Averaging illumination colors of multi-illumination ensembles

Ruiqing Ma, Ruiqing Xue, and Keizo Shinomori

DOI: 10.1364/JOSAA.540921 Received 30 Aug 2024; Accepted 07 Nov 2024; Posted 08 Nov 2024  View: PDF

Abstract: Average extraction from multiple similar items in ensemble perception has been demonstrated in a variety of visual features. This study investigated whether the visual system can extract precisely the average illumination color from multi-illumination ensembles. In a two-interval forced choice (2IFC) task of the constant stimuli method, observers were asked to judge whether the color of four identical test illuminations (homogeneous condition) or the average color of four distinct test illuminations (heterogeneous condition) was yellower than the reference illumination D67. Four types of scenes were used: Munsell surfaces only, Munsell surfaces with dark and light gray background, respectively, and image of color patches on white background. The mean values of the cumulative normal distribution functions fitted to the data under the heterogeneous condition were close to those under the homogeneous condition, indicating that the observer has the ability to precisely extract the average illumination color from a set of illuminations. This suggests that rapid and efficient averaging can also be performed in the high-level illumination estimation task.

Recovery of encoded information from conjugate superimposed perfect vortex beams in scattering environments

Maohua Xu, Peng Sun, Canjin Wang, Zipeng Wang, Ji Liu, Shichao Pan, Rijun Wang, and Yaoyu Cheng

DOI: 10.1364/JOSAA.541751 Received 09 Sep 2024; Accepted 07 Nov 2024; Posted 08 Nov 2024  View: PDF

Abstract: 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, results in degradation of signal quality, and increases 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 Generative Adversarial Network (GAN) and U-Net, which utilizes the image segmentation capability of U-Net to guide GAN in generating accurate information. We have demonstrated its effectiveness in experiments, with the values of Pearson correlation coefficient (PCC) and peak signal-to-noise ratio (PSNR) can reach 0.99 and 46.7, respectively. Compared to other work, 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.

Design of scatterometry with optoelectronic machine-learning for discriminating nanohole cross-sectional structure

Jun-ichiro Sugisaka, Koichi Hirayama, and Takashi Yasui

DOI: 10.1364/JOSAA.541358 Received 04 Sep 2024; Accepted 31 Oct 2024; Posted 31 Oct 2024  View: PDF

Abstract: This paper presents a system for discriminating the verticality of nanohole sidewalls on dielectric substrates. The proposed system comprises optical filters and a compact neural network with only two input ports. The weak scattered field from the nanohole passes through the filters, and the neural network processes the intensity of the focused field. Numerical simulations demonstrate that this system achieves significantly lower error rates compared to conventional systems that use an optical microscope and a neural network. Additionally, we discuss the minimum aperture size of nanoholes that can be effectively discriminated.

Asymptotic behavior of the reflectance of a narrow beam by a plane-parallel slab

Boaz Ilan and Arnold Kim

DOI: 10.1364/JOSAA.544227 Received 08 Oct 2024; Accepted 31 Oct 2024; Posted 31 Oct 2024  View: PDF

Abstract: We consider 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 to 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.

ERG responses and the Ferry-Porter law

Jan Kremers, Avinash Aher, and Cord Huchzermeyer

DOI: 10.1364/JOSAA.538103 Received 01 Aug 2024; Accepted 30 Oct 2024; Posted 31 Oct 2024  View: PDF

Abstract: The Ferry-Porter law states that the psychophysically measured critical flicker fusion frequency (CFF) is linearly correlated with the logarithm of the mean luminance. We studied the relationship between the CFFs of L- and M-cone driven ERGs (five normal trichromats; sinusoidal modulation; 18% cone contrast) and mean luminance. The measurements were performed at seven mean luminances between 2.84 and 284 cd/m². Close to the CFF, the ERG amplitudes vs. temporal frequency could be described by a simple exponential function. The CFFs were higher for L- than for M-cone driven ERGs and depended linearly on the logarithm of the mean luminance (i.e. adhere to the Ferry-Porter law) with steeper slopes compared to psychophysical measurements.

Measurement of Plasma Characteristic Parameters of Copper Foil Explosion using Interferometry

Dangjuan Li, Yuyan Lu, Jia Wang, Rongli Guo, Ke-Xuan Wang, SU Junhong, and Shenjiang Wu

DOI: 10.1364/JOSAA.539467 Received 14 Aug 2024; Accepted 28 Oct 2024; Posted 28 Oct 2024  View: PDF

Abstract: 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 fps 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, maximum plasma temperature is 16,280 K, and maximum plasma electron density is 2.134 × 1017 cm−3. This study provides a theoretical and technical foundation for the detonation performance testing of pyrotechnic energy-conversion components.

Fourier-Optics Imaging Analysis with ABCD Matrices: Tutorial

James Fienup

DOI: 10.1364/JOSAA.538781 Received 08 Aug 2024; Accepted 24 Oct 2024; Posted 25 Oct 2024  View: PDF

Abstract: The use of ABCD (ray-transfer) matrices to analyze wave propagation through paraxial optical imaging systems is described. It is shown how to find the image, Fourier transform, and exit pupil planes. Different forms of the propagation integrals are given. The relationships between the aperture stop and the exit pupil and the impulse response of the system were derived.

Evaluating the effect of partially polarized light sources on the point spread function in optical coherence tomography

XIAO LIU and Patrice TANKAM

DOI: 10.1364/JOSAA.545407 Received 17 Oct 2024; Accepted 21 Oct 2024; Posted 25 Oct 2024  View: PDF

Abstract: Leveraging the polarization property of light to evaluate the birefringence of tissues as well as changes due to pathological conditions has been gaining interest over the past two decades with the introduction of different variants of optical coherence tomography (OCT) including polarization-sensitive OCT (PS-OCT) and cross-polarization OCT (CP-OCT). Because OCT sources are partially polarized, PS-OCT and CP-OCT generally require a linear polarizer and polarization-maintaining fibers to enable a linearly polarized input beam into the interferometer. While recent studies have suggested using an unpolarized input beam to reduce the system's complexity, the effect of unpolarized light on the point spread function (PSF) of OCT has not been fully studied. This work proposed a mathematical framework to evaluate the contribution of unpolarized light to the PSF of OCT. Simulation and experiments were performed for three OCT sources to assess the validity of the proposed model. Overall, simulations were in good agreement with experiments and revealed that unpolarized light introduced two additional reflectors into the reflectivity profile of the source, which were more pronounced in the cross-polarization configuration. This additional information can lead to misinterpretation of the birefringence of tissues in PS-OCT and CP-OCT. Their effect on image quality was evaluated in ex vivo corneal imaging of porcine eyeballs

Three-dimensional reconstruction of light field based on phase restoration for highly reflective surfaces

Wei Feng, JIAHAO FAN, Jiangtao Xu, and Da Liu

DOI: 10.1364/JOSAA.538989 Received 08 Aug 2024; Accepted 15 Oct 2024; Posted 24 Oct 2024  View: PDF

Abstract: This paper proposes a novel phase restoration-based light field method to achieve 3D reconstruction of highly reflective surfaces. Firstly, a focused light field camera which 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 analyze 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’s more, our method requires no additional hardware, camera angle calibration, or point cloud fusion, which significantly reduces both hardware complexity and computational demands.