【摘要】 本文介绍一个值得注意的高灵敏度全息干涉方法.文献[2]指出,在全息干涉两次曝光间对参考光移相,可以提高灵敏度,并报道了移相π/2时的实验结果.本文详细分析了移相技术,指出此法在移相π/2时的分辨率可高达1/1000波长左右,比普通两次曝光全息技术(其移相值为0)的灵敏度高25.4倍;并指出,移相值大于π/2小于π时灵敏度可以进一步提高,最佳移相值应在π附近.本文附有一个低密度变化流场的实验结果,说明本方法显示低密度变化流场的能力.讨论了应用中的一些问题.更多还原

【Abstract】 Gas flows at high Mach numbers are usually associate with very low gas density, especially in simulating flight conditions at high altitudes. In visualizing such flows the question usually arises as to how the sensitivity of the optical method may be increased.Paper [2] has pointed out that, if the reference beam of holography has a certain phase-shift between the two exposures, a higher sensitivity can be achieved. Paper [2] appends an experimental result in which the phase-shift value is λ/2. The present paper analyses the phase-shift interferometric technique in detail. According to this analysis, when the phase-shift value is λ/2, a resolution limit about π/1000 can be achieved. This is 25.4 times higher than the common double-exposure holographic method in which the phase-shift value is zero. Furthermore, the present paper points out that when the phase-shift value increases from λ/2 to λ, the sensitivity also increase monotonously (for instance, when the phase-shift value is 0.89 λ, a resolution limit about π/6000 can be achieved). The optimum phase-shift value is probably near π.This paper presents some experimental results of a low density flow. Some problems in application of this technique are discussed.更多还原