The invention discloses an aspheric surface parameter error interference measuring method combining laser differential confocal positioning and belongs to the field of aspheric surface measurement. Animplementation method comprises the following steps: acquiring nominal parameters of a measured aspheric surface, and by utilizing the acquired nominal parameters of the measured aspheric surface andcombining optical design software, designing and processing a part-compensating lens and aplanatic lenses; according to the part-compensating lens and the aplanatic lenses, establishing an aspheric surface parameter error interference measuring system combining the laser differential confocal positioning; obtaining an optimal compensation position change by utilizing the system; measuring a surface figure change between the measured aspheric surface and an ideal aspheric surface, and calculating a coefficient of a quartic component of the surface figure change; and according to a simultaneousequation set, calculating a surface figure parameter error of the aspheric surface, thus measurement on the surface figure parameter error of the aspheric surface is realized. The method disclosed bythe invention can improve accuracy of measurement on the surface figure parameter error of the aspheric surface, realizes non-contact, full-aperture, fast and high-accuracy measurement and has the advantages of no scanning device and simple structure.

Aspheric surface parameter error interference measuring method combining laser differential confocal positioning

Optically transmissive and reflective objects may have varying surface profiles, which translate to arbitrary phase profiles for light either transmitted through or reflected from the object. For high-throughput applications, resolving arbitrary phases and absolute heights is a key problem. To extend the ability of measuring absolute phase jumps in existing 3D imaging techniques, the dual-wavelength concept, proposed in late 1800s, has been developed in the last few decades. By adopting an extra wavelength in measurements, a synthetic wavelength, usually larger than each of the single wavelengths, can be simulated to extract large phases or height variations from micron-level to tens of centimeters scale. We review a brief history of the developments in the dualwavelength technique and present the methodology of this technique for using the phase difference and/or the phase sum. Various applications of the dual-wavelength technique are discussed, including height feature extraction from micron scale to centimeter scale in holography and interferometry, single-shot dual-wavelength digital holography for high-speed imaging, nanometer height resolution with fringe subdivision method, and applications in other novel phase imaging techniques and optical modalities. The noise sources for dualwavelength techniques for phase imaging and 3D topography are discussed, and potential ways to reduce or remove the noise are mentioned.

A review of the dual-wavelength technique for phase imaging and 3D topography

The invention discloses a digital Moire phase shift interferometry method based on a two-step carrier splicing method, and belongs to the photoelectric detection field The digital Moire phase shift interferometry method based on a two-step carrier splicing method includes the steps: establishing a virtual interferometer, and obtaining an ideal system residual wavefront on an image plane of the virtual interferometer; acquiring two practical interferograms of a measured surface shape under different spatial carriers; solving the two interferograms by means of the digital Moire phase shift interferometry method respectively, and obtaining two surface shape errors with different error regions and different error regions through solution; extracting the correct areas of the two surface shapeerrors to perform splicing; and then finally obtaining the surface shape error without the error regions Therefore, the digital Moire phase shift interferometry method based on a two-step carrier splicing method solves the problem that a digital Moire phase shift method makes solution errors when encountering the large residual wavefront, so as to expand the measurement range of the traditional solving the error in the large residual wavefront by, and then extend the measurement range of the traditional digital Moire phase shift method, eliminate the residual wavefront bandwidth limitation ofthe traditional digital Moire phase shift method and realize measurement of the measured surface shape of the large residual wavefront The digital Moire phase shift interferometry method based on atwo-step carrier splicing method can maintain the advantages of the original digital Moire phase shift interferometry method

Digital Moire phase shift interferometry method based on two-step carrier splicing method

The invention discloses an aspheric parameter error interference measurement method combined with dispersion confocal positioning, and belongs to the field of aspheric measurement. The implementationmethod comprises the following steps: acquiring nominal parameters of a measured aspheric surface, and designing and processing a partial compensation lens and a dispersion objective lens by utilizingthe acquired nominal parameters of the measured aspheric surface and combining optical design software; establishing an aspheric parameter error interference measurement system combined with dispersion confocal positioning according to the partial compensation lens and the dispersion objective lens; measuring the surface shape change between the measured aspheric surface and an ideal aspheric surface, and calculating coefficients of the quartic component of the surface shape change; calculating a surface shape parameter error of the aspheric surface according to an optimal compensation position distance change equation and an coefficient equation, i.e., realizing measurement of the surface shape parameter error of the aspheric surface. According to the invention, non-contact and high-precision displacement measurement can be realized, the position of a lens group needs not to be moved in measurement, and the method has the advantages of simple operation and easy measurement.

Aspheric parameter error interference measurement method combined with dispersion confocal positioning

The invention discloses a digital Mohr phase shifting interference surface shape measurement method based on a region location fitting algorithm. The method comprises the following steps: establishinga virtual interferometer, acquiring an ideal system residual wavefront on an image surface of the virtual interferometer, and pre-marking a solving error region; acquiring a single-breadth actual interferogram in an actual interferometer; solving a surface shape error by using a digital Mohr phase shifting interference method to obtain the surface shape error with the solving error region; selecting data in a solving correctness region for fitting of the surface shape error to obtain a fitting coefficient; and reconstructing the surface shape error by the fitting coefficient to finally obtaina surface shape error result without the solving error region. The digital Mohr phase shifting interference surface shape measurement method solves the problem of a solving error occurring at a largeresidual aberration wavefront caused by the adoption of the digital Mohr phase shifting interference method; the measurement dynamic range of the digital Mohr phase shifting method is extended to beequivalent to that of a traditional phase shifting method; and meanwhile, the real-time, anti-shock and high-precision advantages of the original digital Mohr phase shifting interference method are maintained.

Digital Mohr phase shifting interference surface shape measurement method based on region location fitting algorithm

The invention belongs to the technical field of optical precision testing, and relates to a dual-wavelength phase-shift interference method based on a partial compensation method and an implementationdevice. The method comprises the steps of building a partial compensation method dual-wavelength phase-shift interferometer, and acquiring measured wavefront wrapped phases of two single wavelengths;modeling a partial compensation method dual-wavelength ideal interferometer, and acquiring residual wavefronts and wrapped phases of the two single wavelengths; eliminating known and unknown wavefront variations in the measured wavefront wrapped phases by adopting an error separation and elimination algorithm, and finally optimizing and reconstructing surface-shape error of the measured asphericsurface by adopting reverse iteration. The device comprises a first laser, a second laser, a first slit, a second slit, a first plane mirror, a second plane mirror, a first beam splitter, a second beam splitter, a beam expander, a collimating mirror, a standard plane mirror, a phase shifter, a partial compensating mirror, a measured aspheric surface, an imaging lens and an interferogram acquisition assembly containing a sparse array sensor. The method and device provided by the invention are particularly applicable to processing quality measurement for gradient aspheric surfaces with a small surface-shape error, molded aspheric surfaces with a great surface-shape error and free curved surfaces.

Dual-wavelength phase-shift interference aspheric surface measurement method and device based on partial compensation method

The invention discloses a digital moire fringe phase extraction method combining wavelet analysis and low pass filtering and belongs to the optical measurement and image processing technology field. The method is characterized by using actual interference graph and phase-shift virtual interference graph moire synthesis to generate a phase shift moire composite graph, and using low pass filtering and combining a phase shift interferometry to extract a preliminary result of a moire fringe phase; according to a virtual interference wavefront acquired by a virtual interferometer, combining a filtering radius of a filter to determine a distribution center and a range of a low pass filtering error in the preliminary result of the moire fringe phase; after a low pass filtering error range and the center are positioned, carrying out wavelet decomposition on the preliminary result containing the low pass filtering error; and according to the positioned error center and the range, processing a wavelet coefficient so that the filtering error can be removed, according to an approximation coefficient and a processed wavelet coefficient, carrying out reconstruction and acquiring the moire fringe phase where the low pass filtering error is removed, which means that a measurement range of digital moire interference measurement is expanded.

Digital moire fringe phase extraction method combining wavelet analysis and low pass filtering

Optical components with aspheric surfaces can improve the imaging quality of optical systems, and also provide extra advantages such as lighter weight, smaller volume and simper structure. In order to satisfy these performance requirements, the surface error of aspheric surfaces, especially high departure aspheric surfaces must be measured accurately and conveniently. The major obstacle of traditional null-interferometry for aspheric surface under test is that specific and complex null optics need to be designed to fully compensate for the normal aberration of the aspheric surface under test. However, non-null interferometry partially compensating for the aspheric normal aberration can test aspheric surfaces without specific null optics. In this work, a novel non-null test approach of measuring the deviation between aspheric surfaces and the best reference sphere by using improved two-wavelength phase shifting interferometer is described. With the help of the calibration based on reverse iteration optimization, we can effectively remove the retrace error and thus improve the accuracy. Simulation results demonstrate that this method can measure the aspheric surface with the departure of over tens of microns from the best reference sphere, which introduces approximately 500λ of wavefront aberration at the detector.

Zhang Liqiong

Papers

Dual-wavelength phase-shift interference aspheric surface measurement method and device based on partial compensation method

Digital moire fringe phase extraction method combining wavelet analysis and low pass filtering

Measurement of steep aspheric surfaces using improved two-wavelength phase-shifting interferometer