A digital holographic microscope for complete characterization of microelectromechanical systems

Coppola, Giuseppe; Ferraro, Pietro; Iodice, Mario; Nicola, S. De; Fińizio, Andrea; Grilli, Simonetta

doi:10.1088/0957-0233/15/3/005

Cited by 150 publications

(83 citation statements)

References 27 publications

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“…DHM is particularly useful for MEMS characterization because of the relatively smooth and well-defined surface profile [60,190]. Microcantilever beams, bridges, and membranes are imaged by quantitative phase holography [22].…”

Section: Microscopy and Metrology Of Microstructuresmentioning

confidence: 99%

“…Microcantilever beams, bridges, and membranes are imaged by quantitative phase holography [22]. The multiwavelength optical phase unwrapping of phase images yields shape and deformation measurements with submicron precision over a many-micron range [151,169,190]. Various optical techniques, including digital holography, for characterization of MEMS devices are reviewed in Ref.…”

Section: Microscopy and Metrology Of Microstructuresmentioning

confidence: 99%

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Principles and techniques of digital holographic microscopy

2010

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Abstract. Digital holography is an emerging field of new paradigm in general imaging applications. We present a review of a subset of the research and development activities in digital holography, with emphasis on microscopy techniques and applications. First, the basic results from the general theory of holography, based on the scalar diffraction theory, are summarized, and a general description of the digital holographic microscopy process is given, including quantitative phase microscopy. Several numerical diffraction methods are described and compared, and a number of representative configurations used in digital holography are described, including off-axis Fresnel, Fourier, image plane, in-line, Gabor, and phase-shifting digital holographies. Then we survey numerical techniques that give rise to unique capabilities of digital holography, including suppression of dc and twin image terms, pixel resolution control, optical phase unwrapping, aberration compensation, and others. A survey is also given of representative application areas, including biomedical microscopy, particle field holography, micrometrology, and holographic tomography, as well as some of the special techniques, such as holography of total internal reflection, optical scanning holography, digital interference holography, and heterodyne holography. The review is intended for students and new researchers interested in developing new techniques and exploring new applications of digital holography. C 2010 Society of Photo-Optical Instrumentation Engineers.

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Section: Microscopy and Metrology Of Microstructuresmentioning

confidence: 99%

Section: Microscopy and Metrology Of Microstructuresmentioning

confidence: 99%

Principles and techniques of digital holographic microscopy

2010

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“…The second consequence is that normalization by the reference, Equation 3.14, is not strictly necessary since the reference has already been cancelled from the intensity terms of Equation 3.86. Normalizing by a spherical reference actually adds an unnecessary phase distortion which must be removed after propagation (see, e.g., [75]). …”

Section: Subtle Lessonsmentioning

confidence: 99%

“…The real and imaginary components are useful as diagnostics, as components of focus metrics [89], [274], as representations of the objects, or for computing the quantitative phase of imaged objects [75]. The squared magnitude gives the intensity which would be observed using optical reconstruction methods.…”

Section: Introduction To Digital Holographymentioning

confidence: 99%

Computational imaging and automated identification for aqueous environments

Loomis¹

2011

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Sampling the vast volumes of the ocean requires tools capable of observing from a distance while retaining detail necessary for biology and ecology, ideal for optical methods. Algorithms that work with existing SeaBED AUV imagery are developed, including habitat classi…cation with bag-of-words models and multi-stage boosting for rock…sh detection. Methods for extracting images of …sh from videos of longline operations are demonstrated.A prototype digital holographic imaging device is designed and tested for quantitative in situ microscale imaging. Theory to support the device is developed, including particle noise and the e¤ects of motion. A Wigner-domain model provides optimal settings and optical limits for spherical and planar holographic references.Algorithms to extract the information from real-world digital holograms are created. Focus metrics are discussed, including a novel focus detector using local Zernike moments. Two methods for estimating lateral positions of objects in holograms without reconstruction are presented by extending a summation kernel to spherical references and using a local frequency signature from a Riesz transform. A new metric for quickly estimating object depths without reconstruction is proposed and tested. An example application, quantifying oil droplet size distributions in an underwater plume, demonstrates the e¢ cacy of the prototype and algorithms. Course work at MIT and WHOI was helpful throughout this thesis. In particular, course materials and projects from Dr. Antonio Torralba (computer vision, detection, and boosting), Dr. Frédo Durand (computational imaging, segmentation, and probability), Dr. Rosalind Picard (machine learning, pattern recognition, and probability), Dr. Alan 4 Edelman (parallel computing and algorithms), and Dr. Barbastathis (optical systems) are re ‡ected directly, in several cases extended after the course to become complete sections of this thesis.The MIT Museum has provided unique outreach opportunities for the ideas presented in this thesis. Seth Riskin originally involved our lab in holography activities at the MIT Museum, then Kurt Hasselbalch later proposed and guided the development of an interactive display on plankton holography. The computational approaches I learned for the museum display led to further scienti…c development and spurred the use of GPUs for processing; Section 3.3.5 is a direct consequence, as is the majority of the data processing performed throughout this thesis.In reference to data processing, Matlab/MEX and NVIDIA's CUDA have been daily cornerstones for which I am continually thankful. Finally, mad props go to Dr. José "Pepe" Domínguez-Caballero, the most in ‡uential 5 person in my scienti…c development while at MIT. Pepe taught me digital holography and worked one-on-one with me throughout the beginning of my grad student career. He continued to be involved as a fellow holographer, a mentor, and a friend, discussing ideas, encouraging active experimentation, maintaining a curiosity about optics, and o¤ering eno...

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“…It is suitable for high-resolution label-free analysis of living cells [3], for investigations on reflective surfaces such as microelectromechanical systems [4] as well as surface profiling with nanometer accuracy. To the best of our knowledge, the numercialreconstruction process that is used both in industry and in the research community employs floatingpoint arithmetic.…”

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confidence: 99%

Fixed-point numercial-reconstruction for digital holographic microscopy

Pandey

Hennelly

2010

Opt. Lett.

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In this Letter, we study the reconstruction of digital holograms of microscopic objects using a fixed-point representation of the numercial-reconstruction process. For different bit levels in our fixed-point reconstruction algorithm, we investigate the errors introduced to both the reconstructed image intensity and the unwrapped quantitative phase information. Experimental results based on a microscopic lens array are provided. © To the best of our knowledge, the numercialreconstruction process that is used both in industry and in the research community employs floatingpoint arithmetic. This Letter addresses the numercial-reconstruction of digital holograms using fixed-point integer arithmetic. We investigate the advantages of such an approach as well as the errors introduced into the quantitative phase. There are two major formats for representing real numbers in bit-sequences of 0s and 1s; floating point and fixed point. Computationally fixed-point arithmetic is less demanding than floating-point arithmetic. Fixed-point devices have a simpler architecture with fewer gates and transistors and thus have smaller cycle clock time and are faster. Additionally fixed-point processors consume less power and generate less heat than floating-point processors and are thus well suited to portable devices where battery life is important. Many embedded systems and handheld units have fixed-point processors. Already there are variants of DHM that do entail some degree of portability in the recording side such as submersibledigital inline microscopes for detection of life forms in remote inaccessible areas [5], holographic on-chip cytometry [6], plankton sampling [7], etc. In scenarios such as these, it is essential to optimize the numercial-reconstruction process so that it uses up as little resources as possible if reconstruction is to be carried out on site.A floating-point bit sequence in binary can be broken into two smaller bit sequences, the signed mantissa and the signed exponent. In the Institute of Electrical and Electronics Engineers floating-point notation [8] a number is represented by N = ͑−1͒ s ϫ m ϫ 2 ͑e−127͒ where s is the sign bit, m is the standard binary number represented by the (normalized) fractional mantissa, and e is the (biased) exponent.Employing a mantissa and an exponent allows the radix point to "float" and thus allows calculations over a wide range of magnitudes. Fixed-point notation on the other hand is simpler. The most common fixed-point notation is the "two's complement." In two's complement, the leading bit of positive numbers is 0 and of negative numbers is 1. The value represented is obtained by assuming that the leftmost bit is negative and then calculating the binary value of the number. The spacing between all the numbers is uniform, and thus fixed-point notation can be viewed simply as a scaled integer. The position of the radix point is fixed. A thorough description of fixed-and floating-point arithmetic can be found in [9].The setup for a typical DHM is shown in Fig. 1. In this st...

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A digital holographic microscope for complete characterization of microelectromechanical systems

Cited by 150 publications

References 27 publications

Principles and techniques of digital holographic microscopy

Principles and techniques of digital holographic microscopy

Computational imaging and automated identification for aqueous environments

Fixed-point numercial-reconstruction for digital holographic microscopy

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