JP2001034944A - Optical record playback apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent signals from deteriorating in a still playback. SOLUTION: An optical record playback apparatus for an optical record medium 1 with a mask layer having an ultra-resolution effect on the laser beam irradiation side of a signal record part comprises a signal amplitude variation detector 21 for detecting the amplitude variation of a playbacked signal and a laser output controller 22 for controlling the laser beam output, based on the output of the detector 21, and it controls the laser beam output so that the signal amplitude is held at an adequate value in a still playback mode for playing the same track back.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses a light transmittance variable medium whose light transmittance changes due to a temperature change or the like as a mask layer and reduces the effective spot diameter of laser light to record information at a high density. The present invention relates to an optical recording / reproducing apparatus for an optical recording medium, and more particularly to an improvement in still reproduction characteristics.

[0002]

2. Description of the Related Art In general, with the advent of the information-oriented society, increasing the capacity of recording media for recording information, especially optical disks, is being studied, and various proposals have been made to increase the capacity. The density of this optical disk depends on how the spot of the reproduction laser beam is reduced. An optical disc can form a recording mark smaller than the light spot diameter by controlling the laser beam power during recording. However, there is a limit value that the light spot diameter when the laser beam is narrowed by the lens cannot be narrowed below a certain value. The repetition wavelength (recording wavelength) of the recording mark at the reproduction limit is given by λ / 2NA. Where λ
Is the wavelength of light, and NA is the numerical aperture of the lens. It can be seen that in order to identify and reproduce a recording mark having a shorter recording wavelength, reproduction can be performed with light having a shorter wavelength or a lens having a larger numerical aperture NA can be used. However, it is technically difficult to shorten the wavelength of a laser beam 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 technique called disk super-resolution for reproducing information recorded at high density is required. This super-resolution will be described below.

[0003] The light intensity distribution of the laser beam used for information recording / reproducing usually shows a Gaussian distribution, and the temperature distribution becomes a distribution almost similar to this. When such a laser beam is irradiated onto the light transmittance variable medium, only the portion of the laser beam irradiation spot where the temperature has risen becomes light transmissive, and the other portion in the light spot is masked, which is a so-called disk super solution. An image effect occurs. At this time, the effective spot diameter of the laser beam transmitted through the high-temperature portion is smaller than the irradiation spot diameter. By providing a light transmittance variable medium that causes the disk super-resolution effect as a mask layer on the optical disk, high-density recording and reproduction can be performed without causing crosstalk between adjacent tracks and between adjacent pits. . FIG. 8 shows an optical disk (optical recording medium) with a mask layer developed based on such a concept. In FIG. 8, an optical disk 1 has a light-transmitting substrate 2 made of polycarbonate resin or the like.
An underlayer 3, a mask layer 4, a recording layer 5, a reflective layer 6, and a protective layer 7 are stacked on the base layer 3 in this order. A guide groove 8 formed concentrically or spirally is formed on the inner surface of the light-transmitting substrate 2.

[0004]

By the way, a light transmittance variable medium whose light transmittance changes with temperature, for example, a thermochromic substance, has a change time of a reversible change in light transmittance.
That is, there is a problem with the time when the light transmittance changes from a low state to a high state by absorbing heat and the temperature rises, and the time when the light transmittance changes from a high state to a low state by cooling. there were. In particular, in the latter (cooling) change time, considering the so-called still reproduction in which the same track is continuously reproduced, if the change time is long, the once heated mask layer (light transmittance variable medium) The laser beam will be irradiated again without cooling the sample 4 sufficiently. As a result, heat is accumulated in the mask layer, the area of the portion having a high light transmittance is increased, and the effect of reducing the effective spot diameter is lost. On the other hand, for example, in Japanese Patent Application Laid-Open No. 7-272321, a heat dissipation layer made of a transparent inorganic substance for dissipating the heat absorbed by the mask layer is provided in contact with the mask layer, so that signal degradation during still reproduction is reduced. It has been reduced.

However, in the case of the technique disclosed in this publication, since the heat radiation characteristics depend on the material and thickness of the heat radiation layer, only a constant heat radiation effect is always obtained regardless of the degree of temperature rise actually occurring on the disk. . Therefore, there is a problem that the effective spot is widened if the cooling by the heat radiation layer cannot keep up with the rise in temperature. At this time, as shown in FIG. 9, the signal amplitude of the long mark length increases, and the signal amplitude of the short mark length decreases. As a result, there is a problem that the amplitude ratio (resolution) is reduced. The present invention has been devised in view of the above problems and effectively solving them. SUMMARY OF THE INVENTION An object of the present invention is to provide an optical recording / reproducing apparatus that can prevent signal degradation during still reproduction.

[0006]

According to a first aspect of the present invention, there is provided an optical recording / reproducing apparatus for an optical recording medium having a mask layer for providing a super-resolution effect on a laser beam irradiation side of a signal recording portion. A signal amplitude change detection unit for detecting an amplitude change of the output signal, and a laser output control unit for controlling the output of the laser beam based on the output of the detection unit, and in a still reproduction mode for reproducing the same track. The output of the laser beam is controlled so that the signal amplitude maintains an appropriate value. As described above, in the still reproduction mode, the laser output control unit narrows down the laser output to maintain the signal amplitude at an appropriate value, and as a result, it is possible to prevent the reproduction signal from deteriorating.

According to a second aspect of the present invention, there is provided an optical recording / reproducing apparatus for an optical recording medium having a mask layer for providing a super-resolution effect on a laser beam irradiation side of a signal recording portion. In the still playback mode in which the same track is continuously played back, the still playback mode buffer memory captures the data of the still playback target track into the buffer memory for the still playback mode, and performs still playback by repeatedly reading out the captured data. is there. As described above, at the time of the still reproduction, the data of the track to be reproduced is stored in the buffer memory for the still reproduction mode, and the data is repeatedly read, so that the signal deterioration can be prevented.

According to a third aspect of the present invention, for example, in the still reproduction mode, the optical pickup section may scan an area near a track to be reproduced. Further, the laser beam may be defocused in the still playback mode, for example. Further, as defined in claim 5,
For example, in the still reproduction mode, the output of the laser beam may be reduced within a range where tracking control can be performed.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the optical recording / reproducing apparatus according to the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a block diagram showing a first embodiment of an optical recording / reproducing apparatus for an optical recording medium, and FIG. 2 is a block diagram showing an optical pickup unit. First, an optical disk having a mask layer is used as the optical recording medium 1 as described above. In the figure, reference numeral 12 denotes a spindle motor for rotating the optical disc 1, and reference numeral 13 denotes a light having a laser generating unit for generating laser light L for reading information and a detecting unit for detecting reflected light of the laser light applied to the optical disc 1. The optical pickup unit 13 is a pickup unit. The optical pickup unit 13 is driven by a driving mechanism (not shown).
Are moved integrally in the radial direction.

Reference numeral 14 denotes a preamplifier unit, which is a circuit for generating a reproduction signal and a servo signal from the signal read by the optical pickup unit 13 and a speed signal for CLV control, respectively. A signal generation circuit, a tracking error signal generation circuit, a reproduction signal generation circuit, an equalizer circuit, a PLL circuit, a speed signal generation circuit, and the like are included. Reference numeral 15 denotes a servo block, which includes a focus control function, a tracking control function, a spindle control function, and the like. Reference numeral 16 denotes a driver unit that operates the optical pickup unit 13 and the spindle motor 12, and performs focus control, tracking control, spindle control, and the like.

Reference numeral 17 denotes a signal processing unit which converts a reproduced signal into an EFM (Eight to Fourteen) signal, for example.
(Modulation) + signal to NRZ data, perform error correction processing on the decoded reproduction signal, and obtain a sector address signal and a data signal. This signal is a signal compressed at a variable transfer rate. Reference numeral 18 denotes, for example, an A (audio) -V (video) decoder, which has a decoding function of expanding the compressed data. A speaker that outputs an audio signal, a display that outputs a video signal, and the like are connected to the decoder unit 18 as necessary. Code 19
Is an external input unit for inputting a command such as a still reproduction mode with a key or the like. Reference numeral 20 denotes a system control unit composed of, for example, a microcomputer or the like, which controls the operation of the entire apparatus.

The following configuration is a general device configuration,
In the present invention, further, a signal amplitude change detecting section 21 for detecting an amplitude change of the reproduced signal, and a laser output control section for controlling the drive of a laser element described later based on the output to control the output of the laser light L 22. The signal amplitude detection unit 21 operates according to a command from the system control unit 20 when a still playback mode is set.
An amplitude detector 21A for detecting the amplitude of the output signal from the preamplifier unit 14, a temporary memory 21B for temporarily storing the amplitude value at this time,
An amplitude comparator 21C for comparing the output value of A with the value stored in the temporary memory 21B is provided. The above amplitude detector 2
1A detects, for example, the amplitude value of the long mark length, the amplitude value of the short mark length, or the amplitude values of both when entering the still playback mode. The temporary memory 21B stores the still playback mode. Each of the amplitude values immediately after the entry is stored as a reference value. The laser output control unit 22 determines whether the comparison result in the amplitude comparator 2 is the same as the amplitude value of the reference value, for example, so as to maintain an appropriate value.
Alternatively, the operation is performed so as to suppress the output of the laser light L so as to maintain the tolerance.

FIG. 2 is a schematic structural view of the optical pickup section 13. As shown in FIG. The optical pickup unit 13 includes a laser element 40 that generates a reproduction laser beam L, a collimator lens 23 that converts the laser beam L into parallel light, and a grating 2.
4, a polarizing prism 25, a quarter-wave plate 26, an objective lens 27 for condensing the laser light L on the optical disc 1,
A condensing lens 28 for condensing the reflected light from the optical disc 1 branched from the polarizing prism 25, a cylindrical lens 29 for obtaining focus information and tracking information from the reflected light, and detecting the condensed light. And a photodetector 30.
, The reflected light from the optical disk 1 is detected, and a detection signal is transmitted to the preamplifier section 14 to reproduce the recorded information on the optical disk 1.

Next, the operation of the optical recording / reproducing apparatus configured as described above will be described. First, the system control unit 20 determines a playback start command input from the external input unit 19 or the like such as a key input, and controls the signal processing unit 17 and the servo block unit 15 according to the command. The signal of the optical disk 1 read by the optical pickup unit 13 is input to a preamplifier unit 14, where a reproduced signal and a servo signal are generated. The generated servo signal is input to the servo block unit 15, and based on the servo signal, the focus drive signal and the tracking drive signal are supplied to the actuator of the optical pickup unit 13 via the driver unit 16, and the respective controls are performed. It is. Thus, one round of servo control of the optical pickup unit 13 is performed.

The speed signal is supplied to a PLL (Phase Locked Loop) included in the preamplifier unit 14.
The speed signal is obtained by a circuit. The speed signal is sent to the servo block unit 15 to generate a drive control signal via the driver unit 16, and the drive control signal controls the rotation of the spindle motor 12.
V control is performed. The reproduced signal output from the preamplifier unit 14 is converted into a digital signal by the signal processing unit 17, and synchronization detection is performed from the digital signal.
Decoded to Z data. The decoded signal is subjected to an error correction process to obtain a sector address signal and a data signal. This data signal is a signal compressed at a variable transfer rate, for example, MPEG2. This signal is subjected to absorption of the time axis by a temporary storage means (not shown), expanded by the decoder unit 18, and further expanded into an audio signal. And a video signal.

During such reproduction, when a still reproduction command is input from the external input section 19, a still reproduction mode is entered. In the still reproduction mode, a so-called still image is displayed by repeatedly reproducing the currently reproduced track. When the still reproduction command is input, the driving of the signal amplitude change detection unit 21 is started. That is, the amplitude value of the long mark length or the short mark length, or the amplitude value of both, of the reproduced signal from the currently reproduced track is detected by the amplitude detector 21A, and this amplitude value is stored in the temporary memory 21B. It is stored as a reference value. When the time of the still reproduction mode becomes longer, the laser beam L continues to irradiate only the track to be subjected to the same still reproduction, so that the temperature of this portion rapidly rises and the mask layer 4 (see FIG. 8) is partially formed. May be reduced, and such a phenomenon appears as an increase in the amplitude of the long mark length and a decrease in the amplitude of the short mark length (see FIG. 9). The amplitude is compared with the reference value (the value stored in the temporary memory 21B) by the amplitude comparator 21C in real time, and the laser output is set so that the amplitude value becomes the same value or an appropriate value within a certain value. The control unit 22 suppresses the output of the laser light L. That is, when the temperature of the track to be reproduced still tends to increase, the operation of reducing the output of the laser beam and suppressing the temperature increase is performed.

For example, if attention is paid only to the amplitude of the long mark length, the upper limit value may be set to a value whose amplitude value is equal to the reference value or higher than the reference value by a predetermined allowable amount. In addition, if attention is paid only to the amplitude of the short mark length, the lower limit value may be set to a value whose amplitude value is equal to the reference value or lower than the reference value by a predetermined allowable amount. Furthermore, if attention is paid to the amplitude ratio between the two mark lengths, control may be performed so that this ratio falls within a certain range. As described above, in the present invention, the intensity of the reproduction laser beam is controlled by using the signal amplitude change occurring during the still reproduction as the feedback signal. As described above, the feedback signal may be an amplitude change of a long mark length or an amplitude change of a short mark length. In this case, a signal amplitude change caused by a temperature change of the disk is detected, and the intensity of the reproduction laser beam is controlled so that the signal amplitude or the signal amplitude ratio (the amplitude ratio between the long mark length and the short mark length) falls within an appropriate value. I do. For example, when the amplitude of the long mark length is increased, the temperature of the disk is suppressed by weakening the intensity of the reproduction light to suppress the increase in the transmittance.

As described above, the state where the effective spot is narrowed down is maintained by controlling the temperature rise of the disk. As the mask layer, a thermochromic dye whose absorption wavelength range can be set and whose transmittance changes greatly is particularly effective. Further, if the mask layer is configured so that the transmittance changes stepwise with respect to the temperature rise as shown in FIG. 3, the transmittance change due to the deviation from the appropriate temperature range becomes large, and the feedback signal becomes clear. Can be In the above-described first invention, the output of the laser beam is controlled by using the amplitude change of the reproduction signal as a feedback signal. Instead, the data at that time is stored when the still reproduction mode is entered. In advance, this data may be repeatedly output. FIG. 4 is a block diagram showing an optical recording / reproducing apparatus of the second invention which performs such an operation. 4, the same components as those of the apparatus shown in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. Here, the signal amplitude change detection unit 21 and the laser output control unit 2 shown in FIG.
A still reproduction mode buffer memory 35 is provided in place of the memory 2 except for the still reproduction mode. In the still reproduction mode, still reproduction data is fetched into the buffer memory 35 and still reproduction is performed by repeatedly reading the fetched data. It has become.

According to the device of the second invention, when a still playback command is input from the external input unit 19, the system control unit 20 immediately stores the data of the track being played back at that time in the buffer memory for the still playback mode. Take in 35. In this case, at least a data amount corresponding to the data of one screen is fetched, and during the still playback mode, the fetched data is repeatedly read out and read by the signal processing unit 17.
Supply to According to this, a still reproduced image with good image quality can always be obtained. Further, during the still reproduction mode, the drive of the optical pickup unit 13 is controlled so that the laser light L scans a region near or adjacent to the track to be reproduced at an appropriate speed. In this case, the still playback target track may or may not be included in the scanning range. Thereby, it is possible to prevent heat from accumulating on a specific track of the optical disc.

As described above, according to the second aspect of the present invention, in the still reproduction mode, the still reproduction is performed by repeatedly reading out the data fetched into the buffer memory 35,
At the same time, the optical pickup can perform still reproduction with good image quality by scanning a nearby track, for example, an adjacent track. In this case, by increasing the scanning range of the optical pickup, the cooling time becomes longer, and heat can be prevented from accumulating in a specific portion of the disk. Also,
In order to shorten the switching time from the still playback mode to the normal playback mode, the scanning area is preferably an area including a track during still playback or an adjacent area. FIG. 5 shows an example of the scanning area of the optical pickup unit at this time. In the figure, TR is a track for still reproduction, and a ring-shaped area 36 indicated by a broken line is shown on the inner and outer circumferences of the track. This is a scanning area of the optical pickup unit. During the still reproduction mode, the optical pickup section performs, for example, reciprocating scanning in this scanning area. Also, in the still playback mode, data (both before and after the still playback track) longer than the time required for the optical pickup unit to return to the still playback track after the still playback mode is released is taken into the buffer memory 35. For example, it is possible to smoothly shift to the normal reproduction or the reverse reproduction.

In the present embodiment, during the still reproduction mode, the optical pickup is scanned in the area 36. Instead, the optical pickup is defocused around the still reproduction target track. The light spot diameter may be set large to prevent the temperature of the optical disk from being excessively increased locally. FIG. 6 shows the state at this time, wherein SP1 shows the light spot diameter at the time of focusing, and SP2 shows the light spot diameter at the time of defocusing. At the time of defocus, the light spot diameter SP2
Has been made bigger. As described above, the focus of heat can be prevented by defocusing the reproduction light during the still reproduction and expanding the irradiation spot diameter.

In the above-described modification, the optical pickup unit is in the defocused state in the still reproduction mode.
Instead, as described in FIG. 1, the output of the laser beam may be suppressed. FIG. 7 is a configuration diagram showing an apparatus of such a modification, in which a laser output control unit 22 similar to that described in FIG. 1 is provided. As described above, by reducing the output of the reproduction laser beam within the range where the tracking control can be performed during the still reproduction, it is possible to reduce the local temperature rise of the disk.
The structure of the optical disk described in the present embodiment is merely an example, and it goes without saying that the structure can be applied to any optical disk having a mask layer.

[0023]

As described above, according to the optical recording / reproducing apparatus of the present invention, the following excellent functions and effects can be exhibited. Deterioration of a reproduction signal at the time of still reproduction can be prevented, and good image quality and the like can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first embodiment of an optical recording / reproducing apparatus for an optical recording medium.

FIG. 2 is a configuration diagram illustrating an optical pickup unit.

FIG. 3 is a diagram showing characteristics of a mask layer whose transmittance changes stepwise with a rise in temperature.

FIG. 4 is a configuration diagram showing an optical recording / reproducing apparatus according to a second invention.

FIG. 5 is a diagram illustrating a relationship between a still playback target track and a scanning area.

FIG. 6 is a diagram showing a state of a light spot at the time of focusing and at the time of defocusing.

FIG. 7 is a configuration diagram showing a modification of the second invention.

FIG. 8 is a sectional view showing an optical disc with a mask layer.

FIG. 9 is a graph showing a relationship between a temperature and signal amplitudes of a long mark length and a short mark length.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Optical disk (optical recording medium), 2 ... Light transmissive board, 4
... Mask layer, 5 ... Recording layer, 13 ... Optical pickup unit, 2
0: System control unit, 21: Signal amplitude change detection unit, 21
A: amplitude detector, 21B: temporary memory, 21C: amplitude comparator, 22: laser light output control unit, 35: buffer memory for still reproduction mode, 40: laser element, L: laser light.

Claims (5)

[Claims] In an optical recording / reproducing apparatus for an optical recording medium provided with a mask layer for giving a super-resolution effect on a laser beam irradiation side of a signal recording portion, a signal amplitude change detection for detecting an amplitude change of a reproduced signal. And a laser output control unit for controlling the output of the laser beam based on the output of the detection unit, wherein the laser is controlled so that the signal amplitude maintains an appropriate value in a still reproduction mode for reproducing the same track. An optical recording / reproducing apparatus for controlling light output. 2. An optical recording / reproducing apparatus for an optical recording medium having a mask layer for providing a super-resolution effect on a laser beam irradiation side of a signal recording portion, wherein a buffer memory for a still reproduction mode is provided to continuously reproduce the same track. An optical recording / reproducing apparatus configured to capture still track data in the still playback mode buffer memory in the still playback mode to perform still playback by repeatedly reading out the captured data. 3. The optical recording / reproducing apparatus according to claim 2, wherein in the still reproduction mode, the optical pickup section scans an area near a track to be reproduced. 4. The optical recording / reproducing apparatus according to claim 2, wherein the laser beam is defocused in the still reproduction mode. 5. The optical recording / reproducing apparatus according to claim 2, wherein in the still reproduction mode, an output of the laser beam is reduced within a range where tracking control can be performed.