A new technique is proposed for the characterization of ultrashort optical pulses. The technique includes a simple mathematical treatment of the time-resolved spectrum of the signal that is obtained using an image converter camera. The theoretical description of the technique and several numerical examples modeling the ultrashort pulse reconstruction are presented. The dependence of the reconstruction result on the noise level is evaluated. It is shown that the temporal resolution of the technique can be up to two orders of magnitude higher than that for the used electro-optic device.