Key Engineering Materials Vols. 364-366

Abstract: The highlight of photoacosutic imaging (PAI) is a method that combines ultrasonic resolution with high contrast due to light absorption. Photoacoustic signals carry the information of the light absorption distribution of biological tissue, which is often related to its character of structure, physiological and pathological changes because of different physiology conditions in response to different light absorption coefficients. A non-invasive PAI system was developed and successfully acquired in vivo images of mouse brain. Based on the intrinsic PA signals from the brain, the vascular network and the detailed structures of the mouse cerebral cortex were clearly visualized. The ability of PAI monitoring of cerebral hemodynamics was also demonstrated by mapping of the mouse superficial cortex with and without drug stimulation. The extracted PA signals intensity profiles obviously testified that the cerebral blood flow (CBF) in the mouse brain was changed under the stimulation of acetazolamide (ACZ). The experimental results suggest that PAI can provide non-invasive images of blood flow changes, and has the potential for brain function detection.

Abstract: Capillary array electrophoresis (CAE) is founded with the laser induced fluorescence detection (LIFD) system. The same model as the detection system is simulated in Tracepro and the stray light caused by capillaries is analyzed. The stray light distribution of the observation surface is plotted when the laser scans the different sections of a capillary in the array. The results of simulation indicate that the stray light is strongest when scanning the inner center of a capillary and decreases at edges; in two cases (50μm and 75μm inner diameter, ID) when the ID is larger, the stray light is stronger as a whole. Different ID of capillaries which affects the stray light is analyzed; considering many factors, 50μm ID of capillary is appropriate. Based on the analysis of stray light cross-talk by other capillaries in an array, the spacing between capillaries in an array is suggested more than 50μm which the stray light is steady-going and simple to operate. The results can be helpful for the mode of the laser scanning different capillaries in an array sequentially.

Abstract: A new method of etching micro-grating structures (MGSs) on the surface of glazed stainless-steel directly is reported, which makes good use of the interference of nanosecond laser pulses. Through changing the experimental parameters such as working current of the laser and source beam diameter, the influences of these parameters on the depth of grooves and duty cycle of MGSs are analyzed. The results measured with conventional optical microscopy and atomic force microscopy (AFM) show that the depth of grooves of MGSs varies from 0 nm to 350 nm, the duty cycle of MGSs changes between 0.4 and 0.9, This method can be used to make a stencil-plate for nano-imprinting. It extends the application of nanosecond laser in laser-induced microstructures, and provides a new method for micromachining micro-optical component.

Abstract: In this paper, the modulation transfer function with aberration of a multichannel laser induced fluorescence analyzer is presented. Based on an f-theta lens, the confocal system was used both to transform the exciting laser and to collect the fluorescence emitted from sample. The total MTF is the combination of that of both systems. A simple method for the numerical calculation of that was also given. From the calculating result we could conclude that the aberration had poor impact on the MTF of a confocal multichannel fluorescence analyzer and the imaging performance was uniform in the full field.

Abstract: Recent developments in next generation disc technology, cameras in mobile phones, zoom-lenses for small digital cameras and camcorders, digital SLRs, and television cameras have amplified the demand for affordable optical systems with outstanding image quality, a combination that can only be achieved using aspheric surfaces. The metrology of aspheric surfaces is a classical problem, but solutions so far have not fulfilled all demands for system cost, TACT (Total Average Cycle Time), minimized tooling, measurement uncertainty, spatial resolution, robustness in a production environment and many more. Zygo Corp. presents here a new method [1,2] for measurement of rotationally symmetrical aspheric surfaces using a new commercial system, which has the potential to fulfill these industry requirements. During measurement, the surface is scanned along its symmetry axis in a Fizeau cavity with a spherical reference surface. The coordinates x,y,z at the (moving) zone of normal incidence are derived from simultaneous phase-measurements at the apex and zone. Phase-shifting Fizeau interferometry and displacement interferometry are combined in the new commercial system to realize this new method. Aspheric departure from a best-fitsphere approaching 800 microns can be measured, and absolute measurement is possible with an absolutely calibrated transmission sphere. A custom parabolic artifact is measured with conventional null Fizeau interferometry and by the new commercial system. Data is reported for each technique along with a difference map achieved by fiducialized data subtract where 32.0 nm peak-to-valley (PV) and 3.6 nm R.M.S. are achieved.

Abstract: A novel multi-channel DNA fragment analysis system is presented，which is based on single PMT confocal fluorescence detection and optical scanning adopting an f-theta lens. Capillary electrophoresis experiments were executed in the system for DNA marker pBR322/Hae III. Signal was processed with wavelet denoising. The system’s limit of detection (dsDNA with the probe of Thiazole Orange, TO) was evaluated to be 1.1841×10-11mol/L. Its working noise is much lower compared with that based on mechanical scanning one, and the stability and detecting sensitivity is high. The system was expected to be applied to both capillary array and microchip electrophoresis detection based on laser-induced fluorescence.

Abstract: The characteristic of overall structure for CMOS image sensor has been studied in this research. A three-dimensional solid model of CMOS image sensor based on finite element ANSYS software is developed to predict the thermo-induced strain and the stress induced by moisture absorption. The predicted thermal-induced displacements were found to be very good agreement with the Moiré interferometer experimental in-plane deformation. The developed finite element 3D model, therefore, is applied to simulate the mechanism of thermal and hygroscopic stresses based on JEDEC pre-condition standard JESD22-A120. A series of comprehensive parametric studies were conducted in this research. The design rules for thermal optimization of CMOS image senor are summarized.

Abstract: A fast photo-acoustic (PA) imaging system was developed and tested on phantom sample, which consists of an acoustic lens，a multi-element linear transducer array, and the peak detection circuit. The multi-element linear transducer array consists of 64 elements. By utilizing an acoustic lens, the PA signals generated from the sample are imaged and detected by a multi-element linear transducer array, which directly changes the PA signals into the homologous electronic signals. Thus we can map the image more rapidly, with the peak detection circuit, which was designed specially. Compared to other exiting technology and algorithm, the PA imaging system based on an acoustic lens and the peak detection technology was characterized with speediness and real-time. The images reconstructed in this experiment have high definition and resolution，and may have potential for developing an appliance for clinical diagnosis.

Abstract: In order to do the precision grinding of optical aspheric lens, it is essential to achieve high quality surface roughness. Experiments show that the contacting area between the wheel and workpiece in a grinding process is critical to influence the surface roughness for a fine grit size resin bonded wheel. The precision grinding are performed with BK7 optical lens. This paper deals with the grinding of an aspheric surface optical lens by diamond wheel. This study also compares each machining parameter (work spindle speed, wheel spindle speed, feedrate, etc.) in rough grinding, fine grinding and polishing on the aspheric lens. In this study, several experiments were carried out BK7 optical glass lens by using vitrified, metal, resin bond diamond wheel and the polisher of urethane ball was used to remove the tool marks with an ultra-precision in-line grinding system. It was found that machining parameters significantly influence the surface roughness of aspheric optical lens.

Abstract: This study presents the development of an ultra-precision grinding system based on a new grinding technique called the “In-Process Grinding Method (IPGM)”. IPGM which is used for grinding aspheric lens increases both the production and grinding performance, and significantly decreases total production costs. To enhance the precision grinding productivity of ultra-precision aspheric lens, we present here an ultra-precision grinding system and process for the aspheric micro-lens. The tool path was calculated and CNC program generation and tool path compensation were performed for aspheric lens. Using this ultra-precision grinding system, aspheric lens, 4mm in diameter, were successfully performed. The profile error after the first grinding without any compensation was less than 0.6μm, and surface roughness Ra was 0.01μm. In-process grinding was performed with compensation. Results of the profile accuracy P-V 0.3μm and surface roughness Ra 0.006 μm were obtained.