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通过对散斑场及扩展光源相干性的分析，提出信号的非相干程度与散斑数有一对应关系。信号的这种非相干性对外差效率的减弱可以用散斑数对其产生的影响来表示，即在本振场为单一模式情况下，外差信噪比与散斑数的１／２次方成反比关系。采用发射与接收共用并聚焦在目标上的光学系统降低散斑数，提高信号强度，实现了距离５ｍ处漫反射目标的半导体激光相干探测，信噪比与分析值一致。
By analyzing the coherence of the speckle field and the extended light source, it is proposed that the degree of non-coherence of the signal has a corresponding relationship with the speckle number. The non-coherence of the signal reduces the effect on the heterodyne efficiency, which can be expressed as the effect of the speckle number. That is, in the case of a single mode local oscillator, the heterodyne signal-to-noise ratio is 1/2 of the speckle number The inverse relationship between the square. Using the optical system which is common to transmit and receive and focuses on the target, the number of speckle is reduced and the signal intensity is improved. The coherent detection of the semiconductor laser with diffuse reflection at a distance of 5m is achieved, and the signal-noise ratio is consistent with the analysis value.