Telecentric illumination system

Claim 2

An illumination system for performing telecentric illumination throughout a wide variation range of magnification while maintaining a large distance to an object to be illuminated, said illumination system comprising: a converging first lens group remaining fixed when the magnification is varied; a diverging second lens group movable along the optical axis; a converging third lens group movable along the optical axis; a converging fourth lens group remaining fixed when the magnification is varied; and a light source located at the focal point of said fourth group, said first to fourth groups and said light source being arranged in this order as viewed from the side of said object, and said second and third groups are moved along the optical axis in a determined relation in such manner as to make an image of said light source formed between said first and third groups thereby changing the state of illumination between that for high magnification and that for low magnification.

Claim 3

An illumination system as set forth in claim 1, wherein said second and third groups can be moved along the optical axis in such manner that when said light source image lies between said first and second groups, the position of said image may be coincident with the focal point on the light source side of said first group and when said image lies between said second and third groups, the position of said image may be coincident with the focal point on the light source side of the composite system resulting from said first and second groups.

Claim 4

An illumination system as set forth in claim 2 wherein said first to fourth lens groups have the following numerical data: ______________________________________ Magnification Variation Ratio 7.6 ______________________________________ f.sub.1 = 90.0 f.sub.2 = -28.8 f.sub.3 = 128.6 f.sub.4 = 45.0 ______________________________________ ______________________________________ Third First position Fourth position Second (FIG. 2C) position (FIG. 2A) position for (FIG. 2D) for high (FIG. 2B) for medium- for low magnifi- medium-high low magni- magnifi- cation magnification fication cation ______________________________________ Distance 131.3 111.6 83.2 70.4 between L.sub.1 and L.sub.2 Distance 111.6 116.2 137.4 189.8 between L.sub.2 and L.sub.3 Distance 23.6 38.7 45.9 6.3 between L.sub.3 and L.sub.4 ______________________________________ wherein, L 1 , L 2 , L 3 and L 4 stand for the first, second, third and fourth lens groups respectively and f 1 , f 2 , f 3 and f 4 stand for the focal lengths of said first, second, third and fourth lens groups respectively.

Claim 5

A telecentric illumination system in which the range of area illuminated is variable from a narrow area of the surface of an objected to be illuminated to a large area thereof, said telecentric illumination system comprising: a converging first lens group remaining fixed when the magnification is varied; a diverging second group and a converging third lens group which can be moved along the optical axis relative to each other in a determined relation; and light source means for providing said third group with parallel beams of light, said second and third groups being moved in such manner that said parallel beams coming from said light source means may be focused between said first and third groups thereby effectively changing said illuminated area.

Claim 6

A telecentric illumination system in which the range of area illuminated is variable from a narrow area of the surface of an objected to be illuminated to a large area thereof, said telecentric illumination system comprising: a converging first lens group remaining fixed when the magnification is varied; a diverging second group and a converging third lens group which can be moved along the optical axis relative to each other in a determined relation; and light source means for providing said third group with parallel beams of light, said second and third groups being moved in such manner that said parallel beams coming from said light source means may be focused between said first and third groups thereby effectively changing said illuminated area.

Claim 7

A telecentric illumination system as set forth in claim 4 wherein said light source means includes a converging lens group and a light source located at the focal point of said converging lens group, wherein, L 1 , L 2 , L 3 and L 4 stand for the first, second, third and fourth lens groups respectively and f 1 , f 2 , f 3 and f 4 stand for the focal langths of said first, second, third and fourth lens groups respectively.