Lockheed Martin Corporation

Unisys Corporation

John D Hatlestad

Gerald F Sauter

Michael E Farmer

A conventional color charge-coupled-device (CCD) camera without a near infrared blocking filter is used to detect desired vegetation from undesired vegetation and other background. This detection technique relies on the fact that near-infrared (NIR) wavelengths are received by CCD cameras in predetermined frequency bands. This provides output signals from the green and blue pixels of the CCD camera which are approximately equal in interests to the intensity of the infrared portion of the signal provided by the red pixels. A filter is placed between a target area and the CCD camera to restrict the light received by the camera to a bandwidth (approximately from wavelengths of 600-1400 nm), which allows the NIR signal component of the green or blue pixels in this bandwidth to be compared by a signal processing device to the NIR plus R output of the red pixels. In this bandwidth the intensity of the output from the red pixels due to red light from the target area is maximized. Therefore, a signal processing device can utilize signals from the red, green and blue pixels to detect plants and crops in an area of undesired vegetation.

Single charge-coupled-device camera for detection and differentiation of

An optical system for detecting vegetation with the use of a single image sensor, such as a charge coupled device (CCD) camera is provided by optical elements which project separate red and near infrared (NIR) images onto the CCD camera. The camera then can supply output signals representative of the two images to a signal processing device that determines the nature of the vegetation that provided the original image. Embodiments are described where the imaging sensor utilizes unitary optical splitters to provide wide-angle separate images. In another version a single lens and a group of mirrors provide a narrow-angle telescope device. Another version includes two separate lens, red and NIR filters, each adjacent to one of the lenses so as to project an image on separate areas of the CCD camera.

Optical differentiation between plants and background utilizing a single

A CCD camera is adapted for detecting red and near-infrared wavelengths by employing filters that are constructed to allow for the passage of only red light in certain areas and near-infrared light in other areas of the filter. The areas are designed to match the pixel geometry of the lens of a primary color CCD camera that has a predefined pattern of red, blue and green pixels. The match is such that the red bandpass filter areas overlay the red pixels, and the near-infrared bandpass filter areas match the blue and green pixel areas. The red, green and blue output lines of the CCD camera are supplied to a signal processor which uses the signals on these lines to provide combinations of red and near-infrared magnitude that are capable of detecting vegetation from a background. The camera is suitable for full color use again merely by removing the filter that provides R and NIR sensing without otherwise disabling or modifying the camera.

Red/near-infrared filtering for CCD cameras

Inverse synthetic aperture radar imaging systems that are used to image targets that undergo rotational accelerations are enhanced by signal processing techniques which provide correction factors to reduce the frequency-shift and frequency-stretch errors that occur due to such accelerations. A target scan is subdivided into a number of sub-apertures and a Fast Fourier Transfer (FFT) is performed on the data for each sub-aperture to provide associated frequency sub-images. The FFT is then subdivided in 'sub-swaths' of amplitude versus frequency for a plurality of frequency bands. The change-of-frequency, or frequency shift, data between prominent scattering points of each sub-image are processed to provide a phase correction factor that incorporates range changes and translational acceleration distortions for additional scattering points other than the most prominent scattering point. A frequency-stretch correction factor that compensates for rotational acceleration distortion is also provided.

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Burnsville, MN, United States of America

John D Hatlestad