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Fig. 4 | BioMedical Engineering OnLine

Fig. 4

From: Design, development and validation of a new laryngo-pharyngeal endoscopic esthesiometer and range-finder based on the assessment of air-pulse variability determinants

Fig. 4

Optical fiber assembly, range-finder polar grid and distance calculation. a Laser optical fiber assembly at the endoscope distal end; b polar grid; and c distance calculation using a pinhole camera model [41]. 1 polar grid, 2 image captured from the target surface, 3 center of the polar grid (coincides with the center of the captured image); the polar grid includes circles corresponding to the estimated distances between the endoscope distal end and the target surface as follows: 5: 1.78 mm (used to center the endoscopic camera), 6 3, 7:6, 8:9, 9:12, and 10:15 mm. 4 Laser spot. Distance calculation: a the distance used in the pin-hole camera model from the focal point (camera point) to the image plane; b the distance between the real point of the laser spot impact and the point of intersection of the camera model axis (endoscope axis) and the object plane axis; c the distance between the point of impact of the laser spot if the laser axis were parallel to the endoscope axis and the real point of impact of the laser spot (only the radial component is considered); L the distance between the laser optical fiber (laser axis) and the axis of the camera (endoscope axis) on the image plane; x the distance between the camera image plane and the object plane in millimeters; and y the distance on the image plane between the centroid of the laser spot and the center of the image in pixels (radius)

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