ARRANGEMENT AND METHOD FOR INCREASING THE FUNCTIONAL SAFETY OF AN OPTO-PYROTECHNIC INITIATOR

Abstract

An arrangement has an opto-pyrotechnic initiator, at least one laser, and an optical fibre, via which the laser radiation of the laser is guided to the opto-pyrotechnic initiator. Also disclosed is a method for improving the safety of such an opto-pyrotechnic initiator. At least one optical filter element having power-dependent or intensity-dependent transmission or reflection is arranged in the beam path of the laser radiation between the laser and the initiating impingement location of the laser radiation in the initiator. The filter element and the beam guidance for the laser radiation are selected such that for a laser power of the laser, that is intended to effect an initiation, the filter element has a higher transmission or reflection or can be switched to a higher transmission or reflection than for a lower laser power by application of an optical or electronic signal that is independent of the laser radiation.

Claims

1. Arrangement with opto-pyrotechnic initiator, in which a pyrotechnic mixture can be ignited by the effect of laser radiation, at least one laser which emits the laser radiation, and an optical fibre, via which the laser radiation is guided to the opto-pyrotechnic initiator, characterized in that an optical filter element having power-dependent or intensity-dependent transmission or reflection for the laser radiation is arranged in a beam path of the laser radiation between the laser and an initiating impingement location of the laser radiation in the opto-pyrotechnic initiator, wherein the filter element and a beam guidance of the laser radiation through the filter element are selected such that for a laser power of the at least one laser by which an initiation is to be effected in the opto-pyrotechnic initiator in the arrangement, the filter element has a higher transmission or reflection, or can be switched to a higher transmission or reflection by applying an optical or electronic signal that is independent of the laser radiation than at a lower laser power.

2. Arrangement according to claim 1, characterized in that the optical signal which is independent of the laser radiation of the at least one laser is laser radiation from at least one further laser, which is coupled into the filter element in such a way that the higher transmission or reflection with the laser power of the at least one laser required to effect the initiation is only attained by superimposing the laser radiation of the at least one laser with the laser radiation of the at least one further laser in the filter element.

3. Arrangement according to claim 1, characterized in that the optical filter element is formed by a saturable absorber.

4. Arrangement according to claim 1, characterized in that the optical filter element is formed by a combination of an optically non-linear medium that has power-dependent or intensity-dependent focusing or defocusing properties, with a following shutter on the beam path of the laser radiation which allows the laser radiation to pass unobstructed only with focusing by means of the non-linear medium.

5. Arrangement according to claim 1, characterized in that the optical filter element is formed by a thin-film reflector, whose reflectivity changes thermally by a phase transition.

6. Arrangement according to claim 5, characterized in that the optical filter element includes a controllable device for heating the thin-film reflector.

7. Arrangement according to claim 1, characterized in that the arrangement includes a plurality of lasers for the emission of the laser radiation, wherein laser beams emitted by the lasers are superimposed at least in the opto-pyrotechnic initiator and preferably also in the optical filter element.

8. Arrangement according to claim 1, characterized in that the laser radiation is focused onto or into the optical filter element through an optical system.

9. Arrangement according to claim 1, characterized in that the filter element is arranged in the opto-pyrotechnic initiator or between the optical fibre and the opto-pyrotechnic initiator.

10. Arrangement according to claim 1, characterized in that the filter element is arranged inside a housing for the one or more lasers or between the one or more lasers and the optical fibre.

11. Arrangement according to claim 1, characterized in that the filter element is inserted in the optical fibre.

12. Arrangement according to claim 1, characterized in that the laser is a semiconductor laser.

13. Method for improving the ignition safety of an opto-pyrotechnic initiator, in which a pyrotechnic mixture can be initiated by the effect of laser radiation, characterized in that an optical filter element with power-dependent or intensity-dependent transmission or reflection for the laser radiation is arranged in a beam path of the laser radiation between at least one laser, which emits the laser radiation, and an initiating impingement location of the laser radiation in the opto-pyrotechnic initiator, wherein the filter element and a beam guidance of the laser radiation through the filter element are selected such that with a laser power of the at least one laser, by which an initiation is to be effected in the opto-pyrotechnic initiator, the filter element has a higher transmission or reflection or is switched to a higher transmission or reflection than at a lower laser power by applying an optical or electronic signal that is independent of the laser radiation.

14. Method according to claim 13, characterized in that laser radiation from at least one further laser is used as the optical signal independent of the laser radiation, and is coupled into the filter element in such a way that the higher transmission or reflection at the laser power of the at least one laser needed to effect the initiation is only reached by superimposing the laser radiation from the at least one lasers with the laser radiation from the at least one further laser in the filter element.

15. Method according to claim 13, characterized in that the laser radiation is focused onto or into the optical filter element.

16. Method according to claim 13, characterized in that the filter element is arranged in the opto-pyrotechnic initiator or between an optical fibre via which the laser radiation is guided to the opto-pyrotechnic initiator and the opto-pyrotechnic initiator.

17. Method according to claim 13, characterized in that the filter element is arranged inside a housing for the laser or between the laser and at least one optical fibre via which the laser radiation is guided to the opto-pyrotechnic initiator.

18. Method according to claim 13, characterized in that the filter element is fitted into an optical fibre via which the laser radiation is guided to the opto-pyrotechnic initiator.

19. Method according to claim 13, characterized in that multiple lasers are used for the emission of the laser radiation, wherein laser beams emitted by the lasers are superimposed at least in the initiating impingement location of the laser radiation in the opto-pyrotechnic initiator, and preferably also in the optical filter element.

Description

BRIEF DESCRIPTION OF THE DRAWING

[0014] In the following text, the suggested arrangement and associated method will be explained again, in greater detail, with reference to exemplary embodiments in conjunction with the drawing. In the drawing:

[0015] FIG. 1 shows a construction concept of the ignition chain of an arrangement with opto-pyrotechnic initiator;

[0016] FIG. 2 shows a first example of a design of the suggested arrangement (partial view);

[0017] FIG. 3 shows a second example of a design of the suggested arrangement (partial view); and

[0018] FIG. 4 shows a third example of a design of the suggested arrangement.

WAYS OF IMPLEMENTING THE INVENTION

[0019] An opto-pyrotechnic initiation system consists of an electronically actuated laser 1, in the present example in the form of a laser diode, an optical fibre 2 and the opto-pyrotechnic initiator 3, as is represented schematically in FIG. 1. The opto-pyrotechnic initiator 3 ignites a pyrotechnic mixture, which provokes a corresponding pyrotechnic effect after the initiation. In principle, this may be an optical (light, mist, smoke), an acoustic (sound), a thermal or a mechanical (pressure, motion) effect or combinations thereof.

[0020] With the suggested arrangement and associated method, safety when using an opto-pyrotechnic initiation system is improved with an additional safety mechanism. For this purpose, an optical filter element is introduced into the optical segment between the laser 1 and the initiating impingement location of the laser radiation in the opto-pyrotechnic initiator 3, which element has a power-dependent or intensity-dependent transmission or reflection.

[0021] For this purpose, FIG. 2 shows a schematic representation of a first exemplary embodiment, in which only a part of the ignition chain is shown. In this example, the optical filter element 6 is arranged inside the opto-pyrotechnic initiator 3. The laser radiation 4 exiting the optical fibre 2 is focused into the filter element 6 via an optical system 5. The non-linear transmission function of the filter, i.e. for example the laser power threshold of the laser diode above which transmission increases significantly, is adjusted by the selection of the focal diameter in the filter element 6. The laser radiation 4 transmitted through the filter element 6 is directed, in particular focused via a further optical system 7 on the surface 8 that is sensitive for the optical initiation. In this patent application, the point of incidence of the laser radiation on this surface is called the initiating impingement location. The desired level of safety is achieved by appropriate selection of focal diameter in the filter element 6 and the original transmission of the medium of the filter element 6 at low power or intensity, set for example by the doping or length of a saturable absorber as filter element 6. Focal diameter and transmission at lower laser power are adjusted in such a way that, firstly with a laser power of the laser diode at which initiation is not to take place, the aforementioned threshold is not reached in the filter element and the power that reaches the surface 8 remains reliably, i.e. even during extended irradiation, below the desired ignition threshold or is lowered to below said ignition threshold by the low transmission of the filter element 6. Secondly, the focal diameter is selected such that the abovementioned threshold in the filter element is exceeded with a laser power at which initiation is to take place. If a reflecting instead of a transmitting filter element is used, the laser beam is reflected at this element, wherein the laser radiation 4 in FIG. 2 is then equivalent to the reflected radiation.

[0022] In a further exemplary embodiment, the filter element 6 is inserted in the optical fibre 2 in a stand-alone component 9, as indicated schematically in FIG. 3. FIG. 3 also shows only a part of the ignition chain. This arrangement inside the optical fibre 2 decouples any heating of the filter element 6 from the opto-pyrotechnic initiator 3 in the event of a malfunction, thus further increasing the functional safety of the ignition chain. Here too, the laser radiation is again focused on the optical filter element 6, and then collimated or focused for subsequent guidance in the optical fibre 2.

[0023] In a further exemplary embodiment, as represented schematically in FIG. 4, the filter component with the optical filter element 6 is arranged in the housing of the laser 1 between the laser-active material 10 situated in said housing, for example a semiconductor laser, and the optical fibre 2. This minimises the number of fibre couplings, and accordingly increases the robustness of the system. Here too, the laser radiation is focused into the filter element 6 via two optical systems 5, 7, and is then collimated or also focused for subsequent guidance of the laser radiation.

LIST OF REFERENCE NUMERALS

[0024] 1 Laser [0025] 2 Optical fibre [0026] 3 Opto-pyrotechnic initiator [0027] 4 Laser radiation [0028] 4 Laser radiation after passing through filter element [0029] 5 Optical system [0030] 6 Filter element [0031] 7 Optical system [0032] 8 Surface sensitive for optical initiation [0033] 9 Component with filter element [0034] 10 Laser-active material