The VSH (video-scan head) scan engines have been designed for real-time point scanned image capture systems. The contrast produced by a point-scanned system can exceed those produced by CCD systems for objects such as scratches or low-profile edges. Intended applications range from semiconductor inspection to fluorescent microscopy to biological diagnostics. The capabilities spanned by the VSH-4 (4000 lines/second) and VSH-8 (8000 lines/second) engines are frames up to 1024 by 1024 pixels and frame rates to 100 frames per second. Frame size (zooms to 1/10th full-frame), user-defined lines-per-frame, frame rate, and pan moves in the frame scan direction are supported. To assess the performance of these devices an imaging system was built and the outputs i.e., detector or bit-mapped images, were analyzed and compared to specific criteria. This imaging system is described and measurements including image linearity, pixel stability, and system MTF are presented. Discussions of how scanning systems impact overall imaging performance along with some of the practical lessons learned from interfacing the VSH to optics and a commercial frame- grabber are included.
One of the challenges in designing a confocal microscope is choosing the scan system configuration. The selection is based largely on the microscope application and involves a few distinct schemes. One scheme, moving mirror using galvanometer and resonant scanners, has been shown to offer an excellent solution exhibited by the large number of commercial systems which utilize them. Perceived shortcomings, such as slow image acquisition, are being dispelled due to the advent of large angle, high frequency resonant scanners. These newer devices offer near video rate performance at good scan efficiency.
A space-based optical communications experiment, developed at Lincoln Laboratory, requires a fast steering mirror as part of its spatial pointing, tracking and acquisition system. The High Bandwidth Steering Mirror version C (HBSM-C), has been designed, built and tested. This device steers a small-aperture mirror of 6 mm about two axes, through an operating range of 25 milliradian and a small-signal closed-loop bandwidth up to 2 kHz. The HBSM-C has endured a rigorous space-qualification test program with no special caging mechanism needed during high-level random vibration of 19 g rms. A description of the functional requirements, design and assembly, and analytical methods used is presented. Key results from performance and environmental testing are shown.
A two-axis, high-bandwidth, small-aperture steering mirror called the High Bandwidth Steering Mirror (HBSM) has been designed, fabricated, and tested. The mirror/mechanism prototype functions within a servo loop either scanning a field of view or tracking a radiation source. The design focused on elements making up the beam-steering mechanism: mirror, restoring flexures, actuators, position sensors, and encompassing housing, and the part each component plays in making a mechanical system suitable for high-bandwidth operation. Inclusion of a novel flexural support allows one-degree peak-to-peak angular stroke (shaft space) at low frequencies and a small-signal closed-loop bandwidth of up to 10 kHz without the usual mechanical resonance-induced loop instabilities. This increased bandwidth allows substantial rejection of a disturbance spectrum in the 10-1000 Hz range and execution of fast, complex scan patterns. Pointing accuracies of 0.2 micronrad have been achieved in the laboratory. Details of the mechanical design and fabrication issues as well as the control-loop implementation are discussed. Test data are presented along with reports of the mirror's performance in use as an extended sensor.
The high bandwidth steering mirror (HBSM) prototype is the product of a research program established to develop a high-bandwidth, low angular range, two-dimensional beam steerer frequently found in optomechanical pointing, acquisition, and tracking systems. This research centered around the optimization of a beam-steering mechanism composed of mirror, restoring flexure, actuators, position sensors, and encompassing housing. Various design trade-offs and manufacturing issues involved in building the prototype are discussed, and the performance data are presented. The resulting HBSM design allows integration with a simple closed-loop control scheme. The mirror/controller has a closedloop bandwidth of 10 kHz and 10 peak-to-peak stroke (mirror normal) at low frequencies. This increased bandwidth yields excellent disturbance rejection in the 10 to 1000 Hz frequency band and enables the generation of faster scan patterns.
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