JPS6220484B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to devices for measuring physical quantities by tracking, and more particularly to calibration means in such devices.

As a method for indirectly measuring a changing physical quantity, there is a device that measures the track fluctuation of an information track on a disk-shaped recording medium. The device for optically measuring track runout uses an electro-magneto-mechanical conversion actuator called a movable mirror device including a tracking mirror to track a laser focusing spot on the track (hereinafter referred to as tracking).
The movable mirror device is configured to detect changes in the position of the reflected portion of the light irradiated onto the movable mirror device. The change in the position of light is detected electrically by a one-dimensional position sensor such as a photodetector.

However, since the movable part of the movable device, that is, the mirror part, has a relatively large mass, it is possible to track track shake that changes relatively slowly, but it is not sufficient to track shake that changes relatively quickly. It is difficult to respond. Therefore, although it is possible to accurately measure the low frequency components of track runout, it has been difficult to measure the high frequency components.

The present invention has been made in view of the above-mentioned drawbacks, and its purpose is to provide a measuring device that can accurately measure physical quantities that vary over a wide band.

In the measuring device according to the present invention, the measurement value is a composite signal obtained by adding an error signal corresponding to the deviation between the measuring point and the detection point to the signal corresponding to the displacement of the tracking actuator at a predetermined ratio. It is characterized by

Furthermore, in the device according to the present invention, a test signal of an appropriate frequency is injected as a disturbance into the tracking servo loop that performs tracking, and at that time, the component of the same frequency as the test signal included in the tracking error signal is minimized. The present invention is characterized by having a calibration means for setting the addition ratio so that the addition ratio becomes the same.

Embodiments of the present invention will be described below with reference to the drawings.

In this embodiment, an apparatus for optically detecting track shake of an optical disk-shaped recording medium will be explained. This device measures track runout by detecting changes in the tilt of the tracking mirror. That is, the laser beam 103 emitted from the first laser light source 101 is directed to the fixed mirror 10.
The tracking mirror 109 is irradiated via the light beams 5 and 107. The tracking mirror 109 changes its angle according to the deflection of the track on the surface of the disk 100, as will be described later. Laser beam 1 reflected by this tracking mirror 109
03 is again reflected by the fixed mirrors 107 and 105, and then is irradiated onto the one-dimensional sensor 115 via the fixed mirrors 111 and 113. Therefore, the rotation of the tracking mirror 109 is converted into a movement of the beam on the one-dimensional sensor 115, and detected as an electric signal corresponding to the movement of the beam. On the other hand, the second laser light source 11
A laser beam 119 emitted from the disk 100 is irradiated onto a track on the disk 100 via a beam splitter 121, a quarter wavelength plate 123, a fixed mirror 125, and a tracking mirror 109, and the reflected light is emitted from the tracking mirror. 109, a fixed mirror 125, a quarter wavelength plate 123, and a beam splitter 121, and are detected by a signal detection device 126 including a photodiode or the like. Tracking error information included in this detected change in the amount of reflected light is detected by a tracking error signal detection device 127 and supplied to a tracking servo device 129, and the output of this tracking servo device 129 is transmitted to the laser beam 119. Tracking mirror 109 to ensure correct tracking
Rotate. Here, when the tracking servo device 129 generates the tracking mirror drive signal, the tracking servo device 129 operates the tracking mirror according to a pulse generated once per rotation from a spindle motor (not shown) according to a command. A jump pack pulse that causes a sharp rotation at a small angle and causes a so-called still operation is also generated. This still operation allows
It is possible to continuously measure the same track.

Incidentally, a carriage servo device, a focus servo device, and other optical systems that are deemed unnecessary for the explanation of the present invention are not shown.

The tracking servo device configured as described above is used in video disc players and the like, and is disclosed in US Pat. No. 3,876,842 and the like.

Incidentally, the laser beam 103 moves on the one-dimensional sensor 115 in accordance with the rotation of the tracking mirror 109, and this value is proportional to the track shake. Therefore, the output of the one-dimensional sensor 115 is amplified by the amplifier 139 and output as the amount of track runout.

In addition, the amount of track runout is determined by the second-order differential circuit 13.
4. Bandpass filter (e.g. 80Hz to 2.2KHz)
BPF) 135 and amplifiers 141 and 1, respectively.
After being amplified by step 43, it is output as track runout acceleration and mid-range acceleration.

Further, a predetermined component of the track runout amount is extracted by a high pass filter (for example, 2.2 KHz HPF) 133 and outputted as a high frequency component via an amplifier 137. This high pass filter 133
Instead, it is possible to use various types of characteristics, and by selectively extracting the vicinity of the rotational frequency of the disk, it is also possible to measure the amount of eccentricity of the disk.

In addition, in order to compensate for track shake in high frequencies, we have developed a new system to compensate for tracking errors caused by insufficient tracking of the tracking mirror.
It is added at an appropriate rate to the relatively slow meandering component detected by the one-dimensional sensor 115. That is, the output of the tracking error detection device 127 is added to the output of the one-dimensional sensor 115 via the variable volume 145. A calibration circuit is required to maintain this addition ratio at an appropriate value.
This circuit will be explained below.

First, before measuring, turn on the calibration switch 1.
46 is closed, and the output of an oscillator 147 having a relatively high predetermined frequency is injected into the tracking servo loop. Then, the injected oscillation frequency component is extracted from the track shake signal caused by the movement of the tracking mirror affected by this disturbance.
It is extracted using the bandpass filter 149 and the value is displayed on the display 151. Here, the person measuring
The value of the variable volume 145 is adjusted so that the value displayed on the display 151 becomes the minimum (preferably zero), and the calibration switch 146 is opened to complete the calibration.

This principle will be explained in detail using the block diagram shown in FIG.

Considering the tracking servo loop shown in FIG. 1, the deviation of the position of the irradiated laser focusing spot from the position of the track on the disk at a certain moment is detected, and the tracking mirror 109 is activated in accordance with this detection signal. Feedback control is performed so that the position of the laser focus spot coincides with the position of the track by rotating the laser.

That is, if the track signal indicating the meandering of the track on the disk is Dt, and the signal corresponding to the movement of the laser focusing spot is Dm, then the deviation of the laser focusing spot position with respect to the track position is A(Dt
−Dm). Here, A is a detection gain depending on the sensitivity etc. of the tracking error signal detection device 127. This deviation signal corresponds to a tracking error signal, and this signal is transmitted to the tracking mirror 109 based on the transfer function G _(s).
The rotation of the laser beam is converted into the movement of the laser focusing spot. A change in the angle of the tracking mirror 109 is detected as a movement of the laser beam 103 irradiated onto the one-dimensional sensor 115 via the tracking mirror 109. This movement and disk 100
Since this is equivalent to the movement of the laser collection spot above, the output signal of the one-dimensional sensor 115 can be captured as Dm. On the other hand, if the tracking due to rotation of the tracking mirror 109 is not completed and a deviation remains, a tracking error signal is generated, and the laser focus spot is deviated from the track by a distance corresponding to this value. There is. Therefore, the tracking shake detection signal Dx is the sum of the output of the one-dimensional sensor 115 and a signal obtained by multiplying the tracking error signal by a predetermined control gain k. It is assumed that the control gain k can be set to any value by the variable volume 145.

If the above-mentioned relationship is expressed in a formula, it becomes Dx = Dm + Ak (Dt - Dm). Here, Dt-Dm corresponds to tracking error.

Therefore, if Ak=1, Dx=Dt, and the track signal Dt can be obtained from the track shake detection signal Dx. Generally, the detection gain A fluctuates under the influence of temperature changes, etc., and therefore needs to be calibrated.

Now, when the switch S corresponding to the calibration switch 146 is closed and the test signal e of an appropriate frequency output from the oscillator 147 is injected into the servo loop to measure Dx, Dx=A(k+G _(s) )Dt+ (1-Ak)e/1+
Since AG _(s) , if we extract the same frequency component as e, Dx = (1-Ak)/1+AG _(s) e, so if we adjust k so that this component becomes zero, we get Ak =1 can be satisfied.

That is, the track sway detection signal Dx and the track signal Dt indicating the actual track meandering match.

Therefore, it is possible to accurately measure the track shake in a high range where it is impossible for the tracking mirror 109 to follow it.

As described above, with the measuring device according to the present invention, it is possible to accurately measure physical quantities that vary over a wide band, and it is also possible to easily calibrate measurement errors that vary due to the influence of temperature changes, etc. can.

Although the present invention has been described using an apparatus for optically detecting track shake of an optical disk-shaped recording medium, it can be widely applied to apparatuses that measure physical quantities by tracking.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention;
FIG. 2 is a block diagram for explaining the principle of the present invention. 109... Tracking mirror, 115... One-dimensional sensor, 127... Tracking error signal detection device, 145... Variable volume, 147... Oscillator,
151...Display device.

Claims (1)

[Claims] 1 A measuring device including a tracking means for causing a detection point to follow a physical quantity that changes with the passage of time, which generates a first signal according to a deviation between the physical quantity that changes and the detection point. a tracking error generating means for generating a second signal according to the displacement of an actuator for moving the detection point; means for outputting the composite signal as a measurement value; and adding a disturbance signal of a predetermined frequency to the tracking means, and adjusting the predetermined ratio so that the component of the same frequency as the disturbance signal included in the composite signal is minimized. and means for pre-calibrating the measuring device.