JPH0312041A - Method for measuring phase margin - Google Patents

Abstract

PURPOSE:To measure a phase margin in real time during shifting a reproduction window over hardware by comparing code data and the data in a pattern ROM, detecting a bit error and determining the phase margin. CONSTITUTION:The reproduction signal from a recording medium is divided to reproduction data 101 and reproduction clock 102 by a signal waveform shaping and clock extracting device and is converted to code data by a discriminator 105 using this code and clock. On the other hand, the reproduction clock is partly shifted in phase by a phase shifter 103 and is converted to code data by a discriminator 106. The standard data from the discriminator 105 is inputted to a mark detector 109, by which an SYNC mark is detected. On the other hand, a host computer 104 instructs a shift quantity to the phase shifter 103 and sends a signal to an address selector 108 which switches the address of a pattern ROM for comparison. The shift code data and the data of the ROM 107 are compared 110 simultaneously with the detection of the mark by the detector 109, by which the error is detected. The errors are counted 111 and 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, let the interval in inter-mark recording be tl or the mark length in mark length recording be 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. 6, the horizontal axis represents time and the vertical axis represents appearance frequency. In the conventional phase margin measuring method, a reproduced signal from an optical recording medium is captured using a time interval counter or the like, and the phase margin is determined from this distribution map. 6th
In the distribution shown in the figure, 61 is a normal playback window, and since all data is within this window, no error occurs. Next, when the playback window is shifted as shown at 62, the shaded portion 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 reproduction window.

[Problems to be Solved by the Invention] However, in the conventional phase margin measurement method, the number of errors is counted while shifting the playback window using software after taking in -degree data, which is extremely time consuming. It required Furthermore, for items that deviate significantly from tiI, the number of samples to be inspected tends to be inaccurate regardless of the measurement. The present invention is intended to solve these problems, and its purpose is to provide a method for measuring the phase margin in real time while shifting the reproduction window using hardware.

[Means for Solving the Problems] The phase margin measuring method of the present invention includes an optical recording medium, an optical pickup for recording and reproducing information on the optical recording medium, and an optical pickup that records and reproduces information on the optical recording medium. In a configuration that includes a shift data discriminator that extracts food data using a shifted clock, and a pattern ROM that records the data on the aforementioned recording medium and compares it with the aforementioned code data, this code data and It is characterized in that by comparing the data in the pattern ROM described above, bit errors are detected and position margins are determined.

[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 an optical recording medium, track addresses, sector addresses, etc. are formed in advance on the medium as uneven pits. In FIG. 3, the portion shown at the top is the sector format.

A plurality of these sectors gather together to form a track.

31 is a preformat section formed by the above-mentioned uneven pits, 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 gap part that separates sectors. next,
The portion shown below is a detailed diagram of the user recording section 33. 35 is a vFO unit for clock synchronization; 36
is the 5YNC mark that detects synchronization confirmation, and 37 is the part where user data is recorded.

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, the host computer 104 sends a signal to the address switch 108 to set the read start address of the pattern ROM 107 for recording. At this time, the pattern ROM
The data sent from 35 to 37 in Figure 3
This is the data for the part. The recording signal 23 output from the pattern ROM enters the optical pickup 22 and is recorded on the optical recording medium 21.

FIG. 4 shows a memory layout diagram on the pattern ROM 107. FIG. 4(a) shows an example in which recording data 41 and comparison data 42 are arranged in separate areas, and FIG. 4(b) shows an example in which the same portion of data is shared. The aforementioned address switcher 108 switches the reading start address to the position indicated by (X) during recording and to the position indicated by (y) during comparison.

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 105 converts it into code data. The situation at this time is shown in FIG. In FIG. 5, 51 is reproduced data and 52 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 O.

On the other hand, a portion of the recovered clock enters the phase shifter 103, where the phase of the recovered clock is shifted. Using this shifted clock, the reproduced data is converted into code data by a shift data discriminator 106. In Fig. 5, if the reproduced data is at a normal position as in part (a), no error will occur even if the 52 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 (T u/2
-Δt) or more to the left will result in an error. 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 105 enters the mark detector 109, where the 5YNC mark shown in FIG. 3 is detected. This mark detection signal is used as a signal in a data comparison start trigger, which will be described later.

When measuring the phase margin, the host computer gives a shift amount instruction to the phase shifter 103, and also sends a signal to the address switch 108 to switch the address of the pattern ROM for comparison.

(The position indicated by (y) in FIG. 4) Then, at the same time as the mark detector 109 detects the mark, the data comparator 110 compares the shift hood data with the data in the pattern ROM, and removes the portions that do not match. This is detected as an error, and the error counter 111 counts the number of errors. As an error detection method, for example, pattern ROM
What is necessary is to take the exclusive OR of the data and the shift food data.

The host computer receives the counting results and divides them by the number of data to be measured to find the pit error rate at a certain window shift value. By repeating this procedure while changing the shift value, a phase margin curve is obtained.

[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 it is difficult to read data from an optical recording medium. Phase margin can be measured in real time while reading.

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 memory layout diagram of the pattern ROM used in the present invention. Figure 5 is a diagram of the operating principle of phase margin measurement of the present invention. Figure 6 is a diagram explaining the principle of the conventional phase margin measurement method. , FIG. 7 is a schematic diagram of the optical recording system. 01...Reproduction data 02...Reproduction clock 03...Phase shifter 04...Host computer 05...Standard data discriminator 06...Shift data discriminator 07...Pattern ROM 08...・Address switcher 09...Mark detector 10...Data comparator 11...Error counter 21...Optical recording medium 22...Optical pickup 23...Record signal 31...Prior Format section 32, 34... Gap section 33... User recording section 35... VFO section 36... 5YNC mark 37... User data section 41... Data for recording 42... Data for comparison 51... Reproduction data 52... Reproduction clock 53... Code data

Claims (1)

[Claims] an optical recording medium, an optical pickup that records and reproduces information on the optical recording medium, and a shift data discriminator that extracts code data from a reproduction signal of the optical recording medium using a clock shifted from a normal position. In a configuration including a pattern ROM for recording data on the recording medium and comparing it with the code data, a bit error is detected by comparing the code data and the data in the pattern ROM, and the phase A phase margin measurement method characterized by determining the margin.