DOE-based systems and devices for producing laser beams having modified beam characteristics
View Patent ↗Novel methods are disclosed for designing and constructing miniature optical systems and devices employing light diffractive optical elements (DOEs) for modifying the size and shape of laser beams produced from a commercial-grade laser diodes, over an extended range hitherto unachievable using conventional techniques. The systems and devices of the present invention have uses in a wide range of applications, including laser scanning, optical-based information storage, medical and analytical instrumentation, and the like. In the illustrative embodiments, various techniques are disclosed for implementing the DOEs as holographic optical elements (HOEs), computer-generated holograms (CGHs), as well as other diffractive optical elements.
1. A laser beam production module for producing a laser beam having a desired beam aspect-ratio, a minimized or reduced to zero beam dispersion, and corrected astigmatism, said laser beam producing module comprising:
a module housing;
a visible laser diode (VLD), mounted within said module housing, for producing a laser beam from its junction having divergent and elliptical beam characteristics;
a collimating lens (L 1 ), mounted in said module housing, spaced from said VLD by a distance D, for collimating the laser beam as it is transmitted through said collimating lens L 1 and through components in said module;
a first fixed spatial-frequency diffractive optical element (DOE), mounted in said module housing, having a beam expansion factor M 1 ; and
a second fixed spatial-frequency diffractive optical element (DOE), mounted in said module housing, having a beam expansion factor M 2 ,
wherein the collimated laser beam exiting said collimating lens L 1 is transmitted through said first DOE, and the collimated laser beam exiting said first DOE is transmitted through said second DOE, and wherein:
(a) the collimating lens has a downstream focus location, in the direction of said collimating lens L 1 , that is calculated to adjust or eliminate astigmatism in the beam propagating beyond the second DOE;
(b) for the calculated downstream focus location, D is selected to provide a desired beam spot size, thereby determining an upstream focus location for the lens, in the direction of said VLD; and
(d) the focal length of the collimating lens is selected according to the upstream and downstream focus locations,
whereby the collimated laser beam exiting said second DOE exits has a controlled beam aspect-ratio, a minimized or reduced to zero beam dispersion, and corrected astigmatism; and
wherein said laser beam is transmitted through said collimating lens L 1 and through said module; and wherein the total beam-shaping factor (M=M 1 M 2 ) for the laser beam producing module is less than unity, and the laser beam leaving said collimating lens (L 1 ) is compressed in one dimension, and has a circularized beam aspect-ratio, minimized or reduced to zero beam dispersion, and corrected astigmatism.
2. The laser beam production module of claim 1 , wherein said collimating lens (L 1 ) is realized by an optical element selected from the group consisting of a refractive lens, a HOE, a CGH, a diffractive-type optical element, a grin lens, and one or more zone plate(s).
3. The laser beam production module of claim 1 , wherein each said DOE is realized by an optical element selected from the group consisting of a HOE, a computer-generated hologram (CGHs), and a surface-relief hologram.
4. The laser beam production module of claim 1 , wherein said collimating lens (L 1 ) is realized by an optical element selected from the group consisting of a refractive lens, a HOE, a CGH, a diffractive-type optical element, a grin lens, and one or more zone plate(s).
5. The laser beam production module of claim 1 , wherein each said DOE is realized by an optical element selected from the group consisting of a HOE, a computer-generated hologram (CGHs), and a surface-relief hologram.