Determination of measurement error in an etalon

A light source comprising:

• a light-generation apparatus;
• and
• an optical measurement apparatus comprising:
• an etalon comprising a focusing lens configured to focus light at an image plane, the etalon associated with a calibration parameter related to the focusing lens, and the calibration parameter having a pre-set default value;
• an optical detector configured to detect an interference pattern produced by the etalon and to produce information related to the etalon, the information comprising first spatial information for a first fringe and second spatial information for a second fringe;
• and
• a control system coupled to the optical detector, the control system configured to:
• determine a measurement error value of the etalon based on the first spatial information, the second spatial information, and an initial value of the calibration parameter;
• and
• analyze the measurement error value to determine whether to adjust the pre-set default value.

A method comprising:

• accessing information relating to an etalon, wherein the etalon is associated with a calibration parameter having a pre-set default value, the etalon is configured to produce an interference pattern comprising a plurality of fringes from a received light beam, and the information relating to the etalon comprises first spatial information related to a first fringe of the plurality of fringes and second spatial information related to a second fringe of the plurality of fringes;
• determining a first wavelength value of the received light beam based on the spatial information related to the first fringe and an initial value of the calibration parameter;
• determining a second wavelength value of the received light beam based on the spatial information related to the second fringe and the initial value of the calibration parameter;
• and
• comparing the first wavelength value and the second wavelength value to determine a measurement error value.

A method for calibrating an etalon, the method comprising:

• accessing information relating to an etalon, wherein the etalon is associated with a calibration parameter having a pre-set default value, the etalon is configured to produce an interference pattern comprising a plurality of fringes from a received light beam, and the information relating to the etalon comprises first spatial information related to a first fringe of the plurality of fringes and second spatial information related to a second fringe of the plurality of fringes;
• determining a measurement error value of the etalon based on the first spatial information, the second spatial information, and an initial value of the calibration parameter;
• and
• analyzing the measurement error value to determine whether to adjust the pre-set default value.