JPH0536099A - Information recording and reproducing device - Google Patents

Abstract

PURPOSE:To attain the easy detection of a focus deviation by using the peak value of a tracking error signal. CONSTITUTION:When the seek operation of an optical head is indicated, tracking error signal Te is inputted from a tracking error detector 3 through an I/O control part 7 to the DSP 8 of a digital signal processing part 6. The sampling of the signal Te is operated in a prescribed cycle by the DSP 8. Then, the peak value of the Te signal is detected. The DSP 8 calculates the control amounts of a driver 10 for a linear motor 14 by using a present speed and a preliminarily searched target speed. When the focus deviation is generated during the seek operation of the optical head, the Te signal is turned to the abnormal one, and an amplitude level is attenuated. Then, the generation of the focus deviation is judged, and the seek operation is stopped. When the focus control is returned back to the normal one, the seek operation is restarted. Thus, the focus deviation can be easily detected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information recording / reproducing apparatus for recording / reproducing information on / from an information recording medium such as a magneto-optical disk, and more particularly to a detecting apparatus for detecting out-of-focus during seek of a head. is there.

[0002]

2. Description of the Related Art Conventionally, as a method for stably moving an information recording or reproducing head to a target position, a speed control method is generally used in which the speed of the head is sequentially monitored and moved according to a predetermined operation schedule. However, if external vibration or the like occurs while the head is moving to the target track, the operation of the control circuit (focus control circuit) of the optical system may become unstable. Therefore, if the vibration is large, the focus control may be lost, and in such a case, there is a problem that a tracking error signal cannot be obtained, stable speed control cannot be performed, and a target track cannot be detected.
As a solution to this, for example, as shown in Japanese Patent Publication No. 34089/1990, an out-of-focus control is detected,
A method is known in which, when focus control is lost, head movement control is stopped and temporarily stopped, and then movement control to a target track is started again.

[0003]

However, the above-mentioned conventional method for detecting defocusing requires a large number of additional circuits such as a focus lock detection circuit, which makes the circuit configuration of the apparatus complicated and large-scale. There was a problem.

The present invention has been made to solve the above problems, and an object thereof is to provide an information recording / reproducing apparatus capable of easily detecting an out-of-focus state without requiring any complicated detection circuit. To provide.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to calculate a target speed of an information recording or reproducing head according to a residual distance to a target position, detect the speed of the head, and set a predetermined speed. In an information recording / reproducing apparatus which seeks to a target position while causing the head to follow the target speed by sequentially controlling the head driving means based on the detected speed and the target speed in a cycle, a tracking error during seek of the head Means for detecting the peak value of the signal,
A means for comparing the obtained peak value with a preset predetermined value is provided, and as a result of the comparison by the comparing means, when the detected value of the detecting means is smaller than the predetermined value, the seek operation of the head is performed. This is achieved by an information recording / reproducing apparatus characterized by being temporarily stopped.

[0006]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of the information recording / reproducing apparatus of the present invention. Note that FIG. 1 shows an optical disk device as an example. In FIG.
Reference numeral 1 denotes an optical disk which is an information recording medium, and is rotated at a constant speed by driving a drive system (not shown). Reference numeral 2 denotes an optical system for optically recording information on the optical disc 1 or reproducing recorded information on the optical disc 1.
The optical system 2 is a semiconductor laser that is a light source for recording and reproduction, various optical parts that perform predetermined optical processing on the laser light flux,
It is composed of a sensor or the like for detecting the reflected light from the optical disk. Reference numeral 12 is a tracking actuator that moves a focusing objective lens (not shown) provided in the optical system 2 in the tracking direction, and 13 is a focus actuator that moves the objective lens in the focusing direction. The optical system 2 and these two actuators are incorporated in an optical head so that they can be moved in the radial direction of the optical disc 1. Reference numeral 14 is a linear motor for moving the optical head in the radial direction of the optical disk 1, and 10 is a driver for the linear motor 14.

Reference numeral 3 is a tracking error detector that detects a tracking error signal based on the output of a sensor in the optical system 2, and reference numeral 4 is a focus error detector that also detects a focus error signal based on the sensor output. The error signal detected by each error detector is A /
After being converted into a digital signal by the D converter 5, the digital signal is output to the digital signal processing unit 6. The digital signal processing unit 6 forms the main control unit of the optical disk device of this embodiment, and the speed control of the optical head and the detection of out-of-focus are performed by the digital signal processing unit 6. The speed control of the optical head and out-of-focus detection will be described later in detail. Also,
The digital signal processing unit 6 is an I / O that controls the input / output of signals.
The control unit 7 is composed of a DSP (digital signal processor) 8 that executes arithmetic processing necessary for speed control and out-of-focus detection according to a predetermined control program, and a memory 9 that stores various data. The command values of the tracking actuator 12, the focus actuator 13, and the linear motor 14 that have been arithmetically processed by the DSP 8 are sent to the D / A converters 11 via the I / O control unit 7, where they are converted into analog signals. , To each drive.

Next, the operation of this embodiment will be described. 2 is a flow chart showing the flow of processing of the digital signal processing unit during seek operation of the optical head, FIG. 3 is an explanatory diagram showing target speed and actual speed during seek operation of the optical head,
FIG. 4 is a time chart showing the tracking error signal during the seek operation. Hereinafter, FIG. 2, FIG. 3 and FIG.
The operation will be described with reference to. First, in FIG. 2, when the seek operation of the optical head is instructed, the digital signal processing unit 6
The DSP 8 has an I / O from the tracking error detector 3.
The tracking error signal Te is input via the control unit 7 (S1). This tracking error signal is
In 8, sampling is performed at a predetermined cycle. In FIG. 3, the starting point of the seek operation is shown as P _s . Then
The DSP 8 detects the peak value of the tracking error signal (S2). The peak value of the tracking error signal is obtained as follows. First, the DSP 8 calculates a difference ΔS _n between the input tracking error signal S _n and the tracking error signal S _n-1 at the time of the previous sampling by the following formula.

ΔS _n = S _n −S _n-1 (1) Next, the DSP 8 compares the difference value ΔS _n-1 obtained in the same manner one sampling before and the ΔS _n obtained this time. To multiply. Note that ΔS _n-1 is the DSP8 at the time of the previous sampling.
Is calculated by the following equation and stored in the memory 9.

ΔS _n-1 = S _n-1 -S _n-2 (2) where S _n-1 is the previous sampling value and S _n-2 is the previous sampling value. Then, the DSP 8 determines that it is the peak point of the tracking error signal when the multiplication result of ΔS _n and ΔS _n-1 is negative as follows (S3).

0> ΔS _n × ΔS _n-1 (3) When the peak value of the tracking error signal is detected in this way, the DSP 8 compares the peak value T _emax with a predetermined value T _th . (S4). Then, if the peak value of the tracking error signal is smaller than the predetermined value, it is determined that defocusing has occurred, which will be described later in detail. Therefore, here, the speed control operation of the optical head will be described first assuming that the peak value is larger than the predetermined value and is normal. First, the count value N of the track indicating the moving distance of the optical head is read from the counter in the DSP 8 (S5). Next, based on this, the target distance _Vref is calculated by calculating the residual distance to the target position (S6). The target speed V _ref can be obtained by the following equation.

V _ref = [2 × α (S−λ × N)] ^1/2 (4) where S is the moving distance to the target, and in FIG. 3, P _e −P _s
Is. Further, λ indicates a track pitch, and α indicates deceleration acceleration. The track count number N can be obtained by counting the period of the tracking error signal shown in FIG. One cycle of tracking error signal is 1
Corresponds to the book track.

When the calculation of the target speed is completed, the DSP 8 detects the speed of the optical head (S7). In detecting the speed, first, as shown in FIG.
_int is obtained by measuring the time of one cycle of the tracking error signal. Next, using the obtained time T _int , the current speed V _t of the optical head is calculated by the following equation. The time for one track corresponds to the time for the optical head to cross one track.

V _t = λ / T _int (5) Next, the DSP 8 uses the present speed and the target speed obtained previously to obtain the control amount A _ct to be given to the driver 10 of the linear motor 14. Calculate (S8). The controlled _variable A _ct is obtained by the following equation.

A _ct = K (V _ref −V _t ) ... (6) where K is a gain constant of the speed control system. The obtained control amount is sent to the D / A converter 11 via the I / O control unit 7, where it is converted into an analog signal, and then the driver 1
Sent to 0. The driver 10 drives the linear motor 14 in accordance with the sent control amount, whereby the speed of the optical head is controlled so as to follow the target speed. In this way, one control operation ends, and the process returns to S1 again to repeat the same processing as described above. That is, the control amount to the driver 10 is calculated based on the current speed obtained from the tracking error signal and the target speed at that time for every constant period, and the speed of the optical head is sequentially controlled. As a result, the optical head moves toward the target position while substantially following the target speed as shown in FIG.

Here, it is assumed that defocus occurs due to some cause such as vibration in the portion A of FIG. 3 during seek of the optical head. When the defocus occurs in this way, the tracking error signal becomes abnormal as shown in FIG. 4, and the amplitude level is attenuated as compared with the normal signal. It should be noted that S _n , S _{n + 1,} and S shown by black circles in FIG.
_{n + 2} ... Represent sampling points, and the tracking error signal is sampled at a constant cycle as described above. In S4, the peak value T _emax of the tracking error signal detected as described above is compared with the predetermined value T _th . However, if defocus occurs, the tracking error signal becomes abnormal as shown by B in FIG. And the level of the peak decreases, and T _emax becomes smaller than T _th . As shown in FIG. 4, the predetermined value T _th is set to a value slightly lower than the peak level of the tracking error signal in the normal state. Therefore, when T _emax becomes lower than T _{th in} S4, the DSP 8 determines that out-of-focus occurs because it is not the original tracking error signal, and suspends the seek operation of the optical head (S9). After that, when the focus control returns to normal, the seek operation of the optical head is restarted (S10), and the optical head moves toward the target position again.

In the above embodiment, an example in which the current speed of the optical head is detected is calculated from the track pitch and the transit time of the optical head between the tracks, but the present invention is not limited to this. It goes without saying that there is a method. Further, in the embodiment, the optical recording apparatus in which the tracking error signal is discretely obtained is taken as an example, but it is of course applicable to an apparatus in which the tracking error signal is continuously obtained.

[0018]

As described above, according to the present invention, the defocusing is detected by the peak value of the tracking error signal. Therefore, it is easy to use a special detection circuit dedicated to it, unlike the conventional case. And it is possible to effectively detect the defocus. Therefore, there is an effect that out-of-focus can be easily detected without making the circuit configuration of the device complicated and large.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of an information recording / reproducing apparatus of the present invention.

FIG. 2 is a flowchart showing the operation of the embodiment of FIG.

FIG. 3 is an explanatory diagram showing a target speed of the optical head in the speed control of the embodiment of FIG. 1 and an actual speed following the target speed.

FIG. 4 is a waveform diagram showing how the tracking error signal changes when defocus occurs during seek of the optical head.

[Explanation of symbols]

1 optical disc 2 Optical system 3 Tracking error detector 6 Digital signal processor 8 DSP 9 memory 10 drivers 14 Linear motor

Claims (3)

[Claims] 1. A target speed of an information recording or reproducing head is calculated according to a residual distance to a target position, the speed of the head is detected, and the head speed is sequentially detected at a predetermined cycle based on the detected speed and the target speed. In the information recording / reproducing apparatus configured to seek to a target position while causing the head to follow a target speed by controlling the head driving means, means for detecting a peak value of a tracking error signal during seek of the head, A means for comparing the obtained peak value with a preset predetermined value is provided, and as a result of the comparison by the comparing means, when the detected value of the detecting means is smaller than the predetermined value, the seek operation of the head is performed. An information recording / reproducing apparatus characterized by being temporarily stopped. 2. After suspending the seek operation of the head,
The information recording / reproducing apparatus according to claim 1, wherein the seek operation is restarted again. 3. The information recording / reproducing apparatus according to claim 1, wherein the predetermined value is set to a value slightly lower than a peak value of a tracking error signal in a normal state.