JPH087882B2 - Optical information recording medium and optical memory device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an optical information recording medium that is irradiated with a light beam and reproduces information from the reflected light, and an optical memory device using the same.

[Conventional technology]

This type of conventional optical memory device includes an optical information recording medium on which information is recorded, an optical head for reading information recorded on the optical information recording medium, and a digital reproduction signal from information read by the optical head. And a signal detection circuit for obtaining The optical head projects a laser beam onto the optical information recording medium, inputs the reflected light to output a reproduction signal, and the signal detection circuit converts the reproduction signal into a digital reproduction signal. . The signal detection circuit includes a peak position detection circuit for detecting a peak position of an information pulse in a reproduction signal, or an amplitude detection circuit for detecting a length and an interval of the information pulse. A digital reproduction signal can be obtained from the signal.

That is, as shown in FIG. 6, a recording mark shown in FIG. 6B is recorded on the optical information recording medium as the recording information for the digital data (a). Then, by reading the recording mark with an optical head, a reproduced signal (c) is obtained.
Is obtained. Here, if the signal detection circuit has a peak position detection circuit, the signal detection circuit to which the reproduction signal (c) is input receives a digital reproduction signal (d ) Is obtained. On the other hand, when the signal detection circuit has the amplitude detection circuit, the signal detection circuit obtains the digital reproduction signal (e) which becomes high level within a predetermined width with respect to the peak position in the negative direction. Then, digital data (f) as reproduction information is obtained from these digital reproduction signals.

[Problems to be Solved by the Invention]

However, the above-mentioned conventional configuration has a problem that it is difficult to increase the recording density and the recording capacity of the optical information recording medium.

That is, in the case of the above configuration, the size of the recording mark must be further reduced in order to increase the recording density of the optical information recording medium. However, the smaller the recording mark, the more difficult it becomes to record on the optical information recording medium. For example,
When recording a recording mark by converging the laser light on the optical information recording medium, the smaller the recording mark is, the more appropriate the recording mark may be formed depending on the degree of narrowing down of the laser beam, the characteristics of the optical information recording medium, and the ambient temperature. It will be difficult. This is also the case when the recording mark is formed by transfer, and it is particularly difficult when the recording mark is transferred by plastic molding. Therefore, it is difficult to increase the recording density by reducing the size of the recording mark, and the conventional configuration is not suitable for increasing the recording density. For convenience of explanation, the recording mark is described as an isolated mark corresponding to one code, but the recording mark is made to correspond to a plurality of codes and is formed to have the same size as the portion other than the recording mark. Even in the case, similarly, it is insufficient in terms of increasing the recording density.

An object of the present invention is to provide an optical information recording medium which can be easily transferred at the time of molding and can be highly densified, and an optical memory device using the same.

[Means for solving the problem]

The optical information recording medium according to the first aspect of the present invention has two optical codes, a first code and a second code, depending on the increase / decrease in the amount of light incident on the optical head due to diffraction of a light beam projected from the optical head at a recording mark. In the optical information recording medium configured to represent digital information represented by the code No. 1, the first recording mark having a width wider than the focused spot of the light beam and the second recording mark having a width narrower than the first recording mark are provided. When the mark is irradiated with the light beam, an information pulse corresponding to the second code is generated in the reproduction signal at the end portion of the first recording mark due to the diffraction of light, and at the portion other than the end portion, the information pulse is generated. A reproduction signal corresponding to the first code is generated, and when the second recording mark is irradiated with the light beam, the reproduction signal corresponding to the second code is generated due to diffraction of light, and the first and second recording marks are generated. Unrecorded portion which is not formed, when the light beam is irradiated, and wherein the resulting reproduced signal corresponding to the first code.

Further, in the optical memory device according to the invention of claim 2, the light beam projected from the optical head is applied to the recording mark on the optical information recording medium, and the amount of light incident on the optical head is reduced by the diffraction of the light at the recording mark. In an optical memory device that records and / or reproduces digital information composed of two codes, a first code and a second code, by increasing or decreasing, the optical information recording medium includes a first recording mark and the first recording mark.
A second recording mark having a width narrower than that of the recording mark, and when the first recording mark is irradiated with the light beam, the first recording mark corresponds to the second code by diffraction of light at an end portion of the first recording mark. A reproduced information signal is generated in a reproduced signal, and a reproduced signal corresponding to the first code is generated in a portion other than the end portion. When the second recording mark is irradiated with the light beam, the second recording mark is generated by diffraction of light. When a reproduction signal corresponding to a second code is generated and the unrecorded portion where the first and second recording marks are not formed is irradiated with the light beam,
An optical head for producing a reproduction signal corresponding to the first code, and irradiating a focused spot of the light beam with a diameter smaller than the width of the first recording mark and larger than the width of the second recording mark; The reproduction signal obtained from the optical head is compared with a reference value to detect the end portion of the first recording mark and the second recording mark as the second code, and the portion other than the end portion of the first recording mark and the unrecorded portion. And a signal detecting circuit for detecting the reproduced signal as a first code and converting the reproduced signal into a digital reproduced signal.

[Action]

According to the invention of claim 1, the light beam projected from the optical head is reflected, and the first code, for example, “0” and the second code are calculated from the increase and decrease of the incident light amount of the reflected light on the optical head. That is, in an optical information recording medium that represents digital information composed of two codes of "1", a first recording mark wider than the focused spot of the light beam and a second recording mark narrower than the focused spot of the light beam. And two types of recording marks are formed.

Specifically, for example, when both recording marks are formed to be convex toward the light beam in the incident direction, the first recording mark is formed to be longer and wider than the diameter of the focused spot of the light beam, On the other hand, the second recording mark is formed with a width that is longer and narrower than the diameter of the focused spot.

When the light beam is irradiated, at the end of the first recording mark, the reproduction signal level is lowered by the diffraction of light, and an information pulse corresponding to the second code is generated in the reproduction signal. In addition, a reproduced signal corresponding to the first code is generated in a portion other than the end portion. Furthermore, by the irradiation of the light beam, the reproduction signal level of the second recording mark is lowered by the diffraction of light, and the reproduction signal corresponding to the second code is generated, whereby the first and second recording marks are generated. In a non-recorded portion in which is not formed, a reproduced signal corresponding to the first code is generated.

Therefore, each recording mark can include a large amount of information, so that the recording density can be increased. Further, by forming the recording marks as described above, when the recording density is the same, it becomes easier to form the recording marks into a shape suitable for molding as compared with the conventional technique, and the recording marks can be formed even in plastic molding. Can be easily transferred.

Further, according to the invention of claim 2, the light beam projected from the optical head is reflected, and the first code, for example, “0”, and the second code are calculated from the increase / decrease of the incident light amount of the reflected light on the optical head. That is, in an optical memory device using an optical information recording medium configured to represent digital information composed of two codes of "1", the optical information recording medium has a width wider than the focused spot of the light beam. Two types of recording marks are formed: a first recording mark and a narrow second recording mark.

In response to this, the optical head irradiates the optical information recording medium with a light beam having a focused spot whose diameter is smaller than the width of the first recording mark and larger than the width of the second recording mark. The optical head also generates a reproduction signal from the reflected light from the optical information recording medium and outputs the reproduction signal to the signal detection circuit. The signal detection circuit compares the reproduction signal with a reference value, detects the end of the first recording mark and the second recording mark whose reproduction signal level is lowered due to the diffraction, as a second code, The reproduction signal is converted into a digital reproduction signal and output by detecting the portion other than the end portion of the first recording mark where the reduction of the reproduction signal level due to diffraction does not occur and the unrecorded portion as the first code. In this way, it becomes possible to reproduce the optical information recording medium formed in the above shape.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS.

The optical memory device according to the present invention, as shown in FIG.
Optical disc 1 as an optical information recording medium, and optical head 2
And a signal detection circuit 3.

The optical disc 1 is movable with respect to the optical head 2. As shown in FIG. 2, the optical disc 1 has a recording mark A, which is a first recording mark as information shown in (i), and a second recording mark, with respect to digital data (h) as digital information. A certain recording mark B is recorded. The end of the recording mark A in the direction of relative movement with the optical head 2, that is, the edge, corresponds to one 1 surrounded by 0. Note that 0 represents the first code and 1 represents the second code. On the other hand, recording mark B
Indicates that the edge portion and the portion between the edge portions correspond to 1, and the recording mark B as a whole corresponds to 1111. On the other hand, the portion between the edge portions of the recording mark A and the non-marked portion which is an unrecorded portion other than the recording marks A and B correspond to 0.

The recording marks A and B are diffracted only when the laser beam as the light beam projected from the optical head 2 is applied to the edge portion, and the incident light amount on the optical head 2 is reduced. It is formed so as to generate an information pulse in the reproduction signal output from the optical head 2. Further, when the light beam projected from the optical head 2 is irradiated between the recording mark B and the both edge portions, the amount of light incident on the optical head 2 is reduced due to the diffraction of the light and the optical head 2
It is formed to have a width narrower than the recording mark A so that the level of the reproduction signal output from the recording mark A may be lower than the reference value. That is, when the recording marks A and B are so-called pits protruding in the incident direction of the laser light from the optical head 2, the edge and non-mark of the laser light projected on the edge of the recording mark A Diffraction of light between the optical head 2 and the area occurs, the amount of light incident on the optical head 2 decreases, and a negative information pulse is generated at the output of the optical head 2. Further, in the recording mark B, diffraction similar to that of the edge portion of the recording mark A occurs at the edge portion thereof, and also between the edge portion and the non-mark portion, the optical head 2
Output becomes a negative level over the entire length of the recording mark B.

The optical head 2 is a recording mark A on the optical disc 1.
The laser light having the focused spot 4 having a diameter smaller than the width of the recording mark B and larger than the width of the recording mark B is projected onto the optical disc 1, and the reflected light is input to output the above-mentioned reproduction signal. There is. The optical head 2 has a photodetector (not shown) for converting incident light into an electric signal, and outputs a reproduction signal at a level corresponding to the amount of the reflected light.

The signal detection circuit 3 detects the information pulse of the reproduction signal input from the optical head 2 and a portion having a reference value or less between the information pulses as a second code 1, and converts the reproduction signal into a digital reproduction signal. . That is, the signal detection circuit 3
Has a peak position detection circuit for detecting the peak position of the information pulse in the reproduction signal, and an amplitude detection circuit for detecting the length and interval of the information pulse equal to or less than the reference value. A digital reproduction signal can be obtained from the.

In the above configuration, when the laser light projected from the optical head 2 is incident on the non-marked portion of the optical disc 1 other than the recording marks A and B, this light is reflected almost as it is and is incident on the optical head 2. As a result, the reproduction signal (j) output from the optical head 2 becomes high level, as shown in FIG. When the edge portion of the recording mark A on the optical disc 1 is irradiated with the above laser light, the reflected light from the recording mark A and the non-mark portion interfere with each other to cause light diffraction. Accordingly, the amount of reflected light incident on the optical head 2 decreases, and a negative direction information pulse is generated in the reproduction signal (j). This is because the diffraction efficiency at the edge portion is higher than that at other portions. Further, when the laser light is irradiated between the edge portions of the recording mark A, there is almost no diffraction of the reflected light, and the reproduction signal (j) becomes high level.

On the other hand, when the edge portion of the recording mark B on the optical disc 1 is irradiated with the laser beam projected from the optical head 2, the reproduction signal (j) is generated as in the case of the recording mark A.
An information pulse in the negative direction is generated at. Further, when the laser light is irradiated between the edge portions of the recording mark B, the diameter of the focused spot 4 of the laser light is larger than the width of the recording mark B, so that the reflected light is diffracted and the reproduction signal ( The level is lower than the reference value of j).

Here, FIGS. 3 to 5 show an example of the result of computer simulation on the reproduced signal.

FIG. 3 is an explanatory diagram showing the relationship between the recording mark C and the focused spot 4 in the computer simulation for the reproduced signal of FIGS. 4 and 5. In the figure, for example, the recording mark C has a length of 4 μm, a width of W, a curved portion of the edge portion is a semicircle with a radius of W / 2, and a depth or height in the direction perpendicular to the paper surface is D. The focused spot 4 is a Gaussian beam, and its radius (radius in a circle that becomes 1 / e ² times the beam center intensity) is 0.65 μm. Focusing spot 4
Is the major axis direction of the recording mark C, and the center distance between the center of the recording mark C and the condensing spot 4 is shown in the upper part of FIG. Further, the refractive index of the substrate of the optical disc 1 on which the recording mark C is formed is 1.5, the pitch between adjacent tracks in the longitudinal direction of the paper is 1.6 μm, and the aperture ratio of the objective lens is 0.5.
5. The wavelength of the laser beam forming the focused spot 4 is 0.78μ
m.

FIG. 4 shows that the depth or height D of the recording mark C is D = 0.
The simulation result when it is 13 μm is shown. In the graph of FIG. 5, the horizontal axis is the scanning direction of the light-converging spot 4, and indicates the distance between the center of the recording mark C and the center of the light-converging spot 4. The vertical axis indicates the intensity of the reproduction light incident on the photodetector. However, it is standardized by the amount of light when there is no light interference. At the photodetector, a reproduction signal corresponding to this can be obtained. The width W of the recording mark C (the size twice the radius of the curved portion of the edge portion) is 0.4 μm, 0.6
.mu.m, 0.8 .mu.m, 1.0 .mu.m, 1.4 .mu.m and 1.8 .mu.m were set, and reproduced waveforms were simulated for these seven types. As a result, when W = 1.4 μm and 1.8 μm, the recording mark C
The pulse was remarkable at the edge part of.

FIG. 5 shows the depth or height D of the recording mark C.
Shows the simulation result when D = 0.065 μm. Comparing this figure with FIG. 4 described above, although the signal amplitude is generally reduced, the overall tendency is the same as in FIG.

According to the result of the above simulation, the recording mark C
For a depth or height D of about 0.13 μm, the information pulse can be increased. This is obtained by the equation for maximizing the effect of diffraction, n × d × 2 = λ / 2, where n is the refractive index of the substrate, d is the depth or height of the recording mark C, and λ is the wavelength of the laser beam. When the depth or height D of the recording mark C is 0.13 μm, the information pulse at the edge portion of the recording mark C is maximum.

Regarding the width W of the recording mark C (the size twice the radius of the curved portion of the edge portion), W = 1.8 μm and 1.4 μm
, The information pulse is significant, and W = 1.0 μm and
It can be seen that even at 0.8 μm, the pulse at the edge still remains, and the level at the center of the recording mark C gradually decreases.

Further, this simulation was carried out under the conditions as described above. In addition to this, if the conditions such as the refractive index of the glass substrate, the wavelength λ of the laser light, or the aperture ratio of the objective lens are changed, Naturally, the optimum width and depth or height of the recording mark C also changes accordingly.

Next, the reproduction signal (j) is input to the signal detection circuit 3,
From the peak position detection circuit, a digital reproduction signal (k) whose rising portion coincides with the negative peak position in the information pulse of the reproduction signal (j) is obtained. on the other hand,
From the amplitude detection circuit, a digital reproduction signal (1) having a high level within a predetermined width is obtained with respect to a negative peak position in the information pulse of the reproduction signal (j) and a portion having a level lower than the reference value. Since the pulses of these digital reproduction signals (k) and (l) correspond to 1 of the digital data (h), both signals (k) and (l) are
From this, digital data (m) as reproduction information is obtained.

〔The invention's effect〕

As described above, the optical information recording medium according to the invention of claim 1 has two types of recording marks, that is, the first recording mark having a width wider than the focused spot of the light beam and the second recording mark having a width narrower than that of the light beam. In response to the irradiation of the light beam, at the end of the first recording mark and at the second recording mark, a second code is generated in the reproduced signal due to the reduction of the reproduced signal level due to the diffraction of light, and the first recording is also performed. In the portion other than the end portion of the mark and the unrecorded portion where the first and second recording marks are not formed, the diffraction is small and a reproduction signal corresponding to the first code is generated.

Therefore, the recording density can be increased, and the recording capacity can be increased. Further, since the recording density is not increased by simply downsizing the recording mark, the recording mark can be formed large. Therefore, it is easy to form the recording mark into an appropriate shape, and, for example, it is possible to easily transfer the recording mark even in plastic molding or the like.

In the optical memory device according to the second aspect of the present invention, as described above, the optical recording medium has the first recording mark wider than the focused spot of the light beam and the second recording mark narrower than the focused spot of the light beam. Two kinds of recording marks are formed, and correspondingly,
The optical head is smaller than the width of the first recording mark,
A light beam having a focused spot with a diameter larger than the width of the second recording mark is applied to the optical information recording medium, and a reproduction signal from the optical head is compared with a reference value by a signal detection circuit to cause the diffraction. The end of the first recording mark and the second recording mark whose reproduction signal level is lowered by the second
The portion other than the end portion of the first recording mark and the unrecorded portion, which are detected as a code and in which the reproduction signal level is not lowered due to the diffraction, are detected as the first code.

Therefore, it becomes possible to reproduce the optical information recording medium having the above-mentioned shape.

[Brief description of drawings]

1 to 5 show an embodiment of the present invention. FIG. 1 is a block diagram showing a main part of an optical memory device, and FIG. 2 is a record mark and a signal waveform in each part of the optical memory device. FIG. 3 is an explanatory view showing the relationship between the recording mark and the focused spot in the computer simulation for the reproduction signal shown in FIGS. 4 and 5, and FIG. 4 is the depth of the recording mark. Or height 0.13μ
FIG. 5 is a graph showing the results of computer simulation when m is set to m, and FIG.
FIG. 6 is a graph showing the result of the computer simulation when the thickness is 065 μm, and FIG. 6 is an explanatory diagram showing the relationship between the recording mark and the signal waveform in each part of the optical memory device, showing a conventional example. 1 is an optical disk (optical information recording medium), 2 is an optical head,
3 is a signal detection circuit.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Takeshi Yamaguchi 22-22 Nagaike-cho, Abeno-ku, Osaka, Osaka Within the corporation

Claims (2)

[Claims] 1. Digital information consisting of two codes, a first code and a second code, is represented by increasing or decreasing the amount of light incident on the optical head due to diffraction of a light beam projected from the optical head at a recording mark. In such an optical information recording medium, a first recording mark having a width wider than a focused spot of the light beam and a second recording mark having a width narrower than the focused spot of the light beam are provided, and the first recording mark is irradiated with the light beam. When done,
At the end of the first recording mark, an information pulse corresponding to the second code is generated in the reproduction signal by light diffraction, and at the portion other than the end, the reproduction signal corresponding to the first code is generated, The two recording marks are irradiated with the above light beam,
A reproduction signal corresponding to the second code is generated by light diffraction, and the unrecorded portion where the first and second recording marks are not formed corresponds to the first code when irradiated with the light beam. An optical information recording medium characterized by generating a reproduction signal. 2. A light beam projected from an optical head is applied to a recording mark on an optical information recording medium, and the amount of light incident on the optical head increases or decreases due to the diffraction of light at the recording mark. In an optical memory device for recording and / or reproducing digital information composed of two codes, a code and a second code, the optical information recording medium comprises a first recording mark and a first recording mark narrower than the first recording mark. Two recording marks, the first recording mark is irradiated with the light beam,
At the end of the first recording mark, an information pulse corresponding to the second code is generated in the reproduction signal by light diffraction, and at the portion other than the end, the reproduction signal corresponding to the first code is generated, The two recording marks are irradiated with the above light beam,
A reproduction signal corresponding to the second code is generated by light diffraction, and the unrecorded portion where the first and second recording marks are not formed corresponds to the first code when irradiated with the light beam. An optical head which produces a reproduction signal and irradiates a focused spot of the light beam with a diameter smaller than the width of the first recording mark and larger than the width of the second recording mark, and a reproduction signal obtained from the optical head. Is compared with a reference value to detect the end of the first recording mark and the second recording mark as the second code, and the part other than the end of the first recording mark and the unrecorded part as the first code. And an optical memory device including a signal detection circuit for converting the reproduction signal into a digital reproduction signal.