Laryngeal videoendoscopy combined with stroboscopy is now a mainstay for clinically assessing how the larynx functions to produce voice. Evaluation of the video imagery is currently limited to subjective visual judgments that can result in diminished reliability. A method enabling dimensional calibration of the images, and thus quantification of important vocal parameters, would greatly enhance the clinical and research capabilities of videoendoscopy with stroboscopy. Thus, the main goal of the proposed Phase II effort is to develop a laser-based projection system for dimensional calibration of laryngeal videoendoscopic images. The Phase I study just completed has clearly shown the feasibility of achieving this goal. The focus will be to develop an optically based object sizing system for flexible transnasal as well as rigid transoral laryngoscopes. The Phase II effort will entail: (1) construction of clinical prototypes of the calibrated endoscopic instruments, and (2) extensive clinical testing of the instruments at the Massachusetts Eye and Ear Infirmary (MEEI). PROPOSED COMMERCIAL APPLICATION: The market potential for a user-friendly calibration system customized for laryngeal videostroboscopy is estimated to be several hundred units in the U.S. Similar systems for more general use endoscopy of the upper airway (including larynx) have a potential worldwide market of up to several thousand units. The latter market reflects the large number of otolaryngologists that use such scopes in routine clinical practice.