提出了一种在相移数字全息中提取相移角的方法.该方法通过在相移数字全息中引入随机相位板对物光波的相位进行调制，使得物光波在全息面上的相位分布成为近似理想的随机分布，进而根据这种随机分布的统计性质对相移角进行提取.计算机模拟结果表明，该方法提取出的相移角与设定的相移角之间的相对误差小于千分之一.同时，经过对比采用随机相位板和不采用随机相位板的计算结果发现，物体衍射光波在全息面上的相位分布具有一定的相关性.

An approach is proposed to determine the phaseshifting value in phaseshifting digital holography. By employing a random phase plate behind the object, we successfully made the phase distribution of the object on the holography plane a spatially approximation random distribution. Then an algorithm utilizing this character to extract phaseshifting value is proposed. Computer simulations indicate that the extracted phaseshifting value is very close to the predetermined, and the relatively error is less than 0.1%. At the same time, by comparing the calculation results with and without the random phase plate, we find that the phase distribution of an object has some correlation after diffraction.