Dynamic wavefront measurement with a point diffraction interferometer based on birefringence polarization beam splitting.

In this study, we proposed a point diffraction interferometer based on birefringence polarization beam splitting (BPBS-PDI) for transmission wavefront measurements. Using the polarization beam splitting property of birefringent crystals and a specially designed calcite crystal as a polarization beam splitter, two beams of linearly polarized light with orthogonal polarization directions and a small angular separation can be obtained to produce the reference and test beams with perpendicular polarization directions through a pinhole point diffraction plate. By introducing spatial synchronization phase-shifting technology, influencing factors such as environmental vibrations on the measurement results, are reduced.

Dynamic white-light interferometry via multiwavelength tilt iteration and sliding local least squares.

The growing interest in microprofile measurements for advanced semiconductor manufacturing and electronic glass screens has stimulated the demand for in situ dynamic white-light interferometry (DWLI). However, it is challenging to perform vibration-insensitive measurements because of the broad-spectrum interference. In this Letter, we report a vertical scanning DWLI using multiwavelength tilt iteration and sliding local least squares.

Surface defect measurement of ICF capsules under a limited depth of field.

A surface defect detection device based on null interferometric microscopy (NIM) enables the measurement of surface defects in inertial confinement fusion (ICF) capsules. However, the microscope objective with a large numerical aperture in NIM causes the depth of field (DOF) of the system to be shallow, limiting the field of view (FOV) of the measurement. To expand the measurement FOV, a reconstruction method for the defocused surface defects in the FOV is presented, the angular spectrum diffraction model from the surface to the tilted plane is established, and the phase recovery method of the defocused surface defects is proposed by the theory of angular spectrum diffraction.

Least-squares calibration method for double-grating interferometers used in measurement of long-focal-length lenses.

In this paper, we propose a new calibration method for long-focal-length measurement using a double-grating interferometer. A numerical analysis of the relative error in measurement proves that the main factor affecting accuracy is the angle of inclination between grating grids. Hence, we present a least-squares calibration method using a series of lenses to correct this error.

Optical homogeneity measurement of parallel plates by wavelength-tuning interferometry using nonuniform fast Fourier transform.

Wavelength-tuning interferometry is commonly employed to measure the optical homogeneity of parallel plates. However, the nonlinearity of phase shifts caused by wavelength tuning errors and environmental vibration leads to a spatially uniform error in the calculated phase distribution. Herein, a wavelength-tuning interferometry method based on nonuniform fast Fourier transform (WTI-NUFFT) was developed, which solves the spectral aliasing resulting from the spatially uniform error.

Null interferometric microscope for ICF-capsule surface-defect detection.

Isolated defects on the surface of the inertial confinement fusion (ICF) capsule reduce the probability of ignition. Here, to the best of our knowledge, we present the first null interferometric microscope (NIM) for direct and large-field surface defects detection on ICF capsules. The planar reference mirror in conventional interferometric microscopes is replaced by a spherical reference mirror to achieve null interference in the full field of view.

Dynamic wavefront measurement with a pinhole linear polarizer point-diffraction interferometer.

We propose a pinhole linear polarizer point-diffraction interferometer (PLP-PDI) for dynamic wavefront measurements. The proposed interferometer uses a metallic wire grid linear polarizer that acts as a point-diffraction plate to generate an ideal spherical wave, from which we can obtain orthogonally polarized reference and test beams. The special polarization phase-shifting configuration allows four phase-shifted interferograms to be captured in a single shot with high precision and stability.