Abstract: A stereo image forming apparatus for observing a stereo image based on two images obtained by two image taking systems. In front of each image taking system, such as a television camera, two wedge-shaped prisms are placed and made rotatable in mutually opposite directions, thus deflecting the direction of light for a varying distance to the object, in synchronization with the focusing operation of the image taking system. Thus, the apparatus can promptly focus on the object at varying distances without rotating the image taking systems themselves.

Abstract: A suck-back pump for preventing any additional amount of liquid from dropping out of the tip of a delivery pipe, after a predetermined amount of liquid has been delivered from the delivery pipe. The suck-back pump includes inlet and outlet ports for liquid, first and second chamber respectively connected with the inlet and outlet ports, a communicating passage for connecting the first and second chambers with each other, a shut-off valve movable to close the communicating passage, and a suction element movable to change the volume of the second chamber. The actuation of the suction element is retarded so that it is actuated after the shut-off valve has been actuated.