4. Experimental demonstration
4.1. Setup
Based on available components in our laboratory and by following Fig. 1, our experimental setup is shown in Fig. 3. Our mobile device is a smart phone Samsung Galaxy S GT-I9000 embedded with Android 2.2 operating system, a 2592 × 1944 pixel digital camera, 512 MB of RAM, and a 1 GHz processing unit. The digital camera of this smart mobile phone has a measured 53° full field of view. Our cheap uniformly white reference scene is a white A4 paper available in our office. The measured distance z between the smart phone and the white reference paper is 12 cm. The measured environmental illuminant level is 300 lx, which corresponds to an appropriate illumination level recommended in 2006 Ministeria Regulation under the Ministry of Labor of Thailand.