2004 Vol. 25, No. 2
With the wide use of low-light-level,infrared, laser and image processing technology in the modern weapon systems,the optoelectronic weapon systems are developed rapidly and the reliability of the military optical systems, which will directly effect the combat capability and the requirment for the logistical support etc, will catch more and more attention of the people. The development, management and design of the reliability for the military optical systems abroad are introduced. The function and the stress that the other countries laid on the reliability of the military optical systems can be seen from the introduction. With the knowledge of the importance of reliability, when drawing up technical plan and emphasizing the advanced performance of the military optical systems,we will pay more attention to the reliability so that we raise the completeness of our military optical systems and lower the cost of the logistical support.
ABL is a typical application system of very high energy laser, with the property of high motorized, high accurate and lightning attack to the goal,and also with the ability to deal several objects a crushing blow. This system applies to any complicated environments and can win military and political victory at minimum and resumable damage. However, ABL is also a system that USA invests plenty of manpower and material to give priority to its development. The history, composition and develop ment of ABL are introduced the technical development in recent years and excellent performance in the battle field are described.
The chirp parameter of modulators is an important index of performance evaluation in fiber-optic communicalion system. We deduced the expression of the chirp parameter of LiNbO_3 external modulator with Mach-Zehnder structure. It shows that frequency chirp in this structure modulator is not equal to zero and the effect of bias voltage on the chirp parameter can be eliminated. The effect of DC extinction ratio, applied electrical signal and DC bias voltage was analyzed. It shows that negative chirp can improve the dispersion characteristics of system.
A formula of the axial irradiance distribution of a binary annular aperture is derived in detail by using the Rayleigh-Sommerfeld diffraction integral that is valid to a few wavelengths of the aperture. We calculated and analyzed the axial irradiance distribution throughout the whole space behind the binary annular aperture. The results show that its maximum depth of modulation of the oscillation is sixteen times the incident irradiance and four times that of the circular or annular aperture,and that the optical sectioning strength in the near field is better than in the Fresnel region.In the very near field, the axial irradiance distribution has a variety of subtle effects as changing its aperture parameters. These are of potential interest in photonics and fiber-optics application.
The subpixel dynamic imaging technique will be one of the most effective new methods to minimize optical remote-sensors.It is importent and necessary to studying the modulation transfer function of subpixel dynamic imaging system. The fundamental concept and image formation of the subpixel dynamic imaging system are introduced.In this paper, the numerical analysis of MTF of subpixel imaging system is discussed, and the advantages of subpixel dynamic imaging system is pointed out.
In this paper,the polarization characteristic of the particle group scattering based on Mie scattering theory is analyzed, and the correlative experiment is done with two species of particle ball of different diameters(0.26μm,0.55μm). The result shows the polarity of scattering light of the bigger particle in horizontal direction is smaller than the smaller particle. On the contrary, the polarity of scattering light of the bigger particle in vertical direction is bigger than the smaller particle.
Cube-corner retroreflector is a high precision component, which is often used as a cooperative target of laser rangefinder. The errors of three right angles of a Cube-corner retroreflector influence directly the measurement range and precision of the laser rangefinder. And the analytical result is derived and demonstrated with a large mumber of formulas.The author pointed out that even a small error of any angle can not be neglected during the high-precision measurement.In this paper,the reflecting characteristic of the ideal Cube-corner retroreflector is analyzed with vector expression method. At the same time, the relationship between right angle errors and reflected beam is given by the quantitative analysis.
The OCAD optical design software package,which can carry out the national standards and military standards to draw optical system and various accessory (including prism) diagrams automatically according to the optical design data, is introduced. The optical diagrams drawn by OCAD are standard, practical and accurate, and can be used directly in production, which avoid the past hand-drawn work with the Auto CAD and other drawing benches. The OCAD can also use the data files of the other optical design software produced at home and abroad, and can form the data files for the other optical design software for calculation.
Though several methods has been used to suppress the background noise and eliminate the scene influence for the effective ranging capability and angular accuracy demarcating detection,these methods still can not meet the practical requirement for the target at sea.The calculating method of the infrared demarcating theory is defined.Through validation,this method is proved to be reasonable and convenient for application.In order to resolve the diffculty of infrared demarcation and remedy the equipment deficiency, this method is proposed.
Wavelength-shift detection is the key technology of fiber Bragg grating sensor. Several techniques have been developed for demodulation of fiber Bragg grating sensor, such as passive demodulation, matched grating pairs detection,interferometric detection, etc.Various methods for wavelength-shift detection of FBG sensor are described in detail.The principle of all these methods are analyzed. The non-balanced Mach-Zehander interferometer and tunable narrow band light source detection methods are described emphatically. Their advantages and disadvantages are discussed as well.
Methane is an inflammable and explosive gas and a major constituent of mine atmospheres, natural gas and gas fuels. Becuse gas explosion is a big problem in mining industry,real-time and on-line detection of methane has a critical function both for safety assessment and for control of combustion processes. Based on the mechanism near infrared spectral function both for safety assessment and for control of combustion processes. Based on the mechanism of near infrared spectral absorption of methane, a system using absorbent type optic-fiber for high sensitivity methane detection with DFB LD is demonstrated. Light source modulation harmonic measurement is presented in this paper. The ratio of the fundamental and second-harmonic signal presented can be used for eliminating optical interference. The mathematical model of gas concentration harmonic measurement is built up. The result of methane concentration is also shown. Optical fiber is used as transmission medium,thus the sensor part and measurement circuit can be isolated completely.The safety of the systems is inhanced.
For the unstable Gaussian noise of the CCD image, the conventional method of Fourier transform can not eliminate it,but the wavelet transform is the powerful tools of noise elimination,since the wavelet transform in both the time domain and frequency domain has the excellent localization features, and the arbitrary details of analyzed objects can be focused with gradually detailed time domain or frequency domain step at high frequency. Based on the analysis for the CCD image noise,the noise reduction and edge detection is realized with the method of wavelet transform and histogram division. The results show that the clear image edge can be made out after selecting a proper threshold with the histogram division method.
The multifocus image focus is discussed. Since light imaging system has a limited focus range,all other objects have blurry images to some different degrees besides the focused object,but we often want to acqurire a image on which all objects are clear. In order to get such a image, image fusion method can be applied and two multifocus image can be combined. The property of system function of multifocus imaging system is analyzed according to the circuit and system theory, and the conclusion is that the system function of the optical imaging system is a low pass filter.A multifocus images fusion method based on wavelet packet transform is presented according to the fusion perpose and the property of wavelet packet transform.Two practical multifocus images are fused with the fusion method and a satisfactory clear image is obtained. The experiment results show that the fusion method based on the wavelet packet transform can analyze both the low frequency and high frequency parts of the signal simultaneously at multifocus images.An image on which all objects are clear is provided.
Effect of substrate temperatures (from 120℃ to 300℃) and heat treatment temperature(400℃) on the structure and optical property of TiO2 thin film deposited by electron beam evaporation method is discussed. The XRD analysis results indicates that the structure of TiO2 thin films deposited on common glass at the substrate temperatures of 120℃, 200℃ and 300℃ is amorphous, and after the heat treatment at 400℃ for one hour,the amorphous structure crystallized and the crystal phase is anatase with strong preferred orientation(004) and the size of the crystalline is within 3.6～8.1nm.The analysis on transmittance spectrum of all samples shows that with the substrate temperature increasing, the refractive index of thin films increases, and after heat treatment higher refractive index of the films is raised due to its crystallizing.
At present, the application of optical measurement technique makes the measurement data increase tens of times. This can create the difficulty of reconstruction of CAD model. A new adoptive sampling method based on surface variation is proposed in order to reduce mass data acquired by fringe projection measurement.And the computation method of precision sampling is given. Depending on the surface variation,the adaptive sampling point cloud of object is acquired; the CAD model is reconstructed by the sampling point cloud. The sampling precision and the fitting precision reach 2.3μm and 7.2μm respectively.
With the development of the optical communication and optical information,laser reflective mirror and ITF filter is catching people's attention. With the further development in this field, the organic optical film filters and devices will be laid stress on increasingly. And a excellent narrow-band filter will be produced with a low-pass and a high-pass filter at the passband congruence. In this paper several optical thin film devices such as laser reflective mirror,ITF filter, microchip laser are introducted and their fabricated process as well as design method are given, which is very useful in the optical application field.