At the core of the “proton radius puzzle” is a four–standard deviation discrepancy between the proton root-mean-square charge radii ( r p ) determined from the regular hydrogen (H) and the muonic hydrogen (µp) atoms. Using a cryogenic beam of H atoms, we measured the 2S-4P transition frequency in H, yielding the values of the Rydberg constant R ∞ = 10973731.568076(96) per meter and r p = 0.8335(95) femtometer. Our r p value is 3.3 combined standard deviations smaller than the previous H world data, but in good agreement with the µp value. We motivate an asymmetric fit function, which eliminates line shifts from quantum interference of neighboring atomic resonances.

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The Rydberg constant and proton size from atomic hydrogen

Underwater images typically suffer from color deviations and low visibility due to the wavelength-dependent light absorption and scattering. To deal with these degradation issues, we propose an efficient and robust underwater image enhancement method, called MLLE. Specifically, we first locally adjust the color and details of an input image according to a minimum color loss principle and a maximum attenuation map-guided fusion strategy. Afterward, we employ the integral and squared integral maps to compute the mean and variance of local image blocks, which are used to adaptively adjust the contrast of the input image. Meanwhile, a color balance strategy is introduced to balance the color differences between channel a and channel b in the CIELAB color space. Our enhanced results are characterized by vivid color, improved contrast, and enhanced details. Extensive experiments on three underwater image enhancement datasets demonstrate that our method outperforms the state-of-the-art methods. Our method is also appealing in its fast processing speed within 1s for processing an image of size 1024&#x00D7;1024&#x00D7;3 on a single CPU. Experiments further suggest that our method can effectively improve the performance of underwater image segmentation, keypoint detection, and saliency detection. The project page is available at https://li-chongyi.github.io/proj_MMLE.html. 

Underwater Image Enhancement via Minimal Color Loss and Locally Adaptive Contrast Enhancement

A measure of the degree of polarization for the three-dimensional polarization matrix (coherence matrix) of an electromagnetic field is proposed, based on Rayleigh scattering. The degree of polarization at a point is defined as an average, over all scattering directions, of an imagined dipole scattering of the three-dimensional state of polarization. This gives a well-defined purity measure, which, unlike other proposed measures of the three-dimensional degree of polarization, is not a unitary invariant of the matrix. This is demonstrated and discussed for several examples, including a partially polarized transverse beam.

A three-dimensional degree of polarization based on Rayleigh scattering

We present an active fiber-based retroreflector providing high quality phase-retracing anti-parallel Gaussian laser beams for precision spectroscopy of Doppler sensitive transitions. Our design is well-suited for a number of applications where implementing optical cavities is technically challenging and corner cubes fail to match the demanded requirements, most importantly retracing wavefronts and preservation of the laser polarization. To illustrate the performance of the system, we use it for spectroscopy of the 2S-4P transition in atomic hydrogen and demonstrate an average suppression of the first order Doppler shift to 4 parts in 106 of the full collinear shift. This high degree of cancellation combined with our cryogenic source of hydrogen atoms in the metastable 2S state is sufficient to enable determinations of the Rydberg constant and the proton charge radius with competitive uncertainties. Advantages over the usual Doppler cancellation based on corner cube type retroreflectors are discussed as well as an alternative method using a high finesse cavity.

Active fiber-based retroreflector providing phase-retracing anti-parallel laser beams for precision spectroscopy.

A class of imaging, condensing, and collimating devices for x rays is investigated which is based on the use of an array of small channels of square cross section. The focusing and collimating effect arises from external reflection of near‐grazing‐incidence rays at the interior channel surfaces. Rays are redirected by being singly reflected from two orthogonal channel surfaces and are imaged from a source point to a square region with a side length MT+1 times that of the channel side length, where MT is the transverse magnification. The image and source locations are related by a thin‐lens formula. The point spread function and the efficiency of these focusing devices are calculated. Two energy regimes with different channel reflectivity characteristics are examined in detail: the hard x‐ray regime (E>8 keV) and the soft x‐ray regime (E<200 eV). For these cases the efficiency of focusing x rays depends only on the channel aspect ratio and reflectivity parameters. A discussion is made of channel plates of ...

X ray focusing using square channel-capillary arrays

The output polarization states of corner cubes (for both uncoated and metal-coated surfaces) with an input beam of arbitrary polarization state and of arbitrary tilt angle to the cube have been analyzed by using the three-dimensional polarization ray-tracing matrix method The diattenuation and retardance of the corner-cube retroreflector (CCR) for all six different ray paths are calculated, and the relationships to the tilt angle and the tilt orientation angle are shown When the tilt angle is large, hollow metal-coated CCR is more appropriate than solid metal-coated CCR for the case that the polarization states of output beam should be controlled

Polarization properties of a corner-cube retroreflector with three-dimensional polarization ray-tracing calculus

Polarization descattering imaging through turbid water without prior knowledge

Using three-dimensional (3D) coherency vector (9 × 1), we develop a new 3D polarization algebra to calculate the polarization properties of all polarization sensitive optical systems, especially when the incident optical field is partially polarized or un-polarized. The polarization properties of a high numerical aperture (NA) microscope objective (NA = 1.25 immersed in oil) are analyzed based on the proposed 3D polarization algebra. Correspondingly, the polarization simulation of this high NA optical system is performed by the commercial software VirtualLAB Fusion. By comparing the theoretical calculations with polarization simulations, a perfect matching relation is obtained, which demonstrates that this 3D polarization algebra is valid to quantify the 3D polarization properties for all polarization sensitive optical systems.

Three-dimensional polarization algebra for all polarization sensitive optical systems

Method for detecting smoothness of high-speed railway track

A method and a device for producing vector vortex beam are belonging to the vector vortex beam technology area, to solve the problem of how to adopt a simple method and device to produce high quality vector vortex beam, the emergent laser beam from the laser under collimation and beam expanding after passing beam expander and collimating lens, and arranges pinhole at the focal position between beam expander and collimating lens for laser beam filtering; light beam after collimation and beam expanding is normally incidented on polarizer through aperture diaphragm, and the linearly polarized lights generated is incidented on the depolarization beam splitter, linearly polarized lights through transmission of depolarization beam splitter reaches the effect window of the reflecting pure-phase liquid crystal spatial light modulator, and conducts phase modulation for the linearly polarized lights by load grayscale images of PC control terminal, to acquire the relevant vortex beam; light path of vortex beam after depolarization beam splitter reflects, and becomes circularly polarized light after 1/4 wave plate to incident on radial analyzer, to generate radial polarized vortex beam; and acquires vector vortex beam in need through polarization rotator

Wenjun He

Papers

Polarization properties of a corner-cube retroreflector with three-dimensional polarization ray-tracing calculus

Polarization descattering imaging through turbid water without prior knowledge

Three-dimensional polarization algebra for all polarization sensitive optical systems

Method for detecting smoothness of high-speed railway track

Method and device for producing vector vortex beam