shows an overall arrangement of an iris drive mechanism 1 according to the present invention as shown in fig1 the iris drive mechanism 1 comprises a frame 3 through which an aperture portion 3a for provide an optical path is formed and an ig meter viz motor 5 which is secured to the frame 3 a hall element 7 is mounted on the ig meter 5 the hall element is used to detect the amount of motor operation and therefore the opening and or closing amount of the iris the frame 3 has a support shaft 11 on which a first lever 9 is rotatably supported a first lever 9 is formed with a hollow cylindrical portion 9a through which the support shaft 11 is disposed as will be understood from fig2 the first lever 9 formed of an elongate plate having engagement pins 9b 9c these pins 9b 9c are respectively engaged in oblong holes 13a 15a formed in diaphragms 13 and 15 which open and or close the aperture portion 3a the diaphragm are operatively connected to the first lever 9 on either side of the cylindrical portion 9a an oblong hole 9d is formed through the first lever 9 at its end portion proximate the engagement pin 9b a second elongate flat lever 17 is formed with an engagement pin 17b which engages in the oblong hole 9d the second lever 17 also is formed with a through hole 17a into which an output shaft 5a of the ig meter 5 is force fitted a frame 19 which serves as a cover member is attached to the frame 3 the frame 19 has formed therethrough a through hole 19d.