An improved stepped etalon comprises a transparent body having a stepped surface. The lands of the steps are separated by a non-abrupt or softened transition region. This reduces the diffraction of light caused by the step transitions, thereby reducing the dead spot behind the step transition portions where interference prevents accurate measurements of light transmission from being made. Methods for producing a smoothly stepped etalon and for smoothing the step transitions in an abruptly stepped etalon are also disclosed.
A stepped etalon having a top surface and two bottom surfaces that are parallel to the top surface and are each positioned at different distances from the top surface. Each bottom surface has an edge, wherein the edges face one another and a sloping step is positioned between the two edges so that rays from a beam of light projected onto the top surface of the etalon strike the step at the Brewster angle and pass through the etalon without any light being reflected back therein.
A wavemeter (30) comprises a first wavelength determination unit (40) having a substantially periodic wavelength dependency and being adapted for providing a reference wavelength dependency (100) over a reference wavelength range. A second wavelength determination unit (50) has a substantially periodic wavelength dependency and is adapted for providing a second wavelength dependency (140) over a second wavelength range (120). An evaluation unit (60) compares the second wavelength dependency (140) with the reference wavelength dependency (100) for adjusting (160) the second wavelength dependency (140) in wavelength.
