JP2533879B2 - Position detection device - Google Patents

Description

The present invention relates to a device for detecting the position of a position-detected part. The position detecting device of the present invention is preferably used for detecting the position of an objective lens in an optical head of an optical information recording / reproducing device that records / reproduces information on / from a recording medium using an optical means.

[Prior Art and its Problems] In an optical information recording / reproducing apparatus, a laser beam is focused by an objective lens in an optical head to form a minute spot on an information track, and the information track is scanned by the spot. Is performed. However, in order to perform recording / reproducing accurately, it is necessary to make the minute spot accurately follow the information track always in a sufficiently focused state. Therefore, in the optical information recording / reproducing apparatus, the focusing state on the recording medium and the tracking state on the information track are constantly detected, and if the objective lens is about to deviate from the proper range, the objective lens is changed. The control for moving and maintaining the proper focusing state and tracking state is performed. In such focusing control and tracking control, an objective lens is supported so as to be movable two-dimensionally, and a focusing control coil and a tracking control coil are fixed to the objective lens directly or indirectly. Further, the coil is placed in an appropriate stationary magnetic field, and the amount of electricity supplied to each coil is controlled according to the detection signals of the focusing state and the tracking state.

Therefore, the control as described above can be sufficiently satisfactorily performed only when the focusing state is within a predetermined range (for example, when the objective lens and the recording medium are within a predetermined value ± 1 μm). Therefore, when the objective lens is moved stepwise out of the predetermined range due to the focusing control due to the random access without the focusing control or due to the scratch on the recording medium, the desired focusing control and It becomes difficult to return to the tracking control state. Therefore, it is necessary to detect the position of the objective lens with respect to the optical head main body and immediately move the objective lens to a desired position.

FIG. 5 is a side view showing a schematic configuration of an optical head of a conventional optical information recording / reproducing apparatus equipped with such a device for detecting the position of the objective lens.

In the figure, 2 is a substrate arranged in the x-z plane, and a support plate 4 arranged in the xy plane at the end of the substrate.
Has been fixed. One end of four parallel wires 6a, 6b, 6c, 6d in the z direction is fixed to the support plate (however, 6c, 6d
Is not shown). Each wire has the same length and bending elasticity. The wires 6a and 6c are arranged at the same height, the wires 6b and d are arranged at the same height, and the wire 6b is located below the wire 6a and the wire 6d is Located below 6c. The other ends of the four wires are fixed to the objective lens holding member 8. The objective lens 10 is fixedly held on the holding member, and the optical axis of the objective lens is in the y direction. Further, a focusing coil 12 is wound around the outer surface of the holding member 8 in the vertical direction (y direction), and further two tracking coils 14a, 14a, around the horizontal direction (z direction).
14b is wound.

On the other hand, each of the substrates 2 has a permanent magnet for generating a magnetic field.
U-shaped yoke members 20 and 22 that support 16 and 18 are fixed. One of the yoke members 20 is the objective lens holding member 8
A part of the focusing coil 12 and the tracking coil 14a attached to the above is disposed so as to sandwich the focusing coil 12 and the tracking coil 14a to form a magnetic circuit for focusing control and tracking control. Similarly, the other yoke member 22 is arranged so as to sandwich a part of the focusing coil 12 and the tracking coil 14b attached to the objective lens holding member 8 to form a magnetic circuit for focusing control and tracking control. .

Further, a photo reflector main body 26 supported by a support plate 24 and a photo reflector main body 28 supported by a support plate 25 are solid-stated on the substrate 2. Then, the photo reflector main bodies 26, 28 of the objective lens holding member 8
At the position facing the
30,32 are attached. The photoreflector consisting of the main body 26 and the reflecting plate 30 is for detecting the y direction (focusing direction) position of the objective lens 10 with respect to the optical head main body fixing member, and the photoreflector consisting of the main body 28 and the reflecting plate 32. The reflector is for detecting the position of the objective lens 10 in the x direction (tracking direction) with respect to the optical head main body fixing member.

In the optical head as described above, the holding member 8 is moved in the y direction by the interaction with the magnetic field based on the permanent magnets 16 and 18 by passing a current through the focusing coil 12, and at this time, the current value is appropriately controlled. Objective lens by
The 10 y-direction positions are controlled, and thereby focusing control is performed. Similarly, the tracking coil 14a1
By passing a current through 4b, the holding member 8 moves in the x direction due to the interaction with the magnetic field generated by the permanent magnets 16 and 18, and the tracking control of the objective lens 10 is performed by controlling the current value appropriately at this time. .

The position of the objective lens 10, which is the position-detected portion, with respect to the optical head main body fixing member is detected separately in the focusing direction and the tracking direction. That is, the y-direction position is emitted from the light emitter of the photo reflector main body 26.
The amount of light reflected by the reflection plate 30 having a discontinuous reflectance distribution in the direction and incident on the light receiver of the photo reflector main body 26 again is detected. The position in the x direction is detected from the amount of light emitted from the light emitter of the photo reflector main body 28, reflected by the reflection plate 32 having a predetermined area, and incident on the light receiver of the photo reflector main body 28 again.

However, the conventional objective lens position detecting device as described above has the following problems.

FIG. 6 is a view of the objective lens holding member portion of the optical head of FIG. 5 as viewed in the z direction.

In the optical head as described above, it is ideally desirable that the objective lens holding member 8 be moved in parallel in the x direction and the y direction, but in actuality, in view of the characteristics of the wires 6a to 6d during driving. A mode of rotation around the z direction (rolling mode) as shown in FIG. 6 occurs.
The axis of rotation of the rolling generally passes in the vicinity of the center position C of the objective lens holding member 8, while the objective lens 10 is generally arranged at a position deviated from the center position of the objective lens in the y direction, and further the position detection in the x direction is performed. Since the photoreflector body 28 and the photoreflector reflector 32 for are generally arranged at the intermediate position in the height direction of the objective lens holding member 8, the objective when the rolling angle is θ (small) is set. Although the position of the lens 10 in the x direction is deviated by ly · sin θ from the case without rolling, the position of the objective lens 10 detected by the photoreflector main body 28 in the x direction is lx (1-co
sθ) to 0, and therefore the photoreflector cannot accurately detect the x-direction position of the objective lens when rolling occurs. If the tracking control is performed based on the detection value having such an error, accurate control cannot be expected.

Further, in the conventional objective lens position detecting device as described above, since the position detecting means in the focusing direction and the position detecting means in the tracking direction are arranged completely separately,
There is also a problem that the number of parts increases and the assembling work is troublesome.

Therefore, according to the present invention, the position of the position detection part, which is fixedly held by the holding member and is supported by the external fixing member so as to be movable in two directions orthogonal to each other, is set to the holding member and the external fixing member. It solves the problems of the prior art as described above in the position detection device that detects by measuring the relative position between the and, and can accurately detect the position, reduce the number of parts, and further An object is to provide a simple position detecting device.

[Means for Solving the Problems] According to the present invention, in order to achieve the above object, the position of the movable member, which is supported by the fixed member so as to be movable in two orthogonal directions, with respect to the fixed member. A light source which is attached to one of the movable member and the fixed member and emits a flat light beam; and a light source which is attached to the other of the movable member and the fixed member so as to face the light source. Based on the amount of light detected by each light receiving unit of the four-division sensor,
And a calculation unit that generates a position detection signal indicating the position of the movable member in the two directions, wherein the light-receiving unit of the four-division sensor has axes parallel to each of the two directions and orthogonal to each other. Are arranged symmetrically with each other, the arithmetic means detects the rotation angle of the movable means based on the difference in the amount of detected light between a pair of light receiving portions that are opposed to each other with respect to the intersection of the mutually orthogonal axes, A position detecting device is provided, which corrects the position detection signal based on the rotation angle.

[Examples] Specific examples of the present invention will be described below with reference to the drawings.

FIG. 1 is a side view showing a first embodiment of an optical head equipped with a position detecting device according to the present invention.

In FIG. 1, 2 is a substrate, 4 is a support plate, and 6a, 6b, 6c, 6d are parallel wires in the z direction (however, 6
c and 6d are not shown), 8 is an objective lens holding member, 10 is an objective lens, 12 is a focusing coil, 16 is a permanent magnet, and 20 is a U-shaped yoke member. . These are the same as in FIG. 5 above. Further, 14 is a tracking coil similar to 14a in FIG.

In this embodiment, the structure of the means for detecting the position of the objective lens 10 with respect to the optical head main body fixing member is different from that of the apparatus shown in FIG. That is, the substrate 2 has a supporting plate.
A photodetector 26 supported by 24 is fixed. The photodetector has a light receiving surface in the xy plane. Then, at the position of the objective lens holding member 8 facing the photodetector 26,
A light source 30 such as an LED is fixed. Including the photodetector 26 and the light source 30, the position of the objective lens holding member 8 in the x direction (tracking direction) with respect to the optical head main body fixing member,
Means are provided for detecting the y-direction (focusing direction) position and the angle of rotation about the z-direction.

In the optical head as described above, the holding member 8 moves in the y direction by the interaction with the magnetic field based on the permanent magnet 16 by passing a current through the focusing coil 12, and at this time, the current value is appropriately controlled. The objective lens 10 y
The directional position is controlled, so that focusing control is performed. Similarly, when a current is passed through the tracking coil 14, the holding member 8 moves in the x direction by the interaction with the magnetic field generated by the permanent magnet 16, and the tracking of the objective lens 10 is performed by controlling the current value at this time. Control is performed.

FIG. 2 is a diagram showing details of a photodetector constituting the objective lens position detecting means in the optical head of FIG.

The light receiving surface of the photodetector has four light receiving portions 26a, 26b, 26c, 26d divided by two dividing lines in the x direction and the y direction, and outputs are respectively obtained from these light receiving portions.

In the present embodiment, the light source 30 irradiates the photodetector 26 with a z-direction directional light flux having a predetermined intensity. Then, the irradiation light flux is incident on the photodetector 26 as a flat (for example, rectangular or elliptical) light flux whose cross-sectional shape has different lengths in the x direction and the y direction.

When the objective lens holding member 8 is in the neutral position, the light source
The light beam from 30 is at the position indicated by the one-dot chain line L in FIG. 2 (that is, the position where the longitudinal direction of the light beam cross section coincides with the x direction and the light beam center passes through the intersection of the two dividing lines of the photodetector 26). )
Incident on. In this case, the detection signals of the light receiving parts 26a to 26d of the photodetector are equal.

Further, when the objective lens holding member 8 is at a position appropriately moved in the tracking direction and the focusing direction from the neutral position, the light flux from the light source 30 is at a position indicated by a chain double-dashed line L'in FIG. The light beam is incident on a position which is translated from the position by an appropriate distance in the x direction and the y direction).

Further, when the objective lens holding member 8 is in a position rotated by the angle θ about the z direction from the neutral position by rolling, the light flux from the light source 30 is at a position indicated by a broken line L ″ in FIG. It is incident at a position rotated from the position around the z direction by an angle θ corresponding to the rolling angle).

Therefore, when the objective lens holding member 8 moves in the tracking direction and the focusing direction and is rotated by rolling, the photodetector 26 is incident on a position where the parallel movement of L'and the rotation of L "are combined. Will be done.

FIG. 3 is a schematic configuration diagram of the position detecting means of this embodiment.

The light source 30 is driven by the drive circuit 31, and the light flux from the light source enters the photodetector 26. Light receiving parts 26a, 26b, 26c,
The output signal of 26d is input to the servo circuit 34 as the light amount signals A, B, C, D via the I / V converters 33a, 33b, 33c, 33d, respectively. In the servo circuit, {A + B
+ C + D}, {(A + C)-(B + D)}, {(A +
B)-(C + D)}, {(A + D)-(B + C)} are calculated, and from these signals a signal {(A + C)-(B + D)} corresponding to the tracking direction position of the objective lens holding member 8 is calculated.
/ {A + B + C + D}, a signal corresponding to the position in the focusing direction {(A + B)-(C + D)} / {A + B + C +
D} and the signal {(A + D)-(B + C)} / {A + B + C + D} corresponding to the rotation angle θ around the z direction. The rotation angle of the objective lens 10 depends on the objective lens holding member 10 described above.
6 and the tracking direction position and the focusing direction position of the objective lens 10 are ly.sin.theta. It is obtained by performing an operation to correct only cos θ). When θ is very small, it is (1-cos θ) to 0, so the correction calculation in the focusing direction may be omitted.

The servo circuit 34 forms drive signals for the focusing coil 12 and the tracking coil 14 for moving the objective lens to a desired position based on the position of the objective lens detected as described above.

In the present embodiment, when the position is detected as described above, {A + B +
Since the calculation (normalization) performed by dividing by C + D} is performed, the light source
Accurate position detection can be performed even if the intensity of 30 changes, and the servo circuit described above is based on the position signal thus obtained.
Accurate control is possible by performing tracking control and focusing control with 34.

FIG. 4 is a schematic configuration diagram of the position detecting means in the second embodiment of the optical head provided with the position detecting device according to the present invention. In this figure, the same members as those in FIG. 3 are denoted by the same reference numerals.

In the present embodiment, the outputs of the I / V converters 33a, 33b, 33c, 33d are input to the adder 36, where the operation of {A + B + C + D} is performed, and the result is input to the light source drive circuit 31. . In the drive circuit, when the value of {A + B + C + D} deviates from the set value, the drive voltage is controlled to keep the value of {A + B + C + D} constant.

The outputs of the I / V converters 33a, 33b, 33c, 33d are also input to the servo circuit 34 '. In the servo circuit, a signal {(A + C)-(B +
D)}, a signal corresponding to the position in the focusing direction {(A
+ B) − (C + D)} and the signal {(A + D) − (B + C)} corresponding to the rotation angle θ around the z direction. From these signals, the position of the objective lens is obtained by calculation in the same manner as in the first embodiment.

In the present embodiment, since the intensity of the light source 30 is maintained constant as described above, accurate position detection can be performed even if the servo circuit 34 'does not perform a division operation by {A + B + C + D} in position detection. By performing tracking control and focusing control by the servo circuit 34 'based on the position signal thus obtained, accurate control can be performed as in the first embodiment.

In the above embodiment, the light source is fixed to the objective lens holding member 8 side and the photodetector is fixed to the support plate 24 side. However, in the present invention, the arrangement of the light source and the photodetector is the same as in the above embodiment. And vice versa.

In the above embodiment, the position detecting section is an example of an objective lens of an optical head of an optical information recording / reproducing apparatus, but the present invention detects another position detecting that is two-dimensionally movable. The same can be applied to the position detection of a part.

EFFECTS OF THE INVENTION According to the present invention as described above, the position of the position detection part movably supported by the external fixing member in the two directions orthogonal to each other is set to the third direction orthogonal to the two directions. It is possible to accurately detect the rotation angle around the axis, the number of parts of the detecting means can be reduced, and the assembling work becomes easy.

[Brief description of drawings]

FIG. 1 is a side view showing an optical head provided with a position detecting device according to the present invention, FIG. 2 is a view showing details of a photodetector thereof, and FIG. 3 is a schematic configuration diagram of its position detecting means. Is. FIG. 4 is a schematic configuration diagram of position detecting means in an optical head provided with the position detecting device according to the present invention. FIG. 5 is a side view showing an optical head of a conventional optical information recording / reproducing apparatus equipped with an objective lens position detecting device. FIG. 6 is a view of the objective lens holding member portion of the optical head shown in FIG. 2: Substrate, 4, 24 ,: Support plate, 6a, 6b: Wire, 8: Objective lens holding member, 10: Objective lens, 12: Focusing coil, 14: Tracking coil, 16: Permanent magnet, 20: Yoke Material, 26: Photodetector, 30: Light source.

Claims (1)

(57) [Claims] 1. An apparatus for detecting a position of a movable member, which is movably supported by a fixed member in two orthogonal directions, with respect to the fixed member, and is attached to one of the movable member and the fixed member. A light source that emits a flat light flux, a four-division sensor that is attached to the other of the movable member and the fixed member so as to face the light source, and that detects the light flux emitted from the light source, and each light-receiving unit of the four-division sensor And a calculation means for generating a position detection signal indicating the position of the movable member in the two directions based on the detected light amount of the movable member, and the light receiving unit of the four-division sensor is parallel to each of the two directions. And the arithmetic means are arranged symmetrically with respect to the mutually orthogonal axes, and the arithmetic means detects the detection light between the pair of light receiving portions which are opposed to each other with respect to the intersection of the mutually orthogonal axes. A position detecting device which detects a rotation angle of the movable means on the basis of a difference in amount and corrects the position detection signal based on the rotation angle.