JPH07129972A - On-track detection circuit for optical desk device - Google Patents

Abstract

PURPOSE:To provide an on-track detection circuit for an optical disk device capable of detecting on-track and off-track even in an unrecorded part and stably detecting the on-track even at the time of track jump so as to extend over a recording part and the unrecorded part. CONSTITUTION:A prescribed lower band frequency component is eliminated from a signal corresponding to a return beam from an optical disk forming a guide groove by using a low-pass filter 3, and the values obtained by peak hold and bottom hold means 5, 6 are added. The signal obtained by multiplying the addition result by a prescribed coefficient, e.g. 1/2 is made a comparison reference signal, and is compared with the output signal of the low-pass filter 3, and the comparison result is outputted as an on-track detection signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an on-track detecting circuit for an optical disk device, and more particularly to an on-track detecting circuit for an optical disk device having a guide groove.

[0002]

2. Description of the Related Art FIG. 6 shows a configuration diagram for performing an on-track detection operation of an optical disk device in which a guide groove formed on an optical disk is irradiated with laser light from an optical pickup and an on-track is detected based on return light. Has been done. Also,
A signal waveform timing chart of each part of FIG. 6 is shown in FIG. In FIG. 7, the servo-off period is a period in which tracking control is not performed, the return light crosses between the on-track position and the off-track position, and no pit is formed at the on-track position in the recorded area. Since it is the return light of the mirror part, it is close to total reflection, and a constriction occurs at the bottom of the RF signal. Since no pits are formed in the unrecorded area, only the change in reflectance due to the pregroove appears.

In FIG. 6, a main spot light receiving element 1 including light receiving elements 1a to 1d receives return light from an optical disk and outputs an electrical reproduction signal. The reproduction signal output from the main spot light receiving element 1 is converted into a voltage signal a by the IV conversion circuit 2. This voltage signal a is used for the peak envelope circuit 10 and the bottom envelope circuit 11
Then, the peak envelope signal b and the bottom envelope signal c are respectively detected and output. Attenuator 1
2 attenuates the peak envelope signal b to an appropriate level and outputs an attenuation signal d. The comparator 13
By comparing the bottom envelope signal c and the attenuation signal d,
The on-track is detected by obtaining the comparison output signal e.

[0004]

As described above, in the conventional optical disk device, the on-track is detected based on the peak envelope signal and the bottom envelope signal of the signal from the main spot light receiving element 1.

On the other hand, since the guide groove is formed in the unrecorded portion of the optical disk but no data is recorded,
The return light has no RF signal component, and when the optical pickup passes through the track, only a valley occurs in the reproduction signal level due to the change in the reflectance of the guide groove, as shown by the signal a in FIG. Therefore, as is clear from the comparator output signal e in FIG. 7, there is a problem that on-track detection can be performed in the recorded portion, but on-track detection cannot be performed in the unrecorded portion.

Therefore, an object of the present invention is to enable detection of on-track and off-track even in an unrecorded area, and to provide a stable on-state even during a track jump across the recorded area and the unrecorded area. An object of the present invention is to provide an on-track detection circuit of an optical disk device capable of track detection.

[0007]

In order to solve the above-mentioned problems, the on-track detection circuit of the optical disk device according to the present invention receives the return light from the optical disk having the guide groove and converts it into an electric signal. Means, a low-pass filter for removing a predetermined high-frequency component from the electric signal from the light-receiving means and outputting the signal, a peak-holding means for peak-holding and outputting the output signal from the low-pass filter, and the low-pass filter Bottom holding means for bottom-holding and outputting the output signal of, the peak holding means, an arithmetic circuit for adding the outputs of the bottom holding means, and multiplying the addition result by a predetermined coefficient to output the arithmetic circuit, and the arithmetic circuit. Receive the output signal of as a comparison reference signal,
And a comparator which compares the output signal of the low-pass filter and outputs the comparison result as an on-track detection signal.

[0008]

According to the present invention, a predetermined low frequency component is removed from the signal corresponding to the return light from the optical disk having the guide groove formed by using a low pass filter, and the peak hold value and the bottom hold value are added and added. A signal obtained by multiplying the result by a predetermined coefficient, for example, ½ is used as a comparison reference signal and compared with the output signal of the high pass filter, and the comparison result is output as an on-track detection signal.

[0009]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a configuration block diagram showing an embodiment of an on-track detection circuit of an optical disk device according to the present invention.

The received light signal of the return light from the main spot light receiving element 1 including the light receiving elements 1a to 1d similar to that shown in FIG.
It is converted into a voltage signal by the IV converter 2 and supplied to the low-pass filter 3 via C coupling. By passing through the C bond, the low frequency component is removed. Low pass filter 3
Outputs only the signal from which the high frequency components of the EFM signal have been removed. The output from the high pass filter 3 is sent to the comparator 4, the peak hold circuit 5 and the bottom hold circuit 6.

The output signal from the low-pass filter 3 is peak-held and output by the peak hold circuit 5 with a predetermined time constant, and bottom-held with a predetermined time constant by the bottom hold circuit 6. Arithmetic circuit 7
Is a sum of the output signals g and h of the peak hold circuit 5 and the bottom hold circuit 6, and the added value has a predetermined coefficient, for example, 1
Perform an operation of multiplying by / 2. Further, the arithmetic circuit 7 sends the arithmetic result as an output signal i to the comparator 4 as a comparison reference voltage.

The comparator 4 compares the output signal from the low pass filter 3 with the output signal i from the arithmetic circuit 7 and obtains the comparison result signal j as an on-track detection signal.

As described above, in this embodiment, the signal corresponding to RF is input to the low-pass filter, and the midpoint between the peak-holded voltage and the bottom-holded voltage is set as the comparison voltage of the comparator 4, thereby recording. An on-track detection signal can be obtained regardless of the unrecorded area and the unrecorded area.

FIG. 2 shows a timing chart of signal waveforms of respective portions when the low-pass filter 3 of the embodiment of FIG. 1 is a low-pass filter having an INV amplifier structure. I
The output signal a from the V conversion circuit 2 includes the signals of the servo-off area and the servo-on area of the recorded portion and the unrecorded portion, and the low-pass component by the C coupling and the high-pass component by the low-pass filter 3. The signal from which is removed is shown as signal f. From the peak hold signal g and the bottom hold signal h of this signal f, the arithmetic circuit 7 obtains an average signal i (a signal obtained by multiplying the addition signal of both signals by 1/2). The comparator 4 compares the signal f with the comparison reference signal i, and the comparison result is obtained as the on-track detection signal j.

In the above embodiments, the time constants of the peak hold circuit 5 and the bottom hold circuit 6 are required to be values that do not respond to the traverse frequency required for track jump control or the like. Further, the cutoff frequency of the low-pass filter 3 removes the EFM component,
A value that does not cause a phase delay in the frequency band required for track jump control or the like is required. (It is clear with reference to FIG. 3). Further, since the difference in reflectance between the on-track position (on the guide groove) of the unrecorded portion and the on-track position is small, the S for good on-track detection is small.
Of the circuit to the high pass filter 3 in order to improve / N
It is preferable to have a gain commensurate with the range.

Further, by supplying a signal from the IV converter 2 to the low-pass filter 3 via the C coupling, a correct on-track signal can be generated even when the unrecorded portion and the recorded portion are crossed during the jump. The cut-off frequency of the low-frequency component due to this C coupling cannot be obtained if the value is set to a too low value, so that it needs to be set to an appropriate value. FIG. 3 shows the waveform of each part in this case. Immediately after entering the unrecorded portion from the recorded portion during the track jump, the waveform of the output signal f of the low pass filter 3 is GN.
You can see that it takes time to return to the center of D. As is apparent from the waveform j during this period, the on-track signal is not obtained.

FIG. 4 is a block diagram showing the configuration of another embodiment of the on-track detecting circuit of the optical disk device according to the present invention, in which the constant voltage signal output from the constant voltage generating circuit 9 is added to the output of the arithmetic circuit 7. The addition is performed by the circuit 8 and the addition signal is output as the comparison reference signal of the comparator 4. As described above, the present embodiment is an example in which an appropriate bias is added to the output of the arithmetic circuit 7 and used as the comparison reference signal.

FIG. 5 shows a specific circuit of the on-track detection circuit of the optical disk device according to this embodiment having the above structure.

[0019]

As described above, according to the on-track detection circuit of the optical disk device according to the present invention, not only the guide groove alone enables reliable on-track detection even in the unrecorded portion of the signal, but also the recording portion. A stable track signal can be obtained even during a track jump across the unrecorded area, and the settling to the tracking servo can be significantly improved.

[Brief description of drawings]

FIG. 1 is a configuration block diagram of an embodiment of an on-track detection circuit of an optical disk device according to the present invention.

FIG. 2 is a timing chart of signal waveforms of respective parts when the low-pass filter 3 of the embodiment of FIG. 1 is a low-pass filter having an INV amplifier configuration.

FIG. 3 shows a correct on-track signal obtained from an unrecorded portion to a recorded portion during a jump or vice versa when the cutoff frequency provided on the low frequency side by C coupling is not appropriate. It is a figure for demonstrating the state which cannot be performed.

FIG. 4 is a configuration block diagram of another embodiment of the on-track detection circuit of the optical disk device according to the present invention.

FIG. 5 is a specific circuit diagram of an on-track detection circuit of the optical disc device according to the present embodiment having the above configuration.

FIG. 6 is a diagram showing a configuration for performing an on-track detection operation of a conventional optical disc device.

7 is a diagram showing a signal waveform timing chart of each part of FIG. 6;

[Explanation of symbols]

 1 main spot light receiving element 2 IV conversion circuit 3 low pass filter 4, 13 comparator 5 peak hold circuit 6 bottom hold circuit 7 arithmetic circuit 8 adder circuit 9 constant voltage generation circuit 10 peak envelope circuit 11 bottom envelope circuit 12 attenuator

Claims (1)

[Claims] 1. A light receiving means for receiving return light from an optical disk having a guide groove formed therein and converting it into an electric signal, and a low pass for removing a predetermined high frequency component from the electric signal from the light receiving means and outputting the electric signal. A filter, a peak hold means for peak-holding and outputting the output signal from the low-pass filter, a bottom-hold means for bottom-holding and outputting the output signal from the low-pass filter, the peak-holding means, and the bottom-hold Means for adding the outputs of the means, multiplying the addition result by a predetermined coefficient and outputting the result, and receiving the output signal of the operation circuit as a comparison reference signal, comparing it with the output signal of the low-pass filter, and turning on the comparison result. On-track detection of an optical disk device, comprising: a comparator for outputting as a track detection signal. Circuit.