Microscopic Vision System Research Articles

An REU Experience With Micro Assembly Workcell Research

Under an NSF REU center grant REU-0755355 entitled “Micro/Nano Assembly Workcell Via Micro Visual Sensing and Haptic Feedback”, Texas A&M University – Corpus Christi and Texas State University – San Marcos collaboratively hosted two groups of 10 students from different backgrounds for 10 weeks each in Summer 2008 and 2009 respectively. The research effort involved is part of an ongoing research program developing novel methods for making automated micromanipulation systems. The twenty students and two teachers were divided into four teams developing interrelated aspects of the project. The first team developed the micro-scale parts, such as gears, for assembly. This required the team to develop techniques for etch and release of three dimensional parts from a silicon substrate. The second team developed the microscopic vision system used for locating and identifying parts on a silicon wafer. The vision system is used to determine the position on the wafer of the parts, their diameter (one of several standard parts), and, utilizing a novel technique developed by the team, the thickness of the parts. The third team developed a robotic platform able to locate any portion of a wafer for manipulation within a three-dimensional space with 10μm accuracy. This mechanism is used to first bring any desired portion of the wafer to the vision system for analysis and also to bring a manipulator to “pick and place” parts using the vision system for feedback. The fourth group developed the micro-manipulator in the form of a “gripper” powered by electro-active polymer. This gripper was capable of accurately and repeatably gripping, lifting, moving, placing, and releasing parts at any point within the workspace. Collectively, the REU project successfully produced a prototype system advancing the state-of-art for an important are of micro-manufacturing while offering a stimulating experience for undergraduate students. Assessment of the student experience showed an increase in the likelihood for these students to pursue engineering careers and to encourage their peers to consider STEM careers.

Design, Fabrication, and Visual Servo Control of an XY Parallel Micromanipulator With Piezo-Actuation

This paper presents a complete design and development procedure of a new XY micromanipulator for two-dimensional (2-D) micromanipulation applications. The manipulator possesses both a nearly decoupled motion and a simple structure, which is featured with parallel-kinematic architecture, flexure hinge-based joints, and piezoelectric actuation. Based on pseudo-rigid-body (PRB) simplification approach, the mathematical models predicting kinematics, statics, and dynamics of the XY stage have been obtained, which are verified by the finite-element analysis (FEA) and then integrated into dimension optimization via the particle swarm optimization (PSO) method. Moreover, a prototype of the micromanipulator is fabricated and calibrated using a microscope vision system, and visual servo control employing a modified PD controller is implemented for the accuracy improvement. The experiments discover that a workspace size of 260 mum times 260 mum with a 2-D positioning accuracy and repeatability around 0.73 and 1.02 mum, respectively, can be achieved by the micromanipulator.

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.