Note: Descriptions are shown in the official language in which they were submitted.
0
1 This invention concerns a device for scanning adjacent
profiles in stereo photographs, including an automatic image
correlator comprising at least one light source for producing
two identical light paths. An optical imaging system, an image
plane, a further optical imaging system and a light electric
detector are subsequently arranged, considered in the direction
of light propagation, in each of said light paths. The image
plane is connected via respective means to three servo-
motors which adjust the former with respect to height, to advance
and to a direction at right angles to the advance direction.
The light electric detector is connected via the image
correlator to the servo-motor which controls the height. The
inventional device is used in differential rectification --
operations.
Previous devices for differential rectification
of aerial photographs including an automatic image correlator
permit an automatic positioning of a measuring mark relative
to a model surface when in static operation. -~
Static operation is to be understood throughout the - -
specification as an adjustment operation with respect to the
height of a measuring mark relative to a stereo-model,
whereas in dynamic operation said mark is additionally dis-
placed in a plane at right angles to the height coordinate.
In said devices the center of a light generated raster coincides
with the measuring mark of a photogrammetric plotter.
When in dynamic operation the displacement of the
measuring mark involves an offset in the image correlator.
Such an offset can be compensated for by additionally dis-
placing the stored model profiles relative to each other
in the event of an off-line operation between the differential
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1 rectifier and the stereo plotter, that is, when the photographing
of the model surface and the plotting operation are carried
out separately and the model profiles obtained are temporarily
stored.
This, however, requires a storage which implies
considerably high costs with respect to equipment, apart from
the longer time necessary for the evaluation operation.
In the event of an on-line dynamic operation between
the differential rectifier and plotter the offset causes
0 distortions of neighbouring image details due to the lateral
tilt. To cope with this disadvantage the scanning speed of
the measuring mark has to be considerably reduced.
It is an object of the present invention to obviate
the above disadvantages.
It is a further object of the present invention to
provide a differential rectifier in combination with an automatic
image correlator of high scanning speed concerning the com-
pensation of distortions occuring when dynamically operated.
~ It is still a further object of the present invention
to include a scanning control in a differential rectifier for
scanning adjacent profiles in stereo photographs. These and
other objects of the invention are realised in connecting an
advance control servo-motor via a d.c. tachometer and via a
~ scanning generator and a deflection unit to a light source.
It is still a further object of the present invention
to provide a device for scanning adjacent profiles in stereo-
couples of photographs comprising at least one light source,
being provided with a screen, a raster generating and controlling
means for producing and controlling a flying spot raster on
~ said screen, the controlling means being connected to the light
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1 source, at least one light beam being emitted from the raster,
in each of the light beams being arranged, there being at
least one optical imaging means, a photograph, and at least
one light electric detector, the optical imaging system being
for imaging the flying spot upon the photograph, and the light
electric detector being for scanning the photograph and for
converting the light signals into electric scanning signals, -
a correlator for comparing the scanning signals produced by
the light-electric detectors, a first and a second servo-motor,
the first servo-motor being electrically connected to the
correlator and to the light electric detector and being for
adjustment of the height of the raster, the second servo-motor
being for displacing the raster in a first direction at right - -
angles to the height adjustment direction, a d.c. tachometer
for generating a directional d.c. voltage, the d.c. tachometer
being electrically connected to the second servo-motor and to
the raster generating means for effecting a displacement of
the raster in a second direction in additional to the first
direction, a third servo-motor being for displacing the raster
at right angles to the height adiustment and to the first
direction, the first, second and third servo-motors being for
performing relative displacements between each path of rays
and the respective photograph allocated thereto.
In this manner displacements of adjacent scanned
profiles in differential rectification are eliminated. In
order that the invention may be more readily understood
reference is made to the accompanying drawings which illustrate
diagrammatically and by way of example three embodiments
- thereof and in which:-
Fig. 1 is a schematic view of a previous art device
to illustrate the mode of operation,
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1 Fig. 2 is a schematic view of the operation of the
inventional device,
Fig. 3 is a schematic view of a further embodiment
according to the invention,
Fig. 4 is still another schematic view of an
embodiment of the invention, and
Fig. 5 is a block scheme of a scanning control of
the present invention.
In Fig. 1 a cathode ray tube 1 is displaceably arranged
about the x-, y-, z-axis of a coordinate system 3 set up on
a profile of a stereo-model 2 above which a projector 4 having
an image plane 5 is located. The x-axis is at right angles
to the drawing plane and therefore not represented. A not shown
electronic unit generates a flying spot raster 6, having a
center 7 on the screen of the cathode ray tube 1,
The cathode ray tube 1 is displaceable in the y-
direction to scan the stereo-model 2 by means of the raster 6.
In the course of this scanning operation, an automatic
height adjustment of the cathode ray tube 1, and hence of the
raster 6 relative to the stereo-model, is carried out in
the z-direction.
Due to the lagging error involved in the height
adjustment of the cathode ray tube 1, a height difference az
occurs between the raster center 7 and a measuring mark 8
of an optical evaluation device (not shown for reasons of
greater simplicity), which both, center 7 and mark 8r lie one
above the other upon a straight line identical with the z-axis.
Therefrom a displacement ay of neighbouring model stripes
results when they are projected into the image plane 5. This
evident when considering the points of impingement of the
projection beams 55 and 56 in the image plane 5. In contrast to
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1 Fig. 1, Fig. 2 displaces the raster center 7 in the y-direction
so that the raster center 7 does not any longer coincide with
a measuring mark 8 but advances the latter in the scanning
direction. In this manner displacement errors ~y are eliminated
at the presence of displacement errors ~z.
In Fig. 3 a cathode ray tube 9 being provided with a
screen 9' is displaceable about an x-, y-shaft 10, 11 which
corresponds to the z-, y-axis of the coordinate system 3 of
Fig. 1. For the sake of greater simplicity, the servo-motor
and shaft for displacement of the cathode ray tube 9 in the x-
direction are omitted.
t~ ~
B The raster 12 generated oni~ screen 9' of the cathode
ray tube 9 emits corresponding rays, in one portion of which
a projector 13 with an image 14 is arranged followed by a
light-electric detector 15, and in the other portion of the rays
a projector 16, with an image 17 followed by a light electric
detector 18 is located.
The individual images 14 and 17, respectively, are -
formed in the image planes of the projectors 13, 16, respectively.
The two light-electric detectors 15, 18 are connected
via mechanical control means 57, 58-to the cathode-ray tube 9
and electricaL~ to an electronic correlator 19 which controls
via a servo-motor 20 the shaft 10. A servo-motor 21 is
connected via a d.c. tachometer 22 and an amplifier 23 to
the cathode ray tube 9. A vidicon 24 is electrically
connected to the electronic correlator 19. In the path of rays
of the former an optical imaging system 25, a slit aperture 26
and a film reel 27 are arranged.
- The two images 14, 17 with the projectors 13, 16 are
oriented relative to each other to form a stereo-couple. The
light pulses emitted from the cathode ray tube 9 raster 12 and,
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¦~ 1 directed via the projectors 13, 16 and the image planeq ~,
17 to impinge upon light electric detectors 15 and 18 are con-
verted by the latter into corresponding electric pulses. These
are compared as to their phase position in the electronic
correlator 19, where a differential signal is formed, if any,
which in turn is fed into the servo-motor 20 to effect by
operation of the latter via the shaft 10 a displacement of the
cathode ray tube 9 along the z-direction, until the two phases
are balanced. The scanned terrain surface section, that is, the
image section, is reproduced on the vidicon 24 connected to the
- electronic correlator 19. The reproduced image section is
projected via the optical imaging system 25 and through the
slit aperture 26 on to the film reel 27 or any other suitable
recording means.
A servo-motor 21 automatically displaces the cathode -
ray tube 9 along the spindle 11 in the y-direction which
corresponds to an automatic scanning of the image planes 14,
17. The film reel 27 is synchronously rotated. The d.c.
tachometer 22, connected to the servo-motor 21, supplies a
directional d.c. voltage proportional to the scanning speed in
the y-direction via the amplifier 23. The voltage is applied
to the cathode ray tube 9 where the former is superimposed to the
deflection voltage which is necessary to generate the!raster.
This d.c. voltage serves to advance the raster in the y-
direction, as explained in connection with Fig. 2.
In Fig. 4, the cathode ray tubes 28, 29 are non-
displaceable light sources, each of which produces a light path
(not shown) so that in the resulting two light paths the
following components are arranged; first optical imaging systems
30 and 31 respectively, stereo-couple of photographs 32, 33 in
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1 the corresponding image planes and second optical imaging
systems 34, 35.
The projectors 32 and 33 are displaceable about a
coordinate system x', y' and x", y" respectively. The light
beams emitted from the cathode ray tube 28, 29 are detected
by the respectively coordinated light electric detectors 36,
37 which in turn are connected to an electronic correlator 38
to control a servo-motor 39.
The displacements of the stereo-couple of photographs
32, 33 are accomplished in cooperation with mechanical dis-
placement means 42 by operation of servo-motors 40, 41 and as
mentioned hereinabove by servo-motor 39. An electric
connection is established between the servo-motor 40 and the
cathode ray tubes 28, 29 via a d.c. tachometer 43 and a raster
generating and deflection unit 44.
The path of light beams originating from the cathode
ray tubes 28, 29 and arriving at the photodetectors 36, 37
are indicated by the axes 59 and 60 respectively. The rasters
45, 46 produced by operation of the raster generating unit 4
upon the respective cathode ray tube 28, 29 screens are imaged
through the imaging systems 30, 31 into the projector image
planes 32, 33 to scan the latter, and from whence to the
respective light electric detectors 36, 37 via the second optical
imaging systems 34, 35.
The light pulses which have been modulated by the
stereo-couple of photographs 32, 33 impinging upon the light
electric detectors are converted into corresponding electric
pulses which are compared as to their relative phase shifts in
the correlator 38 to form a differential signal which in turn
effects corresponding mechanical displacements by actuating
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1 the servo-motor 39. The latter operates the mechanical dis-
placement means 42 to displace the image planes 32, 33 relative
to each other until the correlator 38 signals are balanced.
The servo-motors 40 and 41, also via the mechanical displacement
means 42, automatically displace the image planes 32, 33 about
the transformed y-, x~axes of the terrain surface coordinate
system.
The d~c. tachometer 43 connected to the servo-motor 40
supplies a directional d.c. voltage, proportional to the advance
1~ speed in y-direction, which is superimposed to the deflection
voltage of the cathode ray tubes 28, 29 in the raster de-
flection unit 44. Depending on the size of the d.c. voltage the
rasters 45, 46 are subject to an additional displacement in
the y-direction. In Fig. 4 the means for recording the recti-
fication obtained are omitted for the sake of simplicity. The
means can be, for example, a further image connected to one of
the stereo photographs 32 or 33 which is rectified by suitable
means to be imaged upon a cylindrical recording means. When
in static operation the raster control via the d.c. tachometer
20 22 (Fig. 3) and 43 (Fig. 4j are in a non-operative mode.
In Fig. 5 a raster generating unit 47 supplies de-
flection voltages Ux and Uy for the cathode ray tubes 48, 49.
A d.c. tachometer 51 connected to a servo-motor 50 feeds a d.c.
- voltage signal proportional to the motor operation speed and
direction into a summation unit 53 via an amplifier 52. The
summation unit 53 superimposes the voltage Uy to the d.c.
tachometer 51 voltage and varies the deflection voltage of the
cathode ray tubes 48, 49 in the y-direction in accordance
with the fed-in voltage.
Although the description of the invention has been given
with respect to particular embodiments, it is not to be
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1 construed in a limiting sense. Many variations and modifications
will now occur to those skilled in the art. For a definition
of the invention reference is made to the appended claims.
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