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Proceedings Paper

Design of diffractive microlens array integration with focal plane arrays
Author(s): Sihai Chen; Xinjian Yi; Yi Li; Miao He; Sixiang Chen; Lingbin Kong
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Paper Abstract

The IR spectrum from 3 to 5micrometers has numerous applications in both military and civil industries. High performance at high operating temperature is often important in these applications. Conventional Focal Plane Arrays (FPAs) without integration with concentrator such as microlens have poor sensitivity and low signal-to-noise ratio because of their lower fill factor. The binary optics microlens arrays reported in this paper are designed for integration with FPAs. Thus, the FPAs' fill factor, sensitivity, and signal- to-noise ratio can be improved while retaining a given image resolution and optical collection area. In the paper, we discussed the 256(Horizontal)x290(Vertical) microlens arrays designed for a center wavelength of 4micrometers , with 50micrometers (Horizontalx33micrometers (Vertical) quadrate pixel dimension and a speed (F number) of F/1.96. PtSi FPAs were fabricated on the front side of a 400-micrometers -thick Si substrate. The designed diffractive microlens arrays will be etched on the back side of the same wafer in a register fashion and it will be reported in other paper. Considering the diffraction efficiency, 8-phase-level approximation is enough. For the diffraction efficiency of 8-phase-level diffractive microlens reaches 95%. The process only need three mask-level, so we designed and fabricated three masks with the same dimension 4'x4'. Also, a set of fine verniers was designed and fabricated on each mask to allow accurate alignment during the fabrication process. Through a computer simulation, the microlens arrays are nearly diffraction limited, with the diffraction efficiency of 93%, a bit lower than the theoretical value of 95%. Introduction of microlens arrays has the ability to increase the FPAs' fill factor to 100%, while it is only about 21.6% without microlens. To our knowledge, this is the first trial of integration large area microlens arrays with FPAs at home.

Paper Details

Date Published: 11 October 2000
PDF: 4 pages
Proc. SPIE 4224, Biomedical Photonics and Optoelectronic Imaging, (11 October 2000); doi: 10.1117/12.403967
Show Author Affiliations
Sihai Chen, Huazhong Univ. of Science and Technology (China)
Xinjian Yi, Huazhong Univ. of Science and Technology (China)
Yi Li, Huazhong Univ. of Science and Technology (China)
Miao He, Huazhong Univ. of Science and Technology (China)
Sixiang Chen, Huazhong Univ. of Science and Technology (China)
Lingbin Kong, Huazhong Univ. of Science and Technology (China)

Published in SPIE Proceedings Vol. 4224:
Biomedical Photonics and Optoelectronic Imaging
Hong Liu; Qingming Luo, Editor(s)

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