| 摘要 |
PURPOSE:To detect accurately the position of a light source, by leading out part of luminous flux by the light source from the position after projection through a field lens, and forming an image of the light source by the luminous flux from a luminous flux extracting member. CONSTITUTION:An extra-high pressure mercury lamp 11 as the light source is provided at the focal point F1 of an elliptic reflecting mirror 12 and its luminous flux is focused on a focal point F2, where the light source mage is formed. The luminous flux reflected by a dichroic mirror 17 provideed slantingly between the elliptic reflecting mirror 12 and focal point F2 passes through an optical member 18 including an interference filter and an integrator and a condenser lens 20 to illuminate a mask 21 uniformly, thereby projecting and printing a pattern image to reduced scale. On the other hand, the 1st and the 2nd light source position detecting optical systems consisting of positive lenses 13a and 13b, reflecting mirrors 14a and 14b, and mark plates 15a and 15b detects light source images on the mark plates 15a and 15b through a field lens 30 provided at the focal point F2 to set the light source 11 at an optimum position. |
