US 4,744,615 A · Laser beam homogenizer

Abstract

A coherent laser beam having a possibly non-uniform spatial intensity distribution is transformed into an incoherent light beam having a substantially uniform spatial intensity distribution by homogenizing the laser beam with a light tunnel (a transparent light passageway having flat internally reflective side surfaces). It has been determined that when the cross-section of the tunnel is a polygon (as preferred) and the sides of the tunnel are all parallel to the axis of the tunnel (as preferred), the laser light at the exit of the light tunnel (or alternatively at any image plane with respect thereto) will have a substantially uniform intensity distribution and will be incoherent only when the aspect ratio of the tunnel (length divided by width) equals or exceeds the contangent of the input beam divergence angle .theta. and when W.sub.min =L.sub.coh (R+(1+R.sup.2).sup.1/2)>2RL.sub.coh, where W.sub.min is the minimum required width for the light tunnel, L.sub.coh is the effective coherence length of the laser light being homogenized and R is the chosen aspect ratio for the light tunnel.

Claims8

Dependent claims

Apparatus for uniformly illuminating a substantially flat plane with light from a coherent laser source, comprising

means forming a diverging laser light beam which diverges from a central optical axis, the light in said beam having a coherence length L.sub.c an having possibly a non-uniform spatial intensity distribution;
a light tunnel receiving said diverging laser beam, said light tunnel having flat internally reflective sides parallel to said optical axis and to each other to provide a light tunnel with a uniform size cross section for forming an array of apparent laser light sources, the light from each apparent source in said array being superposed by said light tunnel at the exit of said light tunnel, each individual light ray from each apparent source following a distinct light path to an illumination plane, each of said distinct light paths having an individual path length;
and
means providing a minimum difference between the individual path lengths of any two rays coincident at said illumination plane and arising from adjacent apparent sources in said array, said minimum path length difference being equal to or greater than the coherence length L.sub.c of said laser beam.

1 more element

Dependencies are inferred from the claim text.

Laser beam homogenizer

Life of this patent

Laser beam homogenizer

Life of this patent

Abstract

Claims8