JPH0697508B2 - Characteristic evaluation device for disk detector - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a disk-shaped medium on which information is recorded (hereinafter referred to as a disk) and a characteristic measuring apparatus for a detector for reading information from the disk, and particularly to a disk. The present invention relates to a device for measuring characteristics of a disk detector, which is suitable for measuring characteristics for tracks.

(Background of the Invention) (a) A disc is formed with a groove and is detected by a stylus, (b) A disc is formed and detected as a change in capacitance, (c) ) There is a method in which a groove is formed and detected by an optical displacement transducer, (d) a method in which a magnetic recording medium is applied to the surface and the magnetization direction is detected by a magnetic head, and the like.

In these disks, the position where the recording is to be read varies three-dimensionally due to the distortion of the disk surface, the eccentricity between the center of the inner diameter of the disk and the center of the track, and the like.

<Optical Disc> As an apparatus for taking out information stored on a disc, for example, there is an optical video disc developed by Philips of the Netherlands. This is to detect and reproduce by a light from a medium in which a frequency-modulated signal is recorded as unevenness. The disc that is the recording medium of this optical video disc has a diameter of about 30.
On the surface of a disc of cm, grooves containing information called pits are arranged concentrically or spirally. This pit has a width of 0.5 μm, a length of 2 to 15 μm, and a depth of 0.15 μm (He-Ne
At 1/4 wavelength of the laser), the distance between adjacent tracks is 2 μm.

In order to detect the shape of the pit with high resolution, it is necessary to keep the focus position of the optical detector within 0.1 μm in the width direction of the pit and within 0.5 μm in the depth direction. Therefore, in order to automatically focus on detection, a focus servo mechanism,
A track servo mechanism for accurately following the track is provided.

A digital audio disc is a similar read-only disc. Further, as a disk used as a storage device in an electronic computer, there are a write-once disk and a re-recordable disk in which track guide grooves (hereinafter referred to as pregroups) are formed.

<Necessity of Characteristic Measuring Device> However, the actual disc is different from the theoretically accurate geometric standard (hereinafter referred to as a datum) of the disc. That is, (a) the disk surface is moved up and down with respect to the read / write head as the disk rotates (hereinafter referred to as runout).

(B) The geometric center of the track (pit row or pre-grup) formed on the disc and the center of the outer diameter of the disc (or the inner diameter of the disc when there is an inner hole in the center) do not match. (Hereafter referred to as eccentricity).

(C) The disk surface is not completely flat and has an inclination (hereinafter referred to as warpage).

There is a morphological error such as.

For this reason, the focal position of the optical detector on the surface of the rotating disk three-dimensionally fluctuates within a range of several 100 μm. Therefore, when the deviation from the disc datum becomes large, the automatic focus position adjusting device cannot follow. Therefore, an optical detector is used to evaluate whether the eccentricity of the disc is within a specified amount, and to enable the optical detector to retrieve information without error even if the deviation from the disc datum increases. It is necessary to evaluate the characteristics of and to use those above a certain level.

(Prior Art) FIG. 5 is a block diagram of a conventional dynamic characteristic measuring device for a detector.
(A) is a longitudinal sectional view and (b) is a plan view. In the figure, 1 is a bundle of parallel rays having a uniform intensity distribution, 2 is a photodiode that generates a signal in accordance with the amount of irradiated light, 3 is an optical detector using a semiconductor laser, and 4 is an optical detector. A drive circuit 5 for moving the detector 3 in the direction of arrow A (radial direction of the disk) is a displacement converter for measuring the displacement of the optical detector 3 from the output of the photodiode 2.

The optical detector 3 is a semiconductor laser 3a that emits laser light.
A collimating lens 3b that determines the optical axis of the laser beam, a condenser lens 3c that condenses the light on the disc, and a half mirror and a converging lens. A light detection mechanism 3d that converts into an electric signal,
A cylindrical body 3e that integrally supports these optical systems 3a, 3b, 3c, 3d
A spring 3f that supports the tubular body 3e so as to be movable in the optical axis and a direction vertical to the optical axis, a focus actuator 3g that moves the tubular body 3e in the optical axis direction, and the barrel 3e in the direction perpendicular to the optical axis. Track actuator 3h that moves in the radial direction) and housing 3k that integrally holds the above 3e, 3f, 3g, 3h
It is composed of and.

In the apparatus thus configured, the gain and dynamic characteristics of the track actuator 3h are measured using the ratio of the output of the drive circuit 4 and the displacement of the optical detector 3 obtained by the displacement converter 5.

(Problems to be Solved by the Invention) However, in order to measure the characteristics of the track actuator by such a method, it is indispensable to remove the optical detector 3 from the disk device, so that the measurement cannot be performed easily. .

The present invention solves the above-mentioned drawbacks, and an object thereof is to realize an apparatus for easily measuring the characteristics of a detector by using a reference disk.

(Means for Solving the Problems) In the present invention which achieves such an object, a reference disk (6) having tracks formed concentrically or spirally at equal intervals, and the reference disk is recorded. The detector (3) for detecting information, the drive circuit (4) for moving the detection position of the detector on the reference disc in the radial direction of the reference disc, and the detection position of the detector on the reference disc are A tracking error circuit (7) that measures the amount of deviation from the center position of the track, and a corresponding signal (Vb) from the output signal (Va) of the tracking error circuit each time the detection unit passes the track. The generated zero-cross detection circuit (8) and the output signal of the drive circuit (V
and a sample hold circuit (10) for holding c).

(Operation) In the reference disc, the track interval (d) is known.
The zero-cross detection circuit uses the signal from the tracking error circuit to detect the time (t ₁ , t ₂ ,
identify t ₃ , t ₄ ). The sample hold circuit holds the output voltage (V ₁ , V ₂ , V ₃ , V ₄ ) of the drive circuit at the time when the detector passes the track. Thereby, the output voltage of the drive circuit can be obtained for each track interval, and the gain, the nonlinearity, the frequency characteristic, and the like that represent the relationship between the drive circuit and the movement of the detector can be obtained.

EXAMPLES The present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the first invention.
It is to be noted that, in FIG. 1, components having the same functions as those in FIG.

Reference numeral 6 is a reference disk made of a transparent substrate such as glass or polycarbonate, in which concentric or spiral tracks are formed at equal intervals d, and 7 is a disk 6 of the optical detector 3 from the signal of the photodetector 3d. A tracking error circuit for determining whether or not the upper position is a track, 8 is an optical detector 3 from the output signal Va of the tracking error circuit 7.
Signal corresponding to each time when the track passes over the disk 6
Zero-cross detection circuit that outputs Vb, 9 is a signal generator that determines the current signal Vc that the drive circuit 4 supplies to the track actuator 3h, for example, a waveform such as a sine wave or a triangular wave and its period 2To, 10 is an output signal of the zero-cross detection circuit A sample and hold circuit that holds the output signal Vc of the drive circuit 4 by Vb.

The operation of the apparatus thus configured will be described with reference to FIG. The signal (1) is the triangular wave Vc generated by the drive circuit 4.
Thus, the period during which the voltage rises and the period during which the voltage falls are equal. The signal (2) is the tracking error circuit 7
Output Va, the optical detector 3 generates a substantially sinusoidal voltage for one wavelength when passing through the track. The signal (3) is a signal used inside the zero-crossing detection circuit 8 and is a time window for outputting the signal Vb only during the rising period of the triangular wave Vc generated by the drive circuit 4. The signal (4) is a signal used inside the zero-cross detection circuit 8, and when the signal Va exceeds a predetermined positive and negative threshold value Vth, S.S.
R. Flip-flop is used to set the time window. The signal (5) is the output Vb of the zero-cross detection circuit 8, and the signal (2) is output while the time window set by the signal (4) is open.
As it passes zero, it generates a pulse signal to signal that the optical detector 3 has passed the track.

The sample-hold circuit 10 holds the voltages V ₁ , V ₂ , V ₃ , V ₄ of the output signal Vc of the drive circuit 4 at the times t ₁ , t ₂ , t ₃ , t _{4 of} the pulse generated by the signal Vb. . As a result, the voltages V ₁ , V ₂ , V ₃ , and V ₄ for each track interval d can be obtained, and characteristics such as the gain, nonlinearity, and frequency characteristics of the tracking actuator can be obtained. For example, the gain G can be calculated by the following equation.

G = (V ₁ −V ₂ ) / d (1) The frequency characteristic G (f) required to know the dynamic characteristic may be obtained by changing the period 2To of the signal generator 9. Here, the frequency f is given by the following equation.

FIG. 3 is a block diagram showing an embodiment of the second invention.
The object of the first invention is to easily measure the characteristics of the drive circuit 4 and the detector 3, while the object of the second invention is to easily measure the gain of the eccentricity detector 11 and the like. is there. Incidentally, in FIG. 3, those having the same functions as those in FIG. 1 and FIG.

Reference numeral 11 denotes an eccentricity detector for measuring the eccentricity of the disc by causing the inspection device to track the disc to be measured when the disc inspection device operates, and 12 indicates the track by measuring the distance from the cylinder 3e. This is a displacement sensor that determines how much the detection position on the disk of the detector 3 has changed by the actuator 3h.

The operation of the apparatus thus configured will be described with reference to FIG. The signal (1) is the signal Vc detected by the eccentricity detector 11.
Therefore, it is almost similar to the triangular wave Vd generated by the drive circuit 4. The signal (3) is a signal to be used inside the zero-cross detection circuit 8 and is a time window for outputting the signal Vb only during the rising period of the triangular wave Vd generated by the drive circuit 4. The signals (2), (4) and (5) are the same as those in the first aspect of the invention.

The sample hold circuit 10 outputs the output signal Vc of the eccentricity detector 11 according to the time t ₁ , t ₂ , t ₃ , t _{4 of} the pulse generated by the signal Vb.
The voltages V ₁ , V ₂ , V ₃ , and V ₄ are held. This signal is AD converter 1
The analog signal is converted into a digital signal by 3, and the microprocessor 14 also performs a necessary operation, for example, formula (1). As a result, the eccentricity detector 11
Characteristics such as gain, nonlinearity, and frequency characteristics can be obtained. This characteristic is effectively used when the eccentricity of the disk whose shape is to be inspected is obtained instead of the reference disk 6, and the eccentricity amount can be measured without error.

FIG. 4 is a block diagram showing an embodiment of the third invention.
The purpose of the first invention was to easily measure the characteristics of the drive circuit 4 and the detector 3, but the purpose of the third invention is to drive the drive circuit 4 so that the movement amplitude of the detector 3 becomes constant. Is controlled so that changes in frequency characteristics can be easily measured. In addition, in FIG. 4, in FIG.
The components having the same functions as those in the figure are designated by the same reference numerals and the description thereof will be omitted.

Reference numeral 15 is a voltage control circuit that controls the voltage of the drive circuit 4 in order to keep the amplitude of the optical detector 3 constant, and 16 is the drive circuit 4
Is a frequency reference circuit that determines the period 2To of the triangular wave generated by.

The operation of the apparatus thus configured will be described with reference to FIG. Since the signals (1) to (5) are the same as in the first aspect of the invention, their description will be omitted. Signal (6) is the voltage control circuit
A signal for determining the displacement of the optical detector 3 inside 15 is used to determine the time T ₂ during which the optical detector 3 passes between predetermined tracks based on the signal Vb. The signal (7) is a signal for finding the center of displacement of the optical detector 3 inside the voltage control circuit 15, and it is from the time T ₀ when the triangular wave rises to the time T _{2 of the} signal (6).
The times T ₁ and T ₃ at both ends excluding is calculated.

The voltage control circuit 15 knows the displacement of the optical detector 3 from the signal (6) and controls the voltage amplitude of the triangular wave so that the amplitude ratio α (= T ₂ / T ₀ ) becomes constant. For example, when the amplitude ratio α is larger than the predetermined set value α ₀ , the voltage amplitude of the triangular wave is reduced. This set value α ₀ is, for example, 20 as the measurement amplitude.
If μmp-p is set, the groove pitch is 2 μm, and the zero-cross pulse is 10 times at both ends, the time T ₂ is equivalent to 18 μm, so α ₀ = 0.95. The signal (7) is used to control the optical detector 3 so that it is displaced around a predetermined position, and the direct current component of the triangular wave voltage is controlled so that β defined by the following equation becomes constant. .

β = (T ₁ −T ₃ ) / T ₀ (2) For example, when T ₁ = T ₃ , β = 0. Here, α corresponds to the span representing the total amplitude of the detector 3, and β is the detector 3
Corresponding to the zero point in the amplitude of, the movement of the optical detector 3 is kept constant by keeping α and β constant.
If the frequency is changed and the measurement is performed in such a state, a characteristic with less error can be obtained in a wide frequency range.

Although the optical detector 3 is controlled by using the triangular wave in each of the above-described embodiments, the same waveform such as a sine wave may be repeated in a cycle of 2To.

In the first, second and third inventions, the case of an optical detector is shown as an embodiment, but it may be, for example, a capacitance type detector or a magnetic type detector. Anything that detects a broken track may be used.

(Effects of the Invention) As described above, according to the present invention, the characteristics of the detector 3 can be measured by using the reference disk 6 without removing the detector 3 from the disk device. There is an effect that it is possible to easily measure and inspect.

Further, as an effect peculiar to the first invention, the reference disk 6
It is possible to know the drive current required for the drive circuit 4 per track interval d by using the known track interval d formed in the above, and it is possible to easily measure the characteristics of the drive circuit 4 and the detector 3. .

Next, as an effect peculiar to the second invention, the reference disk 6
The output voltage of the eccentricity detector 11 per track distance d can be known by using the known track spacing d formed in the above, and the characteristic of the eccentricity detector can be easily measured.

Finally, as an effect peculiar to the third invention, a voltage control circuit is provided.
Since the drive circuit 4 is controlled by 15 so that the movement amplitude of the detector 3 becomes constant, by changing the drive frequency of the drive circuit 4 by using the frequency reference circuit 16, the drive circuit 4 and the detector 3 are controlled. There is an effect that the frequency characteristic can be easily measured.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the first invention, FIG. 2 is an operation explanatory view of an apparatus of the first invention and the second invention, and FIG. 3 is an embodiment of the second invention. FIG. 4 is a configuration diagram showing an embodiment of the third invention, and FIG. 5 is a configuration diagram of a conventional device. 3 ... Optical detector, 4 ... Drive circuit, 6 ... Reference disk, 7 ... Tracking error circuit, 8 ... Zero cross detection circuit, 10 ... Sample hold circuit, 11 ... Eccentricity detector, 15 ... … Voltage control circuit.

Claims (3)

[Claims] 1. A reference disk (6) having tracks formed concentrically or spirally at equal intervals, a detector (3) for detecting information recorded on the reference disk, and the detector (3). Drive circuit (4) for moving the detection position on the reference disk in the radial direction of the reference disk
And a tracking error circuit (7) for measuring the amount by which the detection position of the detector on the reference disk deviates from the center position of the track, and the detection unit from the output signal (Va) of the tracking error circuit. A corresponding signal (V
b) a zero-cross detection circuit (8), and a sample hold circuit (10) for holding the output signal (Vc) of the drive circuit by the output signal of the zero-cross detection circuit. Detector characterization device. 2. A reference disc (6) having concentric or spiral tracks formed at equal intervals, a detector (3) for detecting information recorded on the reference disc, and an eccentricity of the reference disc. Eccentricity detector (11,1
2) and a drive circuit (4) for moving the detection position of the detector on the reference disc in the radial direction of the reference disc.
And a tracking error circuit (7) for measuring the amount by which the detection position of the detector on the reference disk deviates from the center position of the track, and the detection unit from the output signal (Va) of the tracking error circuit. A corresponding signal (V
A disk comprising: a zero cross detection circuit (8) for generating b); and a sample hold circuit (10) for holding the output signal (Vc) of the eccentricity detector by the output signal of the zero cross detection circuit. Detector characteristic evaluation device. 3. A reference disc (6) having tracks concentrically or spirally formed at equal intervals, a detector (3) for detecting information recorded on the reference disc, and the detector (3). Drive circuit (4) for moving the detection position on the reference disk in the radial direction of the reference disk
And a tracking error circuit (7) for measuring the amount by which the detection position of the detector on the reference disk deviates from the center position of the track, and the detection unit from the output signal (Va) of the tracking error circuit. A corresponding signal (V
a zero cross detection circuit (8) for generating b), a sample hold circuit (10) for holding the output signal (Vc) of the drive circuit by the output signal of the zero cross detection circuit, and an output signal from the zero cross detection circuit. A voltage control circuit (15) that receives and controls the output voltage of the drive circuit to keep the moving amplitude of the detector constant, and a frequency reference circuit that determines the period (T ₀ ) of the output signal of the drive circuit. (16) An apparatus for evaluating characteristics of a disk detector, comprising: