JPH01263946A - Tracking mechanism for optical information recording/ reproducing device - Google Patents

Abstract

PURPOSE:To attain stable tracking even when the interval between tracking pre-groups is narrowed by providing a means to control one side of a means to detect the reflected light quantity of tracking optical beams. CONSTITUTION:The reflected light of the tracking sub-beams received by an optical head 3 passes through current-voltage converters 5a and 5b, and then, respectively made into signals TA and TB. The preceding signal TB is set at a constant level, the signal TA which receives the effect of a pit is modulated by the presence and absence of the pit with the level of the TB as a maximum value, and a DC level is decreased for the portion of modulation. There, when offsetting is added to the TA by an amplifying circuit 6a, offset fluctuation by means of the modulation is eliminated from an output TA' of the amplifying circuit 6a, and the DC level is made the same as the TB (TB'). Consequently, the TA' and TB' are made into a track error signal without an offset error through a differential amplifier 7 and an LPF 8. Thus, the correct tracking can be attained through a phase compensating circuit 9 and an actuator driving circuit 10.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a tracking mechanism for an optical information recording/reproducing device that optically records and reproduces information.

<Prior Art> In recent years, many optical information recording and reproducing devices using record carriers such as optical files, compact discs, and optical cards have been proposed and put into practical use. These optical information recording and reproducing devices record binary data "1".

'01 correspond to the presence or absence of pits, and are arranged in parallel at intervals of several to tens of micrometers.

Conventionally, the following method has been used to record and reproduce recording information in the form of pits at intervals of several to tens of micrometers.

The first method is the push-pull method, which is known as a tracking method in optical information recording and reproducing devices. This is shown in FIG. In FIG. 7(1), reference numeral 103 indicates a spora which the reflected light from the information recording carrier connects to the sensor, and reference numerals 101 and 102 indicate two-split sensors that receive the reflected light. When the light beam for recording and reproducing information is at the center of the track of the information recording carrier, the spot 103 has a symmetrical shape, but as it moves away from the center of the track, it becomes asymmetrical due to the influence of pits. This system detects the gender and performs tracking.

However, when the optical axis is shifted due to the inclination of the information recording carrier or the movement of the objective lens, the push-glue method causes spora on the sensor 101 and 102 as shown in FIG. 7(b).
There was a drawback that an offset error occurred because the position of 03 was shifted. Therefore, conventional optical information recording and reproducing devices are configured to compensate for offset errors using the position detection signal of the objective lens.

The second method is a method called the three-beam method, which is a generally accepted tracking method. Two aspects of this are shown in FIG. 8, which represent the appearance on the information recording carrier.

FIG. 8(a) shows the embodiment, in which 104 is a beam for information recording and reproduction, 105 and 106 are sub-beams for tracking, and 107 is an information pit string.

Approximately half of the beam diameter of each of the tracking sub-beams 105 and 106i is located on the information pit row 107. When the information recording/reproducing beam 104 deviates from the center of the pit row 107, the tracking sub-beams 105, 10
6 is affected differently by the pit row 107,
Tracking is performed based on the difference in the amount of reflected light between the tracking sag beams 105 and 106.

However, in the method shown in FIG. 8(a), the ninth S
There was a drawback that the N ratio was poor.

FIG. 8(b) shows another aspect of the three-beam method, in which 108 is a pre-group for tracking, 109 is an information pit,
104, 105, and 106 represent the same ones as in FIG. 8(a). Sag beam 105.10 for tracking
6 are respectively above the tracking pre-groups 108, that is, the information pits 10 are located between the pre-groups 108.
9 is arranged, and the information recording/reproducing beam 104 is placed in the pit 1.
When the center crow of row 09 approaches, tracking sub-beams 105 and 106 appear! Since the influence from the regroove 108 is different, the tracking sub-beam 10
Tracking is performed based on the difference in the amount of reflected light of 5.106.

This method is considered to be more preferable as a tracking method for an optical information recording/reproducing device because it does not have the problems of the other methods mentioned above.

<Problems to be Solved by the Invention> However, high-density recording and large capacity are generally desired in record carriers for information recording and reproducing devices, and in order to achieve high-density recording, pre-glue! 108 must be narrowed.

FIG. 9 shows the situation when the interval between the grout glues 1108 is narrowed.

FIG. 9(a) shows the situation during playback. Since the interval between the grid groups 108 has become narrower, the tracking sub-beams 105 and 106 are overlaid on the information hits 109, and are affected by the information pits 109. ing. FIG. 10 (&) shows changes in the amount of reflected light from the tracking sup beams 105 and 106 at this time. Light beams 104, 105, 1
Assuming that 06 is moving from top to bottom in FIG. 9, the signal TA indicating the amount of reflected light of the tracking sub-beam 105 is delayed in phase from the signal TB indicating the reflected light i' of 106. Therefore, a waveform as shown in FIG. 10(a) is obtained.

Here, the signals TA and TB differ only in phase, and the phase difference is approximately the same as the frequency of the recording signal, which is several hundred kHz. Also, since the frequency of track deviation is about several hundred Hz,
The tracking error signal is obtained by passing the signals TA and TB'ji through low-pass filters and obtaining a difference signal. Also, at this time, the levels of the signals TA and TB after passing through the low-pass filter change depending on the presence/absence ratio of the pits 109, but since the manner of change is the same for TA and TB, there is no significant effect on the difference signal, that is, the track error signal. do not have.

However, during recording, as shown in FIG. 9(b), the preceding sub-beam 106 always
It irradiates the part without 09, and the sub-beam 105 after
Only the information pits 109 will be affected by the information pits 109. FIG. 10(b) shows changes in the reflected light amount signals TA and TB at this time. As shown in the figure, the signal TB of the amount of reflected light of the sub-beam 106 is not affected by the pits 109 and therefore has a constant value, and changes at high frequency under the influence of the signal TAFi 109 of the amount of reflected light of the sub-beam 105. In addition, since the ratio of the presence or absence of pits 109 varies depending on the data, the level after passing through the low-pass filter is not constant, so there is a drawback that an offset error occurs depending on the data.The present invention solves this problem. The following method was developed in view of the above, and its purpose is to provide a method in which information pits are placed between the next tracking sag beams arranged at narrow intervals, and the entire tracking sag beam is irradiated onto each of the pre-groups. Another object of the present invention is to provide an entire tracking mechanism for an optical Wt information recording/reproducing device that does not cause offset errors when recording information.

Means for Solving the Problems> In order to achieve the above object, the tracking mechanism of the optical information recording/reproducing apparatus according to the present invention includes means for irradiating a tracking light beam on both sides of the information recording/reproducing light beam; It has a means for detecting the total amount of reflected light of the tracking light beam, and the reflected light of the tracking light beam:!
In a tracking mechanism that performs tracking based on the difference in the amount of reflected light obtained by the means for detecting the tracking light beam, means for controlling one of the means for detecting the amount of reflected light of the tracking light beam is provided, thereby recording information. Removed the effect of information pits on time.

<Example> Hereinafter, the tracking mechanism of the optical information recording/reproducing apparatus of the present invention will be described in detail with reference to the drawings.

A first embodiment of the present invention will be described using FIGS. 1 and 2. FIG. 1 is a block diagram showing the configuration of this embodiment.
FIG. 2 is a graph showing the state of signals flowing through each circuit.

In Fig. 1, 1 is a CPU, 2 is a radar diode drive circuit (LDD), 3 is an optical head, 4 is a low-pass filter (LPF), and 5a and 5b are signals from sensors that receive tracking sub-beams. 6m and 6b are amplifier circuits; 7 is a differential amplifier; 8 is a low-pass filter (LPF); 9 is a phase compensation circuit; IO is a tracking actuator in the optical head 3; This is an actuator drive circuit that drives the.

Tracking sub-beam 105 received by optical head 3
, 106 become signals TA and TB after passing through current-voltage converters 5m and 5b, respectively. Signal TA, TB
Each has an amplifier circuit of 6 m.

6b and becomes TA'#TB', which is then amplified by differential amplifier 7.
Enter. The output of the differential amplifier 7 has high frequency components removed by the LPF 8 to become a track error signal, which is then sent to the optical head 3 via a phase compensation circuit 9 and an actuator drive circuit 10.
Returning to , the AT Sade circuit is configured.

During recording, the CPU 1 sends recording data D to the LDD 2, and the LDD 2 uses the data D to send the recording data D to the optical head 3.
Data is recorded by modulating the laser diode. Further, the data D passes through the LPF 4 and becomes the control signal C to control the amplifier circuit 6a.

The operation of the circuit shown in FIG. 1 will be explained below using FIG. 2.

FIG. 2(a) shows the data row 1 control signal C. The data here is the r-time after modulation of the recording signal, and pits are recorded on the information recording carrier when the level is low, and are not recorded when the level is low. Furthermore, the control signal C is obtained by passing the data D through a low-level filter 4, and if there are many high levels in the data D, the level of the control signal C approaches the high level, and if there are many low levels, the control signal The level of C approaches the low level.

Next, the recording sub-beam obtained at this time is 105°10
The sensor outputs TA and TB for the amount of reflected light of 6 are shown in Fig. 2(b).
As shown in , the preceding TB is at a constant level, and the TA affected by the pit is modulated depending on the presence or absence of the pit, with the TB level being the maximum value.

Further, since the phase of TA is delayed from that of the recording/reproducing beam, the phase of TA is delayed compared to data D in FIG. 2(a).

Also, if the radar output increases and pits are formed when data D is at a high level, the amount of reflected light in the signal obtained by TA decreases where there are pits, so data D and signal TA are at a high level. The waveform looks like the low level is inverted.

The DC level of TA has been lowered by the amount of modulation, and if it is input to the differential amplifier 7 as it is, an offset error will occur. However, the offset v2 generated in TA due to modulation is lower than the amplitude of data D v4 and the level of control signal C. v
1. If the amplitude of TA is v2, then the following is true.

Therefore, an offset of Ma2 is added to TA by the amplifier circuit 6m.

Then, the output TA' of the amplifier circuit 6a is TA' in Fig. 2).
The offset fluctuation due to modulation is removed and the DC level becomes equal to TB (TB').

By passing TA'#TB' through a differential amplifier 7 and an LPF 8, a tracking error signal without offset errors can be obtained, and by passing a phase compensation circuit 9 and an actuator drive circuit 10, accurate tracking can be performed. be able to.

In this embodiment, the amplifier circuit 6a adds the offset of MA2 to TA, but the amplifier circuit 6b adds the offset of MA2 to TA.
A similar effect can be obtained by adding an offset of 1/2 to B.

Next, a second embodiment of the present invention will be described using FIGS. 3 and 4. FIG. 3 is a block diagram showing the configuration of this embodiment, and FIG. 4 is a graph showing the state of signals flowing through each circuit.

In FIG. 3, 11 is a delay circuit, and the control signal C input to the amplifier circuit 6a is obtained by delaying data D for a predetermined period of time. The other parts are the same as those in FIG. 1, so the explanation will be omitted.

Hereinafter, the operation of the circuit shown in FIG. 3 will be explained in detail using FIG. 4.

FIG. 4 (6) represents data D, and pits are formed when the level is high, as in the first embodiment. The sensor outputs TA and TB of the amount of reflected light of the sub-beams 105 and 106 during recording obtained at this time are shown in FIG. 4(e). As in the first embodiment, TA has a phase delay with respect to data D.

Therefore, the delay time of the delay circuit 11 is set according to the phase difference.

Then, the control signal C becomes in phase with TA, as shown in FIG. 4(b). Therefore, the control signal C is used to switch the gain of the amplifier circuit 6a.

fffl H. Since no pits are formed when the control signal C is at a low level o, the gains of the amplifier circuits 6m and 6b are set equal, and when the control signal C is at a high level, pits are formed and Since the reflectance decreases, the gain of the amplifier circuit 6a is increased.

Then, the output TA' of the amplifier circuit 6a becomes the same level as TB (=TB') as shown in FIG. can be obtained.

Note that when the relative speed between the information recording carrier and the optical spot is constant, the set delay time of the delay circuit 11 is constant;
For example, when an information recording carrier such as an optical disk is rotated at a constant angular velocity, the relative speed changes in proportion to the distance between the optical spot and the center of rotation of the optical disk, so the delay time should be made inversely proportional to the distance. good.

Next, a third embodiment of the present invention will be described using FIGS. 5 and 6. FIG. 5 is a block diagram showing the configuration of this embodiment, and FIG. 6 is a graph showing the state of signals flowing through each circuit.

In FIG. 5, LPF 4 generates the control signal c1.
The sensor output RF of the reflected light of the information recording/reproducing beam 104 from the optical head 3 is used as an input. The other parts are the same as those in FIG. 1, so the explanation will be omitted.

The operation of the circuit shown in FIG. 5 will be explained below using FIG. 6.

FIG. 6(a) shows the signal RF and the control signal Ct. Assuming that the laser output increases and pits are formed when the data D is at a low level, the signal RF changes according to the laser output intensity, and when the data D is at a high level, it is a high level, and when it is at a low level, it is a high level. becomes low level. Therefore, the control signal C obtained by passing the signal RF through the low-9 filter 4 has a level that fully reflects the ratio of the low level to the low level of the data D.

Therefore, in this case as well, if the amplitude of the signal RF is v1, the level of the control signal C is m, the amplitude of TA is v2, and the offset generated on TA due to modulation is 72, the following offset is generated by the amplifier circuit 6a to the TAiC210.
By doing so, the same effects as in the first embodiment can be obtained.

In this embodiment, an offset is added to TA by the amplifier circuit 6a, but the same effect can be obtained by adding an offset to TB by the amplifier circuit 6b.

In this embodiment, the second
Similarly to the embodiment described above, the gain of the amplifier circuit 6a may be switched using the delay circuit 11, and furthermore, the gain of the amplifier circuit 6a may be switched using the sensor output RF of the reflected light of the information recording/reproducing light beam 104.
A similar effect can be obtained by using the monitor photodiode output of the LD instead of controlling the offset or gain of the LD.

As shown in the above embodiments, by simply adding a simple circuit to the conventional three-beam method configuration in which information pits are placed between tracking pre-groups, stable tracking is achieved that is not affected by information pits even during recording. becomes possible.

<Effects of the Invention> Since the tracking mechanism according to the present invention is provided with a means for controlling one of the means for detecting the reflected light 1tt of the tracking light beam, even when the spacing between the tracking grid groups is narrowed, information is not transmitted during recording. A stable tracking error signal that is not affected by pits is obtained, and therefore stable tracking is possible.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a first embodiment of the present invention, FIG. 2 is a graph showing the state of signals flowing through the circuit in FIG. 1, and FIG. 3 is a block diagram showing a second embodiment of the present invention. Fourth
5 is a block diagram showing the third embodiment of the present invention. FIG. 6 is a graph showing the state of signals flowing through the circuit in FIG. 5. Figure 7 (a) and (b) are illustrations of the conventional push-pull method, Figure 8 (&) 佽) are illustrations of the three-beam method, and Figure 9 (a) and 佽) are illustrations of the 8 (b). Fig. 10 (+1) (b) is an explanatory diagram showing the state when the interval between the grid groups is narrowed in the method described above, and Fig. 9 (a) shows the state of change in the signals TA and TH of the reflected light amount of the tracking sub-beam.
) It is a graph shown about the case of (b). 1...CPU, 2...LDD, 3...Optical head,
4...Low pass filter, 5m, 5b...Current -
Voltage converter, 5m, 6b...Amplification circuit, 7...Differential amplifier, 11...Delay circuit, 104...Light beam for information recording and reproduction, 105.106...Sub beam for tracking. Agent Patent Attorney Johei Yamashita Figure 2 Figure 4 O4. t (time closed) Fig. 6 Fig. 7 (o) (b) (0) (b) (a an (b) Fig. 10

Claims (5)

[Claims] (1) It has means for irradiating tracking light beams on both sides of the information recording and reproducing light beam, and means for detecting the amount of reflected light of the tracking light beams, and detects the amount of reflected light of the tracking light beams. In a tracking mechanism that performs tracking based on the difference in the amount of reflected light obtained by the means, a means for controlling one of the means for detecting the amount of reflected light of the tracking light beam is provided, thereby eliminating the influence of information pits during information recording. A tracking mechanism for an optical information recording/reproducing device characterized by: (2) A tracking mechanism for an optical information recording/reproducing apparatus according to claim 1, wherein the means for controlling one of the means for detecting the amount of reflected light of the tracking light beam uses binary data of recorded information. (3) The optical information recording and reproducing apparatus according to claim 1, wherein the means for controlling one of the means for detecting the amount of reflected light of the tracking light beam uses the output of the information recording and reproducing light beam. Tracking mechanism. (4) The optical information recording and reproducing apparatus according to claim 1, 2, or 3, wherein the means for controlling one of the means for detecting the amount of reflected light of the tracking light beam has a low-pass filter. tracking mechanism. (5) The optical information recording and reproducing apparatus according to claim 1, 2, or 3, wherein the means for controlling one of the means for detecting the amount of reflected light of the tracking light beam has a delay circuit. tracking mechanism.