A new one-step joint transform correlator (JTC) is presented, in which the joint transform of the images to be correlated is filtered by a moving Ronchi ruling. An alternative JTC architecture without moving parts using two Ronchi rulings is also suggested. A lens produces the spatial integral of the product of the joint transform image and the transmission factor of the Ronchi ruling, and a single element detector is used to capture the integral. The amplitude of the light modulation on the detector gives the cross-correlation function of the input images at coordinates (0,0) without major processing. Therefore, in principle this technique significantly reduces the time required to evaluate the crosscorrelation function, compared to that for usual JTCs. Experimental validation of the proposed one-step architecture is presented.