JP2007078954A - Lens barrel and imaging apparatus equipped therewith - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lens barrel formed to be compact, efficiently moving an imaging lens and suitably incorporated in a personal digital assistant as a lens barrel constituted to move an imaging lens by using shape memory alloy. <P>SOLUTION: In the lens barrel having the imaging lens forming an image with subject light and a lens frame holding the imaging lens, and moving the lens frame in a prescribed direction by using the shape memory alloy formed like a string, a part of the shape memory alloy is arranged in the optical path of the imaging lens, and the shape memory alloy is energized and shrunk, whereby the lens frame is moved. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a lens barrel configured to move an imaging lens in an optical axis direction using a shape memory alloy formed in a string shape, and particularly suitable for a small and thin imaging device built in a portable terminal or the like. Related to the lens barrel.

  2. Description of the Related Art Conventionally, in a camera, when an imaging lens is focused or zoomed, a lens barrel is driven by a motor and a gear train connected to the motor to move the imaging lens. On the other hand, regarding the movement of the image pickup lens, there has been proposed a device that uses a shape memory alloy to move the image pickup lens instead of the motor and the gear train connected to the motor, thereby saving the camera space.

  As a driving device using this shape memory alloy, a string-shaped shape memory alloy and a detecting means for detecting the position of the driven body, and controlling the driving of the shape memory alloy based on the information of the detecting means, There has been disclosed a technique in which a string-like shape memory alloy is divided in the longitudinal direction and controlled individually to control the position of the driven body (for example, see Patent Document 1).

Further, a drive mechanism is disclosed in which a string-shaped shape memory alloy is used in a dogleg shape, abuts with a driven body at a substantially central portion, and both ends are fixed (see, for example, Patent Document 2).
Japanese Patent Laid-Open No. 10-307628 JP 2002-99019 A

  In recent years, small and thin imaging devices have been mounted on small and thin electronic devices such as mobile phones and PDAs, so that not only audio information but also image information can be transmitted to a remote place. It is possible.

  Accompanying the widespread use of these portable terminals, imaging devices built in portable terminals are also equipped with ones that have a macro function or ones that have an optical zoom by moving the imaging lens in order to obtain higher quality images. It is becoming.

However, the imaging device built in the portable terminal is required to be very small, for example, 1 cm ³ or less.

  In response to such a requirement, the device having the position detection means of the driven body described in Patent Document 1 has an advantage that the position control of the driven body is accurate. When applied, there is a drawback that the space for the detection means is required and the size is increased. In addition, there is a problem in that the one that is divided in the longitudinal direction and individually controlled has a complicated circuit configuration for control and that the shape memory alloy is linearly arranged and cannot be reduced in size.

  Furthermore, the use of the string-shaped shape memory alloy described in Patent Document 2 in the shape of a letter is not so problematic for incorporation in a large apparatus such as binoculars. However, some device is required to apply to a small-sized imaging device to be built in a portable terminal.

  In view of the above problems, the present invention provides a lens barrel configured to move an imaging lens in the optical axis direction using a shape memory alloy, can be formed in a small size, can move the imaging lens efficiently, and is incorporated in a portable terminal. It is an object of the present invention to propose a lens barrel suitable for the purpose and an imaging apparatus including the lens barrel.

  The above object is achieved by the following configuration.

  In a lens barrel that has an imaging lens that forms an image of subject light and a lens frame that holds the imaging lens, and that moves the lens frame in a predetermined direction using a shape memory alloy formed in a string shape, A lens barrel, wherein a part of the shape memory alloy is disposed in an optical path of the imaging lens, and the lens frame is moved by contracting the shape memory alloy by energization.

  According to the present invention, since the lens frame that holds the imaging lens is moved by the shape memory alloy disposed in the optical path of the imaging lens, the shape memory alloy can efficiently move the lens frame, and the size can be reduced. Since it can be configured, it is suitable for incorporation in a small and thin portable terminal or the like.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a lens barrel and an image pickup apparatus including the lens barrel according to the present invention will be described in detail with reference to the drawings.

  First, an example of a mobile phone as a mobile terminal equipped with an imaging device will be described with reference to the external view of FIG. 1A is a view of the folded mobile phone when viewed from the inside, and FIG. 1B is a view of the folded mobile phone when viewed from the outside.

  In FIG. 1, in the mobile phone T, an upper housing 71 as a case having display screens D <b> 1 and D <b> 2 and a lower housing 72 having operation buttons P are connected via a hinge 73. An imaging device S to be described later is incorporated below the display screen D2 in the upper casing 71, and the imaging lens L is exposed on the outer surface of the upper casing 71.

  The position of the imaging device S may be disposed above or on the side of the display screen D2 in the upper housing 71. Further, the mobile phone T is not limited to a folding type.

  Next, the imaging apparatus S and the lens barrel built in the imaging apparatus S will be described.

  2 is a perspective view of the imaging device, FIG. 3 is a top view of the lens barrel, FIG. 4 is a cross-sectional view taken along the line AA in FIG. 2, and FIG. FIG. 5 is a cross-sectional view taken along the line BB in FIG. 2, FIG. 5A is a diagram in a normal state, and FIG. 5B is a diagram in which the imaging lens is extended.

  In the imaging apparatus S shown in FIG. 2, each member of the internal lens barrel is held by the base plate 11, and a lid member 31 is fixed to the base plate 11 by a set screw or the like (not shown). The upper side and upper surface of the cylinder are covered. The lid member 31 is provided with an opening 31a so that the subject light can pass through the imaging lens L.

  A printed wiring board 32 on which the image sensor C is mounted is fixed to the lower surface of the ground plane 11, and flexible printed boards 33 and 34 are connected to the printed wiring board 32. The flexible printed circuit board 33 is provided with a plurality of contact portions 33a for connecting a power supply, a control signal, an image signal, a signal to a shape memory alloy, and the like on the back surface of the flexible printed circuit board 33. A plate 35 is attached.

  Next, the lens barrel will be described.

  The imaging lens L is composed of a single lens or a plurality of lenses, and forms an image of subject light on the imaging element C. The imaging lens L is held by the first lens frame 12, and the first lens frame 12 is screwed with the second lens frame 13. Accordingly, when the first lens frame 12 is rotated, the first lens frame 12, that is, the imaging lens L moves in the direction of the optical axis O with respect to the second lens frame 13. Adjustments can be made.

  In some cases, the first lens frame 12 and the second lens frame 13 may be integrated.

  A cylindrical portion 13 a having a through-hole parallel to the optical axis O of the imaging lens L is integrally formed on a side portion of the second lens frame 13, and a guide shaft 14 is implanted in the ground plane 11 in parallel with the optical axis O. The through hole of the cylindrical portion 13a is fitted to the guide shaft 14. The guide shaft 14 and the base plate 11 may be formed integrally.

  Further, a U-shaped engaging portion 13b is integrally formed on a side portion of the second lens frame 13 at a position opposite to the cylindrical portion 13a across the optical axis O, and the guide shaft 11a is connected to the base plate 11 by a guide shaft 11a. It stands upright in parallel with the optical axis O, and the U-shaped groove of the engaging portion 13b is fitted to the guide shaft 11a. In addition, you may form the guide shaft 11a and the ground plane 11 by another member.

  Thus, since the through hole of the cylindrical portion 13a is fitted to the guide shaft 14 and the U-shaped groove of the engaging portion 13b is fitted to the guide shaft 11a, the second lens frame 13 has the optical axis O. The first lens frame 12 and the imaging lens L can be moved in the direction of the optical axis O at the same time.

  Further, the lower end of the compression spring 15 is in contact with the upper portion of the cylindrical portion 13 a, and the upper end of the compression spring 15 is in contact with the spring receiving plate 16 fixed to the tip of the guide shaft 14. Therefore, the cylindrical portion 13a, that is, the second lens frame 13 is urged by the compression spring 15 in the direction of the image pickup element C (image forming surface side), and the rear end protrusion of the second lens frame 13 as shown in FIG. The part 13 c is in contact with the receiving surface 11 b of the main plate 11. As a result, in a normal case, the imaging lens L is fixed at a fixed position and forms an image on the imaging device C. Therefore, if the imaging lens L is focused on the hyperfocal distance, the imaging is performed from infinity to a short distance. It becomes possible.

  Further, the columnar portions 11c and 11d having the same shape are formed at positions rotated by 90 degrees with respect to the guide shafts 14 and 11a around the optical axis O and outside the opposite side walls of the second lens frame 13. It is erected from the ground plane 11 and faces the optical axis O. Then, both end portions of the shape memory alloy 18 formed in a string shape are tightly attached and fixed to the columnar portions 11c and 11d by the plate member 19, respectively. Both end portions of the shape memory alloy 18 are connected to the flexible printed board 34.

  On the other hand, the central portion of the shape memory alloy 18 is disposed so as to be in contact with the rear end portion 13d of the imaging element C (image forming surface side) of the second lens frame 13. Accordingly, the shape memory alloy 18 is stretched in a state where the central portion is disposed in the optical path of the imaging lens L across the optical axis O of the imaging lens L.

  In this state, when the shape memory alloy 18 is energized through the flexible printed circuit board 33, the printed wiring board 32, the flexible printed circuit board 34, and the plate member 19, the shape memory alloy 18 that is a resistor generates heat and the temperature is increased. Ascends and contracts in a direction that shortens its overall length. As a result, the rear end 13d of the second lens frame 13 is pressed, and the second lens frame 13 is guided by the guide shafts 14 and 11a against the urging force of the compression spring 15, and is opposite to the image sensor C. Move to the subject side. That is, the imaging lens L held by the first lens frame 12 via the second lens frame 13 moves toward the subject along the optical axis O, so that a subject at a shorter distance forms an image on the image sensor C. To do.

  Therefore, the shape memory alloy 18 may not be energized during normal shooting, and the shape memory alloy 18 may be energized when close-up shooting of a flower or the like is performed.

  In addition, when the imaging apparatus has an AF function or is configured so that distances can be set manually, the power input to the shape memory alloy may be adjusted in multiple steps according to the shooting distance. .

  As described above, the shape memory alloy 18 is arranged in a state of crossing the optical axis O of the imaging lens L, and the second lens frame 13 is pressed evenly. Therefore, the second lens frame 13 is efficiently moved in the direction of the optical axis O. can do.

  In addition, the center part of the above-mentioned shape memory alloy 18 means the part which is not an edge part, and does not mean the center position equidistant from both ends.

  Here, the shape memory alloy 18 is formed of titanium and nickel in a ratio of approximately half, and copper may be mixed therein.

  In the above configuration, the central portion of the shape memory alloy 18 is disposed in the optical path of the imaging lens L. Therefore, a part of the optical path is blocked by the shape memory alloy 18, and it becomes unsightly depending on conditions. Means for solving this will be described with reference to FIG.

  6A is a diagram in which the shape memory alloy 18 is disposed in the optical path of the imaging lens L, and FIG. 6B is a diagram of the shape memory alloy 18 viewed from the optical axis direction.

  First, it is known that if the size of an object arranged in the optical path of the imaging lens is 3% or less of the area of the optical path that crosses the object, it is difficult to visually recognize even if the image is formed on an imaging device or the like. Yes.

In FIG. 6B, when the diameter of the optical path when the shape memory alloy 18 is disposed in the optical path of the imaging lens L is D and the thickness of the shape memory alloy 18 is d, the area of the optical path is πD ^2. / 4, the area of the shape memory alloy 18 in the optical path is d · D. Therefore, the following conditional expression (1) may be satisfied.

d · D / (πD ² /4)<0.03 (1)
Conditional expression (1) can be simplified as follows.

d / D <0.02 (2)
In order to satisfy the conditional expression (2), it is desirable to arrange the shape memory alloy 18 at a position where the area of the optical path is as large as possible in the vicinity of the final surface of the imaging lens L.

  However, if the image of the shape memory alloy 18 formed on the image sensor C is deleted by image processing, the conditional expression (2) may not necessarily be satisfied.

  In some cases, the shape memory alloy may be disposed between the lenses of the imaging lens having a plurality of lenses, or may be disposed on the subject side of the imaging lens.

  In addition, a mobile phone or the like having a built-in imaging device using such a shape memory alloy 18 may be used in a high temperature environment. Therefore, when the shape memory alloy 18 is slightly loosened so that the second lens frame 13 is not drawn out even when the shape memory alloy 18 contracts at a temperature of 50 to 60 ° C. or lower, for example, when the temperature reaches 100 ° C. It is desirable that the shape memory alloy 18 is contracted and stuck to the rear end portion 13d and the second lens frame 13 is fed out.

  Next, lens barrels having different configurations will be described with reference to FIGS. 7 is a top view of a diaphragm type leaf spring, FIG. 8 is a cross-sectional view of a shape memory alloy stretched, FIG. 8 (A) is a normal state, and FIG. 8 (B) is an imaging lens extended. FIG.

  This lens barrel is similar to the lens barrel described above in that the central portion of the shape memory alloy 18 is disposed in the optical path of the imaging lens L, and both ends are fixed to the columnar portions 11c and 11d, respectively. The memory alloy 18 is stretched. On the other hand, the second difference is that the second lens frame 13 does not have the cylindrical portion 13a and the engaging portion 13b, the guide shafts 14 and 11a are not erected on the base plate 11, and the compression spring 15 is not provided. Is a point.

  First, the diaphragm type leaf spring 25 shown in FIG. 7 is made of phosphor bronze or stainless steel, and the outer peripheral flat portion 25a and the inner peripheral flat portion 25c have a step in the central axis direction, and the flat portion 25a is flat. The portion 25c is connected by the inclined portion 25b, and has a spring property due to the deformation of the inclined portion 25b.

  As shown in FIG. 8, the leaf spring 25 is fixed to the upper back surface of the lid member 31 and the upper end portion of the second lens frame 13, and a similar leaf spring 26 is provided at the rear end protrusion of the second lens frame 13. 13c and the lower surface 11e of the main plate 11 are fixed. The leaf spring 25 has a stronger spring pressure than the leaf spring 26. Therefore, as shown in FIG. 8A, when the shape memory alloy 18 is not energized, the leaf spring 25 presses the second lens frame 13 against the leaf spring 26 and the back surface of the leaf spring 26 is received by the base plate 11. The imaging lens L is positioned in the direction of the optical axis O in contact with the surface 11b. Further, when the shape memory alloy 18 is energized for close-up photography, the shape memory alloy 18 contracts, so that the second lens frame 13, that is, the imaging lens L is extended to a predetermined position against the leaf spring 25.

  When the diaphragm-type leaf spring 25 is used in this way, the basic operation is the same as that when the compression spring 15 is used. However, by using two leaf springs 25 and 26, the optical axis O Since the second lens frame 13, the first lens frame 12, and the imaging lens L can be held without tilting the lens, the guide shafts 14 and 11a are not required, and the lens barrel can be downsized from the above-described configuration. Can do.

  In the above configuration, the shape memory alloy 18 does not necessarily cross the optical axis O, but it is desirable to cross the vicinity of the optical axis O as much as possible.

  In addition, the direction in which the shape memory alloy moves the imaging lens in the optical axis direction is not necessarily limited to the subject side, and may be configured to move to the imaging plane side in some cases. For example, during normal shooting, the imaging lens L is made to enter the depth of field only for a short distance, and when shooting a long distance including infinity, the imaging lens is moved to the imaging plane side.

  Furthermore, the lens may be moved in a direction perpendicular to the optical axis for moving the lens for camera shake correction or moving the conversion lens. Even in such a configuration, the shape memory alloy is disposed in the optical path of the imaging lens. However, the shape memory alloy is not necessarily limited to the central portion of the shape memory alloy. Will be placed inside.

It is an external view of a mobile phone. It is a perspective view of an imaging device. It is a top view of a lens barrel. It is AA sectional drawing in FIG. It is BB sectional drawing in FIG. It is explanatory drawing when a shape memory alloy interrupts | blocks an optical path. It is a top view of a diaphragm type leaf spring. It is sectional drawing which stretched the shape memory alloy.

Explanation of symbols

S imaging device L imaging lens C imaging device O optical axis 11 ground plane 11a, 14 guide shaft 11c, 11d columnar part 12 first lens frame 13 second lens frame 13a cylindrical part 13b engaging part 15 compression spring 18 shape memory alloy 25 , 26 Leaf spring 31 Lid member 32 Printed circuit board 33, 34 Flexible printed circuit board

Claims (5)

In a lens barrel that has an imaging lens that forms an image of subject light and a lens frame that holds the imaging lens, and that moves the lens frame in a predetermined direction using a shape memory alloy formed in a string shape,
Arranging a part of the shape memory alloy in the optical path of the imaging lens,
A lens barrel, wherein the lens frame is moved by contracting the shape memory alloy by energization. The lens barrel according to claim 1, wherein the lens frame is moved in an optical axis direction by contracting the shape memory alloy. The lens barrel according to claim 2, wherein the lens frame is moved toward the subject side by contracting the shape memory alloy. The lens barrel according to claim 3, wherein the lens frame is biased toward the image plane. An imaging apparatus comprising the lens barrel according to claim 1.

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