In resent publications we presented PIN photodiodes with a bandwidth of 600MHz implemented in low-cost 0.6μm BiCMOS technology. A new method to increase the response time of these PIN photodiodes is proposed here. This method was applied to design an optical fiber receiver with a maximum possible data rate of 2.5Gbit/s. In addition to the PIN photodiode attached to a transimpedance amplifier it also includes a decision circuit and a 50Ω output driver. The measured bandwidth of the receiver of 1.90GHz is sufficient for 2.5Gbit/s. At an optical wavelength of 660nm, a sensitivity of -17.0dBm was measured. At a supply voltage of 5V, the power consumption of the complete receiver is 171mW, from which the output driver requires 128mW. The overall chip size is 1154μm times 727μm.

The fast development of nitrides has given the opportunity to investigate AlGaN as a material for ultraviolet solar blind detection in competition with technologies based on photocathodes, MCP intensifiers, back thinned CCD or hybrid CMOS focal plane arrays. All of the them must be associated to UV blocking filters. These new detectors present both an intrinsic spectral selectivity and an extremely low dark current at room temperature. First we will present the ultimate properties of the AlGaN based devices. These spectral properties are analysed in regards to the sharp cut off required for solar blind detection around 280nm, and we will quantify how the stringent difficulties to achieve solar blind filters can be reduced. We also investigated the electrical capabilities of Schottky diodes or Metal-Semiconductor-Metal (MSM) technologies to detect extremely low UV signal. We will especially present results from a linear array based on a CCD readout multiplexor.

When Zinc diffuses into undoped InP, the diffusion profiles are severely influenced by the process parameters, such as the diffusion temperature, the diffusion time, etc. In order to reduce the surface damage and enhance reproducibility, the diffusion temperature and the diffusion time are optimized. Under optimized. diffusion temperature, curve of diffusion depth versus the square root of the diffusion time is achieved. From this curve, the diffusion coefficient for zinc under the optimized temperature is calculated. The zinc profile was determined by electrochemical capacitance-voltage profiling (ECV), according to which zinc diffusion mechanism was explained.

Narrow-gap low-doped n-Hg_1-xCd_xTe (x = 0.18-0.35) material with electron concentration at liquid nitrogen temperature (77 K) n₇₇≈(1-10)×10¹⁴ cm^-3 is preferably used by all manufacturers of infrared (IR) radiation detectors as absorbing layer (n-absorber) of high performance Mid-Wave (MWIR), Long-Wave (LWIR) and Very Long-Wave (VLWIR) photoconductors (PC) covering spectral range from 3 to 25 μm. Low-doped n-Hg_1-xCd_xTe (x = 0.21-0.65) material with n₇₇≈(1-5)×10¹⁵ cm^-3 is perspective for development and production of novel small- pitched photovoltaic (PV) Short-Wave (SWIR), MWIR, LWIR and multi- color infrared focal plane arrays (FPA) covering spectral range from 1.3 to 12 μm. Novel FPA is based on photodiodes (PD) with p-n junction opposite to usually used n⁺-p junction. PD with optimal p-n junction could have lower dark current value than same size n⁺-p junction. It is very desirable for adequate multiplexing of PD arrays by Silicon Read-out Integrated Circuits (ROIC). Low-doped n-Hg_1-xCd_xTe could be grown by different techniques: bulk crystallization; liquid phase epitaxy (LPE); molecular beam epitaxy (MBE) having seriously different referring (melting/crystallization/annealing) temperatures. Objective of the present work was to examine and compare some crystalline, chemical and physical parameters and impact of PC device performance on their variation.

We report on the progress achieved in the molecular beam epitaxy of 3" and 4" HgCdTe on CdTe(211)B/Ge composite substrates, and the subsequent fabrication of high performance focal plane arrays. We first describe the growth of the heterostructures, and their characterization. Then we examine the fabrication of a 1280x1024 small-pitch focal plane array, which shows operability in excess of 99% for both the responsivity and the noise-equivalent thermal difference.

The infrared (IR) detectors produced in France are using up to date and well mastered technologies based on Mercury Cadmium Telluride (HgCdTe-MCT) material. Based on the maturity of these IR detectors and technologies, IR systems have been produced and are more and more used in different applications including military, security, process control, environment monitoring, science and space. The produced IR cameras are the so-called second and second and half generations which are very performing but still have some limitation regarding identification, their ability to operate in all weather conditions, and in terms of compactness and reliability. Therefore researches for moving to the next generation (the third one) of cooled detectors have started to overcome these limitations with the use of bi-color or dual-band as well as to offer more performances. To conduct these researches SOFRADIR and CEA-LETI (LIR) have set up a specific organization, called DEFIR (Design of Excellence for the Future of IR), necessary to increase the efficiency and to reduce the time to production of this new generation. The approach in France regarding the key technologies for the third generation considers the different parameters from the performance to the system cost criteria. Among all the technologies candidates, a new HgCdTe technologies based on molecular beam epitaxy (MBE) have been chosen. Then prototype demonstrations are in progress and confirm the validity of the chosen key technologies.

The high-density inductively coupled plasma etching technique was applied to HgCdTe, while using the RF-powered wafer electrode to provide low plasma energy. By using a CH₄/H₂/N₂/Ar chemistry the HgCdTe etch profiles were studied as a function of mask selectivity, chamber pressure, gas ratio and ICP power. The etch rate was found to decrease as etch depth increasing. The LBIC and I-V measurements were employed to investigate the electrical damage of HgCdTe material caused by plasma bombardment.

Short wavelength Hg_1-xCd_xTe infrared detectors were novelly fabricated by loophole technique basing on Liquid Phase Epitaxial materials, rather than conventional ion implantation technology. The Hg_1-xCd_xTe material was p type doped by Hg vacancy. The formed sensitive area is an annulus centered on the circular junction. The dimension of the annulus depends on the diffusion lengths of minority carriers in both the p and n regions. Laser Beam Induced Current (LBIC) signals of Scan Laser Microscope measurement were used to determine the key parameters such as the minority diffusion length, the size of both n type and p type regions as well as uniformities of the arrays. Good uniformities were observed for the 4×4 HgCdTe photovoltaic arrays by LBIC signals analysis. Furthermore, exponential decays in LBIC signals revealed average minority carrier diffusion length in p type region was around 9 micron, and the average diameter of the n type annulus was 17 micron. The I-V characteristic measurement of the photodiodes determined average zero bias dynamic resistance R₀ which was 1.2E9Ω, and zero bias dynamic resistance junction area product R₀A was calculated to be average 7.02E3Ωcm². Further investigations have been performed for the electro-optical performance examination. Infrared spectral response measurement results showed peak wavelength lay around 2.2 micron with cutoff wavelength about 3.5 micron under temperature 77K, average blackbody detectivity D* was 1.71E10cm Hz^1/2W^-1.

Ultimate performance small-pitched infrared focal plane arrays (FPA) are of the great interest for development and production of state-of-the-art special and common use thermal imagers. Novel MBE-grown Hg_1-xCd_xTe/CdZnTe/GaAs heterostructures (MCT/CZT on GaAs HS) are considered perspective for implementation of sophisticated FPA concepts including multi-color and HOT (high operating temperature). Performance of MWIR and LWIR photoconductive (PC) and photovoltaic (PV) infrared detectors fabricated on the base of a. m. heterostructures are presented. The main feature of developed technology is formation of multi-layer device structure in single MBE growth run with precise control of thickness and alloy composition "x" across individual layers and hence throughout heterostructure. Flexible HS design results in half-finished products of PC and PV detectors with optimized parameters of absorber and perfect interfaces between absorber and blocking layers providing effective suppression of surface recombination and surface leakage currents. Giant peak responsivity R_V (λ_co=10.5 μm, 500 K, 1200 Hz) over 6,0×10⁵ V/W was reached on LWIR PC. Average values D* = 1.8×10¹¹ cmHz^1/2W^-1 and NEDT = 9 mκ were measured on 4×288 PV FPA with λ_co = 11.2 μm at T=78 K just as 23 mK and 19 mκ on 320×256(240) PV FPA with λ_co = 5.5 and λ_co = 10.2 μm at T=78 K.

Four-band HgCdTe infrared (IR) detector is developed for the first operational Chinese geostationary meteorological satellite FY-2C launched on October 19, 2004. As the Visible Infrared Spin-Scan Radiometer (VISSR) is the primary payload on FY-2C, the IR detector is one of the most important modules for such an imaging instrument. Compared with its predecessors FY-2A and FY-2B (experimental models, launched in June 1997 and June 2000 respectively), the detector used in FY-2C is quite different in band selection and detector package. The four band IR detector for FY-2C application consists of four photoconductive (PC) detector chips made of Hg_1-xCd_xTe with different compositions x , corresponding to the wavelengths of 3.5 to 4.0μm, 6.3 to 7.6μm, 10.3 to 11.3μm and 11.5 to 12.5μm respectively. Four cooled IR filters are included in one detector package, which enables us to simplify the system without any IR beam splitters and IR filters outside the detector for defining separate bands. The IR detector operates at radiative cooler temperature ranging from 92 to 102K. This paper reviews the design, process and packaging for the four-band IR detector used in FY-2C satellite. The performances and related aspects of this detector are also presented.

Results of fabrication and parameters of infrared detectors based on In-doped lead-tin-telluride (LTT) films are presented. The films were grown using molecular beam epitaxy on BaF₂ substrates. The focal plane arrays operated at 7 to 15 K have shown better parameters than those known for impurity photoconductors. The typical average values of NEP were below 1,0×10^-18 W /Hz^1/2 at T=7K with cut-off λ_c = 20-25 μm. The operability of 2×128 focal plane arrays was over 90%. The model explaining the electrical and photoelectrical properties of the LTT films based on theories of space charge limited currents (SCLC) and ferroelectric phase transition (FEPT) has been developed. The calculations according to this model are in a good agreement with the experimental data. The laser-excited (λ=336.8 μ) photocurrent was observed, and prospects of usage of LTT-based devices as the submillimeter range detectors were discussed.

We present a chip, which is suited for applications in data-communication areas as well as in image-processing applications. Through the combination of parallel signal gathering and processing, we save components and we can increase the processing rate. We think thereby on problems like pre processing in camera systems also called "intelligent sensor". The chip has a structure as follows. Every processor element contains an optical detector, a trans-impedance amplifier and a comparator. A digital logic is directly connected to these components. This logic realizes the programmable processing of the signals. Each processor element is connected to its four direct orthogonal neighbours within the processor array. The digital parts consist of a special processor. It realises simple hard-wired image algorithms. As an example for cooperation of the analogue and digital part we have implemented some morphologic operations. Our receiver consists of a 8×8 photodiode array. A data rate of 625 Mbit/s for an average optical power in the range of 25 µW to 500 µW is possible for a bit-error-rate of 10-9 per channel. Signal processing limits the frequency to 200 MHz for a processor element according to simulations. Using an image with a size of 6×6 according to parallel data transfer a data throughput of 7.2 GHz results.

The evaluation of technological parameters is of primary importance for the detector industry, since it allows both to validate the fabrication process and to optimize the electro-optical characteristics of the detectors. By measuring the spectral response of detectors with a high resolution, it is possible to display specific optical effects. Using a radiometric model of the detecting architecture, we are able to understand their physical origins and to determinate some technological and optical parameters. We have developed a test bench which provides spectral responses of infrared detectors using a Fourier transform spectrometer. The principle of the test bench and the methodology used are detailed. Experimental results, as well as the associated radiometric model, are presented for a dedicated 320×240 MCT LWIR focal plane arrays (FPAs).

Uncooled infrared focal plane arrays are being developed for a wide range of thermal imaging applications. Firefighting, predictive maintenance, process control and thermography are a few of the industrial applications which could take benefit from uncooled infrared detector. Therefore, to answer these markets, a 35 μm pixel-pitch uncooled IR detector technology has been developed enabling high performance 160 x 120 and 384 x 288 arrays production. Besides a wide-band version from uncooled 320 x 240 / 45 μm array has been also developed in order to address process control and more precisely industrial furnaces control. The ULIS amorphous silicon technology is well adapted to manufacture low cost detector in mass production. After some brief microbolometer technological background, we present the characterization of 35 μm pixel-pitch detector as well as the wide-band 320 x 240 infrared focal plane arrays with a pixel pitch of 45 μm.

Contact-less optical distance measurement systems are necessary to obtain 3D-information of an entire scene. To be able to determine depth information of the scene by a sensor without moving parts like e.g. scanner, it is necessary to measure the distance from the camera to an object in every single pixel. A new pixel for such a 3D-camera is presented. The operating principle is based on the time-of-flight (TOF) of laser light from a modulated light source to a diffuse reflecting object and back to the receiver IC. The receiver is implemented as an opto-electronic integrated circuit (OEIC). It consists of a fast, efficient PIN-photodiode having a 3dB bandwidth of about 1.35 GHz, a single-stage transimpedance amplifier and an electronic mixer on a single silicon chip. By correlating the received optical signal and the original electronic modulation signal, the phase-shift between sent and received signal can be determined. By performing correlation with a delayed modulation signal it is possible to eliminate the influence of object reflectivity and background illumination. The measurement time for a single distance measurement is 500μs for a range up to 3.7m. The standard deviation at 2.5m is better than 3cm for a transmitted optical power of 1.44mW at a wavelength of 650nm. The OEIC was fabricated in a slightly modified BiCMOS 0.6μm process. The diameter of the photosensitive area of the integrated PIN-photodiode is 100μm. The effective pixel size is about 220x400μm². Therefore a fill factor of ~9% is reached.

The examination of spectra in the NIR range is necessary for applications like process control, element analysis or medical systems. Typically integrated NIR spectrometers are based on optical setups with diffraction grating and detector arrays. The main disadvantage is price and availability of NIR array InGaAs-based detectors. The implementation of a scanning grating chip realized in a MOEMS technology which integrates the diffractive element makes it possible to detect spectra with single detectors time resolved. Either simple InGaAs photodiodes or cooled detectors may be used. The set up is a shrinked Czerny-Turner spectrometer. The light is coupled in by an optical fibre. After focussing the light passes the scanning grating moving at 150-500 Hz in a sinusoidal way. There it is split off in the different wavelength, the monochrome intensity is caught by a second mirror and led to the detector. The detector signal is amplified by a transimpedance stage and converted to digital with 12 bit resolution. The main part of the signal processing is done by a digital signal processor, which is used to unfold the sinusoidal position and calculate the final spectra. The data rate can be up to 3 MHz, then a spectrum is acquired every 2ms by using a 500Hz Mirror. Using the DSP, the spectrometer can operate autarkic without any PC. Then the spectrum is display on a 160 x 80 pixel graphic LCD. A keypad is used to control the functions. For communication a USB port is included, additional interfaces can be realized by a 16-pin expansion port, which is freely programmable, by the system firmware.

Star trackers are opto-electronic sensors used on-board of satellites for the autonomous inertial attitude determination. During the last years star trackers became more and more important in the field of the attitude and orbit control system (AOCS) sensors. High performance star trackers are based up today on charge coupled device (CCD) optical camera heads. The active pixel sensor (APS) technology, introduced in the early 90-ties, allows now the beneficial replacement of CCD detectors by APS detectors with respect to performance, reliability, power, mass and cost. The company's heritage in star tracker design started in the early 80-ties with the launch of the worldwide first fully autonomous star tracker system ASTRO1 to the Russian MIR space station. Jena-Optronik recently developed an active pixel sensor based autonomous star tracker "ASTRO APS" as successor of the CCD based star tracker product series ASTRO1, ASTRO5, ASTRO10 and ASTRO15. Key features of the APS detector technology are, a true xy-address random access, the multiple windowing read out and the on-chip signal processing including the analogue to digital conversion. These features can be used for robust star tracking at high slew rates and under worse conditions like stray light and solar flare induced single event upsets. A special algorithm have been developed to manage the typical APS detector error contributors like fixed pattern noise (FPN), dark signal non-uniformity (DSNU) and white spots. The algorithm works fully autonomous and adapts to e.g. increasing DSNU and up-coming white spots automatically without ground maintenance or re-calibration. In contrast to conventional correction methods the described algorithm does not need calibration data memory like full image sized calibration data sets. The application of the presented algorithm managing the typical APS detector error contributors is a key element for the design of star trackers for long term satellite applications like geostationary telecom platforms.

Several designs of infrared absorption based gas detector use a Fabry-Perot Interferometer (FPI) to modulate the incident light. In these systems, generally the FPI's fringes are matched with very well defined rotational absorption lines of a target molecule such as CO2, CO, N2O, CH4, etc. In order to obtain modulation the cavity length of the FPI is scanned over one half of the reference wavelength. In this work, we present a simple analytical method based on the Fourier Transform that describes the performance of these systems. Using this method the optimal reflectivity and optical spacing of the FPI can be determined. Furthermore, the modulated signal generated by the system as a function of the cavity length scan can be calculated by applying the inverse Fourier Transform. Finally, this method describes the underlying reasons why for some filters the background amplitude is severe, and gives guidance on the choice of optimised filters. Our method evaluates the optimal FPI parameters and the modulated signal much faster than the direct numerical computation which is used currently. Simulation results for different molecules in combination with diverse filters shapes are presented, with a comparison to directly computed results.

We present our results of the development of some schemes for nondestructive optical profilometry of cylindrically shaped surfaces by using spatially matched conical light beams. A theoretical model is elaborated which describes profilometers with Bessel beams. A special feature of the profilometers proposed is the possibility to control their sensitivity and resolution. To this end, a scheme of tuning the cone angle of the Bessel beam over a wide range is incorporated. The operation regime of the profilometers is characterized by a nonzero spatial frequency of output signal. It allow us to apply a new algorithm for the interpretation of the output signal. This algorithm consists in the calculation of the azimuth spectrum which characterizes the deviation of tested profiles from the circular ones.

A new ultrafast Diffuse Optical Tomography (DOT) has been developed for real time in vivo brain metabolism monitoring in songbird. The technique is based on space resolved time of flight measurements of the photons across the brain tissues. A three dimensional reconstruction of the brain activity is foreseeable by means of a double space and time sampling of the reflectance signal. The setup and the treatment procedure are described in depth and promising preliminary results showing the response of brain tissues to hypercapnia stimulations (increase of CO₂) are presented.

Infrared thermal imaging was first made available to medicine in the early 1960's. Despite a large number of research publications on the clinical application of the technique, the images have been largely qualitative. This is in part due to the imaging technology itself, and the problem of data exchange between different medical users, with different hardware. An Anglo Polish collaborative study was set up in 2001 to identify and resolve the sources of error and problems in medical thermal imaging. Standardisation of the patient preparation, imaging hardware, image capture and analysis has been studied and developed by the group. A network of specialist centres in Europe is planned to work to establish the first digital reference atlas of quantifiable images of the normal healthy human body. Further processing techniques can then be used to classify abnormalities found in disease states. The follow up of drug treatment has been successfully monitored in clinical trials with quantitative thermal imaging. The collection of normal reference images is in progress. This paper specifies the areas found to be the source of unwanted variables, and the protocols to overcome them.

The intratissue multiphoton autofluorescence imaging (MAI) and the second harmonic generation (SHG) based on nonlinear process of femtosecond nanojoule laser pulses at wave length of 750-850 nm emitted from solid-state Titanium: Sapphire Chameleon have been used as a highly precise non-destructive tool to realize the in-vivo differentiation of corneal layers with the assistance of intratissue optical tomography and to visualize the keratocyte structures and collagen lamellas with submicron resolution. Multiphoton nonlinear imaging occurs only with high light intensity on an order of MG-GW/cm² and photon flux density of more than 10²⁴ photons cm^-2s^-1 in a 0.1femtoliter intrastromal focus volume obtained by diffraction-limited focussing with high-numerical objectives. This technique, acting as a novel diagnostic tool, proved to be essential for femtosecond (fs) nanojoule (nJ) cornea surgery to determine the interest of region preoperation, to visualize and verify the outcomes immediately after the laser surgery and has potential to become a powerful tool in advancing understanding of corneal biomechnics and cellular reactions after laser induced lesion.

This paper presents the improvements integrated into the second generation of Enhanced Vision System (EVS) or the Enhanced Flight Vision System (EFVS) (in comparison with the first generation). These improvements are based on the experience and knowledge accumulated during the last 3.5 years of observing more than 300 planes operating with the EVS system. Among the main improvements incorporated into the second-generation product are: - Higher probability of detection for runway lights and flashers, during bad atmospheric conditions. - Extended algorithm for ambient temperature compensation, eliminating the requirement for optics and dewar head temperature stabilization. - The sealed-off system that constitutes the second generation, not requiring any air flow supply or temperature stabilization. (The EVS first generation requires an air flow of 7 liters/second at 23° C with a relative humidity not higher than 30%. The airflow prevents water condensation on the optical parts and also enables stabilizing the optics and dewar head temperatures.) - Improved algorithm for the replacement of clusters of bad pixels. - Reduced size, weight, and power consumption.

This paper presents application of Cavity Ring-Down Spectroscopy (CRDS) and Cavity Enhanced Spectroscopic (CEAS) techniques with blue laser diodes-based system for nitrogen dioxide (NO2) detection. CES technique bases on integration of the light from a resonator. Since the integrated intensity is proportional to the decay time, the experimental signal can be related to the absorption process. The minimum detectable concentration of the absorber for a specific transition is inversely proportional to the effective sample-path length, and directly proportional to the minimum intensity fluctuation detected by a receiving system. In the presented system, the blue laser diode was mounted in a temperature-controlled housing. The light transmitted through the cavity was focused onto a PMT of H5783-03 type. The detector signal enters a lock-in amplifier and next a computer with a 16-bit data acquisition board.

Every year, numerous accidents happen on European roads due to bad visibility (fog, night, heavy rain). Similarly, the dramatic aviation accidents of year 2001 in Milan and Zurich have reminded us that aviation safety is equally affected by reduced visibility. A dual-band thermal imager was developed in order to raise human situation awareness under conditions of reduced visibility especially in the automotive and aeronautical context but also for all transportation or surveillance tasks. The chosen wavelength bands are the Short Wave Infrared SWIR and the Long Wave Infrared LWIR band which are less obscured by reduced visibility conditions than the visible band. Furthermore, our field tests clearly show that the two different spectral bands very often contain complementary information. Pyramidal fusion is used to integrate complementary and redundant features of the multi-spectral images into a fused image which can be displayed on a monitor to provide more and better information for the driver or pilot.

Within the scope of this paper a both compact and economical data acquisition system for multispecral images is described. It consists of a CCD camera, a liquid crystal tunable filter in combination with an associated concept for data processing. Despite of their limited functionality (e.g.regarding calibration) in comparison with commercial systems such as AVIRIS the use of these upcoming compact multispectral camera systems can be advantageous in many applications. Additional benefit can be derived adding online data processing. In order to maintain the systems low weight and price this work proposes to separate data acquisition and processing modules, and transmit pre-processed camera data online to a stationary high performance computer for further processing. The inevitable data transmission has to be optimised because of bandwidth limitations. All mentioned considerations hold especially for applications involving mini-unmanned-aerial-vehicles (mini-UAVs). Due to their limited internal payload the use of a lightweight, compact camera system is of particular importance. This work emphasises on the optimal software interface in between pre-processed data (from the camera system), transmitted data (regarding small bandwidth) and post-processed data (based on high performance computer). Discussed parameters are pre-processing algorithms, channel bandwidth, and resulting accuracy in the classification of multispectral image data. The benchmarked pre-processing algorithms include diagnostic statistics, test of internal determination coefficients as well as loss-free and lossy data compression methods. The resulting classification precision is computed in comparison to a classification performed with the original image dataset.

Until now Microbolometer cameras have been operated only in the long-wave infrared range (LWIR). Since microbolometers are now available with broadband windows and acceptable absorption in the mid-wave infrared range (MWIR), they are becoming more and more interesting for the MWIR range. Primarily for industrial applications, this wavelength range offers many advantages, e.g., for the measuring of glass temperatures or for supervision of furnace rooms. To achieve a sufficiently high measuring accuracy, such crucial MWIR peculiarities like carbon dioxide absorption lines and water-vapor absorption must be known. Such problems can be avoided by usage of narrowband filters. Usually, they have to be adjusted to the particular measurement task. The newly developed camera system is based on a 320 x 240 pixels LWIR microbolometer camera system. The optical channel had to be adapted to the microbolometer. In addition, special correction and calibrating procedures were implemented for the MWIR. The camera system is suitable for stationary use in harsh industrial environments. The robust housing may be completed by integrating water-cooling and air purge for the lens system. The camera is equipped with two trigger inputs for the synchronization with the process to be measured.

Vegetation is a sensitive indicator suitable for testing of ecological stresses and natural anomalies of the technogenic character. First, it is determined by the prompt response of photosynthetic apparatus to changes of environmental conditions, mainly by change of green pigment (chlorophyll) content in leaves. Second, the specific kind of a reflectance spectrum of leaves is due to chlorophyll presence in them, and the area in the range of 500-80 nm is extremely sensitive to variations of its pigment content. Thirdly, there are interesting results now concerning spectral properties of leaves and crops canopies obtaining with high-resolution spectroscopy. The data are high informative in relation to content of chlorophyll and some other biochemical constituents of a cell. The high resistance to various types of noises is inherent to methods developed on the basis of such spectral data. We have developed a method for chlorophyll estimation using the 1-st derivative plots of reflectance spectral curves. The method gives good results for plant-soil systems with both for 100% and incomplete projective covering as our simulation models show. Field measurements of chlorophyll content in closed and open canopies crops confirm the results. A hardware-software complex has been produced by us for chlorophyll determining under field conditions. It consists of spectral and computing blocks. First of them is a two-beam spectrometer of high resolution supplied by a system to visualize of measured object. The irradiance and temperature sensors are included to the spectral block as well as GPS-receiver. The following technical characteristics are inherent to the block: spectral range 500-800 nm, band-pass 1.5 nm, field of view 16x16o, scanning time 0.1-1.0 s, dynamic range of signal 1:1024 (10 bit), signal/noise ratio 400, amount of pixels in image 1240, range of estimated chlorophyll concentrations 1.5-8.0 mg/dm2, supply voltage 12 V, weight 8 kg. Computing block is intended for spectral date processing to obtain chlorophyll estimations using our algorithm. The block is supplied by our original software WINCHL, which includes spectrum and algorithm libraries and various mathematical tools. Accumulation of reflectance spectra of various plants together with data of environmental conditions at measurements gives a good possibility to use all of them for future scientific researches and developing other important parameters of canopy status.

Experiments were designed for analyzing effects of annealing on surface properties of P-type Hg_1-xCd_xTe Liquid Phase Epitaxy (LPE) films. Owing to special surface characteristics of P-type Hg_1-xCd_xTe material, it is necessary and vital to obtain good passivation layer for both high performance photoconductive type and photovoltaic type Hg_1-xCd_xTe detectors. Variable magnetic-field Hall measurement was used to investigate surface properties in temperature range from 1.5 to 200 K for the annealed and unannealed samples. Different temperature behavior of Hall coefficient (R_H) was observed for the two kinds of samples. Surface electrons were observed existing for unannealed samples judging by the low temperature characteristic of R_H (below 10k). In addition to this, C-V measurement of MIS devices made of same annealed and unannealed sample was also used to analyze the effects of annealing. In the C-V measurement applied bias to which annealed samples could bear was larger than that to unannealed one. Meanwhile, fixed charge density in passivation layer of the annealed samples was smaller than that of the unannealed samples. The above results implied surface charge density on the surface of p-Hg_1-xCd_xTe material was reduced by annealing treatment comparing with that without annealing. On conclusion, annealing improved surface status of P-type Hg_1-xCd_xTe material.

The persistent photoconductivity (PPC) effect was generally observed in many III-V compound semiconductors and it was always related to yellow luminescence. In this paper, the PPC effect in unintentionally doped GaN was investigated. The GaN photoconductive detector response time measured by changing the chopper frequency of modulator was studied under various ultraviolet-radiation intensities. The maximum value of UV intensities used in test was approximately 0.2W/m². Experimental results show that the response time of unintentionally doped GaN PC detector is independent of the wavelength of the ultraviolet radiation in the range of 300~365nm and it decreases with the increasing of UV radiation intensity. The longest response time getting in experiments was 7.64ms and the shortest 2.89ms. Fourier transformation and lock-in amplifier was used to reduce the noise at AC frequency of 50Hz and the results show that Fourier transformation was more effective to eliminate the low frequency noise. The experimental data fit the theoretical curve very well, better than the results reported previously. Finally, these phenomena were tried to be explained using a mechanism that minor carriers were captured by deep acceptors. The deep acceptors were deduced to be V_Ga related complexes. In strong UV radiation, the photo-generated holes (minor carriers) were no longer captured by deep acceptors and the recombination opportunities with majority carriers were increased. Consequently the response time was reduced. The other possible reason was that there were metastable states which were related to Ga vacancy.

PbTe based semiconductors are well-known narrow gap IV-VI compounds, which are of interest due to potential application in the fabrication of photo-detectors in the mid- and far infrared spectral range. Among them, Pb_l−xGe_xTe is known to have wider band gap than PbTe, which has been used to fabricate photo-detectors with shorter wavelength (λ<6.7 μm). However, the homogeneity of composition in evaporated Pb_l−xGe_xTe thin films directly from bulk alloys has not been investigated. In the paper, we report the investigation that the homogeneity of composition on the surface was studied using energy-dispersive X-ray analysis (EDAX), and the compositional depth profiles was investigated using Auger electron spectroscopy (AES) in combination with argon ion sputtering. ASE depth profiling and characterization of details in the Ge concentration gradient is demonstrated.

A thermal camera consists of 1024-element MCT line wavelength IRFPA with reading electrocircuit made in china. It is presented the composing of this infrared thermal camera and some key question of this thermal camera: 1) nonuniformity correction; 2) Correction of lines and rows. With same axial transmission optics and a 1-D equality angle scanner and 1024X1600 pixels per frame.the scan efficiency of the sensor is over 88% and the half periods of scanner is 5 seconds. we developed a IR instrument. the main technic target is followed: optics calibre: 90 mm, focus: 270.6 mm, identifiaction ratio:170 urad, wave band: 2-2.5um, the half period: 5 second, NEΔρ: 0.8%.

Gallium Nitride (GaN) UV detectors have become one of the most important UV detectors for much more compact, more robust, higher quantum efficiency and good stability in higher temperature environment than the traditional detectors. We can evaluate the quality of the detectors by detectivity, responsivity, Signal-to-Noise (the detector with read-out circuit), etc. Although these methods can analyze performance quantificationally, they are partial and indirect. The demo imaging system described in this paper provided a simple and more direct way as an assistant method. We can easily assess the performance of the detectors in actual application by the images obtained by the imaging systems. The system is mainly designed for 64x1 linear UV detectors (the band is 330nm ~ 365nm). It is composed of a precise scanner platform to provide 1-D wide field scan (it can be extended to 2-D if needed), UV telephoto optical system, signal transfers and processing system and the software. The detail design of these components is introduced. The images obtained by the system are also given at the end of the paper.

The influence of larger constant current burning was studied and analyses on the failed detectors were given. "1/f" noise is observed in the reign of g-r noise, and the exponential factor had a trend of increasing with burning time. Peak wavelength and cutoff wavelength of the detectors had no apparent change during electrical burning, but there were decreases on the short wavelength side in spectral response. After a long time burning, minority carrier lifetime of the detectors decreased as well as black-body signals. Analyses showed that defects increased at the surface of detectors after burning, which was responsible for decreasing the detector performance, even detector failure.

Comparative analysis of four 4x288 different designed readouts elaborated at the Institute of Microdevices and the Institute of Semiconductor Physics is presented. Also some features of design 576x6 readouts adduced. All the readouts have the direct injection input circuit with incorporated cells allowing testing without photodiodes. TDI registers have three delay elements between neighbor inputs. Some characteristics of 4x288 FPAs with mercury-cadmium-telluride TDI arrays are cited too. 2-phase and 4-phase CCD readouts (2.5 micron technology) have different channel types (surface, buried and semi-buried), which include 10 bit TDI registers in each channel, and 18 channel multiplexing to 16 outputs. Two polysili-con, one metal level and 400 A dielectric layers were used. The readouts characteristics: charge handling capacity, transfer characteristics, output nonlinearity characteristics, bias dispersion, etc. are presented. CCD technology used for data multiplication results in crosstalk increase, because of the presence of rather considerable transfer inefficiency at cryogenic temperatures. Using 2.5 micron CCD technology and 2.0 CMOS technology the readouts, which include the digital interface for dead pixels deselection, preliminary amplification circuits, 36 channel multiplication by CCD registers and 2 beat multiplication by analogue switches to 4 output amplifiers, were manufactured. One pocket CMOS technology with two polysilicon, two metal levels and 350 A dielectric layers were used. To increase the linearity of transfer characteristics and noise level decrease at the output of CCD the circuits of charge-voltage conversion on the base of operational amplifiers were used. This allows getting circuits with parameters close to those obtained by 0.8 - 1.0 micron CMOS technology. Also some characteristics of 4x288 readouts designed by 1.2 micron CMOS technology are discussed (two polysilicon and two metal levels). This one includes the circuits of auxiliary electronics. Comparative analysis shows that the readouts mentioned are different in numbers of outputs, external service but have rather similar parameters.

This paper presents a theoretical analysis of the modal noise in optical fiber communication system. The analysis and Experimental results are carried out to show that to maintain BER, Excess power is required to overcome modal noise due to the splice loss in the single mode optical fibers. The result is useful in the design of long distance fiber optic communication system.