WO1990007720A1

WO1990007720A1 - Electro-optical scanning system for a hemispherical space

Info

Publication number: WO1990007720A1
Application number: PCT/CH1987/000078
Authority: WO
Inventors: James Linick
Original assignee: James Linick
Priority date: 1986-08-07
Filing date: 1987-06-30
Publication date: 1990-07-12
Also published as: CH672961A5

Abstract

Device and research process used in conjunction with an electro-optical sensor not requiring an integrated scanning system to explore the objective hemispherical space in order to find and localise potential targets. Said device includes a plane mirror (12) which is azimuthally mobile about an azimuthal axis of rotation (2) centred on a line perpendicular to and geometrically centred on the focal plane of the electro-optical sensor (26) and also mobile about an axis of elevation (16) perpendicularly offset relative to the azimuthal axis of rotation and situated outside the visual field of the sensor. According to said process, the plane mirror is made to rotate about its azimuthal axis of rotation while being subjected to a movement of inclination (or declination) about its rotational axis of elevation, thus producing a spiral which carries out a complete hemispherical search without the electro-optical sensor moving.

Description

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D E S C R I P T I O N

TITLE OF THE INVENTION;

ELECTRO-OPTICAL SCANNING SYSTEM OF A HEMISPHERIC SPACE

FIELD OF THE INVENTION:

This invention relates to electro-optical systems of active and passive visual representation for the purpose of research and exploration of objective space. More particularly, this invention relates to a device and a method intended to explore the hemispherical and volumetric objective space in order to find and / or locate potential targets and to allow information concerning the target (s) to be seen by the human eye and / or supplied to a weapon delivery system.

KNOWN STATE OF THE ART:

To date, there are many types of visual representation systems for the human eye or for computer systems for the purpose of exploring the objective space considered to be an area of potential targets intended to locate - potential targets and to supply the position of the target to a computer which will process this information and which will then supply a weapon delivery system with the information necessary to trigger and guide projectiles and / or missiles against the selected target _¬ tioned. / 07720.,

Such information relating to the position of the target can also be supplied to a visual representation device, such as a cathode ray tube or the like, allowing a visual examination of the selected target in order to help the operator to identify it and give priority to the selected target (s) (sJ.

Numerous radar systems and sub-systems have been developed for the research and exploration of the hemispherical objective space and in particular terrestrial systems, mounted on vehicles or on boats.

Unfortunately, these electro-optical systems for exploring the hemispherical space are extremely limited. In fact, electro-optical scanning systems have very limited visual fields of the order of two to ten degrees, as is the case with the scanning system incorporated in the Forward Loo ing Infra-Red (FLIR).

The narrow visual field of FLIR prohibits the use of FLIR as an electro-optical exploration system to search and locate targets in a wide search visual field. An attempt to use a FLIR with its incorporated scanning subsystems having narrow visual fields for exploration and research, consists in mounting an entire sensor on a "gimbal" oscil¬ latory and rotating assembly commonly called platform, in such a way that the entire FL-IR, or another electro-optical sensor of the system is panoramic in an X and Y direction to search for part of the objective space inside a predefined search field. In addition to the complexity of the platform itself, the concept of mounting a sensor on an oscillating and rotating platform turns out to be terribly troublesome for two major reasons. FIRST, the mercury-cadmium-tellurium detectors commonly used in a FLIR require cryogenic cooling during the operation; the cryogenic cooling sources must, because of their weight, be mounted next to the platform and connected to the FLIR without interfering with the rotational and elevation movement of the platform. The difficulty of making such a connection between the cryogenic source and the FLIR, as well as the multitude of electrical interfaces, increases dramatically as the "field of research widens. Consequently, electronic scanning systems -optics mounted on platforms generally have very limited fields of research.

SECOND, an important problem with electro-optical visual representation systems lies in the fact that these systems have their incorporated scanning system. While fixed gaze systems (with mosaic detectors) are developed for specific wavelengths, existing scanning systems tend to cause dragging on the image when a panoramic movement in azimuth is carried out and in elevation. As a result, the quality of detection and recognition of the target deteriorates while the false alarm rate increases.

Consequently, one of the aims of this invention is to create a device and a method which overcome the insufficiencies of the existing systems and methods mentioned above in order to contribute to the advancement and progress of the technique of electro- systems. optical and mechanical visual representation. Another novelty of this invention is to create the means of using conventional studies and accessories of the electro-optical technique to explore large areas of the objective space such as the hemispherical objective space.

Another novelty of this invention is to provide the means to explore the hemispherical objective space with conventional electro-optical scanning systems in such a way that distortions and dragging of the image or the lack of clarity of the image are significantly minimized to the point of being practically eliminated in order to allow better image recognition and readability for the human eye and / or a computer system.

Another novelty of this invention resides in the creation of an electro-optical system allowing an electro-optical sensor to explore the hemispherical objective space by completely eliminating the need to use an incorporated, fixed or being part of the sensor.

Another novelty of this invention is the creation of an electro-optical visual representation system including a non-rotating and non-inclined sensor which eliminates the complex platforms and intermediate systems between the sensor and the support team such as cryogenic coolers, computers, power supplies and the like.

We have just outlined the most relevant objectives of the invention. These objectives should be considered as simple illustrations of the most remarkable characteristics and applications of the invention. But it is obvious that other objectives and applications can be obtained by a different use or a modification of the invention; however, be aware that these possible different uses or modifications of the invention remain in the field and the scope of the invention of the device and method used in conjunction with an electro-optical sensor to explore and scan the objective hemispherical space in order to find and locate ¬ read potential targets.

SUMMARY OF THE INVENTION

The invention is defined by the claims with an embodiment set out in the drawings below. In short, the invention includes a. device and method for guiding the flux emitted by targets and backgrounds in the objective space on a dense focal plane located in an electro-optical sensor such as, but not limited to, a FLIR whose bandwidth will allow observation of the flux that interests us while other wavelengths will be filtered.

More specifically, the invention includes a device and a method of exploration which can be used in conjunction with various types of electro-optical visual representation systems in order to explore the hemispherical and voluetric space. to find and locate potential targets and allow the information collected on the target to be seen by the human eye and / or supplied to a computerized arms delivery system.

The device of the invention comprises a plane mirror large enough to encompass the fixed visual field of the sensor. The plane mirror is mounted on a mechanical system which causes an azimuthal movement of the mirror around an azimuthal axis of rotation centered on a perpendicular line, and geometrically centered on the focal plane of the sensor and around an elevation axis. perpendicularly offset from the azimuth axis of rotation and outside the: visual field of the sensor. With appropriate movements actively connected to the azimuth and elevation axes of rotation, it should be noted that the circular and azimuthal path of rotation is parallel to the focal plane and that the mirror rises around its axis of elevation close to the edge of the rotation path and constantly parallel to the focal plane of the sensor. A timing disk is actively connected to each axis of the mirror to provide the sampling commands in order to sample the scanned focal plane, to provide azimuth and elevation information in order to effect coupling with the pixel X addresses. and Y created, and then give the exact position of the target in space as well as the updated positions of the potential targets so that the computer controlling the weapon system can establish one or more predictable positions and then trigger the shot (s).

A computer allowing the control of all the electrical and mechanical functions of the invention controls the azimuthal movement of the mirror, whether it is in constant rotation of 360 degrees or in partial arc, the different rates of beaming and it also controls the extent of scanning and the scanning speed of the mirror elevation movement. This computer also accepts information and commands from the weapon system computer and gives information to the weapon system such as the azimuth and mirror elevation positions and receives and chooses the sampling times of the timing disc. In addition, the processing of information relating to the flux coming from the electro-optical focal plane can be optionally incorporated in this computer. Instead of a flat mirror with only one face, the mirror can optionally have two faces cut in the shape of a flat prism whose angle will be equal to the instantaneous visual field of the focal plane. An advantage of this two-sided mirror is that the system, using two focal planes, could see the objective space in an alternating sequential order and thus use a focal plane with a dense linear device whose elements are separated by a space. equal to their respective size. The method of the invention consists in the new idea of positioning the plane mirror in the manner described above and then simultaneously rotating the mirror around the azimuthal circular path of rotation a- when the mirror s 'pupil or decline ^' around the offset elevation axis.

Thus is created a spiral which tilts (or declines) allowing it to lead to a hemispherical exploration of 175 degrees minimum. In addition, while many test patterns of total or partial hemispherical exploration can be chosen by controlling the azimuth movements and elevation of the mirror using the computer controlling all the functions of the invention, it should be noted that the sensor itself remains static regardless of the test pattern. Consequently, unlike existing visual representation systems, the sensor used by our system does not need to be mounted on a mobile platform X and Y. It therefore follows that the difficulties of connecting the sensor with the others components of a visual representation system, such as cryogenic subsystems, power supply and others, are eliminated.

In conclusion, since the scanning system normally incorporated in a sensor is not necessary and can therefore be eliminated, the dragging, distortions and other parasites of the image which are always associated with a magnetic movement of an electro sensor. -optics which scan simultaneously, are discarded. Surely the use of the invention of the mirror for the scanning operation allows the sensor to be a fixed gaze device.

We have just sketched out the most important and relevant characteristics of the present invention in such a way that the detailed description of the embodiment chosen which follows is better understood and thus so that the present contribution to the technique be fully appreciated. It must be appreciated by those skilled in the art who know the technique perfectly that the specific design and production can be used as a base for modifying and designing other structures having the same objectives as the present invention. . It must also be carried out by these same skilled persons that such equivalent constructions do not depart from the spirit or from the field of the invention as set out in the Claims and that they belong to the field of 'invention.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the nature and objectives of the invention, it is necessary to refer to the detailed description which follows, associating it with the drawings.

Fig. 1 is a perspective view of the basic components of the device of the invention;

Fig. 2 is a simplified diagram illustrating the way in which the computer is connected for the purpose of controlling the various components of the device of the invention; Fig. 3 is a schematic view of the mirror of the invention juxtaposed with an electro-optical sensor illustrating the elevation movement of the mirror and the angles of the resulting hemispherical -research;

Fig. 4 is a schematic view illustrating the extent of the hemispherical search spiral when the mirror simultaneously rotates and tilts around its axes of azimuth rotation and elevation.

DETAILED DESCRIPTION OF THE SELECTED PRODUCTION

Referring to Fig. 1, the search device 10 of the invention comprises a plane mirror 12 actively connected to the chassis 14 to pivot around the elevation axis 16. The chassis 14 is actively connected to the annular surface 18 of the rotary annular base 20 The annular base 20 with the chassis 14 is placed above a conventional sensor, with fixed gaze, generally indicated by the number 22, having an objective lens 24 for focusing the flux coming on the focal plane 26.

More particularly, the different components of the research device 10 are linked together in the following way:

The annular base 20 of the device 10 is placed perpendicularly and this itre with respect to the longitudinal axis Z of the sensor 22. Therefore, the imaginary axes X & Y of the annular surface 18 defines an azimuthal rotation plane of the chassis 14 and the mirror 12 which is parallel to the focal plane 26 and centered on the axis Z. The elevation axis 16 of the plane mirror 12, mounted so as to be able to pivot in the chassis 14, is offset from the Z axis but perpendicular to this Z axis. In addition, the plane mirror 12 is placed relative to the the Z axis so that its longitudinal axis 28 intersects the Z axis each time the plane mirror 12 pivots about its elevation axis 16.

Conceptually, the elevation movements generally indicated by the number 30, are created by rotating the plane mirror 12 about its axis ^τ elevation 16. While the many different types ^"of movements vation élé¬ 30 may suffice , a type of motion of rose-r tion ^'30 may include a rectilinear movement 32 positioned collinearly with the axis Z of the device 10 and operatively connected to the rear of the plane mirror 12. During the operation, the rectilinear movement 32 operates to rotate the plane mirror 12 about its elevation axis 16. In the same way, the azimuth movement, generally indicated by the number 34, is actively connected to the annular base 20 with its annular surface 18 in the plane of azimuth rotation.

Without limitation, a type of movement azimuth 34 can include a rotary movement 36 having a swimming engre¬ wheel 38 rigidly secured to the annular base 20. Thus, the operation of the ^one rotary drive 36 operates by rotating the base annular so that its annular surface 18 rotates in the azi¬ mutal plane of rotation which is perpendicular to the azimuthal axis of rotation and parallel to the focal plane 26.

Numerous azimuthal timing marks 42 A can be provided on the annular gear wheel 10 to be read by a photo sensor 44 A to give information on the aziutal position and on the discrimination points of the annular base 22.De the same way, a similar combination of the elevation timing marks 42 E and the photo sensor 44 E can be provided incorporated into the elevation movement 3.0 to give the information of the elevation position.

As shown in the diagram in FIG. 2, the computer necessary for the invention, indicated by the number 46, is used to control the operations of the search device 10. Also, this computer 46 has a BUS interface 48. The main central processing unit (CPU) 50 of the computer 46 is connected to the BUS interface 48 to control the operation of the elevation movements 30 and azimuth movements 34 through the information received by the sensors 44 A and 44 E.

Others 1/0 52 can be connected to 1 .interface- BUS 48 allowing. the central processing unit 50 to be used for other sensor control systems 22 and / or for weapon control systems.

Fig. 3 and 4 illustrate the method of searching for the invention. More particularly, the method of the invention is best illustrated by the specifications of the chosen embodiment, however, it should be noted that the explanation of the chosen embodiment which follows is given simply by way of example: the elevation position of the mirror can be adjusted so as to see the objective space horizontally at 70 degrees at least elevation, without any obstruction of flow. Suppose that a dense linear focal plane of 360 elements and still suppose that the size of each element is 50 microns square, the length of the plane will then be equal to (360) (50 microns): 18 m. Suppose an instantaneous field of view of 0.5 mr, the focal length will then be equal to:

(element size 50 microns / 0.5 mr (instantaneous visual field) = 100 mm. Therefore, the visual field of the focal plane with fixed gaze will be equal to (0.5 mr) (360) = 180 mr = 10.3 de¬ about 10 degrees.

The desired total angle of the mirror is an angle which would produce a horizontal radius and a radius as close as possible to the vertical plane. With the focal plane with fixed gaze of 10 degrees, it then becomes obvious that the mirror placed so as to produce an extreme horizontal radius would be raised to 47.5 degrees above the horizontal plane. With the mirror at 47.5 degrees elevation, the focal plane with fixed gaze looks at the horizon and all of the objective space up to a point located 10 degrees above the horizon.

The invention, in order to be practical, must require the use of a plane mirror of a reasonable size because it is extremely difficult and expensive to maintain the flatness and the quality of the surface of a very large mirror. . Consequently, for the purposes of this example, the size of the mirror should not exceed 40 cm. The width of the mirror would be governed by the divergence of the fixed visual field as follows:

Minimum width equal to 2 Ç (length) (tan ^{field vlsuel Fixed} ^• ) = 2

L (40) (tan 5 degrees) = 70 m.

Thus, a 40 cm mirror with a reasonable objective lens will have a width of approximately 60 mm. It then becomes obvious that the flux will not experience any obscuration with the mirror raised to 77.5 degrees. With the mirror at 77.5 degrees elevation, the focal plane with fixed gaze looks at the horizon and all the objective space up to a point located 60 degrees above the horizon and an extreme point in the space located 70 degrees above the horizon.

It therefore follows that the more the mirror rises, the more the focal plane will darken. However, we can reasonably wait. that 1/4 of the focal plane can be used even if the other part has ceased to receive the flow of the mirror and we therefore see that the mirror can continue to rise even above 87.5 degrees and still reflect the flux on the focal plane with fixed gaze.

With the mirror at 87.5 degrees elevation, the obscured part of the fixed gaze focal plane looks at the horizon and all of the objective space up to a point 80 degrees above the horizon and an extreme point. in space 82.5 degrees above the horizon. We then see and we can clearly demonstrate that, in a practical and easily achievable sense, the invention can look, search, explore and scan at least 165 degrees of the objective hemispherical space and the opening angle of the mirror will only be 40 degrees, which is very easy to achieve. Indeed, we must not forget that today an electro-optical observation of the hemispherical objective space, as clear and at a speed as fast as that described above cannot be carried out with the means and existing systems today. The azimuthal movement is, in our example, continuous but it can be modified by the operator if he wishes.

The discrimination of the scanning line depends on the resolution of the frame, the size of the element, the overlay and the observation times of each pixel and the sensitivity which are desired. This example assumes a continuous azimuthal rotation speed of 1800 rpm = 30 rps.

Thus, 2 TT rad (30) / sec will be scanned. With a resolution of 0.5 bn, the scanning rate is equal to 377 (10) pixel seconds or an observation time for each pixel ^ = ^ 2.65 vsec / pel. This rate, although rapid, remains in the rate of generation and recombination of linear infrared focal planes, photoconductive typical as well as other optical spectra. The hemispherical objective space, or a part of it, can be explored by the tilting or declining mirror of 5 degrees by 360 degrees of the azimuth movement.

It then becomes clear that, for example, 140 degrees of the hemispherical scene can be explored in 8 revolutions of the mirror; this gives more than 4 explorations per second. In addition, if the instantaneous visual field of the sensors are, for example, increased by 1.0 mr, then the observation time of each pixel will double and the sensitivity will increase by MZ. • The delta elevation angle will then be doubled. Thus, 4 revolutions of the mirror will be able to explore the 140 degrees of the hemispherical objective space and this will give more than 8 complete explorations per second.

For this example, the azimuth and elevation speed of the mirror will be constant and very precisely coordinated. The rate of change of the mirror elevation angle will be 1/2 (total focal plane / 360 degrees of the azimuth movement. So, with a fixed total angle of 10 degrees from the focal plane, the delta elevation angle will be 5 degrees by 360 degrees and with an azimuth speed of 1800 rp, the elevation speed will be 1/72 of the azimuth speed.

In this example, the timing marks 42 A can be placed every 32 pixels with reset times at each revolution to ^' - ^' thus accommodate and correct errors due to mechanical friction and / or variations in speed training. An electronic clock will linearly provide the azimuthal position of the mirror between each timing mark.

Although this invention has been described in our example with a certain degree of specificity, it is understood that our example allows many modifications and improvements but that these modifications and / or improvements in construction, combination and 'arrangement of accessories can be made without departing from the spirit of our invention.

It is, for example, obvious that the present invention can and will be easily, with minor modifications, adapted and will find a useful application for any airborne system such as, but not limited to, airplanes, missiles, satellites, observation balloons, VPNs, and the like.

Claims

R E V E N D I C A T I O N S

1) A device for searching for objective space, characterized in that it is used in conjunction with a visual representation system having flat, dense and linear detectors and comprising in combination:

. a mirror with a reflecting face; and

. the azimuthal means for rotating the said mirror in a position facing the entry of the visual representation system in order to rotate the said mirror about an azimuthal axis of rotation and in an azimuthal plane of rotation, the azimuthal plane of rotation being parallel to and centered on the assembly of elements of the plane detector of the visual display system; and

. the elevation means for pivoting said mi¬ roir around an elevation axis offset relative to the azimuthal axis of rotation of said mirror and perpenicular to said axis of rotation.

2) The search device as described in Reven¬ dication 1 is characterized in that the means of said azimuth rotation continuously rotate said mirror around said axis of azimuth rotation.

3) The search device as described in Reven¬ dication 1 is characterized in that said elevation axis is placed outside the visual field of the visual representation system. 4) The search device as described in Reven¬ dication 1 is further characterized by the fact that it includes the means of capturing the angular position of rotation as well as the speed of rotation of said mirror around said axis. azimuth rotation.

5) The search device as described in Reven¬ dication 1 is characterized by the fact that it also includes the means for picking up the elevation position and the rate of inclination and declination of said mirror around said axis. elevation.

6) The search device as described in Reven¬ dication 1 is also characterized by the fact that it includes the computer means for controlling the operation of the means of said rotation and of the means of said elevation in order to produce a desired research sample from and into the hemispherical objective space by controlling the direction and degree of movement of said mirror around said azimuth axis and said elevation axis.

7) A method of activating the search device used in conjunction with a visual representation system having flat, dense and linear detectors and comprising the following steps:

. the provision of a flat mirror with a reflecting face;

. said mirror is rotatably mounted in position opposite the entrance to the visual representation system and rotates in an azimuth plane of rotation parallel to and centered on the assembly of elements of the plane detector of the visual representation system; and

. said mirror pivots in elevation around an elevation axis offset relative to and perpendicular to the azimuthal axis of rotation of said mirror. 8) The search method described in Claim 7 is characterized in that said mirror rotates continuously around said azimuth axis of rotation.

9) The search method as described in Revendi¬ cation 7 is characterized in that said mirror pivots around the elevation axis but also in that said elevation axis is located outside the visual field of the sys ¬ visual representation theme.

10) The search method as described in Claim 7 is further characterized by capturing the angular rotary position as well as the speed of rotation of said mirror around said azimuth axis of rotation.

11) The search method as described in Revendi¬ cation 7, also includes capturing the elevation position and the rate of inclination and declination of said mirror around said elevation axis.

12) The search method as described in Revendi¬ cation 7 includes, moreover, the control by a computer of the means of said rotation and of the means of said elevation to produce a test and search pattern desired by the control of the direction and the degree of movement of said mirror around said azimuth axis and said elevation axis.

13) The search process as described in Revendi¬ cation 7 is characterized by a way of simultaneously scanning and panning the objective hemispherical space using a plane mirror rotating around an azi¬ mutal plane to create the horizontal lines of the image and the sampling points along these horizontal lines to create the vertical lines of the image and therefore the complete frame, avoiding and almost completely eliminating the shift, the overlap, the curl and the drag pixel by pixel (picture element) and line to line.