High-resolution camera tracks total solar eclipse

Based on a new design, the high-dynamic-range CMOS (HDRC) digital camera of the Institute for Microelectronics Stuttgart (www.ims-chips.de) in Germany was used to acquire images of the total solar eclipse on August 11, 1999. These images revealed details not seen or recorded before, despite the unprecedented dynamic range encountered during the eclipse from blinding brightness to very dark backgrounds within the same image frame and from frame to frame. These details were detected because the 32

High-resolution camera tracks total solar eclipse

George Kotelly

Executive Editor

georgek@pennwell.com

Based on a new design, the high-dynamic-range CMOS (HDRC) digital camera of the Institute for Microelectronics Stuttgart (www.ims-chips.de) in Germany was used to acquire images of the total solar eclipse on August 11, 1999. These images revealed details not seen or recorded before, despite the unprecedented dynamic range encountered during the eclipse from blinding brightness to very dark backgrounds within the same image frame and from frame to frame. These details were detected because the 320,000-pixel HDRC camera can record light intensities with a range exceeding six orders of magnitude or 16 star classes and does not suffer from over- or underexposure. In addition to minimizing exposure errors and eye-glare hazards, the camera detected higher-quality details at the beginning and end of the total eclipse, as well as varying intensities of the corona and simultaneously present stars and planets.

The HDRC camera images of the total solar eclipse are available on the Internet at www.ims-chips.de/ products.html under "Sample Images." These recorded images were obtained as a result of the cooperative efforts by the Hamburg Observatory, the Swabian Observatory Stuttgart, and Thomson Multimedia (all in Germany).

Sequence frames were recorded digitally at a rate of 15 frames/s and 10-bit resolution with a black-and-white HDRC VGA digital video camera from IMS Chips in a field near Bad Bergzabem, Germany. The 0.5-in. imager of 0.35-μm technology faithfully reproduced local intensity ranges that exceeded five decades using a human-eye-like logarithmic compression response. A 400-mm, f/5.6 mirror telescope was also used.

The camera technology, which is the result of a 10-year development effort from invention to product, is based on recent breakthroughs in microchip technology. The HDRC camera is expected to replace electronic CCD cameras. The CCD camera has a dynamic range of 100:1 to 1000:1; the HDRC camera can handle a dynamic range of 10,000:1, which also exceeds the range of film. Furthermore, HDRC digital cameras can record regions of interest in a scene at 10,000 frames/s. For these reasons, they are being installed into machine-vision, intelligent transportation, and security systems.

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