Patent ID: 8390928
Filing Date: 2013-03-05
Classification: G01N,G02B,G03F

Abstract:
1. Apparatus for shaping a light beam, said beam comprising a plurality of mutually coherent beam portions comprising light of the same wavelength, arrayed around a central ray and propagating together as a single beam, so that after said shaping, over a wide range of wavelengths, said central ray has substantially zero intensity, said apparatus comprising a plurality of transparent plates of varying thickness and composition, located in the path of said light beam, and arranged so each beam portion is directed onto and traverses a plate in said plurality of plates, thereby experiencing a phase delay particular to said portion, such that for at least two wavelengths, a shorter one and a longer one, separated by more than 40 nanometers, the phase delay of the first of said two portions at the shorter of said two wavelengths, after traversing its said corresponding plate minus the phase delay of the second of said portions at the shorter of said two wavelengths after traversing its said corresponding plate equals, within less than one hundredth of said shorter wavelength, the phase delay of the first of said two portions at the longer of said two wavelengths, after traversing its said corresponding plate minus the phase delay of the second of said portions at the longer of said two wavelengths after traversing its said corresponding plate, and where for each intermediate wavelength in the range of wavelengths between said two wavelengths, the phase delay of the first of said two portions at the shorter of said two wavelengths, after traversing its said corresponding plate minus the phase delay of the second of said portions at the first of said two wavelengths after traversing its said corresponding plate is equal, to within one hundredth of the smaller of said first and second wavelengths, to the phase delay of the first of said two portions at said intermediate wavelength, after traversing its said corresponding plate minus the phase delay of the second of said portions at said intermediate wavelength after traversing its said corresponding plate, so that said two plates acting on their corresponding beam portions, together with the remaining plates in said plurality of plates acting on their respective beam portions, cause substantially complete destructive interference at said central ray for light of all wavelengths within the wavelength range between said two wavelengths.