Dynamic Focusing System Research Articles

Study on real-time z-scanning of multiple-pulse laser ablation of metal applied in roll-printed electronics

The interaction between a metal surface and multiple pulses was investigated to achieve optimal focusing conditions during ultrashort laser ablation. We report a simple theoretical expression of morphological changes in the ablated channel and demonstrate its advantage in positioning the interactive surface at the focus in real time during multiple-pulse laser ablation of a metallic material. Experimental results on the ablation depth for zinc, nickel, and copper show that the combination of a dynamic focusing system and a theoretical formula of ablation-cycle-dependent ablation depth enables one to control the shape of ablated channels. This model can be applied to a variety of high-efficiency ablation systems and may play an essential role in the development of a high-precision ablation system for the curved surfaces in highly scaled metal gravures used in printed electronics, which currently present challenges for engineers and technicians.

Research on dynamic focusing system of laser scanning projection instrument

Research on dynamic focusing system of laser scanning projection instrument

Wear resistance coatings of nickel alloys obtained by supersonic plasma torch

The research results of coatings of nickel alloys deposited using supersonic atmospheric-plasma spraying are presented. The main feature of the work carried out is that the plasma flow is charged by powder material using the powder ring injector designed by authors. The ring powder injector unit is equipped by a gas dynamic focusing system that makes it possible to ensure the conditions of creating coatings which are not subject to wear and tear under abrasive friction.

The research of compression and generation of high-precision dynamic focusing delay data for ultrasound beamformer

In an ultrasound imaging system, dynamic focusing is crucial in improving the spatial resolution and signal-to-noise ratio. However, the generation of focusing delay data (FDD) requires complex calculations and a large amount of memory. The dynamic focusing system may become extremely complex as the number of focusing channels and the focal depth increase. This paper presents a simplified scheme of a high-precision generator for the FDD in Field-programmable Gate Array (FPGA). First, the original FDD are pre-calculated, quantized, decomposed, and compressed by exploiting the recursive characteristics between focusing channels. Then, the initial value and changing locations of each channel are stored as a reference data set. Finally, the FDD are generated in real time by decompressing the preloaded reference data set during the focusing process. The results indicate that the proposed approach consumes less than l% of the memory space of the original method, which may provide significant resource savings and low hardware power consumption. The proposed method can also be applied to convex or flat transducers array in compact beamformers. Moreover, the focusing accuracy and compression ratio can be flexibly adjusted, and the compression ratio can be further improved when the proposed approach is combined with the dynamic aperture. The proposed approach is contribute to the solution of the problem of the complex and large amount of data in ultrasonic imaging system. It is suitable for designing a specific compact focusing beamformer, particularly for a portable ultrasound imaging system.

Design of voice coil motor dynamic focusing unit for a laser scanner.

Laser scanning systems have been used for material processing tasks such as welding, cutting, marking, and drilling. However, applications have been limited by the small range of motion and slow speed of the focusing unit, which carries the focusing optics. To overcome these limitations, a dynamic focusing system with a long travel range and high speed is needed. In this study, a dynamic focusing unit for a laser scanning system with a voice coil motor (VCM) mechanism is proposed to enable fast speed and a wide focusing range. The VCM has finer precision and higher speed than conventional step motors and a longer travel range than earlier lead zirconium titanate actuators. The system has a hollow configuration to provide a laser beam path. This also makes it compact and transmission-free and gives it low inertia. The VCM's magnetics are modeled using a permeance model. Its design parameters are determined by optimization using the Broyden-Fletcher-Goldfarb-Shanno method and a sequential quadratic programming algorithm. After the VCM is designed, the dynamic focusing unit is fabricated and assembled. The permeance model is verified by a magnetic finite element method simulation tool, Maxwell 2D and 3D, and by measurement data from a gauss meter. The performance is verified experimentally. The results show a resolution of 0.2 μm and travel range of 16 mm. These are better than those of conventional focusing systems; therefore, this focusing unit can be applied to laser scanning systems for good machining capability.

Mobile Optical Coherence Tomography Sensor for Surface Layers Testing

In the paper the new type of mobile sensor based on optical coherence tomography is presented. For increasing the measurement range the special dynamic focusing system which moves imaging plane during axial scanning process is used. Therefore developed system allows focusing on measured layer. Additionally, for image analysis the special type of CMOS matrix (called smart-pixel camera), synchronized with a reference mirror transducer, is applied. Due to hardware realization of a fringe contrast analysis simultaneously in each pixel with high frequency, the time of measurement decreases significantly. These advantages together with a compact design allow the sensor to be used as the mobile device for measurements of surface topography, thickness of surface layers and subsurface defects detection in laboratory, workshop and out-door conditions. Calibration of the designed sensor and its application to the technological measurements of the sticker label layers are presented and discussed.

Real-time focus control in broad flat field laser material processing

Broad flat field laser scanning is critical to the success of laser material processing, used in techniques such as rapid prototyping & manufacturing (RP&M) and micro-machining. For these techniques it is necessary to produce high-performance optical systems that can fulfill the need for a smaller focused spot size over broad, flat field scanning areas. This paper concentrates on the issues of defocus error compensation. A dynamic focusing system is designed, intended primarily for broad flat field galvanometric laser scanning applications. Key technologies are described in detail; corresponding solutions have been used to design and produce a CO 2 infrared optical focusing system, which is capable of scanning a focused spot size of 120 μm or less over areas up to 500 mm 2.

Adaptive dynamic focusing system for ultrasonic nondestructive testing of pipeline girth welds

An adaptive dynamic focusing system used for the ultrasonic nondestructive testing of pipeline girth welds is developed. This system relies on ultrasonic linear phased array transducers connected to a multichannel acquisition system, which provides delay and amplitude laws, allowing one to control the ultrasonic beams dynamically. We introduce a testing method for welds and the system’s structure. Optimization of array transducers has also been pursued based on a mathematical model of the acoustic field for a linear phased array. The experimental results have proved that the phased array transducers system has the same capability to detect as a conventional ultrasonic transducers system, but the components of the system can be simplified greatly, and the testing flexibility and the testing speed can be improved greatly. It provides an excellent basis for further research and development of defect inspection of pipeline girth welds.

Microscopic vision system with all-in-focus and depth images

In this paper, a high-speed digital processed microscopic observational system for telemicrooperation is proposed with a dynamic focusing system and a high-speed digital-processing system using the "depth from focus" criterion. In our previous work [10], we proposed a system that could simultaneously obtain an "all-in-focus image" as well as the "depth" of an object. In reality, in a microoperation, it is not easy to obtain good visibility of objects with a microscope focused at a shallow depth, especially in microsurgery and DNA studies, among other procedures. In this sense, the all-in-focus image, which keeps an in-focus texture over the entire object, is useful for observing microenvironments with the microscope. However, one drawback of the all-in-focus image is that there is no information about the objects' depth. It is also important to obtain a depth map and show the 3D microenvironments at any view angle in real time to actuate the microobjects. Our earlier system with a dynamic focusing lens and a smart sensor could obtain the all-in-focus image and the depth in 2s. To realize real-time microoperation, a system that could process at least 30 frames per second (60 times faster than the previous system) would be required. This paper briefly reviews the depth from focus criterion to Simultaneously achieve the all-in-focus image and the reconstruction of 3D microenvironments. After discussing the problem inherent in our earlier system, a frame-rate system constructed with a high-speed video camera and FPGA (field programmable gate array) hardware is discussed. To adapt this system for use with the microscope, new criteria to solve the "ghost problem" in reconstructing the all-in-focus image are proposed, Finally, microobservation shows the validity of this system.

Ultrasonic defect characterization with a dynamic adaptive focusing system

In order to improve ultrasonic inspection, in terms of detection, sizing and characterization of defects, the French Atomic Energy Commission (CEA) has developed a dynamic adaptive focusing system called FAUST: Focusing Adaptive UltraSonic Tomography. This sytem is based on ultrasonic phased array transducers connected to a multi-channel acquisition system, which provides the delay and amplitude laws, allowing one to control dynamically the ultrasonic beam. This paper presents the general architecture of the system and some applications of it for defect characterization and improvement of the ultrasonic inspections.

Real-time digital dynamic focusing system

In this paper an inexpensive digital dynamic focusing and deflection technique for real-time phased array ultrasonic imaging equipment is proposed. In this system, operating below 10 MHz, a time delay resolution of 10 ns is adopted to reduce quantization grating lobes effects. This equipment allows a 10 ns delay resolution with an RF signal sampling rate of 20 MHz. The resulting electronic circuitry is simple and inexpensive and can be easily expanded to deal with several reception lines.

E-Beam Writing Techniques for Semiconductor Device Fabrication

Electron-beam writing instruments for microcircuit fabrication are currently limited by total cycle time, field coverage, automatic registration, and reliability. A fully computer-controlled electron-beam pattern generator will be described which has been developed to advance the economic feasibility of electron beam writing. The instrument incorporates a fully automated mechanical stage and pattern registration system, computer designed deflection coils and a dynamic focusing system for correction of deflection introduced aberrations. Field coverage at the short working distance is variable, up to 0.120×0.120 in. with 60 000×60 000 addressable points in the field. Resolution over the field is 3500 lines at 8 mrad. Pattern distortion is within 1.0 μ over a 0.1 in. square field. The mechanical stage employs stepping motors driving lead screws to provide 3×3 in. movement in 250 μ in.steps. Additional travel of 7 in. is available in one axis for loading the wafer. The automatic pattern registration system employs four silicon etched “L” shaped fiducial marks located in the corners of each field. The electron beam is used to measure the position of the fiducial marks before each field exposure and position the pattern correctly on the wafer. Pattern position, size, rotation, and orthogonality are all typically set up by the automatic registration system in 300 msec. A vernier test pattern has been used to test the alignment system and shows registration better than ± 0.2 μ.