TRANSFORMATION AND REGISTRATION OF PHOTOGRAPHIC IMAGES

• US 3,564,133 A
• Filed: 01/16/1967
• Issued: 02/16/1971
• Est. Priority Date: 01/16/1967
• Status: Expired due to Term

• Current Assignee: Gilbert L. Hobrough
• Original Assignee: Gilbert L. Hobrough
• Inventors: Hobrough, Gilbert L.
• Application Number:
  US04/609,662
• Time in Patent Office: 1,492 Days
• US Class Current: 250/558
• CPC Class Codes: G01C 11/00 Photogrammetry or videogrammetry, e.g. stereogrammetry; Photographic surveying

Abstract

A method of and apparatus for developing from a stereographic pair of photographic images difficult of registration one with the other for optical inspection of homologous areas because of relative distortions therebetween, area-by-area reproductions of such photographic images suitably registered for optical inspection as a result of relative of relative distortions being corrected. Involved in the system are scanning the photographic images area-by-area with a pair of flying spot scanners, collecting the image-modulated light produced by such scanning with a pair of photoelectric detectors, comparing the output signals from the photoelectric detectors in an electronic correlator and developing parallax error signals representative of relative distortions between the homologous areas being scanned, and providing at a binocular viewer optical reproductions of such areas correctively altered by an electronic transformation unit to relieve relative distortions and thereby provide optical images in registration for inspection. The relative distortions between photographic images are classifiable into zero-, first-, second-, and higher-orders of distortion, and of primary concern herein is the correction of second- and higher-order distortions by means of reverberatory integration techniques.

Claims

1. In a method of transforming the scanning raster of a flying spot scanner to correct for distortion with respect to a reference of an image being scanned by said Scanner, the steps of:

comparing the video output signal of the flying spot scanner which corresponds to said image being scanned with a signal representative of such reference to detect the presence of time differences between the signals and deriving from any time differences therebetween a parallax signal proportional to any parallax between such image and the reference therefor;

selecting from such parallax signal a component thereof constituting a multiple of the scanning frequency of said flying spot scanner to obtain a correction signal; and

combining such correction signal with a deflection signal for said flying spot scanner to effect a corrective transformation in the scanning raster thereof, deriving from any time differences between said video output signal and signal representative of such reference an additional parallax signal, one such parallax signal being proportional to any parallax along one axis of said scanning raster and the other parallax signal being proportional to any parallax along another axis thereof;

selecting from said additional parallax signal a component constituting a multiple of the scanning frequency along said one axis of the scanning raster to obtain an additional correction signal, the first-mentioned signal component being a multiple of the scanning frequency along the other such axis of the scanning raster; and

respectively combining such correction signals with the deflection signals for said flying spot scanner to effect a corrective transformation of the scanning raster thereof along each such axis.

2. In a method of transforming the scanning raster of at least one of a pair of flying spot scanners to correct for relative distortion of a pair of images respectively scanned by said scanners to enable registration of such images, the steps of:

comparing the video output signals of the flying spot scanners which correspond to said images being scanned to detect the presence of time differences between the signals and deriving from any time differences there between a parallax signal proportional to any parallax between such images;

selecting from such parallax signal a component thereof constituting a multiple of the scanning frequency of said flying spot scanners to obtain a correction signal;

combining such correction signal with a deflection signal for at least one of said flying spot scanners to effect a corrective transformation in the scanning raster thereof, deriving from any time differences between said video output signals an additional parallax signal, one such parallax signal being proportional to any parallax along one axis of said scanning rasters and the other parallax signal being proportional to any parallax along another axis thereof;

selecting from said additional parallax signal a component constituting a multiple of the scanning frequency along said one axis of the scanning rasters to obtain an additional correction signal, the first-mentioned signal component being a multiple of the scanning frequency along the other such axis of the scanning rasters; and

respectively combining such correction signals with the deflection signals for the aforesaid one flying spot scanner to effect a corrective transformation of the scanning raster thereof along each such axis.

3. The method according to claim 2 and further including the step of combining each of said correction signals with the respectively corresponding direction signals of each of said flying spot scanners in algebraically opposite senses so as to transform correctively said scanning rasters in opposite directions and thereby reduce the magnitude of the transformation otherwise required for one raster.

4. In a method of transforming the scanning raster of at least one of a pair of flying spot scanners to correct for relative distortion of a pair of images respectively scanned by said scanners to enable registration of such images, the steps of:

comparing the video output signals of the flying spot scanners which correspond to said images being scanNed to detect the presence of time differences between the signals and deriving from any time differences therebetween a parallax signal proportional to any parallax between such images;

selecting from such parallax signal a component thereof constituting a multiple of the scanning frequency of said flying spot scanners to obtain a correction signal;

combining such correction signal with a deflection signal for at least one of said flying spot scanners to effect a corrective transformation in the scanning raster thereof, combining said correction signal with the respectively corresponding deflection signals of each of said flying spot scanners in algebraically opposite senses so as to correctively transform said scanning rasters in opposite directions and thereby reduce the magnitude of the transformation otherwise required for one raster.

5. In apparatus for effecting registration of homologous areas in a pair of similar images, a pair of flying spot scanners for respectively scanning such images, a raster generator for developing the deflection signals for each scanner to provide the scanning rasters thereof, a correlator for comparing the video output signals of said flying spot scanners to provide therefrom a parallax signal representative of relative displacements between such homologous image areas, a frequency selection module including an amplifier having a band-pass filter tuned to a multiple of the scanning frequency of said scanners for selecting from such parallax signal a component thereof constituting a multiple of the scanning frequency of said scanners to obtain a correction signal, and means for combining such correction signal with a deflection signal from said raster generator to one of said flying spot scanners to effect a corrective transformation in the scanning raster thereof.

6. The apparatus according to claim 5 in which said amplifier includes a transistor having base and collector elements, said base being connected with said correlator for receiving such parallax signal, and said filter being connected in the collector circuit of said transistor.

7. The apparatus of claim 6 in which an additional pass-band filter is provided, said transistor having an emitter and said additional filter being connected in the circuit thereof, one of said filters having a narrower band width than the other.

8. In apparatus for effecting registration of homologous areas in a pair of similar images, a pair of flying spot scanners for respectively scanning such images, a raster generator for developing the deflection signals for each scanner to provide the scanning rasters thereof, a correlator for comparing the video output signals of said flying spot scanners to provide therefrom a parallax signal representative of relative displacements between such homologous image areas, a frequency selection module for selecting from such parallax signal a component thereof constituting a multiple of the scanning frequency of said scanners to obtain a correction signal, and means for combining such correction signal with a deflection signal from said raster generator to one of said flying spot scanners to effect a corrective transformation in the scanning raster thereof, said frequency selection module including a plurality of filter networks one of which has a pass-band tuned to the aforesaid multiple of the scanning frequency and the others respectively having pass-bands tuned to other multiples of the scanning frequency, all of the selected multiples being combined to define the aforementioned correction signal.

9. The apparatus of claim 8 in which each of said filter networks comprises a pair of pass-band filters respectively tuned to one of the multiples of the scanning frequency, one of said filters in each pair thereof having a narrower band width then the other.

10. The apparatus of claim 9 in which said frequency selection module further comprises an amplifier including a transistor having base, collector and emitter elements, said base being connected with said correlator for receiving such parallax signal, and one filter in each pair thereof being connected in the collector circuit of said transistor and the other filter in each pair thereof being connected in the emitter circuit of said transistor.

11. In apparatus for effecting registration of homologous areas in a pair of similar images, a pair of flying spot scanners for respectively scanning such images, a raster generator for developing the deflection signals for each scanner to provide the scanning rasters thereof, a correlator for comparing the video output signals of said flying spot scanners to provide therefrom a parallax signal representative of relative displacements between such homologous image areas, a frequency selection module for selecting from such parallax signal a component thereof constituting a multiple of the scanning frequency of said scanners to obtain a correction signal, and means for combining such correction signal with a deflection signal from said raster generator to one of said flying spot scanners to effect a corrective transformation in the scanning raster thereof, means in said correlator to provide from the comparison of the video output signals of said flying spot scanners an additional parallax signal, one such parallax signal being representative of relative displacements of such image areas along one axis of such scanning rasters and the other parallax signal being representative of relative displacements between such image areas along another axis of such rasters, an additional frequency selection module for selecting from such additional parallax signal a component thereof constituting a multiple of the scanning frequency of said scanners along one such axis to obtain an additional correction signal, the first-mentioned parallax signal component constituting a multiple of the scanning frequency of said rasters along the other such axis, and additional means for combining such additional correction signal with the other deflection signal from said raster generator to the aforesaid one flying spot scanner so that a corrective transformation thereof is effected along each such axis.

12. The apparatus of claim 11 in which each of said frequency selection modules includes a filter network having a pass-band tuned to the aforesaid multiple of the scanning frequency along the associated axis of the scanning rasters.

13. In apparatus for effecting registration of homologous areas in a pair of similar images, a pair of flying spot scanners for respectively scanning such images, a raster generator for developing the deflection signals for each scanner to provide the scanning rasters thereof, a correlator for comparing the video output signals of said flying spot scanners to provide therefrom a parallax signal representative of relative displacements between such homologous image areas, a frequency selection module for selecting from such parallax signal a component thereof constituting a multiple of the scanning frequency of said scanners to obtain a correction signal and further including a filter having a comb-type band-pass characteristic having a plurality of band-pass peaks which coincide with whole number multiples of the line scanning frequency, and means for combining such correction signal with a deflection signal from said raster generator to one of said flying spot scanners to effect a corrective transformation in the scanning raster thereof.