CH716368B1 - Optical device for creating aesthetic and technical optical effects. - Google Patents

Abstract

The invention relates to an optical device comprising a transparent support (98) provided with an upper face (100) and a lower face (102) which extends at a distance from the upper face (100), this transparent support ( 98) forming a lens (108) of plano-concave shape delimited on a first side by a flat surface (110), and delimited on a second side, opposite to the first side, by a concave surface (112), the device optical also comprising a shutter (94) which is disposed under the concave surface (112) of the transparent support (98), at a distance from the latter, the optical device finally comprising a substrate (106) disposed after the shutter ( 94).

Description

Technical field of the invention

The present invention relates to an optical device for creating new visual effects and which is suitable for both aesthetic and technical applications.

Technological background of the invention

Imagined by the Scottish physicist Brewster at the beginning of the 19th century, the kaleidoscope is an optical instrument that reflects infinitely and in color the external light which propagates inside this optical instrument by reflection on mirrors. The name of this optical instrument was constructed using the Greek words kalos which means "beautiful", eidos which means "image" and skopein which means "to look". In the form of a tube at a first end from which light penetrates and at a second end from which the observer looks, the kaleidoscope contains a number of colored glass fragments which, when shaken, rearrange themselves according to almost unlimited number of combinations and produce beautiful changing images. As will be understood from reading the following, a kaleidoscope is an example of a device to which the present invention can be applied.

Another example of a device to which the present invention can be applied is given by the moon phase display mechanisms which have long been used in timepieces, in particular wristwatches. The purpose of these moon phase display mechanisms is to tell watch owners what point in the lunar cycle they are in. These moon phase display mechanisms are nonetheless more decorative than they provide a precise indication allowing the owner of the watch to easily determine which quarter of the moon it is in. The simplest moon phase display mechanisms include a needle indicator that points to the different representations of the phases of the moon (first quarter, full moon, last quarter, new moon). Other known moon phase display mechanisms include a disc which carries two representations of the Moon, part of this disc being visible through an opening of suitable shape made in the dial of the watch and successively revealing a waxing moon. , a full moon, a waning moon and a new moon. Such a presentation of the different phases of the Moon is very advantageous from an aesthetic point of view; nevertheless, the way in which the Moon is represented has only a distant relation to the way in which the lunar star appears in the sky. Yet another moon phase display mechanism includes a two-color sphere which rotates completely on itself with each lunar cycle. Such a moon phase display mechanism makes it possible to represent the face of the Moon in a realistic manner. However, because such a moon phase display mechanism uses a sphere to represent the different quarters of the moon, it is thick and takes up a large space, so that it is difficult to integrate into a movement of the moon. horology, in particular a wristwatch.

Summary of the invention

The object of the present invention is to remedy the problems mentioned above as well as others still by providing an optical device making it possible to create aesthetic and technical optical effects.

To this end, the present invention relates to an optical device comprising a transparent support provided with an upper face and a lower face which extends at a distance from the upper face, this transparent support forming a lens of planar shape -concave delimited on a first side by a flat surface, and delimited on a second side, opposite to the first side, by a concave surface, the optical device also comprising a shutter which is arranged under the concave surface of the transparent support, to distance from the latter, the optical device finally comprising a substrate disposed after the shutter, the optical device being arranged to superimpose the image of an edge of the shutter formed through the plano-concave lens with the image of an object disposed above or below said plane-concave lens.

According to special embodiments of the invention: the optical refractive index of the material in which the plano-concave lens is made is between 1.60 and 1.85 and, preferably, equal to or substantially equal to 1.78; the plano-concave lens is made of glass or of polymer; the concave surface of the lens has a curved profile and, preferably but not necessarily, aspherical; the shutter has a curved profile and, preferably but not necessarily, a hyperbolic profile; a representation of the Moon is transferred to one of the upper or lower faces of the transparent support, of the drive means, moved by a clockwork movement, driving the shutter, the shutter and the substrate exhibiting contrasts of display inverted with respect to each other, the shutter being moved from an initial position to a final position for a duration of a lunar cycle, so as to reveal day after day to an observer the appearance of the Moon which passes from the new moon to the first quarter moon, then from the first quarter moon to the full moon, then to the last quarter moon and finally to the new moon, the shutter being recalled by the drive means of its final position at its initial position at the end of the lunar cycle; the drive means comprise a rectilinear rack with which the shutter is fixedly coupled in translation; the drive means comprise a lower wheel and an upper wheel on an axis of rotation of which the lower wheel which meshes with the rectilinear rack is mounted to rotate freely; the clockwork movement comprises a timer mobile which kinematically drives a cam which performs a complete revolution on itself in a whole number of times a lunar cycle, this cam having a profile continuously followed by a first rake, this first rake being provided with a toothed sector through which it meshes with the drive means of the moon phase display mechanism; the first rake is provided with a feeler nose through which it continuously follows the profile of the cam, this profile being shaped as a spiral staircase and being provided with at least one substantially rectilinear recess so that, shortly before the start of 'a new lunar cycle, the feeler nose is at the top of the profile of the cam, then falls along the step, the first rake driving during this movement by its toothed sector a pinion which is kinematically connected to the drive means the moon phase display mechanism; a device for taking up play consisting of the upper wheel engaged, on the one hand with the rectilinear rack, and on the other hand with an intermediate wheel of an intermediate mobile which also comprises an intermediate pinion, this intermediate pinion meshing with a toothed sector of a second rake which is elastically constrained by the return force of a fourth spring.

Thanks to these characteristics, the present invention provides an optical device which, through the plano-concave lens, makes it possible to project the image of an edge of the shutter onto an object disposed above the flat surface. of the plane-concave lens.

[0008] The device according to the invention may be of interest in its use in combination with a kaleidoscope. Indeed, the image of the edge of the shutter, optimized during its passage through the plan-concave lens, is superimposed on the images of the colored glass fragments, which makes it possible to vary the contours of these images and to to multiply even more the combinations of shapes of these images.

The present invention is also of great interest in its application to a moon phase display mechanism. To this end, according to a particular embodiment of the invention, a representation of the Moon is transferred to the flat surface of the transparent support, and the shutter is arranged to move between the transparent support and the substrate, the shutter and the substrate exhibiting inverted display contrasts with respect to each other, the shutter being moved from an initial position to a final position for a period of one lunation, so as to reveal day after day to an observer the aspect of the Moon which continuously passes from the first quarter moon to the full moon, then to the last quarter moon and finally to the new moon, the shutter being recalled by the drive means of its final position to its initial position at the end of the lunation. The different aspects of the Moon are thus represented in an original way that is easily understood by the user. In particular, the representation of the Moon which is provided by the optical device according to the invention is very close to the real aspect of the Moon in the sky, so that it is much simpler for the user to determine at which period of the lunar cycle the Moon is located. The optical device according to the invention is also thinner than those using a sphere rotating on itself, and therefore easier to integrate into a timepiece movement, in particular of a wristwatch. In addition, regardless of the district in which the Moon is located, its representation is always visible to the owner of the watch. It will also be noted that the optical device according to the invention makes it possible to obtain a representation of the different phases of the realistic Moon, formed by two surfaces of different colors and separated by a terminator, that is to say the curve which separates the illuminated part of the dark part of the Moon, the profile of which is very realistic and very faithful to what the user can see when observing the Moon in the sky. This is particularly the case during the first and the last quarter moon, when the optical distortions are almost zero and when the terminator thus appears perfectly rectilinear.

Thanks to the combined use of a plan-concave lens, preferably aspherical, and of a shutter with a curved profile, preferably but not limited to hyperbolic type, the observer sees a terminator, that is to say the curve that separates the illuminated part from the dark part of the Moon, whose profile is very realistic and very faithful to what the user can see when observing the Moon in the sky. In addition, the optical device is compact and can thus be housed in a smaller volume such as that of a case of a timepiece of the wristwatch type. By way of example, it is considered that for a representation of the Moon of the same diameter, the optical device according to the invention is half the thickness of a moon phase display mechanism using a sphere. Likewise, it is understood that, as the surface which receives the representation of the Moon is plane, the optical device according to the invention does not impede the movement of movement of the hands on the surface of the dial.

Brief description of the figures

Other characteristics and advantages of the present invention will emerge more clearly from the following detailed description of an exemplary embodiment of an optical device according to the invention, this example being given for purely illustrative and non-limiting purposes only. in conjunction with the attached drawing in which: Fig. 1 is a plan view of the moon phase display mechanism which can be combined with the optical device according to the invention; FIG. 2 is a detail view on a larger scale of the oblong hole in which the pin carried by the finger projects; Figure 3A is a detail view on a larger scale of the first lever in its intermediate position A FIG. 3B is a detail view on a larger scale of the first lever in its extreme position B in which it bears against the top of the profile of the finger; FIG. 4A is a detail view on a larger scale of the first rake in its position C in which its feeler nose is at the top of the profile of the cam; FIG. 4B is a detail view on a larger scale of the first rake in its position D in which its feeler nose falls along the step of the cam; FIG. 5 is a top view of the transparent support and of the sheet from which the aspherical plano-concave lens and the shutter are obtained; FIG. 6 is a view in elevation and in section of the optical assembly formed by the aspherical plano-concave lens, the shutter and the substrate; FIG. 7 is a schematic top view which illustrates the appearance of the representation of the Moon as it can be perceived by the observer when the shutter begins to penetrate into the space which separates the aspherical plan-concave lens substrate; FIG. 8A is a schematic view of the moon phase display mechanism when it is in its extreme position E at the start of a lunar cycle; FIG. 8B is a view similar to that of FIG. 8A which illustrates the mechanism for displaying the phases of the moon when it is in its extreme position F at the end of the lunar cycle, and FIGS. 9A to 9L illustrate the appearance of the terminator according to several positions of the shutter with a curved profile, preferably hyperbolic.

Detailed description of an embodiment of the invention

The present invention proceeds from the general inventive idea which consists in providing an optical device which makes it possible to project an image of an edge of a shutter on the image of an object disposed above this optical device . To achieve this goal, the optical device according to the invention essentially comprises a transparent support forming an optical lens of plano-concave shape delimited on one side by a flat surface, and delimited on a second side opposite the first by a surface. concave. The optical device also comprises a shutter disposed under the plano-concave lens, on the side of the concave surface, as well as a substrate disposed after the shutter. Preferably, but not necessarily, the obturator is arranged to be able to move in the space which separates the plano-concave lens from the substrate from a proximal position to a distal position, then to return to its proximal position. The advantage of the optical device according to the invention is to create new aesthetic or technical optical effects by making it possible to superimpose the image of the edge of the shutter formed through the plane-concave lens with the image of an object placed above this plano-concave lens, on the side of the planar surface of the latter.

The optical device according to the invention is of very particular interest in its application to a moon phase display mechanism consisting in transferring a representation of the Moon on one or the other of the two upper and lower faces the transparent support which is placed above and at a distance from the substrate, with the shutter interposed between the transparent support and the substrate. The face of the Moon can be represented in a color similar to that of the substrate, while the shutter and the substrate have inverted contrasts: if the substrate is light, then the shutter will be dark and, conversely, if the substrate is dark, the shutter will be bright. Assuming, by way of illustrative example only, that the representation of the Moon and the substrate are dark and that the shutter is clear, it is understood that when the shutter is not in the space between the transparent support and the dark substrate, the representation of the Moon which is above the dark substrate is not perceptible to the observer. Then, as the light shutter enters the space that separates the transparent support from the dark substrate, the representation of the Moon gradually becomes perceptible by the user. The present invention thus provides a compact optical device which makes it possible to display the moon phases in an original and much more realistic manner than most of the prior art moon phase display devices allow. Therefore, it is much easier for the observer to understand what period of the lunar cycle he is in. In addition, the realism is further increased if, in accordance with a special embodiment of the invention, the transparent support is given a plan-concave profile, preferably but not necessarily aspherical, and such a transparent support is combined with a curved shutter, preferably of hyperbolic profile. Such a combination makes it possible to obtain a terminator whose profile is very faithful to that which is observed in reality as the Moon grows, becomes full, then decreases and the lunar cycle resumes.

Housed for example in a timepiece such as a wristwatch, the moon phase display mechanism 1 is driven by a clockwork movement, that is to say a mechanism whose operation depends on the division of time. More precisely, the clockwork movement comprises a timer mobile, a pinion of which (not visible in the figures) drives a twenty-four hour wheel 2 which, as its name suggests, is arranged so as to perform one complete revolution by day.

The twenty-four hour wheel 2 carries a finger 4 on an axis 6 of which this finger 4 is mounted to rotate freely. In order to be able to pivot relative to the twenty-four hour wheel 2, the finger 4 is mounted on the axis 6 with a slight axial play thanks to a ring 8 engaged on this axis 6. Furthermore, the finger 4 is provided with a pin 10 which projects into an oblong hole 12 formed in the thickness of the twenty-four hour wheel 2 and which limits the pivoting freedom of the finger 4 relative to the twenty-four hour wheel 2 (see FIG. 2). It is therefore understood that when the pin 10 abuts against an inner wall 14 of the oblong hole 12, it is rotated by the twenty-four hour wheel 2 and in turn drives the finger 4 which, too, performs a complete revolution. in twenty-four hours.

The moon phase display mechanism 1 also comprises a first lever 16 which is pivotally mounted about a pivot axis 18 and which is elastically applied against a first part 20a of a profile 20 of the finger 4 by an upper spring 22. We also note in the drawing the presence of a star 24 whose position is indexed by a jumper 26 which is held elastically against a toothing 28 of this star 24 by a lower spring 30.

The twenty-four hour wheel 2 rotates clockwise, bringing with it the finger 4. The first lever 16 thus slides along the first part 20a of the profile 20 of the finger 4 and, after having passed through an intermediate position A (FIG. 3A), is found in an extreme position B (FIG. 3B) in which it is supported by a foot 32 against a top 34 of the profile 20 of the finger 4. Furthermore, the first rocker 16 engages via a beak 36 with the teeth 28 of the star 24. When, for example around midnight, the finger 4 advances further, the first lever 16 exceeds the extreme position B in which it bears against the apex 34 of profile 20 of finger 4, and drives star 24 by a step counterclockwise. This movement is allowed by the fact that when the first lever 16 exceeds the top 34 of the profile 20 of the finger 4, a lever effect occurs on the finger 4 which causes the pivoting of this finger 4 and the concomitant displacement of the pin 10 which, in abutment against one end of the oblong hole 12 formed in the thickness of the twenty-four hour wheel 2, will move to come into abutment against the opposite end of this oblong hole 12. Then, the first lever 16 begins to slide again along a second part 20b of the profile 20 of the finger 4 which is located after the top 34 of this profile 20. It will be noted that at the very moment when the first lever 16 causes the advance of a pitch of the star 24, the jumper 26 passes, against the return force of the lower spring 30, from a hollow between two consecutive teeth of the toothing 28 of the star 24 to the immediately following hollow of this toothing 28. By falling back into the following hollow, jumper 26 allows star 24 to complete its advances one step and again ensures the precise positioning of this star 24.

[0018] According to a preferred but non-limiting embodiment of the moon phase display mechanism, the latter also comprises a manual device for correcting the display of the moon phases. Referred to as a whole by the general reference numeral 38, this manual correction device comprises a second rocker 40 pivoted about an axis 42 and which comprises an actuating means 44 such as a pin at an end opposite to the axis. pivot 42. This second lever 40 comprises for example a folded zone 46 against which a corrector (not visible in the drawing) comes to rest when the latter is actuated against the elastic return force of a spring by the owner. of the wristwatch from outside the volume of the watch case. Under the effect of actuation of the corrector, the second lever 40 pivots about its axis 42 and in turn controls the pivoting of the first lever 16 so as to cause the star 24 to advance by one step. This advance of the star 24 takes place under the same conditions as those described above when the first lever exceeds the top 34 of the profile 20 of the finger 4.

[0019] According to a preferred embodiment given for purely illustrative and non-limiting purposes only, a complete revolution of the star 24 corresponds to two successive lunar cycles, a lunar cycle corresponding to the time which elapses between two new successive moons and which is still called lunar month. To this end, the moon phase display mechanism is completed by a first pinion 50 mounted coaxially and fixed in rotation on the star 24, by a return 56 as well as by a cam 52 on the axis of rotation. of which is fixedly mounted a second pinion 54. The first pinion 50 drives the second pinion 54 through the intermediate gear 56, the tooth ratios of this kinematic chain being calculated so that the cam 52 performs one complete revolution per lunar cycle .

The cam 52 has a spiral profile 58 with a substantially rectilinear recess 60. A first rake 62 provided with a toothed sector 64 is also provided with a feeler nose 66 by which it continuously follows the profile 58 of the cam 52. Shortly before the start of a new lunar cycle, for example at around midnight, the feeler tip 66 of the first rake 62 is located at the top of the profile 58 of the cam 52 (position C - Figure 4A), then falls along the step 60 of the cam 52 (position D - Figure 4B). During this movement, the first rake 62 which, by its toothed sector 64, is in permanent engagement with a third pinion 68, turns this third pinion 68 clockwise by an amount corresponding to the fall of the feeler nose 66 along the step 60.

By rotating, the third pinion 68 rotates a wheel 70 with which it forms a mobile 69. In other words, the third pinion 68 is mounted on the wheel 70 in a coaxial manner and fixed in rotation with respect to this wheel 70. As a result, the wheel 70 transmits its rotational movement to drive means 72 of the moon phase display mechanism 1 which comprises a lower wheel 74 and an upper wheel 78 mounted to rotate freely on an axis of rotation 76. The lower wheel 74 meshes with a rectilinear rack 80 which in turn meshes with the upper wheel 78.

The lower wheel 74 is responsible for controlling the moon phase display mechanism 1. For this purpose, by pivoting, the lower wheel 74 drives the rectilinear rack 80 in translation and pushes it back into a first position extreme E illustrated in FIG. 8A which corresponds to the start of a new lunar cycle. Subsequently, when, after having fallen along the indentation 60 of the cam 52 at the start of the lunar cycle, the feeler nose 66 begins again to follow the profile 58 of the cam 52, the feeler nose 66 is gradually pushed back into the clockwise to a second extreme position F (see FIG. 8B), so that the third pinion 68, and therefore the wheel 70, rotate counterclockwise. Consequently, the lower wheel 74 turns clockwise and drives the rectilinear rack 80 in translation from the right to the left of the drawing from its first extreme position E which corresponds to the start of a new lunar cycle to its second position. extreme F illustrated in figure 8B which corresponds to the end of the lunar cycle. Once the feeler tip 66 has traveled the entire length of the profile 58 of the cam 52, it will again find itself at the top of the step 60 of the cam 52 and, at the start of a new lunar cycle, the feeler nose 66 will fall. along the step 60, which will cause the rectilinear rack 80 to return to its initial position.

The moon phase display mechanism is supplemented by a device which makes it possible to catch up with the games and to bring this moon phase display mechanism to its extreme position E at the end of a lunar cycle. This device consists of the upper wheel 78 engaged on the one hand with the teeth of the rectilinear rack 80, and on the other hand with an intermediate wheel 82 of an intermediate mobile 84 which also comprises an intermediate pinion 86. This pinion intermediate 86 meshes with a toothed sector 88 of a second rake 90 which is elastically constrained by the return force of a fourth spring 92. Thanks to this arrangement, all the play of the kinematic chain which extends between the first rake 62 and the second rake 90, so that the positioning of the rectilinear rack 80 is always precise.

The moon phase display mechanism 1 comprises the rectilinear rack 80 with which a shutter 94 is fixedly coupled in translation. The moon phase display mechanism 1 also comprises, on the side of an observer 96, a transparent support 98 provided with an upper face 100 which extends parallel to and at a distance from a lower face 102. A representation 104 of the Moon, for example in the form of a decal, is transferred to the upper face 100 of the transparent support 98. This representation 104 of the Moon could also be transferred to the lower face 102 of the transparent support 98. A substrate 106 is, with respect to the observer 96, arranged under the transparent support 98, at a distance from the latter. The shutter 94 is mounted on the rectilinear rack 80 so as to be able to gradually penetrate into the space which separates the transparent support 98 from the substrate 106 when the rectilinear rack 80 is driven by the lower wheel 74. The shutter 94 and the substrate 106 have inverted contrasts: either the shutter 94 is clear and the substrate 106 as well as the representation 104 of the Moon are dark, or the shutter 94 is dark and the substrate 106 as well as the representation 104 of the Moon are clear. Assuming, by way of example only, that the representation 104 of the Moon and the substrate 106 are dark and that the shutter 94 is clear and reflective, it is understood that when the shutter 94 is not in space located between the transparent support 98 and the dark substrate 106, the representation 104 of the Moon is located above the dark substrate 106 and is therefore not perceptible by the observer 96. Then, as the clear and reflective shutter 94 penetrates into the space which separates the transparent support 98 from the dark substrate 106, the representation 104 of the Moon gradually becomes perceptible by the user. More precisely, when the shutter 94 begins to penetrate into the space between the transparent support 98 and the dark substrate 106, the observer 96 gradually sees the first quarter moon appear. Then, when the reflecting shutter 94 is completely between the transparent support 98 and the dark substrate 106, the observer 96 sees the representation 104 of the entire Moon: it is the full moon. Then, the shutter 94 continues its rectilinear movement in the same direction and begins to come out of the space between the transparent support 98 and the dark substrate 106, so that the observer 96 gradually sees the last quarter moon appear. which corresponds to the moment when the shutter 94 leaves the same free surface as hidden. Finally, when the shutter 94 is completely out of the space between the transparent support 98 and the dark substrate 106, the observer 96 no longer sees the representation 104 of the Moon again (on the assumption that the substrate 106 is the same color as the representation 104 of the Moon) and therefore knows that the lunar cycle has ended and that a new lunar cycle will begin. Thus, the observer 96 has an easily intelligible representation of the different phases of the moon: new moon, first quarter moon, full moon, last quarter moon then again new moon.

According to the invention, the transparent support 98 is in the form of a lens 108 of plano-concave shape delimited upwards, on the side of the observer 96, by a planar surface 110 which receives the representation 104 of the Moon, and delimited downwards by a concave surface 112 to which a preferentially aspherical profile is given. This aspherical plano-concave lens 108 is combined with a shutter 94 bent at its center to give it a curved profile, preferably but not necessarily hyperbolic. We thus obtain an image of the Moon whose terminator, that is to say the curve which separates the dark part from the illuminated part of the Moon, is as close as possible to the real aspect of the Moon in the sky.

To determine the geometric dimensions of the aspherical plano-concave lens 108 and of the shutter 94 with hyperbolic profile, computer-assisted optical system design software such as that sold under the brand LightTools, version 8 of which is used which was published in 2019 was used for the purposes of the present invention.

Once the dimensions of the representation 104 of the Moon that we want to be able to display by means of the optical device according to the invention have been defined, the main parameters on which it is possible to act to obtain a realistic representation of the phases of the Moon are: the material in which the aspherical planoconcave lens 108 will be made and therefore the refractive index of the latter; the profile of the aspherical concave surface 112 of the aspherical plano-concave lens 108 and therefore its taper constant; the dimensions of the shutter 94; the distance between the top of the arch formed by the aspherical concave surface 112 and the shutter 94; the curved profile, preferably hyperbolic, of the shutter 94 and therefore its taper constant.

By way of preferred example only, the aspherical plano-concave lens 108 is made of a transparent material whose refractive index is preferably between 1.60 and 1.85, with an optimum value in the vicinity of 1.78. This value was chosen after numerous tests which have made it possible to observe that, the higher the value of the refractive index of the material in which the lens is made, the more it was necessary to approach the lens of the shutter 94 so that this the latter is not visible to the observer through this lens. It is easily understood that this is favorable from the point of view of size in the case where it is desired to integrate an optical device according to the present invention in a timepiece of the wristwatch type. On the other hand, the higher the refractive index, the more the corresponding material is expensive and difficult to machine. Furthermore, it has been realized that when the lens gets too close to the shutter 94, one ends up seeing the image of the peripheral edge of the lens which forms a lactescent opaline crown around the representation 104 of the Moon. , which is not acceptable. Likewise, it was found that by selecting too low refractive index values, the image of the shutter 94 with a curved and preferably hyperbolic profile which gradually came to cover the representation of the Moon was not very aesthetic. , nor really realistic compared to the true representation of the Moon. This is why a value of the order of 1.60 to 1.85 and preferably equal to or substantially equal to 1.78 for the optical refractive index of the material in which the aspherical plano-concave lens 108 is made appeared to be an optimum making it possible to provide the best compromise between the optical refractive index of the material in which the aspherical plan-concave lens 108 is made and the distance separating the aspherical concave surface 112 from the aspherical plan-concave lens 108 and the shutter 94, and thus obtain a mechanism of display of moon phases, the size of which is compatible with the dimensions of the timepiece in which this mechanism is intended to be housed while providing a terminator whose profile is suitable. An example of a material which is well suited for the purposes of the present invention is the glass produced and marketed by Schott under the reference N-SF 11.

Then introduced into the computer-aided design software the dimensions of a block of transparent or at least translucent material such as a cylinder of glass or polymer such as polycarbonate from which the aspherical plane-concave lens 108 is obtained. In the present case, the aspherical plano-concave lens 108 is obtained by machining a cylindrical glass block whose diameter D is between 6 mm and 7 mm and whose height H is between 0.9 mm and 1.1 mm (see figures 5 and 6).

As regards the shutter 94 with hyperbolic profile, it is obtained from a rectangular sheet whose thickness e is preferably but not limited to between 0.08 mm and 0.2 mm, and whose length I of the side which extends parallel to the direction of movement of the shutter 94 is chosen to be between 7 mm and 8 mm, while the width L of the side which extends perpendicular to the direction of movement of this shutter 94 is chosen between 9 mm and 10 mm. This sheet is provided at its center with a fold 114 which extends in a direction parallel to the direction of movement of the shutter 94 and preferably has flat edges 116 parallel to the fold 114. It will in fact be noted that ' it is not necessary for the shutter 94 to maintain its hyperbolic profile to its ends because, in these areas, the optical distortion effect is produced essentially by the aspherical plano-concave lens 108. These flat edges 116 therefore have solely for the function of completely obstructing the field of view provided by the aspherical plan-concave lens 108 and, because of their flatness, these edges 116 make it possible to reduce the bulk of the moon phase display mechanism.

The profile of the aspherical concave surface 112 of the aspherical plano-concave lens 108 is determined by the values of the distances r and z (r). If we call S the central axis of symmetry of the aspheric plane-concave lens 108, the distance r corresponds to the distance which separates each point of the central axis of symmetry S from the point of the aspherical concave surface 112 which is located opposite (see figure 6). Likewise, the hyperbolic profile of the shutter 94 is determined by the distance r 'which separates each point of the plane of symmetry S' of this shutter 94 from the surface of the latter. These distances r, r 'are determined by means of the same relation below: where k = -e <2>

As visible in Figure 6, the origin of the function z (r) corresponds to the point O which is located at the top of the arch formed by the aspherical concave surface 112. The value of the function z (r) corresponds , at each point of the arch formed by the aspherical concave surface 112, at the height of this point considered from the base of the aspherical plan-concave lens 108.

The values of the constants R and k which characterize the aspherical plano-concave lens 108, as well as those of the constants R 'and k' which characterize the shutter 94 will be determined by successive iterations in the manner described below . As for the coefficients An, they are coefficients of a polynomial sum whose values will also be determined by iterations.

As regards the aspherical plano-concave lens 108, the constant R corresponds to the radius of curvature of the aspherical concave surface 112 at the point O which is located at the top of the arch formed by this aspherical concave surface 112. In order to do so. that the terminator T which is the line of demarcation between the dark part and the lit part of the Moon appears rectilinear in the middle of the lunar cycle, it is necessary that in the vicinity of the point O the aspherical concave surface 112 is practically flat. To this end, a very large value of the radius of curvature R, of the order of several thousand millimeters, is initially introduced into the computer-aided design software. As for the constant "k" which is called "conical constant", it is about a quantity which describes the conic sections. By conical section is meant a plane curve defined by the intersection of a cone of revolution with a plane. When the cutting plane does not pass through the apex of the cone, its intersection with this cone corresponds to one of the following plane curves: ellipse, parabola or hyperbola.

It is noted that k = -e <2> with e which corresponds to the eccentricity of the conical section. The eccentricity of a conical section is a positive real number which characterizes only the shape of this conical section; one can interpret the eccentricity of a conical section as a measure of the amount by which a conical section deviates from a circle. Thus, the eccentricity of a circle is zero. The eccentricity of an ellipse that is not a circle is strictly between zero and one. The eccentricity of a parabola is equal to 1 and the eccentricity of a hyperbola is greater than 1.

The conical constant k comes into the equation y <2> - 2Rx + (k + 1) x <2> = 0 which describes a conical section whose apex is at the origin and whose tangent extends along the axis "y" and where R is the radius of curvature for x = 0. This formula is used in geometrical optics to describe the optical surface of a lens. In this case, we initially indicated to the computer-aided design software that the taper constant was zero (k = 0), in other words that we were dealing with a circle.

Consequently, as regards the aspherical plano-concave lens 108, the simulation is started with a value of the conical constant k zero and a value of the radius of curvature R very large.

The same is true of the shutter 94 for which the simulation is started with a value of the conical constant k 'zero and a value of the radius of curvature R' very large. It is important to note that the shutter 94 can be regarded as the object whose image is perceived through the aspherical plan-concave lens 108 and, as such, its geometric characteristics can be determined by software of computer-aided optical systems design such as LightTools.

Finally, it is considered that the aspherical plano-concave lens 108 is of even order, so that one starts by arbitrarily choosing values for the coefficients A4, A6 and A8. In the initial choice of the values of the coefficients A4, A6 and A8, the person skilled in the art is guided by the fact that he knows that the values of these coefficients are very low and that they keep decreasing as they go. as the index n increases. It is also decided to stop at the coefficient A8 because the contribution of the higher order coefficients on the improvement of the aspect resulting from the terminator T is negligible. Regarding the coefficient A2, this is ignored because the first term of the expression z (r) already contains the square of the variable r.

Using computer-aided design software, a representation 118 of the Moon and its terminator T is simulated for several positions of the shutter 94 (see Figures 7 and 9A to 9L). In Figure 9A, we are at the start of a lunar cycle. In figure 9C, the Moon is in its first quarter. In Figure 9F, we are in the middle of the lunar cycle and the Moon is full. Figure 9I corresponds to the last quarter of the Moon and in Figure 9L we are at the new Moon. To carry out the simulations, one begins, for example, to vary the values of the parameters An as well as of the conical constant k and of the radius of curvature R which characterize the aspherical plane-concave lens 108, while the values are kept unchanged. parameters A ′ as well as the conical constant k ′ and the radius of curvature R ′ which characterize the shutter 94, and we observe on the computer screen the aspect resulting from the terminator T. We renew l 'experiment by keeping constant this time the values of the parameters An, k and R which characterize the aspherical plan-concave lens 108, and by varying the values of the parameters A'n as well as of k' and R 'which characterize the shutter 94, and the resulting aspect of the terminator T is observed on the computer screen by means of the "Photorealistic Rendering" function of the LighTools software. This function makes it possible to visualize the whole of the device formed by the aspherical plan-concave lens, the hyperbolic shutter and the substrate as if this device were photographed at the desired angles and distances. Thanks to the “Photorealistic Rendering” function, it is thus possible to check that the desired optical effect is suitable. We proceed in this way step by step until we obtain a profile of the terminator T which we consider faithful to its real aspect and with which we are satisfied. Of course, this is a purely subjective criterion which is left to the appreciation of each individual.

It will be noted that for the dimensional characteristics of the aspherical plano-concave lens 108 and of the shutter 94 mentioned above, the most satisfactory results as regards the visual appearance of the terminator T were obtained for the values k = -1 and R = 20840 mm and A4 = 3.769.10 <-3>, A6 = 2.9534.10 <-5> and A8 = -1.407.10 <-7> with regard to the aspherical plane-concave lens 108 , and for the values k '= -4,922 and R' = 2.556 mm and A4 = 1.654.10 <-5>, A6 = -1.511.10 <-6> and A8 = 4.686.10 <-8> with regard to relates to the shutter 94. It will be observed that with regard to the value of the conicity constant k, the value adopted for the aspherical plan-concave lens 108 is equal to -1, which corresponds to a parabolic profile. As for the value of the conicity constant k 'which characterizes the profile of the shutter 98, this is less than -1, which corresponds to a hyperbolic profile.

Thus, the point O which is located at the top of the arch formed by the aspherical concave surface 112 is located at a distance P equal to 0.78 mm relative to the base of the cylindrical glass block. Consequently, it is deduced that at this point O, the thickness of the aspherical plan-concave lens 108 is 0.22 mm. This is the minimum thickness of the aspherical plano-concave lens 108.

It goes without saying that the present invention is not limited to the embodiment which has just been described and that various modifications and simple variants can be envisaged by those skilled in the art without departing from the scope of the invention. as defined by the appended claims. It will be noted in particular that, in the case where the shutter is clear, the latter can be covered with a layer of phosphorescent material such as that sold under the registered trademark Super-LumiNova®. It will also be noted that in order to avoid light reflection phenomena, the surface of the shutter can advantageously exhibit roughness. Still with the same concern for limiting light reflections as much as possible, the plano-concave lens may be the subject of an anti-reflective treatment and its edges may be metallized. Although not shown in the drawing, it will be noted that provision may be made to provide the cam 52 with two recesses 60. Given that the star 24 makes a complete revolution in two lunar cycles, it is then possible to put the star 24 in direct engagement with the cam 52, and thus to save the pinions 50 and 54 and the return 56.

Nomenclature

1. Moon phase display mechanism 2. Twenty-four hour wheel 4. Finger 6. Axle 8. Bushing 10. Pin 12. Slotted hole 14. Interior wall 16. First rocker 18. Pivot pin 20 Profile 22. Upper spring 24. Star 26. Collar 28. Teeth 30. Lower spring 32. Foot 34. Top 36. Spout 38. Manual correction device 40. Second rocker 42. Pivot pin 44. Actuating means 46 . Folded area 50. First pinion 52. Cam 54. Second pinion 56. Return 58. Profile 60. Step 62. First rake 64. Toothed sector 66. Feeler nose 68. Third pinion 69. Mobile 70. Wheel 72. Means of drive 74. Lower wheel 76. Axis of rotation 78. Upper wheel 80. Straight rack 82. Intermediate wheel 84. Intermediate mobile 86. Intermediate pinion 88. Toothed sector 90. Second rake 92. Fourth spring 94. Shutter 96. Observer 98. Transparent support 100. Upper face 102. Lower face 104. Representation of the Moon 106. Substrate 108. Aspherical plano-concave lens 110. Flat surface 112. Aspherical concave surface 114. Bend 116. Flat edges 118. Representation of the Moon

Claims (14)

1. Optical device comprising a transparent support (98) provided with an upper face (100) and a lower face (102) which extends at a distance from the upper face (100), this transparent support (98) forming a lens (108) of plano-concave shape delimited on a first side by a flat surface (110), and delimited on a second side, opposite to the first side, by a concave surface (112), the optical device also comprising a shutter (94) which is arranged under the concave surface (112) of the transparent support (98), at a distance from the latter, the optical device finally comprising a substrate (106) arranged after the shutter (94), the optical device being arranged to superimpose the image of an edge of the shutter (94) formed through the plano-concave lens (108) with the image of an object disposed above or below said plan-concave lens (108). 2. Optical device according to claim 1, characterized in that the optical refractive index of the material in which the plane-concave lens (108) is made is between 1.60 and 1.85. 3. Optical device according to claim 2, characterized in that the optical refractive index is equal to 1.78. 4. Optical device according to one of claims 2 and 3, characterized in that the plano-concave lens (108) is made of glass or polymer. 5. Optical device according to one of claims 1 to 4, characterized in that the concave surface (112) is curved. 6. Optical device according to claim 5, characterized in that the concave surface (112) has an aspherical profile. 7. Optical device according to one of claims 1 to 6, characterized in that the shutter (94) has a curved profile. superimposing the image of an edge of the shutter (94) formed through the plano-concave lens (108) with the image of an disposed object 8. Optical device according to claim 7, characterized in that the shutter (94) has a hyperbolic profile. 9. Optical device according to one of claims 1 to 8, characterized in that a representation (104) of the Moon is transferred to one of the upper (100) or lower (102) faces of the transparent support (98). , the optical device also comprising drive means (72) which, intended to be driven by a clockwork movement, drive the shutter (94), the shutter (94) and the substrate (106) exhibiting contrasts display inverted with respect to each other, the shutter (94) being moved from an initial position to a final position for a duration of a lunar cycle, so as to reveal day after day to an observer (96) the aspect of the Moon which changes from the new moon to the first quarter moon, then from the first quarter moon to the full moon, then to the last quarter moon and finally to the new moon, the shutter (94 ) being recalled by the drive means from its final position to its initial position at the end of the lunar cycle. 10. Optical device according to claim 9, characterized in that the drive means (72) comprise a rectilinear rack (80) with which the shutter (94) is fixedly coupled in translation. 11. Optical device according to claim 10, characterized in that it comprises a play take-up device of which an upper wheel (78) comprises an axis of rotation (76) on which a lower wheel (74) of the drive means (72) is mounted to rotate freely, this lower wheel (74) meshing with the rectilinear rack (80). 12. Optical device according to one of claims 10 and 11, characterized in that the clockwork movement comprises a timer mobile which kinematically drives a cam (52) which performs a complete revolution on itself in an integer number of times a lunar cycle, this cam (52) having a profile (58) permanently followed by a first rake (62), this first rake (62) being provided with a toothed sector (64) by which it meshes with the means drive (72). 13. Optical device according to claim 12, characterized in that the first rake (62) is provided with a feeler nose (66) by which it continuously follows the profile (58) of the cam (52), this profile ( 58) being shaped as a spiral staircase and having at least one substantially rectilinear indentation (60) so that, shortly before the start of a new lunar cycle, the feeler nose (66) is at the top of the profile ( 58) of the cam (52), then falls along the step (60), the first rake (62) driving during this movement by its toothed sector (64) a pinion (68) which is kinematically connected to the means of 'training (72). 14. Optical device according to one of claims 12 and 13, characterized in that the upper wheel (78) is engaged, on the one hand with the rectilinear rack (80), and on the other hand with an intermediate wheel ( 82) of an intermediate mobile (84) which also comprises an intermediate pinion (86), this intermediate pinion (86) meshing with a toothed sector (88) of a second rake (90) which is elastically constrained by the force of return of a fourth spring (92).