title: Absolute flatness testing by an extended rotation method using two angles of rotation.
abstract: The rotation method for the absolute testing of three flats is extended by adding a second rotation of one of the flats. This means that altogether five interferograms of pairs of flats (positional combinations) are evaluated: three basic combinations and two rotational combinations. The effect of random measuring errors is minimized by fully applying least-squares methods. Here the addition of a second rotation leads to a substantial increase of accuracy of the results and enables the lateral resolution to be further enhanced.
authors.forename: G
authors.initials: G
authors.lastname: Schulz