JPH0359508B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cross-track detection device for an optical head.

Conventionally, a device has been proposed that records an address signal on a track on a recording medium and searches for a desired track. The address A of the current track is read, the difference (A-B) from the address B of the desired track is calculated, the recording medium and the converting means are relatively moved by the moving means, and the converting means traverses the track. By counting the number of treads, and detecting that the tread has arrived on the desired track, movement by the moving means is stopped.

In this case, it is important to accurately detect when the converting means crosses the track. For example, if a dropout or dust on the recording medium generates a false track crossing signal, the moving means is stopped. When this happens, the track on which the converting means is located will be far away from the desired track, resulting in a very long search time.

SUMMARY OF THE INVENTION It is an object of the present invention to eliminate the above-mentioned drawbacks, to provide an optical head track crossing detection device which accurately detects the crossing of a track by a converting means and which requires a short search time.

The present invention provides a speed detecting means for detecting the speed of relative movement of the recording medium and the converting means by the moving means, and detects when the converting means crosses the track based on a signal from the speed detecting means. Signal passband of detection means or monostable multivibrator (hereinafter referred to as monomulti)
The track crossing signal is accurately detected by changing the time constants such as the following.

The present invention will be described in detail below with reference to the drawings.
FIG. 1 shows an embodiment in which the present invention is applied to an optical recording/reproducing device. To explain the recording/reproduction of this device, a light beam 2 generated from a light source 1 such as a semiconductor laser is made into parallel light by a coupling lens 3, and is then passed through a semi-transparent mirror 4, a reflecting mirror 5, and a converging lens 6 into a disk-shaped recording medium. Medium 7 (hereinafter referred to as recording disk)
Reflected light 8 that is converged upward and reflected by the recording disk 7 is irradiated onto a photodetector 9 via a converging lens 6, a reflecting mirror 5, and a semi-transparent mirror 4. The recording disk 7 is attached to a rotating shaft 11 of a motor 10 and rotates. Since concentric tracks are recorded on the recording disk 7 at a high density with a track width of 1 μm and a track pitch of 2 μm, the light beam focused on the recording disk 7 is controlled so that it is on the track (hereinafter referred to as This control is called tracking control). Tracking control involves obtaining the difference between the respective outputs of the photodetector 9 having a two-split structure using a differential amplifier 12, and driving this signal through a switch 13, a compensation circuit 14, and a drive circuit 15 to drive an element 16. A reflecting mirror 5 attached to the recording disk 7 is rotated to scan a light beam in a direction substantially perpendicular to the track direction on the recording disk 7. To detect that the light beam 2 focused on the recording disk 7 deviates from the track, the dividing line direction of the photodetector 9 is set in the track direction of the track pattern included in the reflected light 8, and the photodetector The differential amplifier 12 obtains the difference between the respective outputs of the 9. The output of the differential amplifier 12 is also input to a compensation circuit 17, which drives a transfer motor 19 via a drive circuit 18 to move a transfer table 20 interlocked with the transfer motor 19 in the radial direction of the recording disk 7. , so that the element 16 rotates around its natural state, that is, the output of the drive circuit 15 is controlled to be zero on average (hereinafter referred to as transfer control). The transfer table 20 includes a light source 1, a coupling lens 3, a semi-transparent mirror 4, a reflecting mirror 5, a converging lens 6,
Moving parts for the photodetector 9, the element 16, and the speed detector 21 are attached, and are configured to move together with the transfer table 20. The speed detector 21 detects the moving speed of the transfer table 20, and detects the speed magnetically, for example. The compensation circuit 14 compensates the phase of the tracking control system, and the compensation circuit 17 compensates the phase of the transfer control system. The relationship between tracking control and transfer control is that tracking control is used to correct relatively high-speed track deviations such as eccentricity and vibration, and transfer control is performed so that the element 16 rotates around its natural state. is being carried out.
The switch 13 is for disabling or activating the tracking control and transfer control, and when the switch 13 is open, the signal from the differential amplifier 12 is transmitted to the compensation circuits 14 and 17. First, the tracking control and the transfer control are inactive, and when the switch 13 is short-circuited, the tracking control and the transfer control are in operation.

A case will be described in which address signals are sequentially recorded as 1, 2, 3, . . . When the address B of a desired track is input to the address input device 22, the address input device 22 sends an address signal to the information processing control device 23. The information processing control device 23 includes a synthesis circuit 24 and a synthesis circuit 2 that synthesize the respective outputs of the photodetectors 9.
The address A of the track where the light beam 2 is currently located is read through the address extracting circuit 25 which extracts a number signal from the output of the light beam 2, and (A-B) is calculated.
Furthermore, the absolute value of (A-B) is M (M is a positive integer)
Determine whether it is greater than or less than |A-B
If |>M, the counting circuit 2 is passed through the line L1.
6 to preset |A-B|, and transfer motor 19
A start signal is sent to line L to start the transfer of
2 to the flip-flop 27, and at the same time sends a transfer direction signal for the transfer motor 19 to the transfer signal generating circuit 28 via line L3. The transfer direction signal is a signal that specifies whether to drive the transfer motor 19 to move the transfer table 20 from the outer circumference to the inner circumference of the recording disk 7 or from the inner circumference to the outer circumference. Flip-flop 27 is used to disable tracking control and transfer control.
Send the LOW signal to AND circuit 29, AND circuit 2
9 sends a LOW signal to the switch 13 to open the switch 13, and at the same time sends a HIGH signal to the counting circuit 26 and the transfer signal generation circuit 28 to open the counting circuit 2.
6 is started, and the transfer signal generating circuit 28 is also operated. The transfer signal generation circuit 28 generates a signal corresponding to the transfer direction signal transmitted from the information processing control device 23 through the line L3, transmits this signal to the drive circuit 18, and drives the transfer motor 19.
is driven to move the transfer platform 20 in the direction of a desired track. Track crossing signal generation circuit 3
The respective outputs of the photodetector 9 and the output of the speed detection circuit 31 are inputted to 0, and when the light beam 2 crosses the track, a signal is generated, and this signal is sent to the counting circuit 26 and the jumping circuit 32. introduce. When the transport motor 19 is driven to move the transport table 20 and the light beam 2 crosses the track, the counting circuit 26 subtracts the signal transmitted from the track crossing signal generating circuit 30 from the value of |A-B|. The output of the counting circuit 26 is input to the coincidence detection circuit 33, and when the output of the counting circuit becomes zero, a coincidence signal is transmitted to the flip-flop 27 and the information processing control device 23 through the line L4. The flip-flop 27 sends a LOW signal to the counting circuit 26 and the transfer signal generating circuit 28, stopping the counting operation of the counting circuit 26, and stopping the generation of the signal of the transfer signal generating circuit 28 for transferring the transfer motor 19.
The movement of the transfer table 20 is stopped. Also, the flip-flop 27 simultaneously sends the HIGH signal to the AND circuit 29.
, the switch 13 is short-circuited, and tracking control and transfer control are operated. Information processing device 2
3 again reads the address A1 of the track where the light beam 2 is located, and if A1=B, the search ends; if A1 and B do not match, (A1-
B), and if |A1-B|>M, perform the above-mentioned search, and if |A1-B|≦M, jump the value of |A1-B| and the scanning direction signal through line L4. The jumping circuit 32 sends a LOW signal to the AND circuit 29 to disable the tracking control and the transfer control, and at the same time sends a signal to the drive circuit 15 to drive the element 16 to set the light beam 2 on the desired track. Scan in a direction. When the light beam 2 crosses the track, a signal is generated by the track crossing signal generation circuit 30, and the jumping circuit 32 counts this signal.
It detects that the light beam 2 has arrived on the desired track, stops generating the signal for driving the element 16, sends a HIGH signal to the AND circuit 29 to operate tracking control and transfer control, and then A termination signal is transmitted to the information processing control device 23 via line L6. The information processing control device 23 reads the address A2 of the track where the light beam is located.
If A2=B, the search ends.

A search for a desired track is performed as described above, and when recording a signal, the intensity of the light beam 2 emitted from the light source 1 is changed and recorded. Further, during reproduction (including the case of search), the intensity of the light beam 2 is made low and constant, and the recorded signal is reproduced.

As shown in FIG. 2, the track crossing signal generation circuit 30
and the speed detection circuit 31 will be explained. The track crossing signal generation circuit 30 is composed of a combining circuit 41 that combines the respective outputs of the photodetector 9, a filter circuit 42, and a waveform shaping circuit 43. The output of the combining circuit 41 is input to the filter circuit 42, The output of the circuit 42 is input to a waveform shaping circuit 43, and the output of the waveform shaping circuit 43 is input to the counting circuit 26 and the jumping circuit 32 in FIG.
has been entered. The speed detection circuit 31 is composed of rectifier circuits 44 and 45, an inversion circuit 46, and a synthesis circuit 47. The output of the speed detector 21 is input to the rectification circuit 44 and the inversion circuit 46, and the output of the inversion circuit 46 is rectified. The outputs of the rectifying circuits 44 and 45 are input to a combining circuit 47, and the output of the combining circuit 47 is input to a filter circuit 42. The rectifying circuits 44 and 45 allow, for example, positive input signals to pass through and prevent negative input signals from passing through, the inverting circuit 46 inverts the input signals, and the combining circuit 47 combines the input signals. be. Filter circuit 42
is for changing the band through which the output signal of the combining circuit 41 is passed, depending on the signal of the combining circuit 47. For example, as shown in Fig. 3, using a FET 51 and a capacitor 52, the signal of the synthesis circuit 41 is input to the drain of the FET 51, and the signal of the synthesis circuit 41 is input to the gate of the FET 51.
By inputting the output of , it is possible to create a first-order low-pass filter whose cutoff frequency changes according to the gate voltage. Therefore, any order band-pass filter or low-pass filter can be used. By detecting the speed of the transfer table 20 using the signal from the speed detector 21, detecting the speed of the crossing truck, and transmitting only the component of the crossing truck to the waveform shaping circuit, the influence of dropouts etc. can be reduced and Accurate track crossing signals can be detected.

Although removal of dropouts and the like has been explained in an analog manner in FIGS. 2 and 3, it can also be done digitally. This will be explained in conjunction with FIG. A combining circuit 61 that combines the track crossing signal detection circuit 30 with the respective outputs of the photodetector 9, and a waveform shaping circuit 6 that shapes the waveform of the signal of the combining circuit 61.
2. The signal from the waveform shaping circuit 62 is sent to the speed detection circuit 31
The output of the monomulti 63 is input to the counting circuit 26 and the jumping circuit 32. mono multi 6
The time constant of the monomulti 63 is changed so that the pulse width of 3 is changed according to the signal from the speed detection circuit 31. Explaining in conjunction with FIG. 5, a is the synthesis circuit 6
1, b is the output of the differential amplifier 12 in FIG.
c is the output of the waveform shaping circuit 62, d is the monomulti 6
3, and even if there is a dropout 71, it will not be output to the output of the monomulti 63, and the influence of the dropout can be removed.

Combining circuit 41 in FIG. 2 and combining circuit 6 in FIG. 4
1 can also be used as the synthesis circuit 24 in FIG. Also, the combining circuits 41 and 61 can be differential amplifiers, in which case the differential amplifier 12 in FIG.
Can also be used.

Further, the output of the waveform shaping circuit 43 shown in FIG. By doing so, the track crossing signal can be detected more accurately.

It goes without saying that the present invention can also be applied to the case where the direction in which the light beam 2 traverses the tracks and the number of tracks traversed are detected from the output of the photodetector 9.

The present invention is applicable not only to optical recording and reproducing devices, but also to magnetic recording and reproducing devices, magneto-optical recording and reproducing devices, and the like.

By using the present invention, an optical disk with a simple configuration can be used to prevent not only general noise and dropout, but also disturbance caused by the address signal or information signal recorded on the information track, and pseudo disturbance caused by dust, etc. Since disturbances peculiar to the apparatus are also removed, it is possible to accurately detect a track crossing signal, and therefore, an accurate and high-speed search can be performed.

[Brief explanation of drawings]

FIG. 1 is an example of the use of the present invention, FIG. 2 is an explanatory diagram of the track crossing detection circuit and speed detection circuit of the present invention, and FIG. 3 is an embodiment of the filter circuit.
FIG. 4 shows an embodiment of the track crossing detection circuit.
FIG. 5 is a timing chart for explaining FIG. 4. 1... Light source, 7... Recording disk, 9... Photodetector, 10
...Motor, 15, 18...Drive circuit, 19...Transfer motor, 20...Transfer table, 21...Speed detector, 22...
Address input device, 23... Information processing control device, 25...
Address extracting circuit, 26... Counting circuit, 28... Transfer signal generation circuit, 30... Track crossing signal generation circuit. 32... Jumping circuit, 33... Coincidence detection circuit.

Claims (1)

[Claims] 1. A converging means for converging and irradiating a light beam generated from a light source onto a recording medium, and a light receiving means for receiving the light beam optically changed by information recorded on the recording medium. a detection means; a moving means for relatively moving the recording medium and the converging means so that the light beam on the recording medium traverses an information track; track crossing signal generating means for outputting a rectangular wave-like pulse signal each time a light beam crosses an information track; a digital signal processing means that processes the signal as if one pulse signal is input when the moving means is driven; and a speed detecting means that detects the relative moving speed of the light beam and the recording medium when the moving means is driven. one of the digital signal processing means according to the signal of the speed detection means.
1. A track crossing detection device for an optical head, characterized in that the width of the predetermined time that is processed as one pulse is changed. 2. The optical head track according to claim 1, characterized in that the track crossing signal generating means is configured to detect that the light beam crosses the information track from the sum of photocurrents of the optical detecting means. Cross-cutting detection device. 3. The track crossing signal generating means is configured to detect the positional deviation between the light beam on the recording medium and the information track from the photocurrent of the photodetecting means, and to detect that the light beam has crossed the information track from this positional deviation signal. An apparatus for detecting track crossing of an optical head according to claim 1. 4. The digital signal processing means is composed of a multivibrator that outputs a pulse with a predetermined time width according to the input pulse, and the time constant of the multivibrator is changed according to the signal from the speed detection means. Claim 1:
A track-crossing detection device for an optical head as described in 2. 5. A converging means for converging and irradiating a light beam generated from a light source onto a recording medium, a light detection means for receiving a light beam optically changed by information recorded on the recording medium, and a recording medium. a first moving means for moving the converging means so that the light beam on the recording medium crosses the information track; and a second moving means for moving the first moving means so that the light beam on the recording medium crosses the information track. means, a track crossing signal generating means for generating a signal indicating that the light beam on the recording medium crosses the information track by processing the signal of the light detecting means, and the second moving means is driven. a counting means for counting signals from the track crossing signal generating means in order to measure the number of information tracks traversed by the light beam on the recording medium; and movement of the first moving means by the second moving means. 1. A moving amount detecting device for an optical head, comprising a speed detecting means for detecting speed, and configured to change a signal pass band of a track crossing signal generating means in accordance with a signal from the speed detecting means. 6. Movement of the optical head according to claim 5, characterized in that the track crossing signal generating means is configured to detect that the light beam crosses the information track from the sum of photocurrents of the optical detecting means. Quantity detection device. 7 Track crossing signal generating means is configured to detect the positional deviation between the light beam on the recording medium and the information track from the photocurrent of the photodetection means, and to detect that the light beam has crossed the information track from this positional deviation signal. An apparatus for detecting the amount of movement of an optical head according to claim 5. 8. The track crossing signal generating means includes a multivibrator that outputs a pulse with a predetermined time width according to the input pulse, and is configured to change the time constant of the multivibrator according to the signal from the speed detecting means. An apparatus for detecting the amount of movement of an optical head according to claim 5.