title: A beam-splitter-type 3-D endoscope for front view and front-diagonal view images.
abstract: OBJECTIVE
  In endoscopic surgery, surgeons must manipulate an endoscope inside the body cavity to observe a large field-of-view while estimating the distance between surgical instruments and the affected area by reference to the size or motion of the surgical instruments in 2-D endoscopic images on a monitor. Therefore, there is a risk of the endoscope or surgical instruments physically damaging body tissues. To overcome this problem, we developed a Ø7- mm 3-D endoscope that can switch between providing front and front-diagonal view 3-D images by simply rotating its sleeves.
  
  
  METHODS
  This 3-D endoscope consists of a conventional 3-D endoscope and an outer and inner sleeve with a beam splitter and polarization plates. The beam splitter was used for visualizing both the front and front-diagonal view and was set at 25° to the outer sleeve's distal end in order to eliminate a blind spot common to both views. Polarization plates were used to avoid overlap of the two views. We measured signal-to-noise ratio (SNR), sharpness, chromatic aberration (CA), and viewing angle of this 3-D endoscope and evaluated its feasibility in vivo.
  
  
  RESULTS
  Compared to the conventional 3-D endoscope, SNR and sharpness of this 3-D endoscope decreased by 20 and 7 %, respectively. No significant difference was found in CA. The viewing angle for both the front and front-diagonal views was about 50°. In the in vivo experiment, this 3-D endoscope can provide clear 3-D images of both views by simply rotating its inner sleeve.
  
  
  CONCLUSIONS
  The developed 3-D endoscope can provide the front and front-diagonal view by simply rotating the inner sleeve, therefore the risk of damage to fragile body tissues can be significantly decreased.
authors.affiliation: Graduate School of Information Science and Technology, The University of Tokyo, Tokyo, Japan. khiroki@atre.t.u-tokyo.ac.jp
authors.forename: Hiroki
authors.initials: H
authors.lastname: Kamiuchi
authors.forename: Ken
authors.initials: K
authors.lastname: Masamune
authors.forename: Kenta
authors.initials: K
authors.lastname: Kuwana
authors.forename: Takeyoshi
authors.initials: T
authors.lastname: Dohi
authors.forename: Keri
authors.initials: K
authors.lastname: Kim
authors.forename: Hiromasa
authors.initials: H
authors.lastname: Yamashita
authors.forename: Toshio
authors.initials: T
authors.lastname: Chiba
mesh_terms: D019723:Endoscopes; D004724:Endoscopy / Q000379:methods*; D004867:Equipment Design; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods*; D059629:Signal-To-Noise Ratio