Digital holographic microscopy
Encyclopedia
Digital holographic microscopy (DHM) is digital holography
applied to microscopy
. Digital holographic microscopy distinguishes itself from other microscopy methods by not recording the projected image of the object. Instead, the light wave front information originating from the object is digitally recorded as a hologram, from which a computer calculates the object image by using a numerical reconstruction algorithm
. The image forming lens
in traditional microscopy is thus replaced by a computer algorithm.
Other closely related microscopy methods to digital holographic microscopy are interferometric microscopy
, optical coherence tomography
and diffraction phase microscopy. Common to all methods is the use of a reference wave front to obtain amplitude (intensity) and phase
information. The information is recorded on a digital image sensor or by a photo detector from which an image of the object is created (reconstructed) by a computer. In traditional microscopy, which do not use a reference wave front, only intensity information is recorded and essential information about the object is lost.
Digital holography has mostly been applied to light microscopy. However, digital holography has also been applied to electron microscopy. Holography was invented by Dennis Gabor
to improve the electron microscope. For various reasons holography never made it into the electron microscope. Digital electron holography may finally bring home holography to its birth place and fulfill Gabor’s vision.
for example. As can be seen in Figure 2, the laser light is split into an object beam and a reference beam. The expanded object beam illuminates the sample to create the object wave front. After the object wave front is collected by a microscope objective
, the object and reference wave fronts are joined by a beam splitter
to interfere and create the hologram. Using the digitally recorded hologram, a computer acts as a digital lens and calculates a viewable image of the object wave front by using a numerical reconstruction algorithm.
Commonly, a microscope objective is used to collect the object wave front. However, as the microscope objective is only used to collect light and not to form an image, it may be replaced by a simple lens. If a slightly lower optical resolution is acceptable, the microscope objective may be entirely removed.
Digital holography comes in different flavors, such as off-axis Fresnel, Fourier, image plane, in-line, Gabor and phase-shifting digital holography, depending on the optical setup. The basic principle, however, is the same; a hologram is recorded and an image is reconstructed by a computer.
The lateral optical resolution
of digital holographic microscopy is equivalent to the resolution of traditional light microscopy. DHM is diffraction-limited by the numerical aperture
, in the same way as traditional light microscopy. However, DHM offers a superb axial (depth) resolution. An axial accuracy of approximately 5 nm has been reported.
Besides the ordinary bright field
image, a phase shift
image is created as well. The phase shift image is unique for digital holographic microscopy and gives quantifiable information about optical distance. In reflection DHM, the phase shift image forms a topography
image of the object.
Transparent objects, like living biological cells
, are traditionally viewed in a phase contrast microscope or in a differential interference contrast microscope
. These methods visualize phase shifting transparent objects by distorting the bright field image with phase shift information. Instead of distorting the bright field image, transmission DHM creates a separate phase shift image showing the optical thickness
of the object. Digital holographic microscopy thus makes it possible to visualize and quantify transparent objects and is therefore also referred to as quantitative phase contrast microscopy.
Traditional phase contrast or bright field images of living unstained biological cells, Figure 3 (right), have proved themselves to be very difficult to analyze with image analysis
software. On the contrary, phase shift images, Figure 3 (left), are readily segmented
and analyzed by image analysis software based on mathematical morphology
, such as CellProfiler
.
3-Dimensional information
An object image is calculated at a given focal distance. However, as the recorded hologram contains all the necessary object wave front information, it is possible to calculate the object at any focal plane by changing the focal distance parameter in the reconstruction algorithm. In fact, the hologram contains all the information needed to calculate a complete image stack
. In a DHM system, where the object wave front is recorded from multiple angles, it is possible to fully characterize the optical characteristics of the object and create tomography
images of the object.
Digital autofocus
Conventional autofocus
is achieved by vertically changing the focal distance until a focused image plane is found. As the complete stack of image planes may be calculated from a single hologram, it is possible to use any passive autofocus method to digitally select the focal plane. The digital auto focusing capabilities of digital holography opens up the possibility to scan and image surfaces extremely rapidly, without any vertical mechanical movement. By recording a single hologram and afterwards stitch sub-images together that are calculated at different focal planes, a complete and focused image of the object may be created.
Optical aberration correction
As DHM systems do not have an image forming lens, traditional optical aberrations do not apply to DHM. Optical aberrations are "corrected" by design of the reconstruction algorithm. A reconstruction algorithm that truly models the optical setup will not suffer from optical aberrations.
Low cost
In optical microscopy systems, optical aberrations are traditionally corrected by combining lenses into a complex and costly image forming microscope objective. Furthermore, the narrow focal depth
at high magnifications requires precision mechanics. The needed components for a DHM system are inexpensive optics and semiconductor components, such as a laser diode
and an image sensor
. The low component cost in combination with the auto focusing capabilities of DHM, make it possible to manufacture DHM systems for a very low cost.
However, due to DHM’s capability of non-invasively visualizing and quantifying biological tissue, bio-medical applications have received most attention.
Examples of bio-medical applications are:
by digitally recording the hologram and numerically reconstructing the image in a computer was published in the late 1960s and in the early 1970s. Similar ideas were proposed for the electron microscope
in the early 1980s. But, computers were too slow and recording capabilities were too poor for digital holography to be useful in practice. After the initial excitement, digital holography went into a similar hibernation as holography experienced about two decades earlier.
In the mid 1990s, digital image sensors and computers had become powerful enough to reconstruct images with some quality. In the 1960s, digital holography could either mean to compute an image from a hologram or to compute a hologram from a 3D model. The latter developed in parallel with classical holography during the hibernation of digital holography. During that time, digital holography was synonymous with what is now known as computer generated holography
.
By the mid 1990s, digital image sensors and computers had improved tremendously, but still lacked the required pixel count and density for digital holography to be anything more than a curiosity. At the time, the market driving digital image sensors was primarily low-resolution video, and so those sensors provided only PAL
, NTSC
, or SECAM
resolution. This suddenly changed at the beginning of the 21st century with the introduction of digital still image cameras
, which drove demand for inexpensive high-pixel-count sensors. As of 2010, affordable image sensors can have up to 60 megapixels. In addition, the CD and DVD-player market has driven development of affordable diode lasers and optics.
The first reports of using digital holography for light microscopy came in the mid 1990s. However, it was not until the early 2000s that image sensor technology had progressed far enough to allow images of a reasonable quality. At that time, the first commercial digital holographic microscopy companies, Lyncée tec and Phase Holographic Imaging, where founded. With increased computing power and use of inexpensive high-resolution sensors and lasers digital holographic microscopy, is today finding applications primarily within life science and metrology
.
Digital holography
Digital holography is the technology of acquiring and processing holographic measurement data, typically via a CCD camera or a similar device. In particular, this includes the numerical reconstruction of object data from the recorded measurement data, in distinction to an optical reconstruction...
applied to microscopy
Microscopy
Microscopy is the technical field of using microscopes to view samples and objects that cannot be seen with the unaided eye...
. Digital holographic microscopy distinguishes itself from other microscopy methods by not recording the projected image of the object. Instead, the light wave front information originating from the object is digitally recorded as a hologram, from which a computer calculates the object image by using a numerical reconstruction algorithm
Reconstruction algorithm
In tomography, a variety of practical reconstruction algorithms have been developed to implement the process of reconstruction of a 3-dimensional object from its projections...
. The image forming lens
Lens (optics)
A lens is an optical device with perfect or approximate axial symmetry which transmits and refracts light, converging or diverging the beam. A simple lens consists of a single optical element...
in traditional microscopy is thus replaced by a computer algorithm.
Other closely related microscopy methods to digital holographic microscopy are interferometric microscopy
Interferometric microscopy
Interferometric microscopy or Imaging interferometric microscopy is the concept of microscopy whichis related to holography, synthetic-aperture imaging, and off-axis-dark-field illumination techniques....
, optical coherence tomography
Optical coherence tomography
Optical coherence tomography is an optical signal acquisition and processing method. It captures micrometer-resolution, three-dimensional images from within optical scattering media . Optical coherence tomography is an interferometric technique, typically employing near-infrared light...
and diffraction phase microscopy. Common to all methods is the use of a reference wave front to obtain amplitude (intensity) and phase
Phase (waves)
Phase in waves is the fraction of a wave cycle which has elapsed relative to an arbitrary point.-Formula:The phase of an oscillation or wave refers to a sinusoidal function such as the following:...
information. The information is recorded on a digital image sensor or by a photo detector from which an image of the object is created (reconstructed) by a computer. In traditional microscopy, which do not use a reference wave front, only intensity information is recorded and essential information about the object is lost.
Digital holography has mostly been applied to light microscopy. However, digital holography has also been applied to electron microscopy. Holography was invented by Dennis Gabor
Dennis Gabor
Dennis Gabor CBE, FRS was a Hungarian-British electrical engineer and inventor, most notable for inventing holography, for which he later received the 1971 Nobel Prize in Physics....
to improve the electron microscope. For various reasons holography never made it into the electron microscope. Digital electron holography may finally bring home holography to its birth place and fulfill Gabor’s vision.
Working principle
To create the necessary interference pattern, i.e. the hologram, the illumination needs to be a coherent (monochromatic) light source, a laserLaser
A laser is a device that emits light through a process of optical amplification based on the stimulated emission of photons. The term "laser" originated as an acronym for Light Amplification by Stimulated Emission of Radiation...
for example. As can be seen in Figure 2, the laser light is split into an object beam and a reference beam. The expanded object beam illuminates the sample to create the object wave front. After the object wave front is collected by a microscope objective
Objective (optics)
In an optical instrument, the objective is the optical element that gathers light from the object being observed and focuses the light rays to produce a real image. Objectives can be single lenses or mirrors, or combinations of several optical elements. They are used in microscopes, telescopes,...
, the object and reference wave fronts are joined by a beam splitter
Beam splitter
A beam splitter is an optical device that splits a beam of light in two. It is the crucial part of most interferometers.In its most common form, a rectangle, it is made from two triangular glass prisms which are glued together at their base using Canada balsam...
to interfere and create the hologram. Using the digitally recorded hologram, a computer acts as a digital lens and calculates a viewable image of the object wave front by using a numerical reconstruction algorithm.
Commonly, a microscope objective is used to collect the object wave front. However, as the microscope objective is only used to collect light and not to form an image, it may be replaced by a simple lens. If a slightly lower optical resolution is acceptable, the microscope objective may be entirely removed.
Digital holography comes in different flavors, such as off-axis Fresnel, Fourier, image plane, in-line, Gabor and phase-shifting digital holography, depending on the optical setup. The basic principle, however, is the same; a hologram is recorded and an image is reconstructed by a computer.
The lateral optical resolution
Optical resolution
Optical resolution describes the ability of an imaging system to resolve detail in the object that is being imaged.An imaging system may have many individual components including a lens and recording and display components...
of digital holographic microscopy is equivalent to the resolution of traditional light microscopy. DHM is diffraction-limited by the numerical aperture
Numerical aperture
In optics, the numerical aperture of an optical system is a dimensionless number that characterizes the range of angles over which the system can accept or emit light. By incorporating index of refraction in its definition, NA has the property that it is constant for a beam as it goes from one...
, in the same way as traditional light microscopy. However, DHM offers a superb axial (depth) resolution. An axial accuracy of approximately 5 nm has been reported.
Advantages
Phase shift imagesBesides the ordinary bright field
Bright field microscopy
Bright field microscopy is the simplest of all the optical microscopy illumination techniques. Sample illumination is transmitted white light and contrast in the sample is caused by absorbance of some of the transmitted light in dense areas of the sample...
image, a phase shift
Phase (waves)
Phase in waves is the fraction of a wave cycle which has elapsed relative to an arbitrary point.-Formula:The phase of an oscillation or wave refers to a sinusoidal function such as the following:...
image is created as well. The phase shift image is unique for digital holographic microscopy and gives quantifiable information about optical distance. In reflection DHM, the phase shift image forms a topography
Topography
Topography is the study of Earth's surface shape and features or those ofplanets, moons, and asteroids...
image of the object.
Transparent objects, like living biological cells
Cell (biology)
The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos....
, are traditionally viewed in a phase contrast microscope or in a differential interference contrast microscope
Differential interference contrast microscopy
Differential interference contrast microscopy , also known as Nomarski Interference Contrast or Nomarski microscopy, is an optical microscopy illumination technique used to enhance the contrast in unstained, transparent samples...
. These methods visualize phase shifting transparent objects by distorting the bright field image with phase shift information. Instead of distorting the bright field image, transmission DHM creates a separate phase shift image showing the optical thickness
Optical depth
Optical depth, or optical thickness, is a measure of transparency. Optical depth is defined by the negative logarithm of the fraction of radiation that is not scattered or absorbed on a path...
of the object. Digital holographic microscopy thus makes it possible to visualize and quantify transparent objects and is therefore also referred to as quantitative phase contrast microscopy.
Traditional phase contrast or bright field images of living unstained biological cells, Figure 3 (right), have proved themselves to be very difficult to analyze with image analysis
Image analysis
Image analysis is the extraction of meaningful information from images; mainly from digital images by means of digital image processing techniques...
software. On the contrary, phase shift images, Figure 3 (left), are readily segmented
Segmentation (image processing)
In computer vision, segmentation refers to the process of partitioning a digital image into multiple segments . The goal of segmentation is to simplify and/or change the representation of an image into something that is more meaningful and easier to analyze...
and analyzed by image analysis software based on mathematical morphology
Mathematical morphology
Mathematical morphology is a theory and technique for the analysis and processing of geometrical structures, based on set theory, lattice theory, topology, and random functions...
, such as CellProfiler
CellProfiler
CellProfiler is free, open-source software designed to enable biologists without training in computer vision or programming to quantitatively measure phenotypes from thousands of images automatically...
.
3-Dimensional information
An object image is calculated at a given focal distance. However, as the recorded hologram contains all the necessary object wave front information, it is possible to calculate the object at any focal plane by changing the focal distance parameter in the reconstruction algorithm. In fact, the hologram contains all the information needed to calculate a complete image stack
Focus stacking
Focus stacking is a digital image processing technique which combines multiple images taken at different focus distances to give a resulting image with a greater depth of field than any of the individual source images...
. In a DHM system, where the object wave front is recorded from multiple angles, it is possible to fully characterize the optical characteristics of the object and create tomography
Tomography
Tomography refers to imaging by sections or sectioning, through the use of any kind of penetrating wave. A device used in tomography is called a tomograph, while the image produced is a tomogram. The method is used in radiology, archaeology, biology, geophysics, oceanography, materials science,...
images of the object.
Digital autofocus
Conventional autofocus
Autofocus
An autofocus optical system uses a sensor, a control system and a motor to focus fully automatic or on a manually selected point or area. An electronic rangefinder has a display instead of the motor; the adjustment of the optical system has to be done manually until indication...
is achieved by vertically changing the focal distance until a focused image plane is found. As the complete stack of image planes may be calculated from a single hologram, it is possible to use any passive autofocus method to digitally select the focal plane. The digital auto focusing capabilities of digital holography opens up the possibility to scan and image surfaces extremely rapidly, without any vertical mechanical movement. By recording a single hologram and afterwards stitch sub-images together that are calculated at different focal planes, a complete and focused image of the object may be created.
Optical aberration correction
As DHM systems do not have an image forming lens, traditional optical aberrations do not apply to DHM. Optical aberrations are "corrected" by design of the reconstruction algorithm. A reconstruction algorithm that truly models the optical setup will not suffer from optical aberrations.
Low cost
In optical microscopy systems, optical aberrations are traditionally corrected by combining lenses into a complex and costly image forming microscope objective. Furthermore, the narrow focal depth
Depth of field
In optics, particularly as it relates to film and photography, depth of field is the distance between the nearest and farthest objects in a scene that appear acceptably sharp in an image...
at high magnifications requires precision mechanics. The needed components for a DHM system are inexpensive optics and semiconductor components, such as a laser diode
Laser diode
The laser diode is a laser where the active medium is a semiconductor similar to that found in a light-emitting diode. The most common type of laser diode is formed from a p-n junction and powered by injected electric current...
and an image sensor
Image sensor
An image sensor is a device that converts an optical image into an electronic signal. It is used mostly in digital cameras and other imaging devices...
. The low component cost in combination with the auto focusing capabilities of DHM, make it possible to manufacture DHM systems for a very low cost.
Applications
Digital holographic microscopy has been successfully applied in a range of application areas.However, due to DHM’s capability of non-invasively visualizing and quantifying biological tissue, bio-medical applications have received most attention.
Examples of bio-medical applications are:
- Label-free cell counting in adherent cell cultureCell cultureCell culture is the complex process by which cells are grown under controlled conditions. In practice, the term "cell culture" has come to refer to the culturing of cells derived from singlecellular eukaryotes, especially animal cells. However, there are also cultures of plants, fungi and microbes,...
s. Digital holographic microscopy makes it possible to perform cell counting and to measure cell viability directly in the cell culture chamber. Today, the most commonly used cell counting methods, hemocytometerHemocytometerThe hemocytometer or haemocytometer is a device originally designed for the counting of blood cells. It is now also used to count other types of cells as well as other microscopic particles....
or Coulter counterCoulter counterA Coulter counter is an apparatus for counting and sizing particles suspended in electrolytes. It is used for cells, bacteria, prokaryotic cells and virus particles....
, only work with cells that are in suspension.
- Label-free viability analysis of adherent cell cultures. Digital holography has been used to study the apoptoticApoptosisApoptosis is the process of programmed cell death that may occur in multicellular organisms. Biochemical events lead to characteristic cell changes and death. These changes include blebbing, cell shrinkage, nuclear fragmentation, chromatin condensation, and chromosomal DNA fragmentation...
process in different cell types. The refractive index changes taking place during the apoptotic process are easily measured with DHM.
- Label-free cell cycleCell cycleThe cell cycle, or cell-division cycle, is the series of events that takes place in a cell leading to its division and duplication . In cells without a nucleus , the cell cycle occurs via a process termed binary fission...
analysis. The phase shift induced by cells has been shown to be correlated to the cell dry mass. The cell dry mass can be combined with other parameters obtainable by digital holography, such as cell volume and refractive index, to provide a better understanding of the cell cycle.
- Label-free morphology analysis of cells. Digital holography has been used in different contexts to study cell morphology using neither staining nor labeling. This can be used to follow processes such as the differentiation process where cell characteristics change. DHM has also been used for automated plant stem cellStem cellThis article is about the cell type. For the medical therapy, see Stem Cell TreatmentsStem cells are biological cells found in all multicellular organisms, that can divide and differentiate into diverse specialized cell types and can self-renew to produce more stem cells...
monitoring, and made it possible to distinguish between two types of stem cells by measuring morphological parameters.
- Label free nerve cell studies. Digital holographic microscopy makes it possible to study undisturbed processes in nerve cells as no labeling is required. The swelling and shape changing of nerve cells caused by cellular imbalance was easily studied.
- Label-free high content analysis. Fluorescent high content analysis/screening has several drawbacks. Label-free alternatives based on phase shift images have therefore been proposed. The capability of DHM to obtain phase shift images rapidly over large areas opens up new possibilities of very rapid quantitative characterization of the cell cycle and the effects of specific pharmacological agents.
- Red blood cellRed blood cellRed blood cells are the most common type of blood cell and the vertebrate organism's principal means of delivering oxygen to the body tissues via the blood flow through the circulatory system...
analysis. Phase shift images have been used to study red blood cell dynamics. Red blood cell volume and hemoglobin concentration has been measured by combining information from absorption and phase shift images to facilitate complete blood cell count by holographic microscopy. It has furthermore been shown that phase shift information discriminates immature red blood cells from mature, facilitating unstained reticulocyteReticulocyteReticulocytes are immature red blood cells, typically composing about 1% of the red cells in the human body.Reticulocytes develop and mature in the red bone marrow and then circulate for about a day in the blood stream before developing into mature red blood cells. Like mature red blood cells,...
count.
- Flow cytometryFlow cytometryFlow cytometry is a technique for counting and examining microscopic particles, such as cells and chromosomes, by suspending them in a stream of fluid and passing them by an electronic detection apparatus. It allows simultaneous multiparametric analysis of the physical and/or chemical...
and particle tracking and characterization. Images created by digital holography are calculated from the recorded hologram at any time after the actual recording and at any given focal plane. By combining several images calculated from the same hologram, but at different focal planes, an increased depth of fieldDepth of fieldIn optics, particularly as it relates to film and photography, depth of field is the distance between the nearest and farthest objects in a scene that appear acceptably sharp in an image...
may be obtained, which is vastly superior to what can be achieved with traditional light microscopy. The increased depth of field makes it possible to image and characterize the morphology of cells and particles while in suspension. Observations may be done directly in a microfluidicMicrofluidicsMicrofluidics deals with the behavior, precise control and manipulation of fluids that are geometrically constrained to a small, typically sub-millimeter, scale.Typically, micro means one of the following features:* small volumes...
channel or statically in an observation chamber.
- Time-lapse microscopyTime-lapse microscopyTime-lapse microscopy is microscopy in which the same object is photographed at regular time intervals over several hours....
of cell division and migration. The autofocus and phase shift imaging capabilities of digital holographic microscopy makes it possible to effortlessly create label-free and quantifiable time-lapseTime-lapseTime-lapse photography is a cinematography technique whereby the frequency at which film frames are captured is much lower than that which will be used to play the sequence back. When replayed at normal speed, time appears to be moving faster and thus lapsing...
video clips of unstained cells for cell migrationCell migrationCell migration is a central process in the development and maintenance of multicellular organisms. Tissue formation during embryonic development, wound healing and immune responses all require the orchestrated movement of cells in particular directions to specific locations...
studies. In Figure 5 a label-free time-lapse of dividing and migrating cells is shown.
- TomographyTomographyTomography refers to imaging by sections or sectioning, through the use of any kind of penetrating wave. A device used in tomography is called a tomograph, while the image produced is a tomogram. The method is used in radiology, archaeology, biology, geophysics, oceanography, materials science,...
studies. Digital holographic microscopy allows for label-free and quantifiable analysis of subcellular motion deep in living tissue.
History
The first reports of replacing the photographic hologram of classical holographyHolography
Holography is a technique that allows the light scattered from an object to be recorded and later reconstructed so that when an imaging system is placed in the reconstructed beam, an image of the object will be seen even when the object is no longer present...
by digitally recording the hologram and numerically reconstructing the image in a computer was published in the late 1960s and in the early 1970s. Similar ideas were proposed for the electron microscope
Electron microscope
An electron microscope is a type of microscope that uses a beam of electrons to illuminate the specimen and produce a magnified image. Electron microscopes have a greater resolving power than a light-powered optical microscope, because electrons have wavelengths about 100,000 times shorter than...
in the early 1980s. But, computers were too slow and recording capabilities were too poor for digital holography to be useful in practice. After the initial excitement, digital holography went into a similar hibernation as holography experienced about two decades earlier.
In the mid 1990s, digital image sensors and computers had become powerful enough to reconstruct images with some quality. In the 1960s, digital holography could either mean to compute an image from a hologram or to compute a hologram from a 3D model. The latter developed in parallel with classical holography during the hibernation of digital holography. During that time, digital holography was synonymous with what is now known as computer generated holography
Computer generated holography
Computer Generated Holography is the method of digitally generating holographic interference patterns. A holographic image can be generated e.g...
.
By the mid 1990s, digital image sensors and computers had improved tremendously, but still lacked the required pixel count and density for digital holography to be anything more than a curiosity. At the time, the market driving digital image sensors was primarily low-resolution video, and so those sensors provided only PAL
PAL
PAL, short for Phase Alternating Line, is an analogue television colour encoding system used in broadcast television systems in many countries. Other common analogue television systems are NTSC and SECAM. This page primarily discusses the PAL colour encoding system...
, NTSC
NTSC
NTSC, named for the National Television System Committee, is the analog television system that is used in most of North America, most of South America , Burma, South Korea, Taiwan, Japan, the Philippines, and some Pacific island nations and territories .Most countries using the NTSC standard, as...
, or SECAM
SECAM
SECAM, also written SÉCAM , is an analog color television system first used in France....
resolution. This suddenly changed at the beginning of the 21st century with the introduction of digital still image cameras
Digital camera
A digital camera is a camera that takes video or still photographs, or both, digitally by recording images via an electronic image sensor. It is the main device used in the field of digital photography...
, which drove demand for inexpensive high-pixel-count sensors. As of 2010, affordable image sensors can have up to 60 megapixels. In addition, the CD and DVD-player market has driven development of affordable diode lasers and optics.
The first reports of using digital holography for light microscopy came in the mid 1990s. However, it was not until the early 2000s that image sensor technology had progressed far enough to allow images of a reasonable quality. At that time, the first commercial digital holographic microscopy companies, Lyncée tec and Phase Holographic Imaging, where founded. With increased computing power and use of inexpensive high-resolution sensors and lasers digital holographic microscopy, is today finding applications primarily within life science and metrology
Metrology
Metrology is the science of measurement. Metrology includes all theoretical and practical aspects of measurement. The word comes from Greek μέτρον , "measure" + "λόγος" , amongst others meaning "speech, oration, discourse, quote, study, calculation, reason"...
.
Books
- Methods of digital holography by L. P. Yaroslavskii and N. S. Merzlyakov, Springer (1980)
- Digital Holography and Digital Image Processing: Principles, Methods, Algorithms by Leonid Yaroslavsky, Kluwer (2004)
- Handbook of Holographic Interferometry: Optical and Digital Methods by Thomas Kreis, Wiley (2004)
- Digital Holography by U. Schnars and W. Jueptner, Springer (2005)
- Digital Holography and Three-Dimensional Display: Principles and Applications by Ting-Chung Poon (Editor), Springer (2006)
- Digital Holography Microscopy applications: Three Dimensional Object Analysis and Tracking by Cedric Schockaert, VDM Verlag (2009)
- Holographic Microscopy of Phase Microscopic Objects: Theory and Practice by Natalya Kizilova, World Scientific (2010)
- Quantitative Phase Imaging of Cells and Tissues by Gabriel Popescu, McGraw-Hill (2011)
- Digital Holographic Microscopy: Principles, Techniques and Applications by Myung K. Kim, Springer (2011)
- Coherent Light Microscopy: Imaging and Quantitative Phase Analysis edited by Pietro Ferraro, Springer (2011)
- Holography, Research and Technologies edited by Joseph Rosen, InTech (2011)
- Digital Holography for MEMS and Microsystem Metrology edited by Erdal Çayirci, Wiley (2011)
- Image Processing For Digital Holography by Karen Molony, VDM Verlag (2011)
Reviews
- General: Principles and techniques of digital holographic microscopy by Myung K. Kim, SPIE Reviews, Vol. 1, 018005 (2010)
- Cell biology: Digital Holography and Cell Studies by Kersti Alm et al., InTech (2011)
External links
- The Optical Society Digital Holography and Three Dimensional Imaging Meeting