A new technique of white light pseudocolor density encoding is described. The exposure to the object to be processed is performed by means of a Ronchi grating in one step. According to the property of the negative encoding plate "the higher the transmittance, the lower the modulation", and when only the zeroth and the first orders of the spectrum of the grating are allowed to pass. Authors the positive and negative images have been obtained respectively, and hence realized contrast reversal. After color filtering, authors accomplished the pseudocolor density encoding.