User Manual

Copyright 2012 Page 13
3.2 Lens System Components
3.2.1 Lens System Overview
The Cooke I Technology lens system contains resistance elements to sense ring
positions, an electronics board to process and calculate lens information, and one or
two serial communications interfaces to receive and send commands and data to a
camera and/or other external device. Cooke 5I lenses also have two sets of LEDs used
to illuminate the focus scale. The LEDs are connected to a secondary electronics
interface board.
The lens electronics board has a communication interface which connects directly to
the camera and may also have a second communication interface that can be connected
to an external device such as a monitor or External Data Source Unit. The camera
interface operates at TTL levels and the external interface operates at RS232 levels.
Each communication interface provides power supply and serial transmit and receive
lines through separate 4 way connectors. See Sections 3.1.2 and 3.1.3 for details.
3.2.2 Potentiometer Connections
Cooke Prime lenses house two sensor resistance elements with wipers to sense the
ring positions for focus and aperture. Cooke Zoom lenses house three sensor resistance
elements, with wipers to sense the ring positions of focus, aperture and zoom. The lens
electronics board connects to the resistance elements using one connector for Prime
lenses and two connectors for Zoom lenses. They are supplied with power from the logic
board and the wiper signals are fed back to the board for sensing. These current settings
are interpreted using analog inputs which have 12 bit resolution. (Some of the earlier
S4I lenses had only 10 bit resolution.)
3.2.3 Illumination Ring
The 5I Prime lens logic boards have an additional 4 way connector which connects
to a secondary electronics board via a cable. This connector carries +5 volts power plus
2 PWM current sinking signals to control the two sets of LED’s and provide scale
illumination. Lighting control instructions are described in Section 8.1.