Optical apparatus

The optical apparatus includes a base member, a shift member holding an image stabilizing lens and movable in a direction orthogonal to an optical axis direction of the optical apparatus with respect to the base member, a biasing member biasing the shift member toward the base member in the optical axis direction, and an aperture stop unit disposed on a side opposite to the base member with respect to the shift member and adjusting an amount of light. The aperture stop unit includes a displacement preventing portion which makes contact with the shift member to prevent the shift member from being displaced toward the aperture stop unit.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to optical apparatuses such as digital still cameras, video cameras, interchangeable lenses and binoculars, and more particular to optical apparatuses including an optical image stabilizing (image blur correcting) function.

2. Description of the Related Art

The above-described optical apparatuses are often equipped with an optical image stabilizing unit which reduces (corrects) image blur caused by shake of the optical apparatus generated due to hand jiggling or the like. As disclosed in Japanese Patent Laid-Open No. 2007-219338, the optical image stabilizing unit shifts a lens (image stabilizing lens), which constitutes part of an image taking optical system or an observing optical system, in a direction orthogonal to an optical axis in synchronization with the shake of the optical apparatus.

However, in the optical apparatus disclosed in Japanese Patent Laid-Open No. 2007-219338, since the image stabilizing lens is biased by a spring toward a base member, an impact applied to the optical apparatus may cause the image stabilizing lens to be displaced to a side (for example, forward) opposite to the base member with deformation of the spring. The displaced image stabilizing lens may hit another lens disposed in a direction of the displacement of the image stabilizing lens.

In many conventional optical apparatuses, a lens holding member holding the image stabilizing lens is provided with a protrusion, and the protrusion makes contact with another lens disposed further forward than the image stabilizing lens when the image stabilizing lens (lens holding member) is displaced forward due to the impact. Such a configuration makes it possible to prevent the image stabilizing lens from directly hitting the other lens, which avoids damages of these lenses.

However, in an optical apparatus in which an aperture stop unit is disposed further forward than and adjacent to the image stabilizing lens, since the lens holding member holding the image stabilizing lens faces stop blades of the aperture stop unit, it is difficult to provide the above-described protrusion on the lens holding member.

SUMMARY OF THE INVENTION

The present invention provides an optical apparatus capable of preventing displacement of an image stabilizing lens caused by an impact or an external force in an optical axis direction.

The present invention provides as one aspect thereof an optical apparatus includes a base member, a shift member holding an image stabilizing lens and movable in a direction orthogonal to an optical axis direction of the optical apparatus with respect to the base member, a biasing member biasing the shift member toward the base member in the optical axis direction, and an aperture stop unit disposed on a side opposite to the base member with respect to the shift member and adjusting an amount of light. The aperture stop unit includes a displacement preventing portion which makes contact with the shift member to prevent the shift member from being displaced toward the aperture stop unit.

Other aspects of the present invention will become apparent from the following description and the attached drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Exemplary embodiments of the present invention will be described hereinafter with reference to the accompanying drawings.

FIGS. 4 and 5show a digital still camera (hereinafter simply referred to as a “camera”) as an optical apparatus that is an embodiment of the present invention.FIG. 4shows the camera in a non-used state (lens retracted state) corresponding to a power-off state.FIG. 5shows the camera in a used state (image capturable state) corresponding to a power-on state.

On a front face of the camera18, a viewfinder objective window16, a photometry/autofocus assist light emitting window15, a strobe (flash)17and a lens barrel19are provided. The lens barrel19is retractable into a camera body as shown inFIG. 4, and protrudable from the camera body as shown inFIG. 5. The lens barrel protruding from the camera body extends and shortens to perform a zoom operation.

On a top face of the camera18, a release switch12, a power switch14and a zoom switch13are provided. Inside the camera18, an image pickup element, a power supply (battery), and a recording medium such as a semiconductor memory are housed though they are not shown in the figures. Moreover, on a back face of the camera18, a display unit displaying electronic viewfinder images and captured images, and various operation switches are provided though they are not shown in the figures.

FIG. 6shows an electrical configuration of the camera18. A CPU46, a ROM45and a RAM47constitute a controlling part (controller). The CPU46, the ROM45and the RAM47are connected via a bus44with various components in the camera18such as the release switch12, the zoom switch13, the power switch14, the above-described various operation switches22, the above-described display unit21, a memory40, a compression/expansion circuit41, a recording medium drive42and a drive circuit43.

The drive circuit43causes a zoom motor drive circuit30, a focus motor drive circuit31, an image stabilizing drive circuit32, an aperture stop drive circuit34, the above-described image pickup element36and the above-described strobe17to activate on the basis of instructions from the CPU46. The zoom motor drive circuit30drives a zoom motor MZto extend and shorten the lens barrel19, thereby changing a focal length of an image taking optical system housed in the lens barrel19. The focus motor drive circuit31drives a focus motor MFto move in an optical axis direction a focus lens48included in the image taking optical system, thereby causing the focus lens48to perform focusing.

The image stabilizing drive circuit32drives an image stabilizing unit20to reduce (correct) image blur caused by shake of the camera18(hereinafter referred to as “camera shake”) generated due to hand jiggling or the like. The aperture stop drive circuit34drives stop blades of an aperture stop unit5in an open-and-close direction to change a diameter of an aperture (hereinafter referred to as a “stop aperture”) being formed by the stop blades, thereby adjusting an amount of light passing through the stop aperture

The image pickup element36is constituted by a CCD sensor or a CMOS sensor, and photoelectrically converts an object image formed by the image taking optical system housed in the lens barrel19to output image pickup signals. The image pickup signals which are analogue signals are input to an A/D converter38through an analog signal processing circuit37to be converted into digital signals. A digital signal processing circuit39performs various image processing on the digital signals to create digital image data (an electronic viewfinder image or an captured image). The digital image data is displayed on the display unit21through the memory40, or is compressed by the compression/expansion circuit41to be recorded in the recording medium through the recording medium drive42.

Next, description will be made of a configuration of the lens barrel19with reference toFIGS. 1,2and3.FIGS. 1 and 2respectively show the lens barrel19in the non-used state and the used state shown inFIGS. 4 and 5.FIG. 3shows the aperture stop unit5and the image stabilizing unit20disposed in the lens barrel19.

The image stabilizing unit20includes a shift base3serving as a base member, an image stabilizing lens1constituting part of the image taking optical system, and a shift frame2serving as a shift member and holding the image stabilizing lens1. The shift frame2is shiftable (movable) with respect to the shift base3in a shift direction orthogonal to an optical axis direction of the image taking optical system (that is, of the camera18).

This embodiment shows a case where the shift direction is the direction orthogonal to the optical axis direction. However, the shift direction is not necessarily needed to be a direction strictly orthogonal to the optical axis direction. In other words, the shift direction may be a direction including a directional component orthogonal to the optical axis direction such as a direction slightly inclining with respect to the direction orthogonal to the optical axis direction and a direction having a curvature.

The shift direction that is the direction orthogonal to the optical axis direction includes a pitch direction corresponding to a vertical direction or an up-and-down direction and a yaw direction corresponding to a horizontal direction or a right-and-left direction.

Plural balls4are disposed between the shift frame2and the shift base3. The shift frame2is biased toward the shift base3(that is, to a base member side) by a spring11serving as a biasing member. Therefore, the shift frame2is pressed against the shift base3via the balls4and guided in the shift direction (pitch and yaw directions) by rolling of the balls4.

At two places on the shift frame2whose phases around the optical axis are different from each other by 90 degrees, two magnets (not shown) are fixed. Further, at two places on the shift base3facing the two magnets, two coils (not shown) are fixed. One of the two magnets and one of the two coils facing each other constitute a pitch shift actuator which shifts the shift frame2in the pitch direction with respect to the shift base3. The other of the two magnets and the other of the two coils facing each other constitute a yaw shift actuator which shifts the shift frame2in the yaw direction with respect to the shift base3.

A shake detection sensor25shown inFIG. 6is constituted by an angular velocity sensor or the like, and detects the camera shake in the pitch and yaw directions. The CPU46controls energization of the coils of the pitch and yaw shift actuators on the basis of outputs from the shake detection sensor25. Thereby, the shift frame2is shifted with the image stabilizing lens1in the pitch and yaw directions to correct the image blur.

InFIGS. 1 and 2, a first lens6is disposed further on an object side (further forward) than the image stabilizing lens1. The first lens6is held by a first lens holding barrel7.

The first lens holding barrel7and the shift base3respectively engage with a straight groove portion (not shown) formed on a guiding barrel8so as to extend in the optical axis direction. A cam barrel is disposed at an outer circumference of the first lens holding barrel7, the cam barrel9being rotatable around the optical axis. Cam groove portions9aare formed on an inner circumferential surface of the cam barrel9. Cam followers (not shown) provided on outer circumferential portions of the first lens holding barrel7and the shift base3respectively engage with the cam groove portions9a. Therefore, rotation of the cam barrel9moves the first lens holding barrel7and the shift base3(in other words, the first lens6and the image stabilizing unit20) in the optical axis direction.

The cam barrel9is rotated with respect to a fixed barrel10disposed at an outer circumference of the cam barrel9to be moved in the optical axis direction by a cam groove portion (not shown) formed on an inner circumferential surface of the fixed barrel10. Therefore, each of the first lens6and the image stabilizing unit20is moved in the optical axis direction by a combined movement amount of a movement amount obtained by the cam groove portion of the cam barrel9and a movement amount of the cam barrel9being moved by the cam groove portion of the fixed barrel10. Thus, the lens barrel19extends and shortens between the non-used state shown inFIG. 1and the used state (wide-angle state) shown inFIG. 2, and extends and shortens between the wide-angle state and a telephoto state in the used state to perform the zoom operation.

Moreover, in the lens barrel19, the aperture stop unit5is disposed on a side opposite to the shift base3with respect to the shift frame2(that is, on an opposite side to a direction in which the spring11biases the shift frame2). In other words, the aperture stop unit5is disposed between the first lens6and the image stabilizing unit20in the optical axis direction.

As described above, the shift frame2holding the image stabilizing lens1is pressed against the shift base3by a biasing force of the spring11. However, when an impact or a large external force is applied to the camera18, the shift frame2may be displaced forward so as to separate from the shift base3against the biasing force of the spring11. In this case, when the lens barrel19is in the non-used state shown inFIG. 1, the shift frame2may hit the stop blades5bof the aperture stop unit5, or the image stabilizing lens1displaced forward with the shift frame2may hit the first lens6.

Thus, this embodiment employs the following configuration to prevent such forward displacement of the shift frame2in the non-used state while shortening a length of the lens barrel19in the optical axis direction in the same state as much as possible.

First, in the non-used state, the diameter of the stop aperture formed by the stop blades5bin the aperture stop unit5is made larger than an optical maximum diameter of the stop aperture which is a largest diameter optically used for image capturing, and a front portion of the image stabilizing lens1is inserted into the stop aperture larger than the optical maximum diameter. In other words, in the camera18changeable between the lens retracted state and the image capturable state, the image stabilizing lens1and the aperture stop unit5are at least partially overlapped with each other in the optical axis direction in the lens retracted state.

In such a configuration, when the impact or the large external force is applied to the camera18, it is highly possible that the shift frame2displaced forward will hit the stop blades5bor the image stabilizing lens1will hit the first lens6.

Thus, in this embodiment, as shown inFIG. 3, protrusion portions5aare provided at three circumferential places (three places around the optical axis) on the aperture stop unit5. The protrusion portions5aserving as displacement preventing portions make contact with the shift frame2to prevent the shift frame2from being displaced toward the aperture stop unit5. Further, groove portions2ainto which the protrusion portions5aare inserted are formed at three places around the image stabilizing lens1on the shift frame2. Contact of the protrusion portions5awith optical-axis-direction end surfaces among inner surfaces of the groove portions2aprevents the shift frame2from being displaced forward. Moreover, engagement of the protrusion portions5awith the groove portions2ain a circumferential direction prevents the shift frame2from being displaced around the optical axis.

Such a configuration can prevent the shift frame2and the image stabilizing lens1from being displaced forward due to the impact or the large external force in the non-used state, which can avoid the hit of the shift frame2against the stop blades5band the hit of the image stabilizing lens1against the first lens6. Accordingly, this embodiment can achieve a high impact-resistant camera.

The groove portions2aformed on the shift frame2are also used as portions into which a tool for correcting (adjusting) decentering of the image stabilizing lens1with respect to the shift frame2is inserted when the image stabilizing lens1is attached to the shift frame2. The use of such groove portions2aalso as portions into which the protrusion portions5aare inserted makes it possible to prevent the shift frame2from being displaced forward and around the optical axis without complicating a shape of the shift frame2.

Moreover, bonding portions2bwhere the image stabilizing lens1is bonded and fixed after the decentering correction thereof are provided at three circumferential places on the shift frame2.

Furthermore, in the used state shown inFIG. 2, the aperture stop unit5and the image stabilizing unit20are apart from each other in the optical axis direction, and therefore the image stabilizing lens1is moved outside (rearward) from the stop aperture. Thus, the stop blades5bcan be narrowed.

As described above, this embodiment can prevent the displacement of the shift frame2and the image stabilizing lens1toward the aperture stop unit5in the optical axis direction due to the impact and the external force in the non-used state. Therefore, even in a camera in which the image stabilizing lens1is inserted into the stop aperture in the non-used state, it is possible to prevent the shift frame2and the image stabilizing lens1from hitting the stop blades5band the other lens (first lens6), which can achieve a high impact-resistant camera.

Although in the above embodiment description has been made of the digital still camera, alternative embodiments of the present invention include other optical apparatuses such as a video camera, an interchangeable lens and binoculars.

This application claims the benefit of Japanese Patent Application No. 2009-182466, filed on Aug. 5, 2009, which is hereby incorporated by reference herein in its entirety.