JP2778428B2 - Optical disk drive - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of recording information on an optical disk in which the effective spot diameter of an irradiation laser beam is reduced by a mask layer made of a light transmittance variable medium whose light transmittance changes due to a change in irradiation light intensity or temperature. Alternatively, the present invention relates to an optical disk device for reproducing information recorded on the optical disk.

[0002]

2. Description of the Related Art In recent years, an increase in the capacity of an optical disk has been studied.
Various proposals have been made. Generally, an optical disc can form a recording mark smaller than the diameter of a light spot by controlling the intensity of a laser beam at the time of recording. Therefore, there is no limit in principle to the improvement of the density at the time of recording. But,
The diameter of the light spot when the laser beam is narrowed by a lens has a limit value that cannot be narrowed below a certain value, and increasing the density of an optical disk depends on how small the reproduction laser spot is.

Here, the repetition wavelength (recording wavelength) of a recording mark at the reproduction limit is λ / 2NA (λ is the wavelength of light, NA
Is given by the numerical aperture of the lens. From this equation, in order to identify and reproduce a recording mark with a shorter recording wavelength,
It can be seen that reproduction with light having a short wavelength λ or use of a lens having a large numerical aperture NA may be performed. However, it is technically difficult to shorten the wavelength of a semiconductor laser used for reproduction, and it is not easy to incorporate a lens having a large numerical aperture NA into an optical disk device.

Therefore, a substance whose light transmittance is increased by a temperature rise due to light irradiation is provided in a layered manner in the optical disk, and only the central part of the light irradiated part is made light transmissive when recording or reproducing information on the optical disk. A method of reproducing information recorded at high density on an optical disk by masking another portion in a light spot has been conventionally known.

As one of the high-density recording techniques for such optical discs, a mask layer made of a temperature-dependent variable light transmittance medium is provided on a light-transmitting substrate, and a light spot on a light spot on the optical disc advances. Japanese Patent Application Laid-Open No. 5-12673 discloses a technique for reducing the apparent light spot diameter by utilizing the fact that the temperature is high in the rear part in the direction. According to this gazette, the optical dependency of the temperature-dependent variable light transmittance medium is reduced from the optical disk by utilizing the fact that the reflectance of the low light transmittance portion is sufficiently lower than the reflectance of the high light transmittance portion. By controlling the output laser power so that the amount of light from the photodetector that monitors the reflected light of the laser beam is always constant, the area ratio of the portion with high light transmittance in the entire area of the light spot is constantly controlled. Can be. Also, with respect to recording, high-density optical recording can be performed by using a recording layer capable of recording at a temperature lower than the change in shape of the variable light transmittance medium.

[0006]

However, while repeating the experiment of high-density recording and high-density reproduction on an optical disk based on the above-mentioned prior art, an area where high-density recording was performed with an optimum recording light intensity was optimized. It has been found that it is not sufficient to keep the amount of reflected light constant in order to reproduce the image while exerting a mask effect with the intensity. This is because the higher the density of the recording medium, the smaller the mark size for forming an information signal, and the deviation of the time axis component of the reproduction signal (so-called jitter component) is greatly affected by the recording light intensity and the reproduction light intensity. Because it is subject to

Generally, an information signal is composed of a combination of signals that are temporally integral multiples within a certain range with respect to a reference frequency, as is conventionally known in a recording method of a compact disk (CD). Pit length is 3 for CD
It consists of a combination of information signals in the range from T to 11T, where 3T is the shortest pit length and 11T is the longest pit length. In a high-density optical disk system, assembling an information signal using a combination of a recording mark having a short mark length and a recording mark having a long mark length is also advantageous for achieving consistency with the CD method.

However, when information is recorded at a high density on an optical recording / reproducing optical disk provided with a mask layer using the above-mentioned variable light transmittance medium, the information is formed by the light intensity of the recording laser beam irradiated as shown in FIG. The length of the mark to be performed differs. 11A to 11C show the light intensity distribution of the recording laser light, 12A to 12C show the recording marks recorded on the recording layer at that time, and 11A and 12A show the recording laser light having a low light intensity. , 11B and 12B show the cases where the recording laser light with the appropriate light intensity is used, and 11C and 12C show the cases where the optical laser light with the high light intensity is used. Also, at the time of reproduction, good reproduction cannot be performed unless the effect of reducing the spot diameter by the mask layer is exhibited. As a result, by providing the mask layer, a recording mark having time information which should be originally output as a reproduction signal is reproduced as different information which is not the same, which causes an increase in errors. If the reproduction light intensity is not optimized, the effect of reducing the spot diameter is not sufficiently exhibited, and the pit adjacent to the pit to be reproduced or the pits before and after the pit cannot be reproduced correctly. When recording at a high density like this or when reproducing by reducing the diameter of the irradiation spot,
Since a small change in the pit length has a large effect, it does not matter for CD density information, but it also becomes a major problem for high density information, and it is necessary to optimize both recording light intensity and reproduction light intensity. is there.

Therefore, the present invention has been made in view of the above points, and an accurate reproduction signal can be obtained even if information is recorded or reproduced at a high density on an optical disk provided with a variable light transmittance medium layer. It is an object of the present invention to provide an optical disk device capable of performing the above.

[0010]

According to the present invention, as a means for achieving the above object, a light-transmitting substrate having a guide groove formed concentrically or spirally and a light having a specific wavelength or heat of light are used. A mask layer for reducing the effective spot diameter of the laser beam irradiated from the device side by utilizing the fact that the light transmittance is reversibly changed by absorption, and an optical recording / reproducible information recording layer are at least in this order. An optical disc device that records information on a stacked optical disc using recording marks having different lengths according to recording signals, and reproduces the recorded information by detecting the mark length of the recording mark recorded on the optical disc. Before performing a recording operation on the optical disc, a predetermined position on the optical disc is irradiated with a recording laser beam to record a test recording signal. An optical disc apparatus is provided, wherein the irradiation light intensity of the recording laser light is set so that the difference between the mark length obtained by reproduction and the mark length that the recorded signal originally has should be minimized. It is assumed that.

[0011]

Embodiments of the present invention will be described below with reference to the accompanying drawings. First, an optical disk used in the optical disk device according to the embodiment of the present invention will be described. FIG.
FIGS. 2A and 2B are diagrams showing a structure of an optical disk used in the optical disk device according to the embodiment of the present invention. FIG. 2A shows a configuration of a signal recording area of the optical disk, and FIG. It is a figure which shows the structure of the cross section of a radial direction. As shown in FIG. 1A, an innermost portion of the optical disc 1 has a region 4 which becomes a lead-in signal area after recording, and an outermost portion has an area 5 which also becomes a lead-out signal region. Here, a part 6 of the innermost part of the innermost part is a part used as the preliminary recording area 6 in this embodiment. The lead-in signal area 4 and the preliminary recording area 6 are not always required to be provided at the innermost circumference. However, in the current optical disk system, since they are provided at the innermost circumference, the current system In consideration of the compatibility with, for example, it is preferable to be provided at the place where the data is reproduced first on the optical disk, that is, at the innermost circumference.

As shown in FIG. 1B, the optical disk 1 is a recordable optical disk, and a tracking groove 3 is formed on the optically transparent substrate 2 as concentric circles as minute irregularities. It is provided continuously in a shape or a spiral shape. Then, a mask layer 7 whose light transmittance changes reversibly by absorbing light of a specific wavelength is formed on the substrate 2. On this mask layer 7, a laser beam irradiated from the apparatus side is formed. A recording layer 8 that can be optically recorded by absorbing a suitable amount to cause a geometrical change or an optical change is provided, and a reflective layer 9 and a protective layer 10 are sequentially laminated on the recording layer 8. Structure.

As is well known, various types of light-transmitting substrates of the optical disk 1 can be used, such as glass, epoxy resin, polycarbonate resin, polymethacrylate resin, and amorphous polyolefin resin. Any of these can be used if they have good transparency. Here, the method for forming the tracking groove on the substrate 2 is not particularly limited. A method of applying a photoresist on a polished glass master, recording grooves as continuous grooves with a recording laser, developing, forming a conductive film, forming a stampa by plating, and obtaining a substrate 2 by injection molding, It is also possible to use any method such as an etching method, a so-called 2P method, and a stamping method using an ultraviolet curable resin.

A mask layer 7 which is a light transmittance variable medium is laminated on the substrate 2, and the mask layer 7 is made of, for example, a light beam as disclosed in Japanese Patent Application No. 4-330149. Dependent light transmittance variable medium, spiropyran,
A temperature-dependent light transmittance variable medium such as a lactone or a fluoran dye is used, and is formed by using an appropriate thin film forming means such as a vacuum evaporation method and a spin coating method. Here, these light transmittance variable media have the light transmittance characteristics shown in FIG. 2A, and when the intensity of the laser light irradiated through the substrate 2 becomes higher than the saturation light intensity, the light transmittance sharply increases. As a result, the effective spot diameter of the irradiated laser beam can be reduced as shown in FIG. In addition, these substances have absorption in a specific wavelength region at room temperature, and the absorption wavelength varies depending on the temperature rise and irradiation light intensity.Therefore, if an appropriate substance is selected according to the laser light wavelength used for recording / reproduction. good.

The recording layer 8 formed on the mask layer 7 is not particularly limited as long as it is a commonly used optically recordable / reproducible substance. In order to prevent deformation, a medium capable of recording at a lower temperature than the shape change of the light transmittance variable medium is used. And this recording layer 8
Is formed from a recordable substance used in a hole-forming method, a phase-change method, a magneto-optical method, a shape-changing method, or the like by using an appropriate thin film forming means such as sputtering, vacuum deposition, and spin coating.

A reflective layer 9 made of aluminum or the like is provided on the recording layer 8 by means such as vacuum evaporation or sputtering, and a protective film made of an ultraviolet curable resin or the like is further laminated thereon. That is, the optical disk 1 is a reflection type optical disk, which facilitates compatibility with the current optical disk system.

The optical disk 1 configured as described above is
At the time of recording, the mask layer 7 is formed using the area A in FIG.
It is possible to perform high-density recording using a portion having a high transmittance, that is, a spot reduced by a mask effect, or to perform recording without using a mask effect using a region B in FIG. . However, in any case, it is very important to optimize the light intensity. If recording is not performed with an appropriate light intensity, accurate recording and reproduction cannot be performed. Therefore, it is necessary to adjust the reproduction light intensity and the recording light intensity in the preliminary recording / reproduction area 6. Hereinafter, an optical disk device of the optical disk 1 will be described.

FIG. 4 is a schematic configuration diagram of an optical disk device according to one embodiment of the present invention. Optical disc device 21 shown in FIG.
An optical head 22 for irradiating the optical disk 1 with a laser beam for recording or reproduction, an amplification circuit 23 for amplifying a reproduction signal reproduced by the optical head 22,
A mark length-voltage conversion circuit 24 for converting the reproduction signal output from the amplifier circuit 23 into a voltage corresponding to the mark length,
A comparison circuit 25 that compares the voltage value output from the mark length-voltage conversion circuit 24 with the voltage value generated from the reference signal voltage generation circuit 26 and generates an output signal according to the comparison result; The reference voltage generation circuit 26 stores a reference voltage value corresponding to the mark length of the mark, and an amplitude detection circuit 27 that detects the amplitude of the reproduction signal output from the amplification circuit 23 and outputs a signal according to the result. A laser driver 3 for irradiating a recording laser beam obtained by optically modulating a recording signal or an output signal of a test signal generation circuit 29 with the light intensity adjusted by the light intensity adjustment circuit 28 from the optical head 22.
0, an optical head driving means 31 for moving the optical head 22 in the radial direction of the optical disk 1 and focusing the irradiation laser light, a control circuit 32 for controlling the operation of the optical disk device 21, and a RAM (Random Accesses).
s Memory).

Next, the operation of the optical disk device 21 will be described with reference to the flowcharts shown in FIGS. FIG. 5 is a flowchart showing the operation of the optical disc device 21 for finding the optimum reproduction light intensity. FIG. 6 is a flowchart showing the operation of the optical disc device 21 for finding the optimum recording light intensity. In the optical disk device 21, when the optical disk 1 is mounted, an optical disk detection signal is input to the control circuit 32 from an optical disk detection unit (not shown). When the optical disk detection signal is input, the control circuit 32 outputs a driving signal 40 to the optical head driving means 31 to move the optical head 22 to the preliminary recording / reproducing area 6 (P1), and to apply the focus servo (P2). Then, the preliminary recording area 6 is reproduced (P3). When the preliminary recording / reproducing area 6 is reproduced for the first time after the optical disc 1 is loaded, the tracking servo is not applied, and the reproduced signal is a tracking error groove bridging signal. To set the optimum reproduction light intensity.

In the state where the focus servo is first applied, the light intensity of the reproduction laser light is higher than the optimum value. Therefore, the control circuit 32 slightly reduces the reproduction light intensity (P4), and then detects the amplitude. The drive signal 41 is output to the circuit 27 to detect the signal amplitude of the cross-groove signal, and it is detected whether the signal amplitude of the tracking error cross-groove signal has increased (P5). The operations of P4 and P5 are performed until the tracking error signal amplitude does not increase. At P5,
When it is detected that the tracking error signal amplitude does not increase, the intensity of the reproduction light is slightly increased (P6), and then it is detected again whether the signal amplitude of the tracking error groove bridging signal has increased (P7). ). In P7, the reproduction light intensity when the tracking error signal amplitude does not increase becomes the optimum reproduction light intensity. Then, the set optimal reproduction light intensity is stored in the memory 33 (P8). Reproduction of a recording mark recorded on the optical disc 1 is performed using a reproduction laser beam set to the optimum reproduction light intensity.

After the optimum reproduction light intensity is determined, the optimum recording light intensity is set. In FIG. 6, after the tracking servo is applied (P9), the control circuit 32 outputs a drive signal 43 to the test signal generation circuit 29 to record a test recording mark in the preliminary recording area 6 of the optical disc 1. Is generated (P10). The laser driver 30 optically modulates the test signal generated from the test signal generation circuit 29, and a recording mark corresponding to the test signal is recorded in the preliminary recording area 6 (P11).

After recording the recording mark corresponding to the test signal in the preliminary recording area 6, the control circuit 32 reads out the optimal reproduction light intensity set previously from the memory 33, drives the light intensity adjustment circuit 28, and drives the laser. The light intensity is set, and the recording mark recorded in the preliminary recording area 6 is reproduced with the optimum reproduction light intensity (P12). Then, after binarizing the reproduced signal, the mark length by the drive signal 44 - it is converts by operating the voltage converter 24 to the reproduction signal voltage E ₁ corresponding to the mark length to the comparison circuit 25. Further, the control circuit 3
2 outputs the drive signal 45 to the reference voltage generation circuit 45,
So as to output the reference signal voltage E ₂ corresponding to the mark length of the test signal generated by the test signal generating circuit 29 to the comparison circuit 25. A reproduction signal voltage E _1, the reference signal voltage E
_The comparison circuit 25 to which ₂ has been input calculates E ₂ −E ₁ and outputs the result to the control circuit 32 (P13).

[0023] In the control circuit 32, when the reproduction signal voltage is greater than the reference signal voltage, i.e., when E ₂ -E ₁ is negative are the recording light intensity excessive, the light intensity adjustment circuit 28 To reduce the recording light intensity slightly (P1
4). Conversely, when the reproduction signal voltage is smaller than the reference signal voltage, that is, when E ₂ −E ₁ is positive, the recording light intensity is insufficient. Is slightly increased (P15). Then, the same recording mark as the above-mentioned recording mark is recorded again in the preliminary recording area 6 with the recording laser beam having the light intensity set by the light intensity adjusting circuit 28 (P11). Then, the above P11 to P11 are calculated until the calculation result of the comparison circuit 25 becomes closest to zero.
The operation up to 15 is repeated.

By the above operations P11 to P15,
E ₂ -E ₁ is stored in the memory 33 as the optimum recording light intensity recording light intensity when began to take the smallest value (P16). Recording of information on the optical disk 1 is performed using the laser beam having the optimum recording light intensity.

It should be noted, by performing the operation until the P11～P15, it is desirable to control as E ₂ -E ₁ is 0, difficult as a practical matter, also, time to the optimum recording light intensity setting Therefore, an allowable range A (A is a positive real number) is set in advance, and E ₂ −E ₁ becomes −A <E ₂ −E ₁
<A may be controlled. The test signal generated from the test signal generation circuit 29 in P10 may be a recording signal of a recording mark (for example, one having the shortest mark length) most susceptible to the influence of the mask layer 7. The recording signals of all types of recording marks recorded on the top (for example, like a current CD,
If the recording mark is composed of a combination of signals that are an integral multiple of time within a certain range with respect to the reference frequency, such as 3T to 11T, the recording signals of all types of recording marks having mark lengths of 3T to 11T). There may be. In that case,
The above-mentioned operations P10 to P15 are performed for each recording signal to obtain the optimum recording light intensity, and the average value of these is stored. Further, it goes without saying that the optical disk device 21 can be used not only in a recording / reproducing device that performs both recording and reproduction, but also in a recording device that performs only recording.

[0026]

As described above, according to the optical disk apparatus of the present invention, by providing a mask layer, the mark length of a recording mark that fluctuates can be kept appropriate, and errors during reproduction can be reduced. Thus, there is an effect that high-density recording and reproduction can be performed smoothly and accurately.

[Brief description of the drawings]

FIG. 1 is a diagram showing a structure of an optical disk used in an optical disk device according to one embodiment of the present invention.

FIG. 2 is a diagram illustrating light transmittance characteristics of a light transmittance variable medium.

FIG. 3 is a diagram illustrating a state in which a recording mark length varies depending on the light intensity of a recording laser beam.

FIG. 4 is a schematic configuration diagram of an optical disk device according to an embodiment of the present invention.

FIG. 5 is a flowchart showing a part of the operation of the optical disk device shown in FIG. 4;

6 is a flowchart showing a part of the operation of the optical disk device shown in FIG.

[Explanation of symbols]

 Reference Signs List 1 optical disk 2 substrate 3 groove (guide groove) 4 lead-in area 5 lead-out area 6 preliminary recording area 7 mask layer (variable light transmittance medium) 8 recording layer 9 reflection layer 21 optical disk device 22 optical head 24 mark length-voltage conversion Circuit 25 Comparison circuit 26 Reference voltage generation circuit 27 Amplitude detection circuit 28 Light intensity adjustment circuit 29 Test signal generation circuit 30 Laser driver 32 Control circuit 33 Memory

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁶ , DB name) G11B 7/00 G11B 7/125

Claims (2)

(57) [Claims] 1. A light transmitting substrate having a guide groove formed concentrically or spirally, and a light transmittance of a specific wavelength being reversibly changed by absorbing light or heat of light. Recording marks having different lengths according to recording signals are formed on an optical disk on which at least a mask layer for reducing the effective spot diameter of a laser beam irradiated from the device side and an information recording layer capable of optical recording and reproduction are laminated in this order. In the optical disc apparatus for recording information by the method and reproducing the information recorded by detecting the mark length of the recording mark recorded on the optical disc, before performing the recording operation on the optical disc, A recording laser beam is applied to a predetermined position to record a test recording signal, a mark length obtained by reproducing the recording signal, and the recorded recording signal which the recorded recording signal originally has. An optical disc device, wherein the irradiation light intensity of the recording laser light is set so that a difference from a mark length is minimized. 2. The optical disk device according to claim 1, wherein the optical disk irradiates the laser beam on the optical disk to record information and reproduces a recording signal recorded on the optical disk to output a reproduction signal. A light intensity adjustment circuit that adjusts the light intensity of laser light emitted from the optical head onto the optical disk; and a test signal generation circuit that generates a test recording signal before performing a recording operation on the optical disk. A voltage conversion circuit that detects a mark length of a reproduction signal output from the optical head, converts the mark length into a voltage according to the detection result, and outputs the converted voltage as a reproduction signal voltage; and the test recording signal. A reference voltage generation circuit that outputs a voltage corresponding to the mark length as a reference voltage, a reproduction signal voltage output from the voltage conversion circuit, and an output from the reference voltage generation circuit. Optical disk apparatus characterized by comprising a comparator circuit for comparing the reference voltage, and a control circuit for the light intensity adjustment of the recording laser light by using the light intensity adjustment circuit based on the comparison result of the comparator circuit.