LENS OBJECTIVE WITH CHANGEABLE FOCAL LENGTH FOR OPERATION WITHIN IR SPECTRUM AREA Russian patent published in 2008 - IPC G02B15/16 G02B9/34 G02B13/14 

FIELD: optical engineering.

SUBSTANCE: objective can be used as objective of devices operating within IR spectrum range for detecting, distinguishing and recognizing objects. Objective has two motionless positive components and mo able negative component disposed those two negative components. First component being dispose along path of beams is made in form of meniscus turned with its concavity to plane of image. Last component is made in form of single menisci turned with its concavity to plane of image. Negative component is made in form of single biconcave lens. Positive component is introduced between negative component and last positive component. Positive component is made in form of menisci turned with its concavity to plane of image. Meniscus is tightly connected with aperture diaphragm and is capable of moving together with diaphragm along optical axis. Surface of menisci, which surface comes in front of aperture diaphragm, is made aspherical. The following conditions are met in the system: n₁=n₂=n₃=n₄=4,0, -f'₃<f'₂<-1,1f'₄, 2,7f'₃<f'₁<3f'₃.

EFFECT: higher technical parameters; improved quality of image; reduced sizes.

4 dwg