JPH0258736A - Track crossing detecting system - Google Patents

Abstract

PURPOSE:To eliminate the influence of disturbance and to accurately detect the moving amount of an optical beam by generating pseudo track crossing pulses and generating a track crossing signal by synthesizing track crossing pulses with the pseudo track crossing pulses when the track crossing of the optical beam cannot be detected within prospective time. CONSTITUTION:The interval of track crossing pulses 2 is measured and, when the track crossing of an optical beam cannot be detected within prospective time when the speed of an optical beam exceeds a prescribed value, pseudo track crossing pulses 4 and 5 are generated. Then the pseudo pulses 4 and 5 are synthesized with track crossing pulses 2 detected from a tracking position error signal 1 and the track crossing signal 3 of the optical beam is generated. As a result, the track crossing signal 3 from which the influence of disturbance to the tracking position error signal 1 is eliminated can be detected. Therefore, even when the signal receives influences of disturbance, the track crossing of the optical beam can be detected accurately.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a track crossing detection method, and particularly to a method for detecting the amount of movement of a light beam and the speed of movement of a light beam during access of an optical information recording/reproducing device. The present invention relates to a method for detecting track crossings used in

[Conventional technology]

In an optical information recording/reproducing device, in order to accurately position a light beam on an information track, a positional error between the light beam and the information track is optically detected.

As a method for detecting positional errors in the tracking direction, there are well-known methods such as the push-pull method. By using these position error detection methods, for example,
An information track 72 provided with unevenness on a recording medium having a substrate 71 as shown in FIG. 7(a) can be detected as a trasoking position error signal as shown in FIG. 7(b).

That is, for example, when the light beam 75 is moved in a direction across the information track 72 from the current track to the target track during access, the tracking position error signal indicates that the light beam 75 is It can be obtained as a signal that changes periodically every time the track 72 is crossed.

In such a conventional track crossing detection method, the eighth
As shown in figure (a), I・racking position error signal 1
is supplied to the inverting input terminal of the comparator 11 to detect the polarity of the periodically changing track error signal,
Alternatively, as shown in FIG. 8(b), a low-pass filter L
By determining the DC component of the I/ranking error signal that changes periodically by the PF and comparing the DC component of the tracking position error signal 1 from the low-pass filter LPF side with the trunking position error signal 1, the optical Methods such as detecting when a beam traverses a rank to information 1 have been used.

[Problem to be solved by the invention]

However, in the access operation of an optical recording/reproducing device, in order to accurately move and position the light beam to the target track, it is necessary to detect the amount of movement of the light beam, that is, to accurately count the number of track crossings of the light beam. However, in the past, there was a problem in that the detection of this amount of movement lacked accuracy.

That is, counting the track crossing pulses described above itself can be easily and accurately performed using a counter, etc., but in the conventional tracking crossing detection method, tracking that is detected optically When the position error signal is affected by disturbance, it is difficult to accurately detect the track crossing of the light beam.

Specifically, factors that cause disturbance to the tracking position error signal include scratches on the surface of the recording medium or the substrate of the optical disk, and preformatted areas on the information tracks. In particular, as shown in FIG. 9, regarding the preformat area created by the unevenness 73 on the information track 72, information necessary for managing the position of the information track within the optical disk in which information is stored during recording and reproduction is required. Unlike scratches on recording media, the effects cannot be eliminated even if careful attention is paid to quality control at the manufacturing stage and handling in the usage environment. FIG. 10(a) shows the 1 to shilling position error signal 1 when the light beam passes through the preformat area while traversing the information track 72, and FIG. 10(b) shows the track crossing pulse 2 at this time. Each is shown below. The trunking position error signal 1 in FIG. 10(a) is
A decrease in amplitude, disturbance in waveform, and occurrence of offset appear within the preformat area. This is information track 7
Changes in the amount of reflected light due to unevenness 73 on 2, information track 7
2) This is due to various factors such as misalignment between the condensing lens for converging the light beam and the optical head, and the inclination between the optical beam and the optical axis. In this way, in the conventional track crossing signal detection method, at point A in FIG. 10(a), due to the disturbance in the tracking position error signal 1, the first
As shown at point B in Figure 0 (b), there was a problem in that it became impossible to detect the crossing of the track by the light beam.

An object of the present invention is to provide a track crossing detection method that can eliminate the influence of disturbance and accurately detect the amount of movement of a light beam.

[Means to solve the problem]

The present invention detects a position error between a light beam and an information track to generate a tracking position error signal, detects from the trunking position error signal that the light beam crosses an information track on a recording medium, and generates a track crossing pulse. The generated track crossing detection method measures the generation interval of track crossing pulses generated from the tracking position error signal, and determines from the generation interval of the track crossing pulses that the relative velocity between the light beam and the information track is above a certain value. If the speed of the light beam is above a certain value, the time for the light beam to cross the track is estimated from the interval between occurrences of track-crossing pulses, and the light beam cannot be detected to cross the track within the expected time. In this case, a pseudo track crossing pulse is generated, and the track crossing pulse and the pseudo track crossing pulse are combined to generate a track crossing signal.

[Effect]

In the track crossing detection method of the present invention, the interval between track crossing pulses is measured, and when the speed of the light beam is a predetermined value, if the track crossing of the light beam cannot be detected within the expected time, a false By generating an image track crossing pulse and combining the 1-rank crossing pulse detected from the trunking position error signal and the pseudo track crossing pulse to form a track crossing signal of the light beam,
It is possible to detect a track crossing signal without the influence of disturbance on the king position error signal. As a result, even if the 1-racking position error signal is affected by disturbance, it is possible to detect track crossing more accurately than in the conventional method.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows an embodiment of the track crossing detection method of the present invention, and FIG. 2 is a configuration diagram of an example of a pseudo track crossing pulse generation block.

In this embodiment, a position error between a light beam for recording and reproducing information on an information track on a recording medium and the information track is detected to generate a 1-ranking position error signal, and the light beam is directed onto the recording medium from the tracking position error signal. This is applied to a track crossing detection method that detects crossing of an information track and generates a track crossing pulse.As shown in FIG. It is equipped with a comparator 11 for outputting the track crossing pulse, and a speed determining means 31, which measures the generation interval of the track crossing pulse 2, outputs a pseudo track crossing pulse in a certain case, and outputs the pseudo track crossing pulse from the comparator 11. 2 to obtain a track crossing signal 3.

The speed determining means 31 is for determining whether the relative speed between the light beam and the information track is greater than a certain value from the generation interval of track crossing pulses, and in the illustrated case, the speed determining means 31 is for determining whether the relative speed of the light beam and the information track is equal to or higher than a certain value. A speed gate signal 32 is output when the speed is equal to or higher than a preset speed.

In this embodiment, the means for outputting the pseudo track crossing pulse is two pseudo track crossing pulse generating blocks 12.
It consists of 13 parts. In both cases, the time for the light beam to cross the track is estimated from the generation interval based on the track crossing pulse 2. Of these, the pseudo track crossing pulse generation block 13 detects the track crossing pulse 2 within the expected time. The other pseudo track crossing pulse generation block 12 outputs the pseudo track crossing pulse 5 when the track crossing pulse 2 is not set to the expected time. It is for outputting .

The former pseudo track crossing pulse generation block 13 includes:
The track-crossing pulse 2 is directly supplied, and the track-crossing pulse 2 is also supplied to the latter pseudo-track-crossing pulse generation block 12 via an inverter 16. Each pseudo track crossing pulse generation block 12.1
The output of NAND gate 17. They are each supplied as one input of an AND gate 18, and a speed gate signal 32 is applied as their other input.

Since this speed gate signal 32 is outputted by the speed determining means 31, under the condition that the speed of the light beam is above a certain value, the generation of each pseudo-track crossing pulse is substantially prevented. It is about to be done.

NAND gate 17. The outputs of the AND gates 18 are the outputs of the AND gates 1-14, respectively. It is supplied as one input of the OR gate 15, and the AND gate 14
The other input is the track-crossing pulse 2, and O
The output of the AND gate 14 is applied to the other input of the R gate 15. These AND gates 140R gates 1 to 15 combine the track crossing pulse 2 and the pseudo track crossing pulse 4 or 5, so that a track crossing signal 3 is obtained as the output of the OR gate 15. .

As described above, in this embodiment, a tracking position error signal is generated by detecting the position error between the light beam for recording and reproducing information on the information track on the recording medium and the information track, and the light beam is detected from the 1-racking position error signal. Information on recording medium 1
In the I-rank crossing detection method which detects the crossing of a track and generates a track crossing pulse, the comparator 11
The generation interval of the track crossing pulse 2 generated from the track crossing pulse 2 is measured, and it is determined from the generation interval of the track crossing pulse 2 that the relative speed between the light beam and the information track is above a certain value, and the speed of the light beam is determined. If the value exceeds a certain value, the time for the light beam to cross the track is estimated from the generation interval of the track crossing pulse 2, and if the light beam cannot be detected to cross the track within the expected time, a pseudo track crossing pulse is generated. The track crossing signal 3 is generated by combining the 1-rank crossing pulse and the pseudo track crossing pulse.

Detection of the track crossing of the light beam with the above configuration is performed as follows.

In FIG. 1, a tracking position error signal 1 obtained by converting an optically detected I-rank position error into an electrical signal is input to a comparator 11. The comparator 11 determines the polarity of the tracking position error signal 1 and outputs the track crossing pulse 2.
Output. The track crossing pulse 2 is sent to a pseudo track crossing pulse generation block (means) 13 and to an inverter 1.
6 to the pseudo track crossing pulse generation block (means) 12, respectively. The pseudo-track crossing pulse generation block 12.13 generates the time interval between the fall times of the human-generated 1-rack crossing pulse 2, as described above, and as will be described in detail with reference to FIG. 3 below. Measure and predict the time when the next track crossing pulse will occur,
If the track crossing pulse is not input at the expected time interval, the pseudo track crossing pulse generating means 13 has a function of outputting a pseudo track crossing pulse (signal). A pseudo track crossing pulse 5 is output when the pulse is not detected within the time limit. Further, the pseudo track crossing pulse generating means 12 and 13 have the same configuration, and the pseudo track crossing pulse generating means 12 inputs and outputs the input and output to the pseudo track crossing pulse generating means 12 to the inverter 16 . By inverting with the NAND gate 17, a pseudo I/rack crossing pulse 4 is generated when the pulse width of the track crossing pulse 2 exceeds the expected time.

NAND gate 17. As described above, the speed gate signal 32 output from the speed determining means 31 is applied to the AND gate 18. Speed determination means 3
1 detects the speed of the light beam from the track crossing signal 3;
Since the speed gate signal 32 is set when the speed is above a certain certain value, the pseudo track crossing pulses 4 and 5 are prohibited when the speed is below the speed set in the speed determining means 31.

Therefore, under conditions where such inhibition is lifted, the rank crossing pulses 4, 5 and 17 to pseudo 1, respectively, are applied to NAND gates 17. AND gate 14 via AND gate 18
is input to the OR gate 15, and the I/rack crossing pulse 2 is input to the OR gate 15.
The track crossing signal 3 is output as the track crossing signal 3.

Further, a detailed explanation will be given using FIGS. 3 to 6.

The speed determining means 31 described above is for detecting the speed of the light beam, and when the light beam moves in a direction across the information track, as shown in FIG. 3(a), the light beam crosses the information track. When the speed V across the trunking position error signal is constant, the fluctuation period T of the trunking position error signal is T-.

Here, the track crossing pulse P(i-1
) from the falling time of track crossing pulse P (i
), then the time T2 from the falling time of the track crossing pulse P(i) to the expected falling time of the next track crossing pulse p(i+1) is still T2 = TI becomes. At this time, it can be predicted that the rise time of the track crossing pulse p (i+1) is within T1 from the fall of the track crossing pulse P (i). If the rising edge of the track crossing pulse is not detected during this period, the third
As shown in Figure (C), pseudo track cross pulses, namely pseudo 1 to rack cross pulses 5 are generated,
As shown in d), the track crossing signal 3 is obtained by performing a logical sum with the track crossing pulse P shown in FIG. 3(b).

Similarly, when the tracking position error signal 1 as shown in FIG. 4(a) is input, as shown in FIG. 4(b), the track crossing pulse as shown in the rightmost pulse in the figure is This results in a pulse with a width longer than the time it takes for the beam to traverse the information track. At this time, the time interval between pulse rises is measured, and when a pulse with a width longer than the expected time is detected, a pseudo track crossing pulse 4 is generated (not shown in FIG. 4C), and a fourth [ffl A track crossing signal is generated each time a logical AND is performed with the track crossing pulse P in (b). In the track crossing detection method of this embodiment, as described above, the interval between two track crossing pulses is measured, and the track crossing is detected within the expected time for a certain 1-rank crossing pulse P (i). A pseudo track crossing pulse is generated when the state of the pulse does not change, and a track crossing pulse 2 detected from the tracking position error signal 1 is synthesized with the above-mentioned pseudo track crossing pulse to generate a light beam track crossing signal 3. Accordingly, it is possible to detect the track crossing signal 3 from which the influence of disturbance on the tracking position error signal 1 is removed.

Next, regarding the accuracy of predicting the track crossing pulse when the light beam moves while accelerating at an acceleration α, a case where there is a detection error in the track crossing pulse will be described as an example. The speed of the light beam V is the speed at a certain point. Then, it is expressed as (2): (2) o−V0+αt. At this time, the period of the tracking position error signal 1 monotonically increases or decreases with time, as shown in FIG. 5(a). Track crossing pulses P (i-1) occurring before and after track crossing pulse P (i),
If the pulse generation interval for P (i+1) is from the falling edge of a 1-rank crossing pulse to the falling edge of the next 1-rank crossing pulse, each can be expressed as T3T4 as shown in FIG. 5(b). can. here,
T3. To find T4, let the acceleration be α, and the speed of the light beam at the falling edge of the track crossing pulse P (i) be ■. , if the distance between the information tracks is X, then the speed of the light beam at the time of the track crossing pulse P(i-1) is ■-
■. Since -α·T3, T3 is first determined as follows.

That is, X=Vo"T3 cx ・T3"/2
・・14) α・T32/2 +Vo43−X=
Since O. ・ 151, considering the movement of the light beam, we can solve for T3 (from and , it becomes .

(6) Formula〇The difference between T3 and (7) formula T4 is ΔT=T3
-T4...(9), then 8T is the track crossing pulse P(+1) and P(i
), the next occurrence of P
It represents the error between the predicted time when the time until the falling edge of (i+1) is estimated as T3 and the time T4 until the falling edge of the track crossing pulse actually appears, that is, the predicted error.

Figure 6 shows the speed of the light beam ■ and the ratio of prediction error to the fall time of the predicted track crossing pulse (ΔT/
The results of calculating T3) using the acceleration α of the light beam as a parameter are shown. The prediction error shown in Fig. 6 is accumulated when the track crossing pulse cannot be detected continuously, and if the duty ratio of the track crossing pulse is m%, when the accumulated prediction error exceeds ±m%. 1- of the light beam
This causes errors in rank crossing detection. Therefore, from the calculation shown in FIG. 6, the lower limit of the speed of the light beam with respect to the acceleration α of the light beam is determined when the prediction error rate is suppressed to less than 2%. For example, if the acceleration to the light beam is α-20m/
s, the minimum speed of the light beam is approximately 18 mm/s when the prediction error is 10% or less.

As shown above, the tree I rank crossing detection method allows for more accurate track crossing detection than the conventional method even when the tracking position error signal is affected by disturbances. We can find the conditions for the speed of the light beam.

FIG. 2 shows pseudo track crossing pulse generation blocks 12 and 1.
A specific example of No. 3 is shown below. In the case of FIG. 2, since the pseudo I-rack crossing pulse 5 is generated, the pseudo 1-rank crossing pulse generation block 13 is targeted.

In FIG. 2, track crossing pulse 2 is input to flip-flop 41, delayed by one clock by flip-flop 4142 in accordance with clock 23 output from oscillator 44, and output.

The d and Q outputs of flip-flops 41 and 42 are applied to the NAND gate 43, and the edge pulse 22 corresponding to one period of the clock 23 is output from the NAND gate 43 in response to the falling edge of the track crossing pulse 2. Output. Since the edge pulse 22 is input to the counter 46 as a clear input via the switch 45, the counter 46 performs a counting operation using the clock 23.
It is cleared every time the trailing edge of track crossing pulse 2 is detected. At this time, A is applied to the clock input of the latch 47.
Since the edge pulse 22 is inputted through the ND gate 48, the value obtained by counting the clock 23 between the falling and falling edges of the track crossing pulse 2 is latched in the latch 47. Count output 24 of counter 46 and latch 47
The latch output 25 is input to a comparator 49, and when the count output 24 and the latch output 25 match, a negative logic match pulse 27 is output. The time at which the coincidence pulse 27 is output is the time when the interval between the falling edges of the track crossing pulse 2 latched by the launch (means) 47 and the time from the falling edge of the immediately preceding track crossing pulse 2 become equal. As mentioned in the explanation of FIGS. 3 to 5, the rising edge of the track-crossing pulse 2 is expected to appear by the time the coincident pulse 27 occurs. During the period in which the track crossing pulse 2 is accurately detected, the rising edge of the track crossing pulse 2 applied to the clock input of the flip-flop 40 resets the output of the flip-flop 40; The coincidence pulse 27 is input as data 1 to signal 21 to the AND gate 50 and output from the comparator 49. Therefore, when the rising edge of the track crossing pulse 2 is detected, the pseudo track crossing pulse 5 is not output. Also, flip-flop 40
is reset by the above-mentioned edge pulse 22 at the falling edge of the l/rack crossing pulse 2, and continues the edge detection operation at the rising edge of the track crossing pulse 2.

Here, a case where rank 1 to rank crossing pulses 2 are not detected due to disturbance will be described.

If the rising edge of the track-crossing pulse 2 is not detected by the time when the coincidence pulse 27 is output from the comparator 49, the gate signal 21 output from the flip-flop 40 is in the set state, so the coincidence pulse 27 becomes an AND signal.
One or more signals are output as track crossing pulses 5 through gates 1 to 50. At this time, the switch 45 is controlled by the gate signal 21 to select the B terminal, and the counter 46 receives the pseudo track crossing pulse 5 via the switch 45.
It is reset by .

In addition, the flip-flop 52 has a pseudo track pulse 5
Since the Q output 28 of the flip-flop 52 is input to the AND gate 48, the input of the edge pulse 22 to the latch 47 is prohibited, and the latch 47
The count output 24 is prohibited from going low. During the period in which the track crossing pulse 2 is not detected, the counter 46 repeats the counting operation up to the launch output 25 latched by the latch 47, and the counter 46 repeats the counting operation up to the launch output 25 latched by the latch 47, and
is output.

When the track crossing pulse 2 is detected from this state, the output 21 is reset to the gate 1 of the flip-flop 40, the switch 45 selects the B terminal again, and the next falling edge of the track crossing pulse 2 is detected. Counter 46 is cleared. Furthermore, the flip-flop 51
As a result, a clear signal 29, which is delayed by one clock from the edge pulse 22, is output and a free signal is generated.

Clear Pfurosop 52. Therefore, the operation of the latch 47 is restarted from the falling edge of the second track crossing pulse 2.

The pseudo track crossing generation block 12 can also be configured in a similar manner.

As described above, the pseudo-track-crossing pulse generation block 12.1.3 predicts the falling and rising edges of the track-crossing pulse 2, and even when the track-crossing pulse 2 cannot be detected due to disturbance, the pseudo-track-crossing pulse generation block 12.1.3 A cross-track pulse of 4°5 can be generated. By combining these pseudo track crossing pulses 4 and 5 with the track crossing pulse 2 to obtain the track crossing signal 3 as shown in FIG. 1, it is possible to obtain the track crossing signal 3 with higher accuracy than the conventional method. can.

〔Effect of the invention〕

As described above, according to the I-rank crossing detection method of the present invention, it is possible to accurately detect the amount of movement of the light beam when the light beam is moved across the information track. This makes it possible to accurately move the light beam to the target track during access and to position the optical beam on the target track at high speed.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the track crossing detection method of the present invention, FIG. 2 is a detailed explanatory diagram showing an example of a pseudo track crossing pulse generation block, and FIG. 3 is a block diagram showing an example of a pseudo track crossing pulse generation block. FIG. 4 is a diagram for explaining the detection method. FIG. 4 is a diagram for explaining the method for detecting the track crossing signal. FIG. 5 is a diagram showing the state of the track crossing pulse when the light beam moves at a predetermined acceleration. , FIG. 6 is a diagram showing the relationship between the prediction error of the track crossing pulse and the speed of the light beam by the track crossing detection method according to the present invention, FIG. 7 is a diagram for explaining the detection of the tracking position error signal with respect to the information track, Fig. 8 is a diagram for explaining the conventional detection method of track crossing pulses, Fig. 9 is a diagram showing the configuration of an optical disc having a preformat area on the information track, and Fig. 10 is a diagram using the optical disc of Fig. 9. FIG. 3 is a diagram for explaining an example of disturbance to a tracking error signal in the case of a tracking error signal. 1... Tracking position error signal 2... Track crossing pulse 3... Track crossing signal 4.5... Pseudo track crossing pulse (signal) 11...
... Comparators 12, 13 ... Pseudo track crossing pulse generation block 31 ... Speed judgment means 32, 44, 46, 47, 49, Speed gate signal, Oscillator, Counter, Launch, Comparator

Claims (1)

[Claims] (1) Detect the positional error between the light beam and the information track to generate a tracking position error signal, detect from the tracking position error signal that the light beam crosses the information track on the recording medium, and generate a track crossing pulse. In the track crossing detection method, the generation interval of track crossing pulses generated from the tracking position error signal is measured, and it is determined from the generation interval of the track crossing pulses that the relative velocity between the light beam and the information track is above a certain value. If the speed of the light beam is above a certain value, the time for the light beam to cross the track is estimated from the interval between occurrences of track-crossing pulses, and the light beam cannot be detected to cross the track within the expected time. In this case, a track crossing detection method is characterized in that a pseudo track crossing pulse is generated, and a track crossing signal is generated by combining the track crossing pulse and the pseudo track crossing pulse.