Patent ID: 7518100

Claim:
A system for detecting a position of a movable element wherein the movable element has a surface, the system comprising: a compartment having a body defining an interior wherein the body has an interior surface and a length defined between a first end and a second end of the compartment wherein the movable element moves within the interior of the compartment between the first end and the second end of the compartment; a cap having bottom surface and walls defining an interior of the cap wherein the walls are connected to the bottom surface wherein the cap is connected to the first end of the compartment wherein the interior of the compartment is adjacent to the interior of the cap; a film connected to the walls of the cap wherein the film encloses the interior of the cap wherein the film diffuses light emitted into the interior of the compartment; and a sensor connected to the cap wherein the sensor is adjacent to the first end of the compartment wherein the sensor detects an intensity of the light within the interior of the compartment which is attenuated by the interior surface of the compartment or by the surface of the movable element wherein the intensity of the light within the interior of the compartment corresponds to the position of the movable element within the interior of the compartment.