JPH03269844A - Eccentric quantity measuring instrument - Google Patents

Abstract

PURPOSE:To measure eccentric quantity with simple constitution by binarizing a tracking error signal due to beam aberration, and counting the number of signals synchronizing with the rotation of a recording medium. CONSTITUTION:The tracking error signal Sr of sinusoidal shape by the irradiation beam of an optical disk is binarized by a binarization means 1 on which a prescribed threshold value is set, and it goes to a pulse PT with high level and short cycle or with low level and long cycle corresponding to the eccentric quantity. The pulse PT is counted by a counter means 3 controlled by a signal SG synchronized with the rotation of the disk outputted from a gate signal generating means 2, and the measured value of the eccentric quantity is displayed on an eccentric quantity display part 5, thereby, the eccentric quantity of the optical disk, etc., can be measured with the simple constitution.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an eccentricity measuring device used in optical disk devices and the like.

BACKGROUND ART In general, eccentricity occurs in recording media such as optical disks as they rotate, and different eccentricities occur depending on how they are inserted into the motor shaft, so it is necessary to measure the amount of eccentricity in advance. be.

Figure 3 shows a conventional eccentricity measuring device (Japanese Patent Laid-Open No. 61-119
40).

In FIG. 3, 6 is an optical disk on which an information trunk 6a is formed, 7 is a motor for rotating the optical disk 6, and 8 is an optical pick amplifier.

The optical pickup 8 is roughly composed of a movable part 9 movable in the radial and axial directions of the optical disc 6, and a drive part 10 such as a voice coil motor for driving the movable part 9. a semiconductor laser (not shown) that irradiates the optical disc 6; an objective lens (not shown) that focuses this beam and irradiates the optical disc 6 with a spot light;
It has a light-receiving element (not shown), etc., for receiving reflected light from and obtaining data signals (RF multiplied signal, tracking error signal, and focus error signal).

The motor 7, optical pickup 8, etc. constitute an optical disk device that drives the optical disk 6.

Reference numeral 11 indicates a light source for measuring the amount of eccentricity and surface wobbling of the optical disc 6, reference numeral 12 indicates a collimator lens that shapes the light from the light source 11 into parallel light, and reference numerals 13a and 13b indicate that the movable part 9 of the optical pickup 8 is a collimator. A portion of the parallel light from the lens 12 is guided to the optical disc 6 so as to be blocked.
Optical fiber for measuring the amount of eccentricity and amount of surface runout, 14
a and 14b are optical fibers that guide light from optical fibers 13a and 13b, respectively; 15a and 15b are photodetectors that detect light guided by optical fibers 14a and 14b, respectively; 16a and 16b are light detectors that respectively detect light guided by optical fibers 14a and 14b; detector 15a,
This is an amplifier that amplifies the output of 15b.

Next, the operation of the above conventional example will be explained.

In FIG. 3, when the optical disc 6 is rotated by the motor 7 and a beam is irradiated onto the track 6a of the optical disc 6, the light receiving element obtains reflected light corresponding to the amount of eccentricity and the amount of surface wobbling of the optical disc 6, and the movable part 9 moves in the radial direction and axial direction of the optical disc 6 according to the amount of eccentricity and surface runout of the optical disc 6 by a driving unit 1o using a tracking servo loop and a focus servo loop (not shown).

When the movable part 9 moves in this way, the optical fibers 13a,
Parallel light from optical fibers 14a and 14b is blocked from optical fibers 13b, and photodetectors 15a and 15b output signals at levels corresponding to the amount of eccentricity and surface wobbling of optical disk 6.

Therefore, the amount of eccentricity and the amount of surface wobbling of the optical disk 6 can be measured by the amplifiers 16a and 16b, respectively.

Problems to be Solved by the Invention However, in the conventional eccentricity measuring device described above, in order to measure the amount of movement of the movable part 9 of the optical pink-up 8, a separate light beam from the semiconductor laser of the optical pickup amplifier 8 is used. T14 requires 1tll and other parts and is therefore expensive.
There is M.

In view of the above problem, it is an object of the present invention to provide an eccentricity measuring device that can measure the eccentricity of a recording medium with a simple configuration.

Means for Solving RB In order to solve the above problems, the present invention binarizes the tracking error signal and counts this binarized signal in synchronization with the rotation of the recording medium.

Effect of the present invention Due to the above-mentioned power, the period of the tracking error signal varies depending on the amount of eccentricity of the recording medium.
To realize an eccentricity measuring device having a simple circuit configuration, capable of measuring the eccentricity of a recording medium by counting a binary signal of a 7-king error signal in synchronization with the rotation of the recording medium. I can do it.

EXAMPLES Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of the eccentricity measuring device according to the present invention, and FIG. 2 shows the eccentricity measuring device of FIG. 1! 5 is a timing chart showing main signals in the measuring device.

In FIG. 1, 1 is a binarization circuit that binarizes a tracking error signal ST indicating the positional deviation of a beam with respect to a track of an optical disc (not shown), which is a recording medium, and 2 is a binarization circuit that is synchronized with one revolution of the optical disc. Gate signal generating means 2 is a gate signal generating means for generating a gate signal S.
The gate signal SG can be generated using, for example, the sector mark or address of the first sector of the trunk of the optical disc.

3 is a counting means for measuring the eccentricity of the optical disk by counting the binary signal P7 from the binarizing circuit 1 while the gate signal SG from the gate signal generating means 2 is open; 4 is a counting means; This is a display section driving means that drives the eccentricity display section 5 in accordance with the count value of the means 3 to display the eccentricity amount of the optical disc.

Next, the operation of the embodiment according to the above configuration will be explained with reference to FIG.

When the amount of eccentricity of the optical disk is relatively large, the tracking error signal SA has a high level and a short period sinusoidal waveform due to the tracking servo loop, as shown in FIG. 2 (A), for example. and therefore,
When this tracking error signal ST is binarized using a predetermined threshold value Vt&, the 2M signal P7 becomes a pulse signal with a short period.

On the other hand, when the amount of eccentricity of the optical disk is relatively small, the tracking error signal ST becomes a sinusoidal signal with a low level and a long period due to the tracking servo loop, as shown in FIG. 2 (b), for example. Therefore, when this tracking error signal ST is binarized using a predetermined threshold value I, the binarized signal P7 becomes a pulse signal with a long period.

Note that when the eccentricity of the optical disc is very small, the level of the tracking error signal Sy becomes lower than the predetermined threshold value Vt1, for example, as shown in FIG. There will be no signal.

The counting means 3 receives a gate signal S as shown in FIG.
While G is open, this 2#! When the rising edge (or falling edge) of the L signal P is counted, the count value becomes a value corresponding to the amount of eccentricity of the optical disk, and when the display section driving means 4 converts this count value into display data, the count value is displayed on the display section. 5 is displayed.

Therefore, according to the above embodiment, by counting the binary signals P while the gate signal SG is open,
The amount of eccentricity of one rotation (1 rack) of the optical disk can be measured as a digital value without using an optical itt or other members separate from the semiconductor laser of the optical pickup 8 as in the conventional example.

As described in detail, the present invention converts the tracking error signal into 2 (+!) and counts this binary signal in synchronization with the rotation of the recording medium, thereby reducing the tracking error signal. Since the period varies according to the eccentricity of the recording medium, the eccentricity of the recording medium can be measured by counting the binary signal of the tracking error signal in synchronization with the rotation of the recording medium. , it is possible to realize an eccentricity measuring device using a simple circuit.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the eccentricity measuring device according to the present invention, FIG. 2 is a timing chart showing main signals in the eccentricity measuring device of FIG. 1, and FIG. 3 is a conventional FIG. 2 is a block diagram showing an eccentricity measuring device. 1... Binarization means, 2... Gate signal generation means, 3... Counting means, 4... Display unit driving means, 5... ... Eccentricity display section.

Claims (1)

[Claims] An eccentricity measuring device comprising: means for binarizing a tracking error signal indicating a positional deviation of a beam with respect to a track of a recording medium; and means for counting and outputting the binarized signal in synchronization with rotation of the recording medium.