JPH04182972A - Method for processing track crossing signals - Google Patents

Abstract

PURPOSE:To accurately control a movement between tracks by providing a through-rate restrictive circuit in the control circuit for movement between tracks. CONSTITUTION:The through-rate restrictive circuit 2 is provided in the control circuit for movement between tracks. The track error signals generated from an optical head 1 contain a track loss signal as well as a noise caused by damage in a prepit or an optical disk. When these signals are inputted into the through-rate restrictive circuit 2, the track loss signals hardly affected by noise are obtained. By receiving these signals, a speed detecting means 4 outputs a speed signal, simultaneously, a target speed generating means 3 counts the number of passing tracks by receiving these signals, and outputs a target speed. In addition, a speed error signal is generated by a speed error detecting means 5, and in response to this signal, a driving motor 7 is driven through a driving amplifier 6 to control the optical head at a target speed. In such manner, seeking a track that is not a target track by mistake is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for processing track crossing signals used in inter-track movement control of an optical disc device.

[Prior Art] In an optical disk device, the inter-track movement (hereinafter abbreviated as "nook") in which the focal point of a laser beam (hereinafter abbreviated as a light spot) is moved from a certain track to a desired track has conventionally been performed using an inter-trunk movement as shown in FIG. It was controlled by a movement control circuit.

That is, the laser beam emitted from the optical disc 1 connects optical spots on the optical disk, and when this optical spot crosses the track, the speed detection means 4 receives the signal generated by the optical head, and based on this signal, the speed is determined. Similarly, the target speed generating means 3 also counts the number of tracks passed from the output signal of the optical head and outputs the target speed.Furthermore, the speed error detecting means 5 generates a speed error signal and responds to this signal. The drive amplifier 6 drives the drive motor to control the light beam to a target speed.

[Problem to be solved by the invention] However, the conventional technology has the following problems.

Formant signals called pre-pits are recorded on the disk in the form of unevenness, and when an optical groove passes over these pre-pits or scratches on the disk, the signal output from the optical head to the speed detection means is disturbed. , the speed detection means will no longer be able to detect the correct speed. This situation will be explained with reference to FIG. Figure 6 shows 1-
It shows how the waveform of the La-Tsuku crossing signal is shaped.

Track crossing signal input to speed detection means (a)
is a sinusoidal waveform with a long period representing the intersection (hereinafter abbreviated as track cross) caused by the relative speed of the track and the optical spot, and a sharp pulse with a short period caused by scratches on the disk, etc. It consists of The track crossing signal is waveform-shaped within the speed detection means, but at this time, it is not affected by pre-pits or scratches on the disc, and is a signal due to track crossing (hereinafter referred to as track crossing signal).
The ideal waveform obtained in this case is the waveform shown in FIG. However, in reality, as shown in FIG. 3C, extra pulses with a short period are generated due to pre-pits, scratches on the disk, etc. Since the speed detection means determines the moving speed of the light spot from the period of the pulse, an erroneous speed signal is output to the speed detection means due to the two extra pulses. As a result, the drive motor is controlled by an erroneous error signal, causing problems such as the seek speed not being able to be controlled correctly, the control becoming unstable, and the seek direction instantaneously reversing and causing a runaway.

Furthermore, other problems arise due to pre-pits, scratches on the disc, and the like. The target speed generating means recognizes one period in FIG. 6(c) as one track cross, reduces the number of remaining tracks to be sought by the number of track crosses, and generates a target speed corresponding to the number of remaining tracks. However, the same figure (
If an erroneous pulse is generated due to pre-pits, scratches on the disk, etc. as in C), the number of track crosses will be incorrect, making it impossible to generate the correct target speed. Furthermore, since the number of remaining tracks cannot be counted correctly, the user mistakenly searches for the wrong track as the target track, making it impossible to seek to the correct track.

As described above, when the light spot passes over pre-pits or scratches on the disk, both the detected speed and the target speed cannot be accurately determined, resulting in disturbances in speed control or inadvertently hitting a track that is not the target trunk. It is an object of the present invention to provide a new method for processing track cross signals in order to prevent seek.

[Means for Solving the Problems] - The present invention provides a method in which a light spot for recording and reproducing information in an optical disc device is moved from one track to another for purposes such as information retrieval and initialization of the light spot position. A track crossing signal processing method for controlling inter-track column movement when moving to a track is characterized in that a slew rate limiting circuit is provided in an inter-track movement control circuit. Signals used as the track crossing signal include a track error signal, the output of one of the detectors in the optical head, or a sum signal of signal outputs of a plurality of detectors.

[Function] The present invention specifies the maximum value (hereinafter referred to as slew rate) of the voltage change rate (absolute value including positive and negative change rates) with respect to time of the input signal, and the voltage change below this slew rate If a signal with a rate of change is input, the waveform is output as is, and if a signal with a voltage change rate greater than this slew rate is input, this input signal changes over time at the maximum rate of change limited by the slew rate. The inter-track movement control circuit includes a slew rate limiting circuit that converts the signal into a signal.

Therefore, if this slew rate is set in advance to be equal to the maximum rate of change of the track cross signal, noise caused by pre-pits, scratches on the optical disk, etc. will be treated as a pulse-like signal (a signal with a very large rate of change and a short period). , the track cross signal is output as is, and noise is output as a signal whose voltage change rate is limited by the slew rate. This noise output signal has a fairly suppressed amplitude and does not affect the track cross signal.

By using the slew rate limiting circuit as described above, it is possible to suppress the influence of noise and obtain a track cross signal that is not significantly disturbed.

[Example] Examples of the present invention will be described below based on the drawings. 1st
The figure is a block diagram of an inter-track movement control circuit according to the present invention. A track error signal is used as the track cross signal. The track error signal output from the optical head 1 includes both a track cross signal and noise due to pre-pits, scratches on the optical disk, and the like. When this signal is input to the slew rate limiting circuit 2, it is possible to obtain a track cross signal with almost no influence of noise due to the effect of the above-mentioned operation. Upon receiving this signal, the speed detecting means 4 outputs a speed signal, and the target speed generating means 3 likewise receives this signal, counts the number of passing tracks, and outputs the target speed. Furthermore, a speed error detection means 5 generates a speed error signal, and a drive amplifier 6 drives a drive motor 7 in accordance with this signal to control the optical head to a target speed. FIG. 2 is a diagram showing a signal before and after passing through the slew rate limiting circuit and how the signal is waveform-shaped within the speed detecting means. The track error signal before passing through the slew rate limiting circuit is depicted in FIG. When this signal passes through the slew rate limiting circuit, the amplitude of the noise is significantly suppressed as shown in the same figure (b).
is output.

Further, when this signal is waveform-shaped within the speed detecting means, it becomes as shown in FIG. 3(C). This signal is the same signal as shown in Fig. 6(b), which is a faithful waveform of only the trunk cross signal generated when the light spot crosses the track, and is used to detect the speed of the light spot, target speed, target track, etc. can be obtained accurately.

FIG. 3 shows an example in which the slew rate limiting circuit is constructed using an operational amplifier. The operational amplifier 14 has a configuration surrounded by a broken line. The detailed configuration will be explained below. First, the input stage amplifier 10 amplifies an input signal, that is, a track error signal. The output of the human power stage amplifier 10 is
It is an input to the output stage amplifier 11, which is a non-inverting amplifier with a gain of l, and its output becomes the output of the slew rate limiting circuit. 8.9 is an external resistor, and by changing the ratio between R1 and R8, the gain for the input signal can be changed. Capacitor 1 is connected to compensation terminal 13.
2 is installed. Assuming that the capacitance of the capacitor 12 is C and the current flowing through the compensation terminal is 2, the change in the output of the input stage amplifier, that is, the output V of the slew rate limiting circuit, is expressed by equation (1).

dV/d t= I/C---(1) As can be seen from equation (1), the change in output V is determined by C and summer, so the operational amplifier used is You need something that can flow a stable current to the compensation terminal when doing so. Assuming that the peak current flowing through the compensation terminal is 2, the slew rate 8 of the slew rate limiting circuit shown in FIG. 3 is expressed by equation (2).

dV/dt=S, so S=r p/c (2) FIG. 4 shows an example of a slew rate limiting circuit constructed by combining transistors. Since the collector and base of the transistor are short-circuited, the transistor functions similarly to a diode. Therefore T
If the voltage drop of r is 0°7V, the current 2 flowing through the resistor 15 of R1 is expressed by equation (3).

I, = (Vyu-0,7)/R, (3) Tr and Tr are current mirror circuits, and since the base voltages are the same, both collectors have the same thickness like mirrors...° The structure is such that it draws a large amount of current. Therefore, the base current I flows from the TrsT emitter to the base.

is equal to ■1. Furthermore, when the current amplification factor of Tr is h□, the collector current ♦ flowing from the emitter to the collector of Tr is expressed by equation (4).

1 , = h□I , = h□■, ...... (4)
Tr, . . . , Tra constitute a differential amplifier between a reference signal and an input signal, and R, . . . R1 are gain variable resistors.

The slew rate is determined by equation (4) (thus, for a given current value, and as h increases, the slew rate also increases. From equations (3) and (4), the slew rate here is , i anti-RI will be tT limited.

[Effects of the Invention] As described above, the present invention provides a track crossing (in words,
A slew rate limiting circuit is used to obtain a signal that is not affected by noise such as pre-pits or scratches on the optical disc.If a noise-free LX track cross signal is obtained, it will be possible to detect the speed of the optical spot. Since the target speed generation, target 1-rack calculation, etc. are accurate, the movement control between trucks can also be performed accurately.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an inter-trunk movement control circuit according to the present invention. FIGS. 2(a) to 2(c) are waveform diagrams showing signals before and after passing through the slew rate limiting circuit and signals whose waveforms have been shaped in the inter-track movement control circuit of the present invention. FIG. 3 is a circuit diagram in which the slew rate limiting circuit of the present invention is constructed using an operational amplifier. FIG. 4 is a circuit diagram in which the slew rate limiting circuit of the present invention is constructed using transistors. FIG. 5 is a waveform diagram showing how a track error signal is waveform-shaped in a conventional inter-track movement control circuit and how an ideal track cross signal that is not affected by noise is waveform-shaped. 1... Optical head 2... Slew rate limiting circuit 3... Target speed generation means 4... Speed detection means 5... Speed error detection means 6... Drive amplifier 7... Drive motor 8 .9.15-19...Resistor 10...Input stage amplifier 11...Output stage amplifier 12...Capacitor 13...Compensation terminal 14...Operation amplifier 20-27...Transistor or more Applicant Seifu Ebson Co., Ltd. Agent Patent attorney Kizobe Suzuki and 1 other person

Claims (3)

[Claims] (1) Inter-track movement control when a light spot for recording and reproducing information in an optical disk device is moved from one track to another for purposes such as information retrieval or initialization of the light spot position. A track crossing signal processing method, characterized in that a slew rate limiting circuit is provided in an inter-track movement control circuit. (2) The track crossing signal processing method according to item 1, characterized in that a track error signal is used as the track crossing signal. (3) The track crossing signal according to item 1, wherein the output of one of the detectors in the optical head or the sum signal of the signal outputs of a plurality of detectors is used as the track crossing signal. Processing method.