JPH0739055Y2 - Optical head position detection mechanism - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to an optical head position detecting mechanism for detecting a position of an optical head in a feeding direction in an optical disk device.

[Prior Art] As a detection method for detecting the position of the optical head in the feeding direction in an optical disk device, there is an induced electromotive force detection method shown in FIG. 6, for example.

In this detection method, a speed detecting coil 2 is attached to the optical head 1 side, and a magnet 3 and a yoke 4 for applying a magnetic field to the speed detecting coil 2 are arranged on the chassis side. The illustrated example employs a linear motor system as an optical head feed drive mechanism. When the optical head 1 is driven by the linear motor 5 and moves in the disk radial direction (direction of arrow a), it is integrated with the optical head 1. An induced voltage proportional to the feeding speed is generated in the moving speed detecting coil 2, and the displacement of the optical head 1 is calculated by integrating the speed based on this induced voltage to detect the position of the optical head. is there.

In FIG. 6, reference numeral 6 is an objective lens of the optical head 1, and reference numerals 7 and 8 are slide shafts that slidably support the optical head 1 in the disk radial direction. Further, the linear motor 5 includes a motor coil 9 provided on the optical head 1 side,
It is composed of a magnet 10 and a yoke 11 provided on the chassis side.

Although not shown, the conductor attached to the optical head side is configured to come into contact with and slide on the coil resistance wire in the optical head feeding direction arranged on the chassis side. There is also a resistance type detection method in which the moving distance of the optical head is calculated based on the resistance change.

[Problems to be Solved by the Invention] In the former induced electromotive force type detection method, since the magnet 3 for acting a magnetic field on the speed detection coil 2 is used, in order to avoid mutual interference with the magnetic field of the linear motor 5, There is a restriction that the head position detection mechanism cannot be installed in the vicinity of the linear motor 5.

Further, there is a problem that a large space is required for arranging the coil 2, the magnet 3, and the yoke 4, and the device becomes large.

Further, due to the frequency characteristic of the induced electromotive voltage, there is a restriction in widening the servo band of the linear motor 5.

In addition, the latter resistance type detection method has a problem that spark noise is generated during movement.

The present invention has been made in order to solve the above-mentioned conventional drawbacks, occupies a large space, can be downsized, has no problem in expanding the servo band of a linear motor, and does not generate spark noise. The purpose is to obtain an optical head position detection mechanism.

[Means for Solving the Problems] The present invention for solving the above problems comprises a cylindrical motor coil attached to the optical head side, and a chassis-side magnet and a yoke for applying a magnetic field to the linear motor coil. An optical head position detection mechanism in an optical disk device for driving an optical head by a linear motor in a radial direction of a disk, comprising: an optical reflection slit plate provided on the magnet surface and having a large number of slits arranged in the optical head sending direction. An optical head position detecting mechanism provided on the motor coil side for optically detecting a slit of the optical reflection slit plate.

The optical reflection slit plate may be formed by depositing aluminum or the like on the surface of the magnet.

[Operation] In the above configuration, the optical head is driven by the linear motor to move in the disk radial direction. At the time of this movement, the optical slit detector provided on the motor coil side detects the slit of the magnet or the slit plate for optical reflection provided on the yoke side, and counts this to calculate the moving distance of the optical head. .

Further, when aluminum or the like is vapor-deposited on the surface of the magnet to form the slit plate for optical reflection, the slit is detected by the difference in the light intensity of the reflected light between the vapor-deposited layer surface and the magnet surface.

[Embodiment] An embodiment of the present invention will be described below with reference to FIGS. 1 to 5.

In FIGS. 1 and 2, reference numeral 20 indicates an optical head, and reference numeral 21 indicates the objective lens thereof. The optical head 20 has a slide shaft 23 fitted to a bearing 22 provided at one side end portion thereof, and a slide shaft 25 on which the roller 24 provided at the other side end portion is mounted, in a disc radial direction, that is, an optical head feeding direction ( It is slidably supported in the direction of arrow a). Sign 26
Shows a linear motor as an optical head feed drive mechanism for feeding and driving the optical head 20 in the disk radial direction. The linear motor 26 includes a motor coil 27 that is provided on the optical head 20 side and has a rectangular tubular shape when viewed from the optical head feeding direction, and a magnet 29 and a yoke 30 that are provided on the chassis side.

As shown in FIG. 3, the magnet 29 is provided with an optical reflection slit plate (hereinafter simply referred to as a slit plate) 31 having a plurality of slits 31a arranged at equal intervals in the optical head feeding direction a. On the other hand, on the bobbin 28 of the motor coil 27, as shown in an enlarged view in FIG. 4, an optical slit detector 34 including a light emitting portion 32 such as a light emitting diode or a laser diode and a light receiving portion 33 such as a photodiode is provided. It is provided. The light emitting section 32 is arranged at an angle so as to irradiate the slit plate 31 with light at an appropriate incident angle α such as 15 °, and the light receiving section 33 is also arranged at an angle corresponding to this. Has been done.

The slit plate 31 can be formed by, for example, vapor-depositing aluminum on the surface of the magnet 29 and using the non-vapor-deposited portion as the slit 31a. In this case, the slit is detected by the intensity difference of the reflected light between the surface of the aluminum and the surface of the magnet.

Next, the operation will be described.

The optical head 20 is driven by the linear motor 26 and moves in the disk radial direction (optical head feeding direction) a. That is, when a feed drive current flows through the motor coil 27 in the magnetic field of the magnet 29, an electromagnetic force in the optical head feed direction a acts on the motor coil 27 according to Fleming's left-hand rule,
The optical head 20 is driven in the feeding direction a.

At the time of this movement, the optical slit detector 34 provided on the bobbin 28 of the motor coil 27 detects the slit 31a of the optical reflection slit plate 31 provided on the magnet 29 side, and counts the slit 31a of the optical head 20. Calculate the distance traveled. That is, the light from the light emitting section 32 is incident on the slit plate 31, and the reflected light is received by the light receiving section 33. However, as shown in the light receiving section output diagram of FIG. 5, the reflected light from the surface of the slit plate 31 is reflected. Has a high light intensity, its output level A is high, and the light intensity of the light reflected from the slit 31a (which is the light reflected from the surface of the magnet 29 in the embodiment) is weak and its power level B is low.
The slit 31a is generated by the output difference of the light receiving section 33 based on the light intensity difference.
Can be detected and counted. This slit 31
The moving distance of the optical head 20 is cumulatively calculated based on the count of a, and the position of the optical head 20 in the disk radial direction is detected.

In addition, the slit plate for optical reflection is not limited to the configuration of the embodiment, and may be a stainless plate or an aluminum plate having slits formed therein. Also, it can be attached to the yoke 26 instead of the magnet 29.

[Advantages of the Invention] Since the present invention is configured as described above, since it is an optical position detection system that does not use a magnetic field, it has the following effects. It is possible to widen the servo band of the linear motor without the occurrence. Further, there is no problem that spark noise occurs during movement in the resistance type detection method.

The optical reflection slit plate and the optical slit detection unit can be provided without occupying a space, and the position detection mechanism is remarkably downsized as compared with the conventional induced electromotive force type detection method.

[Brief description of drawings]

FIG. 1 shows an embodiment of the optical head position detecting mechanism of the present invention. FIG. 1 is a plan view in the vicinity of the optical head, FIG. 2 is a sectional view taken along the line II--II in FIG. 1, and FIG. 3 is in FIG. FIG. 4 is a sectional view taken along the line III-III, FIG. 4 is an enlarged view of the optical slit detecting section in FIG. 1, FIG. 5 is a diagram for explaining the slit detecting procedure, and is an output view of the light receiving section, and FIG. FIG. 6 is a plan view showing the detection mechanism and the vicinity of the optical head. 20 …… Optical head, 26 …… Linear motor, 27 …… Motor coil, 28 …… Bobbin, 29 …… Magnet, 30 …… Yoke, 31 …… Optical reflection slit plate, 31a …… Slit, 3
2 ... Light emitting part, 33 ... Light receiving part, 34 ... Optical slit detecting part,

Claims (2)

[Scope of utility model registration request] 1. A linear motor composed of a cylindrical motor coil attached to the optical head side, a chassis side magnet for applying a magnetic field to the linear motor coil and a yoke, and drives the optical head in the radial direction of the disk. An optical head position detection mechanism in an optical disk device, comprising: an optical reflection slit plate having a large number of slits arranged in the optical head feed direction, which is provided on the magnet surface; and a magnet surface and an optical disc provided on the motor coil side. An optical head position detecting mechanism comprising: an optical slit detecting section having an independent light emitting section and an independent light receiving section for detecting the presence or absence of a slit based on a difference in intensity of reflected light on the surface of a reflective slit plate. 2. The optical head position detecting mechanism according to claim 1, wherein the optical reflection slit plate is formed on the surface of the magnet by depositing a material having a reflectance different from that of the magnet surface.