FR2501370A1 - Two colour temp. distribution measurement - using two optical filters with different transmission regions and transmitted light energy measurement - Google Patents

Abstract

The temp. distribution of an object is determined by passing light from the object through a fitter and measuring the energy of the transmitted light. The temp. distribution is measured very accurately and with high resolution unaffected by the ambient temp. at the measurement point using a two colour thermometer. Light energy is determined after transmission through two optical filters of different transmission regions. The measured energy levels are used to conduct a two colour temp. measurement for each region of the object. The temp. distribution is built up from the regional measurements. The filters can be used for neighbouring object surface zones, whereby light from one zone passes through one filter and that from the adjacent zone passes through the other filter. This process is repeated over the entire surface.

Description

Method and device for measuring a temperature distribution.

 The present invention relates to a method for measuring a temperature configuration, in order to obtain the distribution of surface temperatures on the surface of an object; it also relates to devices for the implementation of this process.

 In general, the methods of measuring the temperature distribution widely use an infrared radiation device which takes, by means of an infrared radiation detection element in a two-dimensional system, the energy optics of infrared rays emitted by an object whose distribution of surface temperature is to be measured. The device scans the two-dimensional system and produces and displays an image of the surface temperature of the object, for example graphically on a cathode ray tube. However, a measurement method using an infrared radiation device is not suitable for an object whose temperature varies rapidly, since two seconds or more are required for scanning in order to obtain an image.In addition, infrared rays - reds taken as representative of the temperature information are likely to be affected by the atmosphere which surrounds the path of light propagation, due to the existence of vapor or dust, which decreases the sensitivity and the precision . It is impossible in practice to avoid the influence of the ambient atmosphere by means of an image guide, since the attenuation of the amount of light inside the image guide is high within the range wavelengths of infrared radiation. In addition, the minimum visual field within which the measurement can be made is an angle of 10 to 20 cm, so that a temperature configuration cannot be measured in a smaller area. cannot be used to measure the temperature distribution of an object, such as an ingot in a continuous casting process in a steelworks or an electrically welded steel tube being welded, which is placed in a charged atmosphere containing a lot of vapor or dust and which undergoes a large temperature variation. In addition, this device is not capable of measuring the temperature distribution in a small area, for example the heated part of the edge of an electrically welded steel tube.

 On the other hand, a two-color thermometer, which is used for the implementation of the present invention, captures two components of particular wavelengths in the visible light emitted by an object, which makes it possible to carry out the measurement, without contact with the object the surface temperature of the object. The two-color thermometer can measure a characteristic temperature within the temperature range in which visible light is emitted, but it cannot measure a temperature distribution. As the methods used in foundry and steel works often require the measurement of a temperature distribution, the temperature measurement methods described above cannot easily meet this condition.

 The present invention avoids, in a new way, the above drawbacks.

 The subject of the invention is a method for measuring the temperature distribution which uses a two-color temperature and video information processing, so that the measurement is not substantially affected by the ambient atmosphere, this method possibly provide a temperature distribution measurement with high accuracy and high resolving power.

 The invention also relates to a device for measuring the temperature distribution, which makes it possible to implement the above method.

 Another subject of the invention is a device for measuring the distribution of temperatures, in which an image guide can be used and which is capable of measuring the distribution of temperatures in a small area or in an area situated inside. of an object and not visible from the outside of the object.

 The invention also relates to a device for monitoring a weld zone of an electrically welded tube, which uses the temperature distribution measurement device of the present invention.

 To achieve these goals, according to the present invention, the temperature distribution measurement method consists in targeting an object, the temperature distribution of which must be measured, by an image sensor device in order to obtain the distribution of the temperatures over the parts of the object, in the reproduced image of the object. The light from the object passes through first and second optical filters which allow different components, of determined wavelengths, to pass through the light emitted by the object. A two-color temperature determination operation is performed for each area of one or more video image frames produced by the light passing through the respective first and second optical filters, so that a temperature is determined for each part of the image. object, corresponding to the respective areas of the grids or image frames.

 The device used in the measurement method described above, to capture the light emitted by the object, can employ: a first system, in which the light emitted by each part of the object inside the visual field simultaneously passes through a first and a second filter placed at slightly different positions in a planar arrangement, in a single filter, for a single detection device a second system, in which the light coming from the object leads to a single detection device , through a first optical filter for a certain period of time, then the light of the object reaches the detection device through a second filter, for a certain period of time; or a third system, in which the light emitted by the object simultaneously passes through the first and second filters to arrive at separate image detection devices. The image parts of the video signal, coming from the detection devices and corresponding to an area for which the temperature is to be determined, are used as input information for a two-color temperature determination operation. In the first system, the areas for which the information is obtained are in slightly different positions and the information is obtained at the same time. In the second system, the zones are in the same position but the information is obtained at different times. In the third system, the obtaining of the information relates to zones in the same position and the information is obtained at the same time.

 Other objects and advantages of the invention will appear to those skilled in the art on reading its non-limiting embodiments, shown in the accompanying drawings.

Figure 1 is a block diagram of a first embodiment of a device according to the invention, for the implementation of the method of the invention by means of the first system
FIG. 2 schematically represents the arrangement of an optical filter
Figure 3 is a block diagram of a video signal processing unit used in the device of Figure 1
Figure 4 balances the waveform of a video signal
FIG. 5 schematically represents the content of a memory
Figure 6 is a flow diagram of an arithmetic unit
Figure 7 is a detailed flow diagram of part of Figure 6
Figure 8 is a block diagram of a second embodiment of a device according to the invention, for the implementation of the method of the invention by means of the second system
Figure 9 schematically illustrates the arrangement of a rotating filter
FIG. 10 schematically represents the content of a memory
Figure 11 is a block diagram of a third embodiment of a device according to the invention, for the implementation of the method of the invention by means of the third system
Figure 12 is a graph showing the relationship between the amplitudes of the waveforms entering an optical filter
FIG. 13 represents examples of output waveforms and illustrates the operation of a circuit for partial elimination of the video signal
Figure 14 shows an image analyzer, showing a scanning area of an image detection device
FIG. 15 is a plan view illustrating the arrangement of the objectives on the production line for electrically welded tubes
Figure 16 is a schematic view of a display on a control device
Figure 17 is an enlarged view showing the relationship between the received images and the scan lines
FIG. 18 illustrates the level of the video signal corresponding to the scanning line and relating to the position of the electrically welded tube
Figure 19 shows the waveforms of the signal outputs of comparator 71
FIG. 20 is a graph showing the relationship between the positions on the abscissa X and the distances between the opposite edges
Figure 21 illustrates the principle of calculating an angle v
Figure 22 is a block diagram of another embodiment of the device according to the present invention
Figures 23 and 24 illustrate arrangements of rotating filters; and
FIGS. 25A, B and C represent a flow chart of a microcomputer.

 We will now describe in detail a temperature distribution measurement method according to the invention, which uses the first system. In this method, an optical filter is disposed on the light path, inside or outside of an image detection device. The filter comprises first and second filter segments combined in a given arrangement, these segments being crossed by first and second components, of different wavelengths. A two-color temperature determination operation is carried out for each zone corresponding to two filter segments 1 in each grid or frame sampled by the image detection device, using the light which passes through the first and second filter segments. temperature of each part of the object corresponding to each of these zones is determined, which makes it possible to obtain a temperature distribution image.

 An embodiment of a device according to, I vention, which implements the above method, is described below with reference to Figures 1 to 7.

 FIG. 1 is a block diagram of a device according to the invention, in which W denotes the object for which the temperature distribution is to be measured. This device comprises an image detection unit 1 facing the object, an optical filter 2 placed near the image detection means of the device 1, a cathode ray tube for checking 3 to display an image of the object picked up by the image detection unit 1, a video signal processing unit 4 for processing information of the video signal output from the image detection apparatus 1, a memory 5 for storing the information of the video signal processing unit 4, and an arithmetic unit 6 which performs a two-color temperature determination operation based on the content of the memory 5 and the output of the processing unit 4 of the video signal.

 The image detection apparatus 1 is a conventional video camera, which must include an image detection tube with a dynamic band sufficient to receive the lights of wavelengths 11 and 12 which pass through the optical filter 2 described more far. One can, for example, use, in the visible wavelength band, a tube of the siliconvidicon or Chalnicon type (manufactured by Toshiba Co.). An image sensing tube of this type can be used as well as a static image sensing element, such as a charge coupled device, if it has good spectral sensitivity. include an indoor control unit, similar to the usual unit for processing a composite video signal, comprising an image signal, a horizontal synchronization signal and a vertical synchronization signal.

 The optical filter 2, shown diagrammatically in FIG. 2, has the shape of a rectangle to correspond to the visual field of the image detection device 1. Its dimensions are not mandatory but may be of the order of 18 x 24 mm when the effective visual field is 3: 4. The optical filter 2 comprises a plurality of first filter segments, not shaded, and second segments of filter, hatched, in the form of small rectangles or squares of the same dimension which are arranged alternately in a matrix with horizontal and vertical bands corresponding to the means of the device for detecting the distribution of the light which penetrates into this device.

Between the first and second filter segments are interposed shadow zones 23, in the form of a strip, to block the passage of light. The first and second filter segments are passband optical filters having respectively wavelengths e't X2 at the center of the wavelengths which they allow to pass and which have a high transmittivity and a low bandwidth, in order to increase the accuracy of the measurement. It is preferable to use an interference filter rather than an absorption type filter.

Such an optical filter 2, if it is assumed that X1 and <X2, comprises, in the areas formed by the filter segments 21, low-pass filters allowing the passage of light with a wavelength between a length d wave slightly less than 1 and a wavelength slightly greater than 1. The filter 2 comprises, in the areas formed by the filter segments 22, high-pass filters allowing the passage of light with a wavelength between a value slightly less than X2 and a wavelength slightly greater than X2. Filter 2 thus consists of a complex arrangement of bandwidth filters, over its entire surface, which allow light to pass with wavelengths located in a wavelength band X1 in the center and in a band of wavelength X2 in the center.

 The design of the arrangement of the filter segments 21 and 22 is not limited to that shown, but can of course have other forms of longitudinal or transverse arrangements. The size of the respective filter segments 21 and 22 determines the resolving power, so it is desirable to reduce their size as much as possible. In practice, the dimension is limited by the methods of manufacturing the optical filters and also by the capacity of the memory 5 and the speed of calculation of the arithmetic unit 6.

In this embodiment, the filter segments 21 and 22 are rectangular and their number in the matrix is 128 in the vertical direction and 128 in the horizontal direction. The shaded areas are approximately 40 microns wide. The wavelengths A1 and A2 are chosen to correspond to the spectral sensitivity of the image detection unit, to a temperature of the object W to be measured and to the atmosphere.

 The video signal processing unit 4 discriminates the image signals among the video signals leaving the image detection unit 1, the image signal parts each corresponding to the light passing through the first and second segments filter. Unit 4 provides a two-dimensional position signal to match each component of the image signal of the video signal to a filter segment.

 Figure 3 is a block diagram of an exemplary construction of the video signal processing unit 4 and Figure 4 shows a waveform of a video signal with negative modulation. The VDS video signal comprises vertical synchronization signals VS which appear once (for a sequential scan) or twice (for a jump scan) for a grid, horizontal synchronization signals HS which appear once for each scan line , and PS image signals that change level depending on the brightness or darkness of the image.The PS image signals include signal components PS1 and PS2 which represent the brightness and darkness of the surface parts of the object W at the positions corresponding to the positions of the respective filter segments, that is to say the information corresponding to the energy radiated at the respective locations of the surface of the object, the information being obtained for each scanning period of the scanning of the light portions coming from the object and passing through the respective first and second filter segments. The signal component PS3, between the components PS1 and PS2, is that which is obtained by scanning the parts of the filter corresponding to the gray areas 23 and it indicates that the areas 23 are dark. The filter segments 21 and 22 are arranged alternately horizontally and the shadow areas 23 are located between the filter segments 21 and 22, so that the elements of the ima signal FSJ. ge appear in order PS1, PS3, PS2 / PS1, ... The signal components between the PS3 segments have smaller black levels and, even when only weak light passes through the filter segments 21 and 22, the the transmittivity of each shadow zone 23 is chosen so that the signal component PS3, between the segments PS1 and PS2, has a higher black level than that of the signal components PS1 and PS2.

In the video signal processing unit 4, which receives the VDS video signal, a control signal processing unit 41 extracts the vertical synchronization signals
VS and transmits an image change signal TP each time a new frame is to start, the image change signal TP being introduced into the arithmetic unit 6. The video signal VDS is also sent to a unit 42 d control signal which transmits a position signal TS which indicates a position in the two-dimensional system, the signal TS being sent to the arithmetic unit 6. The unit 42 for generating the control signal also transmits signals
Door control TG, which are sent to respective doors 43 and 44. The door control TG signals are seen at doors 43 and 44 at a high level, to open the respective doors when the light coming from the objects passing through the respective filter segment 21 or 22 are being scanned. Doors 43 and 44 thus allow the passage of the VDS video signal, so that the information processing units 45 and 46 sent downstream of doors 43 and 44 are sent only the respective parts
PS1 and PS2 of the image signal which correspond to the parts of the light passing through the respective filter segments 21 and 22. The information processing units 45 and 46 consist of peak hold devices and analog type converters -digital and retain a minimum value (the peak value is the white level) of the respective signal components PS1 and PS2, emitted during the opening of the respective doors 43 and 44, and send the output components PS1 and PS2 to the memory 5, as information to be written by means of an analog-digital converter each time the doors 43 and 44 close. Consequently, the information to be written WD1 and WD2 represent the radiated energy values, corresponding to the wavelengths X1 and A2, emitted by the parts of the surface of the object W which correspond to the parts of image signal ci above from the respective filter segments 21 and 22.

 The position signal PS is substantially a pulse signal corresponding to the component PS3 and it is sent to the arithmetic unit 6 as writing address information. The door control signals TG are obtained as outputs from a flip-flop which constitutes the control signal processing unit 42 and which is connected so as to be triggered by PS3.

 When the arithmetic unit 6 allows the memory 5 to write information, the information of an image is written in the memory 5, the writing of information being authorized to start at the moment when the signal TP of change of picture is provided. The memory 5 stores the information WD1 and WD2 in predetermined addresses, as a function of the position signals TS. For example, the recording is carried out so that the arrangement of the filter segments 21 and 22 in the optical filter 2 is that shown in FIG. 2, to show the object W as seen from l image detection unit 1. The part of the light coming from the object which crosses the filter segment 21 in the upper left corner, that is to say in the first line and the first row, is scanned, the information WD1 corresponding to this part is sent to the memory 5, and being associated by the position signal TS with the filter segment 21 in this position, it is stored at the corresponding address.

Then, for the part of light which crosses the following filter segment 22 to the right, that is to say in the first line and the second row, the information WD2 corresponding to this part is sent to memory 5 and , being associated by the position signal TS with the filter segment 22 in this position, it is stored at the corresponding address. Thus, at the end of the recording of the information for the scanning along a line of the filter, a horizontal synchronization signal HS appears to cause the return of the electron beam from the detection unit 1 to the left end The next scan starts with the filter segment 21 in the upper left corner or with the segment 22 directly below in the second row and the first row, depending on the size of the filter segment, the number of scan lines and whether a sequential scan or a jump scan is performed. However, in this embodiment, the scanning density and the size of the segments are chosen so that a line of segments is scanned once per image. These operations are repeated to store the information corresponding to a complete image in the memory. 5, so that the latter sorts and stores the radiated energy values for the respective wavelengths A1 and X2 emitted by the parts of the surface of the object W which are divided in accordance with the arrangement of the filter segments 21 and 22. The stored information, which corresponds to the maximum brightness on the frame, corresponds to a value of the radiated energy. Thus, the content of memory 5, in the arrangement of filter segments 21 and 22, can be expressed as shown in Figure 5. In this figure, if j (i, j, = 1, 2, .. .n, with n = 128) represents the radiated energy value, corresponding to the wavelength
X1 or X2, which crosses the filter segment in line i and row j of optical filter 2.

 The arithmetic unit 6 reads the content stored in the memory and performs a two-color temperature determination operation with the information from each pair of adjacent filter segments. For example, if if j represents the information for the wavelength X1 obtained from the filter segment 21, if j + l is the information for the wavelength 2 obtained from the next adjacent filter element 22.

The known equation (1) for determining the temperature in two colors provides a temperature T (OK) for the zone of the object from which the parts of light giving the two information above come.

in which a and ss are constants determined by X1 and
X restectively. From tolus the watering (1) can be checked temperature since the relationship between the energy ratio #i; j / # i, j + 1 and la / is substantially linear in practice. Thus, the arithmetic unit 6 calculates sequentially the temperature for each zone, in order to obtain a temperature distribution grid for the entire image or frame, that is to say within the visual field of the detection device 1 , the results of this calculation being displayed by an indicator, for example a cathode ray tube, not shown, or recorded by a plotter or a printer, as visual information. FIG. 6 represents a flowchart of the arithmetic unit 6. When the latter receives the signal TP for image change, the initial address of the memory 5 is fixed to the address counter in the arithmetic unit 6 and, each once it receives the TS position signal, the information
WD1 or WD2 is registered and the address is changed. When #TS becomes n i.e. when all the segments have been scanned, the information writing process is terminated and the temperature determination operation start. FIG. 7 represents a flow diagram of this operation.

 Alternatively, the memory 5 may have sufficient memory capacity to store the information for two frames and it may, in operation, store information for the next frame while retaining the information for a previous image for the operation. arithmetic, which makes it possible to perform the measurement once per 1/30 s when using a television system having a capacity of 30 frames or images per second.

 The plotter or printer can also be used to display the average of a plurality of frames. Likewise, instead of the arithmetic unit performing a two-color temperature determination operation from the information for each measurement of the energy level corresponding to wavelengths 1 and X2, it can perform a determination operation two-color temperature measurement based on the average of a plurality of measurements or their maximum value, when one wishes to obtain a particular distribution of temperature over a larger surface.

If the number of filter segments is small, the arithmetic unit can be an analog arithmetic unit.

 We will now describe in detail a temperature distribution measurement method according to the invention, which uses the second system. In this process, the light coming from the object is passed alternately through a first and a second optical filter, to pass respectively a first and a second component of different wavelengths, the temperature determination operation at two colors being made for each zone of the object from information indicating the energy levels for each zone, obtained from the light which passes through the first optical filter and then light for the same zone which passes through the second filter optical. The temperature of each area of the object is thus obtained and all of these temperatures provide the temperature distribution image.

 An embodiment of a device for implementing this method is described below, with reference to FIGS. 8 to 10.

In FIG. 8, it can be seen that the device comprises an image detection unit 1 similar to that of FIG. 2, a video signal processing unit 4 'which operates as described below, a control device 3, a memory 5 and an arithmetic unit 6 similar to those of FIG. 2 respectively, and a rotating filter 2 ′ in the form of a disc, as shown in FIG. 9. The filter 2 ′ comprises a semi-circular part constituting a first optical filter 21 '' with bandwidth having a wavelength
At the center of the through wavelengths, and another semi-circular part constituting a second optical filter 22 'with passband having a wavelength A2 at the center of the through wavelengths. The filter 2' is arranged at the front of the image detection unit 1 and it is parallel to the objective (not shown) of this unit, so that an intermediate part, substantially halfway between the center and the outer periphery of the rotating filter 2 'colr.c- with the optical axis of the objective.

 A motor 7 is coupled to the rotary filter 2 ', to drive it in rotation about its axis. An angular position detector 8, comprising a pulse generator, is coupled to the motor and emits a constant number of pulses at each revolution of the rotating filter 2 ', the detector 8 sending an output signal to the unit 4' of video signal processing.

 The image detection device 1, when it is turned towards the object W whose temperature is to be measured, receives the light which passes through the rotating filter 2 'and reaches the device 1. The present embodiment also includes an auxiliary lens 9 placed between the object W and the rotating filter 2 ′, for concentrating the light emitted by the object W and effectively guiding it towards the image detection unit 1.

 In operation, the motor 7 rotates the rotating filter 2 ′, for example at 15 revolutions / second, so that the time necessary to form a frame, for example 1/30 s, coincides with the frequency of passage of the optical filters 21 'and 22' located at the front of the image detection unit 1. Thus, the unit 1 alternately receives the light which passes through the optical filter 21 'and that which passes through the optical filter 22'. The video signal processing unit uses the vertical synchronization signal for each frame, in the VDS video signal produced by the image detection unit 1, as the pause signal for a frame and writes the video signal generated in the period between such pause signals alternately in two areas of the memory 5. The information signals coming from the individual parts of the detection unit 1 are written to corresponding addresses in one of two groups of addresses in the memory, the addresses being arranged in accordance with successive scan lines separated by the horizontal synchronization signal within the VDS video signal. Consequently, at each address of this group of addresses, there is information corresponding to the level of energy received from an area of the object by the respective part of the detection unit, after passing through one of the filters. The video signal processing unit 4 'provides a time signal for determining the sampling time of the image signal portions of the video signal on the basis of its horizontal synchronization signal, in order to sample the level of the parts of the image signal, the sampled levels being sent to the Xespective addresses in the first group of addresses of the memory 5, as radiated energy information of wavelength X1 or X2 emitted by the object.

The output signal generated by the angular position detector 8 is sent to the arithmetic unit 6, to specify to which group of addresses in the memory 5 the video signal should be directed, that is to say if it the information must be stored as wavelength X1 or X2. Then, when the information has been written in the two address groups of the memory 5, the content of the latter is presented as shown in FIG. 10. This shows that the viewing surface of the detection device is divided into zones, in two matrices of n lines, n corresponding to the number of scanning lines in a frame, and m rows, m corresponding to the number of zones in a scanning line. The zones of the detection unit detect the light passing through the respective optical filters 21 'and 22', so that ei. and
2 if j (i = 1.2, ... n, j = 1.2 ... m) represent the radiated energy values of wavelengths X1 and X2 received by the zones in line i and the row j of the detection unit, after passing through the optical filters 21 'and 22' respectively.

The arithmetic unit 6 reads the contents of the memory 5 and, on the basis of the information of the corresponding addresses of the two groups of addresses, performs a two-color temperature determination operation. For example, for the zone located at line i and at row j, the temperature T (OK) of the surface part of the object corresponding to this zone is given by the following equation

 In other words, while the first system provides the temperature from two pieces of information obtained at the same time but at slightly different positions, the second system provides the temperature from two pieces of information for the same place but recorded at slightly different times. It is of course possible to obtain the temperature from data elements recorded at slightly different times and at slightly different places.

 The arithmetic unit 6 then sequentially calculates the temperature for each zone and sends it to means, for example a cathode ray tube, not shown, as in the first embodiment, to display the desired temperature distribution and / or the record. After the processing of the data from the two address groups has been completed, the recording of information by the next two frames begins.

 The above method is advantageous in that it provides high resolving power while using an optical filter of much simpler construction than that used in the first system. In addition, although the apparatus used in this method does not allow the connection of an image guide directly to the image detection unit 1, when the auxiliary lens 9 is used, as in the case of FIG. 8, the end of the image guide can be optically connected to the side of the lens 9 facing the objective, which makes it possible to use the image guide. In addition, the rotating filter can of course have a different configuration, for example it may comprise four parts allowing the light to pass alternately with wavelengths A1 and A2.

 We will now describe a temperature distribution measurement method according to the invention, which uses the third system. In this method, the light emitted by the object is simultaneously detected by a first and a second image detection unit, after passing through a first and a second optical filter which respectively pass the light of different wavelengths . The information coming from the first and second image detection units is used to perform a two-color temperature determination operation for each zone of the object, the temperature of each part of the object corresponding to the zones constituting the image. temperature distribution of the object.

 An embodiment of a device for implementing this method is described below, with reference to FIGS. 11 to 13.

 Figure 11 is a block diagram of the optical and electrical systems of the device. The reference numeral 30 designates an electrically welded tube, in a welding process, this tube being the object for which the temperature distribution image is to be obtained. The tube 30 faces an objective 32 which is fixed to the front end of an image guide 31. The latter comprises a plurality of optical fibers each having a diameter of the order of 25 microns and grouped in thickness of 5 x 6 mm approximately, which provides at their basic end a constant visual field under the optical conditions of the lens 32 and the object 30. The image guide 31 extends to a housing 33, of so as to avoid contact with a dusty and hot atmosphere and it is fixed by means, not shown, so that the optical axis of the guide 31 corresponds to the horizontal optical axis of an image pickup lens 34.

The housing 33 is closed so as to constitute a dark room and an enclosure for housing the camera heads 51a, 52a of the first and second two-dimensional image detection devices 51, 52, as well as a third device 53 two-dimensional image detection, which are optically placed in the appropriate position. On the optical axis of the image detection lens 34 are arranged a filter 35 at 10% neutral density, a dichromatic mirror 36 and the camera head 52a of the second two-dimensional image detection device 52. The filter 35 reflects 10% of the incident light, regardless of its wavelength, and allows the remainder of the incident light to pass through. The filter 35 is tilted at an angle of 45, so that the light is reflected vertically towards the top in order to be received by the third two-dimensional image detection device 53.

The dichromatic mirror 36 allows the penetration of light with a wavelength A3, for example 650 nm or more, and reflects light with a wavelength less than A3.

The mirror 36 is inclined at 45 relative to the lens 34, so that the light is reflected vertically downwards in order to be received by the camera head 51a of the first two-dimensional image detection device 51. The third image detection device 53 is a conventional color or black-and-white television camera without its image detection lens, the lens 34 serving as the image taking lens for this camera. The device 53 is provided for observing the shape of the object 30 and transmitting video signals to a unit 54 for partial elimination of the video signal.

 The first and second two-dimensional image detection devices 51, 52 each use an image dissector, such as a photoelectric conversion element which is capable of random access scanning, and respectively comprise the camera heads 51a , 52a and the control units 51b, 52b. The image pickup lenses of the camera heads 51a, 52a are removed therefrom, so that the image pickup lens 34, as in the case of the device 53, serves as an image pickup lens for the camera heads 51a, 52a respectively. One can, for example, use for devices 51, 52 of the C1186 type random access cameras manufactured by Hamamatsu Television.

The image pickup lens 34, which is used as the image pickup lens for the three devices 51, 52 and 53 in common, is placed so as to obtain the same distance from the lens 34 to the conversion element photoelectric of each image detection device. Transparent glass is used at the place where the lens of the image detection device 53 has been removed and first and second optical filters 37, 38 are mounted at the place where the image pickup lenses of the heads camera 51a, 52a have been removed, screws being used to fix the image pickup lenses respectively. The first optical filter 37 is of the bandwidth type having a component
X1 of main penetrating wavelength, with X1 less than X3 and the penetrating wavelength component being chosen in the band from X to X12, for example 550 to 600 nm.

The second optical filter 38 is a high-pass filter having a lower limit value X21, for example 700 nm with X21 greater than X3. This substantially forms a filter with a passband between X21 and X22 in which the wavelength X22, for example 850 nm, is the upper limit value of the sensitive wavelength, which is limited by the spectral sensitivity of the device 52 image detection.

The main component of the penetrating wavelength between X21 and x22 is X2. Figure 12 is a graph showing the relationship between the wavelengths X1, X2 and X3. In summary, the image detection devices 51 and 52 receive light from respective passbands centered at X1 and X2 and the image detection device 53 receives light for the entire visible range.

 The video signal partial elimination unit 54 functions to display, by means of an indicator device 56, the upper left area of the image pick-up visual field scanned by the image detection device 53, except for the striped areas of the part of this field located on the right and its lower part. Video signals with positive modulation, as shown in Figure 13, are made black at the back corresponding to approximately 1/4 of the video signal for one line, and black at a predetermined number of lines corresponding to the bottom of about 1/4 of a frame. Such circuits are well known to those skilled in the art and it is not necessary to describe them in more detail. The device 54 comprises: means for receiving vertical and horizontal synchronization pulses coming from the video signals supplied by the image detection device 53; pulse emission means for determining the horizontal position; a predetermined counter which is recalled by the vertical synchronization pulses and which counts the number of horizontal synchronization pulses and generates a signal when this count corresponds to the predetermined value; another predetermined counter which is recalled by the horizontal synchronization pulses and which counts the pulses so as to emit a signal when the count corresponds to the predetermined value; and a gate circuit for inhibiting the output video signal to be transmitted to the indicator 56, until the two predetermined counters are recalled after having respectively transmitted the signals mentioned above. In addition, the output of the gate circuit is transmitted to the indicator 56 via an image composition device 55, in order to display a composite signal containing other signals, described below, which are introduced into the image composition unit 55.

 The reference numeral 60 designates a microcomputer, using for example a Z-80A microprocessor manufactured by Zilog Co., for the central processing unit. The microcomputer 60 performs the scanning command and the two-color temperature determination operation of the signal of the image detection devices 51, 52.

 The scanning control of the devices 51, 52 is first described in detail. The reference 61 designates a register comprising a plurality of digital contacts, for example rotary switches with digital display, the register 61 indicating an area to be scanned in order to obtain the temperature distribution image. FIG. 14 illustrates the scanning zones of the image detection devices 51, 52, that is to say the zones scanned to obtain the temperature distribution. The areas may include any of a laterally elongated area having a vertical main scanning direction Y and a horizontal underscan direction X, or a longitudinally elongated area having a main scanning direction X and a direction of underscan Y, or both areas at the same time, so when the two areas are scanned, the microcomputer is programmed to alternately scan each area. In this embodiment, the register 61 can determine the positions Py, Px of the start of the main scan of each zone and their widths Wy, Wx. The number of their scan lines is made constant, for example 128, in any direction. The microcomputer 60 controls the device so as to carry out the scanning, as shown, on the basis of the stored values Py, Px, Wy and Wx. Between the microcomputer 60 and the X direction deviation input terminals of the control units 51b, 52b, a 62X counter and a 63X digital-analog converter are interposed for the digital-analog conversion of the counted values of the 62X counter, so that the analog output of the 63X converter is used for the direction deviation signals X for the two control units 51b and 52b. Between the microcomputer 60 and the Y direction deviation input terminals of the control units 51b, 52b are interposed a counter 62Y and a digital-analog converter 63Y to convert the counted values of the counter 62Y, so that the analog output of the converter 63Y is used for the direction deviation signals Y for the two control units 51b and 52b. The direction deviation signal X (or Y) of the device 51 has a reverse polarity to that of the detection device 52. image, since the device 51 receives an image symmetrical with respect to the device 52.

We will now describe in detail the operation and control of the microcomputer 60 concerning the laterally elongated scanning zone. The microcomputer 60 determines information corresponding to a value of Py in the counter 62Y and determines information corresponding to the first position in the sub-scanning direction in the counter 62X. The microcomputer 60 supplies high frequency clock pulses to the counter 62Y, so as to increase the count of the latter. When his account reaches a value corresponding to Py + Wy, the counter 62Y is recalled to a value corresponding to Py and at this time the counter 62X receives an impulse to advance his account by one rank. Such an operation is repeated 128 times to cause the laterally elongated band-like area to scan, from Py to
Py + Wy, image detection devices 51 and 52. The microcomputer 60 sends a signal to a television interface 64, so as to display vertical and horizontal lines at the positions of Py, Py + Wy and Px, Px + Wx respectively. The output of the television interface 64 is transmitted; - goes to the image composition unit 55, which causes the display on the indicator 56 of the part of an object image corresponding to the area temperature measurement. In this embodiment, the partial video signal elimination unit 54, the image composition unit 55 and the television interface 64 are separate elements. However, an amplifier can be used for the three circuits. special mixing MEA 5100 or MEA-7500, manufactured by Ikegani Communication
Co., or a special effect color device SEG-120, manufactured by Sony Corp.

 The video signal output terminals of the control units 51b and 52b transmit photoelectric conversion signals from the scanned part, as described above, corresponding to the scanning operation. The outputs of the units Slb and 52b constitute inputs for integrators 651, 652 respectively. The values integrated by these devices are transformed into digital information by analog-to-digital converters 661, 662, then introduced into the microcomputer 60. The reading period of the microcomputer 60 is expected to be substantially synchronous with the moment of completion of the main scan. Consequently, the microcomputer 60 sequentially reads the signals corresponding to the energy of the light of components of main wavelengths λ 1, X 2 contained in the light emitted by the same part, in a substantially synchronous manner and in the same area at inside the visual field obtained by the two image detection devices 51, 52. Thus, the microcomputer 60 reads information for each scan line and, consequently, 128 pieces of information are read for each scan area extended laterally or longitudinally.

 On the other hand, before the commissioning of this device, the image pickup lens 34 is covered by a shutter, not shown, so as to obtain a compensation value for each of the devices 51 and 52 for detecting image, this value being stored in a predetermined area of the memory 67, this information corresponding to the respective laterally and longitudinally elongated areas of the devices 51 and 52.

dans laquelle T(X,Y) (OK) est une température particulière à la position correspondant à une ligne de balayage ;E1(X,Y), e2(X,Y) sont les énergies rayonnées correspondant à chacune des longueurs d'onde À1, X2 avec les valeurs de compensation mentionnées plus haut ; et a, ss sont des constantes choisies pour X 2 De plus, l'équation (3) est vérifiée puisque la relation entre le rapport d'énergie el(X,Y)/e2(X,Y) et la température T(X,Y) est approximativement linéaire.The program of the microcomputer 60 is provided so that, each time it reads information in the analog-digital converters 661, 662, it deduces the compensation value from the corresponding scanning position, from the information read, in order to to determine the radiated energy corresponding to each wavelength A1 or A2 at the measured scanning position, and it performs the operation of determining the temperature in two colors according to equation (3) below

in which T (X, Y) (OK) is a particular temperature at the position corresponding to a scanning line; E1 (X, Y), e2 (X, Y) are the radiated energies corresponding to each of the wavelengths À1, X2 with the compensation values mentioned above; and a, ss are constants chosen for X 2 In addition, equation (3) is verified since the relationship between the energy ratio el (X, Y) / e2 (X, Y) and the temperature T (X , Y) is approximately linear.

 The temperature information thus obtained is stored in a predetermined area of the memory 67 corresponding to a plurality of frames comprising the frames being scanned. The information is entered into the microcomputer 60, so as to be available for a predetermined use and to be able to be transmitted to various external instruments.

A common use of the information is to provide a printout of the temperature values using a printer, or the graphical display of a temperature distribution image, i.e. the temperature distribution at 128 horizontal or vertical points in the visual field of the image detection device. Likewise, when used for welding zone supervision, the temperature is available as heating control information.

 The embodiment of FIG. 11 is provided for the display, on the indicator 56, of the horizontal or vertical distribution of temperature by means of the temperature information developed as described above.

 FIG. 15 is a plan view of an exemplary arrangement of the image guide 31 and the objective 32 when the object 30 is an electrically welded tube, during manufacture.

An open tube 90, of copper foil, is rolled into the desired shape. Its two edges are brought together by contact fingers 92, arranged upstream of clamping rollers 93, and they are welded in pressure contact exerted by the rollers 93, so as to obtain the electrically welded tube. The tube is then transferred to a solder annealing device. The objective 32 is arranged so that an area comprising the welding stop, that is to say the contact point or "V" located slightly upstream rather than the imaginary line passing through the axes of the rollers clamp 93, or used as a visual field for image taking. FIG. 16 shows the shape of the display on the indicator 56, when the above image pick-up visual field is chosen. The upper left zone represents the image received by the image detection device 53, in which appear the open tube 90, the tube 91 electrically welded, the weld bead areas and the point of contact or "V". Likewise, two horizontal and vertical lines, indicating the aforementioned scanning area, appear respectively. The various parts, except the image display area 56a, are uniformly leveled to black by a circuit 54 for partial elimination of the video signal and they are used for displaying the temperature distribution. first, area 56b, located below image display area 56a, is a laterally elongated scan area from Py to Py + Wy and, in this case, it is the horizontal distribution display area used for indicate the longitudinal temperature distribution of the tube along the weld bead. Area 56c, located to the right of areas 56a and 56b, is a vertical distribution display area, used to indicate the circumferential temperature distribution of the tube along the longitudinally elongated scanning area from Px to Px + Wx.

A video signal memory 68, comprising storage locations corresponding to the scanning zones 56b and 56c, is provided for recording therein temperature scales corresponding to set horizontal and vertical lines to be displayed inside the zone 56b horizontal distribution display and vertical distribution display area 56c. Information is stored in this memory, to be used to display temperature values corresponding to the temperature scales. The information to be stored in the video RAM 68 can be displayed, in a known manner, by means of a white dot grid. The address location of the video memory 68 corresponding to the position, within the zones 56b and 56c, to be indicated by the white dots, is calculated from the temperature information obtained by means of the predetermined temperature scales, relative to the signal information and to each scan line, so that the white point information is written to the location of the random access memory 68 corresponding to this address. To write this display information in the video memory 68, a period of time such as that corresponding to the signal determining the moment of the vertical synchronization pulse from the video signal input to the indicator 56 is chosen. coming from the image composition unit 55, and not relating to this display. The display signals transmitted to the indicator 56 relate to the vertical and horizontal synchronization pulses of the video signal, so that the playback address of the video memory 68 is read in correspondence with the playback address, the information read being sent to the image composition unit 55 via the television interface 64, which causes the display on the indicator 56 of a composite design such as that which is represented in FIG. 16. Such a display makes it possible to observe the welding operation and its corresponding temperature distribution, in any direction. On the other hand, the arrows in Figures 15 and 16 indicate the direction of movement of the tube.

In the case where the temperature distribution is measured as indicated above, the information stored in the video memory 68 is not written each time the temperature information is renewed but once for several information renewals; so as to avoid blinking and thus improve viewing. When used in the device described above, the two-color temperature determination operation measures the temperature, so that the measurement is less affected by the ambient atmosphere, compared to the infrared system. according to the prior art, and its accuracy is greater. When the image guide is used, as in the embodiment of FIG. 11, it is possible to measure the temperature distribution without being affected by the atmosphere , or measure the temperature distribution in a small or deep area that is not directly visible from the outside. Furthermore, the resolution power can be increased until it is limited by the resolution of the image detection devices 51 and 52. Likewise, the device of this embodiment uses the image detection device comprising an image dissector to allow random access scanning, which makes it possible to easily obtain the temperature distribution relating to an optimal area. , when using a vidicon camera, a sequential scan is performed so that complicated software is required to obtain temperature distribution images other than those in the vertical or horizontal direction of image reproduction, this which causes practical difficulties.

The device according to the invention on the other hand makes it easier to obtain a temperature distribution in a desired direction and no scanning is carried out on a part which does not relate to its operation. In addition, an image detection tube is used with no accumulation effect, so as to escape the influence of the residual images. Such a tube is suitable for measuring an object whose temperature varies rapidly. On the other hand, the image detection tube has a wider dynamic band than that of a vidicon camera, which is advantageous for measuring a larger temperature range.

 FIG. 22 shows another embodiment of a measuring device according to the invention, which makes it possible to eliminate one of the devices 51 or 52 for image detection. A lens 1, a neutral filter 35 and a mirror 5 are placed so that the device 51 receives the light which passes through the lens 1 and the neutral filter 35 and that the device 53 receives the light which passes through the lens 1 and which is reflected by the mirror 5. A rotating filter 2 is placed between the neutral filter 35 and the device 51. As shown in FIG. 23 or 24, the rotating filter is in the form of a disc and it is divided into two or four zones, respectively.

Each zone consists of an optical filter 21 or 22 whose respective penetration length is A1 or A2, and the filters 21 and 22 are arranged alternately. The rotating filter 2 is driven by a motor 23, so as to rotate at high speed. The device 51 receives the light which passes through the filter 21 or 22 and its output constitutes an input to the arithmetic unit 3. A pulse generator, not shown, is mechanically connected to the motor 23 or to the rotating filter 2 and an arithmetic unit 3 discriminates between the two types of information, one coming from filter 21 and the other from filter 22, as a function of said output of the pulse generator and it performs the two-color temperature operation in a similar manner to that of the elements of FIG. 11. The device also comprises an image composition unit 4 and an indicator 56.

 When the device is used for the supervision of the welding area of an electrically welded tube, it is very practical for the control of the manufacturing line to obtain the point "V" as well as the angle "V", c that is to say the angle formed by the two edges of the open tube 90 at the top "V", which is possible by means of a device according to the present invention. In other words, the video signal output from the second image detection device 52, or from the first device 51, is used as follows.

 The video signal is sent to the input of an analog switch 69 (see Figure 11) which allows the video signal to pass only when the deviation signals in the X and Y directions, which are outputs of the 63X digital-analog converters and 63Y, correspond to the scanning of the laterally elongated zones from Py to Py + Wy, whose main scanning direction is Y and whose underscanning direction is X. The output of analog switch 69 is sent to the input of an integrator 70 whose output feeds a comparator 71 to fix the threshold value at a given level. The image generated by the device 52, from a temperature distribution of the object in its visual field, has an aspect of heat in light red, on the opposite edges of the open tube 90 and in the welded part of the electrically welded tube, and it darkens due to the lower temperatures at a certain distance from the hot parts to red.

It becomes very dark when the background of an interval between the opposite edges of the open tube is detected.

FIG. 17 is a view, on a larger scale, of an example of detected image and scanning lines between Py and
Py + Wy. FIG. 18 represents the levels of the video signal corresponding to the scanning lines and which relate to the position of the tube 91 electrically welded. Since the brightness in this part has the distribution described above, the video signal has waveforms as shown in FIG. 19, with ridges at the opposite edges of the open tube 90 and in the welded part of the tube 91, it that is to say in the red hot parts. The integrator 70 which receives the video signal emits an output signal showing an abrupt change at the location corresponding to. opposite edges, in contrast to the part of the video signal which scans the open tube 90. The output signal from the integrator 70 is sent to the comparator 71, to fix the threshold value at a given level. The comparator 71 emits pulses when the scanning point crosses the opposite edges. If the scanning lines, as indicated in FIGS. 17 and 18, are designated by the numbers 1, 2 ... i from upstream of the open tube 90, the output signal of the comparator 71, as indicated on FIG. 19 is transformed into pulse intervals, sequentially reduced t1, t2 ... t.. Similarly, the output signal of the comparator 71 is sent to a clock device 72 comprising a clock oscillator and a counter and in which the pulse intervals t1, t2 ... ti corresponding to the respective scanning lines are measured, the clock unit 72 comprising deviation signals in the X and Y directions to discriminate each scanning line.

 The microcomputer 60 sequentially reads the output of the counter from the clock unit 72, that is to say t1, t2 ti which corresponds to the dimensions g1, g2 ... gi of the intervals between the opposite edges of the open tube 90 , as shown in FIG. 18. Since the order of each reading, that is to say the numbers of the scanning lines 1, 2 ... i, essentially corresponds to the position in the axial direction of movement, the microcomputer 60 can determine the length of the interval between the opposite edges, at each position, in the X direction. Figure 20 schematically illustrates the relationship between the two measured values, the abscissa representing the position on the X axis and the ordinate representing the dimension g between the two edges. In addition, X1, X2, ... X. are values indicating the corresponding positions of the scanning lines 1, 2, ... i, the left end of the visual field being taken for example equal to zero.

 In this embodiment, the position in the X direction when g = 0, as is the case at the specified point "V", is not taken from the time unit 72 but is obtained by the method below. The information, after the value g has become smaller than the prescribed value, is neglected, and (Xi, g.) With i = 1, 2, ... n, n being greater than or equal to 3, becomes l objective of the operation. From the above, we obtain a straight line by the method of least squares approximation, so that the position in the direction X where the straight line becomes g = O (cross section of the abscissa line X on Figure 20), is considered to be point "V".

Figure 21 illustrates the principle of calculating the angle "V". If an angle between the line obtained as indicated above and the abscissa X in Figure 20 is represented by e, the relationship below is established with the angle V OV to be obtained (angle formed in the vicinity of point V by the opposite edges of the open tube 90, as shown in Figure 17)
tan e = 2 tan 2
The microcomputer 60 then calculates a value of from the equation below, using the preceding relation,
= 2 tan tan e (2)
2 tan 2 in which e is obtained by a known method, on the basis of the straight line previously determined.

 The position of the point V and the angle V OV are sent to a printer 73, for display and recording, and to the heating control unit when they are used for this purpose. Figures 25 (A), (B) and (C) show a flow diagram of the measurement. First, the temperature of an elongated area is measured laterally, then the temperature of an elongated area longitudinally, and then the point V and the angle OV are specified.

 It can be seen from the above description that the method and the device according to the invention make it possible to obtain the image of the temperature distribution of an object, by means of a temperature determination operation at two colors using the energy emitted by the object in respective bands with central wavelengths A1 and A2 this energy is not easily affected by the atmosphere compared to a thermometer using infrared rays. The present invention allows the use of an image guide, which cannot be used with infrared rays due to loss in transmission. In addition, the present invention can measure the temperature distribution of a reduced area or that of a cavity of a structure when the bottom is not directly visible from the outside. On the other hand, the resolution power can be increased, up to the limit of the light-sensitive part of the image detection device.

The method and the device according to the invention are also extremely reliable, compared to known devices of the contactless type, and they can accurately detect the temperature distribution of an object undergoing a large temperature variation, for example electrically tubes. welded during welding on a production line. The present invention therefore has great advantages and constitutes significant progress in this type of temperature measurement.

 It is understood that modifications of detail can be made in the form and the implementation of the method and of the device according to the invention, without departing from the scope thereof.

Claims (24)

 1. A method of measuring the temperature distribution, characterized in that it consists in passing parts of the light coming from parts of a surface of an object for which the temperature distribution image is to be measured. , the latter parts being in a predetermined arrangement, through first and second optical filters which pass respectively different wavelengths of light; determining, for the respective parts of the light, the energy level which passes through the respective filters; and performing, by means of the energy levels thus determined, a two-color temperature determination operation for the respective parts of the surface, in order to determine the temperature of each part of the surface of the object, the distribution configuration of the temperature on the surface of the object which can thus be obtained from the temperatures of the parts of the surface.  2. Method for measuring the temperature distribution according to claim 1, characterized in that the operation of passing the parts of light through the filters comprises the simultaneous passage of a part of light coming from a part of the surface through a filter and the part of light from the next adjacent part of the surface through the other filter, and in that the operation of determining the energy level comprises scanning the light which has passed through the filters successively, the operations being repeated for adjacent parts over the entire surface of the object.  3. Method according to claim 1, characterized in that the operation of passing the parts of the light through the filters first comprises passing the parts of the light coming from a plurality of parts of the surface through only the first filter, then passing parts of the light from the same parts of the surface through only the other filter, in that the operation of determining the energy level comprises scanning the light which has passed through the first filter and then the scanning of the light which has passed through the other filter, and in that the execution of a two-color temperature determination operation comprises the selection of the light coming from the respective parts of the light which has passed through the first filter and light from the respective parts of the light which passed through the other filter, this determination being made for the respective parts of the surface.  4. Method according to claim 1, characterized in that the operation of passing the parts of light through the filters simultaneously comprises passing the parts of light coming from a plurality of parts of the surface through only one filter and the passing parts of light from the plurality of parts of the surface through only the other filter, in that the operation of determining the energy level comprises scanning the light which has passed through the first filter and simultaneously the scanning the light which has passed through the other filter, and in that performing a two-color temperature determination operation includes selecting the light from the respective parts of the light which has passed through the first filter and light coming from the respective parts of the light which has passed through the other filter, the determination being made for the respective parts of the surface.  5. A method of measuring the temperature distribution of an object, characterized in that it consists in: directing the light, coming from the surface of the object whose configuration of temperature distribution is to be determined, along a light guide path; inserting into this path an optical filter comprising a plurality of zones in a determined arrangement, the adjacent zones being constituted by optical filter elements which allow different wavelengths of light to pass; scanning the light coming out of the adjacent areas of the filter by means of a detection device, to determine the level of energy which passes through the adjacent areas; and performing by means of the output of the detection device a two-color temperature determination operation for the respective pairs of adjacent areas.  6. A method of measuring the temperature distribution of an object, characterized in that it consists in: directing light, coming from the surface of the object whose temperature is to be determined, along a path of light guidance; introduce into this light path a first optical filter which lets through a first wavelength of light then introduce into the light path a second optical filter which lets through a second wavelength of light, different from the length wave passing through the first filter; sweep the light coming out of the first filter and then the light coming out of the second filter using a detection device, to determine the levels of energy which passes through the respective filters and which corresponds to parts of the surface of the object; and performing, by means of the output of the detection device, a two-color temperature determination operation for the respective parts of the surface of the object, by using the output of the detection device during the scanning of the light coming from of the first filter for each part of the surface of the object and by using the output of the detection device during the scanning of the light coming from the other filter for the same part of the surface of the object.  7. A method of measuring the temperature distribution of an object, characterized in that it consists in: directing light, coming from the surface of the object whose temperature is to be determined, along guide paths of separate light; placing a first optical filter which lets a first wavelength of light pass through a first path and a second optical filter which lets a second wavelength of light pass, different from the wavelength passing through the first filter, in the second path; simultaneously scanning the light coming out of the filters by separate detection devices, to determine the levels of energy passing through the respective filters in correspondence with the parts of the surface of the object; and performing, by means of the outputs of the detection devices, a two-color temperature determination operation for the respective parts of the surface of the object, by using the output of a detection device, resulting from the scanning of the light coming out of a filter for each part of the surface of the object, and from the output of the other detection device, resulting from the scanning of the other filter for the same parts of the surface of the object.  8. Apparatus for measuring the temperature distribution of an object, characterized in that it comprises: means for directing along a path the light coming from the surface of the object whose distribution of temperature ; an optical filter (2) placed in this light guide path, this optical filter comprising a plurality of zones (21, 22) in a predetermined arrangement, the adjacent zones being of optical filtration material which allow lengths of different light waves; an image detection device (1) positioned to receive the light which has passed through the filter, to scan this filter, to produce a video signal (VDS) corresponding to the energy levels of the light which has passed through the areas of the filter and producing a video signal comprising parts (PS1, PS2) of image signal corresponding to these energy levels; a video signal processing unit (4), connected to the image detection device for extracting the parts of the image signal from this video signal; memory means (5) connected to the video signal processing unit for storing the image signal portions of the video signal at locations corresponding to the positions of the filter areas; and an arithmetic unit (6) connected to these memory means for performing a two-color temperature determination operation for each pair of adjacent filter zones, from the stored portions of the image signal corresponding to the energy levels in these areas.  9. Apparatus according to claim 8, characterized in that the zones in the filter are arranged in a matrix comprising horizontal and vertical rows of zones, the adjacent zones in the horizontal rows being made of different optical filter materials and the adjacent zones in the vertical rows being made of different optical filter materials.  10. Apparatus according to claim 9, characterized in that the filter comprises dark areas (23), between the areas of the filter, which are substantially opaque so that the image signal portions (PS1, PS2) of the video signal are separated by signal portions (PS3) representative of a low energy level.  11. Apparatus according to claim 8, characterized in that the memory means have sufficient capacity to store the image signal parts from at least two sets of filter areas.  12. Apparatus for measuring the temperature distribution of an object, characterized in that it comprises: means (9) for directing along a path the light coming from the surface of the object for which it is desired to determine temperature distribution; an optical filter (2 ') comprising at least two parts (21', 22 ') each having an area as large as the transverse surface of the light along said path, these parts being made of optical filter materials which allow lengths to pass different light wave, the filter being mounted so as to bring the different parts of the filter alternately in the light path; an image sensing device (1) positioned to receive the light which has passed through the parts of the filter, to scan the light coming out of the parts of the filter, to produce a video signal corresponding to the energy levels of the light which passed through the areas of the filter parts and producing a video signal comprising image signal parts corresponding to the energy levels; a video signal processing unit (4 ') connected to the image detection device for extracting the image signal portions of the video signal; memory means (5) connected to the video signal processing unit for storing the image signal parts of the video signal for each of the parts of the filter, at locations corresponding to the positions of the areas of the filter; and an arithmetic unit (6) connected to the memory means for performing a two-color temperature determination operation for each filter zone, from the stored parts of image signal corresponding to the energy levels which have passed through the zones corresponding in the respective parts of the filter.  13. A device for measuring the temperature distribution for obtaining the configuration of the surface temperature of an object, characterized in that it comprises: two-dimensional image detection means; first and second optical filters placed on a path for guiding the light, between the object and the image detection means, these filters being provided for choosing two components of different optical wavelengths of light coming from the object to be measured; and an arithmetic unit operatively connected to the image sensing means for determining the temperature of the surface of the object based on the amplitude ratio of the two components of different wavelengths of the light.  14. Device for measuring the temperature distribution, characterized in that it comprises: a first and a second device (51a, 52a) for image detection each comprising a camera head connected in operation to a control unit ( 51b, 52b); first and second optical filters (37, 38) placed respectively in the passage of light between an object whose temperature distribution is to be measured and the first and second camera heads, the first and second optical filters being provided for passing two components of different optical wavelengths of light, respectively, to the first and second camera heads; first and second integration devices (651, 652), connected respectively to the first and to the second control units to integrate its outputs; first and second analog-to-digital converters (661, 662), respectively connected to the first and second integrators to transform their outputs into digital signals; an arithmetic unit (60) operatively connected to the first and second analog-to-digital converters; means for developing an analog signal to control the first and second control units the arithmetic unit determining the temperature of the surface of the object to be measured on the basis of the ratio of the amplitude of the two components of lengths d different wave of light.  15. Device for measuring the temperature distribution, characterized in that it comprises: first and second image detection devices, each comprising a camera head connected in operation to a control unit; first and second optical filters placed respectively in a passage of light between an object whose temperature distribution is to be measured and the first and second camera heads, the first and second optical filters being provided for passing two components respectively different optical wavelengths from light to the first and second camera heads; first and second integrators connected respectively to the first and to the second control units to integrate their outputs; first and second analog-to-digital converters connected respectively to the first and second integrators to transform their outputs into digital signals; an arithmetic unit comprising a microcomputer operatively connected to the first and second analog-to-digital converters; storage means (61) operatively connected to the microcomputer for storing digital information; first and second digital to analog converters (63X, 63Y) connected in operation respectively between the microcomputer and the first and second control units to transform the digital signals coming from the microcomputer into analog signals to control the first and second control units; indication means (56, 73) connected in operation to the microcomputer; the first and second image detection devices being mechanically directed towards the object to be measured through at least one lens; the arithmetic unit determining the temperature of the surface of the object to be measured on the basis of the ratio of the amplitude of the two components of different wavelengths of light; the arithmetic unit determining the position on the surface of the object so as to obtain the temperature distribution configuration of the object to be measured; the microcomputer controlling the storage means and the first and second control units so that the indication means display a graphic representation of the temperature distribution of the object to be measured.  16. Device for measuring the temperature distribution, for obtaining the surface temperature configuration of an object to be measured, characterized in that it comprises: two-dimensional image detection means; first and second optical filters placed in a passage of light between the object and the image detection means, these filters being provided for choosing two components of different optical wavelengths of the light coming from the object to measure; an arithmetic unit operatively connected to the image detection means for determining the temperature on the surface of the object to be measured, based on the ratio of the amplitude of the two components of different wavelengths of light; additional image detection means (53) for obtaining a two-dimensional video image of the object to be measured; means (54, 55) for combining the outputs of the arithmetic unit (60) and additional means (53) for image detection; and indication means (56) operatively connected to the combining means, the arithmetic unit controlling the image detection means and the combining means so as to form on the indicator a composite display comprising a video image to be two dimensions of the object to be measured and a graphic representation of the temperature distribution of the object to be measured.  17. Device for measuring the temperature distribution, to obtain the configuration of the surface temperatures of an object to be measured, characterized in that it comprises two-dimensional image detection means; first and second optical filters s placed in a passage of light between the object and the image detection means, these filters being provided for choosing two components of different optical wavelengths of the light coming from the object to be measured; an arithmetic unit connected in operation to the image detection means for determining the temperature on the surface of the object to be measured, on the basis of the ratio of the amplitude of the two components of different wavelengths of light, this arithmetic unit determining the position on the surface of the object, so that the temperature distribution configuration of the object to be measured is obtained; additional image detection means for obtaining a two-dimensional video image of the object to be measured; means for combining the outputs of the arithmetic unit and additional image detection means; and indication means (56) operatively connected to the combining means, the arithmetic unit controlling the image detection means and the combining means so as to form on the indicator a composite display comprising a video image to be two dimensions of the object to be measured and a graphic representation of the temperature distribution of the object to be measured.  18. Device for measuring the temperature distribution, characterized in that it comprises: a first two-dimensional image detection device (51) comprising a camera head (51a) and a control unit (51b); an arithmetic unit (3) operatively connected to the first image detection device; filtering means (2) comprising at least first and second optical filters (21, 22) placed movably in a passage of light between an object (W) whose temperature distribution is to be measured and the first device image detection, the filtering means being connected in operation to the arithmetic unit and controlled by the latter, the first and second optical filters being provided for choosing two components of different wavelengths of light; the arithmetic unit determining the temperature on the surface of the object to be measured, based on the ratio of the amplitude of the two components of different wavelengths of light, the arithmetic unit further determining the position on the surface of the object, so as to obtain the temperature distribution configuration of the object to be measured; the arithmetic unit controlling the filtering means so as to bring the first and second optical filters alternately into the light passage; a second two-dimensional image detection device (53), optically directed towards the object to be measured; an image composition unit (4), operatively connected to the arithmetic unit and the second image detection device; indication means (56) operatively connected to the image composition unit; the arithmetic unit controlling the first image detection device, the filtering means and the image composition unit so that the indication means display a two-dimensional video image of the object to be measured and a graphical representation of its temperature distribution configuration.  19. Device for measuring the temperature distribution, characterized in that it comprises: a first and a second image detection device (51, 52) each comprising a camera head (51a, 52a) connected in operation to a controller (512, 522); a third image detection device (53); first and second optical filters (37, 38) placed respectively in a passage of light between an object whose temperature distribution is to be measured and the first and second camera heads, the first and second optical filters being provided to leave passing respectively two components of different wavelengths of light to the first and second camera heads; first and second integrators (651, 652) respectively connected to the first and second control units to integrate their outputs; first and second analog-to-digital converters (661, 662) respectively connected to the first and second integrators for converting their outputs into digital signals; an arithmetic unit (60) operatively connected to the first and second analog-to-digital converters; means (62, 63) for generating an analog signal, for controlling the first and second control units; image composition means (55) operatively connected to the arithmetic unit and to the third image detection device; indication means (56) operatively connected to the image composition means; the arithmetic unit determining the temperature at the surface of the object to be measured, on the basis of the ratio of the amplitude of the two components of different wavelengths of light; the arithmetic unit controlling the first and second control units and the image composition means so that the indication means display a two-dimensional video image of the object to be measured and a graphic representation of its configuration temperature distribution.  20. A device for measuring the temperature distribution, characterized in that it comprises: first and second image detection devices each comprising a camera head connected in operation to a control device; a third image detection device; first and second optical filters placed respectively in a passage of light between an object whose temperature distribution is to be measured and the first and second camera heads, the first and second optical filters being provided for passing two components of different wavelengths of light to the first and second camera heads; first and second integrators connected respectively to the first and second control units to integrate their outputs; first and second analog-to-digital converters respectively connected to the first and second integrators for converting their outputs into digital signals; an arithmetic unit, comprising a microcomputer, operatively connected to the first and second analog-to-digital converters; storage means (61, 68) connected in operation to the microcomputer, for the storage of digital information; first and second digital to analog converters connected in operation respectively between the microcomputer and the first and second control units for transforming the digital signals of the microcomputer into analog signals, for controlling the first and second control units; image composition means operatively connected to the microcomputer and to the third image detection device; indication means connected to the image composition means; the first, second and third image detection devices being mechanically directed towards the object to be measured through at least one lens (34) the arithmetic unit determining the temperature on the surface of the object to be measured, on the basis the ratio of the amplitude of the two components of different wavelengths of light, the arithmetic unit further determining the position on the surface of the object, so as to obtain the temperature distribution configuration of the object to be measured; the microcomputer controlling the storage means and the first and second control units and the image composition means, so that the indication means display a two-dimensional video image of the object to be measured and a graphic representation of its temperature distribution configuration.  21. A device for measuring the temperature distribution according to any one of claims 16 to 20, characterized in that the object (w) to be measured comprises a zone for welding an electrically welded tube during manufacture on a electrically welded pipe production line, additional means (69, 70, 71, 72) being connected in operation to the arithmetic unit for calculating the information useful for the production control of the electrically welded pipe, from the measured configuration temperature distribution.  22. A device for measuring the temperature distribution according to claim 16 or 17, characterized in that the two-dimensional image detection means comprise an image detection device of the random access scanning type.  23. A device for measuring the temperature distribution according to claim 18, characterized in that the first two-dimensional image detection means comprise a random access scanning image detection system.  24. A device for measuring the temperature distribution according to claim 19, or 20, characterized in that the first and second two-dimensional image detection devices each comprise an image scanning system of the scanning access type. random.