The coexistence of anti-vibration and a common optical path is difficult to realize in dynamic Fizeau interferometry. To address this problem, we propose a dynamic low-coherence interferometry (DLI) using a double Fizeau cavity. The DLI method is a new optical model that creatively renders both surfaces of the RM to interfere with the test surface, utilizing a low-coherence source and optical path matching to construct the common-path p-polarized Fizeau cavity (p-FC) and carrier-frequency s-polarized Fizeau cavity (s-FC). The relative tilt phases of the s-FC are calculated using the carrier frequency interferograms; then the final phase is retrieved with the relative tilt phases and p-FC interferograms. The experimental results demonstrate that the DLI method can provide high-precision phase measurement in a vibration environment.

Dynamic low-coherence interferometry using a double Fizeau cavity.

Phase-tilt iteration: Accurate and robust phase extraction from random tilt-shift interferograms

Optical phase-shifting methods based on low coherence laser for large aperture Fizeau interferometer

An oblique incidence dynamic phase-shifting interferometer based on inclination angle deflection is proposed to quickly obtain the surface distribution of optical surface with flatness of micron dimension. A 2×2 point source array is introduced into a Michelson interference system, and the incidence angle of each point source on the interferometer cavity is adjusted precisely to induce equal phase shift. Spatial separation is realized in combination with a lens array. The four phase-shifting interferograms are captured simultaneously on a single CCD, thereby realizing dynamic measurement. The flatness of a 35 mm aperture silicon wafer is measured at oblique incidence angle of 68°, the root mean square (RMS) is 1.631 μm and peak-to-valley (PV) is 9.082 μm. The experimental results indicate that the proposed interferometer overcomes the disturbance of vibration environment and extends the measurement range of interferometer with high precision by introducing the simultaneous phase-shifting interferometry based on inclination angle deflection into the oblique incidence interference system.

Oblique incidence dynamic phase-shifting interferometer based on inclination angle deflection

For a conventional Fizeau interferometer, accommodating both anti-vibration and conventional measurement modes is a challenge. Here, a dual-mode Fizeau interferometer (DFI) for dynamic optical measurement is proposed, which retains the conventional measurement mode. A vibration information measurement system is added to the conventional Fizeau interferometer for vibration-phase extraction. To better extract the vibration phase, a four-step phase-tilting iteration algorithm is proposed. The two combined systems separate the vibration information while retaining the Fizeau interferometry accuracy. Simulations and experiments prove that the two DFI modes both can accurately recover the phase. Thus, the DFI has considerable application potential for optical topography measurement.

Dual-mode Fizeau interferometer with four-step phase-tilting iteration for dynamic optical measurement.

Dynamic Fizeau interferometer based on the lateral displacements of the point sources

The invention discloses a phase defect detection system and method based on a short-phase dry-dynamic Twyman interferometer. The system comprises two parts including a short-phase dry polarization light source and a polarization Twyman interferometer. The method comprises the following steps: firstly, enabling a light beam emitted by a short-phase laser device to pass through a polaroid and a half-wave plate and enter a Michelson interference structure; emitting a pair of linearly polarized light with orthogonal polarization directions and coupling the pair of linearly polarized light into a polarization-maintaining optical fiber; taking the linearly polarized light as a light source of a main interferometer; then adjusting a PZT (Piezoelectric Transducer) to be matched with phase difference of an interference cavity of an interferometer main body part; compensating phase delay between reference light and testing light; finally, acquiring four interference figures with the phase shifting amount difference of pi/2 in sequence by utilizing a polarization camera; solving through a phase-shifting algorithm to obtain information of phase defects. The phase defect detection system and method, disclosed by the invention, have the advantages of large view field, high resolution ratio, good shock resistance and simplicity in operation and can be used for real-time and high-precision detection of the phase defects of an optical element.

Phase defect detection system and method based on short-phase dry-dynamic Twyman interferometer

The invention discloses a measurement device and method of a variable-tilt-angle phase shift grazing incidence interferometer. The device comprises a light source variable-tilt-angle phase shift modulating assembly, a main interferometer system, a diffracting and reflecting mirror and an imaging system; the light source variable-tilt-angle phase shift modulating assembly emits tilt collimating beams to the main interferometer system, transmitted through an isosceles prism in the main interferometer system, and arrive on a to-be-tested face through low grazing incidence, testing light reflectedby the to-be-tested face and reference light returned by the tilt face of the isosceles prism form coherent light beams, and interference figures are collected through the imaging system. The methodincludes the steps that firstly, the light source variable-tilt-angle phase shift modulating assembly generates collimating light parallel to an optical axis, a to-be-tested part is arranged in the main interferometer system, and interference figures with clear imaging are obtained on a CCD; then through the phase shift modulating assembly, the title angle of the collimating light is changed, anddifferent phase shift quantities are introduced into the interference figures; finally, a series of interference figures are collected in sequence, and a phase position is restored through a phase shift algorithm. The measurement device and method have the advantages of being accurate, efficient, compact in structure, easy to operate and low in cost.

Measurement device and method of variable-tilt-angle phase shift grazing incidence interferometer

A dynamic Mach-Zehnder interferometer based on lateral displacement of a point source array is proposed. The point source array is generated by a point source and a phase grating, where four point sources are of identical intensity. The lateral displacement of each point source can be adjusted to introduce π/2 phase steps in the interferograms. With a specially designed lens array in the spatial split imaging system, four separated and clear imaging interferograms can be captured in a single shot. Using a four-bucket algorithm, the phase distribution can be retrieved exactly, thereby realizing dynamic measurement. The experimental results show the feasibility and high precision of this dynamic Mach-Zehnder interferometer.

Dynamic Mach-Zehnder interferometer based on the lateral displacement of a point source array.

The invention discloses a method for measuring a vertex angle offset of an equilateral triangular prism. The method comprises: step one, two reflectors are fixed to form a 60-dgree angle mirror and the angular bisector of the 60-dgree angle mirror is parallel to the optical axis of emergent light of an interferometer, and an included angle between two beams of light returning in an auto-collimation manner is measured; step two, a to-be-measured equilateral triangular prism is placed between the interferometer and the angle mirror and a to-be-measured vertex angle faces the interferometer directly; and an included angle between two beams of light that passes through two lateral surfaces of the to-be-measured vertex angle of the equilateral triangular prism and then is reflected by two surfaces of the angle mirror is measured by an interference pattern; and then the measurement results are integrated to obtain a vertex angle offset of the to-be-measured equilateral triangular prism. Themethod has advantages of a few of steps, simple operation, and high precision and is used for high-precision measurement of the vertex angle offset of the equilateral triangular prism.

Liu Zhiyuan

Papers

Dynamic Fizeau interferometer based on the lateral displacements of the point sources

Phase defect detection system and method based on short-phase dry-dynamic Twyman interferometer

Measurement device and method of variable-tilt-angle phase shift grazing incidence interferometer

Dynamic Mach-Zehnder interferometer based on the lateral displacement of a point source array.

Method for measuring vertex angle offset of equilateral triangular prism