JP3934000B2 - Optical recording / reproducing device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical recording / reproducing apparatus, and in particular, irradiates a recording film of an optical recording medium such as an optical disc with a pulsed light beam (for example, laser light), changes an irradiation area to the recording film, and irradiates the recording film. The present invention relates to a technique effectively applied to an optical recording / reproducing apparatus that records a reproduction mark associated with information to be recorded by area information on the recording film and reproduces the reproduction mark using the reproduction mark.
[0002]
[Prior art]
As an information recording method of a conventional optical disc recording / reproducing apparatus, there are a pulse position modulation method (PPM) and a pulse width modulation method (PWM). Recording by pulse width modulation (PWM) is called mark edge recording.
[0003]
In the PWM recording (mark edge recording), a relatively short mark with a constant pulse width is recorded with various lengths of space, and recording information is assigned to both the mark length and the space length.
When the PWM recording is performed, a long mark is recorded as compared with the PPM recording. However, when a long mark is recorded on the phase change recording medium, the heat storage / heat radiation effect of the recording film and the variety of recording sensitivity cause the mark to be recorded. The width (dimension perpendicular to the track direction) may be non-uniform.
[0004]
Further, it is known that if a recording film is continuously irradiated with a recording light to form one long mark, excessive heat is accumulated in the second half of the long mark and the mark width is widened. For this reason, even when one mark is formed, a system (write strategy) in which the recording light is composed of a plurality of shorter pulses is employed. A method of forming each mark using a plurality of pulses and an optical recording / reproducing apparatus are disclosed in, for example, US Pat. No. 5,490,126 and US Pat. No. 5,636,194.
[0005]
Further, in the conventional optical disk recording / reproducing apparatus, when reproducing and recording / reproducing an optical disk with a circular spot laser, as shown in FIG. 5, a teardrop-shaped, elliptical or oval mark is reproduced or recorded. The mark position or mark edge is digital information.
[0006]
For example, as disclosed in Japanese Patent Application Laid-Open No. 2001-14676, a conventional optical disc recording / reproducing apparatus irradiates an optical disc (recording film of a recording medium) with a pulsed light beam (laser light), and the optical disc of the optical disc. The optical characteristic is changed, and a plurality of marks associated with information to be recorded are formed on the optical disc by the change information.
A recording pulse for forming the mark is generated, information for modulating the light beam is written by the recording pulse, and information is detected by detecting a change in optical characteristics of a portion including the mark formed on the optical disc. Reproduce.
[0007]
At least one test mark having a length equal to or longer than a selected length is written on the optical disc by the information writing means to generate mark data relating to the length, and the change of the optical characteristic is generated in the test mark. Determines whether or not there is a read error inducing portion that is not sufficient for reproduction of the test mark, and if it is determined that the read error inducing portion is present in the test mark, at least the When forming a mark having a length equal to or longer than the length of the test mark, the average value of the power of the light beam is increased from an initial setting level so that the read error inducing portion does not occur in the mark. Some have been proposed that perform the power correction.
[0008]
[Problems to be solved by the invention]
However, in the “means for correcting the power so that the reading error inducing portion does not occur in the mark” disclosed in Japanese Patent Application Laid-Open No. 2001-14676, the mark is formed so that the central portion of the mark shape is not thinned. In order to increase the width, the average value of the power of the light beam is increased from the initial setting level. For this reason, there is a problem that the entire mark becomes large and the setting of the interval for increasing the capacity is limited. Further, there is a problem that the means for correcting the irradiation power is complicated so that the reading error inducing portion does not occur in the mark.
[0009]
Also, in an optical disk recording / reproducing apparatus, when reproducing or recording / reproducing a teardrop-shaped, elliptical or oval mark using an optical head having a circular or elliptical spot shape, the reproduced signal waveform is a laser beam. It is affected by the spot shape and the mark shape on the optical disk. In particular, the mark edge shape affects the rising or falling slope of the waveform of the reproduction signal. Rising slope or falling slope is one of the important factors in signal detection and requires a steeper slope. That is, when increasing the density by reducing the mark interval in order to increase the capacity, in particular, the rising or falling steepness is required.
[0010]
An object of the present invention is to provide a technique capable of making a mark rising or falling sharp when the mark interval is narrowed to increase the density.
The above and other objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings.
[0011]
[Means for Solving the Problems]
The outline of the invention disclosed in the present application will be briefly described as follows.
According to a first aspect of the present invention, a recording film of a recording medium is irradiated with a pulsed light beam to change optical characteristics of the recording film, and reproduction marks associated with information to be recorded are changed by the change information of the optical characteristics. the recorded on the recording film of the run length in the run length limited (RLL) recording code to 1, an optical recording and reproducing apparatus for reproducing the reproducing mark, in order to form one of the play mark A recording pulse generating means for generating a plurality of pulses having a pulse height higher than that of other portions, and a recording medium based on the plurality of pulses generated by the recording pulse generating means. A light beam that irradiates the light beam so that the shape of the edge portion before and after one reproduction mark formed on the recording film is formed larger in the track width direction than the shape of the other portion Means morphism, the reproduction mark shape is larger than the shape of the other portions in the track width direction of the front and rear edges by the light beam irradiating means irradiates a beam spot, the level of the reproduced signal beam spot Reproduction means for obtaining a reproduction signal in which the rising edge of the reproduction signal waveform by the preceding edge portion and the falling edge of the reproduction signal waveform by the subsequent edge portion are steep by being proportional to the area of the reproduction mark covered with The rising and falling edges of the reproduced signal waveform at the time of mark edge detection are made steep.
[0015]
According to a second aspect , in the first aspect , the recording pulse generating means generates a plurality of pulses in which the pulse height and width of the preceding pulse and the subsequent pulse are larger than the pulse height and width of the other part. Features.
[0016]
The point of the present invention is that the amplitude is compensated by increasing the shape of the edge portion of the reproduction mark in the track width direction and making the rise or fall of the beam spot steep.
[0017]
The reproduction signal level of the optical disk is substantially proportional to the area of the mark covered with the beam spot. By slightly expanding the mark edge portion in the track width direction, the rising or falling edge of the reproduction waveform of the edge portion becomes steep, and the amplitude of that portion is compensated.
[0018]
1A and 1B are diagrams for explaining the shape of a reproduction mark according to the present invention. FIG. 1A is a conventional oval mark before compensation, and FIG. 1B is a mark according to the present invention. In FIG. 1, A (black part) is a region where the recording film is burned when the recording film is irradiated with laser light, B is a laser spot (beam spot) diameter, E is a mark edge width, and M is the present invention. The mark center width, M ₀ is the maximum width of the conventional mark in the track width direction, θ ₀ is the rising angle (or rising angle) of the conventional reproduction output signal waveform, and θ ₁ is the rising angle of the reproduction output signal waveform of the present invention ( (Or rising angle).
[0019]
Conventionally, in a phase change optical disc, if the laser power is not controlled well, a portion where the mark width is smaller than the laser spot B is formed as shown in FIG. There is a problem that the output of the reproduction signal is lowered, and it is generally used to control the laser power so as to compensate for the problem.
[0020]
In the present invention, as shown in FIG. 1B, the mark edge portion is enlarged by controlling the laser power. In the case of read-only, the mark edge portion is enlarged in advance. This method is different from this method, and rather uses the characteristics of a phase change optical disk (recording film).
[0021]
Dashed line portion has a maximum width M ₀ of the conventional mark, the mark of the present invention is to increase the edge portions than its width M _0. That is, when the mark center width of the present invention is M, B ≧ E ≧ M and M ₀ ≧ M ≧ B / 2. Further, when the rising angle (or rising angle) of the conventional reproduction output signal waveform is θ ₀ and the rising angle (or rising angle) of the reproduction output signal waveform of the present invention is θ1, θ ₀ <θ _{1 is obtained} , and the conventional mark Compared to the rise or fall of the reproduced output signal waveform at the time of edge detection, the rise or fall of the reproduced signal waveform at the time of mark edge detection according to the present invention becomes steeper.
[0022]
According to the means of the present invention, since the rising or falling edge of the reproduction signal waveform at the time of mark edge detection is made steep, the interval in the track width direction of the marks can be narrowed to increase the density.
Hereinafter, the present invention will be described in detail with reference to the drawings together with embodiments (examples) according to the present invention.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 2 is a block diagram showing a schematic configuration of the optical recording / reproducing apparatus according to the embodiment of the present invention. In FIG. 2, 1 is an optical disk, 2 is a spindle motor, 3 is a semiconductor laser, 4 is a condenser lens, 5 is an objective lens, 6 is a beam splitter, 7 is a detection lens, 8 is a photodetector, 9 is a reproduction amplifier, 10 is an analog / digital (A / D) conversion circuit, 11 is a demodulation circuit, 12 is a modulation circuit, 13 is a recording pulse generation circuit, and 14 is a light beam driving circuit.
[0024]
As shown in FIG. 2, the optical recording / reproducing apparatus of Embodiment 1 includes a spindle motor 2 that rotates an optical disc 1, a semiconductor laser 3 that generates a light beam that irradiates the optical disc 1, and a laser beam emitted from the semiconductor laser 3. A condensing lens 4 for condensing light, light from the condensing lens 4 is converged on the optical disc 1, an objective lens 5 for forming a light spot, and light reflected from the optical disc 1 is reflected in the light detection direction. From the beam splitter 6, a detection lens 7 that condenses the reflected light from the beam splitter 6 on the photodetector 8, a photodetector 8 that converts the reproduction light from the detection lens 7 into an electrical signal, and from the photodetector 8 A reproduction amplifier 9 for amplifying the output reproduction electric signal, an A / D conversion circuit 10 for converting an output signal from the reproduction amplifier 9 into digital data, and the A / D conversion circuit 10 Demodulating circuit 11 for converting the power into digital data, receiving the input data (Write Data), modulating circuit 12 for modulating the data, and generating a recording pulse based on the output of the modulating circuit 12 and the mark modulation data A circuit 13 and a light beam driving circuit 14 that receives the output of the recording pulse generation circuit 13 and modulates the laser light emitted from the semiconductor laser 1 are provided.
[0025]
FIG. 3 is a diagram for explaining the concept of conventional oval mark recording / reproduction and the concept of recording / reproduction of the present invention. Column A is a conceptual diagram of conventional oval mark recording / reproduction, and column B is the present invention. (A) is a recording data waveform, (b) is mark modulation data (recording laser emission pattern), (b ₁ ), (b ₂ ), (b ₃ ) are marks of the present invention. modulation data, (c) an optical disk (recording film) on the mark shape, a (d) shows reproduced output signal waveform.
[0026]
For example, in the case of an optical disc by thermal recording, the shape of the edge portion of the mark is shown in (b ₁ ) of FIG. 3B by increasing the laser power at the beginning of recording and / or at the end of recording. Thus, mark modulation data is obtained in which the pulse width of the preceding pulse and / or the pulse width of the subsequent pulse and / or the pulse width of the preceding and following pulses of the reproduction mark mark modulation data is larger than the pulse width of other portions.
[0027]
Further, the pulse height of the preceding pulse or the pulse height of the post-pulse and / or the pulse height of the preceding and following pulses of the mark modulation data of the reproduction mark shown in (b ₂ ) of FIG. Alternatively, mark modulation data larger than the pulse height of the other part can be obtained by lengthening the laser beam irradiation time at the end of recording.
[0028]
Also, the pulse height and width of the preceding pulse and / or the pulse height and width of the subsequent pulse and / or the pulse height of the preceding and following pulses of the mark modulation data of the reproduction mark shown in FIG. 3B (b ₃ ) width, by increasing recording beginning of and or laser power of the recording end portion and a laser light irradiation time, respectively, a large mark modulation data from the pulse height and width of the other portions is obtained.
[0029]
The reproduction signal waveform when reproducing with a laser beam of a circular beam spot using a conventional mark shape and when reproducing the mark shape according to the present invention with a laser of a similar circular beam spot is: The waveform is as shown in FIG.
[0030]
In the reproduced signal waveform with the mark shape of the present invention, the amplitude of the edge portion becomes large. That is, as can be seen from FIG. 3D, assuming that the inclination angle of the leading edge of the conventional reproduction signal waveform is θ ₀ and the inclination angle of the leading edge of the reproduction signal waveform of the present invention is θ ₁ , θ ₀ < the θ _1.
[0031]
If the track width is almost the same as the conventional mark shape, the amplitude of the edge portion will increase, so the playback spot will be circular, so the rise or fall of the mark edge portion will be increased. Will compensate.
FIG. 4 shows an operation in which the A / D conversion circuit 10 converts the reproduction signal waveform shown in FIG. 3D into reproduction data.
[0032]
FIG. 4 is a diagram for explaining the operation when recording and reproducing the reproduction mark according to the present invention, wherein S ₁ and S ₂ are reproduction signal waveforms, and L is the reproduction signal waveforms S ₁ and S ₂ sampled to generate reproduction data. Slice level (threshold value), ΔL is a variable range of slice level L (range in which amplitude can be varied), and “1” samples reproduction signal waveforms S ₁ and S ₂ and binarizes them to generate reproduction data. Amplitude 1 and “0” are amplitude 0 when reproducing signal waveforms S ₁ and S ₂ are sampled to generate reproduction data, CK is a sampling clock, and SD ₁ and SD ₂ are reproduction data. The levels of the reproduced signal waveforms S ₁ and S _{2 by} the clock CK are detected at the falling edge of the clock CK.
[0033]
In this embodiment, when the reproduction signal waveforms S ₁ and S ₂ are input to the A / D conversion circuit 10, as shown in FIGS. The reproduction data SD ₁ and SD ₂ are generated by binarization depending on whether or not the amplitudes of the waveforms S ₁ and S ₂ exceed the slice level (threshold value) L.
[0034]
In addition, when the amplitude level varies, the range in which the amplitude can be varied becomes wider than in the conventional method. However, as shown in FIGS. 4A and 4B, when the slice level L is relatively changed due to the fluctuation of the amplitude, as shown in FIG. 4C, the spread of the mark edge portion is about 1 clock. In this case, when the sign is inverted after one clock from the edge, it can be dealt with by returning to 1. If a recording code that sets the run length to 1 as in the travel length limit (RLL) is used, it will not be 0 next to 01, so that it is known to be an error. Therefore, it is possible to deal with amplitude fluctuations.
[0035]
The present invention has been specifically described above based on the above embodiment, but the present invention is not limited to the above embodiment, and various modifications can be made without departing from the scope of the present invention. .
[0036]
【The invention's effect】
The effects obtained by the representative ones of the inventions disclosed in the present application will be briefly described as follows.
According to the present invention, since the rising or falling edge of the reproduction signal waveform at the time of mark edge detection is made steep, it is possible to increase the density by narrowing the interval in the track width direction of the marks.
[Brief description of the drawings]
FIG. 1 is a diagram for explaining the shape of a mark of the present invention.
FIG. 2 is a block diagram showing a schematic configuration of an optical recording / reproducing apparatus according to an embodiment of the present invention.
FIG. 3 is a diagram for explaining the concept of recording / reproduction of a conventional oval mark and the concept of recording / reproduction of the present invention.
FIG. 4 is a diagram illustrating an operation of converting a reproduction signal waveform into reproduction data by the A / D conversion circuit of the present embodiment.
FIG. 5 is a diagram showing a conventional mark shape.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Optical disk 2 ... Spindle motor 3 ... Semiconductor laser 4 ... Condensing lens 5 ... Objective lens 6 ... Beam splitter 7 ... Detection lens 8 ... Photo detector 9 ... Reproduction amplifier 10 ... A / D conversion circuit 11 ... Demodulation circuit 12 ... Modulation circuit 13 ... recording pulse generation circuit 14 ... light beam drive circuit

Claims (2)

The recording film of the recording medium is irradiated with pulsed light beam, traveling alter the optical properties of the recording film, the play mark associated with the information to be recorded by the change information of the optical properties, the recording layer An optical recording / reproducing apparatus for reproducing the reproduction mark recorded with a recording code having a run length of 1 in length restriction (RLL) ,
In order to form one of the reproduction marks, a recording pulse generating means for generating a plurality of pulses in which the pulse height of the previous pulse and the subsequent pulse is larger than the pulse height of the other part;
Based on the plurality of pulses generated by the recording pulse generating means, the shape of the edge portion before and after one reproduction mark formed on the recording film of the recording medium is larger in the track width direction than the shape of the other portion. A light beam irradiation means for irradiating the light beam to be formed;
A beam spot was irradiated to the reproduction mark in which the shape of the front and rear edge portions was formed larger in the track width direction than the shape of the other portions by the light beam irradiation means, and the level of the reproduction signal was covered with the beam spot. Reproduction means for obtaining a reproduction signal in which the rising edge of the reproduction signal waveform by the front edge portion and the falling edge of the reproduction signal waveform by the rear edge portion are steep by being proportional to the area of the reproduction mark;
An optical recording / reproducing apparatus characterized by steep rising and falling of a reproduction signal waveform when a mark edge is detected.   2. The optical recording / reproducing according to claim 1, wherein the recording pulse generating unit generates a plurality of pulses in which the height and width of the preceding pulse and the succeeding pulse are larger than those of other portions. apparatus.

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