A transient digital moire phase-shifting interferometric measuring device and method for a surface shape of an optical element solves a defect that an instantaneous vibration resistance needs to be sacrificed for a measurement range when using a two-step carrier splicing method, and expands the measurement range of a digital moire phase-shifting method while retaining instantaneous anti vibration characteristics of the digital moire phase-shifting method. The transient digital moire phase-shifting interferometric measuring device includes a light source, a beam splitter, a reference lens, a first polarization grating, a measured lens, a second polarization grating, a first imaging objective lens, a first camera, a second imaging objective lens and a second camera. Different carriers are loaded through a spectral performance of a polarization grating, and the polarization grating is used to separate two beams of an interference light, and two actual interference patterns are obtained at a same time.

A measurement apparatus (10) for interferometrically determining a surface shape of a test object (14). A radiation source provides an input wave (42), a multiply-encoded diffractive optical element (60), which is configured to produce by diffraction from the input wave a test wave (66) that is directed at the test object and has a wavefront in the form of a free-form surface and at least one calibration wave (70), and a capture device (46). The calibration wave has a wavefront with a non-rotationally symmetric shape (68f), wherein cross sections through the wavefront of the calibration wave along cross-sectional surfaces each aligned transversely to one another have a curved shape. The curved shapes in the different cross-sectional surfaces differ in terms of an opening parameter. The capture device (46) captures a calibration interferogram formed by superimposing a reference wave (40) with the calibration wave after interaction with a calibration object (74).

Methods, apparatus and systems for testing an optical element are described. One example device for measuring a test optical component includes a pre-conditioning optical module positioned to receive an optical beam from a light source and to produce a beam having a non-collimated beam profile or a freeform wavefront. The device further includes a beam splitter positioned to receive the beam output from the pre-conditioning optical module and to direct a first portion of the beam to a reference arm configured to accommodate a reference optical component, and to direct a second portion of the beam to a test arm configured to accommodate the test optical component. The device also includes a beam combiner positioned to receive the beams from the reference arm and the test arm after reflection or refraction by the reference and the test optical components.

An image acquisition apparatus includes a light source configured to emit light, a dividing unit configured to divide the light from the light source into reference light and measurement light, an image forming unit configured to form a tomographic image of a subject based on interfered light in which return light from the subject irradiated with the measurement light and the reference light are interfered, a focus adjusting unit configured to adjust a focus of the measurement light, an optical-path-length adjusting unit configured to adjust an optical path length of the reference light, and a control unit configured to adjust the optical path length of the reference light by controlling the optical-path-length adjusting unit according a change in an optical path length of the measurement light caused by adjustment of the focus using the focus adjusting unit.

A method and apparatus for characterizing the surface form of an optical element, in particular a mirror or a lens element of a microlithographic projection exposure apparatus, includes: carrying out a plurality of interferometric measurements, in each of which an interferogram is recorded between a test wave emanating from a portion of the optical element in each case and a reference wave, the position of the optical element relative to the test wave being altered between these measurements, and calculating the figure of the optical element on the basis of these measurements. This calculation is carried out iteratively such that, in a plurality of iteration steps, the figure of the optical element is ascertained in each case by carrying out a forward calculation, each of these iteration steps being based in each case on a reference wave that was adapted based on the preceding iteration step.

A method and a device for characterizing the surface shape of an optical element. In the method, in at least one interferogram measurement carried out by an interferometric test arrangement, a test wave reflected at the optical element is caused to be superimposed with a reference wave not reflected at the optical element. In this case, the figure of the optical element is determined on the basis of at least two interferogram measurements using electromagnetic radiation having in each case linear input polarization or in each case circular input polarization, wherein the input polarizations for the two interferogram measurements differ from one another.

Reference and test waves are directed in a common path mode in a fiber tip diffraction interferometer. A first fiber can be used to generate the reference wave and a second fiber can be used to generate the test wave. Each fiber can include a single mode fiber tip that defines a wedge at an end without a coating on end surface or a tapered fiber tip. The fiber tip diffraction interferometer can include an aplanatic pupil imaging lens or system disposed to receive both the test wave and the reference wave and a sensor configured to receive both the test wave and the reference wave.

An interferometer for the measurement of a surface or an optical thickness of an optically smooth test object is provided, wherein the interferometer is configured to illuminate the optically smooth test object simultaneously with a plurality of object waves, which have different wavelengths from one another, and to superimpose the object waves 10 deformed by the illuminated test object onto coherent reference waves on an image capture device, and to spectrally decompose the interferograms resulting from the superposition into wavelength-specific partial interferograms.

A method for adjusting a measuring device having an interferometer unit with an optical axis, an optical distance measuring device with a measuring axis and a support slide that is moveable along a slide axis. The measuring axis is first aligned parallel to the slide axis. An adjustment body with a first spherical reflection and/or diffraction surface and a retro reflector at the back side is arranged at the support slide. It is brought into a first confocal position, in which a first center point of the first spherical reflection/diffraction surface coincides with the focus of the spherical wavefront that is emitted from the interferometer unit. The retro reflector defines a vertex that is located close to the first center point, such that the measuring axis of the distance measuring device extends close to the focus of the emitted spherical wavefront. In doing so, Abbe-faults can be reduced or eliminated.

Single-shot, adaptive metrology of rotationally variant optical surfaces, such as toroids, off-axis conies and freeform surfaces. An adaptive interferometric null test uses a high definition liquid crystal phase-only spatial light modulator (SLM) as the reconfigurable null element, on which a simulated nulling phase function is encoded, based on the specifications of the surface under test to generate a null interferogram. The power component of the surface sag is nulled by system design, not the SLM, enabling the SLM to fully compensate the residual departure without the need to tilt the optic or use a custom Offner-null. By wrapping the phase function at multiples of 2*pi radian, the upper limit in sag of the optic under test is theoretically removed.