JP2543362B2 - Optical disk recorder - 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 length) or the blank length (the length of the light spot traveling direction of the blank part between the pits) to reduce the jitter in the reproduced signal,
The quality of the reproduced signal is improved by improving the S / N.

[Conventional technology]

DRAW that can be written as a master disk such as a compact disk (CD) or video disk or as a disk memory for document files
(Write-once type) A disk or the like is coated with a recording film of tellurium, bismuth, or the like, and is rotated at a constant rotation speed or a constant linear speed. The film is melted by a laser beam to form pits, thereby recording information. Perform Conventionally, when this recording is performed, as shown in FIG. 2 (a), the time corresponding to the pit length to be formed (for example, 231n per 1T in CD is used).
s) The laser light is irradiated, or 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 as shown in FIG.

[Problems to be solved by the invention]

The pit length or blank length can take various lengths depending on the number of consecutive "1" s or "0" s of the recorded data (3 to 11T in the case of the CD format). Since the irradiation time becomes long, the degree of heating of the recording film becomes remarkable, and the recording film easily melts. This phenomenon becomes more remarkable as the thermal conductivity of the recording film is higher than the linear velocity of the disk.

Therefore, in the case where the laser light is always irradiated for the time corresponding to the pit length regardless of the length of the pit as shown in FIG. Even if the laser power is adjusted so that
As shown in FIG. 3, as the pit length to be recorded becomes longer, the actually formed pit becomes longer than the specified value. Looking at this with an eye pattern of the reproduced waveform, for example, the eye pattern of the reproduced waveform in which a 3T blank is formed directly in 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 prescribed pit length. Therefore, the reproduced signal includes a lot of jitter of the reproduced signal, has many errors, and has a poor S / N.

The pit length to be formed also changes depending on the blank length immediately before that (hereinafter referred to as "immediate blank length"). That is, the shorter the immediately preceding blank length, the more the heat when forming the previous pit affects the formation of the next pit to facilitate melting, so that the previous blank length remains the same even if the laser light irradiation time is the same. The shorter the length, the longer the pit is formed.

Fig. 10 shows how the formed pit length changes depending on the previous blank length for each pit of 3T, 7T, 11T (based on the combination of the previous blank length of the same length as the pit length, as a reference). , As shown in this figure, the shorter the blank length immediately before is, the easier it is to melt due to the heat of the pit formed before it. Even if the irradiation time is the same, the pit length is long. For this reason,
The previous blank length also causes the 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 comprises a mark length recording type laser light control means for irradiating a rotating disk with laser light to form one data as one continuous pit. In the optical disc recording device, when the laser beam control means forms the one continuous pit, the length of time from the irradiation start point to the irradiation end point is set to the time corresponding to the pit length to be formed. It is characterized in that the shortening amount is increased as the laser beam is irradiated while shortened and the longer pit is formed.

[Work]

As described above, since the pit length tends to be formed longer with respect to the irradiation time in the case of a long pit, the length of time from the irradiation start point to the irradiation end point is set as in the present invention. The longer the pit is formed by irradiating the laser beam with a shorter time corresponding to the pit length, and increasing the shortening amount, the more the pit length tends to be canceled and the pit length is close to the specified value. The pit length 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.

As described above, the pit length tends to be longer than the irradiation time when the immediately preceding blank length is short, so the irradiation time should be set shorter when forming a pit with a shorter immediately preceding blank length. If this is the case, the tendency to form a longer length is canceled and a pit length close to the specified value can be formed. When this is combined with the present invention, a signal with less jitter can be obtained, and a reproduced signal with less error or better S / N can be obtained.

〔Example〕

 Examples of the present invention will be described below.

FIG. 5 shows a head peripheral structure of a DRAW disk recording apparatus to which the present invention is applied. DRAW disk 11
Is a substrate of glass, synthetic resin or the like coated with a metal layer of tellurium or the like. A plurality of spiral tracks are preliminarily formed on the disk 11 by pregroups. 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 controlled by the level control signal during recording> during reproduction. The laser light generated from the laser generation circuit 14 is applied to the surface of the disk 11 by modulating the write data by the pulse division circuit 12 during recording. 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 a substantially defined pit length can be formed regardless of the pit length and 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. Also,
The irradiation time is corrected according to the length of the pit to be formed and the length of the immediately preceding blank so that a nearly regular pit length can be obtained. The correction of the irradiation time will be described.

(1) Correction of irradiation time by the pit length to be formed As described above, the longer the pit, the more the pit length tends to be formed with respect to the irradiation time. Therefore, according to the present invention, as shown in FIG. When forming longer pits, the irradiation time is set shorter (that is, the length of time from the irradiation start time to the irradiation end time is shortened with respect to the time corresponding to the pit length to be formed, and the laser light is irradiated. However, the shorter the pit is formed, the larger the shortening amount is), and this tendency is canceled.

Table 1 shows an example of irradiation time for each pit length when the immediately preceding blank length was set to 3T.

By _obtaining the optimum values of t and α _{n in} Table 1 by 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. 6, 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. 7, which is smaller than that of 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.

(2) Correction of irradiation time by immediately preceding blank length As described above, the shorter the immediately preceding blank length, the longer the pit length is with respect to the irradiation time. Therefore, the pit with the immediately preceding blank length is formed. In some cases, the irradiation time is shortened to cancel this tendency.

Second example of irradiation time for each previous blank length when the pit length to be formed is constant NT (N is 3,4 ... 11)
Shown in the table.

By _obtaining the optimum values of t and β _{n, N in} Table 2 by experiments, it is possible to form a pit length close to the specified value regardless of the length of the immediately preceding blank length.

However, if 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.

For this reason, the irradiation start position is made constant regardless of the immediately preceding blank length, and the irradiation time is corrected by the immediately preceding blank length on the rear side of the irradiation period as shown in FIG. If it is attached 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 almost proportional to the previous blank length), and the blank length becomes longer. You won't get it right. 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 irradiation time is corrected by the immediately preceding blank length as shown in FIG. 9B at the front side of the irradiation period (that is, the correction amount is added at the front side). As a result, pits are formed at regular positions, and the blank length can be obtained correctly. As a result, the jitter of the reproduced signal is reduced, the error is reduced, and the S / N is improved.

(3) Correction of irradiation time by combination of pit length to be formed and immediately preceding blank length As described above, the pit length to be formed is influenced by the pit length and immediately preceding blank length, so the correction value is determined by the combination. For example, a pit length closer to the specified value can be formed. Table 3 shows an example of irradiation time by various combinations of the pit length and the immediately preceding blank length.

Irradiation time of 3T-3T (immediately preceding blank length 3T, pit length 3T) 3 · T ₀ − (t + γ _3,3 ) is T ₃ , irradiation time of 7T-7T 7 · T ₀
-(T + γ _7,7 ) is T ₇ , 11T-11T irradiation time 11 · T ₀ −
When (t + γ _11,11 ) 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 sensor 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 long pit, the pit length tends to be formed longer with respect to the irradiation time. Therefore, the length of time from the irradiation start point to the irradiation end point The longer the pits are formed, the shorter the time corresponding to the pit length to be irradiated, and the longer the pits are formed. A close pit length 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, if the laser light irradiation is ended earlier than the time corresponding to the position of the rear end of the pit to be formed, the pit length will be increased so that the shortening amount becomes larger as the pit becomes longer. Not only that, the position of the rear end of the pit can be formed with high accuracy, and not only the pit length but also the blank length can be formed accurately.

Also, the pit length tends to be formed longer than the irradiation time when the immediately preceding blank length is short, so if the irradiation time is made shorter when forming a pit with a shorter immediately preceding blank length, the pit length becomes longer. The tendency of the formation of the pit is canceled out, and the pit length close to the specified value can be formed. And if this is combined with the present invention, a signal with less jitter can be obtained, and the error or the S /
A good N reproduced signal is obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of a recording laser beam according to the present invention in which the irradiation time is corrected according to the pit length to be formed. FIG. 2 is a diagram showing an example of a conventional recording laser beam. FIG. 3 is a diagram showing the pit length formed by the laser light of FIG. FIG. 4 is a diagram showing an eye pattern of a pit reproduction signal formed by the laser beam of FIG. FIG. 5 is a block diagram showing a head peripheral structure of a DRAW disk recording / reproducing apparatus to which the present invention is applied. FIG. 6 is a diagram showing an eye pattern of a pit reproduction signal formed by the laser beam of FIG. FIG. 7 is a diagram showing a relative ratio of jitter to recording power of a pit reproduction signal formed by the laser beam of FIG. FIG. 8 is a diagram showing the relative ratio of the error occurrence rate to the recording power of the pit reproduction signal formed by the laser light of FIG. FIG. 9 is a diagram showing an example of the recording laser light in which the irradiation time is corrected according to the immediately preceding blank length. FIG. 10 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. 11 is a diagram showing a shift in 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 (3)

(57) [Claims] 1. An optical disk recording apparatus comprising mark length recording type laser light control means for irradiating a rotating disk with laser light to form one data as one continuous pit. When the means forms the one continuous pit, the length of time from the irradiation start time to the irradiation end time is shortened with respect to the time corresponding to the pit length to be formed, and the laser light is irradiated, An optical disk recording apparatus characterized in that the shortening amount is increased as a long pit is formed. 2. The laser beam control means irradiates the laser beam early with respect to the time corresponding to the position of the rear end of the pit to be formed so that the shortening amount becomes larger as a long pit is formed. The optical disk recording device according to claim 1, wherein the optical disk recording device is terminated. 3. The optical disk recording apparatus according to claim 1 or 2, wherein the laser light control means continuously irradiates the laser light while forming one pit. .