Gamma畸变是数字相移测量技术的主要误差源。以通用的均匀步长相移技术为对象，分析了Gamma畸变对相位计算的影响，建立了相位误差与谐波系数的关系模型，证明了各阶谐波系数在Gamma值影响下的递推公式，进而提出了基于离散傅里叶变换的Gamma标定技术。基于此Gamma标定值，通过Gamma预矫正降低相位误差。实验结果表明，标定的Gamma值在整个像平面具有较强的稳定性，Gamma矫正后使相位误差减小了77.5%，在曲面测量的结果中，水波纹明显得到抑制，曲面质量得以提高。

The Gamma nonlinearity is one of the most important factors for the phase error in digital phase measuring profilometry. The phase error model resulting from the Gamma distortion is deduced, which reflects the relation between the phase error and the harmonic coefficients. The recurrence formula of the harmonic coefficients is proved, which is influenced by the Gamma value. Based on this recurrence rule, a Gamma calibration method based on discrete Fourier transform is proposed. Discreet Fourier transform is applied to obtain the harmonic coefficients. Then, this Gamma value is computed and adopted to correct the nonlinearity. In the experiment, the mean Gamma value in the whole image is employed into the gamma pre-encoding process. With the proposed technique, the phase error is reduced by 77.5% in the standard variance and the surface quality is enhanced.