Patent
1984-02-10
1987-01-27
Corbin, John K.
G02B 508
Patent
active
046391002
DESCRIPTION:
BRIEF SUMMARY
The invention relates to optical systems especially used in illuminating apparatus. So, it relates to an astigmatic optical element, to its manufacturing process, to an illuminating apparatus including such an optical element, and to ariticles treated by such an apparatus.
In the following, "optical element" means a reflecting or refracting optical element, such as a mirror or a lens, having an optically polished surface which is not a revolution surface. The word "astigmatic" means that such an optical element is not anastigmatic, that it does not form an image point of an object point. By example, such an optical element distributes energy from a point source along a line or over an extended area.
BACKGROUND OF THE INVENTION AND PRIOR ART
The particular problem originally solved by the invention is forming a focusing line along which energy density is uniform, from a monomode or mixed mode laser beam. Obviously, the invention is not restricted to this field, but this problem is interesting to understand the features of the invention.
In many technical fields, focusing laser beam energy along a line or distributing such energy over an extended area, with a uniform energy density, is desired, but known systems either integrate energy during time, preventing real time treatment and generating different treatment conditions, or chop the greatest part of available power, the energy yield being only about 30%.
The present invention relates to an optical system which gives such an energy distribution. The problem presented by such an optical system is that at least a reflecting or refracting surface must have a shape far different from a revolution shape, which shape cannot be obtained by classical processes used in the optical art because surface polishing can be provided only for plane or revolution surfaces.
Some optical systems having a surface which is not strictly a plane or spherical have been provided. For example, French Pat. No. 2 472 198 discloses a process in which a glass blank is cast and one of its faces is polished either as a plane surface or as a spherical surface. Distorting forces are thereafter applied to the blank, for example by vacuum, and the blank which is suitably maintained along its edges is globally distorted. The obtained deformation is very small and corresponds at maximum to some wavelengths of visible light. This deformation is for correcting aberrations of images formed by optical systems.
NASA has also developed a flexible mirror for correcting aberrations in images of planets and satellites observed by space probes. This mirror includes many piezoelectric actuators providing for local distortions of the reflecting surface, the distortions having an amplitude of about a wavelength of visible light.
So, these optical systems use processes providing for very slight changes of the reflecting surface configuration and which do not give its main curvature to the surface.
Distorting mirrors used for example in fairs and attractions are also known. They are constructed from metallic plates distorted in alternate directions to provide enlarged or reduced images. Mirror thickness is constant and obtained shapes are not precisely determined, the distortions being very great. Optical quality of these mirrors is low.
SUMMARY OF THE INVENTION
The invention relates to providing astigmatic optical elements having at least a surface which is neither plane nor of revolution and which has an excellent optical polish. The surface can be very different from a plane or revolution surface.
According to the invention, when an optician has determined the ruled surface configuration he desires, he computes the thickness variation of a flat member so that when selected stresses or forces are applied to such member one of its surfaces takes the desired configuration. The surface can be polished when the flat member is not yet distorted, and the flat member is then distorted for its polished surface to take the desired configuration. Alternately, the surface is polished when distorting forces are
REFERENCES:
patent: 2129513 (1937-03-01), Wegner
patent: 4043644 (1977-08-01), Humphery
patent: 4119366 (1978-10-01), Lemaitre
patent: 4139270 (1979-02-01), Dotson
patent: 4197157 (1980-04-01), Haggery
patent: 4382657 (1983-05-01), Lemaitre
Breiner A. W.
Corbin John K.
Lewi David
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