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

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(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.