Abstract

An off-axis transmission holographic scheme, in which a 1:1 lens and a hologram are treated as a single rigid entity, is found to reconstruct a 3-D diffraction-limited image when reconstructed, with a reference beam reversed back through the original lens–hologram unit. Reconstruction can be performed with wavelengths other than the recording wavelength, provided achromatic lenses are used, and the reference beam angle is properly changed for reconstruction. Comparisons are made between He–Ne and ruby laser holograms. Two-micron resolution of the combustion of solid rocket propellants at high pressures is achieved at a working distance of 6 cm.

© 1978 Optical Society of America

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References

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  1. L. O. Heflinger et al., Appl. Opt. 17, 951 (1978).
    [CrossRef] [PubMed]
  2. H. Kogelnik, Bell Syst. Tech. J. 44, 2451 (1965).
  3. The 1951 resolution chart consists of both vertical and horizontal three-bar arrays whose spatial frequency (SF) varies according to the equationSF=2{column#+row#−16}(lp/mm).The smallest divisions correspond to the seventh column and six row, a spatial frequency of 228 lp/mm (spatial period of 4.4 μm or individual bar widths of 2.2 μm).
  4. Reconstruction of the 1951 chart holograms to highest resolutions could be achieved without recourse to the special alignment technique described in Ref. 2. For example, holograms recorded with a ruby laser and reconstructed with a He–Ne laser required a 9½° decrease in reference beam angle to compensate for the wavelength difference. The optimum reference beam angle was found by carefully tuning the beam relative to the hologram while microscopically observing the reconstructed image.
  5. A similar test was conducted with transparent 2.4 μm polystyrene spheres. The spheres were harder to reconstruct due to their lower contrast. They could just be seen in the reconstruction.
  6. Larger focusing lenses would permit recording even larger volumes at similar resolutions.
  7. These holograms were reconstructed back through a window section and a piece of glass that simulated the interference filter.

1978 (1)

1965 (1)

H. Kogelnik, Bell Syst. Tech. J. 44, 2451 (1965).

Heflinger, L. O.

Kogelnik, H.

H. Kogelnik, Bell Syst. Tech. J. 44, 2451 (1965).

Appl. Opt. (1)

Bell Syst. Tech. J. (1)

H. Kogelnik, Bell Syst. Tech. J. 44, 2451 (1965).

Other (5)

The 1951 resolution chart consists of both vertical and horizontal three-bar arrays whose spatial frequency (SF) varies according to the equationSF=2{column#+row#−16}(lp/mm).The smallest divisions correspond to the seventh column and six row, a spatial frequency of 228 lp/mm (spatial period of 4.4 μm or individual bar widths of 2.2 μm).

Reconstruction of the 1951 chart holograms to highest resolutions could be achieved without recourse to the special alignment technique described in Ref. 2. For example, holograms recorded with a ruby laser and reconstructed with a He–Ne laser required a 9½° decrease in reference beam angle to compensate for the wavelength difference. The optimum reference beam angle was found by carefully tuning the beam relative to the hologram while microscopically observing the reconstructed image.

A similar test was conducted with transparent 2.4 μm polystyrene spheres. The spheres were harder to reconstruct due to their lower contrast. They could just be seen in the reconstruction.

Larger focusing lenses would permit recording even larger volumes at similar resolutions.

These holograms were reconstructed back through a window section and a piece of glass that simulated the interference filter.

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Figures (12)

Fig. 1
Fig. 1

Schematic of two-beam lens-assisted holographic arrangement.

Fig. 2
Fig. 2

Method of reconstructing lens-assisted holograms.

Fig 3
Fig 3

Comparison between direct photomicrographs and lens-assisted hologram reconstructions. First picture, collimated white light photomicrograph of chart taken with 0.3 N.A. microscope. Second picture, He–Ne photomicrograph. Third picture, photomicrograph of He–Ne laser reconstruction of hologram recorded with He–Ne laser. Fourth picture, same as third except recorded with ruby laser.

Fig. 4
Fig. 4

Comparison between diffuse rear illumination photomicrographs and lens-assisted hologram reconstructions. First picture (left) is direct white light photomicrograph. The second picture is a similar direct He–Ne photomicrograph. The third picture is a photomicrograph (via Fig. 2) of the He–Ne laser reconstruction of a hologram recorded in the Fig. 1 apparatus with a He–Ne laser. The fourth picture is the same as the third except recorded with a ruby laser.

Fig. 5
Fig. 5

Photomicrographs of images reconstructed from conventional (nonlens assisted) two-beam (75°) holograms. Left picture, chart rear-illuminated via collimated scene beam. Middle picture, chart illuminated from behind by ground glass diffuser, including the effects of a second reference beam. Third picture, same as second except with only single reference beam.

Fig 6
Fig 6

Comparison of diffuse (opal glass) rear illumination photomicrograph against He–Ne–He–Ne lens-assisted hologram reconstructions. The first picture (left) is the direct photomicrograph (0.3 N.A.). The middle picture was recorded with two reference beams (60° between each). The third (right) picture was recorded (as per Fig. 1) with a single reference beam.

Fig. 7
Fig. 7

Comparison of collimated rear-illuminated lens-assisted holograms recorded with achromatic lenses. The left picture was recorded with a He–Ne laser, the right with a ruby laser. Both were reconstructed with a He–Ne laser by the Fig. 2 method.

Fig 8
Fig 8

Photomicrographs taken of the reconstruction of a lens-assisted hologram (He–Ne recorded and He–Ne reconstructed). For the left picture, the examining microscope was focused on the reconstruction of the chart. For the right picture, the microscope was focused on the reconstruction of iron carbonyl particles dusted on the near surface of the 1-mm thick glass plate that supported the chart.

Fig. 9
Fig. 9

Low magnification photograph of reconstruction of a (ruby–He–Ne) lens-assisted hologram of the combustion at 25-kTorr pressure of a 6 × 3 × 1-mm sample (initially) of solid rocket propellant (Type MS-23).

Fig. 10
Fig. 10

Enlarged portion of the reconstructed image shown in Fig. 9 (taken with 10×, 0.3 N.A. objective).

Fig. 11
Fig. 11

Further enlargement of portion of same image reconstructed from hologram and shown in Figs. 8 and 9. This picture was taken with 20×, 0.5 N.A. objective.

Fig. 12
Fig. 12

Photographs of reconstruction of holograms taken with microscope with 40×, 0.65 N.A. objective. Left picture is the same grouping of particles seen in Fig. 10. Right picture, resolution chart in bomb prior to combustion.

Equations (1)

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SF=2{column#+row#16}(lp/mm).

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