JPH07334918A - Recorded area detection circuit - Google Patents

Abstract

PURPOSE:To realize various types of fast signal switching control to the recorded area and unrecorded area. CONSTITUTION:RF signals of reproduced signals are inputted to a comparator 56 via a high-pass filter 55 and binarized. A pulse width detection circuit 57 discriminates whether the pulse interval of the binarized signals is longer than the longest pulse width or not to output a detection signal showing that the input signals come from the recorded area or not.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording area detection circuit for detecting whether or not a data recording area is recorded when irradiating a light beam on a write-once type optical disk to record data. .

[0002]

2. Description of the Related Art Conventionally, there is an optical disk device capable of recording information by irradiating a disk-shaped recording medium with a light beam to sequentially form pits. A CD that conforms to the Compact Disc (CD) standard
There is an R (CD-Recordable) drive device.

The optical disk used in this CD-R drive device is irradiated with a strong light beam to change the optical properties of the recording layer in the pre-groove, which is a guide groove formed in advance, so that information is recorded only once. It is a so-called write-once type optical disc capable of performing the above writing operation.

Specifically, in the CD-R drive device,
8-14 modulation on recorded data, that is, EFM (Eight to Fou)
rteen Modulation), a modulated signal S1 is generated as shown in FIG. 6A in which the occurrence probabilities of logic 0 and 1 are equal. Laser light is emitted from the laser diode on the basis of the modulation signal S1, and a light beam is intermittently applied to the optical disc in accordance with the logic level of the modulation signal S1. As a result, a region having a low reflectance, that is, a pit is formed in the recording layer in the pre-groove. The laser light emitted from the laser diode at this time is a high-output recording laser light.

The modulated signal S1 is generated so that the H level and the L level are continuous in the range of the period 3T to 11T with reference to the predetermined reference period T, so that FIG.
As shown in, the pits P are sequentially formed and desired data is recorded. The region where the pits P are not formed and which has a high reflectance is called a land.

At the time of data reproduction, a low-output light beam for reproduction is applied to the optical disk. The reflected light from the optical disc irradiated with the light beam is received by the photodetector. According to the amount of the reflected light, a reproduction signal whose signal level changes as shown in FIG. 6C, that is, an RF signal is obtained. Then, the reproduction data D1 shown in (D) of FIG. 6 is detected by detecting the signal level of the RF signal with reference to the predetermined slice level SL.

At this time, since the recording signal S1 is generated by the EFM and the recording signals have the same probability of occurrence of logic 0 and 1, the reproduced data D1 also has logic 0 and 1.
The slice level SL is selected so that the derivation probabilities of are equal. This reduces the bit error rate.

On the other hand, since pits are formed during data recording, even if a laser beam with a constant emission power is emitted from the laser diode, the size of the pit will vary depending on the ambient temperature and the wavelength of the laser beam. Changes.

Therefore, as the asymmetry value of the recording signal written on the optical disc, a value that minimizes the data error rate when reproducing data from the RF signal when the recording signal is read is selected. . This asymmetry value is called the optimum asymmetry value. The optimum asymmetry value is determined by the characteristics of the optical system of the CD-R drive device, the emission time of laser light, that is, the writing strategy, the characteristics of the optical disc, and the like. Further, the laser light output power for recording the data capable of reproducing the RF signal having the optimum asymmetry value is called the optimum laser light output power.

Here, the asymmetry value represents a time average ratio of pits and lands. Specifically, the RF signal reproduced from the optical disc has the waveform shown in FIG. 7, and the asymmetry value is the slice level SL at which the occurrence probabilities of logic 0 and 1 in the reproduction data D1 shown in FIG. It is represented by the relationship between the level and the bottom level. That is, the asymmetry value Asy is the peak level X ₁ and the bottom level X ₄ of the pulse width 11T detected by holding the peak value and the bottom value of the sampling value after sampling the RF signal, and the pulse width It can be expressed by the following expression (1) using the peak level X ₂ and the bottom level X _{3 of} 3T.

[0011]

[Equation 1]

Here, in the above optical disk device,
A track additional recording operation may be performed. The track additional recording operation is an operation of first performing a data recording operation on a track halfway on the optical disk, and then performing a data recording operation continuously from the position next to the final position of the data recorded area.

In this track additional recording operation, after the data is recorded up to the middle of the optical disc, there is a recorded region in which the data is recorded and an unrecorded region in which the data is not recorded, and the next data is recorded. In order to perform the operation, it is necessary to detect the final position of the recording area.

FIG. 8 shows a schematic configuration of a circuit for detecting a recording area on the optical disk. First, the reproduced R
The F signal is input to the peak hold circuit 51 and the bottom hold circuit 52. The peak hold circuit 51 peak-holds the signal level of the RF signal, detects the signal level I _TOP from the 0 level to the peak level of the pulse width 11T, and the bottom hold circuit 52 bottom-holds the signal level of the RF signal. Pulse width 11T from 0 level
The signal level I _BTM up to the bottom level is detected.

The signal level I _TOP from the peak hold circuit 51 and the signal level I _BTM from the bottom hold circuit 52 are sent to a level comparator 53. As shown in FIG. 9, the RF signal reproduced from the unrecorded area, a so-called mirror signal, has a signal level equal to the signal level I _TOP, and the RF signal reproduced from the recorded area has a signal level I _{TO.
Since the} signal level changes from _P to the signal level I _BTM , the level comparator 53 detects the recording signal from the reproduction signal in the recording area by detecting this signal level width and outputs this detection signal.

[0016]

By the way, when the reproduced signal of the signal recorded in the recording area is detected by the above-mentioned circuit configuration, the variation in the signal level of the RF signal cannot be absorbed.

Further, since the signal level of the RF signal is detected based on the hold time constants respectively set in the peak hold circuit and the bottom hold circuit, the detection speed is slow and there is a problem in responsiveness.

In view of the above situation, the present invention provides a recording area detecting circuit capable of detecting the recording area of data on the optical disk at high speed.

[0019]

A recording area detection circuit according to the present invention comprises a binarizing means for binarizing an RF signal of a reproduced signal, and a pulse of the binarized signal from the binarizing means. The problem described above is solved by having a detection unit that detects the recording area on the optical disc based on the interval.

Here, it is characterized in that the pulse interval is the longest pulse width.

Further, sampling means for sampling the RF signal of the reproduced signal by a predetermined pulse signal, binarization means for binarizing the output signal from the sampling means, and binarization means for binarizing the output signal. And a detection means for detecting an overwrite area on the optical disc based on the pulse interval of the binarized signal.

Here, gate means or switch means may be used as the sampling means.

[0023]

In the present invention, the RF signal is reproduced from the recording area by binarizing the RF signal and determining whether the pulse interval of the binarized signal is longer than the longest pulse width. It is detected whether or not it is reproduced from the unrecorded area.

Further, the RF signal is sampled with a predetermined pulse signal, binarized, and it is judged whether or not the pulse interval of the binarized signal is longer than the longest pulse width. It is detected whether the data has been reproduced from the recording medium or the unrecorded area.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic configuration of a recording area detection circuit according to the present invention.

As shown in FIG. 2A, the signal reproduced from the recording area in which the data is recorded has the signal level changed, but the RF signal input to the recording area detection circuit is unrecorded. The signal reproduced from the area has a substantially constant signal level. The RF signal a becomes an output signal b having a constant signal level centered on the 0 level by passing through the high pass filter (HPF) 55. This HPF
The output signal b from 55 is shown in b of FIG.

The output signal b from the HPF 55 is input to the comparator 56. In this comparator 56,
The output signal b is compared with a predetermined slice level. As a result, as shown in FIG. 2C, during reproduction at the standard speed, signals of '0' and '1' corresponding to the signal of the pulse width of the period 3T to 11T are produced in the recording area, and the pulse width is produced in the unrecorded area. Is longer than the period 11T or there is no pulse, the output signal c which is always "1" is obtained. This output signal c is input to the pulse width detection circuit 57.

From the pulse width detection circuit 57, when the pulse width of the output signal c is shorter than the period 11T, it becomes "1" indicating that it is a reproduction signal from the recording area, and the pulse width of the output signal c is the period. If it is longer than 11T or is not there, a detection signal of "0" indicating that it is a reproduction signal from an unrecorded area is output. This detection signal is shown in FIG. 2d. At this time, in the pulse width detection circuit 57, if whether or not the input output signal c is a signal in the recording area is detected in, for example, 10 μs, the boundary between the recording area and the unrecorded area is detected with a delay of 10 μs. The signal is output. That is, the pulse width detection circuit 57 can determine whether or not it is the recording area only by the delay of 10 μs.

As described above, in the conventional recording area detection circuit, the recorded area and the unrecorded area are detected based on the voltage axis of the RF signal of the reproduction signal, that is, the signal level.
In the recording area detection circuit of the embodiment, it is possible to detect the recording area and the unrecorded area at high speed and accurately by determining whether or not the recording area is based on the time axis of the RF signal, that is, the pulse width. You can

Further, in the case of the in-track additional write operation for performing the additional write operation of the data in the track, when the data is additionally written in the track, the start of the data to be written next to the last portion of the previously written data is started. There is an overwrite area where the portions are overlapped and recorded. Therefore, it is necessary to detect this overwrite area during the write-once operation in the track. The detection of the overwrite area can be performed by detecting the signal level of the reading section during the data additional recording operation. FIG. 3 shows a schematic configuration of an overwrite area detection circuit that detects whether or not this is an overwrite area.

As shown in FIG. 4A, the RF signal input to the overwrite area detection circuit is such that the signal levels of the read sections RD ₁ , RD ₂ and RD ₃ in the overwrite area are the EFM recorded previously. Since the signal leaks, the signal level becomes lower than a certain level, and the signal levels of the read sections RD ₄ , RD ₅ , and RD ₆ in the normal write area, which is a normal recording area, are the same as the land level before data recording. It will be. First, this RF signal is input to the sample hold (S / H) circuit 54. A sample pulse signal for detecting a constant signal level is input from the signal input terminal 58 to the sample hold circuit 54. Therefore, in this sample hold circuit 54, the output signal b shown in b of FIG. 4 is obtained by sample-holding the RF signal using the sample pulse signal.

This output signal b is a high pass filter (HP
An output signal having a constant signal level is output via F) 55 and is input to the comparator 56. In the comparator 56, the HPF 55 is set at a predetermined slice level.
The output signal from is compared. As a result, FIG.
As shown in c of, the signal below a certain signal level is
The output signal c which is 0'is output. This output signal c is input to the pulse width detection circuit 57.

From the pulse width detection circuit 57, when the pulse width of the output signal c is shorter than the period 11T, it indicates that it is a reproduction signal from the overwrite area.
Therefore, when the pulse width of the output signal c is longer than the period 11T or is not present, a detection signal of "0" indicating that it is a reproduction signal from the normal write area is output. This detection signal is shown in FIG. 4d. At this time, if the pulse width detection circuit 57 detects whether it is a signal in the overwrite area in 10 μs, for example, the detection signal is output at a delay of 10 μs at the boundary between the overwrite area and the normal write area. In other words, the pulse width detection circuit 57 can determine whether or not it is the overwrite area only by the delay of 10 μs.

Further, the overwrite area detection circuit shown in FIG. 3 is obtained by adding a sample hold circuit 54 to the recording area detection circuit shown in FIG. 1 and can be easily shared with the recording area detection circuit. it can.

Next, FIG. 5 shows a schematic structure of an optical disk device provided with the above-mentioned recording area detecting circuit.

At the time of data recording, data such as voice sent from an external host computer or the like is input from the signal input terminal 43 via the interface circuit. This data is sent to the data encoder 28, encoded, and converted into a recording signal. This recording signal is sent to the laser modulation circuit 29 via the timing generation circuit 48. In the laser modulation circuit 29, the recording signal is converted into a laser light output power, laser light is output to irradiate the optical disk 7 and the return light from the optical disk 7 is input to a so-called optical pickup. Sent. A recording timing signal of a recording signal is sent from the timing generation circuit 48 to the matrix circuit 11.

Specifically, the laser light output power is emitted from the laser diode 1. Laser diode 1
The laser light emitted from is collimated by the collimation lens 2, is guided to the objective lens 6 via the grating 3 and the beam splitter 4, and is focused on the optical disk 7 by the objective lens 6. Thus, at the time of recording data, desired data is recorded by controlling the intensity of the light beam irradiated onto the optical disc 7 according to "1" or "0" of the data.

A part of the light beam incident on the beam splitter 4 is separated by the beam splitter 4 and incident on the laser monitor 5. A part of the light beam incident on the laser monitor 5 is sent to the monitor head amplifier 30, converted into a voltage, and further sent to the automatic power control (APC) circuit 31. This APC circuit 3
1 uses the signal from the monitor head amplifier 30 to control the emission power of the laser light emitted from the laser diode 1 to be constant without being affected by external factors such as temperature. The control signal from the APC circuit 31 is sent to the laser modulation circuit 29. In the laser modulation circuit 29, the emission power of the laser light emitted from the laser diode 1 is kept constant by using the control signal from the APC circuit 31.

The reflected light of the light beam radiated on the optical disk 7 passes through the objective lens 6 and the beam splitter 4
Is incident on. The beam splitter 4 guides the incident reflected light to the multi-lens 8. The multi-lens 8 is composed of a cylindrical lens, a condenser lens, and the like, and collects incident reflected light on the photodetector 9.

The output from the photodetector 9 is converted into a voltage by the head amplifier 10 and output to the matrix circuit 11. In this matrix circuit 11,
The tracking error signal TE, the focus error signal FE, and the push-pull signal PP are generated by adding and subtracting the output from the head amplifier 10.

The tracking error signal TE and the focus error signal FE are sent to the phase compensation circuits 12 and 13, respectively. The phase compensation circuit 12 adjusts the signal level of the tracking error signal to 0 level, and the adjusted signal is sent to the drive circuit 14. The drive circuit 14 includes the phase compensation circuit 12
By operating the tracking actuator 16 using the signal from, the movement of the objective lens 6 in the radial direction of the optical disk 7 is more accurately controlled to a mechanical neutral position which is a preset tracking position. Further, the phase compensation circuit 13 adjusts the signal level of the focus error signal to 0 level, and the adjusted signal is sent to the drive circuit 15. The drive circuit 15 operates the focus actuator 17 using the signal from the phase compensation circuit 13, so that the objective lens 6 causes the optical disk 7 to focus the light beam at a more accurate position. Movement control in the vertical direction.

The low frequency component of the tracking error signal TE is sent to the thread phase compensation circuit 32, adjusted so that the signal level becomes 0 level, and sent to the drive circuit 33. In the drive circuit 33, the position of the sled mechanism 44 is controlled to move by driving the sled motor 34 using the signal from the sled phase compensation circuit 32. Thereby, the objective lens 6
Is more precisely controlled to move to the mechanical neutral position.

Further, the push-pull signal PP output from the matrix circuit 11 is the wobble detection circuit 2
It is output to 1. The wobble detection circuit 21 detects a wobble and outputs it to the ATIP demodulator 22. The ATIP demodulator 22 detects ATIP and ATIP read clock signals from the detected wobbles, and sends the ATIP and ATIP read clock signals to the ATIP decoder 23. This AT
In the IP decoder 23, the address information is reproduced using the ATIP and ATIP read clock signals. The reproduced address information is read by the CPU 24.

The wobble detected by the wobble detection circuit 21 and the AT detected by the ATIP demodulator 22.
The IP read clock signal is also output to the spindle servo circuit 25. The spindle servo circuit 25 drives the spindle motor 27 via the motor driver 26 using the wobble and the ATIP read clock signal sent as described above. At this time, the spindle servo circuit 25 controls the wobble detected by the wobble detection circuit 21 to have a constant frequency of 22.05 kHz, or the ATIP modulator 22.
ATIP read clock signal output from
The control is performed so that the constant frequency is 5 kHz.

Next, at the time of data reproduction, the laser light for reproduction is emitted from the laser diode 1 and the optical disk 7 is reproduced.
Irradiated on. The reflected light of the light beam applied to the optical disk 7 is received by the photodetector 9, and the amount of the received light is sent to the matrix circuit 11 via the head amplifier 10. The matrix circuit 11 generates a tracking error signal TE and a focus error signal FE. The tracking error signal TE and the focus error signal FE are used to control the movement of the tracking actuator 16 and the focus actuator 17, as described above.

The return light of the light beam applied to the information recording surface is also received by the photodetector 9. The received light amount is sent to the matrix circuit 11 via the head amplifier 10 and is output from the matrix circuit 11 as an RF signal which is an information component of a recording signal. This RF signal is sent to the binarization circuit 18, binarized, and sent to the PLL circuit 19. This PLL
In the circuit 19, a clock signal is reproduced from the sent binary signal, and this clock signal is sent to the decoder circuit 20 together with the binary signal. In the decoder circuit 20, the binarized signal is decoded using the clock signal. As a result, the data signal and the subcode are reproduced. The reproduced data signal is output to the output terminal 42.
Is output from. Further, the sub code is sent to the CPU 24. The CPU 24 controls the data using the sent subcode.

The RF signal output from the matrix circuit 11 is also sent to the RF detection circuit 45. This RF
The recording area detection circuit 49 in the detection circuit 45 detects whether or not the transmitted RF signal is a signal reproduced from the recording area, and outputs this detection signal to the CPU 24. The recording area detection circuit 49 can also detect whether or not the transmitted RF signal is a signal reproduced from the overwrite area. The CPU 24 sends laser light output power control information to the APC circuit 31 based on the sent detection signal.

The clock signal reproduced by the PLL circuit 19 is input to the spindle servo circuit 25 as a read clock of the RF signal and compared with the reference clock signal. This compared output is sent to the motor driver 26 as a rotation error signal during data reproduction. The motor driver 26 controls the drive of the spindle motor 27 using the rotation error signal.

Instead of the sample hold circuit in the overwrite area detection circuit, a gate circuit or a switch circuit for extracting a signal only from the read section during the track-internal write operation may be used.

[0050]

As is apparent from the above description, the recording area detecting circuit according to the present invention comprises a binarizing means for binarizing the RF signal of the reproduced signal, and the binarizing means. Two
Since the recording area can be detected at high speed by having a detecting means for detecting the recording area on the optical disc based on the pulse interval of the binarized signal, switching of the focus servo gain for the recording area and the unrecorded area, Tracking servo gain switching, wobble signal generation circuit switching, spindle servo switching, and R
Various kinds of switching control such as switching of the F signal can be performed at high speed. Further, the detection of the recording area is less likely to be affected by the variation in the signal level of the RF signal. Furthermore, since it is sufficient to perform digital processing in the circuit after the RF signal is binarized, it is advantageous in data reproducibility. In addition, the circuit can be easily digitized and mass productivity is excellent.

Here, by setting the above-mentioned pulse interval to be the longest pulse width, it is possible to accurately detect the recording area.

Further, a sampling means for sampling the RF signal of the reproduced signal by a predetermined pulse signal, a binarizing means for binarizing the output signal from the sampling means, and a binarizing means from the binarizing means. Since the recording area can be detected at high speed by having the detecting means for detecting the overwrite area on the optical disc based on the pulse interval of the binarized signal, the switching of the focus servo gain for the recording area and the unrecorded area. Various switching controls such as tracking servo gain switching, wobble signal generation circuit switching, spindle servo switching, RF signal switching, and recording laser light output power control can be performed at high speed. Further, the detection of the recording area is less likely to be affected by the variation in the signal level of the RF signal. Furthermore, since it is sufficient to perform digital processing in the circuit after the RF signal is binarized, it is advantageous in data reproducibility. In addition, the circuit can be easily digitized and mass productivity is excellent.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of a recording area detection circuit according to the present invention.

FIG. 2 is a diagram showing each signal waveform in the recording area detection circuit shown in FIG.

FIG. 3 is a diagram showing a schematic configuration of an overwrite area detection circuit according to the present invention.

FIG. 4 is a diagram showing each signal waveform in the overwrite area detection circuit shown in FIG.

FIG. 5 is a diagram showing a schematic configuration of an optical disc device using a recording area detection circuit according to the present invention.

FIG. 6 is a diagram showing signal waveforms at the time of recording and reproducing data.

FIG. 7 is a diagram showing asymmetry of an RF signal.

FIG. 8 is a diagram showing a schematic configuration of a conventional recording area detection circuit.

FIG. 9 is a diagram showing signal waveforms of a recording area and an unrecorded area detected by a conventional recording area detection circuit.

[Explanation of symbols]

 7 optical disk 45 RF detection circuit 49 recording area detection circuit 54 sample hold circuit 55 high-pass filter 56 comparator 57 pulse width detection circuit

Claims (3)

[Claims] 1. When data is recorded or reproduced by irradiating a light beam on a write-once type optical disk, the data is reproduced in a recording area detection circuit for detecting whether or not the data is a recorded area. And a detection means for detecting a recording area on the optical disc based on the pulse interval of the binarized signal from the binarization means. Recording area detection circuit. 2. The recording area detection circuit according to claim 1, wherein the pulse interval is the longest pulse width. 3. A recording area detecting circuit for detecting whether or not the data is a recording area when the data is recorded or reproduced by irradiating a write-once optical disc with a light beam. The sampling means for sampling the RF signal of the signal with a predetermined pulse signal, the binarizing means for binarizing the output signal from the sampling means, and the pulse interval of the binarized signal from the binarizing means. A recording area detecting circuit, which comprises: a detecting means for detecting an overwrite area on the optical disc based on the recording area detecting circuit.