| 摘要 |
PCT No. PCT/JP89/01340 Sec. 371 Date Mar. 13, 1991 Sec. 102(e) Date Mar. 13, 1991 PCT Filed Dec. 28, 1989 PCT Pub. No. WO91/10110 PCT Pub. Date Jul. 11, 1991.A double-focus detector utilizing chromatic aberration has a lens system having axial chromatic aberration in which a first object such as a mask is illuminated with a ray of wavelength below 500 nm and a second object such as a wafer is illuminated with plural wavelength rays or a wavelength-band ray above 500 nm, by employing an image forming plane of the first object with respect to the single wavelength ray as one focal plane of the lens system and the same image forming plane of the second object with respect to the plural wavelength rays or the wavelength-band ray as the other focal plane of the lens system. |
