Date of Award

Spring 1998

Document Type

Thesis

Degree Name

Master of Science in Electrical Engineering - (M.S.)

Department

Electrical and Computer Engineering

First Advisor

N. M. Ravindra

Second Advisor

Andrew Sohn

Third Advisor

Edwin Hou

Fourth Advisor

Dentcho V. Ivanov

Fifth Advisor

Feming Tong

Abstract

There is a growing trend in the study of Focal Plane Arrays(FPAs) of very small microlenses, used for a wide variety of imaging and sensing applications, to increase optical efficiency. Present day sensor technology might take a different direction altogether with the development of compact, high quality, high resolution imaging microlenses, which could make the fill factor >90%. A method to increase light sensitivity of Interline Transfer(IT) type image sensors is to position microlens FPAs on top of the image sensors. FPAs are structures of small lenses which focus the incoming light on the photo sensitive part of the image sensor. The objective of this thesis was to develop reliable and efficient microlens FPAs for a 320 X 244 element PtSi-IT infrared image sensor. The proposed FPAs overcome the difficulty most commonly faced with IT image sensors i.e. low light sensitivity, and in fact makes it superior in light sensitivity to Frame Transfer/Frame Interline Transfer types of image sensors. We have introduced additional degrees of freedom into surface profile of microlens. ZEMAX tool was deployed to model, analyze and assist in the design of the lenses. Standard IC processes were applied to fabricate the lenses with a strict control over process parameters. As a result, we have fabricated prototype microlenses which are expected to assist in obtaining the high sensitivity level of the sensor.

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