JPH065576B2 - Optical disc recording device - Google Patents

Description

The present invention relates to a mark length recording type optical disc recording apparatus for recording data by forming pits on a disc with a laser beam. Direction) or the blank length (the length of the blank spot between the pits in the direction of the light spot traveling in the direction of the light spot), the jitter in the reproduced signal is reduced to reduce the jitter.
The quality of the reproduced signal is improved by improving / N.

[Conventional technology]

DR that can be written as a master for compact discs (CDs), video discs, etc. or a disc memory for document files
An AW (write-once) disc is a disc on which a recording film of tellurium, bismuth, or the like is uniformly applied, which is rotated at a constant rotational speed or a constant linear velocity, and the film is melted by a laser beam to form pits. Make a record. Conventionally, when this recording is performed, laser light is irradiated for a time period corresponding to the pit length to be formed (for example, 231 ns per 1T in CD) as shown in FIG. ), The laser light is irradiated for a time obtained by subtracting a certain time t ₀ from the time corresponding to the pit length to be formed.

[Problems to be solved by the invention]

The pit length or blank length can take various lengths depending on the number of times the recorded data "1" or "0" continues (3 to 11T in the case of the CD format), but the pit length formed is the blank length immediately before that. (Hereinafter referred to as "immediately preceding blank length"). That is, the shorter the previous blank length, the more the heat when forming the previous pit affects the formation of the next pit, and the easier it is to melt. The pit will be formed long.

FIG. 3 shows how the formed pit length changes depending on the immediately preceding blank length for each pit of 3T, 7T, 11T (based on the combination of the immediately preceding blank length having the same length as the pit length, The deviations from the reference Ref are shown respectively.) As can be seen from this figure,
The shorter the blank length immediately before is, the easier it is to melt due to the influence of heat when the pit before that is formed, so the pit length is formed longer even with the same irradiation time. Therefore, the reproduced signal contains a lot of jitter, has many errors, or has a poor S / N.

Further, when the immediately preceding blank length changes, not only the pit length but also the relationship between the irradiation start position and the pit start position formed by this irradiation changes. That is, the longer the immediately preceding blank length, the longer the distance from the irradiation start position to the pit start end. This is because as the immediately preceding blank length becomes longer, the influence of heat from the pit immediately before that becomes smaller and the recording film becomes more difficult to melt.

Therefore, if the irradiation start position is fixed regardless of the previous blank length, the longer the previous blank length, the more the pit start position shifts backward, and the blank length cannot be obtained correctly. Since the pit length and the blank length have exactly the same data weight as the recorded data, this also causes the reproduced signal to include jitter.

Further, in the case of forming pits on the disc, the longer the pit length is, the longer the irradiation time of the laser beam is, so that the degree of heating of the recording film becomes remarkable and the recording film is easily melted.

Therefore, as shown in FIG. 2A or FIG. 2B, in the case where the laser beam is always irradiated for the time corresponding to the pit length regardless of the length of the pit length, when the immediately preceding blank length is the same, for example, 3T. Even if the laser power is adjusted so that the pit has a specified pit length, the actually formed pit becomes longer than the specified value as the pit length to be recorded becomes longer as shown in FIG. Looking at this with an eye pattern of a reproduced waveform, for example, an eye pattern of a reproduced waveform in which a 3T blank is formed immediately after each pit of 3 to 11T is as shown in FIG. The blank amplitude is reduced. That is,
The longer the pit length, the longer the specified pit length. Therefore, the irradiation time of the laser beam itself has been a cause of jitter.

The present invention solves the above-mentioned problems in the prior art and reduces the error in the pit length or the blank length to reduce the jitter in the reproduced signal, thereby improving the S / N and reducing the error. The purpose of this is to improve the quality of the reproduced signal.

(Means for Solving the Problems) The present invention is such that the value obtained by subtracting the laser light irradiation time from the time corresponding to the pit length becomes larger when forming a pit having a short blank length immediately before, Control the irradiation time of the laser light according to the blank length of, and,
When forming a pit with a long blank length immediately before, starting the laser beam irradiation earlier than the time corresponding to the position of the front end of the pit to be formed, and forming a long pit, the pit length is longer. The irradiation time of the laser light is controlled according to the pit length so that the value obtained by subtracting the laser light irradiation time from the time corresponding to (1) becomes large.

[Work]

As described above, in the case of a pit having a short last blank length, the pit length tends to be formed longer with respect to the irradiation time. Shorten the irradiation time (that is, when forming a pit with a short immediately preceding blank length, the value obtained by subtracting the laser light irradiation time from the time corresponding to the pit length becomes larger according to the immediately preceding blank length. By controlling the irradiation time of the laser beam), the tendency to form a longer length can be canceled and a pit length close to the specified value can be formed. As a result, a reproduced signal with little jitter can be obtained, and a reproduced signal with few errors or good S / N can be obtained.

Further, as described above, the longer the previous blank length, the more the pit start position tends to shift rearward with respect to the irradiation start position. Therefore, when forming a pit with a long previous blank length as in the present invention, it should be formed. By starting the laser beam irradiation early with respect to the time corresponding to the position of the front end of the pit, the pit start position can be defined as a regular position, and a blank length close to the specified value can be obtained.

Further, as described above, the pit tends to be formed longer with respect to the irradiation time when the pit length is formed longer. Therefore, the irradiation time is shortened as the pit is formed longer as in the present invention. (That is, when forming a long pit, control the irradiation time of the laser light according to the pit length so that the value obtained by subtracting the laser light irradiation time from the time corresponding to the pit length becomes larger) As a result, the tendency to form a longer length is canceled and a pit length closer to the specified value can be formed.

〔Example〕

 Examples of the present invention will be described below.

FIG. 6 shows a head peripheral structure of a recording device for a DRAW disk to which the present invention is applied. The DRAW disk 11 is formed by coating the surface of a substrate made of glass, synthetic resin or the like with a metal layer such as tellurium. A plurality of spiral tracks are preliminarily formed on the disk 11 by pregrooves. Then, at the time of recording data, while tracking is performed on this track, data and address are written at a prescribed constant linear velocity. Also, during reproduction, the recorded address is read to read the data from the target portion. Data is recorded on the disk 11 by melting the metal layer with a recording laser beam to form pits. In addition, data reproduction is performed by detecting pits by reflection of reproduction laser light.

The optical head 13 irradiates the surface of the disk 11 rotating at a constant linear velocity with the recording or reproducing laser light generated from the laser generating circuit 14 to perform recording or reproduction. The intensity of the laser beam is recorded by the level control signal>
Controlled during playback. The laser light generated from the laser generation circuit 14 modulates write data by the pulse division circuit 12 at the time of recording and irradiates the surface of the disk 11.
The irradiation time of this writing laser light is controlled according to the pit length to be formed and the immediately preceding blank length, and the pit length. ,
An almost prescribed pit length can be formed regardless of the blank length.

Next, the irradiation time control of the recording laser light by the pulse division circuit 12 and the laser light generation circuit 14 will be described in detail.

The pulse division circuit 12 and the laser light generation circuit 14 irradiate the laser light for a time period corresponding to the pit length to be formed. Further, the irradiation time and the irradiation start timing are corrected according to the length of the pit to be formed and the length of the immediately preceding blank length so that a substantially regular pit length can be obtained at a substantially regular position. The correction of the irradiation time and the irradiation start timing will be described.

(1) Correction of irradiation time by immediately preceding blank length As described above, the shorter the immediately preceding blank length, the more the pit length tends to be formed with respect to the irradiation time.
As shown in the figure, the shorter the immediately preceding blank length is, the shorter the irradiation time is to cancel this tendency.

The pit length to be formed is constant at NT (N is 3,4 ... 11)
Table 1 shows an example of irradiation time for each immediately preceding blank length in the case of.

However, T ₀ = 1 / 4.3218 MHz t = 0-500 ns β3, N> β4, N> ... β5, N ... β11, N The optimum values of t and βn, N in Table 1 are obtained by experiments, A pit length close to the specified value can be formed regardless of the length of the immediately preceding blank. As a result, the reproduced signal jitter is reduced, errors are reduced, or the S / N ratio is reduced.
Will be good.

(2) Correction of irradiation start timing based on immediately preceding blank length As described above, the longer the immediately preceding blank length, the more the pit start position tends to move 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 irradiation time is corrected by the immediately preceding blank length in (1) after the irradiation period as shown in FIG. That is, if the correction amount is added to the rear side, the pit length can be obtained correctly, but the pit position shifts (it shifts backward as the previous blank length becomes longer. The shift amount is approximately proportional to the previous blank length. ), The blank length cannot be obtained correctly. Since the pit length and the blank length have exactly the same data weight as the recorded data, this also causes an error in the reproduced signal.

Therefore, here, the correction of the irradiation time based on the immediately preceding blank length is performed on the front side of the irradiation period (that is, the correction is added to the front side) as shown in FIG. As a result, pits are formed at regular positions, and the blank length can be obtained correctly.

(3) Correction of irradiation time by the pit length to be formed As described above, the longer the pit, the longer the pit length with respect to the irradiation time. Therefore, as shown in FIG. Shorten the irradiation time to cancel this tendency.

Table 2 shows an example of the irradiation time for each pit length when the immediately preceding blank length is 3T.

However, T ₀ = 1 / 4.3218 MHz t = _{0 to} 500 ns α _n = 0 to 100 ns (n = 4,5, ..., 11) α ₄ <α ₅ <... <α ₁₁ t and α in Table 2. _{By obtaining} the maximum value of _n by an experiment, it is possible to form a pit length close to the specified value regardless of the length of the pit. At that time, as shown in the eye pattern of FIG. 8, the amplitude of the 3T blank after the pits of 3 to 11T is almost constant. As a result, the relative ratio of jitter to recording power is as shown in FIG. 9, which is smaller than that in the conventional irradiation method. Further, as a result, the relative ratio of the error occurrence rate to the recording power is also reduced as compared with the conventional irradiation method, as shown in FIG.

(4) Correction of irradiation time and irradiation start timing by combining the pit length to be formed and the immediately preceding blank length As described above, the pit length to be formed is influenced by the pit length and the immediately preceding blank length. By setting the value, it is possible to form a pit length closer to the specified value. Table 3 shows an example of irradiation time by various combinations of the pit length and the immediately preceding blank length.

However, T ₀ = 1 / 4.3218 MHz t = _{0 to} 500 ns rm, n = 0 to 100 ns (m: blank length, n: pit length, m, n = 3, 4, ..., 11) For the same pit length n Γ _{3, n} > γ _{4, n} <... <γ _{11, n For the} same previous blank length m, γ _{m, 3} > γ _{m, 4} <... <γ _{m, 11} 3T-3T (immediately before Irradiation time 3 · T ₀ − (t + γ _3,3 ) of blank length 3T, pit length 3T) is T ₃ , 7T-7T
Irradiation time of 7 · T ₀ − (t + γ _7,7 ) to T ₇ , 11T
Irradiation time of −11T 11 / T ₀ − (t + γ _11,11 )
When T was set to T ₁₁ , the irradiation time was corrected by the immediately preceding blank length as shown in Table 4, and the pit length center position deviation was as shown in FIG. 11. According to this, the deviation of the pit length was smaller than that in the case where the irradiation time was not corrected by the immediately preceding blank length shown in FIG.

Also here, if the correction of the irradiation time by the previous blank length is performed on the front side of the irradiation time (that is, the correction is added on the front side), a pit is formed at the regular position and the blank length can be obtained correctly. Will be available.

[Modification]

In the above-described embodiment, the case where the present invention is applied to a disk having a constant linear velocity has been described, but the present invention can also be applied to a disk having a constant rotational speed.

Further, in the above-mentioned embodiment, the case where the irradiation power was made constant was explained, but the control for varying the irradiation power according to the pit length to be formed and the immediately preceding blank length (the longer the pit length to be formed, and the immediately preceding blank length is The shorter the irradiation power is, the lower the irradiation power can be used together.

〔The invention's effect〕

As described above, according to the present invention, in the case of a pit having a short last blank length, the pit length tends to be formed longer with respect to the irradiation time. In that case, the irradiation time of the laser beam is set to be shorter, so that the tendency of forming a longer laser beam is canceled and a pit length close to the specified value can be formed. As a result, a reproduced signal with little jitter can be obtained, and a reproduced signal with few errors or good S / N can be obtained.

Further, as described above, the longer the previous blank length, the more the pit start position tends to shift rearward with respect to the irradiation start position. Therefore, when forming a pit with a long previous blank length, the front end of the pit to be formed is Since the laser beam irradiation is started earlier than the time corresponding to the position, the pit start position can be defined as a regular position, a blank length close to the specified value can be obtained, and jitter can be further reduced. be able to.

Also, since the pit length tends to be formed longer with respect to the irradiation time when the immediately preceding blank length is shorter, the irradiation time is shortened as the immediately preceding blank length is shortened, so it is formed longer. The tendency can be canceled and a pit length closer to the specified value can be formed, and the jitter can be further reduced. Then, by combining these control of irradiation time and irradiation start timing, it is possible to obtain a signal with less jitter, less error, or more S / S.
A good N reproduced signal is obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a recording laser beam according to the present invention in which the irradiation time is corrected according to the immediately preceding blank length. FIG. 2 is a diagram showing an example of a conventional recording laser beam. FIG. 3 is a diagram showing a shift in the pit length when the irradiation time is not corrected according to the immediately preceding blank length. FIG. 4 is a diagram showing the pit length formed by the laser beam of FIG. FIG. 5 is a diagram showing an eye pattern of a reproduction signal of a pit formed by the laser beam of FIG. FIG. 6 is a block diagram showing a head peripheral structure of a DRAW disk recording / reproducing apparatus to which the present invention is applied. FIG. 7 is a diagram showing an embodiment of the recording laser light in which the irradiation time is corrected according to the pit length to be formed. FIG. 8 is a diagram showing an eye pattern of a reproduction signal of a pit formed by the laser beam of FIG. FIG. 9 is a diagram showing the relative ratio of the jitter to the recording power of the reproduction signal of the pit formed by the laser beam of FIG. FIG. 10 is a diagram showing the relative ratio of the error occurrence rate to the recording power of the reproduction signal of the pit formed by the laser beam of FIG. FIG. 11 is a diagram showing the deviation of the pit length when the irradiation time is corrected according to the immediately preceding blank length. 12 ... Pulse division circuit, 13 ... Optical head, 14 ... Laser generation circuit.

Claims (1)

[Claims] 1. A mark length recording type laser light control means for forming a pit on a disk by irradiating a laser light for a time substantially corresponding to a pit length to be formed from a position substantially corresponding to a front end portion of the pit to be formed. In the optical disc recording apparatus having the above, the laser beam control means is such that the value obtained by subtracting the laser beam irradiation time from the time corresponding to the pit length becomes larger when forming a pit with a short blank length immediately before, As the irradiation time of the laser beam is controlled according to the immediately preceding blank length, and the pit having a longer immediately preceding blank length is formed, the earlier the time corresponding to the position of the front end of the pit to be formed, the earlier. When the laser light irradiation is started and a long pit is formed, the value obtained by subtracting the laser light irradiation time from the time corresponding to the pit length becomes larger, Optical disk storage device, characterized by controlling the irradiation time of the laser beam in accordance with the length.