JPH0261834A - Optical disk medium and optical disk device using the medium - Google Patents

Abstract

PURPOSE:To allow bit length recording even with an optical disk and to increase recording density by providing tracks for measuring sensitivity to the inner peripheral and outer peripheral parts of the optical disk. CONSTITUTION:The tracks T1, T2 for measuring sensitivity are provided to the inner peripheral and outer peripheral parts of the optical disk 10. A microcomputer 20, a pulse width changing circuit 16, a light emitting driver 14, a head 12 for executing writing/reading to and from the optical disk and a reproduction amplifier 22 are provided. Recording is executed in the tracks T1, T2 by variously increasing and decreasing prescribed pulse widths prior to writing of data to the optical disk. Reading errors are then investigated and the difference between the pulse width at which the errors are min. and the prescribed pulse width is determined and the recording to the ordinary tracks is executed after the pulses are corrected by this difference.

Description

[Detailed Description of the Invention] [Summary of the Invention] An object of the present invention is to provide an optical disk medium and an optical disk device using the medium, and to enable mark length recording even on an optical disk. The structure is such that a track for sensitivity measurement is provided in the section.

[Industrial application field]

The present invention relates to an optical disc medium and an optical disc device using the medium, and particularly to an optical disc medium and an optical disc device that allow mark length recording/reproduction.

Binary data recording includes mark length recording and mark position recording. As shown in Figure 5, the binary data is 1011
Assuming 00..., 1 means there is a hole (mark) and 0 means no hole, but it is a mark position method, and 1
In mark length recording, 0 indicates a change (starting end/end of a hole), and 0 indicates no change.

In this Figure 5, (1) shows the binary data to be recorded, (3) shows the recording by the mark position method (fabricated junior college), (2) shows the recording and reproduction signal, and (5) shows the mark length. (4) shows the recorded/reproduced signal by the method (long length produced). Data reading (decoding) from the reproduced signal is performed using the clock (created from the clock read from the optical disk).In the mark position method, if there is a pulse within the window, it is 1, otherwise it is O, and in the mark length method, it is 0 if there is a pulse within the window. If the internal state changes from before, it is 1, otherwise it is 0.

A mark position record is also called a junior college record, and a mark record is also called a change point record or a long college record.

[Conventional technology]

Mark position recording is currently performed on optical discs. The reason for this is that in optical discs, the size of recorded bits (holes) differs depending on the medium sensitivity and laser power, so it is difficult to control the bit length, making it difficult to use the bit length method. That is, if the hole is large, the bit length (the length of the hole) increases back and forth, and the change point (zero-crossing point) shifts forward or backward, which may cause an error in decoding the reproduced signal. With the mark position method, the presence or absence of marks (holes) is a problem, and the presence or absence of the destination changes depending on the size of the destination, so reading errors do not occur.

In magnetic disks, recording (magnet formation) is performed by sequentially applying magnetic fields in opposite directions to the medium, and it is possible to control the bit length regardless of the performance of the medium. For this reason, mark length recording is performed on magnetic disks.

[Problem to be solved by the invention]

In mark position recording, each bit has one piece of information, 1 or 0, but in mark length recording, it can have two pieces of information, one each at the start and end points of the bit (recording density However, for the reasons described above, it is difficult to record mark lengths on optical discs, and therefore there is a problem in that the recording density cannot be increased.

The present invention was devised to solve this problem.
The purpose is to enable mark length recording even on optical discs.

[Means to solve the problem]

As illustrated in FIG.
2 will be provided.

When this optical disc is inserted into a recording/playback device, the device records on the track under various conditions, plays it back, determines the error rate, determines which recording conditions are optimal for the disc, and determines which recording conditions are optimal for the disc. Recording will be performed based on the conditions.

In FIG. 1, 12 is a head for recording and reproducing information on the optical disk 10, 14 is a light emitting element driver for recording, and 14
a is a recording power changing circuit, and 16 is a pulse width variable circuit. 20 is a microcomputer;
Reference numeral 2 denotes a reproduction amplifier that amplifies the reproduction signal of the optical disc.

[For production]

When an optical disk is inserted into a recording/reproducing device, the device first records data on its sensitivity measurement trunk with various recording pulse widths (set in this way). An optical disk has tens of thousands of tracks, each of which is divided into 10 to 20 sectors. The sensitivity measurement track is also divided into similar sectors, and pulses with different pulse widths are recorded in each sector.

If the maximum recording frequency is 5 MHz, the minimum pulse width is 100 ns, which is half the period, and when recording using the 2-by-7 method (converting 2 bits to 3 bits and preventing more than 7 consecutive O's), Maximum pulse width is 267n
Become S. The maximum pulse width (longest bit) is recorded on the sensitivity measurement track, and if it is 267 nS, the range of ±50 μs, that is, from 217 nS to 317 nS, is changed in 5 nS increments to 217 nS and 222 nS.

A pulse with a width of 227 nS, . . . 317 nS is recorded in each sector. That is, 217nS in the first sector, 222nS in the second sector, 3 in the 20th sector.
A pulse with a pulse width of 17 nS is recorded. This recording is performed by a system including a computer 20, a variable pulse width circuit 16, a light emitting element driver 14, and a head 12.

After the above-mentioned recording is performed, reading is performed, and the computer 20 checks the sector in which an error occurs. This reading is performed by a system including the head 12, regenerative amplifier 22, and computer 20.

As the width of the recording pulse increases, the bit recorded on the medium also increases (the length of the hole increases). If the bit length on the medium is too small or too large, it will not be possible to reproduce and demodulate correctly and errors will occur. For example, errors occur such as when seven pulses are written in one sector but only six pulses are read.

When examining the presence or absence of errors in each sector recorded by changing the recording pulse width, it is found that errors occur in sectors with small pulse widths, errors no longer occur at a certain pulse width when the pulse width becomes large, and errors occur again when the pulse width becomes larger. will begin to occur.

Since it is thought that there is an optimal pulse width between the maximum pulse width and the minimum pulse width within the range where no error occurs, the average value of these maximum/minimum pulse widths is determined as the preferred recording pulse for the medium, which is determined by sensitivity etc. width.

If the pulse width to be recorded is 267 nS as in this example, it would seem that it would be sufficient to record and reproduce with a pulse of that 267 nS width, but this may not be possible due to medium sensitivity etc. (recording power, ambient temperature, etc. are also related). It will be optimal to record with appropriate width pulses wider or narrower than 267 nS. Optimal pulse width found in the above test and pulse width 2 scheduled for recording
If you want to memorize the difference Δw from 67nS and make the difference only positive, set the difference from the minimum value 217nS as Δw), and add this Δw during actual recording.

The width of the recorded pulse, that is, the length of the hole, only fluctuates around the size, so for example, if a 2.1 μm long hole is recorded with a 2 μm wide pulse, then the hole length is 3 μm.
If recorded with a pulse width of , a hole with a length of 3° and 1 μm will be created. Therefore, by adding the above-mentioned Δw, recording of pulses of all pulse widths can be performed optimally (without causing errors).

By adopting this method, even if the sensitivities of the media (optical discs) differ, it is possible to record under the optimum recording conditions for each medium, and mark length recording is also possible on optical discs.

Instead of adjusting the pulse width, the recording power may be adjusted. That is, writing is performed with various powers, the optimum power with the least error is determined, and subsequent recording is performed using that power. The power change circuit 26 performs this recording power adjustment/setting.

〔Example〕

FIG. 2 shows an embodiment of the present invention. As throughout the design, parts that are the same as in other figures are numbered the same. 1
8 is an encoder that converts recording (writing) data output by the computer 20 into a pulse signal. 24 is a decoder which takes out recorded data from the output of the reproducing amplifier.

FIG. 2 (bl is a diagram showing an example of the pulse width changing circuit in FIG. 2(a), and FIG. 2(C) is a diagram showing an example of the light emitting element driver 14 in FIG. 2(a). Pulse width changing The circuit 16 and the power change circuit 26 constitute means for performing recording under optimum recording conditions.

In the variable pulse width circuit 16 shown in FIG. 2(b), L1 to Ln are delay lines, and 81 to Sn are selection switches thereof. Assuming that n=20 and each delay line provides a delay of 5 nS, the pulse width can be increased by 5 nS from 217 ns to 317 nS. That is, the input pulse IN is directly connected to the delay lines L, , L2,
...... to the OR gate OR, and the output OUT of the OR gate is the pulse width of the input pulse W (=2
17nS) as W+5k (k=0.1.2. ・
...-20) becomes nS.

Now, as a result of the test in the above manner, the optimum recording pulse width is determined, the pulse width Δw to be added is determined, and it is determined that this is when the switch Si is closed.
stores the i, and outputs data that closes the switch Si when writing to the optical disc (this time, normal data writing). This closes the switch Si,
In this example, a pulse width of 51 μs is added to the input pulse IN.

To close the switch Si, for example, the switches 81 to Sn are transistors, the base of each transistor is connected to the output terminal of a flip-flop, and the computer 20 outputs data to set the corresponding flip-flop.
Easy to do.

FIG. 2 (In the light emitting element driver 14 of C1, D is a light emitting element (laser diode), and C3 is a transistor constituting a constant current source. The transistor Q3 constantly flows a current 1. to the light emitting element to cause it to emit light. Put the element into the read state. Q, , C2 are a pair of transistors forming a current switch, C4 is a transistor forming a constant current source for the current inch. WA is a write amplifier, and the transistor is turned on according to the write signal WS. Turn on Q1 or C2.

When transistor Q2 is on and Ql is off, in addition to the above-mentioned constant current, a constant current 2 supplied by transistor Q'4 flows through the light emitting element, generating strong light and writing (forming holes) on the optical disc. Let's do it. Transistor Q1 is on, C
When 2 is off, current r2 flows through Ql and does not flow through the light emitting element, so only current 11 flows through the light emitting element, and writing (hole formation) is not performed. Even in the read mode rather than the write mode, 01 is on and C2 is off, and only the constant current 1 flows through the light emitting element.

When the power changing circuit 14a outputs the voltage ΔV to change the constant current I2, the value of the current flowing through the light emitting element during writing changes, and as a result, the writing power changes. Instead of finding the additional pulse width Δw and using this to optimally adjust the recording pulse width, find the power ΔP to be added and use this to adjust the current I2.
may be modified, and the power changing circuit 14a can be used for such power adjustment. The power changing circuit 14a can be composed of, for example, a voltage dividing resistor and a plurality of transistors for taking out the tap voltage, and the control of these transistors can be performed in exactly the same manner as in FIG. 2(b).

FIG. 3 shows the relationship between recording power and recorded bit length for two types of discs A and B. The recording pulse width is 2.
5 μm, but if the recording power is low, no recording is performed (bit length is 0), and if the recording power is high, the bit length is 2.
．． It becomes larger than 5 μm.

Further, disk A has a larger bit length than disk B even if the recording power is the same. That is, disk A has better sensitivity than disk B. The graph in FIG. 2 was obtained by recording with a recording pulse width of 2.5 .mu.m and varying the power, then reproducing, and estimating the bit length from the reproduced waveform.

When recording is performed with a constant recording pulse width, the difference in bit length is large, and it is not possible to correct this optical disk using the same device without sensitivity correction. Furthermore, if there are variations in recording power from device to device, for example, if there is a variation in recording power of ±5% and a variation in medium sensitivity of ±5%, the bit length will change by as much as ±10%, and the mark length will change. It is nearly impossible to record.

FIG. 4 shows the results of carrying out the test of the present invention on these disks. The recording power was 7 mW. For disk A, the error-free range is approximately -30nS to +5nS
0 If the center of this range is optimal, Δw is approximately -12
It is nS. Also, for disk B, the error-free range is from about -10 nS to +25 nS, and Δw is about +8
It is nS. If the unit is 5nS, the former is 1 ounce.

The latter is +10 nS. This allows you to perform optimal recording that is less likely to cause errors.

This is a sensitivity measurement track.

〔Effect of the invention〕

As explained above, in the present invention, the optimal pulse width or recording power is determined by recording on the optical disc, and recording is performed using that. Therefore, bit length recording can be performed even on the optical disc, and the recording density can be increased.

[Brief explanation of the drawing]

Fig. 1 is a diagram explaining the principle of the present invention, Fig. 2 is a diagram showing an embodiment of the invention, Fig. 3 is a graph showing the relationship between recording power and bit length, and Fig. 4 is a graph showing the relationship between recording pulse width and number of errors. FIG. 5 is an explanatory diagram of mark length/mark position recording.

Claims (1)

[Claims] 1. An optical disc medium characterized by comprising tracks (T_1, T_2) for sensitivity measurement on the inner circumference and/or outer circumference of the optical disc (10). 2. Equipped with a microcomputer (20), a pulse width changing circuit (16), a light emitting element driver (14), a head (12) for writing/reading to/from an optical disk, and a regenerative amplifier (22), which allow the data to be read from/to the optical disk. Before writing data, the predetermined pulse width is variously increased or decreased and recorded on the sensitivity measurement track of the disk, and the read error is checked to find out the difference (Δw) between the minimum pulse width and the predetermined pulse width. seek,
An optical disc device characterized in that recording on a normal track is performed by modifying pulses based on the difference. 3. Microcomputer (20), power change circuit (
14a), a head (12) for writing to/reading from an optical disc, and a reproducing amplifier (22), which can increase or decrease a predetermined recording power in various ways before writing data to an optical disc. Then, record on the sensitivity measurement track of the disc, check the read error, find the difference (ΔP) between the minimum recording power and the predetermined recording power, and record on the normal track with the predetermined recording power. An optical disc device characterized in that the power is adjusted.