Computer Microvision User Guide
Introduction
Computer Microvision is a tool for in situ visualization of the motions of internal structures in MEMS, that operates by combining light microscopy, video imaging, and machine vision. Images of microelectromechanical systems are magnified with a microscope and projected onto a CCD camera. Stroboscopic illumination is used to take temporal sequences of images at multiple planes of focus. Recorded images are then viewed at playback speeds chosen to facilitate human interpretation of the motions. Quantitative estimates of motions are also obtained directly from the recorded images using algorithms originally conceived for robot vision.
Computer Microvision System
The Computer Microvision test stations deployed at the MIT Research Laboratory of Electronics (RLE), Carnegie Mellon University (CMU), and the Berkeley Sensor and Actuator Center (BSAC) each consist of a Zeiss Axioplan 2 laboratory microscope, equipped with long working distance objectives. The microscope stage is motorized for remote control of 3D position via an integral motorized Z drive and a Prior Scientific 4" x 3" motorized X-Y stage. A piezoelectric focusing unit (PIFOC, Polytec PI, Wandbronn, Germany) provides precise control of axial position. A mega-pixel CCD camera (Pulnix TM-1010) connects to a Pentium-based computer (Dell) via an Imaging Technology frame grabber.
We are currently using 500 megahertz Pentium processors running the Linux 2.2 kernel in our experimental setups. This platform provides real-time focusing by updating the display with mega-pixel images from the Pulnix TM1010 camera at a 15 hertz frame rate. It also stores images sufficiently fast for online analysis and visualization of results. The 60 dB signal to noise power ratio (10 bits) of the TM1010 is more than adequate for MEMS applications. The systems are set up on vibration isolated tables.
Periodic waveform stimulation, stroboscopic illumination, and exposure control of the camera are accomplished by a single custom hardware module, which is interfaced to the host computer via the parallel port. The logic is entirely implemented by downloadable firmware and is under operational control of the Computer Microvision system data acquisition software at runtime.
A highly flexible set of controls for the experimenter is supported. The user can download arbitrary waveforms for stimulating the MEMS, adjust the intensity, phase, and duration of the stroboscopic illumination, and control the frequency of the periodic stimulus with millihertz resolution to frequencies above 10 megahertz.
A software-controlled relay at the stimulus output protects the MEMS from damage due to startup transients.
Examples of Use
The first step is to locate the target and focus to obtain the desired image with the Focus Image... button on the Data Acquisition (main) panel. For our current Zeiss based systems, an exposure time of .02 seconds (20 milliseconds) is typical, but may vary with the reflectivity of the target and other factors.
This will bring up the Focus window where the device can be viewed as it will appear in the image data. Use the slider bars or the arrow keys on the client terminal to locate and focus on the target.
To observe the motion of the device "live", use the Watch Motion... button on the Data Acquisition panel to select the test Amplitude, Frequency, and number of phases. The device will be activated as specified and stroboscopic images in successive phases will be streamed in real time to the image canvas.
To take and save a full dataset (sweep), use the Hardware Settings... button on the Data Acquisition Panel to make any necessary adjustments. Then use the Parameter Type button on the Data Acquisition panel to select the swept parameter (frequency or amplitude).
To specify parameter values for the focal plane, signal phase, and swept parameter, use the Edit.. button to bring up an edit list box. After the value list for a parameter has been specified, the selected values appear in the Data Acquisition panel window.
You can enter a short descriptive text for your experiment in the Experiment Description: text box. Save your setup and give your experiment a name by selecting Save... from the File pulldown on the Data Acquisition panel.
To run your experiment, click Run Now....Using Computer Microvision with the Matisse Session Manager
If you authenticate yourself to the Session Manager , you can use the Meta Data Server to retrieve experiments you and others have performed and examine all experimental parameters.
Installation Guide
Computer Microvision is a "native" Matisse application. Currently an X server and incr tcl must first be installed on the client machine.
Michael McIlrath