Modern space based optical sensors place substantial demands on the focal plane array readout integrated circuit. Active
pixel readout designs offer direct access to individual pixel data but require analog to digital conversion at or near each
pixel. Thus, circuit designers must create precise, fundamentally analog circuitry within tightly constrained areas on the
integrated circuit. Rapidly changing phenomena necessitate tradeoffs between sampling and conversion speed, data
precision, and heat generation adjacent the detector array, especially of concern for thermally sensitive space grade
infrared detectors. A simplified parametric model is presented that illustrates seeker system performance and analog to
digital conversion requirements trends in the visible through mid-wave infrared, for varying sample rate. Notional
limiting-case Earth optical backgrounds were generated using MODTRAN4 with a range of cloud extremes and
approximate practical albedo limits for typical surface features from a composite of the Mosart and Aster spectral albedo
databases. The dynamic range requirements imposed by these background spectra are discussed in the context of optical
band selection and readout design impacts.
Miniaturized scanners have proven their usefulness in a host of applications including video display, bar code reading, image capture, laser printing and optical switching. In order for these applications to reach fruition, however, the MEMS scanner component must be packaged in a manner that is compatible with the volume manufacturing capabilities of the technology. This paper describes a process that was developed to package an SVGA resolution (800 X 600) biaxial video scanner. The scanner is designed for a head mounted display product, targeted to the medical and industrial markets. The scanner is driven magnetically on one axis and capacitively on the other axis. The first level wafer scale package described here incorporates the capacitive drive electrodes into the mounting substrate. The substrate wafer and the device wafer are then bonded using a glass frit sealing technique. Finally, the scanner and substrate are hermetically sealed into a metal can at reduced pressure.
High-resolution and high frame rate dynamic microdisplays can be implemented by scanning a photon beam in a raster format across the viewer's retina. Microvision is developing biaxial MEMS scanners for such video display applications. This paper discusses the optical performance requirements for scanning display systems. The display resolution directly translates into a scan-angle-mirror-size product and the frame rate translates into vertical and horizontal scanner frequencies. (theta) -product and f<SUB>h</SUB> are both very important figures of merit for scanner performance comparison. In addition, the static and dynamic flatness of the scanners, off-axis motion and scan repeatability, scanner position sensor accuracy all have a direct impact on display image quality.
Scanned displays have potential for achieving high brightness and see-through configurations in many display applications. A MEMS- based solution based on these tradeoffs for SVGA level performance is presented, with test data illustrating optical, mechanical, and electrical performance. Comparison of this scanner against video requirements and other scanners previously reported are illustrated. The feasibility of MEMS-based scanners for Retinal Scanning Displays and other applications is discussed, with extension to higher video performance standards.
The technical and economic rationale for the selection and use of MEMS optical scanning devices for Retinal Scanning Display systems is discussed. While several new technologies and manufacturing approaches to microdisplays have been proposed and demonstrated in the display industry, a number of significant challenges related to cost and complexity of fabricating very dense integrated matrix displays are observed. Factors relating to the choice of a MEMS-based scanned beam approach are presented with special emphasis on the economics of silicon processing and light valve manufacturing. Related imaging applications for the high-precision scanning capabilities of the MEMS scanner are described.
A benchtop optical flow cytometer utilizing microfabricated silicon V-groove flow channels (25 micron diameter) has been constructed and tested using diluted whole blood. A 1.2 mw diode laser probe beam focused onto the flow stream is used to generate scattered light from passing blood cells. Photodiode detectors are used to collect both small and large angle signals which are counted and analyzed for pulse peak intensities. Count rates as high as 1000/second have been obtained using pressure heads of about 0.5 psi. Optical modeling has also been carried out in order to determine the light scattering signature of blood cells passing down various channel flow lines. Results suggest that a significant amount of experimental signal variability may be due to variations in the positions of cells passing through the sampling region, but that this degree of signal variation should not prohibit the discrimination of different cell populations. Experimental and computational results are presented and discussed, as well as the possibility of developing a miniature portable flow cytometer based on microfabricated flow channels.