JPS62202333A - Sector mark recording detection system - Google Patents

Abstract

PURPOSE:To detect the start point of a sector with high reliability by arranging a mark pattern element comprising a recording bit of a prescribed length and unrecorded bits having the same length shorter than the length of the recording bit (or the opposite combination) as the sector mark. CONSTITUTION:The pattern elements 201-204 of the sector mark have the same contents, in which a recording bit 301 having a length 5T and an unrecording bit 302 of a length 1T provided before and after the bit 301 respectively are arranged. Further, the distance between the pattern elements 201, 202 is selected as 1T, the distance between the elements 202, 203 is selected as 2T and the distance between the elements 203, 204 is selected as 3T and they all are recorded on a disk. In hatched lines shown in figure (e), they are the recorded bits and the unrecorded bits. A photodetect signal is obtained as shown in figure (f) at the reproduction, and the signal is AC-amplified by an amplifier 7 and sliced by a comparator 8 to obtain a pulse signal (g).

Description

[Detailed Description of the Invention] Technical Field> The present invention relates to a sector mark used in an optical disk device to detect the starting point of a sector, which is a unit of recorded information, and to generate timing signals for accurate reproduction/recording/erasing, etc. Regarding recording detection method.

<Technical Background and Problems> Conventionally, recording has been performed on a disk-shaped recording medium that has concentric or spiral recording tracks in the radial direction, and each recording track is divided into sectors, which are a plurality of recording units.
In an optical disk device that performs playback, a track format is generally configured as a collection of sectors consisting of an address section A indicating a sector number and a data section B where data is recorded, etc., as shown in Figure 2. Ru.

When recording and reproducing in units of sectors, a means to know the starting point of the sector is required in order to control the timing of recording and reproducing. The sector mark 101 is placed at the beginning of section A, and timing control is activated by detecting the starting point of the sector using this sector mark 101. Next, clock phase synchronization is performed by VFOI02 to recognize address information 103 using PLL, etc., and after recognizing address information +03, VFOI02 is activated at the timing determined by timing control during recording.
I05 and recording data 106 are recorded on the recording medium. Also, during playback, the VFO is activated at the timing determined by the above-mentioned timing control in the same way as when detecting the address section A.
After clock phase synchronization is achieved at I05, data section +06 is read.

Therefore, since the sector mark is the origin of timing control, high detection reliability is required. On the other hand, from the point of view of data utilization, it is desirable to set sector marks with as short a structure length as possible.

However, unlike magnetic disks and the like, in optical disk devices, as shown in Figure 3, not only the area where no data information is recorded, that is, the data area B when normal recording is not performed, but also the area where rotational fluctuations are absorbed, etc. The reproduction signal level is made to be minimum in areas 104 and 107, which are called gigangs and are sandwiched between the address section A and the data section B, where no recording is performed. This is because even write-once and rewritable optical discs cannot be overwritten.For this reason, for example, as shown in Figure 4, the playback signal processing system is AC-coupled through a capacitor 1 and then connected to an amplifier. When a configuration is adopted in which the result of comparison with the comparison voltage in the comparator 3 is obtained as the square wave pulse output C after being amplified by the
) to the information area (for example, 105 in FIG. 3) has a waveform as shown in FIG.
The signal waveform C-coupled and amplified by amplifier 2 is the fifth waveform.
As shown in the figure, transient level fluctuations due to AC coupling occur for a while from the starting point of the information area. In this state, when the comparator 3 obtains a square wave pulse reproduction signal C by comparing it with a predetermined comparison voltage d, the reproduction duty deviates for a while from the starting point of the information area as shown in FIG. 5C. However, the desired reproduction signal cannot be obtained at the starting point.

On the other hand, in FIG. 6, in order to improve the read margins of address section A and data section B, photodetect signal a is amplified by amplifier 4 and then sliced by comparator 5. Based on the result, slice optimization circuit 6 Although this is a method to obtain the desired reproduction duty, even with this configuration, in the vicinity of the information start point where data reaches the information area from an area where no data is recorded, the waveform shown in FIG.
The slice level e fluctuates due to the transient response of the slice optimization circuit 6, and a square wave pulse signal C similar to that of the circuit shown in FIG. 4 is obtained.

Therefore, the detection information of the start position of the reproduced signal cannot avoid the transient influence of the circuit system, and the information on the length of each recording bit cannot be obtained correctly. Therefore, sector marks are set while avoiding this unstable area. There was a need.

OBJECTS OF THE INVENTION In view of the above-mentioned problems, an object of the present invention is to detect sector marks even if there is a change in bit length due to transient responsiveness of the reproduction system or a deviation in recording conditions during the recording process. The goal is to do this correctly and to perform accurate recording/playback timing control.

<Example of the present invention> Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a block diagram showing a detection circuit according to an embodiment of the present invention, and FIG. 7 shows an example of a sector mark pattern sequence and signal waveforms at various parts in FIG.

First, assume that the sector mark pattern shown in FIG. 7d is used. In other words, the sector mark pattern elements 201, 202, 203, and 204 have the same content and are 5T.
It can be configured such that a recorded bit 301 having a length of IT and unrecorded bits 302 sandwiching it are placed before and after it with a length of IT. Furthermore, the element spacing between the pattern element 201 and the pattern element 202 is set to IT, the element spacing between the pattern element 202 and the pattern element 203 is set to 2, and the element spacing between the pattern element 203 and the pattern element 204 is set to 3T. and recorded on the task.

Then, it is recorded on the disk as shown in FIG. 7e.

The shaded areas in the figure are recorded bits, and the areas sandwiched between the recorded bits are unrecorded bits.

When reproducing the above sector pattern, the photodetect signal shown in FIG. 1 (a reproduced optical signal from a rotating disk detected by a photodetector such as a photodiode) is obtained as shown in FIG. 7f. and AC is connected by amplifier 7.
The signal is amplified and sliced by a comparator 8 to obtain a pulse signal g.

Here, as mentioned above, the sentence assumes that the reproduction signal is significantly deviated from the optimal slice level due to the transient response characteristics of the AC amplifier (to make the explanation easier to understand, a -ratio duty shift has occurred). This duty shift state passes through a portion corresponding to the transient response time of the reproduction system, and at the time it reaches the address information portion, it is sent to the demodulator 9 as a signal corresponding to at least a 50% duty sliced from the center of the normal signal. After phase synchronization with PLL etc.,
Address information is recognized.

On the other hand, in the sector mark area, the pulse signal g generated by the comparator 8 is as shown in FIG. 7g, and the rising edge detector IO of FIG. A pulse signal having a length of is obtained. and shift register 11
After parallelization, pattern discriminator (2) matches a predetermined pattern, and if there is a match, it is output as a sector mark detection signal i. By activating the timing control section 13 using this sector mark detection signal i, accurate timing generation for recording and reproduction is performed.

Regarding the pattern matching condition in the pattern discriminator 12, the degree of matching may be determined based on the error rate of the disc. For example, if sector mark detection is permitted when three elements are matched as a result of pattern matching for each mark element, errors in elements can be tolerated. The same applies to the setting of the number of elements, and as the number of elements increases, the sector mark detection reliability and error tolerance can be increased.

Furthermore, not only the transient response characteristics of the playback system but also the duty shift of the recording bit due to disc recording conditions not being met,
Even if there is a playback duty shift due to variations due to the circuit environment, component variations, etc., timing generation can be performed by accurate sector start point detection.

8 is a configuration diagram of a circuit in which the reproducing system detects the peak point of the reproduced signal, unlike FIG. 1;
Figure j+kTl+m+n shows the signal waveforms of each part.

In the configuration shown in FIG. 8, the photodetect signal f is amplified by the amplifier +4, and the signal h is passed through the differentiating circuit 15 to the signal j.
get. By inputting this differential signal j to the zero cross detection circuit 16, a signal k including a signal 4QQ corresponding to the peak position of the photodetect signal f is obtained. However, at this stage, the signal 401 other than the information point is included, and on the other hand, the amplitude detection circuit 17 slices the signal 401 obtained by amplifying the photodetect signal f at a predetermined level.
By obtaining the signal m whose timing has been further adjusted by the delay circuit 18 and ANDing it with the zero cross detection signal by the AND gate 19, the signal n indicating the peak point is finally obtained.

In the above-mentioned reproduction system, the information points of the reproduction signal are the information bits on one side, for example, in the embodiment, only the information points (peak points) of unrecorded bits are used, but for sector mark detection, the peak points are used. The signal n may be input to the rising edge detector 10 in FIG. 1, which is the embodiment described above.

In this case as well, as a sector mark according to the present invention,
Sector marks can be easily detected by forming the mark pattern element with recorded bits having a predetermined length and unrecorded bits having the same length shorter than the recorded bits (or the reverse combination).

Note that the recording detection method for the address information section and data section is N.
If the information is the bit length of both the recorded and unrecorded parts, such as RZ or NRZA-,
Differentiation of the reproduced signal and detection method from the sector mark can be realized, and reliability can be further improved.

<Effects of the Invention> As explained above, according to the present invention, there is the influence of duty shift due to transient response at the signal start portion of the signal reproducing system and steady duty shift due to various causes.
can be placed as a sector mark at the beginning of address information with a small configuration length, and the start point of a sector can be detected with high reliability, so that accurate timing generation for recording and reproduction can be performed.

[Brief explanation of drawings]

Fig. 1 is a block diagram of the detection circuit according to the present invention, Figs. 2 and 3 are explanatory diagrams of the recording state of the recording medium, Fig. 4 is a circuit diagram of the reproduction signal processing system, and Fig. 5 is a signal waveform diagram. - Fig. 6 shows a circuit diagram of the reproduced signal processing system, Fig. 7 shows a signal waveform diagram, and Fig. 8 shows a block diagram of the detection circuit. In the figure, 7: Amplifier 8: Converter 9: Demodulator 10: Start-up shedge detector 11: Shift register 12: Pattern discrimination 513: Timing control section agent Patent attorney Takeshi Sugiyama (and 1 other person) Figure 1 Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] 1. Recording and reproduction in sector units on a disk-shaped recording medium that has concentric or spiral recording tracks in the radial direction and each track is divided into sectors that are a plurality of recording units. In an optical disk device that performs erasing, etc., a sector mark indicating the start point of a sector is made of recorded bits (or unrecorded bits) of a predetermined length and unrecorded bits of a predetermined length shorter than the recorded bits (or unrecorded bits). A plurality of mark pattern elements composed of a combination of recording bits (or recording bits) are arranged at predetermined different intervals,
During playback, pattern elements are detected from the sector marks above,
A sector mark recording detection method characterized in that sector marks are detected by determining whether a predetermined number of pattern elements match.