Correct self-assembling of spatial frequencies in super-resolution synthetic aperture digital holography

CNR-Istituto Nazionale di Ottica Applicata, via Campi Flegrei 34, 80078 Pozzuoli (NA) Italy.
Optics Letters (Impact Factor: 3.29). 12/2009; 34(23):3650-2. DOI: 10.1364/OL.34.003650
Source: PubMed


Synthetic aperture enlargement is obtained, in lensless digital holography, by introducing a diffraction grating between the object and the CCD camera with the aim of getting super-resolution. We demonstrate here that the spatial frequencies are naturally self-assembled in the reconstructed image plane when the NA is increased synthetically at its maximum extent of three times. By this approach it possible to avoid the use of the grating transmission formula in the numerical reconstruction process, thus reducing significantly the noise in the final super-resolved image. Demonstrations are reported in 1D and 2D with an optical target and a biological sample, respectively.

Download full-text


Available from: Pietro Ferraro
  • Source
    • "Aside from autofocusing, resolution enhancement is another important issue in DHM. Off-axis illumination has been used for resolution enhancement in DHM [10] [11] [12] [13] and also for three-dimensional tomographic imaging [14] [15] [16]. Structured illumination was used for both autofocusing and resolution enhancement [17] [18] [19]; for this purpose a phase-shifting operation [20] [21] is applied to separate the waves along different diffraction orders of the structured illumination. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Sequential speckle illumination has been incorporated into digital holographic microscopy (DHM) for autofocusing and resolution enhancement. For autofocusing, the image plane is numerically determined by searching for the minimal deviation among the reconstructed images obtained by different speckle illuminations and propagating the object wave to the image plane accordingly. Furthermore, an iterative method is used to synthesize the numerical aperture from the reconstructed object waves obtained by different speckle illuminations, in order to achieve resolution enhancement. The feasibility of the proposed method is demonstrated by both simulation and experiment.
    Full-text · Article · Aug 2015 · Journal of optics
  • Source
    • "In this manuscript we demonstrate that by incorporating the 2D pixel function of an image sensor chip into lensfree holographic image reconstruction and pixel super-resolution steps, one can improve the numerical aperture (NA) of the reconstructed images by a factor of ~3 compared to a raw lensfree image. Note that our use of the term ‘pixel super-resolution'2829313233 refers to improving the effective NA of an imaging system, and should not be confused with other microscopy techniques that aim to surpass the diffraction limit of light. This numerical aperture improvement is achieved using computational techniques (e.g., pixel super-resolution and hologram deconvolution), and is found to be, by and large, independent of the sensor chip design. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Pixel-size limitation of lensfree on-chip microscopy can be circumvented by utilizing pixel-super-resolution techniques to synthesize a smaller effective pixel, improving the resolution. Here we report that by using the two-dimensional pixel-function of an image sensor-array as an input to lensfree image reconstruction, pixel-super-resolution can improve the numerical aperture of the reconstructed image by ~3 fold compared to a raw lensfree image. This improvement was confirmed using two different sensor-arrays that significantly vary in their pixel-sizes, circuit architectures and digital/optical readout mechanisms, empirically pointing to roughly the same space-bandwidth improvement factor regardless of the sensor-array employed in our set-up. Furthermore, such a pixel-count increase also renders our on-chip microscope into a Giga-pixel imager, where an effective pixel count of ~1.6-2.5 billion can be obtained with different sensors. Finally, using an ultra-violet light-emitting-diode, this platform resolves 225 nm grating lines and can be useful for wide-field on-chip imaging of nano-scale objects, e.g., multi-walled-carbon-nanotubes.
    Full-text · Article · Apr 2013 · Scientific Reports
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: In analog holography, the infrared (IR) range received quite some attention, since it could provide interesting information, not achievable otherwise. Since digital sensors in this band became recently available and affordable, also digital holography (DH) expanded its feasibility beyond the visible wavelengths. In fact, the IR range allows shorter recording distances, unparalleled larger field of view and less stringent requirements on system stability, together with some specific characteristics, like e.g. the possibility to test IR glasses or other materials transparent to IR radiation, which cannot be controlled in visible range. In this paper we review the activities which took place in this field and illustrate the results achieved, referring to the opportunities this technique offers, and the challenges it presents. We show efficient reconstructions of holograms of objects of various materials, recorded with different resolution digital thermal cameras, in various configurations, and moreover we demonstrate optical holographic display through a liquid crystal based Spatial Light Modulator which gives the chance to get direct 3D imaging and display of long IR range. Moreover we believe this opens the route toward holography in THz region. Keywordsdigital holography–infrared radiation–thermal camera–infrared testing
    Full-text · Article · Dec 2010 · 3D Research
Show more