Optical Method for Determination of Aperture Area at High Accuracy

According to the basic relation E =φ/A, a direct optical method for aperture area measurement was provided, based on known constant irradiance over the aperture. A spatially uniform, known irradiance is formed over the aperture by overlapping identical, parallel laser beams centered at constant spacing in an orthogonal lattice. The ratio of the throughput power and irradiance gives the aperture area. The method is described and measurement results are given with a relative uncertainty of 3.6×10-4 for aperture size 6 mm in diameter. The advantages of the method are that it does not require contacting with aperture edge. It can be applied to apertures of any shape, and the calibration setup is similar to the actual use of the aperture.