提出了用于测量物体内部三维变形场的数字体散斑(DVSP)法。利用计算机断层扫描(CT)、磁共振成像(MRI)、激光扫描共焦显微镜(LSCM)或光学相干断层成像术(OCT)获取具有散斑特征的物体变形前后的三维立体图像，将其分别分割成若干具有相同尺寸的子块体，对相对应的子块体进行第一步三维快速傅里叶变换，在频谱域进行数值干涉得到合成谱，对合成谱进行第二步三维快速傅里叶变换，得到含位移信息的扩展脉冲函数，通过求取峰值位置得到子块体的位移矢量，对所有变形前后相对应的子块体逐一进行上述两步三维快速傅里叶变换，就可以求出所有子块体的位移矢量，从而获得物体内部三维变形场。利用模拟生成的三维散斑体图像，通过数字实验，分析了散斑尺寸、数目、子块体尺寸、图像对比度和亮度对DVSP法精度与准确性的影响。利用DVSP法测量了红砂岩单轴压缩内部的三维应变场，由位移场及应变场分布可直观地揭示试件内部变形特征。

Digital volumetric speckle photography (DVSP) technique is proposed to measure three dimensional displacement in solid object. Using computer tomography (CT), magnetic resonance imaging (MRI), laser- scanning confocal microscopy (LSCM) or optical coherence tomography (OCT), three dimensional volumetric images of an object with speckle characteristics before and after deformation are abtained. These three dimensional images are divided into subsets with a certain voxel array and comparable. Afterwards three- dimensional fast Fourier transform (3D- FFT) is applied to a corresponding pair of subsets. A new resultant spectrum can be constructed by a numerical interference from the two procured spectra at the spectral domain. Then another step of 3D- FFT is performed on the resultant spectrum resulting an expanded impulse function whose displacement vector experienced by the speckles contained in the original subset as a whole. This process is carried out for every corresponding pair of subsets. By detecting the position of the crests of these impulse functions, an array of displacement vectors at all every subset is obtained and the 3D displacement fields are mapped. Using simulated 3D speckle volume images, the influences of speckle size, number, subset size, image contrast and image brightness on the accuracy and precision of DVSP are analyzed by digital experiments. We apply the DVSP technique to measure the internal 3D deformation field of red sandstone sample under uniaxial compression, and the resulting displacement and deformation field contours clearly indicate the damage characters of the sample.