A diffractive optical element (10) for a test interferometer (100) measures a shape of an optical surface (102). Diffractive shape measuring structures (16) are arranged on a used surface (14) of the element and generate a test wave (122) irradiating the surface when the element is arranged in the interferometer. At least one test field (18) several profile properties of test structures contained in the test field. The profile properties characterize a profile line of the test structures extending transversely with respect to the used surface and include a flank angle of the profile line, a profile depth and a depth of a microtrench in a bottom region of a trench-shaped profile of the test structures. The test field is arranged at one location of the used surface instead of the diffractive shape measuring structures such that the test field is surrounded by several diffractive shape measuring structures.

A system for testing an optical surface, the system comprising a non-coherent light source, a detector, a test plate positioned between the non-coherent light source and the optical surface, the test plate separated from the optical surface by a gap, and a processor. The processer is configured to cause the non-coherent light source to illuminate the test plate and optical surface with non-coherent light, control the detector to capture an interferogram produced by interference between light reflected from the test plate and light reflected from the optical surface, and perform quantitative analysis on the interferogram to characterize aberrations in the optical surface.

A method for high-accuracy wavefront measurement based on grating shearing interferometry, which adopts a grating shearing interferometer system comprising an illuminating system, an optical imaging system under test, an object plane diffraction grating plate, an image plane diffraction grating plate, a two-dimensional photoelectric sensor, and a calculation processing unit. The object plane diffraction grating plate and the image plane diffraction grating plate are respectively arranged on the object plane and the image plane of the optical imaging system under test. The shearing phase of 1.sup.st-order diffracted beam and −1.sup.st-order diffracted beam is exactly extracted through phase shifting method, and the original wavefront is obtained by carrying out reconstruction algorithm according to a shear ratio of 2s, such that the accuracy of wavefront measurement of the optical imaging system under test is improved, wherein s is the shear ratio of the grating shearing interferometer.

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 inspection device includes an objective lens that transmits inspection light reflected from a sample during inspection and measurement light from a point light source during aberration measurement, a first pupil relay lens that transmits the inspection light and the measurement light, a second pupil relay lens in which an intermediate imaging plane is formed between the second pupil relay lens and the first pupil relay lens, a diffraction grating disposed between the first pupil relay lens and the intermediate imaging plane and that diffracts the measurement light, a point diffraction interferometry plate disposed within a depth of focus of the intermediate imaging plane and that selectively transmits the diffracted light, a first detector that detects an image of the sample, and a second detector that detects a fringe image of the measurement light.

A transmissive diffraction grating for a phase-stepping measurement system for determining an aberration map for a projection system comprises an absorbing layer. The diffraction grating is for use with radiation having a first wavelength (for example (EUV radiation). The absorbing layer is provided with a two-dimensional array of through-apertures. The absorbing layer is formed from a material which has a refractive index for the radiation having the first wavelength in the range 0.% to 1.04.

Methods and mechanisms for correcting a wavefront error in an optical element are disclosed. A wavefront error that is downstream of an optical element in an optical path is determined. A refractive index prescription that reduces the wavefront error is determined. A beam of energy is directed at a surface of the optical element in accordance with the refractive index prescription to alter the surface to change an index of refraction at multiple locations on the surface.

The disclosure relates to a measuring method and a measuring device for measuring a radius of an optical element based on a computer-generated hologram, and belongs to the field of photoelectric technology detection. The present disclosure is characterized in that two conjugated wave surfaces, i.e. a confocal wavefront and a cat's eye wavefront, are simultaneously generated by one piece of computer-generated hologram, and at the same time, interferograms at the cat's eye position and at the confocal position are obtained and surface shape parameters are measured, and the radius of an optical element is solved according to the measurement result.

An analytic tool for supporting alignment of an optical component in preparation for an interferometric test and performance of such a test. Apparatus and methods involve employment of the datum features on the optical component and/or metrology frame supporting such component. The metrology frame may include a secondary set of holograms (provided for use with a conventional system already employing a primary hologram that forms the testing optical wavefront). The conventional primary hologram is preferably substituted with a set of primary holograms (contained in the same, unitary or spatially-complementary housing sets) that perform different but complementary functions and that facilitate the alignment of the metrology frame with or without the tested optical component.

An environmental testing laboratory includes a supply port allowing air-conditioned air at a predetermined temperature supplied through the supply port at a predetermined speed, a discharge port facing the supply port and allowing the air be discharged through the discharge port, a flow passage disposed between the supply port and the discharge port and allowing the air to pass through the flow passage part, an installation part disposed at a center of the flow passage and allowing a measurement target in the installation part, and a flow straightening member which is disposed between a sidewall surface of the flow passage part and the installation part and which is configured to straighten an airflow of the air-conditioned air. The sidewall surface of the flow passage part and the first flow straightening member are disposed in parallel with the airflow of the air-conditioned air from the supply port to the discharge port.