An image pickup apparatus which is capable of being downsized and being power-saved, and is capable of following the focal plane and controlling the exposure during the variably-magnifying operation. One end of the first flexible portion is connected to the main body portion, while the other end of the first flexible portion is configured to come in pressure-contact with the main body portion when the first flexible portion comes in pressure-contact with the second internal wall surface. A support device supports the sealing disk against a gas pressure of the gas acting on the sealing disk in a pressure direction. Parasitic is extracted according to the generated circuit layout. Several embodiments of a computer system are described, wherein each embodiment of the computer system has a storage system including the transfer node coupled in series with a switch between the host computer and the one or more storage devices. The projection optical system for obliquely projecting an image formed by a display device on the screen includes a free curved lens having a rotationally asymmetric free curved surface.