JPS62121932A - Information recording device in optical disk - Google Patents

Abstract

PURPOSE:To obtain a precisely recorded and reproduced signal even on an inner peripheral part by recording a digital signal in the inner and outer peripheral parts of a recording area according to a bit interval modulation system and a bit end interval modulation system, respectively, and making the output of a semiconductor laser on the inner periphery lower than that on the outer periphery. CONSTITUTION:The digital signal is recorded in the inner recording area 4 and the outer recording area 5 by the bit end interval modulation recording system and the bit interval modulation recording system, respectively. Besides, the output of the semiconductor laser in the area 4 of an optical disk is set lower than that in the area 5 of the optical disk. Since a line velocity in the inner peripheral part 4 is slow, the signal can be recorded even if the output of the semiconductor laser is made low, whereby heating of the semiconductor laser can be suppressed and thermal deterioration does not occur. For recording the signal in the area 5, the bit interval modulation recording system capable of setting the duty ratio of semiconductor laser below 50% is employed to prevent the thermal deterioration of the semiconductor laser. Since a recording density can be made high in the inner peripheral part of the optical disk, recording capacity can be increased, and an optical disk information recording system where the thermal deterioration of the semiconductor laser hardly arises can be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of recording digital information on a recording medium (hereinafter referred to as an optical disk) having a light absorbing and reflecting plate on a disk using a semiconductor laser focusing beam 11. be.

Conventionally, there are two methods for recording digital information on an optical disk, that is, for associating modulation codes with pits on a recording medium: a pit interval modulation recording method and a pit end interval modulation recording method.

The pit interval modulation recording method captures recorded pits of the same size (hereinafter referred to as recording pits) as a row, as shown in Figure 2.
This is a method of recording digital signals by giving meaning to the intervals between recording pits. In this case, the recording pits are formed by moving the semiconductor laser with a pulse '#A'.

The pit edge interval modulation recording method is a method in which the interval between pit edges is given meaning as shown in FIG. In other words, it is a method of recording digital signals by giving meaning to the length and interval of recording pits.

Let's evaluate the above two methods from two points: recording density and durability against thermal degradation of the semiconductor laser.

In the pit interval modulation method, since the semiconductor laser is pulse-driven, the duty ratio, which indicates the rate at which the semiconductor laser emits light, is 50% or less. Therefore, the semiconductor laser generates less heat and is less susceptible to thermal deterioration. However, from the viewpoint of recording S density, there is a limit to the size of recording pits, making it unsuitable for increasing density.

Since the pit edge interval modulation recording method makes a determination based on the presence or absence of recording pits, it is more suitable for increasing the recording density than the pit interval modulation recording method, which makes a determination based on the interval between recorded pits. The recording density is 1.5 to 2 times that of the pit interval modulation recording method. However, since the semiconductor laser is not driven by pulses, the duty ratio is 50% on average, and the semiconductor laser generates a lot of heat, causing thermal deterioration.

As described above, the two methods described above do not simultaneously satisfy a high level of durability against thermal deterioration of the semiconductor laser and recording density.

Particularly in a CAV type optical disc, when digital signals are recorded using the pit interval modulation recording method, the deterioration of the recorded/reproduced signal is noticeable in the inner circumferential portion of the optical disc where the linear density is high.

The conventional pit interval modulation recording method and pit edge interval modulation recording method have the above-mentioned problems.

■ The present invention solves these problems of the conventional example.

It is an object of the present invention to simultaneously obtain accurate recording/reproduction signals even in the inner circumferential portion of an optical disk and to suppress thermal deterioration of a semiconductor laser in one optical disk.

In order to achieve this object, the present invention adopts a pit end interval modulation recording method for the inner circumference of the optical disk and a pit interval modulation recording method for the outer circumference of the optical disk as a method for recording information on an optical disk. Then, the output of the semiconductor laser at the inner circumference of the optical disk is set to be lower than the output of the semiconductor laser at the outer circumference of the optical disk. By doing this, the recording density can be increased at the inner circumference of an optical disk that adopts the pit edge interval modulation recording method as an information recording method, thereby preventing deterioration of recording and reproduction signals. In the adopted pit edge interval modulation recording method, the duty ratio of the semiconductor laser is 50% on average, which naturally tends to cause thermal deterioration due to the heat generated by the semiconductor laser. Since the output is set lower than the output of the semiconductor laser, heat generation of the semiconductor laser can be suppressed and thermal deterioration of the semiconductor laser can be prevented.

The present invention overcomes the problems of the prior art for one or more reasons.

One embodiment of the present invention will be described below with reference to FIG.

The optical disc 1 is divided into four areas 3°4.5. as shown in FIG.
Divide into 6. Area 3 near center hole 2. Areas 4 and 5 other than area 6 at the outer edge are recording areas. Digital signals are recorded in the inner recording area 4 using the pit-end interval modulation recording method, and in the outer recording area 5 using the pit interval modulation recording method. In addition, the output of the semiconductor laser is set so that the output of the semiconductor laser at the inner circumference of the optical disk is lower than the output of the semiconductor laser at the outer circumference of the optical disk. That is, in this embodiment, the output of the semiconductor laser is lower in recording area 4 than in recording area 5.

The inner recording area 4 has a smaller v value than the outer recording area 5.
Because A-recording has a high linear density, we adopted a bit edge interval modulation recording method that can increase the recording density.

In this case, since the linear velocity of the inner peripheral portion is low, recording can be performed even if the output of the semiconductor laser is lowered, so that heat generation of the semiconductor laser is suppressed and no thermal deterioration occurs.

Since the linear velocity is faster in the outer recording area 5 than in the inner recording area 4, the output of the semiconductor laser is set higher than that in the inner recording area 4.

If the pit edge interval modulation recording method is adopted for the outer peripheral recording area 5, thermal deterioration due to heat generated by the semiconductor laser is likely to occur. Therefore, the duty ratio of the semiconductor laser is set to 5.
The pit spacing modulation recording method is used to prevent thermal deterioration of the semiconductor laser. In addition, from the point of view of recording density, there is no problem at all even if the pit interval modulation method is used since the outer peripheral part has a higher density than the inner peripheral part.

In this way, the advantages of the pit edge interval modulation recording method in the inner periphery and the advantages of the pit interval modulation recording method in the outer periphery can be obtained simultaneously on one optical disc, and the problems with each recording method are solved. Be it.

In this embodiment (Fig. 1), the ratio of the diameter of the recording area 4°5 was set to 1:1, but this ratio was changed due to factors such as the performance of the semiconductor laser and the demand for higher recording density. There is no problem in moving it back and forth.

Note that the present invention is not limited to the specific embodiments described above, but is within the technical scope of the present invention.As described above, according to the present invention, the recording density is Since the density can be increased, the recording capacity can be increased, and an information recording method for an optical disk can be realized in which thermal deterioration of the semiconductor laser is less likely to occur.

[Brief explanation of drawings]

Fig. 1 is an optical disc showing the information recording method of the present invention, Fig. 2 is a diagram showing a pit interval modulation recording method and the shape of the recording pit, and Fig. 3 is a diagram showing the pit end interval modulation recording method and the shape of the recording pit. The diagram shown. 1... Optical disc, 2... Center hole of the optical disc. 4... Recording area (inner circumference), 5...
Recording area (outer area)

Claims (1)

[Claims] 1) A method for recording information on a disc-shaped recording medium provided with an optically recordable and reproducible recording film, in which the recording area of the recording medium on the disc is The digital signal is recorded using the pit interval modulation method in the outer periphery, and the digital signal is recorded by the pit end interval modulation in the outer periphery, and the output of the semiconductor laser at the inner periphery of the disk is compared with the output of the semiconductor laser at the outer periphery of the disk. 1. A method for recording information on an optical disc, characterized in that the information recording speed is reduced. 2) In the optical disc according to claim 1, wherein when the output of the semiconductor laser at the innermost circumference of the disc is 1, the output of the semiconductor laser at the outermost circumference is 1.5 to 2. Information recording method. 3) Claim 1 characterized in that the output of the semiconductor laser at the inner circumference of the disk is made lower than the output at the outer circumference of the disk so as to be proportional to the linear velocity on the disk. 2. A method for recording information on an optical disc according to paragraphs 1 and 2.