Electro-optical imaging array and camera system with pitch rate image motion compensation

• US 6,088,055 A
• Filed: 09/29/1998
• Issued: 07/11/2000
• Est. Priority Date: 05/07/1996
• Status: Expired due to Term

• Current Assignee: Goodrich Corporation (Raytheon Technologies Corporation d/b/a RTX)
• Original Assignee: Recon/Optical, Inc. (Bourns Incorporated)
• Inventors: Hines, George, Beran, Steven R., Bown, Michael, Bennett, Russell A., Lareau, Andre G.
• Primary Examiner(s): BRITTON, HOWARD W
• Application Number:
  US09/163,088
• Time in Patent Office: 651 Days
• Field of Search: 348/295, 348/208, 348/145, 348/144, 348/146, 348/147, 348/148, 348/113
• US Class Current: 348/113
• CPC Class Codes: G01C 11/02 Picture taking arrangements specially adapted for photogrammetry or photographic surveying, e.g. controlling overlapping of pictures
• CPC Class Codes: G03B 15/006 Apparatus mounted on flying objects
• CPC Class Codes: H04N 23/68 for stable pick-up of the scene, e.g. compensating for camera body vibrations
• CPC Class Codes: H04N 23/6842 by controlling the scanning position, e.g. windowing
• CPC Class Codes: H04N 25/00 Circuitry of solid-state image sensors [SSIS]; Control thereof
• CPC Class Codes: H04N 25/53 Control of the integration time
• CPC Class Codes: H04N 3/155 Control of the image-sensor operation, e.g. image processing within the image-sensor

Abstract

A camera system is described which is based on an electro-optical imaging array performs electronic image motion compensation without moving parts during a reconnaissance maneuver in which the aircraft is experiencing a non-zero rate of change in the pitch axis, such as in a dive bomb maneuver when the pilot is pulling out of the dive. The camera system has a camera control computer that calculates a pixel information transfer rate for the array based on parameters supplied by the aircraft'"'"'s navigation system and pre-mission known parameters, including the aircraft'"'"'s velocity, height above ground, attach angle, pitch angle, and rate of change in pitch during the period in which the array is taking successive exposures of the scene. The camera control computer supplies information to the drive and control electronics that control the transfer of pixel information in the array. In a preferred embodiment, the array is exposed to the scene of interest in a series of rapid exposure intervals and generates a frame of imagery during each exposure. By virtue of the electronic image motion compensation, each frame of imagery is a high resolution image of the scene of interest, far surpassing images created by an electro-optical array if the present image motion compensation technique were not performed.

Claims

1. An electro-optical camera system with electronic image motion compensation, said camera system suitable for installation in a reconnaissance aircraft having a navigation system determining the velocity, height, and pitch information of said aircraft during a reconnaissance maneuver, said pitch information comprising a pitch angle of said aircraft relative to a horizontal frame of reference and a rate of change of said pitch angle, comprising, in combination,

an array of photosensitive cells arranged in rows and columns, said cells storing pixel information representing a scene of interest, said array of cells having a drive circuit supplying pulses to said array to transfer pixel information stored in said cells from one row to an adjacent row;

a camera control computer responsive to said navigation system for computing a pixel information transfer rate for said array of cells based on said velocity, height, pitch angle and rate of change of said pitch angle;

said camera control computer further determining from information supplied by said navigation system a pixel information transfer rate for said array of cells during a period of time in which said aircraft is experiencing a substantial non-zero rate of change of the pitch of said aircraft and said array is oriented in a forward oblique orientation relative to said aircraft;

said camera control computer and control circuitry adjusting the charge transfer rate of said array to substantially match the rate of image motion of said terrain of interest during a series of successive exposures of said array to said terrain of interest during said period of time in which said aircraft is experiencing said substantial non-zero rate of change in the pitch of said aircraft;

wherein said array may generate a series of images of said terrain of interest while compensating for said substantial non-zero rate of chance of the pitch angle of said aircraft during the successive exposures of said array and wherein the resolution of said images may be preserved.

2. The camera system of claim 1, wherein said array of cells comprises a charge-coupled device.

3. The camera system of claim 1, wherein said camera system is installed in a military reconnaissance aircraft.

4. The camera system of claim 2, wherein said array of cells comprises a rectangular array having at least 4,000,000 cells arranged in rows and columns.

5. The camera system of claim 2, wherein said drive circuit is responsive to said camera control computer and further comprises at least one counter receiving a counter signal from said camera control computer and a clock driver responsive to said counter, said clock driver supplying voltages to a set of conductors placed adjacent to said cells so as to cause pixel information stored in said cells to be transferred from one row to an adjacent row in said array.

6. A method of imaging a scene of interest by an aerial reconnaissance camera system installed in an aircraft, said aerial reconnaissance camera system comprising an array of photosensitive cells arranged in rows and columns and a camera control computer for controlling the operation of said array, said aircraft having a navigation system for providing information as to the velocity, height, and pitch information of said aircraft relative to the earth, said pitch information comprising a pitch angle of said aircraft relative to a horizontal frame of reference, comprising the steps of:

descending towards the earth with said aircraft making a pitch angle with respect said horizontal frame of reference in a dive maneuver and then pulling out of said dive, with said aircraft experiencing a substantial non-zero rate of change of pitch during the step of pulling out of said dive;

supplying from said navigation system the current velocity, height and pitch angle of said aircraft to said camera control computer,

obtaining the current rate of change of the pitch angle of said aircraft;

calculating a pixel information transfer rate for said array of cells from said current velocity, height and pitch angle and said current rate of change of the pitch angle of said aircraft that is substantially equal to the rate of motion of an image of said scene of interest on the focal plane of said array; and

during said step of pulling out of said dive, exposing said array of cells to radiation from said scene of interest in a series of exposures taken in rapid succession and simultaneously transferring pixel information in said array of cells row by row in accordance with said pixel information transfer rates calculated for each of said exposures such that the resolution of an image generated by said array of cells is preserved.

7. The method of claim 6, wherein said array comprises a charge-coupled device.

8. The method of claim 6, further comprising the steps of exposing said array in a rapid sequence of exposures so as to generate a set of sequential images from said array of said terrain of interest during a time period in which said rate of change of pitch of said aircraft is substantially non-zero.

9. The method of claim 8, wherein said aircraft defines a roll axis and wherein said camera system is oriented relative to said aircraft in a forward oblique angle relative to said longitudinal axis, wherein said forward oblique angle is substantially constant relative to said longitudinal axis during said sequence of exposures.

10. An electro-optical aerial reconnaissance camera for an aircraft having an array of photosensitive cells storing pixel information representing a scene arranged in rows and columns and a camera control computer for determining a rate at which said pixel information should be transferred in said array in order to be in substantial synchronism with an image of said scene directed onto said array, said camera control computer supplying signals to a clocking circuit transferring said pixel information in said array at said rate, the improvement comprising:

a software routine for said camera control computer determining a pixel information transfer rate for said array when said aircraft is flown in a manner such that the aircraft is subject to a substantial non-zero rate of change of the pitch attitude of said aircraft for more than a transitory period of time during which said array is exposed to said scene and in which said camera is oriented in a forward oblique manner, said software routine processing information including the current pitch angle of said aircraft and the rate of change of the pitch angle of said aircraft to determine pixel information transfer rates for said array;

said camera control computer and clocking circuit responsive to said software routine so as to transfer said pixel information in said array in substantial synchronism with said image of said scene to thereby preserve resolution of an image generated by said array.

11. A method for imaging a scene of interest with an electro-optical imaging array camera system installed in a reconnaissance aircraft, the improvement comprising:

approaching the scene of interest at a pitch angle in which the aircraft makes a depression angle relative to a horizontal frame of reference;

pulling out of said approach by decreasing said pitch angle of said aircraft, and simultaneously during said pulling out of said approach;

(a) exposing said array to said scene in a plurality of discrete exposures;

(b) calculating a pixel information transfer rate for each exposure based on at least the velocity, height, pitch angle of the aircraft, and rate of change of pitch angle;

(c) transferring pixel information in said array of cells at a rate during each exposure based on said calculated pixel information transfer rate;

(d) adjusting the pixel information transfer rate between said successive exposures; and

(e) reading out said pixel information from said array of cells after each of said successive exposure of said array;

wherein a series of high resolution images having image motion compensation of said scene of interest may be generated by said array.