| 摘要 |
PROBLEM TO BE SOLVED: To obtain a projection optical system which can have superior image forming performance by making light passing through the center of a diffraction optical element and light passing through the peripheral part securely interfere with each other. SOLUTION: This optical system has the diffraction optical element 5 which images a pattern on a 1st body, its with light from a laser light source, on a 2nd body: and the half-value overall widthΔλof the spectrum of the light is within a range of 1.5pm<Δλ<100pm, whereλis the mean wavelength of the light. A spherical wave having apparently no aberration is projected on the 2nd body side and the largest optical path difference PDmax that the spherical wave has is within a range of 0<PDmax <λb <2> /Δλ. |
