JPS6113448A - Generating device for tracking error signal - Google Patents

Abstract

PURPOSE:To eliminate the disorder of a tracking error signal and prevent a pickup from operating abnormally by inhibiting a sample holding means which generates a signal for generating the tracking error signal from performing sampling operation when one of a couple of arithmetic outputs is absent. CONSTITUTION:An RF signal outputted by an inverting amplifier 4 is delayed through a delay circuit 14 composed of a delay line, etc., and supplied to a sampling pulse generating circuit 6. At the same time, the RF signal from the inverting amplifier 4 is supplied to a dropout detecting circuit 15. The dropout detecting circuit 15 compares, for example, the envelope component of the RF signal and compares it with a specific reference voltage to generate a high-level dropout detection signal when the signal level of th RF signal drops below a specific level. The output of this dropout detecting circuit 15 is applied to the base of a transistor Q through a resistance R14.

Description

TECHNICAL FIELD The present invention relates to a tracking error signal generation device, and more particularly to a tracking error signal generation device in an optical information reading device.

Background Art In an information reading device, the pickup information detection point and the recording track are perpendicular to each other (disk radius).
A circuit that generates a so-called tracking error signal indicating the state of separation in the direction is used, an example of which is shown in FIG. In Fig. 1, reference numeral 1 denotes a so-called 4-division type light-receiving element, and the light from the information detection spot light of the pick amplifier that passes through the recording disk surface is irradiated onto the light-receiving surface of this 4-division type light-receiving element 1. be done. In the 4-split type photodetector 1, the outputs of the photodetectors arranged diagonally to each other are connected to an inverting amplifier 2.
and 3. Feedback resistors R0 and R2 are connected between the input and output terminals of the inverting amplifiers 2 and 3, respectively. These inverting amplifiers 2, 3 and feedback resistors R, , R2 add the output currents of the light receiving elements arranged diagonally to each other and simultaneously convert them into voltages. Inverting amplifier 2
and 3 are supplied to the inverting amplifier 4 via input resistors R3 and R6, respectively. A feedback resistor R6 is connected between the input and output terminals of the inverting amplifier 40. These resistors.

R4JL and the inverting amplifier 4 form an adder circuit 5, and the outputs of the inverting amplifiers 2 and 3 are added and combined to obtain a voltage output corresponding to the sum of the outputs of the light receiving element 1. The output of the adder circuit 5 is supplied as an RF (high frequency) signal containing read information to a demodulation circuit (not shown) and at the same time to a sampling pulse generation circuit 6. The sampling pulse generation circuit 6 includes, for example, a comparator that compares the RF multiplied signal outputted from the adder circuit 5 with a reference voltage equal to the zero level of the RF multiplied signal, and a comparator that is synchronized with the rising edge and falling edge of the output of this comparator, respectively. It is formed by a differential circuit that outputs two pulses. The two pulses output from this sampling pulse generation circuit 6 are supplied to sample and hold circuits 7 and 8, respectively.

On the other hand, the outputs of the differential amplifiers 2 and 3 are supplied to the negative input terminal and positive input terminal of the operational amplifier 9 via input resistors R6 and R7, respectively. A resistor R8 is connected between the positive input terminal of the operational amplifier 9 and ground. Additionally, a feedback resistor R is connected between the negative input terminal and the output terminal of the operational amplifier 9.
0 is connected.

These operational amplifiers9. A subtraction circuit 10 is formed by the resistors R6 to R0, and a signal corresponding to the difference between the outputs of the inverting amplifiers 2 and 3 (hereinafter referred to as DL multiplied signal) is obtained. DL multiplication signal delay circuit 11 output from this subtraction circuit 10
After being delayed for a predetermined time by , the signals are input to each of the sample and hold circuits 7 and 8. The outputs of the sample and hold circuits 7 and 8 are supplied to a subtraction circuit 13 which, like the subtraction circuit 10, is formed by an operational amplifier 12 and resistors R1o to R13.

The output of this subtraction circuit 13 becomes a tracking error signal.

The tracking error signal generating device as described above is described in detail in Japanese Patent Laid-Open No. 59-2236. In such conventional devices, scratches or defects on the recording disk may cause
When the signal level of the detection output of the split light receiving element 1 changes,
A pair of arithmetic outputs obtained by arithmetic processing the detection output of the four-division light receiving element 1, that is, a RP multiplied signal and a DL multiplied signal disturbance will occur. This causes a disturbance in the output of the delay circuit 11, and the output of the delay circuit 11 is sampled at an abnormal timing, causing a disturbance in the tracking error signal. As a result, a so-called jump operation in which a pick amplifier whose drive is controlled based on a tracking error signal jumps between tracks is erroneously performed, resulting in problems such as the generation of abnormal sounds in digital audio disc players and the like.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a tracking error signal generating device that can prevent abnormal operation of the pickup without disturbing the tracking error signal due to scratches or defects on the recording disk.

The tracking error signal generating device according to the present invention samples and holds the other of the pair of calculation outputs based on one of the pair of calculation outputs obtained by processing the detection outputs of a plurality of light receiving elements. The obtained signal is used to obtain a tracking error signal and one of the pair of calculation outputs.

The configuration is such that when a omission occurs, sampling of the other one is prohibited.

Embodiments Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS. 2 to 4.

In FIG. 2, a 4-split photodetector 1, an inverting amplifier 2,
3, 4, sampling pulse generation circuit 6, sample hold circuits 7, 8, operational amplifier 9, 12° delay circuit 10,
Resistors R1-R13 are connected in the same way as in the device of FIG. However, in this example, a delay circuit 1 consisting of an RF multiplied signal delay line outputted from an inverting amplifier 4, etc.
After being delayed by 4, the signal is supplied to the sampling pulse generating circuit 6. At the same time, the R and F signals output from the inverting amplifier 4 are supplied to the dropout detection circuit 15. The dropout detection circuit 15 includes, for example, R
By detecting the F-fold signal envelope component and comparing it with a predetermined reference voltage, a high-level dropout detection signal is generated when the RF-multiply signal level falls below a predetermined level. The output of this dropout detection circuit 15 is applied to the base of the transistor Q via a resistor R14. The emitter of transistor Q is grounded, and the collector of transistor Q is connected to resistor R.
A power supply voltage is applied via 1. A capacitor C is connected in parallel to the resistor R15. transistor Q
The collector output of AND gates 16 and 1
0NAND gate 16 applied to one input terminal of 7
The pulses output from the sampling pulse generation circuit 6 are applied to the other input terminals of the AND gates 16 and 17.The pulses output from these AND gates 16 and 17 are supplied to the sample and hold circuits 7 and 8 as sampling pulses. be done.

In the above configuration, the signal delay time in the delay circuit 14 is set to be slightly longer than the time required for dropout detection in the dropout detection circuit 15,
And the signal delay time in the delay circuit 11 is the time required for this dropout detection and the sample pulse generation circuit 6
It is assumed that the setting is set to be slightly longer than the time obtained by adding the signal delay time of
As shown in the figure, the signal levels of the R and F signals decrease and the figure (
When a disturbance occurs in the output of the subtraction circuit 10 as shown in FIG. 13), a high level dropout detection signal is output from the dropout detection circuit 15 as shown in FIG. 13C. When this dropout detection signal is supplied to the base of transistor Q, transistor Q is turned on. Then, as shown in the same figure (D), the collector output of the transistor Q becomes a low level, the outputs of the AND gates 16 and 17 become a low level, and the output of the delay circuit 11 in the sample and hold circuits 7 and 8 is no longer held. . As a result, when a dropout detection signal exists, the output of the delay circuit 11 held before the dropout detection signal was generated, that is, the DL signal before disturbance occurs, is supplied to the differential amplifier 131C to form a tracking error signal. be done.

Furthermore, when the dropout detection signal disappears, the transistor Q turns off, but the collector output of the transistor Q does not immediately go to a high level due to the charge in the capacitor C, and as shown in η in the figure, the collector output of the transistor Q
The level rises with a time constant τ determined by S.

Therefore, even after the dropout detection signal disappears, sample pulses are not supplied to the sample and hold circuits 7 and 8 for a period of time corresponding to the time constant τ, and the output of the delay circuit 11, which was held before the dropout detection signal was generated, continues. The tracking error signal is then supplied to the differential amplifier 13 to form a tracking error signal.

FIG. 4 is a circuit block diagram showing another embodiment of the present invention, in which a dropout detection signal and, for example, a play operation mode command signal that is at a high level during a normal play operation mode are input and output is connected to a resistor R24. All parts except for the AND gate 18 which is connected so that the voltage is applied to the base of the transistor Q via the gate are constructed in the same manner as the device shown in FIG. In such a configuration, the dropout detection signal is applied to the transistor Q only in the normal play operation mode.
Since the tracking error signal is applied to the base of the jump operation in a mode other than the normal play operation mode, such as the search mode, the tracking error signal changes during the jump operation as in the conventional device, and the number of skipped tracks changes due to the change in the tracking error signal. can now be detected.

In the above embodiment, the RF multiplied signal is delayed by the delay circuit 14, but the sample pulse generation circuit 6 may also delay the output timing of the pulse.

Effects As detailed above (the tracking error signal generating device according to the present invention performs sampling in the sample hold means for generating a signal for forming a tracking error signal when one of a pair of calculation outputs is missing). Since the configuration is such that even if a pair of calculation outputs is disturbed due to scratches or defects on the recording disk, the sample and hold of the disturbed calculation output will not be performed, and the tracking error signal will not be disturbed. Therefore, abnormal operation of the pickup due to disturbance of the tracking error signal can be prevented, and problems such as the generation of abnormal sounds in digital audio players and the like can be prevented.

[Brief explanation of drawings]

FIG. 1 is a circuit block diagram showing a conventional t-tracking error signal generation device, FIG. 2 is a circuit block diagram showing an embodiment of the present invention, and FIG. 3 shows the operation of the device shown in FIG. 2. The waveform diagram and FIG. 4 are circuit block diagrams showing another embodiment of the present invention. Explanation of symbols of main parts 1... Quadrant type light receiving element 6... Sample pulse generation circuit 7.8... Sample hold circuit 15... Dropout detection circuit 16.17... N mountain gate Q ...Transistor

Claims (1)

[Claims] means for detecting the light that has passed through the recording surface of the spot light for information reading using a plurality of light receiving elements and processing these detection outputs to generate a pair of calculation outputs; and generating a sampling pulse from one of the calculation outputs. A tracking error signal generation device comprising a sampling pulse generation means and a sample hold means for sampling and holding the other of the calculation outputs using the sampling pulses, and obtaining a tracking error signal using the hold outputs. dropout detection means for generating a dropout detection signal when the other one of the calculation outputs is missing, and prohibiting sampling of the other calculation output in the sample hold means when the dropout detection signal is generated. A tracking error signal generation device comprising: means for inhibiting.