Optical Review

, Volume 11, Issue 3, pp 176–181 | Cite as

Building a Simple Model of a Pulse-Frequency-Modulation Photosensor and Demonstration of a 128 x 128-pixel Pulse-Frequency-Modulation Image Sensor Fabricated in a Standard 0.35-$mUm Complementary Metal-Oxide Semiconductor Technology

  • Keiichiro KagawaEmail author
  • Norikatsu Yoshida
  • Takashi Tokuda
  • Jun Ohta
  • Masahiro Nunoshita
Photonics and Optoelectronics


We present a simple model of the pulse-frequency-modulation (PFM) photosensor that provides explicit relationships between circuit parameters and output characteristics. The model treats the PFM photosensor with a feedback loop as an open loop circuit. Several characteristics such as output pulse frequency for light intensity and photosensitivity are expressed by device parameters of a photodiode, reset transistor, and chain of inverters. The relationships derived from the proposed model help us to comprehend the results by simulation program with integrated circuit emphasis (SPICE) or experiments. We design and fabricate a 128 x 128-pixel PFM image sensor with photosensitivity of 0.15 Hz/lux. As a demonstration, a figure of a dinosaur is captured using the fabricated image sensor to discuss its operation. Characteristics of a normal pixel and white and black defect pixels are measured and discussed based on the results of formulations.

Key words

pulse-frequency-modulation photosensor CMOS image sensor vision chip 


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Copyright information

© The Optical Society of Japan 2004

Authors and Affiliations

  • Keiichiro Kagawa
    • 1
    Email author
  • Norikatsu Yoshida
    • 2
  • Takashi Tokuda
    • 1
  • Jun Ohta
    • 1
  • Masahiro Nunoshita
    • 1
  1. 1.Graduate School of Materials ScienceNara Institute of Science and TechnologyIkomaJapan
  2. 2.Matsushita Electric.Kadoma City, OsakaJapan

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