Lens barrel

A lens barrel detachably attached to a camera body includes a fixed tube section that has a base end installed at the camera body, and a top end, a first pitch screw section being formed on an inner peripheral surface of the top end; a movable tube section that is a tube member configured to hold a plurality of lens and has a second pitch screw section on the movable tube side formed at an outer peripheral surface, and is located so as to be movable inside the fixed tube section in such a state that the second pitch screw section is threadedly engaged with the first pitch screw section, the plurality of lens including two group of lenses, a first group and a second group, held within the movable tube section. The movable tube section having a fixed diaphragm plate that is detachable.

TECHNICAL FIELD

The present disclosure relates to a lens barrel that is configured so as to be freely attached to and detached from a camera body.

BACKGROUND

Cameras have been installed indoors or outdoors of a building for various kinds of purposes including detection of an inspection line or the position detection of a robot to be produced in a factory, and security. In some such cameras, a lens barrel can be attached thereto and detached therefrom, and various kinds of lens barrels have been proposed (for instance, see non-patent related document 1 and patent related documents 1 and 2).

FIG. 5is a side view that shows an instance of a conventional configuration of a lens barrel configured to be attached to and detached from a camera body, a reference number B in the figure denotes a camera body, and a reference number100denotes the lens barrel to be attachably and detachably installed on the camera body. Such lens barrel100is comprised of a plurality of tube sections,101A and101B, configured so as to adjust a focus by relatively rotating the tube sections101A and101B. A reference number102denotes a locking screw for fixing the respective tube sections101A and101B so as not to shift their rotational positions.

SUMMARY OF INVENTION

But, the above-mentioned locking screw102has such a problem that it is hard to be tightened due to its small diameter.

An object of the invention is to provide the lens barrel for solving the above-mentioned problem.

The first aspect of the invention is a lens barrel (1,2,3) configured to detachably attach to a camera body (B), exemplarily shown inFIG. 1throughFIG. 3A andFIG. 6, comprising: a fixed tube section (10,20,30) that has a base end (10a,20a,30a) for detachably attaching to a camera body (B), and a top end (10b,20b,30b), a pitch screw section (10d,20d,30d) on the fixed tube side (“the first pitch screw” hereinafter) being formed on an inner peripheral surface (10c,20c,30c) of the top end (10b,20b,30b), a movable tube section (11,21,31) that is a tube member for holding lens (A1, A2) and has a pitch screw section on the movable side (“the second pitch screw” hereinafter) formed at an outer peripheral surface (11a,21a,31a), and is located so as to be movable inside the fixed tube section (10,20,30) in such a state that the second pitch screw (11b,21b,31b) is threadedly engaged with the first pitch screw (10d,20d,30d); and a nut member (12,22,32) configured so as to restrict a relative rotation between the fixed tube section (10,20,30) and the movable tube section (11,21,31) by abutting on the top end (10b,20b,30b) of the fixed tube section (10,20,30), being engaged with the second pitch screw (11b,21b,31b).

The second aspect of the invention is the lens barrel according to the first aspect, detailedly shown inFIG. 2A,FIG. 2B,FIG. 3A, andFIG. 6, wherein the movable tube section (21,31) has a base movable tube section (210,310) that has the second pitch screw (21b,31b), a top movable tube section (211,311) detachably attached to the base movable tube section (210,310), and a fixed diaphragm plate (212,314) held between the base movable tube section (210,310) and the top movable tube section (211,311).

The third aspect of the invention is the lens barrel according to the second aspect, as exemplarily shown inFIGS. 3B through 3D, further comprising a fixed diaphragm plate for exchange (212A,212B,212C) having an opening (212Aa,212Ba,212Ca) different from one (not shown) of the fixed diaphragm plate (212).

The fourth aspect of the invention is the lens barrel according to the first aspect, wherein a through hole (a reference number11cofFIG. 1, and reference numbers211c,213cofFIG. 3A) is formed at a section that holds the lenses (A1, A2) (“the lens holding section” hereinafter) in the movable tube section; whereby adhesive (not shown) can be filled between the outer peripheral surface of the lenses (A1, A2) and the lens holding section (11,211,213) via the through hole (11c,211,213c).

The fifth aspect of the invention is the lens barrel according to the first aspect, as exemplarily shown inFIG. 1,FIGS. 2A and 2B, further comprising a first knurling (see the reference number20e) formed on the outer peripheral surface of the fixed tube section (reference number20ofFIGS. 2A and 2B) that is a projected and recessed section, or/and a second knurling (see the reference number11dofFIG. 1) formed on the outer peripheral surface of the movable tube section (reference number11ofFIG. 1) that is a projected and recessed section, wherein the nut members (12,22) have shapes and/or colors different from the first knurling (20e) and/or the second knurling (11d).

The sixth and seventh aspects of the invention is the lens barrel according to the first aspect, as exemplarily shown inFIG. 6, further comprising an spring member as an elastic member located between the fixed tube section (30) and the movable tube section (31) so as to energize the movable tube section (31) in the optical axis direction (C) of the lens (A1, A2) held by the movable tube section (31).

The number in parentheses shows the corresponding element in the drawings for the sake of convenience, accordingly, the descriptions are not restricted and bound by the descriptions on the drawings.

According to the first aspect of the invention, it is possible to restrict the relative rotation between the fixed tube section and the movable tube section through the nut member even if the lens barrel is installed on the camera body that is fixed indoors or outdoors of a building for a long time and receives various kinds of vibrations for this reason, and to prevent a deviation of a focus or a zoom due to the above-mentioned vibrations. Besides, the nut member is easy to be fastened and hard to be unfastened since it has a bigger diameter in comparison with the locking screw exemplarily shown inFIG. 5.

In a case where the diaphragm to be used for the lens barrel is a variable diaphragm, the diaphragm blades against each other due to a situation of an installation place (the vibrations in a plant, and the vibrations received from arms for production in a plant when the camera is set on such arms or the other movable objects), the vibration with earthquakes or the other reasons, and dusts generate, and at the result, an image noise may be generated. But, above-mentioned problem can be solved since the fixed diaphragm plate is used, not the variable diaphragm according to the second and third aspects of the invention.

According to the fourth aspect of the invention, it is possible to prevent the positional shift of the respective lenses from proper positions even if the lens barrel is attached to the camera body for a long term.

According to the fifth aspect of the invention, it is possible to clearly distinguish the first and second knurlings from the nut members through a visual sense and a sense of touch.

According to the sixth and seventh aspects of the invention, the relative movement between the fixed tube section and the movable tube section in the optical axis direction is restricted through the spring member before tightening by the nut member even if some rattling (the rattling in a thrust direction) occurs between the first pitch screw and the second pitch screw, and it is possible to prevent the deviation of the focus and the like due to the relative movement.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the invention are mentioned, referring to appended drawingsFIGS. 1 to 4, andFIG. 6.

A lens barrel according to the invention is configured so as to be attached to and detached from a camera body. Such a lens barrel is exemplarily shown with reference numbers1,2and3inFIG. 1,FIG. 2A,FIG. 2B,FIG. 3AandFIG. 6, and has a fixed tube section10,20,30that has a base end10a,20a,30a(one end along an optical axis direction C) for detachably attaching to the camera body B, and a top end10b,20b,30b(the other end along the optical axis direction C), a pitch screw section on the fixed tube side10d,20d,30d(“the first pitch screw” hereinafter) being formed on an inner peripheral surface10c,20c,30cof the top end10b,20b,30b, a movable tube section11,21,31, that is a tube member for holding lens A1, A2and has a pitch screw section on the movable tube side11b,21b,31b(“the second pitch screw” hereinafter) formed at an outer peripheral surface11a,21a,31a, and is located so as to be movable in the optical axis direction C inside the fixed tube section10,20,30in such a state that the second pitch screw11b,21b,31bis threadedly engaged with the first pitch screw10d,20d,30d, and a nut member12,22,32(ring nut) that is configured so as to restrict a relative rotation between the fixed tube section10,20,30and the movable tube section11,21,31by abutting on the top end10b,20b,30bof the fixed tube section10,20,30, being engaged with the second pitch screw11b,21b,31b. The nut material12,22,32is preferably formed of hard material (preferably, metal) that is hard to be deteriorated with time.

According to the invention, it is possible to restrict the relative rotation between the fixed tube section10,20,30and the movable tube section11,21,31through the nut member12,22,32even if the lens barrel is installed on the camera body B that is fixed indoors or outdoors of a building for a long time and receives various kinds of vibrations for this reason, and to prevent a deviation of a focus or a zoom due to the above-mentioned vibrations. Besides, the nut member12,22,32is easy to be fastened and hard to be unfastened since it has a bigger diameter in comparison with the locking screw102exemplarily shown inFIG. 5.

In a case of the camera that is fixed inside or outside a building, parts inside of the lens barrel rub against each other due to the vibration with earthquakes or the other reasons, and dusts generate, and at the result, an image noise may be generated. On the other hand, in case of the lens barrel1,2,3according to the invention, dusts are hard to generate even if the vibrations of earthquakes or the like are received since the nut member12,22,32is contacted with the whole top end10b,20b,30bof the fixed tube section10,20,30and the contact area is relatively large, and the above-mentioned problem can be solved.

In such a case, as detailedly shown with a reference number21,31as shown inFIG. 2A,FIG. 2B,FIG. 3AandFIG. 6, the movable tube section may have a base movable tube section210,310that has the second pitch screw21b,31b, a top movable tube section211,311detachably attached to the base movable tube section210,310, and a fixed diaphragm plate212,314held between the base movable tube section210,310and the top movable tube section211,311. For instance, preferably, a pitch screw section (not shown) is formed on an inner or outer peripheral face of the top movable tube section211,311and a pitch screw section (not shown) is formed on an inner or outer peripheral face of the base movable tube section210,310so that the top movable tube section211,311can be detachably attached to the base movable tube section210,310. Preferably, the lenses A1and A2are divided into two lens groups, one lens group A1is held by the base movable tube section210,310(in an instance shown in the figure, a tube member213,313that is attachably and detachably supported by the inside of the base movable tube section210,310) and the other lens group A2is held by the top movable tube section211,311. Then, the fixed diaphragm plate212,314is located between both lens groups A1and A2. With such a configuration (that is, the lenses are divided into two lens groups A1and A2and the fixed diaphragm plate212,314is located between the two lens groups A1and A2), it is possible to restrict an aberration fluctuation at a time of focus adjustment (that is, the fluctuation (degradation) of the aberration of a lens system due to the focus adjustment). On this occasion, the fixed diaphragm plate212,314may have an opening (diaphragm opening) in the shape of a disk.

In a case of a variable diaphragm312as exemplarily shown inFIGS. 4A through 4D, diaphragm blades rub against each other due to the vibration with earthquakes or the other reasons, and dusts generate, and at the result, an image noise may be generated. On the other hand, in a case where the above-mentioned fixed diaphragm plate212is used, it is possible to restrict such a generation of the dusts or the noise.

Preferably, the fixed diaphragm plate212,314can be exchanged by detaching the top movable tube section211,311from the base movable tube section210,310.

Furthermore, as exemplarily shown inFIGS. 3B through 3D, one or more fixed diaphragm plates for exchange212Aa,212Ba and212Ca that respectively have openings212Aa,212Ba,212Ca different from the opening of the fixed diaphragm plate212(not shown) are prepared, so that it can be properly exchanged. For instance, if the camera body B is set at a lighted place, such as the outdoors, the fixed diaphragm plate for exchange212Aa having the smallest opening212Aa as exemplarily shown inFIG. 3BFIG. 3(b)may be attached to the lens barrel2, and if it is set at a dark place, such as an indoor corridor, the fixed diaphragm plate for exchange212Ba,212Ca having the bigger opening212Ba,212Ca as exemplarily shown inFIG. 3C, andFIG. 3Dmay be attached to the lens barrel2. Preferably, the fixed diaphragm plate212,212A,212B,212C are thick in order to shut out the light and ensure mechanical strength. But, such a plate is preferably thin from a viewpoint of optics. Then, the plate has the thickness in a range of 0.05 to 0.1 mm in order to satisfy all points.

Preferably, a through hole11c,211c,213cis formed at a section that holds the lenses A1and A2(“the lens holding section” hereinafter) in the movable tube section (see reference numbers11ofFIGS. 1 and 211, 213ofFIG. 3Aso as to fill adhesive (not shown) between the outer peripheral surface of the lenses A1and A2and the lens holding section11,211,213via the through hole11c,211c,213c. In such a configuration, it is possible to pour the adhesive between the outer peripheral surface of the lenses A1and A2and the lens holding section11,211,213, and to prevent the positional shift of the respective lenses A1and A2from proper positions even if the lens barrel2is attached to the camera body B for a long term.

A method of setting the lens barrel2according to the invention is now mentioned.

At the setting of the lens barrel2, the base end20aof the fixed tube section20is installed on the cameral body B and is fixed. Preferably, on this occasion, adhesive is coated between the base end20aand the camera body B so as to prevent a loosening of the fixed tube section20due to the vibrations.

After attaching the fixed tube section20to the camera body B, the fixed diaphragm plate212,212A,212B or212cthat has a most suitable opening is selected, watching a place for setting the camera (that is, the camera body B and the lens barrel2) and the selected fixed diaphragm plate212,212A,212B or212C is inserted between the base movable tube section210and the top movable tube section211. On this occasion, preferably an adhesive is coated on a portion abutting the base movable tube section210and the top movable tube section211on each other, such as a pitch screw section that is not shown so as not to loosen the movable tube sections210,211due to the vibrations. Preferably, the nut member22is attached to the base movable tube section210, and the base movable tube section210is attached to the fixed tube section20. The adhesive is able to be coated before a step of setting the camera body B or the lens barrel2for the purpose of preventing the loosening, so that it is possible to freely move the position of the camera body B or the lens barrel2in order to easily coat the adhesive and to effectively conduct the coating work of the adhesive. In the above-mentioned embodiment, attachment of the fixed tube section20to the camera body B, the attachment of the fixed diaphragm plate to the movable tube section21, and the attachment of the movable tube section21to the fixed tube section20are conducted in this order, but the order of the respective processes may be changed.

Thereafter, the camera body B attaching the lens barrel2thereto is set at a predetermined place, a focus is adjusted by rotating the movable tube section21, and the camera body B is fixed through the nut member22upon completion of such an adjustment. It is necessary to adjust the focus in a state of setting the camera body B at a proper site. For this reason, when the focus is fixed (that is, when the relative rotation between the movable tube section21and the fixed tube section20is restrained) with the adhesive, it may be difficult to coat the adhesive, depending on the state of setting the camera body B or its setting position. In a case where the camera body B is suspended from a ceiling or an edge of eaves, for instance, it is necessary to coat the adhesive, suspending camera body B from the ceiling or the edge of the eaves and necessary for the worker to coat the adhesive in an uncomfortable position. For this reason, the adhesive may flow into an unintended part or may drip. Besides, the focus may be shifted due to the vibrations, such as the vibrations due to winds and the vibrations from cars traveling on a road close thereto before sufficiently hardening the adhesive. According to the invention, it is possible to solve such a problem since the focus is fixed through the nut member22.

Preferably, a first knurling20e, exemplarily shown inFIG. 2A, andFIG. 2B, formed on the outer peripheral surface of the fixed tube section20that is a projected and recessed section, or/and a second knurling11d, exemplarily shown inFIG. 1, formed on the outer peripheral surface of the movable tube section11that is a projected and recessed section are provided have shapes and/or colors different from the first knurling20eand/or the second knurling11d. By doing so, it is possible to clearly distinguish the first and second knurling20e,11dfrom the nut members12,22through a visual sense and a sense of touch, and to prevent error operation or the like. Especially, if these are formed with different colors, it is possible to indicate a commentary of a product manual to be easily known.

Preferably, as exemplarily shown inFIG. 6, an elastic member33is located between the fixed tube section30and the movable tube section31so as to energize the movable tube section31in the optical axis direction C (that is, the optical axis direction of the lens barrel3, and the optical axis direction of the lenses A1and A2that the movable tube section31holds). By doing so, the relative movement between the fixed tube section30and the movable tube section31in the optical axis direction C is restricted through the spring member33before tightening by the nut member32even if some rattling (the rattling in a thrust direction) occurs between the first pitch screw30dand the second pitch screw31b, and it is possible to prevent the deviation of the focus and the like due to the relative movement. Preferably, the elastic member33is a coil spring member (concretely, a compression coil spring) energizing the movable tube section31in a direction departing from the fixed tube section30(the right direction inFIG. 6, and the direction where the movable tube section31is moved by tightening the nut member32), but a similar construction may be realized with another elastic members, as well as the spring members other than the coil spring member.

EXPLANATION OF REFERENCE NUMBERS