Abstract: A lens apparatus in which plural lenses, each having a different expansion coefficient to others, are adhered to each other at their lens surfaces and some of the plural lenses, which has a smaller expansion coefficient than other lenses and the number of which is fewer than the total number of the plural lenses, are coupled with a lens barrel so that all of the plural lenses are supported by the lens barrel.

Abstract: In a zoom lens apparatus having a lens component which is movable for variation of image magnification, a lens component to compensate for the shift of focus caused by the variation of the image magnification and which is movable to bring an object to be photographed into focus, and a device for driving and positioning each of the lens components, there is provided a controller to control the device. The controller has a position table for each of the lens components and a memory to store the actual positions of the lens components. The controller compares each of the actual positions of the lens components stored in the memory with the position table, based on a signal for a desired magnification so that the zoom lens can focus on a predetermined image plane.

Abstract: A zoom lens comprising, in order from an object side, a first lens group having a positive refracting power, a second lens group having a negative refracting power and movable to vary the power, a third lens group having a negative refracting power and movable to compensate for deviation of an image position caused by varying the power, a fourth lens group having a positive refracting power for making a divergent luminous flux which exits from the third lens group substantially afocal, and a fifth lens group having a positive refraction power to an image, wherein the fourth lens group includes at least one positive single lens having a strong convex surface on the image side, the fifth lens group arranged behind a diaphragm between the fourth and the fifth lens groups and the fifth lens group comprises, in order from an object side, a front unit having a positive refracting power and a rear unit having a refracting power arranged in an air spaced relation with the front unit.

Abstract: As a projection optical system for a measuring projector, a telecentric optical system is required, and, moreover, it is advantageous when a zoom lens system is utilized. The present invention provides a telecentric zoom lens system to be used with a measuring projector wherein an iris is arranged between the lens groups to be moved for variation of magnification and wherein the iris is also moved at the time of zooming in order to prevent increase in the diameter of the front lens and increase in distortion which are caused when the telecentric character is given to a known zoom lens system.To arrange the iris between a second and third lens groups in a zoom lens system comprising four lens groups respectively having positive, negative, positive and positive powers and to enable to move the iris integrally with the third positive lens group, it is preferable to add a negative lens group between the two positive lens groups, i.e.