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    • 专利摘要:
    The invention relates to a bifocal anastigmat telescope (10) with five aspherical mirrors comprising: a first concave mirror (M1), a second convex mirror (M2), a concave third mirror (M3) and a first detector (D), which are common at a first (f1) and a second (f2) focal length of the telescope, - a first fourth mirror (M41) and a first fifth mirror (M51) associated with the first focal length (f1), and a second fourth mirror (M42) and a second fifth mirror (M52) associated with the second focal length (f2), -the first mirror (M1) and the second mirror (M2) being arranged so as to form an intermediate image (lint) of an object at infinity located between the second mirror (M2) and the third mirror (M3), and for each focal length: * the shapes and fixed positions of the mirrors associated with said focal length being determined from the generalized Korch equations with 5 mirrors, with the constraint first, second and third mirror (M1, M2, M3) and the first focal plane (PF) common to both focal lengths, and so as to optimize the image quality in the first focal plane (PF) of the telescope according to a predetermined criterion.
    公开号:FR3066618A1
    申请号:FR1700525
    申请日:2017-05-18
    公开日:2018-11-23
    发明作者:Nicolas TETAZ；Cyril Ruilier
    申请人:Thales SA；
    IPC主号:
    专利说明:

    Five-mirror bifocal anastigmatic telescope
    FIELD OF THE INVENTION
    The field of the invention is that of telescopes, in particular that of observation telescopes embedded in satellites. More specifically, the field of the invention relates to catoptric systems with large focal lengths, more particularly bifocal.
    STATE OF THE ART
    Current space telescopes are single focal length. A known type of telescope is the Korsh 5 telescope with 3 mirrors as illustrated in FIG. 1. The Korsch type telescope, also called TMA (acronym of the English expression “Three Mirors Anastigmat”) is a monofocal telescope anastigmat with three aspherical mirrors (Concave-ConvexeConcave) which comprises at least a first concave M1 mirror, a second convex M2 mirror and a third concave M3 mirror. The first, second and third mirrors M1, M2 and M3 are aspherical, of fixed shapes, each mirror being characterized by at least two parameters, a radius of curvature R and a conic c.
    The three mirrors M1, M2 and M3 are arranged so that the first mirror and the second mirror form an object at infinity of an intermediate image arranged in an intermediate plane P F i located between the second mirror M2 and the third mirror M3, the third mirror forming from this intermediate image a final image in the focal plane of the telescope P F , in which is placed a detector D. A deflection mirror MO makes it possible to fold the beam to reduce the bulk. The final image in the Pf plane is not reversed. The telescope conventionally has an entrance pupil Pe and an exit pupil PsPar application of the Korsch equations well known to those skilled in the art, the respective positions and parameters of the three mirrors are easily calculated. The theoretical solution is of very good quality on a relatively large field, and compact, which makes all the interest of this type of telescope, particularly well adapted to realize systems with long focal length (> 5000 mm) and large pupil (> 300 mm).
    In addition it can be interesting to be able to change the focal length in flight. Indeed, changing the focal length in flight makes it possible to change the field of view and / or the resolution of the image with one and the same instrument. A bifocal solution is already interesting.
    The 3-mirror Korsch equations do not allow an achromatic and anastigmatic solution for two different focal lengths to be obtained from the same combination of M1 / M2 / M3 mirrors.
    There are several types of bifocal instruments.
    A first type is based on the separation of a common channel into two different focal channels by a separator component 20 as illustrated in FIG. 2. Each channel then has a dedicated detector, in example D1 for short focal length and D2 for the long focal length.
    The separation can be done spectrally, for example visible and IR, the component 20 is then a dichroic plate. The separation can also be carried out for the same wavelength range, by a separating blade (for example 50/50).
    This first type of system has the advantage of having two focal lengths simultaneously and a common field of observation. However, specific components must be added to each channel, including detectors, and for a given channel, part of the flow is lost.
    A second type performs a separation in the field of view, as illustrated in Figure 3. It is a bifocal solution simultaneously but the two channels therefore do not have the same field of view and components must be added optics on each channel, a deflection mirror M0 (1), M0 (2), a third mirror M3 (1), M3 (2) and a detector D1, D2.
    A third type of system described in document US6084727 makes it possible to change the focal length by inserting reflective elements into the optical path.
    We then have a single detector and the two channels have a common field, but we must add 3 specific mirrors to one of the channels, some of which may have very large dimensions. In addition, the bifocal function is not simultaneous
    A fourth type of system consists in producing a variable focal length by moving a mirror, as described in document US6333811. This document is based on a Cassegrain type telescope with image recovery. In a Korsch-type architecture, an additional correction mirror should be added for each focal length, as well as means for moving the detector or means for varying the optical path on one of the focal lengths. However, this solution has the disadvantage of requiring the displacement of the large mirror M3 in order to vary the focal length.
    An object of the present invention is to overcome the aforementioned drawbacks by proposing a telescope making it possible to conserve the advantages of an architecture of the conventional Korsch type TMA (aplanetism and astigmatism over a large field, compactness, mono-detector) and having a bifocal function. obtained without moving one of the mirrors forming part of the optical combination of the imaging system.
    DESCRIPTION OF THE INVENTION
    The subject of the present invention is a bifocal anastigmat telescope with five aspherical mirrors comprising:
    a first concave mirror, a second convex mirror, a third concave mirror and a first detector, common to a first and a second focal length of the telescope,
    a first fourth mirror and a first fifth mirror associated with the first focal length, and a second fourth mirror and a second fifth mirror associated with the second focal length, the fourth and the fifth mirror associated with a focal length being retractable, so as to be arranged on an optical path of a beam corresponding to said associated focal length when the telescope operates at said focal length, and outside of an optical path of a beam corresponding to the other focal length when the telescope operates on the other focal length,
    the first mirror and the second mirror being arranged so as to form an object at infinity of an intermediate image situated between the second mirror and the third mirror,
    -and for each focal:
    * the third mirror as well as the fourth and the fifth mirror associated with said focal length being configured to form this intermediate image a final image in a first focal plane of the telescope common to the two focal lengths and in which the first detector is placed, * the shapes and fixed positions of the mirrors associated with said focal length being determined from the generalized Korch equations with 5 mirrors, with the constraint of the first, second and third mirror and of the first focal plane common to the two focal lengths, and so as to optimize the quality of image in the first focal plane of the telescope according to a predetermined criterion.
    According to one embodiment, the first and second fourth mirrors are arranged substantially in the same position, and / or in which the first and second fifth mirrors are arranged substantially in the same position.
    Preferably in this embodiment, the first and second fourth mirrors are mounted on a first single support, the switching taking place by rotation around a first axis, and / or in which the first and second fifth mirrors are mounted on a second single support, switching takes place by rotation around a second axis.
    Advantageously, the first fourth mirror and the second fourth mirror have a radius of curvature greater than 1000 mm.
    Advantageously, the predetermined criterion consists in minimizing a waveform error.
    According to one embodiment, said first and second fourth retractable mirrors are mounted on a single support, said support further comprising a position for which none of the fourth retractable mirror appears on the optical path of the incident beam on said support, the beam then passing through the support along a secondary optical path, the telescope further comprising:
    an optical device disposed on the secondary optical path, the optical device being configured to form said intermediate image, in combination with the third mirror, a final image on a second focal plane of the telescope corresponding to a chosen focal length and to optimize the quality image in the second focal plane according to said predetermined criterion, -and further comprising a second detector disposed in the second focal plane of the telescope, and sensitive in a second spectral band different from a first spectral band of sensitivity of the first detector.
    Preferably, the optical device operates in transmission in the second spectral band.
    Advantageously, the first spectral band is included in the visible range and the second spectral band is included in the infrared region.
    Advantageously, the chosen focal length has a value lower than the first and second focal lengths.
    According to another aspect, the invention relates to a method for determining optical combinations of an anastigmat bifocal telescope with five aspherical mirrors, the telescope comprising:
    a first mirror, a second mirror and a third mirror and a first detector disposed in a first focal plane common to a first and a second focal length of the telescope,
    a first fourth mirror and a first fifth mirror associated with the first focal length, the respective shapes and positions of the first, second, third, first fourth and first fifth mirrors forming a first optical combination associated with the first focal length,
    a second fourth mirror and a second fifth mirror associated with a second focal length, the respective shapes and positions of the first, second, third, second fourth and second fifth mirrors forming a second optical combination associated with the second focal length, the method comprising the steps consists in :
    -To determine, from the Korsh equations generalized to 5 mirrors, a first initial optical combination for the first focal length, the first mirror being concave, the second mirror being convex, the third mirror being concave, the first and the second mirrors being configured so that they form from object to infinity an intermediate image situated between the second mirror and the third mirror, the third, the first fourth and the first fifth mirrors being configured to form of said intermediate image an image in a first initial focal plane of the telescope by optimizing the image quality in said first initial focal plane according to a predetermined criterion,
    -B determine, from the first initial optical combination and the generalized Korsh equations with 5 mirrors, a second initial optical combination for the second focal length, by modifying the shapes and / or the positions of said third, first fourth and first fifth mirrors determined in step B, so as to form from said intermediate image (lint) an image in a second initial focal plane of the telescope by optimizing the image quality in said second initial focal plane according to said predetermined criterion,
    -C determine, from the first and second initial optical combinations, a first and a second final optical combination by an optimization loop, with the constraint of the first, second and third mirrors and of the first focal plane common to the two focal lengths, and so as to optimize the image quality in said first focal plane of the telescope according to a predetermined criterion.
    Preferably the respective shapes of the first fourth and the first fifth mirror determined in step A are imposed spherical.
    Advantageously, the first focal length is the longest focal length.
    Preferably, the shape of the mirror is defined by at least one radius of curvature and one conic, and in which the modifications of step B consist, for the third mirror, in modifying its conic only, either without modifying its radius of curvature or his position.
    According to a variant, step C is carried out with the additional constraint of the positions of the first and second fourth equal mirrors, and of the positions of the first and second fifth equal mirrors.
    Advantageously, the predetermined criterion consists in minimizing a waveform error.
    Other characteristics, objects and advantages of the present invention will appear on reading the detailed description which follows and with reference to the appended drawings given by way of nonlimiting examples and in which:
    Figure 1 already cited illustrates a Korsch type architecture with 3 conventional mirrors.
    FIG. 2, already cited, describes a first type of bifocal system according to the state of the art using an optical separator component and having two detectors.
    FIG. 3, already cited, illustrates a second type of bifocal system according to the state of the art with separation by the field.
    FIG. 4 illustrates a telescope according to the invention.
    FIG. 5 illustrates another embodiment of a telescope according to the invention in which the deflection mirror is arranged differently.
    FIG. 6 illustrates a variant of the telescope according to the invention which comprises an additional channel operating in a wavelength range different from the operating range of the main channel of the telescope.
    FIG. 7 illustrates a single support for the first and second retractable mirrors, adapted to the variant of the telescope of FIG. 6.
    FIG. 8 illustrates the method for calculating optical combinations of a telescope according to the invention.
    FIG. 9 illustrates the first initial combination resulting from step A of the method according to the invention.
    FIG. 10 illustrates the second initial combination resulting from step B of the method according to the invention.
    FIG. 11 12 illustrates an example of the values calculated for the first and second initial combinations of a telescope originating respectively from step A and from step B of the method according to the invention.
    FIG. 12 illustrates an example of a final combination of a telescope according to the invention resulting from the method according to the invention.
    FIG. 13 illustrates values calculated for the first and second final combinations from the values of the combinations CO1i and CO2i of FIG. 11.
    DETAILED DESCRIPTION OF THE INVENTION
    A bifocal anastigmat telescope 10 with five mirrors according to the invention is illustrated in FIG. 4. It has a first focal length f1 and a second focal length f2 and comprises a first concave mirror M1, a second convex mirror M2, a third concave mirror M3 and a first detector D, common to f1 and f2. The mirrors M1 and M2 that they form from an object to infinity an intermediate lint image located between M2 and M3.
    M1 and M2 are arranged according to the configuration of a 3-mirror Korsch as described in the state of the art, and the shape of the M3 mirror is slightly modified compared to the corresponding 3-mirror Korsh as described below.
    The telescope 10 also includes a first fourth mirror M4i and a first fifth mirror M5i associated with f1, and a second fourth mirror M4 2 and a second fifth mirror M5 2 associated with f2.
    The fourth mirror and the fifth mirror associated with a focal length (f1 or f2) are retractable, so as to be arranged on the optical path of the light beam corresponding to said associated focal length when the telescope is operating at said focal length, and outside the optical path of a beam corresponding to the other focal length when the telescope operates at the other focal length. The first light beam LF1 corresponding to the use at f1 and the second light beam LF2 corresponding to the use at focal f2 thus share substantially the same optical path as illustrated in FIG. 4.
    In other words, the telescope presents a first optical combination OC1 for the focal length f1 made up of the respective shapes and positions of M1 / M2 / M3 / M4- | / M5i and a second optical combination OC2: M1 / M2 / M3 / M4 2 / M52 for focal length f2. We go from OC1 to OC2 by retracting the mirrors M4 and M5 from the unused focal length and by positioning the mirrors M4 and M5 from the focal length used on the path of the incident light beam.
    Furthermore, for each focal length, the third mirror M3 as well as the fourth and the fifth mirror associated with said focal length are configured to form this intermediate image lint a final image in a first focal plane Pf of the telescope common to the two focal lengths f1 and f2 and in which is placed the first detector D.
    The shape and position of each mirror are fixed. They are determined from the generalized Korch equations with 5 mirrors with the constraint of M1, M2, M3 and P F common to the two focal lengths, and so as to optimize the image quality in single P F of the telescope according to a predetermined criterion. . We call this architecture 5MA for "5 Mirrors Anastigmat" in English. Typically the predetermined criterion consists in minimizing a WFE waveform error.
    The Korsch equations allow for a given focal length to find an aplanatic and anastigmat solution by calculating the position and the shape of the mirrors M1, M2 and M3. The calculation is rigorous in the center of the field, but with an optimization the image quality can be excellent in the field (generally field <3 ° x0.5 °).
    For a monofocal solution, 3 mirrors are necessary and sufficient to suppress 1st order spherical aberration, astigmatism, coma and field curvature.
    However for a multifocal solution, it is not possible to solve the equations, even by moving the mirror M3.
    The general idea is to obtain a telescope according to the invention whose set of mirrors are fixed (including the M3 which could constitute a means of changing the focal length). To be able to freeze the position of the M3, as well as that of the detector D, while maintaining good image quality for f1 and f2, it is then necessary to add two additional mirrors M4 and M5 to the optical combination, hence the 5MA architecture.
    We then go from one focal to another by changing the mirrors M4 and M5 by retracting them from / positioning in the optical path according to the desired focal length. The optical combinations are made more complex (5 aspherical mirrors instead of 3) in order to drastically simplify the focal change mechanism.
    The calculation of the optical combinations of the telescopelO according to the invention comes from the application of the generalized Korsch equations with n mirrors with n = 5. In his book "Reflective Optics" D. Korsch presents a mathematical formalism allowing in multi-mirror systems to express the main optical aberrations (spherical Aberration, coma, astigmatism, field curvature) according to simple parameters such as the distance between the mirrors, the distance of objects and images and the ratio of the heights of the rays. This simple and efficient formalism makes it possible to find multi-mirror aplanatic and anastigmat systems by solving a few equations.
    By applying these equations, combinations OC1 and OC2 are determined which verify the above-mentioned properties. The final image is not inverted and the diameter of the entrance pupil is constant for the 2 focal lengths.
    An example of a method for determining the shapes and positions of the 7 mirrors of the telescope 10 is given below.
    Typically, we have M1 concave / M2 convex / M3 concave / M4 convex or concave and almost planar (large radius of curvature) / M5 convex or concave.
    The telescope according to the invention thus has the remarkable property of being able to change focal length without moving the mirror (such as a translation), by simple permutation between M4i and M4 2 , and between M5i and M52, the other mirrors M1 / M2 / M3 remaining fixed.
    In addition, it has an optical length (up to the detector) equal for the two focal lengths.
    The telescope 10 also has the classic advantages of a Korsch for the 2 focal lengths: compactness, good image quality, fairly large accessible field of view ...
    In addition, this type of telescope with a 100% reflective architecture has the advantage of operation independent of the wavelength, the mirrors having no chromaticism. The operating spectral band is then determined by the nature of the reflecting material of the mirrors and the sensitivity spectral band of the first detector.
    A telescope with a ratio of at least 2.5 is obtained, and the accessible focal lengths are typically greater than 5 m (generally around 20 m for the long focal length), a pupil greater than 300 mm and a linear field of view up to 5 ° x1 °.
    For ease of implementation, the first and second fourth mirrors M4i, M4 2 are calculated so as to be arranged substantially in the same position. Likewise for the first and second fifth mirrors M5i, M5 2 . In this configuration, according to a preferred embodiment Μ4 Ί and M4 2 are mounted on a first single support and / or M5i and M5 2 are mounted on a second single support. Preferably, the switching takes place by rotation around an axis of the support according to a mechanism called "flip / flop".
    Preferably, the first fourth mirror Μ4Ί and the second fourth mirror M4 2 have a radius of curvature greater than 1000 mm as explained below.
    For compactness constraints, according to one embodiment, the telescope 10 according to the invention comprises a deflection mirror M R.
    FIG. 5 illustrates another embodiment in which the reflecting mirror Mr is arranged differently.
    According to a variant, the telescope 10 comprises an additional channel operating in a wavelength range different from the operating range of the main channel of the telescope, an example of architecture of which is illustrated in FIG. 6.
    The main bifocal channel operates over a first wavelength range SB1, typically visible between 400 and 800 nm, and the first detector D has a sensitivity adapted to SB1. The additional channel operates for a second spectral band SB2 different from SB1, typically included in the infrared band.
    The first fourth mirror M4i and the second fourth retractable mirror M4 2 are mounted on a single support 40, an example of which is given in FIG. 7.
    This support also has a neutral position for which none of the fourth retractable mirrors Μ4Ί and M4 2 appears on the optical path of the optical beam incident on the support (single hole without optical function). The beam then passes through the support 40 to form a light beam LF3 along a secondary optical path 80, the primary optical path being that followed by the visible path.
    According to the example of FIG. 7, the support 40 comprises three positions, respectively obtained by pivoting around an axis of rotation 45, the two aspherical mirrors M4-i and M4 2 being mounted around a hollow structure. In a first position M4i reflects the incident beam, in a second position it is M4 2 which reflects the incident beam, and in a third neutral position the incident beam passes through the support. Other designs are of course possible, such as a barrel wheel.
    This multi-channel telescope 10 further comprises an optical device 85 disposed on the secondary optical path 80 and configured to form the intermediate image lint, in combination with the third mirror M3, a final image on a second focal plane P ' F of the telescope corresponding to a chosen focal length f
    The optical device 85 preferably operates in transmission in the second band SB2, so as to be compatible with a chosen focal value f ’much less than f1 and f2.
    The device 85 is further configured to correct the compensable aberrations of the telescope and to optimize the image quality in the second focal plane of the telescope P ' F according to the predetermined criterion.
    It fulfills the same compensating function as the aspheric mirrors Μ4- | / Μ5ι, M42 / M52. It is typically a dioptric lens made up of several lenses. Due to the flexibility of design, the lenses can be spherical while performing the compensation function.
    A second detector D 'is arranged in the second focal plane of the telescope P' F , and has a sensitivity in the second spectral band SB2. A spectral filter F is preferably placed on the secondary optical path, between the support 40 and the second detector D'pour select the spectral band SB2 and reflect the light outside SB2, to avoid stray light.
    An additional path is thus produced with low mechanical complexification.
    For the example of a telescope 10 having a main bifocal channel in the visible and an additional monofocal infrared channel on board a satellite, it is sought to obtain an infrared channel of lower resolution than the visible channel, but of larger field, this which is obtained with a lower focal length f, typically by a factor of 10, compared to the shortest focal length between f1 and f2. For example a visible focal length of the order of ten meters and an IR focal length of the order of one meter.
    The position of the mirror M3 for infrared operation being identical, for one of the visible focal lengths f1 or f2 a simultaneous visible / IR measurement is possible.
    According to another aspect, the invention relates to a method 100 for determining optical combinations of an anastigmat bifocal telescope with five aspherical mirrors, the telescope comprising a first mirror M1, a second mirror M2 and a third mirror M3 and a first detector D arranged in a first focal plane P F common to a first focal length f1 and a second focal length f2 of the telescope.
    The telescope further comprises a first fourth mirror M4i and a first fifth mirror M5i associated with f 1, and a second fourth mirror M4 2 and a second fifth mirror M52 associated with f2.
    The respective shapes and positions of the first second, third, first fourth and first fifth mirrors form a first optical combination associated with the first focal: M1 / M2 / M3 / M4- | / M5i
    The respective shapes and positions of the first, second, third, second fourth, and second fifth mirrors form a second optical combination associated with the second focal: M1 / M2 / M3 / M42 / M52. These mirrors are aspherical.
    The method 100 according to the invention makes it possible to determine the first optical combination OC1 and the second optical combination OC2 associated respectively with f1 and f2 of the 5MA telescope, having the first three identical mirrors M1 / M2 / M3, and a common focal plane Pf.
    According to a preferred variant, the respective positions of M4i and M4 2 are identical, as well as the respective positions of M5i and M5 2 . This allows, as seen above, to change the focal length by tilting a single support for each the fourth and the fifth mirror.
    The method 100 illustrated in FIG. 8 presents a first step A consisting in determining, from the generalized Korsh equations with 5 mirrors, a first initial optical combination OC1i for the first focal length f1: OC1i: M1, / M2i / M3ii / M4ii / Μ5 ή
    The first mirror M1 is concave, the second mirror M2 is convex, the third mirror M3ü is concave. The first and second mirrors are configured so that they form an infinite lint image from an object to infinity located between the second mirror and the third mirror.
    The third Μ3ι ,, the first fourth M4n and the first fifth Μ5ι, mirrors are configured to form from said intermediate image lint an image in a first initial focal plane P F ii of the telescope by optimizing the image quality in this first initial focal plane P F ii according to a predetermined criterion. Preferably, the predetermined criterion consists in minimizing a WFE waveform error. An example of this first initial optical combination is illustrated in FIG. 9.
    There is a real intermediate pupil close to M4- | j. Indeed in order to effectively correct the constant aberrations in the field, the mirror Μ4-Π must be placed close to the intermediate pupil (ie the image of the entrance pupil by M1 M2 and M3)
    An aspherical mirror is characterized by at least a radius of curvature (spherical component) and a taper or one or more coefficient (s) of asphericity (aspherical component). When the mirror becomes close to a plane mirror (very large radius of curvature) it is more effective to characterize it by the coefficient of asphericity A rather than by a taper. Preferably, to speed up the calculations, the conicity of the mirrors Μ4 Ή and M5ij (or their asphericity coefficient) is fixed at 0, that is to say that they are spherical mirrors. Indeed, an asphericity of these mirrors is not necessary for the first focal length f1 to be aplanatic and anastigmate. Preferably step A is implemented for the longest focal length, here f1.
    In a step B, from the first initial optical combination OC1i and from the generalized Korsh equations with 5 mirrors, a second initial optical combination OC2i is determined for the second focal length f2.
    The calculation is carried out starting from OC1i and by modifying the shapes and / or the positions of the third, first fourth and first fifth mirrors of OC1i determined in step A so as to form from the intermediate image lint an image in a second initial focal plane Pf2î of the telescope by optimizing the image quality in this plane P F 2î according to the predetermined criterion, with operation at a focal length f2. The positrons and forms of M1i and M2i are kept identical.
    OC2i: M1 s / M2j / M3 2i / M4 2i / M5 2i .
    The focal plane P F 2î is a consequence of the calculation by the Korsh equations for obtaining an aplanatic and anastigmatic image without field curvature. The optimization variables are the parameters of the aforementioned mirrors. An example of a second initial combination OC2i is illustrated in FIG. 10.
    Preferably in this step B, the modifications consist, for the third mirror, in the modification of its conic only, that is to say not of its radius of curvature nor of its position. In fact, in the long term, we seek to obtain a single mirror M3 for the 2 focal lengths, we therefore aim for a position and a radius of curvature identical to the focal length f 1, the conicity is in turn determined by the Korsch equations.
    Fig. 11 gives an example of the calculation of OC1 i and OC2i values for a bifocal telescope with an entrance pupil of 500mm, a first focal length f1 of 10m (long) and a second focal length f2 of 6.7m.
    The distance on the line of a mirror reads as the distance between this mirror and the next.
    This calculation corresponds to the variant for which only the conicity of the M3 is changed, which goes from -0.4 for OC1i to -0.39 for OC2i, the radius of curvature and the positron (relative to M2) remaining identical. The calculation is initialized with spherical M4-ii and M5ii.
    The elements which therefore vary between OC1i and OC2i are the taper of the third mirror, the radii of curvature of the fourth and fifth mirrors as well as their shape, which becomes aspherical, and the position of the fifth mirror which changes slightly. The asphericity coefficient A is chosen to characterize the asphericity of M4 2 j and M5 2i .
    Finally in a step C, from the first initial optical combination OC1i and from the second initial optical combinations OC2i, a first final optical combination OC1f and a second final optical combination OC2f are determined by an optimization loop, with the constraint of the first, second and third mirrors (M1, M2, M3) and of the first focal plane (Pf) common to the two focal lengths (f1, f2), and so as to optimize the image quality in said first focal plane (Pf) of the telescope according to a predetermined criterion. In the optimization the shapes and positons of all the mirrors can vary from the starting points OC1i and OC2i. Preferably, because this is not useful, the positions of M1 and M2 are not changed.
    The field of view (off axis) is adapted to each focal length in order to be able to adjust the optical beams LF1 and LF2.
    An example of the final combination of a telescope 10 according to the invention resulting from the method 100 according to the invention is given in FIG. 12.
    Preferably as illustrated in FIG. 12, the optimization is carried out with the additional constraint of the positions of M4 1 and M4 2 identical, and the positions of M5i and M52 identical, so as to make the change of focal easier, by simple tilting of the fourth mirror between M4i and M4 2 and the fifth mirror between M5i and M5 2 , by rotation around an axis ("flip / flop").
    It is here, using as a starting point the two initial combinations CO1i and CO2i, to determine by optimization, the final combinations OC1f and OC2f having the best image quality while sharing a common focal plane P F in which is positioned the first detector D. This optimization is carried out with conventional optical calculation software of the CodeV or Zemax type making it possible to minimize the error function of the optimization macro created.
    According to one embodiment, the radius of curvature of M4i associated with the longest focal length is greater than or equal to 10,000 mm.
    FIG. 13 illustrates values calculated for the combinations CO1f and CO2f from the examples of values of the combinations CO1 i and CO2i in FIG. 11.
    It can be seen that the conicities of the mirrors M1 and M2 have changed very slightly compared to the values of M1i and M2i.
    More generally, we could also have had a slight variation in the radii of curvature of M1 and M2 and in the position of M3.
    The taper of M3 stabilized at -0.39. More generally, it could have evolved more clearly.
    The shapes and positions of M4 1 , M4 2 , M5-i and M5 2 have also evolved, the positrons of M4i and M4 2 having been made equal during optimization to be compatible with a single support, similarly for positions of M5i and M5 2 .
    权利要求:
    Claims (15)
    [1" id="c-fr-0001]
    1. Bifocal anastigmat telescope (10) with five aspherical mirrors comprising: - a first concave mirror (M1), a second convex mirror (M2), a third concave mirror (M3) and a first detector (D), common to a first (f1) and a second (f2) focal length of the telescope,
    - a first fourth mirror (M4i) and a first fifth mirror (M5-i) associated with the first focal length (f1), and a second fourth mirror (M42) and a second fifth mirror (M5 2 ) associated with the second focal length ( f2), the fourth and fifth mirror associated with a focal length being retractable, so as to be arranged on an optical path of a beam corresponding to said associated focal length when the telescope is operating at said focal length, and outside the optical path of a beam corresponding to the other focal length when the telescope operates at the other focal length,
    the first mirror (M1) and the second mirror (M2) being arranged so as to form from an object to infinity an intermediate image (lint) situated between the second mirror (M2) and the third mirror (M3),
    -and for each focal:
    * the third mirror as well as the fourth and the fifth mirror associated with said focal length being configured to form this intermediate image a final image in a first focal plane (Pf) of the telescope common to the two focal lengths and in which the first detector is placed ( D), * the fixed shapes and positions of the mirrors associated with said focal length being determined from the generalized Korch equations with 5 mirrors, with the constraint of the first, second and third mirror (M1, M2, M3) and of the first focal plane (Pf) common to the two focal lengths, and so as to optimize the image quality in the first focal plane (P F ) of the telescope according to a predetermined criterion.
    [2" id="c-fr-0002]
    2. Telescope according to claim 1 in which the first and second fourth mirrors (M4-i, M4 2 ) are arranged substantially in the same position, and / or in which the first and second fifth mirrors (M5i, M5 2 ) are arranged in substantially the same position.
    [3" id="c-fr-0003]
    3. Telescope according to claim 2 in which the first and second fourth mirrors (M4i, M4 2 ) are mounted on a first single support, the switching being effected by rotation around a first axis, and / or in which the first and second fifth mirrors (M5i, M5 2 ) are mounted on a second single support, the switching being effected by rotation around a second axis.
    [4" id="c-fr-0004]
    4. Telescope according to one of the preceding claims wherein the first fourth mirror (M4i) and the second fourth mirror (M4 2 ) have a radius of curvature greater than 1000 mm.
    [5" id="c-fr-0005]
    5. Telescope according to one of the preceding claims in which the predetermined criterion consists in minimizing a waveform error (WFE).
    [6" id="c-fr-0006]
    6. Telescope according to one of the preceding claims wherein said first and second fourth retractable mirrors (M4i, M4 2 ) are mounted on a single support (40), said support further comprising a position for which none of the fourth retractable mirror appears on the optical path of the incident beam on said support, the beam then passing through the support along a secondary optical path (80), the telescope further comprising:
    an optical device (85) disposed on the secondary optical path (80), the optical device (85) being configured to form said intermediate image, in combination with the third mirror (M3), a final image on a second focal plane (P ' F ) of the telescope corresponding to a chosen focal length (f) and to optimize the image quality in the second focal plane (P'f) according to said predetermined criterion,
    -and further comprising a second detector (D ') arranged in the second focal plane of the telescope (P' F ), and sensitive in a second spectral band (SB2) different from a first spectral band of sensitivity (SB1) of the first detector.
    [7" id="c-fr-0007]
    7. Telescope according to claim 6 wherein the optical device (85) operates in transmission in the second spectral band (SB2).
    [8" id="c-fr-0008]
    8. Telescope according to claims 6 or 7 wherein the first spectral band (SB1) is included in the visible and the second spectral band (SB2) is included in the infrared.
    [9" id="c-fr-0009]
    9. Telescope according to one of claims 6 to 8 wherein the chosen focal length (f) has a value less than the first and second focal lengths.
    [10" id="c-fr-0010]
    10. Method for determining optical combinations of an anastigmat bifocal five telescope with aspherical mirrors, the telescope comprising:
    a first mirror (M1), a second mirror (M2) and a third mirror (M3) and a first detector (D) arranged in a first focal plane (Pf) common to a first (f1) and a second (f2) telescope focal length,
    - a first fourth mirror (M4-i) and a first fifth mirror (M5i) associated with the first focal length (f1), the respective shapes and positions of the first (M1), second (M2), third (M3), first fourth (M4i) and first fifth (M5i) mirrors forming a first optical combination associated with the first focal length,
    -a second fourth mirror (M4 2 ) and a second fifth mirror (M5 2 ) associated with a second focal length (f2), the respective shapes and positions of the first (M1), second (M2), third (M3), second fourth (M40 and second fifth (M5i) mirrors forming a second optical combination (0C2f) associated with the second focal length, the method comprising the steps consisting in:
    - To determine, from the Korsh equations generalized to 5 mirrors, a first initial optical combination (OC1i) for the first focal length (f1), the first mirror (Min) being concave, the second mirror (M2n) being convex, the third mirror (M3ü) being concave, the first (M1) and the second (M2) mirrors being configured so that they form from an object to infinity an intermediate image (lint) located between the second mirror and the third mirror, the third (Μ3η), the first fourth (Μ4 Ή ) and the first fifth (M5n) mirrors being configured to form from said intermediate image (lint) an image in a first initial focal plane (Pfiî) of the telescope by optimizing the image quality in said first initial focal plane (Pfiî) according to a predetermined criterion,
    -B determine, from the first initial optical combination (OC1i) and generalized Korsh equations with 5 mirrors, a second initial optical combination (OC2i) for the second focal length (f2), by modifying the shapes and / or the positions said third, first fourth and first fifth mirrors determined in step B, so as to form from said intermediate image (lint) an image in a second initial focal plane (P F 2î) of the telescope by optimizing the image quality in said second initial focal plane (Pf2î) according to said predetermined criterion,
    -C determine, from the first (OC1i) and second (OC2i) initial optical combinations, a first (0C1f) and a second (0C2f) final optical combination by an optimization loop, with the constraint of the first, second and third mirrors (M1, M2, M3) and of the first focal plane (P F ) common to the two focal lengths (f1, f2), and so as to optimize the image quality in said first focal plane (P F ) of the telescope according to a predetermined criterion.
    [11" id="c-fr-0011]
    11. The method of claim 10 wherein the respective shapes of the first fourth (M4i,) and the first fifth (Μ5-π) mirrors determined in step A are imposed spherical.
    [12" id="c-fr-0012]
    12. The method of claims 10 or 11 wherein the first focal length is the longest focal length.
    [13" id="c-fr-0013]
    13. Method according to one of claims 10 to 12 wherein a mirror shape is defined by at least one radius of curvature and a conical, and wherein the modifications of step B consist, for the third mirror, in the modification of its conic only, either without modifying its radius of curvature or its position.
    [14" id="c-fr-0014]
    14. Method according to one of claims 10 to 13 wherein step C is carried out with the additional constraint of the positions of the first (M4i) and second (M4 2 ) fourth equal mirrors, and of the positions of the first (M5i) and second (M52) fifth equal mirrors.
    [15" id="c-fr-0015]
    15. Method according to one of claims 10 to 14 wherein the predetermined criterion consists in minimizing a waveform error (WFE).
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    同族专利:
    公开号 | 公开日
    US20180335616A1|2018-11-22|
    EP3404463B1|2019-10-30|
    US11086120B2|2021-08-10|
    ES2765998T3|2020-06-11|
    EP3404463A1|2018-11-21|
    FR3066618B1|2019-06-28|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    US6333811B1|1994-07-28|2001-12-25|The B. F. Goodrich Company|All-reflective zoom optical imaging system|
    US6084727A|1999-04-28|2000-07-04|Raytheon Company|All-reflective field-switching optical imaging system|
    US9354116B1|2015-04-17|2016-05-31|Raytheon Company|Optical forms for multi-channel double-pass dispersive spectrometers|
    US4101195A|1977-07-29|1978-07-18|Nasa|Anastigmatic three-mirror telescope|
    US4226501A|1978-10-12|1980-10-07|The Perkin-Elmer Corporation|Four mirror unobscurred anastigmatic telescope with all spherical surfaces|
    US4993818A|1988-10-17|1991-02-19|Hughes Aircraft Company|Continuous zoom all-reflective optical system|AU201811365S|2017-09-15|2018-04-19|Zeiss Carl Vision Int Gmbh|Anatomical Model|
    AU201811366S|2017-09-15|2018-04-19|Zeiss Carl Vision Int Gmbh|Anatomical Model|
    USD858631S1|2018-03-27|2019-09-03|Carl Zeiss Vision International Gmbh|Demonstration tool|
    FR3089640B1|2018-12-11|2021-03-12|Thales Sa|BISPECTRAL ANASTIGMATE TELESCOPE|
    法律状态:
    2018-05-01| PLFP| Fee payment|Year of fee payment: 2 |
    2018-11-23| PLSC| Publication of the preliminary search report|Effective date: 20181123 |
    2019-04-29| PLFP| Fee payment|Year of fee payment: 3 |
    2020-05-05| PLFP| Fee payment|Year of fee payment: 4 |
    2022-02-11| ST| Notification of lapse|Effective date: 20220105 |
    优先权:
    申请号 | 申请日 | 专利标题
    FR1700525|2017-05-18|
    FR1700525A|FR3066618B1|2017-05-18|2017-05-18|BIFOCAL ANASTIGMATE TELESCOPE WITH FIVE MIRRORS|FR1700525A| FR3066618B1|2017-05-18|2017-05-18|BIFOCAL ANASTIGMATE TELESCOPE WITH FIVE MIRRORS|
    US15/976,691| US11086120B2|2017-05-18|2018-05-10|Bifocal anastigmatic telescope with five mirrors|
    ES18172268T| ES2765998T3|2017-05-18|2018-05-15|Bifocal anastigmatic telescope with five mirrors|
    EP18172268.7A| EP3404463B1|2017-05-18|2018-05-15|Bifocal anastigmatic telescope with five mirrors|
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