Abdelhameed IBRAHIM^1,2*, Shoji TOMINAGA¹, and Takahiko HORIUCHI¹

¹Graduate School of Advanced Integration Science, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan
²Computers and Systems Engineering Department, Faculty of Engineering, Mansoura University, Mansoura, Egypt

(Received October 21, 2010; Accepted January 5, 2011)

Spectral image acquisition as well as color image is affected by several illumination factors such as shading, gloss, and specular highlight. Spectral invariant representations for these factors were proposed for the standard dichromatic reflection model of inhomogeneous dielectric materials. However, these representations are inadequate for other characteristic materials like metal. This paper proposes a more general spectral invariant representation for obtaining reliable spectral reflectance images. Our invariant representation is derived from the standard dichromatic reflection model for dielectric materials and the extended dichromatic reflection model for metals. We proof that the invariant formulas for spectral images of natural objects preserve spectral information and are invariant to highlights, shading, surface geometry, and illumination intensity. It is proved that the conventional spectral invariant technique can be applied to metals in addition to dielectric objects. Experimental results show that the proposed spectral invariant representation is effective for image segmentation.

Key words: spectral invariant, dichromatic reflection models, spectral imaging system, spectral image segmentation

^*E-mail address: ibrahim@graduate.chiba-u.jp