1. US5895915 - Bi-directional scanning system with a pixel clock system

A bi-directional optical scanning system includes a spring-stiffened, taut-band mechanical subsystem that translates rotational motion of a servo-controlled actuator to translational (scan line or "fast axis") motion of a sample relative to a stationary objective lens. A first taut steel band attaches to a first end of a shuttle that moves the sample over the fast axis. The band then wraps partially in one direction around a light-weight wheel that is rotated by the servo-controlled actuator. The second end of the band attaches to a pre-loaded spring that is, in turn, attached to the wheel. A second taut steel band wraps partially around the wheel in the opposite direction, with one end of the band attached to the wheel and the other end attached to a second end of the shuttle. When the wheel rotates in one direction, the first band pulls the shuttle, and thus, the sample, in the forward scan direction. When the wheel rotates in the opposite direction, the second band pulls the shuttle and the sample in the backward scan direction. As the wheel rotates, the first band fits into a slit in the second band where the two bands would otherwise overlap. Each band thus remains tightly wrapped around the wheel. The wrap angle associated with the overlay of the first band on the wheel is carefully chosen to ensure that the band does not slip relative to the wheel in response to forces associated with the acceleration of the sample or differences in thermal expansion of the wheel and the band. There is thus a known relationship between the rotational movement of the wheel and the translational movement of the sample even under varying environmental conditions.