RU2818997C2 - Installation and method of measuring thickness of walls of glass vessels - Google Patents

Abstract

FIELD: optics.

SUBSTANCE: invention relates to the technical field of optical control of transparent or transparent vessels or hollow objects having a high temperature. Method of measuring thickness of walls of glass vessels coming out of moulding cavities, in which heat radiation emitted by vessel from diametrically opposite sides of vessel is selected for measurement. Radiation emitted by the vessel in the first spectral band (λ1) in range from 2800 nm to 4000 nm and in the second spectral band (λ2). At the same time measuring: on the first side (I) of the vessel, intensity of radiation emanating from first wall (21), in the first spectral band (λ1) and in the second spectral band (λ2); and on the second side (II) of the vessel, the intensity of the radiation emanating from second wall (22) in the first spectral band (λ1) and in the second spectral band (λ2). Determining the thickness of the first and second walls (2₂) based on measurements of the intensity of radiation emanating from the first wall, in the first and second spectral bands and from the second wall, in the first and second spectral bands, Note here that the radiation intensity in the first spectral band is taken into account for the radiation emitted by the wall itself and radiation emitted by the other diametrically opposite wall and passing through the said wall with absorption.

EFFECT: high accuracy of determining thickness of walls of glass vessels at high temperature.

13 cl, 9 dwg

Description

Technical field

The present invention relates to the technical field of optical inspection of translucent or transparent vessels or hollow objects having a high temperature.

In particular, the invention relates to high-speed optical inspection of objects, such as still hot bottles or glass vials, emerging from a production or molding machine. The invention therefore relates to the monitoring of objects in the hot sector of a production plant.

Classically, after melting the glass in a furnace at a temperature of about 1600°, the molten glass flows over the molding machines through the so-called “delivery” channels. The installation also contains a distributor of portions of molten glass or drops of plastic glass falling under the influence of gravity into each blank mold. This element thus forms glass droplets which are distributed towards the various independent molding sections through a set of guides called delivery guides. The forming machine, called the IS machine, consists of various sections, each equipped with at least one blank cavity equipped with a blank mold, and the same number of finishing cavities, each containing a finishing mold, in which the vessels receive their final shape when high temperature. One, two, three or four drops of hot glass (about 1200°C), called a “portion,” are loaded alternately into 1, 2, 3 or 4 empty cavities of the section in a predetermined order. At the exit of the molding machine, the vessels, still at high temperature, typically between 300°C and 600°C, are picked up at their rim level and carried so as to form a row on a conveyor belt. The gap between the vessels can vary and is set by the molding machine depending on its center distance and the diameters of the vessels. The conveyor conveys the vessels sequentially to different processing stations, such as the surface treatment agent spraying hood and the annealing furnace called the annealing lehr.

The molding defect must be identified as early as possible at the exit of the molding machine before entering the various processing stations so that it can be corrected as early as possible in the molding machine. In particular, it is necessary to identify dimensional deviations or deformations of the vessels that are directly related to the adjustments of the molding process, so that if a deviation is detected, the process can be adjusted as quickly as possible.

Quality control of such vessels allows us to reject those that have defects that could affect their aesthetic appearance or, more seriously, that could pose a real danger to future users. Thus, it is necessary to control the quality of the thickness distribution of such vessels in order to exclude vessels that are too thin or vessels with different thicknesses in some areas, which could affect the mechanical strength.

Indeed, the quality of the thickness distribution is a very important parameter, since the thickness can vary, that is, it can be too large or too small in different parts of the vessel. This variation in thickness creates a problem because the products produced are potentially fragile. In addition, manufacturers are trying to find the opportunity to produce lighter and thinner glass vessels, therefore, it is necessary to be able to distribute the glass correctly. Many production parameters are known to affect glass distribution and must be controlled. In particular, the following parameters can be specified as well-known examples:

i) loading parameters, which include the velocity vector and centering of the droplet as it falls into the rough mold;

ii) temperature distribution in the drop;

iii) cooling of molds.

To properly influence production parameters, it is necessary to know the glass distribution of the vessels immediately after molding.

It is clear that to know the thickness distribution means to know in absolute terms the thickness at various points of the vessel or, if this is not possible, to know in relative terms the thickness deviations between different regions of the vessel. For example, a bottle contains from bottom to top: a bottom, a body connected to the bottom through a heel, then a neck connected to the body through a shoulder, and finally a rim designed to be filled and to be closed with a stopper, cap or lid. A glass distribution defect can be observed, for example, vertically with excess glass at the bottom and thinning at the shoulder. Defects in horizontal distribution can also be observed, for example at shoulder level: more glass on one side than on the opposite side relative to the axis. This analysis of not only the minimum and maximum glass thicknesses, but also the distribution of vertical or horizontal deviations, as well as the location of thin or thick zones, is extremely important in order to correctly adjust the process.

Prior Art

In the prior art, various solutions are known that use infrared radiation emitted by still hot vessels and which have been proposed to monitor them at the exit of the molding machine in order to measure the glass distribution.

For example, US Pat. No. 3,535,522 describes a method for measuring the thickness of the glass of a vessel by measuring the infrared radiation emitted by such a vessel at the exit of a molding machine. The infrared radiation measurement is made when the vessel is placed in an oven to obtain a uniform temperature of the vessel with a certain value. The vessel, still inside the oven, is then rotated about a vertical axis in front of the optical axis of the infrared sensor, which during one rotation measures the radiation passing through the wall between 2.06 and 2.5 µm or between 3.56 and 4.06 µm. Since the temperature is assumed to be uniform due to the furnace, perceived changes in radiation can be directly related to differences in thickness. This technology does not allow continuous monitoring of the vessels and requires manipulation of the vessels, which makes the process slow and can lead to vessel deformations.

Patent EP 0 643 297 describes a device that allows analysis and diagnostics during the production of glass products and contains a sensor sensitive to infrared radiation emitted by objects emerging from a molding machine. This system also contains a digital processing device that compares the radiation with a reference mathematical model to determine deviations existing in the distribution of glass and/or the reasons leading to the presence of thermal stresses in the vessel. In addition, this patent does not provide any indication of a means of obtaining a control mathematical model.

It should be taken into account that such an infrared radiation measuring device is installed to monitor the vessels that move along the exit conveyor downstream (in the direction of movement) of the molding machine, that is, at the exit of the last section that is closest to the device. At the other end of the machine there is therefore a section located most upstream. As for the radiation emitted by the vessels, it depends on many parameters, among which we can indicate the distribution of the material, as well as the temperature distribution. As the vessels move between the section and the infrared radiation measuring device, there is heat transfer by radiation and conduction between different sections of the vessel, which tend to establish thermal equilibrium and what can be called "spontaneous homogenization" of temperature, and a general cooling due to radiation and convection, called " cooling." The thermal state of the vessels and, therefore, the temperature distribution in the vessel material during their release from the molds will be referred to as “initial conditions” in the following. The thermal state of the vessels at the time of their control therefore depends, on the one hand, on the specified initial conditions and, on the other hand, on spontaneous homogenization and on cooling during transportation, which naturally differ depending on the distance traversed by the vessel from the molding sections to the control post.

In practice, according to this famous patent, changes in radiation associated with variations in thermal stress or thickness are monitored, but it is not possible to determine the value of stress or thickness or even determine whether the change in radiation is associated with differences in thermal stress or thickness of the material. Consequently, such technology cannot be applied in practice, since infrared radiation depends on many parameters, which are listed below as non-limiting examples:

The intensity of infrared radiation emitted by hot vessels depends largely on temperature according to the Stefan-Boltzmann law: E = sT<A>4, where E = total amount of radiation emitted by the object, in (W⋅m ^-2 ), s = Stefan-Boltzmann constant = 5.67 × 10 ^-8 W⋅m ^-2 ⋅K ^-4 , and T = temperature in degrees Kelvin (K).

The intensity of infrared radiation emitted by hot vessels depends on the characteristics of those hot vessels, such as size, color, shape and composition of the glass.

Please note that the distance between the infrared sensor and the mold exit varies from one mold to the next, hence the cooling time for each vessel is different, so hot vessels have different temperatures when they pass in front of the infrared sensor. In other words, the intensity of infrared radiation measured by the sensor depends on the reference point of the production mold and, in particular, on the position of this mold relative to the sensor.

At the exit of the molding machine, the vessels slide onto a conveyor. Consequently, the vessels are positioned differently on the conveyor relative to the infrared measurement sensor, which leads to changes in the measurements taken.

The molding temperature conditions as well as the interactions during the transport of the vessels may vary depending on the production conditions (start of movement, delay...) and on the environmental conditions (day/night, weather conditions, air flow...).

Since the radiation considered in EP 0 643 297 is through radiation, the perceived radiation is the radiation of two combined walls.

From the above, it follows that infrared radiation is influenced by many parameters, so this patent does not provide a solution for measuring the thickness distribution of glass for vessels at high temperature. This patent discloses only monitoring deviations in glass distribution, provided that the operator ensures that the radiation deviations are related to thickness. Only the relative values of thickness or thermal stress between different regions of vessels or between different vessels and over short periods of time are assessed. The solution to this patent does not allow measuring the thickness of the glass of vessels in absolute value at any time during the measurement.

According to an embodiment, this patent provides for the use of an optical sensor that allows images of glass products to be taken to obtain information about the deviations and/or distribution of the glass. The data is compared with data obtained from the infrared sensor so that the criteria by which the data from the infrared sensor were analyzed can be adjusted. Although the use of this embodiment makes it possible to adjust the criteria used, it does not eliminate the above-mentioned disadvantages associated with the method described in this patent. Thus, this solution does not make it possible to measure the thickness of the glass either in relative value or in absolute value and, therefore, to determine the thickness distribution over an extended area, and especially over the entire vessel.

Patent EP 1 020 703 proposes to measure the thickness of the glass of a vessel using infrared radiation, measuring the first intensity of said radiation in the first spectral band in which the radiation is emitted by the material between the two outer surfaces of the vessel, the outer and the inner. The first spectral band, the signal of which depends both on the temperature of the glass and on the thickness, is preferably from 0.4 to 1.1 microns. The method also consists in measuring a second intensity of said radiation in a second spectral band, in which the radiation is mainly emitted entirely only from the outer surface of the vessel. According to this patent, the second spectral band, in which the emission depends only on the temperature corresponding to the surface radiation, is preferably from 4.8 to 5 microns. According to the method, the thickness of the vessel between the inner and outer surfaces is determined as a combined function of said first and second measured intensities. In other words, thickness and temperature are determined based on two radiation measurements taken in the first spectral band and in the second spectral band.

According to the embodiment shown in FIG. 3, this patent proposes to evenly distribute four chambers around the circumference of the vessel, measuring radiation in the second spectral band, in which radiation depends only on temperature, and a pyrometer measuring radiation in the first spectral band, the signal of which depends simultaneously on the temperature of the glass and on the thickness.

Thus, it turned out that accurate calculation of thickness is possible only for one point measured by a pyrometer and a camera. As a result, a ratio is obtained to find out the thickness as a function of temperature. Other points measured by other cameras are only estimated by extrapolation, assuming that the thickness depends on temperature according to a local mathematical model obtained at one place in the vessel. The assumption that thickness is determined by temperature measurement is erroneous unless the vessels are temperature uniform during molding, that is, unless the initial temperature conditions are the same throughout the bottle.

Additionally, it should be noted that in the first spectral band, the radiation of the vessel in relation to the pyrometer measurement point includes radiation from the so-called front wall, located on the side of the measurement point, depending on its thickness and its temperature, as well as radiation from the opposite wall, called the rear wall , which is emitted into the vessel and passes through the front wall. This "back emission" is combined with the "front emission" of the directly observed surface. The “front wall” only partially absorbs radiation in the first spectral band. Thus, the perceived radiation depends on the thickness of both walls and on the temperature of both walls. In other words, measuring the radiation from the front wall does not allow one to measure its thickness, since the radiation is affected by the rear wall.

Finally, the method described in this patent is intended to measure the thickness of glass of a vessel belonging to a limited family of color shades. However, there is a need to be able to measure the thickness of glass vessels with a greater number of color shades.

Disclosure of the Invention

The invention is intended to overcome the shortcomings of known technologies and to provide a new method for accurately measuring the wall thickness of high temperature glass vessels emerging from molding cavities, taking into account the effect of radiation from one part of the wall to another part of the wall.

The invention is also intended to provide a method for accurately measuring the wall thickness of glass vessels having different shades of color.

To solve this problem, a method for measuring the thickness of high temperature glass vessels emerging from molding cavities comprises the steps of:

- select for measurement the radiation emitted by the vessel from the diametrically opposite first side and the second side of the vessel, in such a way as to take into account the radiation emitted by the first wall of the vessel, located on the first side, and the diametrically opposite second wall of the vessel, located on the second side;

- select for measurement the radiation emitted by the vessel in the first spectral band in the range from 2800 nm to 4000 nm and in the second spectral band, and these two spectral bands are different and are selected in such a way that:

. firstly, the absorption coefficient of radiation by glass was different in two spectral bands at the temperature of the vessels;

. and, secondly, at least in the first spectral band, the absorption coefficient of radiation by the glass was such that the following conditions were met:

* the measured radiation from the first side of the vessel, emanating from the first wall, is the sum of the radiation emitted by the first wall, and the radiation emitted by the second wall and passing with absorption through the first wall, while the specified combined radiation depends on the thickness and temperature of the first and second walls;

* and the measured radiation from the second side of the vessel, emanating from the second wall, is the sum of the radiation emitted by the second wall, and the radiation emitted by the first wall and passing with absorption through the second wall, and the specified combined radiation depends on the thickness and temperature of the first and second walls ;

- simultaneously measuring from the first side of the vessel the intensity of radiation emanating from the first wall, in the first spectral band and in the second spectral band, and from the second side of the vessel the intensity of radiation emanating from the second wall, in the first spectral band and in the second spectral band;

- and determine at least the thickness of the first wall and the second wall based on the measurement of the intensity of radiation emanating from the first wall in the first and second spectral bands and from the second wall in the first and second spectral bands, taking into account in the intensity of the radiation in the first spectral band the radiation emitted wall, and radiation passing through absorption and emitted by the diametrically opposite other wall.

In addition, the claimed method may have in combination at least one and/or other of the following additional features:

- in the second spectral band, the absorption coefficient of radiation by glass differs from the absorption coefficient in the first spectral band and is such that the radiation measured, firstly, from the first side of the vessel, emanating from the first wall, is the sum of the radiation emitted by the first wall and the radiation , emitted by the second wall and passing through the first wall, and, secondly, from the second side of the vessel, emanating from the second wall, is the sum of the radiation emitted by the first wall and passing through the second wall, the combined radiation depending on the thickness of the walls and on the temperature walls;

- the temperature of the first wall and the second wall is also determined based on measurements of the radiation intensity of the first wall in the first and second spectral bands and of the second wall in the first and second spectral bands, taking into account in the radiation intensity in the first spectral band the radiation passing through absorption and emanating from the wall, located on the other side.

The invention is also intended to provide a method for accurately measuring the wall thickness of glass containers at high temperatures for a wide range of glass colors, including white glass.

This problem is solved by a method in which the radiation emitted by the vessel in a first spectral band in the range of 3,000 nm to 4,000 nm is selected for measurement.

In addition, the claimed method may have in combination at least one and/or other of the following additional features:

- in the second spectral band, the absorption coefficient of radiation by glass is such that the radiation measured, firstly, from the first side of the vessel, emanating from the first wall, is radiation emitted only by the surface of the first wall, and, secondly, from the second side of the vessel , emanating from the second wall, is radiation emitted only by the surface of the second wall, and the radiation depends only on temperature;

- determine the temperature of the first wall and the second wall based on, respectively, measurements of the radiation intensity of the first wall in the second spectral band and the second wall in the second spectral band;

- select for measurement the radiation emitted by the vessel in the second spectral band in the range from 1,100 nm to 2,600 nm;

- selecting for measurement the radiation emitted by the vessel in the second spectral band in the range exceeding 4500 nm and preferably exceeding 5000 nm;

- radiation is simultaneously measured using at least two infrared dual-spectrum cameras, each of which produces for each vessel at least two infrared images of the radiation of the vessel wall located in its field of observation.

The invention also provides a device for accurately measuring the thickness of glass walls of vessels.

To solve this problem, an installation for measuring the wall thickness of glass vessels at high temperatures emerging from the molding cavities and moving along a portable path contains:

- at least first and second infrared dual-spectrum cameras located diametrically opposite on both sides of the vessel trajectory to take into account the radiation emitted by the first wall of the vessel located on the first side of the vessel, and the second wall of the vessel located on the diametrically opposite second side, wherein each camera produces two infrared images of radiation from the wall of a vessel within its field of view, in a first spectral band in the range from 2800 nm to 4000 nm, and in a second spectral band, the two bands being different and selected as such in such a way that:

firstly, the absorption coefficient of radiation by glass was different in two spectral bands at the temperature of the vessels;

and, secondly, at least in the first spectral band, the absorption coefficient of radiation by glass was such that:

* the measured radiation from the first side of the vessel, emanating from the first wall, is the sum of the radiation emitted by the first wall, and the radiation emitted by the second wall and passing with absorption through the first wall, while the specified combined radiation depends on the thickness and temperature of the first and second walls;

* and the measured radiation from the second side of the vessel, emanating from the second wall, is the sum of the radiation emitted by the second wall, and the radiation emitted by the first wall and passing with absorption through the second wall, and the specified combined radiation depends on the thickness and temperature of the first and second walls ;

- a system for controlling the operation of infrared dual-spectral cameras in such a way that the first camera simultaneously takes two images measuring the radiation intensity of the first wall in the first spectral band and in the second spectral band, and the second camera - two images measuring the radiation intensity of the second wall in the first spectral band and in the second spectral band;

- and a computing device configured to determine at least the thickness of the first wall and the second wall by analyzing two images providing respectively measurements of the intensity of radiation emanating from the first wall in the first and second spectral bands, and two images of the second wall in the first and second spectral bands bands, taking into account in the radiation intensity in the first spectral band the radiation emitted by one wall, and the radiation passing through absorption and emanating from the wall located on the other side.

In addition, according to an embodiment, the claimed installation may include:

- infrared dual-spectrum camera, which contains:

- a beam splitter, downstream, from which the beams are divided into two separate output beams;

- downstream from the beam splitter - two separate sensors or two sensor sections located in one plane or two image planes, each receiving one of two separate output beams, the first sensor or the first sensor section receiving the first beam of radiation in the first spectral band, and a second sensor or second sensor portion receives a second beam of radiation in the second spectral band;

- in this case, the first and second beams are formed upstream or downstream from the divider using a lens, which, due to optical conjugation on each image plane, forms an optical image of the vessel, respectively, in the first spectral band and in the second spectral band;

- in this case, the first and/or second beams are filtered by an optical filter or optical filters, selecting the first spectral band and the second spectral band, respectively.

According to another embodiment, the infrared dual-spectrum camera contains:

- a lens that, due to optical coupling on the sensor plane, forms an optical image of the field through which the vessel passes;

- two separate linear sections of the sensor with their vertical reference lines, located in such a way that when the vessel moves in the field of the lens, a scanned image is obtained using each of the two linear sections of the sensor;

- in this case, the first linear section of the sensor receives the first section of the radiation beam in the first spectral band;

- in this case, the second section of the sensor receives the second section of the radiation beam in the second spectral band;

- at least one optical filter located in the path of the light beams to select the first spectral band and the second spectral band.

Brief description of drawings

Fig. 1 is a general top view of an apparatus according to the invention suitable for measuring the thickness of the glass wall of a vessel emerging from a molding machine.

Fig. 2 is a schematic view illustrating the radiation principle of a vessel with respect to measurement points located on each side of the vessel in the first spectral band.

Fig. 3 is a view illustrating the thermal radiation of a completely black body.

Fig. 4 is a view illustrating thermal radiation of a glass body.

Fig. 5 is a schematic view illustrating the radiation principle of a vessel with respect to measurement points located on each side of the vessel in the second spectral band.

Fig. 6 is a schematic view illustrating the principle of radiation of a vessel with respect to measurement points located on each side of the vessel, in a second spectral band sensitive only to the surface temperature of the glass wall.

Fig. 7 is a schematic view of an example of a dual-spectrum infrared camera used in the context of the invention.

Fig. 8 is a schematic view of another example of a dual-spectrum infrared camera used in connection with the invention.

Fig. 9 is a schematic view of another example of a dual-spectrum infrared camera used in connection with the invention.

Description of Embodiments of the Invention

In the description of the invention, the first spectral band λ1 and the second spectral band λ2 are used. The spectral band λ is an interval of wavelength centered on some value. According to the invention or variants thereof, each operating spectral band is selected in specific wavelength ranges, which are broader wavelength ranges. This means that the wavelength range for each operating spectral band falls within a specific wavelength range.

In fig. 1 shows the inventive installation 1, which makes it possible to control glass vessels 2, such as bottles or flasks, in a hot state, in order to measure the thickness of the glass wall of these vessels. The installation 1 is arranged in such a way as to provide control of the vessels 2 emerging from a production or molding machine 3 of any known type. At the exit of the molding machine, the vessels 2 have a high temperature, typically ranging from 300°C to 700°C.

The forming machine 3 classically contains a number of cavities 4, each of which provides the formation of a vessel 2. As is known, the vessels 2 formed by the machine 3 are sequentially stacked on the output conveyor 5, forming a row of vessels. The conveyor 5 transports the vessels 2 in a row along a translational path F in order to deliver them sequentially to various processing stations.

According to a preferred, but not limiting, feature of the invention, the inventive installation 1 is located as close as possible to the molding machine 3 so that the output conveyor 5 ensures the sequential movement of the vessels 2 at high temperature in front of this control installation 1. Typically, the installation 1 is located between the outlet of the molding machine 3 and the annealing lehr 6, preferably in front of the surface treatment unit, which usually forms the first of the post-forming processing stations.

The claimed installation 1 contains at least a first infrared dual-spectral camera 11 and a second infrared dual-spectral camera 12, located diametrically opposite on both sides of the trajectory F of the translational movement of the vessels. Each infrared dual-spectrum camera 11, 12 is configured to produce images of infrared radiation from the wall of a vessel located in its field of observation. Each infrared dual-spectrum camera 11, 12 outputs for each vessel 2 at least one first image obtained from infrared radiation received in the first spectral band λ1 and at least one second image obtained from infrared radiation received in the second spectral band λ2 . A spectral band denotes a range of wavelengths. The characteristics of the spectral bands λ1, λ2 will be clarified below in the further text of the description.

According to the embodiment shown in FIG. 1, the claimed installation 1 also contains a second pair 13, 14 of infrared dual-spectrum cameras. These infrared dual-spectral cameras 13, 14 of this second pair are also located diametrically opposite on both sides of the trajectory F of the forward movement of the vessels. For example, the infrared dual-spectral cameras 11, 12 of the first pair are located in such a way that their observation axes are at an angle of 45° relative to the translational trajectory F. In the same way, the infrared dual-spectral cameras 13, 14 of the second pair are located at an angle of 45° relative to the translational trajectory F in such a way that the observation axes of the infrared dual-spectral cameras 11-14 are shifted in pairs by 90°. Of course, this arrangement of infrared dual-spectrum cameras is not restrictive. To adapt to unfavorable spacing conditions between moving vessels, the angles between the four observation axes can be adapted, for example, to the following values: 30°, 150°, 30°, 150°.

The invention can also be operated using three infrared dual-spectrum cameras with axes at an angle of 120°. In this case, it will be considered that the field of each camera is divided into two sections, with each section of the field containing an image of a 60° sector of a cylindrical vessel. Each section of the field of one chamber is opposite to the section of the field of the other chamber.

Finally, the invention can be implemented with more than four cameras, while respecting the principle of obtaining infrared dual-spectral images from the point of view of all walls.

The claimed installation 1 contains a system 15 for controlling the operation of infrared dual-spectral cameras so as to read images K ₁ , K ₂ produced by the infrared dual-spectral cameras, in accordance with a method that will be described in detail below. The claimed installation 1 also contains a computing device 16, configured to determine the thickness of the glass wall of the vessel by analyzing images K ₁ , K ₂ produced by infrared dual-spectral cameras 11-14.

As used herein, computing device 16 is a computer unit, which is known to include, among others, a microprocessor, data input/output buses, memory, computer network connections, and/or a screen. The computing device may be a computer unit specifically designed for the wall thickness measurement unit, or may also be used by other elements of the vessel production line. For example, we can talk about a central line control unit or a part thereof. Among the inputs and outputs, of course, one should include means for reading infrared images. The memory can be specified as a means of storing digital infrared images. The microprocessor is configured to execute programs designed to implement algorithms that implement the claimed method.

Computer analysis of digital images produces an inspection result that may include a binary result (correct/incorrect, present/absent, pass/fail, ...) and/or a qualitative and even quantitative result, for example, in the form of one or more measurements. Thus, the inspection result may include not only the minimum and maximum values of glass thickness, but also the distribution and vertical or horizontal deviations, as well as the location of thin or thick zones, which has implications for process adjustments. In addition to determining the distribution or thickness mapping, that is, the distribution of material in the controlled vessel, the control result may also include temperature mapping of the vessels, marking areas of high thermal stress when locally large temperature differences are observed. This analysis may also include the detection of defects in appearance or composition, such as the presence of inclusions, bubbles, folds or cracks on the surface, or geometric or dimensional defects, such as slanted neck, deviations in external dimensions.

Among the outputs of the computing device, communication lines can be provided towards any control system of the production machine in order to correct process deviations depending on the measurements taken.

The following description is presented only with regard to the first pair of infrared dual-spectrum cameras 11, 12, but this description can also be applied to the second pair of infrared dual-spectrum cameras. The first infrared dual-spectrum camera 11 is located on the first side I of the vessel 2, while the second infrared dual-spectrum camera 12 is located on the diametrically opposite second side II of the vessel.

Considering that each vessel 2 contains a glass wall having the shape of a body of revolution or a cylindrical shape, the diametrically opposed arrangement of the infrared dual-spectral cameras 11, 12 with respect to the vessel implies that for each measurement point the vessel 2 has a so-called front wall and a so-called back wall , with the front and rear walls for one infrared dual-spectrum camera corresponding to the back and front walls for the other camera. In the example shown in particular in FIG. 2, each vessel 2 contains conventionally a first wall 2 ₁ located on the first side I of the vessel, that is, closest to the first infrared dual-spectral camera 11, and a second wall 2 ₂ located on the diametrically opposite second side II, that is, closest to the second infrared dual-spectrum camera 12. Thus, each infrared dual-spectrum camera 11, 12 takes into account the radiation emitted by the front wall of the vessel, and possibly the radiation emitted by the rear wall of the vessel and transmitted through the front wall.

According to the invention, each infrared dual-spectral camera 11, 12 produces for each vessel at least two infrared images of the radiation of the vessel located in its field of observation, one of which is K ₁ in the first spectral band λ1 and the other K ₂ in the second spectral band λ2. This first spectral band λ1 and this second spectral band λ2 are selected depending on the measurement principle described below.

First of all, it is necessary to take into account that the first spectral band λ1 and the second spectral band λ2 are different or separate, that is, they do not have any common meaning. According to another characteristic, the absorption of radiation by glass differs in two spectral bands at vessel temperature 2.

Below is the theory of thermal radiation as a reminder. In the following text of the description, for the sake of simplicity, radiation will be considered infrared radiation perceived in the solid angle by an observer observing the radiating body, for example, a thermal camera observing a vessel.

As shown in FIG. 3, the thermal radiation R _{сn of} an absolutely black body at a given wavelength and at a given temperature, λ and T, respectively, is expressed as follows:

[Equation 1]

According to the definition of a black body, the emissivity ε at thermal equilibrium is equal to the absorption coefficient α:

[Equation 2]

1 = ε = α

For a glass wall (gray body), the expression of the perceived total radiation M (total perceived radiation) shown in Fig. 4 is written as follows:

[Equation 3]

M = R + ρ + Tr,

where R is thermal radiation, ρ is reflected radiation, and Tr is transmitted radiation.

In the operating spectral region, that is, for the wavelength ranges perceived by the sensors according to the invention, the reflected radiation is considered negligible in relation to the intensity of the radiation emitted by the vessel. In the future, the flux perceived during reflection will be considered zero, F=ρ=0.

[Equation 4]

M = R + Tr

For a translucent body, the Beer-Lambert law is taken into account, which determines the absorption coefficient α of radiation A depending on the thickness e through which the radiation A _O passes.

[Equation 5]

Tr = τ × A _O = (1 - α) × A _O ,

where A _O is the incident radiation, and τ is the transmittance.

[Equation 6]

ε(λ,Т,е) = α(λ,Т,е) = (1 - ) = (1 - τ(λ,Т,е),

where μ(λT) is the absorption coefficient (in mm ^-1 ) at a given wavelength λ and at a given temperature T (in K). In practice, μ(λT) is the absorption coefficient integrated over a narrow band of wavelengths centered on wavelength λ.

In the following, the dependence of the emissivity and absorption coefficient on temperature can be neglected in the field of application conditions, that is, at glass temperatures and for selected wavelength intervals.

Radiation R emitted by a glass wall of thickness e and temperature T at a given wavelength λ is written as follows:

[Equation 7]

R(λ,Т,е) = ε(λ,е) × R _cn (λ,Т),

where the wall emissivity is expressed by the equation [6]:

[Equation 8]

ε(λ,е) = 1 -

The application of the theory of thermal radiation in accordance with the invention for a vessel forces both glass walls to be taken into account. Indeed, for example, for the considered measurement point on the first side of the first wall of the vessel, the received radiation of the vessel includes the radiation of the first wall located on the side of the measurement point, to which is added the radiation of the opposite second wall, which is emitted into the vessel and which passes through the first wall. Thus, as shown in FIG. 2, perceived radiation of the first wall 2 ₁ with thickness e1 and with temperature T1 of the vessel in the first spectral band λ1, sensitive to thickness and temperature, includes thermal radiation R(λ1, T1, e1) of the specified wall and transmitted radiation τ(λ1, e1)⋅R( λ1, T2, e2), which is the thermal radiation R(λ1, T2, e2) of the second wall 2 ₂ of thickness e2 and with temperature T2, at least partially absorbed by the wall 2 ₁ , i.e. with transmittance τ(λ1, e1). Likewise, perceived radiation of the second wall 2 ₂ with thickness e2 and with temperature T2 of the vessel in the first spectral band λ1, sensitive to thickness and temperature, includes thermal radiation R(λ1, T2, e2) of the specified wall and transmitted radiation τ(λ1, e2)⋅R( λ1, T1, e1), which is the thermal radiation R(λ1, T2, e2) of the first wall 2 ₁ of thickness e1 and with temperature T1, at least partially absorbed by the wall 2 ₂ , that is, with transmittance τ(λ1, e2) . Here, transmissions τ (λ1, e1) and τ (λ1, e2) at wavelength λ1 depend on the thickness of the wall being passed through according to equation [6] with a negligible influence of temperature.

Likewise, as shown in FIG. 5, in the second spectral band λ2, sensitive to thickness and temperature, the perceived radiation the first wall 2 ₁ with thickness e1 and with temperature T1 of the vessel includes thermal radiation emitted by said wall at wavelength λ2, that is, R(λ2, T1, e1), and radiation τ(λ2, e1)⋅R(λ2, T2 , e2) of the second wall 2 ₂ with thickness e2 and with temperature T2, at least partially absorbed by wall 2 ₁ , that is, with transmission τ(λ2, e1). Likewise, perceived radiation second wall 2 ₂ with thickness e2 and with temperature T2 of the vessel in the second spectral band λ2, sensitive to thickness and temperature, includes radiation R(λ2, T2, e2) of the specified wall and radiation τ(λ2, e2)‧R(λ2, T1, e1) of the first wall 2 ₁ with thickness e1 and temperature T1, at least partially absorbed by wall 2 ₂ , that is, with transmission τ(λ2, e2).

Taking into account the above theory of thermal radiation, the following equations can be written:

[9] = R(λ1,T1,e1) + τ(λ1,e1)⋅R(λ1,T2,e2);

[10] = R(λ1,T2,e2) + τ(λ1,e2)⋅R(λ1,T1,e1);

[eleven] = R(λ2,T1,e1) + τ(λ2,e1)⋅R(λ2,T2,e2);

[12] = R(λ2,T2,e2) + τ(λ2,e2)⋅R(λ2,T1,e1).

These equations [9], [10], [11] and [12] relate to radiation considered from two sides of the vessel, namely for two walls, respectively, with thicknesses e1 and e2 and at temperatures T1 and T2, separated by an air layer. It should be recalled that the emissivity must be different for wavelengths λ1 and λ2, otherwise the system would obviously have only two equations instead of four.

The invention is based on the fact that four equations [9]-[12] make it possible to determine four unknowns, namely, for two walls, the thickness e1, e2 and the temperature T1 and T2, respectively, based on four radiation measurements , , And , produced by measuring instruments such as infrared dual-spectrum cameras observing hot vessels. As stated above, the equations are derived based on Planck's laws for radiation and Beer-Lambert's laws for transmission. Initial knowledge of the vessels and material or parameter identification or calibration methods allows these equations to be accurately determined for a given vessel production.

To facilitate the implementation of the invention, simplification of the equations is used, which allows easier identification of parameters and allows for faster real-time calculations during application of the method using a computing device that analyzes infrared images. Thus, in the following, simplified functions of the black body emissivity and the transmittance and absorption coefficients around the operating points will be determined, that is, for the selected spectral bands, for the spectral transmittance of the glass, for the temperature range of the vessels at the outlet of the molding machine, that is, from 300 to 700° C, for a range of measured thickness, for example from 0.5 to 5 mm.

According to equation [7], the radiation emitted by the wall, that is, the intrinsic radiation of the glass wall, is as follows:

[Equation 13]

R(λ1, T1, e1) = ε(λ1, e1) × R _cn (λ1, T1).

According to the invention and in accordance with equation [8], the emissivity ε in the first spectral band λ1 is a function of the thickness of the translucent body. Consequently, this emissivity differs from 1. For measured values of wall thickness (for example, 0.5-5 mm), the affine thickness function approaches the emissivity for the first spectral band λ1, the parameters of which can be identified by measurement and calibration.

[Equation 14]

ε(е1) = (a ⋅ e1 + b)

with coefficients a, b depending on the wavelength λ1.

Blackbody radiation will be described using the function G(λ1,T), which is simpler than equation [1]. For the operating wavelength λ1, in particular for the operating spectral band centered on λ1, G(λ1, T)=G1(T) is only a function of temperature. G(T) is a simplified model of blackbody radiation for the spectral band λ1, derived from Planck's law, for example, is a polynomial, power or exponential function. In practice, this G1 function takes into account the entire sensing circuit and, in particular, the spectral sensitivity of the sensor and the transmittance of the optical components located between the vessel and the sensor. The parameters of the function G1, for example the coefficients of the polynomial, the exponent, the exponential coefficient, etc., are determined accordingly, in particular experimentally in the calibration phase of the measuring device according to the invention. Of course, for the second wavelength λ G(λ2, T)=G2(T) is determined in exactly the same way.

A simplified model for the radiation R emitted by a glass wall at a given wavelength or for a given spectral band around wavelength λ1 can now be written as follows:

[Equation 15] R(λ1, T1, e1) = R(T1, e1) = (a ⋅ e1 + b) × G1(T1)

In this expression, the parameters or constants G1(T) and coefficients a and b can be determined experimentally or a priori, knowing, in particular, the composition of the glass. Of course, the radiation of the same wall for wavelength λ2, as well as the radiation of another wall of thickness e2 with temperature T2, can be written in exactly the same way, namely:

[Equation 15]

R(λ1, T1, e1) = R(T1, e1) = (a ⋅ e1 + b) × G1(T1)

[Equation 16]

R(λ1, T2, e2) = R(T2, e2) = (a ⋅ e2 + b) × G1(T2)

[Equation 17]

R(λ2, T1, e1) = R(T1, e1) = (c ⋅ e1 + d) × G2(T1)

[Equation 18]

R(λ2, T2, e2) = R(T2, e2) = (c ⋅ e2 + d) × G2(T2)

The transmittance τ of radiation emanating from the rear wall through the front wall of thickness e = e1 or e2 is linearized in the following equation [19], using, in particular, equations [6] and [14], around the operating point determined by the given temperature, the first spectral band centered around the first wavelength λ1, and for the range of thicknesses measured.

[Equation 19]

τ(λ1, e) = e ^-μ(λ1)e = 1 - a = 1 - ε(e) = 1 - (a ⋅ e +b)

Similarly, for the second spectral band centered around λ2, the attenuation of radiation emanating from the front wall through the back wall is expressed as:

[Equation 20]

τ(λ2, e) = e ^-μ(λ2)e = 1 - a = 1 - ε(e) = 1 - (c ⋅ e +d)

The coefficients a and b, c and d are obtained by calibration or determined in advance using any suitable method. They depend on the operating point, in particular on the selected wavelengths λ1 and λ2 and on the temperature zone of the vessels being monitored and on the range of thicknesses being measured.

For wavelength λ1 radiation corresponds to the total radiation of the first wall, to which is added the radiation of the second wall, modified due to absorption by the first wall. Therefore, it can be expressed as follows:

[Equation 21]

= (a ⋅ e1 + b) × G1(T1) + (1 - (a ⋅ e1 + b)) × (a ⋅ e2 + b) × G1(T2)

Likewise, radiation corresponds to the total radiation of the second wall, to which is added the radiation of the first wall, modified due to absorption by the second wall. Therefore, it can be expressed as follows:

[Equation 22]

= (a ⋅ e2 + b) × G1(T2) + (1 - (a ⋅ e2 + b)) × (a ⋅ e1 + b) × G1(T1)

Similarly, for wavelength λ2, the radiation N ₁₂ corresponds to the total radiation of the first wall, to which is added the radiation of the second wall, modified due to absorption by the first wall. Therefore, N ₁₂ can be written as:

[Equation 23]

= (c ⋅ e1 + d) × G2(T1) + (1 - (c ⋅ e1 + d)) × (c ⋅ e2 + d) × G2(T2)

In exactly the same way one can express :

[Equation 24]

= (c ⋅ e2 + d) × G2(T2) + (1 - (c ⋅ e2 + d)) × (c ⋅ e1 + d) × G2(T1)

In this first embodiment of the invention, if the second spectral band λ2 is selected such that the emissivity, although different from the emissivity of the first spectral band λ1, depends on the thickness, in which case the equations [9], [10], [11] ] and [12] can be replaced by equations [21], [22], [23] and [24] respectively.

In addition, the following provisions must be taken into account, in particular taking into account the characteristics that the vessels 2 exiting the molding machine have.

Thus, it should be noted that in a certain wavelength range, the emissivity of glass is very little sensitive to the wall temperature, which varies from 300 to 700°C. For this particular wavelength range, the absorption coefficient (and therefore the emissivity) does not depend on temperature, or this dependence can be neglected. Thus, only the spectral absorption coefficient μ relates absorption to thickness and in the same way relates emissivity to thickness.

According to a feature of the invention, the first spectral band λ1 is selected in the wavelength range in which the emissivity of the glass does not depend on temperature. This allows us to apply equations [7] and [8].

Moreover, for a spectral band defined in the range greater than 4500 nm and preferably greater than 5000 nm, the emissivity of glass is very close to 1, that is, approximately equal to 1. For this spectral band, the radiation is similar to that of a black body. According to a preferred embodiment, the second spectral band λ2 is selected in the wavelength range in which the radiation does not depend on the thickness, in which the observed wall does not transmit radiation from the opposite side, in other words, in this wavelength range the glass is opaque. From this we can derive expressions for the radiation perceived in this spectral band for each side of the wall, that is:

[Equation 25]

N ₁ = R(λ2, T1, e1) = G(T1)

[Equation 26]

N ₂ = R(λ2, T2, e2) = G(T2)

Therefore, in this version, equations [9], [10], [11] and [12] can be replaced by equations [21], [22], [25] and [26], respectively. This option, using a wavelength at which the radiation is independent of thickness, simplifies the calculations to solve a system of 4 equations with 4 unknowns, since the unknowns T1 and T2, that is, the temperatures of the two walls, follow directly from equations [21] and [22 ].

According to the invention, the first spectral band λ1 is selected in such a way that in the first spectral band the absorption of radiation by the glass is such that:

- radiation measured from the first side of the vessel 2, emanating from the first wall 2 ₁ , is the sum of the radiation emitted by the first wall 2 ₁ , and the radiation emitted by the second wall 2 ₂ and passing with absorption through the first wall 2 ₁ , such that the specified the combined radiation depends on the thickness and temperature of the first and second walls,

- and the radiation measured from the second side of the vessel 2, emanating from the second wall 2 ₂ , is the sum of the radiation emitted by the second wall 2 ₂ , and the radiation emitted by the first wall 2 ₁ and passing with absorption through the second wall 2 ₂ , such that this combined radiation depends on the thickness and temperature of the first and second walls.

It should be noted that the invention proposes to measure infrared radiation in the first spectral band λ1, in which the radiation intensity depends on the thickness of the glass wall and the temperature of the wall surface. According to the invention, the first spectral band λ1 is chosen so that the emissivity depends on the wall thickness, that is, it is further from 1, but still high enough to measure a sufficient amount of radiation. In addition, this emissivity should vary little depending on the shade of the glass. Thus, this first spectral band λ1 is chosen such that the emissivity varies, for example, from (approximately) 0.3 to 0.7 for white glass, when the thickness varies from 1 to 5 mm, at a glass temperature in the vicinity of 450° C, more widely - in the range from 300 to 700°C. It should be noted that for glass of green or amber color at the same thickness and the same temperature, the emissivity fluctuates around the same values.

Moreover, this first spectral band λ1 is selected in such a way as to obtain transmission of radiation emanating from the rear side with absorption by the front side. Indeed, this ensures that in equations [10] and [11] the transmittance coefficients, respectively τ(λ1, e1) = e ^-μ(λ1)e1 and τ(λ1, e2) = e ^-μ(λ1)e2, are not equal 1, hence the attenuation is not zero. Zero attenuation would not correspond to a normal vessel. At zero attenuation, it would be impossible to measure the sum of the thicknesses e1 + e2 of the two walls without differentiating the two walls. On the other hand, if the absorption is complete e ^-μ(λ1)e1 = 0 or e ^-μ(λ1)e1 = 0, this means that the glass is opaque in the first spectral band. In this case, only the surface temperature of the front wall could be measured in this first spectral band, regardless of thickness.

It should be noted that the radiation emitted by the vessel in the first spectral band λ1 can be selected in the range from 1100 nm to 2600 nm. However, this range is suitable for green or amber colored glass vessels, but not for white glass vessels, since in this range the emissivity of white (transparent) glass is very low.

According to the invention, the first spectral band λ1 is selected in the range from 2800 nm to 4000 nm and preferably from 3000 nm to 4000 nm. This first preferred spectral band is selected to handle a wide range of glass shades, including white glass.

As stated above, the second spectral band λ2 is chosen in such a way that the absorption of radiation by the glass differs from the absorption of radiation in the first spectral band λ1. It can be recalled that for the selected first spectral band λ1, the emissivity varies from 0.3 to 0.7. According to the first embodiment shown in FIG. 5, the second spectral band λ2 is also chosen in such a way that the radiation measured, firstly, from the first side of the vessel, emanating from the first wall 2 ₁ , is the sum of the radiation emitted by the first wall 2 ₁ , and the radiation emitted by the second wall 2 ₂ and passing through the first wall, and, secondly, from the second side of the vessel, emanating from the second wall 2 ₂ , is the sum of the radiation emitted by the second wall 2 ₂ , and the radiation emitted by the first wall 2 ₁ and passing through the second wall 2 ₂ , in this case, the combined radiation depends on the wall thickness and the wall temperature.

According to this first embodiment, the radiation emitted by the vessel in the second spectral band λ2 is selected in the range from 1100 nm to 2500 nm. In this embodiment, the transmittance is high and the emissivity can be low for some glasses, typically below 0.1 for glass thicknesses of 1 to 5 mm at 450°C. Because the infrared signal is limited, thickness measurement accuracy may not be sufficient for these glass color shades.

According to a second preferred embodiment shown in FIG. 6, the second spectral band λ2 is chosen in such a way that the absorption of radiation by the glass is such that the radiation measured, firstly, from the first side I of the vessel, emanating from the first wall 2 ₁ , is radiation emitted only by the surface of the first wall 2 ₁ . and, secondly, from the second side of the II vessel, emanating from the second wall 2 ₂ , is radiation emitted only by the surface of the second wall, and said radiation depends only on temperature.

Thus, the radiation , emitted by the first wall of the vessel in the second spectral band, is sensitive only to the surface temperature. Likewise, radiation , emitted by the second wall of the vessel in the second spectral band, is sensitive only to the surface temperature.

According to this preferred embodiment, the second spectral band λ2 is selected in the range greater than 4500 nm and preferably greater than 5000 nm. The second spectral band λ2 is chosen so that the emissivity is close to 1, that is, close to the emissivity of a black body. This means that the absorption of radiation by glass in this spectral band is strong, so the emissivity exceeds, for example, 0.9. The radiation N1, N2 perceived in the second spectral band λ2 for the first side and for the second side is quite convincingly represented by Planck’s law or the approximating function in accordance with the invention G(T1) and G(T2), which is expressed by equations [25] and [26 ].

According to this preferred embodiment, preferably simultaneously with the second spectral band λ2 selected in the range greater than 4500 nm and preferably greater than 5000 nm, the first spectral band λ1 is selected in the range from 2800 nm to 4000 nm and preferably from 3 000 nm to 4,000 nm. Thus, to make measurements or obtain images in two spectral bands λ1 and λ2, the same sensor technology such as Medium Wave InfraRed (MWIR) can be used, preferably without cooling. In this case, cooled sensor refers to medium wave IR sensors or long wave IR sensors manufactured by SOFRADIR or LYNRED and equipped with cryogenic cooling systems. Indeed, an uncooled sensor costs much less than a cooled sensor and is more reliable. Of course, mid-wave IR cameras within the scope of the invention are equipped with radiation protection means (cooled screen, window, closed chamber) and means of cooling and/or heat dissipation, for example, such as water circuits, forced ventilation, Peltier effect elements, heat pipes, radiators, etc.

Typically, the first spectral band λ1 is selected in the range of 3000 nm to 4000 nm, and the second spectral band λ2 is selected in the range greater than 4500 nm. Preferably, the first spectral band λ1 is selected to be centered around a wavelength of about 3600 nm, while the second spectral band λ2 is selected to be centered around a wavelength of about 4700 nm.

According to the invention, the system 15 controls the infrared dual-spectral cameras 11-14 in such a way as to measure, from the first side I of the vessel, the intensity of radiation emanating from the first wall 2 ₁ in the first spectral band λ1 and simultaneously in the second spectral band λ2 and from the second side II of the vessel the intensity of radiation emanating from the second wall 2 ₂ in the first spectral band λ1 and simultaneously in the second spectral band λ2. Thus, for each vessel 2 according to the invention, at least two measurements of the radiation intensity received from two opposite walls are made in a first spectral band and at least two measurements of the radiation intensity of two opposite walls in a second spectral band. According to a preferred feature, one-dimensional or two-dimensional images of vessel walls are obtained as radiation measurements according to the invention. Thus, the infrared dual-spectrum cameras 11, 14 each produce, for each vessel, at least two infrared images of the radiation of the vessel wall located in its field of observation. According to an embodiment, both infrared dual-spectral cameras 11, 12 produce for each vessel at least two infrared images in the first spectral band and at least two infrared images in the second spectral band. According to another embodiment, using four infrared dual-spectrum cameras, eight infrared images can be obtained to image the entire vessel wall in two spectral bands. In this case, the observed field is such that each chamber measures at least a quarter of the circumference of the vessel.

It is also possible to provide for increased view overlap by using three pairs of opposing dual-spectrum cameras. In general, it is possible to provide any arrangement of cameras depending on the shape of the vessels and the distance between them, in order to completely observe the circumference of the vessels, regardless of whether their shape is characterized by a round horizontal flat section (cone or simple cylinder body) or a rectangular, polygonal etc. cross-section, in accordance with the practice of specialists in the field or, in particular, depending on the design of online control systems in the cold sector.

According to another feature of the invention, the computing device 16 makes it possible to determine at least the thickness e1 of the first wall 2 ₁ and the thickness e2 of the second wall 2 ₂ based on measurements of the intensity of radiation emanating from the first wall 2 ₁ in the first and second spectral bands and from the second wall 2 ₂ in the first and second spectral bands, taking into account in the radiation intensity in the first spectral band the radiation emitted by the wall and the radiation transmitted with absorption from the diametrically opposite other wall.

Thus, the thickness e1 of the first wall 2 ₁ and the thickness e2 of the second wall 2 ₂ are determined based on four measurements of the radiation intensity in accordance with the general equations [9], [10], [11] and [12] and, in particular, with their simplifications [21], [22], [23] and [24] or [21], [22], [25] and [26], when the second wavelength is chosen so that the emissivity is close to 1. This a system of four equations in four unknowns is solved in linearized versions, and also, if necessary, using more complex models to improve the accuracy of the measurement.

According to the preferred embodiment, in which the second spectral band λ2 depends only on temperature, the thickness and possibly temperature values are determined using the system of equations [21], [22], [25] and [26].

It may be recalled that for this preferred embodiment, the infrared radiation is measured, firstly, in a first spectral band, in which the radiation intensity depends on the wall thickness and on the surface temperature, and, secondly, in a second spectral band, in which the radiation intensity depends only on the surface temperature. In this way, temperature information can be “subtracted from the signal.”

Based on four independent radiation measurements and taking into account in the first spectral band the influence of the opposite side on the radiation perceived for each side, the thickness e1 of the first side, the thickness e2 of the second side, the temperature T1 of the first side and the temperature T2 of the second side can be derived. To carry out this calculation, a mathematical model is used that relates four radiation dimensions and four finite dimensions, that is, two thickness dimensions and two temperature dimensions.

This mathematical model can be empirical or analytical. It can only work under certain operating conditions that allow the constants to be fixed and the model to be linearized. Of course, the simplifications made on equations [15] and [19] are not essential for the invention, they simply make calculations easier and cheaper. Of course, the analytical model can be more complex and provide more accurate measurement results, taking into account the composition, average temperatures or shape of the vessels. The mathematical model may also include a geometric model, which may describe the three-dimensional geometry of the vessel and may have as characteristics a glass thickness distribution and a temperature distribution. For example, for a simple cone-type product, the surface of the body will be a cone, each point of which has a thickness value in mm and a temperature in Kelvin (K).

As follows from the description, the claimed installation 1 contains infrared dual-spectral cameras 11-14. Although non-planar image sensors can be used to implement the invention using non-planar images, in the description, planar sensors are assumed, and the generated image generally refers to a planar image of an object or scene, in this case at least part of the wall of a vessel.

When multiple sensors are used for each camera, there are several ways to connect them. In the following text, the expressions “upstream” and “downstream” specify the position of the optical elements placed on the collected and processed radiation beams in the direction of passage of light emanating from the vessel to reach the sensor.

According to a first embodiment of the invention, the infrared dual-spectrum camera comprises, as shown, for example, in FIG. 7, 8:

- a 20 beam splitter, downstream of which the beams are divided into two separate output beams;

- downstream from the beam splitter 20 - two separate sensors 21, 22 (Fig. 7) or two sensor sections (Fig. 8), located in one plane or two image planes, each receiving one of two separate output beams, wherein the first sensor or first sensor section receives a first radiation beam in the first spectral band, and the second sensor or second sensor section receives a second radiation beam in the second spectral band;

- in this case, the first and second beams are formed upstream or downstream from the divider 20 using a lens 23, which forms, due to optical coupling on each image plane, that is, on each sensor or sensor section, an optical image K1, K2 of the vessel, respectively, in the first spectral band and in the second spectral band;

- in this case, the first and/or second beams are filtered by an optical filter or optical filters, for example, such as a bandpass filter 25, 26, selecting the first spectral band and the second spectral band, respectively.

These at least two separate sensors 21, 22 (Fig. 7) or sensor sections (Fig. 8) each produce, from each vessel, a digital image corresponding to the conversion of optical images K1, K2 of radiation M or N, perceived at least in two different bands of infrared wavelengths.

The beam divider 20 is, for example, a prism, a plate or a dividing cube. This optical component deflects the input optical beam into two output optical beams in two different directions.

The linear section of the sensor is a line of photosensitive elements arranged in a row. Reading the linear portion of the sensor produces only one line of the digital image. Therefore, during the monitoring of moving vessels, it is known that successive lines of a digital image are read in order to, using a simple and known scanning method, reproduce a two-dimensional image of the vessel passing through the flat field of the linear section of the sensor. (Note: flat field = formed by the sensor line and optical center = fan-type field). Of course, the displacement or movement vector is not parallel to the direction of the linear section of the sensor. There are linear sensors on the market that contain only one line of photosensitive elements. There are also sensors that contain several lines of photosensitive elements located next to each other and produce as a signal only the lines of a digital image, which are combinations of information from different lines. Finally, it is possible to control the matrix sensor so as to read only one or two or a few digital image lines from individual sensor lines and so that, based on these individual adjacent digital image lines, one or two or more two-dimensional images of the moving vessel are obtained by scanning over time , separated in time and corresponding to different positions. In other words, a matrix sensor can be used as one or two or more line sensors, it produces digital image lines depending on time. The concept of a linear sensor section covers both methods.

According to a second embodiment of the invention, the dual-spectrum infrared camera comprises, as shown in FIG. 9:

- lens 23, which, due to optical coupling on the sensor plane, forms an optical image K3 of the field through which the vessel passes;

- two separate linear sections 41, 42 of the sensor with their vertical reference lines s ₁ , s ₂ , located in such a way that when the vessel moves in the field of the lens 23, a scanned image is obtained using each of the two linear sections of the sensor;

- in this case, the first linear section 41 of the sensor receives the first section 31 of the radiation beam in the first spectral band;

- in this case, the second section 42 of the sensor receives the second section 32 of the radiation beam in the second spectral band;

- at least one optical filter 45 located in the path of the light beams between the lens and two linear sections 41, 42 of the sensor to select the first spectral band and the second spectral band.

It should be noted that in this version there is no need for a 20 beam divider.

Thus, after the vessel has crossed the field of the lens 23, it has passed through the field of each of the two linear sections of the sensor. By scanning, two two-dimensional images of the vessel are obtained at two selected wavelengths.

In the preferred embodiment, only one two-dimensional sensor 43 is used, located behind at least one optical filter covering only a portion of the sensor, as shown in FIG. 9. In another embodiment, two linear sensors are placed in the image plane.

Of course, in this second embodiment, during the movement of the vessel in the field of the lens 23, its two-dimensional image can currently be formed partially in the first section and partially in the second section of the sensor 41, 42.

In all embodiments, two optical filters can be used to select these two spectral bands. Bandpass filters are preferably used as optical filters.

It is clear that at least one filter is necessary only if both sections of the sensor are made using the same technology, that is, each of them is characterized by the same response or the same intrinsic spectral sensitivity.

According to a preferred embodiment, wherein the second spectral band λ2 is selected in a range greater than 4500 nm and preferably greater than 5000 nm, and the first spectral band λ1 is selected in a range of from 2800 nm to 4000 nm and preferably from 3000 nm to 4000 nm, one or two sensors of the Medium Wave InfraRed (MWIR) type can be used as a sensor or sensors, which do not require any cooling system, as mentioned above. This makes it possible to implement the options presented in Fig. 8 and 9, containing only one sensor. To implement variants containing two sensors, as shown in FIG. 7, the use of two sensors of the same technology simplifies the implementation, in particular, both sensors can have the same resolution for the same field and can be synchronized using common and simplified controls.

The sensor or sensors included in each infrared dual-spectrum camera are, for example, 196 or 300°K PbSe or may be microbolometers.

Of course, the invention is not limited to the dual-spectrum camera embodiments described above.

Claims (37)

1. A method for measuring the wall thickness of glass vessels (2) at high temperatures emerging from molding cavities, comprising the steps of: - select for measurement the thermal radiation emitted by the vessel (2) from diametrically opposite sides of the vessel - the first side (I) and the second side (II), so that the thermal radiation emitted by the first wall (2 ₁ ) of the vessel located on the first side is taken into account sides, and thermal radiation emitted by the diametrically opposite second wall (2 ₂ ) of the vessel located on the second side; - in this case, the radiation emitted by the vessel (2) in the first spectral band (λ1) in the range from 2800 nm to 4000 nm and in the second spectral band (λ2) is selected for measurement, and these two spectral bands are different and are selected in this way , to: the absorption coefficient of radiation by glass was different in two spectral bands at the temperature of the vessels; And at least in the first spectral band (λ1), the absorption coefficient of radiation by glass was such that: the radiation that is measured from the first side (I) of the vessel, emanating from the first wall (2 ₁ ), is the sum of the radiation emitted by the first wall (2 ₁ ), and the radiation emitted by the second wall (2 ₂ ) and passing through absorption through the first wall (2 ₁ ), while the specified combined radiation depends on the thickness and temperature of the first and second walls (2 ₁ , 2 ₂ ); And the radiation that is measured from the second side (II) of the vessel, emanating from the second wall (2 ₂ ), is the sum of the radiation emitted by the second wall (2 ₂ ), and the radiation emitted by the first wall (2 ₁ ) and passing with absorption through the second wall (2 ₂ ), while the specified combined radiation depends on the thickness and temperature of the first and second walls (2 ₁ , 2 ₂ ); - simultaneously measure: on the first side (I) of the vessel - the intensity of radiation emanating from the first wall (2 ₁ ), in the first spectral band (λ1) and in the second spectral band (λ2); and on the second side (II) of the vessel - the intensity of radiation emanating from the second wall (2 ₂ ), in the first spectral band (λ1) and in the second spectral band (λ2); And - determine at least the thickness of the first wall and the thickness of the second wall (2 ₂ ) based on measurements of the intensity of radiation emanating from the first wall in the first and second spectral bands and from the second wall in the first and second spectral bands, while taking into account radiation intensity in the first spectral band, the presence of radiation emitted by the wall itself, and radiation emitted by another diametrically opposite wall and passing with absorption through the specified wall. 2. The method according to claim 1, in which in the second spectral band (λ2) the absorption coefficient of radiation by glass differs from the absorption coefficient in the first spectral band (λ1) and is such that the radiation measured from the first side (I) of the vessel emanating from the first wall (2 ₁ ), is the sum of the radiation emitted by the first wall (2 ₁ ), and the radiation emitted by the second wall (2 ₂ ) and passing through the first wall (2 ₁ ), and the radiation changed from the second side (II) of the vessel , emanating from the second wall (2 ₂ ), is the sum of the radiation emitted by the second wall (2 ₂ ), and the radiation emitted by the first wall (2 ₁ ) and passing through the second wall, with the combined radiation depending on the thickness of the walls and on the temperature of the walls . 3. The method according to claim 1 or 2, in which the temperature (T ₁ ) of the first wall (2 ₁ ) and the second wall (2 ₂ ) is also determined based on measurements of the radiation intensity of the first wall (2 ₁ ) in the first and second spectral bands and the second wall (2 ₂ ) in the first and second spectral bands, taking into account in the radiation intensity in the first spectral band the radiation passing through absorption and emanating from the wall located on the other side. 4. Method according to any one of paragraphs. 1-3, in which the radiation emitted by the vessel in the first spectral band (λ1) in the range of 3000 nm to 4000 nm is selected for measurement. 5. Method according to any one of paragraphs. 1-4, in which in the second spectral band (λ2) the absorption coefficient of radiation by glass is such that the radiation measured from the first side (I) of the vessel emanating from the first wall (2 ₁ ) is radiation emitted only by the surface of the first wall ( 2 ₁ ), and the radiation measured from the second side (II) of the vessel, emanating from the second wall (2 ₂ ), is the radiation emitted only by the surface of the second wall (2 ₂ ), and the radiation depends only on temperature. 6. The method according to claim 5, in which the temperature (T ₁ , T ₂ ) of the first wall and the second wall is determined based on, respectively, measurements of the radiation intensity of the first wall (2 ₁ ) in the second spectral band (λ2) and the second wall (2 ₂ ) in the second spectral band (λ2). 7. Method according to any one of paragraphs. 1-4, in which the radiation emitted by the vessel in the second spectral band (λ2) in the range from 1100 nm to 2600 nm is selected for measurement. 8. The method according to claim 5 or 6, in which the radiation emitted by the vessel in the second spectral band (λ2) in the range greater than 4500 nm and preferably greater than 5000 nm is selected for measurement. 9. The method according to any of the previous paragraphs, in which the radiation is simultaneously measured using at least two infrared dual-spectral cameras (11, 12-13, 14), each of which produces for each vessel at least two infrared images of the radiation of the vessel wall, in her field of observation. 10. An installation for measuring the wall thickness of glass vessels (2) at high temperatures emerging from the molding cavities (4) and moving along a portable path (F), containing: - at least the first (11) and second (12) infrared dual-spectral cameras located diametrically opposite to each other on both sides of the trajectory (F) of the vessels in order to take into account the thermal radiation emitted by the first wall (2 ₁ ) of the vessel (2), located on the first side (I) of the vessel, and the second wall (2 ₂ ) of the vessel, located on the diametrically opposite second side, with each camera (11, 12) producing two images of infrared radiation of the vessel wall located in its field of observation, in the first spectral band (λ1) in the range from 2800 nm to 4000 nm, and in the second spectral band (λ2), the two spectral bands being different, and selected so that the following conditions are met: the absorption coefficient of radiation by glass is different in two spectral bands (λ1, λ2) at the temperature of the vessels; And at least in the first spectral band (λ1) the absorption coefficient of radiation by glass is such that: the radiation measured from the first side (I) of the vessel, emanating from the first wall (2 ₁ ), is the sum of the radiation emitted by the first wall (2 ₁ ), and the radiation emitted by the second wall (2 ₂ ) and passing with absorption through the first wall ( 2 ₁ ), while the specified combined radiation depends on the thickness and temperature of the first and second walls; And the radiation measured from the second side (II) of the vessel, emanating from the second wall (2 ₂ ), is the sum of the radiation emitted by the second wall (2 ₂ ), and the radiation emitted by the first wall (2 ₁ ) and passing with absorption through the second wall ( 2 ₂ ), while the specified combined radiation depends on the thickness and temperature of the first and second walls (2 ₁ , 2 ₂ ); - a system (15) for controlling the operation of infrared dual-spectral cameras (11, 12) in such a way that the first camera (11) simultaneously takes two images that measure the radiation intensity of the first wall (2 ₁ ) in the first spectral band (λ1) and in the second spectral band band (λ2), and the second camera (12) - two images measuring the radiation intensity of the second wall (2 ₂ ) in the first spectral band (λ1) and in the second spectral band (λ2); And - a computing device (16) configured to determine at least the thickness (e ₁ , e ₂ ) of the first wall (2 ₁ ) and the second wall (2 ₂ ) by analyzing two images, respectively giving measurements of the intensity of radiation emanating from the first wall (2 ₁ ) in the first (λ1) and second (λ2) spectral bands, and two images of the second wall in the first and second spectral bands, taking into account in the radiation intensity in the first spectral band the radiation emitted by the wall, and the radiation passing through absorption and outgoing from the wall on the other side. 11. Installation according to claim 10, characterized in that the infrared dual-spectral camera (11-14) contains: - beam divider (20), downstream of which the beams are divided into two separate output beams; - downstream from the beam splitter (20) - two separate sensors (21, 22) or two sensor sections located in one plane or two image planes, each receiving one of two separate output beams, with the first sensor or the first a sensor portion receives a first beam of radiation in a first spectral band, and a second sensor or second sensor section receives a second beam of radiation in a second spectral band; - in this case, the first and second beams are formed upstream or downstream from the divider (20) using a lens (23), which, due to optical conjugation on each image plane, forms an optical image (K1, K2) of the vessel, respectively, in the first spectral band and in the second spectral band; - in this case, the first and/or second beams are filtered by an optical filter or optical filters (25, 26), selecting the first spectral band and the second spectral band, respectively. 12. Installation according to claim 10, characterized in that each infrared dual-spectrum camera contains: - lens (23), which, due to optical coupling on the sensor plane, forms an optical image (K3) of the field through which the vessel passes; - two separate linear sections (41, 42) of the sensor with their vertical reference lines (s ₁ , s ₂ ), located in such a way that when the vessel moves in the field of the lens (23), a scanned image is obtained using each of the two linear sections of the sensor; - in this case, the first linear section (41) of the sensor receives the first section (31) of the radiation beam in the first spectral band; - the second section (42) of the sensor receives the second section (32) of the radiation beam in the second spectral band; - at least one optical filter (45) located in the path of the light beams to select the first spectral band and the second spectral band. 13. Installation according to claim 11 or 12, characterized in that the optical filter or optical filters (25, 26, 45) designed to select the first spectral band in the range from 2800 nm to 4000 nm, and the second spectral band in the range greater than 4500 nm and preferably greater than 5000 nm.

Images