JPS6231548B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention comprises a detector array responsive to thermal energy in the infrared region, each detector element of which is connected to a channel containing a variable gain amplifier. The present invention relates to an automatic responsiveness control device for a thermal image generating device, for automatically controlling the responsiveness (sensitivity) in an infrared detecting device, that is, a thermal image generating device.

An infrared observation device that observes a field of view extending in front of the device is known as a device that forms a real-time image based on differences in thermal emissivity in the observed situation. In order to uniformly and appropriately display the situation on the display device, the responsiveness of each detection element constituting the detector array must be within a predetermined range. Conventional devices for this purpose have adopted a method in which a signal is extracted through a variable resistor and leveled by adjusting the amount of attenuation of this resistor. In such a configuration, during the life of the detector array, constant adjustments must be made in consideration of changes in the circuit system over time. moreover,
When it becomes necessary to replace the detector array, complicated adjustments are required that require a significant amount of time.

Publication “Journal of Physics E:Scientific
Instruments'' 1971, Vol. 4, pages 1091-1035 also discloses a device for automatically adjusting the sensitivity of an infrared detector. The detection target of this infrared detector is optically scanned by a rotating mirror drum and a movable mirror, and is detected using a single detector for each scanning line. In this known device, the infrared energy is interrupted by approximately 5% at the beginning and end of each image train.
Therefore, during the reproduction of each image train, an interruption occurs for a period of about 10% of the total time due to the transmission of infrared radiation provided by the internal reference radiation source. The reference radiation source added for adjustment is done within the retrace period from the end of a completed image to the beginning of the next successive image. The signal obtained during this retrace period is used for gain control of the amplifier connected to the only detector.

Such known devices operate on a similar principle to monopulse radar devices. In such a monopulse radar system, sum and difference signals are formed from the signals received by the four antenna elements, and these signals are processed by separate channels. In this process, information regarding the difference from each antenna row direction is obtained. The premise for accurately determining such a difference is that the transmission characteristics of the sum signal channel and the difference signal channel are equal. A calibration signal is used for the equalization of both channels, which is either coupled directly to both channels via a directional coupler or fed to the antenna element via an auxiliary antenna. The feeding of this calibration signal to the processing channel is
This is done during a period when the received signal is not being processed. In such monopulse radar equipment, the pulse period is longer than the expected echo signal time, so there is a period during which other signals can be processed in place of the received signal while processing continues. do. That is, in the monopulse radar device, the received signal and the calibration signal can be processed by time division multiplexing. Naturally, the calibration signal in this case must be chosen to be at a frequency equal to the transmit signal of the radar equipment in order to synchronize the processing of the received echo signals reflected from the target.

Interrupting the received energy to allow a period of time to retrieve the calibration signal from the received energy has a number of disadvantages. That is, special equipment for interrupting the received energy would be required. Furthermore, this device becomes more complex the greater the radiant energy that has to be interrupted. In particular, the restriction here is that the energy interruption must take place at the site where the reference energy introduced into the optical system is incident on the detector group in the same manner as the received energy. A switchable receiver is also provided for the signals obtained by the detector array consisting of a number of detector groups, and an interruption device and a switchable receiver are provided for processing the signals separately from the signals generated by the reference energy. must be synchronized with the device. Therefore, a considerable portion of the available reception time is required, inevitably leading to information loss. It is therefore impossible to apply known devices for responsiveness control in infrared detectors with only a single detector to thermal imaging devices with detector arrays consisting of a large number of detector elements. Appropriate.

It is well known that infrared optical systems are provided with antireflection coatings. The reflectance of germanium-coated optics applied for such purposes is still quite high, so that the cold image of the entrance window of the cooling vessel surrounding the detector is reflected from the optics and incident on the detector array.
Such a cold image, also known as a Narcissus image, appears as a visible spurious image on a display device when forming an external field image. Since such a Narcissus image occurs when the scanning mirror is at a specific angle, it can be canceled by mixing infrared rays from a Narcissus cancellation source, which is a heat source with a shape comparable to that of a cold image, into the received energy. I can do it. In an infrared monitoring device, ie, a thermal image generating device, equipped with such a Narcissus cancellation system, the Narcissus cancellation source can automatically generate a reference signal for controlling the responsiveness (sensitivity) of the detector array.

In the present invention, the responsiveness (gain ) can be provided.

Such a structure of the present invention is as described in the claims.

Therefore, according to the automatic responsive control system for a thermal imaging device according to the present invention, an amplitude modulated reference signal is continuously applied to the received infrared energy. This reference signal beam passes through the same optical path as the received infrared energy to reach the detector array. The detector elements making up the detector array generate output signals in response to both an incoming received signal and a reference signal. This output signal is amplitude modulated, transmitted through a channel for each element including a variable gain amplifier, and displayed on a display after signal processing. If the amplitude modulated in this way can be detected within the signal processing system, this detection output can be used to constantly compensate for changes in the characteristics of the detector element and control responsiveness by changing the gain of the amplifier. It can be performed. Control by such a method is performed continuously without limiting the differential time to a short time, and the increase in cost is small.

With the automatic responsive control device for a thermal image generating device according to the invention, the signal source for Narcissus cancellation, which is essential in similar devices, can be used as a reference signal source. The basic configuration therefore includes a Narcissus cancellation source, a beam splitter, and an optical modulator to add a reference signal into the received infrared energy.
Thermal energy generated by the Narcissus erasure source and supplied to the optical system is reflected by each member of the optical system and reaches the detector array for erasing the Narcissus image. In addition, a portion of the thermal energy generated by the Narcissus cancellation source and split by the beam splitter then reaches the beam splitter again via a modulator for the reference signal and is used to pass the received signal. is superimposed on the received infrared energy from the optical system of the detector array. The incident signal containing the modulated reference signal provides an electrical output signal from the detector array. Detection of the reference signal component within this electrical output signal is accomplished by rectifying the modulated signal component using a synchronous detector for each channel. By controlling the gain of the in-channel amplifier using the DC control signal obtained from the reference signal in this manner, the responsiveness of the detector can be automatically controlled. Here, the reference signal component contained in the detector output is removed by combining the phase-inverted reference signal component, ie, the reference signal component, and the detector output signal in a multiplexer.

According to the device for automatic responsiveness control,
A wide range of contrast control can also be achieved by varying the output intensity of the Narcissus cancellation source.

Therefore, by utilizing a reference signal source that utilizes a Narcissus cancellation source, an automatically responsive control system for a thermal image generator according to the present invention is obtained. According to the control device according to the present invention, the channels belonging to the individual detector elements of the detector array are individually controlled.
It is controlled as a function of the responsiveness of each element. In this case, the reference signal component used as a control reference is easily removed from the video signal to be displayed on the display as the output of the thermal imager, and no display disturbances occur. Further, by adjusting the output of the Narcissus cancellation signal, it is possible to perform wide range contrast control of the thermal image generating device.

The above and other objects as well as novel features of the invention will become apparent from the following description with reference to the accompanying drawings.

A passive infrared (IR) display or thermal imager according to the present invention is mounted on the bottom of an aircraft flying over a target area and pointing in a desired target direction relative to the field of view or field of view 14, as shown in FIG. It can be used by disposing it in the provided turret 12. The aircraft 10 may be a helicopter, fixed wing airplane, or any other aircraft capable of moving into a position to sense infrared energy from the field of view 14. In the case of a helicopter, a turret forming a rotatable operator station is used to direct the selected field of view in azimuth by rotating the turret and in elevation by controlling a directing mirror. field of view 14
A suitable scanning mechanism may be provided to scan the . The pointing device may include position and velocity gyros and appropriate gimbal stabilization devices responsive to pointing commands, as is well known in the art. In the illustrated configuration, the azimuthal scanning is performed in lines as shown at 21 and 23 during the first scan, and one by two.
During the second scan of the interlacing motion, 25 and 27
This is done using a line as shown in . Vehicle 1 in sight
9. It is assumed that there are various other objects that emit infrared rays.

Reference is now made to FIG. 2, which shows a rotatable or swivelable gunner's station, by way of example, to illustrate the use of the apparatus of the present invention in a helicopter or other slow-speed aircraft. It is shown. The structure includes a turret 12 that is rotatably mounted to a portion 40 of the helicopter and fixedly coupled to a rotating structure 42 in which an operator, such as a gunner, can be positioned in a chair 44. The turret 12 is provided with an outer window 50, which may be made of germanium-coated glass, for example. Directional mirror 52 provides elevational pointing over a selected angle 56, while turret movement controls azimuthal pointing. Energy received by directing mirror 52 is applied to an infrared sensor 60. The sensor has an azimuthal scanning array and an elevation detector array and is temperature controlled by a suitable cooling system 62 which receives compressed gas, such as Freon, from a compressor 64. Structure 66 is provided with a signal processing device to provide a signal to a display indicator 68 so that the scene can be viewed as an infrared image from an eyepiece 72 by means of a suitable veriscope 70. In the illustrated configuration, the IR axis is directed in the azimuthal direction by rotating the turret 12 and by controlling the directing mirror 52.
Suitable control devices are provided for directing the axis in elevation. Veriscope 70 may include a suitable optical path for receiving light energy from a cathode ray tube (not shown) within display indicator 68. The entire device can be controlled by applying pointing signals from a suitable control source and by means of suitable position and velocity gyroscopes (not shown) to achieve stable pointing direction.

FIG. 3 shows a block diagram of a thermal image generator for night observation based on the principles of the present invention. Although this device can be applied to both rotary-wing aircraft such as helicopters and fixed-wing aircraft, for convenience of explanation, it will be used in conjunction with a helicopter as shown in FIG.
Infrared energy is received from the field of view through exterior entrance window 50 by directing mirror 52 and directed to sensing device 74, as shown by respective optical paths 79 and 81.
added to. In addition to the energy incident from the field of view, the Narcissus represented by optical paths 78 and 80 causes infrared energy or thermal images to be reflected from the entrance window 50 via the directing mirror 52 and back to the sensing device 74. The signal processing device 82 includes a composite conductor 86
Respond to the video signal above. This composite conductor is N
In the illustrated example of the device, which utilizes N detectors, it consists of N separate individual conductors, each carrying one video signal. Composite conductor 88
carries appropriate scan synchronization signals, including, in the illustrated example, an azimuthal scan synchronization signal. Display device 90 receives a multiplexed video signal from composite conductor 92 and a synchronization signal from conductor 94 to provide a display as a raster image on a suitable cathode ray tube screen. A suitable optical viewing device or veriscope 70 is provided with a display device 9 for viewing by the operator, for example through an eyepiece 72.
Receive image from 0. The thermal image generator further includes a power supply 98 and a helium compressor 64 controlled from the control panel 102 via a composite conductor 99. Control panel 102 or conductor 104
A brightness control signal is sent to the display device 90 via a conductor 106, a contrast control signal is sent to the signal processing device 82 via a conductor 106, and a wide/narrow field switching signal is sent to the sensing device 74 via a conductor 108. An operator-controlled manual aiming signal is transmitted from the control panel 102 via the composite conductor 112 to the sensing device 74 and the signal processing device 8 to adjust the aiming indication range provided on the display surface.
2 for vertical and horizontal line-of-sight adjustments, respectively.

Referring to FIG. 4, which shows a block diagram of the sensing device 74, the infrared sensing device includes a telescope assembly 120 that passes the IR scene received from the entrance window and the directing mirror (FIG. 3);
It includes a horizontal scanning mirror 122 that receives both IR energy as well as Narcissus energy originating from the cooled entrance window and reflected at the telescope 120. To generate a synchronization signal, a synchronization generator 1
A sync source 126 at 27 applies energy to a horizontal scanning mirror 122 where it is reflected and received by a sync generator pick-off receiver 128 and transmitted via conductor 130 to a suitable amplifier 132 as a sync generator pulse signal. and then provided to signal processing device 82 via conductor 488. In this case, an association is obtained between an aiming pulse for mechano-optically scanning the horizontal scanning mirror 122 and a synchronization pulse for activating the subsequent signal processing device. As will be described later in FIGS. 14 and 15 and their related explanations, the vertical scanning mirror is scanned in synchronization with the horizontal scanning mirror, and a synchronizing pulse is generated at this time. The IR and Narcissus signals are provided from horizontal scan mirror 122 to vertical scan aiming mirror 136. The mirror 136 provides aiming adjustment of the vertical aiming line, which is a horizontally extending aiming indicator. Both the IR signal and the Narcissus signal are 1 to 2 from the vertical aiming mirror.
It is added to the interlaced scan mirror 140 to move the linear range of the field of view during alternating azimuthal scans, as described in FIG. IR energy is applied from an interlaced scan mirror 140 through a beam splitter 142. The splitter has a transmittance of, for example, 90% and 8 to 10
% of the coated optical material. Spectral filter 1
An entry window to a dual vacuum cooling vessel surrounding the detector array 150, shown as 46, allows only IR energy within a selected operating range to be transmitted through a suitable cold shield 148 of the detector assembly 149. can be of a selected thickness to pass through the detector array 150. Beam splitter 142 passes approximately 90% of the IR energy.

Beam splitter 142 receives and transmits energy generated from cold detector array 150 and Narcissus energy from spectral filter 146. In addition, the beam splitter 14
2 injects a Narcissus cancellation energy into the Narcissus cancellation source 160 with the approximate contour of the Narcissus energy to effectively cancel the Narcissus signal in a plane close to the interlaced scan mirror 140 as indicated by the summing unit 162. receive from The residual resulting from incomplete erasure is removed from the telescope 120.
passes through the optical system and is reflected. This residual amount is substantially small and can be reduced to such an extent that it does not affect the operation of the device. Beam splitter 1
At 42, Narcissus image cancellation occurs at an angle, such as when the mirror surface is perpendicular to the optical axis.

Cancellation of the cold Narcissus image from the detector assembly entrance window is accomplished by providing and canceling a thermal or hot image of the same shape from Narcissus cancellation source 160. The Narcissus cancellation source 160 is also utilized by an ARC modulator 168 which receives 90% of its radiant energy and modulates the signal and reflects it onto the surface of the beam splitter 142. At the beam splitter 142, 8 to 10% of the energy is passed through a spectral filter 146 to the detector array 15.
0 as an automatic responsive control (ARC) signal to independently control the N channel gains within the device. The signal output from the detector is carried by N conductors of composite conductor 86 and applied to signal processing device 82 . A cooling device 170 is coupled to cold shield 148 and detector assembly 149. This cooling device is the helium compressor 6 shown in Figure 3.
Contains 4. The sensing device is controlled by the telescope 12.
This is accomplished by a field selection mechanism 171 that controls aiming adjustment in response to the 0 field as well as the selected field. Motors 174, 176, and 180 control horizontal scan mirror 122, vertical scan aiming mirror 136, and interlaced scan mirror 140, respectively.

The construction and operation of the sensing device will now be described with reference to FIG. 5, which is a schematic perspective view of the sensing device with some parts exploded in an exploded position for clarity of illustration. A main housing 180 is provided and attached to the turret structure and telescope assembly 120. The telescope assembly 120 receives IR energy from the directing mirror and passes it through an optical field selection device 182 which is controlled by a field switching actuation motor 172. The optical IR signal is:
Horizontal scan mirror 12 shown with motor 174
2 and is further added to the reflective surface 137 of the vertical aiming mirror 136 and reflected to the interlacing mirror 140. The signal is then passed to interlaced scan mirror 140
from the beam splitter 142 and passes through the entrance window 146, which acts as a spectral filter. Narcissus cancellation source 160 is positioned to apply energy to beam splitter 142 as shown. This energy is then received by ARC modulator 168 to generate a gain control reference signal. Detector assembly 149 has a cooling vessel 190 with a detector array (not shown) mounted within structure 192. A suitable connection box 194 with a cable is provided in the structure 192 for leading out the N leads from the detector.
Also, a connection box 198 with a suitable electrical cable is connected to the main housing 180 for electrical connection.
is provided in the opening 199 of. Aiming drive motor 17
6 may be provided with an axis for positioning the aiming mirror 136 for the purpose of adjusting the vertical line of sight at the display. Telescope assembly 120
along an optical axis extending from the main housing 180 to the
A suitable temperature compensator 202 may be provided.
The device may use a temperature-responsive metallic material that changes its longitudinal dimension in response to temperature fluctuations, as shown in FIG. Aiming mirror 1
36 and an access cover 210 may be provided to close the opening to the synchronous generator structure.

Referring now again to FIG. 6, the sensing device is shown with its optical-mechanical arrangement in a relative operating position with the main housing removed for convenience in explaining its operation as well as its narrow and wide field of view optics. . The telescope assembly 120 includes an optical field selection device 182 in a narrow field position, a focusing device 214 attached to other structure for movement along the optical axis, as shown.
and an aperture stop 220 that may be provided for viewing angle control in some cases. The expansion device 215 is connected to the main housing 180
Arm 217 and structure 202 attached to (Figure 5)
to move the telescope assembly 120 along the optical axis to maintain focus during temperature fluctuations. The horizontal scanning mirror 122 is
It has a horizontal scanning mirror surface 123 that scans in the azimuthal direction, as shown at 24, so that the scene is sensed over the entire azimuthal scanning angle by a detector array arranged in the elevation dimension. The signal from horizontal scan mirror surface 123 is reflected by aiming mirror 136 , reflected back to interlaced scan mirror 140 , and then reflected to beam splitter 142 . The elevation dimension thus becomes the dimension of the detector array of detector assembly 149. The situation is 1
Two fields generated in a pair-two interlaced scan operation are applied alternately to a detector array in detector assembly 149.

Operation will now be described in detail with reference to FIGS. 7 and 8, which show the detector array along with the optical path in azimuthal and elevational directions, respectively. In FIG. 7, for convenience of explanation, the outer window 50 is shown stretched linearly. Further, in FIG. 8, for convenience of explanation, the optical system between the aperture stopper and the detector array 150 is also shown enlarged. The wide and narrow field rays are shown as solid and dotted lines in FIGS. 7 and 8, respectively. The optical field selection device 182 is also in the position shown by the solid and dotted lines. In the wide field mode, a germanium coated triplet is introduced between the narrow field single element and the aperture stop 220. This wide field of view allows the triplet to be
Rotate the axis to narrow-field single objective lens 1
This is obtained by aligning the optical axis 230 of 21 with the optical axis 230 of 21. Note here that the dotted lines show both optical field selection devices 182 positioned in a narrow field condition, and the light beam is provided by an objective consisting of a single germanium-coated reflective element.
Horizontal scan mirror 122 is positioned at a selected distance from detector array 150 to reduce scan defocus. Additionally, the detector array 150
is divided into three segments to obtain an optimal image in the focal plane. The IR detector array 150 converts the IR image formed by the optical system into simultaneously generated electrical signals, and these electrical signals are sequentially multiplexed. Detector assembly 149
for example, a detector array of N elements, a cold shield to improve detection capability, a suitable molecular sieve to trap the gas, and a spectral filter in the entrance window 146. , completely sealed. The detection element may be constructed of a germanium material doped with mercury, for example, although it will be appreciated that other suitable detectors known in the art may be used. Signals are applied from horizontal scan mirror 122 to detector array 150 via aiming mirror 136, interlaced scan mirror 140, beam splitter 142 and entrance window 146.

Referring to FIG. 9, which is a partially cutaway diagram of the azimuth scan drive for controlling the horizontal scan mirror surface 123, the azimuth scan is responsive to motor 174, motor pinion 252, idler gear 254, and gears. Cam 2 on shaft 258 rotated via 256
50. cam follower 2
60 is attached to the cam 25 by the action of the support spring 262.
0, so that the mirror surface 123 scans in the azimuthal direction as the motor rotates. Cam 250 is designed to perform a linear scan during 65% of the cycle and pull back with minimal force during the remaining 35% of the cycle, as indicated by angle 268. Mirror surface 123
can be attached to shaft 270 by suitable pins or flexible pivots known in the art. The horizontal scanning mirror oscillates at a rate of 60 Hz to sweep the IR image horizontally across the detector array 150. Cam 250 is driven by motor 174 at a speed of, for example, 360 Hz. In this case, the motor used is a synchronous hysteresis motor connected to a cam with a gear ratio of 1:6.

A first diagram showing the configuration of the vertical interlaced scanning mirror 140.
Referring to Figure 0, this structure consists of an electromagnetic drive unit 27
2 and 273 to move the mirror surface 141 through appropriate pivots 274, 276 to an alternating jump position.
has. The mirror surface 141 can be stabilized by a suitably flexible leaf spring 278. The permanent magnet vibrates as shown by arrow 280. The interlaced scan mirror is driven by the output of a one-shot drive circuit within the signal processing device.
The skip occurs approximately 6 milliseconds after the vertical aiming pulse due to delay circuitry within the signal processor. In the illustrated configuration, the interlaced mirror surface 141 changes position during the return period of the horizontal sweep. The mirror structure can be mounted to the optical system in such a way that the mirror surface can be rotated by an angle of, for example, 0.5 milliradians.

The control of vertical aiming mirror structure 136 and vertical aiming mirror surface 137 will now be described in detail with reference to FIGS. 11, 12, and 13. motor 17
6 responds to vertical aiming adjustment signals from control panel 102 (FIG. 3) to align mirror surface 13 by a selected angle when the device is set in the narrow field condition.
Move 7. In this case, pin 282 is rotated about axis 286. Follower 284 is pin 28
Get on 2. This pin 282 is the first pin for narrow field of view.
position 288 and, in the case of a wide field of view, a second position 290. Their positions are determined by arm 292 responsive to field switching motor 172. The arm 292, which is in contact with the pin 282 via a rigid lever 287, rotates on the axis 296 and is in the narrow field position as a result of the spring 294.
However, for this purpose, it is necessary that the actuator is not in the position shown by the solid line. Mirror surface 137 rotates on pivot axis 304 as a result of movement of follower 284 . Pivot 304 is attached to fixed structure 300 . In the illustrated configuration, the motor 176 is connected to a suitably hard stop and clutch (not shown).
is limited to an angular range of ±45°. Thus, for vernier adjustment of elevation or vertical line of sight on the scan raster, motor 176
This gives a full range of mirror rotations that can be excited, for example by about 10°. Narrow field of view (NFOV)
The correction is maintained when the device is changed to wide field of view (WFOV) in response to field switching motor 172 after a vertical line-of-sight adjustment is made. This vernier adjustment was found to have a negligible effect on focus.

The vertical aiming and synchronization generator will now be described with reference to FIGS. 14 and 15. This generator includes a light emitting element 312, which may be, for example, a gallium arsenide light emitting diode, a photodetector 314, which may be, for example, a silicon photodiode, and a reflector or a suitable spherical shape, cooperating with horizontal scanning mirror surface 123. It has a relay mirror 316 that can be a reflector. Light emitting element 31
2 constitutes a stationary light source in response to a suitable DC power source. Photoelectric detector 314 applies an output signal to appropriate electronics 320. This device 320 includes an operational amplifier that generates a vertical sync pulse as a voltage. A synchronization pulse is formed when the horizontal scan mirror surface 123 rotates by a predetermined position. In this way, energy is transferred to the light emitting element 31.
2, is transmitted to the horizontal scanning mirror surface 123 and the relay mirror 316, and is reflected back to the horizontal scanning mirror surface 123 and the photodetector 314. Of course, in this case, the horizontal scanning mirror surface 123 is required to be at a predetermined angular position. The synchronization pulses generated during azimuth scanning of the horizontal scanning mirror are used to indicate the horizontal aiming crosshair, display horizontal sync, display blank, and skip mirror drive. The shape of the vertical sync pulse on the output conductor is determined by the light emitting element aperture size and the horizontal scan mirror speed.

Next, optical field switching will be explained in detail with reference to FIGS. 16 and 17. In the case of a narrow field of view position as shown in FIG. It only passes through the narrow field of view. When wide field element 314 is rotated about pivot axis 318 to the position shown in FIG. 17, the triplet provides a wide field of view. The device also includes a switch 32 for stopping the motor in each position for operation.
0 and a stop 322 for positioning the wide field element 314 in either the narrow field position or the wide field position.
It is equipped with

Next, referring to the perspective view of FIG.
Detector array 150 having 32, 334 and 336 will now be described in detail. 338 and 3
A detector element such as 39 can be, for example, a photoconductive type detector. Each module or segment, such as 332, could be constructed by brazing a plate of detector material to a Kovar substrate and bonding the substrate to a sapphire insulator to provide electrical insulation. Detector groups are then formed by removing material between the detector elements using an etching process. Signal contacts to each detector element are provided using a photo-engraved line pattern (not shown).
It can be built by wire bonded to. Suitable cold shields are provided, such as cold stopper surfaces 340 and 342, which also provide a stack of N slits located in front of each detector element. These slits constitute effective apertures to adequately reduce free photons. It should be understood that other suitable types of cold shield configurations may be used in accordance with the present invention.
Dividing the detector array into segments 332, 334 and 336 improves focusing of the optical system.

Next, the elimination of the Narcissus phenomenon according to the present invention will be explained with reference to FIGS. 19 and 20.
The reflectivity of the elements in the optical system, including the outer window 50 and other reflective optical elements, is such that the image of the detector assembly can be horizontally scanned from the outer window 50 and other optical elements, even when anti-reflective coatings are applied. It is large enough to be reflected back to mirror surface 123 and to cooling vessel entrance window 146 and from there to detector array 150 . Horizontal scanning mirror surface 1
23 is placed between the detector array and the optical system, so that a Narcissus image is generated when the scanning mirror surface is perpendicular to the optical axis. As the detector assembly is scanned from one side to the other, the internal temperature distribution pattern of the detector element becomes a weak image that is transmitted through its optical system to a predetermined image when the scanning mirror surface is perpendicular to the optical axis. reflected to the detector array at a scan angle of This spurious apparent temperature pattern is greatly attenuated by the low reflectivity of the entrance window coating. However, cryogenically cooled detector elements within the cold shield assembly exhibit sufficiently strong radiation contrast that even this low temperature is still visible when increasing the detection sensitivity. This Narcissus phenomenon is generated as an image because the detector array is located at the lens focus. Therefore, the optical system is
A weak internal image of the detector assembly will be searched for itself, which image will appear in the vicinity of an axis parallel to the outer window 50 or perpendicular to the optical axis when scanning is being performed. In some arrangements, the Narcissus phenomenon due to internal image reflections is prevented to some extent by tilting the outer window at a preselected angle, and in some arrangements, the detector image is narrowed. Positioned outside the field of view. However, even in such an arrangement, a Narcissus image appears on the detector array in the case of a wide field of view. In this way, the image of Narcissus is generated not only by the window, but also by an optical system with a telescope with two fields of view: wide and narrow. The path of Narcissus after reflection from the optical system is indicated by arrow 345 in FIG. 20, and the path of the Narcissus source energy to the optical system and the path to the beam splitter after reflection is indicated by arrow 347. There is.

In the device of the present invention, Narcissus erasure source 1
60 is coupled to a suitable variable power supply 340;
In the example shown, a temperature of approximately 640° is generated and, after reflection from the optics, is applied to the cooling section entrance window 146.
IR radiation is provided and from Narcissus cancellation source 160 via beam splitter 142 and entrance window 146 to detector array 150 . This operation causes the vertical image 163 of the Narcissus erasure source to
is generated, which offsets and minimizes the effect of the cold Narcissus image. Beam splitter 142 transmits approximately 90% of the energy incident on its surface, so most of the radiation is transmitted to source 1.
60 to Automatic Responsive Control (ARC) Modulator 168
transmitted to. Between 8 and 10% of the radiation reflected by beam splitter 142 is reflected back to detector array 150 by sensing optics to perform a canceling action. Narcissus cancellation source power supply 340 is preferably variable so that optimal Narcissus cancellation can be adjusted and set by Narcissus cancellation source 160 and can be varied to adjust the ARC contrast control in accordance with the present invention. In FIG. 20, the optical system is shown schematically as an overall optical system 344 to indicate that the entire optical system operationally participates in the Narcissus effect. Note that normally the Narcissus image will appear on the detector array only at a particular scan position, and cancellation will occur at the same scan position. That is, the Narcissus image appears only when the scanning position is such that the infrared energy is incident on the axis perpendicular to the window.

The operation of the automatic responsiveness control circuit will be described with reference to FIGS. 21 and 19. An automatic responsive control (ARC) source provides an IR modulation common reference for automatic gain control within all N channels in total in the signal processing apparatus of the present invention. The main function of ARC is to level the responsivity of each detector element in the array by adjusting the gain of each channel individually. This leveling action can also be achieved by means of selected damping resistors, but this method requires continuous manual adjustment to obtain satisfactory action. According to the present invention
The ARC is capable of continuous leveling during the entire life of the detector array, so no manual adjustments are required during that time. Furthermore, the ARC control circuit itself does not require leveling adjustment, and can be used as is to replace some elements of the optical system of the device. ARC operation involves monitoring the responsivity of each modulated detector channel and automatically adjusting the amplifier gain to obtain a uniform response. The ARC modulator 168 as a modulated IR source is uniformly incident on each detector element and the IR from the field of view is
Generates a composite signal that is multiplied with energy and amplified. The reference source modulation signal is extracted from the composite signal in each channel of the signal processing device and rectified by a synchronous detector to obtain a DC control signal proportional to the responsivity. A control signal is then sent to a diode gain control element within each signal amplifier. The device of the invention also allows contrast control over a fairly wide range by varying the intensity of the ARC source.

In self-responsive control operation, IR energy from Narcissus cancellation source 160 passes directly through beam splitter 142 to modulation slit 350 to reflective mirror surface 352. This optical path is indicated by lines 358 and 364. For example, a vibrating fork-like chopper 360 placed in front of the mirror 352 is connected to the ARC source drive circuit 193 and thus also reflects the 45 Hz frequency.
The modulation slit 350 is caused to vibrate sinusoidally in response to the strength of the IR signal. The signal beam modulated by the vibrations of this chopper 360, indicated by line 364, is then reflected off the beam splitter 142 and applied to the detector array 150 as a common reference source modulation signal that is passed through the mounting channel. Ru.
Although only 8 to 10% of the modulated energy is reflected from beam splitter 142, this is sufficient to provide a reference signal upon which to base ARC control within the signal processing system. The modulated energy transmitted through beam splitter 142 is widely distributed and dissipated within the device.

Next, the structure and operation of the ARC modulator 168 will be described in detail with reference to FIGS. 22, 23, and 24. Mounting structure 376 includes mirror 35 mounted adjacent slot 350 formed by shutters 363 and 365.
It has 2. Attached to the ends of structure 376 are synchronous vibrating forks 367 and 369;
One arm of each is connected to shutters 363 and 365. Each synchronous oscillating fork is controlled to oscillate at a selected frequency in slot 35.
It has controls 373 and 389 connected to appropriate circuits (FIG. 25) for opening and closing 0. Each controller, such as 373, has a drive coil 375 extending from a synchronous vibrating fork tooth with an armature 377, and a similar coil 379 and armature 375 for generating a feedback signal.
87. It has coils 381 and 383 with a similar armature of the control device 389 for the synchronous oscillating fork 369 on the other side. The same applies to the upper synchronous vibration fork 367. Upper and lower vibrating forks 367 and 369
is supported by a connecting rod 371 having a centrally located seat spring 372 attached to a base 376.

Referring to FIG. 25, which shows a circuit diagram of the ARC modulation drive circuit 193 shown in FIG. 19, the ARC signal is applied from conductor 380 at 45 Hz to integrator 381A via a coupling capacitor. The circuit generates a sine wave, and drive coil 375 and pickup coils 379 and 383 provide an inverted negative feedback signal to the input of amplifier 383A to reduce Q and response time. In this way, reliable modulation of the Narcissus signal is performed at a rate of 45Hz.

As can be seen from FIG. 26, which is a block diagram of the ARC controller, detector array 150 is responsive to a signal from synchronization circuit 770 representing a 45 Hz signal source and a contrast control signal on conductor 380 from contrast controller 423. It receives energy from an ACR modulator 168 driven by an ARC modulation drive circuit 193 (not shown). The contrast control signal is used to control the strength of the signal system to control the contrast of the display 90. These signals are then applied to preamplifier and filter 390 via N conductors. The output of this preamplifier and filter 390 passes through a synchronous detector 392 to provide individual gain control signals to N preamplifiers 390. Synchronous detector 3
92 receives the 45 Hz reference modulation from the synchronization circuit 770 and performs synchronous detection of the modulation signal incident on the detector array. In this operation, including preamplifier 390, N signals are applied to multiplexer 394 via separate conductors. The multiplexer 394
generates a multiplexed video signal that is applied as a video amplifier 782 to a mixer device 784.
Mixer 784 is derived from synchronizer 770
In response to the ARC cancellation signal, the ARC reference signal utilized within the device is canceled. In this way, the composite signal that is canceled after multiplexing the reference signal components is a time-division multiplexed signal, and combining this signal with the cancellation signal can be performed extremely easily and reliably, and the equipment does not need to be complicated. This is to prevent this from happening. The video signal is thus applied from mixer 384 to display 90. The display produces a visible image on a cathode ray tube, which is viewed by an operator in a telescopic device, for example.

As can be seen from Figure 27, the 45Hz ARC reference signal is displayed on the device shown. There are no odd harmonics that overlap the harmonics of the frame rate of 30Hz. The 45 Hz even harmonics are rejected by the balanced sync detector 392 so that the ARC reference signal does not cause interference or disturbance in the signal processing equipment and display system.

Referring to Figures 28a and 28b, the signal processing apparatus includes circuitry to convert the N detector signals received from detector assembly 149 into a single instance of a time division multiplexed video signal. Additionally, the signal processor generates synchronization signals for display and synchronization and drive signals for the jumping mirrors of the ARC modulator and detector assembly. Signal processing includes two-stage multiplexing of IR scene information of an array of N detector elements. First stage multiplexing is N/4
This is done with modules arranged in groups of channels, each module providing one video output. Each of conductors 149A-149D is a composite conductor representing N/4 individual conductors from the N/4 detector elements in use. Module groups 385 to 388 represent each composite conductor 14.
9A through 149D, each generates a single output signal during each clock period. Considering the module 385, the amplifier 390 has N/4 amplifiers, and the ARC synchronization detector 3
92 has N/4 detectors, each coupled to the amplifier of a corresponding channel, and multiplexer 394 has N/4 switches and one shift register 396. Along the shift register 396, the control pulse A is shifted through N/4 flip-flops and output to the output conductor 398.
A different signal is sequentially generated for each of the N/4 detector signals. Multiplexer modules 386, 387 and 388 are of similar construction to 385 and have output conductors 400, 401.
and 402. Kurotsuku,,
With pulses of and, module 385 samples detectors 1, 5, 9, 13, etc., module 386 samples detectors 2, 6, 10, 14, etc., and module 387 samples detectors 3, 9, 13, etc.
7, 11, 15, etc. are sampled, module 3
88, the detectors 4, 8, 12, 19, etc. are sampled, and these signals are transmitted to each conductor 398, 400, 4.
01 and 402. A synchronous detector such as 392 has a 45 Hz in-phase and
Receives a synchronous detector signal with a 180° phase shift. The 360Hz oscillator 415 applies the AC signal to the rectangularization circuit 416,
It is then applied to push-pull driver 414 via 1/8 divider circuit 418. Divide-by-eighth circuit or divider 418 also applies the 45 Hz signal on conductor 420 to output driver 422, while the latter applies the signal to RC modulator 168 via conductor 380. DC variable contrast control source 423 applies a control signal to output driver 422 and also provides reference signal cancellation circuit 432. As a result, subsequent reference signal cancellation is guaranteed. By controlling the ARC signal, N
The gain of each channel and the degree of contrast on the display are determined. A square wave to sine wave converter 435 receives a 45 Hz signal from circuit 418 and applies the sine wave to reference signal cancellation circuit 432 . This circuit is a gain controlled amplifier responsive to a contrast control signal. The ARC cancellation signal is applied from conductor 434 to more reliably remove the reference signal from the video signal in summing amplifier 440.

The four video outputs from the low speed multiplexers are synchronously subsampled by one high speed multiplexer 450. The multiplexing rate is chosen for the azimuthal scan rate so that all N detectors are sampled during each azimuthal display pixel increment. Since the high speed subsampling occurs at different times for the four low speed multiplexers, the clocks for the low speed multiplexers are delayed so that the subsampling occurs at the peak output of the low speed multiplexers. conductor 398,
400, 401 and 402 are video buffer devices 452 that can have four delay lines.
multiplexer 450 to send the video output signal through
to be applied. Each of the four high speed switches within multiplexer 450 is adjusted by a different clock pulse, designated G1, G2, G3 and G4. Video buffer device 452 acts to minimize switching transients.

Crystal controlled clock 458 provides a clock signal to ring counter 460, which in turn sends a signal to decoder 462. The decoder receives signals G1,
G2, G3 and G4 are applied to output driver 464 and multiplexer 450. The clock signal is also provided from decoder 462 to logic circuit 468 to generate control signals A, B, C and D, a vertical display signal synchronization signal on conductor 469, and a vertical blanking signal on conductor 471. 2
Lead counter 472 also controls logic circuit 468 in response to clock 458 and receives a reset signal from logic circuit 468 via reset logic circuit 474. The video signal is applied from multiplexer 450 via conductor 480 to summing amplifier 440;
The other side is also sent via conductor 482 to the video display device. In addition to receiving the ARC cancellation signal on conductor 435, summing amplifier 440 receives an aim synchronization signal on conductor 484 and
receives the horizontal erase signal pulse through the horizontal erase signal pulse. Summing amplifier 440 is a conventional operational amplifier of the type having a plurality of parallel input resistors at the input terminals connected to the output terminals through bypass resistors.
The aiming synchronization input signal from the aiming synchronization generator 127 (FIG. 4) is passed through conductor 488 to amplitude discriminator 490.
and added to aiming delay circuit 492, horizontal sync delay circuit 494, and interlace delay circuit 496. The delay circuit 492 may be of various types, and the field selection mechanism 171 (FIG. 4) may suitably add the signal to the video signal to display horizontal and vertical lines of sight on the display surface of the cathode ray tube.
can have a parallel delay circuit selectable via conductor 493 from . Gate 498 passes the vertical aim delay signal onto conductor 484 by alternating frame widths in response to the interlaced delay signal. One shot circuit 499 generates a horizontal erase pulse on conductor 486 in response to horizontal sync delay circuit 494. A signal from one shot circuit 499 is also applied to conductor 513 as a display synchronization signal. One-shot driver 504 responds to interlaced delay device 496 to provide mirror coil interlaced signals on conductors 515 and 517, each having a different phase.
It also generates a display interlaced signal on conductor 518. Gate 50 during the cycle of the alternating frame
A clock signal via 6 is applied to the output of center channel detector N/2 (node 549 in FIG. 29) to generate a vertical aiming signal on the display. A reversible switch device 510 is provided for the purpose of applying a signal to the sensor aiming motor to move in a selected direction to adjust the vertical line of sight.

Referring to Figure 29, which shows a filter amplifier and multiplexer for a single channel,
These circuits are responsive to detector 522, which may be referred to as detector number 1 of array 150. The amplifier is
It has a transistor 524 of the pnp type, the emitter of which is connected to ground via a suitable resistor and a bypass capacitor, and the collector of which is connected via a capacitor and resistor to the input conductor of an operational amplifier 528. 526. The output of the detector is applied to the base of transistor 524 and through resistor 530 to the collector of the transistor. This collector is coupled through resistor 531 to the negative detector bias supply. The other input terminal of operational amplifier 528 is grounded and its output is coupled to conductor 536. Conductor 526 is connected to capacitor 538, which in turn is connected to diode 540.
and 542. The cathodes and anodes of these diodes are coupled to node 541, and their anodes and cathodes are connected to capacitors 546 and 544, respectively, which are connected to node 545 and conductor 548. The anode of diode 540 is connected to conductor 550, and conductor 536 is connected through resistor 554 to node 549, the latter being connected to conductor 547.
54 between capacitors 544 and 546 through
5. Conductor 547 is resistor 560
It is grounded via a resistor 562 and connected to a conductor 526 via a resistor 562. The conductor 548 is
It is connected to the drain terminal of a MOS field effect transistor 570, and the conducting wire 550 is connected to a drain terminal of a MOS field effect transistor 572. These two transistors form an ARC sync detector 571. The source electrodes of transistors 570 and 572 are connected to conductor 536 through a low pass filter, their base terminals are grounded, and their gate terminals are connected to conductor 536 through a push-pull driver 414 (FIG. 28). Connected to respective conductors 412 and 410 responsive to derived synchronous two-phase rectangular drive pulses. A bias source 575 is connected to the conductor 536.

In operation, the gain of operational amplifier 528 is determined by the impedance of resistors 562, 554 and 560 and diodes 540 and 542. Transistors 570 and 572 forming synchronization detector 571 are balanced when the ARC signal has a predetermined amplitude and the current through diodes 540 and 542 becomes constant. However, upon a change, such as a decrease, in the amplitude of the ARC signal detected by synchronous detector 571, diodes 540 and 542
The current flowing through diodes 540 and 542 decreases, and the impedance through one of diodes 540 and 542 decreases.
The ratio between resistors 554 and 560 increases. In this way, each individual channel has a synchronization detector 5.
71 and has a gain that is automatically controlled in response to the ARC signal detected by 71.

Thus, in response to the drive signal, one of the field effect transistors becomes conductive at the frequency of the IR calibration signal and the other signal becomes non-conductive. The reverse is also true. The effect of the operation of synchronous detector 571 is that diodes 540 and 542 are coupled in series in parallel to capacitors 544 and 546.
capacitor 54 so that it is forward biased.
4 and 546. Diodes 540 and 542 are preferably of the silicon type with low leakage current, and their impedance to AC signals is determined by the DC bias current. For example, the AC impedance of diode 540 or 542 is 26 divided by the DC bias current in milliamps (=26/
Id).

Therefore, the potential stored in capacitors 544 and 546 is
The AC impedance of these diodes would be approximately 26,000 Ω if sufficient to supply a 1 μA bias current through the diodes.

A node 545 common to capacitors 544 and 546 is coupled to node 549 of a voltage divider circuit of resistor 554 and resistor 560. Resistor 55
The values of 4 and 560 are selected such that the AC signals coupled to nodes 549 through 545 are at relatively low levels. For example, resistor 554 is 1000Ω,
Resistor 560 may be 10Ω. This means that optimal performance with minimal distortion is obtained if the amplitude of the AC signal coupled to node 545 is maintained at a preselected low level, such as a peak-to-peak amplitude of 50 mV. This is because. AC signals coupled through diodes 540 and 542 connect to their common coupling point 541
through capacitor 538 to input conductor 526 of amplifier 528 .

To summarize the operation of the self-responsive control circuit of FIG. 29, the gain of the circuit is a function of the feedback impedance between output conductor 536 and input terminal 526. The value of this feedback impedance and therefore also the circuit gain can be controlled by controlling the AC impedance of diodes 540 and 542 as a function of the DC current supplied to the diodes. Synchronous detector 571 provides this impedance controlled DC current to diodes 540 and 542 as a function of the level of the calibration signal (derived from the ARC signal) in the output signal on conductor 536.

The circuit of FIG. 29 can be implemented with polarization such that as the calibration signal energy in output conductor 536 increases, the control current to diodes 540 and 542 also increases. Since the AC impedance of a diode is an inverse function of the DC current passing through it, this increase in output signal increases the control signal. As a result, the AC impedance of the diode is reduced and a larger negative feedback current can be applied to the input of amplifier 528 to reduce the gain of this stage.

As mentioned earlier, diodes 540 and 5
The AC signal applied to 42 should have a peak-to-peak amplitude of, for example, 50 to minimize distortion.
It should be maintained below a preselected level such as mV. This is accomplished by also coupling diodes to the virtual outputs produced by voltage divider resistors 554 and 560. For example, resistor 554 can typically have a value of 1KΩ, and resistor 560 can have a value of 10Ω. Thus, the signal applied to the diode is reduced approximately 100 to 1.

One feature of the apparatus of the present invention is to maintain a given gain function through the processing channel in response to a calibration signal at a particular preselected frequency, but at the same time responsive to a data signal being processed with the calibration signal. The main point is that an automatic response control circuit is provided to prevent this from happening. In the operation of the circuit of FIG.
A pull synchronous detector 571 is controlled by a drive signal applied to the gates of transistors 572 and 570 such that only the detector extracts a valid output signal from the input signal at the frequency or odd harmonics of the drive signal (27th figure). Output signals generated by the input signal at even harmonics of the drive signal are rejected because the detector is in a balanced push-pull configuration. When used for image generation, the data signal must have a frequency that is a multiple of the vertical scan rate, ie, n·30 Hz (n=any integer). Therefore, unless a multiple of the vertical scan rate equals an odd multiple of the gate control signal that drives the transistors of the sync detector 571, the data signal will not pass through the sync detector 57.
1 cannot be involved in the output signal. To express this in another way, the data signal is
When m is an arbitrary odd integer, n・30Hz=m・
Otherwise, the data signal cannot meaningfully contribute to the gain control of the ARC circuit.

The amplified signal on conductor 536 is then applied through a low pass filter circuit to conductor 580, thus connecting the drain connected to conductor 580 and the source connected to output conductor 398, the grounded base and Added to a low speed multiplexing switch 582 having MOS field effect transistors 584 and 586 each having a gain control terminal connected to a conductor 588. Multiplexing switch 582 receives control from flip-flop 592 through appropriately biased drive transistor 590. The flip-flop may be the first flip-flop of shift register 396 in FIG. flip-flop
Flop 592 receives a clock signal as well as a control signal A that may be applied to its input. Thus, during every fifth clock period determined by control signal A, the sensed gain-controlled signal on conductor 536 is sampled and provided to output conductor 398 to high speed multiplexer 450. (28th
Figure). Shift register 396 is 5
N/4 flips like 92 and 593
Of the flip-flops, only flip-flop 592 receives control signal A, and the input and output terminals are connected alternately for each subsequent flip-flop.

Referring to FIG. 30, which shows one example of a high speed multiplexer circuit that may be utilized in multiplexer 450, the multiplexed signal on conductor 398 passes through buffer 452 (FIG. 28) before being routed through each diode 521 and 523 is applied to the anode and cathode. The cathodes and anodes of these diodes are connected to the respective cathodes and anodes of diodes 525 and 527. The anodes of diodes 523 and 527 are connected through resistors to a source 531 that receives the positive pulse G1 of the G1 signal source, and the cathodes of diodes 521 and 525 are connected through resistors to allow the signal to pass through the switch. 1 source 529 in order to do so. Output signals are applied to conductor 480 from the anode and cathode of each diode 525 and 527. The conductor is connected to ground via a suitable bias resistor. Similar switches are multiplexers 394 and 39.
5, 397, and 399.

Logic and timing operations will now be described in detail with reference to FIG. ring counter 460
has flip-flops Z18 and Z19 of the JK type that count continuously in binary in response to clock 458. Decoder 462 receives signals 18, 19; Z18, 19; 18,
In response to Z19 and 18,19, the signal G
1, G2, G3 and G4 are included. Power driver 464 includes NAND gates 531-534 which generate signals G29, G30, G31 and G32, labeled as signals CLOCK, CLOCK, CLOCK and CLOCK. Gates G1, G2, G3 and G provide high speed multiplexer synchronization signals called G1, G2, G3 and G4 signals, respectively. Signal G1 is applied to gate G7 and inverted to generate clock signal C2. clock signal C1
is the clock signal generated by clock generator 458. Binary counter 472 includes JK flip-flops Z1 through Zn each responsive to clock signal C2 and performing conventional binary counting. Reset conductor 474 includes a flip-flop Z20 for applying a reset signal from gate G11 to flip-flops Z1 and Z2 and for generating a reset signal from gate G12 to flip-flop ZN. Gate G9 responds to signals Z1 to ZN to
gate G8 receives clock C1 and becomes an input to inverter G10, the output of which is applied to the K input of flip-flop Z20.

Logic device 468 applies it to gate G28 via gate G27 which is responsive to inputs Z1-ZN. The input is inverted and applied to conductor 469 as the vertical display sweep synchronization signal. logical device 46
8 is also responsive to inputs Z1 to ZN and gate G1
6 to apply a signal to gate G26. Gate G26 is clock C
1 to generate a vertical erase signal on conductor 471.
Gating signal G1 in response to signal Z1 to ZN
A non-erasing gate G13 is provided to apply to gate G17, and the signal applied to gate G17 is applied to gate G26. Gate G13 provides one condition input to gate G14, which is applied to each of gates G18, G19, G20 and G21 in conjunction with each clock signal C, C, C and C. Gates G22, G2 coupled to gates G18, G19, G20 and G21
3, G24 and G25 perform inversion to generate control signals A, B, C and D.

Referring to FIG. 32, waveform 475 represents the video signal and includes the horizontal blanking that occurs after the completion of each display raster. During each vertical sweep, a vertical line is formed on the display as shown by waveform 477. The vertical sync signal of waveform 652 defines the vertical sweep and the horizontal sync signal is illustrated by waveform 655. Each horizontal sweep of waveform 479 defines one horizontal field and each two fields creates a 2:1 interlaced frame on the display. The jump control signal of waveform 653 is connected to conductor 51.
7 (see Figure 28).

Referring to the waveform diagrams of FIGS. 31 and 33, clock 458 generates pulses of waveform 610 that are utilized by multiplexers and display devices to synchronize their operation. Counter 460 counts each flip-flop Z1
8 and Z19. The flip-flops Z18 and Z19 generate respective waveforms 616 and 62.
Clock signals in inverted forms 18 and 19 as indicated by 0 are generated in divided proportions. Gates G1-G4 generate high speed synchronization signals of waveforms 621-624. The decoder 462 decodes the counter 460 and outputs the signal G1.
Please be careful that a pulse train of G4 to G4 is generated. The signals G1 to G4 are connected to the power driver 464.
A clock signal is generated through the respective clock signals. Signals G1-G4 are also used as synchronization signals to control the four switches in the high speed multiplexer. Low speed multiplexer clock signals G29-G32 are connected to signals G1-G4, as shown by waveforms 628-631, respectively.
A clock or clock signal in an inverted form.

Referring to FIG. 34, the non-erasing signal G13 shown by waveform 634 is the inverted form of signal G14, and is the end of the erasing cycle, i.e., the return cycle of the elevation direction display sweep of waveform 477 used in the display device. Determine the end. Reset pulses G11 and G12 for counter 472 are shown at waveform 645, and pulse G9 is shown at waveform 647. Gener signal G29 to G32
are shown as waveforms 653-656, which are low speed multiplexer control signals applied to the flip-flop registers of a multiplexer, such as multiplexer device 394 of FIG. Control signals A, B, C and D of waveforms 657, 641-643 control high speed multiplexing operations. The high speed clock signal is shown at waveform 659, the vertical signal G15 is shown at waveform 646, and the gate G17 signal is shown at waveform 648. G16, G17 and clock C
The vertical erase signal G26 obtained from 1 signal has waveform 6.
80, and vertical synchronization signal G28 is shown by waveform 652.

Next, the timing circuit will be described in detail with reference to the waveforms in FIG. 35. The pulses of waveform 660 are 360 Hz rectangular pulses generated by the rectangular circuit 416 (FIG. 28), which after being divided into 8 are connected to the ARC reference signal source and waveform 662 with a 180° phase shift. generates a synchronization detection signal.
The ARC reference signal source and the sync detect signal being in phase are shown by waveform 664. Waveform 6
The 66 ARC reference signals are utilized by the ARC modulator within the sensing device.

Referring to FIG. 36, the horizontal aiming signal of waveform 668 is used to synchronize the device to generate the horizontal erase pulse of waveform 670 as well as the mirror interception pulse of waveform 672. The horizontal display sweep utilized in the display is shown at waveform 479 and is generated by delaying the aiming pulse at waveform 668 by the horizontal sync pulse at waveform 655.

Referring now to FIG. 37, a display according to the present invention will be described. The display includes a cathode ray tube 672 with a suitable telescope or optical magnifier 674 spaced apart for viewing the IR scene on a screen 673. The horizontal synchronization signal of waveform 655 is connected to conductor 5.
13 to the horizontal oscillator 676. This oscillator may be a multivibrator designed to operate at a slightly lower free running speed than when operated synchronously. This circuit supplies pulses to a horizontal sweep generator 678, the latter generating a linear ramp signal of waveform 479 in FIG. 36, which is applied to the horizontal yoke of a cathode ray tube, for example. A vertical sync pulse of waveform 652 is applied to vertical oscillator 678 via conductor 469. This oscillator can be a multivibrator and generates square wave pulses to control vertical sweep generator 680. The interlaced pulse of waveform 672 is applied to a vertical sweep generator 680 via conductor 518 to generate a two-to-one interlace to add the square wave interlaced sync to the vertical yoke control signal. A vertical sweep pulse of waveform 477 in FIG. 34 is applied to the vertical yoke of tube 672. A video signal in waveform 690 having a predetermined rate of detector data is connected to conductor 4.
82 to a video amplifier 692. The amplifier receives the multiplexed video signal from the sensor, amplifies it to the required level, and displays it on the display.
Modulate the CRT's scanning beam. Amplifier 692 has a DC sensitivity of 2 volts for black and white, for example.
It can be a differential amplifier. One of the outputs of amplifier 692 is applied to the first grid of tubes 672, and the other half of the output is applied to the cathode of tubes 672. This cathode signal can also be applied to the accelerating electrode via power supply 682 to minimize beam bright spot focusing disturbances due to medium to high brightness signals. The brightness control signal is sent to the control panel 102 (third
is applied to video amplifier 692 via conductor 104 from control source 698 in FIG.

Referring to the schematic representation of screen 673 in FIG. 38, the illustrated raster includes a selected number of scan lines generated by the multiplexing operation as well as a selected number of scan lines generated by the horizontal or azimuthal scan. Has a vertical line. Each vertical and horizontal sight line 698 and 700
is located at the center of the display 673. The dotted region 701 shows the deviation that would be the result of Narcissus at a predetermined scan angle, assuming the eraser of the present invention were not present.

FIG. 39 shows more clearly the cooling system consisting of a helium compressor and a refrigeration device forming part of the sensor. The helium compressor can be comprised of a compression pump 714, a heat exchanger 716, a fan 718, and a conduit 720 that supplies helium to a refrigeration system 726 via an oil separator 722 and an absorber 724. The refrigeration system returns gas to the conduit 730
It may have an expansion valve of suitable thermally conductive construction returning to the compression pump 714 via. Structure 732 is housed within a cooling container and positioned adjacent to the detector as is well known to those skilled in the art. This type of refrigeration system is well known, so a detailed explanation will be omitted.

What has been described above is a simple and improved infrared sensing and display system or apparatus in which the detector is skipped and scanned using a plane mirror over the entire field of view in a horizontal scan. For the vertical dimension, the detector signals are amplified and time division multiplexed into a single video signal stream, which is displayed on the display. The display includes a cathode ray tube that visually presents IR viewing information to the operator in a raster format similar to that of a television. The raster is synchronized horizontally to the mechanical mirror scan of the sensor and vertically to the electronic scan generated by the multiplexing. Since both scans are linear in time and unidirectional, only one synchronization pulse is required for each scan. The device receives emitted infrared radiation and provides a highly accurate and reliable thermal image representation of the observed scene.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a helicopter using a forward-looking synchronous thermal image generator according to the present invention, FIG. 2 is a diagram schematically illustrating a rotating shooter station as an example of the use of the thermal image generator of the present invention, and FIG. is a block diagram of the thermal image generation and night observation device according to the present invention; FIG. 4 is a block diagram for explaining the detector device used in the device of the present invention;
FIG. 5 is a schematic perspective view of the detector device with certain parts exploded to explain the operation of the detector device of the present invention, and FIG. 6 is a mechanical-optical view of the detector device with the main housing removed. FIG. 7 is an optical schematic diagram of the optical system used in the present invention viewed in the azimuth direction; FIG. 8 is a perspective view schematically showing the optical system of the present invention for clarity of illustration. FIG. 9 is a schematic diagram showing a part of the azimuthal scanning mirror drive used in the detector device in elevation; FIG. 10 is a schematic diagram showing the interlacing mirror of the detector device. 11 is a schematic side view to explain the aiming mirror used in the detector device, FIG. 12 is a view taken along line 12-12 in FIG. 11, and FIG. FIG. 11 is an enlarged view of the driven arm of the aiming mirror; FIG. 14 is a schematic diagram of the synchronous generator used in the detector arrangement; FIG. 15 is a schematic diagram along line 15--15 of FIG. 14; FIG. 17 is a schematic side view of the same section in a wide field of view, FIG. 18 is a perspective view schematically showing a divided detector assembly that can be used in the detector device, and FIG. A schematic diagram for explaining the Narcissus source and the automatic responsiveness control device provided in the detector part, FIG. 20 is a schematic perspective view for explaining the radiation principle of the Narcissus source, and FIG. 22 is a schematic perspective view for explaining the ARC modulator, and FIG. 23 is a schematic perspective view for explaining the ARC modulator.
A schematic cross-sectional view taken along line 23--23 of the figure, FIG.
FIG. 25 is a block diagram showing a circuit of an ARC modulator according to the present invention; FIG. 26 is a block diaphragm of a signal processing device to further explain the ARC method of the present invention. , FIG. 27 is a diagram showing the spectrum of energy as a function of frequency to further explain the ARC device of the present invention.
Figures 28a and 28b are block diagrams of a signal processing device according to the present invention, and Figure 29 is a block diagram of a signal processing device according to the present invention.
30 is a block diagram of a filter amplifier and a low speed or first stage multiplexer that may be used in the signal processing apparatus of the present invention; FIG.
Figure 1 shows a block diagram of the control logic device of Figure 28.
FIG. 32 is a waveform diagram showing the voltage versus time relationship to explain the timing operation of the device of the present invention, and FIGS. 33 and 34 are voltage-time relationships to explain the vertical timing operation of the device. 35 and 36 are waveform diagrams showing the voltage/time relationship for explaining the ARC timing and horizontal timing operations of the device of the present invention, and FIG. 37 is a waveform diagram showing the voltage/time relationship used in the device of the present invention. a block diagram showing a display device;
FIG. 38 is a schematic diagram showing the display surface of a cathode ray tube that can be used in the display device of FIG. 37, and FIG.
The figure is a block diagram schematically illustrating one example of a cooling system that can be used in a detector device.

Claims (1)

[Claims] 1. A detector array comprising a plurality of detector elements that respond to infrared energy obtained by mechanical-optical scanning, and a detector array attached to each of these detector elements to amplify each output signal. and a plurality of channels including variable gain amplifiers for transmission, and for electronically processing output signals obtained from the respective channels and displaying them as visible images. , in an automatic responsiveness control device, means for superimposing an infrared reference signal amplitude-modulated with a frequency that does not interfere with the received infrared signal on the received signal and making it continuously incident on the detector array 150; 168; detecting a DC electrical signal proportional to the infrared reference signal component in the received signal from the output signal of the detector array 150, and adjusting the gain of the amplifier in each channel according to the strength of the detected electrical signal; means 392 for controlling the amplitude-modulated infrared reference signal component from the output signal amplified through each of the channels, a cancellation signal obtained by inverting the phase of the reference signal component and the output signal. Means for mixing 7
84. An automatic responsiveness control device for a thermal image generating device, comprising: