-split photodetectors 9a, 9b, the outputs, E, F are difference signal of E-F at the arithmetic amplifier 25, inputted to the arithmetic amplifier 24, and a skew error signal SE is obtained by the arithmetic of [(A+B)-(C+D)]-K(E-F) with the reception of the output (A+B)-(C+D) of the arithmetic amplifier 23, where K is a constant.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an optical disk skew error signal detection device for detecting a skew servo in an original disk playback device in which video signals, audio signals, etc. are recorded. be.

[Background technology and its problems]

In an apparatus for reproducing an original disc on which circumferential overlay information has been recorded, a tracking servo and a focus servo are indispensable in order to optically read a recording track of several μm.

- If a skew occurs in the original disk due to deformation (warpage) of the original disk, chucking error, etc., the reflective surface of the original disk cannot be set at 90 degrees with respect to the irradiation beam. , the reproduction characteristics (MTF, PPF, etc.) deteriorate, and the distortion of the reproduced RF signal increases.

Therefore, a skew servo is also required to control the pickup device lt by detecting the skew and maintain orthogonality between the optical axis and the reflecting surface.

Figure 1 was proposed by the present applicant (Japanese Patent Application No. 58-26213
This is a schematic diagram illustrating a method for detecting the noise error signal, where D is an original disk on which information is recorded on the reflective surface, and PD is an objective lens OLv in which a laser is applied to the reflective surface of the original disk D.
SO represents a skew device that moves integrally with the optical device PD and detects the tilt of the original disk D.

This skew device SD includes a light emitting source 10° lens system 11*PBS (Polarizatlon Be
am 5plitter) 12 + QWP (Qua
rter Wave Plate) 13 z A light receiving element 14 is built-in.

Spora of skew device SO consisting of a structure)Q
moves in the radial direction (F) together with the spora S of the optical device PO as the original disk D rotates, so when the reflected light of the spot Q is detected by the light receiving element 14 divided into four By calculating the detection signals obtained from the A, B, C, and D division planes, the inclination t of the original disk D can be detected.

However, this method does not provide an accurate skew error signal because the positions of the optical device PD (spora) 8 and the skew device SO (spora) Q, which actually read the recording track information, are different. In addition, the weight of the entire original pickup device increases due to the skew device SD,
There is a problem that the response becomes poor and the response becomes high (11i1iK).

[Purpose of the invention]

This invention has been made to overcome these drawbacks.
An object of the present invention is to provide a skew error signal detection device for an optical disc that can detect Skinny error number δ from a conventional focus error detection and tracking error detection optical system.

[Summary of the invention]

The present invention provides an optical disc playback device equipped with an optical system that detects a tracking error signal t using a three-beam method and a focus error signal using an astigmatism method, in which four detection signals A, B, and B are used to detect the focus error signal.
Detecting C, D, and tracking error signals 2
The two detection signals E and FY are each input to the arithmetic circuit, and ((A+B) −(C+D) J −K(E−F
) to detect the skew error signal from k.

Therefore, since the skew error signal can be detected without installing a special optical system, the entire pickup device can be made smaller.In addition, since the skew error is detected from the signal for reading the RF flaw signal, the skew servo w*E
Fc can be applied.

〔Example〕

FIG. 2 shows an overview of the optical system in the skew error signal detection device of the present invention, where l is a laser emission source, 2 is a collimator lens, 3 is a diffraction grating, 4 is a PBS, and 5 is a Q
WP, 8 is objective lens, 1 is cylindrical lens, 8
．． 9m and 9b indicate light receiving elements.

In this optical system, the focus error signal is the astigmatism method, and the tracking error signal is 3
This is a device that uses the beam method for detection.

That is, the main spot hso formed by the diffraction grating 3.

And the reflected light of the sub spot S1.8-1 is shown in Fig. 3(a).
You can see K, 5K, light receiving element 8 divided into 4, and 2
The light-receiving elements 9m and 9bVC, which are divided into two, are each irradiated with light.

Then, from the four detection signals A, B, C, and D of the light receiving element 8 illuminated by the main spot) So, (A+D) - (
B+C)! A focus error signal is detected due to the calculation, and a tracking error signal is detected by calculating E-FY from the detection signals E and F of the light receiving elements 9a and 9b (the sub-spots illuminated by the light receiving elements 9a and 9b) S+ and S-t. Ru.

By the way, in such an optical system device, if the original disk D is now tilted in the radial direction (most of the skinny of the original disk D occurs in the radial direction), the light receiving element 8. Each of the spots (go = L, S - r) about to be irradiated with 9m and 9bK is deviated from the center according to the inclination of the original disk D, as shown in FIG. 3(b)K.

Previously, the main sink) 80 was irradiated and the light receiving elements 80 and 9 detected values were 55 (A+B) with numbers A, B, C, and D.
By calculating -(C+D), the degree of inclination, ie, skew, of the original disk D can be detected.

However, the calculation value t skew error signal of (A + B - (C + D) above can be calculated only when the tracking of the main spot So is good and the main spot S0 is on the recording track. When the image is outside the main slot (S), the image is formed on the light-receiving element 8. Since the light amount distribution within the left and right sides is asymmetric, the calculated value (A+B)-
(C+D) does not necessarily indicate a skew error signal.

That is, as shown in Fig. 3(c), when tracking is occurring with 5Vc skew, the sub-slot (Sl)
, it goes without saying that there is a difference in the amount of light from SI.
Since the intensity distribution of the amount of light within the main slot 80 also changes asymmetrically in the left and right directions, the above-mentioned calculated value includes the tracking error signal. (Main subotsu) S
The intensity distribution of the amount of light in jl is influenced by the diffracted light from the bits of the original disk D, as seen in the push-pull method. When the tracking is deviated by a certain degree, the intensity distribution of the reflected light becomes asymmetrical within the main spot (So). ) Therefore, in the present invention, the test signals E and FY of the light receiving elements 9a and 9a, which detect only the tracking error signal, are used to detect the main slot S. This constitutes an arithmetic circuit that removes the tracking error signal contained in the skew error signal and outputs only the skew error signal.

Fig. 4 shows an example of a calculation circuit, where 8 is 4.
The divided light receiving elements 9a and 9bG are light receiving elements for detecting trunking error signals.

The four detection signals obtained from the light receiving element 8 are amplified by the amplifiers 20a, 20b, 20c, and 20d.
, the input i8t to the adder 21 and the operational amplifiers 22 and 23.
do. The adder 21 calculates the RF by the operation of A+B+C+D.
Outputs the flaw signal and turns on the operational amplifier 22 (A+D)-(C+
The operational amplifier 23 outputs the skew error signal + tracking error signal Ylii from the calculation (A + B (C + D)) as described above. , 9b, the operational amplifier 250 calculates the difference output between the detection signals E and F.
Since the W force is input to the operational amplifier 24, a skew error signal can be obtained by calculating ((A+B)-(C+D)l-K(E-F)).

K is an operational amplifier 2 that outputs and processes a tracking error signal.
5 is the gain of the amplifier 26 which is multiplied by the calculated value (E-F)'t' constant.

This gain includes the main spot S as described above.

This is an example constant.

Then, it is only necessary to remove the tracking in a state where there is no skew, output the skew error signal, and then determine the 5VC gain K so that the output of the operational amplifier 24 is OK.

Strictly speaking, K is the light-receiving piezoelectric 8. Depending on the detection sensitivity of 9a and 9b and the degree of tracking deviation, it is also possible to make it variable to 5 so that the normal f tracking Makiari hV can be canceled.

Note that the skew error signal is supplied to a skew servo (not shown) that automatically corrects the original axis of the optical system.

〔Effect of the invention〕

As explained above, the optical disc skew detection device 11 of the present invention is constructed by adding a simple arithmetic circuit and a detection mechanism for a focus error signal and a tracking error signal using a light receiving element +K to the conventional 6-divided optical disk. Since the skew error signal can be detected, there is an advantage that the pickup device does not increase in weight and can be made compact.

Since the calculated signal reading position and skew detection position are different from each other, there is an effect that skew servo control is performed properly.

[Brief explanation of drawings]

Figure 1 is a diagram showing the Kth prior art for detecting skew error signals, Figure 2 is a schematic diagram of an optical system that can be used to detect skew error signals, Figure 3 (a) = (b)
), (c) shows the movement of skew error No. 46 Y' [bright kth spot (So = S+ -8-+) t.
The eJS diagram and FIG. 4 are skew error signal detection block diagrams showing an embodiment of the present invention. In the figure, 2 is a frimeter lens, 3 is a diffraction grating, and 4 is a PB.
S, 5 is a QWP, 6 is an objective lens, 1 is a cylindrical lens, 8 is a light receiving element divided into 4 parts, 9a + 9b are two light receiving elements for tracking error detection T6 Fig. 1 Fig. 3 (a) , , , (b) (c) Figure 4 Procedural amendments stamped) May 18, 1980 Mr. Commissioner of the Japan Patent Office 1, Indication of the case Patent application No. 59-0021394 2, Title of the invention Skew error of optical disc Relationship between signal detection device 3 and the person making the amendment Patent applicant address 6-7-35, Kitashinyo, Tokyo Parts Store Name (2
18) Sony Corporation Representative Norio Ohga 4, Agent Kobayashi Patent Office 6th floor, Okunomatsu Building, 31-16 Sakuragaoka-cho, Shibuya-ku, Tokyo 150 Tel: 03 (496) 1256-5, Subject of amendment Detailed Description of the Invention in the Specification, Drawing 6, Contents of Amendment (1) "Optical disc reproducing device" in the first line of page 2 of the specification is corrected to "Optical disc reproducing device." (2) Similarly, "optical disc skew error signal detection device" in lines 2 to 3 of page 2 is corrected to "optical disc skew error signal detection device". (3) Same f〈r on page 2, line 13 (MTF, PPE, etc.)
" is corrected as r (MTF, PTF, etc.)". (4) Similarly, on page 3, line 13, "as the optical disc D rotates" is corrected to "when the optical disc D rotates." (5) Amend Figure 4 of the drawing as shown in the attached sheet. Written amendment to the above procedure (voluntary) January 8, 1980 To the Commissioner of the Japan Patent Office 1 Indication of the case Patent application No. 59-0028114 2 Title of the invention Optical disc skew error signal detection device Address Tokyo Parts Co., Ltd. 6-7-35 Name (2
1B) Sony Corporation Representative Norio Oga 4, Agent Address: 6F, Okunomatsu Building, 31-16 Sakurago-cho, Shibuya-ku, Tokyo 150 Kobayashi Patent Office Tel: 03 (496) 1256-5 Details subject to amendment Detailed description of the invention in the book, Drawing 6, Contents of amendment (1) [Reproduction characteristics (MT
F, PPP, etc.) deteriorate, and the playback characteristics (MTF, etc.) deteriorate.
, PTF, etc.) are deteriorated. (2) Similarly, "left and right" in lines 8 and 15 of page 7 are corrected to "top and bottom," respectively. (3) Figures 3 and 4 of the drawings should be corrected as shown in the attached sheet. Figure 3 (a) (b) (c) Figure 4

Claims (1)

[Scope of Claims] The main spot reflected from the disk surface is detected by a light receiving element divided into four parts, and the detected four words A, B, C, and D of the four divided light receiving elements are detected by (A+Dn-(B+Cn). A device detects a focus error signal by calculating In an optical disc playback device equipped with a device for detecting a tracking error signal, the detection signal A
, B, C. By D, E, F and proportionality constant, ((A+B)−
(c−+−D))−K(E−F) is detected by a circuit that calculates the skew error signal? Features: Optical disc skew error signal detection device.