Abstract

Microscopic imaging with a setup consisting of a pseudo-random phase mask, and an open CMOS camera, but without an imaging objective, is demonstrated. The pseudo random phase mask acts as a diffuser for an incoming laser beam, scattering a speckle pattern to a CMOS chip, which is recorded once, as a reference. A sample which is afterwards inserted somewhere in the optical beam path changes the speckle pattern. A single (non-iterative) image processing step, comparing the modified speckle pattern with the previously recorded one, generates a sharp image of the sample. After a first calibration the method works in real-time and allows quantitative imaging of complex (amplitude and phase) samples in an extended three-dimensional volume. Since no lenses are used, the method is free from lens aberrations. Compared to standard inline holography the diffuse sample illumination improves the axial sectioning capability by increasing the effective numerical aperture in the illumination path, and it suppresses the undesired twin images. For demonstration, a high resolution spatial light modulator (SLM) is programmed to act as the pseudo-random phase mask. We show experimental results, imaging microscopic biological samples, such as insects, within an extended volume at a distance of 15 cm with a transverse and longitudinal resolution of about 60 μm and 400 μm, respectively.

© 2011 OSA

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References

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    [CrossRef] [PubMed]
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    [CrossRef]
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    [CrossRef]
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    [CrossRef]
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    [CrossRef] [PubMed]
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2011 (1)

I. Moon, M. Daneshpanah, A. Anand, and B. Javidi, “Cell identification with computational 3-D holographic microscopy,” Opt. Photon. News 22, 18–23 (2011).
[CrossRef]

2010 (1)

2009 (1)

2008 (1)

2007 (1)

F. Zhang, G. Pedrini, and W. Osten, “Phase retrieval of arbitrary complex-valued fields through aperture-plane modulation,” Phys. Rev. A 75, 043805 (2007).
[CrossRef]

2004 (1)

1988 (1)

1982 (1)

1978 (1)

1949 (1)

D. Gabor, “Microscopy by reconstructed wave-fronts,” Proc. R. Soc. London Ser. A 197, 454–487 (1949).
[CrossRef]

1948 (1)

D. Gabor, “A new microscopic principle,” Nature 161, 777–778 (1948).
[CrossRef] [PubMed]

Anand, A.

I. Moon, M. Daneshpanah, A. Anand, and B. Javidi, “Cell identification with computational 3-D holographic microscopy,” Opt. Photon. News 22, 18–23 (2011).
[CrossRef]

Bernet, S.

Cederquist, J. N.

Daneshpanah, M.

I. Moon, M. Daneshpanah, A. Anand, and B. Javidi, “Cell identification with computational 3-D holographic microscopy,” Opt. Photon. News 22, 18–23 (2011).
[CrossRef]

Fienup, J. R.

Fürhapter, S.

Gabor, D.

D. Gabor, “Microscopy by reconstructed wave-fronts,” Proc. R. Soc. London Ser. A 197, 454–487 (1949).
[CrossRef]

D. Gabor, “A new microscopic principle,” Nature 161, 777–778 (1948).
[CrossRef] [PubMed]

Imbe, M.

Javidi, B.

I. Moon, M. Daneshpanah, A. Anand, and B. Javidi, “Cell identification with computational 3-D holographic microscopy,” Opt. Photon. News 22, 18–23 (2011).
[CrossRef]

Jesacher, A.

Kohler, C.

Marron, J. C.

Maurer, C.

Moon, I.

I. Moon, M. Daneshpanah, A. Anand, and B. Javidi, “Cell identification with computational 3-D holographic microscopy,” Opt. Photon. News 22, 18–23 (2011).
[CrossRef]

Nomura, T.

Osten, W.

C. Kohler, F. Zhang, and W. Osten, “Characterization of a spatial light modulator and its application in phase retrieval,” Appl. Opt. 48, 4003–4008 (2009).
[CrossRef] [PubMed]

F. Zhang, G. Pedrini, and W. Osten, “Phase retrieval of arbitrary complex-valued fields through aperture-plane modulation,” Phys. Rev. A 75, 043805 (2007).
[CrossRef]

Paxman, R. G.

Pedrini, G.

F. Zhang, G. Pedrini, and W. Osten, “Phase retrieval of arbitrary complex-valued fields through aperture-plane modulation,” Phys. Rev. A 75, 043805 (2007).
[CrossRef]

Ritsch-Marte, M.

Schwaighofer, A.

Zhang, F.

C. Kohler, F. Zhang, and W. Osten, “Characterization of a spatial light modulator and its application in phase retrieval,” Appl. Opt. 48, 4003–4008 (2009).
[CrossRef] [PubMed]

F. Zhang, G. Pedrini, and W. Osten, “Phase retrieval of arbitrary complex-valued fields through aperture-plane modulation,” Phys. Rev. A 75, 043805 (2007).
[CrossRef]

Appl. Opt. (3)

Nature (1)

D. Gabor, “A new microscopic principle,” Nature 161, 777–778 (1948).
[CrossRef] [PubMed]

Opt. Express (1)

Opt. Lett. (3)

Opt. Photon. News (1)

I. Moon, M. Daneshpanah, A. Anand, and B. Javidi, “Cell identification with computational 3-D holographic microscopy,” Opt. Photon. News 22, 18–23 (2011).
[CrossRef]

Phys. Rev. A (1)

F. Zhang, G. Pedrini, and W. Osten, “Phase retrieval of arbitrary complex-valued fields through aperture-plane modulation,” Phys. Rev. A 75, 043805 (2007).
[CrossRef]

Proc. R. Soc. London Ser. A (1)

D. Gabor, “Microscopy by reconstructed wave-fronts,” Proc. R. Soc. London Ser. A 197, 454–487 (1949).
[CrossRef]

Other (1)

An explanation of iterative Fourier transform algorithms can be found for example in: B. C. Kress and P. Meyrueis (Eds.) “Digital Diffractive Optics,” 1st ed. (John Wiley & Sons, 2000) ISBN-13: 978-0-471-98447-4.

Supplementary Material (1)

» Media 1: MPG (3375 KB)     

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Figures (6)

Fig. 1
Fig. 1

Principle of lensless imaging. Step 1: Image registration: a test hologram displayed at the SLM is illuminated with a slightly divergent laser beam and reconstructed in the camera plane. Mapping the experimentally recorded image onto the numerically reconstructed one, allows one to derive a transformation matrix which is afterwards applied to all other experimentally recorded images. Step 2: A pseudo random phase pattern (with transmission function TR) is displayed at the SLM. The corresponding speckle pattern generated in the camera plane (R) is recorded as a reference. The corresponding complex phase angle (ΦR) of the speckle pattern is numerically computed and mapped pixel by pixel with the experimental speckle intensity image by using the previously determined spatial transformation matrix. Step 3: Actual imaging procedure: Samples in the optical beam path generate a series of new speckle patterns (Si) which are recorded by the camera. Step 4: Image reconstruction: The complex amplitude of the object’s wave field in the camera plane is obtained by numerical subtraction of the (normalized) image and reference intensity images ( ( S i R ) / ( S i + R ) / 2 and by assigning the complex phase ΦR of the reference speckle pattern to the difference. Then the wavefront is numerically propagated to different axial planes between the SLM and the camera (so called ”spectrum of plane waves propagation operator” indicated in Fig. 1), in order to reconstruct sharp images of the sample.

Fig. 2
Fig. 2

Experimental setup. For a detailed explanation see the text.

Fig. 3
Fig. 3

Reconstructed on-axis Fresnel hologram of a test pattern recorded by a CMOS camera. The image is used for geometric mapping (image registration) of the experimentally projected holograms with the numerically reconstructed images. The corresponding phase mask displayed at the SLM was calculated with an iterative Fourier transform algorithm as a phase-only on-axis Fresnel hologram with a reconstruction distance of 15 cm. The imaging distance of 15 cm was chosen, since in this case the diffracted test pattern has approximately the same size as the camera chip. The dashed square (which is not part of the test hologram) was included afterwards to indicate the boundaries of the programmed hologram. The reconstructed image parts around the dashed square are reproductions of the inner image, which appear in higher diffraction orders due to the SLM pixelation.

Fig. 4
Fig. 4

a: Speckle pattern without sample in the beam path. b: Speckle pattern after insertion of a sample on top of the SLM surface. c: Intensity difference between speckle patterns with (S) and without (R) included sample, normalized by S + R. d: Numerically reconstructed intensity image of a “fly” placed on the SLM surface. e: Numerically reconstructed complex phase image.

Fig. 5
Fig. 5

Comparison of axial sectioning for diffuse and for plane wave illumination. Two specimen, namely a “fly” on top of the SLM surface, and an ant on top of the beamsplitter cube at a distance of 5 cm from the SLM surface, were inserted in the optical path. The sequences (a)–(c) and (d)–(f) show the results of the image reconstruction processes at corresponding focal planes for diffuse and plane wave illumination, respectively. (a) and (d): Numerical image reconstruction in the SLM plane. (b) and (e): Numerically refocussed image at a distance of 2.5 cm from the SLM surface. (c) and (f): Numerically refocussed image at a distance of 5 cm from the SLM surface (corresponding to the top surface of the beamsplitter cube). All images were reconstructed from the same experimentally recorded speckle pattern. A continuous version demonstrating the effects of numerical focus tuning is shown in an included movie ( Media 1, 3.6 MB). Obviously, the diffuse illumination enables independent imaging of the axially separated samples, whereas plane wave illumination results in an overlapping of the two images in all numerically refocussed planes.

Fig. 6
Fig. 6

a: Reconstructed test hologram from a resolution target shows a lateral resolution on the order of 50 micron. b,c: Crossed hairs, axially separated by 400 μm, alternately in focus.

Equations (5)

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S = F { T R } F * { T R } + F { T R } F * { Δ O T R } + F * { T R } F { Δ O T R } + F { Δ O T R } F * { Δ O T R } .
S R F { T R } F * { Δ O T R } + F * { T R } F { Δ O T R } .
F 1 { ( S R ) / F * { T R } } / T R = Δ O + F 1 { ( F { T R } / F * { T R } ) F * { Δ O T R } } / T R ,
Δ O = F 1 { ( S R ) / F * { T R } } / T R + speckle noise .
Δ O = F 1 { S R S + R / 2 exp ( i Φ R ) } exp ( i Φ S L M ) .

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