NO800165L - PROCEDURE AND APPARATUS FOR MEASURING THROUGH IR THERMOMETRY OF THE TEMPERATURE IN A TRADE, STAND, ROD OR PLATE - Google Patents

Description

The present invention relates to the use of infrared thermometry for measuring the temperature in threads, rods or rudders and objects that can shift in the longitudinal direction (in what follows, the term "thread" has been used to also denote rods and rudders).

It also relates to control at this temperature by using such a measurement.

French patent 2,109,406, filed on 15 October 1970 by Laboratoires d'Electronique et de Physique Appliquée (LEP), and delivered and published on 26 May 1972, describes a method and a device for measuring temperature in wires which are referred to in this patent as long, straight cylindrical bodies, moving in the longitudinal direction where you can move the wire on which you want to measure the temperature in front of a black wall with a uniform temperature and you focus

on the sensitive element of the infrared detector, a parallel beam emitted by the system consisting of

the black wall and the aforementioned thread and exit tail

for the detector is representative of the temperature in the wire

one and largely independent of the displacement of the thread in relation to the black background. Focusing is ensured by means of a flat, oscillating mirror and a lens

which is transparent in infrared.

Although the application of a parallel beam to examine the thread and the dark background using

of the oscillating mirror gives the advantage that one ensures a temperature measurement that is independent of the position of the wire in relation to the black background, the device in patent 2,109,406 gives the disadvantage that one greatly limits

the optical yield in the system since only a very small part of the infrared rays, namely those that are mostly parallel to the optical axis in the system, are focused on

the sensitive element in the detector and is thus converted into a usable electrical signal, and this signal will further arise when the temperature in the wire is identical to the temperature in the black background since a differential

ential measurement between the radiation of the black background itself and the radiation of the black background on which part of the wire is superimposed.

The present invention relates to an improvement of the method and the device according to the aforementioned patent, which is achieved by using a greater part of the infrared rays coming from the wire and the black background. In order to achieve this, instead of simply focusing with the help of the lens, the infrared rays which are largely parallel to the optical axis are collected, which are reflected by means of a plane mirror, an actually larger part of the infrared rays emitted by the black 'background' and the thread or a piece of plate, where you want to measure the temperature, e.g. using a spherical concave mirror.

The invention thus relates to a method for, by means of infrared thermometry, to measure the temperature in a wire or a plate which is displaced in the longitudinal direction in front of a black background with a constant temperature, where the sensitive element is collected and fed into an infrared detector, in the lbpet of certain periods of time, essentially all infrared radiation emitted by a part of said wire or plate along a predetermined, fixed angle.

The invention also relates to a device for carrying out this method, and this device comprises at least one oscillating, planar mirror which transmits in a certain direction all infrared radiation from a part of the said wire or plate and Cjorte the background along a predetermined fixed angle}, and at least one spherical, concave mirror which collects the infrared beam which is. transferred by the said planar oscillating mirror and directs this bundle of rays which is gathered up towards the said sensitive element.

One might think in advance that the fact that one does not limit infrared rays to mostly those parallel to the optical axis emitted by the examined part of the wire or plate and the surrounding, black

[3akgrunn, would increase the influence on the measurement of displacements of the wire or plate. However, it has been possible to ascertain - and figures are given in the subsequent detailed description for this - that this influence is reduced if you ensure that the wire or plate oscillates around an equilibrium position and if you introduce integration devices for the signal sent out by the infrared radiation detector in order to achieve a statistical response where the fluctuationepsom^Icyldes forgkyning a v the wire or plates is compensated.

More specifically, the purpose of the invention is to provide: - a method for using infrared thermometry to measure the temperature of a body that has a small dimension in at least one direction, such as a wire or a plate, while it moves in the longitudinal direction, in front of a black background, and in particular the difference between the temperature in this body and the black background, and the aforementioned method consists in transferring to the fbls element in an infrared detector alternately and in sequence, on the one hand at least part of the total output ^dth or reflected infrared radiation from a part of the length of the said body and which is emitted by a zone of the said black background /which encloses the said part, and on the other hand at least a part corresponding to the total infrared radiation that is emitted only of the said zone, or a corresponding zone of the said black background without the interference of the said body, and by measuring the difference in intensity between these two parts by measuring the difference between the corresponding output signals of the fbls element and which is characterized by collecting on this said fbls element largely the total radiated or reflected infrared radiation at a fixed, predetermined angle of the said part of the said body and the said zone of the background and alternating and. in sequence largely the total infrared radiation emitted at the same fixed angle only by the said zone, or a corresponding zone of the said black background, without the influence of the said body;

- a device for carrying out the aforementioned method, characterized in that it comprises - in combination with at least one flat mirror which can reflect, alternately and sequentially on one side at least part of the total emitted or reflected infrared radiation from part of the length of the said body and emitted by a zone of the black background that encloses the said part and, on the other hand, at least a corresponding part of the total infrared radiation emitted only by the said zone, or a corresponding zone, of the said black background , without the influence of the said body, and devices which can measure the difference in intensity between the two parts by measuring the difference between the corresponding output signals from the said physical element - devices to collect on the said physical element basically the total emitted or reflected infrared radiation at a fixed, predetermined angle of the said part of the said body and the said so ne of the background and alternating and in sequence largely the total infrared radiation emitted in the same fixed angle only by the said zone or by a corresponding zone of the said black background, without the influence of the said bodies.

According to a first type of implementations are:

- the method further characterized by carrying out the transfer of the total infrared irradiation alternately and in succession using a planar, oscillating mirror and collecting radiations using a spherical, concave, fixed mirror; - the device is further characterized in that said mirror consists of a planar, oscillating mirror and said devices for collecting the infrared radiation consist of a spherical, concave mirror.

According to another embodiment is:

- the method further characterized by carrying out the collection of the infrared rays by means of two flat and fixed mirrors and the collection of the infrared rays that are transferred by means of the flat mirrors, by means of two spherical, concave mirrors, where each spherical mirror is connected to a plane mirror and by alternating and successively interrupting on the one hand the total infrared radiation which is emitted or reflected by a part of the length<&>y the said body and is emitted iay a zone of the black background which surrounds it said part and which is reflected by one of the said, plane,

fixed mirrors and of one of the aforementioned, concave mirrors, and,

on the other hand, the total infrared radiation emitted only by said zone or a corresponding zone of said black background, without the influence of said body, and which is reflected by the second planar mirror and by the second spherical mirror;

- the device further characterized in that the said planar mirror consists of two, planar, fixed mirrors and that the said devices for collecting the total infrared radiation consist of [two, spherical, concave

mirror where each spherical, concave mirror is connected to a plane mirror and by using devices for alternating and successively intercepting the total infrared radiation emitted or reflected by part of the length of said body and emitted by a zone of the black the background which encloses the said part and is reflected by one of the said planar fixed mirrors and by one of the said concave mirrors, and on the other hand the total infrared radiation emitted only by the said zone or by a corresponding zone of the said black background without the influence of the said body and which is reflected

of the other, plane mirrors and the other, spherical mirrors.

Since one would preferably want a high degree of accuracy in the temperature measurement when the temperature in the wire or in the plate corresponds to or is close to the black background, it is recommended to reduce to a minimum the noise that arises in the aforementioned detector and in the preamplifier that feeds this detector .

For this purpose and in accordance with another side of the invention, preferably used simultaneously with the main features indicated above, the electronic part which feeds the aforementioned detector is provided with devices to make the voltage from the detector symmetrical in relation to a reference potential, devices for to allow a detection of positive or negative deviations corresponding respectively to the wire or plate being hotter or colder than the black background and, conversely, means for detecting said positive and negative bias voltages and means for determining the algebraic sum of these positive and negative bias voltages detected in this way.

The invention can be better understood with the help of the following description and likewise the attached drawings which are given as an indication. Fig. 1 shows schematically and in partial section an embodiment of the device according to the invention for measuring the temperature in a wire, with the exception of the electronic part. Fig. 2-7 illustrates the electrical signals used in this embodiment. Fig. 8 shows the electronic part in this embodiment. Fig. 9 and 10 show electrical signals used in the assembly in fig. 8. Fig. 11 corresponds to fig. 1, but relates to a temperature measurement in a plate.

Fig. 12 shows the mechanical part of the device

in fig. 1 and 11.

Fig. 13 shows schematically, in partial section, another embodiment of a device carried out with the improvements according to the invention and specially adapted to temperature measurement

in a rudder or pole.

Fig. 14 shows devices for alternately and consecutively sending infrared rays towards the flexible element in the embodiment shown in fig. 13, side view. Fig. 15 and 16 show, in two planes perpendicular to each other, the optical devices used in the device in fig. 13. Fig. 17 finally schematically shows the entire mechanical system in the device in fig. 13.

According to the invention, it is proposed to carry out a method and a device for using infrared thermometry to measure the temperature in a wire or a plate where one proceeds in the following or equivalent manner.

In what follows, one generally restricts oneself to the case of a wire, but it is understood that the explanations that follow can also be used in the cases where it is a plate and likewise (especially in fig. 13 - 17) when it concerns about a rudder or a pole.

In fig. 1 where, for the sake of simplicity, the openings that allow the infrared radiation to pass through have not been shown, it can be seen that at 1 the wire on which you want to measure the temperature is shown and which is surrounded by a body or a black background 2 such as e.g. consists of a graphite fiber or a material called "p^_r^x"__jwhich allows hby radiation. An insulating, cylindrical sleeve 3, which is made of fiberglass, encloses the black body 2. The infrared rays 4 emitted by the wire 1 and the infrared rays 5 emitted by the black body are transmitted, at certain time periods, by a plant, oscillating mirror 6 as a . beam 7 to mirror 8.

According to a main feature of the invention revolves

it is a spherical, concave mirror which collects, after reflection from the oscillating mirror 6 (when it is in the position shown in Fig. 1) all radiation from

the thread 1 and the area of the black body which encloses it and not only the rays which are largely parallel to the optical axis corresponding to the axial ray 4c which is reflected as 7c on the oscillating mirror 6 in the position shown in fig. 1.

The spherical mirror 8 transfers the rays 7 as the rays 9 to the flexible element 10 in the detector 11

for infrared irradiation. One now notices that the axial beam 7c is reflected from the mirror 8 as the axial beam 9c and that the spherical mirror 8 has its axis shifted in relation to the axis of the infrared radiation 7c; it is thus a spherical spell "off axis".

The advantage of the system which can be described with reference to fig. 1, is that it has a very good yield when compared with a system that only uses the infrared rays emitted by the thread 1 and the surrounding black background in a direction that is largely parallel to the optical axis 4c. This can be shown in the case where one has an embodiment which corresponds to the one seen in fig. 1. In this embodiment, the spherical sepil can have a radius of 75 mm, an opening where the diameter is 40 mm and a magnification of 1, the distance between the thread and the oscillating mirror is 53 mm while the distance between the center 6c of the oscillating mirror and center 8c in. the spherical mirror is 97 mm. The inclination of the central beam in relation to the mirror axis is 7° and the fixed angle under which the thread is viewed corresponds to 5.56.10 steradian.

When a square surface with a side edge of 2 mm is used as a window in the detector 11, i.e. as a fblsom element, a part of 2 mm of the length of the wire (in a direction perpendicular to the plane in fig. l) will appear on it fblsom surface. Assuming that the wire has a diameter of 1 mm, the ratio between the surface of the wire and the surface of the black background, seen from the detector, will be 50%.

In contrast, when it comes to the device according to the aforementioned patent no. 2,109,406, it will be the inner surface in a circle of 23 mm that is investigated, this surface will be determined by two diaphragms that limit and hold constant the length of the wire (which would otherwise be variable, which would distort the measurement). In this case, the ratio between the surface of the thread and the surface of the black background is only 4.35%

(instead of 50% in the case shown in the attached fig. 1), which corresponds to a very weak optical yield which results from the fact that only the rays that are parallel to the optical axis are used.

In contrast, as indicated above, the system in fig. 1, in principle, the disadvantage that it is difficult with regard to the position of the wire in the depth direction (ie when the distance between the wire and the mirror 6 and thus the mirror 8 varies). But calculations have shown that a displacement of 5 mm forwards or backwards causes a relative variation in the surface of the wire 1 which is examined by the detector 11 of less than 2%, which only causes a variation in the flow of infrared rays and thus in the electrical signal emitted by the detector 11 in the same order of magnitude. Likewise, as mentioned above, the disadvantages of this variation will be reduced by the fact that the thread oscillates around an equilibrium position and by the fact that the electronics that follow the detector 11 (as explained below) provide a statistical response that eliminates the fluctuations due to an integrator circuit. For this reason, the average position of the thread 1 in relation to the black background 2 is what is important.

In fig. 11 (where the references in fig. 1 can be found again) have been shown by la the plates that move through a narrow slit 3a which is extended in the black body 2 and the surrounding, cylindrical sleeve 3. All the infrared rays 4 that emanate from the edge lb of the plate la as in the case of the thread, together with the infrared rays from the black body 2, are collected at certain time periods by means of the oscillating mirror 6 as the beam 7 of the spherical mirror 8. The plane la of the plate is set in a certain angle with the axial beam 4c to avoid that the outer rays coming through the gap 3a reach the fbls element 10.

Up until now, no one has indicated why the mirror

6 is an oscillating mirror. The oscillations of the mirror 6 are produced to supply the detector 10 alternately with an infrared beam which includes the rays 4 coming from the wire 1 simultaneously with the rays 5 from the black background on one side, and only the rays 5 coming from the black background on the other page. If you get a difference between the first radiation on the one hand and the second radiation on the other hand, you get a signal which is zero when the wire 1 is at the same temperature as the black body 2 and which is positive or negative depending on whether the temperature in wire 1 is higher or - lower than on the black background 2 (depending on the polarity, one can get such a response or the opposite response as a function of the temperature difference between wire 1

and the black body 2).

In fig. 12 schematically shows the mechanical device which makes it possible to obtain an [oscillation of the plane mirror"6 at the same time as the synchronization signal. A motor and a reduction gear 81 simultaneously pull a pulley 82 with its drive chain 83 and a disc 84 with a gap 85 .The drive chain 83 pulls another pulley 86 which is attached

to the system with a drive rod 87 and a crank pin 88 where the drive rod 87 slides in a sleeve 89 which can rotate around a shaft 90 fixed in the room. This shaft 90 is attached to the plane mirror 6 which oscillates due to the movement of the drive rod 87 with an amplitude which is adjustable by modifying the length of the arm 88. In fig. 12, the elements 1, 8 and 11 from fig. 1. The disk 84 with the slit 85 passes under an optoelectronic detector 91 which detects the passage of the slit 85 due to a light source 92 when

the rays reach the detector 91. By changing the angular position

one on the disc 84 with a gap in relation to the drive pulley 82, the synchronous detection position is modified.

You can thus see that the electronic part which

is not shown in fig. 1 can ensure great success in target-

no around zero detection, when the wire 1 and the black background 2 are at the same temperature. This results in the stby from the detector 11 and that which is written from the amplifier that feeds the detector and which can be integrated with the detector or placed against it, on

known way, becomes very important.

In accordance with characteristic features

according to the invention, it is ensured that there are devices which make the voltage from the detector 11 symmetrical in relation to the reference potential, and in particular by means of a connection capacity with high impedance. The positive or negative deviations are then measured, and one corresponds to the case where the wire is hotter than the black background and the other the opposite case, then positive and negative deviation voltages are measured around the "zero measurement point" and one then produces - the algebraic sum of positive and negative voltage awik.

In fig. 2 - 7 different corresponding signals are shown.

One thus provides a positive measuring

voltage 12 as illustrated in fig. 2 where the amplitude a is the ordinate and the time t is the abscissa.

In fig. 4 has been shown, it is not applicable

same ordinate a and abscissa ftT; the negative measuring voltage 13.

In fig. 6 has been shown with the same ordinate a and abscissa 5, the signal 14 which is measured around zero and you can see that you get a very good accuracy which is e.g. in the order of 0.5°C for a temperature on the black background in the order of 70°C, i.e. that one can detect variations of 0.5°C in the temperature of the wire above or below the temperature above or below the temperature on the black body when this is in the order of 70°C.

Fig. 3, 5 and 7 illustrate with the same ordinate a and abscissa t, the positive voltages 12b, the negative 13b and the algebraic sum 14b which correspond respectively to the signals 12, 13 and 14. In fig. 7, one sees in particular the positive part 14p, the negative part I4n and the part l4o which constitute the algebraic sum of the positive part I4p and the negative part I4n of the integrated signal, in the case where the temperature in the wire is respectively higher, lower or large set equal to the temperature in the black background.

In fig. 8 shows the electronic structure

and in fig. 9 and 10 describe the assembly of the electronic part according to a preferred embodiment according to the invention.

One should start with fig. 9 to better understand the effect of the components in the device of fig. 8.

In fig. 9 has first shown the signal 15 which is the output signal of the detector 12 and which /therefore is not represented in the coordinate system a and /t/, the difference between the temperature in the wire 1 and the temperature of the black body 2.

Synchronous with the oscillations in the mirror 6, the disc 84 rotates with the slit 85 (Fig. 12) which, when this slit passes through beams of radiation from the source 92 towards the photoelectronic detector unit 91, produces an electrical impulse 16 which is synchronous with the signal 15. This means that for each peak 15d of the signal 15 gives an impulse 16. By means of devices which will be described in the following with reference to fig. 8, one obtains, from each impulse 16, two symmetrical impulses 17 and 18, one of which is positive and the other negative, with a specific direction (less than for the impulse 16) and where the fronts are delayed in relation to the leading front in the corresponding impulse 16. Furthermore, always starting from a series of impulses 16, a series of impulses 19 is obtained, each preceding the corresponding pair of impulses 17 and 18.

Fig. 8 schematically shows the electronic system. The output filter of the photoelectronic detector which receives the beam of light passing through the slit in the aforementioned disk, ..i.e. the impulse train 16, is supplied to the input 20 in the circuit in fig. 8. The impulses 16 are amplified by two operational amplifiers 21 and 22 mounted in series; and these impulses, which are found in the output 32, are delayed by the circuit 23 which comprises a capacitor 24 and an operational amplifier 25, and the said capacitor ensures a separation between the impulses between the input and the output of the circuit 23 by means of a dephasing effect. The output 26 of the circuit 23 is on the one hand connected via an operational amplifier 27 mounted facing the diode 28 mounted directly and on the other hand directly to the diode 29 mounted in reverse. In this way, at the output 30 the series of positive impulses 17 and at the output 31 the series of negative impulses 18 (symmetrical with the impulses 17) are obtained and these pairs of impulses 17 and 18 are delayed (with the help of the capacitor 24) in relation to the input impulse one 16.

Furthermore, the output impulse from the amplifier 22 from the point 32 will be fed to the base of a transistor 33 of the PNP type; on the collector of this transistor 33, a negative voltage is obtained when the transistor is not conducting,

i.e. when the base is made negative by the output 32. One thus gets on the collector of the transistor 33, at 34, a negative impulse for each positive impulse 16. The duration of the impulses that appear at 34 is reduced by the transistor 35 due to the connection between the base of the transistor 35 and the output )2é in the circuit 23. When the output 26 produces an impulse (which can be a pair of positive and negative impulses 17 and 18), it receives a negative voltage which makes the transistor 35 conductive and thereby leads the collector of this transistor to ground, which suppresses the part of the impulse that appears at 34 during the generation of impulses 17 and 18. This is clearly seen in fig. 9 where it can be seen that the impulse 19 corresponds to the part of the impulse 16 which does not

corresponds to the impulse pair 17 and 18. At 36, one does not in reality have positive impulses as shown in fig. 9, but negative impulses as indicated above, and it is the operational amplifier 37 which reverses the polarity due to its mounting, and the impulses 19 which are effectively available at 38.

You can thus see that the upper part of the assembly

in fig. 8 makes it possible at 30, 31 and 38 to get a series of impulses 17, 18 and 18 starting from the impulse series 16 that enters the input 20.

In the better part of fig. 8, is the output of the infrared detector 11, i.e. the signal 15d,r^Ipå'fb'rt to the input 39. The system of the capacitor 40 and the resistor 41 provides an input with high impedance which has the effect of making the signal 15 symmetrical in relation to soil while deforming as little as possible. The symmetrical signal available at 42 is applied to an instrumental amplifier with a very high input impedance, which consists of operational amplifiers 43, 44 and 45. The result is a signal which will be processed as shown in the following using the impulses 17, 18 and 19 available at 47, 48 and 49.

Transistors 50 and 51 are always conducting, except at the instant when pulses 18 (arriving at 48) and 17 (sunParriving at 47) are applied to their bases. For this reason, the modified signal 15 entering at 46 is stopped by the transistors 50 and 51, except for the duration of the pulses 17 and 18. The circuit further comprises two blocking circuits 52 and 53 each comprising two operational amplifiers where the operational input amplifier 52e , 53e amplifies the continuous input pulse to charge the capacitors 52c and 53c, while the operational output amplifier 52s[~ and 53s brings to the capacitors 52c and 53c respectively a very small strbm to provide a continuous output voltage corresponding to the input pulse voltage. ...

The blocking circuits 52 and 53 are fed respectively

of the positive and negative parts of the signal 46 through the diodes 54 and 55; the positive parts pass the blocking circuit 52 while the negative parts, after the polarity is reversed in the operational amplifier 56, are passed through the blocking circuit 5£5;. This means that the signal stored in the capacitors 52c and 53c is always positive.

The information finally ends up in the form of a continuous voltage in the blocking circuits 52 and 53 and is used either directly at 57 or at 58 after reversal in the operational amplifier 59. The positive signal that is available at 57 and the negative signal that is available at 58 are added together and fed to the operational amplifier 59.

It is understood that the capacitors 52c and 53c are discharged in advance and this is done by means of the impulses 19 which are available at 49 and which are applied to the base of the transistors 52t and 53t in the blocking circuits 52 and 53; when these transistors 18 and 19 are made conductive by means of the impulses 19, the corresponding capacitors 52c and 53c will be discharged to earth through the emission-collector circuits of these transistors.

Naturally, at 39 and thus at 46, a positive voltage will appear at the same time as the impulse 18, which plays a role as a window, it is charged positively in the capacitor 52c and appears in the form of a continuous negative voltage at the output 60 in the operational mixing amplifier 59; on the other hand, it appears at 39 and possibly at 46, as a negative voltage during the impulse 17, and there likewise plays the role of window, it is stored positively in the capacitor 53c and appears in the form of a continuous, negative voltage at the output 60; finally it appears at 39 and thus at 46, a voltage which can be both positive and negative (it is in the case of stby) and this voltage is stored in the capacitors 52c and 53c and appears at 60 in the form of the difference between the negative and positive tensions, and this for-

shells themselves can be positive or negative.

It is thus seen that the sequence of signals 16 created by the slot in the disc which is not shown, synchronously with the signal 15 in the detector, will produce the impulses 19 which make up the windows, which discharge the capacitors 52c and 53c; after this discharge, the windows 17 and 18 allow storage in the same capacitors of the signal 15 which has been previously processed and produces a continuous voltage at the output 60. This voltage is positive or negative according to the polarity of the signal 15 and according to whether the wire 1 is hotter or colder than the background 2, when one assumes that the amplitude of this continuous voltage varies in the same way as the temperature difference. It is further seen that the influence of stby tends to be eliminated. The continuous positive or negative voltage produced at 60 is renewed at each impulse group 17, 18 and 19, and the number can e.g. be 10 repetitions per second.

It should be noted that this continuous signal can be produced in a small positive or negative zone of the infrared detection signal or the algebraic sum of the two positive and negative zones, if the stby provides an information amplitude covering the zero axis of jorcL;. This device allows a great nbysty in the measurement in the most interesting zone where the temperature in the wire is close to that of the black body.

The voltage produced at 60 is then passed through a filter 61 to remove certain rapid variations, and the time constant in these filters may be of the order of 0.5 seconds. It is finally at 62 that you get a continuous positive or negative voltage which is the signal that represents the difference between the temperature in the wire and the black background.

In fig. 10 has finally been shown on a large scale and with an indication (ojvolt V or millivolt mV) of the polarities as an example (the potential of earth is indicated at level m)

of the different signals, namely:

- the signal 63 from the photoelectric detector

which interacts with the slit disc which is actuated synchronously with the oscillating mirror 6 to provide a synchronizing device, this signal 63 comprising the impulses 16 in fig. 9, which appears! at 20 (Fig. 8),

- the signal 64 which is available at 32,

- the signal 65 which is available at 26,

- the signal 66 with the impulses 18, which is available at 31 and 48, - the signal 67 with the impulses 17, which is available at 30 and 47, - the signal 68 which is available at 34,

-/jsigrialet 69 which is available at 36,

- and finally the signal 70 with the impulses 19, which

is available at 38 and 49.

It can be seen that the embodiment described makes it possible to obtain a very close measurement of the temperature in a wire or in a plate in relation to a black background with a constant temperature, even if the wire or plate oscillates in front of the black background and even if the difference in temperature is very small, e.g. less than 1°C between the wire and the black background.

But the use of an oscillating mirror gives a number of disadvantages: - the setting of the sighting axis must be very close, - transverse displacement of the body produces variations in the output signal frequency in the flexible element, - the ratio "dimension of the optical viewing window in relation to the distance between window and the body" bbr is kept small that there is therefore a need to increase the dimension of the black background when the diameter of the body seen by the plane mirror bkery - the transparency decreases if the aforementioned diameter is reduced.

This leads to problems when the diameter of the body is very large or very small and/or when the body is subjected to transverse displacement in relation to the black background.

In order to avoid these disadvantages, a device according to the invention can be produced by collecting the infrared rays, not only with the help of a single, planar, oscillating mirror, but with the help of two fixed, planar mirrors and a collection of the infrared rays not only by means of a single spherical concave mirror, but by means of two spherical concave mirrors, each spherical mirror connected to a plane mirror, together with means for alternately and successively interrupting, on the one hand, the total infrared radiation which is emitted or reflected by a part of the length of said body and is emitted by a zone of the black background which encloses said part and is reflected by one of said fixed mirrors and by one of said concave mirrors, and, on the on the other hand, the total infrared radiation emitted alone by the said zone or an equivalent zone, by the said black background, without the influence of the said body, and which is reflected by the second planar mirror and the other spherical mirrors.

One thus uses (fig. 13 - 17) the utilization of rays emitted on one side by the elongated body (especially by a thread, a rod or a rudder in the illustrated embodiment) and, on the other side, by the black background , not only by means of an oscillating, planar mirror and a spherical, concave mirror (as in the explorers like you, shown in fig. 1 - 11), but by using two fixed aiming directions which each used a planar fixed mirror and a spherical concave mirror, placed in such a way that the parts used by the rays emitted either by the wire, rod or rudder or by the black background, are transmitted by means of the plane mirror and collected by the concave mirror in each direction of sight towards the same fblsom zone on a detector, and this under the same angle, and where you have devices that make it possible to alternately and sequentially cut off the radiation found in each of these aiming directions.

This design can especially be used to measure the temperature in poles or rudders.

More specifically, you see in fig. 13 that the infrared radiation 4 of the body 1 is sent by a flat, fixed mirror 6a to a spherical, concave mirror 8a which collects all the infrared radiation that is transferred by means of the flat mirror 6a and concentrates this in the fblsable zone 10 in a detector 11.

In the embodiment shown, the black background 2a consists of sheets of copper coated with colloidal graphite for high radiation, and the copper has the advantage of being a good thermal conductor. This black background is heated by means of electrical resistors 101 which are placed in an insulating, cylindrical casing 3a (e.g. made of glass fibre). A temperature gauge 102 (such as a resistance zone or a thermoelectric element) where the output wires are shown at 103, makes it possible by means of a thermostat (which is not shown) to regulate the temperature in the resistance 101 and thus in the black body 2a.

In the embodiment shown, the black background 2a has been given a rectangular cross-section in order to facilitate the construction and to obtain setting on a part 104 of the black background on a flat surface and thus under a constant angle.

The insight into the part or zone 104 is carried out with the help of a plane mirror 6b which transfers the infrared radiation 5 emitted by this zone 104 to a spherical-concave mirror 8b which collects all the infrared radiation transferred by the mirror 6b which is reflected from the zone 104, to the same sensitive zone 10 in the detector 11, and the radiations from the concave mirrors 8a and 8b reach the sensitive zone 10 at the same angle. Care is also taken to ensure that the optical path is the same from the infrared radiation as is written from [zone 104 and from the infrared radiation from thread 1.

Such a device has a double deviation from the optical axis and this deviation is regulated by the mirrors 6a and 6b and on the other hand by the concave mirrors 8a and 8.b.

In fig. 15 and 16, you can see a section in the vertical plane and a section in the horizontal plane respectively, and you can see that if the inspection of the wire 1 is carried out vertically, the planar mirrors 6a and 6b will control the displacement of the infrared rays in a vertical plane, while the concave mirrors 8a and 8b produces the displacement in the horizontal plane. In a particular non-limiting example, the mirrors 8a and 8b are spherical mirrors with a focal length of 110 mm and an aperture of 40 mm, the distance between the wire 1 and between the plane mirror 6a is 110 mm and the distance between the centers of the plane [mirror 6a and in the spherical mirror 8a is likewise 110 mm.

In fig. 14, references have been made to the rays 7 and 9 which are transmitted by the plane mirrors, on the one hand,

and of the spherical mirrors on the other hand, and likewise the central rays 4c, 7c and 9c which correspond to the rays 4, 7 and 9, i.e. the same references shown in fig. 1 and 11.

The slope in the vertical plane controlled by

the plane mirrors 6a and 6b are thus 8°2, while the inclination in the horizontal plane which is controlled by the spherical mirrors 8a and 8b is 5°9 for the two mirrors. Likewise, the fixed angle at which thread 1 is seen is 6.28 x 10"^ steradian.

In fig. 15 and 16 have shown the angles of inclination in the vertical plane and in the horizontal plane.

The device as described includes the devices shown in fig. 13 and 14 which make it possible to block off the infrared radiation 4 from the thread 1 and the infrared radiation 5 from the black background alternately and in succession. As an example, these devices can consist of a disk 105 illustrated in fig. 14, which is made to rotate at a constant speed by a motor 100.

This disc includes:

- on the one hand two openings 106 which are limited by two orthogonal diameters 107 and by four quartz circles 108 and 109, - on the other hand two recesses 110 which are likewise limited by orthogonal diameters 107 and by two quartz circles 111 and 112.

The openings 106 cooperate with a window 113 found in the black body 2a and the insulating sleeve 3a, so that when one of them is at the level of this window 113, the infrared radiation 4 emitted by the body or the wire 1 will mirror 6a and thus towards the flexible element 10 of the detector 11 after collecting the concave mirror 8a could be passed through.

The openings or recesses 110 likewise cooperate with an analogue window 114 which is irradiated by infrared radiation 5 which is emitted by the zone 104 so that this radiation can be guided towards the planar [j3Peil 6fo? and then towards the concave collection mirror 8b from where it' reaches the fbls element 10 when these openings are located just opposite the window 114.

Due to the windows 113 and 114 and the openings 106 and 110 following each other in sequence (since they are limited by the same diameters 107), it is seen that the fbls element 10 receives, after transmission by means of the planar mirrors 6a and 6b and collection of the concave mirrors 8a and 8b, alternating and in a row and under the same angle, the infrared radiation coming from the wire 1 and coming from the black body (zone 104).

The detector 11 is preferably a pyroelectric detector which is sensitive to all infrared radiation emitted by the wire, or another body 1 and the black background (zone 104) at all temperatures, especially e.g. around 150°C.

The final measurement in this embodiment with two flat, fixed mirrors and two spherical, concave mirrors takes place as e.g. described above with reference to fig. 2-10, i.e. by means of synchronous measurement. If the radiation frequency is stable, since the setting is fixed, without using an oscillating mirror, you will be able to get an excellent synchronous measurement.

One notices that they can be used together

with the device in fig. 13 - 17, the same electronic system as for the devices in fig. 1, 11 and 12, for the following reasons: - in the system with one oscillating mirror (fig. 1, 11 and 12), the setting from the thread to the black background and vice versa is gradually adjusted by means of oscillation of the mirror;

- in the device with two pairs of fixed mirrors (fig.

13 - 17) one also gradually advances the setting from the thread to the black background and vice versa, since when the opening 10^3 gradually covers the window 113, the opaque zones 115 will gradually replace the openings 110; for this reason, the radiation that emerges from the body 1 will gradually be replaced by the radiation from the zone 104 on the fbls element Q10 in the detector; there is thus a gradual transfer from one radiation to another; in the same way, when the opening nellO replaces the opaque zones 115 in front of the window 114, radiations from the zone 104 will gradually be replaced by infrared radiation from the wire 1 on the transparent zone 10 in the detector 11.

It is noticed that this fblsome 10 also receives radiation from the opaque zones 115 and 116. In order for this not to disturb the measurement, it is necessary that these zones have the same temperature and this is achieved (by ~^u~irfb re"~ sk Tven l_0_5,jL^e_t_material which is thermally conductive so that the temperature is uniform.One can, for example, make the disc 105 in copper.

In fig. 17 shows schematically the system with two pairs of fixed mirrors with a practical drive device for the disc 105 by means of a motor 100 which drives the shaft 117 on the disc not directly, but by means of a chain 118, the shaft 119 in the motor 100 is offset in relation to the shaft 117 and this makes it possible on the one hand to place the motor 100 without problems, and on the other hand the plane mirrors 6a and 6b.

As indicated above, the device in figC' 13 - 17 has a number of advantages compared to the devices in fig. 1, 11 and 12, especially when it comes to an improvement in sensitivity, ease of regulation, the ability to measure temperature in bodies such as rudders and poles which have a relatively large cross-section, without this making it necessary to use a black background with large dimensions, and finally under improved conditions to use a synchronous measurement due to the stability of the frequency in the measured infrared radiation. But the devices in fig. 1, 11 and 12 fit well for certain dimensions of wire or plate.

However, the invention is not limited to the examples listed, but instead includes variations.

Claims (14)

1. Method of temperature measurement by infrared thermometry of a body which in at least one direction has a small dimension, such as a wire, rod or rudder, or a plate, while moving longitudinally in front of a black background, and in particular the temperature difference between this body and the black background, where the aforementioned method consists in transferring <*> to a fbls element in an infrared detector, alternating and in succession on the one hand at least one part of the total infrared radiation that is emitted or reflected by a part of the length [ajv the said body, and which is emitted by a zone of the black background that encloses the said part and, on the other hand, at least one part corresponding to the total, infrared radiation emitted only by the said zone or an equivalent zone of said black background without the influence of said body, and measuring a difference in intensity between the two parts by measuring the difference between the corresponding outputs ng signals from the said fbls element, characterized in that the said fbls element is collected on the said fbls element largely all the infrared radiation that is emitted or reflected at a fixed, predetermined angle by the said part of the said body and said zone in the background . 2. Method according to claim 1, characterized in that one ensures a transfer of the total infrared radiation alternately and in series using a flat, oscillating mirror and collects this radiation using a spherical, concave, fixed mirror. 3. Method according to claim 1, characterized by carrying out the transmission of the infrared radiation using two flat, fixed mirrors and the collection of the infrared radiation, which is transmitted by the flat mirrors, using two spherical, concave game, where each spherical mirror is connected to a plane mirror, and by alternating and successively interrupting, on the one hand, the total infrared radiation emitted or reflected by a part of the length of the said body and emitted by a zone of the black background which encloses the said part and which is reflected by one of the flat, fixed mirrors and by one of the said concave mirrors and, on the other hand, the total infrared radiation emitted by the said zone or by an equivalent zone of the said black background, without the influence of the said body, and which is reflected by the second plane mirror and the second spherical mirror. 4. Method according to claim 1, 2 or 3, characterized in that the electrical output signal from said detector is processed to make it symmetrical in relation to a reference potential, the positive and negative peak values of the signal which have been made symmetrical are measured separately, determines the algebraic sum of the positive and negative peak values measured in this way. 5. Method according to claim 4, characterized in that one processes the sequence of impulses, each of which forms a window which makes it possible to cut up the said signal which is made symmetrically into parts which form the positive and negative signal signals which are then processed algebraic summation of. 6. Device for carrying out a method according to claim 1, characterized in that it comprises - in combination with at least one plane mirror which alternately and in succession on one side can reflect at least part of the total infrared radiation emitted or reflected by a part of the length of said body and is emitted by a zone of the black background that encloses said part and, on the other hand, at least a part corresponding to the total infrared radiation emitted only by said zone or an equivalent zone of the said black background, without the influence of the said body, and of devices that can measure the intensity difference between the two parts by measuring the difference between the corresponding output signals of said sensitive element - devices for collecting on the said sensitive body of mostly the total infrared radiation emitted or reflected at a fixed, predetermined angle by the said part of the said body and said zone of the background and, alternately and in succession, substantially all the infrared radiation emitted under the same, fixed angle only by said zone or by an equivalent zone of said black background, without the influence of said body. 7. Device according to claim 6, for carrying out the method according to claim 2, characterized in that the said flat mirror consists of an oscillating, flat mirror and that the said devices for collecting the infrared radiation consist of a concave, spherical mirror. 8. Device according to claim 6, for carrying out the method according to claim 3, characterized in that the said at least one plane mirror consists of two fixed, plane mirrors, and that the said devices for collecting the total infrared radiation consist of two concave, spherical mirror, and each spherical, concave mirror is connected to a plane mirror, and by having devices installed to intercept alternately and in succession on the one hand the total infrared radiation emitted or reflected by part of the length of the said body and emitted by a zone of the black background enclosing said part and reflected by one of said planar fixed mirrors and by one of said concave mirrors and, on the other hand, the total infrared radiation emitted only by the said zone or an equivalent zone of the said black background without the influence of the said body, and is reflected by the second planar mirror and the second spherical mirror. 9. Device according to any one of claims 6-8, characterized in that said detector is a pyroelectric detector which is sensitive to all emitted infrared radiation on one side (of said body, and on the other side of the black background at all temperatures. 10. Device according to claim 9, characterized in that the flat mirrors and the concave mirrors are positioned so that the sensitive element in the detector receives the infrared radiation from the said body and the infrared radiation from the black background at the same angle and large seen along the same optical path. 11. Device according to any one of claims 9 and 10, characterized in that said devices for alternating and gradual interruption of the infrared radiation coming from said body and coming from said black background consist of a disk that is brought to to rotate at a constant speed, which is equipped with subsequent openings, half of which allows the infrared radiation emitted by the said body and the background surrounding it to pass and the other half the infrared radiation emitted by the corresponding zone of the black background and each half of the openings cooperates with a window formed in said black body to allow the infrared radiation to pass. 12. Device according to any one of claims 6-11, for carrying out the method according to claim 3, characterized in that it connected to the output of said detector comprises devices for making the signal from said detector symmetrical in relation to the reference potential, devices for separate measurement of the value of the positive and negative signals coming from said devices mentioned in the first row and devices for determining the algebraic sum of the output of devices mentioned in the second row. 13. Device according to claim 12, for carrying out the method according to any one of claims 3 and 4, characterized in that it comprises devices for producing a first series of impulses which are synchronous with the feed signal from the output of the detector, devices for on the basis of ] said first series of impulses to produce another series of symmetrical impulse pairs, where there is a positive and a negative pulse in each impulse pair which have the same amplitude and the same duration, where the leading edge of the impulse in each pair is delayed in relation to the leading edge in the impulses corresponding to the first series and means for determining the value of the positive and negative tip of said signals which are made symmetrical only during the duration of said pairs of impulses. 14. Device according to claim 13, characterized in that it comprises devices for generating from the first mentioned series of impulses a third series of impulses which run before a corresponding pair of impulses from the second series of impulses, devices for storage which can store the said symmetrical signal that writes from said devices to make the signal from said detector symmetrical, devices which in response to each impulse from said third pulse train can discharge said devices for storage and devices which can input said integrated signal into said storage devices for the duration of each impulse of the second mentioned impulse series.