0

Full Content is available to subscribers

Subscribe/Learn More  >
Proceedings Article

QE reduction due to pixel vignetting in CMOS image sensors

[+] Author Affiliations
Peter B. Catrysse, Xinqiao Liu, Abbas El Gamal

Stanford Univ. (USA)

Proc. SPIE 3965, Sensors and Camera Systems for Scientific, Industrial, and Digital Photography Applications, 420 (May 15, 2000); doi:10.1117/12.385460
Text Size: A A A
From Conference Volume 3965

  • Sensors and Camera Systems for Scientific, Industrial, and Digital Photography Applications
  • Morley M. Blouke; Nitin Sampat; George M. Williams, Jr.; Thomas Yeh
  • San Jose, CA | January 22, 2000

abstract

CMOS image sensor designers take advantage of technology scaling either by reducing pixel size or by adding more transistors to the pixel. In both cases, the distance from the chip surface to the photodiode increases relative to the photodiode planar dimensions. As a result, light must ravel through an increasingly deeper and narrower `tunnel' before it reaches the photodiode. This is especially problematic for light incident at oblique angles; the narrow tunnel walls cast a shadow on the photodiode, which in turn severely reduces its effective QE. We refer to this phenomenon as pixel vignetting. The paper presents experimental results from a 640 X 512 CMOS image sensor fabricated using a 0.35(mu) 4-layer metal CMOs process that shows significant QE reduction of up to 50% for off-axis relative to on-axis pixels. Using simple geometric models of the sensor and the imaging optics, we compare the QE for on and off-axis pixels. We find that our analysis results support the hypothesis that the experimentally observed QE reduction is indeed due to pixel vignetting. We show that pixel vignetting becomes more severe as CMOS technology scales, even for a 2-layer metal APS pixel. Finally, we briefly discuss several potential solutions to the pixel vignetting problem.

© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
Citation

Peter B. Catrysse ; Xinqiao Liu and Abbas El Gamal
"QE reduction due to pixel vignetting in CMOS image sensors", Proc. SPIE 3965, Sensors and Camera Systems for Scientific, Industrial, and Digital Photography Applications, 420 (May 15, 2000); doi:10.1117/12.385460; http://dx.doi.org/10.1117/12.385460


Access This Article
Sign In to Access Full Content
Please Wait... Processing your request... Please Wait.
Sign in or Create a personal account to Buy this article ($15 for members, $18 for non-members).
 

Figures

Tables

NOTE:
Citing articles are presented as examples only. In non-demo SCM6 implementation, integration with CrossRef’s "Cited By" API will populate this tab (http://www.crossref.org/citedby.html).

Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging & repositioning the boxes below.

Related Book Chapters

Topic Collections

Advertisement

Buy this article ($18 for members, $25 for non-members).
Sign In