JPS62141639A - Light head for optical recording and reproducing - Google Patents

Abstract

PURPOSE:To detect positional error between a convergent lens and a light head case by providing the first and second magnetic reluctance elements arranged on a part of a plane parallel to the direction of track control of a lens support and a magnetic piece placed and fixed facing the magnetic reluctance elements to give nearly the same amount of magnetic field to both of magnetic reluctance elements, and detecting change of resistance value of the magnetic reluctance elements. CONSTITUTION:The first and second magnetic reluctance elements 9, 9' are arranged side by side on the face of a lens support 5, and a magnetic piece 10 is placed and fixed on a light head case 1 to face the magnetic reluctance elements 9, 9' and to give nearly equal amount of magnetic field to the first and second magnetic reluctance elements 9, 9' when a convergent lens 4 is at the position of approximate optical center in the light head. Electric resistance changes according to the amount of magnetic flux of magnetic field generated by the magnet piece 10 applied to the magnetic reluctance elements 9, 9', and the difference component appears in an output terminal 92 as output voltage VS. Thus, positional relation of the convergent lens 4 to the light head case 1 can be detected accurately.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a light beam for optically recording and reproducing information such as digital information for computers or audio and video onto a record carrier using a light beam. The present invention relates to light having a position error detection function in a track control direction with respect to a head housing of a converging lens that converges a laser beam onto a record carrier.

[Conventional technology]

Information can be recorded by modulating a laser beam with external information or a signal and focusing it onto an optical record carrier, or by irradiating a record carrier with a focused laser beam of a certain intensity. In an optical information recording/reproducing device that reads recorded information, such as an optical head of an optical disk device, the focal position is controlled so that the focused light beam spot accurately hits the surface of the record carrier, and the focus position is controlled so that the focused light beam spot accurately hits the surface of the record carrier. It is necessary to perform tracking position control to position the optical beam spot on the track. In general, the center and king position control is performed by moving the entire optical head equipped with the entire optical system for long-distance movement of the beam spot, and by moving only a focusing lens for short-distance movement of the optical beam spot. This is done by moving the In order to maintain the characteristics of the optical system in good condition during either long-distance or short-distance movement, it is desirable that the position of the focusing lens does not shift relative to the optical head, that is, relative to the optical center position. When the optical head housing moves, the optical head housing moves, and when the light housing moves, the focusing lens and optical head housing move so that the focusing lens follows it or moves together with the housing. It is desirable to control movement.

[Problem that the invention seeks to solve]

In order to realize the tracking control described above, it is necessary to accurately detect the position of the focusing lens with respect to the optical head housing, but conventional optical systems do not have such a position detection means. Therefore, the only way to detect the position is through indirect means such as detecting the current of the actuator that moves the focusing lens, making it impossible to detect the position at high speed and with high precision. It was difficult to control each movement so as to keep the deviations small.

SUMMARY OF THE INVENTION In order to eliminate the above-mentioned drawbacks, it is an object of the present invention to provide an optical head capable of generating a signal indicating the accurate positional relationship of a focusing lens with respect to an optical head housing.

[Means for solving problems]

The optical head for optical recording and reproducing of the present invention supports a focusing lens for focusing a laser beam on the surface of an optical record carrier and is movable in the track control direction. first and second magnetoresistive elements disposed on the optical head housing;
The first and second magnetoresistive elements are arranged and fixed so that substantially the same amount of magnetic field is applied to both the first and second magnetoresistive elements when the focusing lens is positioned approximately at the optical center of the optical head. and a positional error of the focusing lens with respect to the optical head housing in the track control direction is detected by detecting a change in the resistance value of the first and second magnetoresistive elements. It is characterized by this.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIGS. 1(a) and 1(b) are a schematic plan view and a front view, respectively, showing an embodiment of an optical recording/reproducing optical head according to the present invention.

As shown in the figure, the optical head according to the present invention is a swing arm type optical head having a lens support arm 3 rotatably supported in the rack control direction by an arm support shaft 2 in a head housing 1, and a focusing lens 4. The lens support body 5 supporting the lens is connected to and supported by the lens support arm 3 by two leaf springs 6 and 6'. The lens support 5 is driven by a tracking actuator 7 and a focus actuator 8 in a track control direction and a focus control direction, respectively. The positional deviation of the focusing lens 4 in the track control direction is caused by the first and second magnetoresistive elements 9, 9' which are arranged side by side in the track control direction on the surface of the lens support 5 opposite to the surface on which the leaf spring 6 is attached. , and a magnet piece 10 placed in the optical head housing 1 facing it.

FIG. 2 is a diagram explaining the principle of detecting the position of the focusing lens 4 in the track control direction.
b) is a circuit configuration diagram using magnetoresistive element 9.9';
C) is a diagram showing the detection characteristics of the amount of track deviation. Second
As shown in the figure (,), the first and second magnetoresistive elements 9
. The first and second magnetoresistive elements 9,9' are arranged and fixed on the optical head housing 1 so that substantially the same amount of magnetic field is applied to both the first and second magnetoresistive elements 9,9' when they are at the center position. The direction of the magnetic field generated by the magnet piece 10 is set, for example, in a direction perpendicular to the track control direction of the focusing lens 4, as shown by the arrow in FIG.

At the same time, the magnetic field detection directions of the first and second magnetoresistive elements 9, 9' are also set to be in the same direction.

The first and second magnetoresistive elements 9, 9' arranged as described above are differentially connected, that is, as shown in FIGS.
), they are connected in series, and a positive voltage +V is applied to one terminal 91, and a negative voltage -■ is applied to the other terminal 93. As a result, the electric resistance value of each changes depending on the amount of magnetic flux applied to each of the first and second magnetoresistive elements 9, 9' of the magnetic field generated by the magnet piece 10,
The difference component appears at the output terminal 92 as an output voltage Vs. Therefore, the output voltage Vs changes depending on the amount of positional deviation of the focusing lens 4 in the track control direction, and the characteristics shown in FIG. 2(C) are obtained. At this time, the magnet piece 10 outputs a voltage v when the focusing lens 4 is at the optical center position of the optical head.
8 is approximately 0 volts. As described above, the positional relationship of the focusing lens 4 with respect to the optical head housing 1 can be accurately detected.

Note that the characteristic arrangement and configuration of optical elements that are one component of the optical head, such as a laser diode, a photodetector, and an optical prism, are the same as those in the prior art, so a description thereof will be omitted.

〔Effect of the invention〕

As explained above, according to the optical recording/reproducing optical head of the present invention, the positional relationship between the focusing lens and the optical head housing can be accurately detected, and this positional deviation signal can be used to move the optical head housing. Therefore, it is possible to suppress the positional deviation of the focusing lens with respect to the optical head housing. In addition, by feeding back the positional shift signal to the lens actuator when moving the optical head housing, the focusing lens can be moved to follow the optical head housing, and the focusing lens can be fixed to the optical head housing under certain constraints. It has the effect that it can.

[Brief explanation of drawings]

FIG. 1(-) is a schematic plan view showing an embodiment of the optical recording/reproducing optical head according to the present invention, FIG. 1(b) is a front view thereof, and FIG. Diagrams to explain the principle, the same figure (,) is the layout configuration diagram, the same figure (b)
1 is a diagram showing a circuit configuration using a magnetoresistive element, and FIG. 1: Optical head housing, 2: Arm support shaft, 4: Focusing lens, 5: Lens support, 7: Tracking actuator, 8: Focus actuator, 9.9': Magnetoresistive element, 10: Magnet piece. Figure 1 (b) Figure 1 (α) (b) (C)

Claims (1)

[Claims] (1) In an optical head that optically records and reproduces information on an optical information recording carrier, a lens support that supports a focusing lens for focusing laser light on the surface of the optical recording carrier and is movable in the track control direction. first and second magnetoresistive elements arranged on a part of a plane parallel to the track control direction of the optical head housing, and facing the first and second magnetoresistive elements on the optical head housing, and the focusing lens; a magnet piece arranged and fixed so that substantially the same amount of magnetic field is applied to both the first and second magnetoresistive elements when the magneto-resistance element is positioned approximately at the optical center position of the optical head; For optical recording and reproducing, characterized in that a positional error between the focusing lens and the optical head housing in the track control direction is detected by detecting changes in the resistance values of the first and second magnetoresistive elements. light head.