TV Lenses Research Articles

Condenser-free contrast methods for transmitted-light microscopy.

Phase contrast microscopy allows the study of highly transparent yet detail-rich specimens by producing intensity contrast from phase objects within the sample. Presented here is a generalized phase contrast illumination schema in which condenser optics are entirely abrogated, yielding a condenser-free yet highly effective method of obtaining phase contrast in transmitted-light microscopy. A ring of light emitting diodes (LEDs) is positioned within the light-path such that observation of the objective back focal plane places the illuminating ring in appropriate conjunction with the phase ring. It is demonstrated that true Zernike phase contrast is obtained, whose geometry can be flexibly manipulated to provide an arbitrary working distance between illuminator and sample. Condenser-free phase contrast is demonstrated across a range of magnifications (4–100×), numerical apertures (0.13–1.65NA) and conventional phase positions. Also demonstrated is condenser-free darkfield microscopy as well as combinatorial contrast including Rheinberg illumination and simultaneous, colour-contrasted, brightfield, darkfield and Zernike phase contrast. By providing enhanced and arbitrary working space above the preparation, a range of concurrent imaging and electrophysiological techniques will be technically facilitated. Condenser-free phase contrast is demonstrated in conjunction with scanning ion conductance microscopy (SICM), using a notched ring to admit the scanned probe. The compact, versatile LED illumination schema will further lend itself to novel next-generation transmitted-light microscopy designs. The condenser-free illumination method, using rings of independent or radially-scanned emitters, may be exploited in future in other electromagnetic wavebands, including X-rays or the infrared.

Variable-Focus Liquid Crystal Lenses Used in Imaging Systems as Focusing Elements

Liquid crystal (LC) lenses that have hole-patterned electrodes and are driven by two voltages used as imaging devices are reported. Two different LC lenses are applied in image formation systems. One LC lens is used with a polarizer in a relay lens scope, and another LC lens that is polarization independent is used in a TV lens. Both LC lenses play roles of focusing elements in lens systems; objects are separately brought into focus by the LC lenses. Very sharp black-and-white and color images are formed by the systems.

Hanging on and Holding out in New Orleans after Katrina

Hanging on and Holding out in New Orleans after Katrina Photographs and narratives by Thomas Neff Introduction by Moira Crone Photographer Thomas Neff entered the city in the first days after Katrina as a volunteer first responder. He soon began taking large-format black and white photographs and writing down the stories of natives he found marooned there, when the city was eighty percent under water. In these intimate, intense pictures, we see individuals who, though exhausted by grief and shock, are defiant, spontaneous, and resourceful. We see people reorganizing their lives, maintaining their individuality, their souls, their humor, and their culture—their citizenship in New Orleans. This crisis transformed all those who went through it: this is obvious in the face of Antoinette K-Doe, widow of Ernie K-Doe, at the Mother-in-Law Lounge, as she sits in the midst of the damage, assessing her future. It's also in the eyes of Melvin Smith, of Treme, who saved the lives of twenty-five of his neighbors. We see it in the clear gaze of Ride Hamilton, posed with his motorcycle, pausing from his work as a freelance medic, or in the eyes of Tommie Mabry, who, to keep sane while holed up in the Cooper Public Housing complex, became a chronicler, writing a diary about his days directly on the walls. We see it in the expression of Marie Jones, an Uptown matron, bewildered by the disheveled, in an eerily beautiful new world the tempest left her. Thrust suddenly into Fourth World conditions, abandoned by authorities and then under "occupation," these citizens made do, survived, saved lives, kept cool, had attitude: Caroline Koch's defiant stance atop her roof in Faubourg Marigny says it all. Neff's pictures embrace the breadth of New Orleans life, its diversity, quirkiness, creativity, and tolerance. They tell the stories that New Orleanians tell each other now—what happened at the edges, outside the TV lens. These pictures portray individuals who wouldn't abandon the city or their people, pets, or homes; who love it because it never was, exactly, America. These people hung on and held out, waiting with their wild tales when the rest of us came staggering back. [End Page 95] Click for larger view Figure 1 Tommie Elton Mabry November 17, 2005 From the outset, Tommie Elton Mabry documented the events of each post-storm day by writing on the interior walls of his "project" apartment. The daily entries soon covered every wall. City officials finally forced him out when they closed all the public housing complexes. Homeless and without transportation, Tommie moved his possessions to the second floor of another flooded house nearby, which had been abandoned for years. With a little work he made it livable, albeit without services of any kind. As winter approached, the first necessity was to staple black Visquine, which he called "Bisquick," over every glassless window. [End Page 96] Click for larger view Figure 2 Altheus and Gloria Banks May 12, 2006 The Bankses and their three dogs had been holding on for six days in their elevated house. When Gloria's health began to deteriorate, they knew it was time to leave. A passing airboat rescued them, but they had to leave the dogs behind—never to be seen again. The couple evacuated to an eldercare facility in Phoenix, where they stayed until January. Upon their discharge they were taken aback when FEMA paid for only four months. The last month cost them five thousand dollars. The Bankses were afraid to live in their desolate neighborhood after returning to New Orleans, so they have been staying in the home of lifelong friends. [End Page 97] Click for larger view Figure 3 Antoinette K-Doe November 2, 2005 When Antoinette returned to the famed Mother-in-Law Lounge, she found it moldy, rank, and utterly destroyed. Determined to rebuild to honor the memory of her famous late husband, Ernie, she began the arduous task...

Studies on imaging properties of a novel medical digital radiography system and its clinical applications [In Japanese

This dissertation describes the imaging properties of a novel digital radiography (DR) system. This 2048×2048‐matrix image intensifier‐TV‐DR system was introduced in January 1990. The basic imaging properties of the system were investigated in terms of system linearity, resolution, noise, and detectability of low contrast objects. It was found that the image quality is sufficient for close fluoroscopic GI‐tract examinations. The imaging properties of this system depend on the incident exposure rate, the level of signal current from the TV image pickup tube and also the size of the iris (diaphragm) in the TV lens. To obtain high‐resolution images, the incident exposure should be adjusted to obtain a small iris diaphragm and a low level of signal current. If, on the other hand, high resolution is not required the incident exposure can be reduced by increasing the iris diaphragm. Therefore, using the knowledge of these relationships, the DR system parameters and exposure levels should be determined when acquiring clinical images and evaluating the imaging properties. We have ascertained the performance of this DR system through our extensive investigation. This novel medical digital radiography system has been used for mass screening the upper GI‐tract of more than 12 500 patients.

Model-based 3-D scene analysis from stereoscopic image sequences

A vision-based 3-D scene analysis system is described that is capable to model complex real-world scences like buildings automatically from stereoscopic image pairs. Input to the system is a sequence of stereoscopic images taken with two standard CCD Cameras and TV lenses. The relative orientation of both cameras to each other is known by calibration. The camera pair is then moved throughout the scene and a long sequence of closely spaced views is recorded. Each of the stereoscopic image pairs is rectified and a dense map of 3-D surface points is obtained by area correlation, object segmentation, interpolation, and triangulation. 3-D camera motion relative to the scene coordinate system is tracked directly from the image sequence which allows to fuse 3-D surface measurements from different view points into a consistent 3-D model scence. The surface geometry of each scene object is approximated by a triangular surface mesh which stores the surface texture in a texture map. From the textured 3-D models, realistic looking image sequences from arbitrary view points can be synthesized using computer graphics.

Resolution properties of a 2048×2048 matrix image intensifier‐TV based digital radiography system

Spatial resolution properties of a 2048 x 2048 matrix image intensifier (II) TV based real-time digital radiography (DR) system were investigated. The presampling modulation transfer function (MTF), which includes the unsharpness of the detector and the blurring effect of the sampling aperture, was measured by a slit method. Also determined was the limiting resolution using a bar pattern. It was found that, the spatial resolution in this system is substantially improved relative to previous II-TV based DR systems, and is comparable or even superior to that in a computed radiography system depending on the imaging plate employed. However, the presampling MTF for 2048 x 2048 matrix is comparable to that for 1024 x 1024 matrix in this DR system, because the same sampling aperture is assumed to be used for both matrices. Even under these conditions obtained the improved clinical image since the Nyquist frequency is doubled for 2048 x 2048 matrix. It should be noted that the resolution property in the II-TV based DR system depends on the signal current from the TV image pickup tube (level of image pixel value) and also on the size of the iris in the TV lens. We must pay attention to these parameters when acquiring clinical images and evaluating the resolution properties. Finally, it was demonstrated that smaller focus than that used in a screen-film system can be employed in the DR system due to its high sensitivity, so the geometric unsharpness can be reduced. Therefore, the image resolution of our system was found to be superior to a screen-film system at some geometric magnification factors.

Automatic Reconstruction of Buildings from Stereoscopic Image Sequences

A vision–based 3‐D scene analysis system is described that is capable to model complex real–world scenes like streets and buildings automatically from stereoscopic image pairs. Input to the system is a sequence of stereoscopic images taken with two standard CCD Cameras and TV lenses. The relative orientation of both cameras to each other is known by calibration. The camerapair is then moved throughout the scene and a long sequence of closely spaced views is recorded. Each of the stereoscopic image pairs is rectified and a dense map of 3‐D suface points is obtained by area correlation, object segmentation, interpolation, and triangulation. 3‐D camera motion relative to the scene coordinate system is tracked directly from the image sequence which allows to fuse 3‐D surface measurements from different viewpoints into a consistent 3‐D model scene. The surface geometry of each scene object is approximated by a triangular surface mesh which stores the suface texture in a texture map. From the textured 3‐D models, realistic looking image sequences from arbitrary view points can be synthesized using computer graphics.

On the determination of the distribution of creep cavities

It is well known that during high-temperature creep deformation of metals, grain-boundary cavities are formed which grow, link up and eventually lead to the fracture of the specimen. Elucidation of the angular distribution of these cavities with respect to the stress direction provides valuable information concerning the mechanism of cavity growth which underlies creep fracture [1]. This has usually been done on longitudinal sections of creep-deformed samples in either of two ways: (1) measuring angles using a microscope fitted with a rotating eyepiece and linked to a bank of 18 counters so that angles could be registered over intervals of 5°; a count of the number of cavitated boundaries is obtained for each 5 ° interval and plotted as a histogram in terms of per cent relative frequency [2-4]; (2) measurement on individual cavities using a protractor with the microstructure projected on a TV screen [5]. Usually 2001000 cavitated boundaries are used in these measurements and the histograms so obtained represent an apparent angular distribution. True angular distributions are derived from these measurements using an analysis such as that of Scrivens and Williams [6]. The present note describes a procedure for the determination of angular distribution of creep cavities without the requirements of a rotating eyepiece or sighting the specimen through a TV lens. Essentially the method involves the use of an angular grid (Fig. 1) with lines drawn at 5 ° intervals which is inscribed on the ground-glass screen of the ordinary projection microscope. The procedure is as follows: (a) A thin fiducial line is marked on the specimen to indicate the stress axis. (b) Using a low magnification (e.g. 50 X) the axial line is made to coincide with the 0-0 line of the grid. The specimen can now be moved freely in the X and Y directions without disturbing the axial alignment. (c) Using an appropriate magnification and moving the specimen in the X and Y directions only (i.e. without any rotation), the cavities are brought into focus. The two successive radial lines on the grid along which the two sides of a chosen cavity lie are determined and the angle corresponding to these two lines is read off on the grid; e.g. the angular range of cavity 1

Clearing Radiation Darkened TV Lenses

The TV lenses used in high radiation areas here at the Zero Gradient Synchrotron (ZGS) become very brown and totally unusable within a short period of time. A method has been found whereby rotation of lenses from this area to exposure by UV light can keep a constant supply of usable lenses in service. Tests were also conducted on ZGS TV viewing ports to determine the clearing effect of UV on 3/4-in, 1-in, and 4-in-thick plate glass.

Measurement of OTF Using Large Test Pattern of Single Frequency

So as to evaluate TV lenses, large test pattern (2 m×2 m) was constructed. Throughout the pattern, the period of sine charts is 5 mm and the direction of stripes is vertical. Imaged by 1/50, its spatial frequency is 10 lines/mm. By adjusting the uniformity of brightness, the decrease of mean illumination at the corner of the image plane can be measured simultaneously. By scanning the intensity distribution of the image horizontally, OTF at the cut off frequency of TV cameras were measured on a image plane. A temporary standard was obtained by using an area weighted average of OTF, R̄, and a distortion factor, K, which is the rms value of the variation of OTF devided by R̄. That is; R̄ should be larger than 90%, or if R̄ is between 80 and 90%, K should be smaller than 10%.