Analysis of spurious diffraction orders of computer-generated hologram in symmetric aspheric metrology

Yiwei He, Xi Hou, Fan Wu, Xinxue Ma, Rongguang Liang

Research output: Contribution to journalArticlepeer-review

12 Scopus citations


Computer-generated hologram (CGH) has been widely used as a wavefront compensator in symmetric aspheric metrology. As a diffractive element, it generates different diffraction orders, but only the 1st-order diffraction is used to test aspheric surface. The light from spurious diffraction orders (SDO) will produce many high-frequency fringes in interferogram and reduce measurement accuracy. In this paper, we regard the CGH null system as an imaging system and develop an aberration model in Seidel formalism to analyze the SDO. This model has the advantage to address the difference between the SDO (k1, k2) and (k2, k1). We consider the effect of the pupil distortion so that our model can analyze the SDO with a large pupil distortion. We derive the condition to ensure the 2nd-order and 4th-order aberrations have the same sign and calculate the minimum defocused distance (power carrier frequency) of CGH. According to the marginal-ray heights (h1 and h3 ) on the CGH in the first and second passes, we determine the condition that the SDO covers the whole CGH in the second pass. We analyze the SDO of 4 CGH designs and compare the results from our aberration model with these from real ray trace. These results validate that our aberration model is feasible whether the aspheric part is convex or concave and whether CGH is inside or outside the focus of the transmission sphere.

Original languageEnglish (US)
Pages (from-to)20556-20572
Number of pages17
JournalOptics Express
Issue number17
StatePublished - Aug 21 2017

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics


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