This article described the rotation angle system of the bidirectional reflectance distribution function (BRDF) measurement device. A high-precision multidimensional angle platform device is built. The rotation angle system uses two scanning rotational mechanical arms and a two-dimensional coaxial turntable mechanical structure, each rotational axis are driven by high-power motor and completed closed-loop control with high-precision encoder. Rotation of the motors can be automatically measured in accordance with point by the control software. The detecting arm can be rotated to measure any point in hemisphere space, the rotary range of light arm is ± 90 °, the rotary range of sample stage is 360 ° and the angular resolution is 0.01°. The rotation angle system meets the absolute positioning hemisphere space requirements of BRDF device. The experimental result shows that the rotation angle system met the high-precision positioning requirements for the BRDF absolute measurement.
The bidirectional reflectance distribution function (BRDF) diffuse plate as the standard of value transfer and carrier for BRDF, plays an important role in the study of radiometric calibration and scattering properties of. The space spectral characteristics of developed BRDF diffuse standard plate were measured by BRDF standard device. The standard BRDF values were given under more wavelengths and more geometric conditions in the visible to the infrared spectral bands, and the uncertainty is 1%. By comparison, the developed BRDF diffuse standard plate in visible and infrared bands reached the similar international standards plate level.
A large aperture uniform radiation source integrating sphere (URSIS) based on a 4m diameter internally illuminated
integrating sphere with a 1.6m diameter exit port was designed and manufactured. This URSIS was used for pre-launch
test and radiance calibration of large aperture imaging radiometers which fly aboard earth-borne remote satellites. Design
criteria of the large aperture URSIS including sphere source radiance output, spatial radiance uniformity and radiance
stability were presented. Integrating sphere internal lamp sources specifications and sphere coating selection were also
concerned to suit the requirements of the multi-spectral-band imaging remote sensors.
A new radiance calibration method of the URSIS based on Re-C blackbody was applied. The radiance calibration
uncertainties varied from 2.8% to 3.5% with a coverage factor k=2 were achieved.
The spectral radiance of the large aperture URSIS was characterized in the wavelength region from blue to near-infrared
of spectrum. The spatial radiance uniformity of the large aperture URSIS was better than 99.0% and the stability was
better than 0.4% over a period of 2 hours after an initial 30 minutes warm-up.
Although Ray tracing method is an effective aided design method in optical system, the uncertainty caused by this
method is not very clearly. The relationship between the number of rays and uncertainty has been explored in this paper,
while using the Monte Carlo algorithm in Ray tracing method. It shows that if the simulation relative deviation should be
limited to 0.1%, at least 1000000 rays must be used.
Regarding to the mistakes that optoelectronic devices such as CCD focal plane arrays devices are often placed on the exit port plane of integrating sphere source to perform calibration, the output irradiance uniformity of integrating sphere source is analyzed, the basis which rational using the integrating sphere source to calibrate the optoelectronic devices is obtained. Two theoretical output irradiance uniformity models based on numerical analysis method and Monte Carlo method are developed respectively. The models consider two fundamental situations of integrating sphere sources, namely (1) ideal lambertian source and (2) non-ideal lambertian source. The distribution regularity of irradiance uniformity was generalized by contrast of the theoretical data obtained by the models and the measured data obtained by two different actual integrating sphere sources. The results show that when (1) the diameter of optoelectronic device is less than half diameter of the sphere exit port, and (2)the ratio of the distance from device to exit port and the exit port diameter are between 3 and 5, a 99% better output irradiance uniformity can be obtained. The results provide a practical guide to ensure the accuracy of the calibration exercise of optoelectronic devices.
KEYWORDS: Cameras, Optoelectronics, Digital cameras, Digital imaging, Signal to noise ratio, Imaging systems, Visualization, Integrating spheres, Fiber optic illuminators, Sensors
The opto-electronic conversion function (OECF) is defined as relationship between
input luminance and digital output levels for an opto-electronic digital image capture
system. It is a fundamental parameter to evaluate the performance of digital
still-picture camera. An experiment device was set up to measure OECFs by using
test charts with twelve neutral patches stepped in different visual density increments
and a integrating sphere uniform illuminator. To determine the camera OECFs,
images of the test charts were captured under controlled conditions for computer to
calculate. For each trial, the mean digital output level shall be determined from a 64
by 64 pixel area located at the same relative position in each image. Several digital
still-picture cameras were selected as test samples and their OECFs were different
under a larger range of illumination. Besides, the dynamic range, incremental gain
and SNR also have been calculated using the OECF test charts images data.
For measuring large-aperture optical system transmittance, a novel sub-aperture scanning machine with double-rotating
arms (SSMDA) was designed to obtain sub-aperture beam spot. Optical system full-aperture transmittance measurements
can be achieved by applying sub-aperture beam spot scanning technology. The mathematical model of the SSMDA
based on a homogeneous coordinate transformation matrix is established to develop a detailed methodology for
analyzing the beam spot scanning errors. The error analysis methodology considers two fundamental sources of scanning
errors, namely (1) the length systematic errors and (2) the rotational systematic errors. As the systematic errors of the
parameters are given beforehand, computational results of scanning errors are between -0.007~0.028mm while scanning
radius is not lager than 400.000mm. The results offer theoretical and data basis to the research on transmission
characteristics of large optical system.
The comparison goniometer is widely used to measure and inspect small angle, angle difference, and parallelism of two
surfaces. However, the common manner to read a comparison goniometer is to inspect the ocular of the goniometer by
one eye of the operator. To read an old goniometer that just equips with one adjustable ocular is a difficult work. In the
fabrication of an IR reflecting mirrors assembly, a common comparison goniometer is used to measure the angle errors
between two neighbor assembled mirrors. In this paper, a quick reading technique image-based for the comparison
goniometer used to inspect the parallelism of mirrors in a mirrors assembly is proposed. One digital camera, one
comparison goniometer and one set of computer are used to construct a reading system, the image of the sight field in the
comparison goniometer will be extracted and recognized to get the angle positions of the reflection surfaces to be
measured. In order to obtain the interval distance between the scale lines, a particular technique, left peak first method,
based on the local peak values of intensity in the true color image is proposed. A program written in VC++6.0 has been
developed to perform the color digital image processing.
In the progress of wavenumber traceability using polystyrene films, different peak-seeking algorithms are discussed in
this paper. Conclusion shows that in commonly used methods, spline method, center of gravity method and the second
derivative method, spline method is better than the others with simple algorithm and good agreement. It is strongly
recommended to use in practical for calibrating FTIR spectrometer.
A technique of fiber array structure of visible to infrared image transducer for infrared imaging control and guide was
discussed. Be different from the normal fiber array, the structure here is micro-fabricated on quartz glass covered with
visible absorb member in front of the fiber. The fiber array structure works in vacuum and cooling chamber. The 3D
model of fiber array structure for finite element analysis based on the secondary radiation was established. The material
parameter, including density, specific heat and thermal conductivity, and the structure size including section size, length
of fiber array transducer for temperature and time character were studied. The simulation results show that the thermal
conductivity and length of fiber array are key parameters for transducer's property, and the optimized parameters for
fiber array structure transducer were given. The fiber array structure of visible to infrared image transducer has the
advantage of higher spatial and temperature resolution, and less manufacture cost. The optimized parameter for fiber
array visible to infrared image transducer can reach the frequency of 100Hz and higher temperature of 250°C in case of
increasing impulse power which can be used as infrared scene projector in hardware-in-the-loop simulation experiment.
Dichroic beam combiner is the kernel technology of the dual mode guiding simulation system. Based on the photonic
band gap structure of one-dimensional Photonic crystals, a new method of designing a diachronic beam combiner is
proposed in this paper, through which mid-IR region high reflection mirror coating is designed and calculated by using
plane-wave expansion method. Simple construction, combination of broad wave band beams in 2D and wide-angle is
realized, and polarization of off-axis incident beams is prevented. The analysis of infrared reflectivity and radio
frequency transmission rate demonstrates that this new method can perfectly satisfy the demand of design.
Laser fuze is a kind of proximity fuze developed with laser technology. A encountering simulation system for laser fuze
based on environment simulator and fiber retarder is introduced in this paper. The system can simulate the process for
the laser fuze to approach the target quickly, with consideration of changing light path and intensity caused by factors
like environment and distance. It can be a reference for the future design of laser fuze.
Chemically synthesized Ag nanowires (NWs) can serve as waveguides to support propagating
surface plasmons (SPs). By using the propagating SPs on Ag NWs, the surface-enhanced Raman
scattering of molecules, located in the nanowire-nanoparticle junction a few microns away from
the laser spot on one end of the NW, was excited. The propagating SPs can excite the excitons in
quantum dots, and in reverse, the decay of excitons can generate SPs. The direction and
polarization of the light emitted through the Ag NW waveguide. The emission polarization
depends strongly on the shape of the NW terminals. In branched NW structures, the SPs can be
switched between the main NW and the branch NW, by tuning the incident polarization. The light
of different wavelength can also be controlled to propagate along different ways. Thus, the
branched NW structure can serve as controllable plasmonic router and multiplexer.
Compared with other imaging approaches, high resolution angle-angle-range imagery provided by the three dimensional
imaging laser radar increases probability of target identification. Based on scannerless pulsed time-of-flight method, this
paper presents breadboard laser radar for proof-of-principle. A laser transmitter using laser diode flood illuminates a
target area with a relatively short pulse, then a receiver collects the returned energy on a 4x4 PIN diode array where each
pixel measures range respectively. Each of 16 channels consists of a TIA, main amplifier, timing discriminator and a
TDC channel. A processor based on microcontroller processes the output result of all pixels from two TDCs, then
transfers final range data to laptop for visualization. Here we present some preliminary intensity images of target
acquired through indoor experiments. Through these results, the feasibility of direct-detection imaging laser radar for
short-range target identification has been proved. Meanwhile, further development of this system is discussed.
A model of photodetector was established, and the expression of the interference to the photodetector caused by sunlight
directly propagating into the detector was given. With integrals over area elements, the filling of the view field of the
photodetector by the ground was discussed in detail. The expression of the interference to the photodetector caused by
sunlight scattered by the ground was deduced. The research presented in this paper is a contribution to the application of
photodetectors.
KEYWORDS: Digital signal processing, Laser processing, Laser systems engineering, Semiconductor lasers, Data acquisition, Target detection, Pulsed laser operation, Laser applications, Field programmable gate arrays, Signal processing
Because means of target detection is simple, laser short-range detection system using analog processing has high False-
Alarm Rate. The requirement of target detection under complicated background can not be satisfied. Based on DSP and
FPGA, this paper presents a mini laser short-range detection system using real-time digital processing. The modularized
idea is applied to design the system. Every function module is designed respectively. The prototype is finally constituted,
which provides algorithm of target identification and acquisition of echo data with hardware platform. The requirement
of future application under strong clutter is satisfied.
With the development of semiconductor laser technology, laser proximity fuzes have been widely used in various kinds
of guided missiles and routine ammunitions. Combined with the current situation, the digital laser fuzes system based on
the FPGA has been proposed in this paper. Combined with the current situation, the system has been divided into
emitting module, receiving module and signal processing module, the three modules have been analyzed in details. In the
emitting module, the driven circuit based on the FPGA has been developed, the laser pulse with 20ns width and 10kHz
repetition frequency have been obtained. Meanwhile, the emitting optical system and receiving optical system have been
designed. In the receiving module, the receiving circuit with preamplifier and A/D sampling and convert circuit have
been developed. In the signal processing module, anti-interference methods were proposed which can find applications in
the laser proximity fuze research.
An analytical study of THz-waves' intensity measurement generated by Terahertz Parametric Oscillator (TPO) and
detection of the THz pulses occurs via free-space electro optic detection by ZnTe crystal has been studied. The
pump-probe technique has been used to observe the dynamics of an optically excited ZnTe electro-optic crystal. THz
wave will be used as modulation source for electro-optical phenomena in ZnTe crystal. The THz pulses generated by
TPO are 10-25 ns pulses at a repetition rate of 1Hz. ZnTe crystal is being used for intensity measurement of THz-waves.
In this theoretical proposed experiment, a short pump pulse (THz-wave) and probe pulse (near IR laser) with duration of
typically 10 to 25 ns interacts in the ZnTe. In electro-optic sampling the two effects namely Pockels effect and Kerr
effect have been discussed and interaction of two beams from or transmission through the ZnTe, the probe pulse Intensity
contains information about the THz-waves' intensity and so on.
With the development of the laser and radar technology, imaging lidar has been widely used in the fields of military
applications. Without the scanner devices, scannerless imaging lidars have the characteristic of high frame rate, wide
field of view and high reliability. Three kinds of scannerless imaging lidar system, such as based on the phase
scannerless imaging lidar, based on the multiple-slit streak tube imaging lidar and based on the flash lidar have been
analyzed in this paper. Moreover, the principle, the characteristics and limitations were investigated. Valuable
conclusions were proposed for the selection of scannerless imaging lidar in certain circumstance.
Ultrasonic inherent characteristic and underwater environment make underwater ultrasonic image have speckle noise, and image contrast is low. So need a method to reduce speckle noise and enhance image contrast at the same time. In certain applications, however, the removal of speckle and image enhancement may be two contradictory problem each other, so we difficult to gain an ideal image processing result. For this reason, considerations in characteristic of the
underwater ultrasonic image, this paper provides a new speckle reduction and image enhancement anisotropic diffusion method based on wavelet technology. An anisotropic diffusion model has been established based on wavelet transform. We analyze the characteristic of the model and discuss the model's mechanism of action for removing speckle and enhance image edge of the underwater ultrasonic image. A compare experiment for real underwater ultrasonic image has been done using the method and other traditional methods. The experimental result indicates that the method proposed have strong speckle reduction and enhancement image ability. The purpose of removing speckle noise and enhancing edge at same time has been reached.
Laser ranging is to measure the distance of a target with laser beam. Having the advantages of narrow beam and strong resistance to electromagnetic interference, it has been developed and researched by many countries. Because of the complexity of backgrounds and targets, it is necessary to research the related laser echo characteristics. The power, waveform and other identities of laser pulse echo from targets are analyzed based on the experimental results of the laser ranging system. Valuable conclusions were drawn for the laser echo characteristics for different materials.
Laser diodes are widely used in many fields, but the poor beam quality is an obvious deficiency. The intensity
distribution of a beam from a laser diode in the slow axis is so complex that it is difficult to be described by a Gaussian
distribution of a certain order. The beam qualities of a certain type of laser diode in the directions of perpendicular and
parallel to junction are evaluated in this paper. The intensity distributions in two directions are described respectively by
fundamental mode Gaussian distribution and multi-mode Hermite-Gaussian distribution. The computed data is basically
in accord with the experimental data. The mathematical model may provide some suggestions for the designing of optical
system with laser diodes and related simulations.
With the development of semiconductor laser technology, laser proximity fuzes have been widely used in various kinds
of guided missiles and conventional ammunitions. Conventional laser proximity fuzes consisting of separated
components, have the disadvantages such as large volumes and poor anti-jamming abilities, so are not satisfied with the
modern warfare circumstances. Combined with the separated components, the system has been divided into transmitting
module, receiving module and information processing module, the different modules have been analyzed in detail,. Meanwhile, the transmitting driven circuit has been developed and laser pulse with 20ns narrow width was obtained. In order to meet the multifunction and miniaturization, laser fuzes based on MEMS/MOEMS have been introduced in this paper. Technologies include vertical-cavity surface-emitting laser, integrated resonant-cavity photodetector and refractive micro-optics. The entire structure was roughly 1~2mm thick and 1mm on a side.
With the development of VLSI, CMOS image sensor has developed increasingly. The history of CMOS image sensor
was introduced, on the basis of analyzing the principle of CCD and CMOS image sensor, the advantages of CMOS
image sensor was summarized. The current research status and commercial productions of different companies were
described in this paper, moreover, the technical specifications were presented. At last, the current applications and trends
of CMOS image sensor was focused.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.