KEYWORDS: Video, Cameras, Video processing, Image processing, Imaging systems, Analog electronics, Sensors, Digital electronics, Digital signal processing, Image sensors
A miniaturized camera utilizing advanced extended dynamic range CMOS APS imager technology and employing real-time histogram equalization has been developed for capturing scenes having high intra-scenic dynamic range. The camera adapts to changes in scene brightness and contrast in two frame periods, and acquires fully processed images in less than 100 milliseconds after power is applied. The BLINC camera contains an automatic exposure time control and is capable of capturing over 8 equivalent f-stops of optical dynamic range. This exposure time control along with programmable extended dynamic range and built-in 12-bit analog to digital converter allows the Sarnoff APS75 CMOS VGA image sensor to accommodate up to 15 f-stops of intra- scenic dynamic range. The APS75 sensor was fabricated with standard CMOS-7 design rules in a 0.5 micron SPTM process. Progressive scan digital video is stored and processed in real-time by an application specific integrated circuit image processor to provide optimal image contrast and exposure. The processed video is then transformed to 10-bits with a proprietary adaptive non-linear mapper before being converted to standard RS-170 analog video. Small size, light weight and low energy consumption make this camera well suited for UAV, and automotive applications.
KEYWORDS: Digital signal processing, Video, Video surveillance, Cameras, Imaging systems, Signal processing, Algorithm development, Analog electronics, Video processing, Image processing
A real time contrast enhancement system utilizing histogram- based algorithms has been developed to operate on standard composite video signals. This low-cost DSP based system is designed with fixed-point algorithms and an off-chip look up table (LUT) to reduce the cost considerably over other contemporary approaches. This paper describes several real- time contrast enhancing systems advanced at the Sarnoff Corporation for high-speed visible and infrared cameras. The fixed-point enhancer was derived from these high performance cameras. The enhancer digitizes analog video and spatially subsamples the stream to qualify the scene's luminance. Simultaneously, the video is streamed through a LUT that has been programmed with the previous calculation. Reducing division operations by subsampling reduces calculation- cycles and also allows the processor to be used with cameras of nominal resolutions. All values are written to the LUT during blanking so no frames are lost. The enhancer measures 13 cm X 6.4 cm X 3.2 cm, operates off 9 VAC and consumes 12 W. This processor is small and inexpensive enough to be mounted with field deployed security cameras and can be used for surveillance, video forensics and real- time medical imaging.
Field deployable, high frame rate visible CCD camera systems have been developed to support the Test and Evaluation activities at the White Sands Missile Range. These visible cameras are designed around a Sarnoff 1024 X 1024 pixel, backside illuminated CCD with a 32-port, split-frame transfer architecture. The cameras exploit this architecture to provide selectable modes from a 30 Hz frame rate at 1024 X 1024 pixels to a 300 Hz frame rate with 1024 X 512 pixels (2:1 vertical binning). The cameras are configured with a 500 mm, f/4 lens, and a Ferro-electric liquid crystal electro-optic shutter, to provide variable integration times from 0.5 to 32 msec. Video outputs provided are RS170 analog video in a reduced 512 X 480 pixel format, and 12-bit full resolution digital video data stream provided through a high speed serial/parallel digital coaxial interface. At a frame rate of 300 frames per second, these cameras deliver video data at an average rate of 1.9 Gbits/sec, and a burst rate of 2.8 Gbits/sec, with the capability of reaching an average 12 bit digital data rate of 3.8 Gbits/sec when higher frame rate imagers become available.
Experimental Multi-wavelength Imaging Pyrometer (M-WIP) is presented for remote sensing of temperature profiles of targets with unknown spectrally varying emissivity. A software package was developed for calibration and real-time M-WIP measurements. An experimental 7-filter line-sensing M- WIP system was implemented with a 320 X 122-element PtSi IR-CCD imager and an assembly of narrow-band striped IR filters in the spectral range from 1797 nm through 4512 nm. The M-WIP system was calibrated against a commercial blackbody source over temperature range from 450 degree(s)C to 950 degree(s)C. The signal processing included background subtraction, compensation for variation of dark current with detected signal and correction for non-linearities of IR imager response. Initial M-WIP measurements demonstrated real-time temperature resolution (Delta) T of +/- 1 degree(s)C for blackbody target over temperature range from 600 degree(s)C to 900 degree(s)C. Temperature resolution of +/- 4 degree(s)C was demonstrated for the blackbody source viewed through the double polished silicon wafer with unknown spectral transmissivity in the temperature range from 500 degree(s)C to 950 degree(s)C.
Joseph Ambrose, B. King, John Tower, Gary Hughes, Peter Levine, Thomas Villani, Benjamin Esposito, Timothy Davis, K. O'Mara, W. Sjursen, Nathaniel McCaffrey, Francis Pantuso
Field deployable, high frame rate camera systems have been developed to support the test and evaluation activities at the White Sands Missile Range. The infrared cameras employ a 640 by 480 format PtSi focal plane array (FPA). The visible cameras employ a 1024 by 1024 format backside illuminated CCD. The monolithic, MOS architecture of the PtSi FPA supports commandable frame rate, frame size, and integration time. The infrared cameras provide 3 - 5 micron thermal imaging in selectable modes from 30 Hz frame rate, 640 by 480 frame size, 33 ms integration time to 300 Hz frame rate, 133 by 142 frame size, 1 ms integration time. The infrared cameras employ a 500 mm, f/1.7 lens. Video outputs are 12-bit digital video and RS170 analog video with histogram-based contrast enhancement. The 1024 by 1024 format CCD has a 32-port, split-frame transfer architecture. The visible cameras exploit this architecture to provide selectable modes from 30 Hz frame rate, 1024 by 1024 frame size, 32 ms integration time to 300 Hz frame rate, 1024 by 1024 frame size (with 2:1 vertical binning), 0.5 ms integration time. The visible cameras employ a 500 mm, f/4 lens, with integration time controlled by an electro-optical shutter. Video outputs are RS170 analog video (512 by 480 pixels), and 12-bit digital video.
Walter Kosonocky, Michael Kaplinsky, Nathaniel McCaffrey, Edwin Hou, Constantine Manikopoulos, Nuggehalli Ravindra, S. Belikov, Jun Li, Vipulkumar Patel
Multi-wavelength imaging pyrometer (M-WIP) is presented for remote sensing of temperature profiles of targets with unknown emissivity. Fast algorithm and software package were developed for calibration and real-time M-WIP measurements. Experimental 7- filter line-sensing M-WIP system was implemented with 320 X 122-element PtSi IR-CCD imager. The M-WIP system was calibrated against a commercial blackbody source over temperature range from 450 degree(s)C to 900 degree(s)C. Signal processing included background subtraction and compensation for variation of dark current with detected signal and signal off-set sue to apparent BCCD trapping effect. Initial M-WIP measurement demonstrated temperature resolution (Delta) T of +/- 1 degree(s)C for blackbody target over temperature range from 600 degree(s)C to 900 degree(s)C.
Camera designs and radiometric performance evaluation results are presented for two PtSi IR imagers fabricated by the David Sarnoff Research Center. Measurements on the 640 X 480 IR-MOS imaging radiometer with 25 to 150 degree(s)C background temperatures indicated response non-linearity less than +/- 0.3% over 80% of the full signal range. By operation with variable integration time from 240 microsecond(s) ec to 33 msec a scanned image with a NE(Delta) T of less than 0.1 degree(s)C can be maintained over the full temperature range. The 320 X 122 IR-CCD imaging radiometer was designed for operation with integration times ranging from 0.12 to 133 msec to provide for 12 snapshot image settings. The signals from various integration times were effectively matched and scaled to increase the effective maximum measured signal from 1 X 106 to 50 X 106 electrons/pixel. Correction procedures were developed for achieving radiometric accuracy for achieving radiometric accuracy for operation of the imagers over multiple integration times and taking into account the effects of non- linear response of dark current and charge trapping in the readout BCCD registers. The camera stability was shown to be limited by the stability of the calibration source over a three- hour period.
Nuggehalli Ravindra, Fei Ming Tong, Samiul Amin, J. Shah, Walter Kosonocky, Nathaniel McCaffrey, Constantine Manikopoulos, Bawa Singh, Ramazan Soydan, Lawrence White, Pete Zanzucchi, Dorothy Hoffman, James Markham, Shaohua Liu, Karen Kinsella, Richard Lareau, L. Casas, T. Monahan, D. Eckart
The results of our work on the development of emissivity models and IR filters for applications in multi-wavelength imaging pyrometry are presented. Techniques such as Fourier transform IR spectroscopy have been deployed to determine the emissivity of Si and SiO2/Si in the temperature range of 331 to 1235 K. These measurements have been obtained for n-Si, p-Si and SiO2/Si in the oxide thickness range of 60 to 500 nm. These results coupled with calculations of emissivity from first principles lead us to model the wavelength dependence of emissivity. Preliminary measurements of emissivity of HgCdTe are reported.
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