Lens apparatus and image pickup apparatus

A lens apparatus and image pickup apparatus thereof. The lens apparatus includes a first fixed lens-barrel with fixed-side first guide grooves and fixed-side second guide grooves, a first movable lens-barrel arranged at the outside of the fixed lens-barrel, movable-side first guide grooves, a second movable lens-barrel arranged at the inside of the fixed lens barrel, and movable-side guide grooves. Three first rolling element units are provided between the fixed-side guide grooves and the movable-side first guide grooves, and three second rolling element units are provided between the fixed-side second guide grooves and the movable-side second guide grooves. The first movable lens-barrels and the second movable lens-barrels are supported to the one-group lens and the two-group lens in such a manner that they can be independently moved in the optical axis directions of the first and second lenses.

TECHNICAL FIELD

The present invention relates to a lens apparatus consisting of a fixed lens-barrel, first and second movable lens-barrels fitted into the inside and the outside of the fixed lens-barrel and more than two rolling element units provided between the first and second movable lens-barrels so that a plurality of movable lens-barrels can be moved straight and an image pickup apparatus including such a lens apparatus.

BACKGROUND ART

Cited Patent Reference 1, for example, has described an example of this kind of lens apparatus according to the related art. Specifically, the Cited Patent Reference 1 has described a linear actuator, an optical device and a lens-barrel for driving an image pickup lens in an image pickup apparatus such as a camera and a video camera. The lens-barrel described in this Cited Patent Reference 1 is characterized in that this lens-barrel uses a linear actuator in which a moving lens group movable in the optical axis direction, a lens holding means for holding the moving lens group and which can be freely slid along a guide in the optical axis direction, a drive means for driving this lens holding means and a position detecting means are provided at the four corners of the lens-barrel around the moving lens group in the optical axis directions.

According to the lens-barrel having the above-mentioned arrangement described in the Cited Patent Reference 1, there can be expected such effects in which while a bad influence exerted upon magnetism from a magnetic circuit can be decreased to the minimum, the lens-barrel can be reduced in size in the width direction by effectively using vacant spaces of the four corners of the lens-barrel and the lens-barrel can be made compact in size.

Cited Patent Reference 2, for example, has described other example of a lens apparatus according to the related art. Specifically, the Cited Patent Reference 2 has described a lens-barrel for use with a still camera and a video camera. The lens-barrel described in the Cited Patent Reference 2 is characterized in that it includes a movable lens-barrel with a lens held thereon movable in the optical axis direction and which includes a plurality of guide grooves parallel to the optical axis, a fixed lens-barrel having a plurality of second guide grooves opposing to the first guide grooves and which are parallel to the optical axis and a plurality of hard balls sandwiched between the opposing first and second guide grooves.

According to the lens-barrel having the above-mentioned arrangement described in the Cited Patent Reference 2, there can be expected such effects in which the hard balls are sandwiched between the guide grooves parallel to the optical axis so that the movable lens-barrel can be moved forward and backward very smoothly.

Cited Patent Reference 3 has described a further example of a lens apparatus according to the related art. Specifically, the Cited Patent Reference 3 has described a lens-barrel apparatus and a drive apparatus for driving a driven body which can be applied to a lens system of a video camera and the like. The lens-barrel apparatus described in the Cited Patent Reference 3 is characterized in that it includes a lens-barrel, a lens located within the lens-barrel, a holding means for holding the lens, the holding means including a coil, a yoke located within the lens-barrel in response to the circumference of the holding means, a magnet located within the yoke to move the holding means within the lens-barrel, the magnet constructing a linear actuator together with the coil when the coil is energized and a guide means for driving the linear actuator to guide the holding means of the lens along the lens-barrel, the guide means located at the position inside the radius direction as compared with the yoke, the magnet and the coil.

According to the lens-barrel apparatus having the above-mentioned arrangement described in the Cited Patent Reference 3, there can be achieved the effects in which the guide means such as a guide shaft need not be located at the outside of the lens-barrel apparatus so that the outer shape of the lens-barrel apparatus can be simplified.

[Cited Patent Reference 1]: Japanese Published Patent Application No. 11-150972

[Cited Patent Reference 2]: Japanese Published Patent Application No. 8-29656

[Cited Patent Reference 3]: Japanese Published Patent Application No. 8-15593

However, in the related-art lens apparatus using the linear actuator as the driving means, as shown in the Cited Patent Reference 1, it has been customary for most of the lens apparatus to hold the lens hold frame by using the guide shaft. For this reason, it has been customary that the coil of the driving means is fixed to the place of one portion distant from the center of the optical axis of the movable lens holding frame with a constant distance. Also, it has been customary that the permanent magnet and the yoke of the driving means are located so as to pass through the coil or they are located distant from the coil with a constant distance, that is, the permanent and the yoke are of the so-called coil moving system.

On the other hand, although there is a magnet moving system for moving the permanent magnet and the yoke while the coil is being fixed, the place in which the magnet moving system is located is the same as that in which the coil moving system is located. In such case, it is unavoidable that a part of the lens-barrel is projected or that the outer shape of the lens-barrel becomes angular. As a consequence, a part of the lens-barrel is unavoidably increased in thickness and hence it has been difficult to make the lens-barrel become cylinder with a small diameter, thereby making it difficult to miniaturize the whole of the image pickup apparatus. Further, since most of the lens-barrel uses a ring-like coil having a rectangular shape as a coil and the effective portion of the ring-like coil as the magnetic circuit is only one side of the rectangular, it is inevitable that a magnetic loss becomes large from a standpoint of circuit efficiency of the magnetic circuit.

Also, while some related-art lens apparatus had a ring-like coil located at the outer peripheral side of the lens, such related-art lens apparatus had a structure in which a yoke is formed of a different member, the yoke being inserted into the lens-barrel. As a result, the lens-barrel was increased in thickness, the whole of the apparatus was increased in size unavoidably and driving efficiency was not satisfactory.

On the other hand, a related-art collapsible type lens apparatus will be considered. It has been customary for a collapsible type lens apparatus that a lens holding frame with a cam pin restricted by a linearly movable lens-barrel rotates a cam ring with a cam groove to allow the cam pin to trace the cam groove, thereby the linearly movable lens-barrel to be collapsed. In this case, since frictional resistance generated when the linearly movable lens-barrel is slidably moved is extremely large, it has been customary that the collapsible type lens apparatus can be collapsed by using a DC motor which generates large torque, reduction torque increased by a gear arrangement or by manual operations. Accordingly, it has been difficult to collapse the collapsible type lens apparatus by a linear motor. Furthermore, when the collapsible type lens apparatus is provided with the gear arrangement or motors are separately mounted on the collapsible type lens apparatus, it is unavoidable that the outer shape of the lens-barrel of the lens is increased in thickness. As a result, the whole of the collapsible type lens apparatus might not be miniaturized and decreased in diameter as one wants it to be.

The problems which the present invention will solve and with which the related-art lens apparatus encountered will be described below. In the lens apparatus according to the related art, it has been difficult to miniaturize the lens-barrel of the lens while a plurality of lens holding frames is being made movable. In order to reliably move the movable lens-barrel forward and backward, it is necessary to increase an output from a drive mechanism. To this end, it is unavoidable that the whole of the lens apparatus becomes large in size. In particular, when movable lens-barrels are provided at the inside and the outside of a fixed lens-barrel so that a plurality of movable lens-barrels can be moved forward and backward, the lens apparatus is increased in length in the optical axis direction or it is increased in length in the direction perpendicular to the optical axis direction. Therefore, it was difficult to miniaturize the whole of the lens apparatus.

DISCLOSURE OF THE INVENTION

According to an aspect of the present invention, there is provided a lens apparatus which is comprised of a fixed lens-barrel including a plurality of fixed-side first guide grooves extended straight and which are formed on an outer peripheral surface in parallel to each other and a plurality of second guide grooves extended straight and which are formed on an inner peripheral surface in parallel to each other, a first movable lens-barrel to hold a first lens at the outside of the fixed lens-barrel and which includes a plurality of movable-side first guide grooves extended straight, a plurality of movable-side first guide grooves being opposed to the fixed-side first guide grooves with a predetermined gap in parallel to each other, a second movable lens-barrel to hold a second lens of which optical axis is coincident with that of the first lens at the inside of the fixed lens barrel and which includes a plurality of movable-side second guide grooves extended straight, a plurality of movable-side second guide grooves being opposed to the fixed-side second guide grooves with a predetermined gap in parallel to each other, more than two first rolling element units including a plurality of rolling elements being provided between the fixed-side first guide grooves and the movable-side first guide grooves so as to become able to freely roll and which supports the first movable lens-barrel to the fixed lens-barrel such that the movable lens-barrel can be moved in the optical axis direction of the lens and more than two second rolling element units including a plurality of rolling elements provided between the fixed-side second guide grooves and the movable-side second guide grooves so as to become able to freely roll and which supports the second movable lens-barrel to the fixed lens-barrel such that the second movable lens-barrel can be moved in the optical axis direction of the lens, wherein the first and second movable lens-barrels are supported to the fixed lens-barrel such that they can be independently moved in the optical axis directions of the first and second lenses.

In accordance with another aspect of the present invention, there is provided an image pickup apparatus which is comprised of a lens apparatus which includes a fixed lens-barrel including a plurality of fixed-side first guide grooves extended straight and which are formed on an outer peripheral surface in parallel to each other and a plurality of second guide grooves extended straight and which are formed on an inner peripheral surface in parallel to each other, a first movable lens-barrel to hold a first lens at the outside of the fixed lens-barrel and which includes a plurality of movable-side first guide grooves extended straight, a plurality of movable-side first guide grooves being opposed to the fixed-side first guide grooves with a predetermined gap in parallel to each other, a second movable lens-barrel to hold a second lens of which optical axis is coincident with that of the first lens at the inside of the fixed lens barrel and which includes a plurality of movable-side second guide grooves extended straight, a plurality of movable-side second guide grooves being opposed to the fixed-side second guide grooves with a predetermined gap in parallel to each other, more than two first rolling element units including a plurality of rolling elements being provided between the fixed-side first guide grooves and the movable-side first guide grooves so as to become able to freely roll and which supports the first movable lens-barrel to the fixed lens-barrel such that the movable lens-barrel can be moved in the optical axis direction of the lens and more than two second rolling element units including a plurality of rolling elements provided between the fixed-side second guide grooves and the movable-side second guide grooves so as to become able to freely roll and which supports the second movable lens-barrel to the fixed lens-barrel such that the second movable lens-barrel can be moved in the optical axis direction of the lens, wherein the lens apparatus supports the first and second movable lens-barrels to the fixed lens-barrel such that they can be independently moved in the optical axis directions of the first and second lenses.

According to the lens apparatus and the image pickup apparatus of the present invention, although the lens apparatus is small in size, it is able to move a plurality of movable lens-barrels straight reliably and smoothly. Thus, it is possible to provide the small lens apparatus which can be driven linearly and the image pickup apparatus including the lens apparatus.

A small lens apparatus which can reliably and smoothly drive a plurality of movable lens-barrels linearly and an image pickup apparatus including such lens apparatus can be realized by simple arrangements.

BEST MODE FOR CARRYING OUT THE INVENTION

First, a linearly movable rolling guide apparatus for use with a lens apparatus according to the present invention will be described.FIG. 3is an exploded perspective view showing a first embodiment of a linearly movable rolling guide apparatus according to the present invention. As shown inFIG. 3, a linearly movable rolling guide apparatus, generally depicted by reference numeral1, is composed of a guide member2including a first guide groove7, a movable member3including a second guide groove8, a fixed member4for holding the guide member2, a rolling element unit5interposed between the first and second guide grooves7and8so as to become able to roll freely and a pair of leaf springs6A and6B which show an embodiment of a pre-load member.

The guide member2is formed of a plate-like member which is rectangular in plane shape and which has a T-like cross-section in the direction perpendicular to its longitudinal direction. The guide member2has at its substantially central portion of the plane side the first guide groove7which is continuously extended from one end to the other end of the longitudinal direction. The first guide groove7has a V-like cross-section in the direction perpendicular to its longitudinal direction and it has at its bottom portion an escape groove to avoid it from contacting with a rolling element. Inclined surfaces at both sides of the guide groove7are set to substantially 45°, respectively. This guide member2has at its substantially central portion on the opposite surface of the surface with the first guide groove7formed thereon an elongated protrusion9which is continuously extended from one end to the other end in the longitudinal direction. Concave portions at both sides of this elongated protrusion are formed as overhang portions9aand9b.

Each of the overhand portions9aand9bhas a positioning hole10and two engagement holes11and11. In each of the overhand portions9aand9b, the positioning hole10is set at substantially the central portion in the longitudinal direction and the two engagement holes11and11are set to both sides of the longitudinal direction across the positioning hole10at substantially equal spacing therebetween. The two engagement holes11and11are oblong holes which are extended in the direction in which the first guide groove7is extended.

The movable member3has a shape substantially similar to that of the guide member2and it is formed of a plate-like member which is shaped like T. The movable member3has at its substantially central portion of the bottom surface side formed the second guide groove8which is continuously extended from one end to the other end in the longitudinal direction. The second guide groove8has an inverse-V-like cross-section in the direction perpendicular to its longitudinal direction and it has on its bottom surface formed an escape groove to avoid it from contacting with the rolling element. The inclined surfaces of both sides of the second guide groove8are set to approximately 45°, respectively. This movable member3has at its substantially central portion of the surface opposite to the surface in which the second guide groove8is formed provided the elongated protrusion12which is continuously extended from one end to the other end. The overhang portions12aand12bare set to both sides of this elongated protrusion12.

While the dimension of the width direction of the movable member3is substantially the same as that of the width direction of the guide member2, the dimension of the longitudinal direction of the movable member3is longer than that of the longitudinal direction of the guide member2. The reason for this is that the guide member is fixed to the predetermined position while the movable member3may be moved relative to the guide member2in the direction in which the guide groove is extended. The first and second guide grooves7and8are set to be substantially the same in size.

The rolling element unit5is composed of a plurality of cylindrical rollers14(four cylindrical rollers14in this embodiment) which show a first embodiment of a rolling element and a holding device15to hold these cylindrical rollers14such that these cylindrical rollers14may become able to roll freely. While the cylindrical roller14is suitable for the application to the rolling element, it is possible to use other rolling elements such as a spherical roller and a ball. The holding device15has four holding holes14of the number same as that of the rolling elements to accommodate therein the cylindrical rollers14. The four holding holes16of the holding device15are located on the same straight line and the four cylindrical rollers14are held in these holding holes16such that these four cylindrical rollers14may become able to freely roll in the state in which their inclination directions are changed alternately with an inclination of 45°.

The fixed member4is formed of a rectangular frame-like member having a concave portion17which is large enough to house therein the guide member2. The fixed member4has at its substantially central portion of the width direction of the bottom surface an oblong hole18which is extended in the longitudinal direction18. This oblong hole18has at its both sides of the width direction formed bottom surface portions19A and19B. Each of the bottom surface portions19A and19B includes a positioning pin21projected in the upper direction and two fitting pins22and23which are similarly projected in the upper direction.

The positioning pins21are set to substantially central portions of the respective bottom surface portions19A and19B in the longitudinal direction. Also, the two fitting pins22and22are located at both sides of the longitudinal direction across the positioning pin21with a predetermined gap therebetween. These positioning pin21and the fitting pins22and22correspond to the positioning hole10and the fitting holes11and11of the guide member2and thereby they may be engaged with each other upon assembly.

The pair of leaf springs6A and6B may be respectively attached to the left and right bottom surface portions19A and19B of the fixed member4. The leaf springs6A and6B are made of long spring materials of sizes substantially the same as those of the bottom surface portions19A and19B and they have supporting portions6aand6aprovided at central portions of the longitudinal directions. Further, pressure welding portions6band6bare set to respective end portions of the longitudinal directions of the respective leaf springs6A and6B. Resilient portions6cand6cfor applying spring-biasing force to the pressure welding portions6band6bare set between the pressure welding portions6b,6band the supporting portions6aand6a.

Positioning holes23formed of round holes are respectively bored at substantially central portions of the supporting portions6aand6aof the respective leaf springs6A and6B. The positioning pins21on the fixed member4are fitted into the respective positioning holes23. The diameter of the positioning hole23is larger than the shaft diameter of the positioning pin21. Thus, when the positioning hole23has a proper gap between it and the positioning pin21, the positioning hole23can absorb accuracy error between the positioning pin23and the positioning pin21. Escape holes24and24formed of oblong holes are respectively provided near the pressure welding portions6band6bof the resilient portions6cand6cof the two leaf springs6A and6B. The fitting pins22and22on the fixed member4are respectively fitted into the respective escape holes24and24. The escape holes24and24are formed as oblong holes extended in the longitudinal direction so as to allow the resilient portions6cand6cof the leaf springs6A and6B to be deformed with resiliency.

While engineering plastics such as ABS resin (acrylonitrile butadiene styrene resin) may be suitable as materials of the guide member2, the movable member3, the fixed member4and the holding device15, the present invention is not limited thereto and it is also possible to use aluminum alloy and other metals. While metals such as spring steels may be suitable as a material of the leaf springs6A and6B, the present invention is not limited thereto and it is also possible to use engineering plastics such as ABS resin. Also, various materials such as stainless steel, structural carbon steel, cemented carbide and engineering plastics can be used as a material of the cylindrical rollers14.

The linearly movable rolling guide apparatus1having the above-mentioned arrangement can be assembled with ease as follows. First, the pair of leaf springs6A and6B are respectively attached to the left and right bottom surface portions19A and19B of the fixed member4. At that time, in the leaf springs6A and6B, the positioning pins21and21of the two bottom surface portions19A and19B are fitted into the positioning pins23and23of the supporting portions6aand6aand the fitting pins22and22are fitted into the fitting holes11and11at both sides. Next, the guide member2is inserted into the concave portion17of the fixed member4over the pair of leaf springs6A and6B. Then, the positioning pin21is fitted into the positioning hole10and the fitting pins22and23at both sides are respectively fitted into the fitting holes11and11.

At that time, since the fitting hole11is formed as the oblong hole and its longitudinal direction is set to the direction in which it becomes perpendicular to the first guide groove7, accuracy error of the fitting pin22relative to the positioning pin21can be absorbed by this oblong hole and the guide member2can be attached to the fixed member4with ease rapidly.

Next, the rolling element unit5which holds the four cylindrical rollers14thereon is fitted into the first guide groove7of the guide member2. After that, the movable member3is placed on the guide member2and then the second guide groove8is fitted into the rolling element unit5. Thus, the assembly work is completed and thereby the linearly movable rolling guide apparatus1can be obtained.

According to the linearly movable rolling guide apparatus1having the above-mentioned arrangement, the leaf springs6A,6B and the guide member2can be properly positioned by the positioning pin21and the engagement pin22of the fixed member4. In addition, since the two leaf springs6A and6B are provided between the guide member2and the fixed member4so that the guide member2is spring-biased to the side of the movable member3under spring force of the leaf springs6A and6B, the predetermined pre-load, which is determined by spring force of the two leaf springs6A and6B, can be constantly applied to the rolling element unit5. As a result, it becomes possible to decrease the inclinations of the rolling element unit5and the guide member2relative to the movable directions regardless of the position of the moving direction of the rolling element unit5and hence the linearly movable rolling guide apparatus1can be operated stably.

Although not shown, instead of the above-described leaf springs6A and6B, four coil springs, for example, can be used as the pre-load members. To be more concrete, the same four coil springs are attached to the four engagement pins22and22of the fixed member4. Thus, it is possible to achieve actions and effects similar to those of the above-described leaf springs6A and6B. Also, the leaf springs6A and6B can be replaced with plate-like acrylic rubber, silicon rubber, urethane rubber and foam styrol and various kinds of rubber-like resilient materials. Instead of the engagement pins22and22, it is possible to separately provide convex portions by which coil springs can be attached. Further, the four coil springs can be replaced with four leaf springs.

FIG. 4is an exploded perspective view showing a second embodiment of a linearly movable rolling guide apparatus of the lens apparatus according to the present invention. As shown inFIG. 4, in a linear movable rolling guide apparatus31according to the second embodiment of the present invention, the pair of leaf springs6A and6B may be replaced with two sets of pair of permanent magnets, and two sets of plate-like permanent magnets32A and32B may constitute the second embodiment of the pre-load member. Since the second embodiment is different from the first embodiment only in the two sets of the plate-like permanent magnets32A and32B, the plate-like permanent magnets32A and32B will be described below. Therefore, other arrangements are denoted by identical reference numerals and therefore need not be described herein.

Specifically, as shown inFIG. 4, the linearly movable guide apparatus31is composed of the guide member2including the first guide groove7, the movable member3including the second guide groove8, the fixed member4for holding the guide member2, the rolling element unit5provided between the first and second guide grooves7and8so as to roll freely and the two sets of the plate-like permanent magnets32A and32B which show the second embodiment of the pre-load member.

Each of the plate-like permanent magnets32A and32B is composed of first and second magnet plates33and34. The first magnet plate33and the second magnet plate34are identical to each other. Accordingly, in this embodiment, the two sets of the plate-like permanent magnets32A and32B are constructed by using the four identical magnet plates33and34. Each of the magnet plates33and34is formed of a long size magnet of the size substantially the same as those of the bottom surface portions19A and19B of the fixed member4, wherein the N pole is set on the whole surface of its one surface side and the S pole is set on the whole surface of the other surface side.

Positioning holes35and35formed of round holes are formed at substantially the central portions of the longitudinal directions of the two magnet plates33and34. The positioning pin21provided on the fixed member4is fitted into each positioning hole35. The diameter of the positioning hole35is made larger than the shaft diameter of the positioning pin21similarly to the positioning hole23of the above-described embodiment. Thus, a gap of a proper size is set between the positioning hole35and the positioning pin21, whereby errors in positional accuracy between the positioning pin21and the positioning hole35can be absorbed. Also, fitting holes36and36formed of oblong holes are provided on both end portions of the magnet plates33and34. The engagement pins22and22provided on the fixed member4are respectively fitted into the fitting holes36and36. This fitting hole36is formed as an oblong hole which is extended in the direction perpendicular to the direction in which the first guide groove7is extended, similarly to the fitting hold11of the guide member2.

The linearly movable rolling guide apparatus31having the above-mentioned arrangement can be assembled with ease as follows, for example. First, the second magnet plates34and34are respectively attached to the left and right bottom surface portions19A and19B of the fixed member4, for example. At that time, the second magnet plates34and34are attached to the left and right bottom surface portions19A and19B of the fixed member4in such a manner that their same poles (for example, N poles) are directed in the upper direction, the positioning pins21of the respective bottom surface portions19A and19B being fitted into the central positioning holes35, the fitting pins22and22being fitted into the fitting holes36and36at both sides, respectively. At that time, although the second magnet plates34and34should preferably be fixed to the bottom surface portions19A and19A by using a fixing means such as an adhesive, when the second magnet plates34and34are respectively fixed to the bottom surface portions19A and19B by using repulsive force of the permanent magnet as seen in this embodiment, the second magnet plates34and34may be respectively fixed to the bottom surface portions19A and19B by using not the fixing means but by only fitting the positioning pins21into the positioning holes35.

Next, the guide member2with the pair of the first magnet plates33and33fixed thereto is placed on the pair of the second magnet plates34and34. At that time, the pair of the first magnet plates33and33are located with their N poles being opposed to each other such that they may be repulsed with each other from a relationship with the pair of the second magnet plates34and34(conversely, the pair of the first magnet plates33and33may be located with their S poles being opposed to each other). The pair of the first magnet plates33and33may be fixed to the left and right overhang portions9aand9bof the guide member2at both sides of the elongated protrusion9of the surface of the opposite side of the first guide groove7, that is, the surface in which the elongated protrusion9exists.

At that time, the positioning holes35and35of the first magnet plate33are made coincident with the positioning holes10and10of the respective overhang portions9aand9band the fitting holes36and36at both sides of the first magnet plate33are made coincident with the fitting holes11and11of the respective overhang portions9aand9b. The guide member2in which the pair of the first magnet plates33and33was formed as one body is inserted into the concave portion17of the fixed portion4from above the pair of the first magnet plates33and33. Then, the positioning pin21is fitted into the positioning holes35and10and the fitting pins22and22are respectively fitted into the fitting holes36and11.

In that case, since the fitting hole36and the fitting hole11, which were made coincident with each other, are both formed as the oblong holes and their longitudinal directions are set to the direction perpendicular to the first guide groove7, position accuracy error of the fitting pin22relative to the positioning pin21can be absorbed by the oblong holes and hence the attachment work of the guide member2can be carried out simply and rapidly.

After that, similarly to the above-described embodiment, the rolling element unit5that holds the four cylindrical rollers14is fitted into the first guide groove7of the guide member2. Then, the movable member3is placed on the guide member2and the second guide groove8is fitted into the rolling element unit5. Thus, the assembly work is completed and thereby the linearly movable rolling guide apparatus31is obtained. It is possible to use a magnetic member such as an electromagnet and an electromagnetic induction coil instead of the permanent magnet.

According to the linearly movable rolling guide apparatus31having the above-mentioned arrangement, the first magnet plates33,33and the second magnet plates34,34, each of which forms the pair, are located in the two sets of the plate-like permanent magnets32A and32B provided between the fixed member4and the guide member2such that they are repulsed with each other, similarly to the above-described leaf springs6A and6B, it is possible to apply pre-load of a predetermined magnitude to the rolling element unit5by using repulsive force from the pair of the permanent magnets. Therefore, similarly to the above-described embodiment, the rolling element unit5can be avoided from being sunk, the pre-load applied to the rolling element unit5can be prevented from being changed considerably and smooth movement of the movable member3can be maintained.

FIG. 5is an exploded perspective view showing a third embodiment of a linearly movable rolling guide apparatus of a lens apparatus according to the present invention. As shown inFIG. 5, a linearly movable rolling guide apparatus41according to the third embodiment, the pair of the second magnet plates34and34constructing one element of the two sets of the plate-like permanent magnets32A and32B of the linearly movable rolling guide apparatus31in the second embodiment is fixed to the movable member3.

The linearly movable rolling guide apparatus41of the third embodiment is different from the linearly movable rolling guide apparatus31of the second embodiment in that a pair of second magnet plates44and44is provided on a movable member46and that the shape of the guide member45is partly changed concurrently therewith. Therefore, the arrangements of the two sets of the plate-like permanent magnets32A and32B (each of which is composed of the first and second magnet plates33and44), the guide member45and the movable member46will be described below. Other arrangements are denoted by identical reference numerals and therefore need not be described.

Specifically, the linearly movable rolling guide apparatus41is composed of the guide member45including the first guide groove7, the movable member46including the second guide groove8, the fixed member4to hold the guide member45, the rolling element unit5provided between the first guide groove7and the second guide groove8so as to roll freely and the two sets of the plate-like permanent magnets32A and32B (first and second magnet plates33and44) forming the pre-load member.

The shape of the guide member45is substantially similar to that of the guide member2in the above-described embodiment and it is different from that of the guide member2in that concave portions to house therein the first magnet plate33is provided on the side of the first guide groove7of the overhand portions9aand9band that two first magnet plates33and33are attached to these concave portions, thereby being formed as one body. The two first magnet plates33and33may be fixed by using a suitable fixing means such as an adhesive. At that time, the positioning hole35of the first magnet plate33is made coincident with the positioning hole10of the overhang portion9a(or9b) and the fitting holes36and36at both sides are made coincident with the fitting hole11of the overhang portion9a(or9b).

The shape of the movable member46is substantially similar to that of the movable member3of the above-described embodiment and it is different from that of the movable member3in that concave portions to house therein the second magnet plate44are respectively provided on the side of the second guide groove8of the overhang portions12aand12band that the two second magnet plates44are attached to these concave portions, thereby being formed as one body. In this case, the polarity of the first magnet plate33and that of the second magnet plate44may be set in such a manner that the first and second magnet plates33and44may be attracted with each other or that they may be repulsed with each other. The reason for this will be described below. That is, since the two sets of the plate-like permanent magnets32A and32B are located symmetrically across the first and second guide grooves7and8, even when any one of the above-described polarity combinations is employed, balance can be kept in the right and left direction.

The linearly movable rolling guide apparatus41having the above-mentioned arrangement can be assembled more easily as follows, for example. First, the guide member45is attached to the fixed member4. At that time, the pair of the positioning pins21and21of the fixed member4is fitted into the pair of the positioning holes10and35of the guide member45and the two pairs of the fitting pins22and22are fitted into the two pairs of the fitting holes11and36. Next, the rolling element unit5which holds the four cylindrical rollers14is fitted into the first guide groove7of the guide member45. After that, the movable member46is placed over the guide member45and the second guide groove8is fitted into the rolling element unit5. As a result, the assembly work is completed and thereby the linearly movable rolling guide apparatus41can be obtained.

According to the linearly movable rolling guide apparatus41having the above-mentioned arrangement, since the first magnet plates33and the second magnet plates44, each of which forms the pair, are located in the two sets of the plate-like permanent magnets32A and32B provided between the guide member45and the movable member46in such a manner that they may be attracted with each other or that they may be repulsed with each other, similarly to the case in which the above-described leaf springs6A and6B and the above-described magnet plates33and34are used, it is possible to apply pre-load of a proper magnitude to the rolling element unit5by using repulsive force or tensile force of the pair of the permanent magnets. Therefore, similarly to the above-described embodiments, the rolling element unit5can be avoided from being sunk, the pre-load applied to the rolling element unit5can be prevented from being changed considerably and smooth movement of the movable member46can be maintained.

FIG. 1is an exploded perspective view showing main assemblies of a lens lens-barrel50of a first embodiment of the lens apparatus according to the present invention. As shown inFIG. 1, the lens lens-barrel50is composed of a fixed lens-barrel51, a movable lens-barrel52slidably held in this fixed lens-barrel51, three rolling element units5A,5B and5C provided between the fixed lens-barrel51and the movable lens-barrel52, an exterior lens-barrel48serving as a yoke lens-barrel to act as a yoke, two sets of leaf springs6A and6B, two guide members2and2and the like.

The fixed lens-barrel51is formed of a circular cylinder and it has at its one end of the axial direction provided a flange portion51adeveloped toward the outside of the radius direction. The fixed lens-barrel51has at its three places on the outer peripheral surface provided three flat surface portions54a,54band54cwhich are formed as flat surfaces within a predetermined range. The three flat surface portions54ato54care located at an equal angular interval and an outer peripheral guide groove67, which is a first guide groove, is provided on the first flat surface portion54a. Also, opening portions56A and56B, each of which is rectangular in shape, are provided on the second and third flat surface portions54band54c, respectively. The outer peripheral guide groove67is extended straight in parallel to the axial direction of the fixed lens-barrel51. The cross-sectional shape of the outer peripheral guide groove67is shaped like V-letter and guide surfaces with inclinations of 45° are formed at both sides of the outer peripheral guide groove67. One surface side of the first rolling element unit5A is fitted into this outer peripheral guide groove67.

The positioning pin21and the two fitting pins22and22are provided in series on the edge portions of both sides of the width direction (circumferential direction) of the two opening portions56A and56B of the fixed lens-barrel51at a predetermined interval in the axial direction. The pair of the leaf springs6A and6bmay be respectively attached to the edge portions of the respective opening portions56A and56B by fitting the positioning hole23and the escape hole24into these pins21and22. The guide member2is placed over the pair of these leaf springs6A and6B in the state in which the first guide grooves7are directed in the outside. One surfaces of the rolling element units5B and5C are respectively fitted into the first guide grooves7of the respective guide members2, respectively. The three rolling element units5A to5C have similar shape and arrangement to those of the rolling element unit5that has been described so far in the above-described embodiments.

Further, three permanent magnets49,49and49curved in a circular arc fashion are attached to the three curved surface portions among the three flat surface portions54a,54band54cin the outer peripheral surface of the fixed cylinder51. The three permanent magnets49,49and49are formed of plate-like magnets of the same shape and size and they are located at an equal interval in the circumferential direction of the fixed lens-barrel51(in a trisection fashion), whereafter they are integrally fixed to the fixed lens-barrel by a suitable fixing means such as an adhesive.

The movable lens-barrel52is formed of a circular cylindrical body with a diameter larger than that of the fixed lens-barrel51. The fixed lens-barrel51is inserted into the inside of this movable lens-barrel52with a predetermined clearance. Protruded portions58a,58band58c, which are protruded in the inside of the radius direction, are provided on the three places of the inner peripheral surface of the movable lens-barrel52. A part of the three protruded portions58a,58band58cis protruded from one end of the movable lens-barrel52to the outside of the axial direction. The three protruded portions58a,58band58care located at an equal interval in the circumferential direction (that is, in a trisection fashion). Three second guide grooves59A,59B and59C, which are continued in the axial direction, are provided on substantially the central portions of the respective inners surfaces of the three protruded portions58a,58band58c.

As shown inFIG. 9, the three second guide grooves59A,59B and59C are extended straight in parallel to the axial direction of the movable lens-barrel52. Each of the three second guide grooves59A,59B and59C has a V-like cross-section and guide surfaces with inclination angles of 45° are provided on both sides of the V-like cross-section. The other surface sides of the rolling element units5A,5B and5C are fitted into the three second guide grooves59A,59B and59C, respectively. Specifically, the three second guide grooves59A,59B and59C are opposed to a fixed-side first guide groove67of the fixed lens-barrel51and the fixed-side first guide grooves7A and7B of the two guide members2A and2B attached to the fixed lens-barrel51, and the three rolling element units5A,5B and5C are provided among the inner and outer first guide grooves67,59A,7A,59B and7B,59C so as to roll freely.

Further, as shown inFIG. 1, a coil26is attached to the movable lens-barrel52in order to move the movable lens-barrel52forward and backward in the axial direction relative to the fixed lens-barrel51. The coil26has a winding of a predetermined number so as to have diameters (both of an inner diameter and an outer diameter) substantially similar to that of the movable lens-barrel52. Also, the coil26is fitted into the three protruded portions58a,58band58cand thereby integrally fixed to one end portion of the movable lens-barrel52as one body. A wiring plate27for supply power is connected to the coil26. Then, an exterior lens-barrel48formed of a cylindrical body is attached to the outside of the movable lens-barrel52with a predetermined gap. Also, the exterior lens-barrel48is engaged with the flange portion51aof the fixed lens-barrel51at one end of the axial direction and thereby properly positioned.

Magnetic materials with high magnetic permeability, such as pure iron and Permalloy (Ni—Fe alloy) are suitable as the application to the materials of the fixed lens-barrel51and the exterior lens-barrel48. However, the material of the fixed lens-barrel51is not limited to the above-mentioned materials and the fixed lens-barrel51may be made in such a manner that the whole of the fixed lens-barrel51may be formed of a resin cylindrical body, the magnetic material with high magnetic permeability being provided at necessary portions of the resin cylindrical body. In this case, the first guide groove67that should be provided on the fixed lens-barrel51and portions that should be requested to have high dimensional accuracy and plane accuracy can be formed as resin mold products. Further, the first guide groove67and the above-mentioned portions can be formed as die-cast mold products using a suitable material such as aluminum alloy and magnesium alloy or they can be formed as composite material products molded by a die-cast mold product and a resin. When the fixed lens-barrel51is formed as the resin mold product and the like as described above, higher productivity can be expected.

Also, the movable lens-barrel52may be not only formed as a resin mold product but also it can be formed as a die-cast mold product using a suitable material such as aluminum alloy and magnesium alloy or it can be formed as a composite material product molded by a die-cast mold product and a resin in the same way as the fixed lens-barrel51.

The aforementioned coil26, three permanent magnets49,49and49and the fixed lens-barrel51and the exterior lens-barrel48constitute a linear motor drive means. In this case, the fixed lens-barrel51is constructed as a ground-side yoke in which the permanent magnets49,49and49are disposed and the exterior lens-barrel48is constructed as an opposing-side yoke which receives magnetic flux from the ground-side yoke. As a consequence, since the movable lens-barrel52to which the coil26is fixed exists in constant magnetic flux, it becomes possible to drive the linear motor drive means with application of a voltage to connection terminals of the wiring plate27connected to the coil26.

In this case, since the movable lens-barrel52is supported to the fixed lens-barrel51through the three rolling element units5A,5B and5C so as to become freely slidable and it is also applied with the pre-load under spring force of the two sets of the leaf springs6A and6B, the whole of the supporting portion can be prevented from being wobbled. Further, the movable lens-barrel52can be moved in the optical axis direction without displacement relative to the optical axis of the lens and hence it becomes possible to stably move the movable lens-barrel52in the optical axis direction with high accuracy. Also, since the three permanent magnets49,49and49occupy the whole surface other than the portion in which the three rolling element units5A,5B and5C are provided, the area occupied by the three permanent magnets49,49and49can be increased as large as possible. Further, since the coil26exists on the circumference with a constant gap relative to the three permanent magnets49,49and49, efficiency of the magnetic circuit can be demonstrated at the maximum.

FIG. 2is an exploded perspective view showing all assemblies of a lens apparatus200containing the lens lens-barrel50shown inFIG. 1. This lens apparatus200is formed of an optical system having a three lens group arrangement which is roughly composed of three lens groups.FIGS. 6 and 7are perspective view showing an outward appearance of an electronic still camera150which shows an embodiment of an image pickup apparatus incorporating therein the lens apparatus200shown inFIG. 2.FIG. 8is a longitudinal cross-sectional view of the portion of the lens apparatus200of the electronic still camera150,FIG. 9is a cross-sectional view taken along the line X-X inFIG. 8andFIGS. 10A and 10Bare schematic cross-sectional views to which reference will be made in explaining the state in which the movable lens-barrel52of the lens apparatus200is extended, respectively.

As shown inFIG. 2, the lens apparatus200is composed of the exterior lens-barrel48, the first fixed lens-barrel51, a second fixed lens-barrel201, the first movable lens-barrel52, a second movable lens-barrel202, a one-group lens211, a two-group lens212, a three-group lens213, a CCD (charge-coupled device)214, that is, a solid-state image pickup device which shows a specific example of the image pickup means and the like.

The three first permanent magnets49,49and49are located on the outer peripheral surface of the first fixed lens-barrel51at the equal interval and fixed thereto by a suitable fixing means such as an adhesive as mentioned hereinbefore. Also, two second permanent magnets204and204are located on the outer peripheral surface of the second fixed lens-barrel201at an equal interval and fixed thereto by a suitable fixing means such as an adhesive. The first fixed lens-barrel51and the second fixed lens-barrel201are fixed to a camera body (image pickup apparatus body)151of the electronic still camera150at their back sides.

The three permanent magnets49,49and49are formed as plate bodies curved in circular arc-fashion and they are closely fixed to the positions of 120° each (at an equal angular distance) which results from equally dividing the outer peripheral surface of the first fixed lens-barrel51. The first rolling element units5A,5B and5C are located among these three permanent magnets49,49and49. One surface of the first rolling element unit5A of the first rolling element unit is brought in contact with the fixed-side first guide groove67which is the outer peripheral guide groove of the first fixed lens-barrel51and one surfaces of the first rolling element units5B and5C of the second and third rolling element units are brought in contact with the guide grooves75A and75B of the two guide members2A and2B attached to the two opening portions56A and56B of the first fixed lens-barrel51. Then, the pair of the leaf springs6A and6A may be provided between the two guide members2A and2B and the first fixed lens-barrel51.

The one-group lens211is held at the central hole of the one-group lens holding frame216of the annular shape. This one-group lens211is constructed by a combination of a first lens (G01lens)251, a second lens (G02lens)252, a third lens (G03lens)253and a first mask (G01mask)261, it can be prevented from being released from the central hole of the one-group lens holding frame216by a decoration ring271and then it is attached to the one-group lens holding frame216. The one-group lens holding frame216is fixed to the front-side end face portion of the first movable lens-barrel52and thereby formed as one body with the first movable lens-barrel52.

The one-group coil26having a circular winding and whose diameter (outer diameter and inner diameter) is substantially the same as that of the first movable lens-barrel52is fixed to the rear-side end face portion of the first movable lens-barrel52in such a manner that it may be fitted into respective outer peripheries of the three protruded portions58a,58band58c. The one-group coil26is used to drive the first movable lens-barrel52by the linear motor and it is electrically connected to the one-group wiring plate27for supplying electric power. This first movable lens-barrel52is fitted into the outside of the first fixed lens-barrel51with a predetermined gap and the three movable-side first guide grooves59A,59B and59C are opposed to the fixed-side first guide groove67of the first fixed lens-barrel51and the fixed-side first guide grooves7A and7B of the guide members2A and2B attached to the two opening portions68and68. Then, the three first rolling element units5A,5B and5C are located between the fixed-side first guide grooves67,7A and7B and the movable-side first guide grooves59A,59B and59C which form the pairs at the three portions.

The two-group lens212is held on the two-group lens holding frame217which is unitarily formed as one body with the second movable lens-barrel202having the cylindrical shape. This two-group lens212is composed of a combination of a fourth lens (G04lens)254and a second mask (G02mask)262held on the front side of the two-group lens holding frame217and a fifth lens (G05lens)255, a sixth lens (G06lens)256and a fixed stop272held on the rear side of the two-group lens holding frame217. This two-group lens212is thus unitarily fitted into and fixed to the two-group lens holding frame217. The fixed stop272can be replaced with other suitable means such as an iris unit and a shutter unit.

Three movable-side guide grooves72,73and74are formed on the outer peripheral surface of the second movable lens-barrel202. Those movable-side second guide grooves72,73and74are opposed to the fixed-side second guide groove66and the fixed-side second guide grooves75A and75B of the two guide plates69A and69B in the state in which they are inserted into the inside of the first fixed lens-barrel51. Then, the three second rolling element units65A,65B and65C are located between the fixed-side second guide grooves66,75A and75B and the movable-side second guide grooves72,73and74which form the pairs at the three portions.

A two-group coil26A having a circular winding of which diameter (outer diameter and inner diameter) is substantially the same as that of the second movable lens-barrel202is fixed to the rear side end face portion of the second movable lens-barrel202. The two-group coil26A is used to drive the second movable lens-barrel202by the linear motor and it is electrically connected to a two-group wiring plate27A for supplying electric power. The second fixed lens-barrel201is inserted into the inside of the second movable lens-barrel202with a predetermined gap.

As shown inFIG. 2, while a plurality of rolling elements may be held by the plate-like holding device at a predetermined interval in the first and second rolling element units5A,5B and5C and65A,65B and65C, a plurality of click-like cage stoppers273and274and a plurality of ring-like stopper rings275and276are used in order to prevent the holding device15from being displaced or dropped.

The first cage stopper273is fixed to the front side rear end face portion of the first movable lens-barrel52and the second cage stopper274is fixed to the rear side end face portion of the first movable lens-barrel52. Also, the first stopper ring275is fixed to the front side rear end face portion of the opposite side of the flange portion51aof the first fixed lens-barrel51and the second stopper ring276is fixed to the rear side end face portion of the second movable lens-barrel202.

Also, a three-group lens213is formed of a seventh lens and it is held by a three-group lens holding frame218including holding portions located in the right and left direction. Through this three-group lens holding frame218, the three-group lens213is fixed to the rear portion of the second fixed lens-barrel201. A rear lens-barrel278with an optical filter277fixed thereto is located at the rear side of the second fixed lens-barrel201. A CCD (charge-coupled device)214, that is, a solid-state image pickup device serving as an image pickup means is fixed to the back surface of this rear lens-barrel278by other suitable fixing means such as an adhesive.

The three group lenses211,212and213are located in such a manner that their optical axes are made coincident with the same axis. The CCD214is located on such optical axis behind the three-group lens213. A wiring plate215is attached to the back surface of the CCD214and the CCD214is mounted on a predetermined wiring circuit of the wiring plate215. Then, the exterior lens-barrel48is properly positioned by the outermost diameter portion and rear side surface of the first fixed lens-barrel51and it is fastened and fixed through the rear lens-barrel278by three fixed screws281,281and281.

Specifically, the first movable lens-barrel52is fitted into the first fixed lens-barrel51with a predetermined gap in the outside of the radius direction and the exterior lens-barrel48is fitted into the first movable lens-barrel52with a predetermined gap in the outside of the radius direction. Then, the three sets of the first rolling element units5A,5B and5C are located between the first movable lens-barrel52and the first fixed lens-barrel51. Also, the second movable lens-barrel202is located in the inside of the radius direction of the first fixed lens-barrel51with a predetermined gap in the inside of the radius direction, and the second fixed lens-barrel201is fitted into the second movable lens-barrel202with a predetermined gap in the inside of the radius direction. Then, the three sets of the second rolling element units65A,65B and65C are located between the first fixed lens-barrel51and the second movable lens-barrel202.

The three sets of the first rolling element units5A,5B and5C and the three sets of the second rolling element units65A,65B and65C are located at substantially an equal angular distance (120°) in the circumferential direction, respectively. Then, the first rolling element units5A,5B and5C and the second rolling element units65A,65B and65C are located at the positions deviated 60° from each other.

In order to realize the above-mentioned arrangement, as shown inFIGS. 8 and 9, the first fixed lens-barrel51is provided with the fixed-side first and second guide grooves66and67continued in the axial direction, the two opening portions68and68to hold the two guide members2A and2B and two dented portions71and71to hold the two guide members69A and69B.

The fixed-side second guide groove66is formed on the inner peripheral surface of the first fixed lens-barrel51and the fixed-side first guide groove67is formed on the outer peripheral surface of the first fixed lens-barrel51. The fixed-side second guide groove66and the fixed-side first guide groove67are set to the positions which are deviated 180° from each other. The fixed-side first guide groove67is assumed to be a first reference portion by which the relative position between the first fixed lens-barrel51and the first movable lens-barrel52can be determined. The fixed-side second guide groove66is assumed to be a second reference portion by which the relative position between the first fixed lens-barrel51and the second movable lens-barrel202can be determined.

Also, in the first fixed lens-barrel51, the two dented portions71and71are set on the inner peripheral surfaces of the positions deviated 60° each to the respective sides around the fixed-side first guide groove67. Further, the two opening portions68and68are formed on the outer peripheral surfaces of the positions deviated 60° each to the respective sides. In response to the first fixed lens-barrel51, the three movable-side second guide grooves72,73and74continued in the axial direction are provided at three portions of the outer peripheral surface of the second movable lens-barrel202. While the three movable-side second guide groove72,73and74are located at an equal interval in the circumferential direction and the movable-side second guide groove72has a V-like cross-section, other two movable-side second guide grooves73and74have semi-circular cross-sections.

The movable-side second guide groove72is opposed to the fixed-side second guide groove66of the first fixed lens-barrel51, and the second rolling element unit65A is provided between the fixed-side second guide groove66and the movable-side second guide groove72so as to roll freely. Also, the movable-side second guide grooves73and74are opposed to the two dented portions71and71of the first fixed lens-barrel51and the two second rolling element units65B and65C are separately provided between the fixed-side second guide grooves75A and75B of the two guide plates69A and69B held to these dented portions71and71.

While the two of the second rolling element units65B and65C are formed as spheres in this embodiment, they may be formed like cylindrical rollers as rolling elements similarly to other rolling element unit65A. Also, all rolling elements can be formed as spheres. Further, the rolling elements are not limited to the cylindrical rollers and the spheres shown in this embodiment. By way of example, the rolling elements can be formed as not only spherical rollers (barrel-like rollers) but also as other suitable shapes. That is, rolling elements of any shapes can be combined for use as the application to the above-mentioned rolling elements so long as the rolling elements of such shapes can be used as the above rolling elements.

Also, in response to the first fixed lens-barrel51, the protruded portions63, which are protruded toward the inside of the radius direction, are provided at the three portions of the inner peripheral surface of the first movable lens-barrel52. The three movable-side first guide grooves59A,59B and59C continued in the axial direction are formed on the inner surface of the three protruded portions63,63and63. The three movable-side first guide grooves59A,59B and59C are located at an equal interval on the circumferential direction and they have V-like cross-sections. The movable-side first guide groove59A is opposed to the fixed-side first guide groove67of the first fixed lens-barrel51, and the first rolling element unit53A is provided between the movable-side first guide groove59A and the fixed-side first guide groove67such that it can be rolled freely.

The two movable-side first guide grooves59B and59C are opposed to the two opening portions68and68of the first fixed lens-barrel51, and the two first rolling element units5B and5C are provided between the two guide members2A and2B held to these opening portions68and68in such a manner that they can be rolled freely. Further, the pair of the leaf springs6A and6B serving as the pre-load members is provided between the two guide members2A and2B and the supporting portion that is the edge portion of the opening portion68of the first fixed lens-barrel51which supports the two guide members2A and2B. The two sets of the leaf springs6A and6B spring-bias the two guide members2A and2B to the outside of the radius direction, whereby pre-load of substantially a uniform predetermined magnitude can be applied to totally six rolling element units5A,5B,5C and65A,65B and65C of the three first rolling element units5A,5B,5C and the three second rolling element units65A,65B and65C.

According to the above-mentioned arrangement, substantially uniform pre-load can be applied to the six rolling element units5A,5B,5C and65A,65B and65C located at the six portions by spring force of the leaf springs6A and6B which may act from the two directions. Therefore, even when the rolling element units5A,5B,5C and65A,65B and65C are located at any positions in the moving direction, these rolling element units5A,5B,5C and65A,65B and65C can be prevented from being sunk, the pre-load applied to the rolling element units5A,5B,5C and65A,65B,65C can be prevented from being changed considerably and hence it is possible to smoothly move the first movable lens-barrel52and the second movable lens-barrel202with high accuracy.

Specifically, according to this embodiment, the first movable lens-barrel52is supported to the first fixed lens-barrel51at the three portions in the circumferential direction by the rolling element units5A,5B and5C such that they can be rolled freely. In addition, the second movable lens-barrel202also is supported to the first fixed lens-barrel51at the three portions of the circumferential direction by the rolling element units65A,65B and65C such that they can be rolled freely. Then, of the three first rolling element units5A,5B and5C, the guide members2A and2B and the leaf springs6A and6B serving as the pre-load members are respectively located at the two portions and the two guide members2A and2B are spring-biased toward the two rolling element units5B and5C under spring force of the leaf springs6A and6B.

As a consequence, the first movable lens-barrel52can be properly positioned to the first fixed lens-barrel51by the first rolling element unit5A located at one portion, and the second movable lens-barrel202can be properly positioned to the first fixed lens-barrel51by the second rolling element unit65A located at one portion. Then, since spring force is applied to the two first rolling element units5B and5C by the guide members2A and2B and the leaf springs6A and6B between the first fixed lens-barrel51and the first movable lens-barrel52, the pre-load of substantially equal magnitude can be applied to all of the six rolling element units5A,5B,5C and65A,65B and65C including these two first rolling element units5B and5C and hence pressure of the whole of the structure body can be well balanced.

Specifically, under spring force of the leaf springs6A and6B which act from the two directions, the substantially equal pre-load can be applied to the six rolling element units5A,5B,5C and65A,65B and65C located at the six portions. Therefore, even when the rolling element units5A,5B,5C and65A,65B and65C are located at any positions in the moving direction, the rolling element units5A,5B,5C and65A,65B and65C can be prevented from being sunk, the pre-load applied to the rolling element units5A,5B,5C and65A,65B and65C can be prevented from being changed considerably and hence it is possible to smoothly move both of the first movable lens-barrel52and the second movable lens-barrel202with high accuracy separately.

The shapes of the fixed lens-barrels51and201and the movable lens-barrels52and202are not limited to the cylindrical shapes which have been described so far in the aforementioned embodiments and it is needless to say that square cylinders, oval cylinders and cylinders of various shapes can be used as the shapes of the fixed lens-barrels51and201and the movable lens-barrels52and202. Also, the number of the supporting portions is not limited to the three-point supporting or the six-point supporting in the above-described embodiments and the supporting portions for supporting at least three points may be provided. Furthermore, it is needless to say that there may be provided the supporting portions of more than four supporting points.

FIGS. 6 and 7are perspective views showing an electronic still camera150which shows a specific example of an image pickup apparatus using the lens apparatus200having the aforementioned arrangement. The electronic still camera150shown inFIGS. 6 and 7includes a camera body151which shows a specific example of an image pickup apparatus body. The camera body151has the collapsible type lens apparatus200incorporated therein.

The camera body151is formed of an oblong housing having a space formed in its inside, and the lens apparatus200is located on one side (right-hand side toward the camera in this embodiment) of the lateral direction which is the longitudinal direction of the camera body151. Although not shown, a printed circuit board on which various kinds of electronic assemblies are mounted, a battery power supply, various kinds of electronic assemblies and mechanical assemblies, apparatus and the like are accommodated within the inside space of the camera body151.

A shutter release button153for taking a picture of an object is provided on the upper surface of the camera body151. Further, although not shown, a power supply button, a mode selection dial, a flat surface display panel formed of a liquid-crystal display (LCD) to display various modes selected by the mode selection dial, objects and the like, an electronic viewfinder and the like are provided on the camera body151.FIG. 6shows the state in which the collapsible type lens apparatus200is collapsed and housed within the camera body151.FIG. 7shows the state in which the collapsible type lens apparatus200is extended from the camera body151.

FIGS. 10A and 10Bare cross-sectional views showing the state in which the collapsible type lens apparatus200is extended from the camera body151, respectively. At that time, the collapsible type lens apparatus200can be roughly placed in the wide-angle state (wide-angle lens mode) and the telephoto state (telephoto lens mode), respectively. When the lens apparatus including the linearly movable rolling guide apparatus according to the present invention is applied to the electronic still camera150having the above-mentioned arrangement, it is possible to obtain the camera in which the lens apparatus200can be collapsed smoothly and reliably.

FIGS. 11A,11B,11C,FIGS. 12A,12B,12C,12D andFIGS. 13A,13B,13C and13D are diagrams showing other examples of shapes of fixed members and movable members of the lens-barrels of the lens apparatus according to the present invention, supporting methods of supporting movable members and fixed members and the like, respectively. InFIGS. 11A,11B,11C,FIGS. 12A,12B,12C,12D andFIGS. 13A,13B,13C and13D, elements and parts identical to those of the above-described embodiments are denoted by identical reference numerals.

In the example shown inFIG. 11A, a fixed lens-barrel81and a movable lens-barrel82are formed as oval-shapes (two portions of a circle are formed as parallel two sides), the movable lens-barrel82is located at the outside of the fixed lens-barrel81with a predetermined gap and the fixed lens-barrel81and the movable lens-barrel82are supported by three rolling element units83A,83B and83C. As shown inFIG. 11A, the fixed lens-barrel81and the movable lens-barrel82are located in such a manner that their flat surface portions may be located in the upper and lower direction. A first rolling element unit83A which serves as a reference rolling element unit to properly position the two lens-barrels81and82is set to central portions of lower flat surface portions81aand82a.

A guide groove84having a V-like cross-section and whose cross-sectional shape is continued to the axial direction is provided on the outer surface of the lower flat surface portion81aof the fixed lens-barrel81. In response to this guide groove84, a guide groove85having a V-like cross-section and whose cross-sectional shape is continued to the axial direction is provided on the inner surface of the lower flat surface portion82aof the movable lens-barrel82. Then, the first rolling element unit83A is provided between these guide grooves84and85such that it can be rolled freely.

Also, a second rolling element unit83B is located on the upper portion of one circular arc surface of the fixed lens-barrel81and the movable lens-barrel82, and a third rolling element unit83C is located on the upper portion of the other circular arc surface of the fixed lens-barrel81and the movable lens-barrel82. To this end, opening portions86and86to house therein the guide member2are respectively provided on the upper portions of the two circular arc surfaces81band81cof the fixed lens-barrel81. In response to these opening portions86and86, protruded portions87and87, which are protruded in the inside of the radius direction, are provided on the upper portions of the two circular arc surfaces82band82cof the movable lens-barrel82. A guide groove82having a V-like cross-section and whose cross-sectional shape is continued to the axial direction is provided at substantially the central portion of the inner surface of the respective protruded portions87and87.

The second rolling element unit83B and the third rolling element unit83C are respectively provided between the two guide grooves88and88of the movable lens-barrel82and the guide grooves7and7of the two guide members2and2held on the fixed lens-barrel81in such a manner that they can be rolled freely. Further, the two sets of the leaf springs6A and6B serving as the pre-load members are provided between the two guide members2and2and the fixed lens-barrel81. These leaf springs6A and6B spring-bias the two guide members2and2toward the outside of the radius direction to apply pre-load of a substantially uniform and predetermined magnitude to the first to third three rolling element units83A,83B and83C. In this case, since the three rolling element units83A,83B and83C are located at the equal interval in the circumferential direction, it is possible to apply pre-load of a magnitude substantially similar to that of the pre-load applied to other rolling element units83B and83C to the rolling element unit83A by providing a structure in which a leaf spring is not used at only one place.

According to the above-mentioned arrangement, similarly to the above-described embodiments, under spring force of the leaf springs6A and6B acting from two directions, substantially uniform pre-load can be applied to the three rolling element units83A,83B and83C. Thus, even when the rolling element units83A,83B and83C are located at any positions of the moving direction, the rolling element units83A,83B and83C can be prevented from being sunk, the pre-load applied to the rolling element units83A,83B and83C can be prevented from being varied considerably and the movable lens-barrel82can be moved smoothly with high accuracy.

FIG. 11Bshows an example of an arrangement in which the fixed lens-barrel81and the movable lens-barrel82shown inFIG. 11Aare formed as a square fixed lens-barrel91and a square movable lens-barrel92and in which three rolling element units93A,93B and93C are provided between the two lens-barrels91and92. As shown inFIG. 11B, a guide groove94having a V-like cross-section and whose cross-sectional shape is continued to the axial direction is provided at substantially the central portion of the outer surface of a lower surface portion91aof the fixed lens-barrel91. Concurrently therewith, a guide groove95having a V-like cross-section and whose cross-sectional shape is continued to the axial direction is provided at substantially the central portion of the inner surface of a lower surface portion92aof the movable lens-barrel92. Then, the first rolling element unit93A is provided between these guide grooves94and95in such a manner that it can be rolled freely.

The second rolling element unit93B is located at one upper corner portion of the fixed lens-barrel91and the movable lens-barrel92and the third rolling element unit93C is located at the other upper corner portion of the fixed lens-barrel91and the movable lens-barrel92. To this end, opening portions96and96to house therein the guide members2and2are respectively provided on the two upper corner portions of the fixed lens-barrel91. In response to these opening portions96and96, thick portions97and97having proper thicknesses are respectively provided on the insides of the two upper corner portions of the movable lens-barrel92. Two guide grooves98and98having V-like cross-sections and whose cross-sectional shapes are continued to the axial direction are provided at substantially central portions of the inner surfaces of the two thick portions97.

The second rolling element unit93B and the third rolling element unit93C are respectively provided between the two guide grooves98and98of the movable lens-barrel92and the guide grooves7and7of the two guide members2and2held on the fixed lens-barrel91. Further, the two sets of the leaf springs6A and6bserving as the pre-load members are provided between the two guide members2and2and the fixed lens-barrel91. These leaf springs6A and6B spring-bias the two guide members2and2toward the outside to apply pre-load of substantially a uniform and predetermined magnitude to the first to third rolling element units93A to93C.

In this case, since the three rolling element units93A,93B and93C are located symmetrically with respect to the first rolling element unit93A, by the arrangement in which the leaf spring is not used at only one portion of the center, it is possible to apply the pre-load of substantially a similar magnitude to the three rolling element units93A,93B and93C.

FIG. 11Cshows an example in which the arrangements of the three rolling element units93A,93B and93C shown inFIG. 11Bare changed, the shapes of the fixed lens-barrel91and the movable lens-barrel92being the same. As shown inFIG. 11C, a guide groove104having a V-like cross-section and whose cross-sectional shape is continued to the axial direction is provided at substantially the central portion of the outer surface of one lower corner portion101aof the fixed lens-barrel91. Concurrently therewith, a guide groove105having a V-like cross-section and whose cross-sectional shape is continued to the axial direction is provided at substantially the central portion of the inner surface of one lower corner portion102aof the movable lens-barrel102. Then, the first rolling element unit103A is provided between these guide groove104and105in such a manner that it can be rolled freely.

A second rolling element unit103B is located on the upper surface portion of the fixed lens barrel101and the movable lens-barrel102and the third rolling element unit103C is located on the side surface portion of the opposite side of the guide grooves104and105of the fixed lens barrel101and the movable lens-barrel102. To this end, opening portions106and106to house therein the guide members2and2and dented portions107and107are respectively provided at substantially the central portion of an upper surface portion101bof the fixed lens-barrel101and at substantially the central portion of a side surface portion101c. In response to these opening portions106and106and the like, guide grooves108and109having V-like cross-sections and whose cross-sectional shapes are continued to the axial direction are respectively provided at substantially the central portion of an upper surface portion102bof the movable lens-barrel102and at substantially the central portion of a side surface portion102c.

The second rolling element unit103B and the third rolling element unit103C are respectively provided between the two guide grooves108and109of the movable lens-barrel102and the guide grooves7and7of the two guide members2and2held on the fixed lens-barrel101in such a manner that they can be rolled freely. Further, the two sets of the leaf springs6A and6B serving as the pre-load members are provided between the two guide members2and2and the fixed lens-barrel101. These leaf springs6A and6B spring-bias the two guide members2and2toward the outside to apply pre-load of substantially uniform and predetermined magnitude to the first to third three rolling element units103A,103B and103C.

In this case, since the three rolling element units103A,103B and103C are located symmetrically in the diagonal line direction with respect to the first rolling element unit103A, by the structure in which the leaf spring is not used only at the central one place, it is possible to apply pre-load of substantially a similar magnitude to the three rolling element units103A,103B and103C.

FIG. 12Ashows an example of an arrangement in which a fixed lens-barrel111and a movable lens-barrel112are formed as square shapes, four rolling element units113A,113B,113C and113D being located at four corner portions. As shown inFIG. 12A, a guide groove114having a V-like cross-section and whose cross-sectional shape is continued to the axial direction is provided at substantially the central portion of the outer surface of one lower corner portion111aof the fixed lens-barrel111. In response to the guide groove114, a guide groove115having a V-like cross-section and whose cross-sectional shape is continued to the axial direction is provided at substantially the central portion of the inner surface of a lower right corner portion112aof the movable lens-barrel112. Then, the first rolling element unit113A is provided between the guide grooves114and115in such a manner that it can be rolled freely.

The second rolling element unit113B is located at the upper right corner portion of the fixed lens-barrel111and the movable lens-barrel112, the third rolling element unit113C is located at the upper left corner portion of the fixed lens-barrel111and the movable lens-barrel112and the fourth rolling element unit113D is located at the lower left corner portion of the fixed lens-barrel111and the movable lens-barrel112. To this end, opening portions116and116to house therein the guide members2and2are respectively provided at three corner portions except the lower right corner portion112aof the fixed lens-barrel111. In response to these opening portions116and116, guide grooves having V-like cross-sections and whose cross-sectional shapes are continued to the axial direction are respectively provided at other three corner portions than the lower right corner portion of the movable lens-barrel112.

The second rolling element unit113B, the third rolling element unit113C and the fourth rolling element unit113D are respectively provided at three portions among the three guide grooves118,118and118of the movable lens-barrel112and the guide grooves7,7and7of the three guide members2,2and2held on the fixed lens-barrel111in such a manner that they can be rolled freely. Further, the three sets of the leaf springs6A and6B serving as the pre-load members are respectively provided between the three guide members2,2and2and the fixed lens-barrel111. These leaf springs6A and6B respectively spring-bias the three guide members2,2and2toward the outside to apply pre-load of substantially a uniform and predetermined magnitude to the first to fourth four rolling element units113A to113D.

In this case, since the four rolling element units113A,113B,113C and113D are located symmetrically in the diagonal line direction with respect to the first rolling element unit113A, by the structure in which the leaf spring is not used at only one central portion, it is possible to apply the pre-load of substantially a similar magnitude to the four rolling element units113A,113B,113C and113D.

FIG. 12Bshows an example in which the arrangements of the four rolling element units113A,113B,113C and113D shown inFIG. 12Aare changed. Specifically, while the four rolling element units113A,113B,113C and113D are located at the four corner portions of the square fixed lens-barrel111and the square movable lens-barrel112in the embodiment shown inFIG. 12A, according to this embodiment, four rolling element units123A,123B,123C and123D are located at substantially central portions of four flat surface portions of a fixed lens-barrel121and a movable lens-barrel122.

As shown inFIG. 12B, a guide groove124having a V-like cross-section and whose cross-sectional shape is continued to the axial direction is provided at substantially a central portion of the outer surface of a lower surface portion121aof the fixed lens-barrel121. A corresponding guide groove125having a V-like cross-section and whose cross-sectional shape is continued to the axial direction is provided at substantially a central portion of the inner surface of a lower surface portion122aof the movable lens-barrel122. Then, the first rolling element unit123A is provided between these guide grooves124and125in such a manner that it can be rolled freely.

An opening portion126and a dented portion127are respectively provided at substantially central portions of other three flat surface portions than the lower surface portion121aof the fixed lens-barrel121. In response to these opening portions126and the like, guide grooves128having V-like cross-sections and whose cross-sectional shapes are continued to the axial direction are respectively provided on all of other three flat surface portions than the lower surface portion122aof the movable lens-barrel122.

The second rolling element unit123B, the third rolling element unit123C and the fourth rolling element unit123D are respectively provided at the three guide grooves128,128and128of the movable lens-barrel122and the guide grooves7,7and7of the three guide members2,2and2held on the fixed lens-barrel121in such a manner that they can be rolled freely. Further, the three sets of the leaf springs6A and6B serving as the pre-load members are respectively provided between the three guide members2,2and2and the fixed lens-barrel121. When the three guide members2,2and2are spring-biased toward the outside by these leaf springs6A and6B, pre-load of substantially a uniform and predetermined magnitude can be applied to the first to fourth four rolling element units123A,123B,123C and123D.

Also in this case, similarly toFIG. 12A, since the four rolling element units123A,123B,123C and123D are located symmetrically in the right and left direction with respect to the first rolling element unit123A, by using the structure in which the leaf spring is not used at only one central portion, it is possible to apply pre-load of substantially similar magnitude to the four rolling element units123A,123B,123C and123D.

An example shown inFIG. 12Cis a modified example of the example shown inFIG. 12Ain which the supporting structure which does not use the guide member2is applied to two portions. Specifically, a supporting structure of the lower right corner portions of a fixed lens-barrel131and a movable lens-barrel132is also applied to the upper right corner portion. Concurrently therewith, as shown inFIG. 12C, a guide groove134having a V-like cross-section and whose cross-sectional shape is continued to the axial direction is provided at substantially a central portion of the outer surface of a right upper corner portion131aof the fixed lens-barrel131. A corresponding guide groove135having a V-like cross-section and whose cross-sectional shape is continued to the axial direction is provided substantially at a central portion of the inner surface of an upper right corner portion132aof the movable lens-barrel132. Then, the second rolling element unit133B is provided between these guide grooves134and135such that it can be rolled freely. A rest of arrangements is identical to that ofFIG. 12A.

An example shown inFIG. 12Dis a modified example of the example shown inFIG. 12Bin which the supporting structure which does not use the guide member2is applied to two portions. Specifically, a supporting structure of the lower surface portion of a fixed lens-barrel141and a movable lens-barrel142is also applied to the right side surface portion. Concurrently therewith, as shown inFIG. 12D, a guide groove144having a V-like cross-section and whose cross-sectional shape is continued to the axial direction is provided at substantially a central portion of a right side surface portion141aof the fixed lens-barrel141. A corresponding guide groove having a V-like cross-section and whose cross-sectional shape is continued to the axial direction is provided at substantially a central portion of the inner surface of a right side surface portion142aof the movable lens-barrel142. Then, a second rolling element unit143B is provided between these guide groove144and145such that it can be rolled freely. A rest of arrangements is identical to that ofFIG. 12B.

FIG. 13Ashows an example of an arrangement in which the fixed lens-barrel161and the movable lens-barrel162are formed as a square fixed lens-barrel and a square movable lens-barrel, two rolling element units163A and163B being located at central portions of two short sides. As shown inFIG. 13A, a guide groove164having a V-like cross-section and whose cross-sectional shape is continued to the axial direction is provided at substantially a central portion of the outer surface of one short side161aof the fixed lens-barrel161. A corresponding guide groove165having a V-like cross-section and whose cross-sectional shape is continued to the axial direction is provided at substantially a central portion of the inner surface of one short side162aof the movable lens-barrel162. Then, a first rolling element unit163A is provided between these guide grooves164and165in such a manner that it can be rolled freely.

A second rolling unit163B is located at the other short sides161band162bof the fixed lens-barrel161and the movable lens-barrel162. To this end, an opening portion166to house therein the guide member2is provided at substantially a central portion of the other short side of the fixed lens-barrel161. In response to this opening portion166, a guide groove168having a V-like cross-section and whose cross-sectional shape is continued to the axial direction is provided at substantially a central portion of the other short side162bof the movable lens-barrel162.

The second rolling element unit163B is provided between the guide groove168of the movable lens-barrel162and the guide groove7of the guide member2held on the fixed lens-barrel161in such a manner that it can be rolled freely. Further, the pair of the leaf springs6A and6B serving as the pre-load members are provided between the guide member2and the fixed lens-barrel161. When the guide member2is spring-biased toward the outside by these leaf springs6A and6B, pre-load of substantially a uniform and predetermined magnitude can be applied to the first and second two rolling element units163A and163B. In this case, since the two rolling element units163A and163B are located symmetrically in the right and left direction, by using the structure in which the leaf spring is not used at one rolling element unit163A, it is possible to apply pre-load of substantially a similar magnitude to the two rolling element units163A and163B.

FIG. 13Bshows an example in which the arrangements of the two rolling element units163A and163B shown inFIG. 13Aare changed. Specifically, while the two rolling element units163A and163B are provided at the two short sides of the rectangular fixed lens-barrel161and the rectangular movable lens-barrel162in the embodiment shown inFIG. 13A, according to this embodiment, the rolling element units163A and163B are located at two portions in one diagonal line direction of a fixed lens-barrel171and a movable lens-barrel172. A rest of arrangements is identical to that of the embodiment shown inFIG. 13A.

FIG. 13Cshows an example of an arrangement in which the two rolling element units163A and163B are located at the positions deviated toward the outside of the radius direction from the plane passing through the optical axis of the lens. As shown inFIG. 13C, a fixed lens-barrel181and a movable lens-barrel182are both cylindrical in shape, and the movable lens-barrel182is fitted into the outside of the fixed lens-barrel181with a predetermined gap. A pair of overhang portions181aand181b, which are extended in the axial direction, may be provided on the outer peripheral surface of the fixed lens-barrel181. The pair of the overhang portions181aand181bmay be located at the positions displaced 180°. Concurrently therewith, bag-like overhang housing portions182aand182bhaving U-like cross-sections and which are protruded in the outside of the radius direction are provided on the movable lens-barrel182.

Opening portions166and166to house therein the guide members2and2are provided on the pair of overhang portions181aand181bof the fixed lens-barrel181. The guide members2and2are housed in these opening portions166and166through the pair of the leaf springs6A and6B. Guide grooves168and168of the movable lens-barrel182are provided on the inner surfaces of the overhang housing portions182aand182bcorresponding to the respective guide grooves7and7of the pair of these guide members2and2. Then, the two rolling element units163A and163B are respectively provided between the pair of the guide grooves168and168of movable lens-barrel182and the respective guide grooves7and7of the pair of the guide members2and2in such a manner that they can be slid freely.

FIG. 13Dshows an example in which the shapes of the fixed lens-barrel and the movable lens-barrel shown inFIG. 13Care changed. Specifically, while the fixed lens-barrel181and the movable lens-barrel182are circular in shape in the embodiment shown inFIG. 13C, the fixed lens-barrel181and the movable lens-barrel182are formed as rectangular ones to provide a fixed lens-barrel191and a movable lens-barrel192. A rest of arrangements is identical to that shown inFIG. 13C.

According to the arrangements shown inFIGS. 11B,11C,FIGS. 12A,12B,12C,12D andFIGS. 13A,13B,13C and13D, similarly toFIG. 11AandFIG. 9, pre-load of substantially a uniform magnitude can be applied to more than two (two, three, four or more than four rolling element units) rolling element units by using spring force of the leaf springs6A and6B. Therefore, even when the rolling element units are located at any positions in the moving direction, the rolling element units can be avoided from being sunk, the pre-load applied to the rolling element units can be prevented from being changed considerably and the movable lens-barrel can be smoothly moved with high accuracy. It is sufficient that the supporting portion including the pre-load member may be provided at more than one position. Having considered balance of pre-load, it is preferable that the supporting portion including the pre-load member should be provided at more than two portions.

FIG. 14is a perspective view showing an embodiment of a lens apparatus230including a position detecting means to detect the position of a first movable lens-barrel52. Since this embodiment is different from the above-described embodiments only in the presence of a position detecting sensor231which is the position detecting means, the position detecting sensor231will be described herein. Hence, identical other arrangements are denoted by identical reference numerals and need not be described.

InFIG. 14, reference numeral14denotes an exterior lens-barrel and the first movable lens-barrel52, a first fixed lens-barrel and the like, not shown, are housed in the inside of this exterior lens-barrel232. The exterior lens-barrel232is provided with an attachment flange233, and the lens apparatus230is attached to the camera body through the attachment flange233. The position detecting sensor231is attached to the side surface portion of this exterior lens-barrel232. To this end, an oblong234, which is extended in parallel to the optical axis direction, is formed on the side surface portion of the exterior lens-barrel232. Flat surface portions232aand232ato attach the position detecting sensor231are formed on both sides of the width direction of this oblong hole234.

Two positioning pins235and235are provided on the flat surface portions232aand232aof the exterior lens-barrel232with a predetermined gap therebetween. A sensor holding frame236is properly positioned by these pins235and235and thereby fixed to the side surface of the exterior lens-barrel232through a pair of spacers237and237. The pair of spacers237and237are brought in contact with the respective flat surface portions232aand232aon which the sensor holding frame236is extended so as to cross the oblong hole234. To this end, the sensor holding frame236has defined therein four holes236ainto which the four pins235are fitted and the pair of spacers237and237have defined therein holes237ainto which the two pins235are inserted.

The position detecting sensor231is composed of an MR (magnetoresistive) magnet (magnetic scale)238and an MR sensor (magnetic sensing sensor)239. The MR magnet238is formed of a long and narrow rod-like magnetic material on which N poles and S poles are alternately magnetized at a very small pitch. The MR magnet238is fixed to the outer peripheral surface of the first movable lens-barrel52by a suitable fixing means such as an adhesive while its longitudinal direction is made in parallel to the optical axis of the lens. The MR magnet238is housed within the oblong hole234of the exterior lens-barrel232and its height is set in such a manner that it may be prevented from contacting with the inner surface of the sensor holding frame236.

In this case, the height of the MR magnet238can be set by the following means, for example.

(1) A first means for setting the height of the MR magnet238is to decrease the thickness of the MR magnet238sufficiently. Specifically, the thickness of the MR magnet238is made thinner than the thickness of the flat surface portion232aof the exterior lens-barrel232so that, when the MR magnet238is attached to the outer peripheral surface of the first movable lens-barrel52, a proper gap is set between its surface and the inner surface of the sensor holding frame236to thereby prevent the MR magnet238from contacting with the sensor holding frame236.

(2) A second means for setting the height of the MR magnet238is suitable for the application to the case in which the thickness of the MR magnet238may not be decreased as in the case (1) and in which a concave portion is formed on the first movable lens-barrel52, whereby a part of the MR magnet238can be buried into the first movable lens-barrel52.

(3) A third means for setting the height of the MR magnet238is suitable for the application to the case in which the thickness of the MR magnet238may not be made thinner that the thickness of the first movable lens-barrel52and in which the flat surface portion232aof the first movable lens-barrel52is built up so that the sensor holding frame236may be supported at the position higher than the thickness of the first movable lens-barrel52.

In addition, various kinds of structure can be applied insofar as the structures can allow the first movable lens-barrel52to be moved forward and backward while the MR magnet238fixed to the first movable lens-barrel52can be prevented from contacting with the sensor holding frame236fixed to the exterior lens-barrel232. After the position detecting sensor231was attached to the side surface portion of the exterior lens-barrel232, the oblong hole234may be closed by a suitable means such as a cover in order to protect the oblong hole234from being smudged by dusts. A cover member for covering the circumference of the position detecting sensor231may be provided as the above-mentioned cover. Also, cover members for covering the opening portion of the oblong hole234may be provided in the left and right direction of the sensor holding frame236.

The sensor holding frame236is composed of a square holding portion236bto which the MR sensor239is attached and attachment portions236cand236cprovided on opposing two sides of the holding portion236b. Two holes236aand236aare formed on the two attachment portions236cand236c. Also, the holding portion236bhas at its substantially central portion defined a through-hole241through which magnetic fields of the MR magnet238may pass. The MR sensor239is fixed to the outer surface of the holding portion236bby a suitable means such as an adhesive in such a fashion that the magnetic sensing surface of the MR sensor239may be opposed to this through-hole241.

The MR sensor239is adapted to detect intensity of magnetic fields outputted from the MR magnet238. The MR sensor239is mounted at predetermined position of an electric circuit of a sensor wiring plate242and it is electrically connected to the electric circuit. The magnetic sensing surface of this MR sensor239is opposed to the surface of the MR magnet238and the magnetic sensing surface of the MR sensor239is made parallel to the surface of the MR magnet238. In that case, by adjusting the thicknesses of the pair of the spacers237and237, the attachment position of the MR sensor239is changed to adjust the gap between the MR sensor239and the MR magnet238.

According to the above-mentioned arrangement, the position of the first movable lens-barrel52including the one-group lens holding frame216can be detected by the position detecting sensor231. Specifically, when the first movable lens-barrel52is moved in the optical axis direction, it is possible to detect the position of the first movable lens-barrel52relative to the first fixed lens-barrel51, that is, the position of the first movable lens-barrel52in the optical axis direction by detecting the change of intensity of the magnetic field of the MR magnet238with the MR sensor239. When the output from the MR sensor239is obtained, it is possible to control the position of the first movable lens-barrel52by controlling the operation of the first movable lens-barrel52.

As described above, according to the present invention, the movable lens-barrel holding means is formed as the linearly movable rolling bearing and the movable lens-barrel driving means is formed as the linear motor driving means, whereby the movable lens-barrels located inside and outside the fixed lens-barrel can be operated independently. To this end, since the linearly movable bearing mechanism is used as the bearing holding portion, as compared with the related-art holding mechanism based on sliding friction, frictional resistances obtained when the lens apparatus is activated and it is being operated can be made extremely small. Thus, it becomes possible to drive the lens apparatus by a non-contact linear motor with small power based on power saving. Further, since the lens apparatus can be avoided from being restricted by the cam groove unlike the related art, freedom in optical design can be increased and design efficiency can be increased. In addition, since the sliding portion does not need a lubrication material such as grease, working efficiency in the assembly can be improved, production efficiency can be improved and a cost can be decreased.

Also, according to the present invention, since the lens apparatus has the structure in which proper pre-load can be applied to the rolling elements while it has the simple structure, uniform pre-load can be applied to the rolling elements by using the pre-load member. Further, regardless of the moving position of the rolling elements, inclinations of the moving directions of the guide members and the rolling element units can be decreased and hence the movable member can be moved smoothly. In addition, since the sliding portion can be prevented from being wobbled, it is possible to alleviate restrictions on optical sensitivity while shaking of shot images and dropout of images can be decreased. Further, since the pre-load applied to the rolling element units need not be adjusted and accuracy of the rolling elements can be alleviated, the inexpensive assemblies can apply substantially uniform pre-load to the whole of the lens apparatus and more stable linear operations can be realized.

Further, according to the present invention, since the movable lens-barrel is moved linearly and it is never rotated, the lens-barrel need not be formed as the circular and lens-barrels whose cross-sectional shapes are various shapes such as square, other polygons, ellipse or oval can be applied to the present invention. Therefore, freedom in optical design can be improved so that the lens apparatus can be mounted and designed with larger freedom. Further, since a reduction gear need not be used unlike the related art, a disturbing portion such as a large protruded portion can be avoided from being generated and hence a small collapsible lens apparatus with excellent operation property can be obtained. In addition, quick collapsing operations and auto-focus operations become possible.

Further, according to the present invention, since the lens apparatus has no gear mechanism and no surface-contact sliding portion, the movable lens-barrel can be operated at higher speed. Also, while the movable lens-barrel is operated at high speed, operation sounds can be prevented from being generated and hence silent collapsing operation becomes possible. Also, since the driving means of the movable lens-barrel is of the linear motor driving, frictional resistance generated when the lens apparatus is collapsed is small so that the movable lens-barrel can be accommodated into the camera body at high speed. Thus, durability required when the lens apparatus is shocked upon inadvertent dropping can be improved. Further, it becomes possible to carry out moving picture recording, which needs continuous shooting and audio recording, such as recording in the zoom operation and auto-focus operation.

As described above, according to the present invention, it is possible to provide a linear motor drive small collapsible lens apparatus that can achieve the above-mentioned many effects which might not be realized by the related-art cam groove trace type collapsible lens and the image pickup apparatus using such lens apparatus.

As set forth above, the present invention is not limited to the above-described embodiments. While the embodiments in which the image pickup apparatus according to the present invention is applied to the electronic still camera (that is, digital camera) in the above-described embodiments, the present invention is not limited thereto and it is needless to say that the present invention can be applied to image pickup apparatus of other systems, such as a video camera, a personal computer with a camera and a PDA (personal digital assistant).

DESCRIPTION OF REFERENCE NUMERALS