JPH0576111B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to information reproduction in which information is reproduced from an information recording carrier on which binary signals are recorded on concentric or spiral information tracks at a constant linear velocity. The present invention relates to rotation control for controlling the rotation of an information recording carrier at a constant linear velocity in an apparatus.

(Prior Art) Among information recording carriers in which binary signals are recorded on concentric or spiral information tracks, there is one in which recording is performed while keeping the linear velocity constant in order to increase the recording density. A compact audio disc is one such example. To improve the reproduction strength of this type of information recording carrier, the general method is to extract the clock component from the reproduction signal and read the information.
If the linear velocity deviates by more than a certain value, it becomes difficult to extract the clock, so rotation control is required to suppress the linear velocity error to below a certain value even when the clock is not extracted. As one of these speed control methods,
A method has already been put into practical use that utilizes the time from one state inversion of a reproduced signal to the next state inversion, that is, the maximum value of the state inversion interval.

DESCRIPTION OF THE PREFERRED EMBODIMENTS A rotation control means of a conventional information reproducing apparatus that reproduces information at a constant linear velocity will be described below with reference to the drawings. FIG. 5 is a block diagram of rotation control means in a conventional information reproducing apparatus, in which 1 is an information recording carrier, 2 is a motor, 3 is a reading head, 4 is a waveform shaping means, 5 is a maximum reversal interval detection means, and 6 is a It is a motor drive means. First, the read head 3 reads the binary signal recorded on the information track of the information record carrier 1. The reading method at this time may be optical, magnetic, or capacitive. Tracking control and optical focus control are also performed if necessary. The reproduced signal outputted as a result has a rounded waveform because the recording density of the information recording carrier 1 has been increased to near the reproduction limit. Therefore, the waveform shaping means 4 performs waveform shaping to output a reproduced digital signal closer to the recording waveform. Next, the maximum reversal interval detecting means 5 inputs this reproduced digital signal and detects the maximum value of the edge interval, that is, the maximum value of the time from one state reversal to the next state reversal. In general, digital code modulated signals have a limited upper limit on how long one state can last due to the necessity of extracting the clock component thereafter. In the case of a compact disk, the upper limit is 11T, which is 11 times the clock period T, and if a certain interval is taken, the
The standard includes 11T waveform. Therefore, the maximum reversal interval signal obtained by the maximum reversal interval detection means 5 has a value inversely proportional to the linear velocity of the information recording carrier 1. Therefore, the motor driving means 6 compares this maximum reversal interval signal with the maximum reversal interval signal value at the normal linear velocity and drives the motor so as to cancel the difference. The linear velocity of the information recording carrier can be controlled to a constant value in the manner described above (see, for example, "Compact Disc Reader" published by Ohm Publishing).

(Problems to be Solved by the Invention) However, the above configuration has a drawback in that the control linear velocity is easily disturbed due to the asymmetry of the reproduced digital signal. In the case of compact discs, errors in the length of pits formed on the disc information surface may occur during manufacturing. Intersymbol interference due to the frequency characteristics of the read head also affects the state inversion interval. Code modulation methods have been devised to remove these errors using waveform shaping means, but they cannot be completely eliminated, and there are also error sources such as errors in the waveform shaping means itself and temperature drift. . This affected the control linear velocity in the form of an error in the maximum state reversal interval.

The present invention has been made in view of the above-mentioned problems, and is an information reproducing apparatus that can minimize the complexity and increase of the circuit configuration, eliminate the influence of errors in the maximum inversion interval, and perform accurate linear velocity control. is intended to provide.

(Means for Solving the Problems) In order to solve the above problems, the information reproducing apparatus of the present invention provides information in which binary signals are recorded at a constant linear velocity on concentric or spiral information tracks. A motor for rotating a record carrier, a reading head for reproducing a signal from the information recording carrier and outputting a reproduced signal, and a waveform shaping means for shaping the waveform of the reproduced signal obtained from the reading head and outputting a reproduced digital signal. , an alternating maximum inversion interval in which a maximum inversion interval signal is output by alternately repeating a period for detecting the maximum inversion interval from the rise to the fall of the reproduced digital signal and a period for detecting the maximum inversion interval from the fall to the rise. The rotation control means includes a detection means and a motor drive means for comparing the maximum reversal interval signal with a value corresponding to a control target linear velocity and driving the motor so as to cancel the difference.

(Function) With the above-described configuration, the present invention reverses the polarity of the maximum reversal interval detection for each section, so the errors included in the maximum reversal interval signal act to cancel each other for each section, and the control linear velocity impact can be minimized.

(Example) Examples will be described below with reference to the drawings. FIG. 1 shows a block diagram of rotation control means in an information reproducing apparatus according to an embodiment of the present invention. In FIG. 1, the same reference numerals as in FIG. 5 indicate the same components, and 7 is maximum reversal interval alternating detection means.

The operation of the rotation control means configured as described above will be explained using FIGS. 2 and 3. FIG. 2 shows the first inversion interval alternating detection means 7 in FIG.
The specific circuit configuration of the embodiment is shown in FIG.
2 shows signal waveforms at each part in FIG. 2. In the figure, a to g are signals at points A to G in FIG. 2, respectively. First, h in FIG. 3 represents the reproduced signal output from the reading head 3, and the broken line represents the threshold value for waveform shaping by the waveform shaping means. The reproduced digital signal obtained as a result is a. At this time, if the threshold value fluctuates for some reason, the duty of the reproduced digital signal a will also be affected, and the maximum inversion interval will also change. However, since the "H" level pulse width and the "L" level pulse width change in different directions, if the maximum pulse width at each level is detected and averaged, the error component will be canceled out and the correct value will be obtained. You will get it. However, simply trying to execute this would require two identical circuits. The circuit shown in FIG. 2 achieves an equivalent effect with a small addition of circuitry. Second
In the figure, 11 and 12 are AND gates, 13 and 1
5 is a NOR gate, 14 is an OR gate, 16, 23
is an inverter, 24 is an exclusive NOR gate, 21, 22, 26 are analog switches, 1
8, 19, and 25 are operational amplifiers, R1 to R6 are resistors, C1 to C5 are capacitors, and 20 is a diode. The reproduced digital signal a input from point A passes through the logic consisting of gates 12, 14, and 15. At this time, when the switching signal b at point B is "H", it passes through as is, and when it is "L", it is inverted. Reach point C. R1, C1 and gate 16 form a delay circuit, and together with gates 11 and 13, rise and fall edge pulses d,
generate e. When analog switch 21 is closed by rising edge pulse d, capacitor C2 is discharged, but then charged through resistor R2. Next, the falling edge pulse e
When the analog switch 22 closes, point F (f signal) and point G (g signal) pass through the diode 20.
The voltages at point G are compared, and if point G is lower, C3 is charged so that they are equal. The resulting potential at point G, ie, the output of the operational amplifier 19, provides the maximum inversion interval of the "H" level or "L" level depending on the input b. Therefore input b
By alternately switching between "H" level and "L" level faster than the response of the system, error components are canceled out and correct linear velocity control can be performed.
However, if this signal is used as it is as an error signal for driving the motor, there is a possibility that the motor power consumption will increase. Therefore, in this embodiment, the output value is sampled by the analog switch 26, the capacitor C4, and the operational amplifier 25 every time the input b is inverted, and the average value with the output in the next section is outputted through the resistors R4 and R5. It is said that Thereafter, the motor driving means 6 compares the maximum reversal interval signal value with the maximum reversal interval signal value at the normal (that is, control target) linear velocity, and drives the motor 2 so as to cancel out the difference. , which is the same as the prior art example shown in FIG.

Next, FIG. 4 shows a specific circuit configuration when the maximum inversion interval alternating detection means is realized by a digital circuit of the second embodiment. In the figure, 31 is a latch, 32 is a counter, and 33 is a latch.
is a comparator, 34 is an RS flip-flop,
35-39 and 48 are AND gates, 40 is a clock generator, 41-44 are D flip-flops, 4
5 and 46 are NOR gates, and 47 is an OR gate. The basic operation is almost the same as the first embodiment. The reproduced digital signal, which is the output of the waveform shaping means, is input to the Y point, and is passed through the gates 46, 47,
D flip-flops 41 to 44 and ADN gates 36 to 39
It enters a timing generation circuit consisting of. Here, rising and falling edge pulses and their delayed pulses are generated. RS flip flop 3
4 is operated by these pulses and counter 3
The gate 45 of the count clock X of 2 is opened and closed. After being reset by the rising edge pulse W, the counter 32 advances the count by the count clock applied through the NOR gate 45. The outputs of the counter 32 and latch 31 are compared in magnitude by a comparator 33, and if the counter output is greater than the latch output, the latch pulse gate 35 is opened. When the counter 32 finishes counting, a latch pulse is generated from the AND gate 39, and if the gate 35 is open, the contents of the latch 31 are updated to the counter output value. As a result, the content of latch 31 has a value proportional to the maximum inversion interval of the reproduced digital signal. Therefore, if the latch contents are reset by the P input at the beginning of the sample period and the Z input is inverted, and the latch contents at the end of the sample period are output, the error components will be canceled out and the correct linear velocity will be obtained, as in the first embodiment. control can be realized.

(Effects of the Invention) As is clear from the above, the present invention provides a motor for rotating an information recording carrier on which a binary signal is recorded on a concentric or spiral information track at a constant linear velocity; a reading head that reproduces a signal from an information recording carrier and outputs the reproduced signal; a waveform shaping means that shapes the waveform of the reproduced signal obtained from the reading head and outputs a reproduced digital signal;
Maximum inversion interval alternate detection that outputs a maximum inversion interval signal by alternately repeating a period for detecting the maximum inversion interval from the rise to the fall of the reproduced digital signal and a period for detecting the maximum inversion interval from the fall to the rise. and a motor drive means for driving the motor so as to compare the maximum reversal interval signal with a value corresponding to the control target linear velocity and cancel the difference. Accurate linear velocity control can be performed even when the maximum inversion interval of the signal includes an error due to asymmetry.

Furthermore, the maximum inversion interval alternating detection means detects the maximum inversion interval from the rising edge to the falling edge of the reproduced digital signal, and detects the period for outputting the maximum inversion interval signal and the maximum inversion interval from the falling edge to the rising edge of the reproduced digital signal. By alternately repeating the periods in which the maximum inversion interval signal is outputted, the influence of the maximum inversion interval error can be removed without complicating or increasing the circuit.
It is possible to improve performance without increasing costs,
It is extremely useful in practice.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a rotation control means in an information reproducing apparatus according to an embodiment of the present invention, and FIG. 2 is a circuit diagram of a first embodiment of the maximum reversal interval alternating detection means in FIG. 3 is a signal waveform diagram of each part of the circuit of FIG. 2, FIG. 4 is a circuit diagram of a second embodiment of the maximum inversion interval alternating detection means, and FIG. 5 is a rotation control means in a conventional information reproducing device. FIG. DESCRIPTION OF SYMBOLS 1... Information recording carrier, 2... Motor, 3... Reading head, 4... Waveform shaping means, 6... Motor driving means, 7... Maximum reversal interval alternating detection means.

Claims (1)

[Claims] 1. A motor that rotates an information recording carrier on which a binary signal is recorded at a constant linear velocity on a concentric or spiral information track, and a motor that reads the signal from the information recording carrier to generate a reproduced signal. A reading head for outputting, a waveform shaping means for shaping the waveform of the reproduced signal obtained from the reading head and outputting a reproduced digital signal, and a period and a rising edge for detecting the maximum inversion interval from the rise to the fall of the reproduced digital signal. Maximum reversal interval alternating detection means for outputting a maximum reversal interval signal by alternately repeating a period for detecting a maximum reversal interval from falling to rising;
An information reproducing device comprising rotation control means comprising a motor drive means for comparing the maximum reversal interval signal with a value corresponding to a control target linear velocity and driving the motor so as to cancel the difference. 2. The maximum inversion interval alternating detection means detects the maximum inversion interval from the rising edge to the falling edge of the reproduced digital signal, and detects the period for outputting the maximum inversion interval signal and the maximum inversion interval from the falling edge to the rising edge of the reproduced digital signal. 2. The information reproducing apparatus according to claim 1, wherein a period in which the maximum inversion interval signal is output is alternately repeated.