JP2005108277A - Optical information recording and reproducing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform light spot position control in a focus direction optimum for satisfying the performance for assuring the reliability of information relating to an information recording and reproducing technique for performing recording and reproducing by a laser beam. <P>SOLUTION: The correction value of a focus offset is previously stored into a memory of a controller 19 in the assembly and adjustment of the information recording and reproducing apparatus, as a result of which the optimum focus offset of a data section can be set by computing the correction value of the focus offset after implementation of the focus position control to attain the maximum value of a prepit signal and therefore the setting of the optimum recording and reproducing performance according to an information recording medium is made possible. As a result, the focus position control is heretofore so performed as to maximize the prepit signal formed in the information recording medium and the following problems are solved. When the prepits formed in the information recording medium are disposed to deviate from the track center, the case the maximum value of the prepit signal obtained in the optical information recording and reproducing apparatus is not matched with the optimum focus position of the data section arises and such case leads to the degradation in the recording and reproducing performance of the optical information recording and reproducing apparatus. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an information recording / reproducing apparatus for recording / reproducing information on / from an information recording medium, and more particularly to an information recording / reproducing technique for recording / reproducing with a laser beam.

  2. Description of the Related Art Conventionally, an optical information recording / reproducing apparatus capable of recording / reproducing information on / from an optical recording medium such as an optical disc detects the amplitude of a VFO portion of a pre-pit signal recorded in advance on the optical recording medium. And a focus offset adjustment circuit, and the light spot position control in the focus direction is performed so that the amplitude of the detected VFO portion is maximized (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 4-170725 (first page, FIG. 3)

  In the conventional optical information recording / reproducing apparatus, the above-described light spot position control in the focus direction is performed on the premise that the prepit is arranged at the center of the track to be scanned with the light spot.

  On the other hand, in an information recording medium defined by the DVD-RAM standard (JIS X 6243: 120 mm DVD-rewritable optical disk (DVD-RAM), establishment date 1998.1.20), a land portion is formed on a track formed on the information recording medium. Groove portions are alternately formed, and preformatted prepits are provided by being shifted by 1/2 track on the inner and outer peripheral sides from the track center.

  When the prior art is applied to this information recording medium, the prepit amplitude level changes according to the change in focus offset, but the signal amplitudes of the prepits provided on the inner and outer circumference sides shifted from the track center are different. There is a case where the focus offset that maximizes the focus offset and the CNR that is the performance for ensuring the reliability of information and the cross offset (CT: leakage of a signal from an adjacent track to the track) are not matched.

  This is because the pre-pits are phase pits based on the light phase conditions, and are further shifted from the track center (1/2 track) on the inner and outer peripheral sides, and the data signal is shaded by the intensity of the light. This is due to the formation of pits. As a result, there arises a problem that the performance of ensuring the reliability of information in the data portion cannot be satisfied.

  Therefore, in view of the problems in the prior art described above, the present invention provides a light spot position control value in the focus direction that maximizes the signal amplitude of the prepits provided on the inner peripheral side and the outer peripheral side by shifting from the track center. Performance to ensure the reliability of information by correcting using the light spot position control value in the focus direction (value stored in the memory in the controller) set during assembly adjustment of the optical information recording / reproducing device An object of the present invention is to provide a light spot position control in an optimum focus direction to satisfy the above.

  The above problem is that a laser beam is applied to an information recording medium in which land portions and groove portions are alternately formed on a track formed on the information recording medium, and pre-pits that are pre-formatted in advance are shifted from the center of the track. In the optical information recording / reproducing apparatus for reproducing the recorded information by forming a recording part physically different from the unrecorded part of information in the recording area on the information recording medium, Detection means for detecting a prepit signal level provided in a shifted manner, means for holding and calculating each detected level, light spot position control in the track direction and light spot position control in the focus direction on the information recording medium Detecting the signal level of prepits shifted from the center of the track for each control of the light spot position in the focus direction , Means to obtain the maximum signal level of one prepit (after calculation) and the maximum value of the signal level of the other prepit (after calculation) by performing arithmetic operations such as polynomial approximation on the obtained signal level, or both prepits Means for obtaining a maximum value obtained by adding the signal levels (after calculation), and error information obtained from a signal obtained by binarizing the reproduction signal based on the reproduction signal obtained by reproducing the recorded information Alternatively, a controller for detecting performance information is provided, and a controller for controlling the optical information recording / reproducing apparatus and a light spot position control value in the focus direction set during assembly adjustment of the optical information recording / reproducing apparatus are stored in a memory in the controller. And the optical spot position in the focus direction obtained by the pre-pit signal when the information recording medium is inserted. The position control value is improved by correction using a light spot position control value in the focus direction that is stored in memory in said controller.

  According to the present invention, the light spot position control in the optimum focus direction is performed on the basis of the signals of a plurality of prepits provided on the recording medium so as to be shifted from the track center. Can be improved.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. First, FIG. 1 shows the configuration of an optical information recording / reproducing apparatus according to an embodiment of the present invention. 1 is a semiconductor laser, 2 is a collimating lens for converting light from the semiconductor laser into parallel light, and 3 is A prism, 4 is an objective lens that narrows the laser beam to the disk to form a light spot, and 5 is a recording medium comprising a recording film and a substrate that holds the recording film (in this embodiment, a DVD-RAM will be described as an example) 6 is an actuator for controlling the shape and position of the light spot formed on the recording medium 5, 7 and 8 are photodetectors, 9 is a preamplifier, 10 is a reproduction circuit, and 11 is a PLL circuit. , 12 is a discrimination circuit, 13 is a high frequency superposition circuit, 14 is a laser driver, 15 is a recording pulse generation circuit, 16 is a synthesizer, 17 is a power monitoring circuit, 18 is a servo drive circuit, 19 is It is a controller.

  An optical information recording / reproducing apparatus having such a configuration includes an optical head including a semiconductor laser 1, a recording processing system including a recording pulse generating circuit 15, and a reproducing circuit 10 for converting a reproduction signal obtained from the optical head into information. It is comprised from the reproduction | regeneration processing system containing.

  The command and information data from the upper host are decoded by the controller 19 and the recording data is modulated, and converted into a code string corresponding to the employed modulation method. The synthesizer 16 is an oscillator that generates a reference clock for the entire apparatus. ZCAV (Zoned Constant Angular Velocity) that changes the reference clock for each zone provided in the recording medium to make the recording density at the inner and outer circumferences substantially constant. When the so-called recording method is adopted, the oscillation frequency of the synthesizer 16 is also changed according to the zone.

  A focus error signal and a track error signal are obtained by a cylindrical lens (not shown) arranged in front of the photodetector 7 and the quadrant photodetector 7, and the error signal is input to the controller 19 (not shown). The objective lens 4 is moved by outputting a servo signal from 19 to the servo drive circuit 18 and supplying a drive current to the actuator 6. In this way, the servo mechanism (focus servo and tracking servo) controls the shape and position of the light spot for recording / reproducing information.

  When recording information, the code string modulated in accordance with the normal information data from the controller 19 and the reference clock from the synthesizer 16 enter the recording pulse generation circuit 15 to set the length and width of the recording mark. It is converted into a recording pulse train for control. These recording pulse trains converted in the recording pulse generation circuit 15 are first input to the laser driver 14, and the semiconductor laser 1 is oscillated at a high output by the recording current supplied from the laser driver 14. The light emitted from the semiconductor laser 1 is converted into parallel light by the collimator lens 2, passes through the prism 3, and further converges on the recording medium 5 by the objective lens 4, thereby forming a code string of the recording pulse string. A corresponding recording mark is recorded.

  The high frequency superimposing circuit 13 is provided to reduce laser noise caused by the semiconductor laser 1. The high frequency superimposing circuit 13 is used for recording / erasing information or overwriting. The high frequency superposition may be suspended from the viewpoint of the life of the laser.

  In the optical information recording apparatus of the present invention, when the recorded information is reproduced, the semiconductor laser 1 is oscillated at a low output and the oscillation light is incident on the recording medium 5. The reflected light from the recording medium 5 is incident on the photodetector 7 after the optical path is separated by the prism 3. In the photodetector 7, the incident light is photoelectrically converted, amplified by a preamplifier 9, and input to the reproduction circuit 10. The reproduction circuit 10 includes, for example, a waveform equalization circuit, an automatic gain control circuit, a binarization circuit, and the like, and an input reproduction signal is used as a binarization signal. Further, the reproducing circuit 10 includes a peak and bottom detection circuit for detecting the amplitude level of the header section as shown in FIG.

  In this way, the binarized signal output from the reproduction circuit 10 is then input to a PLL (Phase Locked Loop) circuit 11 for self-clocking. The reproduction clock synchronized with the binarized signal obtained by the PLL circuit 11 and the binarized signal are input to the discrimination circuit 12 for data discrimination, and the data discrimination signal as the discrimination result is the control. The data is demodulated.

  A sector layout and header layout of a track of an information recording medium according to an embodiment of the present invention will be described with reference to FIG. The information recording medium defined by the DVD-RAM standard described above is provided with prepits as shown in FIG. Land portions and groove portions are alternately formed on a track formed on an information recording medium, and pre-pits to be preformatted are provided on the inner and outer peripheral sides shifted from the track center (1/2 track). ing.

  When passing through a land track, a light spot passes through the center of Land sector # (n + N-1), and Header1 # (n + N), which is shifted by a half track to the inner circumference, Passes Header2 # (n + N), then passes Header3 # (n + 2N) and Header4 # (n + 2N), which are shifted by one-half track to the outer circumference, and Land sector # (n + Enter N). On the other hand, when passing through the track of the groove part, it passes through Header1 and Header2 which are shifted by 1/2 track on the outer periphery side, opposite to the land part, and then is shifted by 1/2 track on the inner periphery side. Pass through Header3 and Header4. As shown in FIG. 3B, a VFO section is provided at the head of each header.

  Next, a circuit configuration for detecting the amplitude level of the header portion included in the reproduction circuit 10 will be described with reference to FIG. The reproduction signal output from the preamplifier 9 is branched separately from the data discrimination inside the reproduction circuit 10 and input to the envelope detection circuit 20, and the peak level and bottom level of the reproduction signal are determined by the peak detection circuit 21 and the bottom detection circuit 22. Detected. Here, the gate generation circuit 23 receives a command from the controller 19, and generates a gate signal in the VFO1 portion of Header1 and Header3 shown in FIG. This gate signal is supplied to the peak detection circuit 21 and the bottom detection circuit 22 of the envelope detection circuit 20, and the peak level and the bottom level of the VFO1 portion of each Header are sent to the differential circuit 24, and the VFO1 portion of each Header is sent. A signal corresponding to the amplitude is supplied to the AD converter 25. The AD converter 25 AD-converts the amplitude-detected signal, and the controller 19 stores the converted amplitude data.

  Next, the light spot position control value in the focus direction set during assembly adjustment of the optical information recording / reproducing apparatus will be described with reference to FIG. Here, an information recording medium in which random data is recorded in advance for assembly adjustment is used. In FIG. 4, the horizontal axis indicates the focus offset value, the left vertical axis indicates the amplitude of the header portion, and the right vertical axis indicates the jitter of the data portion. The amplitude of the header portion in the illustrated land portion and groove portion is obtained by adding the amplitudes of the VFO1 portions of Header1 and Header3, and the amplitude changes according to the focus offset. The result of performing a second-order polynomial approximation on the obtained amplitude data is shown below.

General formula: quadratic polynomial approximation: y = ax ² + bx + c; y is amplitude x is focus offset y is maximum x: dy / dx = 2ax + b = 0 → x = (− b) / ( 2a)
Groove ^{section: y = -38.084x 2 - 10.363x +} 344.7
: X = (+ 10.363) / (2 * -38.084) =-0.136
Land ^{section: y = -51.992x 2 - 19.111x +} 344.56
: X = (+ 19.111) / (2 * -51.992) =-0.184
As described above, the focus offset at which the amplitude of the header portion is maximum is −0.136 μm in the groove portion and −0.184 μm in the land portion.

  Next, the focus offset for the jitter in the Data portion will be described. After obtaining the amplitude data of the header part, the jitter of the data part with respect to the focus offset is measured in an area where random data is recorded on the same information recording medium. Jitter measurement can be performed by outputting the binarized signal from the reproduction circuit 10 shown in FIG. 1 and the reproduction clock output from the PLL circuit 11 to a TIA (time interval analyzer) (not shown). The jitter of the data part with respect to the focus offset in the groove part and the land part is shown by two curves on the lower side of FIG. The result of second-order polynomial approximation for the obtained jitter and focus offset is shown below.

General formula: quadratic polynomial approximation: y = ax ² + bx + c; y is jitter x is focus offset y is maximum x: dy / dx = 2ax + b = 0 → x = (− b) / ( 2a)
Groove part: y = 55.556x ² + 32.5x + 12.632
: X = (-32.5) / (2 * 55.556) =-0.292
Land part: y = 86.867x ² + 63.795x + 20.154
: X = (-63.795) / (2 * 86.867) =-0.367
As described above, the focus offset that minimizes the jitter in the data portion is −0.292 μm in the groove portion and −0.367 μm in the land portion. Therefore, since the focus offset that maximizes the amplitude of the header section is different from the focus offset that minimizes the jitter of the data section, the focus offset value and data obtained from the amplitude of the header section are adjusted during assembly adjustment of the optical information recording / reproducing apparatus. The focus offset value obtained from the jitter of the part is stored in a memory (ROM) in the controller, and the focus offset value is reflected during normal recording / reproduction, thereby improving the reproduction performance of the data part.

  The focus offset values to be stored are a total of 4 types, two types of values of the groove portion and the land portion obtained from the amplitude of the header portion and two types of values of the groove portion and the land portion obtained from the jitter of the data portion. Stores the type. Further, only two types (the values of the groove part and the land part) that are the difference values between the header part and the data part may be stored.

  Next, a method for setting a focus offset obtained from the amplitude of the header portion according to the embodiment of the present invention will be described with reference to FIG. FIG. 5 shows a focus offset detection method obtained from the amplitude of the header portion when normal recording / reproduction is performed. After an information recording medium for performing normal recording / reproduction is inserted, a curve similar to the focus offset detection obtained from the amplitude of the header portion described with reference to FIG. 4 is obtained. The result of performing a second-order polynomial approximation on the obtained amplitude data is shown below.

General formula: quadratic polynomial approximation: y = ax ² + bx + c; y is amplitude x is focus offset y is maximum x: dy / dx = 2ax + b = 0 → x = (− b) / ( 2a)
Groove ^{section: y = -31.708x 2 - 9.2779x +} 338.84
: X = (+ 9.2779) / (2 * -31.708) =-0.146
Land ^{section: y = -52.627x 2 - 13.369x +} 340.98
: X = (+ 13.369) / (2 * -52.627) =-0.127
As described above, the focus offset that maximizes the amplitude of the header portion is −0.146 μm at the groove portion and −0.127 μm at the land portion.

  Next, with reference to FIG. 6, the reproduction performance of the data portion is compared for the correction of the focus offset obtained in FIG. 5 and the focus offset obtained in FIG. What is used here is an information recording medium in which a CNR and a CT pattern are recorded in advance on the information recording medium used in FIG. Note that the information recording medium used in FIGS. 5 and 6 is the same medium and is different from the information recording medium used in FIG.

  In FIG. 6, the horizontal axis represents the focus offset, the right vertical axis represents CNR, and the left vertical axis represents CT. The CNR and CT obtained from the groove portion focus offset value of -0.146 μm and the land portion focus offset value of -0.127 μm obtained in FIG. 5 are about 52 dB for both the groove portion and the land portion, and CT is the groove portion. About -32 dB at the land, and about -26 dB at the land portion. The focus offset obtained in FIG. 4 is corrected for these performances. The focus offset obtained in FIG. 4 is organized and shown.

Focus offset value by amplitude detection of Header part:
Groove part: -0.136μm
Land part: -0.184μm
Focus offset value by jitter detection in Data section:
Groove part: -0.292μm
Land part: -0.367μm
Corrected focus offset value:
Groove part: -0.156μm
Land part: -0.183μm
The corrected focus offset value is added to the focus offset obtained in FIG.

Focus offset value after correction:
Groove part: -0.146μm + (-0.156μm) = -0.302μm
Land part: -0.127μm + (-0.183μm) = -0.31μm
From the corrected focus offset value, the CNR is about 52 dB in both the groove portion and the land portion, and there is no significant change in the focus offset correction. However, in CT, the groove portion is about −34 dB, and the land portion is about −30 dB. Thus, a CT reduction effect of about 2 dB in the groove portion and about 4 dB in the land portion can be obtained. Thereby, the reproduction performance of the information recording / reproducing apparatus can be improved and the reliability of information can be improved.

  The operation described in FIG. 5 and FIG. 6 will be described using the light spot position control processing flow of FIG. When the light spot position control process is started, the electrical offset of the focus is removed (101). Next, focus control is started (102). In this state, the focus offset is 0 μm (zero electrical offset). The light spot is moved to the target track (land or groove) to be subjected to the light spot position control process (103). While changing the focus offset (104), the prepit signal amplitudes of Header1 and Header3 are detected and the amplitude data is stored in the controller 19 (105). Therefore, the operations 104 and 105 are repeated as many times as necessary (in this embodiment, seven times, see FIG. 5). A polynomial approximation is performed based on the data stored in the controller 19, the focus offset giving the maximum amplitude is calculated, and the focus offset at which the added amplitude of Header1 and Header3 becomes the maximum amplitude is calculated and stored in the controller 19 The focus offset correction value is added (106). The optimum focus offset is reset (107) and the process is terminated. In order to process the land portion and the groove portion, the operations from the above-described processing 103 to 107 may be performed in the land portion and the groove portion, and the obtained optimum focus offset may be reset in the land portion and the groove portion.

  By varying the focus offset as described above and adding the focus offset correction value stored in the controller 19 to the focus offset obtained from the amplitude of the header section, the optimum focus offset according to the information recording medium Can be set.

  Here, the focus offset correction value is calculated for each of the land portion and the groove portion, but the focus offset correction value is not significantly different between the land portion and the groove portion, and is equivalent as shown in FIG. Since performance is obtained, either one of the correction values may be calculated. Accordingly, the memory capacity to be stored can be reduced by setting the correction value of the focus offset stored in the controller 19 to only one value of the groove portion or the land portion.

It is a block diagram which shows the structure of the optical information recording / reproducing apparatus of this invention. It is a block diagram which shows the circuit structure for detecting the amplitude level of this invention. It is a block diagram which shows the sector and header layout of a track | truck. It is a graph which shows the focus offset detection at the time of assembly adjustment of the optical information recording / reproducing apparatus of this invention. It is a graph which shows the focus offset detection using the amplitude of the Header part by this invention. It is a graph which shows the reproduction | regeneration performance of the data part in correction | amendment of the focus offset by this invention. It is a processing flow which performs light spot position control by this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Semiconductor laser 2 Collimating lens 4 Objective lens 3 Prism 5 Recording medium 6 Actuator 7 Photo detector 8 Photo detector 9 Preamplifier 10 Reproduction circuit 13 High frequency superposition circuit 14 Laser driver 15 Recording pulse generation circuit 17 Power monitoring circuit 18 Servo drive circuit 19 Controller 21 Peak detection circuit 22 Bottom detection circuit 23 Gate generation circuit 25 AD converter

Claims (3)

A land portion and a groove portion are alternately formed on a track formed on the information recording medium, and a laser beam is irradiated to the information recording medium in which pre-pits to be pre-formatted are shifted from the track center. In an optical information recording / reproducing apparatus for forming a recording part physically different from an unrecorded part of information in a recording area on the information recording medium and reproducing the recorded information,
Detecting means for detecting the signal level of the pre-pit provided by shifting from the track center;
Means for holding and calculating each detected level;
Comprising means for performing light spot position control in the track direction and light spot position control in the focus direction on the information recording medium;
The prepit signal level shifted from the center of the track is detected for each light spot position control in the focus direction, and the obtained signal level is subjected to computation such as polynomial approximation, and the maximum signal level of one prepit and the other Means for obtaining the maximum value of the signal levels of the prepits, or means for obtaining the maximum value obtained by adding the signal levels of both prepits,
A means for detecting error information or performance information obtained from a signal obtained by binarizing the reproduction signal based on a reproduction signal obtained by reproducing the recorded information;
A controller for controlling the optical information recording / reproducing apparatus, and a light spot position control value in the focus direction set at the time of assembly adjustment of the optical information recording / reproducing apparatus, provided in a memory in the controller;
When the information recording medium is inserted, the light spot position control value in the focus direction is used as the light spot position control value in the focus direction obtained by the pre-pit signal, and the light spot position control value in the focus direction stored in the memory in the controller is used. And an optical information recording / reproducing apparatus. The optical information recording / reproducing apparatus according to claim 1,
An optical information recording / reproducing apparatus, wherein correction is performed using two types of light spot position control values in a focus direction of a land portion and a groove portion of a track formed on an information recording medium. The optical information recording / reproducing apparatus according to claim 1,
An optical system that corrects light spot position control values in two focus directions of a land portion and a groove portion of a track formed on an information recording medium by using one of the correction values of the land portion or the groove portion. Information recording / reproducing apparatus.

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