A method of cancer screening comprising the steps of administering the Blood CA 27,29 test; administering a mammogram; administering an needle biopsy; administering a PET scan; and administering a blood tumor cell count. A gain code generating circuit calculates a gain minimizing the distance between a second speech signal, obtained from the second code sequence, and the first speech signal, and corrects the optimum gain. The first-to-second-lens-group distance becomes the smallest during zooming.