The ability to determine absolute distance to an object is one of the most basic measurements of remote sensing. High-precision ranging has important applications in both large-scale manufacturing and in future tight formation-flying satellite missions, where rapid and precise measurements of absolute distance are critical for maintaining the relative pointing and position of the individual satellites. Using two coherent broadband fibre-laser frequency comb sources, we demonstrate a coherent laser ranging system that combines the advantages of time-of-flight and interferometric approaches to provide absolute distance measurements, simultaneously from multiple reflectors, and at low power. The pulse time-of-flight yields a precision of 3 µm with an ambiguity range of 1.5 m in 200 µs. Through the optical carrier phase, the precision is improved to better than 5 nm at 60 ms, and through the radio-frequency phase the ambiguity range is extended to 30 km, potentially providing 2 parts in 1013 ranging at long distances. Using two coherent broadband fibre-laser frequency comb sources, a coherent laser ranging system for absolute distance measurements is demonstrated. Its combination of precision, speed and long range may prove particularly useful for space-based sciences.

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Rapid and precise absolute distance measurements at long range

Temporal phase unwrapping algorithms for fringe projection profilometry: A comparative review

The orbital angular momentum of photons has the potential to dramatically increase data rates and enhance security in quantum optical communications. Here, Mirhosseini et al. demonstrate a scheme that is able to separate photons with different orbital angular momentum with 92% efficiency.

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Efficient separation of the orbital angular momentum eigenstates of light

A technique to perform two-wavelengths digital holographic microscopy (DHM) measurements with a single hologram acquisition is presented. The vertical measurement range without phase ambiguity is extended to the micron-range, thanks to the resulting synthetic wavelength defined by the beating of two wavelengths with a separation of about 80nm. Real-time dual-wavelength imaging is made possible by using two reference waves having different wavelengths and propagation directions for the hologram recording. The principle of the method is exposed and experimental results concerning a 1.2μm m high test sample as well as a moving micro-mirror are presented. To the extent of our knowledge, this is the first time that real-time synthetic beat-wavelength digital holography measurements are reported.

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Real-time dual-wavelength digital holographic microscopy with a single hologram acquisition

A stacked array magnifier (SAM) forms a magnified, demagnified or unit image of an object. The SAM includes one or more non-refractive lenslet arrays and one or more refractive lenslet arrays to form a plurality of lenslet channels. Each lenslet channel has at least one refractive lenslet and at least one non-refractive lenslet. SAMs are combined and tiled to form a scaleable display of flat panel displays. Multiple SAMs are used to increase magnification selectively. Hybrid lenslet arrays of the invention are also useable for optical processing and non-imaging applications.

Lenslet array systems and methods

In two-wavelength interferometry, synthetic wavelengths are generated in order to reduce the sensitivity or to extend the range of unambiguity for interferometric measurements. Here a novel optoelectronic technique, called superheterodyne detection, is presented, which permits measurement of the phase difference of two optical frequencies that cannot be resolved by direct optoelectronic heterodyne detection. This technique offers the possibility for operation of two-wavelength interferometry in real time with arbitrary synthetic wavelengths from micrometers to meters in length. Preliminary experimental results are reported. An optical arrangement for absolute range-finding applications using tunable-laser sources (e.g., semiconductor lasers) is proposed.

Two-wavelength laser interferometry using superheterodyne detection

In two-wavelength interferometry, synthetic wavelengths are generated in order to reduce the sensitivity or to extend the range of unambiguity for interferometric measurements Here a novel optoelectronic technique, called superheterodyne detection, is presented, which permits measurement of the phase difference of two optical frequencies that cannot be resolved by direct optoelectronic heterodyne detection This technique offers the possibility for operation of two-wavelength interferometry in real time with arbitrary synthetic wavelengths from micrometers to meters in length Preliminary experimental results are reported An optical arrangement for absolute range-finding applications using tunable-laser sources (eg, semiconductor lasers) is proposed

We discuss the realization of highly efficient fan-out elements. Laser-beam writing lithography is available now for fabricating smooth surface relief microstructures. We develop several methods for optimizing microstructure profiles. Only a small number of parameters in the object plane are necessary for determining the kinoform. This simplifies the calculation of M × N arrays also for large M and N. Experimental results for a 9-beam fan-out element are presented.

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Optimized kinoform structures for highly efficient fan-out elements

Continuous surface-relief diffractive optical elements for two-dimensional array generation (fan-out) are designed and fabricated. Separable and nonseparable solutions for the two-dimensional element design are compared. The phase-grating microstructures are generated by laser-beam writing lithography in a single exposure step and converted to nickel shims by electroplating, enabling low-cost replicas to be produced by using laboratory and commercial replication processes. Results are presented for a 9 x 9 fan-out diffractive optical element with a measured efficiency of 94% and an overall uniformity within +/-8%; replicas in epoxy have the same efficiency and a uniformity of +/-15%.

https://doc.rero.ch/record/8761/files/Gale_Michael_T._-_Continous-relief_diffractive_optical_elements_20080213.pdf

Continuous-relief diffractive optical elements for two-dimensional array generation.

This paper reports the calculation and fabrication of periodic phase structures for fan-out elements with a theoretical conversion efficiency close to 100% and perfect uniformity. We have measured an efficiency of 92% for a smooth kinoform structure fabricated in photoresist by laser beam writing lithography.

/pdf/design-and-fabrication-of-highly-efficient-fan-out-elements-cesosww9xm.pdf

D. Prongue

Papers

Two-wavelength laser interferometry using superheterodyne detection

Two-wavelength laser interferometry using superheterodyne detection

Optimized kinoform structures for highly efficient fan-out elements

Continuous-relief diffractive optical elements for two-dimensional array generation.

Design and fabrication of highly efficient fan-out elements