Microlenses enable endoscopy in 3-D

Researchers at the Fraunhofer Institute for Microelectronic Circuits and Systems IMS (Duisburg, Germany) and project partners in the EU MiniSurg project have developed a camera small enough to fit into an endoscope that transmits perfect 3-D images from inside the human body, thanks to special microlenses. The camera features a CMOS image sensor commonly incorporated in single-lens-reflex (SLR) cameras, which is integrated in the slender endoscope tube. This combination enables surgeons to see every detail in 3-D resolution, provides a clear path through tissue without damage, and allows work to be done quickly.

In the CMOS image sensor, a cylindrical microlens is placed in front of every two vertical lines of sensors in the pixel configuration. A superimposed lens captures the light falling on the microlenses, which focus it on the pixels. Two beams of light are captured by the lenses—that arriving from the left passes through the left aperture to be focused on the right-hand vertical line of sensors, and vice versa. The two light rays cross underneath the lens arrangement. As a result, the CMOS sensor receives two sets of image data that are processed separately in the same way that the brain processes images coming from the left and right eye. A software program splits the incoming data and processes each set separately. Depending on the capabilities of the display system, the surgeon either sees the 3-D images directly on the screen or can see them when wearing polarized glasses. Coupling the image sensor's size with the bundle of optical fibers that serves as the light source, the endoscope measures only 10 mm in diameter.

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