As one of the important ways of laser imaging, Microelectromechanical system (MEMS)-based mirror imaging has the advantages of small volume and high frequency. In this paper, the relationship between key parameters of MEMS mirrors is studied. Also, the realization method of scanning imaging based on a one-dimensional MEMS mirror is studied. A method of controlling the number of scanning harnesses based on a MEMS mirror is proposed. The single-lens method is used to design and collimate the transmitting optical system with Zemax simulation software, and the effects of the different numbers of scanning wire harnesses are simulated. The result shows that the number of scanning wire harnesses can be controlled, indicating that the system's dynamic accuracy can be achieved.
In order to analyze the backscattering characteristics of pulsed laser fuze in typical smoke, copper powder and iron powder with a particle size range of 3~15 μm were selected, the detection model of pulsed laser fuzes in typical smoke was established based on Mie scattering theory and Monte Carlo method. The pulsed laser fuze is simulated to scatter echoes behind smoke curtains with different detection distances, different smoke screen thicknesses and different emitting laser pulse widths, and the echo intensities of copper powder smoke screens and iron powder smoke screens under the same smoke screen conditions are compared. The results show that the normalized echo intensity of copper powder smoke screen and iron powder smoke screen is negatively correlated with the detection distance. It is positively correlated with smoke screen thickness and emitted laser pulse width. In addition, under the same smoke screen environmental conditions, the echo intensity of the iron powder smoke screen is significantly stronger than that of the copper powder smoke screen, which can be explained that compared with the iron powder, copper powder is more suitable for use as a smoke generator material, the result can provide support for the anti-smoke interference of the laser fuze.
In order to analyze the backscattering characteristics of graphite smoke in pulsed laser fuze, a pulsed laser fuze detection model in graphite smoke was established based on Mie scattering theory and Monte Carlo method. We simulated the graphite smoke backscattering echoes of pulsed laser fuze at various laser pulse widths and smoke visibilities. The results show that the normalized echo peak intensity of graphite smoke approximately exhibits an exponential growth relationship with the pulse width, while a power function decay relationship with the visibility. Compared with the emitted laser waveform, the graphite smoke echo waveform is distorted, presenting an asymmetrical feature with steep rising edge and gentle falling edge. Moreover, the narrower the laser pulse width, the greater the smoke visibility, and the more obvious the echo waveform asymmetry. This study provides a theoretical basis for exploring ways to enhance the detection performance of pulsed laser fuze in the graphite smoke environment.
As a method of active laser interference, energy laser interference can be used to interfere with laser fuzes. This paper studies how the energy-type laser interference the pulsed laser fuze. By simulating the transmission characteristics of the fundamental mode Gaussian beam in free space, the energy transmission model of the fundamental mode Gaussian beam is established. The thermal conductivity theory is used to calculate the thermal effect of the fundamental mode Gaussian beam irradiating the photosensitive surface of the Si PIN photodetector, and the related physical processes are discussed. The results show that a monopulse laser with a wavelength of 1064 nm, pulse width of 10 ns, and peak power of 11.5 MW can generate a temperature of about 1800 K in the center of the silicon photosensitive surface,which can cause irreversible damage to the photodetector, and the detection performance of the photodetector is sharply weaked or even unfunctioned. This result provides theoretical basis for the further development of the jammer.
In order to solve the problem of overall measurement of smoke mass concentration field and real-time dynamic measurement, a set of method is designed, which by collecting gray scale information of smoke distribution image, and then calculating the smoke mass concentration. The experimental results show that, under a certain environmental condition, the gray scale of smoke image has a strongly related quadratic linear relationship with the laser backscatter echo voltage at the corresponding position. Moreover, combining the relationship between the laser backscatter echo voltage and the mass concentration of smoke in the same position, the mass concentration of smoke can be calculated by the value of gray scale. The method of the paper refer to, breaks through the limitation of the existing equipment which only can measure the partial mass concentration of smoke, and the method provides a basis for the development of smoke real-time dynamic measurement of smoke.
Caliber mortar projectiles and bombs are now tend to use the laser fuze because of its high accuracy in
distance measurement,the strong ability to resist electromagnetic interference, the high angular resolution and the good
concealment. Otherwise, the microlaser can bring about some alluring benefits. For instance, it can generate high quality
laser beam, which has small divergence angle and high power. So, This paper summarizes some key factors which have
impacts on the output of LD-pumped passively Q-switched subnanosecond microlasers, including the initial transmission
of the absorber, the reflection of output coupler, the length of the cavity and the radius of the pumping laser beam, and
gives the conclusion of the simulation based on the variation of the density of the reversal particle in the resonant cavity
derived from the oscillation equation of the LD-pumped passively Q-switched Cr4+:YAG/ Nd:YAG laser, which
provides the basis for the design of the passive Q-switched micro lasers which have high power, high repetition
frequency and narrow pulse width.
With the rapid development of semiconductor technology and laser technology, a kind of proximity fuze named
pulsed laser proximity fuze has been applied. Compared with other fuzes, pulsed laser proximity fuze has high ranging
precision and strong resistance to artificial active interference. It is an important development tendency of proximity fuze.
The paper analyze the characteristic of target echo of laser signal, and then make theoretical analysis and calculation on
the laser signal transmission in the smog. Firstly, use the pulse width of 10ns semiconductor laser fuze to do typical
targets experiment, to get the echo information of target distance is 5m; then to do smog interference experiment, by
comparing the pulse width amplitude and backscattering signal amplitude of laser fuze in simulation and experiment,
analyzing the effect of anti-clutter, providing the evidence for the subsequent of circuit of signal amplification and
processing.
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.
With the development of semiconductor laser technology, laser proximity fuzes have been widely used in various kinds
of guided missiles and routine ammunitions. And its precision of ranging has a direct influence on the overall
performance of the system. This work employed Spartan III series FPGA chip from Xilinx company. Through phase
shifting the primary reference clock and ranging with four doubled-frequency clocks with each phase shiftings of 90
degree, the ranging precision can be improved obviously. The theoretical ranging error is 0.1875m and the result has
been proven by simulation with Modelsim. Valuable conclusions were drawn for improving the ranging precision of
laser fuze.
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.
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.
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.
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.
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.
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