| 摘要 |
PROBLEM TO BE SOLVED: To improve the diffraction efficiency of a Fresnel lens. SOLUTION: In the Fresnel lens 100, there is provided with multiple Fresnel zones 111-115 having multiple discontinuous phase levels, and the number of phase levels per zone of the lens 100 is decreased as the radial distance from the central axis 110 of the lens 100 is increased. High efficiency is attained at the central zone of the lens 100 where the incident energy is the maximum without exceeding the manufacturing resolution in the high-order Fresnel zone. The Fresnel lens 100 is supported at the position of the focal distance from the object plane as an oscillator focusing the energy on the object plane, and it is applicable to a printing device such as an acoustic ink printing device. |
