COMPUTERIZED POLARIMETRIC TERRAIN MAPPING SYSTEM

• US 3,864,513 A
• Filed: 09/11/1972
• Issued: 02/04/1975
• Est. Priority Date: 09/11/1972
• Status: Expired due to Term

• Current Assignee: Herbert B. Hallock, John D. Halajian
• Original Assignee: Herbert B. Hallock, John D. Halajian
• Inventors: Halajian, John D., Hallock, Herbert B.
• Primary Examiner(s): Springborn, Harvey E.
• Application Number:
  US05/287,876
• Time in Patent Office: 876 Days
• Field of Search: 340/172.5 178/6.6A,6.7,7.2,7.7,DIG.20 250/22SP,23CR,558,23CT
• US Class Current: 348/147
• CPC Class Codes: G01C 11/025 by scanning the object
• CPC Class Codes: G01J 4/00 Measuring polarisation of light
• CPC Class Codes: G01S 17/89 for mapping or imaging
• CPC Class Codes: G01S 7/499 using polarisation effects

Abstract

A system for mapping terrain from an overhead position such as from an aircraft by scanning an array of terrain segments to measure at least two polarization parameters of the light reflected therefrom, together possibly with other parameters to represent spectral components of the reflected light, thereby to derive digital indications thereof for parameter measurement matrices corresponding to each measured parameter. A computer is used to perform a matrix operation to derive at least one additional matrix representing an interrelationship between the measured parameters. The additional matrix is used to derive a map-type display of the terrain in terms of the interrelationship of polarimetric values.

Claims

1. A system for mapping an array of terrain segments in order to display a map indicating the interrelationship between at least two polarimetric components of the natural light reflected from each segment comprising:

A. means for scanning the array to generate and store simultaneously a first and a second matrix of digital values corresponding to a first and a second polarimetric component value of the light reflected from segments of the array corresponding to respective values in the matrices, B. computer means for performing a matrix operation with values from the first and the second matrix to derive values for a third matrix indicating said interrelationship, and C. display means for displaying the values of the third matrix as said map.

2. coil means for causing said plurality of scanning aperatures to operate in unison to scan said array of segments in response to a coil driving signal, and B. means responsive to a clock signal for generating a stepping sweep signal as said coil driving signal.

3. A system according to claim 1, wherein at least one additional matrix of digital values is simultaneously derived by measurement to represent the spectral wavelength band within which the reflected light falls.

4. A system for mapping terrain in terms of a plurality of characteristics of the light reflected from each of an array of segments of the terrain while under solar illumination, including at least two polarimetric characteristics comprising:

A. scanning means for causing simultaneous stepwise scanning of a first line of segments in the array and of a second adjacent line of segments parallel to the first line, B. first characteristic determining means operative during the simultaneous stepwise scanning of the first and second lines for measuring the light with a first polarimetric characteristic reflected from each respective segment in the first line and for deriving digital numerical indications representative thereof, C. second characteristic determining means operative during the simultaneous stepwise scanning of the first and second lines for measuring the light with a second polarimetric characteristic reflected from each respective segment in tHe second line and for deriving numerical indications representative thereof, D. scan repeat means for causing said scanning means next to cause simultaneous stepwise scanning of said second line of segments and a third line of segments and for causing the first and second characteristic determining means respectively to derive digital numerical indications of measured reflected light with the first and the second characteristic as respectively reflected from segments in the second and the third lines, said scan repeat means being successively operative to cause first and second characteristic determination of segments respectively in the Nth and (N +

     1)th line scanned simultaneously to derive corresponding digital numerical indications, E. computer means for mathematically interoperating the digital numerical indications representing the first characteristic for each segment in said array of segments with the digital numerical indications representing the second characteristic for the corresponding segment in the array for providing a resulting array of values indicating the interrelationship of the first and second characteristics for each segment of the array, and F. display means for displaying said resulting array as a map.

5. A system according to claim 4 wherein the polarimetric characteristics include the direction of polarization of the reflected light.

6. A system according to claim 4 wherein the polarimetric characteristics include the spectral wavelength band within which the light reflected from each segment falls.

7. A system according to claim 4 wherein said scanning means comprises:

A. an image dissector tube comprising;

8. A system according to claim 4 wherein said scanning means comprises:

A. a solid-state linear array of photosensitive elements stepped into sensing condition by operation of an associated shift register under control of a stepping sweep signal, and B. means responsive to a clock signal for generating the stepping sweep signal.

9. A system according to claim 4 further comprising:

A. means responsive to all of the digital numerical indications for making a digital record thereof on recording tape, and B. means responsive to the digital record for providing corresponding digital numerical indications to the computer means.

10. A system for mapping an array of terrain segments in order to display a map indicating the interrelationship between at least two polarimetric parameters of the natural light reflected from each segment while under solar illumination, comprising:

A. animage dissector tube comprising first and second apertures associated with an anode, and a cathode arrangement for receiving an image, B. lens means for focussing an image of a portion of the array of terrain segments onto the cathode arrangement, C. first and second polarimetric filter means for emphasizing respectively first and second polarization direction parameters of the light being focussed as said image, the first filter affecting a first portion of the cathode arrangement and the second filter affecting a second portion of the cathode arrangement, the first and second portions of the cathode arrangement being located to respectively control the first and second aperture areas of the anode, D. coil means responsive to a coil drive signal and associated with the image dissector tube for causing the first and second aperatures too simUltaneously and respectively scan two parallel adjacent lines off segments from the array of terrain segments, one of the two lines being focused as part of the image on the first portion of the cathode arrangement and another of the two lines being focused on the second portion of the cathode arrangement, E. stepped sweep generator means responsive to a clock signal for generating said coil drive signal as a stairstep sweep, thereby causing the scanning to step to a segment, pause there for an interval, then step on, F. first and second sensing means associated with the anode for deriving first and second sensor signals respectively representative of the magnitude of the emphasized parameter of each segment in the one and the other of the two lines of segments, G. first and second gated integrator means gated in response to the clock signal for respectively integrating and holding the first and second sensor signals over the pause interval, thereby producing first and second integrator output signals having an improved signal-to-noise ratio, H. multiplexer means responsive to the first and second integrator output signals and controlled by the clock signal for generating a time-multiplexed sensor signal, I. analog-to-digital converter means for converting the time-multiplexed sensor signal into a plurality of digital numerical indications of the parameter values of the two adjacent lines, J. tape recording means for recording the digital numerical indications thus obtained, K. means for causing the scanning and other functions to repeat to derive a train of new sets of digital numerical indications corresponding to lines thus scanned, while being synchronized to cause the lines thus scanned to be advanced one line at a time, thereby causing the lines to overlap by one line for each repeat scan from the previous scan, and thereby generating additional sets of digital numerical indications for recording, L. means for playing back the recorded digital numerical indications to provide a playback signal, M. formatter means responsive to the playback signal for arranging the digital numerical indications in a manner suited to treatment as a first and a second matrix of values corresponding respectively to the magnitudes of the first and second parameters in the light reflected from segments of the array corresponding to positions in the first and the second matrix, N. computer means for performing matrix operations on the first and the second matrix to derive a third matrix of values representing said interrelationship of parameters, and O. display means responsive to said third matrix for displaying the interrelationship as said map.

11. A system for mapping an array of terrain segments in order to display a map indicating the interrelationship between at least two polarimetric parameters of the natural light reflected from each segment while under solar illumination, comprising:

A. a plurality of solid-state linear arrays of photosensitive detectors connected as a shift register, whereby the detectors are stepped by a train of pulses to receive an image and provide a sequential output representing each detector in turn, B. lens means for focusing an image of a portion of the array of terrain segments onto the respective linear arrays, C. first and second polarimetric filter means for emphasizing respectively first and second polarization direction parameters of the light being focused as said image, the first filter affecting a first linear array and the second filter affecting a second linear array, D. sweep stepping generator means responsive to a clock signal for causing the first and second linear arrays to scan two parallel adjacent lines of segments from the array of terrain segments, one of the two lines being focused as part of the image on the first linear array and another of the two lines being focused on the second linear array, thereby causing the scanning to step to a segment, pause there for an interval, then step on, E. first and second gated integrator means gated in response to the clock signal for respectively integrating and holding over the pause interval a first and second sensor signal respectively from the first and second linear arrays, thereby producing first and second integrator output signals having an improved signal-to-noise ratio, F. multiplexer means responsive to the first and second integrator output signals and controlled by the clock signal for generating a time-multiplexed sensor signal, G. analog-to-digital converter means for converting the time-multiplexed sensor signal into a plurality of digital numerical indications of the parameter values of the two adjacent lines, H. tape recording means for recording the digital numerical indications thus obtained, I. means for causing the scanning and other functions to repeat to derive a train of new sets of digital numerical indications corresponding to lines thus scanned, while being synchronized to cause the lines thus scanned to be advanced one line at a time, thereby causing the lines to overlap by one line for each repeat scan from the previous scan, and thereby generating additional sets of digital numerical indications for recording, J. means for playing back thee recorded digital numerical indications to provide a playback signal, K. formatter means responsive to the playback signal for arranging the digital numerical indications in a manner suited to treatment as a first and a second matrix of values corresponding respectively to the magnitudes of the first and second parameters in the light reflected from segments of the array corresponding to positions in the first and the second matrix, L. computer means for performing matrix operations on the first and the second matrix to derive a third matrix of values representing said interrelationship of parameters, and M. display means responsive to said third matrix for displaying the interrelationship as said map.

12. A method for mapping an array of terrain segments to display a map indicating the interrelationship between at least two polarimetric components of the natural light reflected from each segment including the steps of:

A. scanning the array to generate and store simultaneously a first and a second matrix of digital values corresponding to a first and a second polarimetric component value of the light reflected from segments of the array corresponding to respective values in the matrices;

B. performing a matrix operation with values from the first and the second matrix to derive values for a third matrix indicating said interrelationship; and

C. displaying the values of the third matrix as a map.

13. The method according to claim 12, including the step of simultaneously deriving an additional matrix of digital values representing the spectral wavelength band within which the reflected light falls.

14. A method for mapping terrain in terms of a plurality of characteristics of the light reflected from each of an array of segments of the terrain while under solar illumination, including at least two polarimetric characteristics, including the steps of:

A. simultaneously scanning a first line of segments in the array and a second adjacent line of segments parallel to the first line;

B. measuring the light with a first polarimetric characteristic reflected from each respective segment in the first line and deriving digital numerical indications representative thereof;

C. measuring the light with a second polarimetric characteristic reflected from each respective segment in the second line and deriving numerical indications representative thereof;

D. simultaneously scanning said second line of segments and a third line of segments and deriving digital numerical indications of measured reflected light with the first and the second characteristics as respectively refleCted from segments in the second and the third lines, and causing first and second characteristic determination of segments respectively in the Nth and (N +

     1)th line scanned simultaneously to derive corresponding digital numerical indications;

E. mathematically interoperating the digital numerical indications representing the first characteristic for each segment in the array of segments with the digital numerial indications representing the second characteristic for the corresponding segment in the array for providing a resulting array of values indicating the interrelationship of the first and second characteristics for each segment of the array; and

F. displaying the resulting array as a map.

15. A method for mapping an array of terrain segments in order to display a map indicating the interrelationship between at least two polarimetric parameters of the natural light reflected from each segment while under solar illumination, including the steps of:

A. receiving an image;

B. focussing an image of a portion of the array of terrain segments;

C. emphasizing respectively first and second polarization direction parameters of the light being focussed as the image;

D. simultaneously and respectively scanning two parallel adjacent lines of segments from the array of terrain segments, and focussing the two lines as part of the image;

E. generating a drive signal as a stairstep sweep, thereby causing the scanning to step to a segment, pause there for an interval, then step on;

F. deriving first and second sensor signals respectively representative of the magnitude of the emphasized parameter of each segment in the one and the other of the two lines of segments;

G. integrating and holding the first and second sensor signals over the pause interval, thereby producing first and second integrator output signals having an improved signal-to-noise ratio;

H. generating a time-multiplexed sensor signal;

I. converting the time-multiplexed sensor signal into a plurality of digital numerical indications of the parameter values of the two adjacent lines;

J. recording the digital numerical indications thus obtained;

K. deriving a train of new sets of digital numerical indications corresponding to lines thus scanned, while being synchronized to cause the lines thus scanned to be advanced one line at a time, thereby causing the lines to overlap by one line for each repeat scan from the previous scan, and thereby generating additional sets of digital numerical indications for recording;

L. playing back the recorded digital numerical indications to provide a playback signal;

M. arranging the digital numerical indications played back in step L. in a manner suited to treatment as a first and second matrix of values corresponding respectively to the magnitudes of the first and second parameters in the light reflected from segments of the array corresponding to positions in the first and the second matrix;

N. performing matrix operations on the first and the second matrix to derive a third matrix of values representing the interrelationship of parameters; and

O. displaying the interrelationship as a map.

16. A method for mapping an array of terrain segments in order to display a map indicating the interrelationship between at least two polarimetric parameters of the natural light reflected from each segment while under solar illumination, including the steps of:

A. receiving an image at a plurality of solid state linear arrays and providing a sequential output from each array in turn;

B. focusing an image of a portion of the array of terrain segments onto the respective linear arrays;

C. emphasizing respectively first and second polarization direction parameters of the light being focused as the image;

D. scanning two parallel adjacent lines of segments from the array of terrain segments, one of the two lines being focused as part of the image on a linear array and another of the two lines being focused on a second linear array, causing the scanning to step to a segment, pause there for an interval, then step on;

E. integrating and holding over the pause interval a first and second sensor signal respectively from the first and second linear arrays, thereby producing first and second integrator output signals having an improved signal-to-noise ratio;

F. generating a time-multiplexed sensor signal;

G. converting the time-multiplexed sensor signal into a plurality of digital numerical indications of the parameter values of the two adjacent lines;

H. recording the digital numerical indications thus obtained;

I. deriving a train of new sets of digital numerical indications corresponding to lines thus scanned, while being synchronized to cause the lines thus scanned to be advanced one line at a time, thereby causing the lines to overlap by one line for each repeat scan from the previous scan, and thereby generating additional sets of digital numerical indications for recording;

J. playing back the recorded digital numerical indications to provide a playback signal;

K. arranging the digital numerical indications played back in step J. in a manner suited to treatment as a first and a second matrix of values corresponding respectively to the magnitudes of the first and second parameters in the light reflected from segments of the array corresponding to positions in the first and the second matrix;

L. performing matrix operations on the first and second matrix to derive a third matrix of values representing the interrelationship of parameters; and

M. displaying the interrelationship as a map.