Abstract. We proposed a zoom homogenizer that can control the size of the illumination field by adding one lens array to the conventional imaging-type beam homogenizer. An equivalent lens system was used to derive the imaging condition and size of the illumination field. The result of the ray-tracing simulation shows the validity of the zoom homogenizer to generate the uniform and sharp-edged beam. We presented the strengths and weaknesses of the zoom homogenizer in terms of its etendue with the maximum acceptance angle of the system. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

We analyzed through numerical simulations the properties of a square beam homogenizer near the target for laser shock peening. The efficiency was calculated near the target by considering the plasma threshold of the metals. We defined the depth of focus of the square beam homogenizer with a given efficiency near the target. Then, we found the relationship between the depth of focus for the laser shock peening and four main parameters of the square beam homogenizer: the plasma threshold of the metal, the number of lenslets in the array-lens, the focal length of the condenser lens and the input beam size.

A knife-edge scanning method was developed to enhance the accuracy in OTF measurement. A slit image formed by the lens under test was scanned by a knife-edge which was moved by a stepping motor. It was possible to increase the signal-to-noise ratio with averaging 4-32 data at each point through a scan. The standard deviation was decreased to under 0.25% in the MTF unit.

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