Navy

High-speed camera calibration

Measuring light integration time of visible and infrared cameras

Electronics

In order to support weapon testing and training activities, many open-air ranges utilize multiple cameras to capture images in both visible and non-visible spectrum. Generally, these cameras are used to record a test event and are synchronized to a precision time source (Coordinated Universal Time) to help create coordination imagery of the test event. The resulting imagery capturing the test event is then fed into image processing software and fused to generate time-space-position information (TSPI) data.

TSPI data is susceptible to error and is only as precise as the least precise data source in the data flow. Thus, any improvement in the accuracy of the timing of the camera shutter speeds will likely result in an improvement in the generated TSPI data. The frame rate for some of these cameras can be altered, thereby modifying how often an image frame is recorded for each specific test. But, depending on the manufacturer, the timing of the camera shutter may vary, even when using the same input synchronization signal. More importantly, the shutter timing might not even conform to the manufacturer-provided specifications. As a result, given the possible shutter timing inconsistencies, it is difficult or impossible to determine the timing of critical events with a necessary degree of precision.

Navy scientists have solved these inconsistent shutter timing issues with a calibration mechanism for measuring with precision the timing of light integration for visible and infrared cameras. In general, the video timing test equipment utilizes a single frame step camera or video recorder to measure the accuracy of video overlay and metadata time stamp. It further incorporates a GPS coordinate universal time message signal along with a one pulse per second output signal to generate a timing accuracy of approximately one microsecond. The timing accuracy is expressed through the use of light emitting diodes (LEDs) and infrared LEDs, which may be synchronized to a video frame rate signal. The video timing test equipment may further utilize high-speed LEDs for switching within nanoseconds.

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