JP2005292512A - Lens driving apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lens driving apparatus whose constitution is simplified so that the miniaturization of the apparatus can be attained, and with which a zooming ratio is switched to a plurality of ratios, and an optical zooming operation is facilitated, and which is suitable for a subminiature camera. <P>SOLUTION: A front lens group 1 and a rear lens group 2 are arranged before and behind on an optical path L, and a driving means for roughly adjusting and positioning the front lens group 1 is connected to the front lens group 1 so that the lens 1 may move and stop in three regular positions, and a driving means for finely adjusting and positioning the rear lens group 2 is connected to the rear lens group 2 so that the lens 2 may continuously move. The front and rear lens groups 1 and 2 are mounted and supported in a cylindrical frame body in the same way, and an imaging element 3 is arranged behind the rear lens group 2. Regarding the zooming operation of the lens constituted with the combination of two front and rear lens groups, the operation (property f) of moving and stopping the front lens group 1 in three regular positions is performed, then, the zooming ratio accompanying the linear movement (property b) of the rear lens group 2 becomes six values. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a lens driving device that moves a lens to perform optical zoom and focusing operations. More specifically, the present invention relates to an improvement in driving operation in a simplified lens configuration for application to a micro camera. About.

  In recent years, mobile phones incorporating ultra-small cameras have become widespread. This ultra-compact camera for built-in use is often of a fixed-focus type for a low-priced model or the like due to severe restrictions on dimensions and shape. However, there is a demand for higher functionality as a development demand for portable terminals such as mobile phones, and one of them is an optical zoom function that is generally employed in digital still cameras and the like.

  In the operation of the optical zoom, a desired zoom is obtained by appropriately moving the two front and rear lens groups in the optical axis direction, and focusing is performed according to the zoom.

As a specific mechanism, for example, as shown in Patent Document 1, there is a mechanism in which two front and rear lenses are moved by independent actuators (stepping motors). In another method, as shown in Patent Document 2, the positional relationship between the front and rear lenses (lens group) is controlled by using a cam for one actuator or motor, and two movements of zoom and focus are performed. Is to be realized.
Japanese Patent Laid-Open No. 7-336938 JP-A-11-52209

  However, such a conventional lens driving device has the following problems. First, since the invention disclosed in Patent Document 1 has a configuration in which a drive system is provided for each lens, the structure is complicated, and advanced data processing and control using a sensor such as a feedback circuit is required. For this reason, the number of man-hours for development and design increases, and the number of parts also increases, resulting in an increase in cost, and there is a problem that power consumption is increased and the size is increased.

  In addition, the invention disclosed in Patent Document 2 is a configuration using a cam, and the movement of a lens related to optical zoom becomes complicated, and a nonlinear curve including reciprocation as well as movement in one direction is drawn. A cam or guide having a plurality of different curves is required to make the nonlinear movement. This complicates the movement and structure of the cam mechanism. In addition, since the behavior pattern of the lens is designed according to the specifications of the lens system, there is a problem that a cam must be developed every time the specification of the lens system is changed.

  In particular, in an ultra-small camera that is embedded in a cellular phone or the like, the lens has an optically effective diameter of 7 mm or less, preferably 5 mm or less. Undesirable, the structure is simple, but the behavior of the lens is required to be reliably positioned and inexpensive.

  SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems, and its object is to simplify the structure, reduce the size of the apparatus, switch the zoom magnification to a plurality, and easily operate the optical zoom. An object of the present invention is to provide a lens driving device that is preferably applied to a camera.

  In order to achieve the above object, a lens driving device according to the present invention includes a lens in a lens unit having an optical zoom function for a microminiature camera using a plurality of lens groups having an optically effective lens diameter of 7 mm or less. A lens driving device for moving, having two movable lens groups, the lens group being mounted on a cylindrical lens frame, and a first lens frame and a second lens frame Is arranged on the optical axis, the second lens frame side faces the image sensor, and driving means are linked to the first and second lens frames, respectively, and one driving means is positioned for coarse adjustment. The other driving means is configured to perform driving for fine adjustment positioning.

  The drive means may be configured to use a linear actuator as a drive source for coarse adjustment positioning, and move to a plurality of fixed positions to hold the stop. Further, in the two drive means linked to the first and second lens frame bodies, the first drive means uses a linear actuator as a drive source for coarse adjustment positioning, and moves to at least 2 to 9 fixed positions. The second drive means uses a stepping motor as a drive source for fine adjustment positioning, and converts the rotation operation of the stepping motor into a linear operation. The second lens frame may be linked to the second lens frame.

  With such a configuration, the present invention adopts a configuration in which driving means is linked to each of the first and second lens frame bodies, but one of the two driving means is configured to perform driving for coarse adjustment positioning. The structure can be simplified and the structure can be simplified as a whole. At this time, since one of the lens frames is positioned for coarse adjustment, the zoom magnification is changed in steps. However, in the vicinity of each zoom magnification, the other of the lens frames is positioned for fine adjustment. , Focus can be obtained properly.

  In addition, since the drive means for driving for coarse adjustment positioning uses a linear actuator as a drive source, unlike a motor drive, there is no need for a rotation / linear motion conversion mechanism, and the drive can be driven directly. Be simple.

  In the configuration in which the first driving means linked to the first lens frame performs coarse adjustment positioning by the linear actuator, and the second driving means linked to the second lens frame performs fine adjustment positioning by the stepping motor. Since the coarse adjustment positioning by the first driving means is at least 2 to 9 fixed positions, the zoom magnification can be switched to a maximum of 4 to 18 steps because it is an optical system with two front and rear lenses, and the second Since fine adjustment positioning is performed in the driving means, the focusing operation can be performed appropriately.

  In the lens driving device according to the present invention, since one of the two driving means is configured to perform driving for coarse adjustment positioning, the structure thereof can be simplified, and the overall configuration is configured. Can be simplified. As a result, the apparatus can be miniaturized, which is advantageous in terms of cost.

  Then, since one of the lens frames is positioned for coarse adjustment, the zoom magnification is changed in stages, but in the vicinity of each zoom magnification, the other of the lens frames is positioned for fine adjustment. Focus can be obtained properly. Therefore, the operation of the optical zoom is easy, the function of the optical zoom can be realized with a simple configuration, the imaging function can be multi-functionalized, and can be preferably applied to a micro camera.

  FIG. 1A is a side view for explaining the concept of zoom operation in the present invention, and FIG. 1B is a characteristic diagram showing the positional relationship between two lens groups. In the lens driving device according to the present invention, a front group lens 1 and a rear group lens 2 are arranged before and after the optical axis L, and the front group lens 1 is linked with a plurality of driving means for driving for coarse adjustment positioning. The rear lens 2 is connected to a driving means for driving for fine adjustment positioning so as to perform a continuous movement operation.

  Similarly, the front and rear group lenses 1 and 2 have a configuration in which a lens group is fitted and supported in a cylindrical frame, and each lens group has a diameter of about 5 mm. In order to function as a lens unit of a microminiature camera, an image pickup device 3 such as a CCD is disposed on the back side of the rear group lens 2. Therefore, in the image pickup device 3, the magnification of image formation changes according to the positional relationship of the three optical elements aligned with the optical axis L, and this zoom magnification generally has characteristics as shown in FIG. That is, in the front and rear lens configuration, the zoom operation is performed by moving the front group lens 1 to the characteristic f that is moved back and forth such that the front group lens 1 is once moved to the image pickup device 3 side and then returned to the subject side. No. 2 is moved to a characteristic b that is linearly moved toward the object side, whereby the zoom magnification is appropriately obtained from wide angle (WIDE) to telephoto (TELE).

  Here, the driving means of the front lens group 1 adopts a configuration in which it moves to and stops at three fixed positions, and performs driving for coarse adjustment positioning. Therefore, by moving the front group lens 1 to the characteristic f, the lens group moves reciprocally with respect to the optical axis L. Therefore, when the rear group lens 2 moves linearly with respect to one fixed position, the zoom magnification becomes binary, At the three fixed positions, the zoom magnification accompanying the movement of the rear lens group 2 becomes 6 values.

  That is, as shown in FIG. 1B, it is possible to realize a lens driving device having zoom magnifications in six steps from 1 to A, B, C, D, and E times. In this case, the driving means for the front lens group 1 is only required to be able to move and stop to a plurality of (three) fixed positions and perform coarse adjustment positioning, so that it can be realized with a simplified structure and the structure is simplified. Therefore, the size can be reduced.

  A more specific configuration for realizing the above operation principle will be described. FIG. 2 shows a first embodiment of the present invention, in which a linear actuator is used as the driving means for the front group lens, and a stepping motor is used as the driving means for the rear group lens.

  In this lens driving device, the planar rectangular base 10 has a high step portion 11 in which a region of about ¼ including one corner portion is raised by one step on the front surface, and a low step portion in the remaining region. 12 is formed. And the small diameter hole part 13 is provided in three places of the four corners of the high step part 11, and the large diameter through-hole 14 is formed in the center. The center of the through hole 14 is the optical axis L, and although not shown, an image sensor such as a CCD is disposed at a predetermined position on the back side of the through hole 14.

  A small stepping motor 20 is installed on the upper surface of the low step portion 12. This stepping motor 20 has a case body 21 that is curved in a substantially arc shape so as to follow the planar shape of the low step portion 12, and an output shaft 22 that protrudes to the outside is provided at the center thereof. Although not shown in the figure, the rotor is arranged in the center, and the output shaft 22 is integrated by being inserted into the center of the rotor. And a stator is arrange | positioned in the both sides which spread in the left and right in the case main body 21. FIG. The tip of the output shaft 22 is threaded to form a lead screw.

  One end of each guide pin 15 is inserted and fixed in each hole 13 provided in the high step portion 11. The rear group lens frame 30 is movably inserted into the guide pin 15. The rear group lens frame 30 has a planar shape substantially the same as that of the base 10, has a guide hole 31 that penetrates at a position facing the hole 13 of the base 10, and a position facing the through hole 14 of the base 10. A through-hole 32 is provided in the front. Then, the guide pin 15 is inserted into the guide hole 31 and arranged, so that the rear group lens frame 30 supported by the three guide pins 15 can move back and forth along the guide pin 15 in a stable posture. Become. Further, a rear lens group (which may be one lens) is mounted in the through hole 32, although not shown. Therefore, as the rear lens group frame 30 moves back and forth, the rear lens group also moves back and forth. Further, when the rear lens group frame 30 is mounted on the guide pin 15, the stepping motor 20 is sandwiched between the base 10.

  A through hole 34 is formed in the portion of the rear group lens frame 30 that faces the output shaft 22 of the stepping motor 20, and a rectangular shape is formed around the through hole 34 on the front side of the rear group lens frame 30. A recess 35 is formed. A lead nut 36 is inserted and fixed in the recess 35. The lead nut 36 meshes with a lead screw provided on the output shaft 22 of the stepping motor 20, and the lead nut 36, that is, the rear group lens frame 30 moves back and forth as the output shaft 22 rotates forward and backward.

  A front lens portion 40 that supports the front group lens is attached to the tip of each guide pin 15. As will be described later, the front lens portion 40 has a driving means inside, and a through hole 41 is provided at a position facing the central portion, that is, the through holes 14 and 32 provided in the base 10 and the rear lens group frame 30. The front lens group disposed in the through hole 41 is moved in the optical axis L direction. That is, in the front group lens, as shown in FIG. 3, the front lens group 46 is attached to a cylindrical front group lens frame 45, and the structure constituting the driving means is arranged outside the front group lens frame 45. The front group lens frame 45 is supported so as to be movable in the direction of the optical axis L, and is moved by a drive means that moves linearly.

  The drive means has a configuration in which a linear actuator combining a permanent magnet 5, a coil (61, 62) and a yoke 7 is used as a drive source, and is moved to three fixed positions in the direction of the optical axis L so as to hold the stop. It has become.

  The permanent magnet 5 is formed in an annular shape and is fixed to the outer periphery of the front lens group frame 45. The annular yokes 75 and 75 are overlapped on the front and back of the permanent magnet 5 to make the whole movable. Magnetization of the permanent magnet 5 forms magnetic poles in the direction facing the front and back yokes 75, 75, that is, the direction along the optical axis L. By providing yokes 75, 75 on the front and back of the permanent magnet 5, the magnetic efficiency is increased. Therefore, it is possible to reduce the size of the permanent magnet 5 that forms the movable part, and contribute to the downsizing of the entire apparatus.

  A cylindrical coil is arranged concentrically on the outside of the permanent magnet 5 so as to face each other. Here, two coils, a first coil 61 and a second coil 62, are arranged side by side, and the yoke 7 is composed of a plurality of members that are positioned so as to surround the outer sides of the coils 61, 62, and the front lens unit. Assemble inside 40.

  The front lens portion 40 has a through hole 41 at a predetermined position, and the peripheral edge of the through hole 41 protrudes to the outer yokes 71 and 71 located at both ends of the coils 61 and 62, that is, the inner side. Is a stopper 42 that contacts the movable part.

  A central pole tooth 76 facing the permanent magnet 5 is formed on the central yoke sandwiched between the two coils 61 and 62, and the length of the facing part of the central pole tooth 76, that is, the length along the optical axis L (fixed) The side pole teeth) are set with respect to the length of the permanent magnet 5 and the total length (movable part side pole teeth) including the front and back yokes 75, 75 of the permanent magnet 5 and the optical axis L of the center pole tooth 76. Similarly, the interval between the pole teeth from the end in the direction to the outer yoke 71 is also set to a predetermined value.

  Therefore, as a drive system for moving the front lens group frame 45, when the permanent magnet 5 faces a predetermined gap with respect to the coils 61 and 62 having the yoke 7, a current is passed through the coils 61 and 62. A linear motion is performed by the generated force, and the permanent magnet 5 side, that is, the movable portion side can be moved. As shown in FIGS. 3 (a), (b), and (c), it is moved to three fixed positions. The stop can be held. In other words, by appropriately controlling the energization of the coils 61 and 62, the movable portion (permanent magnet 5) faces the central pole tooth 76 at the central position (a), and the movable portion (one yoke 75) stops on one side. The position (b) of one end that stops in contact with the portion 42 and the position (c) of the other end where the movable portion (the other yoke 75) stops in contact with the other stopper 42 can be moved to three fixed positions, Since the magnetic flux of the permanent magnet 5 is coupled to the fixed side yoke 7 at each of these positions, the stop can be maintained. In the figure, the center of the fixed side yoke 7 is T-shaped, but its shape is arbitrary such as I-type and L-type.

  Each guide pin 15 is provided with a spacer 43 for fine adjustment of the movable range. By adjusting the thickness of the spacer 43, the rear lens group is a predetermined amount from the fixed position F shown in FIG. 1 in a state where the front lens unit 40 and the rear group lens frame 30 are in contact with each other through the spacer 43. The position is close to the front lens group 46 side. Of course, at this time, the length of the guide pin 15 is adjusted so that the position of the front lens group 46 can take the three fixed positions shown in FIG. In the state where the output shaft 22 of the stepping motor 20 is reversely rotated and the rear group lens frame 30 is most retracted, the rear lens group approaches the image sensor 3 side by a predetermined amount from the fixed position R shown in FIG. It is set to take the position.

  The driving of the stepping motor 20 can accurately position the movement position of the rear lens group frame 30 according to the number of steps. Then, the rear group lens frame 30 is retracted by rotating the output shaft 22 in the reverse direction, and stops at a fixed position R approaching the front surface of the base 10 as shown in FIG. When the group lens frame 45 is at a fixed position approaching the subject as shown in FIG. 3B, the zoom magnification is set to 1 with this as the basic posture. By rotating the output shaft 22 forward from this state, the rear group lens frame 30 is moved forward, stopped at a fixed position F approaching the spacer 43 as shown in FIG. When the lens frame 45 is at a fixed position approaching the subject as shown in FIG. 3B, the zoom magnification is set to E times here.

  As described above, in the present invention, the driving unit is linked to each of the front group lens frame 45 and the rear group lens frame 30, but one of the two driving units performs driving for coarse adjustment positioning. Therefore, there is an advantage that the structure can be simplified and the configuration can be simplified as a whole. At this time, since the front lens group frame 45 is positioned for coarse adjustment, that is, moved to three fixed positions, the zoom magnification is switched in stages. However, in the vicinity of each zoom magnification, the rear lens group frame 30 is positioned for fine adjustment, that is, an operation that moves continuously, so that the focus can be appropriately obtained.

  In other words, the drive means for driving for coarse adjustment positioning uses a linear actuator as a drive source, and therefore, unlike a motor drive, there is no need for a conversion mechanism for rotation or linear motion, and the drive can be directly driven. Be simple. As a result, the apparatus can be miniaturized, which is advantageous in terms of cost.

  In this case, since the coarse adjustment positioning by the first driving means linked to the front lens group frame 45 is set to three fixed positions, the zoom magnification can be switched between six stages because of the optical system with two front and rear lenses. And, since the fine adjustment positioning is performed in the second driving means linked to the rear lens group frame 30, the focus operation can be performed properly and the optical zoom operation is easy. Therefore, the function of the optical zoom can be realized with a simple configuration, the imaging function can be multi-functionalized, and can be preferably applied to a micro camera.

  The linear actuator as a drive source for driving the front lens group frame 45 includes coils 61 and 62 having a yoke 7 and a permanent magnet 5 and is a so-called electromagnetic type, so that the configuration is simple. , There is an advantage in cost reduction.

  In the lens driving device configured as described above, in an example of the size and shape, the base 10 is 11 mm square, and the inner diameters of the front lens group frame 45 and the through-hole 32, that is, the diameters of the front lens group 46 and the rear lens group. Is 5 mm, and the height of the entire apparatus (the distance from the bottom surface of the base 10 to the front surface of the front lens unit 40) is about 11 mm. As a result, the mobile phone can be sufficiently mounted.

  In consideration of the size and shape of the mobile phone, the area of the camera module is an outer size of 13 mm square or less even at a fixed focus. If it fits in this outer size, it can be made a little larger, and the outer size (planar shape of the base 10) can be suppressed to 13 mm square or less up to a lens diameter of about 7 mm. Of course, it does not prevent further downsizing by using a smaller lens.

  In the embodiment described above, the coarse adjustment positioning by the first driving means linked to the front lens group frame 45 is set to three fixed positions. However, the present invention is not limited to this, and for example, as shown in FIG. By configuring as described above, four fixed positions can be obtained. In other words, in this example, the linear actuator including the coil (61a, 62a) provided with the yoke 7 and the permanent magnet 5 is concentric with the optical axis L as a center, and many stages are connected in the optical axis L direction. The structure to be provided is adopted. Constituent elements similar to those of the above-described embodiment are denoted by the same reference numerals and description thereof is omitted.

  In each linear actuator, a yoke 7 surrounding the coil 61a or the coil 61b is assembled to the housing 40a or the housing 40b, and a portion covering the outer yoke 7 protrudes from the housings 40a and 40b. The overhanging portion serves as a stopper 42 that comes into contact with the movable portion, and the permanent magnet 5 side, that is, the movable portion stops against two opposing stoppers 42 and 42. That is, each linear actuator is configured to move at two fixed positions, and the movable portion (permanent magnet 5 or the like) of the outer linear actuator is assembled to the housing 40a of the inner linear actuator.

  Therefore, by driving the inner linear actuator, the permanent magnet 5 fixed to the front group lens frame 45 reciprocates in the housing 40a, and as shown in FIGS. 5 (a) and 5 (b), the A position and the B position. The two fixed positions can be moved. Further, by driving the outer linear actuator, the permanent magnet 5 attached to the housing 40a reciprocates in the housing 40b, so that the C position and the D position of 2 are obtained as shown in FIGS. 5 (c) and 5 (d). It can move about four fixed positions, and as a result, it can move about four fixed positions and can hold the stop at each position.

  Then, the two actuators shown in FIG. 5 are mounted on the front lens portion 40 that supports the front lens group. As a result, the zoom magnification becomes binary by appropriately controlling the linear movement of the rear group lens with respect to one fixed position of the front group lens. Therefore, the movement of the rear group lens is accompanied at four fixed positions. The zoom magnification becomes 8 values.

  Each linear actuator may be configured to be changed to that of the above-described embodiment. That is, the actuator may be replaced with a linear actuator that can move at three fixed positions. In this case, the maximum number of fixed positions that can be moved is nine, the zoom magnification is 18 values, and a more precise lens movement can be performed.

Further, by changing one of the two linear actuators shown in FIG. 5 to one that takes three fixed positions, the number of fixed positions can be set to six and the zoom magnification can be set to 12 values. Further, by providing one linear actuator shown in FIG. 5, it is possible to configure a simple coarse adjustment with two fixed positions and a zoom magnification of 4 values.
In the above-described embodiment, the front side is coarsely adjusted. However, the rear side may be coarsely adjusted.

  Furthermore, in the above-described embodiment, the lens is composed of two lens groups. However, the present invention is not limited to this, and can be composed of three or more lens groups. FIG. 6 shows an example in which three lens groups are used. The first lens group A is fixed, and the second and third lens groups B and C are moved. Then, one of the second and third lens groups B and C is driven for coarse adjustment positioning, and the other is driven for fine adjustment positioning. In FIG. 6, various modifications such as fixing the second lens group B or the third lens group C are possible.

FIG. 5A is a side view for explaining the concept of zoom operation in the present invention, and FIG. 5B is a characteristic diagram showing the positional relationship between two lens groups. It is a perspective view which decomposes | disassembles and shows the 1st Embodiment of this invention. 2 shows the configuration of the front lens unit in FIG. 2, and shows a state where the front lens group is moved to the center position (a), the front position (b), and the rear position (c), respectively. FIG. 3 is a cross-sectional view showing a state where the rear lens group is moved to a rear position (a) and a front position (b) in the movement operation of the rear group lens in FIG. 2. It is sectional drawing which shows the principal part of a modification. It is a conceptual diagram which shows a modification.

Explanation of symbols

1 Front lens group (first lens frame)
2 Rear lens group (second lens frame)
3 Image sensor 5 Permanent magnet 7 Yoke 10 Base 14, 32, 34, 41 Through hole 20 Stepping motor 22 Output shaft 30 Rear group lens frame (second lens frame)
31 Guide hole 36 Lead nut 40 Front lens portion 45 Front group lens frame (first lens frame)
46 Front lens group 61 First coil 62 Second coil L Optical axis

Claims (3)

A lens driving device for moving a lens in a lens unit having an optical zoom function for a micro camera using a plurality of lens groups having an optically effective lens diameter of 7 mm or less,
Having two movable lens groups,
The lens group is attached to a cylindrical lens frame, and the first lens frame and the second lens frame are arranged on the optical axis so that the second lens frame side faces the image sensor,
The first and second lens frames are linked to driving means, one driving means performs driving for coarse adjustment positioning, and the other driving means performs driving for fine adjustment positioning. A lens driving device.   2. The lens driving device according to claim 1, wherein the driving unit is configured to use a linear actuator as a driving source for coarse adjustment positioning, and move to a plurality of fixed positions to hold the stop. In two driving means linked to the first and second lens frame bodies,
The first drive means uses a linear actuator as a drive source for coarse adjustment positioning, moves to at least two to nine fixed positions, and holds the stop so as to be linked to the first lens frame,
2. The second driving means is characterized in that a stepping motor is used as a drive source for fine adjustment positioning, and the rotation operation of the stepping motor is linked to the second lens frame so as to convert it into a linear motion. The lens drive device described in 1.

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