Because of the structural similarity to rhodopsin, bacteriorhodopsin is characterized by some visual response properties. With electrophoresis method, oriented purple membrane films are deposited on stainless steel electrode to construct a photoreceptor with the structure of stainless steel/purple membrane/gel/copper electrode. As illuminated by modulated light, the photoreceptor gives rise to a differential response. The dependencies of the photoreceptor's photovoltages on the modulating frequency and the incident light power are measured. The analogy between the bacteriorhodopsin's response to modulated light and the visual flash and brightness are compared and discussed.