Laser intensity modulated, time dependent exposure is calculated analytically using a diode circuit model. We found that the exposure of individual pulses with different intensities can be spatially superimposed by scaling the exposure based on the intensities. However, when the beam stays on and changes its intensity, this scaling method is no longer appropriate since there is no contribution from the fall time when the intensity changes. In this case, exposure calculation must be carried out from time dependent intensity equations with the current and previous asymptotic intensity levels and the intensity just before the beam changes its intensity. Different exposure integrals are solved separately depending on the relative magnitude of the current intensity. An iterative procedure for calculating the resultant exposure of a pulse with an arbitrary number of intensity modulations is presented and demonstrated.