A high-efficiency, high-frame-rate ultraviolet (UV) charge-coupled device (CCD) camera that is especially well suited for biological and defense applications was developed. This is the first high-frame rate camera using delta-doped CCDs, which is suitable for biological imaging having high speed, high and stable UV quantum efficiency and insensitivity to visible light.
The camera is built around a back-surface illuminated, thinned, delta-doped CCD with antireflection coating and a visible-light-blocking filter. [Issues pertaining to the principle of operation, design, and fabrication of delta-doped CCDs have been discussed in a number of prior NASA Tech Briefs articles, the one most relevant to the present development being "Back-Illuminated CCDs With Integral Ultraviolet-Pass Filters" (NPO-21007), NASA Tech Briefs, Vol. 25, No. 7 (July 2001), page 20a.] Back-illuminated delta-doped CCDs have been found to operate at quantum efficiency of 40 to 60 percent in the 300- to 400-nm region of interest. With addition of antireflection coatings, quantum efficiency can be increased to between 80 to 100 percent. Moreover, the high quantum efficiency of delta-doped CCDs has been shown to be stable for years.
Because CCDs are also sensitive to visible light, filters must be included to block the light at wavelengths greater than 400 nm.
The camera has been demonstrated to operate at a rate of 2 to 10 frames per second with digital output and digital control of the camera parameters and in acquiring images of biological significance in a wavelength band centered at 300 nm (see figure). At the time of reporting, the camera is operating a delta-doped, 1024-by-1024-pixel, 12-μm-pixel-pitch CCD. Camera electronics are capable of operating at a rate of 30 frames per second and subsequent development is required for design and fabrication of video-rate CCDs for use in this camera. The camera is also compact and transportable and is suitable for field observations as well as laboratory measurements.
This work was done by Shouleh Nikzad and Todd J. Jones of Caltech for NASA's Jet Propulsion Laboratory. For further information, access the Technical Support Package (TSP) free on-line at www.nasatech.com/tsp under the Electronic Components and Systems category.
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Refer to NPO-30514, volume and number of this NASA Tech Briefs issue, and the page number.