Color calibration of swine gastrointestinal tract images acquired by radial imaging capsule endoscope

Yang-Mang Ou, Wei De Jeng*, Chien Cheng Lai, Hsien Ming Wu, Jyh Hung Lin

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


The type of illumination systems and color filters used typically generate varying levels of color difference in capsule endoscopes, which influence medical diagnoses. In order to calibrate the color difference caused by the optical system, this study applied a radial imaging capsule endoscope (RICE) to photograph standard color charts, which were then employed to calculate the color gamut of RICE. Color gamut was also measured using a spectrometer in order to get a high-precision color information, and the results obtained using both methods were compared. Subsequently, color-correction methods, namely polynomial transform and conformal mapping, were used to improve the color difference. Before color calibration, the color difference value caused by the influences of optical systems in RICE was 21.45 ± 1.09. Through the proposed polynomial transformation, the color difference could be reduced effectively to 1.53 ± 0.07. Compared to another proposed conformal mapping, the color difference value was substantially reduced to 1.32 ± 0.11, and the color difference is imperceptible for human eye because it is <1.5. Then, real-time color correction was achieved using this algorithm combined with a field-programmable gate array, and the results of the color correction can be viewed from real-time images.

Original languageEnglish
Article number015010
JournalJournal of Biomedical Optics
Issue number1
StatePublished - 1 Jan 2016


  • illumination system
  • light uniformity
  • optimal design
  • radial imaging capsule endoscope

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