Thermal imager

DESCRIPTION of the industrial invention entitled:

"THERMAL REPRODUCERS OF IMAGES"

by Barr & Stroud Limited of British nationality at Caxton Street, Anniesland, Glasgow G 13 111Z SCOTLAND (GREAT BRITAIN)

Inventors: Charles Andrew Berry, Peter John Berry and lan

Harrison llowie

Question nr. 6 1 b / 0 A / 8 1

MAXIMUM $

a thermal reproducer of im. in which from waveform of output, a period T, the wave of wavelengths has a duration T ^, wherein T ^ <synchronization is placed before and very close to the waveform derived from the subject, the duration between the synchronous signal and the end of the waveform derived from the scene is Tg, and the monostable multivibrator has a control time T_Q such that T₉ <T₉ <5C $ T.

The present invention relates to thermal imaging images.

beautiful image thermal reproducers, the scene

Presented the

Improved rnagini is provided by the detector derived from the scene 50 / ί T, the signal of

<img file="IT1145552B_D0001.tif" />

from which infrared thermal radiation emanates is continuously explored by an optical scanning device through a detector whose waveform of the output signal is sent through signal processing circuits to a video output device. The scanning device scans horizontally, but the detector output signal is substantially continuous, consisting of successive waveform portions of the time interval in which the detector is actually explored through the inside of the casing. of the image player and the time interval in which the detector is actually explored through the scene. The detector output signal therefore has a perio structure, "say₁-L f the effectiveness of the exploration of the imager reproducer being the relationship between Tj and T.

In order to synchronize the operation of the signal processing circuit with the detector, it is normal to add a preform terminated waveform to the detector signal in a fixed position during each period T relative to the waveform portion due to information derived from the scene. This synchronization signal is then recognized by a recognition circuit and used to activate a monostable multirevel from which a timing signal is derived for the signal processing circuit. In the known image reproducers, this synchronization signal is arranged immediately after the information derived from the scene, which gives rise to a relatively complicated synchronization recognition circuit;

to ensure that any information derived from g

the scene having a waveform portion similar to that of the synchronization signal not prematurely activating the monostable multivibrator. In practice, in practice, when such a portion of the waveform exists, it is generally repeated in a considerable number of successive scanning lines (i.e., periodes T) since it derives from the hex. steering of a physical object of considerable size in the scene being observed. Thus, the multivibra

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monostable. and therefore the. time tracking are not synchronized with the information de. rivaled by the scene for a considerable number of lines of exploration and a precious infatuation is lost. ne because the corresponding video image becomes_: unintelligible.

It is an object of the present invention to provide an improved reproductive form, 5 ^; thermal image,

According to the present invention, a thermal imaging apparatus is provided in which the output waveform from the detector has a period T, la;

The waveform derived from the scene has a duration Tp in which T ^ &lt;50% T, the synchronization signal is placed before and very close to the waveform deriving from the scene, the duration between the sync signal;

'nisation and the end of the waveform derived from; *¹ The scene is Tg, and the monostable mulching machine has'

I ί An adjustment time Tg such that Tg &lt;Tg &lt;0 50% Tj With the arrangement according to the present invention, the monostable multivibrator is adjusted for a duration greater than Tpina less than 50%. _:

T, so that even if the monosta- _:bile is prematurely activated, it has returned to its inactive condition before the signal of 'c' w

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synchronization during the next period T of the output signal from the detector, so that there is then a correct synchronization, resulting in _:in only one unintelligible line of video.

It should be noted that, since the efficiency of splitting is less than 50 ^, the portion of for; • but wave due to the detector which is explored through the inside of the casing of the reproducer | The images are longer than T₁ and du- J ¹ !

This period requires that the output from the detector be free of a waveform that could be erroneously recognized by the circuit of _;recognition. However, this is easily achieved!

since the inside of the casing of the reproducer;

The kings of images are of a predetermined nature. II!

!

; synchronization signal may conveniently be provided by a mirror within the envelope; of the image reproducer and reflecting back on the detector the infrared radiation obtained from the detector support (which is cooled substantially below the ambient temperature). !

An embodiment of the present invention will now be described by way of example

<img file="IT1145552B_D0002.tif" />

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injury to the attached drawing, in which:

Figure 1 illustrates a block image thermal imaging apparatus; and Figure 2 illustrates the waveforms obtained from this.

The drawing illustrates in Figure 1 a thermal image reproducer 10 comprising an enclosure. I11 has a window 12 through which infrared heat radiation from the scene affects one; scanning device 13. The scanning device 13 focuses this radiation on a detector 14 which leads to an image of the detector_:14 which is actually explored along a line 15 inside the casing 11 on which a mirror 16 lies to provide a synchronization signal for the narcissistic effect from the support 14 A of the detector 14, since the latter is cooled substantially. zially below the ambient temperature. Sa; however, any form of cone would be sufficient

The wise arrangement alternative to provide: such a synchronization signal. The output from the detector is sent along the signal path 18 to a synchronization signal recognition circuit 20, which extracts the synchronization signal and uses the sin signal.

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chronograph extracted to activate a monostable multiviewer and forming part of a synchronization arrangement 22The signal of output from the detector is also sent along the path 23 to the signal processing circuit 24 and then to the video output 25, both which are timed by the timing arrangement, or 22 for synchronization. _;

The shape of the detector output signal;

is shown in Figure 2, and is formed by ^: J ι subsequent waveform portions 30A, 30B, 30CJ,&gt;

30B and 30E. The portion 30A is representative of a first exploration line containing the information derived from the scene; 30B represents the waveform due within the envelope 30C? Il, synchronization signal; 301) is a second exploration likeness having a similar waveform '

I ί, but not necessarily, identical to the portion 30A, i and 30E is equal to 30B. It is clear that the function i¹ i: the ideile portions 30Λ and 30B represent the beginning of uni i

period ? ending at the junction of the portions; .301) and SOL when the next period begins. The portion 303) has a duration T1, such that &lt;50 ^ Ti and the synchronization signal is arranged a lot.

vμ *

0 $ near and before the portion 301).

The duration Tg from:

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the junction of the portions 30B and 300 at the end of the period T, is also lower than 50% T.

The synchronization signal recognition circuit 20, which can conveniently comprise a differentiator and suspension device, recognizes the presence of the synchronization signal portion 300 and adjusts the monostable multivibrator of the timing arrangement 22 for a time interval Τθ such that T₃ &lt;50% T, as shown in Figure 2, the front edge 28Λ of the determined portion of the monostable radiator being aligned in time with the synchronization signal, and the leading edge 28B of the regulated portion of the multivibra # ** tì

The monostable being is after the term of Ί5 tj i / 5 and Tg and T. cs

It should be noted that the waveform portions 30B and SOE are devoid of anything that is better than the portion 300 of the synchronization signal, while the portions 30A and 30B, being a formation derived from the scene, contain peaks, such as 31 which, in the absence of the present invention, could lead to erroneous operation of the acknowledgment signal circuit 20.

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