Patent attributes
A length reference bar system and method that compensates for thermal expansion and allows for testing whether an instrument is working properly using only an inferometer. The length reference bar system has a bar portion with end caps for target positions on either end of the bar portion that extend inward toward each other such that, if a length of the bar portion changes due to a temperature change, a length of the end caps also changes but in an opposite direction to counteract the bar portion length change. As such, any target positions mounted on the end caps remain at a constant distance from each other regardless of the temperature thereby canceling out the effect of thermal expansion. The end caps also provide multiple target positioning capability so that any targets mounted thereon may be positioned in various configurations to provide a user with increased versatility for applications such as checking calibration.
