Pilkington Pe Limited

David Gordon Norrie

Anthony John Kirkham

Martin D Roberts

An objective lens system,uses Germanium lens elements including a positively-powered objective lens (A), a positively-powered intermediate lens (B) and a negatively-powered field lens (C). The field lens (C) flattens the Field curvature of the system. The intermediate lens (B) corrects astigmatism and has an aspheric surface (,).

Three element objective lens system using Germanium lens element

An afocal telescope operating in the thermal infra-red waveband has a three-element objective comprising a positively-powered central lens element disposed between positively powered and negatively powered lateral lens elements, the positively powered lateral lens element being located proximal to the inter-mediate image and incorporating a hybrid surface simultaneously to correct longitudinal and field colour, and wherein one of the positively powered lens elements of the objective is made of a material having a negative temperature refractive index co-efficient and has an optical power selected to render the telescope athermal.

Afocal telescopes

An optical system for a display having a combiner (1) with a non-conformal reflection hologram and in which an intermediate image (II) of a display source is formed at a location in the light path to and spaced from the combiner (1), the system comprising at least one diffractive element (5,7) disposed in the light path between the display source (2) and the intermediate image (II) and arranged to counter, at least partially, the chromatic dispersion of the non-conformal reflection hologram (1).

Lateral and longitudinal chromatic dispersion correction in display

An `eye-piece` system for a non-Galilean afocal infra-red telescope designed to contribute to astigmatism correction, pupil match, and true afocality without undue increase in objective aperture requirements comprises a positively powered back group and a negatively powered front group consisting of a rear lens element with a convex rear surface and a front lens element with a concave front surface, there being a negatively powered gas lens between the rear and front elements of the front group. The objective system may be catadioptric.

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Denbigh, United Kingdom

David Gordon Norrie