| 摘要 |
A method for measuring a correlation function wherein correlation function is determined at a high speed without using a fast analog-to-digital convertor. According to the method, a correlation function between a first observation signal and a second observation signal in a predetermined observation frequency band is measured. The first observation signal and the second observation signal are limited to the observation frequency band and converted to a first signal of a first frequency and a second signal of a second frequency by frequency conversion based on a same reference frequency, respectively. A predetermined frequency difference is set between the first frequency and the second frequency. Then the first signal and the second signal are multiplied and a vector detection based on the reference frequency is performed for a difference frequency component between the two signals to obtain the phase information. An apparatus for measuring the correlation function based on the above method is disclosed. Further, a method and an apparatus wherein the correlation function measurement is performed to visualize a wave source image such as a sound source image and a radiowave source image based on the principle of holography is disclosed.
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