After developing various kinds of photodetectors such as phototubes, photomultiplier tubes, image pick up tubes, solid state photodetectors and a variety of light sources, we also started to develop integrated systems utilizing new detectors or imaging devices. These led us to the technology for a single photon counting imaging and detection of picosecond and femtosecond phenomena. Through those experiences, we gained the understanding that photon is a paste of substances, and yet we know so little about photon. By developing various technology for many fields such as analytical chemistry, high energy physics, medicine, biology, brain science, astronomy, etc., we are beginning to understand that the mind and life are based on the same matter, that is substance. Since humankind has so little knowledge about the substance concerning the mind and life, this makes some confusion on these subjects at this moment. If we explore photonics more deeply, many problems we now have in the world could be solved. By creating new knowledge and technology, I believe we will be able to solve the problems of illness, aging, energy, environment, human capability, and finally, the essential healthiness of the six billion human beings in the world.
Strong interest exists at the Lawrence Livermore National Laboratory in studying the physics of transient, high density, high temperature, hydrogen plasmas. Because sequenced imaging is a major part of the diagnostics of these plasmas a continuous effort is made to improve the components of our imaging system and their calibration and to review operating procedures and techniques. The major components of our transient data, optical imaging systems are gated microchannel plate intensifiers (MCPI), solid-state array cameras, and fiberoptic data acquisition systems. Gated MCPIs are currently used with our solid-state cameras to provide sub-nanosecond snapshots of an optical pulse from a radiation-to-light converter. Efforts are made (1) to characterize photocathode response, modulation transfer function, luminous gain, and gating speed of each MCPI during the gating period, and (2) to improve pertinent MCPI parameters such as extinction ratio, gate pulse shape, resolution, and uniformity. A review of our high-speed imaging systems and components and their developments and calibrations is also presented.
A family of imaging photon-counting detector systems, the multi-anode microchannel arrays (MAMAs), are now under active development for use on a number of space astrophysics missions at far-ultraviolet and extreme-ultraviolet wavelengths. MAMA detector systems are currently being fabricated for use in instruments on the European Space Agency (ESA)/NASA Solar Heliospheric Observatory (SOHO) spacecraft and for a second generation instrument on the NASA/ESA Hubble Space Telescope. The components of the MAMA detector system consist of, (1) the open or sealed tube assembly containing the photocathode, the high-gain curved-channel microchannel plate, and the readout electrode array, and (2) the associated analog and digital electronics circuits. The configurations of the different MAMA detector systems are described in some detail and the use of custom application specific integrated circuits in the electronics is discussed. The performance characteristics of the MAMA detectors are described and compared with those of alternative imaging photon-counting detector systems. Examples of both ground-based data and flight data from sounding rockets are shown.
The present paper gives an overview on the development and current status of photoelectronic imaging devices in China. Particular emphasis is given to devices aimed at image intensification and image conversion, e.g., image intensifiers, low light level pick-up devices, electronographic tubes, high speed photographic converter tubes, intensified CCDs, infrared detectors, as well as basic theory and design, and components and methods of testing for the photoelectronic imaging systems in China.
New synchrotron facilities such as the European Synchrotron Radiation Facility rely on the development of new detectors to take full advantage of the dramatic increase in the brilliance of their x-ray beamlines. A novel detector system based on modified x-ray image intensifiers (XRII) optically coupled to CCD cameras is described. Different options fit specific requirements, essentially trading resolution against speed. The energy range covers from 5 to 25 keV with the special beryllium windowed XRII, and up to 100 keV with standard medical imager tubes. Input size is 200 mm in diameter, with electronic zooming capability down to (phi) 100 mm. A 50% MTF is reached for 17 line pairs/cm. More important is the extremely narrow wings of the point spread function: full width at 0.1% of maximum is less than 1 mm. Noise is negligible in most applications, being equivalent to a few x-ray photons/s.cm2, so that single x-ray photons are easily distinguished. Commercially available slow scan CCD cameras allow 16 bit dynamic range megapixel images to be read-out in 10 - 20s. Faster designs studied at the ESRF using multi-output CCD already make it possible to acquire several images per second, and ultra fast systems with only 512 X 512 pixels are expected to reach up to 300 images/s while maintaining a dynamic range of 1000:1.
With the development of science and technology in modern society, people have not only the demand of observing scenes at night, but also hope to record them vividly. Practical image recording methods are film photography, cassette or electrostatic recording. This article mainly presents the methods of recording LLL image information with films, the application of LLL image intensifying technology in film recording and the problems of it.
Two types of new detectors have been developed to pick up faint x-ray image with high resolution in the x-ray energy range of from 3 keV. One is an x-ray image intensifier type video camera. The other is an ultra high sensitive x-ray image intensifier type video camera and this enables us to pick up faint soft x-ray image even in the photon counting region. Features, specification, and applications of these detectors are described.
The propagation properties of an ultrafast laser pulse through breast tissues are simulated in this paper. It has been shown that the use of time-gated imaging techniques could greatly improve the contrast of transmission image of the breast. Then several time-gated imaging techniques are discussed, and a new time-gated imaging technique -- the use of transient stimulated Raman scattering for both rapid time gating and amplification of the image -- is proposed.
Besides some advantages over conventional optical microscopes, a scanning laser imaging system is the basis of developing another kind of imaging system i.e., a laser-thermal imaging system. The latter provides thermal images reflecting distribution of thermal properties, such as thermal conductivity of the sample, thus it makes imaging of some material parameters other than optical properties possible. Principle and structure of such a laser-thermal imaging system is described and images of ion implantation dose density in crystal obtained from this system are given.
This is a research report on developing a CCD long-range automatic collimator. It presents the application of a new photoelectric detector CCD to initial alignment of the inertial platform in launching large rocket and space craft and describes the principles of the system, design features, and the key technique analysis. Finally, the measured results and applications of the prototype are presented.
This paper reports a novel type of photoelectronic imaging system consisting of laser, image intensifier, secondary electron conduction (SEC) camera, computer, image sample, and hold system, then it sets forth operational principles of the system imaging fluorescence under the control of a computer. Experiment studies on fluorescence detection of biologically organized structure and latent fingerprints also are presented, and a satisfactory result of fluorescence image is obtained. For the use of a first GEN intensifier and integration ability of the SEC target, the system can realize excellent sensitivity and image even in a 10-7 lx illumination environment. Compared with a traditional fluorescence microscope system, the system developed in our laboratory has many good features that the former does not have, such as ultra-high sensitivity, convenience of image processing, quantitative measurement, and display of the spatial distribution of fluorescence intensity.
There are some delay elements in photoelectronic imaging processes, such as phosphor screen, photoconductive target, etc., and these lead to the time delay. The former originates from the transience capture of carriers which is produced before recombination luminescence in the luminous crystal excited process, and the time dispersion of the electrons release in trap level determines the delay of the luminous delay process. Whereas, the latter originates from the lifetime dispersion of semiconductor minority carriers and the capacitive delay of scanning electron beam charging the target. It can be fairly well verified by theoretic analysis and experiment that photoelectronic imaging delay can be approximately divided into: proportionality functional delay type, exponential functional delay type, and hyperbolic functional delay type. The three kinds of delays have different temporal modulation transfer functions. In this paper, we give the concrete analysis of them.
A mathematical model for the visual range prediction of thermal imaging systems, various factors affecting the visual range, as well as the relevant methods of computation are the topics covered. It is suggested that further revision is needed in consideration of the non-linear change of power versus temperature difference when the observed targets are involved in larger temperature difference cases. The concept of equivalent temperature difference is proposed.
The threshold detectivity of I2-CCD is studied based on the new concept of TV signal modulation transfer (STF) and noise modulation transfer function (NTF). The image detective ability equation of I2-CCD is established using the STF and NTF, as well as the theory of image threshold detectability. The detectability of I2-CCD cameras under several different conditions are calculated according to the equation. The theoretical calculation results fit well the experiment results. After analyzing the theoretical results several means to improve detective ability of I2-CCD are available.
We developed an infrared/visual image tracking system. The system consists of a longwave FLIR and TV camera combined sensors, a special image processing system, and some other subsystems. The system passed some field tests. Targets such as airplanes, tanks, and cars were detected, recognized correctly, and tracked stably during day and night. The system might track 15 targets in the field of view simultaneously.
A CCD camera system has been constructed and is in regular use at the Yunnan Observatory. A Texas Instruments-Japan 1024 X 1024 CCD is employed. The TI-Japan CCD is a virtual-phase with high quantum efficiency, 8 electrons rms readout noise, and excellent charge-transfer properties under low-level light. The CCD controller is designed to operate with multi-functions, the pixels of CCD can be binned into any format. The dewar is cooled by a three stage thermoelectronic device.
Video signal-to-noise ratio (SNR) is an important combination performance index of the low light level (LLL) camera, test and analysis on it play a very important role in evaluating and designing new LLL cameras. It is an innovation in our teaching and research section that we test video SNR by using digital storage oscilloscope (DSO) combined with a computer and set up a perfect LLL camera signal and noise property test and analysis system. Using this system, we test and analyze the signal and noise properties of the `variable integration low light level CCD camera' which our teaching and research section developed.
The structure of CCD imagers and peculiarities of their operation modes allows us to realize the control of such CCD characteristics as sensitivity and resolution, and to minimize spurious signals from image sensors which appear in the image detection process. In many cases there is an apriory information about parameters of dynamic images, for example, the velocity vector or the law of objects brightness variation, allowing us to optimize CCD sensor operation mode. The following control methods of CCD imager characteristics are considered in the paper: (1) shift compensation methods, time delay and integration mode, which are met for detection of moving objects images; (2) increase methods of time resolution of CCD imagers which are aimed at quick process detection; (3) control methods of CCD sensitivity in the integration process for the false components rejection in the image caused by insufficient field frequency. Experimental data obtained during the research of considered methods are given in the paper.
High quality amorphous silicon carbon (a-SiC:H) films with the wide bandgap of 2.4 eV are developed by using rf glow discharge deposition from highly hydrogen diluted C2H4 and SiH4. It has been shown that multi-layer photo-diodes using a-Si:H and a-SiC:H tend to have higher gain than 10, and special constructions of three multi-layers presented switching phenomena like a thyrister switch.
A kind of photoemissive thin film which can be exposed or stored in the atmosphere and can be used again in a vacuum system without any activation process for laser pulse detection is presented. They are different from usual photoemissive materials, since they do not contain alkali elements. They consist of metallic oxide thin film or other material thin film embedded with metallic ultrafine particles. A main interesting material is barium oxide thin film embedded with Ag ultrafine particles. This thin film can detect single laser pulse or laser pulses with high repetition frequencies (approximately 108 pulses/sec.), pulse duration ns to ps, and energy mJ to nJ per pulse.
We present the spectral curves of the photoemission from biased semiconductor heterostructures with Schottky barrier InGaAs-InP-Ag in the region of spectrum up to 1.7 micrometers and consider the main processes that determine the efficiency of photoemission from such structures. We also present the characteristics of dark-current emission from InGaAs-InP- Ag heterostructures and show that it is connected with thermal generation of electrons in the space charge region of InGaAs near the interface.
Photoemission stability of the negative electron affinity (NEA) GaAs-(Cs,O) photocathode activated with several cycles of alternate Cs and O2 adsorption at room temperature is mainly determined by the stabilization of the cesium and oxygen adlayer on the GaAs surface, and the bonding strength between this adlayer and the GaAs substrate. It is found that the light treatment (incident white light illumination) during or after the Cs and O2 activation process can improve the emission stability of the NEA GaAs-(Cs,O) cathodes. It is also found that the emission stability of the NEA GaAs-(Cs,O) cathodes is closely related to the electronic states of cesium and oxygen before being adsorbed on the GaAs surfaces, best result being obtained with cesium ions and excited oxygen molecules. In addition to the activation procedure and experimental results, some photoinduced reactions, e.g., photoinduced adsorption, desorption, excitation, dissociation, ionization, and surface migration and surface rearrangement of the cesium and oxygen adsorbates on or from GaAs surfaces are analyzed, and their effects on the emission stability of the NEA GaAs-(Cs,O) photocathodes are discussed.
We examine the basic design issues in the optimization of a GaAs delta-doped quantum well avalanche photodiode structure using a theoretical analysis based on an ensemble Monte Carlo simulation. The device is a variation of the p-i-n doped quantum well structure previously described in the literature. It has the same low-noise, high-gain, and high-bandwidth features as the p-i-n doped quantum well device. However, the use of delta doping provides far greater control of the doping concentrations within each stage possibly enhancing the extent to which the device can be depleted. As a result, it is expected that the proposed device will operate at higher gain levels at very low noise than devices previously developed.
It is well known that the defects of the GaAs-Cs-O photocathode are the poor photoemission stability and short life at room temperature. All these defects are caused by cesium desorption from the photosurface. In this paper, for resolving the problem of cesium desorption, a new surface activation material Cs-Sb is proposed to take the place of Cs-O for reducing the cesium release from the GaAs surface. From the experimental results, the following conclusion may be obtained: using the Cs-Sb to replace the Cs-O covering the GaAs surface, the stable negative-electron-affinity (NEA) photoemitter can be prepared.
A traveling rib-waveguide structure is proposed for single sideband (SSB) modulation. A low- loss parabolic taper is designed to transmit a large infrared laser beam (10 micrometers ) into a narrow channel at an optimal length of 7500 micrometers where the taper opening is 242 micrometers and the rib-channel width is 100 micrometers . The propagation loss of one taper is about 5 to 10%, and this has been confirmed by experimental results.
The effects of vacuum-baking on the chemical state of CsI photocathodes are studied with x- ray photoelectron spectroscopy (XPS) in this paper. The experimental results indicate that when the vacuum-baking temperature is below 180 degree(s)C the chemical states of CsI photocathode are stable, but there is a sublimation of CsI with low rate in high vacuum. When the vacuum-baking temperature is higher than 180 degree(s)C, chemical shifts will occur.
Use of an optical local oscillator for coherent detection with a photoconductor or a photodiode can significantly reduce the responsivity of the detector due to saturation effects. Consequently, local oscillator shot noise limited operation of the detector may not be possible. However, a local oscillator power level can be selected that maximizes the signal to noise ratio.
Silicon photodiodes, photoelectric transistor, and other silicon photoelectric devices have many advantages such as high response speed, good linearity of current vs. illuminance, high quantum efficiency over a wide spectrum range, and long life. However, a whole class of photoelectric detectors is based on low dark current. For example, silicon vidicon, silicon blue sensitive photodiode (SPD) and its integrated amplifier, and silicon photoelectric array have special features which depend on dark current. The dark current must be kept low enough. The reduction of the dark current was investigated by the author in making SPD. Dark current can be ascribed to the following causes: diffusion current, extended defects and generation current on the surface and junction depleted layer. The diffusion current is the unavoidable contribution to the dark current. Extended defects in active zones once decorated by metal atoms bring about an increase of dark current. Generation current plays an important part in dark current. Therefore, it is important to reduce density of the generation center and metal atom in surface and junction to obtain low dark current. HCl treatment, gettering techniques, etc., are the efficient methods. The author has improved HCl oxidation, intrinsic gettering, phosphorus diffusion gettering, and Si3N4 film deposition to obtain further reduction of dark current.
The post-annealing effect in HgCdTe photodiodes ((lambda) c < 3 micrometers ) has been reported. After the post-annealing proceeding, the current responsibility of the photodiodes has no change. However, the noise current of the photodiodes has considerable changes. For the photodiodes with small noise current (in < 300 fA) before the post-annealing, the noise current increases after the post-annealing; for the photodiodes with big noise current (in > 300 fA) before the post-annealing, the noise current obviously reduces. The probable mechanism has been analyzed.
Optimum thickness of polycrystalline semiconductor multialkali photocathodes is studied by the exponential attenuation rate of the radiation intensity and formulas for the quantum yield spectra and optical absorption coefficient of multialkali photocathodes. It has been found that if I(alpha )/IO > 0.4, photocathode optimum thickness D will be in excess of around 1000 angstroms and if I(alpha )/IO increases further, D will tend to increase too, while photoelectrons excited by energetic photons will appear in the inner surface of the photocathode. Furthermore, D should be in the vicinity of 300 angstroms for the first kind of photocathode (S-20, S-20R, and S-25) and 900 angstroms for the second kind of photocathodes (new S-25, Varo, and LEP). It is suggested that the optimum photocathode thickness D be studied by the spectral response peaks of multialkali photocathodes. We came to the conclusion that photoelectron escape depth and incident wavelength tends to increase and along with it the optimum photocathode thickness. It has been calculated that the optimum thickness of multialkali photocathodes possessing good response in visible and infrared light must be in the vicinity of 1200 angstroms.
A new magnetic focusing streak tube with a traveling wave deflection electrode has been developed. In the operation, a pulse voltage is applied between the photocathode and the accelerating mesh electrode. The limiting time resolution of approximately 180 fs has been experimentally obtained.
A high definition x-ray image intensifier (II) has been developed which has a 60 mm large diameter output phosphor screen. This new tube also has another improvement in conjunction with the output phosphor screen, electric lens, and input phosphor screen, it resulted in more than 50% higher resolution than conventional types.
For lack of sensitivity, conventional HDTV cameras can't obtain satisfactory picture quality. A super-sensitive HDTV camera tube, HARPICON (10 times as sensitive as the Saticon), and a new camera tube (more sensitive than the HARPICON) are proposed. The later combines a microchannel plate (MCP) as the electron image storage, a field emission array cathode (FEAC), and high-performance electron-optics. The performances of two experimental Saticon are also given in this paper.
The primary feature of x-ray image intensification is to allow a substantial reduction of the necessary x-ray dose, by offering a luminance gain of about 104 compared to direct view fluoroscopic screens. Such a luminance gain has made possible real time video recording and display of radiological images, by optically coupling a video camera to the output of the screen of the XRII tube. However, the observable field of view of the XRII was initially limited to approximately 15 cm, and the image resolution was not as good as the resolution achievable with radiological films. Progressively, the size of XRII tubes has been increased, and modern tubes can offer useful image diameters up to 40 cm. In addition to that, the electronic zoom, introduced at the beginning of the seventies as a feature of the XRII tubes, allowed the user to achieve an observable resolution very close to that of the radiological films, but at the expense of the observable field of view. Continuously, the manufacturing technology of the most critical parts of the XRII tubes have been improved resulting, for modern tubes, in such an imaging quality that most of the radiological modalities of diagnostic are directly achievable through video observation. Furthermore, the recent progress made in electronics and image processing offers powerful means to make the best possible use of the electronically recorded radiological images. A review is made, hereafter, of the latest progresses in XRII performances and applications.
Our research has been performed by aiming at the measurement in the extreme regions, such as at extreme low light level or ultra high speed. Image tubes are key devices for these purposes, therefore two-dimensional low light level detection tubes and streak tubes have been developed. The low light level detection tubes have realized imaging in the photon-counting region, and the streak tubes have reached the femto second temporal resolution range. These devices have been utilized in various fields.
In this paper, a newly developed gateable SEC tube is presented. Structure, operating principle, and performance of the tube are introduced in detail. Features and preparation of a new mesh-supported target are described. An experiment system, in which combination of selectable switching on and integrating capability of the new gateable SEC tube is used for fluorescence image detection, is given.
A novel experimental x-ray image intensifier tube with simple catadioptric electron optics is presented and its imaging properties are analyzed theoretically by the use of a few simplified relations. The introduction of catadioptric electron optics in an x-ray image intensifier makes it possible to use a unique output phosphor structure which alleviates the imaging defects suffered by most conventional state-of-the-art x-ray image intensifiers. Several important advantages of the novel intensifier are exemplified. A brief theoretical analysis of the x-ray conversion factor, signal-to-noise ratio, modulation transfer characteristic and other imaging properties of the new tube is given to indicate the improved performance that can be realized by the new intensifier. Preliminary results obtained from an experimental tube with a diameter of 18 mm are presented to verify the theoretical analysis and predict the performance of tubes with larger diameters. The characteristics of the x-ray images of test objects recorded with the experimental tube coupled with a relay lens to a CCD camera and video frame grabber are displayed and analyzed.
The article introduces a new type of x-ray wafer image intensifier with a double proximity focusing system, (Phi) 50 CsI-CsI/MCP photocathode, and a series of welding constructions of glass window or ceramic components with metal rings. This kind of x-ray image intensifier has been widely used in the field of medical diagnosis and industrial non-destructive detection by means of sophisticated portable x-ray diagnoscopes, featuring a number of satisfactory performances such as low x-ray dosage, miniature x-ray tube and power supply, high output brightness and good resolution, light weight, small volume, low cost, and easy operation without any condition constrained by working environment and illumination. In the paper, the authors have given a series of formulae to determine characteristic parameters of the device, i.e., the quantum detection efficiencies of both reflection mode (CsI/MCP) and transmission mode (glass window CsI/MCP) photocathode, the brightness conversion factor, and resolution. The relations of the mentioned parameters with the performances of constituent components, which include CsI photocathodes layer thickness, MCP bias angle and gain, phosphor screen conversion efficiency, and double proximity focusing distances, are also briefly analyzed. The analysis thought and methods mentioned in the paper have been successfully used for the optimal design and assessment work of our devices and shows that they have a good coincidence with experimental results.
The present paper applies a constrained variable metric method (CVMM) for the optimization design of image tubes with electrostatic focusing, and a multigrid method (MGM) for the computation of the electrostatic field in designing image tubes, thus to improve the efficiency of field computation and to reduce the time of computation. For the design of diode tubes, triode tubes, zoom tubes, and gated tubes, we have investigated the objective function having a least-square-fit form with weight factors to carry out the optimization computation. The result of optimization has shown that the suggested method for designing image tubes given in the present paper ia a practical and effective one.
The finite difference method (FDM) is used to compute electrostatic potential distributions in photomultipliers. New Fortran packages, using both successive over-relaxation (SOR) and incomplete Choleski conjugate gradient (ICCG) techniques, have been developed for solving the finite difference equations. The effects of the mesh size on the accuracy of the results and the difference between the two methods are highlighted. The electron trajectories are computed by direct ray tracing with a power series method. The software can handle electron transparent grids as well as dynodes. It has been used to characterize the performance of many photomultiplier tubes. The results agree very well with experimental measurements. In addition, the advantages of using three-dimensional field computation in the design of certain PM tubes are illustrated.
The all-electrostatic camera tube with pattern yoke is a new type of vacuum camera device. It has the following advantages: compactness, light weight, low power consumption, and variable scanning rate. The ultracompact camera tubes are able to compete with solid-state imagers. This paper introduces the method of design optimization of its electron optics system and describes the properties of a 2/3 inch, all-electrostatic camera tube designed and fabricated in our laboratory.
From the practical requirements of new astronomical photoelectronic imaging detectors, much attention has been paid to the design of new permanent magnet focusing field systems, in which curved input-image and demagnification are allowable. The constrained inverse design of the focusing magnetic field in electrostatic and magnetic imaging systems applying new permanent magnet materials is discussed and investigated using the constrained optimization constrained variable metric (CVM) method.
The family of widescreen Gen. I image intensifiers with a photocathode active area of 40 mm developed in the RADIAN R&D Centre is reported. There are four types of image intensifiers with different magnification (1:1, 1:0.62, 1:0.46, 1:0.33), monoframe gateable intensifier, streak tube, and a special chronographic intensifier in this family. The exclusive features of all tubes are extremely low in homogeneous distortion, the possibility to combine in different configurations for solving a wide set of scientific and applied tasks. The latest model of chronographic intensifier named SCANCROSS has unique parameters for registration of low intensive, shot light phenomena. This tube is most suitable for employment in laser remote sensing devices. All of those tubes have the possibility to operate either cw, or pulse regimes. Besides, they are relatively cheap.
To observe a waveform of a very fast photoevent, a special phototube is developed. A short photoelectron train produced by the incident light from the photoevent is stretched during its runs through a long drift electrode of the phototube due to the difference of the velocity of each photoelectron which is instantaneously accelerated by a step voltage of the photocathode rapidly raised during the light incidence. In order to discuss the limitation of the stretching operation the performance of the phototube such as spreading of the pulse width, influence of the electron lens, both induction noise and random noise are described. As a consequence the time resolution is estimated to about 10 ps at present.
For fast photon counting cameras and their applications, present centroiding electronics are not fast enough to match the pixel rate. We are designing a new architecture for the centroiding process. The basic principle is to select only the useful pixels where photoevents occur in order to compute the photocenters and to discard the others. The selected pixels are sent to a digital signal processor (DSP) for photocenter computations. The maximum photon rate is only limited by the DSP speed.
The performance of a TeKtronix scientific grade (Grade 1) CCD TK512CF with the METACHROMERII coating, applied as a detector for a solar spectroscopy, and the detailed description of the system configuration for operating the CCD are presented in this paper. The laboratory evaluation is made to the chip and the system prior to its installation on the solar spectrograph. Both the lab test and solar observation results show that the chip is a prospective powerful detector for modern solar spectroscopy.
A kind of specially designed MOS image sensor (IS) with high sensitivity is introduced in the paper. The IS is used to receive moire signals to form a phase-modulated signal. With dynamic phase discriminating and subdivision, a very high resolution and precision can be achieved. This special image sensor is valuable in practical designing of high resolution (<EQ 0.1 micrometers ), high precision, and low cost grating displacement transducer.
This paper introduces an auto-photoelectronic instrument for evaluating the surface defects of the optical parts inside an optical instrument. By analyzing the effects of defects on image quality, we can present the possibility of evaluating the surface defects and its damage objectively and quantitatively by measuring stray-light. Detailed discussion is given about the physical procedure for generating and measuring stray-light. On the basis of this theoretical research a new type of auto-photoelectronic instrument used to evaluate the defects on the optical surface inside the optical system is given. In this instrument the technology of photoelectronics and microcomputer is applied, so a test result is given automatically.
Operation principles of the detection of radiation direction of a CO2 pulsed laser by the use of pyroelectric camera are described. The basic analysis, computation, and field test results are given, some theoretical and technical problems as well as some potential applications are discussed.
This paper describes a measurement system for scanner linearity of angle vs. time. Because the techniques of pinhole filter, high-speed data acquisition, and CCD elaborate division have been successfully used, the system has a high measurement accuracy (2 micrometers ) and powerful data processing capacity.
In this paper we have deduced the theoretical formulae which describe the correction of detectivity nonuniformity introduced by cooling -- nonuniformity of the detector array, and we point out that the fixed pattern noise arising from the difference of D* may be corrected by amending the magnification of each detector element respectively. However, the color noise relating spectrum distribution of input image and spectrum detectivity nonuniformity of the detector element cannot be corrected by a similar method. According to the varying tendency of D* ((lambda) , T) in different temperature, we have explored the method of the cut-off filter, which makes use of the linear relation between D* ((lambda) , T) and T in certain spectrum range, and the probability of removing color noise arising from cooling nonuniformity. We have also analyzed the characteristic of this method and its limitation of practical applicability.
The importance of 2-D photo-electronic measurement has been discussed. A new method to realize 2-D displacement and angle measurement with only one linear CCD array is given. And a low price, high performance 2-D real-time photo-electronic autocollimator is designed.
With the recent development of modern mechanical industry, automatic inspections have been playing more and more important roles. Optoelectric inspection is a major one among them. This article is to discuss a system which can inspect contour sizes of mechanical components in real time by using the method of optoelectric image. This system adopts the methods of optical projection of the `tolerance zone' of components as well as image preprocessing and analysis. According to the different positions of the reflector group, a variety of parameters of a component, such as outer diameter, length, width, height, taper, and thread can be measured. In this article, we first discuss the structure of the system and then analyze its principle and applications in inspecting outer diameter, taper, and thread. In this inspection system, we use image processing and analysis in the process of automatic inspection. We control the complete system and the processing of information with the help of a computer so that the high speed and high precision are obvious. Meanwhile, due to the optoelectric method in getting optical information, the system is of noncontact inspection. And also it can inspect several parameters of a component at the same time since it adopts projection of the tolerance zone of components. For the same reason, the inspection efficiency is high and the system can be made compact.
After discussing the principle of CT technique, the paper develops a thermometry to measure the temperature field of combustion flame, using CT and middle IR spectrum fiber technique. In addition, the temperature distribution of a practical flame temperature field, obtained by the system dependent on the method, demonstrates the feasibility of the method.
The small, put-in, optical testing head described in the paper is available to detect the inner surface defects in a deep hole. It is composed of the following advanced techniques: CCD camera, step motor, grating displacement measurement unit, etc. It can be put in a hole thats diameter is larger than 40 mm and can scan in axial and diametrical directions, recording the image by intermittent CCD camera. The detecting position and image data can be memorized by computer to analyze and process. The resolution of the testing head is better than 0.04 mm.
A fingerprint is reliable evidence for recognizing criminals in detecting cases. There are many conventional chemical and physical methods in detecting fingerprints. In this paper, a newly developed portable TV system for detecting a latent fingerprint is described. This system is suited for field reconnaissance of cases as well as for laboratory testing. It can display a latent fingerprint, which is hard to identify and even cannot be displayed by conventional methods, and it can detect prints or stamps which are faded, altered, or falsified, etc.
Information product qualitative forming and effective use is the aim of any information technology. Information technology as a system provides both computer-aided problem solving for the user and automation of information processes, which in turn support the problem solving process. That's why the information technology methods are the methods for data transmission, processing, and storage. The tools of methodology, mathematics, algorithms, hardware, software, and information are the tools of information technology. We propose to differ between global, basic, and applied information technologies depending on information product significance and characteristics of models, methods, and tools used. The global technology is aimed to use information resources in the social sphere as a whole. The basic technology is oriented on the application sphere (industry, scientific research, design, training). Transition towards new information technology should have in its concern business area model merged with the formal model of problem solving: computing organization based on the data concept; user's intellectual interface development.
Methods of analysis and calculation of chromater thresholds for a multizone image processor have been discussed. Functions of radius-vector sensitivity to variations in color separated signals within color space have been established. The results obtained allow us to describe the procedure of forming windows with minimum dimensions preassigned by probabilities of correct identification of image elements by their chromaticities. Calculation procedures are exemplified and the structural schemes of components which have been used in synthesis of color image recognition systems are demonstrated.
We present the focal instrumentation set up on the 2-m telescope at Pic du Midi, France developed to achieve third order aberration corrections on turbulence-degraded images using a photon-counting detector, a wavefront sensor, and a deconvolution method. This instrument is called DIVAS for visible image deconvolution using wavefront analysis. Our goal is to determine the necessary compromises to adopt in order to obtain high resolution images of low luminosity objects recorded in a photon-counting mode. In addition to the recording of short- exposure images at the telescope focus, a wavefront sensor measures simultaneously the incoming distorted wavefronts. In post-processing, the optical transfer function is calculated from the phase retrieval. The object is then reconstructed through a deconvolution process of the short-exposure images with the corresponding point spread functions.