Image Dissector Camera Research Articles

Multiplex imaging by a frequency-ramped laser-diode interferometer

We propose a method of multiplex imaging by a frequency-ramped laser-diode interferometer. Temporal carrier frequencies that are proportional to the optical path differences between the reference arm and the object arms in the interferometer are introduced by a sawtooth-current modulation of the laser diode. Electronic tuning can extract one interference beat signal from the multiplex ones produced by multiple object arms. Each interference pattern is sampled in synchronism with the laser-diode current modulation by using an image-dissector camera. A source of cross talk between multiple images is discussed. The use of a laser-diode with a wide frequency-modulation range will be promising for overcoming the problem.

A high resolution real-time temporal heterodyne interferometer for refractive index topography

A Mach-Zehnder interferometer for two-dimensional refractive index topography is presented which utilizes the temporal heterodyne technique. High scanning rates and excellent phase resolutions are obtained using an image dissector camera and a lock-in amplifier. The setup is applied for investigation of the photorefractive effect. A macroscopic light pattern is recorded and thermally fixed in iron-doped LiNbO3. The evolution of the refractive index pattern during development by homogeneous illumination is observed with the interferometer. The measured refractive index profiles are in good agreement with the results of computer simulations.

A two-dimensional vision system with optical ranging capability

This paper describes an optical three-dimensional (3D) camera developed by combining a two-dimensional intensity image and non-contact time of flight (TOP) range image. The camera system consists of an amplitude modulated light source, an image dissector tube, a phase measuring circuit, and a host PC for system control. A semiconductor diode laser light source or a white light source and Kerr cell is used to generate continuously high frequency modulated light for bulk illumination of the scene to be viewed. A compact, 25 mm diameter image dissector camera (Hamamatsu N2730 or R4193) is used as a receiver to detect the modulated light and generate both a two-dimensional intensity image and a range image. The range is obtained by measuring the phase between the received signal and the transmitted signal. With the large detection area and the random access property of the image dissector camera, it is easy to scan systematically and electronically the illuminated area, within the frame, to identify the required object. Three different modulated frequencies (between 10 MHz and 45 MHz) have been used to obtain a range accuracy of 4 mm, over a distance of 10 m, within a time period of 10 ms per pixel. A demonstration of the three-dimensional vision system has been given, having an update time of 1 s during which a high resolution intensity image (300 × 300 pixels) is produced together with a limited number (100) of range measurements obtained for important features.

Pioneers of Television — Philo Taylor Farnsworth

This is the third in the series of “Pioneers of Television,” written for the SMPTE Journal. Philo T. Farnsworth was one of the most prolific inventors in television history, with over 75 important inventions in his name. Born in 1906 in Utah, he conceived an all-electric system of television while only 15 years of age. He typified the school of inventors that not only conceived the ideas but built and implemented them. By the time he was 21 he had secured financing and was operating a laboratory in San Francisco, from which came a host of important inventions. Farnsworth was the first inventor in the world to build and operate an all-electric television system, in July 1929. This included an electric camera tube, the image dissector; a vacuum-tube scanning, blanking, and sync generator; and a magnetically focused cathode ray tube. His image dissector camera tube was the first to pick up “live” images in broad daylight. He was the inventor of the method for generating anode high voltage from the scanning currents. His research in camera tubes led him to patent the first camera tube to use a low-velocity electron beam that scanned a target at cathode potential. This led to the Orthicon and Image Orthicon camera tubes that made postwar television possible. Farnsworth's imagination knew no limits, and without his inventions no modern-day television system could operate. Yet in spite of these considerable achievements, he is relatively unknown and has been overshadowed by other pioneers in television history.

In-line holography with a frequency doubled Nd:YAG laser for particle size analysis

An arrangement for determining the size distribution of small particles (e.g., droplets or bubbles) is presented. It consists of taking high speed holograms with a frequency doubled Nd:YAG laser, reconstructing the real image with an argon-ion laser, and a digital image processing system with a random access image dissector camera and two cascaded computers for filtering, segmentation, and higher recognition tasks. Results are presented for cavitation bubbles as test objects. It is shown that the quality of the holograms is sufficient for detecting bubbles with a diameter of <20 mum by digital image processing with the present configuration.

Differential polarization imaging. III. Theory confirmation. Patterns of polymerization of hemoglobin S in red blood sickle cells

In this paper we test the predictions of the differential polarization imaging theory developed in the previous two papers. A characterization of the patterns of polymerization of hemoglobin in red blood cells from patients with sickle cell anemia is presented. This system was chosen because it is relatively easy to handle and because previous studies have been done on it. A differential polarization microscope designed and built in our laboratory was used to carry out this study. This microscope uses an image dissector camera, a photoelastic modulator, and a phase-lock amplifier. This design represents a substantial modification with respect to the instrumentation used in the previous results communicated on this system. Therefore, the results presented here also permit us to confirm the validity of our conclusions. On the basis of the differential polarization images obtained, models of the patterns of polymerization of the hemoglobin S inside the sickle cells are proposed and their M12 and regular images are calculated by the theory. Good agreement between those models and the experimental systems is found, as well as with the results previously reported.

Differential polarization imaging. III. Theory confirmation. Patterns of polymerization of hemoglobin S in red blood sickle cells

In this paper we test the predictions of the differential polarization imaging theory developed in the previous two papers. A characterization of the patterns of polymerization of hemoglobin in red blood cells from patients with sickle cell anemia is presented. This system was chosen because it is relatively easy to handle and because previous studies have been done on it. A differential polarization microscope designed and built in our laboratory was used to carry out this study. This microscope uses an image dissector camera, a photoelastic modulator, and a phase-lock amplifier. This design represents a substantial modification with respect to the instrumentation used in the previous results communicated on this system. Therefore, the results presented here also permit us to confirm the validity of our conclusions. On the basis of the differential polarization images obtained, models of the patterns of polymerization of the hemoglobin S inside the sickle cells are proposed and their M12 and regular images are calculated by the theory. Good agreement between those models and the experimental systems is found, as well as with the results previously reported.

Differential polarization microscope using an image dissector camera and phase-lock detection

A polarization modulation microscope designed to detect and spatially resolve the distribution of optically anisotropic domains in microscopic objects is described. An image dissector camera is used as the detection device. The polarization of the light is modulated by means of a photoelastic modulator and a synchronous demodulation amplifier (lock-in) is utilized to obtain the difference image between the images formed using two orthogonal forms of the incident polarization on the sample. Preliminary results are described for the linear dichroism imaging measurements of polymerized hemoglobin (HbS) in red blood sickle cells. The present limitations of this design are discussed along with various strategies to improve its performance.

Recording and automatical analysis of pulsed off-axis holograms for determination of cavitation nuclei size spectra

The bubble size distribution in a cavitation tunnel is obtained via holography by using a Q-switched ruby laser and diffuse illumination of the object volume in an off-axis arrangement. Analysis of the holograms taken is done by scanning their real image with an image dissector camera under computer control and by calculating size and location of the particles using specially designed software. With this digital image processing system nuclei as small as 20 μm in diameter can be detected in order to yield histograms of their size distribution.

Real-time volume-scanning three-dimensional imaging system for real moving objects

A three-dimensional imaging system is described that optically dissects a real object into cross sections by illuminating it with a thin plane of light made to scan across its depth. An image-dissector camera with its axis perpendicular to the thin plane of light rapidly scans the cross sections so produced in real time. The images are displayed on a cathode-ray tube driven mechanically in an oscillatory sawtooth motion along its long axis in synchronization with the movement of the thin plane of light. A three-dimensional image containing full spatial information is produced 13 times per second.

Determination of size and position of fast moving gas bubbles in liquids by digital 3-D image processing of hologram reconstructions

An experimental setup for digital 3-D image processing from hologram reconstructions is described. The real image as obtained upon reconstruction of the hologram with its conjugated reference wave is scanned by a movable image dissector camera without imaging optics and serves as analog 3-D picture input storage to the computer. This scheme has been developed to analyze automatically fast moving bubble fields in liquids recorded by high speed holographic techniques. A computer code has been written combining standard methods like gradient filtering from the field of image processing with specially developed algorithms for speckle noise suppression to locate and count the bubbles in the image volume and to determine their morphological data.

Finding the edges of the surfaces of three-dimensional curved objects by computer

This paper presents an algorithm for finding the edges of the surfaces of simple curved or planar three-dimensional objects. The object is viewed by an image dissector camera controlled by a computer. The algorithm is divided into four steps—edge marking, edge refining, edge tracing and edge completion. Each step is described in detail and examples are given illustrating each step. The output of the algorithm is a two-dimensional array in which the edges are marked. The performance of the algorithm on scenes composed of simple objects like coffee cups, a hammer, a coke bottle or a block is presented and compared to the performance of other methods.

The Detection of Dust Storms Over Land and Water With Satellite Visible and Infrared Measurements

The position of a large area of dust was successfully located over the Sahara Desert and off the west coast of Africa with infrared measurements from the Temperature Humidity Infrared Radiometer (THIR) and visible information from the Image Dissector Camera System (IDCS) on Nimbus 4 between 20 and 25 April 1970. Over land, near midday, the dust areas were associated with lower equivalent blackbody temperatures (TBB's) than in the surrounding areas due to the mixing of the dust with the cooler air just above the surface. Near midnight dust areas appeared to be located where the TBB's were higher than the surrounding regions. The TBB contrast was insufficient for dust detection over the ocean, but the contrast in the visible was great enough to track the movement of the dust for several days off the African west coast. Measurements from the THIR 6.5-7.2 micron channel were useful for detecting the presence of cirrus clouds which could have caused a misinterpretation of the 10.5-12.5 micron TBB's.

Computer algorithms for the detection of brain scintigram abnormalities.

Abstract Algorithms for computer analysis of digitized brain scintigrams are described. A technique of variable thresholding and region enumeration is used to detect abnormalities which project clear of the calvarium, while a metric comparison detects distortions of the brain outline. The methods have been employed to process scintigrams digitized by means of an image dissector camera operating under control of an SEL-840A computer. It is felt that the algorithms will be equally applicable to brain scintigrams digitized by other means and that they may prove adaptable to the analysis of other organ system images.