An objective lens particularly for use in a low light level or night vision system designed to introduce a controlled amount of barrel distortion at the edges of its field of view to permit use with a flat input faced imaging tube.
A modified Petzval-type optical objective is provided, whose design form has a long focal length (i.e., 1000 mm) at a large relative aperture (i.e., f/2) over a field of view of 4.2.degree. without vignetting, which is well-corrected for both monochromatic and chromatic aberrations, and which is color-corrected at four wavelengths over a spectral band extending from the visible to the near-infrared regions of the electromagnetic spectrum. The optical objective is made from only two different optical glasses. The design form can be scaled up or down from the 1000 mm focal length by using an appropriate scaling factor.
Optical viewing apparatus has an obective lens for focussing radiation from a scene or object to form an image on a detector and means for producing a visible display of the image which is viewed through an eye-piece lens. The objective lens is designed to impose a substantial level of barrel distortion on the image and the eye-piece lens imposes a substantial level of pincushion distortion on the observer's view to give improved central resolution. The radiation focussed by the objective lens may be visible or invisible, e.g. infra-red.
An optical system for night-vision glasses having a long focal length and a large image angle including an objective having a structural length less than 1.6f and an aperture ratio larger than 1.2, with the objective having a high distortion and an image angle of about 50.degree.. An image amplifier is provided for receiving an image from the objective and for providing an amplified image output with a viewing optic being provided for receiving the amplified image output and for compensating for the distortion of the objective to provide a substantially distortion-free image to a viewer.
The goggles include a pair of optical assemblies, each having two intersecting optical paths, including a see-through path with a large field of view on a straight line of sight to the viewed object, and a folded path which includes an objective lens set, an intensifier which converts visible and infrared light to a visible intensified light, and an eyepiece lens set, arranged in a loop in a plane perpendicular to the see-through path. Infrared and visible light from the viewed object enters both paths. A dichroic prism combiner at the intersection of the paths reflects intensified light from the folded path into the see-through path and transmits all other light. In one embodiment a dichroic prism separator is disposed at the intersection of the paths forward of the combiner for transmitting a portion of the incoming visible light along the see-through path and reflecting the remainder of the incoming light to the folded path. In another embodiment, the entrance to the folded path is spaced from the see-through path.
