Low level light(LLL) image contains rich information on environment details, but is easily affected by the weather. In the case of smoke, rain, cloud or fog, much target information will lose. Infrared image, which is from the radiation produced by the object itself, can be "active" to obtain the target information in the scene. However, the image contrast and resolution is bad, the ability of the acquisition of target details is very poor, and the imaging mode does not conform to the human visual habit. The fusion of LLL and infrared image can make up for the deficiency of each sensor and give play to the advantages of single sensor. At first, we show the hardware design of fusion circuit. Then, through the recognition probability calculation of the target(one person) and the background image(trees), we find that the trees detection probability of LLL image is higher than that of the infrared image, and the person detection probability of the infrared image is obviously higher than that of LLL image. The detection probability of fusion image for one person and trees is higher than that of single detector. Therefore, image fusion can significantly enlarge recognition probability and improve detection efficiency.
For the purpose of coloring the night-vision images captured by low-light image intensifiers or infrared thermal imagers, color transfer algorithms were used to transfer natural colors to these gray images. Most of the color transfer algorithms can be divided into two classes: global color transfer and point color transfer. In global color transfer algorithms, the means and variances of the initial false color image were adjusted according to those of the reference color image. In point color transfer algorithms, the matching points were determined between the grayscale image and the reference color image. These two kinds of algorithms are always carried out in two common color spaces: YUV color space and Lab color space. The color space influences the performance of the color transfer algorithms. In this paper, several typical color transfer algorithms, including basic ones and multi-resolution ones, were carried out in different color spaces. The results show that global color transfer algorithms perform better in the YUV color space and the Lab space is more suitable for point color transfer algorithms. The biggest difference between these two color spaces is that the correlation between the channels of Lab space is much lower than that of YUV space. The global color transfer algorithms adjust the color components of the initial false color image with a uniform conversion, linear or non-linear ways. This process can benefit form the correlation between the channels, which is much higher in YUV space. However, the coloring process of the point color transfer algorithms is independent from the points matching process based on grayscale. This is the reason why the point color transfer algorithms should be implemented in the Lab space.
Low light level video is an important method of observation under low illumination condition, but the SNR of low light level video is low, the effect of observation is poor, so the noise reduction processing must be carried out. Low light level video noise mainly includes Gauss noise, Poisson noise, impulse noise, fixed pattern noise and dark current noise. In order to remove the noise in low-light-level video effectively, improve the quality of low-light-level video. This paper presents an improved time domain recursive filtering algorithm with three dimensional filtering coefficients. This algorithm makes use of the correlation between the temporal domain of the video sequence. In the video sequences, the proposed algorithm adaptively adjusts the local window filtering coefficients in space and time by motion estimation techniques, for the different pixel points of the same frame of the image, the different weighted coefficients are used. It can reduce the image tail, and ensure the noise reduction effect well. Before the noise reduction, a pretreatment based on boxfilter is used to reduce the complexity of the algorithm and improve the speed of the it. In order to enhance the visual effect of low-light-level video, an image enhancement algorithm based on guided image filter is used to enhance the edge of the video details. The results of experiment show that the hybrid algorithm can remove the noise of the low-light-level video effectively, enhance the edge feature and heighten the visual effects of video.
UV(ultraviolet) image intensifier is a vacuum image device with Cs2Te (Cesium Tellurium) photocathode. It converts the incident ultraviolet(UV) light from the optical lens into electronic signal, then the electronic signal is converted into responding visible image on the phosphor screen. Defects of different sizes can be seen on the screen when it works. A system is build to inspect the distribution of the defects, then the sources and category of the defects of the view field are analyzed, including photocathode, microchannel plate and phosphor screen, some improving technique is brought to decrease the defects.
Aiming at the uncertainty of traditional 3D video capturing including camera focal lengths, distance and angle parameters between two cameras, a red-blue 3D video fusion system based on DM642 hardware processing platform is designed with the parallel optical axis. In view of the brightness reduction of traditional 3D video, the brightness enhancement algorithm based on human visual characteristics is proposed and the luminance component processing method based on YCbCr color space is also proposed. The BIOS real-time operating system is used to improve the real-time performance. The video processing circuit with the core of DM642 enhances the brightness of the images, then converts the video signals of YCbCr to RGB and extracts the R component from one camera, so does the other video and G, B component are extracted synchronously, outputs 3D fusion images finally. The real-time adjustments such as translation and scaling of the two color components are realized through the serial communication between the VC software and BIOS. The system with the method of adding red-blue components reduces the lost of the chrominance components and makes the picture color saturation reduce to more than 95% of the original. Enhancement algorithm after optimization to reduce the amount of data fusion in the processing of video is used to reduce the fusion time and watching effect is improved. Experimental results show that the system can capture images in near distance, output red-blue 3D video and presents the nice experiences to the audience wearing red-blue glasses.
A novel concept for solar cell technology, photon-enhanced thermionic emission (PETE), was proposed for harvesting photonic and thermionic energy simultaneously. Researches show that the conversion efficiency of PETE is pretty high, calculated efficiencies for idealized devices can be above 50%, which is exceed the theoretical limits of single-junction photovoltaic cells. To explore whether the vacuum device can exhibit good performance under the conditions that combines illumination and heating, a multi-alkali vacuum photodiode is used as a quantum and thermal energy converter. The band gap of multi-alkali cathode is 1.1eV and the multi-alkali photocathode is employed at temperature below 350K.The current-voltage characteristic curve is measured under two different temperature conditions, so is the power-voltage curve. And the conversion efficiency of the multi-alkali vacuum photodiode is also calculated on the basis of experiment data. The experiment results show that the power converted by a heated and illuminated condition is greater than that obtained under illumination at room temperature or heating without illumination. The conversion efficiency of the multi-alkali vacuum photodiode is higher than that not be heated. This paper shows that the multi-alkali vacuum device presents better performance under the combined conditions. Although the power production and conversion efficiency are not very high in this research, the experiment demonstrates how the two forms of quantum and thermal of solar energy can be simultaneously utilized.
High-energy area source electron gun is a key component in image intensifier screen testing instrument. On the basis of
the analysis of relationship between thermal emission characteristics, the shape of filament and the density of thermal
electron emission, high-energy area source electron gun is designed. The distribution of electric field and electronic
tracks are theoretically analyzed and calculated to make it has features of dispersing, uniform, converging and
submerging. By testing a standard screen, correct the structure of high-energy area source electron gun to meet the
requirements of test indexes and obtain reasonable high-energy area source electron gun. Its successful development
provides effective technical support to the luminous screen test for uniformity, brightness, luminescence efficiency and
afterglow and to the examination of other components (such as MCP parameters)of Low-light Image Intensifier.
In the field of applied optics, the evaluation of imaging quality in optical systems has been a problem of public attention.
From the 1970s, with the development of the large-capacity high-speed digital computer and improvement of
high-precision optical testing technology, the calculations and measurements of MTF are maturing and began to promote
the practical application. After years of development, The MTF has been an important evaluating indicator of image
quality of an optical system.
A test system of MTF is designed in the paper; theoretical study related to the MTF testing is introduced, such as
specifying the physics concept of MTF, summarizing the testing methods of MTF and analyzing the testing principle. On
the base of introducing the theory which are related, the framework of system has been established. The devices which
are used in the experiment are also introduced. Testing software has been developed. How to manipulate the testing
system is introduced and the factors which affect the result are pointed out. The experiment is carried out to measure the
optical lens sample in the axis, and the result is given.
To test the parameters of image intensifier screen is the precondition for researching and developing the third generation
image intensifier. The picture of brightness uniformity of tested fluorescence screen shows bright in middle and dark at
edge. It is not so direct to evaluate the performance of fluorescence screen. We analyze the energy and density
distribution of the electrons, After correction, the image in computer is very uniform. So the uniformity of fluorescence
screen brightness can be judged directly. It also shows the correction method is reasonable and close to ideal image.
When the uniformity of image intensifier fluorescence screen brightness is corrected, the testing instrument is developed.
In a vacuum environment of better than 1×10-4Pa, area source electron gun emits electrons. Going through the electric
field to be accelerated, the high speed electrons bombard the screen and the screen luminize. By using testing equipment
such as imaging luminance meter, fast storage photometer, optical power meter, current meter and photosensitive
detectors, the screen brightness, the uniformity, light-emitting efficiency and afterglow can be tested respectively.
System performance are explained. Testing method is established; Test results are given.
This article describes the generation of the laser facula, and analyzes the energy characteristics of the facula. A testing
device is designed to measure the facula of the laser light in the far distance, and the system can collect and analyze the
laser facula. The testing system sets by the laser ranger finder, thousands of meters away from the target. A near infrared
CCD (Charge Coupled Device) camera of high sensitivity is used to collect the facula of 1.06μm laser. Add a filter of
1.06μm before the CCD camera to get more accurate infrared information. A beam of the laser ranger finder shoots to
the target. A infrared CCD and the laser ranger finder is synchronizing triggered. For real-time observation of the
background, the system use another ordinary CCD and telephoto lenses. A series of laser facula which is collected by the
infrared CCD is stored into computer as the form of bitmaps. The testing device uses median filter to denoise the facula
pictures and use image processing to analyze the gray-scale of facula, thus the device can get the intensity distribution,
the centroid position and its variation with the spot. The device uses image fusion to realize the background integration
of white-light CCD and infrared CCD images.
The paper introduces the structure of Cs2Te ultraviolet image intensifier. The manufacturing procedure is introduced
briefly, include the procedure of front group and back group. Its spectral response characteristic is measured with a
specially designed spectral response measuring system, the quantum efficiency is calculated, the diffusing length of the
minor carriers is analyzed. Some other parameters are tested with testing devices. At last some opinions are brought to
improve the technique.
Gallium Nitride (GaN) photocathodes are potentially attractive as UV detective materials and electron sources. Based on
the activation and evaluation system for GaAs photocathode, which consists of ultra-high vacuum (UHV) activation
chamber, multi-information measurement system, X-ray photoelectron spectroscopy (XPS), and ultraviolet ray photoelectron
spectroscopy (UPS), the control and measurement system for the activation of UV photocathodes was
developed. The developed system, which consists of Xenon lamp, monochromator with scanner, signal-processing
module, power control unit of Cs and O source, A/D adapter, digital I/O card, computer and software, can control the
activation of GaN photocathodes and measure on-line the spectral response curves of GaN photocathodes. GaN materials
on sapphire substrate were grown by Metal-Organic Chemical Vapor Deposition (MOCVD) with p-type Mg doping. The
GaN materials were activated by Cs-O. The spectral response and quantum efficiency (QE) were measured and
calculated. The experiment results are discussed.
When testing the uniformity of Image intensifier fluorescence screen brightness, the million scale CCD brightness meter
is used. Due to the distance between the meter and fluorescence screen, the effect of ambient light on the testing result
is essential to the design of testing system. Test with super second generation tube, input a constant voltage to insure the
fluorescence screen brightness to be constant. Collect the brightness of the same fluorescence screen in different ambient
luminance environment of 1×102Lx, 1×101Lx, 1Lx, 1×10-1Lx, 1×10-2Lx, 1×10-3Lx. Study the results with software
MATLAB. It is concluded as: In ambient luminance environment of 1×10-1Lx the CCD has the best result. The
testing result in ambient luminance environment of above 1×103Lx show untrue image. The testing result in ambient
luminance environment of below 1×10-3Lx shows its own noise image and is unbelievable either.
Fluorescence screen of Image intensifier is the key part to imaging quality of micro light and ultraviolet Image
intensifier. To research the performance testing and analysis of Fluorescence screen seems more important in China. The
research will help to understand the performance of Fluorescence screen, know where improvement should be made
and then a best performance entire tube will be achieved. This article will do the theory analysis to part of testing
instrument, area source electron gun's uniformity. Electron gun consists of taper tantalum filament, vacuum environment
and axial symmetry high pressure static field. The uniformity of hot electron emission of filament has been analyzed.
Upon that, this article will specially analyze the uniformity of electron in the effective area after they go through the axial
symmetry high pressure static field and get accelerated.
This article introduces motion detection and estimation of low-level-light video sequence, and, motion detection, motion
estimation and variational problem. Low-level-light video sequence different form others, the time and space domain
noise in the signal not only limit the lowest illuminance of the system but also make the image show random glitter. In
this paper how to improve the signal-to-noise ratio (SNR) of low light level image is discussed too. The results show that
models and estimation algorithms in low-level-light video sequence can lead to improve reliability and accuracy of the
The three elements of photoelectrical cathode, microchannel plate and fluorescence screen are important parts to imaging
quality of low light and ultraviolet Image intensifier. To do research and analysis work on the Fluorescence screen
parameter testing have practical significance to the understanding of the performance of fluorescence screen and then can
help to know where improvement should be made and then achieve a best performance entire tube, This article mainly
introduce the testing theory of the brightness uniformity of fluorescence screen of Image Intensifier and how to build a
The novel approach to the image noise problem of reticle images based on impact condition in low-level-light weapon
sight is proposed in this paper. The condition and process of the low-level-light weapon sight impact experiment were
analyzed, and then averaging algorithm of reticle images consists of two parts has been applied on the experiment. First
averaging and smoothing using a rotating mask methods were operated on Gaussian noise, to obtain a matching precision
with in 0.05 mil. Second the well known efficient median filtering smoothing method is performed to obtain the higher
matching precision. The potential of this averaging method is shown in the experimental results of reticle images in low-level-light weapon sight based on impact condition.
The edge detector operator of image intensifier is a key problem for fluorescent image processing. This paper is intended
to serve for three purposes: (1). To present the general problem of Fluorescent image in a sufficient depth and extent, (2)
to present a complete algorithm for image processing including image sharpening and gradient operator. (3). to search
for a edge detector optimal for fluorescent image processing of image intensifier. It is expected that a edge detector
operator could provide a generic and robust solution to the reticle fluorescent noise images matching problem, which
could be an important breakthrough in computer vision, photogrammetry, and pattern recognition.
The responding time delay characteristic of the detector of PIN photodiode is caused by the different intensity of the signal received by the detector. The responding time delay usually is less several tens nano-seconds. Aaccording to the principle of the responding time delay, the testing system is designed to measure the responding time delay. The test of responding time delay with different laser powers is carried on, and the result of the responding time delays is given.
The x-ray imaging technology has been improved greatly since Roentgen discovered x-ray in 1895 and it is very important in some fields such as medical treatment, nondestructive test and industrial detection. At present, there are many kinds of x-ray imaging technologies based on the different image detectors. To meet the requirement of real time observation, digital image processing and long-distance communication, digital radiography (DR) and direct digital radiography (DDR) are advantageous. The image intensifier is often used by large number of hospitals due to its affordable cost. As the key device of the x-ray imaging system, the conventional x-ray detector is mainly imported from Japan, or France because there is no domestic manufacture, which increases the cost of the whole x-ray imaging system, moreover the imported x-ray image intensifier has 9 inch visual field, thus limiting its application in some fields further. By combing the x-ray imaging technology and the low light level (L3) imaging technology, our research group designed the novel combined x-ray image intensifier, which means it is composed of the x-ray intensifying screen, zoom lens and the L3 image intensifier. In this paper, the principles on how to match the components of the x-ray image detector and how to design the structure of the x-ray image detector are introduced. At the end of the paper, the imaging performance of the x-ray image detector is given by showing the produced images and the MTF curve of the whole x-ray imaging system, which proved that the novel combined x-ray image intensifier is a good choice for many users and can be applied in many fields, such as the medical treatment, nondestructive test and industrial detection and even takes the place of the conventional x-ray image intensifier in some application fields.
In this paper we review simply the surface models. These models have several technical problems not solved appropriately except for having deficiency themselves. So we present a new negative electron affinity (NEA) photocathode photoelectric emission model: [GaAs (Zn): Cs]: O - Cs. After discussing photocathodes activation technique on the model, we design a activation technique, which increases the Cs current to decrease the first peak in appropriate degree after using smaller Cs current to achieve the first peak of photoemission (GaAs (Zn)-Cs dipole layer), then set out Cs-O alternation and do not end the technique until gaining maximal photoemission (Cs-O-Cs dipole layer), in the photocathodes with GaAs (Zn) (100)2×4 reconstruction surface. In the present material configuration and level of technique, it is difficult that the integral sensitivity of cathode excess 3500 μA/lm. However, it is likely to excess 4000 μA/lm by varied doping As-rich GaAs (Zn) (100)2×4 reconstruction surface.
The combination photo electronic sighting device usually composed of different optical devices, including telescope and low light level night vision device or infrared thermal imaging system. Every optical axle of the optical device of the combination sighting device is needed to be parallel. When a target away enough from the sighting device is observed, if the images of the target locate on the center of the field of the vision of the different optical devices, it shows that the axis are parallel. According to this principle, a rectifying device for optical axis of sighting device is designed. It includes off-axle paraboloid reflector, the target of cross line, light sources, precision modifying devices and other devices. The target of cross line is put on the focus of the off-axle paraboloid reflector, thus it forms a parallel light beam through the off-axle paraboloid reflector, the sighting device is immerged in the parallel light beam. The observing effect is like a target of long distance. The target is connected with a precision modifying device, by moving modifying device, until the image of the target coincide with the center of the field of vision of every optical device, whose degree of deviation of the optical axle can be calculated. The paper gives the structure of the rectifying device and the way of testing. The parameters of the device is given too.
The paper introduces the principle and structure of the PIN diode detector, and then describes the researching background and the responding characteristic of the detector. The high responsibility of photodiode response characteristic is important. The paper designs a set of testing device to measure the responsibility. The optical part can produce a laser pulse of 1.06μm with a certain frequency and energy, with the aid of white light source and CCD camera, the laser beam can focus on the surface of the photon detector of PIN diode. The signal-testing instruments can measure the responding characteristic of the photon detector, and the average noise power. The paper gives the waveforms of the laser pulse and the responding signals.
This paper discusses a safety inspection system that applies x-ray technology to check passengers on some important sites, such as airports. In the actual inspection, passengers are required to take off their shoes to be checked at the airports. This system will realize instant inspecting function, utilizing the x-ray’s penetrating property, while people pass with shoes on. X-ray generating module, inspecting module, information receiving and converting module as well as the processing module constitute all of the system. The X-ray generating module brings out x-ray of appropriate and safe dose. The inspecting module introduces infrared detection method to realize automatic checking flow. A LLL system is developed as the third module in which information is collected and digitized to deal with later. Then the processing module is to achieve, process information and show the results by means of information pick-up, image processing, remote conveying and controlling, building bank of information etc. The system improves inspecting speed and accuracy. At the same time, it extends the detection sorts largely so that not only metal but also other organic substances can be perceived. Finally we give a resolution expression of this kind of system and discuss the influence factors. Then some approaches to improve the system’s performance have been presented, which have great significance in improving and developing this kind of system.
Spectral response curves of photoemission materials and spectral matching factors between detectors and reflecting spectrum of scenes are of importance in the study of detectors and imaging devices. For studying the two questions an automatic spectral recording system was developed and the schematic diagram of the system was demonstrated in this paper. A lot of experiments by use of the system were made to obtain spectral response curves and characteristic parameters of multi-alkali and GaAs:Cs-O photocathodes during activation procedure and these experimental results were given. It was found that electron affinity of Na2KSb, Na2KSb+Cs and [Na2KSb+Cs]+Sb+Cs multi-alkali photocathodes were 0.70-0.91eV, 0.35-0.41eV and 0.33eV respectively calculated from threshold wavelength of spectral response curves and quantum yield during preparation. On-line spectral response measurements of GaAs:Cs-O reflection-mode photocathodes during activation process and decay procedure were carried. The prepared GaAs:Cs-O reflection-mode photocathodes which used national p-type GaAs substrate can obtain 1025μA/lm sensitivity.
As compared with III generation intensifiers, IV generations have bigger sensitivity and much broader spectral response for low light level imaging detectors. IV generation intensifier properties are improved for NEA photo-cathode sensitivity and spectral response. In this paper, a new method is introduced to increase NEA photo-cathode sensitivity and expand infrared response. In the method, spectral response of GaAs:Cs-O NEA photo-cathode is controlled with automatic survey instrument of dynamic spectral response on photo-electronic materials. During processing NEA photo-cathode, it is observed that sensitivity rises slowly when photo-cathode is illuminated with incident ambient radiation, and infrared sensitivity begins reduction when photo-cathode is measured with automatic survey instrument. The reduction of infrared sensitivity has influenced on spectral matching factor of photo-cathode-object combination and detecting distance and has resulted in the practical use of low light level night vision instrument. During processing NEA photo-cathode with Cs-O layer, we can keep watching spectral response change with automatic survey instrument: when sensitivity rises slowly as photo-cathode is illuminated with incident ambient radiation and infrared sensitivity reaches a highest peak value, we can achieve optimum GaAs:Cs-O photo-cathode for low light level imaging detectors. We studied the thickness of a layer GaAs:Cs-O photo-cathode with take off X-Ray photo-electron spectroscopy, it is clear that the thickness of Cs-O layer is about 0.7~1.0 nm.
The paper designs a set of system for measuring the responding characteristic of detector of PIN photon diode. The paper introduces the principle and structure of the PIN diode detector, and then describes the researching background and the responding characteristic of the detector. The detailed designing plan is given, and the step of implement is brought out. The system is composed of three subsystems. The first is optical system. The optical system can produce a laser of 1.06μm with a certain frequency and energy, with the aid of light source and CCD camera, the laser beam can focus on the surface of the photon detector of PIN diode. The second is signal-testing system. It can measure the responding characteristic of the photon detector, and the average noise power. The third is temperature control system. The responding characteristic of the photon detector in the high temperature and low temperature can be obtained with the temperature-control device. All the data is recorded and analyzed by the computer. At last, the paper provides the structure of the system and the testing result of the photon detector.
In this paper, the fundamental theory about visual range of LLL imaging system is described. Based on the revised apparent distance detecting equation and combined with the research intention and design principle of night vision goggle, the relation of parameters which have an influence on performances of system are analyzed. The visual range of the goggle under the specific circumstances is estimated, which proves the revised apparent distance detecting equation is effective and the design of the system is feasible.
On-line spectral response curves of GaAs:Cs-O NEA photo- cathode of reflection model is first presented and the relation between spectral response curves and the thickness of Cs-O layer is discussed. When Cs and O is deposited on the surface of cleaning GaAs wafer, photo-cathode's spectral response rises sharply and long-wavelength threshold tends to a fixed value at the beginning of the activation. But, as Cs and O are deposited continually, spectral response rises slowly and the long-wavelength threshold tends to be shortened. When a fine thickness of Cs-O layer is reached, the optimum spectral response is obtained. As a quantity Cs-O is further increased, both the spectral response and the long-wavelength threshold decrease. The thickness of GaAs photo-cathode surface layer that consists of Cs-O layer and GaAs-O layer is researched by take-off angle XPS technology. Thickness of Cs-O layer is approximately equal to 0.7 nm, and the GaAs-O layer is approximately 0.2nm. Our experiments show when the thickness of Cs-O layer is approximately equal to 0.7nm, and the GaAs-O layer is approximately 0.2mm. Our experiments show when the thickness of Cs-O layer is 0.7nm or so and the GaAs-O layer tend to be disappeared, NEA photo-cathode with the optimum spectral response is achieved which can be used widely in low-light level imaging detectors.
This article first describes the background of the research and manufacture of evaluation system of Negative Electron Affinity photocathode. This article designs a set of super high vacuum system for activating NEA photocathode on the base of activation theory, the process of design and debugging is given. The system is composed of three parts: super high vacuum system for GaAs material activation, multi-meter testing system, surface analysis system. The system is used for on-line evaluation of activating of NEA photocathode. The technical parameters and structure of the evaluation system of NEA photocathode are given in the paper. The system is finished and experiments are made. At last the picture of the system is given.
When the films in the optical or photoelectric devices are produced, usually their thickness is an important parameter. The optical method can be used to measure real-time thickness of films if films are producing on the transparent substrates. Based on thin optics, the principles of measuring thickness of optical films by optical method are expounded in the paper. The measuring instruments are developed. The instruments can measure real-time the optical reflectivity of films during producing them. By processing and analyzing data the thickens of the films can be estimated. The measuring system has been applied in the courses producing experimental tubes and image intensifiers. The measured results are given and analyzed.