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Light-in-flight
Light-in-flight imaging — a set of techniques to visualize propagation of light through different media. History and techniques Light was first captured in its flight by N. Abramson in 1978, who used a holographic technique to record the wavefront of a pulse propagating and being scattered by a white-painted screen placed in its path. This high-speed recording technique allowed the dynamic observation of light phenomena like reflection, interference and focusing that are normally observed statically. More recently, light-in-flight holography has been performed in a scattering medium rather than using a reflective screen. Light can also be captured in motion in a scattering medium using a streak camera that has picosecond temporal resolution, thus removing the need for interferometry and coherent illumination but requires additional hardware to raster scan the two-dimensional (2D) scene, which increases the acquisition time to hours. A few other techniques possess the tempora ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Femto-photography
Femto-photography is a technique for recording the propagation of ultrashort pulses of light through a scene at a very high speed (up to 1013 frames per second). A femto-photograph is equivalent to an optical impulse response of a scene and has also been denoted by terms such as a light-in-flight recording or transient image. Femto-photography of macroscopic objects was first demonstrated using a holographic process in the 1970s by Nils Abramsson at the Royal Institute of Technology (Sweden). A research team at the MIT Media Lab led by Ramesh Raskar, together with contributors from the Graphics and Imaging Lab at the Universidad de Zaragoza, Spain, more recently achieved a significant increase in image quality using a streak camera synchronized to a pulsed laser and modified to obtain 2D images instead of just a single scanline. In their publications, Raskar's team claims to be able to capture exposures so short that light only traverses 0.6 mm (corresponding to 2 pi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Single-photon Sensitive Light-in-fight Imaging , a nuclear medicine tomographic imaging technique
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Single-photon may refer to: * Photon counting devices capable of counting individual photons, for example: ** Superconducting nanowire single-photon detectors ** Single-photon avalanche diodes, a class of solid-state photodetectors * Single-photon sources * Single-photon emission computed tomography Single-photon emission computed tomography (SPECT, or less commonly, SPET) is a nuclear medicine tomographic imaging technique using gamma rays. It is very similar to conventional nuclear medicine planar imaging using a gamma camera (that is, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Temporal Resolution
Temporal resolution (TR) refers to the discrete resolution of a measurement with respect to time. Physics Often there is a trade-off between the temporal resolution of a measurement and its spatial resolution, due to Heisenberg's uncertainty principle. In some contexts, such as particle physics, this trade-off can be attributed to the finite speed of light and the fact that it takes a certain period of time for the photons carrying information to reach the observer. In this time, the system might have undergone changes itself. Thus, the longer the light has to travel, the lower the temporal resolution. Technology Computing In another context, there is often a tradeoff between temporal resolution and computer storage. A transducer may be able to record data every millisecond, but available storage may not allow this, and in the case of 4D PET imaging the resolution may be limited to several minutes. Electronic displays In some applications, temporal resolution may instead ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Film And Video Technology
A film also called a movie, motion picture, moving picture, picture, photoplay or (slang) flick is a work of visual art that simulates experiences and otherwise communicates ideas, stories, perceptions, feelings, beauty, or atmosphere through the use of moving images. These images are generally accompanied by sound and, more rarely, other sensory stimulations. The word "cinema", short for cinematography, is often used to refer to filmmaking and the film industry, and to the art form that is the result of it. Recording and transmission of film The moving images of a film are created by photographing actual scenes with a motion-picture camera, by photographing drawings or miniature models using traditional animation techniques, by means of CGI and computer animation, or by a combination of some or all of these techniques, and other visual effects. Before the introduction of digital production, series of still images were recorded on a strip of chemically sensitize ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Computer Tomography
A computed tomography scan (CT scan; formerly called computed axial tomography scan or CAT scan) is a medical imaging technique used to obtain detailed internal images of the body. The personnel that perform CT scans are called radiographers or radiology technologists. CT scanners use a rotating X-ray tube and a row of detectors placed in a gantry to measure X-ray attenuations by different tissues inside the body. The multiple X-ray measurements taken from different angles are then processed on a computer using tomographic reconstruction algorithms to produce tomographic (cross-sectional) images (virtual "slices") of a body. CT scans can be used in patients with metallic implants or pacemakers, for whom magnetic resonance imaging (MRI) is contraindicated. Since its development in the 1970s, CT scanning has proven to be a versatile imaging technique. While CT is most prominently used in medical diagnosis, it can also be used to form images of non-living objects. The 1979 Nob ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dispersion (optics)
In optics, and by analogy other branches of physics dealing with wave propagation, dispersion is the phenomenon in which the phase velocity of a wave depends on its frequency; sometimes the term chromatic dispersion is used for specificity to optics in particular. A medium having this common property may be termed a dispersive medium (plural ''dispersive media''). Although the term is used in the field of optics to describe light and other electromagnetic waves, dispersion in the same sense can apply to any sort of wave motion such as acoustic dispersion in the case of sound and seismic waves, and in gravity waves (ocean waves). Within optics, dispersion is a property of telecommunication signals along transmission lines (such as microwaves in coaxial cable) or the pulses of light in optical fiber. Physically, dispersion translates in a loss of kinetic energy through absorption. In optics, one important and familiar consequence of dispersion is the change in the angle of refra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Laser
A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The word "laser" is an acronym for "light amplification by stimulated emission of radiation". The first laser was built in 1960 by Theodore H. Maiman at Hughes Research Laboratories, based on theoretical work by Charles Hard Townes and Arthur Leonard Schawlow. A laser differs from other sources of light in that it emits light which is ''coherent''. Spatial coherence allows a laser to be focused to a tight spot, enabling applications such as laser cutting and lithography. Spatial coherence also allows a laser beam to stay narrow over great distances (collimation), enabling applications such as laser pointers and lidar (light detection and ranging). Lasers can also have high temporal coherence, which allows them to emit light with a very narrow spectrum. Alternatively, temporal coherence can be used to produce ultrashort pulses of ligh ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nanosecond
A nanosecond (ns) is a unit of time in the International System of Units (SI) equal to one billionth of a second, that is, of a second, or 10 seconds. The term combines the SI prefix ''nano-'' indicating a 1 billionth submultiple of an SI unit (e.g. nanogram, nanometre, etc.) and ''second'', the primary unit of time in the SI. A nanosecond is equal to 1000 picoseconds or microsecond. Time units ranging between 10 and 10 seconds are typically expressed as tens or hundreds of nanoseconds. Time units of this granularity are commonly found in telecommunications, pulsed lasers, and related aspects of electronics. Common measurements * 0.001 nanoseconds – one picosecond * 0.5 nanoseconds – the half-life of beryllium-13. * 0.96 nanoseconds – 100 Gigabit Ethernet Interpacket gap * 1.0 nanosecond – cycle time of an electromagnetic wave with a frequency of 1 GHz (1 hertz). * 1.0 nanosecond – electromagnetic wavelength of 1 light-nanosecond. Equiv ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Computer Hardware
Computer hardware includes the physical parts of a computer, such as the computer case, case, central processing unit (CPU), Random-access memory, random access memory (RAM), Computer monitor, monitor, Computer mouse, mouse, Computer keyboard, keyboard, computer data storage, graphics card, sound card, Computer speakers, speakers and motherboard. By contrast, software is the set of instructions that can be stored and run by hardware. Hardware is so-termed because it is "Hardness, hard" or rigid with respect to changes, whereas software is "soft" because it is easy to change. Hardware is typically directed by the software to execute any command or Instruction (computing), instruction. A combination of hardware and software forms a usable computing system, although Digital electronics, other systems exist with only hardware. Von Neumann architecture The template for all modern computers is the Von Neumann architecture, detailed in a First Draft of a Report on the EDVAC, 1945 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Coherence (physics)
In physics, two wave sources are coherent if their frequency and waveform are identical. Coherence is an ideal property of waves that enables stationary (i.e., temporally or spatially constant) interference. It contains several distinct concepts, which are limiting cases that never quite occur in reality but allow an understanding of the physics of waves, and has become a very important concept in quantum physics. More generally, coherence describes all properties of the correlation between physical quantities of a single wave, or between several waves or wave packets. Interference is the addition, in the mathematical sense, of wave functions. A single wave can interfere with itself, but this is still an addition of two waves (see Young's slits experiment). Constructive or destructive interference are limit cases, and two waves always interfere, even if the result of the addition is complicated or not remarkable. When interfering, two waves can add together to create a wave of g ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Interferometry
Interferometry is a technique which uses the ''interference'' of superimposed waves to extract information. Interferometry typically uses electromagnetic waves and is an important investigative technique in the fields of astronomy, fiber optics, engineering metrology, optical metrology, oceanography, seismology, spectroscopy (and its applications to chemistry), quantum mechanics, nuclear and particle physics, plasma physics, remote sensing, biomolecular interactions, surface profiling, microfluidics, mechanical stress/strain measurement, velocimetry, optometry, and making holograms. Interferometers are devices that extract information from interference. They are widely used in science and industry for the measurement of microscopic displacements, refractive index changes and surface irregularities. In the case with most interferometers, light from a single source is split into two beams that travel in different optical paths, which are then combined again to produce interfer ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Picosecond
A picosecond (abbreviated as ps) is a unit of time in the International System of Units (SI) equal to 10−12 or (one trillionth) of a second. That is one trillionth, or one millionth of one millionth of a second, or 0.000 000 000 001 seconds. A picosecond is to one second as one second is to approximately 31,689 years. Multiple technical approaches achieve imaging within single-digit picoseconds: for example, the streak camera or intensified CCD (ICCD) cameras are able to picture the motion of light. One picosecond is equal to 1000 femtoseconds, or 1/1000 nanoseconds. Because the next SI unit is 1000 times larger, measurements of 10−11 and 10−10 second are typically expressed as tens or hundreds of picoseconds. Some notable measurements in this range include: * 1.0 picoseconds (1.0 ps) – cycle time for electromagnetic frequency 1 terahertz (THz) (1 x 1012 hertz), an inverse unit. This corresponds to a wavelength of 0.3 mm, as can be calculated by m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
