Advances in lasers, solid state detectors, electronics, and computational and display capabilities have made a reality of filmless recording, precision dynamic testing, and real-time processing of optical interference fringe patterns. Stroboscopically produced fringe patterns of the mirror-facet surface of a cylindrically shaped and a conically shaped scanner heat for `monogonal' scanners correlate with the predicted dynamic deformations from finite element analysis (FEA) at rotational speeds of 10 krpm and 20 krpm.
Located in high-tech "Silicon Valley," California, San Jose State University is ideally suited to provide students with a high quality education in optics, and industry with a partner for optics related research and development projects. There are 130 undergraduate majors and 65 graduate (M.S.) students in the Physics Department. For the past five years the Department has offered a special program leading to the B.S. in Physics with a Concentration in Lasers and Optics. Students take the usual core undergraduate Physics courses plus upper division courses in Modem Optics, Lasers and Applications, Advanced Optics Lab, Advanced Lasers Lab, Advanced Instrumentation Lab, and either Individual Studies or a graduate course in Electro-optics, Graduate Optics, Optical Metrology, or Laser Spectroscopy. Graduates are well prepared to enter the lasers and optics industry or go on to graduate school. Recently, a 4000 square foot area in the Science Building has been renovated to house the new Institute for Modem Optics, an organized research unit in the College of Science. One of the major goals of the Institute is to facilitate collaborative research between the local optics industry and the faculty and students at SJSU. The Institute is well equipped with lasers, optical instrumentation, electronics/computers, and about 10 optical tables. A National Science Foundation Research Experience for Undergraduates Program grant provides research support in optics for about eight undergraduates at any time throughout the calendar year. The National Science Foundation also provides support for "Laser Applications in Science Education," a summer program that provides hands-on experience with lasers for high school science teachers.
A system has been developed which is capable of interferometrically measuring optical path length
changes, with high spatial and temporal resolutions. The capability to freeze fast motion is provided
by the pulse length of the laser, the frame rate is determined by the laser and camera, and the spatial
resolution is determined by the camera and data resorder. The system has been applied to measuring
the optical disturbance through an aerocurtain, a shock wave produced by a supersonic projectile,
thermodynamic gas flow, and membrane mirror surfaces. The choice of interferometer type is
determined by environmental and optical considerations such as expected jitter and magnitude of
aberrations. The phase at each point is determined by taking intensity values of the interference
pattern at three sequential pixels, labled A, B, and C, after introducing large amount of tilt fringes and
applying the spatial phase shifting algorithm: 0 = arctan((C-B)/(A-B)}. The current system uses
100 ns pulse at any desired repetition rate or a 10 ns pulse at 30 Hz. The camera and recorder
provide a resolution of 510x480 pixels at 30 Hz or 248x192 pixels at 2000 Hz.
The cross-sections of high-speed aerodynamic phenomena are presently measured by means of a system that interferometrically ascertains optical path length changes with high spatial resolution. Attention is given to the optical disturbance through an aerocurtain, and to the shock wave produced by a hypersonic projectile. While the slowest repetition rate of the laser, camera, and data recorder determines the time-frame rate, the combination of the camera and data recorder determines the spatial resolution. The technique is the spatial equivalent of phase-shifting interferometry. The real-time hardware employed is discussed.
Proceedings Volume Editor (3)
This will count as one of your downloads.
You will have access to both the presentation and article (if available).