Activity

Many researchers from scientific and industrial fields have devoted their efforts to the laser interferometer, aiming to improve the measurement accuracy and extend the practical applications. Here, we present a modified homodyne laser interferometer based on phase modulation for simultaneously measuring displacement and angle. The active sawtooth wave phase modulation enhances immunity of this interferometer to the environmental fluctuations and laser power drift. Based on polarized optic theory and the sinusoidal measurement retro-reflector, a modified Michelson-type interferometer configuration is designed to simultaneously measure displacement and angle. Phase difference between the reference and measurement interference signals can be obtained using the sawtooth wave phase modulation and zero crossing detection technique, where the real-time displacement and angle values can be derived directly. Experimental results demonstrate our proposed interferometer has good static and dynamic performance.Quantitative phase imaging using holographic microscopy is a powerful and non-invasive imaging method, ideal for studying cells and quantifying their features such as size, thickness, and dry mass. However, biological materials scatter little light, and the resulting low signal-to-noise ratio in holograms complicates any downstream feature extraction and hence applications. selleck kinase inhibitor More specifically, unwrapping phase maps from noisy holograms often fails or requires extensive computational resources. We present a strategy for overcoming the noise limitation rather than a traditional phase-unwrapping method, we extract the continuous phase values from holograms by using a phase-generation technique based on conditional generative adversarial networks employing a Pix2Pix architecture. We demonstrate that a network trained on random surfaces can accurately generate phase maps for test objects such as dumbbells, spheres, and biconcave discoids. Furthermore, we show that even a rapidly trained network can generate faithful phase maps when trained on related objects. We are able to accurately extract both morphological and quantitative features from the noisy phase maps of human leukemia (HL-60) cells, where traditional phase unwrapping algorithms fail. We conclude that deep learning can decouple noise from signal, expanding potential applications to real-world systems that may be noisy.A spectral polarization camera based on ghost imaging via sparsity constraints (GISC) is presented. The proposed imager modulates three-dimensional spatial and spectral information of the target into two-dimensional speckle patterns using a spatial random phase modulator and then acquires the speckle patterns at four linear polarization channels through a polarized CCD. The experimental results verify the feasibility of the system structure and reconstruction algorithm. The GISC spectral polarization camera, which has a simple structure and achieves compressive sampling during the imaging acquisition process, provides a simple scheme for obtaining multi-dimensional information of the light field.Conducting research using micrometer-sized X-ray beams with small samples is common at modern synchrotron X-ray sources. Often, the relative alignment between the X-ray beam and sample is time consuming. An on-axis or coaxial camera system with a view of the sample in a direction along the path of the X-ray beam with its depth of field set to coincide with the location of the focal spot of the X-ray beam is preferred. Besides the use of a drilled mirror, I propose the use of a Pellicle mirror to create an on-axis viewer that allows various sample environments and X-ray beam sizes.A photonic scheme that can simultaneously estimate the microwave Doppler-frequency shift (DFS) and angle-of-arrive (AOA) is demonstrated. In the proposed system, the transmitted signal is independently mixed with two echo signals by a dual-channel microwave photonic mixer. By measuring the frequency of the intermediate frequency (IF) signal output from the two channels and the phase difference between them, the DFS (with direction identification) and AOA parameters can be obtained. In a proof-of-concept experiment, the errors are less than $\pm\;0.08\;\rmHz$ for the DFS measurement within a range of $\rm\pm 100\;\rmkHz$ and less than $\rm\pm 1.3\deg$ for the AOA measurement ranging from 0° to 90°, respectively.We report a detailed experimental and theoretical analysis of the $^4\rm F_9/2$ to $^6\rm H_13/2$ lasing transition of a dysprosium ($\rm Dy^3 +$)-doped ZBLAN fiber, a strong candidate for future compact and highly efficient yellow laser emission. Experimentally, we used a gallium nitride laser diode emitting at 447 nm as a pump source and measured yellow laser output generated with a maximum slope efficiency of 33%, which is less than half of the Stokes limit (of $\sim78\%$). This result is commensurate with two other reports of yellow emission from $\rm Dy^3 +$. As a result, we developed a numerical model to understand and analyze the improvement potential of this fiber laser system. For reliable spectroscopic data input to the numerical model, we measured the absorption and emission cross sections from $\rm Dy^3 +$-doped ZBLAN glass. We investigated the potential causes of the low experimental slope efficiency and found contributions from the background loss of the fiber and excited-state absorption (ESA) of the intracavity yellow light. We estimated the signal re-absorption cross section using the emission cross section and the McCumber relation, which was subsequently used in our numerical model to compare successfully with our experimental results. We show that the ESA can be reduced for future $\rm Dy^3 +$-doped yellow laser systems by cascade lasing or co-doping with a suitable rare earth ion desensitizer.For the current problems of extremely complex visible light indoor positioning algorithms and devices and low positioning accuracy, this paper proposes an improved indoor positioning method combining light-emitting diode (LED) visible light and quick response (QR) codes. First, initial positioning is achieved by loading a QR code image containing LED position information on the LED light, which is recognized and decoded by the receiver. Then the position of the receiver is precisely located by proposing an improved indoor positioning method. The experiment shows the smallest average error of 4.0326 cm in positioning, which greatly improves the indoor positioning accuracy.