Devices for taking motion pictures from an aircraft

A device for taking aerial motion pictures, includes a camera (3) disposed at the upper end of a vertical periscopic tube (2) whose lower end (1) projects below a carrying airplane. An optical device is provided, adapted to effect vertical sweeping by pivoting about a horizontal axis. The periscopic tube (2) can pivot about its vertical axis and the camera (3) can pivot coaxially relative to the periscopic tube (2). The periscopic tube (2) is carried by a first turning plate (41) mounted rotatably on a fixed plate (40) and driven in rotation by a motor (43), whilst the camera (3) is carried by a second turning plate (51) mounted for rotation on a second fixed plate (50) and driven in rotation by a second motor (53).

BACKGROUND OF THE INVENTION 
This application corresponds to French application 98 01461 of Feb. 9, 
1998, the disclosure of which is incorporated herein by reference. 
The present invention has for its object improvements in devices for taking 
motion pictures from an aircraft such as an airplane or a helicopter. 
It is known to film one airplane in flight from another airplane, for 
example to present a new airplane or for publicity of aeronautical 
companies. 
To do this, there is used a camera mounted at the upper end of a periscope 
disposed in an airplane, and whose lower end projects outside below the 
cabin. On this end is disposed a total reflection prism which returns the 
image through the periscope to the camera. The prism is movable about a 
horizontal axis so as to be able to undergo vertical swinging of 100 above 
the horizon and 30.degree. below. Moreover, this periscope is carried by a 
turntable which permits pivoting about its vertical axis to sweep the 
horizon around 360.degree.. 
This device has been improved a first time by mounting the camera on the 
periscope such that it can turn relative to this latter. Thus, when the 
periscope is rotated to drive the camera, there is a panoramic sweeping 
and, when the camera is turned relative to the periscope, a modification 
of the inclination of the image which permits correcting as needed the 
horizontality of the image. 
The apparatus now in use is insufficient to turn aircraft films taken at 
high speed, even when this view-taking material is itself installed in a 
jet plane of the business plane type (Learjet, Falcon, Corvette or the 
like). 
SUMMARY OF THE INVENTION 
The present invention relates to an apparatus for taking aerial motion 
pictures of the known rotatable periscope type, characterized by the fact 
that it comprises improvements of the optical periscope system; of the 
means for rotating the periscope and/or the camera, and of the control 
means of the different movements.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring to these figures, it will be seen that the apparatus for taking 
aerial motion pictures from an aircraft, for example from an airplane, is 
constituted: 
by a prism 1, 
by a periscopic tube 2, 
and by a camera 3. 
The periscopic tube 2, at the end of which is located the prism 1, passes 
through the floor of the cabin as well as the wall of the cabin of the 
airplane A. The periscopic tube 2 is mounted rotatably relative to the 
airplane A and projects outside the cabin of the airplane A in a dome 10 
provided with windows such as 11. 
In the known device, the end of the periscope comprises a mirror whose 
inclination can be changed. This mirror is a roof prism, which is to say a 
prism which rectifies the image. This prism is carried by a pivoting lever 
which is subjected to the traction of a cable, under the force of a return 
spring. As a result, the center of gravity of the assembly is not located 
on the axis of rotation of the prism, which has the result that when the 
carrying airplane is subjected, during maneuvers, to acceleration (and 
hence an increase of the "g" number) the mirror pivots by stretching its 
return spring, which makes it practically impossible to follow the target. 
According to the present invention, there is used a special prism 1 (made 
by the KINOPTIC Company and not described because it does not form a part 
of the present invention), which, in short, is a double mirror 13 with a 
prism (14, 15) on each side and which is carried rotatably by a shaft 16 
passing through its axis of symmetry so as to be perfectly balanced and 
hence insensitive to vibrations of the gravity (the variations of the "g" 
number). 
By turning about its axis 16, this prism can carry out a complete vertical 
sweeping about 360.degree.. In practice, because of the obstacle 
constituted by the cabin of the airplane A, this sweeping is limited to 
22.degree. above the horizon on each side of the vertical; as a result the 
sweeping is 224.degree. (22+180+22); which is to say considerably greater 
than that of the known roof prism device which permits a partial sweeping 
only between 10.degree. above the horizon and 30.degree. below. 
Moreover, the roof prism mirror of the prior art device gave rise to an 
increase of the image which on the one hand deformed the image and above 
all did not permit using certain cameras. 
The prism employed in the device according to the invention is an a focal 
system of enlargement 1, having a field of 33.degree. which permits using 
any camera 3. 
The use of a prism such as the prism 1 gives rise to a considerable 
improvement as to the balancing the masses and sweeping, but has the 
drawback of inverting the image, which a roof prism does not. It is thus 
necessary to rectify the image, which can be done only in the periscopic 
tube 2, which requires the use of a prism 20 called a "Pechan prism" which 
carries out rectification of the image along the optical axis 21. 
As is shown schematically in FIGS. 2 and 3, the shaft 16 which carries the 
prism 1 also carries the drive motor 17 and the position detector 18. The 
drive motor 17 is a linear motor such that there is no mechanical movement 
transmission member between the motor 17 and the shaft 16, which 
eliminates any vibration. 
Another improvement relates to the rotatable drive means of the periscopic 
tube 2 about its axis of rotation coaxially with the camera 3 relative to 
the periscopic tube. 
In the known apparatus, when the periscopic tube 2 turns, because it 
carries the camera 3, the latter turns at the same time and, to obtain 
rotation of the camera 3 relative to the tube 2, there is disposed between 
the camera and the periscope a motor. 
The rotation of the periscope is obtained by a transmission comprising an 
endless screw (driven by a motor) engaging with a hollow wheel. The 
rotation of the camera relative to the periscope is obtained by the same 
means. As a result, on the one hand, the movements of rotation are slow, 
on the other hand vibrations connected to flight are transmitted to the 
periscope and to the camera. 
According to the invention, the two elements, namely, the periscopic tube 2 
and the camera 3, are carried independently of each other, each by a 
turning assembly 4 and 5. The two assemblies 4 and 5 are each carried by a 
chassis 6 resting on the floor of the airplane A. 
Each is constituted by a circular plate 40, 50 fixed to the chassis 6, 
bearing a turning plate 41, 51 by means of ball bearings 42, 52. Each 
turning plate is rotated by a linear motor 43, 53 comprising a stator 43a, 
53a and a rotor 43b, 53b, the stator being carried by the fixed plate 40, 
50 and the rotor by the turning plate 41, 51. With each turning plate is 
associated a position detector 44, 54. 
The cylindrical tube 22 which carries at its end a prism 1, passes through 
the fixed plate 40 and the turning plate 41 and is fixed to it. The fixed 
plate 50 and 1he turning plate 51 each comprise a central hole 50a and 51a 
which permits the optical beam passing through the periscopic tube 2 to 
arrive at the camera 3. 
In the example shown, the fixed plates 40, 50, the turning plates 41, 51 
and the motors 43, 53 are identical, which permits standardization of the 
parts. 
One of the particularities of the invention is that this embodiment of the 
means carrying the periscopic tube 2 and the camera 3, permits being able 
to carry the turning elements 41, 51 by bearings 42, 52 of large 
dimensions. By large dimensions is meant that the bearings 42, 52 have a 
diameter of the order of 400 millimeters, whilst in the known device the 
periscope is carried directly by a bearing of 150 millimeters. In the 
known device it is the same bearing (of 150 mm) which carries both the 
periscopic tube 2 and the camera 3 because the latter is carried by the 
periscope, such that vibrations transmitted to the periscope are also 
transmitted to the camera. By arranging each element independently of each 
other on two turning tables 4 and 5 independent of each other and of large 
dimensions, the undesirable effects of vibrations are practically 
eliminated. 
The motors 43-53 are linear motors of high couple permitting a maximum 
speed of rotation of the order of 540.degree. per second and a precision 
of angular movement of the order of 0.005.degree.. The use of such motors 
also leads to the elimination of the undesirable effects of vibrations. 
However, this arrangement, although quite advantageous as to the 
elimination of vibrations, as well as rapidity and precision of movements, 
gives rise to a problem connected to the synchronism of the movements of 
the periscopic tube 2 and of the camera 3 when a panoramic sweeping is 
effected. 
Thus, in the known device, because the periscopic tube 2 carries the camera 
3, this latter turns with the periscope and the synchronism is perfect. In 
this system, the motor causing the camera to turn relative to the 
periscopic tube is only used to correct inclination, and hence carries out 
very small movements. 
On the contrary, in the device according to the present invention, when 
sweeping by turning the periscopic tube, the camera 3 must carry out 
exactly the same movement of rotation, at the same speed, in an absolutely 
synchronous manner; lacking this, parasitic inclinations of the image will 
arise. 
To overcome this drawback, the controls of the motors 43 and 53 are 
controlled by a computer such that the movements of the tables will be 
synchronized to about 0.005.degree. 
This is made possible by the fact that the motors 43 and 53, being linear 
motors, can be controlled by digital computers, which is not the case of 
the DC motor previously used. 
The use of linear motors such as 18, 43 and 53 has numerous advantages 
which are of very great importance. 
About the three axes: pitch, roll and yaw, the transmissions are exempt 
from mechanical means such as hollow wheels or endless screws, which has 
the effect not only of eliminating dimensional errors but also any 
vibration. 
Moreover, the linear motor of strong couple such as motors 43-53 permits 
very rapid accelerations. 
Furthermore, they can also be operated by a computer, which is to say by 
digital control which permits having a control regime based on frequency 
and hence precise synchronization to 10 rotations per second. 
The movements of the camera 3 relative to the periscopic tube 2 have for 
their object to correct variations of horizontality of the image, 
variations which are essentially due to turbulence. 
The compensation of turbulence requires displacements which are of the 
order of 1 to 2 degrees, but at a frequency of the order of 15 to 20 
Hertz: this is quite impossible with the camera/periscopic tube connection 
with a conventional motor driving an endless screw engaging with a hollow 
wheel. 
The arrangement according to the present invention permits among other 
things selecting gyrostabilization of the image, which is impossible with 
the known means. 
It is to be noted that one could, by following the prior art, carry the 
camera 3 on a plate 41 and provide a linear motor between this plate 41 
and the camera 3; but this would not work. Thus, as a linear motor is free 
from any mechanical means, any controlled movement of the camera 3 
relative to the tube 2 (or vice versa) would give rise by reaction or an 
antagonistic couple to a movement in opposite directions from each other. 
It is therefore imperative to have two rotation means that are independent 
from each other, separately controlled. 
The use of a computer to control the movements of the turning tables 
permits computerizing all the system. 
The control system comprises: 
a computer controlling all the system 
a computer keyboard 
two screens, one permitting visualizing the centering, the other giving 
digital data for positioning of the target filmed relative to the carrying 
aircraft as well as the different parameters of the views. 
two mini-control sticks, of which one acts on the vertical sweeping 
movement of the prism 1 and on the rotation movement of the periscopic 
tube 2; the other on the rotation of the camera 3 relative to the 
periscopic tube 2 (correction of horizontality) and on the zooming of the 
camera 3. 
FIG. 4 is a diagram of the computer connections of the system. 
Referring to this figure, it will be seen that the system comprises a 
central computer 100, which can be a P.C., which is connected to a screen 
401, a printer 402 and a keyboard 403. 
Each of the linear motors 17, 43 and 53 is connected to the computer 100 by 
means of a pilot 101, 102, 103 respectively, to which are connected the 
positions detectors 18, 44 and 54. 
The computer 100 is also connected to two minicontrol sticks 201 and 202; 
the displacements of the minicontrol sticks 201 and 202 are shown by 
crossed arrows. The double arrow 201a corresponds to movements of the tube 
2 for panoramic sweeping; the double arrow 201b corresponds to the 
movements of the prism 14 for sweeping along the pitch axis. 
The double arrow 202a corresponds to distance movements, which is to say 
zooming; the double arrow 202b corresponds to displacements along the roll 
axis. 
Thus by means of the two mini-control sticks 201 and 202 there is 
controlled, by means of the computer 100, the pilots 101, 102 and 103 and 
hence the motors 17, 43 and 53 and the displacements along the pitch axis, 
the yaw axis, the roll axis as well as zooming. 
It will also be understood that there can be one or several pairs of 
mini-control sticks to carry out double control or formation. 
Again in FIG. 4, it will be seen that the computer 100 can be connected to 
gyroscopic stabilizers 301, 302 and 303 so as to have gyroscopic stability 
about the three axes. 
The computer can also be connected to a known system called CPMS (Camera 
Pointing Management System) which, by means of a satellite positioning 
apparatus can automatically direct the camera according to a 
pre-established itinerary. 
Thus, for example, if it is desired automatically to film an itinerary 
along route R (FIG. 5) from an airplane which moves from a point X to a 
point Y at constant altitude and on a constant course, there can be 
calculated in advance the distances d.sub.1, d.sub.2, d.sub.3, . . . etc. 
and the variations of the angle of the camera, and then introduce it into 
the apparatus 600 which will automatically control the movements of the 
prism 1 and of zooming. 
There could also be connected to the computer 100 a data recording 
apparatus 500 which would record automatically all the associated data: 
of the pitch angle: 501 
of the roll angle: 502 
of the course of the aircraft: 503 
of the altitude: 504 
of the geographic position: 505 
of the time and date: 506 among others. 
This computerization of the system permits having three modes of operation: 
a a manual mode: the operator, by means of two mini-control sticks, 
controls the four movements, 
b an automatic mode over a given pre-recorded trajectory. The airplane (on 
automatic pilot) and the system following the instructions given by the 
computer, 
c a semiautomatic mode: by gyroscopic stabilization, the random movements 
of the carrying airplane are automatically compensated to have a stable 
image. 
Moreover, this permits recording and memorizing all the positions of the 
camera, of the periscope, those of the carrying airplane, the geographic 
coordinates of movement of the airplane and the time. These recordations 
permit carrying out at low cost the splicing of synthesized images. 
There could also be provided on the mini-control sticks 201 and/or 202, 
buttons 203 which permit selecting different laws of variation of the 
speed of movement of the motors 17, 43 or 53. Thus, when the carrying 
aircraft and the filmed aircraft fly in formation, the relative movements 
are small and the corrections to be made are less great but precise; 
whilst when airplane A flies behind a filmed airplane which maneuvers 
sharply (in the case of an action film for example), the corrections to be 
made are great and abrupt.