High speed photography
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High-speed photography is the science of taking pictures of very fast phenomena. In 1948, the
Society of Motion Picture and Television Engineers The Society of Motion Picture and Television Engineers (SMPTE) (, rarely ), founded in 1916 as the Society of Motion Picture Engineers or SMPE, is a global professional association of engineers, technologists, and executives working in the m ...
(SMPTE) defined high-speed photography as any set of photographs captured by a camera capable of 69 frames per second or greater, and of at least three consecutive frames . High-speed photography can be considered to be the opposite of
time-lapse photography Time-lapse photography is a technique in which the frequency at which film frames are captured (the frame rate) is much lower than the frequency used to view the sequence. When played at normal speed, time appears to be moving faster and thus ...
. In common usage, high-speed photography may refer to either or both of the following meanings. The first is that the photograph itself may be taken in a way as to appear to freeze the motion, especially to reduce
motion blur Motion blur is the apparent streaking of moving objects in a photograph or a sequence of frames, such as a film or animation. It results when the image being recorded changes during the recording of a single exposure, due to rapid movement or lo ...
. The second is that a series of photographs may be taken at a high sampling frequency or frame rate. The first requires a sensor with good sensitivity and either a very good shuttering system or a very fast strobe light. The second requires some means of capturing successive frames, either with a mechanical device or by moving data off electronic sensors very quickly. Other considerations for high-speed photographers are record length, reciprocity breakdown, and
spatial resolution In physics and geosciences, the term spatial resolution refers to distance between independent measurements, or the physical dimension that represents a pixel of the image. While in some instruments, like cameras and telescopes, spatial resolut ...
.


Early applications and development

The first practical application of high-speed photography was
Eadweard Muybridge Eadweard Muybridge (; 9 April 1830 – 8 May 1904, born Edward James Muggeridge) was an English photographer known for his pioneering work in photographic studies of motion, and early work in motion-picture projection. He adopted the first ...
's 1878 investigation into whether horses' feet were actually all off the ground at once during a
gallop The canter and gallop are variations on the fastest gait that can be performed by a horse or other equine. The canter is a controlled three-beat gait, while the gallop is a faster, four-beat variation of the same gait. It is a natural gait pos ...
. The first photograph of a supersonic flying bullet was taken by the Austrian physicist Peter Salcher in Rijeka in 1886, a technique that was later used by Ernst Mach in his studies of supersonic motion. German weapons scientists applied the techniques in 1916, and The Japanese Institute of Aeronautical Research manufactured a camera capable of recording 60,000 frames per second in 1931.
Bell Telephone Laboratories Nokia Bell Labs, originally named Bell Telephone Laboratories (1925–1984), then AT&T Bell Laboratories (1984–1996) and Bell Labs Innovations (1996–2007), is an American industrial research and scientific development company owned by mult ...
was one of the first customers for a camera developed by Eastman Kodak in the early 1930s. Bell used the system, which ran 16 mm film at 1000 frame/s and had a load capacity, to study relay bounce. When Kodak declined to develop a higher-speed version, Bell Labs developed it themselves, calling it the Fastax. The Fastax was capable of 5,000 frame/s. Bell eventually sold the camera design to Western Electric, who in turn sold it to the Wollensak Optical Company. Wollensak further improved the design to achieve 10,000 frame/s. Redlake Laboratories introduced another 16 mm rotating prism camera, the Hycam, in the early 1960s.Pendley, Gil (July 2003). Claude Cavailler, Graham P. Haddleton, Manfred Hugenschmidt. ed. "High-Speed Imaging Technology; Yesterday, Today & Tomorrow". ''
Proceedings of SPIE ''Proceedings of SPIE'' is the conference record of the Society of Photo-Optical Instrumentation Engineers (SPIE).Manhattan Project The Manhattan Project was a research and development undertaking during World War II that produced the first nuclear weapons. It was led by the United States with the support of the United Kingdom and Canada. From 1942 to 1946, the project w ...
, when Berlin Brixner, the photographic technician on the project, built the first known fully functional rotating mirror camera. This camera was used to photograph early prototypes of the first nuclear bomb, and resolved a key technical issue about the shape and speed of the implosion, that had been the source of an active dispute between the explosives engineers and the physics theoreticians. The D. B. Milliken company developed an intermittent, pin-registered, 16 mm camera for speeds of 400 frame/s in 1957. Mitchell, Redlake Laboratories, and Photo-Sonics eventually followed in the 1960s with a variety of 16, 35, and 70 mm intermittent cameras.


Stroboscopy and laser applications

Harold Edgerton is generally credited with pioneering the use of the
stroboscope A stroboscope, also known as a strobe, is an instrument used to make a cyclically moving object appear to be slow-moving, or stationary. It consists of either a rotating disk with slots or holes or a lamp such as a flashtube which produces br ...
to freeze fast motion. He eventually helped found
EG&G EG&G, formally known as Edgerton, Germeshausen, and Grier, Inc., was a United States national defense contractor and provider of management and technical services. The company was involved in contracting services to the United States government ...
, which used some of Edgerton's methods to capture the physics of explosions required to detonate nuclear weapons. One such device was the
EG&G EG&G, formally known as Edgerton, Germeshausen, and Grier, Inc., was a United States national defense contractor and provider of management and technical services. The company was involved in contracting services to the United States government ...
Microflash 549, which is an
air-gap flash An air-gap flash is a photographic light source capable of producing sub-microsecond light flashes, allowing for (ultra) high-speed photography. This is achieved by a high-voltage (20 kV typically) electric discharge between two electrodes o ...
. Also see the photograph of an explosion using a
Rapatronic camera The rapatronic camera (a portmanteau of ''rap''id ''a''ction elec''tronic'') is a high-speed camera capable of recording a still image with an exposure time as brief as 10 nanoseconds. The camera was developed by Harold Edgerton in the 1940s a ...
. Advancing the idea of the stroboscope, researchers began using
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 fi ...
s to stop high-speed motion. Recent advances include the use of High Harmonic Generation to capture images of molecular dynamics down to the scale of the attosecond (10−18 s).


High-speed film cameras

A high-speed camera is defined as having the capability of capturing video at a rate in excess of 250 frames per second. There are many different types of high-speed film cameras, but they can mostly all be grouped into five different categories: * Intermittent motion cameras, which are a speed-up version of the standard motion picture camera using a sewing machine type mechanism to advance the film intermittently to a fixed exposure point behind the objective lens, * Rotating prism cameras, which run film continuously past an exposure point and use a rotating prism between the objective lens and the film to impart motion to the image which matches the film motion, thereby canceling it out, * Rotating mirror cameras, which relay the image through a rotating mirror to an arc of film, and can work in continuous access or synchronous access depending on the design. * Image dissection cameras, which can use a rotating mirror system, and * Raster cameras, which record a "chopped up" version of an image. Intermittent motion cameras are capable of hundreds of frames per second, rotating prism cameras are capable of thousands to millions of frames per second, rotating mirror cameras are capable of millions of frames per second, raster cameras can achieve millions of frames per second, and image dissection cameras are capable of billions of frames per second. As film and mechanical transports improved, the high-speed film camera became available for scientific research. Kodak eventually shifted its film from acetate base to Estar (Kodak's name for a
Mylar BoPET (biaxially-oriented polyethylene terephthalate) is a polyester film made from stretched polyethylene terephthalate (PET) and is used for its high tensile strength, chemical and dimensional stability, transparency, reflectivity, gas and a ...
-equivalent plastic), which enhanced the strength and allowed it to be pulled faster. The Estar was also more stable than acetate allowing more accurate measurement, and it was not as prone to fire. Each film type is available in many load sizes. These may be cut down and placed in magazines for easier loading. A magazine is typically the longest available for the 35 mm and 70 mm cameras. A magazine is typical for 16 mm cameras, though magazines are available. Typically rotary prism cameras use 100 ft (30m) film loads. The images on 35 mm high-speed film are typically more rectangular with the long side between the sprocket holes instead of parallel to the edges as in standard photography. 16 mm and 70 mm images are typically more square rather than rectangular. A list of
ANSI The American National Standards Institute (ANSI ) is a private non-profit organization that oversees the development of voluntary consensus standards for products, services, processes, systems, and personnel in the United States. The organi ...
formats and sizes is available. Most cameras use pulsed timing marks along the edge of the film (either inside or outside of the film perforations) produced by sparks or later by LEDs. These allow accurate measurement of the film speed and in the case of streak or smear images, velocity measurement of the subject. These pulses are usually cycled at 10, 100, 1000 Hz depending on the speed setting of the camera.


Intermittent pin register

Just as with a standard motion picture camera, the intermittent register pin camera actually stops the film in the
film gate The film gate is the rectangular opening in the front of a motion picture camera where the film is exposed to light. The film gate can be seen by removing the lens and rotating the shutter out of the way. The film is held on a uniform plane at a c ...
while the photograph is being taken. In high-speed photography, this requires some modifications to the mechanism for achieving this intermittent motion at such high speeds. In all cases, a loop is formed before and after the gate to create and then take up the slack. ''Pulldown claws,'' which enter the film through perforations, pulling it into place and then retracting out of the perforations and out of the film gate, are multiplied to grab the film through multiple perforations in the film, thereby reducing the stress that any individual perforation is subjected to. ''Register pins,'' which secure the film through perforations in final position while it is being exposed, after the pulldown claws are retracted are also multiplied, and often made from exotic materials. In some cases, vacuum suction is used to keep the film, especially 35 mm and 70 mm film, flat so that the images are in focus across the entire frame. * 16 mm pin register: D. B. Milliken Locam, capable of 500 frame/s; the design was eventually sold to Redlake. Photo-Sonics built a 16 mm pin-registered camera that was capable of 1000 frame/s, but they eventually removed it from the market. * 35 mm pin register: Early cameras included the Mitchell 35 mm. Photo-Sonics won an Academy Award for Technical Achievement for the 4ER in 1988. The 4E is capable of 360 frame/s. * 70 mm pin register: Cameras include a model made by Hulcher, and Photo-Sonics 10A and 10R cameras, capable of 125 frame/s.


Rotary prism

The rotary prism camera allowed higher frame rates without placing as much stress on the film or transport mechanism. The film moves continuously past a rotating prism which is synchronized to the main film sprocket such that the speed of the film and the speed of the prism are always running at the same proportional speed. The prism is located between the objective lens and the film, such that the revolution of the prism "paints" a frame onto the film for each face of the prism. Prisms are typically cubic, or four sided, for full frame exposure. Since exposure occurs as the prism rotates, images near the top or bottom of the frame, where the prism is substantially off axis, suffer from significant aberration. A shutter can improve the results by gating the exposure more tightly around the point where the prism faces are nearly parallel. * 16 mm rotary prism – Redlake Hycam cameras are capable of 11,000 frame/s with a full frame prism (4 facets), 22,000 frame/s with a half-frame kit, and 44,000 frame/s with a quarter-frame kit. Visible Solutions also makes the Photec IV. For a more rugged solution, Weinberger made the Stalex 1B, which frames at up to 3000full frames per second, and had the ability to be mounted on board for car crash testing. Fastax cameras can achieve up to 18,000 frames per second with an 8-sided prism. * 35 mm rotary prism – Photo-Sonics 4C cameras are capable of 2,500 frame/s with a full frame prism (4 facets), 4,000 frame/s with a half-frame kit, and 8,000 frame/s with a quarter-frame kit. * 70 mm rotary prism – Photo-Sonics 10B cameras are capable of 360 frame/s with a full frame prism (4 facets), and 720 frame/s with a half-frame kit.


Rotating mirror

Rotating mirror cameras can be divided into two sub-categories; pure rotating mirror cameras and rotating drum, or Dynafax cameras. In pure rotating mirror cameras, film is held stationary in an arc centered about a rotating mirror. The basic construction of a rotating mirror camera consists of four parts; a main objective lens, a field lens, image compensation lenses, and a rotating mirror to sequentially expose frames. An image of the object under study is formed in the region of a rotating mirror with flat faces (a trihedral mirror is commonly used because it has a relatively high bursting speed, but designs with eight or more faces have been used). A field lens optically conjugates the pupil of the main objective lens in the region of a bank of compensation lenses, and the final compensation lenses optically conjugate the mirror to the surface of a photodetector. For each frame formed on the film, one compensation lens is required, but some designs have used a series of flat mirrors. As such, these cameras typically do not record more than one hundred frames, but frame counts up to 2000 have been recorded. This means they record for only a very short time – typically less than a millisecond. Therefore, they require specialized timing and illumination equipment. Rotating mirror cameras are capable of up to 25 million frames per second, with typical speed in the millions of fps. The rotating drum camera works by holding a strip of film in a loop on the inside track of a rotating drum. This drum is then spun up to the speed corresponding to a desired framing rate. The image is still relayed to an internal rotating mirror centered at the arc of the drum. The mirror is multi-faceted, typically having six to eight faces. Only one secondary lens is required, as the exposure always occurs at the same point. The series of frames is formed as the film travels across this point. Discrete frames are formed as each successive face of the mirror passes through the optical axis. Rotating drum cameras are capable of speed from the tens of thousands to millions of frames per second, but since the maximum peripheral linear speed of the drum is practically around 500 m/s, increasing the frame rate requires decreasing the frame height and/or increasing the number of frames exposed from the rotating mirror. In both types of rotating mirror cameras, double exposure can occur if the system is not controlled properly. In a pure rotating mirror camera, this happens if the mirror makes a second pass across the optics while light is still entering the camera. In a rotating drum camera, it happens if the drum makes more than one revolution while light is entering the camera. Many cameras use ultra high speed shutters such as those employing explosives to shatter a block of glass, rendering it opaque. Alternatively, high speed flashes with a controlled duration can be used. In modern ccd imaging systems, the sensors can be shuttered within microseconds, obviating the need for an external shutter. Rotating mirror camera technology has more recently been applied to electronic imaging, where instead of film, an array of single shot CCD or CMOS cameras is arrayed around the rotating mirror. This adaptation enables all of the advantages of electronic imaging in combination with the speed and resolution of the rotating mirror approach. Speeds up to 25 million frames per second are achievable, with typical speeds in the millions of fps. Commercial availability of both types of rotating mirror cameras began in the 1950s with Beckman & Whitley, and Cordin Company. Beckman & Whitley sold both rotating mirror and rotating drum cameras, and coined the "Dynafax" term. In the mid-1960s, Cordin Company bought Beckman & Whitley and has been the sole source of rotating mirror cameras since. An offshoot of Cordin Company, Millisecond Cinematography, provided drum camera technology to the commercial cinematography market.


Image dissection

Most image dissection camera designs involve thousands of fiber optic fibers bundled together that are then separated into a line that is recorded with traditional streak camera means (rotating drum, rotating mirror, etc.). The resolution is limited to the number of fibers, and commonly only a few thousand fibers can be practically used.


Raster cameras

Raster cameras, which are often referred to as image dissection cameras in literature, involve the principle that only a small fraction of an image needs to be recorded to produce a discernible image. This principle is used most commonly in lenticular printing where many images are placed on the same material and an array of cylindrical lenses (or slits) only allows one part of the image to be viewed at a time. Most raster cameras operate using a black grid with very thin lines etched into it, with hundreds or thousands of transparent lines in between much thicker opaque areas. If each slit is 1/10 the width as each opaque area, when the raster is moved, 10 images can be recorded in the distance between two slits. This principle allows extremely high time resolution by sacrificing some spatial resolution (most cameras only have around 60,000 pixels, about 250x250 pixel resolution), with recorded rates of up to 1.5 billion frames per second. Raster techniques have been applied to streak cameras made from image converters for much higher speeds. The raster image is often moved through a rotating mirror system, but the raster itself can also be moved across a sheet of film. These cameras can be very difficult to synchronize, as they often have limited recording times (under 200 frames) and frames are easily overwritten. The raster can be made with lenticular sheets, a grid of opaque slits, arrays of tapered (Selfoc) fiber optics, etc.


Streak photography

Streak photography (closely related to strip photography) uses a
streak camera A streak camera is an instrument for measuring the variation in a pulse of light's intensity with time. They are used to measure the pulse duration of some ultrafast laser systems and for applications such as time-resolved spectroscopy and LID ...
to combine a series of essentially one-dimensional images into a two-dimensional image. The terms "streak photography" and "strip photography" are often interchanged, though some authors draw a distinction. By removing the prism from a rotary prism camera and using a very narrow slit in place of the shutter, it is possible to take images whose exposure is essentially one dimension of spatial information recorded continuously over time. Streak records are therefore a space vs. time graphical record. The image that results allows for very precise measurement of velocities. It is also possible to capture streak records using rotating mirror technology at much faster speeds. Digital line sensors can be used for this effect as well, as can some two-dimensional sensors with a slit mask. For the development of explosives the image of a line of sample was projected onto an arc of film via a rotating mirror. The advance of flame appeared as an oblique image on the film, from which the velocity of detonation was measured. Motion compensation photography (also known as ballistic synchro photography or smear photography when used to image high-speed projectiles) is a form of streak photography. When the motion of the film is opposite to that of the subject with an inverting (positive) lens, and synchronized appropriately, the images show events as a function of time. Objects remaining motionless show up as streaks. This is the technique used for finish line photographs. At no time is it possible to take a still photograph that duplicates the results of a finish line photograph taken with this method. A still is a photograph ''in'' time, a streak/smear photograph is a photograph ''of'' time. When used to image high-speed projectiles the use of a slit (as in streak photography) produce very short exposure times ensuring higher image resolution. The use for high-speed projectiles means that one still image is normally produced on one roll of cine film. From this image information such as yaw or pitch can be determined. Because of its measurement of time variations in velocity will also be shown by lateral distortions of the image. By combining this technique with a diffracted wavefront of light, as by a knife-edge, it is possible to take photographs of phase perturbations within a homogeneous medium. For example, it is possible to capture shockwaves of bullets and other high-speed objects. See, for example,
shadowgraph Shadowgraph is an optical method that reveals non-uniformities in transparent media like air, water, or glass. It is related to, but simpler than, the schlieren and schlieren photography methods that perform a similar function. Shadowgraph is a ...
and
schlieren photography Schlieren photography is a process for photographing fluid flow. Invented by the German physicist August Toepler in 1864 to study supersonic motion, it is widely used in aeronautical engineering to photograph the flow of air around objects. C ...
. In December 2011, a research group at MIT reported a combined implementation of the laser (stroboscopic) and streak camera applications to capture images of a repetitive event that can be reassembled to create a trillion-frame-per-second video. This rate of image acquisition, which enables the capture of images of moving photons, is possible by the use of the streak camera to collect each field of view rapidly in narrow single streak images. Illuminating a scene with a laser that emits pulses of light every 13 nanoseconds, synchronized to the streak camera with repeated sampling and positioning, researchers have demonstrated collection of one-dimensional data which can be computationally compiled into a two-dimensional video. Although this approach is limited by time resolution to repeatable events, stationary applications such as medical ultrasound or industrial material analysis are possibilities.


Video

High-speed photographs can be examined individually to follow the progress of an activity, or they can be displayed rapidly in sequence as a moving film with slowed-down motion. Early video cameras using
tubes Tube or tubes may refer to: * ''Tube'' (2003 film), a 2003 Korean film * ''The Tube'' (TV series), a music related TV series by Channel 4 in the United Kingdom * "Tubes" (Peter Dale), performer on the Soccer AM television show * Tube (band), a ...
(such as the Vidicon) suffered from severe "ghosting" due to the fact that the latent image on the target remained even after the subject had moved. Furthermore, as the system scanned the target, the motion of the scanning relative to the subject resulted in artifacts that compromised the image. The target in Vidicon type camera tubes can be made of various photoconductive chemicals such as
antimony sulfide Antimony sulfide may refer to either of two compounds of antimony and sulfur: *Antimony trisulfide Antimony trisulfide (Sb2S3) is found in nature as the crystalline mineral stibnite and the amorphous red mineral (actually a mineraloid) metastibn ...
( Sb2 S3),
lead(II) oxide Lead(II) oxide, also called lead monoxide, is the inorganic compound with the molecular formula Pb O. PbO occurs in two polymorphs: litharge having a tetragonal crystal structure, and massicot having an orthorhombic crystal structure. Modern ap ...
(), and others with various image "stick" properties. The Farnsworth ''Image Dissector'' did not suffer from image "stick" of the type Vidicons exhibit, and so related special image converter tubes might be used to capture short frame sequences at very high speed. The mechanical shutter, invented by Pat Keller and others at
China Lake Naval Air Weapons Station China Lake is a United States military facility in California. China Lake may also refer to: Places in the United States *China Lake, Kern County, California, an unincorporated community named for a nearby dry lake * Ch ...
in 1979, helped freeze the action and eliminate ghosting. This was a mechanical shutter similar to the one used in high-speed film cameras—a disk with a wedge removed. The opening was synchronized to the frame rate, and the size of the opening was proportional to the integration or shutter time. By making the opening very small, the motion could be stopped. Despite the resulting improvements in image quality, these systems were still limited to 60 frame/s. Other Image Converter tube based systems emerged in the 1950s which incorporated a modified GenI image intensifier with additional deflector plates which allowed a photon image to be converted to a photoelectron beam. The image, while in this photoelectron state, could be shuttered on and off as short as a few nanoseconds, and deflected to different areas of the large 70 and 90 mm diameter phosphor screens to produce sequences of up to 20+ frames. In the early 1970s these camera attained speeds up to 600 million frame/s, with 1 ns exposure times, with more than 20 frames per event. As they were analog devices there were no digital limitations on data rates and pixel transfer rates. However, image resolution was quite limited, due to the inherent repulsion of electrons and the grain of the phosphor screen, as well as the small size of each individual image. Resolutions of 10  lp/mm were typical. Also, the images were inherently monochrome, as wavelength information is lost in the photon-electron-photon conversion process. There was also a fairly steep trade-off between resolution and number of images. All images needed to fall on the output phosphor screen. Therefore, a four image sequence would mean each image occupies one fourth of the screen; a nine image sequence has each image occupying one ninth, etc. Images were projected and held on the tube's phosphor screen for several milliseconds, long enough to be optically, and later fiber optically, coupled to film for image capture. Cameras of this design were made by Hadland Photonics Limited and NAC. It was difficult to change the exposure time without changing the frame rate with earlier designs, but later models added additional "shuttering" plates to allow exposure time and framing rate to be altered independently. The limiting factor of these systems is the time an image can be swept to the next position. In addition to framing tubes, these tubes could also be configured with one or two sets of deflector plates in one axis. As light was converted to photoelectrons, these photoelectrons could be swept across the phosphor screen at incredible sweep speeds limited only by the sweep electronics, to generate the first electronic streak cameras. With no moving parts, sweep speeds of up to 10 picoseconds per mm could be attained, thus giving technical time resolution of several picoseconds. As early as the 1973–74 there were commercial streak cameras capable of 3 picosecond time resolution derived from the need to evaluate the ultra short laser pulses which were being developed at that time. Electronic streak cameras are still used today with time resolution as short as sub picoseconds, and are the only true way to measure short optical events in the picosecond time scale.


CCD

The introduction of the CCD revolutionized high-speed photography in the 1980s. The ''staring array'' configuration of the sensor eliminated the scanning artifacts. Precise control of the integration time replaced the use of the mechanical shutter. However, the CCD architecture limited the rate at which images could be read off the sensor. Most of these systems still ran at
NTSC The first American standard for analog television broadcast was developed by National Television System Committee (NTSC)National Television System Committee (1951–1953), Report and Reports of Panel No. 11, 11-A, 12–19, with Some supplement ...
rates (approximately 60 frame/s), but some, especially those built by the Kodak Spin Physics group, ran faster and recorded onto specially constructed video tape cassettes. The Kodak MASD group developed the first HyG (rugged) high-speed digital color camera called the RO that replaced 16-mm crash sled film cameras. Many new innovations and recording methods were introduced in the RO and further enhancements were introduced in the HG2000, a camera that could run at 1000 frame/s with a 512 x 384
pixel In digital imaging, a pixel (abbreviated px), pel, or picture element is the smallest addressable element in a raster image, or the smallest point in an all points addressable display device. In most digital display devices, pixels are the ...
sensor for 2 seconds. Kodak MASD group also introduced an ultra high-speed CCD camera called the HS4540 that was designed and manufactured by Photron in 1991 that recorded 4,500 frame/s at 256 x 256. The HS4540 was used extensively by companies manufacturing automotive air bags to do lot testing which required the fast record speed to image a 30 ms deployment. Roper Industries purchased this division from Kodak in November 1999 and it was merged with Redlake (which was also purchased by Roper Industries). Redlake has since been purchased b
IDT
which is today a market leader in the high speed camera market, and continues to serve the automotive crash test market.


Gated intensified CCD

In the early 1990s very fast cameras based on micro-channel plate (MCP) image intensifiers were developed. The MCP intensifier is similar to technology used for night vision applications. They are based on a similar photon-electron-photon conversion as the above-described image converter tubes, but incorporate a micro-channel plate. This plate is given a high-voltage charge such that electrons coming from the input photocathode to the holes create a cascading effect, thereby amplifying the image signal. These electrons fall on an output phosphor, creating the emission of photons that compose the resulting image. The devices can be switched on and off at the picosecond time scale. The output of the MCP is coupled to a CCD, usually by means of a fused fiber-optic taper, creating an electronic camera with very high sensitivity and capable of very short exposure times, though also one that is inherently monochrome due to wavelength information being lost in the photon-electron-photon conversion. The pioneering work in this area was done by Paul Hoess while at PCO Imaging in Germany. A sequence of images at these very fast speeds can be obtained by multiplexing MCP-CCD cameras behind an optical beam splitter and switching the MCP devices using an electronic sequencer control. These systems typically use eight to sixteen MCP-CCD imagers, yielding a frame sequence at speeds up to 100 billion fps. Some systems were built with interline CCDs, which enables two images per channel, or a 32 frame sequence, though not at the highest speeds (because of the minimum time of the interline transfer). These types of cameras were built by Hadland Photonics and then DRS Hadland till 2010. Specialised Imaging in the UK also manufactures these cameras, which achieve rates at up to a billion frames per second. However, the minimum exposure time is 3 nanoseconds which limits the effective framing rate to several hundred million frames per second. In 2003, Stanford Computer Optics introduced the multi-framing camera, XXRapidFrame. It allows Image sequences of up to 8 images with a shutter time down to 200 picoseconds at a frame rate of several billion frames per second.


IS-CCD

Another approach for capturing images at extremely high speeds is with an ISIS (In Situ storage CCD chip, such as in the Shimadzu HPV-1 and HPV-2 cameras. In a typical interline transfer CCD chip, each pixel has a single register. Charge from an individual pixel can be quickly transferred into its register in the microsecond time scale. These charges are then read out of the chip and stored in a serial "read" process that takes more time than the transfer to the register. The Shimadzu camera is based on a chip where each pixel has 103 registers. Charge from the pixel can then be transferred into these registers such that the image sequence is stored "on chip" and then read out well after the event of interest is over. Frame rates as high as a billion fps are possible, with current cameras (Kirana and HPV) achieving up to 10 million fps. ISIS cameras have the obvious advantage over rotating mirror cameras that only one photodetector is needed and the frame count can be much higher. Complex synchronization circuitry necessary for synchronous rotating mirror cameras are also not necessary with ISIS. A main issue with in situ storage chips is ghosting of frames and low spatial resolution, but modern devices such as the Kirana from Specialized Imaging have partially solved the issue. The main use of this type of imaging system is one where the event takes place between 50 µs and 2 ms, such as applications with Split-Hopkinson pressure bar, stress analysis,
light-gas gun The light-gas gun is an apparatus for physics experiments. It is a highly specialized gun designed to generate extremely high velocities. It is usually used to study high-speed impact phenomena (hypervelocity research), such as the formation of ...
, target impact studies and DIC (Digital Image Correlation). ISIS sensors have achieved rates of more than 3.5 terapixels per second, hundreds of times better than the state of the art high speed readout cameras.


Rotating mirror CCD

Rotating mirror film camera technology has been adapted to take advantage of CCD imaging by putting an array of CCD cameras around a rotating mirror in place of film. The operating principles are substantially similar to those of rotating mirror film cameras, in that the image is relayed from an objective lens to a rotating mirror, and then back to each CCD camera, which are all essentially operating as a single shot cameras. Framing rate is determined by the speed of the mirror, not the read-out rate of the imaging chip, as in single chip CCD and CMOS systems. This means these cameras must necessarily work in a burst mode, as they only can capture as many frames as there are CCD devices (typically 50–100). They are also much more elaborate (and therefore costly) systems than single chip high-speed cameras. These systems do, however, achieve the maximum combination of speed and resolution, as they have no trade-off between speed and resolution. Typical speeds are in the millions of frames per second, and typical resolutions are 2 to 8 megapixels per image. These types of cameras were introduced by the Beckman Whitley company and later purchased and made by Cordin Company.


CMOS

The introduction of CMOS sensor technology again revolutionized high-speed photography in the 1990s and serves as a classic example of a disruptive technology. Based on the same materials as computer memory, the CMOS process was cheaper to build than CCD and easier to integrate with on-chip memory and processing functions. They also offer much greater flexibility in defining sub-arrays as active. This enables high-speed CMOS cameras to have broad flexibility in trading off speed and resolution. Current high-speed CMOS cameras offer full resolution framing rates in the thousands of fps with resolutions in the low megapixels. But these same cameras can be easily configured to capture images in the millions of fps, though with significantly reduced resolution. The image quality and quantum efficiency of CCD devices is still marginally superior to CMOS. The first patent of an Active Pixel Sensor (APS), submitted by JPL's
Eric Fossum Eric R. Fossum (born October 17, 1957) is an American physicist and engineer, which with the help of other JPL scientists, co-developed some features of the CMOS image sensor. He is currently a professor at Thayer School of Engineering in Dartmou ...
, led to the spin-off of Photobit, which was eventually bought by Micron Technology. However, Photobit's first interest was in the standard video market; the first high-speed CMOS system was NAC Image Technology's HSV 1000, first produced in 1990. Vision Research Phantom, Photron, NAC, Mikrotron
IDT
and other
High-speed camera A high-speed camera is a device capable of capturing moving images with exposures of less than 1/1,000 second or frame rates in excess of 250 fps. It is used for recording fast-moving objects as photographic images onto a storage medium. After r ...
uses CMOS imaging sensors (CIS) in their cameras. Vision Research Phantom's first CMOS sensor, used in the Phantom 4, was designed at the Belgian Interuniversity Microelectronics Center (IMEC). These systems quickly made inroads into the 16 mm high-speed film camera market despite resolution and record times (the Phantom 4 was a 1024 x 1024 pixel, or 1
megapixel In digital imaging, a pixel (abbreviated px), pel, or picture element is the smallest addressable element in a raster image, or the smallest point in an all points addressable display device. In most digital display devices, pixels are the sm ...
, with a run capacity of 4 s at full frame and 1000 frame/s). IMEC in 2000 spun the research group off as FillFactory which became the dominant player in the design of streaming high speed image sensors. FillFactory was in 2004 purchased by
Cypress Semiconductor Cypress Semiconductor was an American semiconductor design and manufacturing company. It offered NOR flash memories, F-RAM and SRAM Traveo microcontrollers, PSoC programmable system-on-chip solutions, analog and PMIC Power Management ICs, Ca ...
and in sold again to
ON Semiconductor onsemi (stylized in lowercase; legally ON Semiconductor Corporation; formerly ON Semiconductor until August 5, 2021) is an American semiconductor supplier company, based in Phoenix, Arizona and ranked #483 on the 2022 ''Fortune'' 500 based on it ...
, while key staff went on to create CMOSIS in 2007 and Caeleste in 2006. Photobit eventually introduced a 500 frame/s 1.3
megapixel In digital imaging, a pixel (abbreviated px), pel, or picture element is the smallest addressable element in a raster image, or the smallest point in an all points addressable display device. In most digital display devices, pixels are the sm ...
sensor, a true camera-on-chip device found in many low-end high-speed systems. Subsequently, several camera manufacturers compete in the high-speed digital video market, including iX-Cameras, AOS Technologies, Fastec Imaging, Mega Speed Corp, NAC, Olympus, Photron, Mikrotron, Redlake, Vision Research, Slow Motion Camera Company an
IDT
with sensors developed by Photobit, Cypress, CMOSIS, and in-house designers. In addition to those science and engineering types of cameras, an entire industry has been built up around industrial machine vision systems and requirements. The major application has been for high-speed manufacturing. A system typically consists of a camera, a
frame grabber A frame grabber is an electronic device that captures (i.e., "grabs") individual, digital still frames from an analog video signal or a digital video stream. It is usually employed as a component of a computer vision system, in which video fram ...
, a processor, and communications and recording systems to document or control the manufacturing process.


Infrared

High-speed infrared photography has become possible with the introduction of the Amber Radiance, and later the Indigo Phoenix. Amber was purchased by
Raytheon Raytheon Technologies Corporation is an American multinational aerospace and defense conglomerate headquartered in Arlington, Virginia. It is one of the largest aerospace and defense manufacturers in the world by revenue and market capitali ...
, the Amber design team left and formed Indigo, and Indigo is now owned by
FLIR Systems Teledyne FLIR LLC (an acronym for "forward-looking infrared"), a subsidiary of Teledyne Technologies, specializes in the design and production of thermal imaging cameras and sensors. Its main customers are governments and in 2020, approximately ...
. Telops, Xenics, Santa Barbara Focal Plane, CEDIP, and Electrophysics have also introduced high-speed infrared systems.


See also

* 16 mm film * 35 mm film *
70 mm film 70 mm film (or 65 mm film) is a wide high-resolution film gauge for motion picture photography, with a negative area nearly 3.5 times as large as the standard 35 mm motion picture film format. As used in cameras, the film is wid ...
*
Air-gap flash An air-gap flash is a photographic light source capable of producing sub-microsecond light flashes, allowing for (ultra) high-speed photography. This is achieved by a high-voltage (20 kV typically) electric discharge between two electrodes o ...
* Fastax (High-speed camera) * Femto-photography *
Harold Eugene Edgerton Harold Eugene "Doc" Edgerton (April 6, 1903 – January 4, 1990), also known as Papa Flash, was an American scientist and researcher, a professor of electrical engineering at the Massachusetts Institute of Technology. He is largely credited with ...
*
High-speed camera A high-speed camera is a device capable of capturing moving images with exposures of less than 1/1,000 second or frame rates in excess of 250 fps. It is used for recording fast-moving objects as photographic images onto a storage medium. After r ...

IDT
(Compact and Rugged High Speed Cameras) *
Nature photography Nature photography is a wide range of photography taken outdoors and devoted to displaying natural elements such as landscapes, wildlife, plants, and close-ups of natural scenes and textures. Nature photography tends to put a stronger emphasis o ...
* Photron (Photron FASTCAM high-speed cameras) *
slow motion Slow motion (commonly abbreviated as slo-mo or slow-mo) is an effect in film-making whereby time appears to be slowed down. It was invented by the Austrian priest August Musger in the early 20th century. This can be accomplished through the use ...
(less advanced than high-speed photography) * Vision Research Phantom (Vision Research Phantom high-speed cameras) *
Wildlife photography Wildlife photography is a genre of photography concerned with documenting various forms of wildlife in their natural habitat. As well as requiring photography skills, wildlife photographers may need field craft skills. For example, some anima ...


References


Further reading

* * * Mills, Mara (2014)
"(Ultra-High-Speed) Photographic Engineering."
''Flow'' 19 * * *


Notes

* documentary Moving Still (1980 broadcast on PBS Nova and BBS Horizon) has footage of these processes up to the modern solid state era.


External links



{{DEFAULTSORT:High Speed Photography Science of photography Photography by genre Articles containing video clips