U.S. patent application number 10/061750 was filed with the patent office on 2002-07-04 for photogrammetric camera.
Invention is credited to Teuchert, Wolf Dieter.
Application Number | 20020085094 10/061750 |
Document ID | / |
Family ID | 7825738 |
Filed Date | 2002-07-04 |
United States Patent
Application |
20020085094 |
Kind Code |
A1 |
Teuchert, Wolf Dieter |
July 4, 2002 |
Photogrammetric camera
Abstract
A photogrammetric camera for airborne or spaceborne terrain
recording includes several electro-optical sensors which can be
arranged at a distance from each other in the flight direction and
which scan the overflown terrain and record each scanned terrain
region at least twice from a respectively different perspective. At
least two surface detectors are provided as the electro-optical
sensors.
Inventors: |
Teuchert, Wolf Dieter;
(Konigsbronn, DE) |
Correspondence
Address: |
M. Robert Kestenbaum
11011 Bermuda Dunes NE
Albuquerque
NM
87111
US
|
Family ID: |
7825738 |
Appl. No.: |
10/061750 |
Filed: |
February 1, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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10061750 |
Feb 1, 2002 |
|
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09057376 |
Apr 8, 1998 |
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Current U.S.
Class: |
348/144 ;
348/143; 701/514 |
Current CPC
Class: |
G01C 11/025
20130101 |
Class at
Publication: |
348/144 ;
348/143; 701/223 |
International
Class: |
H04N 007/18 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 8, 1997 |
DE |
197 14 396.2 |
Claims
1. A photogrammetric camera for airborne or spaceborne terrain
sensing, comprising a plurality of electro-optical sensors arranged
to be spaced from each other in a flight direction that scan an
overflown terrain and record scanned terrain regions at least twice
from a respectively different perspective, in which said plurality
of electro-optical sensors comprise at least two surface detectors,
further comprising a motor-pivotable deflecting mirror, associated
with each of said surface detectors for compensation of flight
motion during exposure of said plurality of electro-optical
sensors, in which said electro-optical sensors comprise three
surface detectors.
2. A photogrammetric camera for airborne or spaceborne terrain
sensing, comprising a plurality of electro-optical sensors arranged
to be spaced from each other in a flight direction that scan an
overflown terrain and record scanned terrain regions at least twice
from a respectively different perspective, in which said plurality
of electro-optical sensors comprise at least two surface detectors,
further comprising a motor-pivotable deflecting mirror, associated
with each of said surface detectors for compensation of flight
motion during exposure of said plurality of electro-optical
sensors, in which said surface detectors are rectangular in shape
and have a ratio of a dimension in said flight direction to a
dimension transversely of said flight direction in a range of about
1:2 up to about 1:10.
3. A photogrammetric camera for airborne or spaceborne terrain
sensing, comprising a plurality of electro-optical sensors arranged
to be spaced from each other in a flight direction that scan an
overflown terrain and record scanned terrain regions at least twice
from a respectively different perspective, in which said plurality
of electro-optical sensors comprise at least two surface detectors,
further comprising a motor-pivotable deflecting mirror, associated
with each of said surface detectors for compensation of flight
motion during exposure of said plurality of electro-optical
sensors, in which said surface detectors include a plurality of
monolithic individual surface detectors that optically abutt
transversely of said flight direction.
4. The photogrammetric camera according to claim 3, in which each
of said surface detectors includes three monolithic individual
surface detectors and three camera objectives each respectively
associated with one of said individual surface detectors with
optical axes that run mutually obliquely.
5. A photogrammetric camera for airborne or spaceborne terrain
sensing, comprising a plurality of electro-optical sensors arranged
to be spaced from each other in a flight direction that scan an
overflown terrain and record scanned terrain regions at least twice
from a respectively different perspective, in which said plurality
of electro-optical sensors comprise at least two surface detectors,
further comprising a motor-pivotable deflecting mirror, associated
with each of said surface detectors for compensation of flight
motion during exposure of said plurality of electro-optical
sensors, in which said surface detectors comprise CCD
detectors.
6. The photogrammetric camera according to claim 5, in which said
surface detectors have respectively about 1,024 sensor lines
directly adjoining in said flight direction, with respectively
about 2.times.1,024 to about 9.times.1,024 individual pixels, each
of said individual pixels being about 12 .mu.m.times.12 .mu.m in
length and width.
7. A photogrammetric camera for airborne or spaceborne terrain
sensing, comprising a plurality of electro-optical sensors arranged
to be spaced from each other in a flight direction that scan an
overflown terrain and record scanned terrain regions at least twice
from a respectively different perspective, in which said plurality
of electro-optical sensors comprise at least two surface detectors,
further comprising a motor-pivotable deflecting mirror, associated
with each of said surface detectors for compensation of flight
motion during exposure of said plurality of electro-optical
sensors, further comprising a separate camera objective associated
with each of said surface detectors, said camera objectives having
optical axes that run mutually obliquely.
8. A photogrammetric camera for airborne or spaceborne terrain
sensing, comprising: a plurality of electro-optical sensors
arranged to be spaced from each other in a flight direction that
scan an overflown terrain and record scanned terrain regions at
least twice from a respectively different perspective, in which
said plurality of electro-optical sensors comprise three surface
detectors, further comprising a separate camera objective
associated with each of said surface detectors, said camera
objectives having optical axes that run mutually obliquely.
9. A photogrammetric camera for airborne or spaceborne terrain
sensing, comprising: a plurality of electro-optical sensors
arranged to be spaced from each other in a flight direction that
scan an overflown terrain and record scanned terrain regions at
least twice from a respectively different perspective, in which
said plurality of electro-optical sensors comprise at least two
surface detectors, and in which said surface detectors are
rectangular in shape and have a ratio of a dimension in said flight
direction to a dimension transversely of said flight direction in a
range of about 1:2 up to about 1:10, further comprising a separate
camera objective associated with each of said surface detectors,
said camera objectives having optical axes that run mutually
obliquely.
10. A photogrammetric camera for airborne or spaceborne terrain
sensing, comprising: a plurality of electro-optical sensors
arranged to be spaced from each other in a flight direction that
scan an overflown terrain and record scanned terrain regions at
least twice from a respectively different perspective, in which
said plurality of electro-optical sensors comprise at least two
surface detectors, in which said surface detectors include a
plurality of monolithic individual surface detectors that optically
abutt transversely of said flight direction, further comprising a
separate camera objective associated with each of said surface
detectors, said camera objectives having optical axes that run
mutually obliquely.
11. The photogrammetric camera according to claim 10, in which each
of said surface detectors includes three monolithic individual
surface detectors and three camera objectives each respectively
associated with one of said individual surface detectors with
optical axes that run mutually obliquely.
12. A photogrammetric camera for airborne or spaceborne terrain
sensing, comprising: a plurality of electro-optical sensors
arranged to be spaced from each other in a flight direction that
scan an overflown terrain and record scanned terrain regions at
least twice from a respectively different perspective, in which
said plurality of electro-optical sensors comprise at least two
surface detectors, and in which said surface detectors comprise CCD
detectors, further comprising a separate camera objective
associated with each of said surface detectors, said camera
objectives having optical axes that run mutually obliquely.
13. The photogrammetric camera according to claim 12, in which said
surface detectors have respectively about 1,024 sensor lines
directly adjoining in said flight direction, with respectively
about 2.times.1,024 to about 9.times.1,024 individual pixels, each
of said individual pixels being about 12 .mu.m.times.12 .mu.m in
length and width.
Description
CROSS-REFERENCES TO RELATED APPLICATIONS
[0001] This is a divisional application of U.S. patent application
Ser. No. 09/057,376, filed Apr. 8, 1998 of the same inventor.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] Not applicable.
BACKGROUND OF THE INVENTION
[0003] The invention relates to a photogrammetric camera, and more
particularly, to a photogrammetric camera for airborne or
spaceborne sensing of overflown terrain, and to a photogrammetric
process for airborne or spaceborne sensing of overflown
terrain.
TECHNICAL FIELD
[0004] Such cameras and recording processes are known, for example,
from U.S. Pat. No. 4,689,748; 4,504,914; and 4,708,472 which are
examples of the three-line camera, and are arranged in an aircraft
or in a satellite, in order to record the overflown terrain,
according to coordinates or in multiple spectra.
[0005] However, it has been found that recording terrain with such
three-line cameras requires precise knowledge of the flight motions
of the camera platform. In this regard, see the article, "Digital
Photogrammetric Assembly (DPA)--An Airborne Stereo and
Multispectral Imaging and Evaluation System" by A. Kaltenecker, F.
Muller and O. Hofmann in Photogrammetric Week '95/Dieter Frisch;
Dierk Hobbie (eds.), Heidelberg, Wichmann, 1995, in particular the
second paragraph on page II-119. Above all, the frequently arising
yaw, roll and pitch motions that are superimposed on a relatively
smooth flight path of the aircraft carrying the photogrammetric
camera lead to the terrain lines, that is, the terrain regions in
the form of lines, that are scanned in succession in time, do not
adjoin and fit accurately together, to the contrary the terrain
lines are mutually rotated, and can even be interchanged in their
positions in the succession.
[0006] A solution was sought in the state of the art for this
problem by sensing the three spatial coordinates and three
direction data of the camera at each point in time as precisely as
possible by means of a combination of GPS and INS (inertial
navigation). The spatial coordinates and direction data sensed at
the instant of recording are associated with each terrain line and
the actual positions of the terrain lines are to be deduced from
this data.
[0007] However, the measurement inaccuracy in spatial and
directional determinations itself leads, even when the highly
accurate differential GPS and inertial navigation systems are used,
to an unavoidable statistical residual error of the spatial
coordinates and direction data, of the order of magnitude of a
third of the pixel dimensions of a CCD sensor, which in general is
what is used as the electro-optical sensor. The result is that two
pictures of the same area of terrain that were recorded in
succession are generally not identical.
[0008] This statistical residual error presents in principle a
problem for digital photogrammetry, which in fact depends on the
computer analysis of picture element groups within digital aerial
pictures. While the photometric errors can be reduced to a
practically optional degree, e.g., by slow scanning of aerial
pictures on photographic film, elimination from the picture of the
residual error of pictures of the three-line camera is in principle
not possible.
[0009] Furthermore, in order to be able to scan the overflown
terrain without gaps, the electro-optical sensors, which are built
up of individual CCD lines, of the known cameras of this kind must
have very short exposure times, of an order of magnitude of
microseconds. The known three-line cameras therefore require good
light conditions in their use. In unfavorable light conditions,
such as arise, e.g., at very high flying speeds, the picture signal
can sink into the noise of the electro-optical sensors.
SUMMARY OF THE INVENTION
[0010] The object of the invention is to provide a photogrammetric
camera that, in contrast to the state of the art, makes possible a
precise photogrammetric evaluation, and/or has smaller requirements
on the exact knowledge of, or the stability of, the flight path of
the camera platform, and/or has a higher photosensitivity.
[0011] This object is achieved by a photogrammetric camera for
airborne or spaceborne terrain sensing having a plurality of
electro-optical sensors arranged to be spaced from each other in a
flight direction that scan an overflown terrain and record scanned
terrain regions at least twice from a respectively different
perspective, in which the plurality of electro-optical sensors have
at least two surface detectors. A motor pivotable deflecting mirror
is associated with each of the surface detectors for compensation
of flight motion during exposure of the plurality of
electro-optical sensors. The electro-optical sensors have three
surface detectors. Because the photogrammetric camera according to
the invention includes at least two mutually spaced apart surface
detectors, a large number of scanned line-shaped terrain regions
fit accurately and unambiguously together at any given time,
without rotation or interchange. Each of the successively scanned
terrain lines no longer has to be correctly pre-oriented by
evaluating the positional coordinates and alignment information
supplied by GPS and INS, which are extraneous to the picture.
[0012] According to the invention, an orientation is possible even
without the auxiliary determination of spatial coordinates and
direction of the camera. On the other hand, however, picture
evaluation with the use of INS and GPS, i.e. with georeferenced
auxiliary information, is facilitated by means of the invention,
since the whole picture line area of the camera provides
self-consistent two-dimensional picture information. Furthermore,
the accuracy requirement on the GPS/INS process can be reduced, so
that, for example, an earth station for differential GPS can be
dispensed with. The reason for this is based on the orientability
of the partial image surfaces from the two-dimensional picture
information.
[0013] The strip pictures produced with the photogrammetric camera
according to the invention are always self-consistent, and thus
accessible to a surface correlation and hence also to the
conventional digital photogrammetric evaluation process. At least
two surface detectors, according to the invention, which are
arranged at a distance from each other, take the form of a single
virtual surface detector, the surface of which includes, not only
the surface of the surface detectors, but also the surface located
between these surface detectors. The basic photogrammetric concept
of the three-line camera can however also be retained by the
invention and can be made considerably more powerful. Here even the
middle line, which solely improves the numerical stability of the
three-line camera, can be dispensed with: that is, two line-type
surface detectors are sufficient according to the invention.
[0014] A further advantage over the three-line camera results from
the use of three surface detectors according to the invention.
Namely, the three-line camera is always evaluated from the pictures
of the two outer lines, so that a nadir view is generally not
possible, since the middle line is used only for support or for
joining lines. The photogrammetric camera according to the
invention, however, by means of the flat nature of the picture,
makes possible a picture representation in a nadir view, the
terrain model data being derived from the data of the two outer
surface detectors.
[0015] In addition to this, a surface detector whose exposure time
is greater by a factor of the number of sensor lines of the surface
detector is made available for the individual sensor lines by the
groupwise simultaneous exposure of numerous individual sensor
lines. The photosensitivity of the photogrammetric camera according
to the invention can thereby be considerably increased, and in
spite of this the total exposure time of the overall picture
assembled together from the individual line pictures is
reduced.
[0016] In analogy to the classic three-line camera, the
photogrammetric camera advantageously includes three surface
detectors which are arranged at spacings from each other, so that
the joining of successive pictures based on the principle of the
three-line detector with line-type surface detectors, as claimed in
U.S. Pat. No. 4,689,748, for example, is possible with the
photogrammetric camera according to the invention and basically
also with only two line-type surface detectors.
[0017] According to an advantageous embodiment, the surface
detectors are of a rectangular or strip shape, the ratio of the
dimension in the direction of flight to the dimension transverse to
the direction of flight being in a range of about 1:2 to about
1:10. The optical and mechanical components of the photogrammetric
camera which are associated with the surface detectors, in
particular a possible deflecting mirror, can thereby be optimally
dimensioned. A substantially square arrangement, i.e. a ratio of
sides of about 1:1, would have the disadvantage that a deflecting
mirror suited to it would have to be larger than necessary.
Furthermore, with a square detector that fills the whole picture
field in an appropriate manner, a compensation of the picture
movement caused by the motion of flight is not possible, since a
picture movement compensation is equivalent to a tracking of the
detector within the picture field. A further advantage of the
strip-shaped surface detectors is the high readout speed which can
be attained by the use of transversely readable CCD
arrangements.
[0018] When the surface detectors include numerous individual,
monolithic surface detectors, which are optically abutted, i.e.
fitted together, transversely of the flight direction, strip-type
surface detectors which are available commercially can be used,
according to the invention. A particularly long length of the
scanned terrain lines which run transversely of the flight
direction can thereby be attained, when each surface detector from
today's viewpoint, includes e.g. three monolithic individual
surface detectors and three camera objectives, one for each of the
individual surface detectors and having their optical axes running
mutually obliquely.
[0019] Such surface detectors are preferably constructed as flat
CCD arrays and preferably have respectively about 1,024 sensor
lines, directly adjoining in the flight direction, with
respectively about 2.times.1,024 to about 9.times.1,024 individual
pixels, each about 12 .mu.m.times.12 .mu.m.
[0020] Depending on the flying speed and height, a picture movement
can occur in the photogrammetric camera that considerably reduces
the resolution of the camera. To compensate for the flight motion
during the exposure, a mirror that can be pivoted by a motor can be
associated with each of the surface detectors.
[0021] An expensive special objective can be dispensed with when a
separate camera objective is associated with each of the surface
detectors, and the optical axes of the camera objectives run
mutually obliquely and are calibrated. In contrast to a
conventional aerial mapping camera objective, the picture field is
reduced to a third, with which commercially obtainable, high
quality intermediate format objectives can be used, at the same
focal length.
[0022] According to a further aspect of the invention, a
photogrammetric process for airborne terrain sensing is proposed,
in which the terrain which is overflown is scanned linewise by
electro-optical sensors, and each scanned line-shaped terrain
region is recorded at least twice at successive times from
respectively different perspective. Then numerous directly adjacent
line-shaped terrain regions that run transversely of the flight
direction and are directly adjacent to each other are
simultaneously recorded by the electro-optical sensors.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] The invention will now be explained with reference to the
accompanying drawings.
[0024] FIG. 1 shows a schematic representation of the principle of
the invention;
[0025] FIG. 2 shows a schematic representation of two embodiments
of the invention with image movement compensation by means of
pivotable deflecting mirrors;
[0026] FIG. 3 shows a schematic representation of an embodiment
with optically abutted sensor lines; and
[0027] FIG. 4 shows a perspective, schematic representation of the
embodiments of FIG. 3.
DETAILED DESCRIPTION OF THE INVENTION
[0028] A photogrammetric camera according to the invention is shown
schematically in FIG. 1. It is arranged in an aircraft (not shown)
and overflies a terrain which is symbolically represented by the
wavy line 2.
[0029] The camera 1 has three surface detectors 3, 5 and 7 which
are arranged at spacings from each other in the flight direction
shown by the arrow 9. Here, according to the invention, only the
surface detectors 3 and 7 are absolutely necessary. The surface
detector 5 essentially serves for imaging directed toward the
nadir.
[0030] Each of the surface detectors 3, 5 and 7 includes directly
adjacent sensor lines running transversely of the flight direction
9, each with a series of individual picture elements or pixels.
Thus the surface detector 3 includes the sensor lines 31, 32, 33,
34 and so on.
[0031] At the instant shown in FIG. 1, line-shaped terrain regions
or terrain lines 131, 132, 133, 134 and so on are imaged on the
sensor lines 31, 32, 33, 34 and so on of the surface detector 3, by
means of an imaging objective 15 which, according to the invention,
can consist of an array of individual objectives.
[0032] In a similar manner, the directly adjacent line-shaped
terrain regions 151, 152, 153, and so on are imaged on the sensor
lines 51, 52, 53 and so on of the surface detector 5, and the
line-shaped terrain regions 171, 172, 173, and so on are imaged on
the sensor lines 71, 72, 73 and so on of the surface detector
7.
[0033] The known photogrammetric evaluation process of the
three-line camera can be carried out by means of the thereby
acquired line pictures of the terrain regions together with
pictures recorded later of the same terrain regions. Thus e.g. the
terrain line 131 at the instant shown in FIG. 1 is scanned by the
sensor line of the surface detector 3, at a later instant by the
sensor line 51 of the surface detector 5, and at a still later
instant by the sensor line 71 of the surface detector 7.
[0034] In contrast to the three-line camera of the state of the
art, in the photogrammetric camera according to the invention, with
surface detectors, the scanned terrain regions 171, 172, 173 and so
on are mutually parallel and directly adjoin each other, so that
the evaluation of the line pictures is improved in principle.
[0035] A photogrammetric camera 20 is shown in FIG. 2 and includes
three surface detectors 23, 25 and 27, seen from the side. The
individual sensor lines of the surface detectors 23, 25 and 27 thus
run orthogonally to the plane of the drawing in FIG. 2 and
transversely to the flight direction shown by the arrow 29. Each of
the surface detectors 23, 25 and 27 has associated with it an
assembly with an objective 31 and a deflecting mirror 33; the
optical axes denoted by 24, 26 and 28 and associated with the
objectives 31 run mutually obliquely. The deflecting mirrors 33 are
pivotable, as indicated by the double arrow 37, around pivot axes
35 which run orthogonally to the plane of the drawing of FIG. 2.
The picture movement caused by the motion of flight can be
compensated for by a pivoting of the deflecting mirrors 33 which is
matched to the relationship of flying speed to aircraft height. As
a further embodiment, an embodiment is represented with only one
objective 39, shown dashed in FIG. 2, without the individual
objectives 31.
[0036] FIG. 3 shows how a very much longer, line-shaped terrain
region G can be scanned from three individual sensor lines 41, 43
and 45 of a surface detector by optical abutting by means of the
objectives 47, 49 and 51 respectively associated with each of these
lines. Here the lines which have been drawn starting at the ends of
the three sensor lines 41, 43 and 45 and passing through the
respective objectives 47, 49 and 51, indicate the angle of view of
each individual sensor line, and the dash-dot lines 42, 44 and 46
indicate the respective optical axes of the objectives 47, 49 and
51. The flight direction of the photogrammetric camera 40 runs
orthogonally to the plane of the drawing of FIG. 3, so that the
sensor lines arranged directly adjacent to the sensor lines 41, 43
and 45 are not to be seen in FIG. 3.
[0037] The embodiment of FIG. 3 is to be seen in a schematized
perspective representation in the direction of the arrow IV of FIG.
3, the flight direction being indicated by the arrow 52.
[0038] It can be recognized from FIG. 4 that the lines 41, 43 and
45 belong to the line-shaped surface detectors 53, 54 and 55, which
form a single surface detector A in the sense of the invention, by
optical abutting by means of the objectives 47, 49 and 51 and
subsequent correction of the perspective, in the photogrammetric
evaluation.
[0039] The directions of outlook of the objectives are represented
by showing them in perspective, as stubs of circular cylinders.
Thus the objective 47, seen in the flight direction and from above
to below, looks toward front and left; the objective 60 toward the
left, and also downward, orthogonal to the flight direction; the
objective 69 looks backward to the left; the objective 49 looks
forward in the flight direction; 62 looks toward the nadir; the
objective 71 looks backward in the flight direction; the objective
51 looks forward and to the right; the objective 64 looks toward
the right and also downward, orthogonal to the flight direction;
and the objective 73 looks backward to the right.
* * * * *