JPH03116448A - Detection device for head position - Google Patents

Abstract

PURPOSE:To reduce the effect due to a disturbance light and to correctly detect the position of a head by demodulating the output of a light receiving means into a modulation signal and constraining the noise component of a demodulation output by a low pass filter. CONSTITUTION:A parallel light emitted from a light source 11 is made incident on a cylindrical lens 12, converted into a diffused light, made incident on a light receiving element 13 and various disturbance lights excepting the light emitted from the cylindrical lens 12 are made incident on the light receiving element 13. However the output of a demodulator 23 is input to a low pass filter 24, which not only smooths the signal input from the demodulator 23 but also restrains the noise component included therein. A detector 25 detects the position(distance between the cylindrical lens 12 and light receiving element 13) of a carriage 14 from the signal input from the low pass filter 24. Thus the effect due to the disturbance light, etc., is reduced and the head position can correctly be detected.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a disk radius of a head that records or reproduces information on a recording medium in, for example, an optical disk device, a magnetic disk device, a video disk player, a compact disk player, etc. The present invention relates to a head position detection device suitable for use in detecting a position in a direction.

[Prior Art] FIG. 3 is a block diagram showing the configuration of an example of a conventional head position detection device, which was previously proposed by the applicant in Japanese Utility Model Application Publication No. 63-29704.

In the figure, 11 is a light source such as a semiconductor laser or an LED, which is driven by a drive circuit 10 and generates substantially parallel light. Reference numeral 12 denotes a cylindrical lens as a light diffusing means, which diffuses the light from the light source 11 only within one plane including its optical axis (in the case of the embodiment, within a plane parallel to the plane of the paper).

The cylindrical lens 12 can be considered to be included in the light source 11 if the light source 11 itself generates sufficiently diffused light.

Reference numeral 14 denotes a carriage on which a head for recording or reproducing information on the disk is mounted, and is driven by a motor or the like and guided by a guide bar 15 to move in the radial direction of the disk (both not shown). Reference numeral 13 denotes a light receiving element, which is fixed to a carriage 14 as a moving means so as to receive light emitted from the cylindrical lens 12 on its front axis. The light receiving element 13 is a cylindrical lens 1
The cylindrical lens 2 is set to have a sufficiently small area compared to the area of the surface perpendicular to the optical axis of the emitted light, so that the cylindrical lens 12 receives only a part of the emitted light. 1
A detector 6 detects the position of the carriage 14 from the output of the light receiving element 13.

Next, its operation will be explained.

The parallel light emitted from the light source 11 enters the cylindrical lens 12 and is converted into diffused light.

This diffused light is incident on the light receiving element 13.

When the head is moved in the radial direction of the disk to access a predetermined track, a motor (not shown) is driven and the carriage 14 is moved in the radial direction of the disk. The light receiving element 13 is attached to the carriage 14, and the carriage 14
cylindrical lens 1
2 is fixed to a fixed object such as a substrate (not shown). As a result, as the carriage 14 moves, the distance between the light receiving element 13 and the cylindrical lens 12 changes.

As described above, the area of the light receiving element 13 is sufficiently smaller than the area of the diffused light emitted from the cylindrical lens 12. Therefore, the shorter the distance to the cylindrical lens 12, the greater the amount of light received by the light receiving element 13.
The longer the distance, the smaller the amount of light. That is, the sight that the light receiving element 13 receives is inversely proportional to the distance from the cylindrical lens 12. Since the light-receiving element 13 outputs a current at a level corresponding to the light-receiving scene, the relationship between the output j of the light-receiving element 13 and the position of the carriage 14 (distance between the cylindrical lens 12 and the light-receiving element 13) is as shown in FIG. become.

FIG. 5 shows the configuration of another example of the conventional head detection device.

In the example shown in FIG. 3, the cylindrical lens 12 is fixed and the light receiving element 13 is movable, but in the example shown in FIG. Element 1
It is arranged to move relative to 3.

In this example as well, since the distance between the cylindrical lens 12 and the light receiving element 13 changes in response to the movement of the carriage 14, the position of the head (carriage 14) can be detected by the detector 16.

[Problems to be Solved by the Invention] In this way, the conventional device detects the head position from the output of the light receiving element 13 when the distance between the cylindrical lens 12 and the light receiving element 13 is changed.

Therefore, when disturbance light is incident on the light receiving element 13, the detector 16 detects it, and the position of the head may be erroneously detected.

The present invention was developed in view of the above circumstances, and is intended to reduce the influence of ambient light and to accurately detect the position of the head.

[Means for Solving the Problems] A head position detection device of the present invention includes a light source that emits diffused light, a generating device that generates a predetermined signal, and a signal that is output from the light source in response to the signal output from the generating device. a modulating means for modulating the emitted light; a light receiving means having an area sufficiently smaller than the area of a plane perpendicular to the optical axis of the diffused light emitted from the light source and disposed in the optical path; and the light source or the light receiving means. a moving means for moving one of the two relative to the other in conjunction with movement of a head for recording or reproducing information on a recording medium; and a demodulating means for demodulating the output of the light receiving means in synchronization with the signal output by the generating means. , and low-pass filter means for suppressing noise components included in the output of the demodulation means.

[Operation] In the head position detection device having the above configuration, a light receiving means such as a light receiving element is disposed in the optical path of the diffused light modulated by a predetermined signal such as a system clock. For example, the light receiving element is moved along the optical axis of the diffused light in conjunction with the movement of the head. The scene of light received by the light receiving element changes in accordance with the position of movement of the head. A system clock component is demodulated from the output of this light receiving element. Noise components are suppressed from the demodulated signal by a low-pass filter.

Therefore, the influence of external light and the like can be reduced, and the position of the head can be detected accurately.

[Embodiment] FIG. 1 is a block diagram showing the configuration of an embodiment of the head position detection device of the present invention, and parts corresponding to those in FIGS. 3 and 5 are denoted by the same reference numerals. be.

In FIG. 1, 21 is a clock generator that generates a system clock (No. 8) of a predetermined frequency and outputs it to the modulator 22 and demodulator 23. 24 is a low-pass clock generator that suppresses noise components from the output of the demodulator 23. The filter 25 is a detector that detects the position of the head from the output of the low-pass filter 24. The amplifier 26 amplifies the output of the light receiving element 13 and supplies it to the demodulator 23.

The other configurations are the same as in FIG. 3.

Next, its operation will be explained.

Clock generator 21 generates a system clock of a predetermined frequency. This system clock is input to modulator 22. The modulator 22 controls the drive circuit 10 in accordance with this system clock, and causes the light source 11 to generate light modulated with the system clock.

The parallel light emitted from the light source 11 enters the cylindrical lens 12 and is converted into diffused light.

This diffused light is incident on the light receiving element 13.

In this way, similarly to the case described above, the light receiving element 13
The cylindrical lens 12 outputs a current that is inversely proportional to the distance. This current is input to the amplifier 26, converted into a voltage, and supplied to the demodulator 23.

The demodulator 23 demodulates the signal inputted from the amplifier 26 with a clock component synchronized with the system clock inputted from the clock generator 21 and supplied to the modulator 22 .

In addition to the tip from the cylindrical lens 12, various disturbance lights are incident on the light receiving element 13. Therefore, amplifier 26
The output of the light receiving element 13, which is input to the demodulator z3 via the demodulator z3, contains a noise component corresponding to the disturbance light.

However, the output of the demodulator 23 is
The low-pass filter 24 not only smoothes the signal input from the demodulator 23 but also suppresses noise components contained therein.

Therefore, the output of the low-pass filter 24 becomes a signal in which the influence of disturbance light is reduced.

The detector 25 detects the position of the carriage 14 (the cylindrical lens 12
and the distance between the light receiving element 13).

The cylindrical lens 12 is not in physical contact with the carriage 14. Further, in order to detect the position of the head with the above-described configuration, the only load added when moving the carriage 14 is the mass of the light receiving element 13.

However, the mass of the light receiving element 13 is extremely small and can be practically ignored. Therefore, there is virtually no increase in the load.

FIG. 2 is a block diagram showing the configuration of another embodiment of the head position detecting device of the present invention, and parts corresponding to those in FIG. 1 are given the same reference numerals.

In the embodiment shown in FIG. 2, the light receiving element 13 is fixed on the substrate, whereas the cylindrical lens 12 is attached to the carriage 14 and moves therewith. The other configurations are the same as in FIG. 1.

In this embodiment as well, since the distance between the cylindrical lens 12 and the light receiving element 13 changes in accordance with the movement of the head, the position of the head can be accurately detected without being affected by ambient light.

In this embodiment, the light source 11 is fixed and only the cylindrical lens 12 is moved. However, since the light source 11 generates parallel light, the light source 11 is fixed and the cylindrical lens 12 is moved.
It operates in the same way as when moved with 2.

In the above description, since the light from the light source 11 is diffused only in the direction of one surface by the cylindrical lens 12, the output of the light receiving element 13 is inversely proportional to the distance. However, for example, if the light is diffused so that the cross section perpendicular to the optical axis is approximately circular, the output of the light receiving element 13 will be inversely proportional to the square of the distance. The present invention is theoretically applicable to such cases as well. However, the former case is practically preferable because the circuit configuration is easier.

[Effects of the Invention] As described above, according to the head position detection device of the present invention, light is modulated with a predetermined signal and diffused, and one of the light source and the light receiving means is switched to the other in response to the movement of the head. The output of the light receiving means is demodulated in synchronization with the modulation signal, and the noise component of the demodulated output is suppressed by a low-pass filter, so the influence of disturbance light can be reduced. It becomes possible to accurately detect the position of

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the head position detection device of the present invention, FIG. 2 is a block diagram showing the configuration of another embodiment of the head position detection device of the invention, and FIG. 3 is a conventional one. 4 is a block diagram showing the configuration of an example of a head position detection device, FIG. 4 is a diagram showing the output characteristics of the detector in FIG. 3, and FIG. 5 is a block diagram showing the configuration of another example of the conventional head position detection device. be. 10... Drive circuit 11... Light source 12... Cylindrical lens 13... Light receiving element 14... Gear ridge 15... Guide bar 16... Detector 21... Clock generator 2...・Modulator 3...Demodulator 4...Low pass filter 5...Detector 6...Amplifier

Claims (1)

[Scope of Claims] A light source that emits diffused light; a generating means that generates a predetermined signal; and a modulating means that modulates the light emitted from the light source in response to the signal output from the generating means. , a light receiving means having an area sufficiently smaller than the area of a plane perpendicular to the optical axis of the diffused light emitted from the light source and disposed in the optical path of the light receiving means, and one of the light source or the light receiving means relative to the other, a moving means that moves in conjunction with the movement of a head that records or reproduces information on a recording medium; a demodulating means that demodulates the output of the light receiving means in synchronization with a signal output by the generating means; and an output of the demodulating means. A head position detection device comprising: low-pass filter means for suppressing noise components included in the head position detection device.