An optically addressed spatial light modulator (OA-SLM) is presented by using the excellent nonlinear-optical characteristics of bacteriorhodopsin films (BR films). The BR films have two dominant photoactive states (B state and M state) which have well-separated absorption bands with maxima of B state at 570nm and M state at 412nm. Using the ratio of the shift between the forward （B→M）and backward（M→B）photoreactions, the experimental study on the conversion of coherent-to-incoherent image is realized on BR films. Using the genetic manipulation of the BRD96N film as a sample, the 670nm coherent light as a writing light and the 530nm incoherent light as a readout light, the experimental results for the resolution of ～200 lines/mm and the contrast of about 2.1∶1are achieved.