Abstract:
A pulsed radiation produced by an intense optical source is applied to the inner surface of a wooden container having a surface layer of organic and/or mineral deposit. Each pulse is of sufficiently short duration having sufficiently high treating energy density per unit area to bring about sublimation of the surface layer. The resulting exposed container surface is sanitized by the heat released by the radiation.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to a process for stripping and sterilizing the internal surface of a container, for example made of wood, metal, concrete or any other material, especially a wooden cask having a surface layer of a coating of organic and/or mineral material, especially a coating of tannin resulting from the maturation of a wine in a cask, as well as to a device for its implementation.  
           [0002]    Wooden casks will be of particular interest in the remainder of the description, but it should be well understood that the invention is in no way limited thereto and that it can be applied to any type of container, whatever it is made of.  
         BACKGROUND OF THE INVENTION  
         [0003]    During the period of maturing wines in a barrel, it is generally accepted that the wood transfers various substances, such as furans, lactones, aldehydes, phenolic acids, phenols and ketones to the wine. The barrel puts the wine in an oxidizing balance and acts as a kind of micro-doser of oxygen, which allows a first oxidation-reduction aging of the wine. It is generally assumed that a new barrel transfers tannic substances to the wine while an old barrel transfers substances from the decomposition of the wood. A one-year-old barrel, i.e. a barrel having already served to mature a wine for one year, generally gives a taste of pure wood to the wine, while a six-year-old barrel generally gives a rancid taste.  
           [0004]    To mature certain wines, wooden barrels, the inside of which has been scorched on the surface, are also used to transfer other substances, such as phenolic compounds, furanic aldehydes and color, to the wine.  
           [0005]    Usually a barrel may serve to mature up to four wines over a period of 4 to 6 years. After this period, the barrel can no longer serve as a maturing tool since the wine has penetrated by about 5 to 10 mm into the thickness of the barrel which has a thickness of about 22 to 27 mm, this penetration of the wine causing sealing of the wood pores by the tannin coatings and by the alterations in the compounds of the wood, such as the phenolic compounds, tartaric acid, etc., which prevents the subsequent transfers of substances between the wood and the wine, which transfers are essential to the maturation of the wine. These old barrels may still serve as storage containers, but this is not usually the case, since microbe-related accidents may arise during storage, between the wine and the coatings covering the internal surface of the barrel.  
           [0006]    For the maturation barrels, the quality of the wood used is very important and, in French vineyards, the wood used generally comes from oaks of about 150 to 300 years of age, which therefore have a very long renewal time faced with a very greatly increasing recent demand.  
           [0007]    In order to reduce the cost of the barrels and to save the limited national heritage in oaks, a process for renovating the barrel has already been proposed.  
           [0008]    One solution consists in carrying out a mechanical stripping, using a plane or a sander, inside the barrel, then in possibly carrying out scorching, in order to regain the organoleptic nature which is characteristic of a new barrel. However, this solution is lengthy and expensive to implement and does not allow the barrel to be sterilized against microbial infections. Furthermore, such a mechanical stripping leads to removing an appreciable thickness, several millimeters, of the barrel, which limits the number of possible renovations.  
           [0009]    Another solution consists in chemically cleaning the barrel, but this solution is very cumbersome to implement and expensive.  
           [0010]    Furthermore, the current renovation processes give quite disappointing results for the quality of the wines, since stripping which is too intense leads to a “plank” taste by completely renovating the raw wood, while stripping which is too light has no effect. Furthermore, during the renovation of the barrel, it is difficult to reproduce the initial traditional scorching, since when the barrel is too scorched, it develops strange characteristics.  
         SUMMARY OF THE INVENTION  
         [0011]    The object of the invention is to propose a process for stripping and sterilizing the internal surface of a container, which is both simple to implement and which allows a very high number of renovations.  
           [0012]    The invention is based on the principle of renovation by laser which ensures accurate and selective stripping at a controlled temperature, by photoremoval of the biological stains, for example fungal, mold, polychlorophenol and chloroanisole compounds, and/or mineral stains which are deposited over the internal surface of the container. Since the biological stains have physical characteristics which are different to those of the material forming the container, the heat increase during the absorption of the light produced by the laser will be faster in the coating of organic and/or mineral material than in the container, which makes it possible to remove the biological and/or mineral stains without causing a transfer of energy to within the material forming the cask.  
           [0013]    For this purpose, the subject of the invention is a process for stripping and sterilizing the internal surface of a container made of wood, metal, concrete or some other material, having a surface layer of a coating of organic and/or mineral material, especially a coating of tannin resulting from the maturation of a wine in a cask, characterized in that it consists in applying, over the surface to be treated, pulsed radiation produced by an intense optical source, each pulse having a duration which is short enough and an energy density per unit area to be treated which is high enough to cause the sublimation of the said surface layer, the surface of the container thus stripped being sterilized by the heat released by the radiation. Using the invention, the layer of organic and/or mineral material is sublimed, which generates a gaseous plasma in the form of smoke, which avoids the drawbacks connected with the use of an aqueous solution.  
           [0014]    Advantageously, each pulse has a duration of between 10 and 200 ns and an energy density of between about 1 and 9 J/cm 2 , preferably between 6.5 and 8 J/cm 2 , and an energy of about 2J. For example, each pulse has a duration of about 100 ns and an energy density between about 1 and 8 J/cm 2 .  
           [0015]    A long pulse duration, for example of the order of ms or μs, would lead to a transfer of energy into the material forming the container and a low rate of ejection of the sublimed marks, while the organic and/or mineral coatings have to be removed over a small thickness, quickly and without consuming too much energy. With a pulse duration of about 100 ns, a very high peak value is obtained for the beam, which causes a high ejection rate of the sublimed organic and/or mineral material and low diffusion of the heat into the material forming the container.  
           [0016]    According to another characteristic, the process consists in applying, over each unit area, from 2 to 20 pulses, preferably between 2 and 10 pulses, depending on the type of material of the container to be treated, the state of the surface to be treated and the thickness of the organic and/or mineral coating.  
           [0017]    According to another characteristic, the radiation is determined so as to cause a quasiadiabatic sublimation of the layer of organic and/or mineral material on the surface to be treated. In particular, provision can be made for 80% of the heat produced by the radiation to be absorbed by the surface layer during sublimation, the remaining 20% being dissipated within the thickness of the material forming the container.  
           [0018]    Preferably, each pulse causes the sublimation of about 20 μm thickness of material on the surface to be treated.  
           [0019]    Advantageously, the process consists in evacuating the gaseous plasma produced during the sublimation, by sucking it up or blowing it out using an inert gas or air.  
           [0020]    According to another characteristic, the intense optical source is a laser source, for example a CO 2  laser source at atmospheric pressure and with transverse excitation.  
           [0021]    Advantageously, the process further comprises the steps of starting to strip a portion of the internal surface, measuring at least one property among a calorimetric property of the portion, an acoustic property of the interaction between the portion and the pulsed radiation and a physical property of smoke generated by the stripping of the portion, and comparing measurement data corresponding to the said at least one property with predetermined target data representative of a final state of the internal surface to be obtained, and stopping stripping the portion when the measurement data substantially matches the target data.  
           [0022]    Preferably, the step of measuring a calorimetric property of the internal surface portion comprises illuminating the portion with visible light and measuring a spectral property of the light reflected by the portion to determine a dominant color of the portion.  
           [0023]    Advantageously, the step of measuring a physical property of smoke generated by the stripping of the portion comprises measuring a optical extinction coefficient of the smoke for at least one of an infrared wavelength, a visible wavelength and an ultraviolet wavelength.  
           [0024]    Preferably, the step of measuring an acoustic property of the interaction between the portion and the pulsed radiation comprises measuring ultrasounds emitted by a plasma generated by the said interaction.  
           [0025]    According to another aspect of the invention, for a wooden container, the process consists, simultaneously with or subsequent to the step of stripping and sterilizing, in applying over the surface to be treated a second intense optical radiation, the said second radiation being applied continuously or quasi-continuously for a duration which is long enough and with an energy density per unit area to be treated which is high enough to cause scorching of the wood on the surface. Advantageously, this second radiation is applied by a laser source with a defocused beam or by beam scanning.  
           [0026]    Preferably, the second radiation has a power density of between 50 and 200 W/cm 2  for a duration of application of about 0.05 to 0.2 seconds. In this case, the second radiation preferably has an energy density per unit area to be treated of about 20 J/cm 2 .  
           [0027]    Although the energy density received by the wood, in the case of scorching or toasting, is greater than that for stripping, the total energy is transferred over a long time during scorching, which means that the heat diffuses into the wood and chars it on the surface, while, in the case of stripping, the energy is applied over a very short time, causing instant sublimation of the organic layer.  
           [0028]    In another variant, the second radiation is applied by an infrared or ultraviolet lamp, for example, a lamp having a power of 70 W for an application time of several minutes, with a distance of a few centimeters between the radiation source and the surface to be treated.  
           [0029]    Advantageously, the process further comprises the steps of starting to scorch a portion of the internal surface, measuring at least one property among a calorimetric property of the portion and a physical property of smoke generated by the scorching of the portion, and comparing measurement data of the said at least one property with predetermined target data representative of a final state of the internal surface to be obtained, and stopping scorching the portion when the measurement data substantially matches the target data.  
           [0030]    The subject of the invention is also a device for implementing the aforementioned process, characterized in that it comprises an intense optical source capable of producing pulsed radiation in order to strip and sterilize the internal surface of the container, a waveguide connected to the optical output of the source, an optical focusing head connected to the output of the waveguide, in order to define the cross section of interaction with the surface to be treated and thus the energy density to deposit per unit area, a robot for the relative movement between the optical head and the internal surface of the container to be treated, and a central control unit in order to control and synthesize, on the one hand, the source parameters such as the number of pulses to be applied per unit area, the impulse frequency and the radiation power of the source, and on the other hand, the movements to be carried out by the robot in order to treat the entire internal surface of the container.  
           [0031]    Advantageously, the robot is capable of making the said optical head pivot through an angle of about 120° with respect to the axis of the container.  
           [0032]    According to another characteristic, the robot is capable of driving the optical head in relative rotation about the axis of the container with respect to the container.  
           [0033]    According to yet another characteristic, the robot is capable in driving the container in relative axial translation with respect to the optical head, which may in this case be connected to a telescopic or extensible waveguide.  
           [0034]    Preferably, the optical head is located at a distance from the surface to be treated of about a few tens of centimeters.  
           [0035]    According to another aspect of the invention, the device comprises a camera for displaying the surface treatment, the said camera being connected to a display screen and to the central control unit in order to control the surface treatment visually and in real time.  
           [0036]    According to another characteristic, the optical head is arranged so as to penetrate inside the container, for example by the bunghole of a cask made of wood, or by a hole specially made in one of the heading pieces of the cask or else by one of the ends of the cask from which the heading piece has been removed.  
           [0037]    Preferably, a calorimetric sensor is coupled to the central control unit for measuring a dominant color of the internal surface, the calorimetric sensor being capable of relative orientation with respect to the internal surface.  
           [0038]    Advantageously, in that case, the robot is capable of aiming the optical head and the calorimetric sensor at a same portion of the internal surface for measuring the dominant color of the portion between two pulses of the pulsed radiation. The central control unit is capable of comparing the dominant color of the portion measured by the calorimetric sensor with a predetermined target color to be obtained, the robot being capable of aiming the optical head and the calorimetric sensor at another portion of the internal surface in response to a substantial match between the target color and the dominant color of the portion as measured.  
           [0039]    Advantageously, the device comprises a pipe for sucking up or blowing out smoke generated by the stripping.  
           [0040]    The purpose of removing the gaseous plasma is to avoid, on the one hand, any recontamination of the treated surface and surroundings, on the other hand, any interference with the optical beam and with any display camera.  
           [0041]    Preferably, a smoke analyzer is coupled to the central control unit for measuring an optical extinction coefficient of the smoke sucked up by the pipe for at least one of an infrared wavelength, a visible wavelength and an ultraviolet wavelength.  
           [0042]    According to another characteristic, the robot is capable of moving the pipe in coordination with the optical head such as to keep an inlet portion of the pipe adjacent to a portion of the internal surface at which the optical head is aimed.  
           [0043]    According to another characteristic, a microphone is coupled to the central control unit for measuring a sound pattern generated by the interaction between the pulsed radiation and the internal surface.  
           [0044]    According to another characteristic, the device comprises a second intense optical source for producing the second radiation for scorching a container made of wood. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0045]    In order to better understand the object of the invention, several embodiments shown on the appended drawing will now be described, by way of purely illustrative and non-limiting examples.  
         [0046]    In this drawing:  
         [0047]    [0047]FIG. 1 is a block diagram of a first embodiment of the device of the invention adapted for a test on a sample;  
         [0048]    [0048]FIG. 2 is a simplified partial diagram of a second embodiment of the device of the invention for stripping a cask;  
         [0049]    [0049]FIG. 3 is an enlarged view of a detail of FIG. 1, showing the stripping region.  
         [0050]    [0050]FIG. 4 is a schematic diagram showing a third embodiment of the device of the invention for stripping and scorching a cask;  
         [0051]    [0051]FIG. 5 is a block diagram of a measurement system of the device of FIG. 4, and  
         [0052]    [0052]FIG. 6 is a block diagram of a process for operating the device of FIG. 4. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0053]    In FIG. 1, a laser source  1  is shown which is intended to produce a laser beam  2  in the direction of a convergent lens  3  which causes a beam  4  to converge on a stave  5  of a wooden cask. The stave  5  is held by a robot  6 . A central control unit  7  is connected by a robot control interface  8  to the robot  6 , and by a synchronization interface  9  to the laser source  1 . The central control unit  7  is combined with a peripheral unit  10  formed by a screen  11  and a keyboard  12 . A camera  13  may also be connected to the central control unit  7 , as shown by dashed lines, in order to display the treatment of the surface of the stave  5 . Although the apparatus illustrated in FIG. 1 is adapted to carry out tests on a sample  5 , the general principle of the invention remains substantially the same.  
         [0054]    [0054]FIG. 2 shows a wooden barrel  14 , bulging in the middle, made in a known manner from staves which are assembled and hooped, one of the ends of which is closed by a circular heading piece  16  and the other end of which is open in the direction of the laser source  1 . The barrel  14  rests by the external convex surface of its side wall  17  on rotating rollers  18  which are intended to be rotated about an axis parallel to the axis  15  of the barrel  14 , by the aforementioned robot  6 .  
         [0055]    The aforementioned convergent lens  3  is included in an optical focusing head  19  which is connected to the laser source  1  by a waveguide  20  which in this case is telescopic in the axial direction indicated by the double arrow L, but which, as a variant, could be extensible. The waveguide  20  is substantially aligned with the axis  15  of the barrel  14 . The optical head  19  is articulated with respect to the waveguide  20 , about a horizontal axis  21  which is perpendicular to the axis  15  of the barrel. The optical head  19  is designed to pivot about this axis  21  through an angle θ of about 120° , such that the convergent beam  4  exiting from the optical head  19  is able to pivot between a position (not shown) where the said beam  4  is aligned with the axis  15  of the barrel in the direction of the heading piece  16 , and a position inclined by 30° with respect to the vertical, in the direction of the open end of the barrel. Thus the optical head  19  can scan the entire internal surface of the barrel, that is the internal surface of the heading piece  16  and the internal concave surface of the side walls  17  of the barrel.  
         [0056]    The rotating rollers  18  allow the barrel  14  to be turned about its axis  15 , as shown by the arrow  22 . Of course, as a variant, the waveguide  20  could be designed to rotate axially, instead of rotating the barrel  14 .  
         [0057]    [0057]FIG. 3 shows that the beam  2  coming from the optical source  1  is converted into a convergent beam  4  by the lens  3 , in order to make this beam converge on a region of predetermined limited area of the internal wall of the stave  5 , in order to sublimate a layer of organic material coating  23 . The smoke produced by the sublimation of the layer of organic material  23  may be sucked up or blown out via a pipe  24  inserted in the barrel  14 , preferably close to the region of treatment of a stave  5 .  
         [0058]    The pipe for sucking up or blowing out the smoke  24  may be combined with the camera  13 . The camera  13  is, preferably, provided with an autofocus objective lens, making it possible to view the surface to be treated on the control screen  11 , and therefore for the operator to control, without risk, the quality of the stripping and of the scorching.  
         [0059]    Using the combined movements of the waveguide  20  in the axial direction of the barrel, of the axial rotation of the barrel  14  and of the limited angular pivoting of the optical head  19 , the entire internal surface of the barrel can be treated.  
         [0060]    A third embodiment of the device for stripping and scorching a wooden cask is now described with reference to FIGS.  4  to  6 , in which elements analogous to those of the above-described embodiments are referred to by the same numerals increased by 100.  
         [0061]    In FIG. 4, the wooden cask  114  includes a side wall  117  and two heading pieces  116  and is shown in a lateral sectional view. A bunghole  125  is formed through the top of side wall  117 . A rigid waveguide  120  is engaged in cask  114  through bunghole  125 . The bunghole  125  may be of a conventional type with a diameter of the order of 50 mm, or with a larger diameter depending on the size of waveguide  120  and the components carried thereon.  
         [0062]    Waveguide  120  couples an optical source  101  to an optical head  119 . Optical source  101  comprises a pulsed laser source  130  for the stripping treatment of the cask and a continuous laser source  131  for the scorching treatment of the cask. Both laser sources are infrared CO 2  lasers with a central wavelength of 10.6 microns and an overall power between 100 and 200 W. For example, pulsed laser source  130  has a peak power between 30 and 80 MW. An optical coupler  132  is arranged between the outputs of laser sources  130  and  131  and an end  120   a  of waveguide  120  so as to superimpose the beams produced by both laser sources and feed them into the waveguide  120 . Optical coupler  132  comprises mirrors  133  and a cooling system (not shown) for cooling mirrors  133 .  
         [0063]    Coupled to the other end of waveguide  120  is the optical head  119  of the device, which includes two pivotable portions  119   a  and  119   b.  An output lens assembly  103  is fitted to optical head portion  119   b.  For example, output lens assembly  103  is a convergent lens with diameter 30 mm. In order to aim the laser beams at a given portion of the internal surface of cask  114 , optical head portion  119   a  is capable of modifying the azimuthal angle of output lens assembly  103  and optical head portion  119   b  is capable of modifying the elevation angle of output lens assembly  103 . Optical head portion  119   a  includes a tilted mirror, not shown, for reflecting the radiation from waveguide  120  to the axial direction of optical head portion  119   b.  Optical head portion  119   b  includes a second tilted mirror, not shown, for reflecting the radiation from optical head portion  119   a  to output lens assembly  103 . Output lens assembly  103  allows to configure the laser beams so as to define a cross section of the laser beams.  
         [0064]    Scanning actuators, not shown, are provided in optical head portions  119   a  and  119   b  for pivoting optical head portions  119   a  and  119   b  to aim the laser beams at different portions of internal surface  129  and controlled by a central control unit  107  through robot control interface  108  and control lines  127  so as to scan the entire internal surface  129 .  
         [0065]    A pipe  124  is secured to optical head  119  and coupled by a flexible coupling  134  to a drawing pump  135 . For example, air is sucked up from cask  114  with an average speed of 2 m/s in flexible coupling  134 . Pipe  124  is pivoted together with optical head portion  119   b  with respect to optical head portion  119   a.  In the embodiment shown, pipe  124  comprises two telescopic portions for adjusting the length of pipe  124 . Central control unit  107  controls through robot control interface  108  actuators mounted on pipe  124  for adjusting the length of pipe  124  as a function of the orientation of optical head  119 , so as to keep an inlet  136  of pipe  124  close to the portion of internal surface  129  aimed at. In a modified embodiment, not shown, pipe  124  has a fixed length.  
         [0066]    The smoke that is generated by the interaction between the radiation and the portion of internal surface  129  is sucked up out of cask  114  through pipe  124 , coupling  134  and pump  135  so as to keep a low level of absorbing and/or scattering particles in suspension inside cask  114 . An accumulation of smoke inside cask  114  would result in both losing radiation power between optical head  119  and internal surface  129  and sooting up output lens assembly  103 , which could lead to overheating and damaging of output lens assembly  103 . To further avoid such overheating in operation, a blower (not shown) may be provided for blowing air or an inert gas at output lens assembly  103  so as to cool and clean output lens assembly  103 .  
         [0067]    As mentioned, central control unit  107  controls actuators for orienting optical head  119  and pipe  124  by way of robot control interface  108 . Central control unit  107  also controls laser sources  131  and  130  by way of laser control and synchronization interface  109 . Wooden cask  114  lies on a mobile support  126  that is coupled to robot control interface  108  by control line  128 . Mobile support  126  comprises hydraulic actuators  118  that allow to raise and lower wooden cask  114 .  
         [0068]    Before operation, in order to insert optical head  119  into cask  114 , mobile support  126  is set to the lowest position. Waveguide  120  and optical head  119  are brought in alignment with bunghole  125 . Mobile support  126  is then raised until optical head  119  is appropriately positioned about the center of cask  114 .  
         [0069]    In a modified embodiment, not shown, adapted for heavier wooden casks, the cask is set in a fixed position on an appropriate support, and waveguide  120  is constructed in the form of a variable length waveguide with an actuator controlled by central control unit  107  for varying the length of waveguide  120 . For example, waveguide  120  has two telescopic portions, with a portion having a smaller section able to be extended from and retracted into a portion having a larger section, so as to adjust the overall length of the waveguide.  
         [0070]    The device of the third embodiment also comprises a measurement system  137 , best seen on FIG. 5, coupled to central control unit  107  by measurement data lines  138 . Measurement data lines  138  run between central control unit  107  and measurement system  137  and carry control data from central control unit  107  to measurement system  137  and measurement data from measurement system  137  to central control unit  107 . The measurement data is processed in real time by central control unit  107  to control and drive the stripping and scorching treatment of the internal surface  129 , as will be explained here-below.  
         [0071]    With reference to FIGS. 4 and 5, measurement system  137  comprises a calorimetric measurement device for measuring a dominant color of the internal surface under treatment, an acoustic measurement device for measuring ultrasounds generated by the interaction between the laser radiation and the internal surface, and a smoke analyzer  140  for measuring an optical absorption coefficient of the generated smoke.  
         [0072]    The calorimetric measurement device comprises a preprocessing unit  141  arranged outside cask  114  and an objective  113  attached to optical head portion  119   b  inside the cask so as to point to a same portion of internal surface  129  as output lens assembly  103 . Preprocessing unit  141  comprises a flashlight  142  coupled to an acquisition trigger module  146  for triggering flashlight  142 , and an optical sensor  145  coupled to acquisition trigger module  146  through an amplifier  147  and a color/tension converter  148 . An emitting optical fiber  143  runs between an output of flashlight  142  in preprocessing unit  141  and objective  113 . A collecting optical fiber  144  runs between objective  113  and an input of optical sensor  145  in preprocessing unit  141 . In operation, the calorimetric measurement device operates as a simplified digital camera. When acquisition trigger module  146  triggers an acquisition, a flash of white light is emitted by flashlight  142 , carried to objective  113  by fiber  143  and outputted through objective  113  on internal surface  129  whose color is to be measured. The light is reflected by internal surface  129 , different spectral components of the flash of light being reflected with different efficiencies depending on the state of internal surface  129 . The dominant color of the surface is defined as the visible wavelength or range of wavelength for which the reflectivity of the surface is the highest. The reflected light, including the different spectral components, is collected by objective  113  and carried to optical sensor  145  through fiber  144 . Optical sensor  145  includes a number of sensing cells sensitive to different spectral components of the collected light, for example sensing cells for red, sensing cells for green and sensing cells for blue. Optical sensor  145  outputs an electric signal representative of the relative intensity of each of the spectral components of the reflected light. For example, optical sensor  145  is an array of photodiodes or charge-coupled devices (CCD) with spectral filters. Note that a grating spectrometer can also be used as optical sensor  145 . The output of optical sensor  145  is amplified by amplifier  147  and converted by converter  148  into an electric signal representative of the dominant color of the reflected light. Acquisition trigger module  146  then supplies color measurement data representative of the dominant color in a format appropriate for processing by central control unit  107 .  
         [0073]    The acoustic measurement device comprises a preprocessing unit  139  arranged outside cask  114  and an ultrasound directional microphone  149  attached to optical head portion  119   b  inside the cask so as to be capable of relative orientation with respect to the internal surface, and to point to the portion of internal surface under treatment. Microphone  149  is coupled by a line  150  to an amplifier  151  in preprocessing unit  139 . Amplifier  151  is coupled to a filter  152  having a frequency filtering template adapted for filtering out noise and keeping a signal of use. Filter  152  is coupled to an acquisition module  153  for supplying acoustic measurement data representative of the measured ultrasound pattern in a format appropriate for processing by central control unit  107 .  
         [0074]    Directional microphone  149  can also be replaced by a wide-angle microphone that does not have to be oriented towards a given portion of internal surface  129  to measure the ambient ultrasound in cask  114 .  
         [0075]    Optical fibers  143  and  144 , control line  127 , flexible coupling  134  and measurement line  150  are attached to waveguide  120  by an attachment ring  166 . They are shielded from waveguide  120  to avoid interference with the laser beams.  
         [0076]    Smoke analyzer  140  is arranged between coupling  134  and pump  135  so that the smoke drawn up by pump  135  flows through analyzer  140 . Smoke analyzer  140  comprises three pairs of diodes  154   a - b ,  155   a - b  and  156   a - b  arranged on the pathway of the smoke so as to pass a predetermined radiation through a predetermined layer of the smoke between an emitting diode  154   a ,  155   a ,  156   a  of each pair and a receiving diode  154   b ,  155   b ,  156   b  of each pair. Pair of diodes  154   a - b  passes an infrared light, with wavelength above about 0.8 microns, pair of diodes  155   a - b  passes a visible light, with wavelength between about 0.4 and 0.8 microns, and pair of diodes  156   a - b  passes an ultraviolet light with wavelength between about 0.2 and 0.4 microns. Each pair of diodes outputs to a respective amplifier  154   c ,  155   c ,  156   c  a signal representative of the ratio of the radiation power received by receiving diode  154   b ,  155   b  and  156   b  to the radiation power emitted by emitting diode  154   a ,  155   a  and  156   a , i.e. representative of a transmission coefficient T for each of the three wavelengths or wavelength ranges. For each wavelength or wavelength range, this signal allows to measure an extinction coefficient e of the smoke, which is defined as:  
         [0077]    e=−Log(T)/Λ, where Λ is the thickness of the layer of smoke passed through. This extinction coefficient is a function of a chemical composition of the smoke.  
         [0078]    A converter module  157  receives the signals outputted by the amplifiers  154   c ,  155   c ,  156   c  and combines them into a frequency modulated electric signal, wherein the respective output of each amplifier  154   c ,  155   c ,  156   c  is converted in a respective band of modulation frequency. A second converter module  158  converts the combined signal outputted by converter module  157  into a measurement signal representative of the extinction coefficient measured for each of the three wavelengths or wavelength ranges in a format suitable for processing by central control unit  107 .  
         [0079]    Of course, more of less than three pairs of diodes and different values of wavelength can be used for analyzing the smoke.  
         [0080]    Smoke analyzer  140  is arranged outside cask  114  because the bulk of smoke analyzer  140  makes it difficult to introduce through bunghole  125 . However, in a modified embodiment, not shown, smoke analyzer  140  is constructed in two parts connected together: one part includes the pairs of diodes and is arranged in pipe  124  close to inlet  136 , so as to reduce the delay between the time of generation of the smoke and the time of analysis of the smoke, and the other part with a bigger size remains outside cask  114 . In all cases, the smoke is drawn up for measuring the optical extinction coefficient of the smoke at a location isolated from the radiation emitted by the portion being stripped or scorched.  
         [0081]    Central control unit  107  comprises a comparator unit  160  that is coupled to measurement lines  138  for receiving the measurement signals from the measurement system  137  and a memory unit  159  in which is memorized target data comprising target values for all types of measurement data delivered by measurement system  137 . For example, the target data is loaded in memory unit  159  by recording the results of measurements performed with a reference wooden part, or is extracted from a reference database.  
         [0082]    Memory unit  159  contains a target color value, for example in the wavelength range between 0.45 and 0.5 micron which corresponds to light oak wood. Comparator unit  160  compares the measured color value received from the calorimetric measurement device to that target color value. In the course of a typical stripping treatment, the dominant color of the internal surface  129  will change from dark red, with wavelength around 0.65 microns, to light oak wood.  
         [0083]    Memory unit  159  also contains a target sound pattern, for example in the form of an ultrasound spectrum to be obtained or a dominant wavelength to be obtained. Comparator unit  160  compares the measured sound pattern received from the acoustic measurement device to that target sound pattern.  
         [0084]    Memory unit  159  also contains target extinction coefficient values for the three wavelengths used by smoke analyzer  140 . Comparator unit  160  compares the measured extinction coefficients received from smoke analyzer  140 to those target extinction coefficient values.  
         [0085]    The operation of the device in the third embodiment will now be described.  
         [0086]    In operation, central control unit  107  controls in real time the movements of optical head  119  and pipe  124  and the operation of laser sources  130  and  131  so as to scan and treat the entire internal surface  129 . Since the deposit layer in not homogeneously distributed in the original state of the cask to be treated—for example the layer is thicker on the bottom surface of the cask and absent on the top surface—central control unit  107  also locally adapts the intensity and duration of the stripping and scorching treatment from one portion of the internal surface to the other, as a function of the results of at least one of the above-mentioned comparisons, so as to obtain an homogeneous surface aspect without layer of deposit and with a desired color over the entire internal surface.  
         [0087]    Two configurations can be used for outputting both laser beams through lens assembly  103 . In a first configuration, the beams are input in waveguide  120  by coupler  132  so as to be coaxial. The radiation generated by both laser sources  130  and  131  is aimed through optical head  119  to precisely the same portion of internal surface  129  for simultaneously carrying out both stripping and scorching treatments of the portion without changing the orientation of optical head  119 . This is possible because the pulsed radiation affects the surface layer of deposit while the second radiation affect a layer of wood under the layer of deposit.  
         [0088]    In the second configuration, the beams are input in waveguide  120  by coupler  132  so as to be parallel with their respective axes laterally offset, for example by 1 cm. In that configuration, the radiation generated by both laser sources  130  and  131  is aimed through optical head  119  to two respective adjacent portions of internal surface  129 . In that case, the stripping and scorching treatments are carried out sequentially for each portion of internal surface  129 .  
         [0089]    With reference to FIG. 6, the operation of the device comprises the following steps:  
         [0090]    At step 161, optical head portion  119   b  together with output lens assembly  103 , microphone  139  and objective  113  is aimed at a given portion of internal surface  129  for the treatment to begin.  
         [0091]    At step 162, pulsed laser source  130  and/or continuous laser source  131  is/are actuated to carry out an elementary step of stripping and/or scorching treatment of the portion. For example, the elementary steps consists of a given number of pulses from source  130  and/or a predetermined duration and intensity of scorching irradiation by source  131 .  
         [0092]    At step 163, while step  162  is carried out, measurement system  137  is actuated to measure at least one of the above-mentioned dominant color, sound pattern and extinction coefficients. In this step, the calorimetric measurement is actually carried out after the given number of laser pulses have been fired or between two pulses.  
         [0093]    At step 164, the above-mentioned comparisons between the measurement data acquired at step  163  and the target data are performed. If no substantial match is obtained between the measurement data and the target data, the process of steps  162  and  163  is repeated. For example, the comparisons between the measurement data acquired and the target data indicates that the stripping treatment and/or the scorching treatment of the portion is not sufficient. In that case, step  162  is repeated so as to carry out another elementary step of stripping and/or scorching treatment of the portion, depending on what is needed to obtain the desired final state of surface, i.e. for example the desired color of surface and the desired composition of smoke.  
         [0094]    At step 165, when the desired final state of surface is obtained for the portion aimed at, central control unit  107  aims optical head portion  119   b  together with output lens assembly  103 , microphone  139  and objective  113  at an adjacent portion of internal surface  129  for the treatment to continue.  
         [0095]    The above steps are repeated until the entire surface is in the desired final state. For example, central control unit  107  is set to operate according to the above-mentioned process by corresponding programming.  
         [0096]    Note that instead of constructing optical head  119  with two degrees of rotation, so as to obtain a so-called spherical coordinates scan, the degree of rotation provided by optical head portion  119   b , and corresponding to the elevation angle, can be replaced by a degree of translation between the cask  114  and optical head  119  parallel to the axis of waveguide  120 , in order to obtain a so-called cylindrical coordinates scan.  
         [0097]    Although it is preferred to scan the entire internal surface  129 , the top side can be omitted when the layer of deposit is negligible.  
       Stripping Step  
       [0098]    In the course of the stripping tests which were carried out, it was found that, with a pulsed laser beam having an energy density of 2 J over a surface to be treated of 24 mm 2 , i.e. an energy density of 8 J/cm 2  which corresponds to a peak power density of 80 MW/cm 2  for a pulse duration of 100 ns, each pulse causes the removal of 20 μm thickness of wood, which is negligible with respect to the thickness of a stave which is generally between 22 and 27 mm. This is because the coating of organic material is generally intimately linked to a surface layer of the internal surface of the wood, which, during stripping, causes the removal of the organic material and of a layer of wood of a corresponding thickness, which layer is impregnated by the said layer of organic material.  
         [0099]    The laser source is preferably a CO 2  laser at atmospheric pressure and operating with transverse excitation (TEA), having a wavelength of 10.6 μm, with a beam output cross section of 16×32 mm.  
         [0100]    Preferably, the focusing head will have a long focal length with respect to the distance between the said head and the surface to be treated, so as to reduce the accuracy of positioning the head with respect to the cross section for interaction of the beam with the surface to be treated by producing a beam with a sufficient cross section. Indeed, if the beam were too narrowly focalized on the surface to be treated, it would instantaneously drill a through-hole in the wooden part, which should obviously be avoided. The distance between the optical head  19  and the surface to be treated may vary between 30 and 50 cm.  
         [0101]    To industrialize the process, several laser sources, for example three sources, could be coupled in parallel, each one having a pulse frequency of 200 Hz, in order to alternately deliver energy over a same optical path, which makes it possible to obtain an overall pulse frequency of 600 Hz, each pulse having, for example, an energy density of between 150 and 200 mJ/cm 2 , the rate of displacement of the laser beam with respect to the surface to be treated being determined by the central control unit which comprises a computer, so as to obtain an energy density of 8 J/cm 2  over the surface to be treated.  
       Scorching Step  
       [0102]    To scorch the wood, three different solutions were tested:  
         [0103]    with a CO 2  laser source, for example having a power of 3 kW, and generating an out-of-focus beam having a power density of 180 W/cm 2   1  the exposure time needed is greater than 50 ms;  
         [0104]    with a CO 2  laser source having a power of 10 W and generating a scanning beam having a power density of about 10 W/cm 2 , the distance between the focusing head and the surface to be treated being about 60 cm, the exposure time needed is markedly longer, about 5 min, in order to obtain the desired scorching, but in this case, the scorching affects a depth of the order of mm and the quantity of energy deposited is much greater;  
         [0105]    with an infrared lamp of 1 μm wavelength, having a power of 80 W and a beam aperture angle of 28°, at a distance of about 3 cm from the surface to be treated, the exposure time needed is markedly longer at about 9 min.  
         [0106]    These three scorching solutions are not all illustrated in the drawings, but they could be mounted on the robot so as to couple the intense optical source for scorching and the laser source for stripping. A single double-beam optical source could also be provided, producing simultaneously or successively pulsed radiation for stripping and continuous radiation for scorching. These two radiations can be produced simultaneously since their characteristics of interaction with the surface to be treated are markedly different, which avoids any interference.  
         [0107]    For the stripping, the number of pulses per unit area, the duration of each pulse and the energy density per unit area, will be able to be determined as a function of the surface state, the quality of the wood and the thickness of the layer to be removed.  
         [0108]    For the scorching, the exposure time and the power density of the intense optical source will be determined as a function of the degree of scorching desired by the user.  
         [0109]    Although the invention has been described in connection with several particular embodiments, it is clearly obvious that the invention is in no way limited to them and that it comprises all the technical equivalents of the means described as well as their combinations if these come within the scope of the invention.