JPS58150144A - Tracking control circuit of optical digital disc player - Google Patents

Abstract

PURPOSE:To perform tracking control accurately and to prevent malfunction in the stage of missing of signal, by providing a generating circuit for tracking error detection signal, an adder, a phase comparator, and a forming circuit for tracking error control signal. CONSTITUTION:The inversion input terminals (-) of differential amplifier circuits 25, 26 are commonly connected, and the connected point thereof is grounded through a resistor R16 and is grounded through an oscillator 32. The oscillator 32 generates the high frequency signal having a frequency higher than the frequency of the tracking error detection signal which is generated ordinarily. Therefore, the high frequency signal outputted from the oscillator 32 is superposed in the same phase on the tracking error detection signal by the circuits 25, 26. Thus, even if no tracking error detection signal is produced any longer by missing of the signal on account of drop-out, etc., the 1st and the 2nd pulse signals are formed in the comparators 27, 28 in accordance with the high frequency signal from the oscillator 32; therefore, the tracking error control signal is obtained.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to an optical digital disc player,
Sometimes related to the improvement of the tracking control circuit.

[Technical background of the invention]

Recently, audio signal and image signal temple fIlt￥1d
With the aim of achieving the highest possible fidelity and high density recording of the data, the information signal is converted to PCM (Pulse Code Monography).
An optical 4-disk player has been developed that directly records digitally encoded signals on a 4-disc disc and uses a 44-type pickup to extract and demodulate the digitally encoded signals from the disc during playback. In other words, in this type of device, a digitally encoded code 1d obtained by converting an information signal into PCM is directly recorded on one side of the disk as a bit string with uneven on/off and different intervals. The bit string is irradiated with an original beam from an optical pickup.

Then, this light beam hits the bit string and is reflected,
The light is received by the pickup. For this reason, the pickup detects the intensity and temporal length of the light and outputs an electrical signal corresponding to the intensity, from which the 'digital encoded signal recorded on the f4 disk is output.

By the way, what is particularly important in the above-mentioned optical denotal disk grayer is that r notal 4gf'
In order to accurately trace the light beam on the bit string, the optical pickup must be controlled so that the light beam accurately traces the bit string without causing a tracking error. It is for the sir to perform the following. FIG. 1 shows such conventional tracking control means. That is, in FIG. 1, reference numeral 11 denotes a photodetector which is a light receiving portion of an optical pickup, and as shown in the figure, it is configured in a so-called 4-division system with four light receiving areas (po, ) to (PDa). The photodetector 11 has four light receiving areas (PD, ) to (PDd).
), when an original beam that has been reflected by hitting a disk (not shown) is received, it independently outputs a signal with a voltage level corresponding to the intensity of the light. However, each of the light receiving regions (PD, ) to (PDd) is set to output a voltage signal of the same level when light of the same intensity is received.

Then, the four light receiving areas (
Each output voltage signal from PD, ) to (PDa) is
0 supplied to each of the four input terminals of the matrix circuit 120 Here, if each voltage signal output from the four light receiving regions (PD, ) to (PDd) of the photodetector J1 is respectively (Pl) to (Pd), The above matrix lI! The circuit 12 is (Pa + Pb) t (P
c-1-pd) e<, P@+Pb0Pc+
It generates and outputs five types of signals: Pd) - (Pa + Pc) - CPb + Pd). Of these, the key signals (Pa+Pb) and (pc-+-p4) are supplied to a focus error signal generation circuit (not shown) via connection terminals 13 and 14. In addition, the above (pa
+pb+pa+Pd) No. 16 is the capacitor C1,
After passing through the DC blocking circuit such as the resistor R1 and the amplifier circuit 15, it is supplied to the RF1g output coil 16, and
Rising edge detection circuit 11 and falling edge detection circuit 7
1 respectively through the S/Norhold circuit 19.20
3 supplied to the control terminals of the matrix circuit 12, and (pa+pc) and (Pb
The signal +Pa) is applied to the non-inverting input 4 (+Pa) of the comparator circuit 21.
) and the inverting input terminal (→.This comparator circuit 21 compares the signal (pm+pc) with the signal (Pb+P
It takes the difference from the signal a), which ends up being (Pa+Pe)
A signal (Pb+Pa) is output to each input terminal of the sample hold circuit 19.20. Also, each output from the sample hold circuit 19.20 is output to the comparison circuit 2.
2, the non-inverting input terminal (g) and the inverting input terminal ←) are respectively supplied. This comparison circuit 22 is connected to the sample and hold circuit 19. The output signal from the JIG is subtracted and the resulting signal is supplied to a tracking control device (not shown) via the output terminal 23.

The operation of the conventional tiger/king control means configured as described above will be explained with reference to the timing chart shown in FIG. The timing diagrams shown in FIGS. 2(b) to 2(h) show the waveforms at points (b) to (h) in FIG. 1, respectively. First, in Figure 2(a), (
I) to (2) are each dis.

This is a part of the bit string recorded in the same figure.
The mark is the beam spot of the irradiated light beam.

This shows the And now, P2. In the case where the beams/, ) are not on the bit indicated by the oval shape in the figure, the beam spot is shown in the case where the beams/,) are not on the bit indicated by the oval shape in the figure.

Since the reflectance is different depending on when the point is on the bit, it appears at point (b) in Figure 1 (p1 to pb
The waveform of the signal (+p, +p4) is constructed so that it becomes an alternating current waveform with a higher voltage level as the Kz beam spot is located on the bit, as shown in FIG. 2(b).

By doing this, (Pa
The signal waveform of 10Pc) (Pb+Pd) is shown in Figure 2 (
The AC waveform shown in c) is obtained. It should be noted that the waveform shown in FIG. 2 (,) becomes the buried "0" level when the beam spot is on the principal bit. The AC signal shown in FIG. 2(b) is generated by the rising edge 9 and falling edge detection circuit 11
．． 18. This rising and falling 9 steps, -) detection circuit 17/, 1g is the 55th flow 16 shown in FIG. 2(b).
At the "0" level crossing point of the rising and falling of the number, the second
It outputs a .9 pulse signal as shown in Figures (d) and (.). And Sansol hold circuit 19.
20 is the rising edge and falling edge detection circuit 1F, I
Every time a pulse signal is output from ll, the second
The level of the AC signal shown in FIG. 2(a) is held, and the signals shown in FIG. Then, the comparator circuit 22 subtracts the signal shown in FIG. 2(f) from the signal shown in FIG. 2(f), and the signal shown in FIG. This serves as an error control signal.

In other words, the above tracking error control signal becomes a negative voltage and a positive voltage when the beam spot deviates upward and downward (in other words, in the forward and reverse directions) in FIG. 2 (,) with respect to the pit row (If). At the same time, the absolute value of the voltage level increases according to the amount of deviation. therefore,
By setting the tracking control device so that the positive and negative polarities of the tracking error control signal determine the forward and reverse movement directions of the beam spot, and the magnitude of the absolute value of the voltage level determines the movement amount in the forward and reverse directions. It is possible to perform "tiger" and "king" control.

[Problems with background technology]

However, the conventional tracking control means as described above has the following problems. First, in order to obtain the tracking error control signal shown in FIG. 2(h),
) and (g) are both shown in fgz diagram (e)
The alternating current I5 shown in is obtained by holding the voltage level and amplitude of the signal. However, in Figure 2 (
Since the AC signal shown in e) is obtained by calculating the output signal from the photo r protector 11, for example, if the intensity of the light beam irradiating the disk changes, the change will occur.
However, the problem arises that the amplitude of the AC signal 16 shown in FIG. 2(c) is affected until 70 minutes, and as a result, accurate tracking control cannot be performed. Additionally, this problem is caused by noise components (particularly caused by pinholes, etc.) mixed into the optical system of the entire digital disc player, and the four light receiving areas (PD) of the protector 11.
It also occurs due to various causes such as variations in sensitivity of P) to (PDd).

Furthermore, the tracking error control signal has a long period in which it has a negative characteristic (as shown in the lower right corner of the figure), for example, as shown in the middle period T1 in FIG. 2(h). During this period T1, the beam spot is between pit rows, and is not subjected to tiger or king control for a particular pit row. That is, for example, if we focus on a specific pit in the pit row (If) in FIG. There is also the problem that the effective range of dragging control is narrow only during Ts.

In addition, since the rising 9 and falling 9 position detection circuits 17, 18, sample hold circuits 19 and 20, etc., are required to operate at high speed, the configuration becomes complicated and is economically disadvantageous. It is what it is.

[Purpose of the invention]

This invention was made in consideration of the above-mentioned circumstances, and is capable of accurate tracking and king control without being affected by, for example, fluctuations in the intensity of the light beam irradiated onto the disc or noise components mixed into other optical systems. It is an object of the present invention to provide an extremely good tracking control circuit for an optical digital disk solayer, which is capable of handling the following problems and also prevents malfunctions even when a signal is lost due to Pg horn out or the like.

[Summary of the invention]

That is, the present invention provides first and second optical signals having phase information corresponding to the shift in the forward and reverse directions of the light beam with respect to the pit row.
A tracking error detection signal generation circuit that generates tracking error detection No. 16, and a tracking error detection signal generation circuit that generates tracking error detection signal No. 16, and a tracking error detection signal generation circuit that generates tracking error detection signal No. Tracking error detection No. 16 also includes an adder circuit that adds high-frequency signals with different frequencies in the same phase, and the adder circuit adds the first and second tracking error detection signals to which the high-frequency signal is added in phase with each other. a phase comparator circuit that compares and outputs a signal corresponding to the phase difference component; and a controller that corrects a shift in the forward and reverse directions of the light beam with respect to the P and T arrays based on the output signal from the phase comparator circuit. The tracking error control signal generation circuit generates a tracking error control signal.

[Embodiments of the Invention] Before describing one embodiment of the present invention, the basic configuration of a tiger/king control means to which the present invention is applied will be described below with reference to the drawings.

That is, in FIG. 3, DI to D4 are first
The four light-receiving areas (P
D, ) to (PDa). The cathodes of the photodiodes D1 to D4 are commonly connected to a power supply terminal 24 to which a DC voltage (+B) is applied. Further, each cathode of the phototransistors D1 to D4 is grounded via resistors R to R, respectively.

The connection point between the photodiode DI and the resistor R1 and the connection point between the photodiode Ds and the resistor R4 are connected in common through the resistor R11pR7, respectively, and the connection point is connected through the capacitor C3. , resistance R,
It is connected to the non-inverting input terminal (E) of the differential amplifier circuit 25. In addition, the connection point between the photodiode D2 and the resistor Rs and the connection point between the photodiode D4 and the resistor R@ are each connected to a resistor "9".
m are commonly connected via J6, and the connection point is grounded via a resistor R11 after passing through a capacitor cs, and is also connected to the non-inverting input terminal (a) of the left-hand dynamic amplifier circuit 2ε. There is. And the differential amplifier circuit 25, 26
The inverting input terminal (→ is both grounded).

Here, each output of the differential amplifier l#525.26 is connected to a resistor Rs through capacitors C, , C, respectively.
a + R1j k, and are connected to the non-inverting input terminals (g) of comparison circuits 27 and 28, respectively. Also, the inverting input terminals of these comparison circuits 21 and 28←)
are both grounded.

The output terminal of the comparison circuit 21 is a D type free terminal,
It is connected to the clock terminal C of the gate (hereinafter referred to as DFF) 29, and also to the clear input terminal CL of another DFF 30. Further, the output terminal of the comparison circuit 28 is connected to the clock terminal C of the DFF j O, and also to the clear input terminal CL of the DFF 29 . Furthermore, the D input end of the above OFF 79, 30 is
Both are connected to the power supply terminal 24.

Also, if the above is OFF,? 9 output end Q and DFF 3
0 inversion output terminal 4 is resistor R141Rlm respectively.
The connection point thereof is grounded via a capacitor C6, and is also connected to the connected output terminal 31 of the tracking control device.

The operation of the above configuration will be explained below with reference to FIG. 4. Note that FIGS. 4(a) to (g) show the waveforms at points (a) to (g) in FIG. 3, respectively. That is, the light irradiated onto the disk and reflected is received by the photodiodes Dl to D4 constituting the four light receiving areas (PDa) to (PDd) of the photodetector 11, so that the connection with the resistors R, IR, The signals fc(P, +P, R and (Pb+Pd) shown in FIG. 1) are output at the point and the connection point between the resistors R and R50.

-t, and the signals (Pa+Pc) and (Pb to Pa) are connected to the capacitors C, Icm and the resistor RHat + R1.
The AC component is taken out by a DC blocking circuit other than 1, and eventually the third
At points (a) and (b) in FIG. 4, the AC signals 16 shown in FIGS. is output as These first and second tracking error detections (m) are performed when the beam spot is accurately located on the pit row and there is no tracking error.
The phase difference becomes zero. In addition, these first and second tracking error detection signals 18 calculate the phase of the other tracking error detection signal based on the phase of one tracking error detection signal with respect to the deviation in the beam spot, forward and reverse directions with respect to the bit string. is advanced or delayed, and the phase difference changes depending on the magnitude of the shift.

The first and second tracking error detection signals are each amplified by differential amplifier circuits 25 and 26, and then compared in voltage with a reference potential (in this case, ground potential) by comparison circuits 27 and 28. By the way, points (e) and (d) in Figure 3 are in phase with the first and second tiger and king error detection signals, respectively, as shown in Figure 4 (c) and (d). First and second pulse signals are output.

That is, the first, first, and second base pulse signals also have the same properties as the first and second tracking error detection signals in terms of their phase relationship.

The first and second pulses (No. 1) thus obtained are compared in frequency and phase with each other by Dll'F 29 #30. That is, in this case, OF
When the phase of the first .9 signal is ahead of the phase of the second .9 signal, FJ9 generates a .9 signal according to the phase difference component as shown in Fig. 4(-). Output. In addition, when the phase of the first pulse signal is delayed by 9 times compared to the phase of the second pulse signal, the OFF JO・Outputs a 9 pulse signal.

Then, the capacitor C is charged and discharged by the pulse signals shown in FIGS. 4(.) and 4(f). In this case, at point -) in Fig. 3, a signal having a voltage corresponding to the phase difference of the first and second tracking error detection (No. 4) as shown in Fig. 4(g) Output as error control signal.

Here, when the first and second tracking error detection signals are in the same phase, the tracking error control signal has a voltage of approximately (V2) 9, which causes the beam spot 9 to shift in the forward and reverse directions with respect to the bit string. , tb According to the phase lead/lag of the first and second tracking error detection No. 4g, the voltage is less than or more than (B/2), and the voltage level is changed according to the amount of deviation. are different. Therefore, by supplying the tracking error control signal to the tracking control device via the output terminal 31, tracking and king control is performed here.

Therefore, according to the above basic configuration, since the tracking error control signal is generated from the phase difference component of the first and second tracking error detection signals,
If the intensity of the light beam irradiated to the disc changes, noise components may be mixed into the optical system of the entire digital disc player, or the four light receiving areas of photodetector 1 (
Even if the voltage level and tb amplitude of the first and second tiger and king error detection signals change due to variations in the sensitivity of PD, > to (PDd), the tracking molar control signal will not be affected. First, accurate tracking control can be performed.

By the way, in the basic configuration shown in FIG. 3, for example, a dropout or the like may occur due to dust or dirt on the surface of the surface, and the signals (P, ) to (
If Pa) is missing, the first and second tracking error detection signals 18 will naturally no longer occur, and the first and second tracking error detection signals will generate JL error control. The signal is no longer legitimate and tracking cannot be performed.

In addition, especially when the signal is missing, (e), (
d) If there is a noise component at the point, the tracking control is performed by this noise component, and -(L goes around).

Therefore, one embodiment of the present invention will be described below with reference to the drawings. In FIG. 5, the same parts as in FIG. 3 are indicated by the same symbols, and only the different parts will be explained here. In other words, the inverting input terminals (-) of the anti-industrial amplifier circuits 25 and 26 are commonly connected, and the connection point is connected to the resistor aSS.
It is grounded via the oscillator 32 and grounded via the oscillator 32. This oscillator 32 generates a high frequency signal having a higher frequency than the frequencies of the normally generated first and second tracking error detection signals. Therefore, the high frequency signal output from the oscillator 32 is superimposed on the first and second tiger and king error detection signals in phase by the differential amplifier circuits 25 and 26.

Therefore, the signal is lost due to mud, seaaud, etc.
Even if the first and second error detection signals are no longer generated, the comparator circuits 27 and 28 generate the first and second C)INN signals based on the high frequency signal from the oscillator 32, so the above-mentioned error detection signals are generated. , a king error control signal can be obtained. In this case, the tracking error control signal is maintained at a voltage of approximately (B/2') because the first and second signal signals are in phase.

Note that this invention should not be limited to the above-mentioned embodiments, and can be implemented with various modifications without departing from the gist thereof. [Effects of the Invention] Therefore, as detailed above, this invention According to the invention, it is possible to perform accurate tracking control without being affected by, for example, fluctuations in the intensity of the light beam irradiated onto the disc or noise components mixed into other optical systems, and it is also possible to perform accurate tracking control without being affected by fluctuations in the intensity of the light beam irradiated onto the disc or noise components mixed into other optical systems. Accordingly, it is possible to provide an extremely good tracking control circuit for an optical r notal disc solayer that does not malfunction.

[Brief explanation of drawings]

Fig. 1 is a block circuit diagram showing the tiger and king control means of a conventional optical digital disc player, and Fig. 2 (
a) to (h) are a plan view showing the relationship between the pit row and the beams /,) and a timing diagram of each part in FIG. 1, respectively;
Figure 3 is a circuit configuration diagram showing the basic configuration of this invention, Figure 4 (a) is a timing diagram of each part of Figure 3, and Figure 5 is an optical digital circuit diagram according to this invention. Part of the tracking control circuit for the disc player m911t-
FIG. 2 is a block circuit diagram showing the configuration. 11... Photo r idector, 12... Matrix retrospective, 13.14... Connection terminal, 15... Amplifier circuit,
'146... RF signal output terminal, 17... Rising edge machine route, 11... Falling edge machine route, 19... Falling edge machine route, 19...
゜21F 't・Sample hold circuit, 21.22・
...Comparison circuit 1.2S...Output terminal, 24...Power supply terminal, 25.116...Differential amplifier circuit, 27.28...
-Comparison circuit, xs, so...DFF, 31...output terminal, 32...oscillator.

Claims (1)

[Claims] The digital code can be obtained by tracing the bit string by irradiating the disk with a light beam and tracing the bit string by irradiating the disk with the R notal encoded signal obtained by encoding the Qiho E code as a bit string of the number of sections. In accordance with the optical system for producing the optical system No. 16, the light beams with respect to the pit row, the first and second (/>) having phase information corresponding to the deviation in the opposite force direction. Tracking error detection ID No. d generation regeneration circuit that generates a shisoking error detection signal, and tracking en-detection 1 of FAI and wJ2 output from this tracking error detection signal generation circuit
5g1 and the second tiger for No. 6, -? lrd wave 1ti@k with a higher frequency than the learning error signal
A nose circuit that applies signals in the same phase, and a four-time Ayu circuit that applies a high-frequency signal to the first and second tracking error detection circuits (1 and 2), which apply high-frequency signals, respectively, compare the phases of the i signals with each other and respond to the phase difference component. and a tracking error control No. 16 generation unit that generates a tracking error control signal that corrects the deviation of the light beam in the forward and reverse directions with respect to the pit row based on the output signal from the phase comparison circuit. A control circuit for an optical r-notal f4 scraper, characterized by comprising a circuit.