A spectro reflectance camera for in vivo human blood evaluation

In this paper, we present a new non invasive diagnosing device, the spectroscopy reflectance camera. This device combines the spectro-reflectrometry with a CMOS image sensor to evaluate the oxygen saturation in living organs. This combination is realized by merging an image sensor to an optical fibre linked to a spectrograph. While the image sensor helps targeting precisely the blood vessel to be evaluated, the spectrograph gathers the reflected light spectrum from the vessel. The optical fibre is 50 microns diameter and has one end inserted in the back side of the image sensor. This end reaches the first silicon oxide layer on the component side, which is transparent. The other end is connected to the spectrograph; it transmits the intensity of the reflected light. In order to insert the optical fibre in the image sensor, we propose a process to achieve a highly directional etching technique with high aspect ratio. Also, we present a new image sensor structure allowing the presence of a hole in the center of the pixel array. The presence of the hole adds some design constraints leading to divide a conventional pixel array into four independent sub-arrays, where every pixel is addressed and read out separately.