JPS63204565A - Disk device - Google Patents

Abstract

PURPOSE:To detect accurate speed by making parallel beams radiated from a laser fixed on a base incident upon a reflecting mirror fixed on a carriage and the base and allowing respective reflected beams to interface with each other to detect the position of the carriage in the half wavelength period of light. CONSTITUTION:A semiconductor laser 4 and a detector 9 are fitted to a support 10 fixed on the base 3, a full reflector 7, a half mirror 5 and a full reflector 8 are also fixed on the base and a full reflector 6 is fixed on a carriage. Laser beams emitted from the laser 4 are converted into parallel beams by a collimeter lens 11 and branched to two optical paths by the half mirror 5. Respective beams are reflected by the full reflectors 5, 6, combined again by the half mirror 5 and reach the detector through the reflector 8 and a convergent lens 12 and the quantity of light is converted into current by the detector. Since the laser beams from the laser 4 have a determined wavelength and have extremely high interference, the positional change of the carriage from the base 3 can be detected by the half wavelength period.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to magnetic and optical disk devices, and more particularly to a speed detection method for speed control.

[Conventional technology]

In conventional disk drives, a mechanical tachometer using a coil and a magnet or an electronic tachometer described in US Pat. No. 3,820,712 has been used to detect the speed of the carriage when moving the head.

[Problem that the invention seeks to solve]

The mechanical tachometer described above has problems such as a complicated mechanical system, which is therefore expensive, a tendency to generate mechanical vibrations, and difficulty in improving accuracy at low speeds. In addition, in electronic tachometers, since the position error signal and the current flowing to the voice coil motor are combined, errors tend to occur between the actual speed and the actual speed when transitioning from acceleration to deceleration. There was also the problem that verification was not easy at low speeds. This problem was a bottleneck in adjusting the speed control, and at the same time, the inaccuracy of this speed deviation.

This was hindering high-speed positioning.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an inexpensive means to provide accurate speed relative to the base at all times, as well as the wide dynamic range required of the tachometer of the disk drive. Another object of the present invention is to provide a speed detection method which is suitable even for a type of disk device known as a sector servo in which a position signal is intermittently recorded on a data surface, that is, a device in which an electronic tachometer cannot be used. There is a particular thing.

[Means for solving problems]

The above purpose is, for example, to fix a semiconductor laser on a base, to make part of the parallel light from the laser enter a reflector attached to a carriage, and to send the other part to a reference reflector fixed to the base. incident.

This method is achieved by interfering each reflected light to detect the position of the carriage in a half-wavelength cycle of the light, and detecting the temporal change in that position.1 For example, an electrical pulse is created at a position every half-wavelength. However, the speed can be detected by counting the number of pulses within a unit time and converting it into an equivalent analog quantity. [Operation] Light from a laser has a fixed wavelength and is extremely Because of the high coherence, changes in the position of the carriage relative to the base can be detected at half-wavelength intervals. Now, 1
Considering the low speed of ell/s, we can reduce the wavelength to 0.8μ
In the case of m, the period is 25 kHz, and if one period has 4 pulses, a pulse frequency of 100 kHz can be easily obtained. Therefore, at a speed of 1 cM/S, 1 μm is moved in 0.1 ms, and if one period has 4 pulses, 10
A pulse is obtained.

Therefore, if pulses are counted every 0.1 mg, a velocity resolution of 0.1 cm/s will be obtained in this case. Similarly, assuming one pulse per period, it is 0.4 cm/
A velocity resolution of s is obtained. Further, considering a high speed of 1.5 m/s, the period is 3.75 MHz, and if one pulse per period, 150 pulses are obtained in 0.1 ms. Therefore, even at low speeds, assuming one pulse per cycle, it is possible to achieve high precision by performing, for example, 8-bit D/A conversion over a wide speed range from 0.4 cxa/s to 1.5 m/s. Analog speed signals can be obtained.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. 1st
The figure is a diagram illustrating the outline of the device configuration of the present invention, and will be described in detail below. A semiconductor laser 4 and a detector 9 are attached to a support 10 fixed to a base 3. Also, total reflection mirror 7. Similarly, the half mirror 5 and the total reflection mirror 8 are fixed to the base. On the other hand, the total reflection mirror 6 is
fixed to the carriage. The laser beam emitted from the laser 4 is converted into parallel light by a collimating lens 11, and then split into two optical paths by a half mirror 5. The respective lights are reflected by the total reflection lights 5 and 6, are combined again by the half mirror 5, pass through the reflecting mirror 8 and the condensing lens 12, and reach the detector. A detector converts the amount of light into electric current.

The amount of light changes depending on the position of the carriage λ
It changes into a sine wave shape with a period of /2 (λ: wavelength of light).

Therefore, if N pulses (N≧1) are generated every cycle from the output of the detector, the speed can be detected by counting the pulses within a unit time. An example of a speed detection circuit is shown in FIG. 2. The output of the detector 9 is converted into a voltage by an amplifier 13, and converted into a pulse by a comparator. The counter 15 is counted pulse by pulse and is controlled by a reset signal A at a suitable time interval 1, for example 0.1.
Every ms, the counter value is set to 1 (071).The reset pulse is naturally set to be sufficiently small compared to the reset interval (t2 (tl) in Figure 3). and holds the value of counter 15 (t8 - tl).

The states of the latch signal (clock) and reset signal of the latch 16 are shown in FIG. In other words, the value immediately before the counter is reset is held. The signal of latch 16 is
The D/A converter 17 converts the signal into a stepped analog signal. This analog signal is entirely proportional to the speed signal. Note that it is more desirable to smooth the analog signal using a smoother circuit (not shown).

Incidentally, the speed can also be detected by finding the reciprocal of the time it takes for a certain number of pulses to arrive. The 41st example! 6 counters shown in I 15
First, the specified number of pulses is set by the load (LOAD) signal. This set value is counted down every pulse by the pulse signal P pulsed by the converter. When the count number becomes “O”, the count 0” signal changes from H to L. Also, the LOA
Assuming that the Dm number is set at 'L', the count g
When the "to" signal reaches "L pt", the specified number of pulses is set in the counter, so it moves to "Hpp". Then, the countdown is performed again. Therefore, the count "0" signal becomes a thin pulse signal and the pulse period becomes This indicates a time proportional to the reciprocal of the speed.The integrator 20 consists of a capacitor that stores a constant current and a switch 19 that discharges the charge stored in the capacitor.

Therefore, by closing the switch 19 every count "OII times signal "'L" pulse, the pulse period is converted to the voltage immediately before discharge. That voltage is transferred to the hold circuit 21
is held and sent to the divider. Note that the play circuit 18 is for adjusting the timing of the hold circuit. The divider 22 is a circuit for outputting constant voltages Vo and Vz, and may have a generally known configuration.

Therefore, V o /V 1 indicates the speed signal of the D/A converter output value in FIG.

Note that the configuration shown above is an example and is not intended to limit the embodiment. For example, in FIG. 1, the arrangement of lasers, mirrors, and detectors is not limited to two types. For example, it is possible to reverse the relationship between the carriage and the base. In that case, the carriage has four types. .11, 5, 7, 8, 12, 9, etc. are fixed, and 6 is fixed to the base. In addition, there is no limitation on the means by which the light is normally transmitted, such as measures against returning light to the laser. Similarly, in FIG. 2 and FIG. It is also clear that it is possible to use a digital processing technique according to the present invention, and in that case, it can be easily applied to a digital servo or the like. In addition, regarding pulse processing methods, techniques such as widening the dynamic range by changing the number of pulses per period between low and high speeds can be easily achieved with existing technology and are not limited. It's not something you can do.

〔Effect of the invention〕

According to the present invention, speed can be detected from position measurement based on the wavelength of light with a simple configuration using an inexpensive semiconductor laser and a photodetector.

Speed verification *a is easy, and accuracy can be easily improved even at a low speed of 1.5/s.
Since high-precision speed detection can be performed even at high speeds, speed control of the disk device can be easily adjusted, and since high-speed speed control is possible, high-speed positioning can be achieved.

Additionally, since it is possible to measure the absolute position of the carriage, servo patterns can be written on the disk device itself without using a dedicated servo writer, which improves productivity and makes it cheaper. It is possible to provide a disk device that is

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an outline of an example of the device configuration of the present invention, FIG. 2 is a diagram showing an example of a speed detection circuit, FIG. 3 is a diagram showing the timing relationship of control signals during speed detection, and FIG. FIG. 3 is a diagram showing an example of another speed detection circuit. DESCRIPTION OF SYMBOLS 1... Disc, 2... Carriage, 3... Base, 4... Semiconductor laser, 5... Half mirror,
6,7゜8... Total reflection mirror, 9... Photodetector, 10... Support column, 11... Collimating lens, 1
2... Condensing lens, 13... Amplifier, 14... Comparator, 15... Counter, 16... Latch circuit, 17... D/A converter, 18... Delay circuit , 19... Analog switch, 20... Integrator, 21... Hold circuit.

Claims (1)

[Claims] 1. In a disk device having a mechanism for positioning a head on a rotating disk, the amount of movement of a carriage or head can be measured based on the wavelength of light using laser light from a semiconductor laser. A disk device characterized by: 2. The disk device according to claim 1, wherein a change in the position of the carriage or the head is converted into a pulse generated every fixed distance, and the speed is detected based on the pulse. 3. The disk device according to claim 2, characterized in that the arriving pulses within a certain period of time are counted, and the number of counts is correlated to the speed. 4. The disk device according to claim 2, characterized in that the time it takes for a certain number of pulses to arrive is measured and the reciprocal thereof is correlated to the speed.