Projection optical system and projection and light exposure apparatus using it
View Patent ↗A projection optical system is disclosed that includes six lens groups, four of which are positioned in pairs symmetrically about a stop. The second and fifth lens groups, in order from the object side, may be positioned symmetrically about the stop but are also adjustable asymetrically about the stop in order to adjust the magnification of the projection optical system. The first and sixth lens groups, in order from the object side, function to make the projection optical system substantially telecentric on both the object side and the image side, respectively. Also disclosed is a projection and light exposure apparatus that uses the projection optical system of the present invention. The projection and light exposure apparatus automatically detects the image magnification and, based on the detection result, adjusts the positions of the second and fifth lens groups G 2 and G 5 as a unit so as to maintain a specified magnification.
1. A projection optical system comprising, in sequential order from the object side:
a first lens group having positive refractive power;
a second lens group;
a third lens group that has one of positive or negative refractive power;
a stop;
a fourth lens group that has the same sign of refractive power as the third lens group;
a fifth lens group having the same sign of refractive power as the refractive power of the second lens group, the amount of refractive power of the second and fifth lens groups being small in comparison to the amount of refractive power of the third lens group; and
a sixth lens group having positive refractive power;
wherein
the first and sixth lens groups are positioned at substantially symmetric locations on opposite sides of the stop;
the second and fifth lens groups may be moved asymmetrically with respect to the stop along the optical axis from substantially symmetric locations on opposite sides of the stop so as to achieve magnification adjustment, and
the third and fourth lens groups are positioned at substantially symmetric locations on opposite sides of the stop.
2. The projection optical system according to claim 1 , wherein the first lens group and the sixth lens group, in order from the object side, are designed such that light that enters one side of said projection optical system will be substantially telecentric as it exits the opposite side of said projection optical system.
3. The projection optical system according to claim 2 , wherein the second lens group and the fifth lens group are moved along the optical axis in the same direction and the same distance in adjusting the projection optical system to a different magnification.
4. The projection optical system according to claim 1 , wherein the second lens group and the fifth lens group each consist of a single positive lens element.
5. The projection optical system according to claim 2 , wherein the second lens group and the fifth lens group each consist of a single negative lens element.
6. The projection optical system as set forth in claim 2 , in combination with a light exposure apparatus which projects a light pattern onto a surface.
7. The projection optical system according to claim 1 , wherein the second lens group and the fifth lens group are moved along the optical axis in the same direction and the same distance in adjusting the projection optical system to a different magnification.
8. The projection optical system according to claim 1 , wherein the second lens group and the fifth lens group each consist of a single positive lens element.
9. The projection optical system according to claim 1 , wherein the second lens group and the fifth lens group each consist of a single negative lens element.
10. The projection optical system as set forth in claim 1 , in combination with a light exposure apparatus which projects a light pattern onto a surface.