| 摘要 |
PURPOSE:To analyze the frequency of a high frequency signal with high precision at low cost by forming the 1st and the 2nd optical waveguide lenses as mode index type lenses which are a thin film type and have effective refractive indexes different from the effective refracting index of an optical waveguide. CONSTITUTION:The radii of curvature of the inscribed circles of the incidence/ projection surfaces of the 1st and the 2nd optical waveguide lenses are set within a specific range and the higher-order aberrations of the 1st and the 2nd mode index type lenses 15 and 16 are compensated. Consequently, even if the 1st mode index type lens 15 projects parallel light 6 without fail even if a semiconductor laser 3 shifts from the optical axis, and the parallel light 6 is diffracted with a surface acoustic wave (SAW) 11. Then, the 2nd mode index type lens 16 receives said refracted light, i.e. a paraxial light beam and converged on a photodetector array 9 at a specific position corresponding to the angle of diffraction of the refracted light, e.g. point F without any aberration. Consequently, the frequency of a high frequency signal is analyzed with high precision. |
