Optical user input device

An analogue control for an input apparatus, the analogue control comprising:

• a shaft pivotally mounted for movement about at least two orthogonal axes arranged normal to a longitudinal axis of the shaft and about a third orthogonal axis parallel to the longitudinal axis of the shaft;
• a target surface disposed at a proximal end of the shaft;
• at least one light source;
• a first sensor for capturing images, at a polling interval, of the target surface illuminated by the light source when the shaft is moved in one or more of the two orthogonal axes normal to the longitudinal axis of the shaft;
• a processing unit configured to:
• compare a current image of the target surface with the immediately preceding image of the target surface captured by the sensor to determine magnitude and direction of any incremental movement of the target surface relative to the sensor between the compared images,
• accumulate data, in a memory cache, indicative of the incremental movements to calculate an absolute position of the target surface relative to a predefined or origin position;
• a second sensor configured to capture an input when the shaft is moved along the third orthogonal axis parallel to the longitudinal axis of the shaft;
• and
• an origin position detection system for determining return of the target surface to a predefined origin position,
• wherein the processing unit is configured to clear the cache of accumulated incremental movement data upon detection of the target surface being disposed at the predefined origin position.