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US 4,398,786 AGranted
Collimation lens system
AssigneeBarr & Stroud Limited
InventorIain A. Neil
Life of this patent
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AssigneeBarr & Stroud Limited
InventorIain A. Neil
Estimating the term…
An eyepiece or collimation lens system (22) is formed by three optically-powered lens elements (A, B, C) aligned on a common optical axis (23) and arranged to accept radiation in the infrared wavelength region from a real image (I) and provide a bundle of parallel rays at an exit pupil (.0.), each of the lens elements (A, B, C) is positively powered and made of a material which has a useful spectral bandpass in the infrared wavelength region and the refractive surface (6) of lens element (C) which lies adjacent the real image (I) is flat whereas the other refractive surfaces, (1, 2, 3, 4, 5) of the lens elements (A, B, C) are substantially spherical. A graticule may be mounted on or adjacent the flat refractive surface (6) and each refractive surface may be anti-reflection coated. Conveniently lens element (c) is made of zinc selenide whereas lens elements (A, B) are each made of germanium.
An eyepiece or collimation lens system formed by three optically-powered lens elements aligned on a common optical axis and arranged to accept radiation in the infrared wavelength region from a real image and to provide a bundle of parallel rays at an exit pupil, each said lens element being positively powered and made of a material which has a useful spectral bandpass in the infrared wavelength region, the refractive surface of the lens element adjacent said real image being flat and the five other refractive surfaces of said lens elements being substantially spherical.
Dependencies are inferred from the claim text.