STUDY ON THE HIGH-SPEED SCANNING AND HIGH RESOLUTION OF CT-SCAN TYPE LASER-SHEET 2D-INSTANTANEOUS CONCENTRATION METER

(1)目的：从硬件和软件的角度对先前报道的试验仪器（“ct扫描型无旋转部件瞬时浓度计”）进行了一些改进。(2)激光脱落和扫描机构的改进：(a)激光脱落机构由由发射器的激光束通过步进电机进行机械扫描，改为由圆柱透镜展开的激光片脱落，完全避免了旋转部件。来自一系列发射器的激光依次打开和关闭。(b)通过浓度场的发射器发出的激光信号已被一系列接收单元接收并连续记录。通过连续记录信号强度，大大缩短了采样周期。(3)分析系统的改进：(a)“虚拟负载法”：如前文所述，在反问题中，传统的通过双傅立叶表达式来表示未知场的方法，由于仪器在没有转动部件的情况下对场进行单向搜索所获得的信息过于稀缺，因此不能给出良好的结果。而Hino（1974）提出的类似于样条近似的“虚拟负荷法”则得到了成功的应用。(b)应用小波变换去除噪声：利用小波变换抑制噪声，恢复出纯净的信号。(4)结果与结论：小波变换技术的效果：通过对硬件和软件小波变换的改进，实现了仪器的高性能和高分辨率。

(1) Aims : Several improvements to the trial instrument ("CT-scan Type Instantaneous Concentration Meter with no rotating parts") previously reported have been made from the standpoint of both hardware and software.(2) Improvement in Laser Shedding and Scanning Mechanism : (a) Laser shedding mechanism has been changed from a mechanical scan by stepping motor of laser beams from emiters, to shedding laser sheet expanded by cylindrical lens, avoiding rotating parts completely. Laser lights from an array of emitters are switched on and off, successively. (b) Signals of laser light from emitters which are passed through the concentration field have been received by an array of receiving units and recorded continuously. By the continuous recording of signal intensities, the sampling period was considerably shortened.(3) Improvement in Analysis System : (a) 'Virtual Load Method' : As described in the previous paper, the conventional means to express an unknown field in the inverse problem through the double Fourier expression, does not give a favorable result, because the information obtained from the one directional search of the field by the instrument without rotational parts is too scarce. While the "Virtual Load Method" proposed by Hino (1974), an idea similar to the spline approximation, is successfully applied. (b) Application of Wavelet Transform to Remove Noise : Wavelet transform is applied to suppress noise and recover the pure signals.(4) Result and Conclusion : Effect of Wavelet Transform Technique : High performance and high resolution of the instrument have been accomplished by these improvements of hardware and software wavelet transform.