Nodal slide rangefinder

Claim 2

In an optical instrument having a focusable objective lens, an image plane receiving an image of a remote subject from said objective lens, the invention comprising: a ranging device for determining the distance from the instrument to the subject, and for assisting focusing of said objective lens on the subject, the ranging device including: optical means having a nodal point through which light rays from the subject pass generating an image of the subject on the image plane of the instrument; and means for cyclically displacing said optical means about said nodal point, whereby the image of the subject moves on said image plane when said objective lens is not focused on said subject and is stationary on said image plane when said objective lens is focused on said subject.

Claim 3

A ranging device as in claim 1 wherein said optical means includes a lens system carried in a barrel portion arranged for cyclical movement about the rear nodal point of said lens system.

Claim 4

A ranging device as in claim 2 wherein said means for periodically displacing said optical means is a drive motor.

Claim 5

A ranging device as in claim 3 wherein said drive motor for periodically displacing said lens system about said nodal point is connected to said barrel portion through a motion transfer mechanism to cause oscillation of said lens system.

Claim 6

A ranging device as in claim 4 wherein the objective lens generates an image through said ranging device on said image plane, which image is viewable through viewing means of said instrument.

Claim 7

A ranging device as in claim 5 wherein the objective lens forms an optical path in said instrument, and a reflector means is interposed in said optical path to cause an image of the subject to be formed at a first image plane for recording an image and at a second image plane for viewing of an image comparable to the image recorded, said image planes being conjugate whereby said viewable image is stationary when said recordable image is in focus.

Claim 8

In an optical instrument having a focusable objective lens, an image plane receiving an image of a remote subject from said objective lens, the invention comprising: a ranging device for determining the distance from the instrument to the subject for focusing of said objective lens on the subject, the ranging device including: optical means including a lens system having a rear nodal point through which light rays from the subject exit to form an image of the subject on an image plane of the instrument, said optical means being disposed in an optical path generated by the objective lens, and drive means for cyclically oscillating said optical means about said nodal point to cause the image of the subject to move on said image plane responsive to said oscillation and displaced from said optical axis when said objective lens is not focused on said subject and to cause the image to be stationary on said image plane when the objective lens is focused on the subject.

Claim 9

In an optical instrument having a focusable objective lens, an image plane receiving an image of a remote subject from said objective lens, the invention comprising: a ranging device for determining the distance from the instrument to the subject for focusing of said objective lens on the subject, the ranging device including: optical means including a lens system having a rear nodal point through which light rays from the subject exit to form an image of the subject on an image plane of the instrument, said optical means being disposed in an optical path generated by the objective lens, and drive means for cyclically oscillating said optical means about said nodal point to cause the image of the subject to move on said image plane responsive to said oscillation and displaced from said optical axis when said objective lens is not focused on said subject and to cause the image to be stationary on said image plane when the objective lens is focused on the subject.