Shutter speed

Abstract: Ultrafast real-time optical imaging is used in many areas of science, from biological imaging to the study of shockwaves. But in systems that undergo changes on very fast timescales, conventional technologies such as CCD (charge-coupled-device) cameras are compromised. Either imaging speed or sensitivity has to be sacrificed unless special cooling or extra-bright light is used. This is because it takes time to read out the data from sensor arrays, and at high frame rates only a few photons are collected. Now a UCLA team has developed an imaging method that overcomes these limitations and offers frame rates at least a thousand times faster than those of conventional CCDs, making this perhaps the world's fastest continuously running camera, with a shutter speed of 440 picoseconds. The technology — serial time-encoded amplified microscopy or STEAM — maps a two-dimensional image into a serial time-domain data stream and simultaneously amplifies the image in the optical domain. A single-pixel photodetector then captures the entire image. Ultrafast real-time optical imaging is used in diverse areas of science, but conventional imaging devices such as CCDs are incapable of capturing fast dynamical processes with high sensitivity and resolution. This imaging method overcomes these limitations and offers frame rates that are at least 1,000 times faster than those of conventional CCDs. The approach is applied to continuous real-time imaging of microfluidic flow and phase-explosion effects that occur during laser ablation. Ultrafast real-time optical imaging is an indispensable tool for studying dynamical events such as shock waves1,2, chemical dynamics in living cells3,4, neural activity5,6, laser surgery7,8,9 and microfluidics10,11. However, conventional CCDs (charge-coupled devices) and their complementary metal–oxide–semiconductor (CMOS) counterparts are incapable of capturing fast dynamical processes with high sensitivity and resolution. This is due in part to a technological limitation—it takes time to read out the data from sensor arrays. Also, there is the fundamental compromise between sensitivity and frame rate; at high frame rates, fewer photons are collected during each frame—a problem that affects nearly all optical imaging systems. Here we report an imaging method that overcomes these limitations and offers frame rates that are at least 1,000 times faster than those of conventional CCDs. Our technique maps a two-dimensional (2D) image into a serial time-domain data stream and simultaneously amplifies the image in the optical domain. We capture an entire 2D image using a single-pixel photodetector and achieve a net image amplification of 25 dB (a factor of 316). This overcomes the compromise between sensitivity and frame rate without resorting to cooling and high-intensity illumination. As a proof of concept, we perform continuous real-time imaging at a frame speed of 163 ns (a frame rate of 6.1 MHz) and a shutter speed of 440 ps. We also demonstrate real-time imaging of microfluidic flow and phase-explosion effects that occur during laser ablation.

Abstract: A micro-electromechanical bistable shutter display device is provided capable of being implemented for both small screen, high resolution devices and for large billboard-type displays. The micro-electromechanical shutter assembly has bi-stability characteristics which allow the use of only a holding voltage to maintain an image. The micro-electromechanical shutter assembly includes a shutter having petal-like shutter segments covering reflective or transmittive films. To expose the film in a particular shutter assembly, its shutter segments are moved from the horizontal to a vertical position using electrostatic attraction forces to “collapse” the torsionally-hinged shutter segments. The shutter assembly can have a number of segments, as long as the resulting shutter assembly shape can be stacked to form a dense 2D array.

Abstract: An electronic still camera comprising a shutter release, a solid state imaging device on which an image of an object is focused through an optical system, a driver for driving the imaging device to derive an object picture signal, an analog-to-digital converter for converting this signal into a digital image signal, and a semiconductor memory card detachably loaded into the housing, for recording the digital image signal. The memory card has semiconductor memory chips mounted on a printed circuit board. The camera operates in a motion image display mode by half depression of the shutter release, and operates in a still image mode by full depression of the release. In the motion image display mode, the driver drives the imaging device on a real time basis to sequentially derive object picture signals and supplies them to an electronic view finder to display the object in the motion image mode. In the still image mode, a shutter pulse corresponding to the shutter time external set is generated. In response to this shutter pulse, the drive controls the charge storage time of the imaging device in accordance with the shutter time and drives the picture signal, which is stored during the charge storage time at a speed lower than the motion image mode, and is then recorded on the memory card.

Abstract: We present femto-photography, a novel imaging technique to capture and visualize the propagation of light. With an effective exposure time of 1.85 picoseconds (ps) per frame, we reconstruct movies of ultrafast events at an equivalent resolution of about one half trillion frames per second. Because cameras with this shutter speed do not exist, we re-purpose modern imaging hardware to record an ensemble average of repeatable events that are synchronized to a streak sensor, in which the time of arrival of light from the scene is coded in one of the sensor's spatial dimensions. We introduce reconstruction methods that allow us to visualize the propagation of femtosecond light pulses through macroscopic scenes; at such fast resolution, we must consider the notion of time-unwarping between the camera's and the world's space-time coordinate systems to take into account effects associated with the finite speed of light. We apply our femto-photography technique to visualizations of very different scenes, which allow us to observe the rich dynamics of time-resolved light transport effects, including scattering, specular reflections, diffuse interreflections, diffraction, caustics, and subsurface scattering. Our work has potential applications in artistic, educational, and scientific visualizations; industrial imaging to analyze material properties; and medical imaging to reconstruct subsurface elements. In addition, our time-resolved technique may motivate new forms of computational photography.