Patent ID: 8780333

Claim:
A range finder adapted for finding the distance of a subject from said range finder, the subject having a specific height, said range finder comprising: a shell unit having an objective end and an eyepiece end; an objective lens assembly disposed on said objective end, and forming a first imaging plane at a first focus position; a magnifying unit disposed in said shell unit and between said objective end and said eyepiece end, said magnifying unit forming a second imaging plane behind said first imaging plane at a second focus position, and having a plurality of magnification ratios one of which is selected through operation of said magnifying unit; and a range finding unit disposed in said shell unit, and including a first comparing component disposed at the first imaging plane and having a first reference point, a second comparing component disposed at the second imaging plane and having a second reference point, a scale formed on one of said first and second comparing components, a pointer formed on the other one of said first and second comparing components, and a mark formed on said second comparing component, said scale having a plurality of distance graduations each corresponding to a respective one of said magnification ratios and representing an object distance value that is proportional to the respective one of said magnification ratios, said mark being spaced apart from said second reference point by a comparing height, such that when said magnifying unit is set to one of said magnification ratios to allow an image of the subject formed on the second imaging plane to have an image height that is substantially equal to said comparing height, the distance of the subject from said range finder is known by comparing said scale and said pointer that are observed on the second imaging plane.