LENS DEVICE

This application is based on and claims priority under 35 U.S.C §119 from Japanese Patent Application No. 2007-260246, filed on Sep. 30, 2007, the entire disclosure of which is herein incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a lens device, and more particularly to a lens device which is provided in a portable imaging device and which has an image blur compensator.

2. Description of Related Art

In an image blur compensator, a correction lens is supported so as to be freely movable in a plane perpendicular to a photographic optical axis. When vibrations are exerted on a camera, the correction lens is moved by means of an actuator in a direction for canceling image movement. For instance, in an image blur compensator described in Japanese Patent No. 2641172, a fixed frame of a correction lens is held by a first holding frame so as to become freely movable in the pitch direction, and the first holding frame is held by a second holding frame so as to become freely movable in a yaw direction. By means of a pitch coil attached to the fixed frame and a yaw coil attached to the first holding frame, the correction lens is moved in either the pitch direction or the yaw direction, thereby compensating for image blur.

However, in the image blur compensator of Japanese Patent No. 2641172, the first holding frame is attached onto the second holding frame. Hence, when the second holding frame is moved, the first holding frame is moved as well, and the lens is moved at low speed, so that high-precision image blur compensation cannot be performed.

In view of the above, an image blur compensator of JP-A-2006-215095 has two sliders for performing sliding actions independently of a housing (a main body), and the sliders are separately engaged with a lens holding frame. Specifically, in JP-A-2006-215095, two movement guide bars are attached to the lens holding frame in different directions, and the sliders are engaged with the two movement guide bars, respectively. The two sliders are separately supported by two fixed guide bars secured to the housing and can perform sliding actions along the fixed guide bars. Consequently, in the image blur compensator of JP-A-2006-215095, the lens holding frames can independently move in two directions, so that the lens holding frame can be moved quickly and that high-precision image blur compensation can be performed.

However, the image blur compensator of JP-A-2006-215095 has many portions where the lens holding frame and the sliders are engaged with each other, which incurs the possibility of occurrence of an operation failure caused by excessive constraints. Specifically, in JP-A-2006-215095, the respective movement guide bars are engaged with two guide sections of the sliders at a total of four locations. When machining precision or mounting precision goes down, excessive constrains may arise in any of four engagement sections, to thus hinder smooth sliding action of the sliders or the movement guide bars and cause an operation failure.

SUMMARY OF THE INVENTION

An object of an illustrative, non-limiting embodiment of the invention is to provide a lens device capable of smoothly moving two sliders which support a lens holding frame.

According to an aspect of the invention, there is provided a lens device comprising: a housing having a first fixed axis which is fixed to the housing in a transverse direction and a second fixed axis which is fixed to the housing in a longitudinal direction; a first slider supported so as to be slidable along the first fixed axis; a second slider supported so as to be slidable along the second fixed axis; a first movement bar fixed to the first slider in the longitudinal direction; a second movement bar fixed to the second slider in the transverse direction; a lens holding frame that holds a lens and is supported so as to be slidable along the first movement bar and slidable along the second movement bar, the first and second sliders being slid with respect to the housing so as to move the lens holding frame in a plane perpendicular to an optical axis of the lens; and a guide bar fixed to the housing in a direction perpendicular to the optical axis, wherein one of the first and second sliders has an engagement section engaged with the guide bar so as to be regulated in a direction of the optical axis.

According to an aspect of the present invention, the guide bar is fixed to the housing, and the engagement section of the slider is engaged with the guide bar, thereby preventing occurrence of rattling of the slider in the direction of the optical axis. The lens device of such a configuration can prevent occurrence of rattling for each slider and enables smooth movement of each of the sliders. In the specification, the longitudinal direction and the transverse direction are two different directions perpendicular to the optical axis, and the longitudinal direction and the transverse direction may also be inverted.

In an aspect of the invention, the housing may have an elongated hole in a direction perpendicular to the optical axis, and an end of one of the first and second movement axis which corresponds to the other of the first and second sliders may inserted into the elongated hole so as to regulate the other of the first and second sliders in the direction of to the optical axis. According to this aspect, separate mechanisms can prevent rattling of the respective sliders in the direction of the optical axis.

In an aspect of the invention, the engagement section may have a recess portion and the guide bar may be inserted into the recess portion to be slidably engaged. According to this aspect, the guide bar is inserted into and engaged with the recess portion of the engagement section, and hence the slider can be assembled by inserting only the guide bar into the recess portion of the engagement section, thereby facilitating assembly operation.

In an aspect of the invention, each of inside lateral surfaces of the recess portion may have a projection section extended continually in a direction perpendicular to the guide bar and having a circular-arc cross section, and the engagement section is brought into contact with the guide bar at the projection section.

According to this aspect, since the projection section having a circular-arc cross section is formed on each of inside lateral surfaces of the recess portion of the engagement section, and hence point contact always exists between the engagement section and the guide bar. Therefore, even when variations arise in machining precision, mount precision, or the like, the sliders can be stably slid at all times.

BRIEF DESCRIPTION OF THE DRAWINGS

The features of the invention will appear more fully upon consideration of the exemplary example of the invention, which are schematically set forth in the drawings, in which:

FIG. 1 is a side cross-sectional view showing a lens device of an exemplary embodiment of the invention;

FIG. 2 is a perspective view of a housing including a vibration-proof lens when viewed from the back;

FIG. 3 is a perspective view of the housing shown in FIG. 2 from which an actuator is removed;

FIG. 4 is a view of a vibration-proof mechanism shown in FIG. 3 when viewed in the direction of an optical axis;

FIG. 5 is a view of a vibration-proof mechanism shown in FIG. 4 from which a lens holding frame is removed;

FIG. 6 is a perspective view showing a principal section for a vibration-proof mechanism from which the housing is removed; and

FIG. 7 is a perspective view showing an engagement section of a slider.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

Although the invention will be described below with reference to exemplary embodiments thereof the following exemplary embodiments and modifications do not restrict the invention.

According to an exemplary embodiment of the present invention, the guide bars are fixed to the housing, and the engagement sections of the sliders are engaged with the guide bar, thereby preventing rattling of the sliders in the direction of the optical axis. Therefore, rattling can be prevented for each slider, and the respective sliders can be smoothly moved.

An exemplary embodiment of a lens device of the present invention will be described in detail according to the accompanying drawings.

FIG. 1 is a side cross-sectional view of a lens device 10 of an exemplary embodiment. The lens device 10 has a first lens group 12, a second lens group 14, a third lens group 16, and a fourth lens group 18 in order from the front (a subject side) to the rear (an imaging side) along a photographic optical axis. Subject light passed through the first through fourth lens groups 12 to 18 forms an image on imaging elements 22, 24, and 26 disposed at respective R, G, and B exit ends of a color separation prism 20 by way of the color separation prism 20 that constitutes a color separation optical system. The camera main body (not shown) equipped with the lens device 10 has a signal processing circuit (not shown) that subjects image signals from the imaging elements 22, 24, and 26 to processing (white balance processing, γ correction, and the like), thereby generating a video signal in a format.

The first lens group 12 is a so-called front lens; the second lens group 14 is a variator lens that changes a focal length; the third lens group 16 is a vibration-proof lens that is driven in a direction for canceling vibrations stemming from hand movement, or the like; and the fourth lens group 18 is a focusing lens that adjusts a focus.

The first through fourth lens groups 12 through 18 are held within a lens barrel main body 11. A pair of guide bars 28 (one of them is not illustrated) parallel to an optical axis are inserted and held in the lens barrel main body 11. A holding frame 32 of the second lens group 14 and the holding frame 34 of the fourth lens group 18 are slidably supported by the pair of guide bars 28, and a housing 36 of the third lens group 16 is secured to the pair of guide bars 28. The housing 36 may also be fixed directly to the lens barrel main body 11.

The second lens group 14 is provided with a nut (not shown) that constitutes a screw feeder, and a feed screw (not shown) constituting the screw feeder is screw-coupled to the nut. The feed screw is positioned in parallel to the optical axis, and the end of the feed screw is coupled to an output shaft of a zooming step motor (not shown). When a zoom signal is output from the camera main body to a zoom driver circuit (not shown) of the zooming step motor, the zooming step motor rotationally drives the feed screw in a direction conforming to the signal; thereby, the second lens group 14 is moved front and back in the direction of the optical axis along the pair of guide bars 28, to thus be adjusted to a desired focal length.

Likewise, the fourth lens group 18 is also equipped with a nut (not shown) constituting a screw feeder, and a feed screw (not shown) constituting the screw feeder is screw-coupled to the nut. The feed screw is positioned in parallel to the optical axis, and an end of the feed screw is coupled to an output shaft of the focusing step motor (not shown). When a focus signal is output from the camera main body to the focus driver circuit (not shown) of the focusing step motor, the focusing step motor rotationally drives the feed screw in a direction conforming to the signal; thereby, the fourth lens group 18 is moved front and back in the direction of the optical axis along the pair of guide bars 28, whereupon a focus is obtained.

Next, a configuration of the vibration-proof mechanism will be described.

FIG. 2 is a perspective view of the housing 36 equipped with the vibration-proof lens 16 when viewed from the back, and FIG. 3 is a perspective view achieved when the actuator is omitted from the housing 36 shown in FIG. 2. FIG. 4 is a view of the housing 36 shown in FIG. 3 when viewed in the direction of the optical axis L, and FIG. 5 shows a state in which a lens holding frame 50 is removed from FIG. 4. FIG. 6 is a perspective view showing only a principal section of a vibration-proof mechanism.

The third lens group (herein referred to as a “vibration-proof lens” for the sake of convenience) 16 shown in the drawings is supported by the lens holding frame 50, and the lens holding frame 50 is supported so as to be freely movable in two different directions in a plane perpendicular to the photographic optical axis L. The moving directions of the vibration-proof lens 16 are assumed to be a direction X (a transverse direction in FIGS. 2 through 5) and a direction Y (a longitudinal direction in FIGS. 2 through 5). The mechanism for moving the vibration-proof lens 16 in the direction X is referred to as an X movement mechanism, and a mechanism for moving the vibration-proof lens in the direction Y is referred to as a Y movement mechanism.

First, the X movement mechanism will be described.

As shown in FIG. 5, the housing 36 is attached to a fixed guide bar 60. The fixed guide bar 60 is disposed in the direction X, and both ends of the fixed guide bar are fastened to the housing 36. An upper side portion of the slider 54 formed into the shape of the letter L is engaged with the fixed guide bar 60. A guide opening (not shown) is formed in the upper side portion of the slider 54 in the direction X. As a result of the fixed guide bar 60 being inserted into the guide opening, the slider 54 is supported so as to be slidable in the direction X.

A movement guide bar 52 is attached to a left side portion of the slider 54. The movement guide bar 52 is disposed in the direction Y and fitted into the fitting sections 55, 55 of the slider 54, to thus be secured to the slider 54. As shown in FIG. 4, guide sections 56, 56 of the lens holding frame 50 are engaged with the movement guide bar 52. The guide sections 56, 56 of the lens holding frame 50 are disposed at positions (i.e., upper and lower sides in FIG. 4) outside of the fitting sections 55, 55 of the slider 54. A square opening (not shown) is opened in each of the guide sections 56, 56 so as to penetrate through in the direction Y. As a result of the columnar movement guide bar 52 being inserted into the square openings, the lens holding frame 50 is engaged with the slider 54. Hereby, the lens holding frame 50 is configured so as to be able to slide in the direction Y along the movement guide bar 52 and move in the direction X along with the slider 54 in an integrated fashion. As shown in FIG. 2, a lower end 52A of the movement guide bar 52 is engaged with an elongated opening 36A formed in a lower surface of the housing 36 in the direction X, whereby the slider 54 is prevented from swaying in the direction of the optical axis L.

As shown in FIG. 2, a plane motor coil (whose trade name is “Fine Pattern Coil” (Registered Trademark)) 62 is fastened to the upper side portion of the foregoing slider 54, and an output end of a flexible printed board 64 is bonded to a lower surface of the motor coil 62. The motor coil 62 is disposed at an outer perimeter of the vibration-proof lens 16 in the direction X, and a positioning sensor 66, such as the Hall device, is fixedly positioned on the flexible printed board 64.

The flexible printed board 64 is pulled from the motor coil 62 in the direction X and withdrawn to the outside of the housing 36 by way of a side opening 68 of the housing 36. The thus-eternally-withdrawn flexible printed board 64 is curved into the shape of the letter U and affixed to an upper surface of the housing 36. Subsequently, the flexible printed board is folded in an overlapping manner and withdrawn to the outside of the lens barrel main body 11 from a predetermined position on the lens barrel main body 11 (see FIG. 1). The thus-withdrawn flexible printed board 64 is connected to a unit that controls power supply and operation of the vibration-proof lens 16. As shown in FIG. 3, the side opening 68 of the housing 36 is brought in mutual communication with an end face of the housing 36 by way of a slit 70. As a result of the flexible printed board 64 being inserted into the slit 70, the flexible printed board 64 is positioned within the side opening 68.

A magnet 72 is disposed opposite and outside of the motor coil 62. The magnet 72 is formed into the shape of a rectangular plate by arranging two magnet pieces 72A and 72B in the direction X and configured in such a way that the south pole and the north pole are arranged in the direction X and that the south pole and the north pole become different from each other even on the upper and lower surfaces of the magnet pieces. The foregoing position sensor 66 is disposed opposite the center of the magnet 72 in the direction X (i.e., a boundary between the magnet pieces 72A and 72B); detects a change in the magnetic field; and outputs the thus-detected signal to the unit by way of the flexible printed board 64.

A metal plate (not shown) that is to become a yoke is provided outside of the magnet 72. The metal plate is attracted to the magnet 72 by means of magnetic force of the magnet 72. The metal plate is formed into a rectangular shape that is larger than the magnet 72 and attached while four edges of the plate protrude from the magnet 72. A recess equal in size to the metal plate is formed in an exterior surface of the housing 36, and an opening 74 equal in size to the magnet 72 is further formed in the recess in a penetrating manner. Thus, the metal plate is housed in the recess of the housing 36, and the magnet 72 is housed into the opening 74.

The metal plate 76 that is to sever as a yoke is disposed in and opposite the motor coil 62 along the direction X. One end of the metal plate 76 is inserted into the slit 70, and the other end of the metal plate is inserted into a groove 78 formed in the housing 36, to thus be fixed to the housing 36.

In the X movement mechanism configured as mentioned above, the motor coil 62 is disposed within a magnetic field generated by the magnet 72 and the two metal plates 76 (one is not illustrated); hence, the motor coil 62 and the slider 54 supporting the motor coil undergo force in the direction X as a result of the motor coil 62 being energized. Consequently, the slider 54 and the lens holding frame 50 are moved in the direction X, whereby the vibration-proof lens 16 is moved in the direction X. The above refers to the structure of the X movement mechanism.

The Y movement mechanism will now be described.

As shown in FIG. 5, the housing 36 is provided with the fixed guide bar 90. The fixed guide bar 90 is disposed in the direction Y, and both ends of the fixed guide bar are fixed to the housing 36. An upper side portion of the slider 84 formed into an L-shaped geometry is engaged with the fixed guide bar 90. A guide opening (not shown) is formed in the upper side portion of the slider 84 in the direction Y, and the fixed guide bar 90 is inserted into the guide opening, whereby the slider 84 is supported so as to be freely slidable in the direction Y.

A movement guide bar 82 is attached to a lower side portion of the slider 84. The movement guide bar 82 is disposed in the direction X and fitted into fitting sections 85, 85 of the slider 84, to thus be secured to the slider 84. As shown in FIG. 4, guide sections 86, 87 of the lens holding frame 50 are engaged with the movement guide bar 82. The guide section 86 of the lens holding fame 50 is located between the fitting sections 85, 85 of the slider 84, and a cross section of the guide section 86 orthogonal to the X axis is formed into the shape of a recess opened in one side of the optical axis L. In the meantime, the guide section 87 is disposed outside of the fitting sections 85, 85, and a cross section of the guide section 87 orthogonal to the X axis is formed into the shape of a recess opened to the outside (a lower side in the drawing). The movement guide bar 82 is inserted into these guide sections 86, 87, whereby the lens holding frame 50 is engaged with the slider 84. Thereby, the lens holding frame 50 is configured so as to be able to slide in the direction X along the movement guide bar 82 and move in the direction Y along with the slider 84 in an integrated fashion.

As shown in FIG. 6, the slider 84 is provided with a guide section 83. The guide section 83 is provided at a leading end (a left end) of the lower side portion of the slider 84, and the leading end side (the left side) is formed into the shape of an opened recess. A guide bar 88 is inserted into the guide section 83 and engaged in a slidable manner. The guide bar 88 is disposed in the direction Y, and ends of the guide bar 88 are fixed to the housing 36 (see FIG. 5). Hereby, the guide bar 88 can prevent the slider 84 from swaying (or tilting) in the direction of the optical axis L.

As shown in FIG. 2, a plane motor coil (whose trade name is “fine pattern coil” (Registered Trademark)) 92 is fixed to a right side portion of the foregoing slider 84, and an output terminal of a flexible printed board (hereinafter called a “flexible printed board”) 94 is bonded to the left surface of the motor coil 92. The motor coil 92 is disposed in the outer perimeter of the vibration-proof lens 16 in the direction Y, and a positioning sensor 96, such as a Hall device, is fixedly positioned on the flexible printed board 94.

The flexible printed board 94 is withdrawn from the motor coil 92 in the direction Y and to the outside of the housing 36 by way of the side opening 98 of the housing 36. The thus-externally-withdrawn flexible printed board 94 is curved into the shape of the letter U and affixed to the external side surface of the housing; is subsequently folded and superimposed; and is further superimposed on the flexible printed board 64 on the upper surface of the housing 36 (see FIG. 1). The thus-withdrawn flexible printed board 94 is connected to a unit that controls power supply and operation of the vibration-proof lens 16. The side opening 98 of the housing 36 is brought in mutual communication with an end face of the housing 36 by way of a slit 100. As a result of the flexible printed board 94 being inserted into the slit 100, the flexible printed board 94 is positioned within the side opening 98.

A magnet 102 is disposed opposite and outside of the motor coil 92. The magnet 102 is formed into the shape of a rectangular plate by arranging two magnet pieces 102A and 102B in the direction Y and configured in such a way that the south pole and the north pole are arranged in the direction Y and that the south pole and the north pole become different from each other even on the right and left surfaces of the magnet pieces. The foregoing position sensor 96 is disposed opposite the center of the magnet 102 in the direction Y (i.e., a boundary between the magnet pieces 102A and 102B); detects a change in the magnetic field; and outputs the thus-detected signal to the unit by way of the flexible printed board 94.

A metal plate (not shown) that is to become a yoke is provided outside of the magnet 102. The metal plate is attracted to the magnet 102 by means of magnetic force of the magnet 102. The metal plate is formed into a rectangular shape that is larger than the magnet 102 and attached while four edges of the plate protrude from the magnet 102. A recess equal in size to the metal plate is formed in an exterior surface of the housing 36, and an opening 104 equal in size to the magnet 102 is further formed in the recess in a penetrating manner. Thus, the metal plate is housed in the recess of the housing 36, and the magnet 102 is housed into the opening 104.

The metal plate 106 that is to serve as a yoke is disposed in and opposite the motor coil 92 along the direction Y. One end of the metal plate 106 is inserted into the slit 100, and the other end of the metal plate is inserted into a groove 108 formed in the housing 36, to thus be fixed to the housing 36.

In the Y movement mechanism configured as mentioned above, the motor coil 92 is disposed within a magnetic field generated by the magnet 102 and the two metal plates 106 (one is not illustrated); hence, the motor coil 92 and the slider 84 supporting the motor coil undergo force in the direction Y as a result of the motor coil 92 being energized. Consequently, the slider 84 and the lens holding frame 50 are moved in the direction Y, whereby the vibration-proof lens 16 is moved in the direction Y. The above refers to the structure of the vibration-proof mechanism.

A mechanism for preventing fall of the slider 54 and the slider 84, which are features of the present invention, will now be described.

As mentioned previously, the slider 54 supports the movement guide bar 52 in the Y direction, and an end 52A of the movement guide bar 52 is engaged with the elongated hole 36A of the housing 36. The elongated hole 36A is formed in the direction X. When the slider 54 moves in the direction X, the elongated hole acts as a guide for the movement guide bar 52, thereby preventing rattling of the movement guide bar 52 in the direction of the optical axis L.

As shown in FIG. 6, the slider 84 has an indented guide section 83. A guide bar 88 fixed to the housing 36 in the direction Y is inserted into the guide section 83. Consequently, when the slider 84 moves in the direction Y, the guide section 83 is guided in a slidable manner by the guide bar 88, thereby preventing rattling of the slider 84 in the direction of the optical axis L.

As mentioned above, in a lens device of the present embodiment, each of the sliders 54 and 84 is provided with the mechanism for preventing occurrence of rattling in the direction of the optical axis L. Therefore, as in the case where one of the sliders 54 and 84 is provided with the rattling prevention mechanism, occurrence of excessive constraints in the sliders 54, 84 is prevented, and the sliders 54 and 84 can be smoothly moved. Consequently, according to the present embodiment, high-performance vibration-proof can be performed.

Incidentally, as shown in FIG. 7, the guide section 83 of the slider 84 is formed in such a way that an interval of a leading end side (an open side) becomes wider. Specifically, the guide section 83 has side surfaces 83X, 83X formed in parallel to a given width and side surfaces 83Y, 83Y formed in an inclined manner such that leading end sides of the surfaces becomes wider. Therefore, when the guide bar 88 is engaged with the recess guide section 83, the side surfaces 83Y, 83Y serve as guides, to thus enable easy insertion of the guide bar 88 between the side surfaces 83X, 83X of the guide section 83.

A projection section 83A is formed in a protruding manner on each of the side surfaces 83X, 83Y of the guide section 83. The projection section 83A is formed continually in the direction X and into an arched shape whose cross section is perpendicular to the direction X. Consequently, the guide bar 88 inserted into the guide section 83 is held in a point contact with the guide section 83 at all times. Thereby, when the slider 84 performs sliding action in the direction Y, the guide section 83 and the guide bar 88 perform sliding action while remaining in a point contact whereupon operation of the slider 84 can be stabilized.

In the foregoing embodiment, the mechanism for preventing rattling of the slider 54 in the direction of the optical axis L and the mechanism for preventing rattling of the slider 84 in the direction of the optical axis L may also be inverted. Specifically, the slider 84 prevents rattling in the direction of the optical axis L by engaging the end of the movement guide bar 82 with the elongated hole of the housing 36 in the direction Y. The recess guide section 83 may also be formed, and the guide bar 88 fixed to the housing 36 in the direction X may be engaged with the guide section 83, thereby preventing rattling of the slider 54 in the direction of the optical axis L.

In the foregoing embodiment, the projection section 83A protruding so as to assume a circular-arc cross-sectional profile is formed. However, the shape of the projection section 83A is not limited to the cross-sectional profile and may also assume a triangular cross-sectional profile.

LENS DEVICE

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Abstract

Description

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Priority Claims (1)