Abstract: Provided is a highly reliable optical filtering device used as a spatial filter for an optical inspection apparatus and configured to prevent a shutter from sticking to a wall surface of a shutter opening. The optical filtering device includes the shutter openable and closeable by voltage control and a substrate having the shutter opening serving as a movable range of the shutter, in which the substrate includes a sticking prevention part configured to prevent the shutter from sticking to the wall surface of the shutter opening when the shutter is opened.

Abstract: A zoom lens of five-unit construction includes, in succession from the object side, a first lens unit having a positive refractive power and fixed during magnification change, a second lens unit of negative refractive power having the function as a variator effecting magnification change and movable linearly on the optic axis toward the image side during the magnification change from the wide angle end to the telephoto end, a third lens unit and a fourth lens unit having the function as a compensator for correcting the fluctuation of the image surface caused by the magnification change of the second lens unit and keeping the position of the image surface constant and movable on the optic axis with different locuses so as to describe a curve convex toward the object side in conformity with the movement of the second lens unit, a fifth lens unit having the imaging function and fixed with the first lens unit during magnification change, and a stop disposed more adjacent to the image side than the fourth lens uni

Abstract: A zoom lens has, in succession from the object side, a first lens group of positive refractive power, a second lens group of negative refractive power, a third lens group of positive refractive power and a fourth lens group of positive refractive power. The first lens group, the third lens group and the fourth lens group are movable toward the object side for a magnification change from the wide angle end to the telephoto end. The focusing up to a short distance object is made possible by moving the second lens group along the optic axis from the position of its telephoto end toward the object side and moving the third lens group along the optic axis from the position of its telephoto end. The zoom lens satisfies the following condition:-0.5<.chi.3/.chi.2<0.5,where .chi.2 is the amount of movement of the second lens group from the telephoto end toward the object side for short distance focusing and .chi.

Abstract: A zoom lens comprising four lens groups the fourth group of which is composed of a front group and a rear group and the rear group is movable in a determined relation with the third lens group along the optical axis for compensating the variation of aberrations caused by zooming so that the zoom lens can always maintain good image-forming performance through the wide zooming range.

Abstract: A zoom lens including a wide angle of view has, in succession from the object side, a first lens group of positive refractive power, a second lens group of negative refractive power and a third lens group of positive refractive power. The zoom lens is capable of effecting magnification change by the second lens group being moved relative to the first and third lens groups. When zooming is effected from the wide angle end to the telephoto end, the first and third lens groups are monotonously moved toward the object side and the second lens group is moved toward the object side at least near the wide angle end.

Abstract: A gradient index lens system in which spherical aberration and coma are well corrected and which has an excellent imaging performance comprises a first gradient index lens and a second gradient index lens. The second gradient index lens has a gradient index different from that of the first gradient index lens and is either cemented to the first gradient index lens or disposed with a predetermined air space with respect to the first gradient index lens.

Abstract: A zoom lens comprises, in the order from the object side, a first lens group which has a positive power and is fixed in position during zooming, second and third lens groups which have negative powers and movable during zooming, and a fourth lens group which is fixed in position during zooming.When the zoom lens is zoomed from a side angle end to a telephoto end, the second lens group is monotonously moved along an optical axis from the object side to the image side, and the third lens group reciprocates along the optical axis. The zoom lens satisfies the certain conditions.

Abstract: A zoom lens is composed of, in the order from the object side, a focusing lens unit of a positive refractive power, a variation lens unit of a negative refractive power, a compensator lens unit of a negative refractive power, a front relay lens group of a positive refractive power and a rear relay lens group of a positive refractive power. The rear relay lens group is composed of, in the order from the object side, a negative lens component and a positive lens component. Optimum conditions are employed in the refractive power arrangement of the front and rear relay lens groups and of the negative and positive components of the rear relay lens group, and in the distance between the negative and positive components of the rear relay lens group.