In order to optimize the design of underwater light screens, the transmission process of the light beam in water is analyzed with the Monte Carlo method. The trajectories and power attenuation of emitted photons, propagating in different types of water from the light source towards the receiver with different initial light powers and transmission distances, are simulated and calculated. The output power can then be obtained to calculate the transmission ratio quantitatively. According to the simulated data, by using the curving fitting method, the exact expression of transmission ratio is derived, which is in the same form as the Beer-Lambert-Bouguer law. Meanwhile, experiments are conducted in a light screen with a vertical line beam laser in clear water to verify the simulations. The experimental results are in agreement with the simulated results, and the differences between them are within ±0.04. The presented results give insight into the design of underwater laser screens.We report on a polarizing interferometer-ellipsometer arrangement that overcomes the need for additional measurements with a retarder for the unambiguous determination of the ellipsometric parameters in the far infrared spectral range. It consists of a Martin-Puplett interferometer and a wire-grid polarizer as an analyzer. The application of such interferometer-ellipsometer is experimentally demonstrated on a polyethylene sample deriving the refractive index and the thickness in the spectral range between 15 and 35cm-1. Based on these results, a similar solution without a retarder for the mid-infrared spectral region is additionally proposed.Fresnel incoherent correlation holography (FINCH) is a technology that can acquire three-dimensional information of incoherent objects such as fluorescence with an in-line optical system. However, it is difficult to apply FINCH to dynamic phenomena, since FINCH has to detect phase-shifted holograms sequentially to eliminate twin and zero-order images. In this paper, a method in which the phase-shifted holograms can be obtained simultaneously with an in-line setup by using an optimized simulated diffraction optical element (sDOE), realized by a phase-only spatial light modulator, is proposed. The optimized sDOE is an optical device with a dual-focus lens, 2D grating, and spatial phase shifter. Therefore, the sDOE is called a dual-focus checkerboard lens. The optical experiment confirms the feasibility of the proposed method.Both accuracy and depth of field (DOF) are required for small objects' measurement in advanced manufacture and accurate robotics industries. In this paper, a stereo vision system with structured light based on the thin-lens model is developed to measure small objects with high accuracy and extended DOF at high magnification. The model of the proposed stereo vision system is built. The new system calibration scheme and measurement procedures are proposed. The DOF of the used thin-lens model is extended by utilizing autofocus capability. With the thin-lens model, accurate calibration and extended DOF at high magnification can be achieved. Three measurement experiments are conducted with the proposed system to evaluate its effectiveness and accuracy. The error of the protrusions' height on the reconstructed aluminum part is lower than 0.55%, and the standard deviation (STD) of a fitting plane reaches 1.7 µm.  https://www.selleckchem.com/products/bexotegrast.html  Low cost, high accuracy, and extended DOF can be simultaneously achieved for measuring small objects with the proposed system based on the thin-lens model.A new, non-contact, three-dimensional (3D) bullet signature measuring system based on a chromatic confocal sensor is developed. The system is composed of a precision rotary table and a chromatic confocal sensor. The measurement uncertainty of the system is less than 1 µm. When measuring the surface topography of the object, the sensor acquires wavelength information reflected from the object instead of intensity information. This advantage is very suitable to bullet signature measurements. The chromatic confocal sensor works in the point measuring mode and can acquire data continuously with high speed. One round section measurement on the bullet body takes less than 1 minute.This publisher's note amends information in the Funding section of Appl. Opt.59, 5642 (2020).APOPAI0003-693510.1364/AO.391234.In this work, a numerical modal decomposition approach is applied to model the optical field of laser light after propagating through a highly multi-mode fiber. The algorithm for the decomposition is based on the reconstruction of measured intensity profiles along the laser beam caustic with consideration of intermodal degrees of coherence derived from spectral analysis. To enhance the accuracy of the model, different approaches and strategies are applied and discussed. The presented decomposition into a set of linearly polarized modes enables both the wave-optical simulation of radiation transport by highly multi-mode fibers and, additionally, the analysis of free-space propagation with arbitrarily modified complex amplitude distributions.3D measurement plays an important role in the processing and assembling of large components in the aviation and aerospace industry. However, precision control is a challenging problem due to the complex on-site illumination environment and serious background interference. For the binocular stereovision measurement system based on auxiliary laser scanning, this paper proposes an extraction method of laser stripe for 3D reconstruction. First, an evaluation method for the laser stripe is proposed by analyzing the features of the stripe image. Then, a laser stripe extraction method based on self-adaptive threshold is proposed. To further improve the efficiency of image processing, an improved Kalman filter algorithm is adopted to fast-track and locate the region of interest of laser stripes in the sequence images. Finally, measurement experiments for a large-scale aircraft panel are carried out on-site. The results show that the center extraction error is less than 0.1 pixel and 3D reconstruction error is less than 0.06 mm. The proposed methods improve the efficiency and accuracy of 3D reconstruction of large components, and the feasibility of on-site application is also verified.