JPS5998325A - Tracking control device of optical disk player - Google Patents

Abstract

PURPOSE:To improve accuracy and efficiency of control by converting a tracking error detecting signal to a prescribed square wave signal, and reading a level at a prescribed time point of the square wave signal obtained by comparing said signal in voltage with a fixed level. CONSTITUTION:A tracking error detecting signal SE is supplied to a signal synthesizing circuit 80 and is synthesized with a triangular wave signal SF. A composite signal SG of an output of the synthesizing circuit 80 is supplied to a voltage comparing circuit 42, compared as to voltage with a zero level, and a square wave signal SGZ which becomes a high level in a period in which the composite signal SG is in a positive level, and becomes a low level in a period in which said signal is in a negative level is obtained. Subsequently, by this signal SGZ, a level of the signal SGZ at the time point of rise of a square wave signal SRZ is read, and two output signals SX and SY of a D flip-flop circuit 51 are supplied to a driving circuit 60 and a control signal of tracking. In this way, an analogical control is executed, and accuracy and efficiency of a control can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to the recording and processing of information signals from a disc, such as an optical digital audio disc, in which the information signals are optically readable recorded in a spiral track. The present invention relates to a tracking control device for an optical disc player that plays back, and in particular for controlling a spot on the disc of an original beam for reading information signals incident on the disc to always be at the correct position with respect to the tracks of the disc.

In 16-style digital audio and video discs, information signals are written on a spiral track so that they can be read optically, and the gray-
〜“−, the optical beam of the optical head moving in the radial direction of the disk is used to read all of the information No. 1a from the tracks of the disk and perform playback. of)
As an example, a disk 10VC is recorded with a digitized information signal formed into a spiral track by an arrangement of pits, and an optical head, 2
0 moves in the radial direction of this disk 10! It is possible to do Fυ. In one row of optical heads λ0, the original beam from the laser light source 2/ is collimated to the collimator lens 2. !
, polarizing prism, 23. Mirror, 2/l, Wave plate, 2
5 and the objective lens λ are sequentially incident on the disk 10, are modulated and reflected by the disk/θ, and are transmitted to the objective lens λ, -wavelength plate 2 left, mirror, 211. σ so that it passes through the polarizing prism 23 and the prism 27 sequentially and reaches the sensing yC part 2g,
A light beam modulated by the disk 10 is detected by a photosensitive element made of gold in the photosensitive portion 2g.

In such an optical disc player, the spot on the disc of the source beam for reading the information signal incident on the disc is always correct with respect to the disc track.
Tracking control is necessary to control the position so that the b! We have proposed this type of tracking control device that does not use ISF.

FIG. 2 shows an example of a tracking control device already proposed by the applicant, which includes a signal generation circuit 30 including the photosensitive section 2g of the optical system shown in FIG. 1, and a voltage comparison circuit of Ω. It consists of ll/ and ll,2, a D flip-flop circuit configuring a digital latch circuit left/, and a drive circuit 0.

The photosensitive portion 2g includes, for example, photosensitive elements 2gA, , 28B, , 23C and U, 2gD arranged around one point around the circumference 9.
In the signal generation circuit 30, the element 2gA
and 2gD·h outputs are added in the adder circuit 3/, and the outputs of the elements, 2gB and 2gc are added in the adder circuit 3/3.
Further, the outputs of adder circuits 3/ and 3.2 are added in adder circuit 33, and the outputs of adder circuits 3/ and 3.2 are subtracted in subtracter circuit 3, and the outputs of adder circuits 3/ and 3.2 are added together in subtracter circuit 3. ;
From the bath 33, one symbol SR of the sum of the outputs of all the elements, 2gA to 2gD, is obtained, and the sum of the outputs of the subtracting circuit 3 elements, 2gA and 2gD, and the elements 2gB and 2g.
A signal SE of the difference between the sums of the outputs of C is obtained.

A light beam incident on the cocoa disk 10 is diffracted and reflected by the pits forming the trunk on the disk 10. , Therefore, the original beam that reaches 2g and forms a sporatra on the photosensitive element 2gA - 2gD as shown in Fig. Ω is a pit on the disk /θ. There are 7 trays of diffraction butter corresponding to the positional relationship between the beam spot and the spot of the light beam that irradiates all of them.

Figure 3 shows this situation; Figures A and B in the same figure.

In each of C, the left side shows the positional relationship between P) and the light beam σ) spora l-S that irradiates it, and the right side shows the diffraction of the spot of the light beam on the photosensitive element: 1gA to 2gD in that positional relationship. Indicate each pattern, right side ρ1
] The shaded area is the area where the amount of light is low. The pit P moves from an upper state to a lower state with respect to the spora S of the original beam that irradiates the pit P. Figure A shows the case where the spot S is shifted to the left with respect to the pit P, figure B shows the case where the spot S is correctly positioned in the center of the pit P, and figure C shows the case where the spot S is located correctly in the center of the pit ) This is a case where the spot S is shifted to the right with respect to P.

Therefore, if the spot s is correctly positioned with respect to P, the spot of the original beam on the photosensitive elements 2gA-2gD will have a completely symmetrical light intensity distribution with respect to the elements 28A-2gD. , if the spot s deviates to the left or right with respect to the ping (I), the element, 2. g
The symmetry of the light quantity distribution for A- and 2gD is broken, and the way the [chi] symmetry is broken is reversed between the case where it shifts to the left and the case where it shifts to the right, and the larger the shift, the more the symmetry breaks down.

Therefore, the signal generating circuit 300 and the three subtracting circuits provide an element of 2 gA and 2. ? I) sum of outputs and elements, 2
The signal S, which is the difference between the sum of the outputs of gB and 2gc, indicates the position of spot S with respect to pit 1], that is, spot S
This is a truck error detection signal indicating the direction and amount of deviation relative to the trunk. All elements 2gfi, -2gD obtained from the adder circuit 33 of the signal generation circuit 3θ
The signal SR, which is the sum of the outputs of , is a reproduction information signal.

Figure 47 shows the case where the spot S moves diagonally across the trunk from left to right, and Lc is the point in time when the spot S is correctly positioned with respect to the trunk. As is clear from this, the tracking error detection signal S
When the spot S is shifted to the left with respect to the track as shown in FIG.
When the raw information No. 18 SR completely crosses the zero level from positive to negative, it becomes a positive level, and the spot S is reached as shown in Figure 3 C.
When deviates to the right with respect to the trunk, the reproduction information signal SR becomes a positive level when it crosses the zero level in the negative to positive direction, and the reproduction information signal SR crosses the zero level in the positive to negative direction. Spot S becomes a negative level when it crosses ! - The phase with respect to the reproduced information signal Sa is reversed depending on whether it is shifted to the left or right with respect to the rack, and the larger the shift, the greater the amplitude.

Reproduction information signal SR obtained from this 1 horoscope generation circuit 3θ
and tracking error detection signal SE are supplied to voltage comparator circuit 14f, voltage comparator circuit da/and tl, 2, and are compared with the zero level, respectively, and as shown in FIG.
Rectangular wave signals SRZ and SEZ are obtained in which the signals SRZ and SE are at a high level during the period when the signals SR and SE are at a positive level, and the rectangular wave signals SRZ and SEZ are at a low level during a period when the signals SR and SE are at a negative level. Then, a rectangular wave signal SRZ corresponding to the reproduced information signal SR is supplied to a clock terminal CK of a D flip-flop circuit as a digital latch circuit, and a rectangular wave signal SEZ corresponding to a tracking error detection signal SE is supplied to the circuit. , da /'s data terminal I) (/ζ is supplied, the square wave is signal S n,
At the rising edge of z, i.e., i11/-1 information signal S
The level of the rectangular wave 1st signal SEZ at the time when R completely crosses the zero level in the direction from negative to positive is read6.
As is clear from the figure, when the spot S moves to the left by -1 on the track as shown in FIG. 3A, one output 7. of the D flip-frog circuit S/. The J signal SA becomes low level, the other output signal SB becomes high level, and the third
When the spot S shifts to the right with respect to the track as shown in Figure C, conversely, one output J signal SA of the circuit S/ becomes high level and the other output signal SR becomes low level, and the left output signal SA of the circuit S/ becomes a low level. Output signals SA and SE3 indicating the direction of deviation of the spot S with respect to the trunk are obtained.

The two output signals SA and SB of this D flip-frog circuit are the tracking control signal
- is supplied to the drive circuit Otsu0. Driving times ll saving 60,
Ritsunoto/・InstaOtsu/~Otsuga constitutes a set of complementary transistors to perform switching operation, and the emitters of transistor Otsu/ and Otsuyu and the emitters of transistor Otsu3 and Otsuke are connected. In the meantime, for example, the objective lens Ω6 shown in FIG. A coil 70 is connected, and one output signal SA of the circuit 1 is supplied to the bases of the transistors 2 and λ, and the other output signal SB is supplied to the bases of the transistors 43 and 2.

Therefore, when the spot S shifts to the left with respect to the track as shown in FIG. Otsuno and Otsu 3 are turned on, a constant current flows through the coil 70 in the direction of arrow a, objective lens Otsu is moved in the - direction, spot S is moved to the right, and conversely the third Spora)S as shown in Figure C
If the signal SA is shifted to the right side with respect to the track, the signal SA is turned on.

Transistors Otsu and Otsu 3 are turned off, and Koi 1'
70, a constant current flows in the direction of the arrow 1], and the objective lens λ is moved in the other direction, causing the spot S to move to the left. It will be controlled to be in position.

This tracking control device already proposed by the present applicant has a non-reproducible information signal S obtained from a signal generating circuit 30.
rt and tracking error detection 1 word SE'z voltage comparison circuit tl/ and square wave signals SRZ and SEZ
The D flip-flop circuit S/ converts the level of the rectangular wave signal SEZ corresponding to the tracking error detection signal SE at the rising edge 9 of the rectangular wave signal S it z corresponding to the reproduced information signal SR. By reading
Control signals SA and SB are obtained that change in binary L/bevel depending on the direction of deviation of S with respect to the track, and the control signals SA and SB are used to operate the entire switching operation of the drive circuit B. And Sangh.

Since analog circuits such as ring-hold circuits are not used, the circuit configuration is simple and has the advantage of being suitable for IC implementation.

However, on the other hand, control 1 given to driving circuit O
The words SA and SR indicate only the direction of the deviation of the subtool I-S with respect to the track, and are independent of the amount of deviation. As shown by the current ■ in FIG. 9, the current σ has a constant magnitude regardless of the amount of deviation, which has the disadvantage that control accuracy deteriorates and the coil 7θ becomes saturated, increasing power loss. Furthermore, the control device as a whole constitutes a self-oscillation system, which has the disadvantage of generating noise having an undefined frequency.

Purpose of the Invention In view of the above points, the present invention makes full use of the advantages of the device already proposed by the applicant shown in Fig. Ω, and
Can the circuit configuration be simplified by eliminating defects and inconveniences? In addition to being suitable for IC implementation, the control accuracy is improved, efficiency is improved, and no noise is generated.

Summary of the Invention In the present invention, instead of converting the tracking error detection signal into a rectangular wave signal by comparing it with a constant level of the total iα tangent, the tracking error detection signal is set at a frequency sufficiently lower than the minimum frequency of the reproduced information signal. The synthesized signal is synthesized with a triangular or sawtooth wave signal of frequency, and the resulting signal is converted into a rectangular wave signal by comparing the voltage with a constant level. By observing the entire level at the rising or falling point of the rectangular wave signal, the control signal is a binary signal, but a pulse signal with a period equal to the period of the above-mentioned triangular wave signal or sawtooth wave signal, Furthermore, the pulse width is modulated in accordance with the direction and position of the deviation of the spot on the disk of the original beam incident on the disk with respect to the track.

Embodiment The first figure shows an example of the tracking control device of the present invention, in which the tracking error detection signal SF obtained from the subtraction circuit 3 of the signal generation circuit 30 is supplied to the signal synthesis circuit go, and the DC blocking signal is output from the terminal 9/. Here, the triangular wave signal SF is synthesized with the triangular wave signal SF given through the capacitor 92, as shown in FIGS. 7 and 8. sufficiently lower than the minimum frequency of the information signal SR, e.g.
It is of kHz. This signal synthesis circuit g.

A composite signal Sc of the output triangular wave signal SF and tracking error detection signal SF is supplied to the voltage comparator circuit '12, where the voltage is compared with the zero level, and the composite signal SG becomes high level during the period when it is at a positive level. Thus, a rectangular wave signal Scz is obtained which becomes low level during the period when the composite signal Sc is at a negative level. Then, a rectangular wave signal SGz corresponding to this composite signal SG is sent to a D-flip circuit as a digital latch circuit.
A rectangular wave signal 5rtz corresponding to the reproduced information signal SR, which is supplied to the data terminal of the left flop circuit and obtained from the voltage comparator circuit 11, is supplied to the clock terminal CK of the left circuit, and the rectangular wave signal SRZ is generated. The level of the rectangular wave signal SOZ at the time of rising, that is, the time when the reproduction information signal SR crosses the zero level from negative to positive, is read, and the λ output signals SX and sy of the circuit left/right are tracked. is supplied to the drive circuit O as a control signal.

When the spot S on the disk 10 of the light beam incident on the disk 10 is shifted to the left with respect to the track as shown in FIG. 3A, the tracking error occurs as shown in FIG.
The error detection signal SE is detected at the point in time when the reproduced information signal SR crosses the zero level from negative to positive, that is, at the rectangle e1 word SRZ.
It becomes a negative level at the time of the rising edge of , and its amplitude increases as the deviation of the spot S from the track increases.

Therefore, when the spot S deviates to the left (till) of the track, and when the deviation is large, the synthesized word Sc becomes like the broken line in FIG. 7, and the rectangular wave signal Saz
*The control signal Sx and the current flowing through the S Y r coil 70 are as shown in case AI in the same figure,
The high level period of , arrow a to the coil 70 as a total
This is equivalent to a large current flowing in the direction of , and the spot S is moved significantly to the right. When the spot S deviates to the left with respect to the track, and the deviation is small, the composite signal ScM becomes as shown by the solid line in the same figure, and the square wave signal Scz + control 1 words Sx and S y + coil 70
The current ■ flowing through the coil 70 becomes as shown in case A2 in the figure, and the period of the 7-high level of the signal Sx is somewhat shorter than the period of the low level, and the current flows in the direction of the arrow 70 in the coil 70. The period is somewhat shorter than the period in which the current flows in the direction of arrow a, and the total becomes equivalent to a small current flowing in the coil 7θ in the direction of arrow a, and the spot S is moved slightly to the right.

Conversely, when the spot S shifts to the right with respect to the track as shown in FIG. 3C, the tracking error detection signal SE indicates that the reproduction information signal SR changes from negative to positive. The point in time when the square wave signal SR crosses the zero level
It becomes a positive level at the time of rise of 2.

Therefore, when the spot S shifts to the right with respect to the track, and when the shift is small, the combined signal Sc becomes as shown by the solid line in FIG. The current flowing through the coil 70 becomes as shown in case C, 2 in the figure, and the high level period of the signal SX is somewhat longer than the low level period, and the current flows through the coil 70 in the direction of the arrow. The period during which the current flows in the direction of the arrow a becomes somewhat longer than the period in which the current flows in the direction of the arrow a, and the total becomes equivalent to a small current flowing in the direction of the arrow a in the coil 70, and the spot S is moved slightly to the left. . When the spot S deviates to the right with respect to the track, and the deviation is large, the composite signal Sc becomes as shown by the broken line in the same figure, the rectangular wave signal SGZ, and the control signal S.
x and S Y + current I flowing through the coil 7θ becomes as shown in case CI in the figure, and the high level period of the signal SX is considerably longer than the low level period, and the current I flows into the coil 7θ in the direction of the arrow. The period during which the current flows is a little longer than the period during which the current flows in the direction of arrow a, and the total is equivalent to a large current flowing in the direction of arrow a through the coil 70. Moved.

After all, according to the control device of FIG. 3, the control signals SX and S
Although y is a binary signal, it is a pulse signal with a period equal to the period of the triangular wave signal SF, and its pulse width is the same as the direction of deviation of the spot S on the disk 10 of the light beam incident on the disk 10 with respect to the track. It is modulated according to the amount, and is controlled in an analog manner.

FIG. 4 shows another example of the tracking control device of the present invention.
Another D flip-flop circuit S2 is provided as a digital latch circuit, and a rectangular wave signal Scz corresponding to the composite signal Sa and a rectangular wave signal SRZ corresponding to the reproduced information signal SR are transmitted to this D flip-flop circuit 5. Also supplied to the data terminal 'r-D and clock terminal CK of 2,
In the circuit left λ, the level of the rectangular wave signal Scz is read at the falling edge of the rectangular wave 1δ 5rtz, that is, at the time when the reproduced information signal SR crosses the zero level from positive to negative direction, and the D flip ψ flop circuit is read. Left/Above output signal S
x and the output signal Sz of the D flip-flop circuit 5.2 are supplied to the drive circuit O as a tracking control signal.

In the example of FIG. 4, when the spot S is shifted to the left with respect to the track as shown in FIG. 3A, and the shift is large, the composite signal Sc becomes as shown by the broken line in FIG. The square wave signal Scz *control signal Sx and SZ + current flowing through the coil 70 becomes as shown in case A/ in the figure, and the high level period of the signal Sx is considerably shorter than the low level period. On the other hand, the high-level period of the signal Sz becomes considerably longer than the low-level period, and current flows through the coil 70 in the direction of arrow a for a long period of time, causing the spot S to move significantly to the right. When the spot S shifts to the left with respect to the track, and when the shift is small, the composite signal SG is as shown by the solid line in the figure, the square wave signal SGz, the control signals Sx and Sz
+The current ■ flowing through the coil 7θ is shown in case A2 in the same figure.
As a result, the high level period of the signal SX is somewhat shorter than the low level period, whereas the signal S
The high level period of z becomes somewhat longer than the low level period, current flows through the coil 70 in the direction of arrow a for a short period of time, and the spot S is moved to the right by 11·1.

When the spot S is shifted to the right with respect to the track as shown in FIG. 3C, and the shift is small, the composite signal Sc becomes like the solid line in FIG.
The y control signals Sx and Sz + the current I flowing through the coil 70 are as shown in case C2 in the figure, and the high level period of the signal Sx is somewhat longer than the low level period, whereas the high level period of the signal SZ is slightly longer than the low level period. The level period is somewhat shorter than the loan period, current flows through the coil 70 in the direction of the arrow for a short period of time, and the spot S is moved slightly to the left. When the subpot l-S shifts to the right due to the track, and when the shift is large, the composite signal SG becomes as shown by the broken line in the same figure, and the rectangular wave signal 5az
p control signal Sx and S'Z + current flowing through coil 7θ■
As shown in case CI in the figure, the high level period of the signal Sx is considerably longer than the low level period, while the high level period of one word Sz is much longer than the low level period. , the current flows through the coil 70 in the direction of the arrow for a long period of time, and the spot S is moved largely to the left.

Effects of the Invention According to the tracking control device of the present invention, the disk 10
The disc of the original beam incident on /, O''2 Subono l
-A tracking error detection signal SEe whose phase with respect to the reproduced information signal SR changes according to the direction of deviation of S with respect to the track, and whose amplitude changes according to the amount of deviation.
It is synthesized with a triangular wave signal SF or a sawtooth wave signal having a frequency sufficiently lower than the minimum frequency of the reproduced information signal SR, and the voltage is compared with a constant level of the synthesized signal Sc'z to form a rectangular wave signal SG.
This rectangular wave signal Scz is converted into a reproduction information signal 5.
By reading the level at the rising or falling point of the rectangular wave signal SRZ obtained by comparing the voltage with a fixed level of Re, the control signal can be used as a control signal, but it can be a triangular wave signal SF or a sawtooth wave signal. A pulse signal with a period equal to the period, and whose pulse width is equal to that of disk 1.
The spot S on the disk lO of the light beam incident on
Since the signals Sx and Sy or Sx and Sz'ffi are modulated according to the direction and amount of deviation with respect to the track, analog control is performed, and control accuracy is improved. power loss is reduced and efficiency is improved. In particular, in the example shown in FIG. 4, there is a period during which no current flows through the coil 7θ, so the efficiency is further improved. Furthermore, since such precise control is performed, almost no noise is generated. Moreover,
Since analog circuits such as sampling and holding circuits are not used, the circuit configuration is simple and suitable for IC implementation.

[Brief explanation of the drawing]

Figure 7 shows an example of the optical system of a C-type disc play-'r-. Figure 2 is a connection diagram showing an example of a tracking control device previously proposed by the applicant. 9 and 9 are diagrams for explaining its operation, FIGS. S and 3 are connection diagrams each showing an example of the tracking control device of the present invention, and FIGS. 7 and S are examples of FIG. FIGS. 9 and 70 are waveform diagrams for explaining the operation of the example in FIG. Objective lens as a means of measurement, 2g is the photosensitive part, 2gA ~ 2gl)
is its photosensitive element, 30 is a signal generation circuit, and lIΩ
5/ and S2 are D-flick/7-Rozzo circuits as digital latch circuits, Otsu0 is a drive circuit, g. is a signal synthesis circuit. 4-51A 11 God 00 Akira (IS, j・(1 ÷ heart,;
,;,,,,,)Figure 3A B C Figure 4c

Claims (1)

[Claims] By calculating the output of a plurality of light-sensitive condensers, the information signal is incident on a disk recorded on a spiral track to be optically read out, and the entire original beam modulated by this disk is detected. The reproduction information 1 according to the reproduction information signal and the direction of deviation of the spot on the disk of the light beam incident on the disk with respect to the track.
A signal generation circuit that obtains a tracking error detection signal whose phase changes with respect to the word and whose amplitude changes according to the amount of deviation, and converts it into a rectangular wave signal by comparing the voltage with the entire constant level of the reproduction information signal. a first voltage comparison circuit,
No. 18 synthesis circuit which combines all of the tracking error detection signals with a triangular wave signal or sawtooth wave signal having a frequency sufficiently lower than the minimum frequency of the reproduction information signal, and the synthesized signal of the output of this signal synthesis circuit, which has a constant level and voltage. a second voltage comparator circuit that compares and converts into a rectangular wave signal; and a rectangle of the output of the λ-th voltage comparator circuit at the time of rising or falling of the rectangular wave signal output of the first voltage comparator circuit. a digital latch circuit that obtains a binary signal having a level corresponding to the level of the wave signal; and a light beam that is incident on the disk by driving an optical means based on the output signal of the digital latch circuit. and a drive circuit for controlling the position of a spot on the disc with respect to the track.