A novel method for optical beam collimation measurement is presented. The collimating lens is utilized in four parts of quadrants with the beam aligned onto the first quadrant and configured to pass the subsequent quadrants. This allows the test beam to pass the collimating lens for four times. Subsequently, the test beam is reversed to achieve a total number of eight passes. Hence, for a defocus introduced, the collimation state of the test beam can be evaluated at the amplification of eight. The evaluation of the test beam is performed based on the approach of collimation testing using lateral shearing interferometer. The proposed technique provides a differential collimation sensitivity for accurate setting of a highly collimated beam.
A novel method of using two prisms to perform lateral-shear interferometry for wavefront analysis and collimation
testing over a wide dynamic beam size range is presented. Two
right-angled prisms are utilized to establish an adjustable
air gap with a small wedge angle. A test beam directed into the air wedge will result in reflected beams that are laterally
sheared and produce an interference pattern which can be analyzed in the conventional manner. The thickness of air gap
can be adjusted to allow a wide range of beam sizes to be tested down to a few millimeters in diameter. By using rightangled
prisms instead of shear plates, several advantages such as the elimination of unwanted beam reflections, increase
in the amount of shear per unit separation, and the enhancement of intensity and contrast of the output beams. The gap
separation and wedge angle can be varied to maintain high sensitivity over the wide beam size range. Theoretical and
experimental investigation into the sensitivity achievable in collimation testing with the method will be reported.
A novel method for testing the collimation of coherent optical beam is presented. Two prisms are used to define a thin air
wedge with a wedge angle. A wide range of beam sizes can be tested down to a few millimeters in diameter. By
redirecting the transmitted beam back to the air wedge so that it experiences a shear in the reversed direction, a double-shearing
interferometry can be established. The gap separation and wedge angle can be varied to maintain high
sensitivity (twice that of the wedge plate design) over the wide beam size range.