Encircled energy

Encircled energy

Zone-plate Lenses for Sound Waves in Water

Published in Jakob J Stamnes, Waves in Focal Regions, 2017

In many practical situations the encircled energy is a better measure of image quality than the intensity distributions in figure 17.8. The encircled energy is defined as the fraction of the total energy that is contained within a circular area centred at the image point (cf §12.2.4). Plots of the encircled energy for the two lenses are presented in figure 17.9, from which it follows that the zone-plate lens is better than the Fresnel zone plate as far as encircled energy within the main lobe is concerned.

Combined implementation of smoothing technologies for improving illumination uniformity of laser quad in multi-directions

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Journal Information

Published in Journal of Modern Optics, 2019

Muyu Yi, Zheqiang Zhong, Bin Zhang, Xiao Yuan, Jian Chen, Jianhua Zhao

The illumination uniformity of the focal spot can be evaluated by the contrast of focal spots and fraction power above intensity (FOPAI) (16), i.e. where A is the area of the integral region in far field on the focal plane of the laser beam and I0 = I/Imean, Imean is the average intensity. In addition, power spectral density (PSD) curves are also used to illustrate the spatial high-frequency modulation of the intensity distribution. The area of 86.5% of the encircled energy is analyzed to calculate the contrast of focal spot and FOPAI.

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Zone-plate Lenses for Sound Waves in Water

Combined implementation of smoothing technologies for improving illumination uniformity of laser quad in multi-directions