NO156104B - OPTICAL OBJECTIVES FOR A TARGET RECORDING AND CONSEQUENCE SYSTEM. - Google Patents

Description

-L

The present invention relates to optical sights for target registration and tracking systems, and systems that include such sights.

In today's weapon systems extensive use is made of laser pointers, where an advanced observer visually locates a military target and then directs a coded laser beam at the target. The observer coordinates with a weapon firing system to direct the fire at the target. Such firing will include a control system, which recognizes the laser point and directs the firing at the target. This instruction can be carried out by ground personnel on foot or in vehicles. A more effective operation can, however, be carried out with a reconnaissance helicopter. In known helicopter systems, visual reconnaissance and localization of targets lead to the entire helicopter and crew being in an exposed position vis-a-vis the enemy and becoming particularly vulnerable.

Systems have been proposed, where the observer can be hidden from the enemy and the target can be located using a television system. In the case of a proposed solution, a sight is mounted on

a mast that extends above the rotor level of the helicopter, allowing the helicopter to remain behind covering foliage or terrain, with the scope mounted on the mast projecting high enough above the te-levis ion camera to locate the target. Although the idea is appealing, the implementation of this type of system presents a number of problems. It is e.g. necessary to stabilize the sight's optical elements due to the helicopter's natural movements. Stabilization of the entire sight will require relatively heavy servo motors etc. Another possibility is to use a rigid sight, where only the optical elements are stabilized. This could be done with lighter elements.

The robust design required of such a sight to be mounted on a mast above the rotating helicopter blades and the required stabilization create a major weight reduction problem, as known robust stabilized systems have proven

to have too much weight for this application. It is also necessary to combine the TV system, which provides the visual localization of the target, with a laser guidance system to enable

indication of the target after it has been located. The highly collimated laser beam usually produces a very small spot and is therefore very sensitive to movement if it is to be held on the target. Therefore, very precise stabilization is required.

According to the invention, an optical sight has been provided for a target registration and tracking system, as the sight can be mounted on a mast and comprises an optical substrate with a longitudinal axis, a laser pointer, a laser rangefinder, a television ion camera for the production of a video signal representing an optical image of a target, first optical means mounted on the optical substrate to direct a laser beam reflected from the target to the laser range finder,

and other optical organs which function to direct the light forming the optical image of the target towards the television camera, which is characterized in that a gyro-stabilized mirror with a two-axis gyroscope is mounted integrally with the optical substrate, whereby the mirror is held at a selected level in relation to the longitudinal axis of the optical substrate, the two-axis gyroscope including a wobble hoop arrangement which is supported by a pair of wobble hoop brackets which are integrally formed with the optical substrate, the wobble hoop arrangement can be a elevation axis, at the same time that the gyro-stabilized mirror reflects both the light that forms the optical image towards the first optical device and the laser beam from the first optical device towards the target and vice versa, and the second optical device is mounted on the optical substrate and cooperates with it first optical means for directing the optical image light of the target towards the television camera while the second optical means comprises a rotating rt adjustable density optical filter which is arranged so that the optical density varies with rotation, a lens system for a narrow field of view, a movable lens system for a wide field of view, as well as a drive motor for both selective adjustment of the optical filter during its rotation and for movement of the lens system for a wide field of view into and out of the optical axis of the second optical organ.

A number of new structures have been arranged in the aiming unit, and these in combination have enabled the necessary lightweight design. Firstly, the optical laser system and the optical camera system are largely integrated. The optical substrate is also utilized for the integration of the separate elements in the aiming unit, so that the weight of the support structures that were necessary in known units is reduced to a minimum. The aerodynamic housing has an optical window at its front end, at right angles to the longitudinal axis. Just behind the optical window is a gyro-stabilised mirror. The optical substrate comprises support brackets for mounting a first wobble bracket for the stabilizing gyroscope, so that the housing and mounting elements that were common and necessary in known systems are eliminated. A second wobble bar is rotatably mounted in the first wobble bar and contains the two gyro scopes. The mirror is also rotatably arranged in the first wobble hoop and is operatively connected to the second wobble hoop by means of bands of the steel band type and washers. The axis of the first wobble bar extends across the longitudinal axis of the housing and forms an elevation axis for the gyroscope, while the second wobble bar has its axis running vertically to form an azimuth axis. The wobble bracket-suspended mirror can therefore be turned both in azimuth and elevation. But the mirror has a limited angular range in the azimuth direction. It can e.g. be ± 2°, which is sufficient to remove residual aiming and stabilization errors resulting from movement of the housing and azimuth. When greater azimuth movement than 2° is required, the entire unit can be rotated around the mast at an angle of - 160°. In elevation, the mirror can be turned at an angle of - 15°.

The laser pointer and the laser rangefinder are mounted on the optical base. The optical path through the house window, from the wobble bar-suspended mirror and to the laser designator and rangefinder passes through a dichroic beam splitter, which is essentially transparent to the laser frequency energy and reflects visible light. An optical image on the mirror will therefore be reflected by the beam splitter and sent to the camera via the optical television system. The optical television system comprises a fixed lens unit for narrow field of view (NFOV), a neutral density filter with adjustable light transmission characteristics and a movable lens unit for wide field of view (WFOV). The filter is a disc, which can be rotated to vary the light transmission and is automatically controlled by the video circuits in the electronics unit to maintain optimal contrast of the television scene. The WFOV lens unit is moved out of the path to provide a narrow field of view for the TV system. When a wide field of view is desirable, e.g. during target localization, the WFOV lens assembly is moved into the optical path.

A new feature of the optical television system, which advantageously greatly reduces the weight of the aiming unit, is the use of a single drive motor for the filter disc and for the moving WFOV lens unit. A small, lightweight motor drives the filter disk via a gear train, where the motor is mounted at one end of a balanced rocker arm, which is rotatable about the axis of the filter disk. On the opposite end of the rocker arm, the WFOV lens unit is mounted. A switch mechanism, operated by a solenoid, holds the rocker arm in one of two positions, where the WFOV lens assembly is in the camera optical path in one position, while the WFOV lens assembly is out of the optical path in the other position.

A clutch unit is connected to the filter disc and is used as a brake when the clutch is engaged. During normal operation the solenoid is not energized and the rocker arm is locked in one of the two positions, the filter disc clutch is disengaged and when the motor is activated it will therefore rotate the filter disc. When the operator wishes to change the optical system's field of view, the solenoid is activated, so that it simultaneously engages the clutch unit, which brakes the filter disc and disengages the switch mechanism. In this condition, with the engine running, the gear connected to the filter disc is held stationary and therefore the engine gear ratio will cause the motor and rocker arm to "wander" around the stationary filter disc gear. This movement of the arm will bring it into its second position. At this point, a limit switch will release the solenoid, causing the arm to set in the new position and stop the motor. The switching can advantageously take place within a fraction of a second and will therefore not interfere with the normal automatic operation of the filter disc.

Rotation of the entire aiming unit is achieved by means of a small motor and a gearing in a small support which is used for mounting the aiming unit on the mast.

The electronic units that can be mounted in the helicopter fuselage include the electronic video unit and the electronic servo unit. There is a control panel for the operator with a cathode ray tube TV display with a crosshair in the center of the screen, framed by a rectangular window. Auromatic tracking circuitry in the electronic video unit controls the rectangular tracking window in the display to center it in a selected manner. The circuits register the contrast difference between the target and the background and form control signals for the electronic servo unit. The electronic servo unit sends control signals to the torque motors on the gyroscope in the aiming unit and to the azimuth drive motor, so that the aiming unit and the stabilized mirror follow the target. The laser beam is centered in the reticle, which represents the aiming unit's line of sight. When a target is kept centered in the tracking window, operation of the laser pointer will thus cause a laser point to be placed directly on the target.

To ensure that the laser beam is correctly created in relation to the center of the reticle, a new barrel sighting system has been installed. The aiming unit includes a small corner reflector, which has the characteristic that it reflects a laser beam at a 180° angle, regardless of its angle of incidence on the reflector. When the aiming system is first engaged, a barrel aiming routine causes the stabilized mirror to rotate against its mechanical stop, causing the laser designator beam to be reflected from the stabilized mirror to the corner reflector, back to the stabilized mirror and thus to the beam splitter, where a small proportion of the laser beam reflected to the optical television system. The laser point therefore induces a video signal in the electronic video unit. The crosshair circuitry will automatically vary the reticle position to accurately center the laser dot. The operator can also initiate the automatic barrel aiming procedure manually, when this is required.

The electronic servo unit also receives signals from the azimuth and elevation measurement verifiers for the stabilizing gyroscope in the aiming unit. Thus, any deviation of the aiming unit's aim in space will result in control signals, which drive the torque motors to keep the mirror in the correct position.

The electronic video unit is also used to record the contrast in the televised scene and to automatically control the variable density filter to maintain maximum contrast between the target and the background.

At the operator's place is provided a lever, which includes switches, which can be operated with the operator's thumb and fingers to allow manual target tracking in azimuth and elevation, for changing the tracking polarity, depending on whether a target is very dark or very bright, for instant changing the television system's field of view and to operate the laser pointer and the laser rangefinder. Digital readouts are provided on the control panel to indicate range, line of sight direction in azimuth and line of sight angle in elevation.

Other purposes and advantages of the invention will

proceed from the following description of the best ways of carrying out the invention, seen in the light of the drawing.

Fig. 1 shows a greatly simplified block diagram of the main elements of the invention. Fig. 2 is a perspective view of a helicopter equipped with the invention while following a military tank and targeting this target. Fig. 3 is a rendering in perspective, showing an alternative mounting of the invention on the tank, with the aiming unit mounted on an extendable mast which can be raised above obstacles in the foreground. Fig. 4 is a functional block diagram of the aiming unit according to

the invention.

Fig. 5 is a simplified, partially functional diagram of the aiming unit and shows an approximate arrangement of the components. Fig. 6 is a partial view of the optical substrate and shows the integration of the gyro stabilizer in the substrate and suggests the stabilized mirror. Fig. 7 is an elevation of the aiming unit with the housing removed, showing a typical arrangement of the physical elements. Fig. 8 is a side view of the aiming unit according to fig. 7, partially broken away to illustrate the physical relationships between the elements including the azimuth drive mechanism. Fig. 9 is a simplified, exploded view of the automatic control mechanism for the light filter and the mechanism for changing the field of view. Fig. 10 shows a front view of a typical control panel and TV display, and also shows the manual control lever. Fig. 11 is a simplified, functional diagram of the entire system according to the invention and illustrates the electronic control parts connected to the aiming unit's elements.

The TV/laser aiming system according to the invention for mounting on a mast can be used for a number of scenarios. The basic elements of the system will, however, be the same for all applications. In fig. 1 is a block diagram of the elements of the invention shown with reference to a particular installation, such as the vehicle 2. The vehicle 2 may be a helicopter, a tank or another land-based vehicle, or it may represent a fixed building or the like. At each installation, a mast 5 is arranged to raise the sighting unit 10 above elements in the terrain. The aiming unit 10 comprises a laser system and a television camera system, as discussed in more detail below. The control panel 50 and display 60 are grouped at the operator's place, which e.g. could be in a helicopter cabin. When using the control board 50, the operator can control the sighting unit manually to initiate tracking or to set the sighting unit 10 to automatic operation for automatic tracking and for other functions. The information gathered by the aiming unit 10 is received by the control board 50 and directed to the display 60, which utilizes a television screen, where one can see the target area, the target and a laser point. An optional mast guide 70 is suggested and required in fixed ground installations and in ground vehicles, where an extendable mast is used to repel the aiming unit 10.

Figures 2 and 3 show two typical applications of the invention. When the aiming unit 10 is used in a helicopter 100, as shown in fig. 2, it is advantageously mounted on a short mast projecting above the rotor blades, as indicated. The helicopter can hover behind natural terrain formations, such as trees 102, and the sighting unit 10 is able to locate and follow the target, such as a tank 104. An embodiment of the invention provides for following a target over -160° in azimuth and -15 ° in elevation, as indicated in fig. 2. Fig. 3 illustrates use of the sight which is mounted on a mast, adapted for a tank 106 and comprises an extendable mast 105, which is mounted on a tank 106, where the mast is shown in a partially extended position. As indicated in fig. 1, the system in this case will comprise a mast control 100 to raise the sighting unit 10 to the desired level to see over obstacles for target location and tracking.

In fig. 4 shows a functional block diagram of the aiming unit 10. The aiming unit comprises two separate

rate systems: a laser designator/rangefinder system 24,26; and a television camera capture system 20,22. These and other elements in the aiming unit 10 are installed on a rigid, optical base which will be described later. A common optical system 16 is mounted on the optical substrate and leads light to and from the laser system and to the TV system. To allow movement of the vehicle, a final exit mirror is 12

stabilized by a gyro stabilizer 14, which allows the optical substrate and housing to move relative to the mirror 12 over a limited range, while the mirror 12 maintains the line of sight fixed in space. The laser designator 24 generates coded laser pulses in the conventional manner of a military laser designator system. Indicated by the line A, these pulses are sent via a common optical system 16 and a mirror 12 to the desired target. General illumination of the target area by light in the surroundings enables the television camera 22 to form a television image of the scene. The optical image is reflected by the mirror 12 through the common optical system 16 to the optical TV system 20, to the camera 22 as indicated by line C. A crosshair image in the center of the television frame in the display 60 can be used for insight. The system's crosshairs are adjusted so that the laser point from the laser pointer 24 on a target will arrive exactly at the crosshairs of the crosshairs on the television screen. The adjustment element 18 for the barrel sight is arranged so that it allows precise adjustment of the system so that the laser beam A is centered in the reticle. In addition to receiving optical images from the scene, the reflection of the laser pulse from the laser designator 24 on the output line A, which hits the target, will be received by the mirror 12, as indicated by line B, and will be directed to the laser range finder 26 via the common optical system 16. The distance meter 26 can, by measuring the delay between the sent indicator pulse and the received distance measurement pulse,• measure the distance from the vehicle to the target.

A simplified diagram of the mechanical elements of the aiming unit 10 can be noted with reference to fig. 5. Here, the rigid optical substrate is indicated by a dashed frame 11 with the fixed elements indicated by the earth symbols. A gyro unit 14 is shown rigidly attached to the optical substrate 11 and used to stabilize the mirror 12, as indicated by the dashed line. An optical window 13 is provided in the unit, which is completely encapsulated to prevent contamination. As indicated by the beam tracking lines, the output from the laser designator 24 (line A) first passes a dichroic beam splitter 17, is then reflected off the adjustable mirror 15 to the gyro-stabilized mirror 12 and then through the window 13 to the target. The laser return, shown by beam trace B, enters through the optical window 13 and is reflected by the stabilized mirror 12, by the adjustable mirror 15 and through the dichroic beam splitter 17 to the laser range finder 26. The optical image implied by the beam trace C is reflected by the mirrors 12 and 15 and to the dichroic slit window 17, which then reflects the light through the optical TV system 20, which may comprise a fixed lens system 19, a movable lens system 23, an optical filter system 21 and a prism 27 to the vidicon camera 22. The lens system which is schematically indicated with the lens 19 is a narrow-angle element which is fixed in place and rigidly mounted on the optical substrate 11 and provides a narrow field of view (FOV). The filter 21 is a neutral density filter wheel, which is used to maintain an optimal light level at camera 22. The filter can be controlled manually or used in an automatic (ALC) mode of operation under the control of is servo loop to vary the filter density as the light level outside changes. The lens 23 schematically represents a wide-angle optical FOV unit, which is arranged so that it can be moved in the optical path of the TV camera 22 for initial target acquisition and is adapted to be swung out of the path on the direction of the target, so that only the narrow FOV lens system 19 are in operation.

As mentioned above, it is necessary that the beam from the laser pointer 24 is centered in relation to the running sight of the TV display which is generated by the vidicon 22. A running sight adjustment can be made with the help of the corner reflector 18. A corner reflector, like the corner reflector 18, as is known, has a characteristic which means that it will direct a collimated beam 180° backwards from the angle of incidence. Therefore, the mirror 12 is temporarily turned against a mechanical stop to cause the laser beam A to be reflected against the corner reflector 18, which will reflect the received beam back along its incident path, and it will hit the surface of the mirror 15 at the same point as the beam from the laser pointer 24. The geometry of the unit is arranged so that this reflected beam is sent to the dichroic beam splitter 17, which reflects a small fraction of the beam through the optical system 20 to the vidicon 22. The operator will see the point la approximately in the center of the display 60. Camera 22 is equipped with control means in the electronic parts of the control board 50 for electronic adjustment of the TV frame's position in relation to the laser point, so that the point appears on the crosshairs in the TV display. It can also be ensured that the barrel sight adjustment takes place automatically via a servo-type system. When the system is first energized during such operation, it will automatically adjust or trim the barrel sight, and the correction will be stored in digital form. In addition, the operator can at any time trigger a restoration of the race sight. After the barrel aiming operation, the mirror 12 is returned to its normal position.

In order for the aiming unit 10 to be able to mount

raised on a mast above the rotor blades of a helicopter and at the top of a tall mast, it is crucial that the weight is minimised. For this purpose, the aiming unit advantageously uses a new optical substrate 11, where support frames and ribs are arranged which provide the necessary rigidity for the optical elements by integrating the optical substrate 11 and the supports. As an illustration of such an integration, fig. 6

a simplified representation of the mirror 12 with its gyro stabilization system 14, supported by brackets 42 and 41 which are integrated into the improved structure of the optical substrate 11. Gyro stabilization units are known in the art, but until now have only been available as a complete unit with an external framework with sufficient strength and mass to support the sway bars, the gyro elements, the torque motors, the measuring value transmitters and other elements of the gyro unit. Such known devices were not suitable for the preferred embodiment of the present invention because of their size

weight. As shown in fig. 6, a pair of support brackets 41 and 42 are molded into the base plate 11 and braced with steps and suitable reinforcements, so that sufficient rigidity is created with a fraction of the mass and weight required in known units. The gyro unit 14 consists of the wobble bracket 43, which is rotated about a central axis through the brackets 42 and 41. The elevation axis of the wobble bracket 43 runs across the aiming unit 10, where the window 13 (Fig. 5) is considered as the front of the aiming

the unit 10. The inner wobble bracket 40 is mounted on the outer wobble bracket 43 with its axis vertical to represent the azimuth axis. Inner wobble bar contains the azimuth detection gyroscope and the tilt detection gyroscope. An elevation measurement value transmitter and torque generator 49 is assigned to the elevation swing bracket and an azimuth measurement value transmitter and torque generator 48 is assigned to the azimuth swing bracket. The azimuth axis can be moved - 2°, which is sufficient to remove residual line-of-sight errors that were caused during azimuth-disturbing rotations of the optical substrate 11. As previously mentioned, the tower drive on azimuth has a range of - 160°, and is operated in response to signals from the azimuth measurement value - the sensor on the sway bar axis to keep the internal axis within its - 2 degrees of freedom. When a change in azimuth is commanded, the slew rate is up to 40°/second, but

will rotate one radian/second in the stabilized mode of operation to accommodate the yaw rates of the aircraft. The elevation sway bar has - 15 degrees of freedom, which can be extended to 45°, with 50% vignetting. When a change in elevation is commanded, the elevation yaw rate of movement is up to 15°/second and will accommodate flight pitch rates of one radian/second.

As will be seen from fig. 6, the stabilized mirror 12 rotates on bearings 47 and is controlled by the inner wobble bracket 40 via a tight steel band 46 on discs 4 4 and 45. When the wobble bracket 40 turns about its axis in response to the torque generator 48 as shown by arrow E, the mirror disk 4 5 is turned as shown by arrow F.

The physical arrangement of the aiming unit's 10 elements can be seen from the outline of the preferred embodiment according to fig. 7. An outer, rolled edge 38 of the substrate 11 is indicated in cross-section. The optical window 13 can be seen in the front of the unit with the optical center line indicated by the dashed line. The stabilized window 12 can be seen stabilized by the gyro stabilizer 14. The optical centerline is shown reflected by the adjustable mirror 15 and the dichroic beam splitter 17 through the optical TV system, including the narrow FOV optic 19. Next in the optical path is the filter disc 21 which has a continuously variable neutral filter density characteristic over a range of 0 to 3 in density, giving a dynamic illumination range of 1,000 to 1. The filter wheel 21 has a spectral emission range of 0.68 to 1.1 microns, which extends into the near infrared. This increases the contrast of scenes where there is infrared reflective vegetation. The filter wheel 21 is controlled by the drive unit 37, which comprises a drive motor, a solenoid and a potentiometer for position control for barrel screening. The operation of the drive unit 37 will be described in more detail below and can be controlled manually or automatically to control the filter wheel 21 to a selected illumination level for camera 22. Then follows a wide-angle lens unit 23 in the optical path. The system's field of view, when only the narrow viewing angle lens 19 is active, is 2.5°. With the wide-angle lens unit 23 for the field of view in operation, the field of view is increased to 10°. The wide-angle lens unit 23 is movable and can be driven by the motor drive unit 50 into the optical path of the camera 22 or out of the path, so that it changes from a wide-angle field of view to a narrow-angle field of view. The filter and prism unit 27 is the next unit in the optical line and directs the incoming image to the vidicon camera 22.

Preferably, a high-resolution camera is used, e.g. gives the J.ie-t television camera with 875 lines, 30 images/second and a 2 to 1 line jump factor ("interlace") a satisfactory resolution. Camera 22 thus converts the near-infrared images from the device into a video signal, which is sent to the TV display. The camera can use a silicon target vidicon, which in combination with a filter on prism 27 and the filter wheel will have a response of 0.65 to 1.1 microns. The camera circuitry allows adjustment of the scan grid position horizontally and vertically for barrel sight control. The camera's electronic circuitry is also adapted to allow only the middle half of the field of view to be scanned. By combining this electrical subscan and the optical wide field of view and the optical narrow field of view, four fields of view are available, 10°, 5°, 2\° and 1.25°.

The laser system consisting of the pointing laser 24 and the rangefinder receiver 26 is mounted in the rear of the unit with the input lenses mounted vertically, one above the other, behind the dichroic beam splitter 17. The beamsplitter 17 will reflect energy at 0.7 to 0.9 microns for the optical TV path and will send energy at 1.06 microns, which is the laser's light wavelength for laser guidance and distance measurement. The adjustable mirror 15 is made of beryllium. When the stabilized mirror 12 is in its barrel aiming position against the mechanical stops, it will reflect the laser beam from the pointer 24 to the corner reflector 18, then from the reflector 18 back in the opposite direction to the dichroic mirror 17, which reflects part of the energy through the optical TV system and into camera 22. The electronic circuits for the scanning grid position can then be controlled for centering on the reflected laser point to obtain a barrel sight. These circuits are arranged so that they automatically adjust the barrel sight, when the unit is first switched on, and under the control of the operator they can also be ordered for repeated barrel sighting of the system when this may be advisable.

As previously mentioned, the aiming unit 10 can be scanned - 160° in azimuth. Fig. 8 shows a partially broken cross-section of the aiming unit 10, which shows the azimuth drive mechanism. The upper part of the sight is enclosed in a streamlined housing 25, which is".

shown partially broken away with the optical window 13 in the front".<*>»

(Mirror 15 has portions of the gyro structure.) The dichroic beam splitter 17 is shown in front of the optical television camera unit 20. A connecting cable 35 is shown connecting to the various electrical elements in the aiming section. The drive section 31 is provided with an azimuth drive motor 32, which

includes a brake and a tachometer. The drive motor 32 is connected to the shaft 30 via gear 34 and gear 36. An annular bearing 33 and a shaft support bearing 39 are shown and the tower unit is mounted on these.

The details of the motor drive device 37 which drives both the neutral density filter wheel 21 <p>g the wide field of view (WFOV) optical unit 23 is shown in Fig.9. As previously stated, weight is a critical parameter when it comes to a sight mounted on a mast. Advantageously, a novel dual function motor controller 37 is used to operate the neutral density filter 21 and also to move the WFOV optical unit 23 from a non-operational to an operational position and vice versa. This results in noticeable weight savings compared to the use of separate drive systems for each element. A simplified and exaggerated representation of the motor drive system 37 with the filter 21 and the WFOV lens unit 23 is shown. Certain parts have been cut away and certain support structures have been omitted for reasons of clarity. The neutral density filter wheel 21 in the front of the unit is mounted on a rear projecting short hollow shaft 91, which is shown in an exploded view. Hub and shaft 91 rotate in an appropriate bearing in the center support 80b. The drive gear 87 is attached to the hollow shaft 91 and, as will be described, will drive the filter disc 21 to a desired position. A clutch cup 93 is attached to the front surface of the filter disc 21 collinear with the shaft 91. A cooperating clutch cup 94 is mounted facing the disc clutch cup 93. The clutch cup 94 is displaceably mounted on the hub 96, which is rigidly attached to the front support 80c. The opposing edges of the clutch cups 93 and 94 are toothed so that their teeth can mesh with each other. The bowl 94, which is displaceably arranged on the hub 96, is held at a distance from the filter disc bowl 93 by a spring 95. The drive rod 59, which extends through and is concentric with the shaft 91 and extends through the clutch bowls 93,94 is connected to the displaceable bowl 94 The drive rod 59 is connected to the armature 97 for the solenoid 55, which is mounted on the rear support 80a. As will be noted, solenoid 55 armature 97 is also coupled to rod 57, which abuts detent pins 65. When solenoid 55 armature 97 is in its non-driven position, plate 57, detent pins 65, and rod 59 are in an advanced position and the clutch cup 94 is out of engagement with the clutch cup 93. When the solenoid 55 is in operation, the rod 59 pulls the clutch cup 94 rearward as. shown by arrow J, and in engagement with the clutch cup 93. This movement also pulls the pins 65 backwards, as shown by arrow H. Although the clutch cup 94 is displaceable on the hub 96, it is wedged and therefore prevented from rotating. Thus, the operation of the solenoid 55 and the engagement between the clutch bowls 94 and 93 will keep the filter disk 21 in a fixed position and prevent the gear 87 and the shaft 91 from rotating, while the solenoid is energized and the field of view changes, as further discussed below.

A balanced transverse rocker arm 98 is provided and has a central bearing 92, which sits on the shaft 91, but is shown in exploded view. As shown, the arm 98 can tilt between two fixed positions, as indicated by arrow G. The two positions are limited by adjustment holes 81 and 82 in the hub of the arm 98. When the solenoid 55 is in its non-energized position, the detent pins 65 will engage in each of the adjustment holes 81 or 82. In fig. 9, the arm 98 is shown so that the locking pins 65 will engage in the adjustment holes 81 and in such a position the figure represents the wide field of view condition of the optical television system. The solenoid armature 97 is inhibited from rotation, therefore the locking pins 65 serve to prevent the arm 98 from rotating. The arm 98 is attached to the optical WFOV unit 23 at one end and supports at its other end the drive motor 53 and the position sensor 99, which may be a potentiometer. The motor 53 is gear-connected to the filter disc drive gear 87 by a small gear 89 and the intermediate gear 88, both of which are mounted on the arm 98, but only shown in the extended position in the figure.

As will now be understood, operation of the motor 53, when the arm 98 is locked in the wide field of view position in fig. 9, result in rotation of the filter disk 21, as shown by arrow K. In normal operation, the motor 53 can be servo-controlled via an electronic control system to be activated when the light level is either too high or too low. When the filter disc 21 is moved to correct filtering to achieve the determined light level,

the motor 53 is switched off to maintain said light level. As the clutch cups 93 and 94 are held apart by the spring 95

in the non-driven position of the solenoid 55, there is nothing to inhibit rotation of the filter disk 21. When it is desired to

te from the wide angle of view, which is shown as an example in fig. 9, to the narrow viewing angle, it is necessary to move the arm 98 to its second position, which removes the WFOV lens unit 23 from the TV optical path. This operation is carried out by energizing the solenoid

55, which evokes two functions. Firstly, the locking pins 65 are pulled out of the setting holes 81, so that the arm 98 is freed for rotation about the shaft 91. Secondly, the fixed brake cup 94 is pulled backwards to engage with the filter clutch cup 93 and thereby lock the filter disc 21 in its current position. Next, the CCW winding of the motor 53 is activated to cause rotation of the drive 88, which is engaged with the now locked drive 87, for rotation in the direction L and thereby to move the arm 98 from its position for the wide field of view to the position for narrow field of view, as indicated by the arrow G. In order to stop the arm 98 in the correct position, a shutter 85 is arranged with two openings 86a and 86b. A light-emitting diode (LED) 83 and a photosensitive detector 84 are shown, while their supporting structure is omitted for reasons of clarity, so that the output from the detector 84 is only obtained in the two positions where one of the openings 86 is in line with the LED and the detector. But other devices can be used, such as limit switches. When the motor 53 rotates the arm 98 to the narrow field of view position, the opening 86b in the shutter 85 will thus cause appropriate switching circuits to de-energize the winding of the motor 53 and engage the clockwise winding of the motor 53 for subsequent return of the arm 98 to the wide position field of vision and for energizing signals indicating which field of vision is in use. When the arm movement stops, the solenoid 55 is released, so that the locking pins 65 can engage in the setting holes 82, which represent the position for narrow field of view. As will be appreciated, the WOFV optical unit 23 will have moved out of the centerline optical path of the optical television system and will leave only the narrow field of view optical system 19, as previously discussed, remaining in said optical path. At the same time, the clutch cup 94 is brought out of engagement with the clutch cup 93 by the spring 95 and the filter disc 21 is then free to operate

as needed to maintain the desired medium light level.

It is necessary that the switching of the optical system from one field of view situation to the other field of view situation can be achieved within a very short time in order not to disturb the automatic light level control function of the filter disc 21 and to give the operator an opportunity for continuous observation of the target area. The new motor control unit 37 performs the change of viewing angle in a fraction of a second in an advantageous manner.

When the optical WFOV unit 23 is in the driven position as indicated in fig. 9, it is crucial that it is held firmly to prevent jitter in the observed images. For this purpose, the detent pins 65 and adjustment openings 81 are spring biased with the spring pin 66. When the motor 53 is activated to move the arm 98 from the narrow field of view position to the wide field of view position, the optical unit 23 contacts a spring pin 66 and presses it together against a spring. When the engine stops and the locking pins 65 enter the openings 81, the spring-loaded pin 66 will press the arm 98 against the pins 65 to create the necessary rigidity. This feature makes it possible to allow the setting openings 81 to be somewhat larger than the locking pins 65, so that alignment problems are eliminated in the setting unit.

When the structure of the preferred embodiment of the aiming unit 10 has now been described in detail, the operation of the system shall be explained with reference to fig. 10 and 11. Fig. 10 illustrates a typical control panel position and fig. 11 shows a simplified functional block diagram of the control system.

In fig. 10, the TV monitor 60 is shown installed in the control panel unit 50. The TV monitor may be a high resolution Conrac 8" monitor. The TV viewfinder 54 in FIG. 11 generates a rectangular viewfinder window 62 which appears on the display monitor 60. In addition, a crosshair is generated 61, where a target will be centered when the system is operated for automatic search. Video circuitry 54 generates four "field of view" beams ("bars") 63, spaced across the top of the image with a beam illuminated, to represent the field of view of the system's four fields of view that is in use at any given time. In addition, tic marks 64 are generated, which may appear on one side of the screen and along the bottom of the screen. These tic marks are moved in accordance with the azimuth and elevation yaw bar position by the gyro unit 14 and will therefore indicate the position of the line of sight of the aiming unit 10 in relation to the line of sight of the aircraft for the operator. The control panel 50 comprises a number of push button switches and indicator lamps 68 along the left side. These switches controls the system's power, the laser power and allows selection of a directed or stabilized mode of operation. Indicator lights indicate the status of motion sickness, laser operation and other monitoring functions. A code selection switch 78 controls the laser coder 69 in fig. 11 to enable selection of the correct triservice code for the laser pulse repetition frequency. The digital digit readout 75 shows the distance of a target in meters. The azimuth reading 76 gives a digital reading of the target's azimuth in degrees, and the elevation reading 77 gives the target's elevation in degrees. The azimuth potentiometer 79 and the elevation potentiometer 67 allow manual control of the sight in azimuth and elevation.

As shown in fig. 11, servo control circuits 56 control the gyro unit 14, activate the torque motors for turning the wobble brackets as needed and receive position and speed information from the encoders in the gyro unit 14. When rotation in azimuth of more than -2° is required, servo circuits 56 control the azimuth drive motor 32 which serves to turn the entire aiming tower to the desired azimuth course. The control of the gyro unit 14 and the azimuth drive motor 32 can be operated in a directed or stabilized manner. With the directed method, the scope's line of sight is subordinate to the cell ("airframe") and will change with changes in the aircraft's attitude. The line of sight can be adjusted in relation to the aircraft's course using the azimuth potentiometer 79 and the elevation potentiometer 67 on the board 50. In the stabilized method, the azimuth and elevation gyroscopes in the gyro unit 14 act as a platform in free space with respect to the mirror 12 and the line of sight of the optical system and the laser system will remain fixed in space when the aircraft is maneuvering. Measured value signals from the gyro unit 14 are processed by the servo control circuits 56, which then control the torque transmitters and the azimuth drive motor 3 2 to keep the platform fixed in space. The operator can override the stabilized steering by using the thumb control 71 for the lever. The control 71 can be operated in both the X and Y directions to generate the control signals for the servo circuits 56. By pushing the control 71 up or down with the thumb, the operator can thus control the field of view of the sight in elevation, and by pressing to the right or left, he can control field of view in azimuth. The switch 73 is a two-position switch that can be pressed down to reduce the field of view. The switch 7 2 is used when the system works according to the automatic following method and can choose whether the follower works with a black-on-white or a white-on-black target type.

The operator can choose manual or automatic light control. When the light control is automatic, the ALC servo circuits 58 will activate the motor 53 for turning the filter disc 21 with feedback obtained from the video circuits 54, which measure the top light level of the television scene. The motor 53 will thus stop when the correct part of the filter disc 21 is in the optical path. The operation of the field of view circuits is by means of the switch 73, which controls the servo circuits 58. The solenoid 55 is operated, braking the filter disc 21 and unlocking the WFOV lens 23, as previously described, to allow the motor 53 to move the lens 23 in and out of the optical track as needed.

When the system power is first switched on by operating the corresponding switch on the control board 50, the barrel aiming sequence is automatically carried out, which causes the wobble hoops to turn to their stops, the mirror 12 in the aiming unit 10 reflects the laser beam to the corner reflector 18, where the beam is reflected back to the vidicon device. The TV follower circuitry 54 then automatically follows the laser image, generating error signals that move the raster to accurately center the laser. A momentary contact switch is also provided, which allows the operator to manually transfer the system to the barrel aiming method at any time, when signs of trouble arise. The television tracking system uses the well-known balanced area tracking technique, which develops error signals proportional to the displacement of a target image from the center of the television field of view. These error signals are fed to the servo system to cause the wobble bar to move the camera's field of view to bring the target into the center of the monitor's field of view. The operator can manually rotate the turret's field of view to place a target in the center of the reticle 61 on the display 60 using the switch 71 on the lever 52.

A tracking window 62, which is represented by corner tick marks and is centered on the crosshair 61, will then automatically expand to cover the target area. The target area can be either a white area, surrounded by a darker background, or a dark area, surrounded by a lighter background with at least 10% contrast between them. It is also necessary that the target covers at least 12 television scanning lines in height. Once the operator has centered the target, the automatic tracking system will cause the system to lock onto the target and follow as the target or airframe moves. When the TV follower 54 is locked on a desired target, which is centered in the reticle, the operator can obtain distance information using the lever trigger switch 74 which has two positions. The first position will cause the laser to fire with one pulse per second and the laser rangefinder 26 will then provide a distance measurement that appears on the rangefinder 75. When the trigger switch 74 is closed in its second position, the laser pointer 24 will fire using the code that is selected by the selector switch 7 8 and distance measurement and indication of the target will take place.

An optical aiming system is described, which in combination has a number of features which advantageously greatly reduce the weight of the aiming unit, so that it can be mounted on a mast above the level of a helicopter rotor. The system includes gyro stabilization of an output mirror in the aiming unit, instead of stabilizing the entire aiming unit. Control and display elements are arranged to allow manual or automatic tracking of targets and a laser system is arranged for target distance measurements and for target guidance to enable the use of guided fire. Although particular elements are described in detail, it should be noted that this description is intended solely as an illustration of an example and that many variations, substitutions and changes can be made by those skilled in the art. Such variations are considered to fall within the scope of the invention as stated in the claims.

Claims (20)

1. Optical sight for a target registration and tracking system, the sight (10) can be mounted on a mast and comprises: an optical substrate (11) with a longitudinal axis, a laser pointer (24), a laser rangefinder (26), a television camera ( 22) for providing a video signal representing an optical image of a target, first optical means (16) mounted on the optical substrate (11) for directing a laser beam from the laser pointer (24) towards a target, and for directing a laser beam which is reflected from the target of the laser rangefinder (26), and other optical means (20) which function to direct the light which forms the optical image of the target, towards the tele-vis ion camera (22), characterized in that: a gyro-stabilized mirror (12 ) with a two-axis gyroscope (14) is mounted in one (41, 42) with the optical substrate (11), whereby the mirror (12) is held at a selected level in relation to the longitudinal axis of the optical substrate (11) , the two-axis gyroscope (14) includes a wobble bar arrangement (4 3) which is is supported by a pair of wobble bracket brackets (41, 42) which are integrally formed with the optical base (11), as the wobble-rebow arrangement (43) can rotate about an elevation axis, while the gyro-stabilized mirror (12) reflects both the light forming the optical image, towards the first optical element (16) and the laser beam from the first optical element (16) towards the target and vice versa, and the second optical element (20) is mounted on the optical substrate (11) and cooperates with the first optical member (16) to direct the optical image light of the target towards the television ion camera (22) while the second optical member (20) comprises a rotatably adjustable density optical filter (21) which is arranged so that the optical density varies by rotation, a lens system (19) for a narrow field of view, a movable lens system (23) for a wide field of view, as well as a drive motor (37) for both selective adjustment of the optical filter (21) by its rotation and for moving the lens system (2 3) in and out for a wide field of view from the optical axis of the second optical member (20). 2. Sight as stated in claim 1, characterized in that the two-axis gyroscope (14) comprises another sling-rebound arrangement (40) which is stored by means of the first-mentioned swing-bar arrangement (4 3), and can be rotated about an azimuth axis , as the mirror (12) is rotatably mounted on the first wobble hoop arrangement (43) and is operationally connected to the second wobble hoop arrangement (40), so that the gyroscope (14) keeps the mirror (12) stabilized in the selected position. 3. Sight as stated in claim 2, characterized in that the mirror (12) is connected to the second wobble-bar arrangement (40) by means of discs (44, 45) and belt (46). 4. Sight as stated in claim 1, 2 or 3, characterized in that it comprises barrel sight adjustment means (18) for aligning the laser beam from the laser pointer (24) with the center of the video representation of the optical image incident on the stabilized mirror (12) . 5. Sight as specified in one of the preceding claims, characterized in that the gyroscope has ± 2° freedom with respect to azimuth and approx. - 15° freedom with regard to elevation. 6. Sight as stated in one of the preceding claims, characterized in that the first optical element (16) comprises another mirror (15) which is positioned so that it reflects light to and from the stabilized mirror (12), as well as a beam splitter (17) which is placed between the second mirror (15) and the laser pointer (24) and the laser rangefinder (26), the beam splitter (17) being transparent to the laser beam and at least partially reflective of the light that forms the optical image, so that the second mirror (15) reflects a laser beam that arrives after reflection from the target, and is reflected from the stabilized mirror (12) to the laser rangefinder via the beam splitter (17), and reflects the laser beam from the laser pointer (24) to the stabilized mirror (12) ). 7. Sight as stated in claim 6, characterized in that the beam splitter (17) reflects light energy in the area approx. 0.7 to 0.9 microns and is transparent to light energy of approx. 1.06 microns. 8. Sight as stated in one of the preceding claims, characterized in that the lens system (19) for a narrow field of view has a field of view of approx. 2.5° and that the line system (23) for a wide field of vision forms a field of vision of approx. 10° for the sight. 9. Sight as stated in one of the preceding claims, characterized in that the optical filter (21) with adjustable density has a dynamic illumination range of at least 1,000 to 1. 10. Sight as stated in one of the preceding claims, characterized in that the optical filter (21) with adjustable density has a spectral cut-through range of approx. 0.6 8 to 1.1 microns. 11. Sight as stated in one of the preceding claims, characterized in that the optical filter (21) comprises a rotatable, transparent filter disc with continuously variable, neutral filter density characteristics over a defined area, a shaft and a hub (91) which is concentrically connected to the disc, the shaft and hub (91) being rotatably mounted on a support bracket (80b), a clutch unit (93, 95, 94), which is fixed to the disc and arranged between the disc and a support bracket (80c), the clutch unit (93, 95, 94) being adapted so that it is in a free position under rotation of the disc, and a gear drive device (87) which is attached to the shaft (91) and can be driven by the drive motor (37) to induce rotation of the filter disc. 12. Sight as stated in claim 11, characterized in that the drive motor (37) comprises a transverse rocker arm (98) which is mounted on and rotatable about the shaft (91), a reversible drive motor (5 3) mounted in an outer end of the arm (98) ), a drive gear unit (89, 88) which is operatively connected to the motor (53) and in engagement with the gear drive device (87), where the lens system (2 3) for a wide field of view is mounted on the other outer end of the arm (9 8), a solenoid device (55, 97, 59) for bringing the clutch means (93, 94, 95) into engagement and thereby preventing the filter disc from turning and setting means (57, 65, 81, 82) which respond to the operation of the solenoid device (55, 97, 59) and the drive motor (53) to hold the lens system (2 3) for a wide field of view either in a first position in the optical path of the television camera (22) or in a second position outside the optical path of the television camera (22). 13. Sight as stated in claim 12, characterized in that the setting means comprise a setting pin unit (57, 65), setting holes (81) for a first position in the arm (98), second setting holes (82) in the arm (98) for a second position, and a control device (85, 83, 84, 86a, 86b) for the arm position, operation of the solenoid device (55, 97, 59) brings the clutch (93, 95, 94) into engagement and thus prevents rotation of said washer and extraction of the detent pins (65), so that the drive motor (53) is brought to drive the drive gear unit (89, 88) against the now stationary gear drive device (87) for turning the arm (98) on the shaft (9) to a point where the setting sensor -ers (83, 84, 85, 86a) indicate a desired position, so that the motor (53) is stopped and the solenoid device (55, 97, 59) is released and the pins (80) can be engaged in the position setting holes (82) or ( 81). 14. Sight as stated in claim 13, characterized in that the control device for the arm position comprises a closing plate (85) attached to said arm and rotatable with this, a first limiting hole (86a) at one end of the closing plate (85) and a second limiting hole (86b) ) at the opposite end of the closing plate (85), a light source (83) in line with said restriction holes (86a, 86b), and a light detector (84) which is arranged opposite the light source (83) and reacts to this source when one of the restriction holes ( 86a, 86b) coincide with the light source (83). 15. Sight as stated in claim 13 or 14, characterized in that the adjustment means further comprise spring-actuated pins (66) which are adapted to be pressed down by the lens system (23) for a wide field of view in the system's first position in order to bias the pins (65) when engaged with the first position adjustment holes (81) to provide stability. 16. Optical target registration and tracking system comprising an optical sight as specified in one of the preceding claims, and a housing (25) for mounting on a mast (5) above the superstructure of an aircraft, vehicle or the like, characterized in that the optical sight (10) room in the housing (25) and that azimuth drive means (31) are arranged for turning the housing (25) in azimuth in relation to the mast (5). 17. System as stated in claim 16, characterized in that the azimuth drive means (31) can be controlled over approx. - 160° in azimuth. 18. System as stated in claim 16 or 17, characterized in that the azimuth drive means (31) comprise an azimuth drive motor (32), drive shaft (30) and gear exchange (34, 36). 19. System as stated in claim 16, 17 or 18, characterized in that it comprises a control board (50) which can be placed at a distance in relation to the optical sight (10), the control board (50) comprising: i. Servo control circuits (56 ) which is connected to the gyroscope (14) and the azimuth drive means (31) for receiving control signals from the gyroscope (14) and for controlling the gyroscope (14) and the azimuth drive means (31) for maintaining a selected line of sight of the laser beam fixed in azimuth and elevation at variations in the vehicle's course and position, ii. manual control means (52, 50) connected to the servo control circuits (56) for providing manual control signals for moving the line of sight of the laser beam to a desired orientation in azimuth and elevation, television display means (54, 60) associated with the television camera (22) for producing a visual reproduction of the optical image which produces the video signal from the television camera (22), the television display means (54, 60) having a display screen (60), iv. television follower circuit means (54) connected to the television display screen (60) and the servo control circuits (56) for providing follower control signals, so that the servo control circuits (56)' control the gyroscope (14) to maintain a selected target area for the optical image mainly centered on the forward the display screen (60), and v. distance projector means (75) connected to laser av the position meter (26) for indicating the distance between the vehicle and a selected target. 20. System as stated in one of claims 16-19, characterized in that the housing (25) for the optical sight includes a window (13) mounted mainly normal to the longitudinal axis of the optical substrate C11).' and near the mirror (12).