EP1012637A1 - Improved telescope - Google Patents

Abstract

A telescope comprising a membrane mirror (6) and a control membrane (7) of which the edges are free while the central areas are joined together. The telescope further comprises an auxiliary folding membrane (8) and a curvature analyser (10) providing sagittal scanning and having a single screen (23)

Description

IMPROVED TELESCOPE AREA OF THE INVENTION.

The field of the invention is that of membranous mirror telescopes. PRIOR ART

French applications 94/11458, 95/07947, and 96/01132 describe, (Figure 1), a telescope 1 consisting of a mirror stage 2, a focus stage 3 and a mirror control stage 4.

The mirror stage 2 comprises a mirror membrane and a control membrane, secured by a spacer 5.

The foyer stage 3 comprises means 9 for examining the image.

The mirror control stage 4 comprises a sagittal analyzer 10.

These three stages are joined by an envelope 11 or a parallelepipedic frame and spiders 12, or by an inner pyramid frame.

For their folding, the parabolic mirror (or of another shape), and the associated control membrane are brought into contact and made quasi-plane by a succession of alternating concentric deformations, and the quasi-plane obtained is wound on itself one or more times to form a cylinder.

The control membrane 7 has conductive and semiconductor elements constituting buses or integrated circuits, and making it possible to carry electrodes to selected potentials or to circulate currents therein.

The precise shaping of the mirror and its positioning are ensured by electromagnetic fields.

The sagittal analyzer 10 consists ((Figure 2) of a perforated screen 13 perpendicular to the optical axis 14, centered on this axis at the sagittal segment 15, and movable along this axis, and which can be simulated by a stack of polarizing screens 16 with an inactive central circular area 17, and a photoelectric matrix 18 perpendicular to the optical axis and located beyond the polarizing screens with respect to the mirror.

Insulated conductors 19 or coils .20 are located at the level of the mirror stage, of the hearth stage, of the control stage, and on the envelope for securing the stages. SUMMARY OF THE INVENTION

Disadvantages. The disadvantage of folding the mirror and the control membrane as described is the difficulty of maintaining without artifice the almost flatness of the folding and its winding on itself, during orbiting.

The drawback of circular electrodes is poor optimization of the possibilities for maneuvering the membrane. Auxiliary folding membrane. To facilitate the folding of the mirror 6 and its control membrane 7, there exists, according to the invention, a preformed auxiliary membrane 8 comprising concentric undulations on which the control membrane and the mirror will be applied and which we will call auxiliary folding; we will call the optical assembly the assembly consisting of the mirror, the control membrane and the folding aid.

These undulations consist of a concentric succession of circular elements whose developed length of the generator is equal to the developed length of the generator 51 of the mirror 6, and the outside diameter equal to the diameter of the mirror.

In a preferred embodiment, each undulation of the generator has a minimum curvature.

This preformed folding aid, after unfolding, can be fixed by its periphery, with damped elastic means, at the top of the lower part of the telescope.

This fixing will ensure the flatness of the folding aid and the circularity of the top of this bottom element of the telescope.

Electrical circuits integrated into this folding aid participate in the positioning of the control membrane. Sectorization of electrical control circuits. To increase the efficiency of the electrical circuits for positioning the control membrane or the folding aid, these are sectorized.

To improve the control of the mirror 6, the invention improves the control of the control membrane 7, the mirror membrane interactions, and the sagittal analyzer 10.

The control of the membrane 7 is improved by ensuring the circularity of its periphery 21 made reflective, using the sagittal analyzer 10.

Membrane-mirror interactions are improved by introducing electromagnetic effects and radiation pressure effects.

The damping of the vibrations of the membrane is improved, in the case of a significant difference in the surface masses of the membrane and of the mirror, by introducing a second membrane 22 with a surface mass close to that of the first, and whose mechanical properties are first with those of this first membrane.

The sagittal analyzer 10 is improved by introducing successive independent circular central screens and by adapting the diameters of the central screens to the diameters of the diffraction spots or of their rings.

The sagittal analyzer is also improved, (FIG. 3), by replacing the multiple superimposed screens with a single screen 23 with multiple concentric annular polarizing zones 24.

The direct control of the membrane is improved by alternating magnetic fields causing eddy currents in the reflective conductive deposit of the mirror.

The performance of the telescope is improved (FIG. 4), by allowing it, thanks to a geostationary deflection mirror 25, to perceive the whole of the sky. BRIEF DESCRIPTION OF THE FIGURES Figure 1: telescope 1. Figure 2: sagittal analyzer 10. Figure 3: single screen sagittal analyzer. Figure 4: geostationary mirror.

Figure 5: illuminating beam of the sagittal analyzer. Figure 6: section of the control membrane 7. Figure 7: action matrix of the control membrane. Figure 8: polarizing screen with multiple central rings. Figures 9a and 9b: circular electrodes of the single polarizing screen in two different states. Figure 10: annular photoelectric matrix. Figures 11 and 12: groups of pixels.

Figure 13: illuminating arc or segment in groups of pixels.

Figure 14: annular slot of the single polarizing screen.

Figure 15: knife screens.

Figure 16: central knife screens.

Figure 17: star analyzer.

Figure 18: sagittal star analyzer.

Figure 19: quasi-plane mirror.

Figures 20, 21 and 22: weakly convex mirrors.

Figure 23: mast end.

Figure 24: Herschell assembly.

Figures 25 and 26: convex mirrors.

Figure 27: sections of the mirror 6 and the folding aid 8.

Figure 28: principle of folding.

Figure 29: generator element of the folding aid 8.

Figure 30: generator element with minimum curvature.

Figure 31: overall section of the optical unit.

Figure 32: detail of the connecting rings on a ball joint.

Figure 33: bi-cylindrical winding.

Figure 34: mono-cylindrical winding.

Figure 35: meeting of the folded optical unit and the mirror stage.

Figure 36: magnetic control windings.

Figure 37: sectored windings.

Figure 38: sectorization of the control membrane.

DETAILED DESCRIPTION

Basic form of the generator of the folding aid.

FIG. 27 shows the generator 51 of a mirror 6 and the generator 52 with angular connection of a folding aid 8.

The generator 52 of the folding aid 8 consists of the succession of orthogonal projections of direct elements 51a and 51b inverted from the generator 51 of the mirror 6 cut by planes 53, equidistant and parallel to each other, perpendicular to the axis optic 14 of the mirror, and separated by a distance 54.

In practice, the angular connection implies unacceptable deformations of the mirror or of the control membrane at the level of this angular deformation, but it makes it possible to better understand the principle of the folding of the membrane.

According to the invention, in FIG. 29, the connection elements 55 are arcs of circles of radius R, centered on the straight lines 56 projecting the generator elements 51a and 51b.

The radius of curvature R and the position of the centers of curvature of the arcs of the circle constituting the connecting elements 55 must be such that the sum of the lengths of the different elements of the elementary generatrix constituted by the high circular arc AB, the arc of low circle CD, and the quasi-parabolic element BC with tangential connection with the two arcs of a circle, either equal or slightly greater than the length of the corresponding element 51a or 51b of the generator 51 of the mirror.

On a generator element 52a or 52b of the folding aid 8 slightly longer than the corresponding generator element 51a or 51b of the mirror, the mirror may be applied with a slight tension favorable to correct positioning, without this generating large-scale radial deformation. Ripples with constant pitch. In another embodiment of the invention, the generator 51 is cut by equidistant lines parallel to the optical axis 14, generating generator elements 51a and 51b of decreasing height from the periphery towards the center. Simultaneous or successive folding of the mirror and the control membrane.

The folding of the control membrane is necessarily done before the folding of the mirror membrane, or simultaneously.

The generator 51 of FIG. 27 can represent the control membrane, the mirror membrane, or both simultaneously. Principle of folding a membrane. (Figure 28) The membrane to be folded is placed on the folding aid 8 by a vertical displacement parallel to the optical axis 14. According to the invention, the pressure above the membrane to be folded is greater than that existing below. , so as to cause tension in the membrane to be folded in the direction of its concavity.

This is obtained, in a first embodiment according to the invention, by closing with a tight cover the volume formed by the concavity of the membrane to be folded, and by creating an overpressure inside this enclosure, the periphery of the membrane to fold and the lid being held by a rigid ring that can move vertically.

In a second embodiment according to the invention, the volume of the concavity of the mirror is filled with a liquid which ensures the overpressure.

Firstly, the first generator element 51a is brought into contact with the corresponding generator element 52a of the folding aid 8 of which it has the shape.

This is done without deformation of the membrane to be folded.

As the closing movement continues, the membrane slightly stretched by the overpressure is applied to the folding aid along the curvature of the first connection element 55. Then the membrane to be folded is gradually deformed to be applied to the reverse element generator 52, until it reaches the second connecting element 55.

During the descent of the membrane to be folded, outside a circular folding zone 57 which takes place on the inverted generator element 52, the free remainder of the membrane to be folded practically retains its original generator and the element generator 51a following is substantially parallel to the corresponding element 52a of the folding aid 8 on which it is applied.

The folding cycle is then repeated until the entire membrane to be folded is applied to the folding aid 8. Folding aid with minimum curvature.

To minimize the bending stresses, each elementary generator of the bending aid consists of two arcs of circles of the same radius R, connected by an inflection point BC.

These arcs of circles are the extensions of the connection elements 55 of FIG. 29, which connect to each other by eliminating the almost linear part.

We see, Figure 30 on a very enlarged vertical scale, an original element of inverted generator 52b, and in solid line two arcs of circles of the same radius R constituting the optimal generator with minimum curvature whose length is the same as that of the reverse generator 52b.

The arcs in dashed lines show that there is always at least one such arc of a circle, between the arc too small and the arc too large.

These arcs of a circle are centered on the straight lines 56 of projections of the ends of the generator element 51b of the mirror; they can therefore be connected to the arcs of the adjacent generatrices, centered on these same projection lines, but of different radii. Ease of manufacture.

For reasons of ease of manufacture of the folding aid, the generator elements, direct or inverted, can be replaced, while retaining the same developed length, or a slightly greater length, by a particular curve whose maximum curvature n 'does not cause permanent deformation of the mirror. Orders of magnitude.

A relative elastic elongation of 1/1000 allows, for a film 10 microns thick, a radius of curvature of 5 mm.

The slope of the periphery of a mirror open at F 1 is 1/4; planes at a distance of 1 mm cut generator elements 4 mm wide at this periphery, the arcs of a circle of minimum curvature having a radius of approximately 5 mm.

The folding aid 1 mm thick must have, with the same yield strength, a minimum winding radius of 500 mm. Maintained by depression.

According to the invention, the air is extracted between the membrane to be folded and the folding aid 8. so as to keep the membrane folded against this folding aid, and allow the cylindrical winding of the assembly without separation of the folded membrane. Maintenance by electrostatic attraction.

In another embodiment of the invention, the folded membrane is secured to the folding aid by electrostatic attraction. Separation of the folded membrane and the folding aid.

After unfolding of the cylindrical winding, the folding aid regains its pseudo flatness. Electrostatic separation.

According to the invention, the folding aid has centered circular conductors which can be brought individually to a selected potential.

By setting the folded membrane to a certain potential, and setting the first peripheral circular conductor of the folding aid to the same potential, the resulting force will draw the periphery of the folded membrane away from the folding aid.

By successively loading the various circular conductors of the folding aid 8, the membrane will gradually be moved away from it.

Under the effect of its electrical charges, the membrane will resume its paraboloidal shape as it is freed from the folding aid. Separation by gas insufflation. In a particular embodiment, the folding aid is porous or micro-perforated, it is doubled on its dorsal surface by a waterproof film.

By introducing a gas between the film and the folding aid, a layer of gas appears between this folding aid and the membrane, causing their separation. Separation by acceleration.

By accelerating the folding aid perpendicular to its surface, the membrane is helped to return to its original shape under the effect of electrical charges. Linking rings. (Figures 31 and 32)

The various membranes of the optical unit, mirror 6, control membrane 7 and folding aid 8, have a central opening, and are provided, at this opening, with rigid connecting rings 58, 59. 60 allowing the joining of these membranes inside the mirror stage of the telescope. Rigid operating elements. (Figures 33 and 34)

To allow the operation of the folding aid and the membranes which are joined thereto, there is, according to the invention, a diametrical linear reinforcement 61 of the folding aid ensuring its rigidity along the diameter parallel to the axis of l cylindrical winding and dividing this folding aid into two semicircles.

In another embodiment, according to the invention, there is a linear diametral rigid element 62 integral in its middle with the central rigid ring of the folding auxiliary, slightly longer than the diameter of this auxiliary, and around which that - it is rolled up.

In another embodiment, there is a second rigid linear element which can be arranged crossed with respect to the first, after unwinding of the folding aid.

In another embodiment, there are, to facilitate the winding and unwinding of the folding aid, multiple linear dorsal reinforcements parallel to the reinforced diameter. Rigidity and flatness of the folding aid. (Figure 31)

To restore the folding aid 8 to its pseudo-flatness and ensure its rigidity, there is, according to the invention, at its periphery an inflatable and rigidifiable circular tube 63, and on its dorsal face symmetrically arranged inflatable radial tubes and rigid iables.

In another embodiment, there are inflatable and rigidifiable tubes perpendicular to the diametrical reinforcement, and which allow their swelling to unwind the folding aid Cylindrical windings. (Figures 34 and 35)

In a first embodiment, the two half-membranes are wound separately to give two cylinders 64 and 65 parallel to the linear rigid element.

In a second embodiment, the cylindrical folding is carried out in two stages.

Firstly, one of the half-membranes is wound above the linear rigid element 62 to form a cylindrical winding parallel to this rigid linear element and external to it, and secondly, the other half-membrane is wrapped around the first cylindrical winding and the rigid element linear.

Anisotropy of the folding aid.

In order to give maximum strength to the folding aid in the direction of the orbiting constraints, and optimal flexibility in the direction of the cylindrical winding, there is, according to the invention, an anisotropic arrangement of the fibers of the material. composite component. Square folding aid.

In order to facilitate the maintenance of the folding aid during its orbiting, it has the shape of a square.

In this way the folding aid can be simply suspended, which eliminates possible buckling problems.

A circular set of perforations facilitates cutting of the circular central part when the folding aid is unrolled; this cutting is obtained using a tool fixed on the rigid linear element secured to the connecting rings, and in front of which the folding aid rotates.

Original attachment of the bottom element of the telescope and the folding aid.

With the aim of not having to reunite in space the optical unit and the mirror stage, this optical unit is definitively secured to the mirror stage before its orbiting.

FIG. 35 shows the union of a bi-cylindrically wound optical unit and a bottom element 66 folded by telescopic invagination and tangential winding. Magnetic control fields. Figure 36.

The conductive surface of the mirror constitutes a screen for the magnetic fields generated by coils 20 or 67 located on the hearth stage, or the coils 68 located a short distance above said mirror.

Conductors 69 located at the periphery of the conductive surface of the mirror will interact with these windings 20, 67 and 68. and allow control of the shape and the position of the mirror.

These windings 20, 67, and 68 will also interact with the conductors of the peripheral part of the membrane possibly external to the reflecting surface of the mirror.

A coil 20 of the enclosure of the mirror stage, or a centered circular coil 70 of the casing of the telescope, located under the mirror, will have an action on the conductors 71 linked to the control membrane 7, or the conductors 72 linked to the folding auxiliary 8. Sectorization of electrical circuits. Figure 37.

In order to locate the magnetic fields controlling the shape and position of the control membrane, the electrical circuits are partly radiating and partly shielded.

Each turn of the centered circular windings of the telescope casing is cut symmetrically into several elements isolated from each other and able to be supplied individually.

Figure 37 shows in plan and elevation such a turn. The small circles 73 symbolically represent the shields 74 eliminating the influence of the conductors supplying the elements 75 of the turns.

Figure 38 shows the 76 sectorized circular turns of the control membrane or the folding aid, and the shielding 77 of their radial feeds.

According to the invention, there are radial conductors which can be supplied individually, and whose supply is made by shielded conductors.

In a particular embodiment of the invention, the number of radial conductors of the control membrane differs at least by one unit from that of the folding aid.

This makes it possible to generate a torque between the membrane and the auxiliary, whatever their relative position.

In a particular embodiment of the invention, there are radial conductors on the dorsal face of the mirror, making it possible to generate a torque between this mirror and the control membrane or the folding aid. Imprint layer.

According to the invention, the mirror membrane is composed of several layers of different materials.

In order to take the best possible imprint of the rotating liquid, the first layer deposited on this liquid is made up of small molecules.

Once this layer has solidified, a composite layer comprising long fibers is deposited.

A final layer, of the same composition as the first layer, will be deposited to equalize the surface, and to avoid an asymmetry inducing deformations by differential expansion. Turning over the mirror membrane.

In order to have the best surface as a reflecting surface, the mirror membrane is inverted, the convex surface becoming the concave surface. Peripheral control of the control membrane. (Figure 1)

In order to allow the control of the periphery of the control membrane by the sagittal analyzer and to ensure its circularity, the diameter of the membrane is greater than that of the mirror, and, according to the invention, the part 21 of the membrane protruding from the mirror is reflective.

A circular screen 26 linked to the envelope of the telescope, and of an inner diameter smaller than that of the mirror, is placed above the mirror in such a way that the peripheral reflecting ring of the membrane cannot receive photons parallel to the optical axis of the telescope, but that the light beam from the sagittal analyzer can illuminate it.

The light beam of the sagittal analyzer is such, according to the invention, that the mirror or the reflecting ring of the control membrane can be illuminated individually.

This is obtained, in a particular embodiment, (FIG. 5), by a polarizing screen 27 intercepting the beam and having two individually polarizing zones.

The first zone 28 is a central circular zone such that when this zone is transparent, the mirror is illuminated and the reflecting ring of the control membrane is not illuminated, and the second zone 29 is a peripheral annular zone such that when this area is transparent, the reflecting ring of the control membrane is lit, and the mirror is not lit. In this way the illumination of the peripheral ring of the control membrane located behind the mirror does not disturb the examination of the shape of the mirror by the sagittal analyzer, and vice versa. Strain gauges.

In order to roughly control the restitution of the original shape of the control membrane, there are strain gauges on this membrane. Membrane with reflective surface.

In a particular embodiment of the invention, there is no independent mirror; the upper surface of the single membrane is reflective. Shielding. (Figure 6)

The face of the membrane facing the mirror has action electrodes 30 on the mirror, and the other face has action electrodes 31 allowing control of the shape and positioning of the membrane itself.

Electromagnetic shielding 32 exists in the membrane between the two faces so that the magnetic fields controlling the membrane do not induce eddy currents in the conductive surface of the mirror. Electric voltage of the mirror.

In order to stretch the mirror, it is brought to a certain potential.

This assembly is placed in the conductive envelope of the telescope.

There is an image effect between the charged mirror and the envelope, and a reciprocal attraction modifying the shape of the mirror.

By having electrodes 33 at the focal point and on the casing of the telescope, it is possible to create a parabolic equipotential on the surface of the mirror which, under these conditions will not be deformed. Forced vibrations of the membrane and the mirror.

In order to remove any non-radial vibrations from the membrane or the mirror, these are subject to forced radial vibrations caused by the connecting rings or by the membrane's action electrodes.

In this way the local faults in the perfect paraboloid will be revolutionary and easier to integrate into a correction program.

On the other hand, these radial undulations behave like stiffening folds accelerating the obtaining of circularity. Membrane with fractal distribution of physical properties.

In order to prohibit the establishment of parasitic waves affecting the whole of the membrane and to damp the waves originating locally, the local mass of the membrane, its local thickness, or its local physical properties are distributed in a plurality of zones where these properties are, from one zone to another, primary between them.

In each of the zones of this first plurality also exist a second plurality of zones of the same type, and so on up to zones where there can practically be only one natural frequency.

In this way the zones having neighboring natural frequencies, from a certain order, are not contiguous, and 7/28469 10 PC17FR97 / 00189

this reduces the possibility of coupling between several zones. Double control membrane. (Figure 1)

In the case where the mirror has a much lower surface mass than that of the membrane, it is not possible to dampen the parasitic vibrations or movements of the membrane by a reciprocal action.

According to the invention, there exists a second control membrane 22, with a surface mass close to that of the first, and whose mechanical properties are first with those of this first membrane.

This second membrane has all the features of the first, and is located at a distance such that the interactions between the mirror and the first membrane can exist between these two membranes.

These two membranes have different and prime natural frequencies between them.

The control of their mutual distance makes it possible to maintain this constant distance and therefore to dampen and prohibit all vibrations of the two membranes, these vibrations being unable to be in phase because of the raw mechanical properties between them. Thermal control of the mirror.

Unequal temperatures between different points on the mirror can lead to deformations of this mirror.

In order to standardize the temperature of the mirror, thermometric elements and heating elements exist on the control membrane.

In a particular embodiment of the invention, the central computer determines the temperature differences of the mirror by analyzing its shape.

In another embodiment, the mirror image is formed on a photoelectric matrix sensitive to infrared. Raw properties between them.

In order to minimize the dynamic reactions between the mirror and the membrane, their mechanical characteristics are primary to each other. Tolerance to meteorites.

In order to reduce the sensitivity of the telescope to meteorites, various elements are redundant, bus, local processors, strain gauges, electromagnetic circuits, without this list being limiting. Local action matrices with multiple electrodes. (Figure 7)

In order to reduce the work of the central unit, to reduce the electronic connections and to increase the global speed of treatment, each semiconductor assembly integrated into the control membrane, and called local processor 34, controls the potentials of a plurality of electrodes 35, or linear 36 or circular inductor elements 37 united in a local action matrix 38.

The local processors 34 of the contiguous local action matrices are interconnected so that the voltages applied to the boundary electrodes, or the currents flowing in the boundary circuits obey the same law in the two matrices, to produce identical potentials, or gradients without discontinuity. Local mirror-membrane distances. According to the invention, the local mirror-membrane distances are determined from local accelerations of the mirror under the effect of electric fields or magnetic fields whose action depends on the distance.

The sagittal analyzer measures the local relative positions of the mirror at known time intervals.

The central unit deduces from this the local displacement speeds of the mirror and its local accelerations.

In a particular embodiment of the invention, the central unit, knowing the local potentials or the local inducing currents, deduces the local mirror-membrane distances.

In another embodiment of the invention, this determination of the local mirror-membrane distances is made by the local processors. Reciprocal shaping of two membranes.

The distances between two identical and almost parallel control membranes are known as soon as we know the shape of the membranes and the distance of any two homologous points.

Two control membranes can be positioned relatively to each other by their only means of control and interaction.

These two membranes can establish their local mutual distances in such a way that they resume their natural form of paraboloid of revolution.

These dishes will then be centered on the optical axis if their central rings are.

Measurement of the mirror-membrane distance by electromagnetic coupling.

We know that we can detect the movements of a conductive body by the eddy currents induced by a variation of magnetic flux, and that, when we know the conductive properties of this body and the characteristics of the magnetic field, we can determine the distance between this body and the magnetic field generator.

According to the invention, turns 37 situated on the membrane, on the side of the mirror, are supplied by a device capable of detecting the variation of their inductance and of deducing therefrom the distance, or the variations in distance, between the mirror and the membrane.

According to the invention, when this distance detector is operating, an electrostatic return field is applied to compensate for the distance pulse generated by this distance measurement. Eddy currents; damping of the mirror. (Figure 7)

The local action matrices on the mirror have electrodes with electrostatic action 35, and circular electrodes 37 with magnetic action.

The magnetic fields created by these circular electrodes create eddy currents in the conductive surface of the mirror, either when they are established or, once they are established, when the distance between mirror and membrane varies.

These established currents slow down the relative mirror-membrane movements and combine their action with the fields produced by the conductive elements and the windings located above the mirror.

In a particular embodiment of the invention, the magnetic electrodes and the electrostatic electrodes are separated.

In another embodiment, they are combined. Balance between an eddy current repulsion and an electrostatic attraction.

It is known that the eddy currents generated in a conductive body by a variable magnetic field create a repulsive force tending to distance the conductive body from the source of the variable magnetic field.

According to the invention, a plurality of inductive turns 37, single or multiple, controlled by the local processors, and united in local matrices, generate variable magnetic fields repelling the mirror.

This repulsive action is associated with attractive electrostatic forces generated by the potentials of electrostatic electrodes associated with these turns, and also controlled by the local processors.

The combination of these two antagonistic actions allows, according to the invention, the control of the mirror-membrane distance with a constant sign potential.

In a particular embodiment of the invention, ferromagnetic cores are located inside the electromagnetic action turns. Positioning by eddy currents only.

In a particular embodiment of the invention, a coil 20 of the hearth stage, or located above this hearth stage, generates a variable electromagnetic field.

The conducting mirror is repelled by the eddy currents generated by this field.

There are antagonistic actions between the eddy currents due to this field and those due to the multiple turns 37 of the control membrane. Positioning by radiation pressure of laser diodes.

We know that there are surface laser diodes. whose thickness does not exceed two microns, and whose yield is high.

These laser diodes are particularly suitable for integration into the control membrane during its manufacture, on the side looking at the mirror.

The emissive surfaces can be of any shape and they can form an almost continuous emitting matrix, the surface not occupied by one emitting having to be sufficient to supply the surface elements.

The advantage of the radiation pressure of such diodes to repel the mirror, is that their action is independent of the distance, and that their field of action is well located.

According to the invention, there exist, on the surface of the control membrane looking at the mirror, successive deposits of conductive, semiconductor and insulating bodies, organized according to the prior art in laser diodes emitting coherent light perpendicular to the membrane. , towards the mirror.

According to the invention, these laser diodes are combined into action matrices controlled by local processors which establish Uniform transmit power fields, or transmit power gradients.

This is obtained either by controlling the voltages and currents, or, according to the invention, by controlling successions of transmission times.

Given the high number of individual diodes, there are, according to the invention, secondary local processors dependent on primary local processors which receive their instructions from the central unit.

The high number of action points on the mirror allows the use of a very fine membranous mirror. Protection of the hearth by vibration of the mirror.

It is known that space optical systems are generally provided with means which prohibit the direct exposure of the mirror to solar radiation.

In particular, Hubble has a cover.

Such a device is difficult to implement in a telescope of the type described here.

There is, according to the invention, a control program deforming the membranous mirror so as to make it almost diffusing.

In a particular embodiment of the invention, the mirror is animated by centered circular waves moving radially.

In another embodiment, there is a set of standing waves.

The advantage of such a system is that it is naturally available and very quick to implement.

Simultaneously, according to the invention, the optical unit tilts so that possible focusing cannot occur in the environment of the hearth, and this hearth itself is closed by a reflective cover. Calibration of the sagittal analyzer stored in permanent memory.

To compensate for any manufacturing defects and integrate diffraction phenomena, the sagittal analyzer is calibrated on a parabolic mirror, for example a rotating liquid mirror, and a model of sagittal exploration is stored in a permanent memory.

In a particular embodiment, a centered annular slot, of variable diameter, moves close to the surface of the liquid.

When checking a mirror, the data stored in memory is used to interpret the data provided by the sagittal analyzer. Polarizing screens with variable central range. (Figure 8)

In order to facilitate the search for the diffraction spot, the superimposed polarizing screens 16 of the sagittal analyzer have in their center circular rings which can be activated and deactivated individually so as to modify the diameter of the continuously transparent central zone. Diffraction spot diameters.

By traversing the sagittal segment, the sagittal analyzer tests successive rings of the mirror.

These rings have a variable diameter from the useful inside diameter to the outside diameter, and the diffraction spots therefore also have a variable diameter of one end to end of the sagittal segment.

According to the invention, the central rings of the polarizing screens have a diameter close to the diameter of the diffraction spot corresponding to the goint of the sagittal segment, or a diameter close to the diameter of the first ring or of one of the following rings accompanying this spot, so as to be able to use one of these rings as a means of control in the event that a ring of smaller diameter cannot be made correctly. Knife screens. (Figure 15)

The central opening of the polarizing screens determines the fineness of the conical sheet reaching the photoelectric matrix, apart from the diffraction phenomenon.

When this central opening is of the order of magnitude of the diffraction spot, the slightest decentering or lack of circularity of the latter will result in a large variation in illumination of the light ring formed on the photoelectric matrix.

The inner edge of the central screen is illuminated by the light beam from the mirror, and diffraction phenomena are superimposed on the geometric variations in illumination; they can lead to improved measurements.

In Foucault's method, the "knife", or mobile screen intercepting light rays, can pass exactly through the optical axis, which is not the case with the central screen which surrounds this optical axis.

To combine the advantages of the central screen and the knife, there are, according to the invention, polarizing screens 39, called knife screens, associated with annular screens, and made up of two adjoining independent zones whose rectilinear border passes through the optical axis of the sagittal analyzer, and which can be alternately or simultaneously transparent.

To determine the optical axis, two screens of this type are associated, according to the invention, so that the borders are orthogonal.

In a particular embodiment of the invention, an optical system divides the converging beam from the mirror into two converging beams illuminating two photoelectric arrays, and the knife screens are arranged on one of these beams. In a particular embodiment of the invention, the knife screens exist at the center of the annular openings (FIG. 16). Single polarizing screen with concentric annular zones. (Figures 3 and 14)

The simulation of the displacement of an opaque screen pierced with a central hole centered on the optical axis can be performed by a single complex polarizing screen 23. (Figure 3)

According to the invention, there exists, in the vicinity of the sagittal segment, between this segment and the mirror, or between this segment and the photoelectric matrix, or simultaneously at these two locations, a circular polarizing screen 23 centered on the optical axis 14 and perpendicular to this optical axis.

This screen, according to the invention, consists of a plurality of polarizing rings 24 individually controllable and centered on the optical axis.

When one of these polarizing rings 24 is only transparent. the screen only lets through a thin light cone, the apex of which is on the sagittal segment.

The radial displacement of the rings 24 made transparent allows the exploration of the sagittal segment by the top of the cone.

To allow optimal exploration of the sagittal segment, the polarizing rings have the practically practicable minimum width, and the width of the annular slot is determined by the transparency of several contiguous rings.

To accelerate the exploration of the sagittal segment, several transparent non-contiguous rings can exist simultaneously while keeping a sufficient radial distance between them so that the diffraction phenomena accompanying each light ring on the photoelectric matrix are very distinct and separate, for each transparent ring of the polarizing screen. Meniscus screen.

In a particular embodiment of the invention, the screen with multiple rings is not planar but has the shape of a thin spherical meniscus with parallel faces whose radius of curvature is such that its center of curvature is in the vicinity of the middle of the sagittal segment.

In this way the light rays will be almost perpendicular to the surface.

In another particular embodiment, the thin meniscus with parallel faces is a paraboloid of revolution arranged so that the light rays are perpendicular to its entry and exit surfaces.

The different annular screens must be supplied i ndividually.

The arms of the spiders supporting the control stages of the mirror and the focus determine unused areas of the mirror.

According to the invention, the annular screens are supplied from one or more spokes arranged to coincide with the arms of the spiders. Annular screens. (Figure 9)

The electrodes 24 of the polarizing screens are necessarily separate, and this interval does not intercept the light rays.

According to the invention, to eliminate this defect, the polarizing screens are doubled, either on two different supports, or on the two faces of the same support, or on two levels superimposed on the same face.

The electrodes of these two screens mutually cover the inter-electrode spaces of each.

The non-activatable spaces are incorporated into the exploration of the screen by the annular slot.

This annular slot moves by successive activations or deactivations of the elementary electrodes bordering each lip.

The minimum annular slot corresponds to the space between the electrodes, but in this case there exists between two successive minimum annular slots an opaque ring which is the overlap area of two successive screens.

Assuming the overlap of two successive electrodes of the two associated screens equal to the space separating two successive electrodes of the same screen, and therefore the width of an electrode equal to 3 times the inactive space we see that the pitch of the screen will be double this inactive space. (Figures 9a and 9b) Diffraction of the annular gap.

The value of the desirable diffraction determines the width of the annular slot which will be greater than the width of an elementary screen.

The displacement step, associated with the radial separating power of the photoelectric matrix, conditions the separating power of the sagittal analyzer at the level of the mirror.

An exploitable step of 1 micron roughly corresponds to a separating power of 1 mm on a mirror with 48 meters of average radius of curvature and 24 meters in diameter. Purpose of the sagittal analyzer.

The purpose of the sagittal analyzer is to obtain a paraboloid of revolution.

Practically, the sagittal analyzer must center on the optical axis the diffraction spot of a ring of the mirror, and put it in its place on the sagittal segment.

It must therefore be optimized to center this diffraction spot, and to measure the diameter of the illuminated ring of the photoelectric matrix, corresponding to the studied ring of the mirror. Photoelectric annular matrix. (Figures 10, 11, and 12)

Matrices with orthogonal rows of square or rectangular pixels are not particularly suitable for the study of centered annular figures.

If a narrow rectilinear or quasi-rectilinear light zone moves or deforms inside a row of pixels, these pixels do not detect this displacement or this deformation.

In order to adapt the photoelectric matrix to control the centered annular illuminations, the final object of the sagittal analyzer, the photoelectric matrix 18 is, according to the invention, annular.

To improve knowledge of the exact shape of the centered annular illumination, the pixels arranged in concentric rings are, according to the invention, triangular 40 and parallelepipedic 41.

In a particular embodiment of the invention, the pixels are grouped in consecutive sequences of two head-to-tail triangles and of a parallelepiped. (Figures 11 and 12)

The dimensions are such that two consecutive rings have either the same number of sequences or differ by an integer number of sequences.

The advantage of such an arrangement is that it detects the movement of a thin illuminating ring, or the edge of an illumination, included in the same ring of pixels, by measuring the differential illuminations of two head-to-tail triangles, the rectangular pixels giving the average value of the illumination.

The radial separating power of a single ring of pixels is necessarily better than the height of a pixel.

Whereas, with a matrix with square pixels, it is only by smoothing a histogram that we obtain the distribution of the illumination, with this arrangement we will know in each pixel, and prior to smoothing, the point precise of the average value of its illumination. This allows an improvement in the knowledge of the lighting inside the ring, and of the shape of the ring.

This arrangement makes it possible to detect very small radial or tangential anomalies which would go unnoticed with a rectangular matrix. Control matrix. (Figure 5)

To take account of variations in the illuminating beam of the sagittal analyzer, a photoelectric matrix 42, identical to that of this analyzer, is placed on a branch of the illuminating beam. Entering a star.

When the quality of the mirror is sufficient, a star is seized, on the optical axis or outside, at the center of an annular opening behind which there is, at a certain distance, an annular matrix (Figure 17).

When the mirror is perfect, and the star on the optical axis, the matrix is uniformly illuminated; if it is not perfect, the high radial separating power of the matrix makes it possible to go back without any artifice to its real form.

If the star is paraxial, the parabolic mirror gives an imperfect diffraction spot, whose imperfections are detected by the annular matrix.

This controls the shape corrections to be given to the mirror, while preserving its symmetry of revolution.

In this way, the quality of the image will be improved on a ring centered on the optical axis, and the surface of this improved ring may be much larger than the circular image area acceptable accepting originally the optical axis.

In another embodiment, the star is captured in a sagittal analyzer.

By radially arranging (FIG. 18) a plurality of star capture devices, it is possible to give the mirror the shape corresponding to a given image quality in a given field, by combining the information given by the star analyzers, and the sagittal mirror analyzer.

If the telescope has an image transporter, this can be a membranous mirror, and the information collected on the secondary image is associated with that given by the sagittal analyzers of the two mirrors. Improvement of interf erential curvature analyzers.

In the prior art, the photoelectric matrix is simultaneously illuminated by a beam coming directly from the light source, and by a beam coming from the same source and reflected by the mirror.

In this way there is formation of interference on the photoelectric matrix.

This system is improved, according to the invention, by using the annular slit screen of the invention, which selects the interfering conical sheet. Correction of radial aberrations.

We know that the images given by simple optical systems, and in particular by parabolic mirrors, are marred by increasing aberrations with incidence, for example the coma and distortion.

An annular matrix with triangular pixels is particularly suitable for the electronic correction of such aberrations.

Indeed, the coma or the distortion being zero in the center and increasing with the radius, the computer processing ring by ring, and pixel by pixel, can simply take into account these aberrations to eliminate the effects, from rings to rings.

To obtain this result, according to the invention, each optical system is accompanied by a read-only memory in which is stored a model of the aberrations which it is desired to correct.

This model, according to the invention, is obtained by forming the image of suitable targets on an annular matrix, or by the only calculation.

This stored information is associated with the data of the matrix, and the correction is made during the reading or delayed. Improved rectangular photoelectric matrix. (Figure 13)

It is possible, according to the invention, to improve the capacity of rectangular matrices to read circular images by replacing square or rectangular pixels by groups of triangular and parallelepiped matrices similar to those of the annular matrix. (Figure 13)

We see that the displacement of an arc or of a rectilinear segment contained in a row of square or rectangular pixels will not be detected, whereas it will be detected and evaluated if the pixels are in groups of two head-to-tail triangles and of a parallelepiped, whether this movement is transverse or longitudinal. Annular zones for independent readings.

A plurality of non-contiguous rings simultaneously transparent in the annular screen makes it possible, according to the invention, to decompose an annular photoelectric matrix into several annular zones which will be read simultaneously, and to entrust the analysis of these zones to different electronic units. .

In another embodiment of the invention, the photoelectric matrix is broken down into several independent angular sectors.

Synchronous exploration of the photoelectric matrix and the sagittal segment.

In the case where the photoelectric matrix has a concentric annular arrangement of pixels, the exploration of this matrix by the conical sheet can be done at the same time as the reading of successive rings of pixels, which optimizes the amount of information to be processed. .

This allows faster exploration of the sagittal segment and therefore better control of the mirror. Relocation of the light source.

By moving the light source on the optical axis, the sagittal segment is simultaneously moved on this axis.

A screen pierced with an annular centered hole is then arranged, according to the invention, so that the sagittal segment moves in the central opening of the screen.

In a particular embodiment of the invention, the screen is polarizing, and the central opening consists of a plurality of independent polarizing rings, so as to adapt the diameter of the central opening to that of the diffraction spot.

In a particular embodiment there are knife rings in the vicinity of the screen, or only in the central part of the screen.

Maps of distances, speeds, accelerations and slopes of the mirror.

The central unit has, according to the invention, maps of the local mirror-membrane distances, local accelerations, local speeds, and local slopes. Local measurement points. Orders of magnitude.

The number of local measurement points necessary for checking the mirror depends on the elastic modulus of this mirror.

Indeed, this modulus of elasticity determines the maximum deformations that can be produced locally on the mirror by the action of the elementary electrodes of the local control matrices or by parasitic vibrations.

Since the voltages used by the semiconductors are generally less than 5 volts, the local distances are between a few tenths of a millimeter and a few centimeters.

The optimum is a local distance less than a centimeter, allowing elementary electrodes in limited numbers, and satisfactory accelerations.

Lightening of the support of a terrestrial telescope with a membranous mirror.

To exert an electrostatic action liable to levitate an exemplary membranous mirror 10 microns thick, with voltages less than 5 volts, it is necessary that the membrane-mirror distance be of the order of tenths of a millimeter.

This supposes that the rigid support receiving the mirror does not undergo greater deformations.

In the case of a large size, this constraint results in a high weight of this support.

To reduce this stress, by increasing the acceptable deformations of the support, the control membrane is integrated into a thin meniscus whose shape is ensured by jacks of the prior art.

The control of this shape is made, according to the invention, by measuring the mirror-membrane distance. Deflection mirror associated with a terrestrial telescope. (Figure 4)

The roundness of the earth prohibits a telescope located in one hemisphere from seeing all objects visible from the other hemisphere.

In order to allow a total observation of the sky, there is, according to the invention, a reflecting mirror 25 in geostationary orbit returning to the telescope the light rays coming from invisible objects directly from the telescope. Self-winding of the folding aid.

In a particular embodiment of the invention, the shape at rest of the folding aid is that corresponding to a double cylindrical winding.

The inflatable tubes arranged, according to the invention, on the concave face of the windings, allow the unwinding of the auxiliary and its rewinding. After the deployment of the mirror and the control membrane, the folding aid rewinds so as to minimize the occultation of the mirror.

In another particular embodiment of the invention, the folding aid can be separated from the optical unit. Flat membranous mirror. (Figure 19)

We know that a parabolic mirror gives a light source placed at its focal point a beam parallel to its optical axis.

If this beam meets a plane mirror perpendicular to its direction, it is returned on itself and converges towards the source located at the hearth, and which gave birth to it.

If the plane mirror is perfect, the image will be reduced to a diffraction spot and its rings.

If the plane is not perfect, the diffraction spot and its rings will be deformed.

If the quasi-plane mirror is concave for the incident beam, the reflected beam will be convergent and the image will form at a certain distance from the focal point, towards the parabolic mirror, and if it is convex, the beam will be divergent and the image on the other side of the fireplace.

A sagittal analyzer located at the focal point of the parabolic mirror makes it possible, according to the invention, to go back to the shape of the quasi-plane mirror, and ensure its flatness, or give it a controlled curvature by bringing the mirror locally or moving it away from the control membrane. . Quasi-plane optical unit. (Figure 19)

The quasi-plane optical unit is made up, like the optical unit of the parabolic mirror, of a membranous mirror, of a control membrane and of an eliminable folding aid.

The mirror and the control membrane having zero or very weak arrows, the undulations of the folding aid will be few.

This allows greater rigidity of these membranes, and greater spacing of the action electrodes.

To allow the passage of light rays parallel to the optical axis and the return of the reflected rays, the control membrane is pierced, according to the invention, with a plurality of holes. Convex mirror with low curvature. (Figures 20 to 23)

From the moment when the radius of curvature has a sufficiently small dimension, it is possible to directly control the curvature of the mirror by a sagittal analyzer.

FIGS. 20 and 21 show a cylinder or a cone of connection 43 having at one of its ends the optical unit without the folding aid, and at the other the sagittal analyzer 10.

The optical unit, mirror 6 and control membrane 7, is joined at the base of the cone, or at one end of the cylinder, by a spider 12.

In these arrangements, the beam of the sagittal analyzer is inside the cone or the cylinder.

FIG. 22 shows a conical mast 43 situated inside the bundle of the sagittal analyzer and having at one end the mirror 6 and the control membrane 7, and at its other end the sagittal analyzer 10.

The mast is limited (FIG. 23) by a hyperbolic mirror 44 which sends the sagittal analyzer 10 towards it. A skirt 45 protects the transparent window 46 which allows the passage of the beam of the sagittal analyzer 10.

In another embodiment of the invention, an additional mirror returns the sagittal analyzer beyond the hyperbolic mirror, through a central window of this mirror.

As before, the control membrane is pierced with a plurality of holes to allow the passage of light rays from the sagittal analyzer.

Convex mirror with low curvature and approximate shape. (Figures 25 and 26)

The deflection being weak, the undulations of the folding aid will be much longer than in the case of a mirror with a large aperture, the radii of curvature are greater, and the rigidity of the mirror may be much greater.

It is also possible to add a skirt forming a fold of stiffening to the periphery of the mirror.

In the case where it is possible to be satisfied with an approximate shape of the convex mirror, French application 94/11458 describes an optical device making it possible to maintain such a shape.

Centered circular rings are drawn on the mirror, and an optical system controls the flatness of these rings.

The disadvantage of such a system is that if the curvature is small, the accuracy cannot be good.

In the application to the control of the convex mirror, the folding aid 8 is moved away, and the control membrane 7, if it is kept, is perforated.

In order to increase the precision of shaping a mirror 6 on the back of which concentric rings are drawn, the image of these alternately white and black rings is formed on a photoelectric matrix 48, by a lens 49.

In a particular embodiment of the invention, the photoelectric matrix is replaced by a plurality of linear matrices arranged symmetrically and radially around the optical axis.

In another embodiment of the invention, the image of the centered circular rings is formed on a mask 50, the opaque parts of which correspond to the white rings.

The surface of the mask, to improve the contrast of the device, follows the surface of the image.

Photoelectric cells are located behind the mask.

When the mirror has returned to its original shape, the white bands have their images on the opaque rings of the mask, and the photoelectric cells receive very little light.

When the circles are deformed, there is selective illumination of the cells behind the deformation.

The value of the illumination is proportional to the deformation.

The sensitivity to deformation depends on the quality of the design of the rings, their contrast, the quality of the mask, and the quality of the optics forming the image.

The prior art knows devices of this type capable of detecting movements or deformations of the order of a micron. In a particular embodiment of the invention, the mask is obtained from an image of the back of the mirror given by the objective which will be used for the control, so as to integrate the defects of this objective.

In order to improve the lighting efficiency of the white rings, they are covered, according to the invention, with glass microbeads preferably returning the light in the direction of the light source.

The light source illuminating the rings is a real or virtual point source located on the optical axis, or a real annular source, or a plurality of sources, surrounding the objective.

The mirror, the image stage, and the securing elements have all the means of control and action of a control membrane, of the focal stage and of the telescope envelope.

No proportionality exists between the elements of FIGS. 25 and 26, in particular between the mirror and its image, the real homothetic ratio of which is greater than 100.

Lighting of a terrestrial area from the satellite secondary mirror.

A narrow illuminating beam coming from a terrestrial source and striking the satellite secondary mirror will be reflected in various ways depending on the shape of this secondary mirror.

If the mirror is plane, this beam will be reflected without deformation and will illuminate an area with a diameter greater than that of the mirror, but of the same order of magnitude.

If the mirror is concave for this illuminating beam, with a radius of curvature of the order of magnitude of the distance from the source to the mirror, if the source can be considered as a point, or double if it can be considered as a parallel beam, this mirror gives this source an image on the earth's surface reduced to a diffraction spot accompanied by rings.

This allows, with an adaptive optic freeing the light beam from atmospheric turbulence, to illuminate with excellent efficiency a target located at a great distance from the light source, and invisible from this source.

If the mirror is convex for the illuminating beam, this beam is open and illuminates a more or less large area, always with excellent efficiency. Optical unit with flexible central opening.

The optical unit, when the control membrane and the mirror are folded on the folding aid, is reduced to a flexible flat disc with central opening, if there are no central connecting rings, or if these central rings are flexible.

According to the invention, such a disc is folded into conical elements, with a minimum radius of curvature such that the materials constituting the mirror, the control membrane and the folding aid, always remain within the elastic limit.

This is achieved, according to the invention, by performing a first folding along a diameter, and then performing a cone winding.

In another embodiment, the folding aid and its integral membranes are folded into a "pleated skirt". Editing by Herschell. (Figure 24) In Herschell's montage, the image is considerably degraded.

The use of membranous mirrors as the main, and elliptical secondary mirror 47, controlled by sagittal analyzers 10, and by one or more star analyzers, makes it possible, according to the invention, to obtain improved images.

The mirror and the control membrane are portions of a paraboloid of revolution, whether or not including the axis of revolution, or paraboloids of revolution.

An advantage of the Herschell assembly is that it allows the use of a diaphragm at the level of the main mirror. Acoustic control.

In order to minimize the acoustic vibrations of the mirror, devices making the air vibrate are arranged, according to the invention, inside the protective sheath, or outside, to suppress, by phase opposition, sound waves likely to reach the mirror. Mass loads of the membrane and the mirror.

With the aim of making the natural frequencies of two contiguous zones of the membrane or of the mirror first, these zones are charged with different contents of the same inert charge, or with different mixtures of two or more inert charges differing between them by their specific masses. Deformable molds.

In order to simplify the manufacture of membranes, mirror or control membrane, these are not formed on a rotating liquid as described in French application 94/11458, but on a fixed or rotating mold.

In a particular embodiment of the invention, the mold consists of a deformable meniscus shaped by jacks, or other means of the prior art, and the shape of which is controlled by a sagittal analyzer or means of prior art.

Claims

Claims. 1- Telescope comprising in whole or in part: a) a first stage containing a membranous mirror and devices for controlling and protecting this mirror, b) a second stage located at the focal point of the mirror and containing means for observing the image, c) a third stage located at the center of curvature of the mirror and containing a sagittal analyzer making it possible to know the shape of the mirror, d) a means joining the three stages; and such that: e) the mirror and its control device consist of concentric membranes, free at their peripheries and joined by their central regions, directly or through an intermediary, g) the membranes, or only the control membrane, include surface patterns, conductors, insulators and semiconductors, separate, contiguous or superimposed, constituting integrated electronic circuits, and surface action electrodes having in particular the form of turns. characterized in that the action electrodes of the membrane on the mirror are combined into local action matrices controlled by a local processor.

2- Device according to claim 1, characterized in that there are on the surface of the control membrane strain gauges, thermometers and heating elements.

3- Device according to claim 1, characterized in that the local distances of the mirror and the membrane are determined by the accelerations or displacements of the mirror under the effect of forces from the membrane and varying with the distance, or by the variation of the characteristics of the emitters of these forces according to the mirror-membrane distance.

4- Device according to claim 1, characterized in that an electromagnetic shield isolates the two faces of the control membrane.

5- Device according to claim 1, characterized in that the circular electrodes of the control membrane, possibly with ferromagnetic core, produce magnetic fields in order to dampen the movements of the mirror by eddy currents.

6- Device according to claim 1, characterized in that variable magnetic fields produced by the membrane repel the mirror, and that electrostatic forces existing between the membrane and the mirror, simultaneously attract the mirror.

7- Device according to claim 1, characterized in that a winding of the hearth stage produces a variable magnetic field repelling the mirror.

8- Device according to claim 1, characterized in that there are on the surface of the membrane, and up to a depth of several microns, successive deposits of conductive, semi-conductive and insulating bodies, organized in laser diode, emitting towards the mirror and grouped in matrices local action.

9- Device according to claim 1, characterized in that the control membrane has a diameter slightly greater than the diameter of the mirror, and that the peripheral ring exeeding the mirror is reflective.

10- Device according to claim 1, characterized in that the mirror and the control membrane are subject to radial vibrations.

11- Device according to claim 1, characterized in that the control membrane and the mirror are broken down into a plurality of zones, of fractal organization, such that the natural frequencies of two contiguous zones are prime between them.

12- Device according to claim 11, characterized in that the membrane and the mirror are loaded with two or more types of loads of specific masses d ifferent.

13- Device according to claim 1, characterized in that there is a second surface mass control membrane close to that of the first, and of mechanical properties and first natural frequencies with those of the first membrane.

14- Device according to claim 1, characterized in that there is a photoelectric matrix sensitive to the infrared on which is formed an image of the mirror.

15- Device according to claim 1, characterized in that a program can generate deformations of the mirror defocusing the light rays, creating mobile or stationary waves.

16- Telescope comprising: a) a first stage containing a membranous mirror and control devices, b) a second stage located at the focal point of the mirror and containing means for observing the image, c) a third stage situated in the center of curvature of the mirror and, containing a means of recognizing the shape of the mirror, called a sagittal analyzer, and consisting of a movable screen perpendicular to the optical axis of the telescope, having a circular centered opening, and moving along the segment sagittal, which mobile screen can be simulated by superimposed fixed screens, and a photoelectric matrix perpendicular to the optical axis, d) a means integrating the three stages; and such that: characterized in that the mobile pierced screen exploring the sagittal segment is simulated by a single fixed screen with circular slot centered with variable radius and width.

17- Device according to claim 16, characterized in that the centers of the superimposed polarizing screens of the sagittal analyzer are provided with polarizing rings making it possible to modify the diameter of the continuously transparent zone.

18- Device according to claim 16, characterized in that polarizing screens consisting of two independent contiguous zones with rectilinear border passing through the optical axis, and joined in pairs with crossed borders, are associated with circular screens, either directly or on a secondary beam.

19- Device according to claim 16, characterized in that the sagittal analyzer is calibrated on a mirror of known shape, for example a parabolic liquid mirror, and that a model of sagittal exploration is stored in a permanent memory.

20- Device according to claim 16, characterized in that the single screen consists of two close together screens, or by two sets of electrodes.

21- Device according to claim 16, characterized in that the photoelectric matrix of the sagittal analyzer is annular centered.

22- Device according to claim 16, characterized in that the pixels of the annular matrix are grouped in each ring by sequences of triangular head-to-tail pixels, accompanied by parallelepipedic pixels.

23- Device according to claim 16, characterized in that a rectangular photoelectric matrix has groups of triangular head-to-head pixels, and parallelepipedic pixels.

24- Device according to claim 16, characterized in that a photoelectric matrix consists of a central rectangular matrix surrounded by an annular matrix.

25- Device according to claim 1, characterized in that it is equipped with a geostationary deflection mirror.

26- Device according to claim 25, characterized in that a sagittal analyzer located at the focus of a parabolic mirror controls the deformation of a parallel beam emitted by said parabolic mirror and reflected by the rear of the return mirror.

27- Device according to claim 25, characterized in that alternately light and dark rings exist on the back of the mirror, and that the image of these rings is formed on a photoelectric matrix, or on a mask behind which are cells photoelectric.

28- Device according to claim 1, characterized in that the mast supporting the sagittal analyzer is limited by an optical system returning to the said mast the sagittal segment.

29- Device according to claim 1, characterized in that there is a memory accompanying an optical system, and that the characteristics of the aberrations of this optical system are contained in this memory in the form of experimental values or of a function which can be directly used to correct said aberrations an image given by this optical system.

30- Device according to claim 1, characterized in that in a Herschell assembly with secondary mirror, each mirror is controlled by a sagittal analyzer.

31- Device according to claim 1, characterized in that the membranes are formed on a mold fixed or rotating, and in particular consisting of a deformable meniscus shaped by means of the prior art.

32- Flat disc of which at least one surface has concentric circular undulations, and called bending aid, characterized in that the generator of these undulations consists of the succession of generator elements, orthogonal projections of the direct or inverted elements of the generator of a concave membrane of revolution centered on the axis of circular undulations and cut by planes perpendicular to this axis.

33- Device according to claim 32, characterized in that the direct or inverted generator elements are replaced by two arcs of a circle centered on the straight lines of orthogonal projection, of equal or neighboring radii, tangentially connected at a point of inflection, and whose developed length is equal to or slightly greater than the developed length of the generator element they replace.

34- Device according to claim 32, characterized in that the direct or inverted generator elements are replaced by curve elements whose minimum radius of curvature is such that the deformation of a membrane which follows its shape will remain within the limit elastic, and whose developed length is equal to or slightly greater than the developed length of the generator elements they replace.

35- Device according to claim 32, characterized in that the pressure in the concavity of the membrane is greater than the pressure between said membrane and the folding aid, and that the membrane is brought together and brought into contact with said auxiliary folding until it is fully applied to this folding aid.

36- Device according to claim 32, characterized in that air is eliminated between the membrane and the folding aid, and in that the membrane is held against the folding aid by an external pressure, and / or a electrostatic attraction.

37- Device according to claim 32, characterized in that there is a linear diametral reinforcement, integrated or associated, dividing the folding aid into two semicircles.

38- Device according to claim 32, characterized in that there are multiple linear reinforcements parallel to the diametral linear reinforcement, these reinforcements may result from the anisotropic distribution of the fibers of the composite material constituting all or part of the folding aid.

39- Device according to claim 32, characterized in that the folding aid is wound parallel to one of its diameters, each of the semicircles determined by the diametrical linear reinforcement being wound independently to form two contiguous cylindrical windings.

40- Device according to claim 32, characterized in that the folding aid is wound parallel to one of its diameters, a semicircle being first wound in an inner winding, and the other semicircle then being wound in an outer winding incorporating the first winding.

41- Device according to claim 32, characterized in that the folding aid has inflatable and stiffening tubes, peripheral, radiating or perpendicular to the diametric linear reinforcement, the swelling of which ensures the unfolding and planning of said folding aid.

42- Device according to claim 32, characterized in that the folding aid is porous or micro-perforated and has a dorsal tight film, and that gas is blown between this film and the folding aid.

43- Device according to claim 32, characterized in that the electrical circuits of the casing of the telescope, of the mirror, of the control membrane and of the folding aid are sectorized.

44- Device according to claim 32, characterized in that the mirror is inverted before its attachment to the folding aid, its concave surface becoming its convex surface.

45- Device according to claim 32, characterized in that the mirror and the membrane joined on the folding aid and forming with it a thin disc with annular central opening, are first folded according to a diameter, and then according to a cone.

46- Device according to claim 32, characterized in that the natural shape of the folding aid is that of two parallel cylindrical windings.

47- Terrestrial device according to claim 1, having a thin meniscus whose shape is provided by jacks, characterized in that the control membrane is secured to this thin meniscus, and that the control of the shape of the meniscus is provided by the measurement of the mirror-membrane distance.