JPH0472295B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical reading device that can be used as an optical pick-up for a video disk or a digital audio detector, and in particular, the present invention relates to an optical reading device that can be used as an optical pick-up for a video disc or a digital audio detector. The present invention relates to an optical reading device that can be driven not only in two orthogonal directions within a dimensional plane, but also in a focusing direction perpendicular to this plane, and capable of highly accurate tracking control of the convergence point of a light beam over three dimensions.

Taking the optical pickup of a video disc as an example, an optical reading device is used to
Because the pit row to be read on the disk is displaced in three-dimensional directions due to deformation and irregular movement during rotation of the disk, it is necessary to constantly control the convergence point of the light beam in three-dimensional directions. Conventionally, in tracking control in these three directions, a deflection mirror is used in two-dimensional directions (radial and tangential) to deflect the light beam emitted by the optical reading device, and the focusing direction is controlled by using the lens barrel as an outer frame. The most common method is a combination of an optical mechanism and a mechanical mechanism that slides against the body, and other methods include lenses and optical mechanisms that utilize electromagnetic interaction between permanent magnets and coils. A method has also been proposed in which a lens barrel containing a reading section is simultaneously controlled and moved in three dimensions to track the convergence point of the light beam. However, the former method has the disadvantage that the control method becomes complicated because two different types of mechanisms, an optical mechanism and a mechanical mechanism, are controlled simultaneously. On the other hand, in the latter method, there is still room for structural improvement in order to eliminate friction and hysteresis factors in the components of the elastic suspension means and maintain a high level of precision in the servo system for tracking control, and there is also room for structural improvement in the structure itself. It also has the disadvantage of being complex. Furthermore, since the spring constant of the above-mentioned elastic suspension means affects the gain of the electric servo circuit in the tracking control system, it is desirable that the spring constant be as low as possible.

Therefore, the main purpose of the present invention is to eliminate the various problems associated with the conventional optical reading device as described above, and to control the three-dimensional tracking of a lens barrel containing a lens and an optical reading section with high precision. The object of the present invention is to provide an optical reading device that can completely constrain the objective lens of the reading device or the entire optical system including the objective lens in each of the operating directions of the focusing direction, tracking direction, and jitter direction. An object of the present invention is to provide an optical reading device which is improved so that there is no room for movement in unnecessary directions due to the movement of the three directions, and deterioration of controllability due to mutual interference between the movements in these three directions can be suppressed. . That is, according to the present invention, the positional deviation between the recording track provided on the information surface of the disk and the convergence point of the light beam is optically detected, and the position of the convergence point of the light beam is adjusted according to the detected amount of deviation. and optically detecting a defocus between the information surface of the disk and the convergence point of the light beam, and controlling the position of the convergence point of the light beam in the optical axis direction according to the detected amount of deviation. In the device for optically reading information recorded on the disk, the lens barrel includes: an objective lens that focuses a light beam on the information surface of the disk or an optical system including the objective lens; at least a pair of thin-walled deflection retaining members having one end fixed and movably supporting the lens barrel in a direction perpendicular to the recording track on the disk; a first drive device that displaces the first lens barrel, which supports the cylinder via the deflection holding member, in a direction perpendicular to the recording track on the disk; one end attached to the first support member; a pair of elastic support members that support the first support member so as to be movable in a direction perpendicular to the disk surface and independently of a direction perpendicular to the recording track of the disk; a second support member attached to the other end and fixed to the substrate; and a second support member that displaces the first support member together with the lens barrel in a direction perpendicular to the disk surface with respect to the second support member. An optical reading device is provided, characterized in that it includes a driving device. Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings.

FIG. 1 is a longitudinal sectional view showing the configuration of an optical reading device according to an embodiment of the present invention. In FIG. 1, the optical reading device has a cylindrical outer frame 10 forming a second support member, and this cylindrical outer frame 10 supports the entire optical reading device with respect to, for example, a video disc 14. It is configured so that it can be attached to a substrate in a slide drive device that slides while tossing. Elastic suspension plates 18 and 20 are fixed near the upper and lower ends of this cylindrical outer frame 10, and these elastic suspension plates 18 and 20 allow the cylindrical outer frame to
A certain amount of upward and downward movement is allowed inward of 0, and
A cylindrical inner frame body 12 forming a first support member is attached. The inner flange 12a formed at the lower part of this cylindrical inner frame 12 has a cylindrical outer shape, which will be described later, and a deflection retainer 22 with one groove (slit) is fixed to this deflection retainer 22. A lens barrel 16 is held. This deflection retainer 2
2, by holding the lens barrel 16 integrally with the inner frame 12, the lens barrel 16 and the inner frame 12 can be integrally moved by a certain amount in the focusing direction;
At the same time, the lens barrel 16 is configured to be movable by a certain amount in a radial direction and a tangential direction that are perpendicular to each other with respect to the inner frame 12 in a plane perpendicular to the focusing direction. Note that a lens system and an optical reading section are housed within the lens barrel 16 as in the conventional case. Now, an annular permanent magnet 26 held by appropriate retaining rings 24a and 24b is provided below the inner frame body 12, with the upper surface side being the N pole and the lower surface side being the S pole. Inside the annular permanent magnet 26, a return path member 28, which is also annular, is provided on the inner frame 12.
An annular magnetic gap _G1 is formed between the permanent magnets 26 and the return path member 28.
A magnetic circuit is formed by the return path member 28 and the magnetic cap _G1 . A coil bobbin 30 fixed to the flange of the lens barrel 16 is inserted into the magnetic cap _G1 of this magnetic circuit.
A pair of air-core coils are provided on the coil bobbin 30 in each of the orthogonal radial and tangential directions, and in FIG. The coils 32a and 32b are shown intersecting the magnetic circuit. Of course, in addition to the air-core coils 32a and 32b, there is an air-core coil 3 not shown in FIG. 1 in other orthogonal directions.
4a and 34b (see FIG. 5) are provided.
And these air core coils 32a, 32b, 34
a, 34b and the above-described magnetic circuit of the permanent magnet 26 to control the movement of the lens barrel 16 in the radial direction and the tangential direction, that is,
A first drive device is thus formed. In other words, when an electric control signal is applied to the air-core coils 32a, 32b, 34a, and 34b provided to intersect with the magnetic circuit of the permanent magnet 26, it can be regarded as a linear displacement in the radial direction and tangential direction due to the Lorentz effect. The desired amount of movement can be produced. Note that, generally, the amount of movement in the radial direction and the tangential direction is a minute movement of about several hundred microns.

On the other hand, a permanent magnet 40 is attached to the upper part of the outer frame 10, and is held between an annular holding member 36 and a cylindrical yoke member 38, which form part of the magnetic path. An annular magnetic gap is formed by the member 36, the cylindrical yoke member 38, and the permanent magnet 40.
A magnetic circuit with G ₂ is formed. A voice coil 44 wound around a cylindrical bobbin 42 attached to the center of the inner frame 12 is inserted into the magnetic cap _G2 . Therefore, by applying an electrical control signal to the voice coil 44, the inner frame 12 and the lens barrel 16 integrally attached to the inner frame 12 are controlled to move in the focusing direction shown by arrow F. It is possible. In other words, a second drive device is formed. In FIG. 1, 46 indicates an input line for electrical control signals to the air-core coils 32a, 32b or 34a, 34b, and 48 indicates an input line for electrical control signals to the voice coil 44. A stopper 50 is provided to prevent movement displacement of the lens barrel 16 in the radial direction and tangential direction, and is formed of a well-known elastic O-ring. Furthermore, 52 is an input to an optical reading section (not shown) housed in the lens barrel 16;
This is the output line.

Next, the structure, function, and effect of each part of the optical reading device shown in FIG. 1 will be explained.

FIGS. 2A and 3B are an enlarged perspective view and a side view of the flexible retainer 22 as seen from two directions perpendicular to each other, respectively.

As is clear from FIGS. 2 and 3, one grooved flexure retainer 22 has a hollow cylindrical shape as a whole, and has an upper slit 125 and a lower slit 1.
Upper ring 121, intermediate gimbal 122, lower fixed ring 1 partially separated from each other by 26
23. Upper ring 12
1 is formed as a part that firmly holds the lens barrel 16 shown in FIG. 1, a lower fixing ring 123 is formed as a part that is firmly held by the inner frame body 12 shown in FIG. 1, and an intermediate gimbal 122 is explained below. It is formed as a bending part. Note that these upper ring 121, intermediate gimbal 122, and lower fixed ring 123 are formed into a hollow ring body and a hollow cylindrical body having the same wall thickness for processing advantages, but if necessary, for example, the intermediate gimbal 122 The wall thickness of the upper and lower rings 121 and 123 may be different from that of the other upper and lower rings 121 and 123.

The intermediate gimbal 122 has the intermediate gimbal 122
A pair of flexible portions 124a, 124b are formed to face each other on one diameter line, and another pair of flexible parts 127a, 127b are formed to face each other on another diameter line perpendicular to the one diameter line. There is. Each of these bending parts 124a, 124b, 127
As is clear from the illustration, a and 127b are formed as hourglass-shaped thin parts formed between two circular holes bored in parallel in the peripheral wall of the intermediate gimbal 122, and the thickness of this thin part is, for example, several tens of microns. The dimension is selected to be extremely small compared to the wall thickness of the intermediate gimbal 122 itself. Therefore, in the illustrated example, the pair of flexures 124a, 124b allows the upper ring 121 to be deflected relative to the intermediate gimbal 122 around the diameter line passing through the flexures 124a, 124b, and The upper ring 1 is
21 and the intermediate gimbal 122 are integrally connected to the lower ring 123, and the two flexible portions 127a, 12
It becomes possible to bend and displace around the diameter line passing through 7b. Note that both deflection displacements can be regarded as linear displacements in two orthogonal directions in a minute displacement region of microns. Therefore, in the optical reading device shown in FIG.
The lens barrel 16 held by the upper ring 121 is configured to be movable in two dimensions, that is, a radial direction and a tangential direction, which are orthogonal to each other in a plane with respect to the inner frame body 12 to which the lower fixing ring 123 is fixed. -ing Note that the lens barrel 16 is connected to the inner frame body 1.
When it is desired to give a degree of freedom in only one direction in the two-dimensional direction to 2, one pair of the flexible portions 124
This can be easily realized since it is not necessary to process the circular holes forming the holes a, 124b or 127a, 127b in the intermediate gimbal 122. Note that this deflection retainer 22 may be formed in such a way that it can reliably return to its initial state when the external force is removed, or it may be heat-treated after machining to impart appropriate elasticity. taken.

Next, FIG. 4 shows the elastic suspension plate 18 shown in FIG.
20 is a plan view showing an embodiment of the elastic suspension plate 18 or 20. As shown in the same figure, the elastic suspension plate 18 or 20 has a center circle 130 bored in a disc member made of an elastic material, and Many concentric circular arc slits 1
31.
Note that the center circle 130 and the circular arc slit 131 can be easily formed by a punching method.
Further, the thickness of the disc member may be appropriately selected depending on the desired elastic strength.

FIG. 5 is a perspective view conceptually showing the configuration of a drive mechanism for controlling and moving the lens barrel 16 in FIG. A pair of air-core coils 32 are attached to a coil bobbin 30 in a magnetic circuit formed by an annular permanent magnet 26, a return path member 28, and a magnetic gap _G1 .
a, 32b and these pair of air core coils 32a, 3
2b, air core coils 34a and 34b are inserted at a distance of 90 degrees from each other on the circumference, and as described above, these air core coils 32
When an electric control signal is applied to a, 32b, 34a, and 34b, the coil bobbin 30 holding the air-core coil is displaced relative to the outer frame 12 in the radial direction (arrow A) or tangential direction (arrow B). In the illustrated example of FIG. 5, movement displacement is induced in the radial direction of arrow A due to the interaction between the magnetic circuit and the pair of air-core coils 34a, 34b, and the other pair of air-core coils 32a, 32b A displacement is induced in the tangential direction of arrow B by the interaction between the magnetic circuit and the magnetic circuit. It goes without saying that by controlling the magnitude and polarity of the electrical control signal, it is possible to control the amount of displacement and the orientation in each direction.

As mentioned above, as is clear from the configuration of the optical reading device according to the embodiment of the present invention shown in FIGS. It is possible to control the convergence point of the light beam with high precision in three-dimensional directions, including the radial direction and the tangential direction, which are orthogonal to each other within a plane perpendicular to this direction. Hanging means 18, 20
Since the inner frame body 12 and the lens barrel 16 are held with respect to the outer frame body 10 using the elastic deflection retainer 22, the light beam is constantly moved and displaced in three-dimensional directions from a constant initial position. The convergence point can be tracked to the target position. Moreover, according to the present invention, the outer frame body 10, the inner frame body 12,
Since the various components such as the deflection retainer 22 are each formed into a cylindrical body or an annular body whose outer shape can be machined by turning, it is possible to reduce the machining cost, and moreover, it is possible to reduce the machining cost. Cylinder 16
Since the other components can be adjusted simply by relatively increasing or decreasing the dimensions according to the external dimensions of the device, the device has the advantage of being highly flexible in design and being able to reduce design costs. In particular, since the deflection retainer 22, which regulates the degree of freedom in the two-dimensional direction in a plane perpendicular to the focusing direction, basically has a cylindrical outer shape, the design of the deflection retainer itself does not need to be changed in any way even if the lens barrel dimensions differ. This can be easily dealt with by changing the diameter dimension in a similar manner without causing the problem, so an inexpensive optical reading device can be realized. In addition, the movable frame holding the entire optical system can be placed in the focus direction, tracking direction, and jitter direction using the deflection retainer and the pair of elastic support members, and the movable frame body that holds the entire optical system can be positioned in the focus direction, tracking direction, and jitter direction, and these movements can be completely controlled without causing mutual interference. By supporting with a structure that is constrained in each of the three directions and does not cause unnecessary movement, it provides good controllability and allows independent design conditions to be introduced for the support structure in each direction, increasing the degree of freedom in design. It is possible to expand the system and, in turn, obtain good controllability and operational performance. On the other hand, as mentioned above, the fact that the optical reading device according to the present invention has a cylindrical outer shape as a whole means that there are no unnecessary protruding parts when this device is installed in a video device, etc., so that the installation space is minimized. This makes it possible to save money and contribute to downsizing of the entire device such as a video device.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of an optical reading device according to an embodiment of the present invention, FIG. 2 is an enlarged perspective view showing the structure of a flexible retainer, and FIG. 3 is a side view of the same flexible retainer as seen from two orthogonal directions. 4 is a plan view of the elastic suspension means, and FIG. 5 is a perspective view illustrating the concept of a drive device that controls and moves the lens barrel in the radial direction and tangential direction. DESCRIPTION OF SYMBOLS 10... Outer frame body, 12... Inner frame body, 14... Video disk, 16... Lens barrel, 18, 20... Elastic suspension means, 22... Deflection retainer, 26... Permanent magnet, 28 ...Return path member, 30...Coil bobbin, 32a, 32b, 34a, 34b...
...Air core coil, 40...Permanent magnet, 42...Coil bobbin, 44...Voice coil.

Claims (1)

[Claims] 1. Optically detecting the positional deviation between the recording track provided on the information surface of the disk and the convergence point of the optical movie, and adjusting the position of the convergence point of the light beam according to the detected amount of deviation. At the same time, it optically detects the defocus between the information surface of the disk and the convergence point of the light beam, and controls the position of the convergence point of the light beam in the optical axis direction according to the detected amount of deviation. A device for optically reading information recorded on a disk, comprising: a lens barrel holding an objective lens or an optical system including the objective lens for converging a light beam onto the information surface of the disk; and one end attached to the lens barrel. a deflection holding member having at least a pair of thin-walled bending portions to which the lens barrel is fixed and movably supporting the lens barrel in a direction perpendicular to the recording track on the disk; , a first support member that supports the lens barrel via the deflection holding member; a first drive device that displaces the lens barrel in a direction perpendicular to recording tracks on the disk; and the first support. a pair of elastic support members having one end attached to the member and movably supporting the first support member in a direction perpendicular to the disk surface and independently of a direction perpendicular to the recording track of the disk; a second support member attached to the other end of the pair of elastic support members and fixed to the substrate; and with respect to the second support member, the first support member and the lens barrel are perpendicular to the disk surface. An optical reading device comprising: a second driving device for displacing the device in a direction in which the reading device is moved;