A novel, simple method is developed and tested (experimentally and by simulations) for effective, high-resolution retrieving of time- resolved lidar profiles for long rectangular-like laser pulses with arbitrary shapes of their leading and trailing edges. Such pulses are typically created by chopping cw optical radiation. The processing algorithm is based on differentiation and iteration procedures and avoids the use of divisions or deconvolutions that are often responsible for some errors and increases in the noise. Comparisons with pulsed and pseudo-random noise modulation lidar methods are given. The method enables a simplification of the entire lidar hardware. No powerful pulsed supplies, high driving pulsed voltages, complicated optical modulations, etc. are required. it could be very attractive for high-resolution, wide-spectral-band lidar measurements in the atmosphere, ocean, etc., using arbitrary optical emitters, especially for closer distances.