JP2005071526A - Recording device and method of over-writable optical disk - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a recording and reproducing device of an optical disk where high-quality recording is performed by reducing jitter in the case of over-writing into a recorded area even in the optical disk for high density recording and reproducing where a track pitch is narrow. <P>SOLUTION: The reproduction signal of the optical disk 1 is detected by a recorded/unrecorded area detection circuit 11 to discriminate an unrecorded area and the recorded area. Recording to the optical disk 1 is carried out by controlling an optical power control part 15 so that recording power Po2 when over-writing into the recorded area may be smaller than recording power Po1 when recording into the unrecorded area for the first time, that is 0.96 Po1≤Po2<Po1 concretely. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an optical disc recording apparatus and a recording method for recording information on an overwritable optical disc.

  In an optical disk recording apparatus, optical intensity adjustment (OPC) is performed in order to perform recording with an optimum recording power by correcting characteristics of an optical disk (recording medium), characteristics of a laser diode (LD), fluctuations in recording power due to laser light, and the like. (Optimum Power Control)) is executed to obtain the optimum recording power for recording on the optical disc in advance.

  The recording power is generally set to the same strength at the first recording time when data is first recorded in an unrecorded area of the optical disc and at the time of overwriting when the recorded area is overwritten. By the way, Japanese Patent Laid-Open No. 2002-319132 (Patent Document 1) has an overwrite characteristic (DOW characteristic) different from the initial recording in an overwritable optical disk, and the jitter at the initial recording is the best value. It is described that even when overwriting is performed using the optimum recording power, the best jitter value at the time of overwriting may not always be obtained.

For this reason, Patent Document 1 describes that by increasing the recording power at the time of overwriting than at the time of the initial recording, the jitter becomes the best value at the time of overwriting and better recording can be performed. The overwrite characteristic is determined by the type of drive (optical pickup) and optical disc.
JP 2002-319132 A

  When the track width (track pitch), which is a guide groove formed on the optical disk, is reduced as the recording density increases, not only the track for recording and reproduction but also the adjacent track is used for recording and reproduction. A light spot (laser spot) is applied. When recorded data exists in this adjacent track, during reproduction, crosstalk, which is a leakage of a laser spot from the adjacent track, occurs, and the quality of the reproduced signal is degraded. Also during recording, heat from laser recording is spread to adjacent tracks from the recorded track, causing cross-erasure that erases or degrades the recorded data, which also reduces signal quality. There is a problem.

  In an optical disc having a relatively wide track pitch such as a CD-RW, the signal quality is improved by performing OPC in which the recording power is increased at the time of overwriting rather than at the time of initial recording as described in Patent Document 1. There seems to be something. However, as described above, when the track pitch of the optical disk is narrow and the laser spot overlaps to the adjacent track, the influence on the adjacent track is increased by performing OPC as in Patent Document 1, and crosstalk and cross erase are performed. It has become clear that the recording quality may deteriorate on the contrary.

  Accordingly, the present invention is an optical disc that can reduce jitter and perform high-quality recording even when it is a high-density recording / reproducing optical disc with a narrow track pitch when overwriting a recorded area. An object of the present invention is to provide a recording apparatus and a recording method.

  The present invention provides the following optical disk recording apparatuses and recording methods (a) to (d) in order to solve the above-described problems of the prior art.

(A) In an overwritable optical disc recording apparatus, an optical pickup (5) for recording / reproduction that irradiates the optical disc (1) with laser light for recording / reproduction and detects reflected light from the optical disc, and the optical disc Prior to recording information on the optical disc, trial writing is performed on a predetermined area of the optical disc, whereby the first optimum recording power used at the time of initial recording on the unrecorded area of the optical disc and overwriting on the recorded area are performed. An optimum recording power determining means (10) for determining a second optimum recording power smaller than the first optimum recording power used sometimes, and an area for recording the information by detecting a reproduction signal of the optical disc is not recorded. Discriminated by the recorded / unrecorded area detecting means (11) for discriminating whether it is an area or a recorded area, and the recorded / unrecorded area detecting means Based on the state of the recorded area, recording is performed with the first optimum recording power when recording to the unrecorded area for the first time, and with the second optimum recording power when overwriting to the recorded area. An overwritable optical disc recording apparatus comprising control means (8, 15) for controlling the recording power of the optical pickup with the laser beam to perform recording.
(B) The optimum recording power determining means (10) controls the second optimum recording power to be 0.96 times or more and less than 1 time of the first optimum recording power. (A) The overwritable optical disk recording apparatus described in (a).
(C) In an overwritable optical disc recording method, by performing trial writing on a predetermined area of the optical disc (1), the first optimum recording power used at the time of initial recording on the unrecorded area of the optical disc, and recording An optimum recording power determination step for determining a second optimum recording power smaller than the first optimum recording power to be used when overwriting a completed area, and an area for recording information by detecting a reproduction signal of the optical disc. Based on the determination process for determining whether the recording area or the recorded area and the state of the area determined in the determination process, the first optimum recording power is used at the time of initial recording in the unrecorded area. Overwriting is possible, including a recording step of recording at the second optimum recording power when recording and overwriting the recorded area Recording method of the optical disk.
(D) In the optimum recording power determination step, the second optimum recording power is set to 0.96 times to less than 1 time of the first optimum recording power. A writable optical disc recording method.

  According to the present invention, even when there is crosstalk and cross erase in recording on a high density recording / reproducing optical disk with a narrow track pitch, the jitter at the time of overwriting to the recorded area is always kept to a minimum. There is an effect that the highest recording quality can be realized.

  FIG. 1 is a block diagram showing a configuration of a main part of an optical disk recording apparatus according to an embodiment of the present invention. The optical disc 1 is an overwritable recording medium and has a one-stroke spiral track from the innermost circumference to the outermost circumference of the recording area. As an example, the optical disk 1 of the present embodiment has a land-groove structure composed of lands L and grooves G, as partially enlarged in FIG. The groove G is formed so that the inner peripheral side wall and the outer peripheral side wall are parallel to each other. The inner and outer peripheral walls of the land L are non-parallel. Then, groove recording for recording in the groove G as a track is performed. A recording linear density control signal for defining the recording linear density of data with a constant linear density is superimposed along the track. As shown in FIG. 2, the recording linear density control signal is a wobble including an ATIP (Absolute Time In Pregroove) time code that is absolute time information.

  The optical disk 1 is rotationally driven by a spindle motor (SPM) 2. A frequency generator (FG) 3 composed of a Hall element or the like is connected to the rotating shaft, and an FG pulse output from the frequency generator 3 is input to the servo circuit 4.

  The servo circuit 4 controls the rotation of the spindle motor 2 so that the FG pulse and the reference clock are synchronized when the optical disk 1 is subjected to constant angular velocity control (CAV control). As a result, the rotation of the optical disk 1 is controlled at a constant angular velocity. When the servo circuit 4 performs constant linear velocity control (CLV control) of the optical disk 1, the wobble signal read from the optical disk 1 via the optical pickup (PU) 5 and amplified by the RF amplifier 6 is used as a reference. The spindle motor 2 is controlled to rotate in synchronization with the clock. As a result, the optical disc 1 is controlled to rotate at a constant linear velocity.

  The wobble signal output from the RF amplifier 6 is supplied to the address detection circuit 7. The address detection circuit 7 extracts the ATIP time code and the ATIP clock from the wobble signal, and detects the address of the optical disc 1. The detected address is supplied to a system control unit (CPU) 8. The system control unit 8 recognizes the recording position in the radial direction of the optical disc 1 from the input address, and supplies a reference clock varied based on the recording position to the servo circuit 4.

  The output of the RF amplifier 6, that is, the reproduction signal (RF signal) is input to the decoder 9, decoded and output as reproduction data, and the C1 error and SYNCQ (synchronization signal) due to the decoding are detected and the system is detected. It is supplied to the control unit 8. Further, the reproduction signal output from the RF amplifier 6 is also supplied to an optical intensity adjustment (OPC) circuit 10 and a recorded / unrecorded area detection circuit 11 as optimum recording power determination means.

  The OPC circuit 10 executes OPC prior to recording on the optical disc 1. In this embodiment, the γ method, which is also used in CD-RW, is used as OPC. In the γ method, first, test data is test-written at a predetermined recording speed (linear velocity) by changing the recording power P of the optical pickup 5 step by step for each frame. The test writing is performed using a power adjustment area (PCA (Power Calibration Area)) 1a formed on the innermost periphery of the optical disc 1 as shown in FIG. The place where the power adjustment area 1a is formed is not limited to the innermost circumference of the optical disc. The trial writing is performed over, for example, 15 frames.

  When the test data part written by trial is reproduced, a reproduction signal is obtained with a waveform as shown in FIG. The amplitude Itop of the reproduced signal from the EFM reference level (EFM Reference level) to the peak value (EFM Peak level), the amplitude Lp from the ADC reference level (ADC Reference level) to the peak value, and the bottom value (EFM) from the ADC reference level. The amplitude I11 of the difference from the amplitude Lb up to (Bottom level) is sampled and held for each recording power P. Based on these Itop and I11, the modulation degree (Modulation) m11 and its normalized slope γ are calculated using the equations (1) and (2). The slope γ is obtained by dividing dm11 / dP, which is a change in m11 / P, by m11 / P when the recording power P is changed stepwise.

  m11 = I11 / Itop (1)

  γ = (dm11 / dP) / (m11 / P) (2)

  As shown in FIG. 4, the obtained modulation degree m11 becomes a curve as shown by a solid line, and the slope γ becomes a curve as shown by a broken line. As the recording power P increases, the modulation degree m11 gradually increases and the slope γ decreases gradually.

  Here, using a test disk as the optical disk 1, the recording power P is changed stepwise to obtain the jitter at the time of initial recording in advance. The recording power P that minimizes the jitter at the time of the initial recording is set as the optimum recording power Po1. Note that the recording power P at which the jitter is minimized during the initial recording and overwriting is referred to as the optimum recording power Po. Subsequently, an arbitrary γtarget is determined, and the recording power Ptarget from which γtarget is obtained is obtained from the slope γ curve (FIG. 4) obtained above. Then, the parameter ρ is obtained from the optimum recording power Po and Ptarget using the equation (3).

  Po = Ptarget × ρ (3)

  The arbitrary γtarget determined here and the parameter ρ determined here are stored in the OPC circuit 10 as fixed values. When obtaining the optimum recording power Po of the optical disc 1 in an actual product, the modulation degree m11 and the slope γ are measured by the OPC circuit 10, Ptarget is obtained from γtarget, and the optimum recording power Po is virtually calculated from the equation (3). Ask. In the present invention, the parameter ρ is set at the time of initial recording and at the time of overwriting, and the size thereof is made smaller at the time of overwriting, as will be described later. When the first recording parameter is ρ1 and the overwrite parameter is ρ2, the relationship of equation (4) is satisfied.

  ρ1 × k = ρ2 (4)

  Returning to FIG. 1, the recording / unrecorded area detection circuit 11 reproduces the optical disk 1 prior to recording on the optical disk 1, and discriminates the unrecorded area and the recorded area over the entire program area of the optical disk 1. To do. When the optical disk 1 is inserted into the apparatus, the system control unit 8 drives the spindle motor 2 and the optical pickup 5 to detect a reproduction signal over the entire program area of the optical disk 1 and monitor the output of the decoder 9. On the other hand, the start position and end position of the unrecorded area, and the start position and end position of the recorded area are detected, and information (address) representing each position is stored in the system control unit 8. To shorten the search time, a rough rough search and a detailed fine search should be combined.

  At the time of recording, the OPC circuit 10 changes the parameter ρ based on the address of the area determined by the recorded / unrecorded area detection circuit 11. Specifically, if it is determined that the address to be recorded is an address in the unrecorded area, the parameter ρ1 at the time of initial recording is used, and if it is determined that the address is in the recorded area, the parameter ρ2 at the time of overwrite is used.

  The recording data is input to the encoder 12. The encoder 12 encodes the recording data according to the EFM clock from the system control unit 8 and supplies it to the write strategy circuit 13. The write strategy circuit 13 generates a recording pulse suitable for recording from the encoded recording data. This recording pulse is supplied to the laser driver 14. The system control unit 8 controls the laser driver 14 via the optical power control unit 15 based on the optimum recording power Po determined by the OPC circuit 10. With this control, the optical disc 1 is irradiated with a laser beam having an optimized recording power from the optical pickup 5, and recording pits having a linear density based on the EFM clock are formed on the optical disc 1.

Next, an embodiment of an optical disk recording method according to the present invention will be described. First, a polycarbonate substrate having a diameter of 120 mm with a track pitch of 0.32 μm, a reflective layer made of an Ag alloy, a first protective layer made of ZnS—SiO ₂ , a total content ratio of Ge, Sb, Te, and Ti is an atomic ratio. An optical disk 1 was prepared in which a recording layer consisting of 95% or more and a second protective layer consisting of ZnS—SiO ₂ were formed in this order, a UV curable resin was used as an adhesive layer, and a cover sheet was bonded thereto. The thickness of each layer at this time was 200 nm for the reflective layer, 8 nm for the first protective layer, 14 nm for the recording layer, and 36 nm for the second protective layer.

  Next, with an initializer having a laser beam spot diameter of 120 μm, the initialization conditions were fixed at a linear velocity of 4 m / s and a feed pitch of 40 μm, and the optical disc 1 was initialized with a laser output of 570 mW.

  Thereafter, the 1-7 modulated information signal was recorded / reproduced at 5.28 m / s with the strategy (T) shown in FIG. 1T = 15.1 nsec, P1 is the optimum recording power Po1 = Ptarget × ρ1 = 5.0 mW, P2 = 2.7 mW, P3 = 0.1 mW, P4 = 0.1 mW as the reference power, and the strategy (T) is Recorded in groove G at T1 = 0.4T, T2 = 0.4T, T3 = 0.7T, T4 = 0.7T, sliced at the center of the modulation factor and amplitude of the reproduction signal, and clock-to-data jitter (Clock to data jitter) was measured.

  Under the above recording conditions, the jitter at the time of initial recording in the unrecorded area was 6.65%, and the modulation factor was 50.2%. Subsequently, overwriting was performed once (DOW1) on the recorded area under the same recording conditions, and measurement was performed. From the equation (4), k = 1 (that is, ρ1 = ρ2, and the recording power at the time of initial recording and overwriting is equal) is set. Here, the jitter of DOW1 was 8.58%, and the modulation factor was 47.8%. Table 1 shows the values of jitter and modulation factor at the first recording when DO is changed and DOW1 (k = 1).

  First, the value of jitter and the degree of modulation was measured by changing P1 between 3.5 and 5.5 mW. In accordance with the Blu-Ray Disc standard, the appropriate range of P1 was determined by determining the good range of the recording quality of the optical disc as jitter of 10% or less and the modulation degree of 40% or more. In the initial recording and in DOW1 (k = 1), P1 which can satisfy the conditions of the jitter and the modulation degree is 3.8 to 5.4 mW. Compared with the initial recording, the jitter and the degree of modulation after the DOW1 are deteriorated due to the overwrite characteristic of the same track and the crosstalk and cross erase with the adjacent track.

  Next, for four points P1 = 3.8, 4.0, 5.0, and 5.4 mW from the range of P1 determined above, k is changed within a range of 1 to ± 0.08, That is, the jitter and modulation factor values of DOW1 were measured as 0.92ρ1 ≦ ρ2 ≦ 1.08ρ1. The measured values are shown in Tables 2 to 5. The values in Tables 2 to 5 are based on the above-described Blu-Ray Disc standard, and the range of k in which the jitter is reduced and the modulation degree is increased as compared with the case of k = 1 is obtained.

  At any four points of P1 defined above, the recording power of DOW1 is lower than the recording power of initial recording (k <1) than the recording power of DOW1 is higher (k> 1). It can be seen that the jitter of the signal decreases and the degree of modulation increases. That is, the deterioration of jitter and modulation degree is small. This is because there is no recorded data in the track in the initial recording, so the higher the recording power, the better the jitter and the degree of modulation, but overwriting that is greatly affected by crosstalk and cross erasing is compared to the initial recording. It can be said that the lower the recording power, the less the signal deterioration. Thus, according to the present invention, ρ2 <ρ1 is characteristic.

  Further, from Tables 2 to 5, k satisfying the range of jitter and modulation degree in accordance with the Blu-Ray Disc standard at all four recording powers is 0.96 ≦ k <1, that is, 0. It is preferable that 96ρ1 ≦ ρ2 <ρ1.

  As described above, according to the present invention, when recording on a high-density recording / reproducing optical disk having a narrow track pitch, the recording power Po2 is set to the recording power Po2 at the time of overwriting as shown in FIG. By performing OPC so as to be smaller than Po1 (Po2 <Po1), the jitter at the time of overwriting could be minimized. Further, it is preferable that the recording power Po2 at the time of overwriting satisfies the relationship of 0.96 times to less than 1 time of the recording power Po1 at the time of initial recording, that is, 0.96Po1 ≦ Po2 <Po1.

It is a figure which shows one Embodiment of the optical disk recording device based on this invention. It is a figure which shows one Embodiment of the power adjustment area | region of the optical disk which concerns on this invention. It is a figure which shows the reproduction | regeneration signal of the optical disk based on this invention. It is a figure which shows the relationship between the recording power which concerns on this invention, and the modulation degree, slope, and jitter of an optical disk. It is a figure which shows the strategy pattern at the time of the optical disk recording based on this invention.

Explanation of symbols

1 Optical disk 2 Spindle motor (SPM)
3 Frequency generator (FG)
4 Servo circuit 5 Optical pickup (PU)
6 RF amplifier 7 Address detection circuit 8 System controller (CPU)
9 Decoder 10 OPC circuit 11 Recorded / unrecorded area detection circuit

Claims (4)

In an overwritable optical disc recording device,
An optical pickup for recording / reproduction for irradiating a laser beam for recording / reproduction on the optical disc and detecting reflected light from the optical disc;
Prior to recording information on the optical disc, by performing trial writing on a predetermined area of the optical disc, the first optimum recording power used at the time of initial recording on the unrecorded area of the optical disc and the recorded area Optimum recording power determining means for determining a second optimum recording power smaller than the first optimum recording power used at the time of overwriting;
A recording / unrecorded area detecting means for detecting a reproduction signal of the optical disc and determining whether the area for recording the information is an unrecorded area or a recorded area;
Based on the state of the area determined by the recording / unrecorded area detection means, the first optimum recording power is recorded if the first recording to the unrecorded area, and the overwriting to the recorded area is performed. An overwritable optical disc recording apparatus, comprising: a control unit that controls the recording power of the optical pickup with the laser beam so that recording is performed with the second optimum recording power, if any.   2. The overwritable method according to claim 1, wherein the optimum recording power determining means sets the second optimum recording power to 0.96 times to less than 1 time of the first optimum recording power. Optical disk recording device. In an overwritable optical disc recording method,
By performing trial writing on a predetermined area of the optical disc, the first optimum recording power used at the time of initial recording on the unrecorded area of the optical disc and the first optimum recording power used at the time of overwriting on the recorded area An optimum recording power determination step for determining a second optimum recording power which is also small,
A discriminating step of detecting a reproduction signal of the optical disc and discriminating whether an area in which information is recorded is an unrecorded area or a recorded area;
Based on the state of the area determined in the determination step, recording is performed at the first optimum recording power when recording to the unrecorded area for the first time, and when writing to the recorded area is performed, the second And a recording step of recording with an optimum recording power. 4. The overwritable method according to claim 3, wherein the optimum recording power determining step sets the second optimum recording power to 0.96 times to less than 1 time of the first optimum recording power. Optical disc recording method.

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