| 摘要 |
PURPOSE:To suppress speckle noise by constituting an illumination optical system of N pieces of optical elements while satisfying specified conditions and analyzing the speckle noise caused by the optical element in relation to the arrangement and constitution of each optical element. CONSTITUTION:When an illumination optical system is constituted of N pieces of optical elements, a coherent light satisfying formulas I, II is employed. In the formulas, C is a numeric value representative of the intensity fluctuation caused by a speckle pattern formed on an object to be illuminated due to scattering through optical elements constituting the illumination optical system, alpha1 is the scattering rate of each optical element, F1 (q) is the angular characteristics of scattering light obtained through experiment at an operating wavelength, q<i>max is an angle for viewing an optical element from the cross point of the object to be illuminated and the optical axis, q<i>min is an leaving angle of scattering light for equalizing the phase difference from the illumination light to lambda/4 on the object, phi1 is the transmittance of each optical element, and theta1 is the arranging angle of each optical element. This constitution can limits the fluctuation in the quantity of light caused by the speckle pattern. |
