EP0351380A2 - Optical system for permanent luminous signals of different colours, especially for railway signalling - Google Patents

Abstract

In order to form an optical system for permanent luminous signals of three different colours, in particular for railway signalling, which has a smaller size, a greater luminosity and a higher stigmatism as compared with the systems known hitherto, and comprising three light sources 5 of different colour, with three corresponding mirrors 3 and three corresponding dichroic filters 6,7,8 arranged according to the Gouiler-Prande pentagonal prism, and with an aspheric emergence lens 9, it is provided for the aspheric lens 9 to be arranged with its focal point F coinciding with the centre 10 of the pentagonal prism, and for a divergent lens 11 of quadric surface and with virtual focus to be placed between the said centre 10 and the said aspheric lens 9, and with the axes of the divergent lens 11 and of the aspheric lens 9 coinciding. The said divergent lens 11 is of the negative-elliptical meniscus type, the spherical convex face of which, turned towards the aspheric lens 9, has its centre of curvature coinciding with the focal point of the said aspheric lens, and the concave face of which, ellipsoidal or spherical, can be obtained from Descartes' general equation. As an alternative, the divergent lens 11 is of the concave plano-hyperbolic type, or spherical plano-concave type, with the concave face turned towards the aspheric lens 9 and with the focal point coinciding with that of the said aspheric lens 9. The said mirrors 3 are of the parabolic type with maximum relative output. <IMAGE>

Description

The present invention relates to an optical system for a signaling device with signals of variable color, permanently illuminated, in particular for railway signals.

It is known that before the advent of dichroic filters, the devices for permanently emitting light signals used an electro-optical-mechanical system constituted by a spherical mirror at the center of curvature of which the light source of a bulb and an aspherical lens having its focal point coincide with the center of the light source. The different colorations of the signal were obtained using several flat filters, of colored glass, arranged in series, perpendicular to the axis of the conical beam of the light rays, at a point located between the light source and the aspherical lens. The selection and control of the mechanism of the color filters was obtained by means of a relay, and therefore proved to be complex and expensive, of low efficiency and resulting in high energy consumption.

With the advent of dichro c filters, their application to railway signaling with permanent light signals helped to eliminate the moving parts of the system; dichro ques filters arranged in an appropriate way, being able to operate in a static way the selection of the radiations coming from several light sources by switching on and off of the lamps, allow obvious energy savings and a constructive simplification.

However, in the context of such solutions, considerable problems still remained unsolved, which adversely affected the brightness, the bulk and the optical perfection of the optical systems used. Indeed to solve, in both mobile and static optical systems, the problem of the convergence of the real filament of the lamp in the focal point of the main aspherical lens, were used either optical capacitors or elliptical mirrors. On the other hand, optical capacitors had the disadvantage of increasing the axial path due to the need to redo converge the image of the filament in the focal point of the aspherical lens, resulting in an unacceptable increase in the size of the device. signaling; in addition, the use of optical elements which are not perfectly corrected for spherical aberrations causes a considerable lack of stigmatism, to which is added the possibility of obtaining only small apertures. For their part, elliptical mirrors have the drawback of enlargement. The requirement a greater luminosity indeed requires the increase of the relative opening, but, with equal openings, it is necessary to reduce the first focus of the elliptical mirror and this causes a greater enlargement of the light source in the superposition on the focal point of the main lens, leading to a major aberration of the emitted radiation and lower luminous efficacy. In addition, the fact of not having to use very enveloping mirrors further compromises the brightness which results from the maximum solid angle received.

The present invention aims to eliminate the aforementioned drawbacks in relation to the mechanical bulk, the brightness and the stigmatism of a signaling device with signals of variable color of the type with dichroic filters.

This result was achieved in accordance with the invention by providing an optical system for a signaling device, with permanently light signals, of the dichroic filter type, in particular for railway signals, comprising several light sources (filament lamp ) suitably arranged with respect to a dichroic filter system and an aspherical lens of emergence of the beam of rays which constitute the signal, having an appropriate focal distance and with its focal point placed in the center of said filter system dichro ques, a system in which each light source, if it is of the filament type, is placed on the focal point of a parabolic mirror. An intermediate diverging lens, on the second degree surface, with its virtual focus superimposed on that of the output aspherical lens, is arranged at an appropriate distance, perpendicular to the axis of the system, between said center of the dichro filter system and said aspherical emergence lens.

According to a first preferred embodiment of the invention, said divergent lens with a second degree surface is characterized by a convex spherical face turned towards said aspherical lens, and the center of curvature of which coincides with the focal point of said lens. aspherical, and by a concave ellipso dal face which is determined from the distance between the aspherical lens and its focal point and by the section necessary for the beam of rays coming from the parabolic mirrors. As a variant, the concave face is the osculating surface of the abovementioned ellipsoidal surface.

According to another preferred embodiment of the invention, the intermediate diverging lens is a concave plane-hyperbolic lens with the planar face facing the dichroic filter system, with the hyperbolic concave face facing the aspherical lens and with its virtual focus coincides with that of the aspherical lens.

Advantageously, it is possible to obtain parabolic mirrors of maximum relative efficiency by performing the calculations of the distances and curvatures of the surfaces of the second degree starting from the oval of Descartes and taking into account the photometric solid of the light source.

According to other characteristics, in accordance with the invention, between each light source and the corresponding dichro filter, a colored paste filter is interposed to increase the chromatic security of the optical system and / or a spherical recovery mirror having its center of curvature. coincide with the focus of the parabolic mirror in order to prevent the divergent lens from also seeing the real focus of the parabola, in addition to the virtual focus of the aspherical lens

According to other characteristics, in accordance with the invention, and in place of the beams emitted by the parabolic mirrors, the light sources consist of beams of laser rays.

The solution proposed by the present invention allows the production of an illumination or signaling device of variable color, in particular, but not exclusively, for railway signaling, which makes it possible to reduce the axial bulk, to increase the brightness , use lamps with more concentrated filaments or xenon lamps of lower power, to reduce energy consumption, to obtain a better stigmatism, to correct possible aberrations even chromatic, especially if the diverging lens is transformed into an aspherical achromatic doublet able to correct chromatically the whole system.

• la FIG. 1 représente une vue de dessus en coupe suivant un plan horizontal axial, d'un dispositif de signalisation, conformément à l'invention, selon une première forme de réalisation;
• la FIG 2 représente la vue de dessus d'une première lentille divergente intermédiaire (ménisque elliptique-négative) pour le dispositif de la Fig 1;
• la FIG 2A représente la vue en coupe partielle suivant la ligne A-A de la Fig. 2;
• la FIG. 3 représente la vue de dessus du détail d'une deuxième lentille divergente intermédiaire (plan-hyperbolique concave) pour le dispositif de la Fig.1;
• la FIG. 3A représente la vue en coupe partielle suivant la ligne A-A de la Fig. 3;
• la FIG. 4 représente le schéma géométrique pour le calcul d'une lentille ménisque elliptique-­négative conformément à l'invention;
• la FIG. 5 représente la vue de face du détail d'un miroir de récupération pour le dispositif de la Fig.1;
• la FIG. 5A représente la vue en coupe suivant la ligne A-A de la Fig. 5;
• la FIG. 6 représente la vue en plan du détail d'un miroir parabolique de rendement maximum pour le dispositif de la Fig.1;
• la FIG. 6A représente la vue en coupe suivant la ligne A-A de la Fig. 6;
• la FIG. 7 représente la vue en plan d'un miroir parabolique simplifié (F=8) pour le dispositif de la Fig.1;
• la FIG. 7A représente la vue en coupe suivant la ligne A-A de la Fig. 7;
• la FIG. 8 représente la vue en plan du détail d'une lentille plane négative de "Fresnell";
• la FIG. 8A représente la vue en coupe partielle suivant la ligne A-A de la Fig. 8.

These advantages and characteristics as well as others will be more and better understood by each person skilled in the art in the light of the description which follows and with the aid of the appended drawings given by way of practical example of the invention, but to do not consider in the limiting sense; drawings in which:

• FIG. 1 shows a top view in section along an axial horizontal plane, of a signaling device, according to the invention, according to a first embodiment;
• FIG 2 shows the top view of a first intermediate diverging lens (elliptical-negative meniscus) for the device of Fig 1;
• FIG 2A shows the partial sectional view along line AA of FIG. 2;
• FIG. 3 shows the top view of the detail of a second intermediate diverging lens (concave hyperbolic plane) for the device of FIG. 1;
• FIG. 3A represents the view in partial section along the line AA of FIG. 3;
• FIG. 4 represents the geometrical diagram for the calculation of an elliptical-negative meniscus lens according to the invention;
• FIG. 5 shows the front view of the detail of a mirror recovery for the device of Fig.1;
• FIG. 5A shows the sectional view along line AA of FIG. 5;
• FIG. 6 shows the plan view of the detail of a parabolic mirror of maximum efficiency for the device of FIG. 1;
• FIG. 6A shows the sectional view along line AA of FIG. 6;
• FIG. 7 shows the plan view of a simplified parabolic mirror (F = 8) for the device of FIG. 1;
• FIG. 7A shows the sectional view along line AA of FIG. 7;
• FIG. 8 shows the plan view of the detail of a negative planar "Fresnell"lens;
• FIG. 8A shows the partial sectional view along line AA of FIG. 8.

Reduced to its essential structure and with reference to FIG. 1 of the accompanying drawings, an optical system for a signaling device with signals of three different colors, permanently lit, in accordance with the present invention, comprises:
- three parabolic mirrors 3, with the relative axes respectively, coaxial, at 45 ° and perpendicular to the longitudinal axis XX of the device and with a lamp 5, with very concentrated filament, for example of the xenon type, placed in the focal point F each of said mirrors;
- three dichroic filters 6,7 and 8 respectively opposite said mirrors 3 and arranged at appropriate angles according to the principle of the pentagonal prism of Goulier-Prande and produced so that the filter 7 is transparent to a first color (for example yellow) and reflecting a second color (for example green), filter 8 is transparent to said second color (green) and filter 6 is transparent to a third color (for example red) and reflecting for the two aforementioned colors (yellow and green). In this way, depending on the activated light source 5, one obtains, along the longitudinal axis XX of the device, a beam of parallel rays, of the color which the dichro filter which corresponding has left behind and which is reflected by the others. filters encountered on its route;
- a main aspherical exit lens 9, arranged with its axis coinciding with the axis XX of the beam of rays coming from the system and with its focal point F1 coinciding with point 10 which we will call hereinafter the center of symmetry of the system;
- An intermediate diverging lens 11 with a second degree surface, and virtual focus, disposed between the center 10 of the system and said aspherical lens 9 and with its axis on that XX of the system. Said lens 11 is a lens of the type called negative meniscus-elliptical with the concave face 12 facing the filter system and the spherical face 13 facing the aspherical lens 9 and whose center of curvature coincides with the focus F1 of the aspherical lens 9. The concave face of said lens 11 is preferably ellipsoidal and defined by the equation of the Descartes oval, or else spherical following the corresponding osculating sphere.

L'épaisseur de la lentille "s" le long de l'axe x-x sera comprise entre 0,2 et 15 mm.In the first case, by setting a = 0.5 - 200 mm and the nature of the material (N) constituting the lens, it is possible to obtain "b" and therefore the x, y coordinates of each point of the concave face , by the formula:

The thickness of the lens "s" along the axis xx will be between 0.2 and 15 mm.

In the second case, the radius of the osculating sphere is provided by r = 2 l. d / l + d (where l = V1F1 = V2F2 and d = a + c = F2V1 = F1V2 see fig. 4) and may have a value between 5 and 200 mm; the thickness could be s = 0.2 - 15 mm.

The definition and positioning of the various elements of the system are carried out as follows. By way of example, the lenses can be made of optical or semi-optical glass, worked optically or semi-optically, or possibly of plastic material CR39 or any other having an index of between 1.33 and 1.95. The parabolic mirrors can be produced by electroforming of nickel or the like and treated with Rhodium or the like. After determining the focal distance of the aspherical lens 9, the distance between the face 12 of the intermediate lens 11 and the flat face of the lens can be determined. aspherical lens 9 which is turned towards the dichroic filter system and this on the basis of the dimension of axial dimension desired. The intersection of said face 12 with the cone having its apex at point 10 of the system and its base on the flat face of the aspherical lens 9, determines the useful diameter of the beam of parallel rays which must come from each parabolic mirror. This diameter, in combination with angular connotations concerning the emission of the light source relative to its photometric solid, allows, according to a calculation scheme starting from the Descartes oval and well known to those skilled in the art, to determine the maximum relative efficiency mirror and the useful diameter of the intermediate diverging lens.
This diameter, with the distance from the focal point of the aspherical lens, provides the basic elements for determining the curvature of the concave face 12 of the intermediate lens 11.

Dans ce cas "a" pourra être fixé entre 0,5 et 200 mm et l'épaisseur "s" entre 0,2 et 15 mm. La face de ladite lentille plan-hyperbolique (14) qui est tournée vers la lentille asphérique (9) peut être avantageusement du type "Fresnell" avec les elements prismatiques positionnés de manière à obtenir l'effet divergent désiré (Fig 8 et 8A).The essential characteristics which the diverging lens 11 must have:
- be located in the conical beam of rays with the virtual focal point placed on the focal point of the aspherical lens so as to obtain the smallest axial bulk;
- be correlated, with regard to the aperture and the inter-distance, with the other elements of the system, in relation either to the maximum optical exploitation of the aspherical lens, or to the maximum energy yield of a parabolic mirror of maximum efficiency to obtain the maximum brightness;
- have a second degree surface to solve the problem of spherical aberration and achieve the stigmatism of the desired optical path. As for the final choice of the divergent lens, there are many solutions. One of them is represented by a concave plane-hyperbolic lens 14, indicated as a second embodiment, (see FIGS. 3 and 3A of the appended drawings) with the plane face 15 facing the dichro filter system and the concave face 16 towards the aspherical lens 9. In this case also, the various calculations are carried out in an analogous manner taking into account the fact that the Descartes oval is transformed into a hyperbola whose focal point is coincident with the focal point F1 of the aspherical lens 9

In this case "a" can be fixed between 0.5 and 200 mm and the thickness "s" between 0.2 and 15 mm. The face of said plane-hyperbolic lens (14) which faces the aspherical lens (9) can advantageously be of the "Fresnell" type with the prismatic elements positioned so as to obtain the desired diverging effect (FIGS. 8 and 8A).

Other solutions can be envisaged with divergent spherical lenses, even if they have disadvantages in terms of stigmatism and spherical aberration.

While the aspherical lens can remain devoid of anti-reflective treatment, it is preferable that the convex face of the diverging lens 11 is treated at least with a monomolecular layer of magnesium fluoride (Mg F2), in particular in the case of non-exuberance of energy and to significantly reduce the so-called "fantasy effect". Anti-reflective treatment can be more effectively multi-layered.

.With regard to the reflective parables of the glass mirrors 3, the equation of the parabolic curve concerned is, by simplifying: y = 4 fx with f = focal distance; in addition, a treatment should be carried out which is, in the visible range, also reflecting for all wavelengths, and preferably:
- an aluminizing and protective treatment with SiO or SiO₂, a simpler, safer and more repeatable process to obtain reflections with optical yields of up to 90%; or
- a multilayer treatment improving the reflection capacity, but not selective, to obtain a yield of approximately 96%; or
- a dichro treatment only in cold light to avoid a reflection of the heat radiation on the other optical elements of the system while retaining an optimal capacity of reflection; or
- a silvering (or similar) treatment of the posterior face and with the required protection and by making this face with

f = f1 - $\frac{\text{Δ}}{\text{not}}$

.

Advantageously, in accordance with the invention, provision is made, upstream of each dichro filter that 6,7,8 a spherical mirror 18 for recovering radiation, preferably obtained by an aluminizing treatment and protection with silicon monoxide , which is oriented so that the center of curvature coincides with the focal point F of the corresponding parabolic mirror, in order to prevent the divergent lens 11 from also directly seeing the real focal point of the parabola, in addition to the beam of rays coming, by reflection, from parabolic mirrors.

In order to prevent possible positioning errors of the dichroic filters and to eliminate considerable damage in the event of deterioration over time of the sandwich of the interference filters relating to the Gouiler-Prande solution, it is advantageously provided, in accordance with to the invention, to have upstream of each dichro filter that, a filter 19 colored in paste, the corresponding loss of radiation caused being able to be insignificant compared to the excess of radiation that it is possible to obtain thanks to the parabolic mirrors d maximum efficiency. This arrangement makes it possible to increase the security of the system, which is why even a possible downstream error or deterioration would be automatically detected and / or controlled both during the assembly phase and at the actual operating location.

It goes without saying that any measure known in self aimed at subsequently correcting chromatic or extra-axial aberrations can be applied to the optical system according to the invention.

The advantages obtained with the optical system according to the invention compared to the systems known to date, especially in the field of railway signaling, essentially consist in greater brightness with equal light efficiency of the light sources used and therefore in possible energy savings; in a reduction in dimensions in the axial direction, with obvious savings in design and manufacturing costs; in a greater stigmatism of the system perfectly corrected from the optical-geometric point of view with regard to the spherical aberration for a point located on the axis XX and a lower aberration for the points located off the axis, so that the beam emitted turns out to be more correct and more exactly repeatable.

In order to reduce the non-homogeneous and non-repeatable effects of the photometric solid in the case of filament light sources, it is proposed, in accordance with the invention, to use an anti-Newton glass plate to allow a slight diffusion of the beam. issued; this plate can be placed in front of each light source or at any useful point on the axis XX and perpendicular thereto. As a variant, it is possible to treat with an anti-Newton effect the flat face of the aspherical lens 9 or one face of the divergent lens 11 and / or that of the parabolic mirrors 3.

In order to further improve the brightness of the signal, provision is made, in accordance with the invention, for using monochromatic light sources of the laser type, for example in the solid state, moreover making it possible to eliminate the parabolic mirrors 3. The diverging lens 11 may thus have a thickness "s" of between 0.2 and 10 mm; and its concave face, if it is spherical, may have a radius of r = 0.5 ÷ 100 mm. The lens 11, when it is of the concave plane-hyperbolic type, can be determined by setting a = 2 mm and its thickness can have a value s = 0.2 ÷ 10 mm.

Examples of realization

The values of the coordinates of two diverging lenses and of two parabolic mirrors, used in concrete embodiments considered, will be indicated below. a) Elliptical-negative meniscus lens y (mm) x (mm) y (mm) x (mm) 5 0.553 20 10,052 10 2,261 25 17.609 15 5.294 30 35,764 b) Plan-hyperbolic lens (with a = 10 and N = 1.523) y (mm) x (mm) y (mm) x (mm) 11 5.264 21 21,212 12 7.619 22 22.509 13 9.541 23 23.79 14 11,254 24 25,061 15 12,842 25 26,320 16 14.347 26 27,568 17 15,792 27 28.809 18 17,192 28 30,042 19 18.557 29 31,269 20 19,896 30 32,490 c) Parabolic mirror of maximum relative efficiency (with f = 3.751 mm) y (mm) x (mm) y (mm) x (mm) 5 1,664 25 41,652 10 6.664 28 52,248 15 14.994 30 59.979 20 26,657 d) Simplified parabolic mirror (with f = 8mm) y (mm) x (mm) y (mm) x (mm) 2.5 0.195 15 7.031 5 0.781 17.5 9.570 7.5 1.757 20 12,500 10 3.125 22.5 15,829 12.5 4.692 25 19.531 15 7.031 27.5 23,632

Claims (21)

1) Optical system for permanent light signals, of the dichroic filter type, in particular for railway signaling, comprising several light sources (5) with reflecting glass mirrors (3) and dichroic filters (6,7 , 8) correspondents arranged according to the pentagonal prism of Gouiler-Prande, and an aspherical lens (9) of emergence of the beam of light rays which constitute the signal, characterized in that said aspherical lens (9) is arranged so that that its focus (F1) coincides with the point (10) considered as the optical center of symmetry of the pentagonal prism; in that a divergent lens (11,14), on the second degree surface, is interposed between said point (10) of the pentagonal prism and said aspherical lens (9) and with its axis coincide with that XX of the aspherical lens (9); and in that said mirrors (3) are parabolic and advantageously of maximum relative efficiency. 2) Optical system according to claim 1, characterized in that said diverging lens (11) is an elliptical-negative meniscus lens whose spherical convex face (13), which faces towards said aspherical lens (9), has its center of curvature coincide with its own virtual focus and with the focus of said aspherical lens (9). 3) Optical system according to claim 2, characterized in that the concave face (12) of said lens (11) elliptical-negative meniscus is ellipso dal and that its coordinates can be taken from the equation of the Descartes oval by fixing the nature of the lens material and the major semi-axis: a = 1 ÷ 200 mm. 4) Optical system according to claim 2, characterized in that the concave face (12) of said lens (11) elliptical-negative meniscus, is spherical and its radius, which corresponds to that of the osculating sphere, is between 1 and 200 mm. 5) Optical system according to claim 2 and 3, characterized in that the thickness of the negative meniscus-elliptical lens (11) along the axis X-X is: s = 0.1 ÷ 15 mm. 6) Optical system according to claim 1, characterized in that said diverging lens (14) is a concave plane-hyperbolic lens, with the hyperbolic face (16) facing the aspherical lens (9) and with its focal point coinciding with that of the aspherical lens (9). 7) Optical system according to claim 6, characterized in that the coordinates of the concave face of said lens (11) concave hyperbolic plane (14) can be taken from the equation of the Descartes oval by setting a = 0 , 5 - 200 mm. 8) Optical system according to claim 6, characterized in that the concave face of said plan-hyperbolic lens (14) is spherical with a radius corresponding to that of the osculating sphere and between 1 and 200 mm. 9) Optical system according to claim 2 and 3, characterized in that the plane-hyperbolic lens (14) has, along the axis XX, a thickness:
s = 0.1 ÷ 15 mm. 10) Optical system according to claim 6, characterized in that said diverging lens (11,14) has the face which is respectively turned towards the dichro c filters or towards the aspherical lens (9), of the "Fresnell" type and with the prismatic elements positioned so as to obtain a divergent effect. 11) Optical system according to claim 1, characterized in that a color filter (19) is interposed between each light source (5) and the corresponding dichro filter. 12) Optical system according to claim 11, characterized in that a spherical mirror (18) is interposed between each light source (5) and the corresponding color filter (19) and with its center of curvature coincide with the focus of the mirror parabolic corresponding to allow the recovery of radiation. 13) Optical system according to claim 1, characterized in that the light sources (5) are sources of laser rays, and that the parallel beam emitted replaces that of the parabolic mirrors. 14) Optical system according to claim 1, characterized in that said lenses (9,11,14) are made of optical or semi-optical glass or other transparent materials with refractive index between 1.33 and 1.95. 15) Optical system according to claim 1, characterized in that said parabolic mirrors (3) are made by electroforming of nickel, chromium, silver, aluminum or the like, and preferably treated with rhodium or the like. 16) Optical system according to claim 1, characterized in that the reflective parabolas of said parabolic mirrors (3) are made of glass with a reflective surface treatment such as aluminization and with protection with SiO or SiO2. 17) Optical system according to claim 1, characterized in that the reflecting parabolas of said parabolic mirrors (3) are provided with a multilayer treatment to allow the increase of the reflection capacity. 18) Optical system according to claim 1, characterized in that the reflecting dishes of said parabolic mirrors (3) are provided with a treatment with cold light. 19) Optical system according to claim 1 and 15, characterized in that the reflective parabolas of said parabolic mirrors are made of glass, with the silvered rear face duly protected and in that said face is a parabolic surface parallel or practically parallel to the front face , and with the focal length (f) equal to that (f1) of the anterior face reduced by the thickness at the center divided by the refractive index (n) of the material

(f = f1 - $\frac{\text{Δ}}{\text{not}}$

). 20) Optical system according to claim 1, characterized in that it comprises at least one anti Newton glass plate placed at a point any useful light beam constituting the signal. 21) Optical system according to one or more of the preceding claims, characterized in that at least one of the faces of the lenses (9,11,14) and / or that of the parabolic mirrors (3) is treated with an anti Newton effect.

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