JP2727631B2 - Speed detector - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a speed detecting device for detecting the speed of a converting means on a record carrier having a large number of tracks.

2. Description of the Related Art As a conventional device, there is, for example, an optical recording / reproducing device.

An optical recording / reproducing apparatus is an information carrier (hereinafter, referred to as a disk) in which a material film that can be optically recorded and reproduced is formed on a substrate surface having tracks of concentric concavo-convex structure by a method such as evaporation. A light beam generated from a light source such as a semiconductor laser is converged and irradiated by a converging lens, and a relatively weak constant light amount is used for reproducing a signal, a signal is read from the reflected light from a disk, and a signal is recorded according to a signal to be recorded. The signal is written by modulating the light intensity of the light beam to be strong or weak.

In such an optical recording / reproducing apparatus, focus control for controlling a light beam to be almost always in a predetermined convergence state on a recording material film, and tracking control for controlling a light beam to always be positioned on a predetermined track. Control is being performed. In order to further move the beam to any desired track on the disk, the tracking control is deactivated and the light beam is moved in the radial direction of the disk toward the target track, and tracking is performed again when the light beam reaches the target track. Track search control for operating the control is performed.

One of the important things in the track search control is the speed at which the light beam crosses the target track, that is, the tracking pull-in speed. The control band of the tracking control is finite, and is usually about several KHz. Therefore, if the tracking pull-in speed is too fast, pull-in of the tracking control to the target track fails. Conversely, if the tracking pull-in speed is too slow, the time required for the track search becomes long.

Therefore, when transferring the light beam in the disk radial direction in the track search, the speed control to precisely control the tracking pull-in speed and to control the speed of the light beam to stably pull in the tracking control to the target track. It is carried out.

The track search is performed by moving the light beam in the radial direction of the disk such that the speed of the light beam becomes a predetermined reference speed corresponding to the current position of the light beam during the track search operation.

The moving speed of the light beam required to perform the speed control is detected from the period of the track crossing signal generated when the light beam crosses the track. The current position of the light beam can be obtained by counting track crossing signals from the start track of the track search. FIG. 2 shows a tracking error signal and a track crossing signal generated when the light beam crosses the track in the disk radial direction.

The tracking error signal has an optical depth of approximately λ / 8 (λ
(A) and (b) can be taken out by a push-pull method as shown in FIGS. 2 (a) and 2 (b), and a description thereof will be omitted. FIG. 2 (c) is a binarized signal obtained by binarizing the tracking error signal, and FIG. 2 (d) is an edge detection signal obtained by detecting the rising edge. This edge detection signal is generated when the light beam crosses the center of the track, and is a track crossing signal. Therefore, a value obtained by counting this signal from the start of the track search indicates the current position of the light beam. The detection of the position of the light beam by this method is hereinafter referred to as a groove counting method. Since the tracks are provided at substantially the same interval P in the radial direction of the disk, if the period of the track crossing signal is T, the speed V of the light beam can be obtained by V = P / T. The speed detection by this method is hereinafter referred to as a period measurement type speed detection method. FIG. 2 (e) shows a signal obtained by detecting the rising and falling edges of FIG. 2 (c). Assuming that the period of this signal is t, the speed V of the light beam can be similarly obtained as V = P / 2t.

In the period measurement type speed detection method, the period of the track crossing signal is generally measured using a digital timer. However, when an attempt is made to transfer the light beam at a higher speed, the clock cycle of the digital timer and the cycle of the track traversing signal become close to each other. As a result, the accuracy of the cycle measurement deteriorates and accurate speed detection becomes impossible.

Also, when the speed of the light beam is almost stopped for a track that has extremely decreased for some reason, a track traversing signal will not be generated, and the track search operation will be stopped in a state where the speed cannot be detected indefinitely. I will.

Immediately after the start of the track search operation, the relative speed of the light beam with respect to the track is low, so that the eccentricity of the disk causes the light beam to move instantaneously in the opposite direction to the target track and traverse the track, causing erroneous speed detection. .

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and provides a speed detecting device capable of accurately detecting a speed even when a light beam is transferred at a high speed and a clock cycle of a digital timer is close to a cycle of a track crossing signal.

Also, the speed of the light beam drops extremely for some reason,
It is an object of the present invention to provide a speed detecting device in which a track search operation is not interrupted even when the track is almost stopped.

Also, immediately after the start of the track search operation, a speed detecting device capable of accurately detecting the speed even when the light beam moves in the opposite direction to the target track for a moment and crosses the track due to eccentricity on the disk is provided. is there.

Means for Solving the Problems The present invention has conversion means for recording information or reproducing or recording a signal from an information carrier having a track on which information is recorded, wherein the conversion means is provided at least a plurality of times. The speed is detected by measuring the time taken to cross the track or the midpoint between the tracks.

The present invention also provides a conversion means for recording information or reproducing or recording a signal from an information carrier having a track on which the information is recorded, wherein the conversion means uses a track or a midpoint between tracks. a timer means for measuring time to cross, said a speed detecting device for detecting the speed of the converting means from the output of the time measuring means, when the output of said time measuring means becomes _one more than a predetermined value T is It said forcibly terminate time counting operation of the time measuring means is obtained by forming the output of the clock means to a predetermined value T _2.

Further, the present invention provides a conversion means for recording or reproducing a signal from or on an information carrier having a track on which information is recorded, wherein the conversion means records a track or a midpoint between tracks. A time detecting means for measuring a time for traversing the vehicle, and a speed detecting device for detecting a speed of the converting means from an output of the time measuring means, wherein a desired target track other than the track where the converting means is located The timing means is not operated for a predetermined period at the start of the track search for moving to.

Operation The present invention, by having the above configuration, allows the light beam to traverse a plurality of tracks even when the speed of the light beam becomes high and the clock cycle of the digital timer and the cycle of the track traversing signal become close to each other. Because it measures,
Speed detection can be performed with high accuracy.

Even when the speed of the light beam is extremely reduced for some reason, when the measured value of the timer for period measurement becomes equal to or more than a predetermined value, the measured value of the timer is replaced with the predetermined value, and the speed detection operation is performed. Is forcibly terminated, so that the track search operation can be prevented from being stopped.

Also, since the relative speed of the light beam to the track is low immediately after the start of the track search operation, even if the light beam moves in the opposite direction to the target track for a moment and crosses the track due to the eccentricity of the disk, the track search is started. By prohibiting the timer operation for a predetermined period, it is possible to prevent erroneous speed detection.

Embodiment Hereinafter, a track search device according to an embodiment of the present invention will be described with reference to the drawings. SUMMARY OF THE INVENTION It is an object of the present invention to provide (1) a speed detecting device capable of accurately detecting a speed even when a light beam is transferred at a high speed and a clock cycle of a digital timer is close to a cycle of a track crossing signal.

Another object of the present invention is to provide (2) a speed detecting device which does not stop the track search operation even if the speed of the light beam is extremely lowered for some reason and the track is almost stopped. To provide.

Further, another object of the present invention is to provide (3) even if, immediately after the start of the track search operation, the light beam moves in the opposite direction to the target track for a moment due to the eccentricity on the disk and crosses the track, An object of the present invention is to provide a speed detecting device capable of detecting a speed.

FIG. 1 is a block diagram showing one embodiment of the present invention. The converging lens 1 and the reflecting mirror 2 are mounted on a transfer table 3, and are configured to be driven by a voice coil motor 4 in a substantially radial direction of a disk 6 rotated by a disk motor 5. Light source 7 such as a semiconductor laser
Passes through a collimator lens 8 for collimating the light beam, and passes through a polarizing beam splitter 9 and 1 /
The light passes through a 4λ plate 10 (where λ is the wavelength of the light beam) and is applied to a reflection mirror 2 mounted on a transfer table 3. The light beam reflected by the reflection mirror 2 is converged by the converging lens 1 and irradiated on the disk 6. Light reflected from the disc 6 passes through the converging lens 1 and is reflected by the reflection mirror 2, passes through the 1λ plate 10, is reflected by the polarization beam splitter 9, and enters the two-divided photodetector 11. The dividing line of the two-divided photodetector 11 is arranged so as to be in the longitudinal direction of the track on the light receiving surface. The output signal of the split photodetector 11 is input to the differential amplifier 12. It is known that the output signal of the differential amplifier 12 configured as described above becomes a tracking error signal as shown in FIG. 2B.

Tracking error signal is phase compensation circuit 14, switch
The signal is input to the voice coil motor 4 via the adder 16, the adder 16 and the drive circuit 17 to form a tracking control.

The phase compensation circuit 14 is provided to secure the control stability of the tracking control, and the switch 15 is provided to switch between the operation and the non-operation of the tracking control. The tracking error signal is also input to the track crossing signal detection circuit 18. The track crossing signal detection circuit 18 is configured to output a track crossing signal TC (the signal in FIG. 2d) based on the tracking error signal as described in FIG.

The track crossing signal TC is also input to the timer block 20. The timer block 20 measures the period of the track crossing signal TC, and the measured value DT can be read by a microcomputer (hereinafter referred to as a microcomputer) 26. The timer block 20 is configured so that the period can be measured by dividing the track crossing signal TC by 1 / M, and the dividing ratio M can be set by the microcomputer 26. Track crossing signal TC from timer block 20
An end signal ACMP notifying that the measurement of the period has been completed is sent to the microcomputer 26, and a timer block is sent from the microcomputer 26.
A clear signal CLR that clears 20 measured values DT and inhibits period measurement is connected to each other. Track crossing signal T
C is also input from a microcomputer 26 to a counter 25 capable of presetting a count value. The counter 25 counts the number of crossing tracks, and the count value DC is connected so that the microcomputer 26 can read it. The count value DC of the counter 25 is input to the coincidence detection circuit 29. The match detection circuit 29 compares the count value DC of the counter 25 with zero, and outputs a match signal X1 to the microcomputer 26.

Further, the microcomputer 26 is connected to a D / A converter 33 whose output is inputted to the adding circuit 16 via a switch 34, so that the microcomputer 26 can drive the transfer table 3.

The control signals of the switches 15 and 34 are output from the microcomputer 26, and the operation thereof is controlled by the microcomputer 26.

Match signal X1, X2, X3, clear signal CLR, end signal ACM
P is a binary signal. In the following description, the high level of the binary signal is represented by "H" and the low level is represented by "L". FIG. 3 shows a detailed configuration diagram of the timer block 20. Truck crossing signal
TC is input to the counter 40 via the gate 46. The count value of the counter 40 is compared with the comparison value M from the microcomputer 26 by the comparison circuit 41. When the values match, the match signal X2 is set to "L", and when they do not match, it is set to "H". Match signal X2 is gated
46 is entered. Accordingly, when the counter 40 starts from a state of zero, the coincidence signal X2 becomes "H" until M pulses of the track crossing signal TC are inputted, and becomes "L" when M or more pulses are inputted. The clock CK is input to the timer 42 via the gate 47. The measurement value DT of the timer 42 is input to the comparison circuit 43 and the latch circuit 44. The comparison circuit 43 compares the measured value DT with a predetermined value P, and sets the coincidence signal X3 to "L" if they match, and to "H" if they do not match. Match signal X2, X3
Is input to the gate 47. OR circuit 48 has match signal X
2 and X3 are inverted and input, and the output is input to the latch circuit 44 and the flip-flop 45.
The latch circuit 44 is configured to latch the measurement value DT of the timer 42 when detecting the rising edge of the output signal of the OR circuit 48, and the latched value can be read by the microcomputer 26. The flip-flop 45 has the output signal of the OR circuit 48 connected to the clock terminal, detects a rising edge, and outputs “H”. The output of the flip-flop 45 is inverted and input to the microcomputer 26 as the end signal ACMP. The clear signal CLR is input from the microcomputer 26 to the clear terminal of the counter 40, the timer 42, and the flip-flop 45. When the clear signal CLR is “L”, the counter 40 and the timer 42 count and count the time value DT, respectively.
Is reset to zero, and the counting operation and the timing operation are not performed. The flip-flop 45 resets its output to “L” when the clear signal CLR is “L”. Therefore, the timer 42 performs the counting operation until M pulses of the track crossing signal TC are input or the measured value DT becomes equal to P.

Hereinafter, the detailed operation of each unit will be described by describing the track search operation in order. This embodiment is of a software-servo system in which a part of the track search control system is programmed and processed by the microcomputer 26. FIG. 4 shows a flowchart of a part of the processing performed by the microcomputer 26, which is particularly related to the present invention. Before the track search is performed, the switch 15 is turned on and the switch 34 is turned off, the tracking control is operated, and the light beam is positioned on a predetermined track. Prior to the track search, first, a track difference from the track search start track to the target track is preset from the microcomputer 26 to the counter 25, and a predetermined drive initial value for accelerating the light beam toward the target track is set to D / A. Set in converter 33.
At this time, the coincidence signal X1 is "H". The drive initial value will be described later. The clear signal CLR is set to "L" from the microcomputer 26, the counter 40, the timer 42, and the flip-flop 45 are cleared, and the coincidence signals X2, X3 and the end signal ACMP are "H". The comparison value M of the comparison circuit 41 is set to 1 by the microcomputer 26. FIG. 5 shows a time chart at the start of the track search operation. FIG. 5 (a),
(B) is a control signal for the switches 15 and 34, "H" indicates that the switch is OFF, and "L" indicates that the switch is ON. FIG. 5 (c) is a tracking error signal, (d) is a track crossing signal TC,
(E) is a clear signal CLR, (f) is an end signal ACMP,
(G) is the output of the D / A converter 33. Microcomputer 26
The switch 15 is turned off and the switch 34 is turned on in response to the command, the light beam starts moving toward the target track, and the track search operation is started. The microcomputer 26 switches the clear signal CLR to "H" after a predetermined period of delay. This is caused by the light beam moving in the opposite direction to the target track and traversing the track for a moment due to the eccentricity of the disk because the relative speed of the light beam to the track is small immediately after the start of the movement of the light beam. This is to prevent measurement of the cycle of the track crossing signal TC. Then, when the light beam crosses one track, the counter 40
Count value becomes 1, the coincidence signal X2 becomes "L", and the OR circuit 48
Changes to “H”. Then, the latch circuit 44 latches the measured value DT of the timer 42, and the output of the flip-flop 45 becomes "H", so that the end signal ACMP becomes "L". When ACMP becomes “L”, the microcomputer 26 does not read the measured value DT of the timer 42 and immediately sets the clear signal CLR to “L”. At this time, the measured values of the counter 40 and the timer 42 become zero, the flip-flop 44 is cleared, and the end signal ACMP becomes “H”. The reason why the speed value is not calculated from the measured value of the cycle of the first track crossing signal TC after the start of the track search operation is that the start of the cycle measurement operation by the timer 42 is delayed by the delay from the start of the movement of the light beam as described above. This is because the period measurement error resulting from this is included in the first measurement value of the timer 42 after the start of the track search operation.
Subsequently, the microcomputer 26 sets the clear signal CLR to "H" again, and restarts the cycle measurement of the track crossing signal TC. When the light beam traverses one track, the measured value of the counter 40 becomes 1, the coincidence signal X2 becomes "L", and the output of the OR circuit 48 changes to "H". And the latch circuit 44 is a timer 42
Is latched, and the output of the flip-flop 45 becomes “H”, so that the end signal ACMP becomes “L”. Microcomputer
26 reads the measured value DT of the timer 42 when the ACMP becomes "L", and calculates the light beam detection speed Vreal based on the measured value DT according to the following equation.

 Vreal = P * M / DT where P is the distance between tracks.

On the other hand, the counter 25 decrements the count value each time the track crossing signal TC is input during the track search operation. Therefore, the count value of the counter 25 during the track search indicates the current position of the light beam with respect to the target track. Subsequently, the microcomputer 26 reads the count value DC of the counter 25, and calculates the command speed Vref based on the DC. Count value DC
As shown in FIG. 6, the relationship between the command speed Vref and the command speed Vref is set such that the larger the count value DC, the larger the command speed Vref. The reason why the command speed Vref is constant when the count value DC of the counter 25 is larger than the predetermined value is to prevent an adverse effect due to the limitation of the dynamic range of the speed control.
The microcomputer 26 has a light beam detection speed Vreal and a command speed Vref.
And outputs the result to the D / A converter 33. The output of the D / A converter 33 drives the voice coil motor 4 via the switch 34, the adding circuit 16, and the driving circuit 17. When the track search is started, the light beam accelerates from a state where the track is almost stopped to the command speed Vref. Thereafter, as the light beam moves toward the target track, the count value of the counter 25 decreases, and accordingly, the command speed decreases, and the movement speed of the light beam also decreases. Subsequently, the microcomputer 26 compares the detected speed Vreal with a predetermined speed value N1, and determines that N2> Vreal ≧ N1 (where N2> N
If 1), set M = 2; if Vreal ≧ N2, set M = 4. After that, the clear signal CLR is once set to “L”, and then set to “H” again to restart the cycle measurement of the track crossing signal TC. This is because the speed of the light beam becomes faster, the period of the clock CK for measuring the period of the timer 42 becomes closer to the period of the track crossing signal TC, and the measured value of the timer 42 becomes
This is to prevent the accuracy of the DT from lowering. FIG. 7 shows the relationship among the track crossing signal TC, clock CK, clear signal CUR, and end signal ACMP when the light beam is at high speed and M = 4. 7A shows a track crossing signal TC, FIG. 7B shows a clock CK, FIG. 7C shows a clear signal CUR, and FIG. 7D shows an end signal ACMP. In FIG. 7, the timer 42 measures the period indicated by Z, and the measured value DT becomes 8. In order to measure the period of the track crossing signal TC using a digital timer, the measured value DT has an error of up to one clock. Therefore, the expected measurement error when M = 4 is (1/8) * 100% ≒ 13%. On the other hand, if the period measurement is performed at M = 1, the measurement by the timer 42 is performed for the period indicated by W in FIG. 7, the measured value DT becomes 2, and the measurement error is (1/2) * 100% ≒ 50. %, And the effect is clear.

On the other hand, the coincidence detecting circuit 29 is configured to output the coincidence signal X1 to the microcomputer 26 when the count value of the counter 25 becomes zero, and to output “H” to the microcomputer 26 when the coincidence does not coincide. When the count value of the counter 25 becomes zero, the light beam has reached the target track. When the coincidence signal X1 becomes "L", the microcomputer 26 immediately turns off the switch 34 and turns on the switch 15, activates the tracking control, and ends the track search. Next, the above-described drive initial value for accelerating the light beam toward the target track at the start of the track search will be described. The initial drive value is calculated by calculating the command speed Vref and the output to the D / A converter 33 without setting the detection speed Vreal by the timer 42 and unconditionally setting Vreal = 0. In the flowchart shown in FIG. 4, the process at the start of the track search operation is performed by using a flag named FIRST, distinguishing that when FIRST = 0, the calculation is the drive initial value. With this configuration, even when the light beam at the start of the track search operation is almost stopped with respect to the track, the light beam can be correctly driven toward the target track.

FIG. 8 shows the relationship between the tracking error signal, the track crossing signal TC, the clear signal CLR, and the end signal ACMP when the speed of the light beam with respect to the track is abnormally reduced due to vibration or shock applied to the apparatus from the outside. FIG. 8A shows a tracking error signal, FIG. 8B shows a track crossing signal TC, FIG. 8C shows a clear signal CLR, and FIG. 8D shows an end signal ACMP. FIG. 8 shows a case in which the light beam has almost stopped with respect to the track near the time Q due to an external impact or the like. When the speed of the light beam is reduced and the period of the track crossing signal becomes abnormally long, the coincidence signal X3 becomes "L" when the measured value TC of the timer 42 becomes P, and the gate 47 is closed. The timer 42 counting operation is forcibly stopped to prevent the timer 42 from overflowing. At the same time, the output of the OR circuit 48 becomes “H”, so the latch circuit 44
DT is latched, and the end signal ACMP becomes “L”. As described above, the microcomputer 26 determines the Vrea based on the measurement value DT and the count value DC.
l, Vref is calculated, and the difference is output to the D / A converter 33. The measured value DT at this time is equal to P.
A period indicated by Y in FIG. 8 is a period until the measured value of the timer 42 becomes P from zero.

In the present embodiment, the comparison value M is switched to three stages of M = 1, M = 2, and M = 4 in accordance with the speed of the light beam, but the same effect can be obtained by switching to two or more stages. can get.

The track traversing signal detecting circuit 18 detects that the light beam has traversed the center of the track as shown in FIG. 2D. However, as shown in FIG. It is apparent that the same effect can be obtained even if the system is configured to detect that a track has crossed the middle point of the track. In that case, the microcomputer 26 calculates the light beam detection speed Vreal from the measured value DT of the timer 42 according to the following equation.

 Vreal = M * P / (2 * DT) where P is the distance between tracks.

Further, before the track search, first, a value twice as large as the track difference from the track search start track to the target track is preset in the counter 25 from the microcomputer 26.

According to the present invention, the speed can be detected with high accuracy even when the speed of the light beam becomes high and the clock cycle of the digital timer and the cycle of the track crossing signal become close to each other.

Further, even when the speed of the light beam is extremely reduced for some reason, it is possible to prevent the track search operation from being stopped.

Further, even when the light beam traverses the track in the reverse direction due to the eccentricity of the disk at the start of the track search operation, an erroneous speed detection can be prevented.

[Brief description of the drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a waveform diagram for explaining a tracking error signal and a track crossing signal when a light beam crosses a track, and FIG. FIG. 4 is a detailed block diagram of a timer block, FIG. 4 is a flowchart of processing performed by a microcomputer in one embodiment of the present invention, FIG. 5 is a time chart at the start of track search, and FIG.
FIG. 7 is a graph for explaining the relationship between the count value of 25 and the command speed, FIG. 7 is a relationship diagram of a track crossing signal, a clock, a clear signal, and an end signal at a high speed, and FIG. 8 is tracking at an abnormal low speed. It is a relation diagram of an error signal, a track crossing signal, a clear signal, and an end signal. 1 convergent lens, 3 transfer table, 4 voice coil motor, 7 light source, 11 split photodetector, 12 differential amplifier, 15, 34 switch, 16 Adder circuit, 18…
Track crossing signal detection circuit, 20 Timer block, 25, 40 Counter, 26 Microcomputer, 29 Match detection circuit, 33 D / A converter, 4
1,43: comparison circuit, 42: timer, 44: latch circuit, 45: flip-flop.

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shinichi Yamada 1006 Kazuma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) References JP-A-62-262283 (JP, A) JP-A-1- 158624 (JP, A) JP-A-1-236481 (JP, A)

Claims (3)

(57) [Claims] 1. A conversion means for recording or reproducing a signal from an information carrier having a track on which information is recorded or on which information is recorded, wherein the conversion means determines a track or a midpoint between tracks. and a measuring means for measuring a time to traverse the a velocity detecting unit for detecting the speed of the converting means from the output of the time measuring means, when the output of said time measuring means becomes _one more than a predetermined value T is said forcibly terminate time counting operation of the time measuring means, the speed detecting device, characterized in that the output of the clock means to a predetermined value T _2. 2. The speed detecting device according to claim ₁ , wherein the predetermined value T ₁ is substantially equal to the predetermined value T ₂ . 3. The speed according to claim 1, wherein the output is made substantially zero before the start of a track search for moving the conversion means from the track where the conversion means is located to another target track. Detection device.