now , the best mode for carrying out the present invention ( hereinafter referred to as an embodiment ) will be described with reference to the drawings . a retractable lens lens - barrel 100 ( hereinafter referred to as a lens lens - barrel 100 ) in the embodiment will be described with reference to fig1 to 5 . fig1 is an exploded perspective view of the lens lens - barrel 100 when viewed from a subject . fig2 is an exploded perspective view of the lens lens - barrel 100 when viewed from an image surface . fig3 is a sectional view of the lens lens - barrel 100 in use at a telephoto end . fig4 is a sectional view of the lens lens - barrel 100 in use at a wide angle end . fig5 is a sectional view of the lens lens - barrel 100 according to the embodiment when retracted . the lens lens - barrel 100 is provided in an imaging apparatus such as a digital camera or a video camera ( hereinafter referred to as a camera ), and retracted into a main body of the camera in a non - photographing state . a subject image is formed by a photographing optical system in the lens lens - barrel 100 , and the subject image is recorded on a silver film provided in the camera or recorded on a recording medium via a solid - state image pickup device . the photographing optical system in the embodiment is a zoom lens system including five groups of lenses having positive , negative , positive , positive , and positive refractive power in that order from the side of the subject , and first lenses l 1 to fifth lenses l 5 are all moved to perform a zoom operation . the photographing optical system may include at least two groups of lenses , and for example , may include five groups of lenses having positive , negative , positive , negative , and positive refractive power , or four groups of lenses having positive , negative , positive , and positive refractive power . the lens - barrel 100 includes a first lens frame 10 , a second lens frame 20 , a third lens frame 30 , a fourth lens frame 40 , and a fifth lens frame 50 holding the first lenses l 1 , the second lenses l 2 , the third lenses l 3 , the fourth lenses l 4 , and the fifth lenses l 5 , a cam barrel 60 that is a cam member that moves the first to fourth lenses l 1 to l 4 to a predetermined position along an optical axis , a fixed barrel 70 holding the cam barrel 60 rotatably around the optical axis z , and a base plate 80 to which the fixed barrel 70 is fixed , in order from the side of the subject . on the base plate 80 , a motor 82 that rotates the cam barrel 60 around the optical axis z and a motor 84 ( not shown ) that moves the fifth lenses l 5 to a predetermined position along the optical axis z are provided . the first lens frame 10 is constituted by a cylindrical member , and a lens holding portion 10 a is formed inside a subject side end surface of the first lens frame 10 . in the lens holding portion 10 a , the first lenses l 1 are secured so that the centers of the first lenses l 1 passes the optical axis z . further , in the lens holding portion 10 a , a pair of guide shafts 12 a and 12 b facing each other around the optical axis z are implanted toward the image surface so as to be inserted through the cam barrel 60 parallel to the optical axis z . besides , from an inner peripheral surface of the first lens frame 10 near an image surface side opening , six first cam pins 14 a , 14 b , 14 c , 14 d , 14 e and 14 f ( partially shown ) protrude inward of the frame at substantially 60 degree intervals around the optical axis . the first cam pins 14 a , 14 b , 14 c , 14 d , 14 e and 14 f engage first cam grooves 61 a , 61 b , 61 c , 61 d , 61 e and 61 f of substantially spiral shape formed in an outer peripheral surface of the cam barrel 60 , and the first cam pins 14 a to 14 f are moved along the first cam grooves 61 a to 61 f to cause the first lens frame 10 , that is , the first lenses l 1 , to slide in an optical axis direction . the number of first cam pins that protrude is not limited to six , and for example , three first cam pins may protrude at substantially 120 degrees intervals around the optical axis . the second lens frame 20 holds the second lenses l 2 in the center thereof . first guide through holes 22 a and 22 b are formed in an outer peripheral surface of the second lens frame 20 along the optical axis z so as to face each other around the optical axis z . the first guide through hole 22 a is formed into a circular shape when viewed from an end surface , and the first guide through hole 22 b is formed into a u - shape so as to open outward of the frame when viewed from the end surface . the first guide through holes 22 a and 22 b fit or engage the first guide shafts 12 a and 12 b . thus , the first guide shafts 12 a and 12 b function as guide rails of the second lens frame 20 , the second lens frame 20 is supported slidably along the optical axis z direction in the lens - barrel 100 , and rotation of the second lens frame 20 around a shaft perpendicular to the optical axis is restricted . the shapes of the first guide through hole 22 a and the first guide through hole 22 b when viewed from the end surface , that is , sectional shapes thereof , may be both circular shapes or u - shapes . the same applies to other through holes or through grooves described below . further , first through grooves 24 a and 24 b are formed in the outer peripheral surface of the second lens frame 20 along the optical axis z so as to face each other around the optical axis z . the pair of first through grooves 24 a and 24 b are formed at positions substantially 90 degrees apart from the pair of first guide through holes 22 a and 22 b around the optical axis . the first through grooves 24 a and 24 b prevent a pair of second guide shafts 86 a and 86 b , erected substantially vertically from the base plate 80 so as to be inserted through the cam barrel 60 , from coming into contact with the second lens frame 20 . thus , the widths of the first through grooves 24 a and 24 b are formed to be sufficiently larger than the diameters of the second guide shafts 86 . besides , one second cam pin 26 a protrudes outward of the frame from the outer peripheral surface of the second lens frame 20 . the second cam pin 26 a engages a second cam groove ( not shown ) formed in the inner peripheral surface of the cam barrel 60 , and the second cam pin 26 a is moved along the second cam groove to cause the second lens frame 20 to slide in the optical axis direction . the third lens frame 30 holds the third lenses l 3 in the center thereof a pair of second guide through holes 32 a and 32 b are formed in an outer peripheral surface of the third lens frame 30 along the optical axis z so as to face each other around the optical axis z . the second guide through hole 32 a is formed into a circular shape when viewed from an end surface , and the second guide through hole 32 b is formed into a u - shape so as to open outward of the frame when viewed from the end surface . the second guide through holes 32 a and 32 b fit or engage the second guide shafts 86 a and 86 b . thus , the second guide shafts 86 a and 86 b function as guide rails of the third lens frame 30 , the third lens frame 30 is supported slidably along the optical axis z direction in the lens lens - barrel 100 , and rotation of the third lens frame 30 around a shaft perpendicular to the optical axis is restricted . further , a pair of second through grooves 34 a and 34 b are formed in the outer peripheral surface of the third lens frame 30 along the optical axis z so as to face each other around the optical axis z . the second through grooves 34 a and 34 b are formed at positions substantially 90 degrees apart from the second guide through holes 32 a and 32 b around the optical axis . the second through grooves 34 a and 34 b prevent the first guide shafts 12 a and 12 b , implanted in the lens holding portion 10 a so as to be inserted through the cam barrel 60 , from coming into contact with the third lens frame 30 . thus , the widths of the second through grooves 34 a and 34 b are preferably formed to be sufficiently larger than the diameters of the first guide shafts 12 . besides , one third cam pin 36 a protrudes outward of the frame from the outer peripheral surface of the third lens frame 30 . the third cam pin 36 a engages a third cam groove ( not shown ) formed in the inner peripheral surface of the cam barrel 60 . the third cam pin 36 a is moved along the third cam groove to cause the third lens frame 30 to slide in the optical axis direction . the fourth lens frame 40 holds the fourth lenses l 4 in the center thereof . in the fourth lens frame 40 , third guide through holes 42 a and 42 b and third through grooves 44 a and 44 b are formed as in the third lens frame 30 . thus , the second guide shafts 86 a and 86 b function as guide rails of the fourth lens frame 40 , the fourth lens frame 40 is supported slidably along the optical axis z direction in the lens lens - barrel 100 , and rotation of the fourth lens frame 40 around a shaft perpendicular to the optical axis is restricted . one fourth cam pin 46 a protrudes outward of the frame from an outer peripheral surface of the fourth lens frame 40 . the fourth cam pin 46 a engages a fourth cam groove ( not shown ) formed in the inner peripheral surface of the cam barrel 60 . the fourth cam pin 46 a is moved along the fourth cam groove to cause the fourth lens frame 40 to slide in the optical axis direction . besides , the fourth lens frame 40 is provided along an x - axis with an x - axis drive mechanism ( not shown ) that slightly moves the fourth lenses l 4 in an x - axis direction perpendicular to the optical axis z , and provided along a y - axis with a y - axis drive mechanism ( not shown ) that slightly moves the fourth lenses l 4 in a y - axis direction perpendicular to the optical axis z and the x - axis . the x - axis drive mechanism and the y - axis drive mechanism include a magnet coil and a magnet . a driving current based on a signal output from a vibration sensor such as an angular acceleration sensor provided in a camera is supplied to the magnet coil , and electromagnetic interaction between the magnet coil and the magnet slightly moves the fourth lenses l 4 in the x - axis direction and the y - axis direction to compensate for camera shake when photographing a subject . the x - axis drive mechanism and the y - axis drive mechanism are placed along the x - axis direction and the y - axis direction , respectively , in the plane of the fourth lens frame 40 . thus , dead spaces of the fourth lens frame 40 are created between the x - axis drive mechanism and an edge of the fourth lens frame 40 and between the y - axis drive mechanism and an edge of the fourth lens frame 40 . in order to make use of the dead spaces of the fourth lens frame 40 to prevent increase in the size of the fourth lens frame 40 , the third guide through holes 42 a and 42 b and the third through grooves 44 a and 44 b are preferably formed in the dead spaces , and in this case , the first guide shafts 12 a and 12 b and the second guide shafts 86 a and 86 b are placed at positions 90 degrees apart from each other around the optical axis z . the fifth lens frame 50 holds the fifth lenses l 5 in the center thereof . in the fifth lens frame 50 , fourth guide through holes 52 a and 52 b are formed as in the third lens frame 30 . thus , the second guide shafts 86 a and 86 b function as guide rails of the fifth lens frame 50 , the fifth lens frame 50 is supported slidably along the optical axis z direction in the lens lens - barrel 100 , and rotation of the fifth lens frame 50 around a shaft perpendicular to the optical axis is restricted . the motor 84 provided on the base plate 80 moves the fifth lens frame 50 along the optical axis z . the cam barrel 60 is constituted by a cylindrical member with both ends open , and fits inside the first lens frame 10 . in the outer peripheral surface of the cam barrel 60 , six first cam grooves 61 a , 61 b , 61 c , 61 d , 61 e and 61 f ( partially shown ) are formed , and engage the first cam pins 14 a , 14 b , 14 c , 14 d , 14 e , 14 f protruding from the inner peripheral surface of the first lens frame 10 . on an outer peripheral surface of an image surface side opening of the cam barrel 60 , a gear portion 66 is formed that transmits a driving force of the motor 82 to the cam barrel 60 , and rotates the cam barrel 60 around the optical axis z . further , in the inner peripheral surface of the cam barrel 60 , a second cam groove , a third cam groove , and a fourth cam groove ( not shown ) of substantially spiral shape are formed , and engage the second cam pin 26 a of the second lens frame 20 , the third cam pin 36 a of the third lens frame 30 , and the fourth cam pin 46 a of the fourth lens frame 40 . the fixed barrel 70 is constituted by a cylindrical member with open both ends . the fixed barrel 70 fits the inside of the cam barrel 60 . the pair of first guide shafts 12 a and 12 b and the pair of second guide shafts 86 a and 86 b are inserted through the fixed barrel 70 . in an outer peripheral surface of the fixed barrel 70 , straight grooves 72 a , 72 b and 72 c are formed in parallel to the optical axis z . thus , the straight grooves 72 a , 72 b and 72 c are formed , and the second cam pin 26 a , the third cam pin 36 a , and the fourth cam pin 46 a pass through the straight grooves 72 a , 72 b and 72 c , and engage the second cam groove 62 a , the third cam groove 63 a , and the fourth cam groove 64 a formed in the inner peripheral surface of the cam barrel 60 as described above . on an inner peripheral surface of the fixed barrel 70 near a subject side opening , a pair of support portions 74 a and 74 b are provided , and fitting holes 76 a and 76 b are formed in the support portions 74 a and 74 b . the second guide shafts 86 a and 86 b fit in the fitting holes 76 a and 76 b . the motors 82 and 84 and the fixed barrel 70 are secured to the base plate 80 as described above . further , in the base plate 80 , the second guide shafts 86 a and 86 b are implanted toward the subject parallel to the optical axis z so as to face each other around the optical axis z inside the fixed barrel 70 . the configuration of the embodiment is as described above , and an operation of the lens lens - barrel from a telephoto end to a wide angle end , and further to a retracted state , will be described with reference to fig3 to 5 . an operation from the retracted state to the telephoto end is reverse of the above described operation , and a description thereof will be omitted . when the motor 82 is driven to rotate the cam barrel 60 from a telephoto end state to a wide angle end state around the optical axis z , the first lenses l 1 are moved toward the image surface along the optical axis z . the second lenses l 2 are first moved toward the image surface along the optical axis z and then moved back toward the subject , though this is not apparent from the drawings . the third lenses l 3 and the fourth lenses l 4 are moved toward the image surface along the optical axis z . the fifth lenses l 5 are first moved toward the subject along the optical axis z and then moved back toward the image surface by driving the motor 84 , though this is not apparent from the drawings . when the cam barrel 60 is rotated from the wide angle end state to the retracted state around the optical axis z , the first lenses l 1 , the second lenses l 2 , and the third lenses l 3 are moved toward the image surface along the optical axis z . on the other hand , the fourth lenses l 4 and the fifth lenses l 5 remain at the current positions . movement paths of the lenses along the optical axis z are not limited to the above , and may be changed according to configurations of the lenses . in the embodiment , the first guide shafts 12 a and 12 b and the second guide shafts 86 a and 86 b ( hereinafter , generally referred to as “ guide shafts ” when particular distinction is not needed ) are implanted in the respective positions so that a first plane including the central axis of the first guide shafts 12 a and 12 b and the optical axis z , and a second plane including the central axis of the second guide shafts 86 a and 86 b and the optical axis z are different planes . the guide shafts are implanted in such positions as to prevent the guide shafts from forming barriers when the first lens frame 10 is retracted toward the image surface . the first plane and the second plane are different planes , that is , the pair of first guide shafts 12 a and 12 b and the pair of second guide shafts 86 a and 86 b are placed at different phases rather than the same phases when the lens lens - barrel is viewed in the optical axis z direction , thereby allowing the first guide shafts 12 a and 12 b and the second guide shafts 86 a and 86 b to be provided on the same circumference around the optical axis z when viewed in the optical axis z direction , and reducing the diameter of the lens lens - barrel . the guide shafts are provided so that the first plane and the second plane are perpendicular to each other with the optical axis z at the center , that is , the phase difference is 90 degrees , thereby ensuring space utility and reducing the diameter of the lens lens - barrel .