JPS61280042A - Measuring instrument for quantity of eccentricity of disk - Google Patents

Abstract

PURPOSE:To measure the real quantity of disk eccentricity by fixing the relative positions of an optical table and an optical disk and correcting the resulting lens inclination of a stop lens, and then measuring the displacement of the diaphragm lens in a tracking direction. CONSTITUTION:The quantity of eccentricity of the disk is measured by a displacement gauge 6. The displacement gauge uses, for example, an eddy current displacement type and a signal from the displacement gauge is amplified by an amplifier 5, so that data on the quantity of eccentricity corresponding to one turn of the disk is inputted to a data processing part 13. The mean value of the data is calculated and the number of jumped tracks corresponding to the value (y) when the center line of the diaphragm lens and the optical axis of a laser beam are parallel to each other is set in a jump pulse generating circuit. Consequently, a jump is made from a track which is followed up currently to another track and the quantity of eccentricity is measured when the center line of the diaphragm lens becomes parallel to the optical axis of the laser beam. The relative positions of the optical table 10 and optical disk 1 are fixed to eliminate an error due to the displacement of the optical table. Further, the center line of the diaphragm lens 2 is made parallel to the optical axis of the laser beam 7 and then the displacement of a lens support 4 is the real quantity of disk eccentricity.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to an optical disc evaluation technique.

Conventional technology FIG. 6 shows an example of a conventional eccentricity I measuring device.

The light emitted from the laser 19 passes through the beam splitter 2° and is focused onto the disk recording surface by the aperture lens 14.
The reflected light from the disk enters the light receiving element 21. A tracking error signal from the light receiving element 21 is input to a tracking servo circuit 24 and a transfer servo circuit 23. A signal from the tracking servo circuit is applied to the tracking coil 15 and follows the tracking guide groove or recording signal track. On the other hand, the signal from the transfer servo circuit is applied to the transfer motor to drive the optical bench 22 so that the DC component of the tracking error signal becomes zero.

The amount of eccentricity is determined by measuring the movement of the lens support 16 following the eccentricity of the guide groove or recording signal track using the displacement type 18. As the displacement type, for example, an eddy current displacement type is used. FIG. 7 is a flowchart for measuring eccentricity.

Problems to be Solved by the Invention In FIG. 7, the movement of the aperture lens when the transfer servo is on is taken as the amount of eccentricity. In this case, the transfer table moves in accordance with the eccentricity of the disk, and the movement of the lens support will be somewhat different from the true eccentricity of the disk. Figure 7 shows the transfer servo turned off. In this case, since the transfer table is fixed, the movement of the lens support corresponds to the true eccentricity of the disk. However, the transfer servo is often turned off. In this case, the lens support does not move in translation but moves in a combination of translational movement and rotational movement, so that the amount of displacement differs from the true value.

Means for Solving the Problems In order to solve the above problems, the present invention fixes the relative positions of the optical bench and the optical disk so that the center fm of the aperture lens and the optical axis of the laser beam are parallel to each other. to follow the same track, and measure the displacement of the lens support in the tracking direction.

By fixing the relative position of the optical table and the optical disk, errors caused by displacement of the optical table are eliminated. Furthermore, by making the center line of the diaphragm lens parallel to the optical axis of the laser beam, the displacement of the lens support becomes the true amount of disk eccentricity.

Embodiments First Embodiment A first embodiment of the present invention will be described with reference to FIGS. 1 and 2. In FIG. 1, the amount of eccentricity of the disk is measured using a displacement type 6. For example, an eddy current displacement type displacement meter is used, and a signal from the displacement meter is amplified by an amplifier 5, and eccentricity data for one rotation of the disk is taken into a data processing section 13 through an AD converter.

The average value I of this data is determined, and the number of jumps is set in the jump pulse generation circuit according to the difference between the value y when the center line of the aperture lens and the optical axis of the laser beam are parallel. This 7a-chart is shown in FIG. This jumps from the track currently being followed to another track, and measures the amount of eccentricity in a state where the center line of the aperture lens and the optical axis of the laser beam are parallel.

Second Embodiment A second embodiment of the present invention will be described with reference to FIGS. 3 and 4. This embodiment includes a transfer servo circuit 37, a transfer motor 36 for driving an optical bench 36, and a transfer servo switch 38. First, the amount of eccentricity is measured with the transfer servo on, and the average value y is determined. This average value y is considered to be a state in which the center line of the aperture lens and the optical axis of the laser beam are parallel.

Next, the transfer servo is turned off, the eccentricity is measured with the relative position of the optical bench and the optical disk fixed, the average value i is obtained, and a jump pulse corresponding to (x-y) is output.

This changes the track to be followed, measures the amount of eccentricity again, and repeats this until the average value falls within a certain range, thereby correcting the inclination of the aperture lens. This flowchart is shown in FIG. In this way, by using the average amount of eccentricity in the transfer servo-on state as a reference, it is possible to accurately measure even if there is a drift in the single circuit system or a positional deviation due to temperature between the lens support and the displacement meter. .

Third Embodiment A third embodiment of the present invention will be described with reference to FIG. In this embodiment, the inclination (xy) between the center line of the aperture lens and the laser beam optical axis is applied to the transfer motor 62,
Correction is made by moving the optical bench 61.

In addition, the second. In the third embodiment, the transport motor drives the optical bench, but a disk motor may also be driven.

Effects of the Invention The disk eccentricity measuring device of the present invention solves the problems in the transfer servo of conventional devices.

That is, by fixing the relative position of the optical bench and the optical disk and correcting the resulting tilt of the aperture lens, the displacement of the aperture lens in the tracking direction is measured, thereby making it possible to measure the true amount of disk eccentricity.

[Brief explanation of the drawing]

Fig. 1 is a principle diagram of a disk eccentricity measuring device according to a first embodiment of the present invention, Fig. 2 is a measurement flowchart of the first embodiment of the present invention, and Fig. 3 is a disc according to a second embodiment of the present invention. 4 is a flowchart of the measurement, FIG. 6 is a principle diagram of the disk eccentricity measuring device in the third embodiment of the present invention, and FIG. 6 is a diagram showing the disk eccentricity in the conventional example. FIG. 7 is a flow chart for explaining the principle of the quantity measuring device. 1... Optical disk, 2... Aperture lens, 3... Old tracking coil, 4... Lens support, 6... Displacement meter, 10... optical bench. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
TIII! 〉Hidanzu 2 Previous 2! ! I Fig. 3 Planting amount Fig. 5 Fig. 5 Amount of side sillage Fig. 6 Fig. 7! ! !

Claims (2)

[Claims] (1) an aperture lens for condensing a laser beam onto the recording surface of the optical disk; and means for driving the aperture lens to cause the aperture light to follow the guide groove or recording signal of the optical disk;
The optical bench is composed of an optical bench that supports the tracking means, a means for making the center line of the aperture lens parallel to the optical axis of the laser beam, and a displacement meter that measures the displacement of the aperture lens in the tracking direction. The relative positions of the optical disc and the optical disc are fixed so that the center line of the aperture lens and the optical axis of the laser beam are parallel to each other, and the disc eccentricity is measured by making the disc follow the same track. Disc eccentricity measuring device. (2) The disk eccentricity measurement device according to claim 1, wherein the non-parallelism between the center line of the aperture lens and the optical axis of the laser beam is detected from the average value of the eccentricity.