WO2008095843A1 - Electro-optical blocking device for an anti-glare including at least one photo-sensitive layer - Google Patents

Abstract

The invention relates to an electro-optical blocking device (1000) including at least two first electrodes (1001, 1002) and at least a first cell including a layer of an electro-optical material, said first cell(s) being provided between said first electrodes, wherein each of said first cell(s) can be switched between at least on passing state, which it transmits a light beam, and at least one blocking state, in which it does not transmit the light beam, essentially based on the electric field applied t said first cell through the first electrodes. According to the invention, the blocking device also includes at least one solid layer of a first photo-sensitive material having a high transverse resistance and provided between said first electrodes.

Description

 Electro-optical shutter device for anti-glare system based on at least one photosensitive layer. 1. Field of the invention

The field of the invention is that of anti-glare devices for optical or optoelectronic sensors.

The invention finds particularly, but not exclusively, its application in the protection of such optical or optoelectronic sensors in the context of the monitoring of arc welding operations or the presence of dazzling sources in a scene. 2. Solutions of the prior art

The use of an arc with intense radiation requires precautions.

Indeed, in the case of a welding robot equipped with an optical sensor (or optoelectronic) to view the scene, the radiation emitted by the arc can damage the sensor disposed near the scene and in any case , makes the observation of the scene difficult. An example such sensor is a camera

CCD on which is projected the scene observed by means of an optical objective.

A conventional anti-glare technique to protect the sensor of the welding robot is the implementation of an optical shutter device based on a diaphragm (controlled automatically or manually) which blocks (in a blocking state) on any its surface light comes from the scene during intense light emission by the arc and is transparent (or in a passing state) in other cases.

Such an optical shutter device makes it possible: - when the arc is activated, to block (blocking state of the shutter device) globally the luminous flux coming from the scene comprising a component emitted by the intense arc in the center of the scene in order to protect the sensor from the robot welder and when the arc is not activated, let the light coming from the scene pass through (shut-off state) so that the welding robot's sensor can view the scene.

However, this conventional shutter device does not allow the robot sensor to view the scene when the arc is activated and therefore the shutter device is in the blocking state.

There are techniques for spatial filtering a light beam based on a plurality of shutters arranged in the form of a matrix (for example as described in European Patent Application No. EP1698166Al). However, in order to obtain the targeted filtering pattern, these techniques require that each shutter of the array be controlled individually by means of a controller. This therefore imposes a multiplication of control devices and thus makes it complex, expensive and cumbersome of such techniques. In addition, the presence of inter-pixels within the framework of such a matrix modifies and complicates the transmittance of the matrix and does not guarantee complete security.

3. Objectives of the invention

The invention particularly aims to overcome these disadvantages of the prior art. More precisely, an objective of the invention, in at least one of its embodiments, is to provide a technique that makes it possible to block (respectively let pass) the portion of a luminous flux whose intensity in a plane transverse to the flow is the most important, while allowing (respectively blocking) the less intense part of the luminous flux and which does not require the implementation of several control devices.

Another object of the invention, in at least one of its embodiments, is to provide an anti-glare technique which selectively blocks the light emitted by an intense light source into a luminous flux coming from a scene observed comprising the light source and let the rest of the luminous flux through. Another object of the invention, in at least one of its embodiments, is to implement such a technique that is compatible with conventional optical shutter devices.

The invention, in at least one of its embodiments, still aims to provide such a technique that is simple to implement and for a low cost.

4. Presentation of the invention

According to one particular embodiment, the invention relates to an electro-optical closure device comprising at least two first electrodes and at least one first cell comprising a layer of an electro-optical material, the first said (s) (s) cell (s) being disposed between said first electrodes, each of said first cell (s) being switchable between at least one on state, in which it transmits a light beam, and at least one a blocking state, in which it does not transmit the light beam, depending in particular on the electric field which is applied to said first cell via the first electrodes.

According to a particular embodiment of the invention, the closure device also comprises at least one solid layer of a first photosensitive material and high transverse resistivity provided between said first electrodes.

A photosensitive material according to the invention is, for example, amorphous silicon (for example silicon carbide), a semiconductor (optionally doped), polyvinylcarbazole, etc.

Of course, in the context of the closure device according to the particular embodiment, the closure device may comprise one or more layers (s) massive (s) of the first photosensitive material, but it may also include several layers of different photosensitive materials, each of this or these layers possibly being doppée. For example, the closure device according to the present embodiment of the invention may comprise a photoresistor and / or a photodiode and / or a junction semiconductor made (s) based on several layers of different photosensitive materials, each associated with a specific doping.

By solid layer is meant a layer that extends at least over the entire useful surface of the closure device. By useful surface is meant the surface of the device that is intended to receive light from a scene. For example, the edges of the closure device on which may be provided fixing elements of the shutter device to a viewing camera of a welding robot are not part of the useful surface. The general principle of the invention is that, the light intensity distribution in the plane of the shutter device of a luminous flux incident on the device (supplied by means of a single control voltage) generates a distribution substantially identical electric charges at the terminals of the photosensitive layer (due to the creation of electrons at the level of the photosensitive layer) which therefore generates a substantially identical distribution in resultant electric field intensity (applied electric field which is subtracted the electric field generated by the electrons) at the cell (s).

The photosensitive material must be chosen so that it has a high transverse resistivity to prevent the diffusion of charges laterally.

In the context of the present invention, the term material with high transverse resistivity means a material whose transverse resistivity is greater than or equal to 10 ⁹ Ω.cm (which corresponds to a conductivity of 10 ^{~ 9} (Ω.cm) ^-1 ).

This photosensitive layer must also have a threshold for generating the charges as a function of the applied voltage and or the luminous intensity. For example, hydrogenated amorphous silicon may be chosen as the photosensitive material.

Thus, a shutter amplitude distribution is obtained in the plane of the shutter substantially identical to the electric field strength, conductivity and light intensity distributions in the plane of the shutter. shutter device.

Consequently, in the case where the first cell (s) is (are) in an on state when an electric field (their) is applied to them (and in a blocking state when no field is present) is applied), such a shutter device (which does not require the implementation of several control devices, that is to say several control voltages, because it can operate with the application of a single voltage) makes it possible to block the portion of a luminous flux, the intensity of which in a plane transverse to the flux is the greatest, while allowing the less intense part of the luminous flux to pass. Such a shutter device makes it possible to attenuate the portion of a luminous flux whose intensity in a plane transverse to the flux is the greatest, while nevertheless allowing the least intense part of this luminous flux to pass.

Thus, in this case, this closure device is an anti-glare technique that selectively blocks the light emitted by an intense light source in a light flux from an observed scene including the light source and let the rest of the luminous flux.

In addition, in the case where the first cell (s) is (are) in a blocking state when an electric field (their) is applied to them (and in an on state when no field is is applied), such a shutter device allows to pass the portion of a luminous flux whose intensity in a transverse plane to the flow is the largest, while blocking the less intense part of the luminous flux.

The technique of the invention is compatible with conventional optical shutter devices because it proposes to add in such a conventional shutter device a layer of a photosensitive material.

Thus, the first cell (s) is (are) electrically controlled by the layer of first photosensitive material.

Thus, in the context of the arc welding, such a photosensitive material allows the observation (for example by a visualization camera of a welding robot) of the surroundings of the dazzling source (the welding arc) and allows so to locate it.

Advantageously, the electro-optical closure device comprises at least two second electrodes and at least one second cell comprising a layer of an electro-optical material, the said second cell (s) being arranged ( s) between said second electrodes, each of said second cell (s) being switchable between at least one on state, in which it transmits the light beam, and at least one blocking state, in which it does not transmit the light beam, in particular as a function of the electric field which is applied to said second cell via the second electrodes, and the closure device also comprises at least one massive layer of a second photosensitive material with high transverse resistivity provided between said second electrodes .

Thus, the first and second cells are electrically controlled respectively by the layer of a first photosensitive material and the layer of a second photosensitive material.

Preferably, the closure device comprises attenuation means with quasi-continuous variations of an optical signal, said attenuation means comprising at least a third cell of a first type comprising at least one layer of a first material based on a nematic liquid crystal.

Each of the cells of the first type is switchable between at least one on state and at least one blocking state depending on the electric field applied to said cell.

Preferably, the third cell (s) of said attenuation means are arranged between the first electrodes.

According to an advantageous characteristic of the invention, the closure device comprises optical closure means comprising at least a fourth cell of a second type comprising at least one layer of a second material based on a smectic liquid crystal. . Advantageously, said second material comprises at least one crystal ferroelectric type smectic liquid and / or at least one anti-ferroelectric type smectic liquid crystal.

Preferably, the second material comprises a combination of at least one ferroelectric liquid crystal and / or at least one anti-ferroelectric liquid crystal and a polymer, said association belonging respectively to the families of PSFLCs and / or PSAFLCs.

These PSFLCs and / or PSAFLCs are gel type materials.

According to an advantageous characteristic of the invention, the fourth cell (s) of said closing means are arranged between the second electrodes.

Advantageously, at least said first and second photosensitive materials belong to the group comprising: polyvinylcarbazole; silicon carbide. Thus, such photosensitive materials are of high transverse resistivity.

Thus, in the context of the implementation of the closure device in an arc welding application, such a photosensitive material is both sensitive to the radiation of the dazzling source (the solder arc) and sufficiently transparent. to allow local observation of the scene for example by the optical sensor.

Advantageously, the closure device comprises at least one photoresistor comprising at least one of said layer (s) of first photosensitive material or second photosensitive material.

Advantageously, the closure device comprises at least one photodiode comprising at least one of said layer (s) of first photosensitive material or second photosensitive material. each of these photoresistances or photodiode can be made based on at least one junction based on at least two layers of semiconductor photosensitive materials (at least one being optionally doped) making it possible, for example, to increase the speed or order sensitivity shutter device.

Preferably, said one or more electrodes are made of ITO. Thus, these electrodes are optically transparent in the spectrum of the light beam. 5. List of figures

Other features and advantages of the invention will appear more clearly on reading the following description of a preferred embodiment, given as a simple illustrative and nonlimiting example, and the appended drawings, among which: FIG. 1 shows a block diagram of a first shutter device according to a first embodiment of the invention; Figure 2 shows the block diagram of a second closure device according to a second embodiment of the invention; - Figure 3 shows a diagram illustrating an implementation of the first closure device of Figure 1; Figure 4 shows the block diagram of a third shutter device according to a third embodiment of the invention; FIG. 5 illustrates the continuous level and the maximum level of the standard operating mode in accordance with the MIG / MAG technique; FIG. 6 illustrates a diagram of a shutter device according to a first embodiment of the invention; FIG. 7 illustrates a diagram of a shutter device according to a second embodiment of the invention; FIG. 8 illustrates a diagram of a shutter device according to a third embodiment of the invention. 6. Description of an embodiment of the invention

We place in the following in the context of a welding robot equipped with an arc welding station implementing a standard operating regime for example according to the MIG process (for "Metal Inert Gas") and MAG (for "Metal Active Gas").

As illustrated by FIG. 3 hereinafter described, the robot has a display camera comprising an optical sensor, for example a CCD sensor, the camera being equipped with a shutter device according to a preferred embodiment. of the invention.

The shutter device is disposed in front of the optical sensor (for example a CCD sensor). For example, the optical sensor comprises amplification means (for example with a variable gain) of the light intensity received from the welding scene making it possible to compensate for the losses sustained by the light intensity during the crossing of the device. shutter (and in particular of the photosensitive layer or layers described below of the closure device).

Of course still, a shutter device according to the invention can also be implemented in any other application.

Of course, a shutter device according to the invention can be implemented for any other application and in particular for performing spatial filtering on a luminous flux (or beam).

With reference to FIG. 1, the block diagram of a first shutter device 1000 according to a first embodiment of the invention is presented.

A luminous flux 1800, originating from the scene during the intense light emission by the arc to be welded, is incident on the first shutter device 1000. For example, the luminous flux has a spectrum included in the visible.

The first shutter device 1000 comprises at least two first electrodes 1001, 1002 between which are arranged a first shutter module 1100 and a first solid layer of a first photosensitive material 1200. By solid layer is meant a layer which is extends over the entire surface of the shutter device. The first photosensitive material (as well as the second photosensitive material mentioned below) are selected to be sensitive in the glare range under consideration (i.e., in this case, the spectrum of the arc to be welded , which is included in the visible) while allowing a sufficient amount of light to pass so that the viewing camera can view the scene.

Since the emission spectrum of the arc to be welded is sufficiently wide, it is easy to satisfy this double constraint of sensitivity and transparency.

For example, the first photosensitive material is a material with a high transverse resistivity of silicon carbide (SiC) type and the first layer has a thickness of the order of 2 to 3 μm. According to a variant of this preferred embodiment, the first photosensitive material is polyvinylcarbazole (or PVK) and the first layer has a thickness of 100 .mu.m.

Indeed, for example, SiC and PVK make it possible to satisfy the aforementioned double constraint because they are both sensitive to the radiation of the dazzling source (the arc to be welded) and sufficiently transparent to allow the local observation of the scene (by the viewing camera).

On the other hand, these materials are high transverse resistivity.

Thus, such a material is almost transparent for the spectrum (in the visible) of the luminous flux 1800.

A first voltage source 1700 delivers a first constant voltage (possibly variable), for example 10V, between the first electrodes 1001, 1002.

The first electrodes are for example made of ITO and have for example a thickness of a few tens of nm. Thus, these electrodes are optically transparent in the spectrum of the luminous flux 1800.

A luminous flux 1800, originating from the scene during the intense light emission by the arc to be welded, is incident on the first shutter device 1000. For example, the luminous flux has a spectrum included in the visible. In relation to FIG. 2, the block diagram of a second shutter device 2000 according to a second embodiment of the invention is presented.

The second shutter device 2000 is identical to the first shutter device 1000 except that it further comprises at least two second electrodes 2001, 2002 between which are disposed a second shutter module 2100 and a second layer mass of a second photosensitive material 2200.

A second voltage source 2700 delivers a second constant voltage (possibly variable), for example 10V, between the second electrodes 2001, 2002.

For example, the second layer of second photosensitive material 2200 is identical to the first layer of first photosensitive material 1200.

For example, the first and second electrodes are identical. According to a variant of this second embodiment, the first electrode 1002 and the second electrode 2001 are merged and are connected to the common ground at the first 1700 and second 2700 voltage sources.

The first and second shutter modules respectively comprise at least a first cell and at least a second cell, each of said cells comprising a layer of an electro-optical material (for example a nematic liquid crystal, a smectic liquid crystal, etc. .) and being switchable between at least one on state, in which it transmits the luminous flux 1800, and at least one blocking state, in which it does not transmit the luminous flux 1800, depending on the electric field which is applied to the cell . The spatial dimensions in the transverse plane (plane perpendicular to the axis of propagation of the light beam which is also the plane of the device of the shutter device) of the shutter devices 1000, 2000 according to the invention are adapted to the optical sensor on which is pictured the observed scene. For example, such a shutter may have transverse dimensions of the order of a few cm ² to a few tens of cm ² . In the context of the above-mentioned shutter devices 1000, 2000, the first and second photosensitive materials of the first 1200 and second 2200 layers convert the received photons into electrons.

Under the action of the electric field (resulting from the first and second voltages applied respectively between the first 1001, 1002 and second 2001, 2002 electrodes) applied at these first 1200 and second 2200 layers, these electrons do not move in the plane transverse aforementioned because the first and second photosensitive materials are selected high transverse resistivity and accumulate at the boundaries between the first 1200 and second 2200 photosensitive layer and the first 1100 and second 2100 shutter modules based on electro-optical materials , thus giving an electronic image of the optical intensity distribution.

However, the spatial distribution, in the plane of the shutter device 1000, 2000, of the intensity of the incident light flux 1800 (coming from the scene during intense light emission by the arc to be welded) being non-uniform (the maximum intensity at the source point of the arc), the distribution in electrical conductivity (depending on the light intensity received) resulting (or generated) at the level of the photosensitive layer (due to the generation of electrons at the level of the photosensitive layer) is also nonuniform (because the photosensitive material is of high transverse resistivity). This therefore generates an identical distribution in resultant electric field strength (applied electric field to which is subtracted the electric field generated by the electrons) at the cells of the first 1100 and second 2100 shutter module.

Thus, a shutter amplitude distribution is obtained in the plane of the shutter substantially identical to the electric field strength, conductivity and light intensity distributions in the plane of the shutter device.

Thus, the cells of the first 1100 and second 2100 shutter modules are electrically controlled, respectively by the first 1200 and second 2200 layers of photosensitive material. Thus, in the case where, thanks to a suitable polarizer arrangement (as illustrated hereinafter with reference to FIG. 7), the cell (s) of a shutter device 1000, 2000 according to FIG. invention is (are) in an on state when an electric field it (their) is applied (and therefore in a blocking state without an electric field), such a closure device (which does not require the implementation of several control devices because it can operate with the application of a single voltage) makes it possible to block the portion of a luminous flux, whose intensity in a plane transverse to the flow is the largest, while allowing to pass the least intense part of the luminous flux. Thus, in this case, this closure device is an anti-glare technique that selectively blocks the light emitted by an intense light source in a light flux from an observed scene including the light source and let the rest of the luminous flux.

Moreover, in the case where, thanks to a suitable polarizer arrangement (as illustrated below in relation to FIG. 6), the cell (s) is (are) in a blocking state when a electric field it (their) is applied (and therefore in a passing state without electric field), such a closure device allows to pass the portion of a luminous flux, whose intensity in a plane transverse to the flow is the more important, while blocking the least intense part of the luminous flux.

Consequently, thanks to the implementation of the layer of photosensitive material with high transverse resistivity in the shutter device 1000, 2000 according to the invention, the shutter is selectively in space and locally, contrary to the case of a conventional shutter device for which the shutter is produced by means of the use of a conductive electrode to which a uniform voltage is applied.

Thus, in the context of the visualization of an arc welding scene by a viewing camera of a welding robot, the photosensitive material allows the observation (by the visualization camera of the welding robot) of the surroundings of the dazzling source (the arc welding) and thus allows to locate it. Moreover, the setting of the first voltage 1700 (respectively first and / or second voltage (s)) at the first shutter device 1000 (respectively second shutter device 2000) makes it possible to shift the threshold value of the electronic material. optical cells of the shutter device thus making it possible to switch the shutter device spatially in the highly illuminated zone while leaving the other parts of the shutter device transparent, as illustrated by FIG.

In this FIG. 3, the light emitted by the arc 31 is imaged by means of the objective 32 of the CCD camera on the CCD sensor 33 of the CCD camera via the shutter device 1000.

Only the region where the arc is imaged is switched at the shutter device 1000, which protects the CCD sensor 33.

With reference to FIG. 4, the block diagram of a third shutter device 3000 according to a third embodiment of the invention is presented.

The third shutter device 3000 is identical to the first shutter device 1000 except that it further comprises at least two third electrodes 3001, 3002 between which are disposed a third shutter module 3100. A third source voltage 3700 delivers a third constant voltage (possibly variable), for example 10V, between the third electrodes 3001, 3002.

Of course, according to a variant of this third mode of implementation, the first and third shutter modules may each comprise a photosensitive layer.

In the context of this third embodiment, it is assumed that each of the first and third modules comprises a liquid crystal cell. The cells of the first 1100 and third 3100 modules can be made based on nematic liquid crystal or smectic liquid crystal. The third module 3100 is able to homogeneously adjust its transparency thanks to the control performed, for example, by a photodiode 3900 detecting the total light intensity. This photodiode 3900 controls the voltage applied to this third module. The first module behind the third module has a transparency that is locally controlled by the layer 1200 of photosensitive material.

The light 1800 projected on the third module produces in the photosensitive layer an image of photons which is the copy of the received light intensity. This photon image is transformed into an electron image by the voltage 3700 applied to the third module (from a threshold voltage value). This image of electrons is translated into a voltage image applied to the liquid crystals of the cell (voltage drop). This results in an anisotropic modulation of the liquid crystal by electro-optical effect.

We place in the following in the context of the first implementation mode mentioned above.

The first shutter module 1100 comprises, for example, a superposition of an optical attenuator with quasi-continuous variations and an optical shutter whose shutter and opening times are short (of the order of a few hundred pixels). microseconds). Of course, according to variants of this first mode of implementation, the first shutter module comprises an optical attenuator with quasi-continuous variations but no optical shutter or the first shutter module comprises an optical shutter but no shutter. optical attenuator with almost continuous variations. The optical attenuator comprises at least one nematic cell, whose attenuation is adjustable almost continuously.

The optical shutter comprises at least one smectic cell, whose transition times between the on state and the off state and vice versa are very short. Each nematic cell (respectively smectic) comprises for example two blades of optically transparent material (such as glass for example) between which is disposed a layer of a nematic liquid crystal material (respectively smectic) properly aligned. The nematic cells comprise at least one nematic liquid crystal, for example the liquid crystal marketed by MERCK under the reference MLC 14000-000.

According to a first characteristic of the invention, the smectic cells comprise at least one ferroelectric liquid crystal and / or at least one anti-ferroelectric liquid crystal.

An example of chiral ferroelectric smectic liquid crystal that can be used in the context of the invention is commercially available from Avantis-Sanofi France, previously Hoechst, under the trade name Félix 015/100. An example of antiferroelectric smectic liquid crystal that can be used in the context of the invention is, for example, a liquid crystal based on (S) I-methylheptyloxybiphenylyl-4-yl 4- (perfluoroalkanoyloxyalkoxy) benzoates (one could also implement (S) 1-methylheptyloxyphenyl 4- (perfluoroalkanoyloxyalkoxy) biphenylates or even a mixture of (S) I-methylheptyloxybiphenylyl-4-yl 4- (perfluoroalkanoyloxyalkoxy) benzoates and (S) 1 -methylheptyloxyphenyl 4- (perfluoroalkanoyloxyalkoxy) biphenylates) .

According to a second characteristic of the invention, the smectic cells comprise a combination of at least one ferroelectric liquid crystal and / or at least one anti-ferroelectric liquid crystal and a polymer. An example of a polymer that can be used in the context of the invention is a polymer obtained by the polymerization of a monomer that is commercially available from Merck, France under the trade designation RM257. Its polymerization is carried out by UV irradiation in the presence of a photoinitiator (Irgacure 651 from Ciba). Preferably, such an association is chosen in polymer / liquid crystal proportions such that the resulting material belongs to the families of PSFLC ("polymer stabilized ferroelectric liquid crystal") and / or PSAFLC ("polymer stabilized anti-ferroelectric liquid crystal"). These PSFLCs and / or PSAFLCs are gel type materials.

The cells are switchable between at least one on state and at least one blocking state.

Each of the nematic cells of the optical attenuator is for example powered by means of an alternating electric signal for adjusting the attenuator attenuation level.

The attenuator and shutter of the closure device are assembled as illustrated below, in connection with FIGS. 6 to 8.

FIG. 5 illustrates the continuous level 41 and the maximum level 42 of the standard operating speed according to the MIG / MAG technique implemented in the context of the welding machine.

Thus, the intensity of the arc current I may be in the continuous level 42 or in the maximum level 42.

This operating principle according to the invention makes it possible to envisage, in order to manufacture the closure device, several possible implementations of the optical attenuator and shutter from nematic and smectic cells and polarizers. Examples of embodiments according to the invention of the optical attenuator and shutter of the closure device are described below.

According to a first embodiment of a shutter device 700

(illustrated in FIG. 6) according to the first embodiment of the invention mentioned above, in order to produce the optical attenuator, a nematic cell 720 placed between crossed polarizer and analyzer (ie say between two polarizers 710 and 730 whose axes 711 and 731 are perpendicular).

Thus this nematic cell is in an on state when no electric field is applied to it, which allows the operator to see the scene when the attenuator is not powered. Moreover, the nematic cell 720 may be either a TN or STN type nematic cell (represented under the reference 722 in a conducting state without an applied electric field or, under the reference 723, in a blocking state with an applied electric field or an N-type nematic cell (shown under the reference 724 in a conducting state without an applied electric field or, under the reference 725, in a blocking state with an applied electric field).

Of course, according to variants of this first embodiment, the attenuator is produced with several superimposed nematic cells, each of the cells being in an on state when no electric field is applied to it (for example placed between crossed analyzer and polarizer ).

In order to realize the optical shutter, it is possible to have a smectic cell 740 (which may be a ferroelectric smectic cell or an antiferroelectric smectic cell) between crossed polarizer and analyzer (that is to say between a first 730 and a second 750 polarizer whose axes 731 and 751 are perpendicular).

Thus, this smectic cell 740 is in a blocking state when no electric field is applied to it, which makes it possible to ensure the protection of the optical sensor of the display camera in the event of a shutdown of the power supply of the shutter device 700 According to a second embodiment of a shutter device 800

(illustrated in FIG. 7) in accordance with the first embodiment of the invention mentioned above, in order to produce the optical attenuator, a nematic cell 820 placed between parallel polarizers (that is to say between two polarizers 810 and 830 whose axes 811 and 831 are parallel). Thus this nematic cell is in a blocking state when no electric field is applied to it, which ensures the protection of the eyes of the operator in case of failure of the power supply of the attenuator.

Furthermore, the nematic cell 820 can be either a TN type nematic cell (represented, under the reference 822, in a conducting state without an applied electric field or, under the reference 823, in a blocking state with a applied electric field) is an N-type nematic cell (shown, under the reference 824, in a conducting state without an applied electric field or, under the reference 825, in a blocking state with an applied electric field).

Of course, according to variants of this second embodiment, the attenuator is made with several superimposed nematic cells, each of the cells being in an on state when no electric field is applied to it (for example placed between parallel polarizers). In the case where n nematic cells are superimposed in order to achieve the variable attenuator, it is possible for example to use n + 1 parallel polarizers, each of the polarizers being arranged between two nematic cells.

In order to realize the optical shutter, it is possible to have a smectic cell 840 (which may be a ferroelectric smectic cell or an antiferroelectric smectic cell) between crossed polarizer and analyzer (ie between a first 830 and a second 850 polarizer whose axes 831 and 851 are perpendicular).

Thus this smectic cell 840 is in a blocking state (by aligning the stable state without an electric field applied to the axis of a polarizer) when no electric field is applied thereto, which makes it possible to ensure the protection of the sensor optics of the visualization camera in case of power failure of the shutter device 800.

In the context of each of the first (FIG. 6) and second (FIG. 7) embodiments mentioned above, the smectic cell 740, 840 can be either a ferroelectric type smectic cell (whose stable states 7421 and 7422, for a first case). , or 74210 and 74220, for a second case, with applied electric field are respectively illustrated by graphs 742 and 7420) or a smectic cell of antiferroelectric type (whose stable states 7431 and 7432 with applied electric field and stable state without Applied field 7433 are shown in Figure 743).

Thus, in the case of a smectic cell 740, 840 of the antiferroelectric type, this smectic cell is oriented so, with respect to the nematic cell 720, 820 of the attenuator, that its stable state in the absence of applied electric field 7433 is aligned with the polarizer of the nematic cell 720, 820.

According to a third embodiment of a shutter device 900 (illustrated in FIG. 8) according to the first embodiment of the invention mentioned above, the optical attenuator comprises first 920 and second 9200 nematic cells, the first cell 920 being in a blocking state when no electric field is applied thereto and the second cell 9200 being in an on state when no electric field is applied thereto. For example, the first cell 920 is placed between two polarizers 910 and 930, the axes 911 and 931 of the polarizers being parallel and the second cell 9200 is placed between two polarizers 930 and 9300, the axes 931 and 9310 of the polarizers being perpendicular.

Furthermore, the first 920 and second 9200 nematic cells may be either TN-type nematic cells (represented, under the references 922 and 9220, in a conducting state without an applied electric field or, under the references 923 and 9230, in a state blocking with an applied electric field) or N-type nematic cells (represented, under the references 924 and 9240, in a conducting state without an applied electric field or, under the references 925 and 9250, in a blocking state with an applied electric field ). Of course, one may be of a TN (or STN) type and the other of an N type.

In order to realize the optical shutter, it is possible to have a smectic cell 940 (which may be a ferroelectric smectic cell or an antiferroelectric smectic cell) between crossed polarizer and analyzer (that is to say between a first 9300 and a second 950 polarizer whose axes 9310 and 951 are perpendicular).

Thus this smectic cell 940 is in a blocking state when no electric field is applied thereto, which makes it possible to ensure the protection of the optical sensor of the visualization camera in the event of a shutdown of the power supply of the shutter 900 . Of course, according to variants of these embodiments, the shutter can be made with several superimposed smectic cells, each of the cells being in an on state when no electric field is applied to it (for example placed between parallel polarizers). In the context of the aforementioned second implementation mode, the first shutter module 1100 comprises, for example, an optical attenuator with quasi-continuous variations (for example as previously described) and the second shutter module 2100 comprises a shutter optical (for example as previously described). Of course, any combination of the aforementioned embodiments can be envisaged within the scope of the present invention. For example, the first shutter module 1100 comprises a superposition of an optical attenuator with quasi-continuous variations (for example as previously described) and an optical shutter (for example as described above) and the second module shutter 2100 comprises an optical shutter (for example as previously described).

Of course, in FIGS. 6 to 8, the individual components of the closure device are shown spaced apart and having a parallel surface, however, depending on the intended application of the closure device, these components may be plated and can for example have a curved surface.

The supply circuit of the electrodes of the closure devices of FIGS. 6 to 8 have not been represented because it is part of the general knowledge of the person skilled in the art. Of course, some transparent electrodes and some polarizers may be common to at least two cells in the context of the embodiment of a closure device according to the present invention.

Claims

An electro-optic shutter device (1000; 2000) comprising at least two first electrodes (1001, 1002; 2001, 2002) and at least one first cell (720; 820; 920, 9200) comprising a layer of a electro-optical material, where said first cell (s) being (are) arranged between said first electrodes, each of said first cell (s) being switchable between at least one passing state; , in which it transmits a light beam, and at least one blocking state, in which it does not transmit the light beam, as a function in particular of the electric field which is applied to said first cell via the first electrodes, characterized in that also comprises at least one solid layer of a first photosensitive material (1200, 2200) and a high transverse resistivity provided between said first electrodes. Electro-optical sealing device according to claim 1, characterized in that it comprises at least two second electrodes (2001, 2002) and at least one second cell comprising a layer of an electro-optical material, the said second cell (s) being disposed between said second electrodes, each of said second cell (s) being switchable between at least one on state, in which it transmits the beam light, and at least one blocking state, in which it does not transmit the light beam, depending in particular on the electric field which is applied to said second cell via the second electrodes, and in that it also comprises at least one massive layer (2200) a second photosensitive material with high transverse resistivity provided between said second electrodes. 3. Device according to any one of claims 1 and 2, characterized in that it comprises attenuation means with quasi-continuous variations of an optical signal, said attenuation means comprising at least a third cell (720 820; 920, 9200) of a first type comprising at least one layer of a first material based on a nematic liquid crystal. 4. Electro-optic shutter device according to claim 3, characterized in that the third (or) cell (s) of said attenuation means are disposed between the first electrodes. 5. Device according to any one of claims 1 to 4, characterized in that it comprises optical closure means comprising at least one (740; 840; 940) fourth cell of a second type comprising at least one layer of a second material based on a smectic liquid crystal. 6. Device according to claim 5, characterized in that said second material comprises at least one ferroelectric type smectic liquid crystal and / or at least one anti-ferroelectric type smectic liquid crystal. 7. Device according to claim 5, characterized in that the second material comprises a combination of at least one ferroelectric liquid crystal and / or at least one anti-ferroelectric liquid crystal and a polymer, said association respectively belonging to the families of PSFLCs and / or PSAFLCs. 8. Electro-optical shutter device according to claim 2 and any one of claims 5 to 7, characterized in that the fourth cell (s) of said shutter means are arranged between the second electrodes. . 9. Electro-optical closure device according to any one of claims 1 to 8, characterized in that at least one of said first and second photosensitive materials belongs to the group comprising: polyvinylcarbazole; silicon carbide. 10. Electro-optical shutter device according to any one of claims 1 to 9, characterized in that it comprises at least one photoresistor comprising at least one of said layer (s) of first photosensitive material or second photosensitive material. 11. Electro-optical shutter device according to any one of claims 1 to 10, characterized in that it comprises at least one photodiode comprising at least one of said layer (s) of first photosensitive material or second photosensitive material. 12. The electro-optical shutter device according to any one of claims 1 to 11, characterized in that said one or more electrodes are made of ITO.