CA1120757A

CA1120757A - Device for separating a light beam emitted by a source from a coaxial reflected beam received by a sensor

Info

Publication number: CA1120757A
Application number: CA000329256A
Authority: CA
Inventors: Jean Neyroud; Francois Danel
Original assignee: La Telemecanique Electrique SA
Current assignee: Telemecanique SA
Priority date: 1978-06-07
Filing date: 1979-06-07
Publication date: 1982-03-30
Also published as: GB2027222A; CH634420A5; JPS54160253A; IT7923314A0; IT1120779B; FR2428268B1; BR7903580A; GB2027222B; FR2428268A1; DE2922974A1

Abstract

BREVET D'INVENTION ORGANE SEPARATEUR D'UN FAISCEAU DE LUMIERE EMIS PAR UNE SOURCE ET D'UN FAISCEAU REFLECHI COAXIAL RECU PAR UN CAPTEUR Invention : Jean NEYROUD François DANEL Société dite LA TELEMECANIQUE ELECTRIQUE Pour séparer le faisceau émis par un laser du faisceau réfléchi par une surface suivant le même trajet, on utilise un miroir sphérique percé d'un orifice qui transmet le faisceau émis et focalise le faisceau réfléchi sur un photo-détecteur. Figure unique Par procuration de la société dite : LA TELEMECANIQUE ELECTRIQUEPATENT OF INVENTION SEPARATOR OF A BEAM OF LIGHT EMITTED BY A SOURCE AND OF A COAXIAL REFLECTED BEAM RECEIVED BY A SENSOR Invention: Jean NEYROUD François DANEL Company known as ELECTRIC TELEMECANIQUE To separate the beam emitted by a laser from the beam reflected by a surface following the same path, a spherical mirror pierced with an orifice is used which transmits the emitted beam and focuses the reflected beam on a photo-detector. Single figure By proxy from the company known as: ELECTRIC TELEMECANIQUE

Description

~ 7 L'invention a pour objet un organe destine a séparer des .
faisceaux lumineux respectivement emis par une source et refle-chis5 suivant le même trajet, en vue de la reception par un photo-detecteur.
Une application interessante mais non limitative de l'inven-tion concerne la realisation d'un emetteur-recepteur opto-electronique destine a detecter la presence, la forme ou la posi-tion d'objets, ou à capter une information se presentant sous 'la forme de zones plus ou moins reflechissantes formant un code, et 10 dans lesquels, pour des raisons pratiques et, en particulier, afin de reduire l'encombrement, les faisceaux emis et reflechis suivent 'le même trajet. Le recepteur ne pouvant alors evidem-ment pas se trouver sur ledit trajet, il faut devier le faisceau reflechi avant qu'il n'atteigne le point d'emission et l'organe qui separe ainsi les deux faisceaux doit perturber le moins possible le faisceau emis et provoquer la plus faible perte de lumière possible.
Dans l'art antérieur, on utilise le plus souve~., comme organe separateur, une lame semi-transparente inclinee à ~5 sur 20 le faisceau d'emission et renvoyant le faisceau reflechi vers le recepteur. Cette solution presente divers inconvénients, qui seront exposes dans la suite et dont le plus evident est une perte notable de lumière.
L'invention propose de remplacer une telle lame semi-transparente par un miroir perce, de preference spherique.
Elle sera mieux comprise à l'aide de la description ci-après :
La figure unique du dessin annexe represente un separateur conforme à un mode d'execution prefere de l'invention~ utilise 30 dans un emetteur-recepteur opto-electronique du type à faisceaux coaxiaux.
.~

Ce separateur est constitue d'un miroir spherique 1, de centre 0, perce d'un petit orifice 2 de preference situe au centre de sa surface. La source emettrice de lumiere, par exem ple un laser 3, est disposee pour emettre un faisceau -fin Fl incline par rapport à la surface d~ miroir et qui traverse sans pertes l'orifice 2. Ce faisceau eFfectue une exploration de surfaces reflechissantes, telles que S, sous l'action d'un dispositif de balayage, qui peut revêtir diverses formes d'exe-cution, et que l'on a symbolise par deux miroirs plans 4 et 5.
10 Ceux-ci tournent, par exemple, autour de deux axes perpendicu-laires entre eux, de façon à effectuer un balayage ayant une composante horizontale et une composante verticale.
La lumière réfléchie par la surface S effectue le trajet inverse, mais se présente sous la forme d'un faisceau F2 beau-coup plus divergent que Fl. Ce faisceau est reflechi par le miroir 1 qui le focalise au voisinage de son foyer F, où est situe un photo-détecteur 6.
Une partie du faisceau F2 traverse évidemment l'orifice 3 et est perdue. Toutefois, si l'on considère, a titre d'-20 exemple, un miroir 1 de 20 mm de diamètre, ayant un rayon decourbure de 100 a 200 mm, muni d'un orifice de 2 mm de diame-tre (suffisant pour laisser passer le faisceau laser d'un dis-positif emetteur-receptellr opto-electronique), la perte de lumiere resultante sera de 1 %. Cette valeur ect tres inferieure a celle que causerait un separateur a lame semi-transparente.
En effet, la rnoitie de la lumiere emise est reflechie par une telle lame et inutilisee pour l'exploration tandis que la perte est egalement de 50 % au retour9 c'est-a-dire que la lumiere captee par le recepteur n'est finalement que de 25 % de ce qu'~
30 elle serait en l'absence de pertes (à comparer a une valeur theorique de 99 % dans l'exemple ci-dessus).

7 5i'7 Il convient de noter par ailleurs qu'en cas de presence de poussière sur une lame semi transparente, la lumiere peut être transmise directement de l'emetteur au recepteur par diffusion, ce qui engendre un bruit nuisible à la sensibilité de réGep-t;on.
Cet inconvenient est supprime par l'utilisation d'un miroir spherique perce.
Finalement, la portée d'un tel emetteur-recepteur de de-tection opto-electronique se trouve largement accrue.
Il va de soi que la forme du miroir, son inclinaison sur l'axe du faisceau émis ainsi que la position et les dimensions de l'orifice pourront varier, sans s'ecarter de l'esprit de l'invention. Celle~ci ne porte pas sur le dispositif de balay ge, qui pourra revetir des formes diverses. ~ 7 The subject of the invention is a member intended to separate .
light beams respectively emitted by a source and reflected chis5 following the same route, for reception by a photo-detector.
An interesting but non-limiting application of the invention tion concerns the realization of an opto-transceiver electronics intended to detect the presence, the form or the posi-tion of objects, or to collect information presented under 'the form of more or less reflective zones forming a code, and 10 in which, for practical reasons and, in particular, to reduce clutter, beams emitted and reflected follow the same route. The receiver cannot then obviously not lie on the said path, you have to deflect the beam reflected before it reaches the point of emission and the organ which thus separates the two beams must disturb the least possible the beam emitted and cause the lowest loss of light possible.
In the prior art, most often used.
separator, a semi-transparent blade inclined at ~ 5 on 20 the emission beam and returning the reflected beam to the receiver. This solution has various drawbacks, which will be exposed in the following and the most obvious of which is a noticeable loss of light.
The invention proposes to replace such a semi-blade transparent by a pierced mirror, preferably spherical.
It will be better understood using the description below.
after:
The single figure in the accompanying drawing represents a separator in accordance with a preferred embodiment of the invention ~ uses 30 in an opto-electronic beam type transceiver coaxial.
. ~

This separator consists of a spherical mirror 1, of center 0, with a small hole 2 preferably located at center of its surface. The light emitting source, for example ple a laser 3, is arranged to emit a beam -end Fl inclines with respect to the mirror surface and which passes through without losses orifice 2. This beam performs an exploration of reflective surfaces, such as S, under the action of a scanning device, which can take various forms of exe-cution, and which we symbolized by two flat mirrors 4 and 5.
10 These rotate, for example, around two perpendicular axes.
between them, so as to carry out a sweep having a horizontal component and a vertical component.
Light reflected by surface S travels reverse, but is in the form of a beautiful F2 beam blow more divergent than Fl. This beam is reflected by the mirror 1 which focuses it in the vicinity of its focus F, where is locates a photo detector 6.
Part of the beam F2 obviously crosses the orifice 3 and is lost. However, if you consider, as a-20 example, a mirror 1 of 20 mm in diameter, having a radius of curvature of 100 to 200 mm, provided with an orifice of 2 mm in diameter.
tre (sufficient to allow the laser beam of a device to pass positive optoelectronic transceiver), loss of resulting light will be 1%. This value ect very lower to that which a separator with semi-transparent blade would cause.
Indeed, the half of the light emitted is reflected by a such blade and unused for exploration while loss is also 50% on return9 i.e. the light captured by the receiver is ultimately only 25% of what ~
30 it would be in the absence of losses (compare to a value theoretical of 99% in the example above).

7 5i'7 It should also be noted that in the presence of dust on a semi transparent slide, the light can be transmitted directly from the transmitter to the receiver by broadcast, which generates a noise harmful to the sensitivity of réGep-your.
This disadvantage is eliminated by the use of a spherical mirror pierced.
Finally, the range of such a transceiver opto-electronic tection is greatly increased.
It goes without saying that the shape of the mirror, its tilt on the axis of the emitted beam as well as the position and dimensions orifice may vary, without departing from the spirit of the invention. This does not relate to the scanning device ge, which can take various forms.

Claims

1. Optical device comprising a source of light cooperating with a first face of a mid glow and emitting a first narrow light beam constant direction along its entire length, said mirror being inclined relative to said first beam skin and having a central opening through which passes substantially all the light of said first beam, which is reflected after passing through through the hole, by a reflecting surface angularly movable which provides a second beam having a direction of propagation of light pours from that of the first beam, from said sur-reflecting side to the second side of the mirror, said second beam being substantially more diverse gent than the first and having a continuous surface of-impact on said second face, said surface of im-pact permanently surrounding said orifice and having a surface in relation to which that of said aperture is negligible, and a light sensor cooperating with said second face and arranged for permanently receive all the light from the second beam reflected by said second face.

2. Device according to claim 1, characterized in that said mirror is a mirror concave spherical arranged to focus the second beam on the sensor.