DD281456A5 - METHOD FOR ACTUALLY CORRECTING MOTION DISTORTION OF SCANNERS RECORDED FROM AIRCRAFT, SATELLITE OR OTHER AIR OR SPACE VEHICLES - Google Patents

Abstract

The invention relates to a method for actively correcting the motion-induced distortions in scanner images obtained from aircraft, satellites or other aircraft or spacecraft. The method according to the invention is suitable for correcting the distortions of the image content of a scanner recording in the real-time regime caused by undesired angular periodic and aperiodic movements of the aircraft or spacecraft. The proposed solution ensures, at each recording time, that the image contents corresponding to the target attitude are within the detection and evaluation range of the optoelectronic system. At the same time a high geometric accuracy and detail recognition is guaranteed. According to the invention, an optoelectronic detector matrix is used as the pickup sensor of a pushbroom line scanner, one or more sampling windows are determined from the entirety of the pixels of the matrix, and a synthetic target scan line corresponding to the desired flight position is used, using the flight movement and attitude signals obtained in a known manner. certainly. Furthermore, the coincidence of the longitudinal and lateral masking scans of the scanner recording is achieved by decreasing or increasing the read-out clock of the synthetic target scan lines according to the conventionally obtained metric of the quotient from the airspeed to the flight altitude over ground (vg / hg). Aerial photography; Image content; Motion correction; Real time regime; Array sensor; Sollschwadstreifen; synthetic target scissors}

Description

For this 1 page drawing

Field of application of the invention

The inventive method is for correcting the unwanted angular periodic or apariooischon movements de? Aircraft or spacecraft hervorgerufeinen distortions of the image content of a scanner recording suitable. The erfinoungsgemäße Lösuny the restoration of the actual geometry of the aerial photograph is guaranteed.

Characteristic of the known state of the art

It is known that when using scanners for aerial photography by the unwanted movements of the respective carrier, z.U. an aircraft, a distortion of the geometry of the recording or image data takes place. Responsible for these distortions are the angular periodic and aperiodic movements of the aircraft or spacecraft. To solve this problem, it has been proposed to equip the respective aircraft with an autopilot and flight control system. However, practical investigations have shown that the remaining angular velocity values as a measure of the angular vibrations can only be lowered to about Va to V * of the manual control value. For this reason, taking into account the high demands on scanner images further measures were necessary. So it is known, position-stabilized platforms z. B. to be arranged with gimbal suspension between the aircraft and optoelectronic recording system. However, such devices have a complicated mechanical structure and a large mass.

These drawbacks, as well as the imperfect dynamic stabilization of the angular vibrations about all three major axes, have led to solutions that electronically acquire attitude and aircraft motion data and correct for scanner imaging distortion in real time.

According to DE-OS 2 322379 it is known, the rolling component of the aircraft z. B. by means of a gyrometer and by a parallel displacement of the image lines, which can be done via a mirror system to perform a correction of the image caused by the rolling motion image distortions. A transgression of this principle to a correction in all three major axes, i. including pitch and yaw correction, is not possible due to the inertia of the solution system.

In the method for correcting a video signal according to DE-OS 3334147 the position and motion signals for real-time equalization in registers and frame memories are used from assumed aircraft equipment, wherein only every n-th pixel of a line and every mth line of the frame memory are used for recording. In this case, the resolution of the overall arrangement goes back by the quantities m or η.

Furthermore, with such a method, the scan line caused by the pitching attitude of the aircraft and not picked up at the adequate position of the ground can be transferred to the correct picture position by simple register shift, but the wrong pixel or line content will remain.

From DE-OS 3544863 a method for motion correction of digital images is known, which caches individual image line contents and analyzes the differences between the image contents of successive lines. In this case, a decision on the assignment of the image contents of successive image lines after the smallest differences get ff ff · 6. and a sampling regime for the subsequent image line selection and their representation on a viewing device, eg. B. a cathode ray tube set. A requirement in such a method is the actual presence of a large number of defined pixels on the image template, eg. B. a straight road. This requirement correlates with the scanning speed of the carrier of the aerial imaging device. These conditions severely limit the possible fields of application. Another disadvantage of the method described is the non-existent possibility to correct the effects of pitching movements of the aircraft on the scanner recording. In summary, neither with the previously known mechanically acting damping arrangements or dynamically

Possibilities satisfactory motion-corrected scanner images are obtained.

Object of the invention

The aim of the invention is the development of a method for active correction of the motion-induced distortions in scanner images obtained from aircraft or spacecraft, this on-board correction being carried out in the real-time regime without a reduction in the dot-resolution of the scanner.

Explanation (.es essence of the invention

The object of the invention is to provide an active correction method, which ensures scanner images high geometric accuracy and detail recognition, with a regime is to find that ensures at each recording time that the desired attitude corresponding. Image contents in the detection and evaluation of the optoelectronic system are

 According to the invention is proposed

to use an opto-electronic detector matrix as the pick-up sensor of a push-to-zoom cell scanner,

determine one or more scanning windows from the total number of pixels of the recording sensor, the scanning windows being designed so that the complete detection of the desired swath strip on the ground, independently of the angular range of motion, is pushed, this being achieved by an extension of the recording angle along and transverse to the aircraft longitudinal axis around the angular range of motion,

from the total number of pixels of the respective sampling window using the Flugbewegungssin, nale, d. H. the roll angular velocity, the pitch angular velocity and the yaw angular velocity, and the attitude signals, d. H. the bank, the pitch and the lead angle, these values being provided in a known manner to determine the pixels of a row which in their entirety corresponds to the target attitude and the thus obtained synthetic target scan lines symmetrical to the nadir, perpendicular to the horizontal plane and perpendicular to the true Direction of flight,

- or that from the total number of pixels of at least two sampling windows in stereo recording or multispectral images under Inr. ^ spruchnah ./ E e Flugbewegungs- and flight attitude signals, the pixels are determined at least one synthetic Sollscanzeile per sampling window, which correspond to the desired attitude and the thus obtained synthetic target scan lines are symmetrical to the nadir and perpendicular to the true flight direction

- And by reducing or increasing the read-out of the synthetic Sollscanzeilen according to the obtained in a known manner measured value of the quotient from the airspeed to the altitude above ground v _g / h _e a match between longitudinal and transverse scale of the scanner recording is realized.

By determining the matrix size and imaging optics of the scanner according to the essence of the invention, i. taking into account the maximum unwanted movements or the angular movement range, a complete detection of the target swath is ensured. By this measure, no image contents necessary for the evaluation are lost. By means of the possibility of determining from the totality of the information stored in the pixels of the matrix sensor, taking into account the information provided by known flight and signal position sensors, to determine the coordinates for the pixels forming a target scan line corresponding to the target attitude, a motion correction is without loss of resolution realizable. In this context, it is possible to speak of a quasi-electronic corrective movement of a line on or off the entirety of the lines or the pixels of the matrix recording sensor. If the number of lines of the matrix sensor is sufficiently large, it is possible to read out a plurality of desired scan lines each from one sampling window.

If in this case defined spectral excerpts of the incident radiation are realized in a known manner per scanning window, then real-time-corrected multispectral images can be obtained.

Likewise, the same line by line images of the earth's surface at the beginning and at the end of the matrix, in each case based on the direction of flight, unü temporal succession, take place. These are then synchronously motion-compensated by the method according to the invention. Continuous scanning of these image contents produces in each case identical images of the earth's surface with central perspectival coherence, which are recorded from different perspectives. By evaluating corresponding pixels, an application of the data thus obtained and processed for stereo mapping is possible.

Ausführungsbelsplel

The invention will be explained in more detail with reference to an example and a figure.

FIG. 1 shows the position of two synthetic nominal lines Duf of the detector matrix.

To implement the solution according to the invention, either an optoelectronic detector matrix (CCD matrix, TIR matrix, inter alia, depending on the spectral range to be recorded) can be used with random access to the detector elements (CID) or the entire image content of the detector matrix is loaded into a register during each scan line cycle there in the proposed manner, the respective Sollscanzeile read.

The coordinates of the Detektorelement- or register locations of the respective Sollscanzeilen be synthetically determined in a coordinate from the incoming angular position signals so that they correspond to the desired position within the Sollschwadstreifens on the ground. As quasi-static (slowly changing) position signals, ω ,,,, are used for the bank angle, v> _sUl for the longitudinal inclination and K _stlt for the advancement or drift angle. The dynamic (fast changing) position signals co _dyn , v? _dyn and K _dyn are obtained from the time integration of angular rate signals of RcII, pitch and yaw motion, while c * eo ratio of forward speed to altitude over ground (Vg / hj) is measured opto-electronically. The latter v _g / h _g signal first controls the recording line clock so that a match of the image scales is achieved longitudinally and transversely to the direction of flight.

In Fig. 1, the position of two synthetic Sollscanzeilen 5 and 6 is shown arbitrarily within a detector matrix 1. Line 5 represents the connecting line of the detector elements of those synthetically determined instantaneous desired scanning lines, in which the scanning beam plane (which extends transversely to the direction of flight x ') is directed perpendicular to the ground, which corresponds to the configuration with a single-channel scanner. For multichannel application, the target scan line 6, which corresponds in time to 5, is also shown as an example in the case of a prospective scanning beam plane. Lines 5 and 6 and possibly further (eg retrospective) can then be combined into separate image strips and used for a stereoscopic evaluation, or z. B. in advance of appropriate chromatic bandpass filter before each sampling window (ABCD, EFuH and possibly others) are used for multispectral applications.

The instantaneous total attitude angles ω, φ and κ of the aircraft or of the recording system, which are determined as intermediate values in the coordinate calculator, the attitude parameters κ, x ^ and γ _ω of the synthetic, momentary nominal ranges corresponding to the target attitude, and the Bewogungsbereiche 2,3,4 and 10 are shown in FIG. 1 for illustrative purposes.

The φ and K moving range of the target scanning line 5 is denoted by 2, and the φ and K moving range of the target scanning line 6 is denoted by 3. The positive ω-moving range of all the scan lines is represented by 4 and the negative-ω moving range by 10.

In Figure 1, the true flight direction over ground with x ', the aircraft longitudinal axis with x, the aircraft transverse axis with y, the x-displacement of synthetic, current Sollscanzeilen 5 and 6 due to the pitch or pitch with x, and the y-displacement the Sollscanzeilen 5 and 6 in succession of the bank or roll movement with y _u marked.

In summary, the following operations are performed within a row clock.

- Determine v _g / hg and calculate the longitudinal lap correction

- Control the line clock frequency after the deviation from the nominal value of the v _g / h _e ratio until the longitudinal and transverse scales match

- Determine quasistatic and dynamic values of ω, φ and κ

- Calculate coordinates of those detector elements or image pixels of the recording or register matrix, which correspond to the desired position of the object pixels on the ground

- Read out matrix elements of the calculated (synthetic) instantaneous desired scan line and load them into a frame memory and have them ready for further processing.

Claims (1)

Procedures for actively correcting for warp distortions in scanner images obtained from aircraft, satellites or other aircraft or spacecraft are characterized by: an optoelectronic detector matrix is used as the scanning sensor of a pushbroom line scanner, a js the total number of pixels of the recording sensor one or more sampling windows set v, ji den, wherein the sampling windows are to be formed so that the complete detection of the target swath on the ground is independent of the angular range of motion given by an extension of the recording angle along and transverse to the aircraft longitudinal axis about the angular range of motion, from the total number of pixels of the respective sampling window using the flight motion signals, i. the roll angular velocity, the pitch angular velocity and the yaw angular velocity, and the attitude signals, i. the bank, the pitch and the lead angle, these values being provided in a known manner, the pixels of a row being determined in their entirety corresponding to the desired fly position, and the thus obtained synthetically? Target line is symmetrical to the nadir, perpendicular to the horizontal plane and perpendicular to the true direction of flight, - or auii the total number of pixels of at least two current sampling window when recording for stereocorrection or multi-spectral images using the Flugbewegungs- and Fiuglagesignale, the pixels of at least one synthetic Sollscanzeile per sampling window are determined that correspond to the desired attitude and the thus obtained synthetic Sollscanzeilen symmetrical to nadir and perpendicular to the true flight direction. - And by a reduction or increase in the read-out of the synthetic target scan lines · according to the obtained in a known manner measured value v _g / h _g a match between the longitudinal and transverse scale of the scanner recording is realized.