1. A method for estimating a distribution of a frequency response of a transfer system based on original information and degraded information obtained as a result of transfer of the original information in the transfer system, the frequency response including a phase characteristic of the transfer system, the method performed by a computer including a storage unit and a control unit, and comprising: identifying, with the control unit, a distribution of the degraded information represented by a complex probability density function; acquiring, with the control unit, a spectrum distribution of a distribution of the original information by applying a Fourier transform to the distribution of the original information which is represented by a complex probability density function; identifying, with the control unit, an initial estimated distribution of an impulse response of the transfer system, the impulse response is the probability density function representing the distribution of the degraded information when the distribution of the original information is represented by a unit impulse function; (1) acquiring, with the control unit, a first function by applying a Fourier transform to the estimated distribution of the impulse response; (2) acquiring, with the control unit, a second function by multiplying the first function by the spectrum distribution of the distribution of the original information; (3) acquiring, with the control unit, a third function by applying an inverse Fourier transform to the second function; (4) acquiring, with the control unit, a fourth function by dividing the distribution of the degraded information by the third function; (5) acquiring, with the control unit, a fifth function by applying a Fourier transform to the fourth function; (6) acquiring, with the control unit, a sixth function by multiplying the fifth function by a phase-reverse function of the spectrum distribution of the distribution of the original information; (7) acquiring, with the control unit, a seventh function by applying an inverse Fourier transform to the sixth function; (8) acquiring, with the control unit, a next estimated distribution of the impulse response by multiplying the estimated distribution of the impulse response by the seventh function; replacing, with the control unit, the estimated distribution of the impulse response by the next estimated distribution of the impulse response, and repeating said steps (1) to (8); and applying, with the control unit, a Fourier transform to the estimated distribution of the impulse response to acquire and output the distribution of the frequency response of the transfer system.