Abstract

Small limiting apertures of endoscopes cause gross speckles when using coherent light sources in holographic endoscopy. Thus, for a high optical signal-to-noise ratio, imaging systems with high numerical apertures and low f/Nos. are required, which under given geometrical constraints can be provided in particular by gradient-index rod lenses. For additional speckle reduction the limiting aperture has to be enlarged within the given outer diameter of the instrument. This can be achieved by using the same gradient-index rod lens for both imaging and illumination, so that no separate illuminating fiber bundle is necessary. Holographic recording problems due to reflections of the illuminating object beam from the end faces can be solved by appropriate positioning and shaping of the rod as well as by holographic subtraction.

© 1984 Optical Society of America

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References

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  1. D. Hadbawnik, Optik 45, 21 (1976).
  2. G. von Bally, Ed., Holography in Medicine and Biology (Springer, Berlin, 1979).
  3. G. von Bally, P. Greguss, Eds., Optics in Biomedical Sciences (Springer, Berlin, 1982).
  4. G. von Bally, “Otoscopic Investigations by Holographic Interferometry: a Fiber Endoscopic Approach Using a Pulsed Ruby Laser System,” in Optics in Biomedical Sciences, G. von Bally, P. Greguss, Eds. (Springer, Berlin, 1982), pp. 110–114.
  5. M. Francon, Laser Speckle and Applications in Optics (Academic, New York, 1979).
  6. R. J. Collier, C. B. Burckhardt, L. H. Lin, Optical Holography (Academic, New York, 1971).
  7. C. Sieger, “Suppression of Disturbing Light Reflexes in Holography Applied to Practical Recording Problems in Medicine and Technology,” in Optics in Biomedical Sciences, G. von Bally, P. Greguss, Eds. (Springer, Berlin, 1982), pp. 126–130.
  8. J. A. Gilbert, M. E. Schultz, A. J. Boehnlein, Exp. Mech. 22, 398 (1982).
    [CrossRef]
  9. O. J. Løkberg, “Speckle Techniques for Use in Biology and Medicine,” in Optics in Biomedical Sciences, G. von Bally, P. Greguss, Eds. (Springer, Berlin, 1982), pp. 144–153.

1982 (1)

J. A. Gilbert, M. E. Schultz, A. J. Boehnlein, Exp. Mech. 22, 398 (1982).
[CrossRef]

1976 (1)

D. Hadbawnik, Optik 45, 21 (1976).

Boehnlein, A. J.

J. A. Gilbert, M. E. Schultz, A. J. Boehnlein, Exp. Mech. 22, 398 (1982).
[CrossRef]

Burckhardt, C. B.

R. J. Collier, C. B. Burckhardt, L. H. Lin, Optical Holography (Academic, New York, 1971).

Collier, R. J.

R. J. Collier, C. B. Burckhardt, L. H. Lin, Optical Holography (Academic, New York, 1971).

Francon, M.

M. Francon, Laser Speckle and Applications in Optics (Academic, New York, 1979).

Gilbert, J. A.

J. A. Gilbert, M. E. Schultz, A. J. Boehnlein, Exp. Mech. 22, 398 (1982).
[CrossRef]

Hadbawnik, D.

D. Hadbawnik, Optik 45, 21 (1976).

Lin, L. H.

R. J. Collier, C. B. Burckhardt, L. H. Lin, Optical Holography (Academic, New York, 1971).

Løkberg, O. J.

O. J. Løkberg, “Speckle Techniques for Use in Biology and Medicine,” in Optics in Biomedical Sciences, G. von Bally, P. Greguss, Eds. (Springer, Berlin, 1982), pp. 144–153.

Schultz, M. E.

J. A. Gilbert, M. E. Schultz, A. J. Boehnlein, Exp. Mech. 22, 398 (1982).
[CrossRef]

Sieger, C.

C. Sieger, “Suppression of Disturbing Light Reflexes in Holography Applied to Practical Recording Problems in Medicine and Technology,” in Optics in Biomedical Sciences, G. von Bally, P. Greguss, Eds. (Springer, Berlin, 1982), pp. 126–130.

von Bally, G.

G. von Bally, “Otoscopic Investigations by Holographic Interferometry: a Fiber Endoscopic Approach Using a Pulsed Ruby Laser System,” in Optics in Biomedical Sciences, G. von Bally, P. Greguss, Eds. (Springer, Berlin, 1982), pp. 110–114.

Exp. Mech. (1)

J. A. Gilbert, M. E. Schultz, A. J. Boehnlein, Exp. Mech. 22, 398 (1982).
[CrossRef]

Optik (1)

D. Hadbawnik, Optik 45, 21 (1976).

Other (7)

G. von Bally, Ed., Holography in Medicine and Biology (Springer, Berlin, 1979).

G. von Bally, P. Greguss, Eds., Optics in Biomedical Sciences (Springer, Berlin, 1982).

G. von Bally, “Otoscopic Investigations by Holographic Interferometry: a Fiber Endoscopic Approach Using a Pulsed Ruby Laser System,” in Optics in Biomedical Sciences, G. von Bally, P. Greguss, Eds. (Springer, Berlin, 1982), pp. 110–114.

M. Francon, Laser Speckle and Applications in Optics (Academic, New York, 1979).

R. J. Collier, C. B. Burckhardt, L. H. Lin, Optical Holography (Academic, New York, 1971).

C. Sieger, “Suppression of Disturbing Light Reflexes in Holography Applied to Practical Recording Problems in Medicine and Technology,” in Optics in Biomedical Sciences, G. von Bally, P. Greguss, Eds. (Springer, Berlin, 1982), pp. 126–130.

O. J. Løkberg, “Speckle Techniques for Use in Biology and Medicine,” in Optics in Biomedical Sciences, G. von Bally, P. Greguss, Eds. (Springer, Berlin, 1982), pp. 144–153.

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Figures (11)

Fig. 1
Fig. 1

Endoscope with rod lens imaging system (Hopkins optic) for outer and middle ear inspection (otoscope) with specially modified ocular for holographic recording: (a) complete instrument; (b) tip (EO, endoscope objective; IFB, illuminating fiber bundle).

Fig. 2
Fig. 2

Example for increase in speckle noise due to a small limiting aperture in holographic endoscopy; holographic recordings through (a) a lens (f/2.5) and (b) the otoscope as shown in Fig. 1.

Fig. 3
Fig. 3

On-axis arrangement for simultaneous imaging and illumination through the same gradient-index rod lens to achieve an optimal limiting aperture of the optical system.

Fig. 4
Fig. 4

(a) High intensity light spot within the hologram area in the hologram plane caused by reflection from the entrance face of the gradient-index rod lens when illuminating and imaging through the same optical system as outlined in Fig. 3; arrangements to remove this reflection spot (b) by positioning and (c),(d) by shaping of the gradient-index rod lens.

Fig. 5
Fig. 5

Degradation of image information in a holographic interferogram caused by reflections of the illuminating object beam when illuminating and imaging through the same gradient-index rod lens as outlined in Fig. 3 using the arrangement as in Fig. 4(b).

Fig. 6
Fig. 6

Experimental setup for stroboscopic double-exposure holography and holographic subtraction.

Fig. 7
Fig. 7

Example of the phase relation between piezocrystal-driven mirror oscillation (upper trace), laser pulses, and sinusoidal object vibration (lower trace).

Fig. 8
Fig. 8

Holographic interferogram of a loudspeaker recorded (a) without and (b) with holographic subtraction, here imaged through gradient-index rod lens but illuminated separately (gradient-index rod lens diameter = 4 mm, length = 50 mm).

Fig. 9
Fig. 9

Same object as in Fig. 8 but here imaged and illuminated through gradient-index rod lens recorded (a) without and (b) with holographic subtraction.

Fig. 10
Fig. 10

Same object as in Fig. 8 but here imaged and illuminated through a lens recorded (a) without and (b) with holographic subtraction.

Fig. 11
Fig. 11

Fringe contrast in holographic interferograms recorded with multimode fiber bundle illumination (a) without and (b) with projection of the fiber bundle endface onto the object.

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