DE2735985A1 - Protection unit for human eye against electromagnetic beam - comprises liq. crystal unit with absorbent compound between two optically polarised glass plates - Google Patents

Abstract

The optical device is intended to protect the human eye from the deleterious effects of electromagnetic radiation, typically from laser beams. It consists of a substance (1) with optically non-linear characteristics, typically a liquid crystal with a nematic, smectic or cholesteric structure or a mixture of these. The crystal is enclosed by two plates (2) of optically, polarised materials. The liquid crystal is able to absorb a beam of laser light (3) impinging on the side remote from the eye. The optically polarised plates (2) are held between eye plates (4) which form a thermostat and reduces the heating effect which follows on from the absorption of the beam.

Description

The invention relates to a method and a pre

direction to protect the human eye or more sensitive optical Elements from the action of high intensity electromagnetic radiation, for example of a laser, with the help of a device arranged in the beam path of the object to be protected, the radiation at least weakening the medium.

From US-PS 32 66 370 is a filter system for limiting the radiation output an intense radiation source known, for example, to protect the eye serves against atomic lightning that occur in thornionukiearon explosions.

The protective effect is based on chemical processes, at best in time intervals of milliseconds and dunit run far too slowly to human Organs or sensitive optronic devices from damage by extremely short-term, to effectively protect intensive radiation effects.

From the DT-AS 12 53 824 there is then a controllable optical absorber mode known that besides its complicated composition for its intended purpose also has switching times that are far too long.

From the generic DT-PS 15 89 721 it is also known 8, Achieve switching times <10 sec. Here, the scattering of laser light becomes higher Intensity or the change in the refractive index in different irradiated Layers exploited1 whereby it is assumed that with low light intensities the same and, at high light intensities, different refractive indices in the different ones Layers occur. Since when radiating through these layers there is a scattering of the When light enters, a laser beam experiences a corresponding intensity depending on its intensity Weakening. However, this undoubtedly fundamental knowledge still has the disadvantage that at that time not enough media were known to deal with a realization ran without further ado The task of Invention consists in finding suitable classes of substances and their application, thus in time intervals of a few 10 9sec emitted pulse powers of several 10 EI watts for human organs or sensitive devices with the greatest possible safety can be rendered harmless. According to the invention, this object is achieved by that the radiation with the help of optically nonlinear substances with large nonlinear optical constants (e.g. Kerr constant) weakened or through self-focusing is suppressed. Although for these substances properties like the nonlinear ones Relationships between light intensity (field strength) and z. B. refraction or electrical Polarization are characteristic are only of interest in the present context the changes in the propagation behavior of the substance that can be achieved in the substance itself Radiation, less the effects that change it, such as frequency changes and the like.

The internal changes include, above all, self-focus, which occur when the refractive index changes while the substance is irradiated can. Here, the course of the refractive index changes within the irradiated Canal from the outside to the inside with an increasing tendency up to the occurrence of the focusing effect, so that a laser beam can be weakened or completely suppressed.

An advantageous development of the invention is seen in the fact that the radiation in the substance is broken down into partial beams by birefringence and then by means of a z. B.

changeable by an external electric or magnetic field Phase difference is deleted. The deletion effect comes here in a simple manner due to the fact that the externally supplied electrical or magnetic Fields can adjust the gradient of the refractive index.

As for the # actually eligible individual substances, liquid crystals with nematic, smectic or cholesteric structure or mixtures of liquid crystals with at least two different structures. Schiff bases are preferred or azo compounds in question. They have nonlinear optical constants that are at least two to three powers of ten above the value of quartz and are suitable therefore particularly in favor of fast switching from good transmission with low light level too strong absorption with high radiation intensity. One but such a concept also ensures a good interaction between the Window surfaces and the liquid crystal with regard to good intrinsic transmission as well as the smallest possible installation depth. This is important because a device of this type, for example, in the beam path in front of the human Eye should accommodate.

With a mixture of different liquid crystals, the focusing effect can be increased, so that on the one hand the own transmission, on the other hand also has a favorable influence on the overall length of the embodiments used for this purpose, d. H. can be shortened. This advantage as well as an improvement in the own mission is also supported by the fact that the liquid crystals - with suitable Treatment of the delimiting surfaces - get a good orientation.

In order to be able to apply the method according to the invention in practice, the substances detailed above must be enclosed in a cuvette be at least in the areas of the beam entrance and the beam exit each with one optically polished, electrically conductive layer to the Generating an external electric field aufweisellden windows are provided. Since the optical parameters are temperature-dependent, it is advantageous that the cuvette with the help of a thermostat designed to be temperature-controlled or in a temperature-controlled Container is housed. In the upcoming context, it can also be advantageous be when the most important substances in an external electric or magnetic Field are arranged and are appropriately oriented by treating the surfaces. When the laser beam is superimposed by such a field, the effective Longitudinal focus has been shortened considerably. Appropriately, a magnetic Field of this type by means of a coil winding preferably applied to the outer surfaces show.

According to a further feature of the invention, the substance or the cuvette containing them to determine the response level of the self-focusing arranged in a focal plane of the beam path of an optical device to be protected be.

In the following, exemplary embodiments of the Invention explained in more detail, the corresponding in the individual figures Parts have the same reference numbers. 1 shows a device according to the invention for suppressing intense light radiation and FIG. 2 shows a cuvette for receiving of substances with optically non-linear properties.

In Fig. 1, the reference number 1 is a substance with optically non-linear Characteristics denotes which, in the present exemplary embodiment, is a liquid Crystal is. This is on at least two opposite sides crystal each provided with an optically polished window 2, which corresponds to the respective conditions is to be selected accordingly; so come z. B. for an infrared radiation in this Transparent glasses area in question. These are provided in those places where the laser beam 3 enters the crystal and also where it aas the same again exit. The crystal is held in the thermostat 4 with its two narrow sides. The latter can, for. B. consist of an iieizfolie.

The inclusion of such optically non-linear substances 1 can be made from Fig. 2 visible cuvette 5 are used. As above, the thermostat is on its narrow sides 4 while the two opposite long sides are attached to the beam entrance and the radiation exit point contain the optically polished window 2, the outside each with an optically transparent, electrically conductive layer 6 for production an external electric field and on the inside each with pretreated surfaces 7 is provided for extensive orientation of liquid-crystalline phases.

In addition, the thermostat 4 carries the coil winding 8, which the Generation of an external magnetic field is used.

This or a similarly constructed device is used if necessary into the beam path of the organ to be protected or a sensitive device, z. B. a detector or optics or the like. Introduced, where they are depending on the design and need to transmit harmless low-intensity radiation and radiation higher to highest intensity weakens or completely suppressed.

L e r s e i t e

Claims (9)

Method and device for protection against the effects of electromagnetic radiation Radiation PATENT CLAIM 1.) Method for the protection of the human eye or sensitive optical elements from the effects of electromagnetic radiation higher Intensity, for example a laser, with the help of a in the beam path of the to protective object arranged, the radiation at least weakening medium, d a d u r c h e k e n n n z e i c h n e t that the radiation (3) with the help of optically non-linear substances (1) with large non-linear optical constants weakened or suppressed by self-focusing. 2. The method according to any one of the preceding claims, d a -d u r c h g e k e n n n z c i r h n e t that the radiation (3) in the substance v1) through Birefringence broken down into partial beams ~ imid then by means of a z. B. by an external electric or magnetic field of variable phase difference is deleted will. 3. The method according to claim 1 and 2, d a d u r c # W c n n -z e i c h n e t that the substances (1) from liquid crystals with nematic, smcktischer or cholesteric structure or from mixtures of liquid crystals with exist at least two different structures. 4. Lrerfallren according to claim 3, d a d u r c h g c k o n n -z e i c h n c t, that Schiff's bases or azoxyvelzbindunsen are used as liquid crystals will. 5. Apparatus for carrying out the preceding process according to one of the preceding Claims that the substances (1) are enclosed in a cuvette (5), which at least in the areas of the radiation and the beam exit each with an optically polished, electrically conductive layer (6) provided for generating an external electric field having window (2) are. 6. Apparatus according to claim 5, d a d u r c h g c k e n n -z e i c hn e t that the cuvette (5) is designed to be temperature-controlled with the aid of a thermostat (4) or housed in a temporary clay container. 7. Device according to one of the preceding claims, d a -d u r c h g e k e n n n n e i c h n e t that the substances (1) in an external electrical or magnetic field are arranged and suitable by treating the surfaces be oriented. 8. Apparatus according to claim 7, d a d u r c h g e k e n n -z e i c h n e t that the external magnetic field by means of a preferably on the outer surfaces applied coil winding (8) is generated. 9. Device according to one of the preceding claims, d n -d u r c h e k e k e n n n e i c h n e t that the substance (1) or cuvette (5) for the purpose of reduction the claim level of the self-focusing in a focal plane of the beam path an optical device to be protected is arranged.