JPS62159351A - Detecting system for tracking error signal of optical information signal reproducing device - Google Patents

Abstract

PURPOSE:To inexpensively form a high performance optical information signal reproducing device, by combining individual output signals from photodetector elements respectively positioned to the 1st-4th quadrants. CONSTITUTION:A photodetector 6 is provided with photodetector elements PD1, PD2, PD3, and PD4 which are respectively positioned to the 1st-4th quadrants in an X-Y plane and output signals S1, S2, S3, and S4 are respectively outputted from the photodetector elements PD1-PD4. On the basis of the sum signals (S1+S3) and (S2+S4) of the output signals from the two pairs of diagonal photodetectors, the difference signal S5=(S2+S4)-(S1+S3) between the two sum signals is obtained and, at the same time, the difference signal S6=(S 1+S4)-(S2+S3) between two sum signals is obtained on the basis of the sum signals of the output signals from the two pairs of photodetector elements. Then the signals S5 and S6 are multiplied by each other and a tracking error signal S7=S5XS6 is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a tracking error signal detection method in an optical information signal reproducing device.

(Prior Art and Problems) A light flux emitted from a light source is focused and irradiated onto the signal surface of an information recording medium having a recording trace on which an information signal is recorded as geometrical unevenness, and the above-mentioned information recording medium is In an optical information signal reproducing device that obtains a reproduced information signal by photoelectrically converting the reflected light modulated by the recorded information generated on the signal surface using a photodetector, the reflection from the signal surface of the information recording medium is JP-A-52-93 proposed a method for detecting a tracking error signal by utilizing the fact that the distribution of diffracted light changes depending on the relative positional relationship between the light spot and the recorded trace.
It is disclosed in Publication No. 222.

The tracking error signal detection method described in Japanese Patent Application Laid-Open No. 52-93222 mentioned above is based on a method for detecting a tracking error signal at a position divided into four by a line in the direction of the recording trace and a line in a direction perpendicular to the direction of the recording trace. The sum signal of the output signals from each of the two light receiving elements arranged diagonally in the output signal from the photodetector consisting of four light receiving elements is transmitted through a π/2 phase shifter. At the same time, a difference signal of the sum signal of the output signals from each of the two light receiving elements arranged diagonally in the output signal from the photodetector is supplied to the multiplier. ! Although the tracking error signal is obtained as the output signal of the calculator, since the above-mentioned π/2 phase shifter cannot always give a phase shift amount of π/2 to the recorded signal,
The problem is that it is not possible to obtain an accurate tracking error signal, and if the above-mentioned π/2 phase shifter is configured by a phase-locked loop to eliminate the above-mentioned drawbacks, the cost will be high. It became a problem.

A proposal for improving the drawbacks of the conventional example described above was disclosed in Japanese Patent Application Laid-open No. 74837/1983.

This improvement proposal involves sampling and holding the difference signal between the sum signals of the output signals of the light receiving elements at the diagonal positions separately at the zero-crossing points at the rise and fall of the total sum signal (reproduction information signal), and extracting each individual signal. The difference signal between these signals is used as the tracking error signal.According to this proposed tracking error signal detection method, an accurate tracking error signal can always be obtained, but the difference signal between the signals recorded on the information recording medium is The signal is a high-frequency signal, and for example, the recording signal on a compact disc reaches several MHz, and a circuit that generates zero-cross pulses or samples and holds such high-frequency signals requires a sufficiently high-speed circuit. Due to the required operating characteristics, there was a drawback that the design and manufacture required technology and the circuit configuration was complicated and expensive, so a solution was sought.

(Means for Solving the Problems) The present invention is applicable to information recording media, such as compact discs, in which the bit height and depth for light of a predetermined wavelength are predetermined.

The rising and falling positions of the bit can be easily known, and when the height of the bit is different from 1/4 of the wavelength of light, the distribution of diffracted light with respect to the edge of the bit is asymmetrical with respect to the edge. A tracking error signal detection method that detects the tracking error signal by detecting the edges before and after the bit, focusing on the fact that the information signal is distributed as geometric unevenness. A light beam emitted from a light source is focused and irradiated onto the signal surface of the information recording medium having a recording trace, and a photodetector detects the reflected light modulated by the recorded information generated on the signal surface of the information recording medium. In an optical information signal reproducing device that obtains a reproduced information signal by photoelectric conversion, the above-mentioned photodetector is connected to a first line parallel to a recording trace on an information recording medium and to the first line. 2 with orthogonal second line
The light-receiving element is placed in each of four sections divided by the main line, and the intersection of the two lines is located on the optical axis of the reflected light. , the first line is the X axis.

The first ~ ~ of the XY plane obtained with the second line as the Y axis
Individual output signals from the light receiving elements located in the fourth quadrant are respectively SL, S2. S3. When setting S4,
Based on sum signals (Sl+S3) and (S2+S4) of output signals from two diagonal light receiving elements.

Difference signal 55 between the above two sum signals = (S2+S4)
−(S1+S3), and the sum signal (81+S4) and (S2+S3) of the output signals from two light-receiving elements in the area divided by the second line. Difference signal between signals 56=(Sl+S4
)-(S2+S3) and the above two signals S5
．． Multiply by S6 to obtain tracking error signal 57=S5×S
The present invention provides a tracking error signal detection method in an optical information signal reproducing device comprising means for obtaining 6.

(Example) Hereinafter, optical information 48 of the present invention will be described with reference to the attached drawings.
The specific details of the tracking error signal detection method in the code reproduction device will be explained in detail.

FIG. 1 is a perspective view of an optical information signal reproducing device to which the tracking error signal detection method in the optical information signal reproducing device of the present invention is applied, and in FIG. 1, 1 is a light source (
2 is a collimating lens, 3 is a beam splitter, 4 is a condensing lens, 5 is an information recording medium (disc), 6 is a photodetector, and 7 is a light spot, which is emitted from the light source 1 described above. The laser beam is collimated by the collimating lens 2.
The light beam is made into parallel light by the beam splitter 3 and then applied to the condenser lens 4, where the condenser lens 4 forms a minute light spot 7 on the signal surface of the disk 5. The reflected light from the light spot 7 described above is transmitted to a photodetector 6 via a condenser lens 4 and a beam splitter 3.
is given and photoelectrically converted.

The photodetector 6 described above is divided into four by two lines: a first line 6x parallel to the recording trace on the information recording medium and a second line 56y perpendicular to the first line 6x. In other words, the first to
Light receiving elements P DI, P D2 . are individually provided in the f54 quadrant.
P D3. PD4, and the two lines 6x described above.

The intersection point of 6y is located on the optical axis of the reflected light, and individual output signals 81 . S2. S3. S4 is output.

FIG. 2 shows the output signals 5 from the four light receiving elements PDI to PD4 in the photodetector 6 shown in FIG.
1-84 to generate a tracking error signal. In Figure 2, ADDI to ADD
4 is an adder, 5UBI and 5UB2 are subtracters, MUL is a multiplier, and 8 is an output terminal.

The adder ADDI receives the output signal Sl from the two diagonal light receiving elements PDI and PD3 among the four light receiving elements PDI to PD4 in the photodetector WA6.

A sum signal (S1+S3) of S3 is generated, and it is sent to the subtracter 5.
The adder ADD2 is applied to the UBI as a subtraction signal, and the adder ADD2 is applied to the four light receiving elements PD in the photodetector 6.
Two diagonal light-receiving probes PD2.I to PD4.
Output signal S2 from PD4. S4 sum signal (S2+S4
) and gives it to the subtractor 5UBl as the minuend signal. Then, from the adder 5UBI described above, a difference signal S5 between the two sum signals described above: (S2+S4)
-(Sl+S3) and supplies it to the multiplier MUL.

Further, the adder ADD3 generates a sum signal (Sl+S4) of the output signals of the two light receiving elements PDI and PD4 in the area divided by the second line 6y in the photodetector 6.
is generated and given as a minuend signal to the subtractor 5UB2, and also sent to the adder 〇D4, which is applied to the two light receiving elements PD2 . Sum signal of output signals from PD3 (S2+S3
) occurred.

It is given as a subtraction signal to the subtractor 5UB2, and the subtracter 5UB2 outputs a difference signal 56=(S1+S4)-2+S3) between the two sum signals mentioned above and sends it through the Schmitt trigger circuit ST. Supplied to multiplier MUL.

FIG. 3 shows how the distribution of reflected light on the main surface of the condenser lens 4 changes in response to changes in the relative positional relationship between the bit P and the light spot 7 on the signal surface of the disk 5. FIG. 3 is a diagram illustrating and explaining the
) to (C) show the case where the center of bit P and the center of light spot 7 are aligned and the light spot 7 is passing through bit P. d)～
(f) shows a state in which the light spot 7 is passing through the bit P with the center of the spot 7 being located at a position shifted to the right from the center of the bit P.

Note that this figure 3 is for a case where the bit P is convex and the height of the bit P is smaller than 1/4 of the wavelength of light, for example, approximately 115 times the wavelength of light. .

Further, in FIG. 3, the shaded area indicates the area where the diffracted light is strong.

Now, if the light spot 7 is moving over the pit P with the center of the light spot 7 and the center of the bit P matching, that is, the light spot 7 is moving on the bit P with no tracking error. In the case of the state where the light passes over P, the diffracted light generated on the signal surface of the disk 5 is shown in (a) in FIG.
) to (c), the main surface of the condenser lens 4 exhibits a symmetrical distribution state with respect to the X axis.
3) and the output signal (S2+S4) from the adder ADD2 are equal, so the signal 55=(S2+S4)-(S1+S3) output from the subtracter 5UBI becomes zero.

Next, if the center of the light spot 7 is shifted to the right with respect to the center of the bit in the state shown in (d) to (f) of FIG. As shown in (d) to (f) of FIG. 3, the diffracted light generated in FIG. In case (d), disk 5
The diffracted light generated on the signal plane of FIG.
), the diffracted light generated on the signal surface of the disk 5 is unevenly distributed in the third quadrant on the main surface of the condenser lens 4, so that the diffraction light generated on the signal surface of the disk 5 is unevenly distributed in the third quadrant as shown in FIG. 3(d). If the center of the light spot 7 is shifted to the right with respect to the center of the bit in this state, the output signal from the adder ADDI (S1+
S:l) is the output signal from adder ADD2 (S2+
S4), so wt calculator 5UBI
Signal 55 = (S2+S4) - (S1+
S3) is positive, and.

As shown in FIG. 3(f), if the center of the light spot 7 is shifted to the right with respect to the center of the bit, the output signal (S1+S3) from the adder ADDI is is greater than the output signal (S2+S4) from ADD2, and therefore the signal 5 output from the subtractor 5UBI
5=(S2+94)-(SL+S3) is negative. Note that if the center of the light spot 7 is biased to the right with respect to the center of the bit in the state shown in FIG. 3(e), the output signal from the adder IADD1 (SL+S3) is The output signal (S2+S4) from the subtractor ADD2 becomes equal, and therefore the signal 55=(S1+S3)-(S2+S4) output from the subtractor 5UBL becomes zero.

FIG. 4 shows that when the center of the light spot 7 is biased to the right with respect to the center of the bit in the states shown in (d) to (f) of FIG. 4 is a diagram showing the waveforms of signals at each part in the circuit in correspondence with the bit P on the signal surface of the disk, and (a) in FIG. 4 is the cross-sectional shape of the bit P on the signal surface of the disk 5, In the figure, fe indicates the leading edge of bit P, and be indicates the trailing edge of bit P.

4(b) is a waveform diagram of the signal S5 output from the subtracter 5UBI, FIG. 4(c) is a waveform diagram of the signal S6 output from the subtracter 5UB2, and (d) of FIG. ) is a waveform diagram of the signal 36g outputted from the Schmitt trigger circuit ST, and (e) of FIG. 4 is a waveform diagram of the tracking error signal S7 outputted from the multiplier MUL.

When the center of the light spot 7 is shifted to the right with respect to the center of the bit, the polarity of the signal S5 output from the subtractor 5UBI is at the leading edge of the bit P, as is clear from FIG. 4(b). It is always positive in the part fe of the bit P, and always negative in the trailing edge part be of the bit P.
At the center of the pit P, the light is diffracted only to the sides as shown in FIG. becomes zero, and since the reflected light at the land is symmetrical with respect to the origin, the signal S5 becomes zero.

Furthermore, the polarity of the signal S6 output from the subtractor 5UB2 is always positive at the leading edge fa of the pit P, and at the trailing edge be of the pit P, as shown in FIG. 4(c). It is always negative and becomes zero at the center of the pit P.

When the center of the light spot 7 is shifted to the right with respect to the center of the pit, the signal S5 and the signal S6 are in the same phase, so the signal S7 obtained by multiplying the signal S5 and the signal S6 is The signal becomes positive as shown in FIG. 4(e).

When the center of the light spot 7 is deviated to the left with respect to the center of the pit, the diffracted light generated on the signal surface of the disk 5 will be in the states shown in (d) to (f) in Fig. 3. On the other hand, the polarity of the signal S5 output from the subtractor 5UBI is in the state shown in (b) of FIG. is the opposite, but
Even if the center of the light spot 7 is shifted to the left with respect to the center of the pit, the polarity of the signal S6 output from the subtracter 5UB2 is the same as the state shown in (Q) of FIG. 4. Signal S5 and signal S6 in this case have opposite phases, and therefore signal S7 obtained by multiplying signal S5 and signal S6 becomes a negative signal.

Therefore, the signal S7 sent from the multiplier MUL to the output terminal 8 depends on whether the center of the light spot 7 is shifted to the left or right with respect to the center line of the pit P on the signal surface of the disk 5. This is a signal whose polarity is reversed and whose magnitude changes corresponding to the magnitude of the deviation described above, that is, a signal containing tracking error information. error signal S
7 is sent out.

As mentioned above, if the signal S6 output from the subtractor fisUB2 is shaped into a rectangular wave signal 86g with a constant peak value by waveform shaping, it is possible to increase the signal level of the tracking error signal and improve the S/-N. can. The Schmitt trigger circuit ST in FIG. 2 is provided for waveform shaping of the signal S6, and when the signal S6 is made into a rectangular wave signal by waveform shaping in this way, the signal S5
The signal form will be completely transmitted. Further, as the signal S6 described above, a difference signal between one of the signals S1 and S2 and one of the signals S3 and S4 may be used.

Note that the tracking error signal S sent to the output terminal 8
7 is made up of twice the frequency component of the information signal, as shown in FIG. removed when Also.

The signal S7 shown in FIG. 4(e) may be used as a tracking control signal after passing through a peak value detection circuit.

(Effects) As is clear from the above detailed explanation, the tracking error signal detection method in the optical information signal reproducing device of the present invention is effective for detecting information that has a recording trace where an information signal is recorded as geometrical unevenness. The light beam emitted from the light source is focused and irradiated onto the signal surface of the recording medium, and the reflected light modulated by the recorded information generated on the signal surface of the information recording medium is photoelectrically converted by a photodetector to reproduce the reproduced information. In an optical information signal reproducing device configured to obtain a signal, the photodetector has a first line parallel to the recording trace on the information recording medium and a second line perpendicular to the first line. It is divided into four sections by the two lines, and each section is equipped with an individual light-receiving element, and the intersection of the two lines is located on the optical axis of the reflected light. Along with being.

Individual output signals from the light receiving elements located in the first to fourth quadrants of the xY plane obtained with the first line as the X axis and the second line as the Y axis are respectively SL, S2 . S3. S
4, the difference signal between the above two sum signals 55=(S
2+S4)-(S1+S3), and a sum signal (S1+S4), (S2+S3) of the output signals from each two light receiving elements in the area divided by the second line described above.
Based on , the difference signal 56 between the two sum signals described above = (
S1+S4)-(S2+S3), and means for obtaining the two signals S5. The tracking error signal 57 is multiplied by S6.
A tracking error signal detection method in an optical information signal reproducing device comprising means for obtaining =S5×S6,
When reproducing information signals from a disc on which information signals are recorded in a row of pits having a predetermined height shape, 1/4 of the wavelength of the light used during reproduction is equal to the height of the pits. For example, a light source that emits light with a wavelength of 175 at the height of the pit is used to generate a signal S6 that distinguishes between the leading edge and the trailing edge of the pit. - Since the polarity of the signal S5 having information on the magnitude of the racking error is determined, it is possible to provide an inexpensive device with a simpler configuration than the conventional device described above. Further, the signal S5 has a magnitude proportional to the tracking error.

Since the calculation is performed symmetrically with respect to the optical axis, the effects of the inclination of the disk, the movement of the condenser lens 4 due to the tracking control operation, the scratches on the disk, etc. are canceled out and reduced. Furthermore, since the signal S6 described above is obtained when the diffracted light is maximally polarized at least in the direction in which the recording trace extends, a good signal is obtained, and since this signal S6 is a signal that simply indicates the polarity, It is also possible to format it.

Noise etc. can also be removed by shaping.

Therefore, by adopting the tracking error signal detection method in the optical information signal reproducing device of the present invention,
It is possible to provide a high-performance optical information signal reproducing device at a low cost, which does not have the problems of the conventional devices described above.

[Brief explanation of drawings]

FIG. 1 is a perspective view of an example configuration of an optical information signal reproducing device to which the tracking error signal detection method in the optical information signal reproducing device of the present invention is applied, FIG. 2 is a block diagram of the tracking error signal detection method, and FIG. The figure shows how the distribution of reflected light on the main surface of the condenser lens 4 changes in response to changes in the relative positional relationship between the pit P and the light spot 7 on the signal surface of the disk 5. The illustrated diagram, FIG. 4, is a waveform diagram for explaining the operation. DESCRIPTION OF SYMBOLS 1... Light source (semiconductor laser), 2... Collimating lens, 3... Beam splitter, 4... Condensing lens, 5... Information recording medium (disc), 6... Photodetector , 7... Spot of light, P DI, P D2.
P D3. P D4... Light receiving element, ADDI~AD
D4...Adder, 5UBI, 5UB2...Subtractor,
MUL... Multiplier, 8... Output terminal. Patent applicant: Japan Victor Co., Ltd. Procedural amendment (spontaneous) March 6, 1985 Michibu Uga, Commissioner of the Japan Patent Office Patent application No. 1517, 1988 2, Title of invention Tracking error in optical information signal reproducing device Signal detection method 3, relationship with the amended person case Patent Applicant Location 3-12 Moriyo-cho, Kanayō-ku, Yokohama-shi, Kanagawa Prefecture Name (432) Victor Company of Japan Co., Ltd. 4, Agent facsimile 03 (472) No. 2257 No. 5, Date of amendment order (self-initiated) Showa year, month, day (Ship date: Showa year, month, day) 6, Subject of amendment Detailed explanation of the invention in the specification column 7, Contents of the amendment Page 4 of the description Correct the 6th line "sum signal by π" to "difference signal by π".

Claims (1)

[Scope of Claims] 1. A light beam emitted from a light source is focused and irradiated onto the signal surface of an information recording medium having a recording trace on which an information signal is recorded as geometrical unevenness, and the above-mentioned information recording medium is In an optical information signal reproducing device that obtains a reproduced information signal by photoelectrically converting reflected light modulated by recorded information generated on a signal surface using a photodetector, the aforementioned photodetector is connected to an information recording medium. A device that is divided into four sections by two lines, a first line parallel to the recording trace and a second line perpendicular to the first line, and each section is equipped with an individual light-receiving element. The intersection of the above two lines is located on the optical axis of the reflected light, and the X obtained by setting the above first line as the X axis and the second line as the Y axis.
Individual output signals from the light receiving elements located in the first to fourth quadrants of the Y plane are respectively S1, S2, S3, and S4.
Then, based on the sum signals (S1+S3) and (S2+S4) of the output signals from two diagonal light receiving elements, the difference signal between the two sum signals S5=(S2
+S4)-(S1+S3);
Based on the sum signals (S1+S4) and (S2+S3) of the output signals from two light receiving elements in the area divided by the line, the difference signal S6=(S
1+S4)-(S2+S3) and the above-mentioned 2
Multiplying the signals S5 and S6 yields the tracking error signal S7=
Tracking error signal detection method 2 in an optical information signal reproducing device comprising means for obtaining S5×S6, a tracking error signal S7 is obtained by multiplying the signal S6 by waveform-shaping the signal S6 into a rectangular wave with a constant peak value. Tracking error signal detection method 3 in the optical information signal reproducing apparatus according to claim 1, which is configured to obtain one of the signal S1 and the signal S2, and the signal S
3 or signal S4 and the difference signal from one of the signals S6
A tracking error signal detection method in an optical information signal reproducing device according to claim 1 used as