JPH10124886A - Optical head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable an optical head used for an optical disk device to reduce the detection output in a focusing direction of a position detector of a tracking direction disposed oppositely to the reflection surface of a movable body holding an objective lens and to accurately perform the position control of the objective lens held by the movable body in a tracking direction. SOLUTION: Oppositely to a pair of reflection surfaces 18 of a movable body 15 holding an objective lens 11 and having the pair of reflection surfaces 18 in a side corresponding to a tracking direction, the body 15 being made movable in focusing and tracking directions with respect to an optical recording medium, two reflection type photosensors 23a and 23b having light emitting and receiving elements disposed in different positions, the photosensors being disposed adjacent to each other having the equal height positions of the light emitting and receiving elements, are disposed such that the light emitting and receiving elements thereof are symmetrical to each other, and the displacement of the movable body 15 in its tracking direction is detected based on a difference in detected outputs between the two photosensors 23a and 23b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical head used in an optical disk device, and more particularly, to narrowing a light beam for recording or reproducing information to a minute spot by driving an objective lens in an optical axis direction. The present invention also relates to an objective lens drive control mechanism of an optical head that controls the displacement of the spot to a predetermined predetermined planar position on an optical recording medium with high precision.

In recent years, in an optical disk device, higher sensitivity has been required for detecting the position of an objective lens in a tracking direction in an optical head with the increase in the density of an optical recording medium. There is a need for a detection means that is highly sensitive and somewhat insensitive in the focusing direction.

[0003]

2. Description of the Related Art In an optical disk drive, an objective lens is driven in the direction of an optical axis to narrow a light beam for recording or reproducing information to a minute spot, and the spot is positioned at a predetermined position on the surface of the optical recording medium. As a configuration for detecting the position in the tracking direction of a movable body that holds an objective lens of an optical head that controls minute displacement with high accuracy, a reflection type detector (hereinafter, referred to as a reflection type photodetector) in which a light emitting element and a light receiving element are adjacently integrated. A configuration using a sensor is called
-214925.

FIG. 8 shows such a reflection type photosensor.
FIG. 4 is a plan view of a main part showing an example of an objective lens drive control mechanism of the optical head used. That is, the objective lens drive control mechanism controls the displacement in the tracking direction by rotating the cylindrical movable body 8 holding the objective lens 7 around the axis 9 by magnetic drive means as shown in the figure. The displacement is controlled in the focusing direction by sliding in the axial direction.

At this time, the position of the objective lens 7 in the tracking direction is detected by reflecting a reflecting surface 6 provided on the outer peripheral surface of the cylindrical movable body 8 as shown in FIG. This is performed by two reflective photosensors 1a and 1b in which a light emitting element and a light receiving element are arranged adjacent to each other. For example, light emitted from the light emitting elements of the respective reflective photosensors 1a and 1b is opposed to each other. The light is reflected by the reflection surface 6 of the body 8 and is incident on the adjacent light receiving elements, and the difference between the output signals from the respective light receiving elements is detected to detect the position of the objective lens 7 in the tracking direction, whereby various environments can be detected. It is resistant to noise generated by changes and the like, enabling correction of the beam shift of the objective lens 7 and the like, and also enables accurate tracking control.

[0006]

By the way, in recent optical disk devices, with the increase in the density of the optical recording medium, a considerably high sensitivity is required for detecting the position of the objective lens 7 in the tracking direction. However, there is a problem that the position detection signal in the tracking direction shifts when the movable body 8 follows the surface runout due to the focusing control, and the position detection in the tracking direction cannot be accurately obtained.

Therefore, a photosensor which is highly sensitive in the tracking direction for position detection and insensitive in the focusing direction is required. On the other hand, since there is a demand for miniaturization and thinning of the optical disk device,
As the reflection type photo sensors 1a and 1b, for example, FIG.
As shown in the side sectional view of the main part of FIG. 1, a chip of a light emitting diode (LED) 2a as a light emitting element and a phototransistor (PTr) as a light receiving element are placed in one thin package 5 molded with resin together with the lead frames 4a and 4b. Attempts have been made to mount and bond a 2b chip, bond the chip, and apply a commercially available small reflective photosensor buried with a resin material 3.

FIG. 8 shows such reflection type photo sensors 1a and 1b.
As shown in FIG. 10 (a), when it is disposed so as to face the reflecting surface 6 of the movable body, as shown in FIG.
The movable body is positioned at a neutral point where the output from the phototransistor (PTr) 2b, which is the light receiving element of 1b, is equal, and the movable body moves in the tracking direction indicated by the arrow in FIG. 10 (b). The output of one of the reflective photosensors 1a increases, and the other
Since the output of 1b decreases, the position of the objective lens held by the movable body is detected by taking the difference between the outputs.

However, such a reflection type photosensor
In FIGS. 1a and 1b, the disposition positions of the incorporated light emitting diode (LED) 2a chip and phototransistor (PTr) 2b chip are shifted to one side from the center in the package 5 as shown in FIG. As shown in FIG. 10 (a), the reflection type photosensors 1a and 1b are arranged so as to face the reflection surface 6 of the movable body so that their light emitting diodes (LEDs) 2a are located inside. In this case, as shown in FIG. 11A, the light emitting diode (LED) 2a and the chip center of the phototransistor (PTr) 2b of one reflective photosensor 1a and the light emitting diode (LED) of the other reflective photosensor 1b The height positions of 2a and the phototransistor (PTr) 2b with respect to the chip center are shifted.

Further, in order to eliminate such a shift in the height position of the chip center, as shown in FIG. 11B, the chip center of one reflection type photosensor 1a and the reflection center of the other reflection type photosensor 1b are arranged. If the height positions are aligned so as to coincide with the chip center, the height of the package of each of the reflective photosensors 1a and 1b is shifted.

For this reason, when the movable body moves in the focusing direction, the output of the position detection of the objective lens held by the movable body is shifted, and the position detection in the tracking direction cannot be accurately performed. The problem had arisen.

In view of the above-mentioned conventional problems, the present invention reduces the sense output for the movement in the focusing direction of the position detection sensor in the tracking direction, which is disposed to face the reflecting surface of the movable body holding the objective lens. New sensitivity that improves the sensitivity in the tracking direction by reducing the sensitivity and improving the efficiency of light reflection on the reflection surface enables accurate control of the position of the objective lens held by the movable body in the tracking direction. It is an object to provide a simple optical head.

[0013]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides an optical recording medium having a pair of reflecting surfaces on a side corresponding to a tracking direction, holding an objective lens on a support base. A movable body movable in a focusing direction and a tracking direction, a focusing drive unit for driving the movable body in an optical axis direction of the objective lens, and a tracking drive unit for driving the movable body in a direction orthogonal to the optical axis of the objective lens. I have.

The light-emitting element and the light-receiving element are arranged at different positions, and the chip height positions of the elements are arranged adjacent to each other so as to face the pair of reflecting surfaces of the movable body having such a configuration. The two detectors are arranged such that the light emitting element and the light receiving element of each detector are symmetrical left and right, and light emitted from the two detectors is reflected by the reflection surface,
An optical head is characterized in that the displacement of the movable body in the tracking direction is differentially detected based on each output detected by receiving the reflected light.

With such a configuration of the optical head, the sense output for the movement in the focusing direction of the position detector in the tracking direction arranged opposite to the reflection surface of the movable body holding the objective lens is reduced, and the movable body is reduced. It is possible to accurately control the position of the objective lens held in the camera in the tracking direction.

Further, the two detectors are attached to a detector mounting member to which a flexible printed circuit board is attached or a detector mounting member made of a printed circuit board, and are fixed to the support base. Thereby, electrical connection of the two detectors to the detector mounting member is easy, and the number of electrical and mechanical connection parts can be reduced.

Further, the reflecting surface of the movable body is formed of a resin material and has a white surface or a white surface having a plurality of rectangular grooves, V grooves, U grooves and the like in the focusing direction of the reflecting surface. With the configuration having the high reflectivity means, the amount of reflected light of the light emitted from the detector on those reflection surfaces increases, and the amount of light received by the detector also increases, so that the efficiency is improved. Since the current flowing through the light emitting element in the detector can be reduced to some extent, the life of the light emitting element can be extended.

[0018]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a perspective view showing a main part of an embodiment of an optical head according to the present invention.

This embodiment is directed to an optical head of a type in which a movable body holding an objective lens is supported by four parallel leaf springs. That is, in the present embodiment, a movable body 15 holding an objective lens 11 into which a light beam emitted from an optical system including a laser emission source (not shown) is reflected by a rising mirror such as a beam splitter and the like is incident on a support base.
Elastic members such as four parallel leaf springs as shown in FIG.
By 19, it is movably supported in the focusing direction and the tracking direction.

A pair of reflecting surfaces 18 are provided on one side of the movable body 15 corresponding to the tracking direction.
On both sides of the movable body 15, a focusing coil 13 and a yoke 12 for moving the objective lens 11 including the movable body 15 in the optical axis direction (focusing direction), and a tracking coil 14, a yoke 17 and a magnet 16 for moving the objective lens 11 in the tracking direction.
Is arranged.

Further, as shown in FIG. 2, a light emitting diode (LED) 24a, which is a light emitting element, and a phototransistor (PTr) 24b, which is a light receiving element, face the pair of reflecting surfaces 18 provided on the movable body 15. And the position of each diode is different.
Two detectors (LED) 24a and phototransistor (PTr) 24b that are arranged adjacently and integrally with the same chip height position (chip center), for example, reflective photosensors 23a and 23b, Each of the reflective photo sensors 23a and 23b
Light emitting diode (LED) 24a and phototransistor (PTr) 2
As shown in FIG. 4, each of the connection terminals 26 is attached to the detector attachment member 20 in which a flexible printed circuit board 25 is attached to a metal plate or a resin plate by soldering or the like so that 4b is symmetrical. It is configured to be screwed to the support base 10 using at least one horizontally long hole 21 or fixed by an adhesive or the like.

The two reflection type photo sensors 23a
Support the detector mounting member 20 with the
When the movable body 15 is moved in the focusing direction, the two reflective photosensors 23a and 23b
And the detector mounting member 20 is adjusted so that the output difference approaches zero, and the angle is adjusted in-plane in the tracking direction and the focusing direction so that the output change with respect to the movement in the focusing direction is reduced. I do.

With such a fixed structure, the support base 10 is mounted on a carriage (not shown), and the position of the movable body 15 and the two reflective photosensors 23a and 23b can be adjusted even when the tilt of the objective lens 11 is adjusted. There is no deviation in the relationship.

Then, as shown in FIG.
The reflection type photosensor is arranged so as to face the reflection surface 18 of 15
23a and 23b are adjusted and arranged at a neutral point where the outputs from the phototransistors (PTr) 24b, which are both light receiving elements, are equal.
When the light moves in the tracking direction indicated by the arrow in FIG.
, The reflected light is received and the detected output increases, the output light from the other reflective photosensor 23b is reflected by the reflection surface 18, and the reflected light is received and the detected output decreases. Therefore, the displacement of the objective lens 11 held by the movable body 15 in the tracking direction is detected by calculating the difference between the outputs.

Therefore, in the configuration of this embodiment, even if the movable body 15 holding the objective lens 11 moves in the focusing direction, the deviation of the detection output by each of the reflective photosensors 23a and 23b is reduced, and It is possible to accurately control the position of the objective lens 11 held by the body 15 in the tracking direction.

In this embodiment, the light-emitting diodes (LEDs) 24a of the reflection type photosensors 23a and 23b are positioned symmetrically in the left-right direction with the chips inside as shown in FIG. 3 (a) or (b). Although the example of the case of arrangement in the relationship was explained,
The present invention is not limited to such an example.For example, as a configuration in which the chips of the respective light emitting diodes (LEDs) 24a of the reflective photosensors 23a and 23b are arranged in a symmetrical positional relationship in a state where they are outside. Is also good. The light receiving element is not limited to the general phototransistor (PTr) 24b, but may be, for example, a photodiode or a Darlington type phototransistor.

The two reflection-type photo sensors 23a
And 23b are not limited to the example in which the detector mounting member 20 facing the reflection surface 18 of the movable body 15 is arranged in parallel with the tracking direction as in the present embodiment, for example, the reflection surface is movable. It is also possible to adopt a configuration in which reflection photosensors 23a and 23b are respectively disposed on both side surfaces orthogonal to the tracking direction of the body and opposed to both reflection surfaces.

Further, in this embodiment, an example in which a member in which a flexible printed circuit board 25 is bonded to a metal plate or a resin plate as shown in FIG. However, the present invention is not limited to such an example. For example, a metal plate on which a flexible printed circuit board 25 is bonded is stamped to form a detector mounting member or a printed circuit board as a sensor. It can also be used as a mounting member.

In this case, the electric power of the two reflection-type photosensors 23a and 23b with respect to the detector mounting member 20,
There is an advantage that mechanical connection can be made easily at low cost. Further, as the reflecting surface 18 of the movable body 15, in a configuration in which a reflecting mirror is attached, the movable body 15 is heavy, and the cost is high. In addition, as shown in FIG. Edges may be tilted due to poor sticking accuracy, or fine irregularities may occur.When the movable body moves in the focusing direction due to this, the position detection output by the opposing reflective photo sensor may This causes a problem that the position of the objective lens held by the movable body in the tracking direction cannot be accurately detected.

In order to solve such a problem, in this embodiment, first, as shown in FIG. 5 (a), the reflecting surface 27 of the movable body 15 and the movable body 15 are combined with, for example, a polyphenyl sulfite resin. Forming the reflecting surface 27 wide by integrally molding with, for example, has an advantage that the edge of the reflecting surface 27 of the obtained movable body 15 and the reflecting surface 27 itself are also finished with high precision.

Further, by forming a wide reflecting surface 27,
The problem that the light emitted from the light emitting diode (LED) composed of each light emitting element of the reflection type photo sensor is irregularly reflected by the tracking coil is solved, and even if the movable body 15 is moved in the focusing direction, the reflection type photo sensor is used. The position detection output does not change, accurate tracking control is possible, and the weight and cost of the movable body 15 can be reduced because no reflector is used.

Further, the movable body 15 and its reflection surface 27 or the portion of the reflection surface are formed by integrally molding with a white resin material (for example, polyphenylsulfite resin). As shown in FIG. 5 (b), by applying a white paint or the like to the reflection surface 29 and applying a white paint film 28, the reflectance of the reflection surface 29 on the white paint film 28 is effectively increased. Since the amount of light received by the phototransistor (PTr) comprising each light receiving element of the reflection type photosensor can be increased, the light emitting diode comprising each light emitting element
Since the current flowing through the (LED) need not be increased more than necessary, the life of the light emitting diode (LED) including the light emitting element can be extended.

Further, as a configuration for effectively increasing the reflectivity of the movable body 15 on the reflecting surface, for example, as shown in FIGS. 6 (a), (b) and (c), the focusing direction (height Direction), a reflecting surface 30 provided with a large number of rectangular grooves, a reflecting surface 31 provided with a large number of U-shaped grooves, or a reflecting surface 32 provided with a large number of V-shaped grooves. The same effect can be obtained.

Further, as a modification for effectively increasing the reflectivity of the movable body 15 on the reflection surface, for example, as shown in FIG. 7A, the angle θ is set in the tracking direction (lateral direction) of the reflection surface. The taper shape is inclined at about 5 degrees, and the taper direction of both reflecting surfaces 33 of the movable body 15 is symmetrical, or the tracking direction (lateral direction) of the reflecting surface as shown in FIG. In addition, for example, by providing a shape having a plurality of steps, and by making the shape of the steps of both reflecting surfaces 34 of the movable body 15 left-right symmetrical, the same effect as in the case where various grooves are provided in the reflecting surface can be obtained. can get.

[0035]

As is apparent from the above description, according to the optical head of the present invention, the positions of the light emitting element and the light receiving element are opposed to the pair of reflecting surfaces of the movable body holding the objective lens. By arranging two reflective photosensors symmetrically arranged and aligning the height position of the chip center of each element, the position detection in the tracking direction composed of the two reflective photosensors is performed. It is possible to reduce the sense output to the movement of the sensor for focusing in the focusing direction to make it insensitive, and to accurately control the position of the objective lens held by the movable body in the tracking direction.

Also, by increasing the light reflectivity by making the reflective surface white, it is possible to improve the sensing sensitivity in the tracking direction and extend the life of the reflective photosensor. It has an excellent effect in practical use.

[Brief description of the drawings]

FIG. 1 is a perspective view of a main part configuration showing an embodiment of an optical head of the present invention.

FIG. 2 is a plan view showing an embodiment of an arrangement configuration of a reflection type photosensor in the optical head of the present invention.

FIG. 3 is a plan view illustrating an arrangement configuration of a reflection type photosensor in the optical head of the present invention.

FIG. 4 is a perspective view of an essential part showing an embodiment of a mounting structure of a reflection type photosensor in the optical head of the present invention.

FIG. 5 is a perspective view of a main part showing one embodiment of a reflecting surface of a movable body in the optical head of the present invention.

FIG. 6 is a perspective view of a main part showing another embodiment of the reflecting surface of the movable body in the optical head of the present invention.

FIG. 7 is a perspective view of a main part showing still another embodiment of the reflecting surface of the movable body in the optical head of the present invention.

FIG. 8 is a plan view of a main part showing an example of a conventional optical head.

FIG. 9 is a side sectional view of a main part for explaining a reflection type photosensor used for an optical head.

FIG. 10 is a plan view illustrating an arrangement configuration of a reflective photosensor in a conventional optical head.

FIG. 11 is a plan view for explaining a problem of an arrangement configuration of a reflection type photosensor in a conventional optical head.

FIG. 12 is a main part perspective view for explaining a problem in the reflecting surface of the movable body in the present optical head.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 Support base 11 Objective lens 12, 17 Yoke 13 Focusing coil 14 Tracking coil 15 Movable body 16 Magnet 18, 27, 29, 30, 31, 32, 33, 34
Reflecting surface 19 Elastic member 20 Detector mounting member 21 Horizontal oblong hole 22 Fixing screw 23a, 23b Reflective photo sensor 24a LED 24b PTr 25 Flexible printed circuit board 26 Connection terminal 28 White paint film

Claims (4)

[Claims] 1. A movable body that holds an objective lens on a support base and has a pair of reflective surfaces on a side surface corresponding to the tracking direction and is movable in a focusing direction and a tracking direction with respect to an optical recording medium. A focusing drive unit for driving the body in the optical axis direction of the objective lens, and a tracking drive unit for driving the body in a direction perpendicular to the optical axis of the objective lens; The two detectors in which the arrangement positions of the light-receiving elements are different and the chip height positions of the respective elements are the same and adjacent to each other are set so that the light-emitting element and the light-receiving element of each detector are symmetrical. The light emitted from each of the two detectors is reflected by the reflection surface, and the reflected light is received and each of the detected outputs detects the displacement of the movable body in the tracking direction differentially. The optical head according to claim. 2. The optical head according to claim 1, wherein the two detectors are attached to a detector attachment member to which a flexible printed circuit board is attached, and are fixed to the support base. . 3. The optical head according to claim 1, wherein the two detectors are mounted on a sensor mounting member formed of a printed circuit board and fixed to the support base. 4. The optical head according to claim 1, wherein the reflecting surface of the movable body is formed of a resin material, and has a high-reflectance unit of a white type.