Light sheet fluorescence microscopy (LSFM) is one of the leading technique for high resolution imaging. To image mouse lungs, optical sectioning and high-speed image acquisition are required. In addition, light scattering, reflection, and attenuation limit the application of light sheet microscopy in the visible region to imaging small and transparent animals and organisms. In this work, we present a light sheet microscope that works in the NIR-II wavelength range and demonstrate deep mouse lung imaging. We utilized light with excitation at 532 nm and detection in the NIR-II range of approximately 1450 nm. Our method is expected to find important applications for deep tissue imaging.
The feature of rapid divergence of conventional Gaussian beam restricts the field of view in light sheet microscopy.
Comparison with Gaussian beam, the Airy beams provides many advantages in light sheet microscopy such as larger field
of view (FOV), longer penetration path, and self-reconstruction. C. elegans is a model organism for developmental
biological studies. Here, we design Airy light sheet microscope to perform in-vivo imaging of C. elegans. A spatial light
modulator is used to generate 1D Airy beam for illumination purpose. Imaging performance is experimentally evaluated
for our system. Present results may find important applications for studying internal structures in-vivo imaging of C.
elegans.
A widefield endoscope with optical sectioning capability using digital micro-mirror device (DMD) is proposed and demonstrated. With the addition of DMD, uniform and grid illumination pattern can be created for HiLo algorithm to remove out-of-focus noise in widefield images. By applying spectral filters to raw images, high frequency in-focus component of uniform illumination image and low frequency in-focus component of grid illumination image can be extracted, respectively. An in-focus image with full resolution can then be reconstructed by combining these two images. To verify the optical sectioning capability of the proposed system, 45μm fluorescent beads and mouse heart tissues were observed. The improvement of signal-to-noise ratio (SNR) can be obviously seen from the results.
Differential phase contrast microscopic (DPCM) imaging is a popular methodology to recover quantitative phase image of thin transparent sample under multi-axis intensity measurements. To improve the accuracy and stability of phase recovery in conventional DPCM imaging effectively, we propose a new illumination method to achieve isotropic differential phase contrast microscopic (iDPCM) imaging efficiently. Our iDPCM imaging is implemented with a partially coherent microscopy, and a programmable thin-film transistor panel to modulate the illumination pattern. We demonstrate our theoretical approach for iDPCM imaging and experimental results of quantitative phase image of a microlens array and unstained live human cells.
An approach to the spot-centroiding algorithm for the Shack–Hartmann wavefront sensor (SHWS) is presented. The SHWS has a common problem, in that while measuring high-order wavefront distortion, the spots may exceed each of the subapertures, which are used to restrict the displacement of spots. This artificial restriction may limit the dynamic range of the SHWS. When using the SHWS to measure adaptive optics or aspheric lenses, the accuracy of the traditional spot-centroiding algorithm may be uncertain because the spots leave or cross the confined area of the subapertures. The proposed algorithm combines the Hough transform with an artificial neural network, which requires no confined subapertures, to increase the dynamic range of the SHWS. This algorithm is then explored in comprehensive simulations and the results are compared with those of the existing algorithm.
For the optical resolution measurement, the Modulation Transfer Function (MTF) is widely applied. This
paper presents the RD result of our developed optical resolution measurement system with the slanted slit
method for small lenses. The MTF is built up by the Fourier's transformation of the Line-Spread Function
(LSF) that is acquired by analyzing the projected dark-bright image of the measured lens. In order to obtain a
smooth LSF, we propose a slanted slit method. And the slanted slit lets a part of the collimated light transmit
through the measured lens, and a dark-bright slit-image is projected on the CCD-camera. Through a proper
selection of the region of interest (ROI), a smooth LSF with dense sampled data can be formed by arranging
pixels according to their distances to the slanted slit. And these sampled data of the LSF can effectively
eliminate the aliasing effect and furthermore can accurately derive the MTF.
The influences of the angle of the slanted slit and the ROI-selection on the performance of this optical
resolution measurement system are thoroughly studied. The accuracy of its processing algorithm is
experimentally verified by using the statistic factors GRR and STD-error. Based on a calibrated lens, the
developed processing system and algorithm can achieve the industrial level with GRR of 27% and STDerror
of 8%.
This paper presents our development of a compact and magnetic-aerostatic vibration isolation platform for small
equipments such as AFM-system, which combines the electromagnetic and aerostatic principles to create a semiactive
damping effect. For the aerostatic principle, the concept of cap-shaped bearing form is applied to combine radial and
axial bearings inside a cap-shaped air film to enhance the bearing capacity. The axial aerostatic bearing provides the
main supporting force for the vibration isolation platform, and the radial aerostatic bearing creates frictionless and
accurate guide for the platform. The electromagnetic coil is used to generate attractive force to counterbalance the axial
aerostatic bearing force. Through this force counterbalance, not only the axial bearing stiffness can be minimized but
also the axial position of the platform can be precisely controlled. In the axial positioning control, a hall element and a
magnet are used to realize a non-contact displacement measurement with less loading effect. Besides, the robust PID
control algorithm is chosen as the main core of the positioning control. For optimization and performance verification,
finite element analyses and experiments are carried out to comprehend its electromagnetic and aerostatic effects.
Many organisms have diverse hair cells to instantaneously perceive the change of surroundings so that they can keep away from threats. These organs can precisely detect the tiny variations of airflow, water flow, sound, or pressure, and also resolve their affecting directions. Through this brilliant inspiration by the insects' cilia, we decided to design and develop a hair sensor for detecting two-dimensional airflow and pressure waves by using photoelectronic principles. The hair sensor inherently consists of an artificial cilium supported by an elastic membrane. A light-emitting diode and a quadrant photodiode are used as the photoelectronic sensor. The airflow or pressure wave directly stimulates the cilium to sway, and this motion contributes to let the projected light beam shift over the quadrant photodiode, whose four photodiodes produce then corresponding output signals. Because of dynamic and high-sensitive properties of the photoelectronic sensor, the hair sensor we developed possesses a high measurement resolution to be able to detect very tiny stimulation and its affecting direction. According to its multifaceted characteristics and simple structure, the hair sensor can be applied in numerous potential application fields, such as intrusion alarm system, noise detection system, as well as a tactile sensor.
KEYWORDS: Motion measurement, Photodiodes, Signal processing, Clocks, Error analysis, Optical testing, Reflectivity, Digital signal processing, Sensors, Signal detection
The miniaturization trend has enhanced the rapid development of small precision machines. The operational performance of a precision machine is mainly determined by its bearing clearance, the balancing quality of its shafts, and the actuation smoothness of the rotating shafts. In comparison with large shafts, small shafts are more susceptible to external interference and the loading effects of the measurement equipment. Accordingly, the inspection concepts for small shafts should be quite different from those for large shafts. This paper presents our approach to developing an economical optical measurement system with which the error motions of small rotating shafts can be inspected. The shadow method is applied as the measurement concept for the radial error motion. Two perpendicularly installed laser beams are partially shaded by the shaft, and the radial error motion is transformed into the alternations of light and shade on two photodiode arrays. For measuring the tilt error motion, a reflective method is realized to transform a tilt error motion into a 2-D movement of a reflective cross-hair pattern, which is detected by two photodiode arrays. To increase the measurement sensitivity, a novel bilateral configuration using offset pairs of photodiode detectors is developed; the signals of the detectors are processed by the differential principle. The shadow method shows better sensitivity and faster measuring speed than the reflective method because of its distinct projected beam.
This paper presents a new design of a Shear Motion Mode (SMM) actuator for ultra-high precision positioning in nanotechnological applications. In the SMM Actuator, a V-shape stage is driven by four parallel polarized piezoelectric plates with shear displacement. Based on its simple mechanism, the SMM actuator can be built very compactly. For fast and precision positioning tasks, we develop three different driving modes to control the SMM actuator. For large stroke, the inertial and frictional driving modes are applied for fast and precision positioning, respectively. The scanning mode enables the adjustment of the scanning distance in highest resolution. Positioning function of the developed SMM actuator may also be brought into applications in the low temperature and Ultra High Vacuum (UHV) environment. These three driving modes are experimentally tested to measure their dynamic performance. The stroke of the SMM actuator is 5mm. By applying the frictional driving mode, the SMM actuator can achieve a positioning resolution of 3nm with a pay load of 500g.
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