JPH0312040A - Method for measuring phase margin - Google Patents

Abstract

PURPOSE:To measure a phase margin in real time by comparing the standard code data form a standard data discriminator and the shift code data form a shift data discriminator and determining the phase margin from a bit error. CONSTITUTION:The reproduction signal from an optical recording medium is divided to reproduction data 101 and reproduction clock 102 by a signal waveform shaping and clock extracting device. The data 101 and clock 102 are converted to the code data by the standard data discriminator 104. On the other hand, the reproduction clock 102 is partly inputted to a phase shifter 103 by which the phase of the reproduction clock is shifted. The reproduction data 101 is converted to the code data by using this clock. The standard data from the discriminator 104 is subjected to the detection of a SYNC mark with a mark detector 107. The shift code data from the discriminator 105 and the standard data from the discriminator 104 are compared by a comparator 108 simultaneously with the detection of the mark by the detector 107, by which the error is detected. The errors are counted by a counter 109, by which the phase margin curve is obtd.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention focuses light such as a laser into a minute spot,
The present invention relates to a method for measuring the phase margin of an optical recording medium for recording information.

[Prior Art] Generally, in optical recording, there are two types of recording methods: inter-mark recording 71 and mark length recording 72, as shown in FIG. In inter-mark recording, the length of the marks (recorded pits) has no meaning, but the interval has meaning as data. On the other hand, in mark length recording, the length of the mark has meaning. Now, assume that the interval in inter-mark recording is t, or the mark length in mark length recording is t. In actual optical recording, the value of t will be distributed around the reference value tθ due to causes such as noise jitter and peak shift. This situation is shown in FIG.

In FIG. 8, the horizontal axis represents time and the vertical axis represents appearance frequency. In the conventional phase margin measurement method, a reproduced signal from an optical recording medium is captured by a time interval 1<) counter or the like, and the phase margin is determined from this distribution map. In the distribution shown in FIG. 8, 81 is a normal detection window, and since all data is within this window, no error occurs. Next, when the detection window is shifted as shown at 82, the shaded area in the figure deviates from this window and an error occurs. In this way, in the past, the phase margin was determined by once capturing the reproduced signal, determining its distribution, and calculating the number of times this distribution deviated from the detection window.

[Problems to be Solved by the Invention] However, in the conventional phase margin measurement method, the number of errors occurring is counted by taking in -degree data and then shifting the detection window using software. It took time. Furthermore, for items that deviate significantly from tlI, the number of samples to be inspected tends to be inaccurate regardless of the measurement. SUMMARY OF THE INVENTION The present invention is intended to solve these problems, and its purpose is to provide a method of measuring the phase margin in real time while shifting the detection window in a nodal manner.

[Means for Solving the Problems] The phase margin measurement method of the present invention uses an optical recording medium, an optical pickup for recording and reproducing information on the optical recording medium, and a standard clock from the reproduced signal of the optical recording medium. In a configuration including a standard data discriminator that extracts code data and a shift data discriminator that extracts code data using a clock shifted from a normal position, standard code data from the standard data discriminator and shift code from the shift data discriminator are provided. It is characterized by detecting bit errors and determining phase margins by comparing data.

[Example code] The present invention will be explained below based on the drawings.

First, an example of the physical format of an optical recording medium will be explained based on FIG. 3. In optical recording media, track addresses, sector addresses, etc. are formed in advance on the medium using uneven bits. In FIG. 3, the portion shown at the top is the sector format.

A plurality of these sectors come together to form a track. 3
1 is a preformat section formed of the above-mentioned uneven bits, and 33 is a user recording section in which the user records data. 32 is a gap part that separates 31 and 33, and 34 is a gear knob part that separates sectors. Next, the portion shown below is a detailed diagram of the user recording section 33. 3.5 is a VFO section for clock synchronization;
36 is a 5YNC mark for detecting synchronization confirmation, and 37 is a part for recording user data.

Before measuring the phase margin, it is necessary to record data in the area to be inspected on the optical recording medium. FIG. 2 shows the procedure for recording. When performing a recording operation, recording data is transferred from the host combination coater 106 to the RAM 24. The data sent from RAM at this time is
This is data for portions 35 to 37 in FIG. 3. R.A.
The recording signal 23 output from M enters the optical pickup 22 and is recorded on the optical recording medium 21.

Next, the phase margin measurement procedure will be explained based on FIG. 1. A reproduced signal from the optical recording medium 21 passes through a waveform shaper/clock extractor (not shown) and is divided into two parts: reproduced data 101 and reproduced clock 102. Using this reproduced data and the reproduced clock, the standard data discriminator 104 converts it into code data. The situation at this time is shown in FIG. In FIG. 4, 41 is reproduced data and 42 is a reproduced clock. At the rising edge of the clock, depending on whether the reproduced data is at a high level or a low level, it is converted into code data of 1 or 0.

On the other hand, a portion of the recovered clock enters the phase shifter 103, where the phase of the recovered clock is shifted. The reproduced data is converted into code data by a shift data discriminator 105 using this shifted clock. In Fig. 4, if the reproduced data is in the normal position as in part (a), no error will occur even if the 42 clocks are shifted by ±Tu/2, but as in part (b), an error will not occur. When shifting to the right, change the clock to (Tu/2-Δ
If it is shifted to the left by more than t), an error will occur. By changing the phase relationship between the reproduced data and the reproduced clock in this way, the phase margin can be measured. In the example shown in FIG. 1, the phase of the reproduced clock is shifted, but the reproduced clock may remain unchanged and the reproduced data may be shifted. The standard code data from the standard data discriminator 104 enters the mark detector 107, where the 5YNC mark shown in FIG. 3 is detected. This mark detection signal is
It is used as a start trigger signal for data comparison, which will be described later.

When measuring the phase margin, the host computer 10
6 gives a shift amount instruction to the phase shifter 103 and starts reproducing data. Then, at the same time as the mark detector 107 detects the mark, the data comparator 108 compares the shift code data from the shift data discriminator 105 and the standard food data from the standard data discriminator 104. The portion is detected as an error, and an error counter 109 counts the number of errors. As a method for detecting errors, for example, exclusive OR of standard code data and shift code data may be performed. The host combicoater receives the counting results and divides them by the number of data to be measured to find the bit error rate at a certain detection window shift amount. By repeating this procedure while changing the shift amount, a phase margin curve is obtained.

- In boat fishing, there are many defects caused by scratches, dents, etc. on optical recording media. An example thereof is shown in FIG. Fifth
In the figure, 51 is a reproduced waveform from an optical pickup, and there is a defect in the part indicated by (X), and data that should be there is missing.

52 is the reproduced waveform of 51 which is peak-detected and binarized. 53 is code data obtained by converting 52 into code data using a reproduced clock. The data corresponding to the part indicated by (X) is incorrect from 1 to 0.

As mentioned above, since there are many defects on optical recording media, the error rate is usually around 1O-5, and with conventional measurement methods, in order to determine the phase margin at 10-6 or less, I had no choice but to extrapolate. However, using the measurement method of the present invention, standard code data and shift code data are equally affected by defects on the medium, so errors caused by defects are not counted. An example of measurement by the phase margin measurement method of the present invention is shown in FIG. In FIG. 6, the horizontal axis represents the detection window shift amount, and the vertical axis represents the bit error rate. The ○ mark is the measurement result using the method of the present invention, and the Δ mark is the measurement result using the conventional method. In the measurement results using the present invention, when there is no error at all, the error rate value is expressed as 1O-7. As can be seen from this figure, when attempting to obtain the phase margin at an error rate of 10-' using the conventional method, the only option was to extrapolate the data, which was inaccurate; however, using the method of the present invention, it is possible to obtain it accurately. It will be done.

[Effects of the Invention] As described above, when the phase margin measurement method of the present invention is used, the phase relationship between the reproduced data and the reproduced clock is shifted by hardware and the measurement is performed, so that data cannot be read from an optical recording medium. Phase margin can be measured in real time while reading. Moreover, since errors caused by defects on the medium are not measured, there is no need to extrapolate data to determine the phase margin (accurate values can be obtained).

In addition, in this measurement method, any data may be recorded in the user data section 37 shown in FIG. 3, and measurement may be performed using data of the measurer's preference. Therefore, it is also possible to measure which pattern reduces the margin the most.

[Brief explanation of drawings]

Figure 1 is a block diagram of the phase margin measurement method of the present invention. Figure 2 is a block diagram of data recording for phase margin measurement of the present invention. Figure 3 is the layout of the physical format of the optical recording medium. Figure 4 is a diagram of the operating principle of phase margin measurement according to the present invention. Figure 5 is a schematic diagram of data reproduction. Figure 6 is a diagram showing an example of phase margin measurement according to the present invention. , a schematic diagram of an optical recording system, and FIG. 8 is a diagram explaining the principle of a conventional phase margin measurement method. 101... Reproduction data 102... Reproduction clock 103... Phase shifter 104... Standard data discriminator 105... Shift data discriminator 106... Host computer 107... Mark detector 108... ...Data comparator 109...Error counter 21...Optical recording medium 22...Optical pickup 23...Record signal 24...RAM 31...Preformat section 32.34... Gap section 33... User recording section 35... VFO section 36... 5YNC mark 37... User data section 41... Playback data 42... Playback clock 43... Food data 51... Reproduction waveform 52...Binarized waveform 53...Food data

Claims (1)

[Claims] an optical recording medium, an optical pickup for recording and reproducing information on the optical recording medium, a standard data discriminator for extracting code data from a reproduction signal of the optical recording medium using a standard clock, and a standard data discriminator for extracting code data from a normal position. detecting a bit error by comparing the standard code data from the standard data discriminator and the shift code data from the shift data discriminator;
A phase margin measurement method characterized by determining the phase margin.