JPH0556574B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a dynamic characteristic measuring device for a disk device that reads information from a disc-shaped medium (hereinafter referred to as a disk) on which information is recorded.

(Background of the Invention) As a device for retrieving information stored on a disk, there is, for example, an optical video disk developed by Philips of the Netherlands. This uses light to detect and reproduce a frequency-modulated signal from a medium on which it is recorded as unevenness. The recording medium of this optical video disk is a disc with a diameter of about 30 cm. On its surface, grooves containing information called pits are lined up 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.
(1/4 wavelength of the H _e -N _e laser), and the distance between adjacent tracks is 2 μm.

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

Furthermore, there is a digital audio disk as a similar playback-only disk. Further, as disks used as storage devices in electronic computers, there are write-once disks and re-recordable disks in which track guide grooves (hereinafter referred to as pre-groups) are formed.

<Need for a disk shape measuring device> However, an actual disk differs from a theoretically accurate geometric standard (hereinafter referred to as a datum) of the disk. That is, (a) as shown in FIG. 6, the disk surface moves up and down with respect to the read/write head as it rotates (hereinafter referred to as wobbling).

(b) As shown in Figure 7, the geometric center of the track (pit row or pre-groove) formed on the disk and the outer diameter of the disk (or the inner diameter of the disk if it has an inner hole in the center) (hereinafter referred to as eccentricity).

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

It has morphological errors such as.

For this reason, the focal position of the optical detector on the surface of the rotating disk is three-dimensionally several hundred microns.
It will fluctuate irregularly within a range of m. Therefore, if the deviation of the disk from the datum becomes large, the track and focus servo mechanisms will be unable to follow it, so for example, for digital audio disks, standards for runout and eccentricity are established as shown in Figures 8 and 9. There is. Therefore, a disk shape measuring device is used to inspect whether the disk complies with this standard.

(Prior Art) FIG. 10 is a block diagram of a conventional disk shape measuring device, and here the case of run-out measurement is shown. In the figure, 1 is a disk made of transparent plastic, such as polycarbonate, and has concentric or spiral tracks formed at equal intervals d, 2 is a motor that rotates the disk 1, and 3 is an optical system using a semiconductor laser. Detector 4 is a servo circuit that moves the focus of the light beam to the optical axis (in the direction of arrow A); 5
A detection circuit detects whether the focus of the optical detector 3 is on the disk 1, and constitutes a servo mechanism that operates the servo circuit 4 so that the focus of the light beam is on the disk 1.

6 is a displacement converter that detects the amount of movement of the optical detector 3 in the optical axis direction, that is, the shake; 7 is an angle converter that measures the rotation angle of the disk 1; and 8 is a displacement converter that measures the rotation angle and shake of the disk 1. It is a temporary storage device for storing data.

In the case of eccentricity measurement, the detection circuit 5 determines whether the light beam is on the track or not. If the light beam is not on the track, the output of the servo circuit 4 moves the optical detector 3 in the radial direction of the disk 1. A servo mechanism is configured so that the focus of the optical detector 3 is always on the track.

The optical detector 3 includes a semiconductor laser 3a that emits a laser beam, a collimating lens 3b that determines the optical axis of the laser beam, a condensing lens 3c that condenses the light onto the disk 1, a half mirror, and a converging lens. A light detection mechanism 3d that includes a light detection mechanism 3d that uses reflected light from the disk 1 to obtain a focus error signal, a cylinder 3e that integrally supports these optical shapes 3a, 3b, 3c, and 3d, and a cylinder 3e. a spring 3f that supports the optical axis and is movable in a direction perpendicular to the optical axis;
A focus actuator 3g that moves the barrel 3e in the optical axis direction, a track actuator 3h that moves the barrel 3e in a direction perpendicular to the optical axis (radial direction of the disk), and these 3e, 3f, 3g,
3h and a housing 3k that integrally holds the housing 3h.

In the device configured in this way, the disk 1 is rotated to measure the deflection of the disk 1, and then this deflection is converted from the frequency in the spatial domain to the frequency in the time domain according to the predetermined readout rotation speed Ω of the disk 1. to determine whether it complies with the disk standards.

(Problems to be Solved by the Invention) However, when trying to measure the shape of a disk using the above-mentioned device, the following problem occurred.

(a) Since the mass of the cylinder 3e is several grams and the rigidity of the spring 3f is small, the resonance frequency of this vibration system is several tens of Hz, and the dynamic characteristics of the actuator are poor.

(b) Therefore, in order to accurately measure the runout of the disk, the rotational speed Ω of the disk must be made small, which requires time to measure.

(c) On the other hand, the resonant frequency and gain of the actuator vary with temperature and also change significantly over time, making it impossible to accurately measure the deflection of the disk over a long period of time.

(d) The deflection of disk 1 only needs to be large enough to be followed by the track and focus servo systems, so in addition to the deflection shape of disk 1 itself, the dynamic characteristics of the deflection when the disk is rotating should also be considered. It's more convenient to know.

The present invention solves the above-mentioned problems, and is capable of controlling the dynamic characteristics of the disk (such as vibration and eccentricity of the disk) while rotating at a predetermined rotational speed Ω without being affected by changes in the dynamic characteristics of the actuator. When the actuator in question operates at a frequency that exceeds the frequency at which it operates statically (usually 1/5 or less of the resonant frequency), minute vibrations, etc. are measured), and if necessary, the dynamic characteristics of the actuator are measured. The purpose of the present invention is to realize a disk dynamic characteristic measuring device that can measure the dynamic characteristics of a disk.

(Means for Solving the Problems) A first invention that achieves the above object includes a rotating disk having concentric or spiral tracks, and detecting the deviation of this disk from a datum. In a dynamic characteristic measuring device comprising a detector that moves the detector, an actuator that moves the detector, and a servo circuit that operates the actuator, a frequency analysis result of the actuator at a first rotation speed (Ω ₁ ) is stored. a first storage device, a second storage device that stores frequency analysis results of the actuator at a second rotation speed (Ω ₂ ), and a static gain of the actuator and the results stored in these storage devices; The present invention is characterized in that it is provided with an arithmetic device that uses the disk to calculate the dynamic characteristics of the disk.

A second invention to achieve such an object includes a rotating disk having concentric or spiral tracks, a detector for detecting deviation of the disk from a datum, and a rotating disk for moving the detector. A dynamic characteristic measuring device comprising an actuator that operates the actuator and a servo circuit that operates the actuator, a first storage device that stores a frequency analysis result of the actuator at a first rotation speed (Ω ₁ ); a second storage device for storing frequency analysis results of the actuator at the rotational speed (Ω ₂ ); and a second storage device for calculating the dynamic characteristics of the disk using the results stored in these storage devices and the static gain of the actuator. The present invention is characterized in that it includes one arithmetic device and a second arithmetic device that calculates the dynamic characteristics of the actuator using the results of this arithmetic device.

(Example) The present invention will be explained below based on the drawings.

FIG. 1 is a configuration diagram showing an embodiment of the first invention. In FIG. 1, components having the same functions as those in FIG. 10 are designated by the same reference numerals and their explanations will be omitted.

9 is a spectrum analyzer that analyzes the frequency of the output signal of the drive circuit 4; 10 is a tachometer that measures the rotational speed Ω of the disk ₁ ; and 11 is a first storage device that stores the frequency analysis result at the first rotational speed Ω1. , 12 is a second storage device that stores the frequency analysis results at the second rotational speed Ω ₂ , and 13 is a first calculation device (hereinafter referred to as a calculation device) that calculates the dynamic characteristics of the disk 1 using the results of the storage devices 11 and 12. 14 is a drawing device that prints or draws the results calculated by the ALU 13.

Next, the operation of the apparatus of the first invention will be explained based on FIGS. 2 and 3. As shown in the block diagram of Fig. 2, the dynamic characteristics of the disk runout are expressed by D (jω), the dynamic characteristics of the actuator by G (jω), and the actuator drive signal (output of the servo circuit 4) by Y (jω). The following equation holds.

D(jω)=G(jω)・Y(jω) (1) On the other hand, each angular frequency ω is specified by the standard.
Since the phase is not a requirement, the absolute value of the disk runout is δ(ω), the absolute value of the dynamic characteristics of the actuator is g(ω), and the absolute value of the servo circuit 4 is y(ω). ), equation (1) becomes as follows.

δ(ω)=g(ω)y(ω) (1)' Here, δ(ω)=|D(jω)| g(ω)=｜G(jω)｜ y(ω)=｜Y(jω)｜ It is.

Next, the measurement procedure will be described along the flowchart in FIG. First, the disk 1 is rotated at a rotational speed of Ω ₁ , and the output of the servo circuit 4 is frequency-analyzed by the spectrum analyzer 9 and stored in the first storage device 11.
This result is expressed by the following equation.

δ ₁ (ω ₁ )=g(ω ₁ )y ₁ (ω ₁ ) δ ₁ (2ω ₁ )=g(2ω ₁ )y ₁ (2ω ₁ ) δ ₁ (4ω ₁ )=g(4ω ₁ )y ₁ (4ω ₁ ) δ ₁ (8ω ₁ ) = g (8ω ₁ ) y ₁ (8ω ₁ ) δ ₁ (16ω ₁ ) = g (16ω ₁ ) y ₁ (16ω ₁ ) 〓 (2) Next, the rotation speed of the operation Measure similarly at a rotational speed Ω ₂ larger than Ω ₁ (for example, Ω ₂ = 2Ω ₁ ), and
to be memorized. In this case, the dynamic characteristics of the actuator do not change, so the following equation holds.

δ ₂ (2ω ₁ )=g(2ω ₁ )y ₂ (2ω ₁ ) δ ₂ (4ω ₁ )=g(4ω ₁ )y ₂ (4ω ₁ ) δ ₂ (8ω ₁ )=g(8ω ₁ )y ₂ (8ω ₁ ) δ ₂ (16ω ₁ )=g(16ω ₁ )y ₂ (16ω ₁ ) 〓 (3) Furthermore, since the runout of the disk 1 does not change depending on the rotation speed, the following function holds true.

δ ₁ (ω ₁ ) = δ ₂ (2ω ₁ ) = δ(1) δ ₁ (2ω ₁ ) = δ ₂ (4ω ₁ ) = δ(2) δ ₁ (4ω ₁ ) = δ ₂ (8ω ₁ ) = δ(4) δ ₁ (8ω ₁ ) = δ ₂ (16ω ₁ ) = δ(8) 〓 (4) Here, the fundamental frequency component of the deflection of δ(1) (for example,
When the disk rotates 30 times per second, the runout is 30
Refers to the Hz component. δ(2) is the second harmonic component of runout,
δ(4) is the fourth harmonic component of runout, and δ(8) is the eighth harmonic component of runout.

Focusing on this point, if the static actuator gain g(0) (referring to the amount of displacement of the housing 3e per unit output) is known, each angle in a geometric series can be calculated using the following equation. Frequency α ⁿ ω ₀ (α = Ω ₂ / Ω ₁ in the above example, α = 2, n is a natural number, ω ₀ is an angular frequency sufficiently lower than the resonance angular frequency of the actuator, and in the above example, ω ₀ = ω ₁ ) Deflection δ(ω) of disk 1 at
can be found one after another.

δ(ω ₀ )=g(0)y ₁ (ω ₀ ) (5) δ(αω ₀ ) = δ(ω ₀ )・y ₁ (αω ₀ )/y ₂ (ω ₀ ) (6) 〓 δ( α ⁿ ω ₀ ) = δ (α ^n-1 ω ₀ )・y ₁ (α ⁿ ω ₀ )/y ₂ (α ⁿ ω ₀ ) (7) The first arithmetic unit ALU1 has the following equation (5), ( 6),…,(7)
are calculated one after another to find the dynamic characteristics of the disk.

FIG. 4 is a configuration diagram showing an embodiment of the second invention. In FIG. 4, parts having the same functions as those in FIGS. 1 and 10 are given the same reference numerals, and their explanations will be omitted. 15 is a second ALU that calculates the dynamic characteristics of the actuator. 16 is a drawing device that prints or draws the results calculated by the ALU 15;

FIG. 5 is an explanatory diagram of the operation of the second invention. Note that the explanation of the parts that overlap with those in FIG. 3 will be avoided, and only the calculations of the ALU 15 will be explained. ALU15 is expressed by formulas (5), (6),...
The dynamic characteristics of the actuator are calculated using the disc deflection δ (α ⁿ ω ₀ ) obtained from (7). That is, g(ω ₀ )=g(0) (8) g(αω ₀ )=δ(ω ₀ )y ₂ (αω ₀ ) (9) 〓 g(α ⁿ ω ₀ )=δ(α ^n-1 ω ₀ )/y ₂ (α ⁿ ω ₀ ) (10) The second calculation unit ALU2 calculates equations (8), (9), ..., (10) one after another to determine the dynamic characteristics of the actuator. There is.

Although this example shows run-out measurement using a focus servo, the present invention is not limited to this. The present invention may also be applied to a jitter servo that measures the jitter that occurs when the jitter is generated.In short, it may be applied to a jitter servo that has a detector and a servo that controls the jitter so that it can be measured.

In addition, in the first invention, the runout of the disk is first measured, but in the second invention, the dynamic characteristics of the actuator are measured by the ALU 15, and then the measured values of the dynamic characteristics obtained using a geometric series are used. The estimated dynamic characteristic G^(ω) may be obtained by interpolating a frequency located in the middle, and the disk runout may be obtained from this using the following equation.

δ(ω)=G^(ω)y ₁ (ω) (11) Also, in the above example, only Ω ₁ and Ω ₂ were shown, but
It is also possible to obtain an intermediate G(ω) using a plurality of rotational speeds such as Ω ₁ and Ω ₃ or Ω ₃ and Ω ₄ .

(Effects of the Invention) As described above, according to the present invention, since the dynamic characteristics of the disk are measured at different rotational speeds Ω ₁ and Ω ₂ , the dynamic characteristics of the disk can be measured without being affected by the dynamic characteristics of the actuator. can be measured, and the dynamic characteristics of the actuator can also be determined if necessary.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the first invention, FIGS. 2 and 3 are explanatory diagrams of the operation of the apparatus shown in FIG.
The figure is a block diagram showing an embodiment of the invention in Figure 2, Figure 5 is an explanatory diagram of the operation of the device in Figure 4, Figures 6 to 9 are diagrams to explain the dynamic characteristics of the disk, and Figure 10 is a conventional diagram. An explanatory diagram of the device. 1... Disk, 2... Motor, 3... Optical detector, 4... Servo circuit, 5... Detection circuit, 9
... Spectrum analyzer, 10 ... Tachometer, 11, 12 ... Storage device, 13, 15 ... Arithmetic unit (ALU).

Claims (1)

[Claims] 1. A rotating disk having concentric or spiral tracks, a detector for detecting deviation of this disk from a datum, an actuator for moving this detector, and this actuator. A dynamic characteristic measuring device comprising a servo circuit for operating the actuator, a first storage device storing a frequency analysis result of the actuator at a first rotation speed (Ω ₁ ), and a second rotation speed (Ω ₂ ). a second storage device that stores frequency analysis results of the actuator in the second storage device; and an arithmetic device that calculates the dynamic characteristics of the disk using the results stored in these storage devices and the static gain of the actuator. A dynamic characteristic measuring device featuring: 2. A rotating disk having concentric or spiral tracks, a detector for detecting deviation of this disk from a datum, an actuator for moving this detector, and a servo circuit for operating this actuator. A dynamic characteristic measuring device comprising: a first storage device that stores a frequency analysis result of the actuator at a first rotation speed (Ω ₁ ), and a frequency analysis result of the actuator at a second rotation speed (Ω ₂ ); a second storage device for storing results; a first calculation device for calculating dynamic characteristics of the disk using the results stored in these storage devices and the static gain of the actuator; and a second calculation device that calculates the dynamic characteristics of the actuator using the actuator.