Northrop Grumman Systems Corporation

Harold J Orlando

Marco A Lopez

Dean L Weideman

Michael Lee Pappas

James A Wes

Neil R Nelson

Steven R Zammit

Lawrence M Scherr

An apparatus and method for removing offset and shading from a video signal include a filter that convolves the video signal with a second derivative. The derivative can include first and second non-zero values centered about a third non-zero value, zero-filling between the first and third values, and zero-filling between the second and third values. The filter can be applied to Modulation Transfer Function measurement of an electro-optical sensor, in which offset and shading are removed from the sensor's video signal prior to Fourier analysis. Filtering and Fourier analysis are performed by a digital signal processor, which allows the measurement to be fully automated.

Apparatus and method for removing offset and shading from a video signal

Modulation Transfer Function of an electro-optical sensor is measured by focusing a square or rectangular target image onto the sensor and deriving the Modulation Transfer Function in two directions simultaneously from an output of the sensor. The target image is tilted with respect to the sensor's focal plane array such that the target image's edges cross different detector elements at different phases. The target image can be rotated over finely spaced intervals. Modulation Transfer Function can be derived using a least squares method or using a one-dimensional Fourier Transform in both horizontal and vertical directions.

Two-dimensional modulation transfer function measurement technique

A system for automatically performing the Minimum Resolvable Contrast (MRC) test on an image sensor, such as a TV camera, using a digital signal processor for controlling the testing, wherein an edge response from a square aperture target edge is used to generate a Modulation Transfer Function (MTF) which, in combination with signal and noise data obtained using the square aperture target, provides an input to automated MRC (AMRC) processing equations, from which a value can be calculated for an AMRC output. Alternatively, a slit target may be substituted for the square target aperture when measuring camera MTF.

Automated minimum resolvable contrast (AMRC) test

This invention is an apparatus and method that is able to accurately measure the system level modulation transfer function in the presence of fixed pattern noise from an imaging system electronics.

Fixed pattern compensation with adaptive window for MTF testing

This is a target projector projecting a vertical line source of infrared energy for testing of thermal imaging sensors. A vertical wire of a material which heats and emits infrared energy when an electrical current is passed therethrough is heated by a DC source. There is a projector for intercepting a portion of infrared energy from the wire, for passing only a line source beam portion which comprises a narrow beam of about 10 milliradians width and subtends a vertical angle of about 40.degree., and for directing the narrow beam on an optical center line of a thermal imaging sensor being tested. One type of projector comprises a narrow vertical mirror oriented about a longitudinal axis of rotation which is in a common plane with the wire disposed between 4' and 10' from the wire and rotatable about the axis of rotation to project the line source beam in a desired direction. In another projector, the mirror is replaced by a slit. The wire and projector in combination are also rotatable to a position 45.degree. from vertical so that dead channels of a sensor tied to adjacent live channels can be identified.

Infrared line source projector

An apparatus and method for simulating atmospheric scintillation includes a scintillation disk and a motor for rotating the disk at a substantially high speed. The disk has a dense varied pattern of substantially small closely spaced holes. The holes have different sizes and are arranged with a spatial distribution that is gaussian in amplitude and poisson distributed in separation. The motor can spin the disk to produce desired temporal variations as energy from the energy source passes through the holes of the disk.

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Costa Mesa, CA, United States of America

Harold J Orlando