Objective lens driving apparatus

Abstract: Objective lens driving apparatus has a driving mechanism to move a bobbin (12) provided with an objective lens (11) in a direction parallel to the optical axis of the objective lens (11) and in a direction perpendicular to the optical axis of the objective lens (11), first and second supporting arm members (14, 15) each comprising a pair of hinge portions (14 a , 14 b , 15 a , 15 b ) and parallel links (14 c , 14 d , 15 c , 15 d ) coupling the hinge portions to support the bobbin (12) for movement in the direction parallel to the optical axis and in the direction perpendicular to the optical axis and a frame (13) to which the first and second supporting arm members (14, 15) are attached. The bobbin (12) is movable in the direction parallel to the optical axis by the first and second supporting arm members (14, 15) and in the direction perpendicular to the optical axis by a parallelogram linkage formed by the bobbin (12), the first and second supporting members (14, 15) and a part (13b) of the frame (13).

Description: The invention relates generally to objective lens driving apparatus. Objective lens driving apparatus can be used to drive an objective lens to converge a light beam emitted from, for example, a light source on the signal recording plane of an optical disc in the focus direction and tracking direction or in one of these directions. Objective lens driving apparatus has been previously proposed constructed such that a movable body to which an objective lens is attached is supported by a single supporting arm having a hinge and a parallel link on a base (see US Patent No. 4,766,583). Another apparatus is constructed, as shown in Figure 1 of the accompanying drawings, such that a bobbin 4 supporting an objective lens 1 and having a driving coil 2 for focusing control and a driving coil 3 for tracking control is disposed between magnets 6 arranged opposite to each other on a base 5 which serves as a yoke and supported in a cantilever manner by supporting rods 8. The supporting rods 8 are made of metal having resiliency and are respectively fixed to upper right, upper left, lower right and lower left portions of the front surface of a fixing plate 7 implanted on the base 5 such that they are in parallel to each other in a cantilever manner. In said another apparatus the bobbin 4 is moved by the resilient displacement of the supporting rods 8 which is caused by supplying a driving current to the driving coil 2 for focusing control or the driving coil 3 for tracking control and consequently the objective lens 1 supported by the bobbin 4 is moved on the basis of a focusing error signal or a tracking error signal in the focusing direction (the direction of the optical axis of the objective lens 1 or the direction parallel to the optical axis) or the tracking direction (the direction perpendicular to the optical axis of the objective lens 1 or the plane direction perpendicular to the optical axis). The objective lens driving apparatus of US Patent No. 4,766,583, has the hinge of the supporting arm positioned at the rotating centre of the movable body, which causes restriction to the form of the movable body. For example, freedom of location of the optical system is decreased when the apparatus is integrally driven, consequently presenting difficulties on making the apparatus thinner. On the other hand, in said another apparatus, that is, the objective lens driving apparatus as shown in Fig. 1, since it comprises a cantilever spring supporting system, the interval between the upper and lower resilient supporting rods is decreased as the apparatus is made thinner, thus presenting obstacles in that the optical axis of the objective lens is readily inclined. Further, when it is integrally driven, it requires additional signal line lead-out method so that the construction is made complicated. Moreover, four resilient supporting rods do not allow setting the vibration characteristics independently to the focusing direction and the tracking direction, thereby incurring troubles such as the operation lacks smoothness. According to the invention there is provided an objective lens driving apparatus comprising: a movable body mounting an objective lens; a supporting arm mounting the movable body and including a hinge portion and first and second parallel links, a frame to which the supporting arm is attached and electro-magnetic driving means to drive the objective lens in a direction parallel to the optical axis of the objective lens and in a direction perpendicular to the optical axis; characterised in that the supporting arm comprises first and second supporting arm members each having a pair of hinge portions; the first and second parallel links are provided on each of the first and second supporting arms and couple the respective pair of hinge portions; and the objective lens is movable in a direction parallel to the optical axis of the objective lens by the respective parallel links of the first and second supporting arm members and is movable in the direction perpendicular to the optical axis of the objective lens by a parallelogram linkage formed by the movable body, a part of the frame and the first and second supporting arm members. Such an objective lens driving apparatus can provide a large freedom in the shape of the movable body which supports the objective lens, can be thinner and can permit setting of the vibration characteristic independently of the focusing direction and the tracking direction thereby to extend the setting range. The movable body may mount, in addition to the objective lens, a laser light source, optical parts to introduce a light beam from the laser light source to the objective lens and a light receiving element to receive the light beam which passes through the objective lens and the optical parts. The invention is diagrammatically illustrated by way of example in the accompanying drawings, in which:- Fig. 1 is a perspective view showing an objective lens driving apparatus of previously proposed kind; Fig. 2 is a perspective view showing a first embodiment of an objective lens driving apparatus according to the invention; Figs. 3A - 3C are respectively a perspective view, a plan view and a side view of an arm member employed in the apparatus shown in Fig. 2; Fig. 4 is a perspective view showing a second embodiment of an objective lens driving apparatus according to the invention; Fig. 5 is an exploded perspective view of a yoke serving as a frame in the apparatus of Fig. 4; Fig. 6 is a back view of the objective lens driving apparatus shown in Fig. 4; Fig. 7 is a side view of the objective lens driving apparatus shown in Fig. 4; Figs. 8A - 8C are respectively a perspective view, a plan view and a side view of another example of an arm member; Figs. 9A - 9C are respectively a perspective view, a plan view and a side view of a yet further example of an arm member; Figs. 10A - 10C are respectively a perspective view, a plan view and a side view of a yet further example of an arm member. Referring to the drawings, a first embodiment of an optical pickup has objective lens driving apparatus as shown in Fig. 2 comprising a bobbin 12 supporting an objective lens 11 as a movable body. The objective lens 11 is supported on a middle portion of the upper surface of the bobbin 12, with its optical axis directed vertically. The bobbin 12 is supported through first and second supporting arm members 14 and 15 to a yoke 13 as a frame movable in a direction parallel to the optical axis of the objective lens 11, that is, the focusing direction and in a direction perpendicular to the optical axis, that is, the tracking direction. The bobbin 12 in the above construction is made of synthetic resin such as ABS resin or the like which has heat durability and high rigidity. A driving coil 16 for focusing control is wound on the outer periphery of the bobbin 12 in the direction perpendicular to the optical axis. Also, a driving coil 17 for tracking control wound in a substantially rectangular shape is attached, by adhesive or the like, on the front and rear faces of the driving coil 16 and on both sides thereof. The yoke 13 is formed as a quadrilateral frame which surrounds the bobbin 12 with a predetermined spacing therebetween. On the inner surface of inner front and rear sides 13 a and 13 b of the yoke 13 there are secured magnets 18 opposite the driving coil 16 for focusing control and the driving coil 17 for tracking control with a predetermined distance therebetween. The magnets 18 and the yoke 13 constitute an opened magnetic circuit. The inner surface of the rear side 13 b of the yoke 13 is provided with a protrusion 13 b ₁ and one of the magnets 18 is fixed on the inner end face thereof to maintain a predetermined spacing from the coils 16 and 17. The arm members 14 and 15 which support the bobbin 12 on the yoke 13 as the frame, are made of elastic synthetic resin and are formed with hinge portions 14 a , 14 b and 15 a , 15 b and parallel links 14 c , 14 d and 15 c , 15 d therebetween, respectively. The arm members 14 and 15 are symmetrical and only one of them, i.e. the arm member 14 will be hereinafter explained in detail with reference to Figs. 3A to 3C. As shown in the perspective view of Fig. 3A, the pair of hinge portions 14 a and 14 b are formed at front and rear end portions of the arm member 14 by forming recesses 14 a ₁, 14 a ₂, and 14 b ₁, 14 b ₂ in opposite side faces. The arm member 14 can be bent and swung at the pair of the hinge portions 14 a and 14 b as shown by chain-dotted lines in Fig. 3B. The parallel links 14 c and 14 d between the hinge portions 14 a and 14 b extend in the direction perpendicular to the direction in which the arm member 14 is bent around the hinge portions. The parallel links 14 c and 14 d are provided with flexible portions 14 c ₁, 14 c ₂ and 14 d ₁, 14 d ₂, respectively, in the front and rear end portions thereof, formed concavely, in a manner such that the arm member 14 can swing smoothly parallel as shown by chain-dotted lines in Fig. 3C. The arm members 14 and 15 are disposed in the yoke 13 with the protrusion 13 b ₁ interposed therebetween and fixed at their rear end surfaces such that the parallel links 14 c , 14 d and 15 c , 15 d are vertically, that is, in a condition corresponding to the optical axis of the objective lens 11. The front surfaces of the arm members 14 and 15 are secured to opposite side portions of the rear surface of the bobbin 12 whereby the bobbin 12 is supported by the yoke 13. Also, flexible printed connected strips 19 and 20 on which a predetermined number of wiring patterns are printed are connected to the opposite side portions of the bobbin 12 as power supply leads. The flexible printed connection strips 19 and 20 are fixed to the yoke 13 on the upper edge of the rear wall portion 13 b and lead out to the outside after being twisted through 90°. Such distortion given to the flexible printed connection strips 19 and 20 removes directional bias. Thus, it can be avoided that the bobbin 12 tends to move readily in a particular direction but is prevented from moving in the direction perpendicular to the readily movable direction due to the elasticity of the flexible printed connection strips, as will be later referred to. The objective lens driving apparatus of this embodiment constructed as described above generates a driving force which moves the bobbin 12 in the upward or downward direction, that is, in the direction parallel to the optical axis of the objective lens 11 attached to the bobbin 12 (focus direction) by interaction of the magnetic flux from the magnets 18 forming the magnetic circuit and the magnetic flux generated from the driving coil 16 wound around the bobbin 12 for the focusing control when the driving coil 16 is supplied with a driving current through the flexible printed connection strips 19 and 20 as power supply leads. The arm members 14 and 15 supporting the bobbin 12 to the yoke 13, as described above, are bent and swung by upward and downward parallel movements of the upper and lower parallel links 14 c , 14 d and 15 c , 15 d at the flexible portions thereof, whereby the bobbin 12 is displaced in parallel in the upward or downward direction, and consequently the objective lens 11 is moved in the focusing direction. In this event, the flexible printed connection strips 19 and 20 flexibly move with a telescopic elasticity of the distorted portions thereof in the horizontal plane, whereby the bobbin 12 can be displaced without any trouble. When the driving coil 17 for tracking control is supplied with driving current through the flexible printed connection strips 19 and 20, a driving force which moves the bobbin 12 in the lateral direction, that is, the direction perpendicular to the optical axis of the objective lens 11 (tracking direction) is generated by the interaction of the magnetic flux generated from the driving coil 17 and the magnetic flux from the magnets 18. Then, the arm members 14 and 15 supporting the bobbin 12 to the yoke 13 are bent and swung in the leftward or rightward direction at the front and rear hinge portions 14 a , 14 b and 15 a , 15 b thereby to displace the bobbin 12 in the lateral direction or in the leftward or rightward direction. The lateral displacement of the bobbin 12 will be evenly effected because the bobbin 12 and the yoke 13 are connected by the arm members 14 and 15 to form a parallelogram, that is, a third horizontal link as a whole, whereby the objective lens 11 is moved in the tracking direction. In this event, the flexible printed connection strips 19 and 20 are flexibly moved by a telescopic elasticity of the distorted portions thereof in their vertical portions, thus allowing the bobbin 12 to move without any trouble. A second embodiment of optical pickup will now be explained with reference to Fig. 4. In a second embodiment the objective lens 11 and an optical pickup unit 21 are incorporated in a bobbin 22. Detailed explanation on parts in common with those in the first embodiment will be omitted. The bobbin 22 of the second embodiment is made of heat-durable and highly rigid synthetic resin such as ABS resin or the like and formed in a housing shape. On the upper surface thereof, there is supported the objective lens 11 with its optical axis directed in the vertical direction. The bobbin 22 includes therein the optical pickup unit 21 which has a semiconductor laser as a light source, a beam splitter and a reflecting mirror for introducing a light beam from the semiconductor laser to the objective lens 11, a photo detector for detecting a returning beam reflected by an optical disc through the beam splitter and other components. A yoke 23 of the second embodiment is formed by a first yoke member 23 a and a second yoke member 23 b , each formed substantially in a "U" shape, and angularly adjustably connected to each other at their opposite ends to form a quadrilateral frame. The first and second yoke members 23 a and 23 b respectively have inner yoke portions 23 a ₁ and 23 b ₁ inwardly protruded within the yoke members 23 a and 23 b . The magnets 18 are secured to the inner surfaces of the front and rear walls of the yoke 23, that is, the inner surfaces of the first and second yoke members 23 a and 23 b which constitute a magnetic circuit with the yoke 23. Opposite the magnets 18 are disposed the driving coil 16 for focusing control and the driving coil 17 for tracking control which are wound on the bobbin 22. Next, the construction of the yoke 23 utilised in the present embodiment will be explained with reference to Fig. 5. As described above, the yoke 23 is formed by the first and second yoke members 23 a and 23 b which are clamped at their opposite end portions by clamping means, with the second yoke member 23 b being fitted inside the first yoke member 23 a , to form a quadrilateral frame, A vertically elongate guide slot 30 is formed in one end portion of the first yoke member 23 a as a connecting portion. A vertically elongate angle adjusting slot 31 is also formed in said one end portion of the yoke member 23 a at a predetermined distance from the guide slot 30. A dowel 34 projects from the inner surface of the other end portion of the yoke member 23 a . On the other hand, a screw threaded bore 35 is formed in one end portion of the second yoke member 23 b corresponding to the guide slot 30 of the first yoke member 23 a . A dowel 32 is protrusively formed corresponding to the angle adjusting slot 31 on the outer surface of said one end forwardly of the screw threaded bore 35, that is, at a location nearer the end of the yoke member 23 b . A reference bore 33 for angle adjustment is bored through the other end portion of the yoke member 23 b corresponding to the dowel 34 of the first yoke member 23 a . To couple the first yoke member 23 a with the second yoke member 23 b , the end portions of the first yoke member 23 a are fitted to the respective end portions of the second yoke member 23 b , with the dowel 32 engaged with the angle adjusting slot 31 and the dowel 34 engaged with the angle adjusting reference bore 33 thereby to effect preliminary coupling of the first and second yoke members 23 a and 23 b with each other. In this condition, a fixing screw 29 is screwed into the screw bore 35 of the second yoke member 23 b through the guide slot 30 of the first yoke member 23 a and a washer 37, if necessary, whereby the yoke members 23 a and 23 b are fastened to each other and also connected magnetically to form the yoke 23. As shown in Fig. 4, the yoke 23 thus constructed is provided on the front surface of the first yoke member 23 a with a guide shaft holder 24 which is penetrated by a guide shaft 25 serving as a reference axis for movement. Further, on the rear surface of the second yoke member 23 b a level determining pin 27 is protrusively provided through a fixing block 26, the level determining pin 27 being in contact with the upper surface of a level determining base 28. Then, the bobbin 22 is supported on the yoke 23 by the arm members 14 and 15 in a manner such that both driving coils 16 and 17 are disposed between the magnets 18 and the inner yoke portions 23 a ₁ and 23 b ₁. The arm members 14 and 15, which respectively have hinge portions and parallel links, each have their rear face fixed to the rear side of the yoke 23, i.e. the second yoke member 23 b and their front end face fixed to the bobbin 22. In Fig. 4, the reference numeral 36 designates a flexible printed connection strap as a leader for power supply which is led out from the yoke 23. Also in the second embodiment constructed as described above, in the same manner as in the first embodiment, when the driving coil 16 for focusing control and the driving coil 17 for tracking control are supplied with a driving current, the bobbin 22 is moved respectively in the direction parallel to the optical axis of the objective lens 11 and in the direction perpendicular to the optical axis by the swinging movement of the parallel links and the hinge portions of the arm members 14 and 15 thereby to displace the objective lens 11 for focus and tracking controls. In the optical pickup apparatus constructed and operating as described above, it is necessary to correct the inclination of the optical system, i.e. the objective lens 11 and optical pickup unit 21, with respect to the recording medium or optical disc. Such correction is effected, in the second embodiment, about the guide shaft 25 which serves as a movement reference axis maintaining a positional relationship with the optical disc and the level determining base 28. Specifically, the guide shaft holder 24 attached to the first yoke member 23 a is penetrated by the guide shaft 25, which limits the overall optical pickup apparatus to have rotating freedom only in the sending direction and the direction around the guiding shaft 25. On the other hand, the level determining pin 27 protrusively provided on the second yoke member 23 b of the yoke 23 makes contact with the level determining base 28 to limit the freedom only in the sending direction, whereby the attitude of the optical pickup apparatus is determined. In this event, the inclination of the optical system, including the objective lens 11, is corrected with respect to the guide shaft 25 and the level determining base 28. The abovementioned correction of the inclination of the optical system, including the objective lens 11, is effected in two directions ϑ and  as shown in Figs. 6 and 7. Referring first to Fig. 6, the correction in the direction ϑ is effected as follows: In a condition that the fastening screw 29 for fastening the first and second yoke members 23 a and 23 b of the yoke 23 is loose, the position of the dowel 32 of the second yoke member 23 b is changed with respect to the angle adjusting slot of the first yoke member 23 a to form an angle in the direction ϑ, whereby the bobbin 22 supported by the second yoke member 23 b through the arm members 14 and 15 is inclined. In other words, the optical system including the objective lens 11 is inclined with respect to the guide shaft 25. As a result, the junction plane between the first and second yoke members 23 a and 23 b is displaced form the parallel plane by the angle ϑ, however, such displacement is absorbed by the elasticity of the construction material. On the other hand, the correction in the direction  as shown in Fig. 7 is effected by rotating the second yoke member 23 b with respect to the first yoke member 23 a about a rotating axis extending from the engaged position of the angle adjusting slot 31 and the dowel 32 to the engaged position of the dowel 34 and the angle adjusting reference bore 33 of the first and second yoke members 23 a and 23 b , without changing the engaged position (level) of the angle adjusting slot 31 and the dowel 32 as is effected for positioning in the direction ϑ as described above. By this manipulation, the optical system including the objective lens 11 can be inclined in the direction . After the optical system, particularly the objective lens 11, has been appropriately corrected, the fastening screw 29 is tightened to fix the optical system in the correct position. In other words, the optical system correcting mechanism is locked. As described above, the present embodiment can correct the inclination of the optical system including the objective lends 11 by adjusting the angle between the first and second yoke members 23 a and 23 b of the yoke 23. Figs. 8 - 10 show further examples of the arm members. Also for these examples, only one of the arm members will be explained. An arm member 44 shown in Figs. 8A to 8C has the positional relationship between a pair of hinge portions 44 a and 44 b and flexible portions of parallel links 44 c and 44 d opposite to that of the arm member 14. Specifically, the parallel links 44 c and 44 d have flexible portions 44 c ₁, 44 c ₂ and 44 d ₁ and 44 d ₂ at the opposite ends thereof formed closely adjacent the ends of the arm member 44, with the pair of hinge portions 44 a and 44 b formed further towards the middle of the arm member 44. The arm member 44 thus constructed is provided with its parallel links 44 c and 44 d longer than those of the foregoing example, so that the recovery force of the objective lens 11 is reduced in the focusing control operation, thereby making it possible to increase the extent of movement of the bobbin as a movable body relative to a voltage applied to the driving coil for focusing control, with the result that the movable area of the objective lens for focusing control can be extended. An arm member 54 shown in Figs. 9A and 9C has a pair of hinge portions 54 a and 54 b formed as a parallel link structure. More specifically, the hinge portions 54 a and 54 b are formed as flexible portions 54 a ₁, 54 a ₂ and 54 b ₁, 54 b ₂ cut in the sides of the front and rear end portions of an opening 54 e extending in the lengthwise direction through the top and bottom planes of the arm member 54. Parallel links 54 c and 54 d have flexible portions 54 c ₁, 54 c ₂ and 54 d ₁, 54 d ₂ formed in the end portions thereof, in the same manner as the aforementioned example. However, the parallel links of the present example are reduced to rod-like shape because of the opening 54 e formed through the parallel link planes. The arm member 54 thus constructed is advantageous in that each of the arm members on both sides can individually move when the bobbin is moved in the horizontal direction, i.e. in the tracking control operation of the objective lens. An arm member 64 shown in Figs. 10A to 10 C has flexible portions of hinge portions 64 a and 64 b and parallel links 64 c and 64 d disposed in a positional relationship opposite to that of the arm member 54 shown in Fig. 9. Specifically, flexible portions 64 c ₁, 64 c ₂ and 64 d ₁, 64 d ₂ at the sides of the parallel links 64 c and 64 d are formed at the end portions of the arm member 64, while parallel link-like flexible portions 64 a ₁, 64 a ₂ and 64 b ₁, 64 b ₂ serving as the hinge portions 64 a and 64 b are formed at inside portions of the arm member 64. Since the arm member 64 has the parallel links 64 c and 64 d longer than those of the foregoing examples, the recovery force of the objective lens is reduced in the focusing control operation, thereby making it possible to increase the moving amount of the bobbin as a movable body with respect to a voltage applied to the driving coil for focusing control, with the result that the movable area of the objective lens for the focusing control can be extended. The arm members of the respective examples constructed as described above can be integrally moulded of synthetic resin. The hinge portions and parallel links can have their vibration characteristics in the respective moving directions, that is, the tracking direction and the focusing direction individually set to support the objective lens with high accuracy by changing the thickness of the flexible portions thereof. In the above-described embodiments, each of the objective lens 11 and the optical pickup unit 21 is attached to the bobbin 22. However, the invention can be applied to a construction in which only the objective lens 11 is attached to the bobbin 22. Also, members for supporting the bobbin 22 to the yoke 23 can be replaced by other alternatives. The inclination of the optical system including the objective lens can be corrected by angularly adjusting the frame which supports the movable body to which the optical system is attached with respect to the reference member, so that the correcting operation is easily effected. Further, since the correcting mechanism is disposed at the side of the optical system, it does not require spacing in the vertical or height direction, whereby the optical pickup apparatus can be made relatively thin and accordingly the whole optical disc recording/reproducing apparatus can be reduced in thickness. The movable body supporting the objective lens is supported to the frame by first and second supporting members each having a pair of hinge portions and first and second parallel links coupling the two hinge portions, so that movements of the movable body in the direction parallel to the optical axis of the objective lens and in the direction perpendicular to the optical axis are individually made by different flexible actions of the respective supporting members, whereby the torsional rigidity and inclination accuracy are maintained, with the result that the objective lens can be always precisely driven with stability. Also, since the movement of the movable body in the direction perpendicular to the optical axis of the objective lens is made by the parallel link mechanism, the movable body has a large freedom in shape so that the optical pickup apparatus can be reduced in thickness, and also the vibration characteristics can be set individually in the respective directions, thereby making it possible to extend the setting range and accordingly increase the freedom of design of the whole apparatus.

Claims: Objective lens driving apparatus comprising: a movable body (12) mounting an objective lens (11); a supporting arm (14, 15, 44, 54, 64) mounting the movable body (12) and including a hinge portion (14 a , 14 b , 15 a , 15 b , 44 a , 44 b , 54 a , 54 b , 64 a , 64 b ) and first and second parallel links (14 c , 14 d , 15 c , 15 d , 44 c , 44 d , 54 c , 54 d , 64 c , 64 d ), a frame (13, 23) to which the supporting arm is attached and electro-magnetic driving means (16, 17, 18) to drive the objective lens in a direction parallel to the optical axis of the objective lens and in a direction perpendicular to the optical axis; characterised in that the supporting arm comprises first and second supporting arm members (14, 15, 44, 54, 64) each having a pair of hinge portions (14 a , 14 b , 15 a , 15 b , 44 a , 44 b , 54 a , 54 b , 64 a , 64 b ); the first and second parallel links (14 c , 14 d , 15 c , 15 d , 44 c , 44 d , 54 c , 54 d , 64 c , 64 d ) are provided on each of the first and second supporting arms and couple the respective pair of hinge portions; and the objective lens (11) is movable in a direction parallel to the optical axis of the objective lens (11) by the respective parallel links (14 c , 14 d , 15 c , 15 d , 44 c , 44 d , 54 c , 54 d , 64 c , 64 d ) of the first and second supporting arm members and is movable in the direction perpendicular to the optical axis of the objective lens by a parallelogram linkage formed by the movable body (12), a part of the frame (13, 23) and the first and second supporting arm members (14, 15, 44, 54, 64). Objective lens driving apparatus according to claim 1, wherein the first and second supporting arm members are constructed such that supporting portions formed respectively at one end thereof to support the movable body (12) and attaching portions formed respectively at the other end thereof to be attached to the frame (13, 23) are coupled by the first and second parallel links (14 c , 15 c , etc) and the pair of hinge portions (14 a , 14 b , etc). Objective lens driving apparatus according to claim 2, wherein the pair of hinge portions (14 a , 14 b , etc) are formed such that the bending direction thereof is arranged in the direction perpendicular to the optical axis of the objective lens (11). Objective lens driving apparatus according to claim 3, wherein the first and second parallel links (14 c , 14 d , etc) are formed between the pair of hinge portions (14 a , 14 b , etc) and in the direction perpendicular to the bending direction of the hinge portions (14 a , 14 b , etc) and are provided at both ends thereof with flexible portions (14 c ₁, 14 c ₂, 14 d ₁, 14 d ₂, 15 c ₁, 15 c ₂, 15 d ₁, 15 d ₂, 44 c ₁, 44 c ₂, 44 d ₁, 44 d ₂, 54 c ₁, 54 c ₂, 54 d ₁, 54 d₂ , 64 c ₁, 64 c ₂, 64 d ₁, 64 d ₂) which enable the objective lens (11) to swing in the direction parallel to the optical axis. Objective lens driving apparatus according to claim 3, wherein the first and second supporting arm members (44, 54, 64) are provided, adjacent the ends of the first and second parallel links (44 c , 44 d , 54 c , 54 d , 64 c , 64 d ) with flexible portions (44 c ₁, 44 d ₁ etc) which enable the objective lens to swing in the direction parallel to the optical axis, and the pair of hinge portions (44 a , 44 b etc) are located inwardly of the flexible portions (44 c , 44 d etc). Objective lens driving apparatus according to claim 3, wherein the pair of hinge portions (54 a , 54 b , 64 a , 64 b ) are constituted by a pair of parallel links. Objective lens driving apparatus according to claim 6, wherein an opening (54 e ) formed through the upper and lower planes of the pair of parallel links constituting the hinge portions is provided at both ends thereof with a pair of flexible portions (54 a ₁, 54 a ₂, 54 b ₁, 54 b ₂, 64 a ₁, 64 a ₂, 64 b ₁, 64 b ₂) so as to enable the objective lens (11) to swing in the direction perpendicular to the optical axis, and an opening formed in a central portion of the first and second parallel links is provided at both ends thereof with a pair of flexible portions (54 c ₁, 54 c ₂, 54 d ₁, 54 d ₂, 64 c ₁, 64 c ₂, 64 d ₁, 64 d ₂) so as to enable the objective lens (11) to swing in the direction parallel to the optical axis of the objective lens. Objective lens driving apparatus according to claim 7, wherein the flexible portions (54 c ₁, 54 c ₂) of the first and second parallel links are located inwardly of the flexible portions (54 a ₁, 54 a ₂, etc) of the hinge portions. Objective lens driving apparatus according to claim 7, wherein the flexible portions (64 c ₁, 64 c ₂, etc) of the first and second parallel links are located outwardly of the flexible portions (64 a ₁, 64 a ₂) of the hinge portions. Objective lens driving apparatus according to claim 1, wherein the first and second supporting arm members (14, 15, 44, 54, 64) are integrally moulded of flexible synthetic resin. Objective lens driving apparatus according to claim 1, wherein the frame (23) is formed by coupling first and second frame members (23 a , 23 b ) each formed substantially in a "U" shape. Objective lens driving apparatus according to claim 11, wherein the first and second frame members (23 a , 23 b ) have an angle adjusting mechanism for adjusting an angle of one of the first and second frame members with respect to the other. Objective lens driving apparatus according to claim 12, wherein the angle adjusting mechanism comprises a slot (30, 31) for adjustment provided through one of the frame members (23 a ) and a protrusion (29, 32) provided on the other of the frame members (23 b ) at a location corresponding to the slot (30, 31) for adjustment. Objective lens driving apparatus according to claim 12, wherein the angle adjusting mechanism can adjust the inclination of the optical axis of the objective lens (11). Objective lens driving apparatus according to any one of claims 1 to 14, in which the movable body (12) mounts, in addition to the objective lens (11), a laser light source, optical parts to introduce a light beam from the laser light source to the objective lens (11) and a light receiving element to receive the light beam which passes through the objective lens and the optical parts.

Inventors: MITSUMORI KOJI, MITSUMORI, KOJI
Applicants: SONY CORP, SONY CORPORATION
Application year: 1989
Main classification: G11B7
IPC codes: G11B7