| 摘要 |
PURPOSE:To reduce the statistic noise, by providing several radiant ray sources so that the radiation beams cross at a point, making the subject to be measure pass through the above-mentioned crossing point of the radiation beams and then detecting and adding together the transmitted quantity of the radiation beams. CONSTITUTION:The radiant ray sources 11-1n are provided so that the radiation beams cross at a point, and the radiation detectors 21-2n are provided in opposition to the sources 11-1n for the radiant rays passed through the subject 6 to be measured. The coutputs of the detectors 21-2n are supplied to the operational amplifiers 41-4n via the preamplifiers 31-3n. The amplification factor is decided for the amplifiers 41-4n so as to give a correction to the error of distance between the sources 11-1n and the detectors 21-2n. The outputs of the amplifiers are added together by the adder 7 and then supplied to the deviation amplifier 9 via the logalithm amplifier 8. The output of the amplifier 9 is compared with the voltage proportional to the plate thickness of the subject 6. Thus the thickness of the radiant ray can be displayed on the indicator 11. The statistic noise can be reduced in adversely proportional to the root of (n) by making the radiant rays cross with each other. |
