JPH01236431A - Optical disk recording device - Google Patents

Abstract

PURPOSE:To improve the S/N and to decrease errors by controlling the radiating state of the laser light in accordance with the immediately preceding blank length for reduction of the error of the pit length or the blank length due to the value of the immediately preceding blank length and for reduction of jitters of the reproduced signals. CONSTITUTION:An optical head 2 radiates the recording or reproducing laser light emitted from a laser light generating circuit 3 onto the surface of a disk 1 revolving at a fixed linear speed for recording or reproducing jobs. This recording data is supplied to a data production means 4 for production of the pit length data and the immediately proceeding blank length data corresponding to these lengths respectively. Based on these produced data, a laser light control means 5 controls the time of irradiation and the irradiation start timing of the laser light. As a result, the normal pit length is obtained at an approximately normal position and therefore the error due to pit length or the blank length due to the value of said immediately preceding blank length is reduced together with reduction of the jitters of the reproduced signals. Thus it is possible to improve the S/N and to decrease errors.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an optical disc recording device using a mark length recording method that records data by forming bits on a disc using laser light. By reducing the error in the blank length (the length in the direction in which the light spot travels between the bits) or the blank length (the length in the direction in which the light spot travels), the jitter in the reproduced signal can be reduced and the S
The quality of the reproduced signal is improved by improving /N.

[Conventional technology]

Can be written to as disk memory for compact discs (CDs), video discs, etc., and document files.
In AW (write once) disks, a disk coated with a recording film of tellurium, bismuth, etc. is uniformly rotated at a constant rotational speed or linear speed, and the film is melted by a laser beam to form bits and information is stored. Conventionally, when performing this recording, laser beam irradiation was controlled only in accordance with the bit length to be formed. That is, for example, when forming the bit shown in FIG. 2(a), the bit shown in FIG.
As shown in b), the time corresponding to the bit length to be formed (
For example, in the case of a CD, a laser beam (23ins per IT) is irradiated, or as shown in FIG. The laser beam was to be irradiated for the time subtracted by .

[Problem to be solved by the invention]

The bit length or blank length can take various lengths depending on the number of consecutive "1"s or "0"s in the recording data (3 to IIT in the case of CD format), but the bit length formed is the blank length immediately before it. (hereinafter referred to as "immediate blank length r"). In other words, Figure 2 (
As shown in d), the shorter the immediately preceding blank length, the more the heat from forming the previous bit will affect the formation of the next bit, making it easier to melt, so even if the laser beam irradiation time is the same, the immediately preceding blank The shorter the length, the longer the bit is formed.

Figure 3 shows how the formed bit length changes depending on the immediately preceding blank length for each bit of 37, 7T, and IIT (based on the combination of the immediately preceding blank length having the same length as the bit length). As can be seen from this figure, the shorter the immediately preceding blank length is, the more likely it is to melt due to the heat generated when forming the previous bit. Even if the time is the same, the bit length is longer. For this reason, the reproduced signal contains a lot of jitter, has many errors, or has a poor S/N ratio.

Further, when the immediately preceding blank length changes, not only the bit length but also the relationship between the irradiation start position and the bit start position formed by this irradiation changes.

That is, as shown in FIG. 2(d), the longer the immediately preceding blank length becomes, the longer the distance from the irradiation start position to the bit start end becomes. This is because the longer the immediately preceding blank length is, the less the influence of heat from the immediately preceding bit becomes, making it difficult for the recording film to melt.

For this reason, if the irradiation start position is kept constant regardless of the immediately preceding blank length, the longer the immediately preceding blank length is, the more the bit starting position will shift backward, making it impossible to obtain the correct blank length. Since both the bit length and the blank length have exactly the same data weight as recorded data, this will still result in jitter being included in the reproduced signal.

This invention solves the drawbacks in the conventional techniques, and
By reducing errors in bit length or blank length, jitter in the reproduced signal is reduced, improving S/N.
It is an object of the present invention to provide an optical disc recording device that improves the quality of reproduced signals by reducing errors.

[Means to solve the problem]

The present invention provides an optical disk recording apparatus equipped with a laser beam control means of a mark length recording method that forms bits on a disk by irradiating a laser beam for a time corresponding to the length of a bit to be formed, based on a data signal to be recorded. The method further comprises a data creation means for creating and outputting bit length data and blank length data just before the bit length data, and the laser light control means controls the laser light irradiation state based on the output data of the data creation means. It is something to do.

[For production]

According to this invention, bit length data and immediately preceding blank length data are created and output based on a data signal to be recorded, and the laser beam irradiation state is controlled.

According to this, the laser beam irradiation state is controlled according to the bit length and the immediately preceding blank length, so compared to the conventional method in which the laser beam irradiation state is controlled only according to the bit length, it is based on the length of the immediately preceding blank length. Errors in bit length or blank length are reduced, jitter in the reproduced signal is reduced, and S
The quality of the reproduced signal can be improved by improving /N and reducing errors.

〔Example〕

The present invention will be described in detail below. Here, a case will be described in which the present invention is used as a recording/rewriting/reproducing apparatus for a DRAW disc to record a CD format signal. 1st
In the figure, a DRAW disk 1 is a substrate made of glass, synthetic resin, etc., whose surface is coated with a metal layer such as tellurium.

On this disk 1, a plurality of tracks are formed in advance in a spiral shape by pre-groups.

When recording data, this track is tracked and the data is recorded at a prescribed constant linear velocity.
Data is written on the disc 1 by writing subcodes, etc., and during playback, reading the recorded subcodes, etc. to read data from the target section.Bits are formed by melting the metal layer with a recording laser beam. Do by doing.

Further, data reproduction is performed by detecting bits by reflection of a reproduction laser beam.

The optical head 2 performs recording or reproduction by irradiating a recording or reproduction laser beam generated from a laser generation circuit 3 onto the surface of a disk 11 rotating at a constant linear velocity.The intensity of the laser beam is determined by a level control signal. Accordingly, the recording time is controlled so that the time of playback is greater than the time of recording. Recorded data S to be input
O is EFM
duration) is the modulated data. This recording data is input to the data creation means 4, and data corresponding to the bit length (bit length data) and data corresponding to the immediately preceding blank length (immediate blank length data) are created.

The laser beam control means 5 controls the irradiation time and the timing of starting irradiation according to the bit length data 4 and the immediately preceding blank length data so that a substantially normal bit length is obtained at a substantially normal position.

An example of the configuration of the data creation means 4 is shown in FIG. Input data SO is EFM modulated serial data, which is sequentially input according to a predetermined clock. This input data SO becomes "1" for one clock at the rising and falling edges of the bit to be formed.

Therefore, the time from when the input data SO rises to "1" to when it next rises to "1" corresponds to the bit length or blank length.

The priority encoder 10 detects the bit length or blank length from the input data SO, and sequentially outputs the detected values as parallel data.

Each parallel data is transferred to the register 12 at the timing when the data SO', which is obtained by delaying the input data SO by a predetermined time, becomes 1.The data transferred to the register 12 is then transferred to the register 12 at the timing when the input data SO becomes 1. register 14
will be forwarded to. In this way, the input data SO becomes “1”.
'', the immediately preceding bit length data or the immediately preceding blank length data is alternately detected as parallel data and sequentially transferred from the register 12 to the register 14.

The delayed input data SO' is sent to the flip-flop 71 via a two-clock delay circuit 16 for timing alignment.
The EFM signal is input to the circuit 18 and outputs an EFM signal that is "1" for bits and "O" for blanks using a bit/blank identification signal (for example, a synchronization detection signal).

A rising edge detection circuit 20 detects a rising edge of the EFM signal. The data held in the register 12.14 is transferred to the register 22.24 by this rising edge detection signal ST. At the timing when the rising edge detection signal ST is output, the bit length data is held in the register 12 and the immediately preceding blank length data is held in the register 14. Therefore, the bit length data is held in the register 22, and the immediately preceding blank length data is held in the register 24. be transferred. In this way, register 2
From 2.24 onwards, each parallel data of bit length data and immediately preceding blank length data is output in parallel. Therefore, these bit length data and immediately preceding blank length data are
By inputting the data to the laser light control means 5 shown in the figure, the laser light control means 5 controls the irradiation time and irradiation start timing based on these data, and outputs bits at approximately regular positions with approximately regular bit lengths. can be formed.

FIG. 5 shows a specific example of the circuit shown in FIG. 4, and FIG. 6 shows the signals of each section indicated by A to J in FIG. The priority encoder 10 is a 10-bit shift register 26.
and a logic circuit 28. logic circuit 2
8 indicates that a signal is input from a line whose crossing point is surrounded by O. Logic circuit 28 alternately outputs 4-bit parallel data (higher bits on the right) of bit length or blank length and inputs them to each bit of register 12.

The shift register 26 outputs data SO' which is the input data SO delayed by 10 clocks. Data So'
At the timing when becomes "1", the logic circuit 28 outputs bit length data or blank length data (in this example, data obtained by subtracting 3 from the bit length or blank length, that is, 3T=0°4T=1.57=2. ...11T=8>
Since the data has been output, the data is held in the register 12. Note that each bit of the register 12 is composed of two AND circuits 30 and 32, one OR circuit 34, and a 1-bit register 36. When the signal SO' rises to "1", each bit signal of bit length data or blank length data alternately output from the logic circuit 28 is held in the register 36 after one clock via the AND circuit 32 and the OR circuit 36. is held as it is via the AND circuit 30 and the OR circuit 34. Every time new bit length data or blank length data is output from the logic circuit 28, the contents of the register 36 are rewritten.

The other registers 14, 22, and 24 are configured similarly to register 12. The output of register 12 is input to register 14, and data held in register 12 is transferred by signal SO'.

The flip-flop circuit 18 is composed of an exclusive OR circuit 38, an AND circuit 40, and a 1-bit register 18. The signal SO' is delayed by two clocks in the delay circuit 16 and then input to the flip-flop 71 circuit 18. Signal SO'
The output of the flip-flop circuit 18 is inverted every time the bit becomes "1", and an output becomes "1" for a bit and "0" for a blank. The output of the flip-flop circuit 18 is delayed by one clock in a delay circuit 44 and outputted as F and FM signals.

The output of the flip-flop circuit 18 and the output of the delay circuit 16 are connected to an AND circuit 21 that constitutes a rise detection circuit 20.
The AND circuit 21 outputs a rising edge detection signal of the EFM signal.

The rising edge detection signal is input to registers 22 and 24,
The output data of register 12.14 is transferred to register 22.24.
used to transfer to. The rising edge detection circuit 20 is EF
At the timing of detecting the rising edge of the M signal, the register 12
．． 14 respectively hold bit length data and immediately preceding blank length data, the bit length data and immediately preceding blank length data are transferred to registers 22 and 24, respectively. Note that the delay circuit 16 is connected to the register 12.
This is for timing adjustment for transferring the data to the registers 22 and 24 after the data of No. 14 has been determined.

The output of the rising edge detection circuit 20 is sent to a two-clock delay circuit 4.
6. This rising detection signal ST is sent to a register 22.
The delay circuit 46 is used as a shift signal to transfer the data in the registers 22 and 24, and the delay circuit 46 is used to adjust the timing for transferring the data after the data in the registers 22 and 24 is determined.

Note that the circuit shown in FIG. 5 can be implemented as an LSI.

Next, a specific example of variable control of the irradiation time and irradiation start timing by the laser light control means 5 (FIG. 1) based on the bit length data and immediately preceding blank length data output from the data creation means 4 explained above will be explained. .

(1) Variable control of irradiation time using the immediately preceding blank length As mentioned above, the shorter the immediately preceding blank length, the longer the bit length tends to be formed relative to the irradiation time. The shorter the preceding blank length, the shorter the irradiation time to counteract this tendency.

The bit length to be formed is constant NT (N is 3.4...
Table 1 shows an example of the irradiation time for each immediately preceding blank length in the case of 11).

Table 1■ [However, T, = 1/4.3218 Ml (zt = O
~500 ns β3. N > β4. N> β5. N〉...〉
β11. The optimal values for t, βn, and H in Table 1 are determined through experiments and stored in the memory as a table, and the corresponding irradiation time data is read out based on the combination of bit length data and immediately preceding blank length data, and the laser beam irradiation is performed. By controlling the time, it is possible to form a bit length close to a specified value regardless of the length of the immediately preceding blank length. As a result, the jitter of the reproduced signal is reduced, errors are reduced, or the S/N ratio is improved.

(2) Variable control of irradiation start timing based on the immediately preceding blank length As described above, the longer the immediately preceding blank length is, the more the bit starting position tends to shift backward with respect to the irradiation start position. For this reason, the irradiation start position is kept constant regardless of the immediately preceding blank length, and the variable control of the irradiation time according to the immediately preceding blank length described in (1) above is performed at the rear of the irradiation period, as shown in (a) in Figure 7. (In other words, by attaching the variable part to the rear), the correct bit length is obtained, but the bit position is shifted (the longer the immediately preceding blank length is, the further it shifts backwards. The amount of shift is approximately proportional to the immediately preceding blank length). ), the blank length will not be obtained correctly. Since both bit length and blank length have exactly the same data weight as recorded data, this will still result in errors being included in the reproduced signal.

Therefore, by shifting the irradiation start timing forward as the immediately preceding blank length increases, as shown in FIG. 7(b), bits are formed at regular positions and the blank length can be obtained correctly.

According to the laser beam irradiation control as described above, the deviation of the bit length center position becomes as shown in Fig. 8, and the bit length error and the bit length center position become smaller than in the case of the conventional device shown in Fig. 3. The deviation becomes smaller.

[Example of change]

In the embodiment described above, the irradiation time and irradiation start timing are variably controlled according to the immediately preceding blank length, but the irradiation time and irradiation start timing can also be variably controlled in consideration of the bit length. In other words, when forming long bits, the irradiation time of the laser beam becomes longer, and the degree of heating of the recording film increases, making it easier to melt and forming long bits. When forming, shorten the irradiation time.

In addition, in the above real square example, the irradiation time and irradiation start timing are variably controlled. ) The immediately preceding blank length data can also be used for the purpose of various laser beam irradiation control purposes.

Furthermore, the bit forming laser light may not be irradiated continuously over one bit, but may be divided into a plurality of pulses and irradiated.

〔Effect of the invention〕

As explained above, according to the present invention, since the laser beam irradiation state is controlled according to the immediately preceding blank length, compared to the conventional method in which the laser beam irradiation state is controlled only according to the bit length, Errors in bit length or blank length based on length are reduced, jitter in the reproduced signal is reduced, and the quality of the reproduced signal can be improved by improving S/N and reducing errors.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention. FIG. 2 is a diagram showing an example of a conventional recording laser beam. FIG. 3 is a diagram showing a shift in the bit length center position when the irradiation time and irradiation start timing are not variably controlled according to the immediately preceding blank length. FIG. 4 is a block diagram showing an example of the configuration of the data creation means shown in FIG. 1. FIG. 5 is a circuit diagram showing a specific example of the data creation means shown in FIG. 4. FIG. 6 is an operational waveform diagram of FIG. 5. FIG. 7 is a diagram showing an example of a recording laser beam produced by the apparatus shown in FIG. 1. FIG. 8 is a diagram showing the bit length center position shift when the irradiation time and irradiation timing are variably controlled according to the immediately preceding blank length. ■... Disc, 2... Optical head, 3... Laser generation circuit, 4... Data creation means, 5... Laser light control means.

Claims (1)

[Scope of Claim] In an optical disc recording apparatus equipped with a laser light control means of a mark length recording method that forms bits on a disc by irradiating laser light for a time corresponding to the length of the bit to be formed, there is provided a data signal to be recorded. data creation means for creating and outputting bit length data and immediately preceding blank length data based on the bit length data, and wherein the laser light control means controls a laser light irradiation state based on the output data of the data creation means. Characteristic optical disc recording device.