Abstract

An optical model of an ultrathin scanning fiber endoscope was constructed using a non-sequential ray tracing program and used to study the relationship between fiber deflection and collection efficiency from tissue. The problem of low collection efficiency of confocal detection through the scanned single-mode optical fiber was compared to non-confocal cladding detection. Collection efficiency is 40x greater in the non-confocal versus the confocal geometry due to the majority of rays incident on the core being outside the numerical aperture. Across scan angles of 0 to 30°, collection efficiency decreases from 14.4% to 6.3% for the non-confocal design compared to 0.34% to 0.10% for the confocal design. Non-confocality provides higher and more uniform collection efficiencies at larger scan angles while sacrificing the confocal spatial filter.

© 2005 Optical Society of America

Full Article  |  PDF Article

References

  • View by:
  • |

  1. K-. B. Sung, C. Liang, M. Descour, T. Collier, M. Follen, and R. Richards-Kortum, �??Fiber-optic confocal reflectance microscope with miniature objective for in vivo imaging of human tissues,�?? IEEE Trans. Biomed. Engr. 49, 1168-1172 (2002).
    [CrossRef]
  2. A. R. Rouse, A. Kano, J. A. Udovich, S. M. Kroto, and A.F. Gmitro, �??Design and demonstration of a miniature catheter for a confocal microendoscope,�?? Appl. Opt. 43, 5763-5771 (2004).
    [CrossRef] [PubMed]
  3. K. Murakami, �??A miniature confocal optical scanning microscope for endoscope,�?? in MOEMS Display and Imaging Systems III, H. Urey and D. L. Dickensheets, eds., Proc. SPIE 5721, 119-131 (2005).
    [CrossRef]
  4. W. McLaren, P. Anikijenko, D. Barkla, P. Delaney, and R. King, �??In vivo detection of experimental ulcerative colitis in rats using fiberoptic confocal imaging (FOCI),�?? Dig. Dis. Sci. 46, 2263-2276 (2001).
    [CrossRef] [PubMed]
  5. E. J. Seibel, Q. Y. J. Smithwick, C. M. Brown, and P. G. Reinhall, �??Single fiber flexible endoscope: general design for small size, high resolution, and wide field of view,�?? in Biomonitoring and Endoscopy Technologies, I. Gannot, Y. V. Gulyaev, T. G. Papazoglou, and C. F. P. van Swol, eds., Proc. SPIE 4158, 29-39 (2001).
    [CrossRef]
  6. E. J. Seibel and Q. Y. J. Smithwick, �??Unique features of optical scanning, single fiber endoscopy,�?? Lasers Surg. Med. 30, 177-183 (2002).
    [CrossRef] [PubMed]
  7. D. Yelin, B. E. Bouma, S. H. Yun, and G. J. Tearney, �??Double-clad fiber for endoscopy,�?? Opt. Lett. 29, 2408-2410 (2004).
    [CrossRef] [PubMed]
  8. R. S. Johnston and E.J. Seibel, �??Scanning fiber endoscope prototype performance�?? in Frontiers in Optics / Laser Science XX, Topical Meetings on CD-ROM (The Optical Society of America, Washington, DC, 2004), presentation summary # FWM2,�?? given in Rochester, NY, 10-14, Oct. 2004.
  9. S. L. Jacques, C. A. Alter, and S. A. Prahl, �??Angular Dependence of HeNe Laser Light Scattering by Human Dermis,�?? Lasers in the Life Sciences I, 309-334 (1987).
  10. N. S. Nishioka, S. L. Jacques, J. M. Richter, and R. R. Anderson, �??Reflection and Transmission of Laser Light From the Esophagus: The Influence of Incident Angle,�?? Gastroenterology 94, 1180-1185 (1988).
    [PubMed]
  11. ASTM E 1392-96, �??Standard Practice for Angle Resolved Optical Scatter Measurements on Specular or Diffuse Surfaces.�?? Am. Soc. Test. Meas. (1996).
  12. R. Kiesslich, J. Burg, M. Vieth, J. Gnaendiger, M. Enders, P. Delany, A. Polglase, W. McLaren, D. Janell, S. Thomas, B. Nafe, P. R. Galle, and M. F. Neurath, �??Confocal laser endoscopy for diagnosing intraepithelial neoplasias and colorectal cancer in vivo,�?? Gastroenterology 127, 706-713 (2004).
    [CrossRef] [PubMed]
  13. S. L. Jacques, J. R. Roman, and K. Lee, �??Imaging superficial tissues with polarized light,�?? Lasers Surg. Med. 26, 119-129 (2000).
    [CrossRef] [PubMed]

Am. Soc. Test. Meas.

ASTM E 1392-96, �??Standard Practice for Angle Resolved Optical Scatter Measurements on Specular or Diffuse Surfaces.�?? Am. Soc. Test. Meas. (1996).

Appl. Opt.

Dig. Dis. Sci.

W. McLaren, P. Anikijenko, D. Barkla, P. Delaney, and R. King, �??In vivo detection of experimental ulcerative colitis in rats using fiberoptic confocal imaging (FOCI),�?? Dig. Dis. Sci. 46, 2263-2276 (2001).
[CrossRef] [PubMed]

Frontiers in Optics / Laser Science XX

R. S. Johnston and E.J. Seibel, �??Scanning fiber endoscope prototype performance�?? in Frontiers in Optics / Laser Science XX, Topical Meetings on CD-ROM (The Optical Society of America, Washington, DC, 2004), presentation summary # FWM2,�?? given in Rochester, NY, 10-14, Oct. 2004.

Gastroenterology

R. Kiesslich, J. Burg, M. Vieth, J. Gnaendiger, M. Enders, P. Delany, A. Polglase, W. McLaren, D. Janell, S. Thomas, B. Nafe, P. R. Galle, and M. F. Neurath, �??Confocal laser endoscopy for diagnosing intraepithelial neoplasias and colorectal cancer in vivo,�?? Gastroenterology 127, 706-713 (2004).
[CrossRef] [PubMed]

N. S. Nishioka, S. L. Jacques, J. M. Richter, and R. R. Anderson, �??Reflection and Transmission of Laser Light From the Esophagus: The Influence of Incident Angle,�?? Gastroenterology 94, 1180-1185 (1988).
[PubMed]

IEEE Trans. Biomed. Engr.

K-. B. Sung, C. Liang, M. Descour, T. Collier, M. Follen, and R. Richards-Kortum, �??Fiber-optic confocal reflectance microscope with miniature objective for in vivo imaging of human tissues,�?? IEEE Trans. Biomed. Engr. 49, 1168-1172 (2002).
[CrossRef]

Lasers in the Life Sciences

S. L. Jacques, C. A. Alter, and S. A. Prahl, �??Angular Dependence of HeNe Laser Light Scattering by Human Dermis,�?? Lasers in the Life Sciences I, 309-334 (1987).

Lasers Surg. Med.

E. J. Seibel and Q. Y. J. Smithwick, �??Unique features of optical scanning, single fiber endoscopy,�?? Lasers Surg. Med. 30, 177-183 (2002).
[CrossRef] [PubMed]

S. L. Jacques, J. R. Roman, and K. Lee, �??Imaging superficial tissues with polarized light,�?? Lasers Surg. Med. 26, 119-129 (2000).
[CrossRef] [PubMed]

Opt. Lett.

Proc. SPIE

E. J. Seibel, Q. Y. J. Smithwick, C. M. Brown, and P. G. Reinhall, �??Single fiber flexible endoscope: general design for small size, high resolution, and wide field of view,�?? in Biomonitoring and Endoscopy Technologies, I. Gannot, Y. V. Gulyaev, T. G. Papazoglou, and C. F. P. van Swol, eds., Proc. SPIE 4158, 29-39 (2001).
[CrossRef]

K. Murakami, �??A miniature confocal optical scanning microscope for endoscope,�?? in MOEMS Display and Imaging Systems III, H. Urey and D. L. Dickensheets, eds., Proc. SPIE 5721, 119-131 (2005).
[CrossRef]

Cited By

OSA participates in CrossRef's Cited-By Linking service. Citing articles from OSA journals and other participating publishers are listed here.

Alert me when this article is cited.


Figures (9)

Fig. 1.
Fig. 1.

Fiber microscanner assembly contained in a housing of one millimeter outer diameter.

Fig. 2.
Fig. 2.

SFE image of 1951 USAF test target

Fig. 3.
Fig. 3.

A plot of the scatter model function in ASAP 8.0.3, based on the above H-G’ function (2) with ϕo = 25 degrees, a = 17.25*π, and β = 0.58[9].

Fig. 4.
Fig. 4.

(above). A schematic showing the overall system and the relationships between various parameters. The fiber tip displacement to inner edge of housing is exaggerated for clearly illustrating scan angle. Rays shown are representations only, and do not represent energy traveling along actual ray paths. (below). The optical fiber end face is shown with illustrative cones of acceptance angles (NA) denoting light collection in confocal and non-confocal. The optical fiber end face is shown as the detector with illustrative cones of acceptance angles (NA) denoting light collection in confocal and non-confocal geometries. The vertex of the two cones is located at the effective point source of the single-mode optical fiber, slightly within the endface surface along the optical axis.

Fig. 5.
Fig. 5.

The plots above show a profile of the system tracing rays at theta values of 0, 1, 2 and 3, and the corresponding location of the energy distribution on the sample. The scanning optical fiber is shown in Green. The vertical arrow indicates the location of the (ideal) lens.

Fig. 6.
Fig. 6.

(a) (Left). shows the spot from a global perspective. (b) (Right) shows the same spot centered in the picture window. The majority of the sampled rays are distributed within a 2 micron spot size.

Fig. 7.
Fig. 7.

Intensity of the rays scattering off of the sample at θ=2 degrees plotted ± 90 degrees on both axes.

Fig. 8.
Fig. 8.

Energy incident on an oversized 6-mm diameter detector at a reflection angle of 20 degrees (θ=2) that slightly overfills the square window. Note the specular component on the left region of the detector, and the “hole” in the detector is where the microscanner housing and lens interface the surface of the much larger detector.

Fig. 9.
Fig. 9.

Flux on internal components as a function of rotation angle. Note that the dashed lines combine to give the solid Cyan colored line.

Tables (1)

Tables Icon

Table 1. Images of energy density on non-confocal and confocal detection systems

Equations (2)

Equations on this page are rendered with MathJax. Learn more.

H G = 1 4 π 1 g 2 ( 1 g 2 2 g cos ϕ ) 3 / 2
H G = a * β cos ( ϕ ) ( 1 a ) + ( 1 β ) 1 g 2 ( 1 g 2 2 g cos ( ϕ ϕ o ) ) 3 / 2

Metrics