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.
Image intensifier is a device to observe in night. To evaluate the quality of Image intensifier, there are two important data
which are resolution and SNR. Analyzing the testing principles of resolution and SNR, a test to super second generation
image intensifier is designed. Under the luminance of 1Lx,1×10-3Lx and 1×10-5Lx, test with the same resolution card. It
was found that image quality of Image intensifier has the best quality when in luminance of background 1×10-1Lx to 1×
10-3Lx. When luminance of its background is above 1×10-1Lx the noise will be high, see fig.2. When luminance of its
background is below1×10-3Lx the signal will be weak. It provides a testing foundation for evaluating the quality of an
An infrared target tracking system has been introduced in details for unmanned monitor application and its
corresponding method for extracting and tracking moving targets from real-time infrared video has also been described.
To ensure its real-time implementation on the tracking system, mature motion estimation techniques such as the
time-domain statistics method and the DT method are adopted in the tracking method which includes three stages: target
extracting, target classification and target tracking. A two-strategy classification method is adopted to improve
classification accuracy. The tracking process involves correlation matching between a template and the current motion
regions. The motion region with the best correlation is tracked and is used to update the template for subsequent tracking.
The infrared target tracking system is based on a high-speed DSP chip with an internet interface, which may transmit the
doubtful targets information to monitor center in time. To illustrate the effectivity of the infrared target tracking system,
experimental results has been given in the end of this paper.
An uncooled thermal imaging system with multiple working temperatures will be presented. Transient response
performance of α-si microbolometer detectors is simulated firstly when the working temperature varies in the range from
-40deg. to +60deg. Simulating results show that α-si microbolometer detectors have coherent response performance in a
large range of working temperature, which lay basis for designing uncooled thermal imaging system with multiple
working temperatures. Different from traditional thermal imaging systems, this thermal imaging system has three
working temperature with an accuracy range of less than ±0.01deg. When working, the temperature control circuit will
switch between the working temperatures according to the variety of the environmental temperature. To evaluate this
thermal imaging system, we measure its power consumption and NETD in the environmental temperature range from
-40deg. to +60deg. The measurement results are that the total power is less than 2500mW and the NETD is less than
120mk. This indicates that the thermal imaging system has nearly the same imaging quality and obviously lower power,
compared with traditional thermal imaging systems.
Microbolometer focal plane array (FPA), as a popular kind of uncooled infrared detector, has a wide range of low cost
thermal imaging applications due to its high sensitivity and simple micro-fabrication process. The performance of
microbolometer imaging system is determined by many factors such as the property of the FPA, the effect of
nonuniformity correction, the condition of operation and so on. In this paper, the micro-structure and heat transfer
mechanism of microbolometer FPA are analysed to find out the substrate temperature characteristic. The response
nonuniformity of the FPA and corresponding two-point correction method are discussed to find out the calibration
temperature characteristic. And the power dissipation property of the thermal-electrical cooler (TEC) integrated under
the FPA is described to find out the ambient temperature characteristic. According to the simulation and experiment
results obtained from a 320×240 amorphous silicon microbolometer imaging system, it is concluded that all these
temperature parameters have a great influence on the system performance and should be well considered for different
working conditions to gain high system performance and imaging quality.
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.
Reasons that thermal imaging systems consume power have been analyzed, and a low-power design scheme of thermal
imaging systems has been presented with multiple working temperature points. Transient response performance of α-si
microbolometer detectors is simulated firstly when the working temperature varies in the range from -40°C to +60°C.
Simulating results show that α-si microbolometer detectors have coherent response performance in a large range of
working temperature, which lay basis for designing uncooled thermal imaging system with multiple working
temperatures. Different from traditional thermal imaging systems, this thermal imaging system has three working
temperature with an accuracy range of less than ±0.01°C. When working, the temperature control circuit will switch
between the working temperatures according to the variety of the environmental temperature. To evaluate this thermal
imaging system, we measure its power consumption and NETD in the environmental temperature range from -40°C to
+60°C. The measurement results are that the total power is less than 2500mW and the NETD is less than 120mk. This
indicates that the thermal imaging system has nearly the same imaging quality and obviously lower power, compared
with traditional thermal imaging systems.
Microbolometer detector is very competent as uncooled infrared detector for a wide range of thermal imaging
applications, since it has been found to be more sensitive and has the advantage of using standard Si micro-fabrication
process compared with pyroelectric or ferroelectric technology. The heart of microbolometer detector is a two
dimensional array of thermal sensitive thin-film layers, which can change their temperatures and resistivities depending
on the radiation absorbed. During the entire thermal imaging process, the microbolometer detector's substrate
temperature, calibration temperature and ambient temperature are the key parameters which determine the thermal-electrical
performance and the ultimate imaging quality of the microbolometer detector. In this work, based on the
analysis of the characteristics of these parameters, the experiment has been conducted with the uncooled infrared thermal
imaging system based on 320×240 amorphous silicon microbolometer detector working at different substrate
temperatures, adopting different calibration temperatures for different ambient temperatures. The corresponding
measurement results of the system's NETD, residual nonuniformity and power consumption, as well as the system's
imaging results are presented, which all have a great agreement of the theory analysis above.
Recent advances of microelectromechanical system (MEMS) technology have opened new opportunities for amorphous
silicon (α-Si) microbolometer focal plane arrays (FPAs) both for military and civil applications. α-Si membrane is
chosen for sensitive material of microbolometer FPAs due to its high temperature coefficient of resistance (TCR), high
resistivity and good mechanical properties. However, α-Si membrane also has the disadvantage of high 1/f noise, strict
preparation conditions and metastable effect. So nowadays, researches are focused on properties of α-Si membrane to
gain high performance of microbolometer FPAs. Since the pulsed bias readout mode of microbolometer FPAs causes a
non-steady-state of α-Si membrane during the operation, the transient thermal-electrical response process of the sensing
pixel is analyzed detailedly in this paper to predict the thermal and electrical performance of α-Si microbolemeter FPAs
such as responsivity, noise equivalent temperature difference (NETD), detectivity and power dissipation. Numerical
simulations are presented to investigate the factor which affects the performance of α-Si microbolometer FPAs. The
imaging experiment results obtained from a 320×240 α-Si microbolemeter FPA are in good agreement with the
theoretical analysis. The way to improve the performance of α-Si microbolemeter FPAs is given in the end of this paper.
Recent advances in MEMS and focal plane array (FPA) technologies have led to the development of manufacturing
microbolometers monolithically on a readout integrated circuit (ROIC). Since the response of microbolometer detectors
depends on the modification of temperature in micromachined bridge structures, it is useful to model and simulate
thermally the corresponding structures in order to predict their performance parameters. In this work, finite element
methods are performed to simulate the transient temperature field of thermistor films of microbolometer detectors. The
varisized supporting legs' impacts on the performance of detectors are discussed and the transient response for three
microbolometer configurations was investigated. At the same time, variation of the operation temperature's impacts on
total noise, noise equivalent to temperature difference (NETD) and detectivity (D*) are also discussed in details. These
performance analyses are helpful for optimum design of microbolometer infrared detectors' structure and rational choice
of operation temperature of infrared focal plane arrays.
Thermal imager can transfer difference of temperature to difference of electric signal level, so can be application to
medical treatment such as estimation of blood flow speed and vessel 1ocation, assess pain and so on. With the
technology of un-cooled focal plane array (UFPA) is grown up more and more, some simple medical function can be
completed with un-cooled thermal imager, for example, quick warning for fever heat with SARS. It is required that
performance of imaging is stabilization and spatial and temperature resolution is high enough. In all performance
parameters, noise equivalent temperature difference (NETD) is often used as the criterion of universal performance. 320
x 240 α-Si micro-bolometer UFPA has been applied widely presently for its steady performance and sensitive
responsibility. In this paper, NETD of UFPA and the relation between NETD and temperature are researched. several
vital parameters that can affect NETD are listed and an universal formula is presented. Last, the images from the kind
of thermal imager are analyzed based on the purpose of detection persons with fever heat. An applied thermal image
intensification method is introduced.
In this paper, on the base of simple introduction of inner structure of 320×240 pixels UFPA in electronics and
calorifics, the relationship of NETD (noise equivalent temperature difference) and bias voltage are researched and
presented through the formulas about noise and NETD. The relation between NETD and four kinds of temperatures is
presented. Moreover the two bias voltages are adjusted to observe the changing of NETD. Some experiments on power
consumption and image quality of thermal imaging system is done, the result data is given. On the basis of the theory and
experiments, how to enhance the NETD performance of UFPA (Focal Plane Array) at much lower or higher than room
temperature is researched by analyzing experiment data. At last, the conclusion is summarized: in order to get the best
image and the lest power consumption, we should adjust these parameters to find the optimized configuration at different
Uncooled microbolometer infrared detectors are being developed for a wide range of thermal imaging applications. To design and manufacture high-performance microbolometer infrared detectors, numerical calculation and simulation is necessary. In this work, finite element methods are performed to simulate the transient temperature field of thermistor films of microbolometer infrared detectors. The varisized supporting legs' impacts on the performance of detectors are discussed. At the same time, variation of the bias voltage and the substrate temperature's impacts on total noise, noise equivalent to temperature difference (NETD) and detectivity (D*) are also discussed in details. These performance analyses are helpful for optimum design of microbolometer infrared detectors' structure and rational choice of working temperature of infrared focal plane arrays.
A 320×240-uncooled-microbolometer-based signal processing circuit for infrared focal-plane arrays is presented, and the software designs of this circuit system are also discussed in details. This signal processing circuit comprises such devices as FPGA, D/A, A/D, SRAM, Flash, DSP, etc., among which, FPGA is the crucial part, which realizing the generation of drive signals for infrared focal-plane, nonuniformity correction, image enhancement and video composition. The device of DSP, mainly offering auxiliary functions, carries out communication with PC and loads data when power-up. The phase locked loops (PLL) is used to generate high-quality clocks with low phase dithering and multiple clocks are to used satisfy the demands of focal-plane arrays, A/D, D/A and FPGA. The alternate structure is used to read or write SRAM in order to avoid the contradiction between different modules. FIFO embedded in FPGA not only makes full use of the resources of FPGA but acts as the channel between different modules which have different-speed clocks. What's more, working conditions, working process, physical design and management of the circuit are discussed. In software designing, all the function modules realized by FPGA and DSP devices, which are mentioned in the previous part, are discussed explicitly. Particularly to the nonuniformity correction module, the pipeline structure is designed to improve the working frequency and the ability to realize more complex algorithm.
Nonuniformity is a pressing problem particularly for uncooled focal-plane arrays imaging systems. Based on the theory of Least Mean Square (LMS), an algorithm is developed to compensate for the nonuniformity response in focal-plane arrays (FPA). The proposed algorithm is able to reduce various errors caused by noises, sampling, etc. A correction model of multi-order function is presented which has least-mean square error, and then by utilizing response values at several known temperature points the coefficients of this function are obtained via the theory of LMS fitting. Taking one pixel as example, the graph of the correction error is drawn. The ability of the algorithm is demonstrated by using simulated and real data. What’s more, the effects of this algorithm in nonuniformity correction are revealed as opposed to those of some traditional algorithm. To compensate response drift along time, a method based on estimating motion in continuous frames is presented.
In real-time system, the Infrared Focal Plane Array (IRFPA) should be compensated in traditional method of two-point temperature non-uniformity correction (NUC) before system was used every time, which make the system complex. Based on discussion of traditional two-point temperature NUC algorithm, Two-point temperature NUC based on least mean square (LMS) algorithm was proposed in the paper. In the view of the LMS algorithm theory, the correction gain and offset coefficients were iterated one by one during image processing, so that the expected correction result were obtained in little time. At the same time, the correction and coefficients iteration processes were completed in FPGA and DSP respectively, and make the arithmetic structure simple. The simplified structure, low cost and out-door suitable operation-systems are the merits of the system.