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

We consider the radiative transfer of a finite width collimated beam incident normally on a plane-parallel slab composed of a uniform absorbing and scattering medium. This problem is fundamental for modeling and interpreting non-invasive measurements of light backscattered by a multiple scattering medium. Assuming that the beam width is the smallest length scale in the problem, we introduce a perturbation method to determine the asymptotic expansion for the solution of this problem. Using this asymptotic expansion, we determine the leading asymptotic behavior of the reflectance. This result includes the influence integral, which gives the influence of the phase function on the leading asymptotic behavior of the reflectance. We validate this asymptotic theory using a novel implementation of the Monte Carlo method that is fully vectorized to run efficiently in MATLAB. We evaluate the usefulness of this asymptotic behavior for different phase functions and show that it provides valuable insight into the influence of the phase function on spatially resolved non-invasive measurements of light backscattered by a multiple scattering medium.

This paper proposes, a novel, to our knowledge, phase-restoration-based light field method to achieve 3D reconstruction of highly reflective surfaces. First, a focused light field camera whose angular and spatial resolutions can be adjusted according to the needs has been designed and fabricated to capture 4D light field information. Then, according to the pixel offsets between different sub-aperture images, a phase restoration method based on multi-view complementary information is proposed to restore the missing absolute phase information caused by highlights. Finally, a cubic B-spline curve method is used to directly fit the relationship between absolute phase and coordinates to achieve 3D reconstruction of highly reflective surfaces. The experimental results demonstrate that the proposed method effectively utilizes the multi-view information from the light field to restore missing absolute phase data in the phase unwrapping, ensuring accurate 3D reconstruction of highly reflective surfaces. What is more, our method requires no additional hardware, camera angle calibration, or point cloud fusion, which significantly reduces both hardware complexity and computational demands.

In this paper, the focusing characteristics of a circular Airyprime Gaussian beam (CAPGB) propagating in a gradient refractive index (GRIN) medium is studied for the first time, to the best of our knowledge, and some interesting features are observed. We find that the CAPGB exhibits periodic focus-defocus behavior and completes a period propagation process with two focal points within a half variation period L/2 of the GRIN medium. Meanwhile, the CAPGB has singularity at the positions of z=(2j+1)L/4 on the optical axis. The focal lengths of bifocal points, the distance between two focal points, the focal intensity, and the focusing ability can be manipulated by beam parameters and the GRIN factor. It is noteworthy that the number (one or two) of focal points in one focusing period, and the focusing period or frequency of the CAPGB in the GRIN medium could be controlled by the beam distribution factor and GRIN factor, respectively. Moreover, the focusing ability of the CAPGB is much higher than that of a circular Airy Gaussian beam in the GRIN medium.

Research on high dynamic range (HDR) color management imposes critical requirements on calibration methods between imaging systems and standard radiation. This paper proposes a colorimetric calibration method based on digital chain measurement for imaging systems. First, a HDR colorimetric calibration process model for imaging systems is constructed based on an imaging chain. It includes a light source, target reflectance, optical system parameters, spectral sensitivities, and color matching functions. Subsequently, visual tristimulus values and three-channel response values of an imaging system are obtained using the proposed model in response to the same target, and the target characteristic parameters are adjusted to simulate different HDR imaging scenarios. Following that, various regression algorithms can be employed for HDR colorimetric calibration of imaging systems. The experimental findings demonstrate that the method proposed in this paper boasts a broader dynamic range and denser sampling, thereby enhancing the accuracy of colorimetric characterization models and achieving superior resolution in color measurement.

Using orbital angular momentum (OAM) encoding for signal transmission enables optical communication in the spatial domain. However, during the transmission process of vortex optical communication, environmental factors such as atmospheric turbulence and haze cause scattering effects, resulting in the degradation of signal quality and increasing the complexity of decoding. Our goal is to design a framework that can recover the encoded signal from the speckle field, reducing the effects of scattering. We have designed a neural network model that combines a generative adversarial network (GAN) and U-Net, which utilizes the image segmentation capability of U-Net to guide the GAN in generating accurate information. We have demonstrated its effectiveness in experiments, with Pearson correlation coefficient (PCC) and peak signal-to-noise ratio (PSNR) values of 0.99 and 46.7, respectively. Compared to other works, our work focuses on the conjugate superimposed of perfect vortex beam (PVB), offering valuable insights into the beneficial aspects of vortex optical communication in long-distance transmission, interference resistance, and enhanced data transfer performance.

The accurate testing of plasma temperature and electron density and shock wave pressure during an electroburst in a copper foil transducer is critical for the characterization of the detonation performance of its elements. In this paper, the sequence of interferograms during the detonation of a copper foil transducer is captured at a frame rate of 3×10⁶ f p s in conjunction with Mach-Zehnder interferometry and high-speed photography, and the results clearly demonstrate the propagation of the shock wave wavefront and plasma. The phase differences disturbed by plasma are extracted using the Fourier transform method, and the refractive index distributions are reconstructed with the Abel algorithm. Subsequently, based on the refractive index models of the shock wave and plasma, the shock wave pressure and plasma temperature and electron density are partitioned and reconstructed. Results show that the maximum shock wave pressure in the detonation of the copper foil transducer element is 1.297 atm, the maximum plasma temperature is 16,280 K, and the maximum plasma electron density is 2.134×10¹⁷ c m ^-3. This study provides a theoretical and technical foundation for the detonation performance testing of pyrotechnic energy-conversion components.

This study presents an innovative methodology to analyze a blood sample from a healthy donor, providing a quantitative characterization of white blood cells (WBCs). It aims to evaluate the effectiveness of holographic quantitative phase imaging (QPI) flow cytometry (FC) in examining phase-contrast maps at the cellular level, thereby enabling the identification and classification of granulocyte types. Additionally, we demonstrate that an unsupervised method can differentiate granulocyte sub-types, i.e., neutrophils and eosinophils. The results instill strong confidence in the potential future use of QPI FC for liquid biopsies and/or for assessing the heterogeneity of WBCs and, more broadly, to facilitate label-free blood tests.

Metasurfaces have been used to make various optical devices such as beam splitters because of their excellent capability to control light. The most recent work on metasurface beam splitters focused on realizing one-dimensional beam splitting. Based on generalized Snell's law, we designed the beam splitters using a coding strategy by phase gradient metasurfaces, which can divide vertically incident light into two-dimensional space. Meanwhile, the beam splitters are polarization-insensitive because highly rotationally symmetric nanorods are used as structure units. Using different code groups, especially applying 0 and π binary phases, the proposed beam splitters have various functions such as beam deflection, two-beam splitting, and multi-beam splitting. The flexible design of the coding maps allows the light transmission to cover a full-view field. The maximum splitting angles in two-beam and multi-beam splitters are 35.7° and 28.3°, respectively. All the designed beam splitters have a power efficiency of over 80%. The beam splitters have the advantages of small size, easy integration, large beam splitting angle, wide beam splitting area, and high efficiency. They could be applied to many optical systems, such as multiplexers and interferometers in integrated optical circuits.

We study the formation of caustic surfaces produced by concave Fresnel-type mirrors, whose parent curve is defined by an aspherical curve rotationally symmetric about the optical axis. We assume that a point light source is placed at arbitrary distances along the optical axis considering three different cases, providing either real or virtual caustic surfaces. Alternatively, varying the parameters of design, it is possible to reduce the size and modify the shape of the caustic surfaces, which have wide potential applications in both fields of imaging and non-imaging optical systems based on Fresnel-type mirrors. Finally, the cuspid of the caustics formed around the central groove near the optical axis coincides with the position of paraxial images in such a way that we provide the mirror-image equation for Fresnel-type mirrors.

Retrieving the reflectance spectrum from objects is an essential task for many classification and detection problems, since many materials and processes have a unique spectral behavior. In many cases, it is highly desirable to capture hyperspectral images due to the high spectral flexibility. Often, it is even necessary to capture hyperspectral videos or at least to be able to record a hyperspectral image at once, also called snapshot hyperspectral imaging, to avoid spectral smearing. For this task, a high-resolution snapshot hyperspectral camera array using a hexagonal shape is introduced. The hexagonal array for hyperspectral imaging uses off-the-shelf hardware, which enables high flexibility regarding employed cameras, lenses, and filters. Hence, the spectral range can be easily varied by mounting a different set of filters. Moreover, the concept of using off-the-shelf hardware enables low prices in comparison to other approaches with highly specialized hardware. Since classical industrial cameras are used in this hyperspectral camera array, the spatial and temporal resolution is very high, while recording 37 hyperspectral channels in the range from 400 to 760 nm in 10 nm steps. As the cameras are at different spatial positions, a registration process is required for near-field imaging, which maps the peripheral camera views to the center view. It is shown that this combination using a hyperspectral camera array and the corresponding image registration pipeline is superior in comparison to other popular snapshot approaches. For this evaluation, a synthetic hyperspectral database is rendered. On the synthetic data, the novel approach, to our knowledge, outperforms its best competitor by more than 3 dB in reconstruction quality. This synthetic data is also used to show the superiority of the hexagonal shape in comparison to an orthogonal-spaced one. Moreover, a real-world high-resolution hyperspectral video database with 10 scenes is provided for further research in other applications.