New technique to record and playback holographic color video memories

A low-cost and simple color-encoding technique for holographic video memories is proposed and designated as a “stripe-coded” method. The playback system requires a laser of a single wavelength, a black-and-white vidicon installed TV camera and a common color TV monitor. One frame can be stored in a hologram of 4-mm diameter, and the storage density is several times higher than that of the conventional TV films. Color images of satisfactory hue and saturation were successfully restored.     

Submillimeter laser interferometry with pyroelectric image recording

The interferometer with a submillimeter laser and standard pyroelectric TV camera for visualization of interference fringe pattern is described. Problems typical for the development of such interferometer are solved by choosing of a proper arrangement and a mutual spacing of its elements with respect to laser. The interferograms of a teflon wedge and an arcing plasma are presented as an example.     

Electronic speckle pattern interferometry using a CO2 laser

The advantages and problems of using electronic speckle pattern interferometry (ESPI) at longer (infra-red) wavelengths are discussed. The adjustment and use of an ESPI set-up with a CO₂ laser and pyroelectric vidicon are described and illustrated by some experimental results.     

Investigations of optically pumped submillimeter wave laser modes

A complete theory for waveguide laser modes for oversized metallic and dielectric waveguides with circular cross section has been developed for the submm wavelength region. The experimental investigations have been done by a submm heterodyne technique for the first stage using a Schottky barrier diode in an open structure mixer.     

Holographic vibration measurement using a tv speckle interferometer with silicon target vidicon

A basic realization of a TV speckle interferometer applying a silicon target vidicon is described. The increased detectivity compared with other vidicons reduces the laser power requirements. This enables stroboscopic operation in a fairly straightforward manner with a He-Ne laser source. Time average- and stroboscopic fringe patterns for a vibrating test object are presented.     

Autler-Townes effect in a Submm laser interacting with a radiofrequency field

Coherence effects due to interaction of an optically pumped submm laser with a strong radiofrequency field have been observed on the D₂CO line at 733 μm, the submm emission mode is split into two components, in a way similar to the Autler-Townes effect. Higher order multiphoton interactions are shown to distort the lineshape of the absorption changes. New emission due to population transfer induced by the radiofrequency field to levels not directly pumped by the infrared laser has also been observed. These effects are helpful not only to assign the levels involved in the submm emission process but also they can be used to amplitude modulate or to switch the submm emission.     

红外光学透镜焦距测量

采用CO₂激光器作为光源,热释电摄像机作为探测器,采集了单缝衍射图像.根据单缝衍射原理,测量了不同焦距的一组红外光学锗透镜的单色焦距,给出了实测结果.讨论了影响测试的主要误差因素.通过计算采样数据的调制传递函数,精确确定被测透镜焦平面的位置.介绍了图像采集系统长度尺寸的精确标定方法.     

Diffusion and vibrational bottleneck in optically pumped submillimetre lasers

By observing the time dependence of the onset of the submm laser power in the millisecond time scale, just after the switching on of the pump laser, the vibrational bottleneck due to diffusion and vibrational relaxation has been clearly exhibited in CH₃F, D₂CO and HCOOH submm lasers. Experimental results are compared with those deduced from a simplified rate equation model. Both show a diffusion limited regime and a collisional regime.     

Measurements of velocity distributions with a laser doppler imaging system

A laser Doppler imaging system with a TV camera has been constructed and velocity distributions of fluid flow in cross sections of a rectangular channel have been measured. Consequently, it has been found that the system has some advantages in comparison with usual laser Doppler velocimeters, for example, the visualization of flow can be easily achieved.     

The pyroelectric signal from triglycine sulphate

The pyroelectric signal from triglycine sulphate has been studied by a focussed He-Ne laser beam and a phase sensitive detection method. It is observed that anti-parallel domains give rise to pyroelectric signals of opposite polarity. The pyroelectric signal is zero when the laser spot is in between anti-parallel domains. The intensity of the pyroelectric signal is recorded and the domain structure is determined.     

Real-time, continuous-wave terahertz imaging by a pyroelectric camera

Real-time, continuous-wave terahertz (THz) imaging is demonstrated. A 1.89-THz optically-pumped farinfrared laser is used as the illumination source, and a 124 × 124 element room-temperature pyroelectric camera is adopted as the detector. With this setup, THz images through various wrapping materials are shown. The results show that this imaging system has the potential applications in real-time mail and security inspection.     

D. CCD视频技术、等离子体诊断和脉冲辐射摄影

本文对CCD摄象技术、等离子体诊断和脉冲辐射摄影的国内外最新发展作了评述,并涉及到在高技术领域的应用。     

Domain pattern in ferroelectric triglycine sulphate using pyroelectric effect

A method to study domain structure in ferroelectrics, using pyroelectric effect is described. Variation of pyroelectric signal from the surface of a triglycine sulphate crystal plate has been studied by scanning the surface of the crystal with a low wattage He-Ne laser beam. The integrated pyroelectric signal is due to two components, namely, (1) the primary component arising out of the change in spontaneous polarization with temperature and (2) the delayed component arising out of the possible polarization reversal. The component of an electric field along the ferroelectric axis due to thermal hemisphere within the crystal plate formed by the laser beam has been calculated and shown to exceed coercive field, making polarization reversal possible. The delayed pyroelectric signal is a measure of polarization reversal within the patch illuminated and its observed variation over the surface yields information of the domain structure.     

Submillimeter galaxies

A cosmologically significant population of very luminous high-redshift galaxies has recently been discovered at submillimeter (submm) wavelengths. Advances in submm detector technologies have opened this new window on the distant Universe. Here we discuss the properties of the high-redshift submm galaxies, their significance for our understanding of the process of galaxy formation, and the selection effects that apply to deep submm surveys. The submm galaxies generate a significant fraction of the energy output of all the galaxies in the early Universe. We emphasize the importance of studying a complete sample of submm galaxies, and stress that because they are typically very faint in other wavebands, these follow-up observations are very challenging. Finally, we discuss the surveys that will be made using the next generation of submm-wave instruments under development.     

The applications of the stark effect to the stabilization of the CO2 laser and the submillimeter laser

Methods based on the Stark effect are described for dither-free frequency stabilization of the optically pumped submm laser. The CO₂ pump laser was stabilized using a Stark Lamb dip signal of the submm lasant in an external Stark cell. An estimated frequency stability (f/f) better than ±1.4×10^–8, for one hour recording, was obtained by this method. The frequency of the submm laser was stabilized using the d.c. and a.c. Stark effects for a metal-dielectric rectangular waveguide laser. An estimated frequency stability of ±6×10^–8 was obtained for 119 m line of CH₃OH laser for one hour recording.     

Techniques for improving illumination and recording in endoscopy

Various light sources (illuminators), light transmitters, and recording apparatus are listed, and the shortcomings or inefficiencies of each group are analysed. A new, small and safe, high intensity illuminator is described together with possibilities of improved light transmission. The first results obtained using a small lightweight 35 mm full frame camera, with motorized film transport, as well as with a small 16 mm movie camera are mentioned. Finally, a miniature colour vidicon tv camera for endoscopic purposes is described.     

A new methodology for comparing IR reflectographic systems

IR camera systems can be used for reflectographic analyses to detect and visualize underdrawings in paintings. Five technologies have been compared: CCD Si, FPA InGaAs, FPA HgCdTe and InSb detectors, and a vidicon tube. The comparison has been performed studying the relative contrast measured on homogeneous pictorial layers in infrared regions between 800 and 5000 nm. This comparison was completed through measurements of spectral transmittance (400–2500 nm) made with a spectrometer. The results have been related to the kind of pigment and of medium and to the thickness of the layer. All the systems have been tested also on the field, on paintings belonging to different museums. Some results are discussed.     

Continuous-wave terahertz digital holography by use of a pyroelectric array camera

Terahertz (THz) digital holography is realized based on a 2.52?THz far-IR gas laser and a commercial 124 × 124 pyroelectric array camera. Off-axis THz holograms are obtained by recording interference patterns between light passing through the sample and the reference wave. A numerical reconstruction process is performed to obtain the field distribution at the object surface. Different targets were imaged to test the system's imaging capability. Compared with THz focal plane images, the image quality of the reconstructed images are improved a lot. The results show that the system's imaging resolution can reach at least 0.4 mm. The system also has the potential for real-time imaging application. This study confirms that digital holography is a promising technique for real-time, high-resolution THz imaging, which has extensive application prospects.     

基于热释电探测器的重频脉冲激光诊断

摘以热释电探测器的工作原理为基础,研究了热释电探测器对重频脉冲激光的瞬态响应特性,建立了热释电探测器对单脉冲激光辐照响应的工作模型,分析了影响探测器频率特性的主要因素。根据材料和结构参数模拟计算了实际应用中的响应模型。设计了信号检测电路并对其进行计算仿事。完成了探测器的频率响应、脉宽响应等实验测量,验证了热释电探测器用于高重频、窄脉冲激光能量测量的可行性。     

A 500-Channel Silicon-Target Vidicon Tube as a Photodetector for Atomic Absorption Spectrometry

The suitability of a vidicon TV tube as a detector for atomic absorption spectrometry (AA) was investigated. The spectral response was seen to be adequate throughout the range 217.0-313.8 nm. The instrument was then used as a detector in determining several elements by flame AA, and the results compared favorably with those obtained by a conventional detection system. The system should thus be feasible for simultaneous multielement analysis.