Low light level vision apparatus

Claim 1

Optical apparatus for low light level or night vision use to enable in-focus viewing of two different objects or scenes at different distances from the apparatus, comprising: image intensifier means for producing an intensified image of said objects or scenes for viewing through the apparatus; viewing means for enabling an observer to view a magnified version of the image produced by said image intensifier means; and filter and focussing means disposed in the light path between said objects or scenes and said image intensifier means for transmitting filtered and focussed light from said objects or scenes to said image intensifier means, said filter and focussing means comprising: an objective lens disposed in said light path for focussing light from one of said objects or scenes on said image intensifier means; a wavelength selective filter disposed in said light path for transmitting therethrough along a first optical path incident light of a selected wavelength band or bands, said filter having a hole therein through which incident light of other wavelengths can pass along a second optical path; and focus correction means arranged to act only on light passing along one of said two optical paths and cooperative with said objective lens to focus on said image intensifier means the light from the other of said objects or scenes which passes along said one optical path, while light of said other wavelengths from said one object or scene which passes along the other of said optical paths is focussed on said image intensifier means by said objective lens without the aid of said focus correction means, whereby in-focus images of the two objects or scenes at different distances from the apparatus are presented for viewing by the observer.

Claim 23

A method of producing under low light level or night vision conditions in-focus images of two different objects or scenes located at different distances from a viewing apparatus, comprising the steps of: passing incident light through a wavelength selective filter and transmitting light of wavelengths passed by the filter to an image intensifier; focussing onto the image intensifier light being passed by the filter from an object or scene at one distance; passing incident light of other wavelengths through a hole in the filter and transmitting that light to the image intensifier; focussing onto the image intensifier light of said other wavelengths which passes through the hole in the filter from the other object or scene at another distance; producing by means of the image intensifier an intensified image of the object or scene from which light is focussed onto the image intensifier; and magnifying the intensified image for viewing by an observer.

Claim 24

A method of producing under low light level or night vision conditions in-focus images of two different objects or scenes located at different distances from a viewing apparatus, comprising the steps of: passing incident light through a wavelength selective filter and transmitting light of wavelengths passed by the filter to an image intensifier; focussing onto the image intensifier light being passed by the filter from an object or scene at one distance; passing incident light of other wavelengths through a hole in the filter and transmitting that light to the image intensifier; focussing onto the image intensifier light of said other wavelengths which passes through the hole in the filter from the other object or scene at another distance; producing by means of the image intensifier an intensified image of the object or scene from which light is focussed onto the image intensifier; and magnifying the intensified image for viewing by an observer.