Phase difference measuring device, beam output apparatus and phase difference measuring method

A beam output apparatus comprising:

• a first beam splitter configured to split a laser beam configured to be seed light into a first laser beam and another laser beam from which a second laser beam derives;
• a phase conversion device configured to convert the first laser beam that passes therethrough, so that the first laser beam that has passed therethrough includes a phase distribution of one cycle in an azimuth direction in a cross section of the first laser beam included in an arbitrary virtual plane perpendicular to an optical axis of the first laser beam that has passed therethrough;
• a detection device configured to detect an azimuth angle of an intensity centroid of an interference pattern and detect an inter-beam phase difference of the second laser beam with respect to the first laser beam based on the azimuth angle;
• and
• a phase controller configured to control a phase of the second laser beam based on the inter-beam phase difference,
• wherein the interference pattern is generated by a shaped detection beam in a cross section of a detection beam,
• wherein the cross section of the shaped detection beam is a circle having a predetermined radius and having a center at a point, where the cross section of the detection beam and an extension line extended along an optical axis from an optical axis of the phase conversion device intersect,
• wherein the cross section is perpendicular to an optical axis of the detection beam,
• wherein a part outside the circle is masked,
• wherein the detection beam is obtained by combining a first partial intensity laser beam and a second partial intensity laser beam on a same optical path,
• wherein the first partial intensity laser beam has at least a part of an intensity component of the first laser beam that has passed through the phase conversion device, and
• wherein the second partial intensity laser beam has at least a part of an intensity component of a second laser beam.

A phase difference measuring method including:

• converting a first laser beam that has passed through a phase conversion device, so that the first laser beam includes a phase distribution of one cycle in an azimuth direction in a cross section of the first laser beam included in an arbitrary virtual plane perpendicular to an optical axis of the first laser beam;
• detecting an azimuth angle of an intensity centroid of an interference pattern;
• and
• detecting an inter-beam phase difference of a second laser beam with respect to the first laser beam based on the azimuth angle, wherein the interference pattern is generated by a shaped detection beam in a cross section of a detection beam,
• wherein the cross section of the shaped detection beam is a circle having a predetermined radius and having a center at a point, where the cross section of the detection beam and an extension line extended along an optical axis from an optical axis of the phase conversion device intersect,
• wherein the cross section is perpendicular to an optical axis of the detection beam,
• wherein a part outside the circle is masked,
• wherein the detection beam is obtained by combining a first partial intensity laser beam and a second partial intensity laser beam on a same optical path,
• wherein the first partial intensity laser beam has at least a part of an intensity component of the first laser beam that is converted, and
• wherein the second partial intensity laser beam has at least a part of an intensity component of a second laser beam derived from a laser beam as seed light from which the first laser beam derives.