JPS60143441A - Tracking error detecting circuit - Google Patents

Abstract

PURPOSE:To surely fetch a tracking error signal without being influenced by disturbance, by supplying a multiplied signal which is obtained by multiplying the difference signal of both diagonal sum signals of a photoreceiving element by the difference signal of both added signals of the element to a low-pass filter and sending out the tracking error signal. CONSTITUTION:Output signals of buffer amplifiers 2b and 2d are added to each other at an adder 11, and output signals of buffer amplifiers 2a and 2c are added to each other at another adder 12. Difference between both added results is found at a subtractor 13. An output signal H of a value corresponding to the difference between output signals C and D of adders 3 and 4 is generated from a subtractor 10. The output signal H of the adder 10 is multiplied by an output signal G generated from the subtractor 13 at a multiplier 14 and an output signal I is generated. The multiplied output signal I is averaged at a low-pass filter 15 and a tracking error signal TE showing the deviated quantity and deviating direction of tracking is outputted. Therefore, the tracking error signal which is not influenced by the inclination of a disk, etc., can be fetched.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to tracking error detection and recording of an optical head used in a digital audio disc playback device, etc., and in particular, to detecting and recording tracking errors reliably without being affected by disturbances caused by the inclination and equal pressure of the disc. An object of the present invention is to provide a tracking error detection circuit that can detect tracking errors.

BACKGROUND ART In recent years, with the rapid development of electronic technology, there has been a trend toward digital recording in audio devices, one of which is a digital audio disc playback device. This digital audio disc playback device rotates a disc as a recording medium at a constant linear velocity, optically reads a digital audio signal optically recorded on the surface of this disc, and converts it into an electrical signal. It is something to take out. This extracted electrical signal is then subjected to signal processing such as error correction and decoding, converted into an analog signal, further stabilized and averaged, and then passed through a low-pass filter to produce a reproduced audio signal. This is what you get.

In this case, the optical head irradiates a light beam onto the surface of the disk that is rotating at a constant linear velocity, and reads recorded information by detecting the reflected light.
In this case, if the tracking of the optical head with respect to the recording track deviates, it becomes impossible to read the recorded information, so it is necessary to always perform accurate tracking control. A tracking control circuit accurately irradiates a target recording track with a light beam, and a tracking error detection circuit for detecting the amount of tracking deviation is provided at the front stage of this tracking control circuit.

FIG. 1 is a circuit diagram showing an example of a conventionally commonly used tracking error detection circuit. In the figure, reference numeral 1 denotes a light detection unit that detects reflected light from the disk, and the light is divided into four parts by light receiving elements 18 to 1d, which are divided into a direction along the scanning direction AK and a direction perpendicular thereto. It constitutes the detection section.

28 to 2d are buffer amplifiers, and light receiving elements xa-
The output signals B a - and -B d of td are each amplified and output. 3 are output signals Ba and Bb supplied from the light receiving elements 1a and 1b via buffer amplifiers 2a and 2b.
4 is an adder that adds and outputs output signals Bc and Bd supplied from light receiving elements 1c and 1d via buffer amplifiers 2c and 2d, and 5 is an adder that adds and outputs output signals from adder 3.4. A subtracter 6 generates the tracking error signal TE by calculating the difference between the generated output signals, and a subtracter 6 adds the output signals 33a-, -33d supplied via the DC component cutting capacitors 7a to 7d. In particular, it is an adder which outputs the read signal RF.

In the one-beam type tracking error detection circuit configured as described above, when a light beam is irradiated toward the disk from a light emitting section (not shown), the reflected light is incident on the photodetecting section 1 via the optical system. The light receiving spot when tracking is normal is in the scanning direction A K ? E? It is symmetrical in the 5 divided parts. Therefore, the light receiving element la.

The output of the adder 3 which adds the output signals Ba and 13b of 1b, the output of the light receiving elements IC and ld, and the output of the adder 4 which adds the signals Bc and Bcl match. The z-tracking error signal TB output from the subtractor 2 is at the bottom.

Next, when the tracking deviates (2), the light receiving switches become non-opposite in the divided portions along the scanning direction A.

As a result, a difference occurs between the output signals generated from the adders 3 and 4, and the subtracter 5, which calculates the difference between the two signals, generates a tracking error signal TE of polarity and level indicating the direction and amount of tracking deviation. Output.

In addition, an output signal B generated from each light receiving element 1a to 1d
After DC components are removed from the signals a and f3d in the capacitors 7a to 7d, they are added together in the adder 6 and output as a readout signal F.

However, in the tracking error detection circuit with the above configuration, if the disc is tilted due to disc tilt, etc., or if the disc is tilted due to disc distortion or deviation of the disc rotation axis, the light beam irradiated on the disc will be reflected. The optical path of the light is shifted and the state of the light receiving spot on the photodetector changes depending on the change in the disc tilt.As a result, the tracking error signal also pulsates due to the influence of the disc tilt, so it is reliable. This has the problem that precise tracking control cannot be performed.

Therefore, an object of the present invention is to provide a tracking error detection circuit that can easily extract a tracking error signal that is not affected by disturbances such as the inclination of a disk.

In order to achieve such an object, the present invention has two types of pairs (by cutting the DC component and adding the output signals of the light receiving elements located on the diagonal of the light receiving elements arranged in a cross shape). By calculating the square sum signal and adding the output signals of the light receiving elements divided in the light spot scanning direction of the four light receiving elements, ! A Sitra Young error signal is sent out by supplying the difference between the two diagonal sum signals and the 12 types of addition signals to a low-noise filter.

Therefore, in the tracking error detection circuit configured in this way, since the signal component due to the inclination of the disk is canceled, it is possible to reliably extract a tracking error signal that is not affected by the inclination of the disk. It has excellent effects.

BEST MODE FOR CARRYING OUT THE INVENTION FIG. 2 is a circuit diagram showing an embodiment of a tracking error detection circuit according to the present invention, and the same parts as in FIG. 1 are indicated using the same symbols. In the figure, 8a to 8d are capacitors provided on the input side of each buffer amplifier 2a to 2d to cut the DC component of the output signals Ba-Bd supplied from each light receiving element 1a to 1d, and 9 is a capacitor in the scanning direction. Output signals Ba and Bb of light receiving elements 1a and 1b divided into two along
The capacitors Ba, Bb and the amplifier 28.2
The output signal C of the adder 3 is added by taking in the input signal C through bt-, and the output signal C of the adder 3 is added by taking in the signal BC9Bd for 2 minutes in the scanning direction through the capacitor 8c, Bd and the buffer amplifier 2C@2d. An adder circuit 10 outputs a reading signal F in a state in which the DC cut outputs of all the light receiving elements 1a to 1d are added by adding the output signals of the adder 4. 10 is an adder 3. The output signal generated from 0.4. 11 is an adder that adds the output signal of buffer amplifier 2 bt 2 ', 12
13 is an adder that adds the output signals of the buffer amplifiers 2a and 2c, and 13 is an output signal generated from the adder 11.12.
This is a subtracter that outputs the difference between B and F, and the output of this subtracter 13 (Ft G is the output of the light receiving elements located on the diagonal of the light receiving elements 1a to 1d arranged in a cross shape. is added and becomes the difference signal of the two types of diagonal sum signals.14
is a multiplier that adds the output signal H of the subtracter 10 and the output signal G of the subtracter 13 to generate an output signal I.

Reference numeral 15 denotes a rotary filter which smoothes the output signal of the multiplier 14 and sends out a tracking error signal TE indicating the amount of tracking deviation and the direction of the deviation.

In the tracking error detection circuit configured in this way, a case will be explained in which, for example, the bit string shown in FIG. 3 (a%) is scanned with a tracking detection light beam as shown by the dotted line. In this case, if we look at the relationship between the output generation ratio of each light receiving element 1a and 1d and the total light reception output ratio when the center of the light beam scans the lower part, center part, and lower part of the pit, 4(a) to (C) to FIG. 6(a).

It becomes as shown in ~(C). In other words, the state of irradiation of the light beam onto the bits in the α, β, and γ portions of FIG. 3 is as shown in FIG. 4(a). The light receiving pattern of the photodetector 1 in each state is as shown in FIG. 2(b). In this case, the output generation ratio of the six light receiving elements 18 to 1d is 0.15.0.55°0.19.0.
11, and in the β part it is 0.42.0,42°'
0.08.0.08, 0.55 in the γ part
゜0.15.0.1110.19. Also α, β,
γ part becomes 0.15.0.23.0.15, and α
The relationships among the light beam irradiation pattern, light receiving pattern, and total light receiving output ratio in the areas ′, /, γ′ and α〃, β″, r# are shown in Figures 5(a), (b), (c) and 5. It becomes as shown in Figure 6 (a) I (b) and (C).

In this way, each light receiving element 12 to 1d detects reflected light.
The output g signals Ba and Bd generated from the capacitor 8a
After only the alternating current components are taken out in steps 8d to 8d, they are amplified in buffer amplifiers 2a to 2d, respectively. And buffer amplifier 2a.

The output signals of buffer amplifiers 2b and 2b are added together in adder 3, and the output signals of buffer amplifiers 2c and 2d are added together in adder 4. Therefore, from the adders 3 and 4, the light receiving elements 1a to 1d arranged in a cross shape are used in the scanning direction of the light spot, and the light receiving element 1a is divided into two.

The summed output for the alternating current portion of the light receiving output generated from 1b and the summed output for the alternating current portion of the light receiving output generated from the light receiving elements IC, ld are output as an output signal 0°D. And this Kayuki 82-A output report (
1-D is a readout signal RF which is added in the adder 9 and has the largest amplitude when the center of the projection light beam scans the center of the pit, and whose amplitude decreases according to the tracking deviation. is generated as shown in FIG. 3(b).

On the other hand, the output signals of buffer amplifiers 2b and 2d are output to adder 1.
1, and the output signals of buffer amplifiers 2a and 2c are added in an adder 12.
The diagonal sum (i
Numbers E and F are output respectively. Then, the difference between the diagonal sum signals E and F is determined in a subtracter 13. The values of the diagonal sum signals E and F output from the adders 11 and 12 in the α portion shown in FIG. 3(a) are shown in FIG. 4(a).
b), From the values shown in the α column in (C), E=(0-55+
0.11) X O,55= 0.099. P=
(0,15+0.19)X O,5=0.051. The output signal G of the subtractor 13 is as follows: G=F-Fi=0.051-0.099=-0,04
It becomes 8.

Also, the output signal G in the β part is output from the adder 11
Since the output signals E and F have the same value, they become zero. Furthermore, in the γ portion, the light receiving pattern is opposite to that in the α portion, so the output signal E becomes +0.048 with the polarity reversed.

Next, the light reception pattern in the α′, β′, and r′ portions where the tracking matches is as shown in FIG. 5(b) for the division along the scanning direction. Since the values are symmetrical, the values of the diagonal sum signals E and F output from the adders 11 and 12 are the same, and the output signal G of the subtracter 12 is all zero.

Next, the light reception and turn in the α'', β/, r'' parts of Figure 3(a), where the tracking is shifted in the opposite direction to the α, β, and γ parts, are shown in Figure 6φ). As shown in the columns α'', β'', and r'', the light receiving pattern is rotated by 180' with respect to the light receiving pattern shown in the columns α, β, and γ in FIG. 4(b). If the output signal G generated from the subtractor 13 is
The value of + is obtained by reversing the polarity of the values in α, β, and r parts.
0.048.0. -0.048.

The output signal G when the pit row shown in FIG. 3(a) is scanned with the center of the light beam as shown by the dotted line.
If you look at the waveform of , as shown in Figure 3 (C),
It has an amplitude corresponding to the amount of tracking deviation.

Further, from the subtracter lO, the output signal 0.4 of the adder 3.4 is sent.
An output signal H having a value corresponding to the difference in D is generated. and,
The output signal H in the α, β, and γ portions is as shown in FIG. 4(b).
From the values of α, β, and r columns in (C), (0,55+0.1
5) Xo, 15-(0,19+0.11)Xo, 15=
0.105(0,42+0.42)Xo, 23-(0,
08+0.08)Xo, 23=0.156(0,15+
0.55)Xo, 15-(0,11+0.19)Xo,
15 = 0.06.

In addition, in the α', /', r/ parts, Fig. 5(b)
As is clear from the light reception signals shown in the α', β', and r' columns, respectively, the output signals 0. Since the values of D are the same, the output signal H of the subtracter 10 is always zero.

゛ Furthermore, in the α'', β'', and r'' parts, see Figure 6 (
Since the light receiving pattern is obtained by rotating the brightness by 180 degrees from the light receiving pattern shown by the 'α'', β'', and γ'' row buttons in b), the value of the output signal H in this case is α.

The value with the value in the β and γ parts as the negative pole, is 0.0
6. -0.156. -0.105.

When the value H of the subtractor IO determined in this manner is expressed as a waveform, it becomes a waveform as shown in FIG. 3(d), which indicates the amount and direction of tracking deviation.

The output signal H of the subtracter 1O generated in this way is used as the output signal G generated from the subtracter 13 in the multiplier 14.
By multiplying by , an output signal I shown in FIG. 3(e) is generated. Then, this multiplication output signal I is averaged in the ronogus filter 15, so that
A tracking error signal TE indicating the amount and direction of tracking deviation is output.

As explained above, in the tracking error detection circuit with the above configuration, the output signals of the light receiving elements located on the diagonal of the light receiving elements arranged in a cross shape are added by cutting the DC component. shi 2 connection resistance θ) tsujiru 4h ji 4th ji shi ~n pay su, shi shi & r μ you F'
By adding the output signals of the light-receiving elements divided along the optical spot scanning direction of the A-biased delta element, 92 kinds of addition signals are obtained, and the difference signal of both diagonal sum signals and the difference signal of both addition signals are obtained. Since the tracking error signal is sent by multiplying the difference signal and extracting the next multiplied signal through a low-pass filter, it is possible to reliably extract a tracking error signal that is not affected by the tilt of one disk, etc. I can do it.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an example of a conventional tracking error detection circuit, FIG. 2 is a circuit diagram showing an embodiment of a tracking error detection circuit according to the present invention, and FIGS. 3(a) to (f)
are operation waveform diagrams of each part of the circuit shown in Fig. 2, and Fig. 4 (aL
(b), (CL Fig. 5 < 8) * (b)t (C) and Fig. 6 (a), (b), (C) show the scanning state of the light beam with respect to the pit, the received light beam, and the total received light output. It is a figure showing the relationship with a ratio. l... Light detection section, 1a to 1d... Light receiving element, 2a to
2d...Buffer amplifier, 3*4e 9. 11.
12...Adder, 10.13...Subtractor, 14.
... Multiplier, Applicant: NEC Home Electronics Co., Ltd.

Claims (1)

[Claims] (1) First and second addition in which a diagonal sum signal is output by cutting the DC component of the output signals of the light receiving elements located at the diagonal parts of the light receiving elements arranged in a cross shape and adding them together. a first subtracter that calculates the difference between output signals generated from the first and second adders; and a light spot divided along the scanning direction of the light receiving elements arranged in a cross shape. third and fourth adders that add the output signals of the light-receiving elements after cutting off their direct current components, and a second adder that adds the output signals of the third and fourth adders; a subtracter, a multiplier that multiplies the output signals generated from the first and second subtracters, and a tracking error signal that represents the amount of tracking deviation and the direction of the deviation by smoothing the output signal of the multiplier. and a low-pass filter that generates
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uZ old road.