JPH0969231A - Optical pickup apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To decrease the number of parts and to improve assembling property by providing a permanent magnet and a driving coil or the like for focusing or tracking, which is fixed to the fixing base stage of an optical pickup apparatus as a reference, in a bobbin. SOLUTION: In the case of this optical pickup apparatus, a magnetic detector 5a is arranged on a fixing base stage 26 in the vicinity of a permanent magnet. When the degree of leaking magnetic flux is detected with the magnetic detector 5a, whether the relative position of the permanent magnet 2a is in the range where precise seeking is possible or not can be found based on the degree of the detected signal. Furthermore, when the decrease in strength of the magnetic field is detected, rough seeking is performed in the stable radial direction by an optical disk 35, and reading can be performed under the stabilized conditions. Since the relative position with respect to the fixing base stage 26 can be detected without providing position detecting member and element in this way, the number of parts is decreased and the assembling property is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup device for reproducing data optically by condensing a laser beam on an optical recording medium in a minute spot, and more particularly to a moving magnet system (a permanent magnet is provided on a bobbin). The present invention relates to an optical pickup device suitable for recording / reproducing information on / from an optical recording medium such as an optical disc using a focusing tracking actuator of MM type).

[0002]

2. Description of the Related Art In recent years, an optical pickup device has been widely used for reading a data signal recorded on an optical disk surface such as a read-only compact disk (hereinafter referred to as a CD-ROM). This optical pickup device uses a semiconductor laser or the like as a light emitting element, collects laser light emitted from this semiconductor laser as a minute spot on the optical disc surface by a condensing lens, etc., and reflects it on the optical disc surface. Light is guided to a light receiving sensor by a prism or the like, and the guided optical signal is photoelectrically converted into an electric signal to reproduce data. here,
The optical pickup device has a bobbin equipped with an objective lens and a focus function for keeping the spot diameter minute and focusing by following fluctuations in optical disk surface deviation and eccentricity in order to stably read data. Also, a coarse seek function for moving the fixed portion to make the spot follow the data track and a precision tracking function for making the spot follow the waviness of the data track caused by eccentricity of the optical disk or the like are provided. In such an optical pickup device, in order to improve the data transfer rate and enable it to be mounted on a portable personal computer or the like, it is required to be thin, low in power consumption, and low in cost.

A conventional optical pickup device will be described below with reference to the drawings. FIG. 5 is a sectional end view of a main part of a conventional optical pickup device. Reference numeral 21 is a conventional optical pickup device, 22 is an objective lens (or a condensing lens) that condenses light from the semiconductor laser 37 as a minute spot diameter on an optical disc 35 described later, and 23 is a far-caching adjustment for the objective lens 22. A lens holder (hereinafter, referred to as a bobbin), which is formed in a substantially plate shape and has an objective lens 22 mounted thereon for performing tracking adjustment and is movably supported in two axial directions, and 24 are substantially central portions of a side surface of the bobbin 23 and the right side. A supporting member such as a wire extending from one side and having elasticity to make the bobbin 23 movable in two axial directions of the focusing driving direction and the tracking driving direction, and 25 is the supporting member 2
4, a fixing member for fixing one end of 4, a fixing member 25 for supporting the bobbin 23, and a fixing base for holding an actuator 28, a rising mirror 34, etc., which will be described later, at a fixed position in the radial direction of the optical disc 35, and 27 is fixed. It is a base member provided on the end side of the base 26, and is integrally formed with the fixed base 26 in a substantially inverted L-shaped cross section. 28 is an actuator for focusing and tracking arranged on the upper surface of the base member 27, 29 is a yoke having a concave cross section which constitutes the actuator 28, and 30 and 31 are the yoke 2
Permanent magnets arranged and fixed on the inner wall surfaces of 9 facing each other, 3
2 is a focusing coil in which a conductor wire is wound around an iron core for forming a magnetic circuit with the permanent magnet 30 of the yoke 29 in a direction orthogonal to the focusing direction, and the focusing coil is arranged on the bobbin 23. 33 is the permanent magnet 31 of the yoke 29. And a tracking coil in which a conducting wire is wound around an iron core for forming a magnetic circuit in a direction orthogonal to the tracking direction and is arranged on the bobbin 23. Reference numeral 34 denotes a light beam emitted from a semiconductor laser 37 and coming in the horizontal direction. This is a rising mirror that refracts in the direction of, and is composed of a prism or the like having a reflecting surface fixed to the fixed base 26 below the objective lens 22. Reference numeral 35 is an optical disk which is an optical recording medium such as a CD-ROM which rotates at a high speed above the objective lens 22, and 36 is a light emitting portion which is provided on the right upper surface of the fixed base 26 so as to face the reflecting surface of the mirror 34. Laser unit 37, a semiconductor laser 37 mounted inside the laser unit 36, 38 mounted on the side of the semiconductor laser 37 inside the laser unit 36, and the reflected light from the optical disc 35 as a data signal and a focus error signal. A multi-divided sensor for photoelectrically converting into a tracking error signal, 39 is an optical member fixed to the light emitting portion of the laser unit 36, and 40 is a laser emitted from a semiconductor laser 37 formed substantially in the center of the right end face of the optical member 39. 3 beam generating diffraction grating for diffracting light into a main beam (0th order light) and tracking sub-beams (+ 1st order light, -1st order light), 4
Reference numeral 1 denotes a diffraction grating which is formed substantially in the center of the left end surface of the optical member 39 and which guides the reflected light from the optical disk 35 to the multi-division sensor 38. Here, the focusing / tracking actuator 28 has a magnetic circuit configured by the focusing coil 32 and the tracking coil 33 fixed to the bobbin 23, and the permanent magnets 30 and 31 fixed to the yoke 29. The magnetic circuit having such a configuration is called a moving coil system (hereinafter referred to as MC system). On the other hand, the coil and the permanent magnets 30, 3
The relationship of 1 is reversed, that is, a magnetic circuit in which a coil is fixed and a permanent magnet is fixed to a bobbin is called a moving magnet system (hereinafter referred to as MM system).

The operation of the optical pickup device configured as described above will be described below. First, in the laser unit 36, the laser beam emitted from the semiconductor laser 37 is transmitted by the three-beam generating diffraction grating 40 to the main beam (0th order light) and the tracking sub-beam (+ 1st order light,
−1st order light). Next, the laser light diffracted into three beams is transmitted through the optical member 39, and then is deflected by 90 degrees toward the optical disk 35 by the rising mirror 34. Next, the laser light deflected by 90 degrees is focused on the optical disc 35 as a minute spot by the objective lens 22.
Next, the reflected light reflected by the optical disc 35 reaches the optical member 39 by following an optical path substantially opposite to the outward path. The light reaching the optical member 39 is diffracted and deflected by the diffraction grating 41 and guided to the multi-division sensor 38. The reflected light guided to the multi-division sensor 38 is photoelectrically converted by the multi-division sensor 38 and detected as a data signal, a focusing error signal, and a tracking error signal. Next, according to the focusing error signal and the tracking error signal obtained by the multi-divided sensor 38, a current is passed through the focusing coil 32 or the tracking coil 33, and the focusing / tracking actuator 28 causes
The position of the bobbin 23 is adjusted and focusing control is performed by a focusing control unit (not shown), and precise tracking control is performed by a tracking control unit (not shown).

Here, there are optical and mechanical restrictions in the range where the precise tracking control is possible. As an optical constraint, when the reflected light from the optical disc 35 returns to the multi-division sensor 38 in a direction substantially opposite to the forward path, the position of the objective lens 22, that is, the position of the bobbin 23 is fixed to the fixed base 26.
If it is far from the steady position relative to,
Aberrations at the focal point on the optical disk 35 are aggravated, and it becomes impossible to condense light and read signals cannot be read. As a mechanical constraint, there has been a constraint on the adjustment range caused by the limit of the spring property of the support member 24 mainly made of a wire having a spring property for supporting the bobbin 23. Here, the optical constraint is that the objective lens 2
It is generally about 0.2 mm, although it depends on the performance of No. 2 and other conditions. Also, mechanical constraints are generally greater than optical constraints. Therefore, when the bobbin 23 is controlled to a position where the data track to be read by the precise tracking control exceeds either the optical or mechanical range, the bobbin 23 is subject to optical and mechanical restrictions. The control unit (not shown) of the coarse seek mechanism (not shown) is notified that the range is exceeded, and the coarse seek mechanism is driven to move the fixed base 26 within the range of optical and mechanical constraints. It will be necessary to let them do. Therefore, conventionally, in order to detect the relative position between the bobbin 23 and the fixed base 26, a lens position detection mechanism using an optical sensor or the like has been used.

Next, a lens position detecting mechanism of a conventional optical pickup device will be described below with reference to the drawings. FIG. 6 is a perspective view of a lens position detection mechanism used in a conventional optical pickup device. In FIG. 6, 22 is an objective lens, 23 is a bobbin, 24 is a supporting member, 25 is a fixing member, and 34 is a rising mirror. 42 is a light emitting diode (LE) fixed to the fixed base 26 (see FIG. 5).
D) is a light source, 43 is a light receiving portion fixed to the fixed base 26, and 44 is a light shielding plate which is disposed between the light source 42 and the light receiving portion 43 and is integrally formed with the bobbin 23. Here, the conventional lens position detecting mechanism of the optical pickup device is the bobbin 23.
The light source 42 and the light receiving portion 43 on the fixed base 26 and the light shielding plate 4 on the fixed base 26.
4 may be provided and the position of the light shielding plate 44 may be detected.

The operation of the conventional lens position detecting mechanism of the optical pickup device constructed as described above will be described with reference to FIG. Light emitted from the light source 42 of the fixed base 26 is located at the relative position of the bobbin 23, that is, the light shielding plate 44.
The amount of light reaching the light-receiving unit 43 changes depending on the position of the light source 43, and a control unit (not shown) detects the relative position of the bobbin 23 and the fixed base 26 in accordance with the amount of change in the light amount. When it is determined that the position 23 is out of the precision tracking control range, the bobbin 23 is moved within the range of optical and mechanical restrictions.

[0008]

However, the above-mentioned conventional configuration has the following problems. That is, (1) In both the MC method and the MM method, when detecting the relative position of the bobbin and the fixed base by an optical method, a member such as a light-shielding plate or a light source and a light-receiving unit that is not directly involved in driving Had to be installed on the bobbin. Therefore, the number of parts of the bobbin increases, the number of assembling steps becomes complicated, and mass production is lacking. Further, since the weight of the bobbin is increased, the performance of the focusing / tracking system is improved, so that the driving unit is increased in size and the degree of freedom in design is reduced, which hinders downsizing of the apparatus itself. (2) Further, in the position detection by the light amount detection, it is generally not easy to obtain a light receiving element or the like having sufficient linearity and sensitivity in the light receiving unit and the like, and the positional relationship between the light source, the light shielding plate, and the light receiving unit, It was difficult to design the shape and the like while considering the assemblability. (3) At the same time, when a light-shielding plate or the like is provided at a position away from the center of the bobbin, the lens position detecting means needs a space of a considerable size around the bobbin in the tracking direction, which reduces the size of the apparatus. It was an obstacle. (4) In the actuator adopting the MM method,
Focusing / tracking direction The drive coil provided in the fixed part is positioned with a certain degree of accuracy with respect to the permanent magnet of the movable part,
It is necessary to guarantee drive sensitivity above a certain value over the movable range in the tracking direction, but the conventional positioning accuracy is
It relied heavily on the mechanical tolerances of the parts. In consideration of this, it is necessary to design the drive coil to have a large size with some allowance, resulting in an increase in the size of the device and an increase in the drive current. In addition, when driven by the combined force of a plurality of permanent magnet-coil drive systems, there is also strength variation of the permanent magnets, the drive system center is displaced with respect to the center of gravity of the movable part, and it is not necessary to adversely affect the reading accuracy of the device. Such resonance causes an increase in recording density of the recording medium and hinders reading accuracy.

The present invention solves the above-mentioned conventional problems, and realizes a lens position detecting mechanism by using a magnetic detecting element, thereby reducing the size by reducing the number of parts, reducing the cost and man-hours, and reducing the position accuracy by reducing the weight. It is an object of the present invention to provide an optical pickup device which can be improved in reliability and is excellent in mass production.

[0010]

In order to achieve this object, an optical pickup device according to claim 1 of the present invention comprises a bobbin for mounting an objective lens, and a fixed base for movably supporting the bobbin. A focusing control unit that adjusts the bobbin vertically by a focusing coil and a permanent magnet to perform focusing control, and a tracking coil and a permanent magnet that adjusts the bobbin horizontally in the radial direction of the optical disc to perform tracking control. An optical pickup device comprising: a tracking control unit for performing the above; and a permanent magnet arranged on the bobbin, a focusing coil and a tracking coil arranged on a fixed base, and a permanent magnet and a focusing magnet. Detecting a change in magnetic field generated by a difference in position of the caching coil or the tracking coil 1 to Comprising a number of magnetic detection elements, and has a structure controlling the position of the bobbin by the detection amount of change in magnetic field by the magnetic detecting element.

An optical pickup device according to a second aspect is
In claim 1, the magnetic detection element is arranged at least between the bobbin and the focusing coil or the tracking coil.

An optical pickup device according to a third aspect is
In claim 1 or 2, the magnetic detection element has a configuration in which the magnetic detection element is arranged at a symmetrical position with respect to the center axis of the focusing coil or the tracking coil in the magnetic flux direction.

An optical pickup device according to a fourth aspect is
According to any one of claims 1 to 3, the magnetic detection element is arranged at a predetermined position with respect to the drive coil.

An optical pickup device according to a fifth aspect is
According to a fourth aspect of the present invention, the magnetic detection element is arranged inside the focusing coil or the tracking coil.

Here, a Hall element, an MR element or the like for detecting the magnetic flux density is used as the magnetic detection element. or,
The change in the magnetic field can be detected by detecting the leakage magnetic flux amount or the like.

[0016]

With this structure, the following actions can be achieved. That is, (1) a bobbin, which is a movable part on which an objective lens is mounted, is provided with a permanent magnet, and a focusing or tracking drive coil fixed to a fixed base or the like of an optical pickup device serving as a position reference. As a change in the magnetic field from the permanent magnet to the drive coil, the leakage flux changes depending on the distance between the drive coil and the permanent magnet. The position of the bobbin with respect to the table, that is, the position of the objective lens can be detected. As a result, focusing or tracking control can be performed. In particular, since it is possible to detect the relative position of the bobbin with respect to the fixed base without the need to provide complicated position detection members and elements, the number of bobbin parts is reduced, assembly is improved, and mass production is excellent and low. Cost reduction can be realized. Furthermore, since it is not necessary to increase the size of the magnet to compensate the assembly accuracy, the weight of the bobbin can be reduced, and the weight of the bobbin can be easily balanced. Therefore, the center of gravity can be stabilized and unnecessary resonance of the bobbin can be reduced. Therefore, the positional accuracy of the optical system can be improved. As described above, since the driving unit of the focusing / tracking system can be downsized, the degree of freedom in design is increased, and the downsizing of the entire device and the reduction in design time can be realized. (2) An optical pickup device (coarse seek body) is provided by providing the position of the magnetic detection element between the bobbin and the drive coil.
It is possible to reduce the volume occupied by the optical disk drive, and it is possible to reduce the size of the entire optical disk drive. (3) By arranging a plurality of magnetic detection elements, the leakage magnetic flux and the magnetic field strength of the drive coil and the permanent magnet are detected at a plurality of positions, and the plurality of magnetic field strength signals are arithmetically processed to further detect the position detection range. Also, the sensitivity can be improved. Especially, with respect to the central axis of the magnetic flux direction of the drive coil,
By arranging the magnets at symmetrical positions, the calculation is easy and the position of the permanent magnet from the drive coil can be calculated. (4) By providing the magnetic detection element with a certain positional accuracy with respect to the drive coil, the output from the magnetic detection element is monitored during assembly and the drive coil and iron core of the bobbin equipped with the permanent magnet are monitored. Since the relative position can be adjusted and initially set, it is possible to suppress variation in magnetic intensity due to a difference in distance between the permanent magnet and the drive coil or the iron core. As a result, the range to be corrected can be ensured accurately, and the deviation between the center of gravity of the bobbin, which is the movable part, and the point of application of the driving force can be reduced, and unnecessary resonance during driving of the movable part can be prevented, which improves accuracy. High position correction is possible.
Therefore, there are few recording and reproducing errors, and it is possible to cope with high density recording. In particular, by arranging the magnetic detection element inside the focusing coil or the tracking coil, it is possible to secure a certain positional accuracy of the magnetic detection element with respect to the drive coil, and it is possible to realize the miniaturization of the device.

[0017]

An embodiment of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 is a perspective view of an optical pickup device according to a first embodiment of the present invention. 1A is an optical pickup device (coarse seek body) in the first embodiment of the present invention. Reference numeral 22 is an objective lens, 23 is a bobbin, 24 is a support member, 25 is a fixed member, 26 is a fixed base, and 34 is a rising mirror. Since these are the same as those in the conventional example, the same reference numerals are given and description thereof is omitted. The difference from the conventional example is that the permanent magnets 2a and 2b for adjusting the positions of focusing and tracking provided on the movable bobbin 23, and the iron cores 3a and 3 provided on the fixed base 26.
drive coils 4a and 4b each including a focusing coil 32 in which a conductor wire is wound in a direction orthogonal to the focusing direction and a tracking coil 33 (both refer to FIG. 5) in which a conductor wire is wound in a direction orthogonal to the tracking direction. The fixed base 2 is located between one of the drive coils 4a and the permanent magnet 2a and detects the amount of magnetic flux leaked from the permanent magnet 2a.
The point is that the magnetic detection element 5a fixed to 6 is provided.

The operation principle of the magnetic detection element 5a of the optical pickup device 1A of the first embodiment of the present invention having the above-described structure will be described below. Here, most of the magnetic flux from the permanent magnet 2a goes in the direction of the iron core 3a, but the magnetic flux emitted from the vicinity of the edge of the permanent magnet 2a is a leakage magnetic flux as it is as the opposite magnetic pole on the opposite side of the permanent magnet 2a. Face to face or elsewhere. Since this leakage magnetic flux is generated in the vicinity of the permanent magnet 2a, if the leakage magnetic flux is detected by the magnetic detection element 5a installed on the fixed base 26 in the vicinity of the permanent magnet 2a,
The relative position of the permanent magnet 2a can be detected from the intensity of the detection signal. For example, when performing coarse seek control in tracking control, the accuracy of the magnetic detection element 5a is not so required, and the magnetic detection element 5a is used to the minimum necessary amount to perform position shift control so that precise seek in tracking control is possible. be able to. That is, by controlling the detection signal of the magnetic detection element 5a to detect whether or not the precise seek is possible, it is determined that the precise seek is impossible when the decrease in the strength of the magnetic field is detected. As a result, rough seek is performed along the radial direction of the optical disc within a range where precision seek is possible, the optical pickup device 1A (coarse seek body) is readjusted to a position where precision seek is possible, and data is read under stable conditions. You will be able to do it reliably.

The operation of the optical pickup device 1A according to the first embodiment of the present invention will be described below. First, the optical pickup device 1A (coarse seek body)
It is moved to the vicinity of the position of the desired data track on the optical disc 35. Next, precision seek is performed to reproduce the data on the optical disc 35. Optical pickup device 1
A (coarse seek body) has iron cores 3a and 3b and a permanent magnet 2
A magnetic flux is generated between a and 2b. Electric currents in the focusing coil 32 and the tracking coil 33 (both of which are shown in FIG. 5) act on the magnetic flux in the orthogonal direction to generate a driving force according to Fleming's left-hand rule. This driving force becomes a thrust for driving the bobbin 23 supported by the support member 24 having a spring property, and moves the objective lens 22 fixed to the bobbin 23 in the focusing direction and the tracking direction with respect to the optical disc 35. In this way, the data on the optical disc 35 can be reproduced. Here, the optical pickup device 1 moved to the vicinity of the position of the desired data track on the optical disk 35 by the rough seek.
The position of the objective lens 22 is adjusted with respect to A (coarse seek body) by the above-described precision seek mechanism, but the optical pickup device 1A including the raising mirror 34 and the like as the reproduction progresses.
The position with respect to the (coarse seek body), that is, the position with respect to the reproducing optical system occurs. As for the positional deviation, a certain range is allowed as described above, but if it exceeds the certain range, reliable reproduction becomes difficult. Therefore, a lens position detection mechanism is required. Therefore, a fixed base 26 near the permanent magnet 2a
If the intensity of the leakage magnetic flux is detected by the magnetic detection element 5a installed at 1, it is possible to know from the intensity of the detection signal whether or not the relative position of the permanent magnet 2a is within the range where precise seek is possible. With this configuration, when a decrease in the strength of the magnetic field is detected, it is possible to read data under stable conditions by performing a rough seek in the constant radial direction by the optical disc 35.

As described above, according to this embodiment, the position of the bobbin 23 with respect to the fixed base 26, that is, the position of the objective lens 22 can be detected by the magnetic detection element 5a. Particularly, the magnetic detection element 5a is connected to the drive coils 4a and 4b.
By arranging it at a position interposed between the bobbin and the bobbin 23,
The overall size of the device can be minimized and the overall size of the device can be reduced. As described above, since it is possible to detect the relative position with respect to the fixed base 26 without providing a complicated position detecting member / element, the number of parts of the bobbin 23 is reduced, the assemblability is improved, and the cost is reduced. Can be realized. Also, since the weight of the bobbin 23 can be reduced,
The driving unit of the focusing / tracking system can be downsized. Furthermore, the weight of the bobbin 23 can be easily balanced and the position of the center of gravity can be stabilized.
The unnecessary resonance can be reduced, and the positional accuracy of the optical system can be improved.

(Second Embodiment) FIG. 2 is a perspective view of an optical pickup device according to a second embodiment of the present invention. 1B is an optical pickup device (coarse seek body) in the second embodiment of the present invention. 2a and 2b are permanent magnets, 3a and 3b are iron cores, 4a and 4b are drive coils, 22 is an objective lens, and 23
Is a bobbin, 24 is a support member, 25 is a fixed member, 26 is a fixed base, and 34 is a stand-up mirror. Since these are the same as those in the first embodiment, the same reference numerals are given and the description thereof is omitted. The optical pickup device 1B in the second embodiment of the present invention is different from the first embodiment in that it is located between the iron core 3a and the permanent magnet 2a, and with respect to the central axis of the permanent magnet 2a in the magnetic flux direction. , 2 arranged symmetrically
This is the point that two magnetic detection elements 6a and 6a 'are provided.

The magnetic detecting elements 6a, 6a 'of the optical pickup device 1B of the second embodiment of the present invention configured as described above.
The magnetic detection will be described below with reference to FIG. FIG. 3 is a graph showing the amount of magnetic detection with respect to the relative position of the magnetic detection element of the optical pickup device of the second embodiment of the present invention. The signal output from each magnetic detection element 6a, 6a 'is shown in FIG.
Shown in In FIG. 3, circles are detection signals of the magnetic detection element 6a, and squares are detection signals of the magnetic detection element 6a '. The results of calculating these signals are indicated by black circles. In the calculation method of this embodiment, the detection signals of the magnetic detection element 6a and the magnetic detection element 6a 'are subtracted. As is clear from FIG. 3, linearity near the relative position 0 can be obtained, and the direction of deviation of the calculation result from positive and negative can be detected in a wide range. Therefore, when playing back an optical disc 35 having an extremely large eccentricity, it is necessary to perform rough seeks in both the outer and inner circumferential directions while the optical disc 35 makes one round. Becomes

As described above, according to this embodiment, the first embodiment
In addition to the above effect, by disposing a plurality of magnetic detection elements 6a and 6a ', it is possible to further improve the position detection range and sensitivity by processing the plurality of magnetic field strength signals. Particularly, by arranging the drive coils 4a and 4b in symmetrical positions with respect to the central axes of the magnetic flux directions of the drive coils 4a and 4b, the calculation is easy and the permanent magnets 2a,
The position of 2b can be relatively calculated.

(Third Embodiment) FIG. 4 is a perspective view of an optical pickup device according to a third embodiment of the present invention. 1C is an optical pickup device (coarse seek body) in the third embodiment of the present invention. 2a and 2b are permanent magnets, 3a and 3b are iron cores, 4a and 4b are drive coils, 22 is an objective lens, and 23
Is a bobbin, 24 is a support member, 25 is a fixed member, 26 is a fixed base, and 34 is a stand-up mirror. Since these are the same as those in the first and second embodiments, the same reference numerals are given and the description thereof is omitted. The optical pickup device 1C according to the third embodiment of the present invention is different from the first and second embodiments in that the magnetic detection elements 7a and 7b are attached to the drive coils 4a and 4b while securing a certain positional accuracy. The focusing coil 32 and the tracking coil 33 (both of which are shown in FIG. 5) are positioned by 8a and 8b. In the actuator 28 driven by a plurality of magnetic circuits, if the strengths of the permanent magnets 2a and 2b are extremely different, the driving force balance is disturbed, rolling motion occurs in the movable part, and unnecessary resonance occurs, so that the driving coils 4a and 4b.
The positions of the permanent magnets 2a and 2b with respect to the
The point is that the initial setting can be performed using a and 7b.

The assembling method of the optical pickup device 1C of the third embodiment of the present invention constructed as above will be described below. The drive coil 4a, 4b is fixed to the base 26
In the production process of fixing to the magnetic detection element 7a, 7b
Is monitored and the drive coils 4a and 4b are fixed at a point where a predetermined reference value is indicated. As a result, even if the strength of the permanent magnets 2a, 2b varies, the permanent magnets 2a, 2b
Since the magnetic field conditions between the 2b and the drive coils 4a and 4b can be generally equalized, it is possible to prevent the driving force for driving the bobbin 23 from varying.

As described above, according to this embodiment, the magnetic detecting elements 7a and 7b are provided with a certain positional accuracy with respect to the drive coils 4a and 4b, so that at the time of assembly,
Since the relative positions of the drive coils 4a and 4b with respect to the bobbin 23 carrying the permanent magnets 2a and 2b can be adjusted by monitoring the outputs from the magnetic detection elements 7a and 7b, the permanent magnets 2a and 2b and the drive coil 4a can be adjusted. , 4b, it is possible to suppress variations in magnetic intensity due to the difference in distance.
As a result, it is possible to prevent unnecessary resonance while driving the movable part,
Highly accurate position correction is possible.

[0028]

As described above, the present invention has the following excellent effects. That is, (1) since the bobbin, which is the movable part on which the objective lens is mounted, is provided with the permanent magnet and the drive coil for focusing or tracking fixed to the fixed base or the like of the reference optical pickup device. Focusing or tracking control can be performed by detecting a magnetic field change such as a leakage magnetic flux from the permanent magnet to the drive coil. As a result, it is possible to detect the relative position of the bobbin with respect to the fixed base without the need to provide complicated position detecting members and elements, which reduces the number of bobbin parts and improves the assemblability, which is excellent for mass production. Cost reduction can be realized. Further, by reducing the weight of the bobbin, unnecessary resonance of the bobbin can be reduced, the positional accuracy of the optical system can be improved, and an optical pickup device that is small in size and has excellent reliability in recording and reproducing data can be provided. Can be realized. (2) By arranging the position of the magnetic detection element at a position interposed between the bobbin and the drive coil, the volume occupied by the optical pickup device (coarse seek body) can be reduced, and the optical pickup device excellent in downsizing can be achieved. Can be realized. (3) By arranging a plurality of magnetic detection elements, the leakage magnetic flux, the magnetic field strength of the drive coil and the permanent magnet, etc. are detected at a plurality of positions, and the plurality of magnetic field strength signals are arithmetically processed to further detect the position. Range and sensitivity can be improved. In particular, by arranging at a symmetrical position with respect to the central axis of the magnetic flux direction of the drive coil, it is possible to calculate easily and calculate the position of the permanent magnet from the drive coil.
Wide control range of focusing and tracking,
An optical pickup device excellent in bobbin position calculation can be realized. (4) By providing the magnetic detection element with a certain positional accuracy with respect to the drive coil, the output from the magnetic detection element is monitored during assembly, and the drive coil and the iron core of the bobbin equipped with the permanent magnet are monitored. Since the relative position can be adjusted and initially set, it is possible to suppress variation in magnetic intensity due to a difference in distance between the permanent magnet and the drive coil or the iron core. As a result, the range to be corrected can be accurately ensured, and the shift between the center of gravity of the bobbin, which is the movable part, and the point of application of the driving force can be reduced, and unnecessary resonance during driving of the movable part can be prevented, which improves accuracy. High position correction is possible.
Therefore, it is possible to realize an optical pickup device which has few recording / reproducing errors and can cope with high-density recording and which is excellent in reliability. In particular, by arranging the magnetic detection element inside the focusing coil or the tracking coil, it is possible to secure a certain positional accuracy of the magnetic detection element with respect to the drive coil, and at the same time, an optical pickup excellent in downsizing of the device. The device can be realized.

[Brief description of drawings]

FIG. 1 is a perspective view of an optical pickup device according to a first embodiment of the present invention.

FIG. 2 is a perspective view of an optical pickup device according to a second embodiment of the present invention.

FIG. 3 is a graph showing the amount of magnetic detection with respect to the relative position of the magnetic detection element of the optical pickup device of the second embodiment of the present invention.

FIG. 4 is a perspective view of an optical pickup device according to a third embodiment of the invention.

FIG. 5 is a sectional end view of a main part of a conventional optical pickup device.

FIG. 6 is a perspective view of a lens position detection mechanism used in a conventional optical pickup device.

[Explanation of symbols]

 1A, 1B, 1C Optical pickup device (coarse seek body) 2a, 2b Permanent magnets 3a, 3b Iron cores 4a, 4b Drive coils 5a, 6a, 6a ', 7a, 7b Magnetic detection elements 8a, 8b Mounting member 21 Conventional optical pickup Device 22 Objective lens 23 Bobbin (lens holder) 24 Support member 25 Fixing member 26 Fixed base 27 Stand member 28 Actuator 29 Yoke 30, 31 Permanent magnet 32 Focusing coil 33 Tracking coil 34 Erecting mirror 35 Optical disk 36 Laser unit 37 Semiconductor Laser 38 Multi-Sensor Sensor 39 Optical Member 40 3 Beam Generation Diffraction Grating 41 Diffraction Grating 42 Light Source 43 Light-Receiving Section 44 Light-Shielding Plate

Claims (5)

[Claims] 1. A bobbin on which an objective lens is mounted, a fixed base for movably supporting the bobbin, a focusing coil and a permanent magnet to adjust the bobbin in a vertical direction to perform focusing control. And a tracking control unit for performing tracking control by adjusting the bobbin in the horizontal direction, which is the radial direction of the optical disc, by a tracking coil and a permanent magnet, the optical pickup device being disposed on the bobbin. Each of the permanent magnets, the focusing coil and the tracking coil disposed on the fixed base,
1 to a plurality of magnetic detection elements for detecting a change in a magnetic field generated due to a difference in position between the permanent magnet and the focusing coil or the tracking coil,
An optical pickup device, wherein the position of the bobbin is controlled by the amount of change in the magnetic field detected by the magnetic detection element. 2. The optical pickup device according to claim 1, wherein the magnetic detection element is disposed at least between the bobbin and the focusing coil or the tracking coil. 3. The magnetic detection element according to claim 1, wherein the magnetic detection element is arranged at a symmetrical position with respect to a center axis of the focusing coil or the tracking coil in the magnetic flux direction. The optical pickup device described. 4. The magnetic detection element is arranged at a predetermined position with respect to the drive coil.
Or the optical pickup device according to item 2. 5. The optical pickup device according to claim 4, wherein the magnetic detection element is disposed inside the focusing coil or the tracking coil.