AUTOMATED STEREO-PHOTOGRAMMETRIC INSTRUMENT

• US 3,783,294 A
• Filed: 05/19/1972
• Issued: 01/01/1974
• Est. Priority Date: 05/19/1972
• Status: Expired due to Term

• Current Assignee: Robert Koper
• Original Assignee: Robert Koper
• Inventors: Koper, Robert
• Primary Examiner(s): Lawrence, James W.
• Assistant Examiner(s): Grigsby, T. N.
• Application Number:
  US05/255,231
• Time in Patent Office: 592 Days
• Field of Search: 250/22SP 356/2 178/6.8
• US Class Current: 250/558
• CPC Class Codes: G01C 11/00 Photogrammetry or videogrammetry, e.g. stereogrammetry; Photographic surveying
• CPC Class Codes: G01C 11/06 by comparison of two or more pictures of the same area
• CPC Class Codes: G01C 11/26 using computers to control the position of the pictures

Abstract

An automated photogrammetric instrument adapted to observe conjugate areas in a stereo-pair of photographs for the purpose of determining terrain elevation and for carrying out other measurements. In order to measure X-parallax, the instrument includes means to scan each of the photographs along a path in which X-parallax is present, but which is substantially free of Y-parallax and the effects of image rotation, thereby producing first and second video signals representative of the scanned paths in the pair of photographs. The first and second video signals are applied to a correlator to produce an output value reflecting the degree of differential X-parallax.

Claims

1. In a photogrammetric system adapted to observe conjugate areas for the purpose of measuring X-parallax in a pair of photographs taken from separate spaced positions, the combination comprising:

A. means to scan each of said photographs along an epipolar ray in which X-parallax is present and in which Y-parallax and image rotation are substantially absent, to produce first and second video signals representative of the scanned path on said photographs, and B. means to apply said first and second signals to a correlator to produce an output value reflecting the value of X-parallax.

2. The combination set forth in claim 1, wherein said correlator includes means to derive from said video signals an output reflecting the value of X slope.

3. In a system as set forth in claim 1, wherein said means to scan each of said photographs along an epipolar ray include a scanner having a sensitive face, optical means to project an image of said photograph onto said face, and optical means to rotate the projected image to cause the scanner to scan along said epipolar ray.

4. In a system as set forth in claim 1, wherein said means to scan each of said photographs along an epipolar ray include a scanner having a sensitive face, optical means to project an image of said photograph onto said face, and electronic means coupled to said scanner to rotate the scan thereof to cause the scan to scan said epipolar ray.

5. In an automated stereo-photogrammetric system adapted to observe conjugate areas in a stereo-pair of photographs for the purpose of determining X-parallax, the combination comprising:

A. first and second scanners, each observing a respective photograph, B. a first sweep generator coupled to the first of said scanners to produce a single line scanning pattern which lies in an epipolar ray whereby said first scanner produces a video signal representing the varying photographic densities in the scanned path on one of said photographs, C. a second sweep generator coupled to the second scanner to produce a single-line scanning pattern which lies in an epipolar ray whereby said second scanner produces a video signal representing the varying photographic densities in the corresponding scanned path on the other of said photographs, D. an electronic correlator responsive to the first and second video signals to produce an output value reflecting the degree of similarity between the first and second video signals and correction values, indicative of the sense of the correction necessary to enhance said similarity, and E. means responsive to said correction values to modify the sweep produced by at least one of said generators to an extent causing an enhancement in the degree of similarity of said first and second video signals.

6. An automated photogrammetric system as set forth in claim 5, wherein said scanners are image-dissector tubes, lens means being provided to project illuminated images of portions of said photographs onto a photocathode whose photoelectrons are focused on an anode having an aperture which is an elongatEd slit form whose long dimension is at right angles to said single-line scanning pattern, each image-dissector tube being provided with deflection means coupled to a respective sweep generator.

7. An automated photogrammetric system as set forth in claim 5, wherein said sweep generators for producing a single-line scanning pattern are constituted by a clock producing a square wave which is applied to first and second integrating amplifiers to convert the square wave into triangular sawtooth sweep voltages for said first and second scanners.

8. An automated photogrammetric system as set forth in claim 5, wherein said photographs are mounted on a common carriage and are illuminated to produce images on the surface of the system scanners.

9. An automated photogrammetric system as set forth in claim 8, further including a servo system coupled to said correlator and adapted to shift one of said photographs relative to the other in a direction and to an extent causing said video signals to approach a condition of identicality.

10. In an automated photogrammetric system as set forth in claim 5, wherein said correlator is provided with a full scan coarse control section responsive to said first and second video signals to effect low-order correction causing said signals to approach a condition of identicality, and having a fine control section responsive to the same signals operative for only a small portion of the full scan to effect a higher order of correction.

11. In an automated photogrammetric system as set forth in claim 10, further including manually-adjustable means associated with said fine control section to effect a higher order of correction for a selected small portion of the scanning pattern.

12. In a system as set forth in claim 10, wherein said coarse control section includes two low-frequency channels responsive to said first and second video signals, each channel including a low-pass filter followed by a video processor, the outputs of the video processors of the two channels being fed to a full-scan processor to produce an anamorph error signal and a displacement error signal.

13. In a system as set forth in claim 12, wherein said full-scan processor also produces a correlation level signal.

14. In a system as set forth in claim 12, wherein said anamorph error signal and said displacement error signal are both integrated to produce a voltage modifying the sweep voltage from at least one of said generators to effect said low-order correction.

15. The combination as set forth in claim 10, wherein each section operates in cooperation with a separate pair of tubes.

16. The combination as set forth in claim 10, wherein said photographs are diapositives.

17. The combination as set forth in claim 10, wherein said photographs are negatives.

18. In an automated stero-photogrammetric system adapted to observe conjugate areas in a stereo-pair of diapositives for the purpose of determining X-parallax, the combination comprising:

A. first and second image-dissector tubes each observing a respective diapositive, each tube including a magnetic deflection coil adapted to deflect the electron trajectory between a photocathode and a defining aperture in an anode in a given direction, B. first and second sweep voltage generators coupled to respective deflection coils of said first and second tubes to produce single-line scanning patterns which lie in epipolar rays whereby said first tube produces a first video signal representative of the varying photographic densities of one of said diapositives in a scanned path, and said second tube produces a second video signal representative of the varying photographic densities of the other diapositive in a corresponding scanned path, C. an electronic correlator responsive to said first and second video signals to produce an output value reflecting the degree of similarity between the video signals and correction values indicative of the sense of the corrections necessary to enhance said similarity, and D. means responsive to said correction value to modify the sweep voltage produced by at least one of said generators and/or the position of at least one of the diapositives to an extent causing said first and second video signals to enhance the degree of similarity.

19. In a system as set forth in claim 18, wherein said correlator includes a coarse control section and a fine control section, said coarse control section being provided with two separate channels responsive to the respective video signals, each including a low-frequency band-pass filter and a signal processor to quantize the applied video signal, the signal processors of said coarse control channels being coupled to a signal processor producing a coarse anamorph error signal and a coarse displacement error signal;

said fine control section being provided with two separate channels responsive to the respective video signals, each including a high-frequency band-pass filter and a signal processor producing a fine anamorph error signal and a fine displacement error signal, a summing amplifier having three inputs, one of which is the integrated value of said coarse anamorph error signal, the second of which is the integrated value of said fine anamorph error signal, the third of which is the integrated value of said fine displacement error signal, said summing amplifier producing a modifying voltage which is applied to at least one of said sweep generators to provide a higher order of correction to effect identicality.

20. In a system set forth in claim 19 further including electronic switching means to render said fine control section effective for a small portion of the full scan, said switching means having manual controls to select the position and width of said small portion.