Journal of The Optical Society of America A-optics Image Science and Vision最新文献

The quantitative phase image formation process is posed as a problem of parameter estimation from intensity measurements. This approach is inclusive of traditional pixel-oriented imaging, where the sought parameters are the pixel values. The resulting optimization process to find the parameters is then seen to depend on the sensitivity field: this is the gradient of the scattered field with respect to the parameters, and it turns out to obey a scattering relationship that is analogous to that of the original scattered field. Examples are given from several regimes of scattering strength.

With the extended Huygens-Fresnel principle, we derive the expressions for the spectral intensity, coherence, and effective beam width of circular and rectangular multi-sinc Schell-model (MSSM) beams propagating through uniaxial crystals. Numerical simulations are employed to extensively explore how beam and crystal parameters modulate the optical field. The results reveal that the propagating field exhibits multiple ring-shaped and array-like intensity distributions, with adjustable features such as the number of concentric rings, central brightness, array dimensions, and the morphology and diversity of sub-beams. Additionally, the spectral coherence displays an oscillatory distribution that evolves into a Gaussian distribution as the transmission distance increases. The anisotropy of uniaxial crystals not only influences the morphology of intensity distribution but also affects the evolution rate of coherence and the expansion rate of effective beam width. Our work contributes to optimizing beam propagation through uniaxial crystals, potentially benefiting precision optical systems in laser technology.

Optical wireless communication (OWC) encompasses the utilization of optical frequencies, including visible light (VL) and infrared (IR), for unguided data transmission. Two common terms within this field are free-space optical (FSO) communication, which involves laser-based systems for long-distance point-to-point transmission at IR wavelengths, and visible light communication (VLC), which refers to LED-based systems with shorter transmission ranges at VL wavelengths. For outdoor operation of these systems, it is critical to understand the interaction of optical signals with the propagation environment. The extinction coefficient measures how strongly a light at a specific wavelength is attenuated as a result of its passage through a medium. Over the years, many studies have attempted to determine the extinction coefficient in various atmospheric conditions; however, the majority of these studies are limited to the IR spectrum and also come with several other constraints. In this paper, we use MODTRAN (MODerate resolution atmospheric TRANsmission) software, which solves the radiative transfer equation (RTE) for the given input parameters of operation wavelength, the observer altitude, target altitude, and path length in km. First, we extract the transmittance of the optical beam through fog, rain, cloud, drizzle, and aerosol through extensive simulations in the MODTRAN for optical wavelengths of 350-1550 nm. Then, we use a non-linear curve fitting to obtain closed-form expressions for all these atmospheric conditions.

Phase distribution of Hermite-Gauss (HG) beams generated by a gas laser is investigated experimentally by studying their interference with a plane wave and diffraction by a single slit by selecting pairs of bright lobes with different phases. Experimentally recorded interference and diffraction profiles support HG mode phase profiles expounded on in this paper. We find that the phase difference between one bright lobe and another is not simply zero or π but increases (or decreases) uniformly in steps of π as the number of zeros between them increases, in agreement with analytic function theory. An immediate application of this phase profile is that an HG mode can serve as a phase ruler with bright lobes as markers in steps of π.

Spatial color algorithms (SCAs) are algorithms grounded in the retinex theory of color sensation that, mimicking the human visual system, perform image enhancement based on the spatial arrangement of the scene. Despite their established role in image enhancement, their potential as dequantizers has never been investigated. Here, we aim to assess the effectiveness of SCAs in addressing the dual objectives of color dequantization and image enhancement at the same time. To this end, we propose the term dequantenhancement. In this paper, through two experiments on a dataset of images, SCAs are evaluated through two distinct pathways: first, quantization followed by filtering to assess both dequantization and enhancement; and second, filtering applied to original images before quantization as further investigation of mainly the dequantization effect. The results are presented both qualitatively, with visual examples, and quantitatively, through metrics including the number of colors, retinal-like subsampling contrast (RSC), and structural similarity index (SSIM).

In this paper, we discuss a mathematical model for inverse freeform design of an optical system with two reflectors in which light transfers from a point source to a point target. In this model, the angular light intensity emitted from the point source and illuminance arriving at the point target are specified by distributions. To determine the optical mapping and the shape of the reflectors, we use the optical path length and take energy conservation into account, through which we obtain a generated Jacobian equation. We express the system in both spherical and stereographic coordinates, and solve it using a sophisticated least-squares algorithm. Several examples illustrate the algorithm's capabilities to tackle complicated light distributions.

Laguerre-Gaussian (LG) modes are known as carriers of orbital angular momentum (OAM) and, for this reason, such modes have potential applications in optical communications. In this work, we present a study of the effects of aberration and turbulence on LG modes and propose a correction for these effects using a spatial light modulator. The aberrations are introduced by a phase mask obtained through a combination of Zernike polynomials. A scaling factor in the corrective phase mask enables us to optimize the recovery of the transverse structure of the LG beam, opening, to our knowledge, a new investigative avenue on aberration and turbulence mitigation. Numerical simulations and experiments are presented with good agreement.

The complex water environment makes the underwater imaging process very variable. For a more intuitive understanding of the underwater imaging process, in this paper, the Monte Carlo algorithm is combined with the Oren-Nayar polarization bidirectional reflection function to establish a visualization model of underwater laser polarization imaging. The model fully considers the specular reflection and diffuse reflection effects of the target surface. The Oren-Nayar model compensates for the deficiencies of the Lambert model in describing the diffuse reflection of target surfaces. The method is applied to analyze the effect of diffuse reflection on the laser polarization characteristics. The imaging process of high-polarized underwater targets and low-polarized underwater targets is simulated, and the effect of suspended particles on underwater optical transmission characteristics and underwater imaging is analyzed. The variation of backscattering light and system polarization characteristics with medium concentration is investigated in the simulation and experiment, respectively. The results show that the simulated images and experimental images have the same characteristics and change rules, indicating that the model can simulate the process of underwater polarization imaging correctly.

A dual-lens collimation and shaping system which is composed of a rotationally symmetric lens and an aspherical cylindrical lens is proposed in this paper. The system design method is discussed in detail, and the divergent elliptical laser beams are finally converted into collimated circular beams. The simulation results show that the maximum divergence angle of the beams can be collimated to 2.58 µrad, the standard deviation of the edge beam radius samples (SDRS) can be decreased from the original 4.227 to 0.135 mm, and the ratio of beam waist (RBW) drops from 1.554 to 1.0093 in the case of the output beam radius of 40 mm. The effects of transmission distance, astigmatism, wavelength deviation, light source offset, and lens offset on the collimation shaping effect are discussed. The collimation system can be widely used in long-distance optical communication systems and the design method in this paper can provide some new ideas for optical design researchers.

An end-to-end image reproduction method is proposed to render cultural heritage images under arbitrary illuminating conditions. When displayed on a characterized display, the appearance of paper-based cultural heritages is reproduced as actually observed under the target illumination, by leveraging spectral images of the artworks and spectral power distribution (SPD) of the identical illumination. Psychophysical experiments are conducted to verify that the proposed method outperforms the traditional pipelines on reproducing real scenes, including the CIECAM02 color appearance model. The method has the potential to be applied in the digitization and exhibition of paper cultural heritages.