2013 Vol. 6, No. 4
Smart optics is an emerging concept developed from conventional optics based on the active optics and adaptive optics. This paper introduces the evolution and development of smart optics and explains and extends its concept and scopes further. Then, it summarizes and comments the developing states and applications of the smart optics, which mainly includes the dynamic optical modulation, dynamic optical sensing, and smart optics systems, involving the telescopes, microscopes, lasers, etc. in the applications of astronomy, military, space, biology, medicine, etc.. Finally, the future outlooks of developments and applications of smart optics are given.
Due to the compatibility of Si-based light emitters with Si CMOS processes, Ge/Si heterostructures based light emitters have developed significantly. This paper reviews the most recent progress of this field, including Ge/Si Quantum Dot(QD) Light Emitting Diode(LED), Ge light emitting diode on Si, Ge laser on Si, and Ge/SiGe Multiple Quantum Well(MQW) light emitting diode. It describes the characteristics of these light emitting devices and how to enhance their luminescent properties. Finally, it discusses the challenges and opportunities associated with these approaches and suggests that much innovation should be promoted in material and device structures.
As the performance changes of thermal control materials in-orbit effect the temperature of a spacecraft, the performance of Multi-layer Insulators(MLI) in-orbit are studied in this paper. Firstly, the destructive testing of thermal control materials at a simulation test for space environments is introduced. Then, the test data of the of MLI samples from Hubble Space Telescope(HST), Long Duration Exposure Facility and the International Space Station are compared. At last, the ground-based test of thermal control replacement materials for the HST is expatiated. Compared to the data of flight and ground testings, it is concluded that the coincidence from atomic oxygen and thermal cycling is the primary factor to damage the outer surface of the MLI, while ultraviolet radiation and charged particle radiation have a weaker effect. The conclusion might provide a reference for planning and revising the ground acceleration testing and thermal design for long-life spacecrafts.
Digital speckle correlation(DSCM) is a noncontact measuring method for displacements and strains, which obtains the mechanical properties of an object by calculating the gray information correlation of the object images before and after deformations. The method has been applied successfully in mechanical measurements in the past twenty years. This paper introduces the developing states of the DSCM and gives application examples. Some new technologies involved in the DSCM are reviewed, such as genetic algorithm, neural networks and wavelet transform. Finally, it points out that DSCM research will focus on improving measuring accuracy and image processing speeds in the future, including improving speckle image quality and researching higher effective algorithms.
The principle and optical design of digital sun sensors widely used in different fields are reviewed and their applications and development are given. Firstly, it describes the working principle of sun sensors. The digital sun sensors are constructed with the principle of pinhole camera, and it consisted of a optical system, a photo detector and a information processing unit. Then, the paper gives the optical systems, which may be implemented with a single aperture, or a single split, or multiple apertures, or multiple splits. Furthermore, it focuses on the development of the digital sun sensors based on conventional photo detectors and micro detectors integrating the optical system, image sensor and the information processing unit, and also introduces centroiding algorithms for sun spots. Finally, the future challenge and development trends for space sun sensors are discussed.
Laser-induced Breakdown Spectroscopy(LIBS) based on atomic emission spectral technology is a kind of convenient and sensitive approach for the qualitative and quantitative detection of elements. In this paper, the mechanism, detecting element types, detection limit and the recent progress of LIBS technology are reviewed. The progress of LIBS technology in component testing for solid, liquid and gas samples is expounded in detail. The applications of LIBS in the environment test, food security, biological and medicines, material sciences, military and space fields are also presented. Finally, the challenges and problems for the LIBS technology in high power and stable laser sources and accurately quantitative analysis method are discussed.
3~5 m mid-infrared laser sources have significant applications in many fields and have been intensively studied by researchers. Main technical methods to generate mid-infrared laser radiation are reviewed in this paper, which are as follows:second harmonic generation of CO2 laser, first-overtone CO laser, optical parametric oscillator, DF laser, Fe2+: ZnSe solid laser. The key techniques and problems of each method are concluded and analyzed. The technology tendencies of mid-infrared laser sources are summarized.
In this article, the degradation mechanism of contaminants with nano-TiO2 in a photocatalytic reactor is introduced. Then, it points out that the design, modification and development of the fiber-typed photocatalytic reactors have been performed to improve the photocatalytic efficiency and the loading technology and reultilization of photocatalysts also been plaid much attention. Finally, it summarizes the research and application progress of fiber typed photocatalytic reactors at home and abroad, and gives a brief analysis and recommendations to the future development of these technologies based on the technical difficulties of the photocatalytic reactors.
To reduce the interference of color coupling and color unbalance and to increase the reconstruction accuracy of shape and color in a coded structured light system, a color coded structured light system was established and two color-related sections(coding principle and color reconstruction) and their color calibration methods were investigated. First, based on the coding principle by color trapezoidal phase-shifting intensity ratio, the mutual coupling phenomenon between RGB primary colors in coding process was analyzed, and color coupling calibration scheme by Caspi model and hardware calibration was designed. Then, based on point-by-point color reconstruction method, the unbalance phenomenon caused by surface curvature in color reconstruction process was analyzed, and color unbalance calibration scheme using surface geometry information was designed. Calibration experimental results indicate that the red component in pure green after calibration is about 1/10 of that before calibration; and calibrated chromatic aberration of unicolor surface is about 0.1, which approaches to the visual resolving power and is significantly less than that before calibration(0.4). Moreover, the reconstructed unicolor complex surface has uniform color and good visual effect and is accorded with measured surface. It can satisfy the system requirements of strong anti-interference, and is conduced to the reconstruction accuracy of shape and color.
On account of the characteristics of laser double-pass processing, a Nd: YAG pulsed laser is chosen as the light source, and a laser time-sharing control system for double-pass outputs is developed. A concrete implemented project for time-sharing spectral technology is put forward, the beam split device is designed to achieve time-sharing beam split, and the time-sharing control circuit is designed to control the device in real time. Then, system program procedure is determined. Finally, laser outputs from different ports in different time are obtained under keeping the output powers. In order to avoid fiber damaging because of the jittering from beam split device, black photographic paper is used to sample of facula. The result shows that the best delay time is 300 ms from changing the holophote position to laser output. This system can not only realize time-share multiplexing and dynamic spectral splitting, but also can satisfy the need of double-pass outputs. Furthermore, the system has a stronger expanding ability, and can provide the convenience for laser improvement and upgrade according to the laser processing condition in reality.
A compound guided system by combining the laser 3D active imaging and passive IR imaging was proposed to improve the operational effectiveness for air-ground missiles and the recognition ability for IR stealthy targets. The detail design program and reasonable guided strategy were also given. This system has the ability of IR wide field searching and laser 3D imaging in a narrow field and its abundant image information makes the operational object recognition more easy. The structure of the whole system is simple and easy to process. When the aperture of the compound guided system is limited at about 100 mm, the guided distance is longer than 4 km. This technology is important to develop compound guided systems and improve the missile operational ability in our country.
To meet the high stability requirements of the extreme ultraviolet(EUV) light source driven by a CO2 laser under the Laser Produced Plasma(LPP) system, the simplified CO2 laser transmission system model is established. The monitoring and controlling methods of the beam power, pointing and the location are studied theoretically and experimentally based on the requirements of the beam stability. The beam monitoring and controlling experimental system is set up in a laboratory according to the characteristics of the high-power CO2 laser transmission system. The system includes a beam power control module, a beam pointing control module and a beam parameter monitoring module. The beam parameter monitoring module can accomplish the real-time measurements of beam powers, pointing, sizes and divergence angles and other important parameters. The simulation and experimental results show that the beam power control module can control the linearly polarized laser power from 1% to 100% and the beam pointing control module can control the beam pointing stability to be less than 10 rad, which meets the high stability requirements of the extreme ultraviolet(EUV) lithography for the CO2 laser source under the Laser Produced Plasma(LPP) system.
A type of wideband anti-reflection film in the visible light spectrum from 0.4 m to 0.8 m was designed based on a ZF6 substrate, then the coatings were fabricated by Electron Beam Physical Vapor Deposition(EBPVD). Two types of coating materials, titanium oxide(TiO2) and silicon oxide(SiO2), were treated as high index and low index materials, respectively to use in this process. Edinburgh spectrometer was used to measure the transmittance of the sample which was coated the anti-reflection coatings on both side. The test result indicates that its average transmittance is about 98.15%. It shows wideband anti-reflection characters and little surface residual reflection, and almost accords with the designing result. The measurement of stability and firmness indicates that the coatings have good performance, which makes it possible to be used in some rigorous optical systems.
According to the special requirements of space communication, a 1 555 nm high transmittance and broad band-pass filter was designed and prepared to operate under high temperature and high humidity environments. TiO2 and SiO2 were selected as coating materials to produce a large refractive index difference and the Quarter-wave Optical Thickness(QWOT) film was designed based on the design theory. Then, the non-QWOT film was optimized by using the needle optimization and double sided coating by Optilayer software. The monitoring technique in the experiment was combined with direct monitoring and indirect monitoring, and the method were also discussed. A filter film with a transmittance of 97% in the center wavelength and a half-width of 50 nm was manufactured under electron beam evaporation by ion assisted. Experiments show that the wavelength shift of the filter film is only 0.2 nm in a high temperature of 100℃ and a low temperature of -30℃ for 3 hours each. Moreover, the film maintains high stability and reliability, which meets the requirements of space communication.
A new single digital stereo dual-channel projection system is introduced and a dual-channel projection lens is designed by using ZEMAX software and an artifical structure method. The structure of lens based on refraction type is off-axis and with three optic axes. It includes a former group and a back group. The former group is composed of seven glass sphere lenses and the back group consists of two identical and symmetrical structures composed of four glass sphere lenses. The lens has a total length of 243.8 mm, a maximum diameter of 93 mm, and a focal length of 20.23 mm. Moreover, its Field of View(FOV) and F-number are 36 and 2.01 respectively, and the distance of two assistant optic axes and the Back Focal Length(BFL) are 8.2 mm and 37.8 mm, respectively. The system performs excellently in image quality, and has advantages of small size, simple structure and low cost.
This paper designs and develops a class AAA solar simulator and its spectral matching, Irradiance non-uniformity and irradiance temporal instability all can reach class A standard. It firstly describes the light source selection of the solar simulator and gives the design process of the filter. Then, it introduces the optical system and mechanical structure of the solar simulator. Finally the technical specifications of the simulator are measured. The experiments show that the solar simulator spectral match meet the ASTM E927-10 the AM1.5G class A requirements in the wavelength range of 400-1 100 nm. In an effective irradiated surface area of 55 mm55 mm, its average irradiance, Irradiance non-uniformity, and irradiance temporal instability have been up to 1 000 W/m2, 1.35% and 1.27%, respectively. Obtained data demonstrate that the solar simulator meets the standard ASTM E927-10 class AAA.
In order to realize the rapid and real-time data pre-processing of an imaging spectrometer based on Acousto-optic Tunable Filter(AOTF), the data characteristics and a pre-processing algorithm of the imaging spectrometer based on AOTF were analyzed. Then, a scheme of dual Digital Signal Processor(DSP) parallel processing system based on two chips of ADSP-TS201 coupled the external bus sharing and the link ports was proposed by using DSP instead of the traditional computer processing platform as the key device. Proceeding from practical requests, a pipeline processing was designed, pre-processing tasks were allocated rationally, and the functional verification was implemented. The practical application shows that it takes 23.5 ms to accomplish the pre-processing task for one frame data of imaging spectrometer based on AOTF, which increases 13 times than that of PC and meets the real-time requirement. The system proposed in this paper promotes the development of systematism, modularization, miniaturization and the capability of real-time processing of the imaging spectrometer based on the AOTF.
To obtain a high quality image from the new type imaging spectrometer, the uniformity correction method for the image was studied according to the characteristics of the image. The new type imaging spectrometer was placed on the rotation stage to simulate the pushbroom of the imaging spectrometer, then the image was got by the imaging spectrometer. The sun was used as the uniformity correction source of the image for the imaging spectrometer, and the data cubic was progressed by the software. Experimental results indicate that high quality image is obtained by using this method, and it also verifies the high performance of the new type imaging spectrometer. The correction time for one pixel is 210-6 s, but much time is needed for large volume of images in the image uniformity correction. Moreover, a diffuser was used as a extended source to correct the image with uniform luminance, and the correction uniformity is less than 4%.
To develop a diffuser for CO2 detector calibration, the process of physical grinding and chemical etching was used to produce the test specimens of the aluminum diffuser for the CO2 detector calibration, and their test devices for relative Bidirectional Reflectance Distribution Function(BRDF) and hemispherical reflectance were built. In the case of 0 and 45 of the incident lights, the test results for visible to near-infrared band, show that the surface roughness affects Lambert characteristics of the aluminum diffuser and the Lambert characteristics of the diffuser made of 240# abrasive grit is the best. Chemical corrosion can not only improve Lambert characteristics of the aluminum diffuser, but also can improve the hemispherical reflectance. When etching temperature is selected at 20℃ and the concentration of NaOH solution is in 52.6 g/L, the optimal time of corrosion is about 4 min. Aluminizing makes hemispherical reflectance of aluminum diffuser to be improved by 20% on average, but it makes Lambert characteristics deteriorated. Furthermore, the relative BRDF of aluminum diffuser is slightly different at different wavelengths, but shows the same trend. The experiments in this paper determine the key parameters affecting the diffuse reflection characteristics of the diffuser, quantitatively optimize process parameters, and provide a basis for the further development of the diffuser for CO2 detector calibration on orbit.
An automatic detection system was designed to quickly and accurately detect the precision of a miniature photoelectric encoder. A 21 bit high precision photoelectric encoder was used as the reference to detect the low precision miniature photoelectric encoder. The control system was taken to rotate the encoder first, and the difference of the high precision encoder and the miniature encoder was the error of the miniature encoder. After the testing was completed, the errors of encoder were transmitted to the host computer through the USB interface to save and to perform an in-depth analysis. A 15-bit encoder was detected by using the system, the mean square deviation of the encoder is 29.1 s, however the mean square deviation of the encoder is 28.5 s when the detection is done by the traditional methods. Obtained results meet the accuracy requirements.