Measuring laser beam parameters using non-distorting attenuation and multiple simultaneous samples

An optical system for the non-distorting attenuation of a light beam while preserving the relative light intensities across the beam to permit accurate measurements of the light beam profile comprising in operative combination:

• a) attenuation means disposed along a beam optical pathway for absorbingly attenuating a light beam received from an existing light source without thermal distortion of the beam profile;
• b) an optical lens assembly disposed adjacent to and down stream of said attenuation means and including a positive lens means and a plurality of beam-splitters oriented in series with said positive lens means, said positive lens means for focusing the attenuated beam received from said attenuation means into said plurality of beam-splitters such that portions of said beam are reflectively redirected from selective surfaces of each of said beam-splitters for simultaneous collection of said beam portions at a common measurement plane;
• and
• c) whereby each of said attenuation means and said lens assembly having optical surfaces selectively tilted so that fringe and interference effects between successive optical surfaces are eliminated.

An optical attenuator for receiving a light beam along an optical path and for absorbingly attenuating the light beam comprising in operative combination:

• a) an assembly of opposed facing absorbing glass wedges of the kind wherein light absorption varies with total glass thickness, said glass wedges disposed along said optical path of said beam and including:
• i) a first glass wedge having a first optical surface and a second opposed facing optical surface, said first optical surface oriented to receive incoming light along an optical path;
• ii) a second glass wedge having a first optical surface and a second opposed facing optical surface, said first optical surface disposed facing said second optical surface of said first glass wedge;
• b) each of said glass wedges being adjustable in a direction transverse to said beam optical path to provide continuous adjustment of a constant thickness path length across the beam for attenuation over a range of about optical density 1.0 to about optical density 5.0;
• and
• c) each of said glass wedges being selectively tiltable to eliminate interference effects therebetween.

A method for attenuating a light beam while preserving relative distribution of light intensities across the beam for performing accurate measurements of the beam comprising in operative sequence the steps of:

• a) attenuating without absorbing a high power light beam having a power level which causes thermal distortion of the beam profile in an absorbing media to a desired low power level having a power level below which said thermal distortion is present and without angular deviation of said beam by reflecting from essentially lossless optical materials such that a polarization characteristic of said beam remains substantially unchanged;
• b) using a pair of opposed facing neutral density glass wedges for absorbing attenuation of the beam after it has been attenuated to said desired lower power level;
• c) using an optical assembly for trapping and splitting the beam after the absorbing attenuation of the beam for simultaneous collection of split portions of the beam at a measurement plane;
• and
• d) selectively tilting all optical surfaces of said lossless optical materials, said glass wedges and said optical assembly at minimum angles with respect to each other and said beam sufficient to eliminate fringe and interference effects between successive optical surfaces.