DE3418394A1 - Image recording and image processing methods and devices for airborne video cameras - Google Patents

Abstract

This image recording method is intended for use in airborne video cameras (3) which are equipped with light-sensitive semiconductor image sensors (1) which are arranged on a surface. In order to improve the imaging clarity and to reduce the influence of image explosion, it is provided that an electronic image intensifier (2) having an adjustable gain factor be connected upstream of the semiconductor image sensors (1), which image intensifier (2) is operated in a pulsed manner. In consequence, the semiconductor image sensors (1) are in each case illuminated only briefly, at an increased intensity, during one frame period. An image processing method, which is intended for the video images thus recorded, provides that actual data concerning the movements of the aircraft (1) are obtained continuously with the aid of movement sensors (9) and are transmitted to an evaluation station (10) together with the video data. A comparison of the actual data with the corresponding required data is carried out there, and the images are corrected with respect to their mutual position and orientation such that any deviation between the actual and corresponding required data associated with the time at which the respective image is recorded is compensated for. This results in a jitter-free image sequence. <IMAGE>

Description

Image recording and image processing methods and devices for in aircraft carried video cameras

The invention relates to an image recording method for video cameras carried in aircraft that use planar arranged, light-sensitive semiconductor image sensors are equipped, a corresponding image recording device, an image processing method for the recorded video images and a corresponding one Image processing device.

Video cameras are built into modern missiles, with the help of which the terrain overflown is observed, to be able to identify possible targets, such as tanks. The ones recorded with the help of the video cameras Images are transmitted to a steering system or evaluation station, for example with the help of a Missile connected, during the flight unwinding, electrically conductive wire or also Light guide, or on the radio path. The recorded video images are generally recorded in the steering system made visible on a monitor, and from there steering commands are also transmitted back to the missile. Dives, for example, in the field of view of the missile's video camera, which is generally obliquely forward an attack target on, this is also visible on the monitor, so that the missile with the help corresponding steering commands can be controlled into the target.

Such a missile image recording system should be designed in such a way that perfect, i.

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sharp and tremor-free images are delivered, if possible up to the edge areas of the image format into it. In this regard, however, the systems previously used have not been satisfactory. here On the one hand the phenomenon of the image explosion plays a role, and on the other hand that caused by the engine and by the constant corrective movements of the missile steering system caused vibrations. The vibrations lead to that successive images are offset from one another, for example with respect to the roll or pitch axis, so that a blurred sequence of images appears on the monitor. The explosion of images means the fact that only the part of the image lying in the optical axis of the camera appears relatively calm, while for The picture elements rush past with ever greater apparent speed towards the edge of the picture. As a consequence, that the images are increasingly blurred in the edge areas. From all of this it follows that it is desirable Steps to be taken to improve image quality with missile video cameras to improve.

The use of image pickup tubes in missile video cameras is disadvantageous for various reasons tied together. The so-called blooming should be mentioned here, i.e. the phenomenon that after a one-off Scanning the target with the electron beam, the charge image is not erased, so that with dex * Recording of fast moving objects in the picture flags occur. All image pick-up tubes show this Blooming to a greater or lesser extent. Another disadvantage of most image pickup tubes is in that the photosensitivity cannot be controlled with the aid of the target voltage. Such a one Control options exist only with the Vidicon, which in turn has a strong blooming effect

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is pronounced. Most image pick-up tubes have special and to regulate the light sensitivity complex optical or mechanical control systems are required. The controllability of the light sensitivity however, it is a decisive criterion for image quality.

For the reasons mentioned, it is advisable to use video cameras in missiles that are not equipped with image recording tubes, but with semiconductor image sensors arranged over a large area as light-sensitive elements are equipped. As such semiconductor image sensors, for example, CCD sensors, i.e., charge-coupled sensors Sensor elements, are used. Such semiconductor image sensors have above all with regard to significant advantages over the blooming effect the image pickup tubes. In addition, there is good sensitivity, relatively low energy consumption, a high reaction speed as well as the elimination of focusing and deflection elements, and in connection with this high vibration resistance. However, such semiconductor image sensors are not straightforward either in their sensitivity to light by an external signal adjustable.

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The invention is based on the object of an image recording method of the type mentioned at the beginning and an image recording device serving to carry it out make it possible to use video cameras with areally arranged semiconductor image sensors to produce sharp images at any time in aircraft or missiles, especially the adverse influence of the image explosion is reduced as much as possible. It is also intended to be expedient 5 further development of the invention may be possible by

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Elimination of the influence of the missile vibrations to generate tremor-free images.

This object is achieved according to the invention with regard to the image recording method in that the semiconductor image sensors an electronic image intensifier with an adjustable gain factor is connected upstream, which is operated in a pulsed manner, so that the semiconductor image sensors only briefly during an image period exposed with increased intensity.

An image recording device for performing this image recording method is characterized by a The semiconductor image sensors are optically directly upstream of the electronic ones that can be used in pulsed operation Image intensifier with variable gain.

According to the invention, an electronic image intensifier should be optical for the semiconductor image sensor array be connected upstream, which is to be used in pulse mode, so that it is only relatively for one frame period is translucent for a very short time. At the same time during this short exposure time the light intensity incident through the lens within the electronic image intensifier is considerable amplified, whereby the amplification factor can be varied as required by the level of the applied voltage. the Significant shortening of the exposure time compared to the entire picture period, the duration of which is due to the television standard is determined, is therefore offset by the increase in light intensity during the exposure time. Of the Electronic image intensifiers can contain, for example, a microchannel plate, in whose microchannels per incident electron a more or less strong electron cascade is generated depending on the applied voltage.

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Other types of electronic image intensifiers can also be used, with it being a continuous The principle to be considered is that the photons incident on the input side from the lens of the video camera

^ next hit a photocathode and there a corresponding one Release number of electrons. These electrons are then picked up by an applied high voltage high energies accelerated and possibly increased in a microchannel plate so that they are able to either when hitting a luminescent screen there to trigger a large number of photons in each case or when they strike the photosensitive semiconductor material an image sensor to excite a large number of charge carriers there. When using a Limines-5 The photon stream on the output side becomes directly the one following the electronic image intensifier Sensor component fed. Is applied to the electronic image intensifier for amplification When pulsed voltage is used, the image intensifier is only 0 during the short period of these voltage pulses translucent, but otherwise not.

The invention makes it possible because of the very short exposure time and the simultaneous high intensity gain, Sharp, sufficiently bright individual images that can be regulated in terms of image brightness at any time to create. The disadvantage associated with the use of semiconductor image sensors is the lack of This eliminates the ability to regulate the sensitivity to light.

The image recording method according to the invention can be used for the purpose of achieving jitter-free image sequences by a Image processing methods are supplemented, which is characterized in that with the help of in the missile

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attached motion sensors constantly obtained actual data about the missile movements and together with the the recorded images generated video data are transmitted to an evaluation station that there is a : -, made equal to the actual data with the corresponding nominal data and the images are corrected with regard to their mutual position and orientation so that a deviation of the actual data belonging to the point in time when the respective image was taken from the corresponding nominal data is compensated.

According to this image processing method, movement data measured at the point in time of the recording are recorded for each individual image assigned to the aircraft. If 5 of these measured data deviate from the specified target data the individual images transmitted to the evaluation station are then shifted and / or rotated there as the aircraft would have maintained its target trajectory at all times, even without vibrations, so that a tremor-free Sequence of images results. Extremely sensitive and quickly reacting motion sensors are available, whereby For example, accelerometers on an inductive basis or using piezo crystals come into question. Accelerations can be measured and evaluated in all three axis directions will.

A device for carrying out said image processing method is essentially characterized by movement sensors arranged in the aircraft constantly repeated determination of the actual data for the movements of the aircraft, one the actual data and the

Transmission device transmitting video data from the aircraft to the evaluation station and one in the evaluation station existing comparison unit for comparing the 5 actual data received with the

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Target data and one depending on the target / actual data deviation the coordinate correction computer effecting the image correction.

The image processing method mentioned can then be used when there is none or not in the aircraft Adequate precautions have been taken to protect the video camera from undesired movements of the aircraft, about vibrations, to decouple. Are such facilities in the missile available and sufficient? Measures effective, so can on the application of the image processing method according to the invention or the corresponding device can be dispensed with. On the other hand, this part of the invention enables to dispense with the possibly complex devices in the missile, which the mechanical decoupling the video camera from the interfering movements of the missile. This leaves the equipment The only effort in the missile is the motion sensors.

The image correction with regard to the disturbing movements is then carried out electronically, predominantly in the Evaluation station or the steering position.

Advantageous further developments of the invention can be found in the 5 subclaims.

In the following the invention is explained in more detail with reference to the figure in an exemplary embodiment. the The single figure shows a block diagram of both an image recording device arranged in the missile and also an associated image processing device present in the evaluation station or the steering system.

An aircraft or missile 11 is indicated by a ge-5 dashed border symbolizes. The missile leads

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a video camera 3 with the essential parts of a lens 27, an electronic image intensifier 2 and has a downstream module which has an array of semiconductor image sensors 1 arranged over a large area contains. Also shown are a television standard generator 4, a pulse generator 5, and a signal combination unit 7, an amplifier 8 and a data modulator 6. The electronic image intensifier has on the input side a photocathode, which is preceded by a fiber board consisting of bundled light guides can be. The incident photons from the lens pass through the essentially parallel to the Optical axis oriented light guides on the photocathode and release electrons there. These are in 5 a subsequent vacuum zone is accelerated by an applied high voltage, the high voltage of the pulse generator 5 is supplied. Then hit the electrons accelerated to high energies, possibly. After passing through an imaging, electron-optical device, either on a output-side luminescent screen with subsequent planar semiconductor image sensors 1, preferably CCD sensors, or directly onto them. The high voltage supplied by the pulse generator only appears in form short-term pulses, the duration of which is in the range of microseconds or a few milliseconds. In contrast, the duration of an image period is 40 msec, for example, corresponding to a conventional one Television standard. During this time, the image information stored as charge distribution in CCD sensors remains obtained without significant signs of degeneration and can be read out as usual.

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The image signals read out are fed to a downstream amplifier 8 and arrive from there a signal linking unit 7. In this, the synchronization signals generated by the television standard generator 4 are added so that standardized video signals are available at the output of the signal combination unit 7 stand. The television standard generator 4 also ensures that the voltage pulses of the pulse generator with are synchronized with the readout frequency. The one from the Signal combination unit 7 output video signals arrive at a data modulator 6, which is used for coding in a manner that is favorable for image transmission and at the output of which e.g. digitized video data are available for transmission.

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The transmission path from the missile to a steering system or evaluation station 10 located on the ground is symbolized by a transmission device 12 shown in dashed lines. This transmission facility 12 contains both in the missile 11 and in the evaluation station 10 arranged components such as Transmitting and receiving devices, as well as, if necessary, electrical or fiber optic cables for wired Transmission of the video coming from the data modulator 6

2 5 dates.

If in the missile 11, the video camera 3 is not of the Interfering movements is decoupled, the transmission device 12 is still fed actual data from Movement sensors 9 originate which supply measured values for the movements of the missile 11.

The device parts essential for the invention in the evaluation station 10 are a comparison device 13, a coordinate correction calculator 14

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Demodulator 15 and generally a monitor 22. By a trajectory control device 29, which is operated, for example, by the person monitoring the flight of the missile 11 on the monitor 22 the comparison unit 13 is supplied with nominal data for the desired missile movements. This comparison unit 13 simultaneously receives the corresponding actual data arriving via the transmission device 12 the missile movement and determines the deviations from the target data. From the transmission device 12 become video data to the demodulator 15 in accordance with the sequence of the recorded images supplied. In the demodulator 15 these data are converted into pixel intensities and split up pixel coordinates. The image point intensity data are sent from the data output 20 of the demodulator 15 to the data input 21 of the monitor 22 fed. Between the address outputs 16, 17 of the demodulator 15 and the pixel address inputs 23, 24 of the monitor 22, the coordinate correction computer 14 is switched on, the data inputs 18, 19 of which the Data corresponding to x or y image coordinates from the assigned address outputs 16, 17 of the demodulator 15 obtain. The provided by the comparison device 13, The data corresponding to the target / actual value deviations are sent to the coordinate correction computer 14 via further inputs 30, 31, 32 are supplied. The coordinate correction computer 14 corrects in accordance with the target actual value differences the transmitted pixel coordinates in such a way that at its data outputs 25, Any positional and trajectory disturbances of the missile 11 that have occurred are corrected, i.e. those for image stabilization on the monitor 22 required pixel coordinate transformations (translations and Rotations) according to the determined actual-target value deviations the missile movement performed

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are. The data corrected in this way for the pixel coordinates arrive at the pixel address inputs 23, 24 of the monitor 22, with the result that this is a corrected, jitter-free and sharp individual images existing image sequence generated.

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Claims (7)

Patent department 06/18/19W 8394 El / hl 9549 I SUBSEQUENT Image recording and image processing methods and devices for video cameras carried in aircraft claims 1. Image acquisition method for carried in aircraft Video cameras equipped with areally arranged, light-sensitive semiconductor image sensors are, characterized in that the semiconductor image sensors (1) an electronic image intensifier (2) is connected upstream with an adjustable gain factor, which is operated in a pulsed manner, so that the semiconductor image sensors (1) only briefly with increased intensity during an image period to be exposed. 2. Image recording device for performing the Method according to Claim 1, with a video camera, the areally arranged, light-sensitive semiconductor image sensors has, characterized by one of the semiconductor image sensors (1) optically directly upstream, which can be used in pulsed operation electronic image intensifier (2) with variable amplification. 3. Apparatus according to claim 2, characterized by the synchronization signals ^ O for the television standard generator providing the video image (4), one connected to this, the electronic image intensifier (2) with high-voltage pulses supplying pulse generator (5) as well as one on the input side with both the electronic image intensifier (2) as well as with the television standard generator (4) and : Patent Department 06/18/1984 el / hl 9549 signal linking unit (7) connected on the output side to a data modulator (6). 4. Apparatus according to claim 3, marked by an amplifier (8) connected on the input side to the semiconductor image sensors (1) and on the output side to the signal linking unit (7). 5. Image processing method for the recorded according to claim 1 video images, characterized in that with the help of motion sensors (9) constantly actual data about the movements of the Plug device (11) obtained and together with the 5 recorded images generated video data are transmitted to an evaluation station (10) that there a Comparison of the actual data with corresponding nominal data is made and the images with regard to their mutual position and orientation are corrected so that a deviation of the at the time of recording actual data belonging to the respective image is compensated by the corresponding nominal data. 6. Apparatus for performing the method according to 5 claim 5, characterized by im Aircraft (11) arranged movement sensors (9) for continuously repeated determination of the actual data for the Movements of the aircraft, the actual data and the video data from the aircraft (11) to the evaluation station (10) transmitting transmission device (12) and a comparison device (13) present in the evaluation station (10) for comparing the actual data received with the target data and effect the image correction depending on the target / actual data deviation-5 the coordinate correction computer (14). j 3 IR.nfi.1 MBB 25 30 Patent department 06/18/1984 el / hl 9549 7. Apparatus according to claim 6, characterized by one in the evaluation station (10) located, the transmitted video data receiving demodulator (15), its forwarding the pixel coordinates serving address outputs (16, 17) with corresponding data inputs (18, 19) of the Coordinate correction computer (14) and its data output serving to forward the pixel intensity data (20) are connected to the data input (21) of a monitor (22), which continues to have pixel address inputs (23, 24) for taking over the corrected pixel coordinates from the corresponding data outputs (25, 26) of the coordinate correction computer (14). 15th 35