A test setup for static and dynamic measurements of a centroid circuit is presented in this paper. Centroid computations are used in wavefront sensing, motion tracking and in fiber optic sensors. Pixel arrays were fabricated using CMOS photodetectors and analog circuitry was designed to compute the centroid of an image. Generally, for testing the functionality and performance characteristics of pixel arrays and readouts built on an integrated circuit (IC), high precision optical setup and test equipment are required. This cost presents a limitation in testing optoelectronic integrated circuits. This paper provides a novel approach to building a simple test setup using optical lenses, filters/attenuators, a He-Ne laser, an IC probe station and other low-cost equipment present in an IC testing facility. Using this test setup the centroid of an image incident on a pixel array was measured and the performance of the centroid computation circuitry was also verified. The setup includes simple schemes to change the spot size of the laser beam incident on the pixel array. This provides the flexibility to test pixel arrays of different sizes with the same setup. Another scheme to pulse the laser beam externally using a chopper is also described. This scheme can be used for measurements involving time varying inputs. The test setup was used to successfully characterize the static and dynamic characteristics of a fully integrated CMOS centroid computation circuit.

Date Published: 14 June 2004
PDF: 11 pages
Proc. SPIE 5356, Optoelectronic Integrated Circuits VI, (14 June 2004); doi: 10.1117/12.531888

Published in SPIE Proceedings Vol. 5356:
Optoelectronic Integrated Circuits VI
Louay A. Eldada, Editor(s)