Search Results (5)

Three-dimensional imaging of live processes at a cellular level is a challenging task. It requires high-speed acquisition capabilities, low phototoxicity, and low mechanical disturbances. Three-dimensional imaging in microfluidic devices poses additional challenges as a deep penetration of the light source is required, along with a stationary setting, so the flows are not perturbed. Different types of fluorescence microscopy techniques have been used to address these limitations; particularly, confocal microscopy and light sheet fluorescence microscopy (LSFM). This manuscript proposes a novel architecture of a type of LSFM, single-plane illumination microscopy (SPIM). This custom-made microscope includes two mirror galvanometers to scan the sample vertically and reduce shadowing artifacts while avoiding unnecessary movement. In addition, two electro-tunable lenses fine-tune the focus position and reduce the scattering caused by the microfluidic devices. The microscope has been fully set up and characterized, achieving a resolution of 1.50 $\mathsf{\mu }$m in the x-y plane and 7.93 $\mathsf{\mu }$m in the z-direction. The proposed architecture has risen to the challenges posed when imaging microfluidic devices and live processes, as it can successfully acquire 3D volumetric images together with time-lapse recordings, and it is thus a suitable microscopic technique for live tracking miniaturized tissue and disease models. Full article

The mirror galvanometer is a crucial component of laser cutters/engravers. Novel two-dimensional mirror galvanometers demonstrate less trajectory distortion than traditional one-dimensional ones. This article proposes an optoelectronic sensor that measures a mirror’s inclinations in two dimensions simultaneously. The measuring range, resolution, and sampling rate are ±10°, 0.0265°, and 2 kHz, respectively. With the proposed sensor, a closed-loop control can be further implemented to achieve precision laser machining. Its compact size and low cost meet the requirements of miniature laser engravers, which have become popular in recent years. Full article

Rotational Risley prisms are one of the fastest two-dimensional (2D) optomechanical scanning systems. Their drawback is the strong non-linearity of the scan patterns they produce, in contrast to the most common (but slower) raster scanning modalities of 2D dual axis galvanometer scanners (GSs) or Micro-Electro-Mechanical Systems (MEMS) with oscillatory mirrors. The aim of this work is to develop a graphical method, which, to our knowledge, we have introduced to determine and characterize, using a commercially-available mechanical design program (for example CATIA V5R20 (Dassault Systems, Paris, France)) to simulate the exact scan patterns of rotational Risley prisms. Both the maximum and minimum angular and linear deviations of this type of scanner are deduced theoretically to characterize the outer diameter/Field-of-View (FOV) and the inner diameter (of the blind zone) of its ring-shaped patterns, respectively. This multi-parameter analysis is performed in correlation with the shape of the scan patterns, considering the four possible configurations of laser scanners with a pair of rotational Risley prisms, as well as all their parameters: prisms angles, refractive indexes, rotational speeds, distance between the two prisms, and the distance from the system to the scanned plane. Marshall’s synthetic parameters are also considered, i.e., the ratios of the rotational velocities and of the angles of the prisms. Rules-of-thumb for designing this optomechanical scanner are extracted from this analysis, regarding both shapes and dimensions of the scan patterns to be produced. An example of experimental validation completes the mathematical analysis and the performed simulations. Full article

The movable super-diffraction optical needle (MSON) is a tightly focused beam like a “needle”, which can realize vector scanning on the focusing plane. Not only does it have a long focal depth, but its resolution also exceeds the diffraction limit. The modulation and control technology required for generating MSON by oblique incidence is explored in this manuscript for the purpose of processing high-aspect-ratio, sub-wavelength structures. As the optical needle generated by traditional methods is static and sensitive to variation of the angle information of the incident beam, here we introduce a confocal scanning system by using a two-dimensional galvanometer system, a scan lens, and a tube lens to control the oblique incidence angle. The effects of the oblique incidence angle on the resolution, depth of focus, uniformity, and side lobes of the MSON were analyzed. Further, the voltage-controlled liquid crystal located between the scan lens and the 2D galvanometer system can be used to compensate for the additional phase difference caused by oblique incidence. The aspect ratio is defined as the ratio of depth of focus to resolution. By modulating and controlling the light field, the MSON with high aspect ratio (7.36), sub-diffractive beam size (0.42λ), and long depth of focus (3.09λ) has been obtained with homogeneous intensity, and suppressed side lobes. High speed, high axial positioning tolerance, and high-resolution laser processing can also be achieved, which removes the restrictions presented by traditional laser processing technology, for which high resolution and long depth of focus cannot be achieved simultaneously. Full article

The online calibration method of a two-dimensional (2D) galvanometer requires both high precision and better real-time performance to meet the needs of moving target position measurement, which presents some challenges for traditional calibration methods. In this paper, a new online calibration method is proposed using the wavelet kernel extreme learning machine (KELM). Firstly, a system structure is created and its experiment setup is established. The online calibration method is then analyzed based on a wavelet KELM algorithm. Finally, the acquisition methods of the training data are set, two groups of testing data sets are presented, and the verification method is described. The calibration effects of the existing methods and wavelet KELM methods are compared in terms of both accuracy and speed. The results show that, for the two testing data sets, the root mean square errors (RMSE) of the Mexican Hat wavelet KELM are reduced by 16.4% and 38.6%, respectively, which are smaller than that of the original ELM, and the standard deviations (Sd) are reduced by 19.2% and 36.6%, respectively, indicating the proposed method has better generalization and noise suppression performance for the nonlinear samples of the 2D galvanometer. Although the online operation time of KELM is longer than ELM, due to the complexity of the wavelet kernel, it still has better real-time performance. Full article