An x linear encoder, which is configured of a pickup placed on a measurement mount and facing an x scale fixed on the lower surface of a barrel that houses a projection optical system, measures the displacement of the barrel with the measurement mount serving as a reference. A wireless network identified by arbitrary identification information is wirelessly connected. Higher level performance indicators can be determined based on tower level state assessments. When the power source drives the long rocker arm to rotate upwards around the pin on the backboard, the long rocker arm leads the short linking rod, and the short linking rod drives the slide to move upwards along the rail which results in an upward rectilinear motion, and vice versa. A simple technique for upgrading a standard digital camera for depth of field-improvement operation, including an adequate method for preselecting focuses, is illustrated by FIG.