Zoom lens unit, imaging device, and monitoring video camera
AssigneeRicoh Company, Ltd.
InventorKazuyasu OHASHI
Life of this patent
Estimating the term…
Abstract
A zoom lens unit includes, in order from an object side to an image side, a first lens group having positive refractive power and a focus function, a second lens group having negative refractive power, which moves when changing a magnification, a third lens group which moves when changing a magnification, and a fourth lens group having positive refractive power, which is fixed when changing a magnification, wherein the following condition (1) is fulfilled: |M2W·M3W·M4W|<0.14 (1) where M2W represents an imaging magnification of the second lens group at a wide-angle end, M3W represents an imaging magnification of the third lens group at the wide-angle end, and M4W represents an imaging magnification of the fourth lens group at the wide-angle end.
Claims12
A zoom lens unit comprising, in order from an object side to an image side;
- a first lens group having positive refractive power and a focus function;
- a second lens group having negative refractive power, which moves when changing a magnification;
- a third lens group which moves when changing a magnification;
- and
- a fourth lens group having positive refractive power, which is fixed when changing a magnification, wherein the following condition (1) is fulfilled:
- |M2W·M3W·M4W|<0.14 (1)
- where M2W represents an imaging magnification of the second lens group at a wide-angle end, M3W represents an imaging magnification of the third lens group at the wide-angle end, and M4W represents an imaging magnification of the fourth lens group at the wide-angle end, and
- a change in focus position with a temperature change is corrected by moving an entire or a part of the fourth lens group at least at the wide-angle end.
Dependencies are inferred from the claim text.