Chromatic aberration compensating image optics

An objective lens system comprising:

• an aperture stop,
• a fore objective lens group in front of the aperture stop, the fore objective lens group having a negative focal length and comprising at least two concave lenses and a convex lens, and
• a rear objective lens group behind the aperture stop, the rear objective lens group having a positive focal length and comprising a convex lens located immediately behind the aperture stop and a plurality of lens elements located behind the convex lens, the plurality of lens elements including a concave lens and a plurality of convex lenses, wherein the fore objective lens group, the aperture stop, and the rear objective lens group are located in order from an objective side, and the aperture stop is located out of the imaging plane and shields a light flux passing through a peripheral area of the fore objective lens group, the rear objective lens group being configured to concentrate a portion of an incident light flux close to a limit line of the light flux from each respective imaging point into a peripheral area of a certain one of the lens elements, and such that rays of light incident on the peripheral area of the certain one of the lens elements make approximately the same incident angle as one another, wherein for imaging points off of the optical axis, the concentrated portion of the incident light flux is close to the limit line of the light flux on an opposite side of the optical axis from the imaging point, and
• approximately annular light shielding means located on the surface of the certain one of the lens elements in the peripheral area thereof where the portion of the incident light flux is concentrated and on an area of the surface of the certain one of the lens elements of the rear objective lens group in the vicinity of the position where the rays make approximately the same incident angle, for non-circularly shielding the incident light flux from imaging points off of the optical axis and for decreasing lateral chromatic aberration components of a specified wavelength of the incident light flux when the incident light flux passes the peripheral area of the surface of the certain one of the lens elements where the portion of the incident light flux is concentrated.

An objective lens system comprising:

• an aperture stop,
• a fore objective lens group in front of the aperture stop, the fore objective lens group having a negative focal length and comprising at least two concave lenses and a convex lens, and
• a rear objective lens group behind the aperture stop, the rear objective lens group having a positive focal length and comprising a convex lens located immediately behind the aperture stop and a plurality of lens elements located behind the convex lens, the plurality of lens elements including a concave lens and a plurality of convex lenses, wherein the fore objective lens group, the aperture stop, and the rear objective lens group are located in order from an objective side, and the aperture stop is located out of the imaging plane and shields a light flux passing through a peripheral area of the fore objective lens group, the rear objective lens group being configured to concentrate a portion of an incident light flux close to a limit line of the light flux from each respective imaging point into a peripheral area of a certain one of the lens elements, and such that rays of light incident on the peripheral area of the certain one of the lens elements are approximately identical in height from the optical axis, wherein for imaging points off of the optical axis, the concentrated portion of the incident light flux is close to the limit line of the light flux on an opposite side of the optical axis from the imaging point, and
• approximately annular light shielding means located on the surface of the certain one of the lens elements in the peripheral area thereof where the portion of the incident light flux is concentrated and on an area of the surface of the certain one of the lens elements of the rear objective lens group in the vicinity of the position where the rays are approximately identical in height from the optical axis, for non-circularly shielding the incident light flux from imaging points off of the optical axis and for decreasing lateral chromatic aberration components of the incident light flux of a specified wavelength when the incident light flux passes the peripheral area of the surface of the certain one of the lens elements where the portion of the incident light flux is concentrated.