JPH03228225A - Optical information recording system - Google Patents

Abstract

PURPOSE:To surely form a self-clock signal so that easy reproduction can be made by executing recording in such a manner as to leave unrecorded regions where the recording is not executed at an optically recognizable size between respective recording pits and recording the respective recording pits in the state that these pits can be recognized at plural slice levels. CONSTITUTION:The unrecorded regions which can be optically recognized are provided between the respective recording pits at the time of applying such plural recording states as to vary the reflected light quantity or transmitted light quantity of the optical recording medium to the recording pits. Namely, the recording pit arrays 3 which are recorded are recorded in accordance with a binary data/quanternary data conversion table. Although the non-handling of the unrecorded regions as the recording data regions is a loss in the intrinsic higher density of a many value recording system, there are no significant problems if the degree of multiplexing is increased at the time of the many valued recording. The respective recording pits are respectively divided in the unrecorded regions in such a manner. This dividing is helpful for the formation of the self-clock signal and the easy and sure reproducing is executed.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention expresses a plurality of pieces of information with one pit based on the difference in the amount of reflected light or the amount of transmitted light from the pits recorded on an optical recording medium. This invention relates to an optical information recording method that enables recognition.

(Prior Art) Conventionally, when recording information using light and reading recorded information, the optical recording medium used is in the form of a disk, card, or tape. .

Some of these optical recording media are capable of recording and reproduction, while others are capable of only reproduction.

Information is recorded on the medium by focusing a light beam modulated according to the recorded information into a minute spot and scanning it on the information track so that it becomes an optically detectable information pit row during playback. One line is done. In addition, information is reproduced by scanning an optical beam spot with a constant power such that recording is not performed on the medium on the information track, and reading based on the difference in the amount of reflected light or transmitted light from the information pit row. It has been realized.

In this case, the size of the light beam spot on the recording medium is controlled by autofocusing (AF) control means, and the deviation of the information track arrangement is controlled by autotracking (AT) control means. In order to use such a control means, there are naturally restrictions on the size of the light beam spot, and the dimensions and pitch of the information pit array generated by this light beam spot are also fixed. The signals handled are binary ones, but the amount of information to be retrieved for one recording medium is determined by the dimensions and pitch of the information pit rows, and this is an impediment to higher density. .

(Problem to be solved by the invention) Therefore, in order to be able to optically recognize multiple recording states,
For example, λ to represent multiple information per pit.
For example, it has been proposed to perform multilevel recording by weighting each pit according to its density and recording on the recording medium. This can be achieved by creating pits such that when a light spot is applied on the recording medium, the amount of reflected light or transmitted light differs.

FIG. 6 shows the difference in the amplitude of the reproduction signal corresponding to the recording power of the laser beam, in other words, the amount of reflected light or the amount of transmitted light. As is clear from the graph, pits are not formed on the recording medium where the power of the laser beam does not reach the threshold A, and from the point where the power of the laser beam exceeds the threshold A to the position of point B, although it is nonlinear, the power decreases. As the number increases, the reproduction signal level also increases. And B
Beyond this point, a so-called saturation region occurs in which the reproduced signal amplitude hardly changes even if the laser power is changed.

Focusing on these characteristics, consideration has been given to the signal-to-noise ratio (S/Nl) in the region from point A to point B, and to what value accurate quantization (multilevel quantization) can be realized. At this time, by generating pits using the divided slice level as the recording condition, multi-value information can be applied to each pit, and this multi-value recording allows for high-density recording on one recording medium. For example, when N recording states are created, log.

This means that the density can be increased by N times. FIG. 7 shows the recording pit row 3 generated in this way. Here, in order to simplify the explanation, a case of four-value recording is illustrated. In other words, two pits of binary data correspond to one pit (“0” =
(001, “1” = (011, “2” = (10),
"3" = (1111°) Therefore, in the illustrated example of the pit row, the binary data represented by (1230310011) is (011011001101000001).

The reproduced signal waveform generated in response to this is the seventh
It will look like Figure tb+. Here, the reason why a small dent occurs in the reproduced signal at the portion where the 3'' is continuous is due to the existence of an unrecorded portion in the width direction that occurs at the portion where each graphic pit is in contact with each other.

However, as shown in FIG. 7 [bl], when adjacent pits are in different recording states, the pit boundaries can be identified as edges on the reproduced signal, and this can be used as an edge signal to generate a self-clock signal. ,
If an unrecorded state continues, or if pits in the same recorded state continue, no edge signal will be detected for a long time during reproduction, making it difficult to generate a self-clock signal.

(Objective of the Invention) The present invention has been made based on the above circumstances, and it is an object of the present invention to provide an optical information recording method that can reliably generate a self-clock signal and facilitate playback when realizing multi-value. That is.

(Means for Solving the Problems) For this reason, the present invention provides an optical method for recording on an optical recording medium so that a plurality of pieces of information are expressed per pit so that a plurality of recording states can be optically recognized. In the information recording method, recording is performed to leave an unrecorded area between each recording pit where no optical recording is performed, at least a size that can be recognized optically, and each recording pit is recorded at multiple slice levels. It is recorded in a recognizable state.

(Function) For this reason, each recording pit is divided into unrecorded areas, which helps in generating a self-clock signal, making reproduction easy and reliable. This makes it possible to realize completely effective multi-value optical information recording and reproduction.

(Example) Hereinafter, an example of the present invention will be specifically described with reference to FIGS. 1 to 5. FIG. 1 fat shows a recording pit row 3 recorded by the optical information recording method according to the present invention. This is recorded based on the binary data/quaternary data conversion table shown in FIG. In this conversion table, the binary data °'00' does not correspond to the unrecorded area as '0', but corresponds to '°1' which is one of the recorded states. In this way, not handling the unrecorded area as a recorded data area is a loss in terms of the original high-density multilevel recording method, but 1For example, in the case of four-level recording, it is possible to use five recording states. is possible, so the originally obtained high density (log, 4/(l
ogx5) = 0.8614 times, in the case of 16-value recording,
(1oga1.6/ (logtl 7) = 0, 97
In the case of 86x, 64-value recording, (loga64) /
(logz65) = 0.9963 times, and if the degree of multiplicity is increased during multilevel conversion, it will not be a big problem.

According to the conversion table in Figure 2, binary data (01101
When converting 100111 to 4-value recording data (234141), there is a length of one pit between each recording pit, for example.
In other words, there will always be an unrecorded area equivalent to the size of a light spot. When reproducing the pit string 3 generated in this way, the reproduced signal exhibits a signal level with an amplitude corresponding to the multi-level data at each recorded pit portion, and a signal amplitude of °C in the unrecorded area between the recorded pits. In this way, the reproduced signal amplitude becomes °'0" before and after the recording pit, so by setting the slice level to 05, which is indicated wirelessly, as in the example in Fig. 3 fbl, , it is possible to easily obtain a self-clock signal as shown in FIG. Normally, a self-clock generated from the reproduced signal is used to reproduce a digital signal, but if the reproduced signal shown in Figure 1 (bl) can be obtained, a simple circuit configuration as shown in Figure 3 can be used as described above. In other words, when the above-mentioned reproduced signal is input to the terminal 4, the comparator 5 outputs a digital signal to the terminal 6 based on the voltage 1 corresponding to the slice level shown in Fig. 1 fbl. The signal thus obtained is shown in Fig. 1 (cl).

In the above embodiment, the reproduction signal level corresponding to the unrecorded area was set to 0, but as shown in FIG. It can also be taken as an amplitude.
A predetermined DC component is added to the signal fbl in FIG. 1. For example, in the circuit configuration shown in FIG. 3, for example, V, =
By setting the voltage to 3.5 V, a lock signal similar to that shown in FIG. 1 can be obtained.

Next, in the case of the reproduced signal shown in FIG. 4 (bl), 2■ is the reproduction signal level indicating an unrecorded area. 1.5V) or a level higher than 2■ (like 1.5V)
For example, as shown in the figure, a signal that always crosses 2.5V) is read as a reproduction signal. Clock generation from such a reproduced signal is realized by a circuit as shown in FIG.

Here, the playback signal is input to terminal 7, and comparator 8
and input to 9. The comparator 8 outputs a net value signal when the reproduced signal is higher than V (2.5V here), and on the other hand, the comparator 9 outputs a net value signal (3) (1.5V here)
Outputs a positive value signal when the reproduction signal is lower. For this reason,
A clock signal is output from both to the terminal 11 via the adder 10.

(Effects of the Invention) The present invention has been described in detail above, and it is possible to adopt a recording method that gives recording pits a plurality of recording states in which the amount of reflected light or the amount of transmitted light differs for an optical recording medium. By providing an optically recognizable unrecorded area between each recording pit, it is possible to ensure the generation of a self-clock signal and ensure reliable reproduction.

[Brief explanation of drawings]

FIG. 1 (al to tel are waveform diagrams of recording pits, reproduction signals, and clock signals in the recording method according to the present invention, FIG. 2 is a multi-value conversion table, FIG. 3 is a clock generation circuit diagram according to the present invention, and FIG. Figures ial and (bl are waveform diagrams of each reproduced signal in another embodiment of the present invention, Figure 5 is a clock generation circuit for this purpose, Figure 6 is a diagram showing the amplitude characteristics of the reproduced signal with respect to optical power, and Figure 7 is a diagram showing the amplitude characteristics of the reproduced signal with respect to optical power. Figure ial, (bl is a diagram showing recording pits and reproduction signals of the conventional multilevel recording system, No. 8
The figure is a schematic diagram of a situation where a light beam spot is focused on an information pit. 1...Pit, 2...Focused beam spot, 3...
・Record pit.

Claims (1)

[Claims] In an optical information recording method that records on an optical recording medium so that multiple pieces of information are expressed per pit so that multiple recording states can be recognized optically, optical recording is performed between each recording pit. Optical information characterized in that recording is performed so that unrecorded areas are left with at least a size that can be recognized optically, and each recording pit is recorded in a recording state that can be recognized at a plurality of slice levels. Recording method