Optical: systems and elements – Lens – Fluid
Patent
1995-08-08
1997-10-28
Tokar, Michael J.
Optical: systems and elements
Lens
Fluid
359666, G02B 314
Patent
active
056822685
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to the focusing of beams of electromagnetic radiation, and, in particular to the focusing of beams of laser radiation by a lens formed by colliding shock waves in a gaseous medium.
Much attention is being paid at present to the development of high power lasers and to optics capable of focusing the beams of radiation that they produce. These focused beams are useful both in industry and research for such purposes as the drilling, cutting and welding of materials. The focusing is usually accomplished with solid lenses made of material appropriately transparent to the particular type of radiation emitted by the laser. Infra red beams may be focused with lenses made from such expensive materials as zinc-selenite or germanium. Visible beams may be focused with ordinary glass lenses and ultraviolet beams with quartz lenses. All three types of radiation also .may be focused with gas lenses that use hot and cold air or gas to refract the radiation. Such optical systems are not entirely satisfactory for at least two reasons. Firstly, the solid lenses are delicate and need to operate in clean room conditions, which are not normally available or practical in industrial environments. Moreover, the amount of radiation they can transmit and focus is limited; high power laser beams frequently interact explosively with solid optical components. Secondly, gas lenses although able to focus large amounts of radiation are very weak lenses and tend to be heavy and bulky. For example, French patent 2 410 293 discloses various arrangements for producing density waves in the atmosphere to focus solar radiation and Martynenko et al in Revue de Physique Appliques Vol 13, No. 7 July 1978 disclose a number of arrangements of gas lenses formed by thermal density gradients produced in a gaseous medium by various arrangements of heated and cooled pipes. However, none of these arrangements disclosed in either of these documents is capable of producing anything other than a weak focusing action.
Most research and industrial applications require strong lenses, that is to say, with short focal lengths. They must also be light and compact.
It is an object of the present invention to provide a gas lens which is compact and capable of focusing strongly intense beams of electromagnetic radiation.
According to the present invention there is provided a method of focusing a beam of electromagnetic radiation, comprising the operation of generating in the path of the beam of electromagnetic radiation a localised region of high density in a gaseous medium which is transparent to the beam of electromagnetic radiation and has a symmetrical density profile with respect to the optical axis of the beam of electromagnetic radiation such as to bring the beam of electromagnetic radiation to a focus.
Also according to the invention there is provided an apparatus for focusing a beam of electromagnetic radiation, comprising at least three spark gaps, as herein defined, symmetrically disposed about a region of space through which a beam of electromagnetic radiation to be focused can be caused to pass such that shock waves produced by electric discharges in a gaseous medium at the spark gaps interact to form a localised region of high pressure in the gaseous medium centred on the optical axis of the beam of electromagnetic radiation and having a density profile such as to bring the beam of electromagnetic radiation to a focus.
Preferably the spark gaps are located inside a cylindrical chamber which confines the shock waves and also the gas if this be different from air. The chamber is provided with two co-axial apertures to allow passage of the electromagnetic radiation.
It should be noted that the term spark gap is used to denote a pair of electrodes between which an electrical discharge can be made to occur.
The means for generating the central high density may comprise electronic means for generating a plurality of sparks synchronously and at points equally spaced around the circumference of the circle.
The means for generating th
REFERENCES:
patent: 5067801 (1991-11-01), Mirels et al.
Iga et al, "Experimental Studies on the limitation of focussing power of hyperbolic-type gas lens", Japanese Journal of Applied Physics, vol. 8, No. 2, Feb. 69, p. 255.
Martynenko et al, "Thermo-gasdynamic control in laser beam guidance", Revue De Physique Appliquee, vol. 13, No. 7, Jul. 78, p. 329.
Hanig Richard
Hinds William R.
Tokar Michael J.
LandOfFree
Gas lens does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Gas lens, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Gas lens will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1029645