JPH07311991A - Optical disk recording/reproduction device - Google Patents

Abstract

PURPOSE:To improve magnetic field strength and to stabilize recording characteristics by providing a means for screening flux of magnet leaked from a means for driving a magnetic head with electromagnetic force. CONSTITUTION:First, the distance deviation between the recording surface of an optical disk 10 and a magnetic head 16. Namely, light discharged from a light emitting element is reflected by the optical disk 10 and is applied to a two-division photodetector. Since the intensity distribution of the applied light changes depending on the above distance, the distance deviation between both can be detected by the two-division photo detector. Then, current based on the distance deviation information is applied to a coil 53 for control and the magnetic head 16 can be driven in the direction of an arrow V due to the electromagnetic force with a permanent magnet 48, thus canceling distance deviation and hence maintaining the distance between the recording surface of the optical disk 10 and the magnetic head 16 to be nearly constant.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk recording / reproducing apparatus, and more specifically, by applying an external magnetic field to a disk and raising the temperature by a light spot, the magnetic recording surface of the disk can be recorded. The present invention relates to an optical disk recording / reproducing apparatus that performs recording by reversing the direction of a magnetic field, irradiates a recording surface with a light spot having a lower power than during recording, and optically reads the direction of the magnetic field.

[0002]

2. Description of the Related Art In this type of optical disc recording / reproducing apparatus,
Although it is necessary to always detect the position of the optical disk, a detection method using light is generally well used for distance detection when the distance between the detector and the object to be measured is short.
FIG. 53 is a side sectional view showing an example of a conventional optical distance detecting device of this type. In the figure, a light emitting diode 1 as a light source and a photodetector 3 are mounted on a substrate 2, and a condenser lens 4 is arranged in front of it. A glass window 5 is attached to an opening of a case 6 that accommodates the light emitting diode 1, the photodetector 3 and the condenser lens 4, and an object to be measured 7 whose position changes in front of the glass window 5. Next, the operation will be described. A certain amount of light is emitted from the light emitting diode 1, converted into converged light by the condenser lens 4, and emitted from the glass window 5 to the outside of the case 6. Reference numeral 8 indicates the optical axis of this emitted light. The emitted light is reflected by the DUT 7, passes through the glass window 5 and the condenser lens 4 again, and illuminates the photodetector 3. Reference numeral 9 indicates the optical axis of this reflected light. The light amount of the light irradiated on the photodetector 3 is determined by the distance between the DUT 7 and the detection device, the reflectance and the shape of the DUT 7, and the distance to the same DUT 7 and the photodetector 3 are the same. 54 shows the relationship with the light intensity of. As shown in the figure, the light intensity reaches a maximum value at a distance of about 4.5 mm, and decreases as the distance from the light intensity increases. therefore,
If the same optical measurement object 7 is used and the detection distance is limited so as to fall within the linear range of the light intensity, the output of the photodetector 3 and the distance correspond to each other, and the distance can be detected. Becomes

FIG. 55 is a side view showing an essential part of a conventional optical disk recording / reproducing apparatus equipped with the above distance detecting means. In the figure, the conventional optical disk recording / reproducing apparatus is
Generally, an optical disk 10 as an object to be measured, a motor 11 installed on the main body base, a base 14 mounted on the main body base via bearings 12 and 13, and the base 1
4 and a magnetic head 16 supported by the base 14. The optical head 1
Reference numeral 5 denotes a light source that emits the light beam L, optical components such as an objective lens that guides the light beam L to the optical disc 10, and the optical disc 1.
It is composed of an optical component for guiding the reflected light from 0, a light receiving element for receiving the reflected light and converting it into an electric signal, an optical sensor for detecting the focus shift and the track shift of the light spot S, and the like.

Next, the operation of the above-mentioned conventional example is shown in FIG.
This will be described with reference to (a), (b), (c) and FIG.
56A to 56C are side views showing the positional relationship between the magnetic head 16 and the optical disk 10, and FIG. 57 shows the magnetic field strength B on the disk recording surface and the distance H between the optical disk 10 and the magnetic head 16. It is a characteristic view which shows a relationship. First, the optical disc 1
0 is rotated by the motor 11. Then, the optical head 15 and the magnetic head 16 are driven in the arrow A direction by the bearings 12 and 13 and the base 14. The optical head 15 records the modulation (information) of the bias magnetic field generated by the magnetic head 16 by the light spot S.
The light spot S generally has a diameter of 1.0 to 1.5 μm.
It is about m. Here, as shown in FIGS. 56A to 56C, when the optical disc 10 rotates, the distance H (H _{1 to} H ₃ ) between the recording surface of the optical disc 10 and the magnetic head 16 changes. The magnetic field generated by the magnetic head 16 is about 100 to 5000e, but as shown in FIG. 57, the magnetic field strength increases as the distance H between the recording surface of the optical disk 10 and the magnetic head 16 increases. B decreases.

[0005]

In the conventional optical disk recording / reproducing apparatus as described above, the magnetic field strength fluctuates greatly due to the surface wobbling of the optical disk, so that the magnetic field strength is inefficient and the recording characteristics greatly vary. was there. Further, there is a problem in that the magnetic head cannot be brought close to each other to prevent the magnetic head from colliding with the optical disk, and the mechanical accuracy is severe. The present invention has been made to solve the above problems, and can improve the efficiency of magnetic field strength, stabilize the recording characteristics, and relax the mechanical accuracy. It is an object of the present invention to obtain an optical disc recording / reproducing device capable of performing

[0006]

An optical disk recording / reproducing apparatus according to the present invention is an optical head for irradiating an optical disk with light to record / reproduce a signal, a magnetic head for applying a bias magnetic field to the optical disk, and the optical disk. Distance detecting means for detecting the distance between the magnetic head and the distance information and outputting the distance information, driving means for driving the magnetic head by electromagnetic force so that the distance becomes constant based on the distance information, and the driving means. Shielding means for shutting off magnetic flux leaking Equipped with driving means for driving the magnetic head by electromagnetic force so that the distance becomes constant based on the distance information from the distance detecting means, and shielding means for shutting off magnetic flux leaking from this driving means. It is a thing. In the present invention, during the series of operations in which the optical head irradiates the optical disk with light to record and reproduce a signal, and the magnetic head applies a bias magnetic field to the optical disk, the magnetic head leaks from the driving means for driving the magnetic head. The magnetic flux is blocked by the shielding means.

[0007]

EXAMPLE An example of an optical disk recording / reproducing apparatus will be described below with reference to the drawings. First, FIG. 3 is a plan view of each optical element viewed from the direction of its optical axis. In the figure, the light emitting diode 20 as a light source, one of two photodetectors (hereinafter referred to as PD1) 21a, and the light emitting diode 20 are arranged at a position farther from the PD1 21a. The other photodetector 21b (hereinafter referred to as PD2) 21b is arranged in the same plane as each other, and this plane is hereinafter referred to as a detector plane. In addition, the light receiving area of PD2 21b is set to be larger than the light receiving area of PD1 21a for the reason described later. Next, the operation will be described. The light emitting diode 20 has a flat light emitting surface and serves as a light source having a light intensity distribution which is perpendicular to the paper surface and upward in FIG. 3 and which is close to a perfect diffusion surface, and emits light at a constant output. If there is a mirror surface of the object to be measured parallel to the detector plane above the light emitting diode 20,
The light emitted from the light emitting diode 20 reaches the detector plane again, and enters the PD1 21a and PD2 21b.

FIG. 2 shows the state of the light intensity distribution of the light applied to the detector plane. 2A and 2B show the light intensity with respect to the position on the alternate long and short dash line j-j in FIG. 3, and FIG. 2C shows the arrangement of the optical elements.
FIG. 2A shows a light intensity distribution when the object to be measured is in a short distance, and the peak intensity concentrated near the light emitting diode 20 is a strong distribution. On the other hand, FIG. 2B shows the light intensity distribution when the object to be measured is at a long distance, which is a broad distribution with a low peak intensity. Here, the phenomenon shown in FIGS. 2A and 2B will be examined from the characteristics of the photodetector in FIG. FIG. 1 shows the arrangement shown in FIG.
It is a diagram in which the relationship between the light intensity at the positions of PD1 21a and PD2 21b and the distance to the object to be measured is shown in an overlapping manner. That is, in terms of the distance range to be measured, PD1 21
The characteristic of a corresponds to the area of the negative gradient exceeding the maximum value of the light intensity, and the characteristic of PD2 21b corresponds to the area of the positive gradient up to the maximum value of the light intensity. Compared to PD1 21a
The maximum point of PD2 21b is shifted downward and leftward and rightward in FIG.
This is because it is arranged at a position farther from the PD1 21a. The details of the relative positions between the optical elements in FIG. 3 are described in the PD1 21a and PD2 2 in the distance range to be measured.
As shown in FIG. 1, the light intensity characteristics of 1b are adjusted and set so as to correspond to mutually opposite gradient regions.

FIG. 4 is a characteristic diagram showing the relationship between the photodetector output and the distance in the distance range to be measured. In the figure, the output of the PD1 21a is the curve 22, and the output of the PD2 21b is the curve 23. However, the magnitudes of the outputs of the PD1 21a and the output of the PD2 21b are almost equal to each other. Therefore, the light receiving area of PD2 21b is set larger than the light receiving area of PD1 21a. Then, the outputs 22 and 23 obtain a difference x between them by the electric circuit shown in FIG. 5, and further take a ratio of the difference x to the sum y of the outputs to calculate a standardized differential output 24. This differential output 24
FIG. 6 shows the characteristics of. That is, by obtaining the distance to the object to be measured by the above-described calculation, the influence of the change in reflectance of the object to be measured, which has been a problem in the past, can be eliminated.

By the way, as shown in FIG.
Zero-crosses at some distance. When this distance detecting device is used for a control device that keeps the distance to the object to be measured constant, if the distance of the zero cross point N is set to a target value, the differential output 24 becomes an error signal for the target value. Is good. The distance of the zero-cross point N is determined by the parameters l ₁ , l ₂ , w ₁ , w ₂ , g ₁ , g ₂ in FIG. 3, and by changing these parameters, the zero-cross point can be changed with a considerable degree of freedom. N can be set. For example, if the distance g ₂ between the PD1 21a and the PD2 21b is shortened, the amount of light incident on the PD2 21b starts to increase from a position where the distance is shorter, and thus becomes shorter than the zero cross point N. On the contrary, if the distance g ₂ is extended, the distance of the zero cross point N becomes longer. The distance of the zero-cross point N can be changed also by the area ratio of PD1 21a and PD2 21b. In this case, if the areas of the two are equal, the zero-cross point N becomes the point at infinity, and the distance of the zero-cross point N becomes closer as the area of PD2 21b increases.
The desired zero-cross point N can be obtained by selecting an appropriate area ratio in which at least the area of PD2 21b is larger than the area of PD1 21a.

Next, another example studied with particular consideration given to the radiation distribution of the light emitting diode 20 will be described. That is, the emission of light from the light emitting diode can be regarded as substantially rotationally symmetrical about the center of the light emitting diode.
Therefore, in order to accurately detect the change in distance, it is most efficient to use a photodetector having a concentric circle shape with the center of the light emitting diode as an axis so that the change in light intensity is detected at the same place. However, since it is difficult to attach the electrodes for driving the light emitting diode and the photodetector with the perfect concentric shape, as shown in FIG. 7, PD1 21a, PD2 2
1b has a shape in which a concentric circle is partially cut off, and the electrodes 25a to 25d are taken out from the part.

FIG. 8 shows still another example. Basically, as in FIG. 7, the concentric photodetectors PD1 21a and PD2 21
b and the light emitting diode 20. PD1 2
Both 1a and PD2 21b are cut in a string so as to be smaller than a semicircle, and the light emitting diode 20 is arranged at the center of the circle. In this case, the light receiving efficiency of the photodetector is lowered, but the light emitting diode 20 and the PD1 21
Since it can be formed as a different chip on the mounting substrate from the a and PD2 21b, there is an advantage that its manufacture becomes easy. By the way, when the optical disc is at a very short distance and the detection is performed only at the short distance, in order to improve the detection resolution, the area of the photodetector, especially PD1 21a, is made small, and the light emitting diode 20 and PD1 21a, PD2 21b are arranged. It is necessary to narrow the space between and. In this case, in principle, even if the light emitting diode 20 and the PD1 21a and PD2 21b are on the same plane, it is possible by making the distance between them extremely small, but these optical elements must be electrically non-contact. Since they must be made, they cannot be brought close to each other in manufacturing.

FIG. 9 and subsequent figures show other examples suitable for the case where the optical discs are very close to each other as described above. Figure 9
10A and 10B show optical elements formed on a printed wiring board. FIG. 10A is a front view thereof, FIG. 10B is a plan view thereof, and FIG.
[Fig. 3] is a plan view of a printed wiring board. In the figure, the light emitting diode 20 is a light source having a flat light emitting surface and having a light intensity distribution which is close to a perfect diffusion surface in the upward direction, and is electrically conductive to the light emitting diode board side electrode printed wiring 27 of the printed wiring board 26. It is attached with an adhesive and is connected to a printed wiring 28 for the light emitting surface of the light emitting diode by a bonding wire 29 for the light emitting diode, which emits light at a constant output. The photodetector chip 30 has a conductive spacer 31.
It is pasted on the cathode wiring 32 of the photodetector with a conductive adhesive. The back surface of the photodetector chip 30, which is the cathode of the photodetector, is electrically connected to the photodetector cathode printed wiring 32. Here, the distance between the conductive spacer 31 and the light emitting diode 20 is such that the printed wiring 3 for the photodetector cathode may be formed even if the conductive adhesive is squeezed out during manufacture.
2 and the light emitting diode substrate side electrode printed wiring 27 need to be sufficiently separated so as not to short-circuit. Therefore, as shown in FIG. 9A, the thickness of the conductive spacer 31 is set to be thicker than the thickness of the light emitting diode 20, and the light emitting surface of the light emitting diode 20 and the light receiving surface of the photodetector chip 30 are in the optical axis direction. In addition, the structure has a step difference of at least the thickness of the photodetector chip 30. PD1 21a and
PD2 21b Anode bonding pad 3 for each
3a and 33b are respectively bonding wires 34a
And printed wiring 35 for PD1 anode via 34b
a and PD2 connected to the anode printed wiring 35b.

As described above, by providing a step between the light emitting diode 20 and the photodetector chip 30 as shown in FIGS. 9 and 10, the light emitting diode 20 and the conductive spacer 31 are sufficiently separated to electrically insulate them from each other. The light emitting diode 20 and the photodetector chip 30 can be extremely close to each other while being ensured. That is, the projection surfaces of the light emitting surface and the light receiving surface of the two in the direction of the optical axis can be sufficiently close to each other, and if necessary, they can be partially overlapped. FIG. 11 shows the conditions of light emission / reflection and light reception in the above-mentioned example with respect to the optical disk 10.

FIG. 12 shows the above-mentioned optical distance detecting means,
This is an example of application as a distance sensor for controlling the distance between the coil and the magneto-optical recording medium for applying a magnetic field to the magneto-optical recording medium. FIG. It is sectional drawing which cut | disconnected the same figure (a) by the dashed-dotted line kk. In the figure, a magnetic coil 36 is wound around the magnetic head 16. In this case, the optical disc 10 is an object to be measured whose distance is to be detected. The magnetic head 16 and the distance detection device are attached to a base 37, which also serves as an actuator for position control. As a means for creating a gap between the magnetic head and the magnetic medium, an air levitation method is generally used to form a gap of several μm, but the magnetic head 16 in magneto-optical recording is several tens of μm so as not to kill the advantage of being resistant to dust. It is necessary to control with a gap of ˜100 μm, and the air levitation method is not used. For this reason, it is necessary to detect the distance between the magnetic head 16 and the optical disk 10 by some method and perform control to keep the distance constant.
In addition, since it is necessary to drive an actuator for control, it is necessary to make the distance detection device small and lightweight. This example fulfills such requirements in particular. In FIG. 12, the magnetic head 16 and the optical disk 10
When the gap between and is the target value g, that is, the detector chip 30
PD1 21a and PD2 21b so that the differential output 24 of the distance detection device becomes 0 when the gap between the optical disc 10 and the optical disc 10 is d.
Set the shape arrangement of and. And this differential output 2
By performing the target value control so that 4 becomes 0, the gap between the magnetic head 16 and the optical disk 10 is set to the target value g.
Can be kept constant.

Next, another example will be described. As described above with reference to FIG. 7, since the intensity distribution of light emitted from the light emitting diode can be regarded as substantially rotationally symmetric about the center of the light emitting diode, light emission can be detected in order to detect the distance from the light intensity distribution. It is most accurate and efficient to use a photodetector in the shape of a concentric circle centered on the diode. However, in this case, it is technically difficult to mount each optical element in the same chip. The following example solves these points. First, in FIG. 13, the disc-shaped photodetector chip 30 is provided with a through hole 30a at its center. Similarly, the spacer 38 made of an insulating material formed in a disk shape has a through hole 38a having a diameter larger than that of the through hole 30a of the photodetector chip 30 in the center thereof, and the through holes 38a are formed on both sides thereof. 1
As shown in FIG. 4, each electrode and wiring are patterned. FIG. 14A shows a pattern on the photodetector chip 30 side, and FIG. 14B shows a pattern on the light emitting diode 20 side. Each optical element is arranged so that the centers of both through holes 30a and 38a coincide with the center of the light emitting diode 20.
The photodetector chip 30 is attached onto the cathode printed wiring 32 with a conductive adhesive. Also PD1
21a and PD2 21b are connected to anode printed wirings 35a and 35b by bonding wires 34a and 34b, respectively. The light emitting diode 20 is
The spacer 38 has a chip size larger than that of the through hole 38a, and the light emitting surface of the spacer 38 is attached to the light emitting diode side electrode printed wiring 28 with a conductive adhesive so that the light emitting surface thereof faces the through hole 38a. Bonding wires 29 connect the printed wirings 27 for the electrodes on the light emitting diode substrate side through the substrate 20.

With the above structure, the light emitting diode 20 emits light toward the through hole 30a of the photodetector chip 30, passes through the through holes 38a and 30a, and radiates above the photodetector chip 30. To do. In such a case, the emission port on the surface of the photodetector chip 30 can be regarded as a secondary light source. 16 and 17 show the states of light emission, reflection, and light reception in the above example [each figure
(a)] and distribution of light intensity [each figure (b)] are shown. In the former case, when the optical disk 10 is located at a relatively short distance, and when the latter is located at a relatively long distance, the light intensity distributions are rotationally symmetric about the optical axis of the light emitting diode 20. Therefore, as described above, the distribution of the light intensity received by the PD1 21a and the PD2 21b becomes more uniform, and accurate and efficient distance detection can be performed. Furthermore, the emission port 30a, which is a secondary light source, and the light receiving surface of the PD1 21a can be arranged very close to each other, and distance detection at a close position is possible.

FIG. 18 shows another example in which the workability of patterning on a printed wiring board is improved. FIG.
18 (a) is a plan view thereof, and FIG. 18 (b) is a cross-sectional view of FIG. 18 (a) taken along the alternate long and short dash line mm. In the figure, the conductive spacer 39 has a shape as shown in FIG. The printed wiring board 26 to which the spacer 39 and the light emitting diode 20 are attached is shown in FIG. In the spacer 39, the bonding wire 29 of the light emitting diode 20 is the photodetector chip 30.
It is attached to the cathode printed wiring 32 on the printed wiring board 26 with a conductive adhesive so as not to come into contact with. The rear surface of the photodetector chip 30, which is the cathode, is also adhered to the upper surface of the spacer 39 with a conductive adhesive. In this case also, the light from the light emitting diode 20 passes through the through hole 30a and is emitted. Is similar to the previous example. However, the printed wiring board 26 in this example differs from the case of the spacer 38 in FIG. 14 in the previous example in that the patterning of the wiring electrodes on the board is performed only on one side thereof, and the mounting of each component is concentrated only on that one side. It has the advantage that it can be easily manufactured.

21 to 23 show still another embodiment. In the figure, the conductive spacer 40 having the same thickness as the light emitting diode 20 has a shape as shown in a developed perspective view in FIG. The upper surface of each of the light emitting diode 20 and the spacer 40 is attached to the cathode side electrode of the photodetector chip 30 with a conductive adhesive, and the lower surfaces thereof are printed wirings 41 and 42 patterned on the printed wiring board 26, respectively. It is also attached with a conductive adhesive. However, in this example, since the photodetector chip 30 and the light emitting diode 20 are not electrically independent, special attention needs to be paid to the driving method, and FIG. 23 shows an example of the driving circuit in that case. In the figure,
A light emitting diode driving power source 43, a load resistor 44 of the light emitting diode 20, IV conversion amplifiers 45a and 45b,
These load resistors 46a and 46b are connected as shown. The inside of the wiring in the figure corresponds to the optical element portion in the case of this example, and operates by setting the anode of the light emitting diode 20 and the cathodes of PD1 21a and PD2 21b to a common potential. In the case of this example, as can be seen from FIG. 21, the distance between the light emitting surface of the light emitting diode 20 and the upper end of the through hole 30a, which is substantially the exit port thereof, has the same value as the thickness of the photodetector chip 30. Therefore, there is an advantage that the amount of light emitted to the optical disk 10 is increased and the detection sensitivity is increased.

Next, the present invention will be described. Figure 24
2 is a side view showing an essential part of an embodiment of the present invention, and FIG.
5 is an exploded perspective view of a main part of the electromagnetic actuator in the embodiment. In these drawings, a cylindrical yoke 47 fixed to the base 14, a permanent magnet 48 positioned and joined inside the yoke 47, a ring-shaped magnetic member 49 fixed to the yoke 47, and a yoke 47. Elastic support members 50 and 5 fixed at two upper and lower positions inside
1, the coil bobbin 52 supported by the elastic support members 50 and 51 at two positions above and below, the control coil 53 wound around the coil bobbin 52, the substrate 54 supported at one end of the coil bobbin 52, and the lump substrate 54. Light emitting element 20 installed on the substrate and the two-segment photodetector 2 installed on the substrate 54.
It consists of 1. The yoke 47 to the control coil 53 form an electromagnetic actuator. The magnetic head 16 is installed on the substrate 54, and the optical head 15 is composed of a reflection mirror 55, an objective lens 56 and the like. By the way, in this embodiment, the light emitting element 20 and the two-split photodetector 21 are used.
The distance detecting means is formed from the above and the driving means is formed by the electromagnetic actuator. The shielding means is a magnetic member 49. With the above configuration, first, the distance shift between the recording surface of the optical disc 10 and the magnetic head 16 is detected. That is, the light emitted by the light emitting element 20 is reflected by the optical disc 10 and is split into two photodetectors 21.
Incident on. Since the intensity distribution of the incident light changes depending on the above-mentioned distance, the two-divided photodetector 21 can detect the distance shift between the two. Then, a current based on the information on the distance deviation is applied to the control coil 53,
The magnetic head 16 is driven in the direction of arrow V by the electromagnetic force between the permanent magnet 48 and the distance deviation is eliminated. Therefore, the distance between the recording surface of the optical disc 10 and the magnetic head 16 is kept substantially constant. The magnetic member 49 is
It functions as a shield for magnetic flux leaking from the magnetic circuit including the yoke 47 and the permanent magnet 48 to the magnetic head 16.
As a result, the fluctuation of the magnetic field strength can be significantly reduced, and the magnetic head 16 and the optical disk 10 can be brought close to each other.

FIG. 26 is a side view showing an essential part of another embodiment of the present invention. In the figure, a supporting member 57 supported at one end of the coil bobbin 52 and an end portion of this supporting member 57 are attached. And a balancer 58. In addition, the same reference numerals as those in FIG. 24 denote the same parts. The magnetic head 16 is supported by the yoke 47 only by the elastic support member 51 via the support member 57 and the coil bobbin 52. The electromagnetic actuator includes a yoke 47 to a magnetic member 49, a magnetic support member 51 to a control coil 53, a support member 57, and a balancer 58. The substrate 54 is fixed to the support member 57.

FIG. 27 is a side view showing an essential part of still another embodiment of the present invention. A fixed base 59 fixed to the base 14 and an elastic support member 6 supported by the fixed base 59 are shown.
It has 0 and. In addition, the magnetic head 16 includes the substrate 54
It is supported by the elastic support member 60 via. The electromagnetic actuator includes a yoke 47 to a magnetic member 49, a coil bobbin 52, a control coil 53, a fixed base 59, and an elastic support member 60. As described above, in each of the embodiments shown in FIGS. 26 and 27, the operation of detecting the distance between the optical disk 10 and the magnetic head 16 and the operation of driving the magnetic head 16 are the same as those of the embodiment of FIG. It is the same. In each of the above embodiments, the cylindrical yoke 47 is used.
Although the magnetic circuit is formed by the permanent magnets 48 magnetized in the radial direction, the same operation can be expected if the magnetic circuit is formed by other members. Further, the method for detecting the distance between the optical disk 10 and the magnetic head 16 is not limited to the above-mentioned method, and the method using electrostatic capacitance or the method using the signal of the optical head achieves the intended purpose. It goes without saying that you can do it. By the way, in the above description, the case where it is used for eliminating the distance deviation between the optical disk 10 and the magnetic head 16 has been described, but it is also used for the escape of the magnetic head when loading or unloading the optical disk. It goes without saying that you can do it. That is, when the optical disc is attached or detached, the magnetic head is displaced in the direction away from the optical disc (about 3 to 10 mm).

Next, another example of the optical disk recording / reproducing apparatus will be described with reference to FIGS. 28 is a side view of a main part, FIG. 29 is a perspective view of a piezoelectric element actuator, and FIG.
FIG. 6 is a side view showing a positional relationship between a disk, a magnetic head, and an optical spet. In the drawings, the same or corresponding parts as those in FIGS. 1 to 27 are designated by the same reference numerals. In the figure, the magnetic head 16 is attached to the free end of a bimorph piezoelectric element 61 whose one end is fixed to the base 14. The objective lens 56 provided on the optical head 15 is driven by the lens actuator 62. Next, the operation will be described. The piezoelectric element actuator 61 can be displaced in the direction of the arrow (B) according to the energization amount with reference to the fixed end. As shown in FIG. 30, the objective lens 56 is displaced in the arrow (C) direction by the lens actuator 62. At this time, the distance between the recording surface 10a of the optical disc 10 and the lens 56 is kept substantially constant (D). The magnetic head 16 is driven by energizing the piezoelectric element 61 with a voltage proportional to the input voltage of the lens actuator 62 that drives the lens 56 provided in the optical head 15. As a result, the distance (H) between the magnetic head 16 and the optical disk recording surface 10a can be kept substantially constant.

Next, another example will be described with reference to FIGS. In FIG. 31, a holder 63 fixed to the base 14 is provided with two pairs of position sensors. That is, as shown in FIG. 32, the first position sensor detects the position of the surface of the optical disc 10 by the light emitting element 20A and the two-divided light receiving element 21A. The second position sensor is
As shown in FIG. 33, similarly, the light emitting element 20b and the two-divided light receiving element 21b are used to detect the position of the surface of the piezoelectric element 61. With the above configuration, the distance (H) between the surface of the optical disk 10 and the magnetic head 16 can be detected, and the piezoelectric element 61 is adapted to correct the variation amount (Δx) of this distance.
By driving, the fluctuation of the magnetic field strength (B) can be significantly reduced (see FIG. 34).

Next, still another example will be described with reference to FIGS. In FIG. 35, the light emitting element 20 and the two-divided photodetector 21 are installed on the piezoelectric element actuator 61. However, the optical disk 10 is omitted in the figure. In FIG. 36, a cross section is shown along the alternate long and short dash line (E), and the light emitted from the light emitting element 20 is reflected by the optical disk 10 and is incident on the photodetector 21. The light intensity distribution on the photodetector 21 changes as shown in FIG. 2 depending on the distance between the piezoelectric element actuator 61 and the optical disk 10. Therefore, the difference output of the two-division photodetector 21 is as shown in FIG. 37, and the distance can be detected from this differential output. In practice, the distance signal fluctuates at various frequencies, and the drive voltage for the piezoelectric element also becomes an AC voltage having the same frequency as the distance signal. Therefore, the bimorph piezoelectric element 61
Are displaced in the direction of arrow B at various frequencies. At this time, the frequency characteristic of the displacement amount of the bimorph type piezo-voltage element 61 is determined by the design dimension at the time of manufacture, and is as shown in FIG. 38, for example.

FIG. 38 shows frequency characteristics when the drive voltage is constant, where the horizontal axis represents frequency f and the vertical axis represents displacement amount d, where f ₀ is the primary resonance frequency and f ₁ is the secondary resonance frequency.
f ₂ represents the third resonance frequency. When the bimorph type piezoelectric element 61 having such frequency characteristics is actually driven and controlled, when a required driving voltage is applied to the distance signals near the frequencies f ₁ and f ₂ , the displacement amount d becomes larger than necessary. I will end up. Normally, 2 of the bimorph type piezoelectric element 61
The second and third resonance frequencies f ₁ and f ₂ are relatively low frequencies, and the resonance level is high. Therefore, the actuator using the bimorph type piezoelectric element 61 has the frequency f ₁
It can be controlled accurately only in the narrow band below.

The example described below was made in order to solve the above-mentioned problems, and the bimorph type piezoelectric element capable of accurately controlling the displacement amount even at the secondary and tertiary resonance frequencies and widening the control band. It embodies an actuator. FIG. 39 is a perspective view showing an example thereof, in which a part of the vibrating end of the bimorph type piezoelectric element 61 composed of the piezoelectric elements 61a and 61b and the conductive plate 61c is peeled off to expose one piezoelectric element 61a. A second electric terminal 66 is led out from the first electric terminal 65 and the piezoelectric elements 61a and 61b. The third electric terminal 67 connected to the cutout portion 64 is connected to the drive circuit 68.

Next, the operation will be described with reference to the frequency characteristic diagram of FIG. First, the frequency characteristic of the bimorph type piezoelectric element 61 is measured, and a coefficient for outputting an appropriate drive voltage V at each resonance frequency f ₁ and f ₂ is calculated and preset in the drive circuit 68. And
As shown in FIG. 40, the displacement amount d is reduced at each resonance frequency f ₁ and f _{2 so} that the characteristic of the displacement amount d of the bimorph piezoelectric element 61 is changed uniformly with respect to the frequency f. When actually controlling the drive of the bimorph type piezoelectric element 61, the drive circuit 68 controls the drive voltage V based on the distance signal H to keep the distance between the magnetic head 16 and the optical disk 10 constant as described above. At this time, since the piezoelectric element 61a outputs a voltage according to the motion acceleration at that time, the cutout 6
Third electrical terminal 6 connected to the piezoelectric element 61a via
An acceleration voltage C representing the vibration state of the bimorph type piezoelectric element 61 is output from 7. The drive circuit 68 detects the frequency of the bimorph-type piezoelectric element 61 based on the acceleration voltage C, and if the secondary and tertiary resonance frequencies f ₁ and f ₂ or in the vicinity thereof, the drive voltage V according to a preset coefficient. To reduce. As a result, unnecessary resonance is suppressed, the bimorph piezoelectric element 61 is appropriately driven, and the distance between the magnetic head 16 and the optical disk 10 is controlled to be constant. At this time, since the surface of the piezoelectric element 61a exposed in the cutout portion 64 acts as an acceleration sensor and directly outputs the acceleration voltage C, the vibration state of the bimorph piezoelectric element 61 is detected with a simple structure without increasing the cost. can do. In the above example, the case where the magnetic head 16 for generating the bias magnetic field is driven has been described as an example.
As another example, it may be used for drive control of an objective lens for light beam irradiation as shown in FIG. In this case, in order to displace the objective lens 56 in the direction of the arrow B while maintaining the parallelism, a bimorph type piezoelectric element 70 having no notch is arranged in parallel with the bimorph type piezoelectric element 61, and each bimorph type piezoelectric element 61. And the objective lens 56
A holder 59 for holding is fixed. Also,
Although not shown, it is not limited to the optical disc recording / reproducing device,
It may be applied to an actuator of a magnetic head for VTR tracking control. Here, the bimorph piezoelectric element 6
42, the elastic shims 61c and the electric terminals 6 also serve as the piezoelectric elements 61a and 61b polarized in the same thickness direction and the conductive plate made of a metal material such as copper, as shown in FIG.
5, 66a and 66b. When a voltage is applied so that the electric terminals 66a and 66b have the same polarity and the electric terminals 65 have different polarities, one of the piezoelectric elements 61a and 61b extends in the length direction of the arrow and the other extends in the length direction of the arrow. Shrink to.
Elastic shims 61c are adhered to opposite sides of the respective piezoelectric elements 61a and 61b, and the length of the elastic shims 61c does not change. As a result, the bimorph piezoelectric element is flexibly deformed in the (α) direction in the figure. Therefore, the focus shift is detected by a known method, and a voltage corresponding to the shift amount is applied to the bimorph type piezoelectric element to drive the objective lens holder 69, and thus the objective lens 56, to perform focus control.

Looking at the frequency characteristics in the above operation,
As shown in FIG. 43, relatively low frequencies f ₂ , f ₃ , f ₄
However, there is a problem that the second, third and fourth resonances occur and the vibration level is high, so that the control band cannot be wide. In addition, as shown in FIG. 41, if two objective bimorph piezoelectric elements 61a and 61b are arranged in parallel so that the objective lens 56 does not tilt when it is displaced, the assemblability is poor and the displacement amount is small. There was a problem that it could not be taken big. The following example is made in order to solve the above problems, and embodies an actuator for a recording / reproducing apparatus having a simple structure, good assembling ability, a wide control band, and a large movable amount.

An example thereof will be described below with reference to FIGS. In the figure, bimorph type piezoelectric elements 61 are piezoelectric elements 61a, 61 which are polarized in the same thickness direction.
b, and an elastic shim 71 which is sandwiched between the piezoelectric elements 61a and 61b and also serves as a conductive plate. The elastic shim 71 is formed in such a shape that its width is almost inversely proportional to the value of the primary reference function of the beam for fixed-roll support. That is,
In FIG. 45, assuming that the width of the elastic shim 71 is b, the length is l, and the x axis is along the length direction, the elastic shim 71 is supported at x = 0.

[0031]

[Expression 1] b∝ 1 / {cos βl−coshβl) (coshβx−c
osβx) + (sinβl + sinβl) (sinβx-sinβx)} βl = 2.365

The shape is as follows. Piezoelectric elements 61a and 61b are adhered to both surfaces of the elastic shim 71. With the above configuration, by applying a desired voltage to the piezoelectric element 61, the objective lens holder 6 can be operated on the same principle as the conventional one.
9, by extension, the objective lens 56 is driven in the direction of the arrow (B) to control the defocus of the light spot condensed by the objective lens 56. At this time, the elastic shim 71 of the piezoelectric element 61
Is a shape as described above, and generally, the bending displacement is inversely proportional to the second moment of area, that is, when the thickness is constant, it is inversely proportional to the width, so that the piezoelectric element 61 is displaced in the vibration mode of fixed-roll support. As shown by 46, the objective lens holder 69 does not always tilt, but is displaced in the arrow (B) direction. The frequency characteristic of this actuator is shown in FIG.
As shown in (2), since the second and higher order vibration modes are suppressed, the control band can be expanded. In the above example, the shape of the elastic shim 71 is formed so that its width is inversely proportional to the value of the linear reference function of the beam of the fixed-roll support beam.
As shown in FIG. 8, it may be formed so as to be inversely proportional to the value of the quadratic reference function. The principle of operation is exactly the same as that described above. As for the frequency characteristic at that time, as shown in FIG. 49, since the secondary resonance frequency f ₂ is excited and the other vibration modes are suppressed, the so-called system resonance frequency f ₀ is set to a higher frequency. be able to. The shape of the elastic shim 71 may be set based on a cubic or quaternary reference function, or may be based on a superposition of a plurality of reference functions, depending on the application. In addition, not only fixed-roll support conditions but also fixed-free,
Freedom-A reference function based on freedom etc. may be used.
In the above example, the focus control is described, but
As shown in FIG. 50, it is clear that the same effect can be achieved when the objective lens 56 is driven in the tracking control direction orthogonal to the optical axis, that is, in the arrow (B) direction. Further, it can be easily inferred that the focus control shown in FIG. 44 and the tracking control shown in FIG. FIG. 51 shows another example of performing the tracking operation of the magnetic head. The magnetic head chip 16a is attached to the free end of the piezoelectric element 61, and the magnetic head chip 16a is driven according to the same principle as described above to correct the deviation between the track recorded on the magnetic tape and the magnetic head chip 16a. Control.

FIG. 52 shows an external magnetic field applying device in an optical disk recording / reproducing device as yet another example. The magnetic head 16 is provided at the free end of the piezoelectric element 61,
The distance between the optical disk 10 and the magnetic head 16 is detected by an appropriate method, and the magnetic head 16 is driven according to the same principle as described above in order to eliminate the deviation from the predetermined distance.
In each of the above examples, the piezoelectric element 61 is provided on both surfaces of the elastic shim 71.
Although a and 61b are provided to form the bimorph piezoelectric element 61,
A piezoelectric element may be bonded to only one surface of the elastic shim to form a bimorph piezoelectric element.

[0034]

As described above, according to the optical disk recording / reproducing apparatus of the present invention, since the shielding means for shielding the magnetic flux leaking from the driving means for driving the magnetic head by the electromagnetic force is provided, the efficiency of the magnetic field strength is improved. In addition, the recording characteristics can be stabilized and the mechanical accuracy can be relaxed.

[Brief description of drawings]

FIG. 1 is a light intensity-distance characteristic diagram in a distance detecting unit according to an example of an optical disk recording / reproducing apparatus.

FIG. 2 is a characteristic diagram showing a distribution of light intensity with respect to a position on a one-dot chain line j-j in FIG.

FIG. 3 is a plan view showing an arrangement of optical elements of the distance detecting means.

FIG. 4 is an output-distance characteristic diagram of both photodetectors.

FIG. 5 is a circuit diagram for obtaining a differential output.

FIG. 6 is a differential output-distance characteristic diagram.

FIG. 7 is a plan view of an optical element arrangement in consideration of a light intensity distribution of a light source.

FIG. 8 is a plan view of an optical element arrangement of another example in consideration of the light intensity distribution of the light source.

FIG. 9A is a side view and FIG. 9B is a plan view of a main part of the optical disc recording / reproducing apparatus.

10 is a plan view of the printed wiring board in FIG.

FIG. 11 is an explanatory diagram of an optical path in that of FIG.

12A is a plan view of still another example, and FIG. 12B is a cross-sectional view taken along the line kk of FIG.

FIG. 13 is a plan view of another example and a cross-sectional view taken along a line ll of FIG.

FIG. 14 is a plan view showing patterning of each wiring to the spacer in FIG.

FIG. 15 is a plan view showing another example of patterning each wiring to the spacer in FIG.

FIG. 16 is an explanatory diagram showing a light situation and a light intensity distribution of the light source shown in FIG.

FIG. 17 is an explanatory diagram showing a light situation and a light intensity distribution of the light source shown in FIG.

18A is a plan view of still another example, and FIG. 18B is a cross-sectional view taken along a line MM in FIG. 18A.

19 (a) is a side view and FIG. 19 (b) is a plan view of the spacer in FIG.

FIG. 20 is a plan view showing patterning of each wiring on the printed wiring board of FIG. 18;

FIG. 21 is a side sectional view of still another example.

22 is an exploded perspective view of that of FIG. 21. FIG.

FIG. 23 is a wiring diagram of the drive circuit shown in FIG. 21.

FIG. 24 is a side sectional view of an essential part of an embodiment of the present invention.

FIG. 25 is an exploded perspective view of the electromagnetic actuator in FIG. 24.

FIG. 26 is a side sectional view of a main part of another embodiment.

FIG. 27 is a side sectional view of a main part of still another embodiment.

FIG. 28 is a side view of essential parts of an example of an optical disc recording / reproducing apparatus.

29 is a perspective view of the piezoelectric actuator shown in FIG. 28. FIG.

FIG. 30 is a partial side view for similarly explaining the operation.

FIG. 31 is a perspective view of a main part of another example.

32 is a partial side view for explaining the operation of the one shown in FIG. 31. FIG.

FIG. 33 is a partial side view for explaining the operation of the one shown in FIG. 31.

FIG. 34 is a diagram of magnetic field strength variation on the recording surface of the disc.

FIG. 35 is a perspective view of a main part of still another example.

FIG. 36 is a side view of the position detection sensor portion of FIG. 35.

FIG. 37 is an output characteristic diagram of the position detection sensor.

FIG. 38 is also a displacement amount-frequency characteristic diagram.

FIG. 39 is a perspective view of an essential part of the optical disc recording / reproducing apparatus.

40 is a variable position-frequency characteristic diagram of the bimorph-type piezoelectric element in FIG. 39. FIG.

FIG. 41 is a perspective view of a main part of another example.

42 is a side view of the bimorph-type piezoelectric element in FIG. 41. FIG.

FIG. 43 is a gain-frequency characteristic diagram of that of FIG. 42.

FIG. 44 is a perspective view of essential parts of the optical disc recording / reproducing apparatus.

FIG. 45 is a plan view of that of FIG. 44.

FIG. 46 is a side view showing the same operation.

FIG. 47 is also a frequency characteristic diagram.

FIG. 48 is a plan view of another example.

FIG. 49 is a frequency characteristic line of that of FIG. 48.

FIG. 50 is a perspective view of still another example.

FIG. 51 is a perspective view of still another example.

FIG. 52 is a perspective view of still another example.

FIG. 53 is a side sectional view of the distance detecting means.

54 is a light intensity-distance characteristic diagram of that of FIG. 53. FIG.

FIG. 55 is a schematic side view of an essential part of the optical disc recording / reproducing apparatus.

FIG. 56 is a partial side view for explaining the operation.

FIG. 57 is a magnetic field strength variation characteristic diagram of the recording surface of the optical disc.

[Explanation of symbols]

10 optical disk, 15 optical head, 16 magnetic head, 20 light emitting diode (light source), 21a, 21b
Photodetector, 49 magnetic member (shielding means), 56 objective lens, 61 bimorph piezoelectric element (piezoelectric element actuator), 61a, 61b piezoelectric element, 64 cutout portion,
65, 66, 67 First, second and third electric terminals, 71
Elastic shim (conductive metal plate).

 ─────────────────────────────────────────────────── ─── Continuation of front page (31) Priority claim number Japanese Patent Application No. Sho 63-178025 (32) Priority date Sho 63 (1988) July 19 (33) Priority claim country Japan (JP) (31) Priority Claim number Japanese patent application No. 1-28597 (32) Priority date 1 (1989) February 9 (33) Country of priority claim Japan (JP) (72) Inventor Hajime Nakajima 8-1-1 Tsukaguchihonmachi, Amagasaki Industrial Systems Research Center, Mitsubishi Electric Corporation

Claims (1)

[Claims] 1. A distance detector for detecting a distance between an optical head for irradiating an optical disk with light to record and reproduce a signal and a magnetic head for applying a bias magnetic field to the optical disk and the optical disk and outputting the distance information. An optical disk recording / reproducing apparatus comprising: means, a driving means for driving the magnetic head by an electromagnetic force so that the distance becomes constant based on the distance information, and a shielding means for shielding a magnetic flux leaking from the driving means. .