Based on mathematical morphology and digital umbra shading and shadowing algorithm, a new approach for realizing optical morphological erosion of one dimensional (1-D) gray images is proposed. The mathematical expression for the parallel processing of morphological erosion of 1-D gray images is described, and the principle of morphological erosion from binary images to gray images is presented. The advantages of this scheme are simple in structure, high resolution in gray level, and good in parallelism. It can raise the speed of performing morphological erosion of gray images greatly and obtain accurate results.