JPH01263964A - Optical disk recording and reproducing system - Google Patents

Abstract

PURPOSE:To access data at a high speed without producing out-of-track by providing one pre-pit pattern for synchronization at every plural pre-pit pairs and detecting positional information as well as the phase of a displaced pit. CONSTITUTION:Pit patterns are repeatedly provided at every section (n), (n+1), etc., which are punctuation units of data along one track on the surface of a disk and an ID section having address information and other control information is provided at the leading section of each sector (n). In addition, pre-pits which slightly meander on both right and left sides against the center of the track are arranged and data are recorded in the sections between the pre-pits. Moreover, marks for synchronization are formed on the disk in the form of pre-pits and the phase of the meandering and positions of the pre-pits are decided by detecting the marks and, furthermore, empty areas are provided around the pre-pits. While recording pulses are dislocated from a magnetic domain formed in a magnetic field modulation overwrite system, self-clocking is performed for producing reproducing clocks, since the dislocation between the magnetic domain and recording pulses are fixed. Therefore, data can be accessed without out-of-track.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a recording/reproducing method for an optical disk device, and particularly to a format configuration suitable for recording/reproducing.

[Prior Art] Conventionally, as a tracking method, a method is known in which pre-pits are meandered a small amount left and right, and data is recorded between the pre-pits (Japanese Patent Laid-Open No. 56-3439).
.

[Problems to be Solved by the Invention] This conventional example discloses one tracking operation, but only describes write-once media regarding recording and reproduction.
However, recently, reversible optical disc media have been developed, and particularly overridable media are attracting attention. Among these, an override method using magnetic field modulation is promising.

When attempting to configure an optical disk device using this method, it is necessary to reconfigure the tracking method, and to configure the access method, data recording/reproduction, etc. so that it can operate as a device.

Until now, there has been no proposal for such an overall configuration.

The challenges faced by such a system are as follows.

(2) By using a medium that can be overridden, the timing of the domains formed during recording will deviate from the recording pulse.

■Comparing the signal amount of the magneto-optical signal and the (= sign from the pre-pit), since the signal amount from the pre-pit is large, the pre-focus signal leaks into the magneto-optical signal.

- A means to reliably detect the meandering phase of pre-pits is required.

(2) For access, a means for detecting the position information of the optical spot from the disk surface is required.

[Means for Solving the Problems] In the present invention, to solve the problem (1), self-clocking is used as a data clock generation method.

Regarding the problem (2), an empty area was provided between the data recording area and the prepits.

Regarding the problem (2), something that is not in the pre-pit pattern or something that is not in the data pattern is provided in advance as a synchronization mark along with the pre-pit. and,
Recognize this during playback.

Regarding the problem (2), a special pattern for access is provided on the disk surface so that the track address can be almost detected simply by passing a light spot through the track, and this pattern is provided in advance in the synchronization area together with the synchronization mark. In order to detect even more minute track positional axes, the positions of meandering pits or special pits are changed.

[Operation] Since the deviation between the recording pulse and the formed domain is constant within the same sector, this deviation can be absorbed by self-clocking.

By providing an empty area, interference between prepits and magneto-optical signals can be reduced.

Even if data and pre-pits are present, synchronization patterns can be detected with high reliability.

The position information of the optical spot can be detected directly from the disc surface.
By controlling the actuator, you can quickly access the desired track.

By combining the above effects, an optical disk drive device can be realized.

[Example] An example of the present invention will be described below with reference to FIG. For magnetic field modulation override method, please refer to JAPANESE
JAOURNAL OF APPLIED
'PHYSIC8Vol, 26 (1987) Sup
pl, 26-4. It is described in detail in pp. 149-154, and further information on the optical system for recording and reproduction is given in the same book, pp.
7-120, the operating principle is omitted here, and the system configuration as an optical disk device will be described. In FIG. 1, a disk 1 is driven by a rotating spindle 2, and a magnetic coil 3 is placed on the disk surface.
is set and floats above the disk surface with a gap of several microns. An optical head 4 is placed opposite the magnetic coil, and a light spot from the optical head is positioned in a magnetic field area generated by the magnetic coil 3. The detection signal from the optical head 4 enters the arithmetic processing circuit 10, where it is separated into a magneto-optical signal and a signal from the pre-pit, and the magneto-optical signal enters the data demodulation circuit 11, where it is converted into a reproduced clock RCK and a gate signal indicating the location of the data. It is demodulated by the RDT and sent to the data controller 15.

The pre-pit signal from the arithmetic processing circuit 1o first enters the clock generation circuit 12, which generates lock RCK and WCK necessary for data recording/reproduction and tracking. Further, the pre-pit signal enters the track deviation detection circuit 14, and uses the control signal from the timing generation circuit 13 to generate the track deviation signal TE. Further, the pre-pit signal enters the timing generation circuit 13, and uses the clock signal from the clock generation circuit 12 to generate a control signal for detecting track deviation, a control signal for detecting position information for access, and a control signal for recording and reproducing. Signals and the like for controlling data are generated and sent to the track deviation detection circuit 14, the access controller 16, and the data controller 15, respectively.

The pre-pit signal from the arithmetic processing circuit 10 first enters the clock generation circuit 12, where it is locked and RCK required for data recording/reproduction and tracking.

Develop WCK. Further, the signal enters the track deviation detection circuit 14 and generates the track deviation signal TE using the control signal from the timing generation circuit 13. Furthermore, the timing generation circuit 13 enters and uses the clock signal from the clock generation circuit 12 to control a control signal for detecting track deviation, a control signal for detecting position information for access, and data for recording and reproduction. Generate signals etc.

The signals are sent to the track deviation detection circuit 14, access controller 16, and data controller 15, respectively.

A signal from the pre-pit is input to the access controller, and information representing the position of the light spot is detected using the signal from the timing generation circuit 13.

Further, a signal from a track deviation detection circuit 14 is inputted to detect minute track information.

Based on these signals and the target track number commanded from the host CPU 1, command information FA and CA for controlling the two actuators is sent out. The playback data processed by the data controller is sent to the host CPU 17. On the other hand, data to be recorded is sent from the host CPU 17 to the data controller 15, added with control data such as ECC (error correction code), subjected to processing such as interleaving, and then sent to the data modulation circuit 20. This circuit uses signals from the clock generation circuit 12 and timing generation circuit 13 to generate data pulses to be actually recorded on the disk surface. According to one signal, coil driver 7
drive and modulate the magnetic field. The power of the spot on the disk surface is controlled by the laser drive circuit 6.
This timing is synchronized with a signal WRC indicating the recording/reproducing state output from the host CPU. A part of the detection signal from the optical disk is input to the focus error detection circuit 19 to create a control signal AF for the autofocus servometer.
After inputting this to the optical spot control circuit 9 and performing one phase compensation, the voice coil lens 21 is driven to perform focus servo. The optical spot control circuit 9 receives a track deviation signal T.
E is input, and after processing such as phase compensation, a signal for controlling the fine actuator and coarse actuator is created.

The signal to the coarse actuator is the coarse drive circuit 8
, the coarse actuator 5 is driven to move the entire head in the radial direction of the disk. The signal FA from the access controller is input to the optical spot control circuit 9, which controls the fine actuator to enable minute and high-speed optical spot control during access. Furthermore, signal C
A is input to the coarse drive circuit 8 and controls the macroscopic movement of the entire optical head during access. A signal WRC representing recording/reproduction is generated by the clock generation circuit 12. The signals are input to a timing generation circuit 13, and each output signal is controlled according to the recording/reproduction state. The above is the overall configuration of the optical disk drive device of the present invention.

Next, the pre-pit shape will be explained using FIG. 2 b). A pit pattern is repeatedly provided on one track on the disk surface for each sector of data.

An ID section having address information and other control information is provided at the beginning of this sector, and furthermore, pre-pits are arranged which meander a small amount to the left and right with respect to the center of the track. Data is recorded between these pre-pits. In the conventional method, as shown in FIG. 4, a pit pulse indicating the pit position is created from the pre-pit, and a clock signal and a track deviation signal for recording and reproducing data are simultaneously detected from this pit pulse.

A specific waveform of the track deviation signal is shown in FIG. As shown in FIG. 3, the meandering state of pre-pits includes in-phase pits and phase-inverted pits.

For these pit patterns, the track deviation signal when the servo operation is OFF and the following state when the servo operation is ON are shown.

For data, a clock signal synchronized with the pit pulse shown in FIG. 4 is created, the recording data is modulated using this clock, and is recorded in the data area between the pre-pits. In the magnetic field modulation override method, the formed magnetized domain has a rectangular shape as shown in FIG. Conventionally, a clock created from pre-pits has been used to read out this data as well. This has the following problems. That is, in FIG. 5, due to the irradiation of the data pulse, the temperature distribution on the disk surface matches the intensity distribution of the light spot, resulting in a distribution that trails by Δ1 behind the light spot. According to the principle of magnetic field modulation override, points on the disk surface that are below the cue temperature are recorded following the magnetization direction of the external magnetic field. Therefore, if the temperature falls below the cue point at a point deviated from the center of the distribution by Δ2, the deviation Δ3 between the edge of the data pulse and the edge of the recording domain will be the sum of Δ1 and Δ2.

From the above, in principle, in the magnetic field modulation override method, the recording pulse and domain deviate. However, it is thought that this amount of deviation depends on irradiation power, linear velocity, disk sensitivity, etc., or is almost constant within the same sector and does not vary from domain to domain. For this reason, a self-clocking method, in which a clock is created from data, is adopted as a method for creating a recovered clock.

There is one more problem. When the magneto-optical signal and the signal from the pre-pit are detected by the difference and sum of the two polarization components as described later, the intensity ratio of these two signals is 1:50-100.
To some extent, the pre-pit signal leaks into the magneto-optical signal. For example, if the reproduction spot diameter is 1.5 μmφ and the prepit diameter is 0.6 μmφ, the prepit signal becomes equal to the magneto-optical signal at a distance of about 1.3 μm.
Considering the margin of signal detection, it is 2 to 2 inches from the center of the hit.
Data must be separated by about 5 μm. Therefore, a vacant area of about 4 to 5 μm is provided around the pre-pit.

Furthermore, when bits are differentiated to detect prepit positions, there is a problem in that an erroneous signal is generated due to noise, defects, etc. on the disk, a signal that is incorrect for the prepit position, and a track deviation signal is mistaken. Also,
In order to detect the track deviation signal, it is necessary to know the phase of the meandering. For this reason, synchronization marks are created in advance on the disk in the form of prepits, and the synchronization marks are detected to determine the meandering phase and at the same time identify the position of the prepits.

FIG. 6 shows a track format that takes the above into account.

One track has N sectors, and one sector has M sectors.
Each block consists of L pre-pit pair areas. One pre-pit pair area consists of a pre-pit, an empty area sandwiching the pre-pit, and a data area. Taking a 3.5' optical disk as an example, the number of data bytes in one track is 18KB when unformatted.

Number of sectors N is 20-24, M is 20-4o, L is 8-1
It will be about 6. Also, the number/track of pre-pits related to the ability to create a tracking servo clock is 6000.
~3000 pieces.

As the modulation method, a fixed length code is suitable because the data is held in a fixed length. Examples of such modulation systems that are self-clockable include 8/9 conversion, 415 conversion, and certain 2-7 modulation systems. However, in consideration of recording density efficiency, variable length codes are also applicable.

Among them, 2-7 modulation and 1-7 modulation are excellent methods, from the viewpoint of density, 2-7 modulation, and from the detection margin, 1-7 modulation.
7 modulation has advantages. In a recording/reproducing system such as a magneto-optical disk where the S/N ratio is severe and amplitude deterioration at the data frequency used is small, 1-7 modulation is advantageous because it has a generous detection margin.

Recording methods include bit position recording as shown in FIG. 6 or edge recording as shown in FIG. Although pit position recording does not require special consideration in the modulation method, the recording density is lower than that of bit edge recording. In bit edge recording, the data has a fixed length, so it is possible to control the start and end points of the recorded data to match one of the recording levels.One way to avoid this is to adjust the data according to the data before modulation. However, it is necessary to add additional bits to the modulated data to match the recording level.

A detection signal processing method using this format will be explained with reference to FIGS. 7 and 8. When the light spot 7o on the disk 1 passes through the tracks 71°72,
The reflected light is transmitted through the voice coil lens 21 and the galvano mirror.
Through the deflector 34, by the beam splitter 3o,
A portion of the beam is reflected, the beam is further separated by the beam spiriter 33, and a portion enters the defocus detection system 19. The other side is a polarizing beam splitter 36 following the 1/2 plate 35.
The polarized light components are separated by and focused by lenses 37 and 39 onto detectors 38 and 40, respectively. By adding and subtracting the signals from the detectors 38 and 40, the pre-pits and the reflected light from the disk can be detected from the sum signal, and only the magneto-optical signal component can be obtained from the difference signal. The sum signal 73 passes through the pre-pits 74 to 83 and changes in accordance with the pre-pits as shown in FIG. This signal 73 is passed through an amplifier 41 to a low-pass filter 42 for removing high-frequency sounds, and the output is differentiated by a differentiating circuit 43. A comparison 1° signal 89 is obtained from the differential signal 88 by the comparator 44 at a certain threshold, and this is expanded in pulse width by the mono multivibrator 45 to obtain a signal 90, which is combined with a signal 91 at the zero cross point of the differential signal 88. is determined by the cross point detection circuit 46, and the above signal 90
By performing a logical product with , a pit signal 92 indicating only the pre-pit portion is obtained. This signal 92 is input to the shift register 48, the pit signal is time-shifted by the specific clock 47, and the synchronization mark consisting of the pre-pit 86.87 and the time interval between 77 and 82 is set to the delay of the register 48. Synchronous timing 93 is generated from time. The pit signal 92 is also input to a PLL (phase locked loop) 49 for clock generation, and a clock WCK synchronized with the pit signal is generated.

A frequency dividing circuit 50 consisting of a counter divides this signal WCK into
is input, and an estimated pulse 94 is generated in accordance with the timing at which prepits exist in the prepit cycle. The start timing of the counter 50 is determined by the synchronization timing 93 described above. A signal 94 is input to the flip-flop 53.

Create a signal with a period twice the pre-pit period,
When logically ANDed with signal 94, signal φ1. φ2, and the timing information corresponds to the position of the pit on the left or right side with respect to the center of the track. Also, the clock signal W
Input CK to a frequency dividing circuit 51 consisting of a counter,
The start timing of the counter is determined by the signal 94 so that a pulse is generated exactly in the middle of the pre-pit, and this pulse is generated by the flip-flop 52 as the signal φ3.

The outputs of the reduction filters 42 are input to sample and hold circuits 57 and 58, respectively, and the signals φ1. The respective outputs are sampled and held by φ2, and are input to a differential amplifier 59, and the difference is taken. Although this output can be used as a track deviation signal as it is, the signal passed through the inversion circuit 6o and the same signal are input to each input of the analog switch 61, and this is inverted by the signal φ3 and the inverter 62. By switching alternately, the tracking deviation detection sampling frequency can be effectively doubled.

As a synchronization pattern, a specific pattern such as pre-pits 86 and 87 with a time arrangement that is not found in the left-right meandering pre-pit row may be used, but as shown in Fig. 9, a long hole pattern 95°96 that is not in the data may be used. However, slotted holes can also be placed between the tracks. Similarly, pit 84
, 85°86.87 patterns can also be inserted between tracks. In this way, the synchronization mark can be detected even if the light spot is located between tracks. Furthermore, considering future applications of optical discs, this device can also play back write-once discs that have been used up until now. At this time, the data is detected from the sum signal, and the signal is at the same level as the track deviation signal and the synchronization mark. In order to distinguish the synchronization marks, it is sufficient to provide a pit pattern that is not present in the recorded data.

Let's talk about data processing. The difference signal is converted into a digital signal by the binarization circuit 54, and this is converted to a digital signal by the phase comparator 55.
Enter. A signal obtained by shifting the WCK phase of the clock from the PLL 49 is input to the other input, and the phase shift circuit 56 is controlled by the output of the 1-phase comparator 55. In this way, even if there is a domain shift during recording, only the phase can be moved and synchronized with the recorded data.

This reproduction clock RCK is input to the demodulation circuit 11 to demodulate the data. In this way, since the pre-pit synchronized clock WCK is used during recording, recording can be performed without being affected by disk eccentricity or rotational fluctuations.

On the other hand, during playback, the disk eccentricity 9 is synchronized with the pre-pit.
A clock that is not affected by rotational fluctuations and whose frequency matches the recording data is detected. Here, by detecting only the phase shift from the data and performing phase matching, the clock RCK can be reproduced in synchronization with the data.

Another embodiment for generating a reproduced clock will be described with reference to FIG. The signal φ4 is input to the F/V converter 101, the frequency is converted to voltage, and then compared with the reference speed voltage by the differential amplifier 102. Put it in. On the other side of the adder 104, a phase comparator 10 detects the phase difference between the output of the voltage controlled oscillator 105 and the binary signal of the magneto-optical signal.
7, and the result of passing this output through the phase compensation circuit 106 is input. In this way, it becomes a two-man power, one-output controller. This loop is used in the F/V system and usually in the PL
It is preferable that the loop characteristic is as shown in the diagram (b). Since the F/V system has inertia,
The cross-link frequency fc2 is selected to be approximately 2 to 5 kHz. Normal self-clocking of the phase control system is several hundred kHz, but as the band is expanded in this way, the influence of noise increases, so fcl is about one order of magnitude larger than fc2.

It is desirable to set it to 20-50kHz. This prevents the reproduced clock from running out of control due to defects, etc., and also increases the normal self-clock gain and improves the tracking characteristics.

FIG. 11 shows an embodiment of access on an optical disc according to the present invention.

FIG. 12 shows an embodiment of the spot position signal generating device of the present invention. The detected optical signal is binarized by a known method and input to the synchronization detection section 48 and the gate circuit 100. The synchronization detection section detects a synchronization area using a known method such as pattern matching, and generates a synchronization pulse 93. A first phase comparator A detects the phase difference between the synchronizing pulse 93 and the clock pulse frequency-divided by the counter circuit 50.

If the phase difference is large at the start of operation or due to rotational fluctuations due to off-loading, etc., the switch is changed and the coarse synchronization mode is entered. In coarse synchronization mode, the synchronization pulse is closed and the phase control loop (PLL) is closed. After the output of the phase comparator A passes through a low pass filter (LPF) 102, a clock is generated by a voltage controlled oscillator (vC○) 103.
The frequency is divided by a counter circuit 50.

The determination circuit 104 detects that the coarse synchronization mode has entered, and switches the switch 101 to enter the fine synchronization mode. In the fine synchronization mode, PLL is performed on the servo bits. The gate circuit 100 receives the gate signal 100 from the counter circuit 50 at a timing when a servo bit should be detected, and extracts a servo pulse 91', which is a servo bit signal, from the data signal. The phase comparator circuit B compares the phase with the clock 105 every time the servo pulse 91' is input manually.

Even in the fine synchronization mode, the output of phase comparator A is monitored. If the PLL fluctuates greatly due to a defect on the disk, the absolute value of the output of the phase comparator A will increase, so this is detected at a predetermined slice level and the mode shifts to coarse synchronization mode.

The ability of the PLL in fine synchronization and coarse synchronization modes is determined by the number of servo areas and the number of synchronization areas per track. In the synchronization area, special patterns having a length of about 1 to 5 bytes are recorded, and about 100 patterns are arranged per track. On the other hand, the servo area has a length of 0.5 to 1 byte and 1 to 2 servo bits, and approximately 3000 to 6000 servo bits are arranged per track.

The PLL servo band is the frequency 1 of the input pulse to be synchronized.
It can be increased to about /10. Therefore, in the coarse synchronization mode, by using the signal of the synchronization area, a certain lock is generated and the servo area is separated from the data area. This allows the servo area to be configured in a simpler manner and improves data efficiency. Furthermore, the synchronization area can be shortened by replacing part of the synchronization pattern with servo bits. Since the servo bits and data bits are separated by gate signals, the clock phase and frequency errors in coarse synchronization mode are within the allowable range, and the gate will not shift even in the transient state when switching to fine synchronization mode. is necessary.

This condition determines the number of synchronization areas.

FIG. 13 shows signal waveforms at each part. With respect to the synchronization pulse 93, the phase comparator A exhibits the characteristics shown in the figure. in this case,
It may have a sawtooth wave shape or a positive grain wave characteristic. It is also possible to use a phase frequency comparator. Servo pulse 91' is already detected in the rough synchronization state. In the non-tracking state, the detection position of the servo pulse shifts step by step, as shown by the number of points in the figure, but by having phase comparator B with sawtooth wave characteristics as shown in the figure,
PLL can operate normally. Such a phase comparator is used, for example, in a clock demodulation circuit for a 2 to 7 modulated signal, and is not particularly illustrated.

Once the two steps to which the track the optical spot is scanning belong are known from the synchronization pattern and address data, they can be continuously measured using only the phase of the servo bit. The number of steps is required to be approximately the number of tracks that the light spot can traverse between periods of servo bits. This number is determined based on consideration of access capability as described later.

Since the number of servo bits is large, the clock generated in the fine synchronization mode is accurate and can be used as a reference clock for data recording and reproduction.

FIG. 14 shows a second example of access to the optical disk of the present invention.
An example is shown. The servo area is shorter, and the synchronization area and data area are also out of phase from track to track. The first embodiment of the spot position signal generating device in this case is described below.
It is shown in Figure 5. The number of steps is recorded as data in the synchronization area, the synchronization recognition circuit 48 detects the number of steps at the same time as discrimination from the data pattern, the selector circuit selects the corresponding clock pulse P, and the phase comparator A also detects the synchronization pulse. In this case, the synchronous rear becomes longer, but the servo area becomes shorter, so overall efficiency can be improved.

JP-A-62-143232 describes a method of adding a track identification pattern. In this case, clock synchronization information and track farewell information are obtained from different areas. That is, as shown in FIG. 16, a PLL is configured with a synchronization pattern detection signal, and a track identification pattern is decoded based on it. However, with this configuration, if you try to obtain the clock used for recording and playback from the PLL, the number of synchronization patterns increases, and if you try to access faster, the number of track identification patterns increases, resulting in poor data efficiency as a whole. The present invention solves this problem with the above-described configuration.

In the embodiment of the present invention described above, preferred examples of the number of bytes of the servo area and data area and the number of access steps are summarized as follows.

In the conventional pre-pit pattern of JP-A-62-143232, one access information 1 cannot be obtained starting from a pair of pre-pits, so when comparing with the same number of pre-pits, the number of required steps is doubled. I can't fit in.

Further, as an access pattern, there is also a pattern as shown in FIG. 17. In this case, the track intermediate position can be determined even during high-speed seek, so resolution can be improved.

Even at low speeds, the speed at which the pull-in operation is started can be reduced by about 1/2 using the track deviation signal from the mode in which speed control is performed using signals from the servo area, so that settling time is short and stable pull-in can be performed.

[Effects of the Invention] According to the present invention, it is possible to detect tracking signals and clock information with high reliability from pre-pits meandering left and right even in an overridable optical disc, and to detect optical spot position information for access. can. In addition to write-once discs, compatibility between devices and media can also be ensured for other media. In other words, a new type of light that receives signals from pre-pits with a single photodetector, does not cause track deviation due to disk tilt or movement of the optical spot, and is not affected by the time shift of recorded data due to thermal recording. Realize a disk device.

4. Brief explanation of the drawings (*Describe what the figure shows) Fig. 1 is a block diagram of the optical disc device of the present invention, Fig. 2 is a basic block diagram of the track format, and Fig. 3 is a diagram of detection from pre-pits. Figure 4 is an explanatory diagram of the signal, and Figure 5 is a waveform diagram of the reproduced signal.
6 is an explanatory diagram of the recording timing deviation, FIG. 6 is an explanatory diagram of the format of the present invention, FIG. 7 is a diagram of the detection application of the present invention, FIG. 8 is a time chart diagram of the detection system, and FIG. 9 is a diagram of the detection system. An explanatory diagram of a synchronization pattern, FIG. 10 is a reproduction clock generation nof lock diagram, FIG. 11 is a layout diagram of one of the access patterns of the present invention, FIG. 12 is a block diagram of a clock system using the access pattern in FIG. 11, FIG. 16 is a block diagram of a clock system using a conventional access pattern, and FIG. 17 is an explanatory diagram of another embodiment of the access pattern of the present invention.

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Claims (1)

[Claims] 1. Using an optical disc that has pre-pits that are slightly displaced to the left and right with respect to the track center, and on which data is additionally recorded between the pre-pits, one pre-pit pattern for synchronization is provided for each pre-pit pair, and the displaced pits are An optical disc recording and reproducing method characterized by detecting the phase and also detecting position information for access.