JPH03216819A - Optical tape recording and reproducing device - Google Patents

Abstract

PURPOSE:To shorten a servo settling time by setting a servo target value every time a rotary mirror rotates odd number times and every time it rotates even number times and constituting a servo circuit which follows the servo target value in a free running period. CONSTITUTION:The circuit means of two systems which form the servo target value formed when the rotary mirror rotates odd number times and even number times is provided. Namely, when the rotary mirror rotates odd number times, the contact (a) of a changeover switch 21 is selected and when the rotary mirror rotates even number times, the contact (b) of the switch 21 is selected, so that different smaple-hold circuits are controlled. Every time the rotary mirror rotates odd number times or even number times, the servo target value in the case of rushing in a scanning period from the free running period is sampled. Then, the servo circuit is constituted so that the servo target value is outputted from the respective different sample-hold circuits every time the rotary mirror rotates once to be the servo target value at the time of rushing in a scanning period. Thus, the settling time from rushing in the scanning period to leading in the servo is extremely shortened and the transfer speed of the data is made high.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical tape recording/reproducing device using a rotary scanning optical head.

[Summary of the Invention] The present invention provides an optical tape recording and reproducing device capable of recording and reproducing information on an optical tape using a rotary scanning optical system, in which a light spot is wound around a rotating drum or the like. The position signal of the actuator and the focus (or tracking) error signal at the time when the optical tape enters the irradiation section are sampled, and based on the servo target value set by the sampled value,
The focus (or tracking) position is controlled at the time when the first rotation drum enters the next scanning section after one revolution.

[Prior Art] In recent years, recording and reproducing devices using optical tape as a recording medium have been developed. This will be explained with reference to FIG.

In FIG. 3, l indicates a laser emission source, 2 indicates a light beam separator, and the laser light incident on the light beam separator 2 is reflected in the direction of the carbanomirror 3. 4 denotes an image rotator, which rotates the plane of polarization of the evening light reflected by the albano mirror 3, and as described later, the plane of polarization of the light reflected by the rotating mirror is on the optical tape. Always in the same direction,
It rotates at the speed of the rope in synchronization with the rotating drum.

Reference numeral 5 indicates a focus actuator, and by controlling the movement of an optical lens within the focus actuator 5 from the outside, a light spot is controlled to be in focus on the optical tape.

Reference numeral 6 denotes a rotating mirror disposed at the center of the rotating drum 7, and the laser beam reflected by the rotating mirror 6 is irradiated onto the optical table 9 via the objective lens 8.

Note that the rotating drum 7 may be fixed, and only the rotating mirror 6 and the objective lens 8 may be rotated.

The optical tape 9 is a recording medium whose surface is sensitive to light, and its running is controlled by a guide roller (not shown) that runs diagonally along the circumferential surface of the rotating drum 7. The angle at which the tape 9 and the rotating drum 7 come into contact (tape angle) is usually about 180°, but the tape angle can be set to 180°±α.

Further, the power mirror 3 is controlled by an actuator driven by a tracking error signal, and can be subjected to tracking servo.

As is well known, such an optical tape recording/reproducing device modulates a laser beam outputted from a laser light emitting source 1 according to recording data, and when the laser beam is irradiated onto an optical tape 9, an oblique light is generated on the recording surface of the optical tape 9. A recording track is formed in the direction.

Also, by guiding the reflected light when scanning this recording track from the optical separator 2 to the optical detection unit 10, the optical table 9
At the same time, the focus error signal and the tracking error signal are detected, and the focus and tracking servo of the light spot irradiated onto the optical tab 9 is performed. Problems to be Solved] Incidentally, in the case of the Ω-wound type optical tape recording and reproducing apparatus as described above, the laser beam reflected by the rotating mirror 6 is not always irradiated onto the optical tape 9.

In other words, when the rotating mirror 6 is irradiating the range A in the figure (hereinafter referred to as scanning period A), the reflected light from the optical tape 9 is incident on the optical separator 9, and the reflected light is detected by the photodetector 10. At the same time, a focus error signal and a tracking error signal are formed from this reflected light, and the focus actuator 5 and carbano mirror are
3, it is possible to control the spot on the optical table 9 so that it is in focus and on track, but the rotating mirror 6 illuminates the range B in the figure. (hereinafter referred to as idle running period B)
The reflected light from the optical tape 9 cannot be obtained, and the focus error signal and tracking signal cannot be detected during this idle running period B.

Therefore, at the time of entering the scanning period A from the idle running period B,
Even if a focus error signal or a tracking error signal is obtained, it is difficult to quickly control to the just focus state or just tracking state at that moment, and it is difficult to control the state to the just focus state or just tracking state at that moment. record data until
Or there is a problem that playback cannot be performed.

Furthermore, as the time required for this pull-in (settling time) becomes longer, the transfer rate of the recording signal decreases.

Therefore, an optical spot control device is disclosed in Japanese Patent Application Laid-Open No. 2003-110020, which is provided with means for detecting the amount of variation in the track direction of the optical tape 9 and the amount of variation in the running speed, and predicts the tracking position when entering the scanning period A from the space period B. Although proposed in Japanese Patent No. 60-136927, the above-mentioned invention requires means for detecting the amount of variation in running of the optical tape 9, which poses a problem of increasing the cost of the device.

Furthermore, since the setting of the focus servo has not been resolved, it is not possible to shorten the pull-in time as a result.

Furthermore, the invention disclosed in the above-mentioned publication has a problem in that the initial servo error caused by the deviation of the optical axis of the image rotator 4 cannot be settled.

That is, the image rotator 4 rotates the image C-D of the incident light as shown in FIG.
For example, as shown in Figure 5, 3
In the case of spot laser light, correction is made so that the three light spots @, ■, ■ reflected by the rotating mirror 6 are always in the same direction on the optical table 9, regardless of the rotational position of the rotating mirror. However, if the optical axis of the image rotator 4 is even slightly deviated from the rotation axis, the position of the light spot irradiated onto the optical tape 9 will change with each rotation, resulting in The focus distance and tracking position are different when the rotary mirror 6 is rotated on odd-numbered rotational axes and on even-numbered rotational axes, which lengthens the servo settling time.

[1,000 Steps to Solve the Problems The present invention has been made in view of the above problems, and it is possible to irradiate a light beam onto a rotating mirror through an image rotator, and use this rotating mirror to generate images on a rotating drum. In an optical tape recording and reproducing apparatus capable of sequentially scanning recording tracks of an optical tape running on a tape, a position detection means is provided to detect the deviation of a servo actuator of a light spot irradiated onto a front light distribution tape. , the servo target value formed by the output signal of the position detecting means when the light spot enters the scanning period A from the spatial period B and the servo error signal detected at the time of entry is set to an odd number of rotations of the rotating mirror; and every even number of revolutions, and a servo circuit that follows this servo target value is constructed during the idle running period B.

[Effect 1: The servo target value when entering the scanning period A from the space period B is sampled at every odd or even number of rotations of the rotating mirror, and this servo target value differs every rotation of the rotating mirror. Since the servo circuit is constructed so that the output from the sample hold circuit becomes the servo target value at the start of the scan period A, the settling time until the servo is pulled in after entering the scan period A is extremely short. Data transfer speed can be increased.

Embodiment 1 FIG. 1 shows an embodiment of the focus servo circuit employed in the optical tape recording/reproducing apparatus of the present invention.
In this embodiment, by replacing focus with tracking, the circuit can be directly used as a tracking servo circuit.

In this figure, reference numeral 1l indicates a light detector built in the light detection section 10 of FIG.
By supplying the output of 1 to the arithmetic circuit 12, a focus error signal e is generated. Reference numeral 12 denotes an adder for offset adjustment, to which an offset voltage (2) for just focus adjustment is added from a variable voltage divider 19.

l4 is a servo switch that is controlled to be switched between scanning period A and idle running period B, and in the normal focus servo state (in scanning period A, this servo switch
The focus error signal ef is supplied to the phase compensation circuit 15 through the A contact point 4, and the drive circuit 16 controls the focus actuator I7 by the diameter.

The focus actuator l7 is provided with a position sensor 18 for detecting its deviation.
The output indicates the absolute position of the focus lens.

As the position sensor 18, for example, the reflected light of the light irradiated on the actuator may be detected by a four-division detector, and the deviation thereof may be detected.

20 controls the servo switch l4 and the changeover switch 21, and also controls the idle running period r. The raw portion of the pulse that generates the sampling pulse for forming the focus servo target value output to B is shown.

This pulse generator 20 forms control pulses p. p2, P3, and P4 as described later based on the PG signal and FG signal of the rotating mirror ((rotating drum) described above.

The control pulse Pl is applied to the A of the servo switch l4 during the scanning period A.
A control pulse that selects the contact and selects contact B during the idle running period B; P2 is a control pulse that selects the a contact of the changeover switch 2l when the rotating mirror 6 rotates an odd number, and the b contact of the changeover switch 2l when the rotating mirror 6 rotates an even number; The control pulse P3 is supplied to a sample and hold circuit 24a that samples the output of the position sensor 18 every odd rotation of the rotating mirror 6, a sample and hold circuit 24b that samples the output of the position sensor l8, and a focus error signal e. Sampling hold circuit 25b that samples the output
is controlled.

In addition, 23. , 23I, is an adder that forms a focus target value, 22, 22b is a filter circuit, and 26 is a subtracter that constructs a servo circuit that sets the focus actuator 17 to the position of the servo target value.

Next, the operation shown in FIG. 1 will be explained with reference to FIG.

In this figure, PG. is a PG pulse indicating the rotation period of the image rotator 4, and PG2 is a PG pulse indicating the rotation period of the rotating mirror 6, which is the rotation speed of the crosspiece of the image rotator 4.

er' indicates a focus error signal that occurs when the focus servo is not applied, and this focus error signal er' is generated when the rotating mirror 6 rotates by an odd number (1, 35, . . . ) as seen in the figure. and even number rotation poem (2,
4, 6, ...) show different trends. This mainly occurs because the optical axis of the image rotator 4 is slightly deviated.

P3 indicates a control pulse for sampling the focus error signal and the output Pf of the position sensor when the light spot enters the scanning period A during the odd rotation period of the rotating mirror 6, and P4 indicates the control pulse for sampling the output Pf of the position sensor during the even rotation period of the rotating mirror 6. 2 shows a control pulse for sampling the focus error signal and the output Pf of the position sensor when the light spot enters the scanning period A.

These control pulses P3, P. The sample and hold circuits 24a and 25a and the sample and hold circuit 2 described above by
4b and 25b hold the focus error signal and the output Pf at the beginning of the scanning period A. Then, this hold value is supplied to the adders 23a and 23b, and the filter circuit 22a
, 22b, an average servo target value at the beginning of the scanning period A is formed.

Although this servo target value does not necessarily coincide with the just focus position, it includes the value detected at least two revolutions before entering the scanning period A, so it is very close to the just focus position.

The control pulse P2 controls the changeover switch 2l, and outputs the servo target value to the subtracter 26 during odd number rotations and even number rotations, and compares it with the current focus actuator position input to the subtracter 26. and add the servo. Therefore, just before entering the scanning period A from the idle running period B, servo is applied so that the position of the focus actuator 17 reaches the servo target value.

Then, by selecting the contact point A at the same time that the servo switch l4 enters the scanning period A, the optical detector 1
A focus error signal er output from l is supplied and the servo state is entered.

As described above, in the embodiment of the present invention, the focus actuator is controlled to the position of the servo target value during the idle running period B before the focus error signal ef is supplied, so the settling time is Can be shortened.

In particular, in the embodiment of the present invention, in an optical system that employs the image rotator 4, odd number rotations of the rotating mirror 6,
Or sample and hold circuits 24a and 24b for two different servo target values at even rotations? and 25a, 25b, and the focus actuator is controlled to the servo target value every odd and even rotation. This has an excellent effect in that fluctuations in the light spot during scanning period B can be corrected when scanning period A begins.

The focus error signal e in Fig. 2 is
, 3, 5...) period T. , shows that the focus actuator is controlled to the servo target value in the space period B, and the period T1■ shows the focus servo period of the scanning period A. Also, at even number rotations (2, 4, 6,
), T21 similarly indicates that the focus actuator is controlled to the servo target value, and T2■ indicates the focus error signal output during the focus servo period of the scanning period A.

It goes without saying that the above embodiment can be applied as is to a tracking servo circuit to settle tracking fluctuations occurring during the idle running period B.

[Effects of the Invention 1 As explained above, the optical tape recording/reproducing apparatus of the present invention uses an image rotator to irradiate a rotating mirror with laser light output from a fixed laser light source. In a device that forms an optical recording track on an optical tape wound around a rotating drum by a rotating mirror, an actuator is set to a target value at the beginning of scanning period A in a servo circuit that controls focusing or tracking of a light spot. Since a servo circuit for control is added, there is an effect that the servo settling time immediately after entering the scanning period A can be shortened.

In addition, the preprocessing 2 target value is configured so that it can be set independently during odd and even rotations of the rotating mirror, so even when the optical axis of the image rotator is misaligned, a stable servo circuit can be maintained. This has the effect of being pulled in.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a signal waveform diagram showing the operation of FIG. The figure shows an explanatory diagram of the image rotator. In the figure, 1l is a light detector. l4 is a servo switch, I
7 is the focus actuator, l8 is the position sensor
2 4 a, 2 4 b, 2 5 a, 2 5
b indicates a sample and hold circuit, and 26 indicates a subtracter. ? ■D D'C' Fig. 4 ■O■ b Fig. 5 Procedures... Original (self-sponsored) May 22, 1990

Claims (1)

[Claims] A laser light emitting source, an image rotator that polarizes the output light of the laser light emitting source, and an optical tape that is wound around a rotating drum so that the light spot output from the image rotator is passed through a rotating mirror. an optical system that illuminates the optical tape, reads information by detecting reflected light reflected from the optical tape, and includes a photodetector that detects a servo error signal of a light spot that is irradiated onto the optical tape. In the optical tape recording and reproducing apparatus, the following elements are provided: a position sensor means for detecting the deviation of a servo actuator that controls the light spot; an output signal of the position sensor at the time when the light spot enters a scanning period from an idle running period; Two systems of circuit means are provided to form servo target values formed during odd number rotations and even number rotations of the rotary miller according to a servo error signal at the time of entry, and at least in the latter half of the idle running period, the two systems of rotation means The optical tape recording and reproducing apparatus is characterized in that the position of the servo actuator is set based on the servo target value outputted from the servo actuator, and then the switching period is switched to a scanning period in which a servo error signal is supplied to the servo actuator. .