Optical: systems and elements – Single channel simultaneously to or from plural channels – By surface composed of lenticular elements
Patent
1992-12-18
1995-08-15
Lerner, Martin
Optical: systems and elements
Single channel simultaneously to or from plural channels
By surface composed of lenticular elements
359620, 359652, G02B 112, G02B 513, G02B 2712
Patent
active
054424828
DESCRIPTION:
BRIEF SUMMARY
THIS INVENTION relates to light diffusing screens and other artefacts comprising arrays of microlenses, to methods of making such screens and artefacts or light diffusing materials therefor to the manufacture of such artefacts and materials using photopolymerisable materials, to the fabrication of microlenses and other microstructures, and to the manufacture of graded refractive index lenses and other products. The invention also relates to an optical printing method and apparatus capable of being realised using a component formed of graded refractive index material.
Our published British Patent Application GB2206979A (8812644.6) discloses, inter alia, a technique for forming a microlens diffusing screen, for example for television, which comprises a transparent sheet bearing an array of microlenses, and in which the microlenses are in the form of graded refractive index lenses formed by selective exposure of a photopolymer to a pattern of dots, such exposure being in ultra-violet light or suitable visible light and being effected by "contact" exposure through a mask having an array of circular holes formed therein, or by spot-by-spot exposure using a scanned ultra-violet laser, or by ultra-violet holography.
It is one object of the present invention to provide an improvement in the above-noted technique disclosed in GB2206979A whereby such a screen may be arranged to disperse light substantially more in one dimension parallel to the plane of the screen than in a perpendicular direction, that is to say, whereby the screen will have different polar distribution for light diffused thereby, about two mutually perpendicular axes. Thus, for example, as applied to a television screen onto which light is projected from a luminous source such as a cathode ray tube, it may be arranged that the range of angles about a vertical axis relative to the screen over which the screen will appear acceptably bright to an observer will be substantially wider than the corresponding range about a horizontal axis, thereby utilising more efficiently the image-forming light directed to the screen from the luminous source, bearing in mind that, in a typical viewing situation in which a plurality of observers are viewing the screen simultaneously, or in which a single observer may view the screen from various positions, the screen will generally be approximately at the eye-level of the observer, but the observer will not necessarily be in front of the screen.
According to one aspect of the present invention, the individual microlenses in the array are elongated in one direction in the plane of the screen, so that a middle region of each microlens acts as a cylindrical lens whilst the end regions thereof act as respective parts of respective spherical lenses.
The terms "cylindrical" and "spherical" used above are used merely to describe the mode of operation of the lenses. The lenses themselves are preferably, as in GB2206979A, formed by graded refractive index effects in a photopolymer layer bounded by substantially planar surfaces, or by surfaces having some surface relief effects as an artefact or by-product of the method used to form the graded refractive index lenses.
The present invention, in another aspect, concerns various other uses for a microlens screen or analogous light-transmitting material, hereinafter referred to as "the microlens material", in the form of a transparent polymeric sheet incorporating an array of graded refractive index microlenses. Such a microlens screen acts as a very efficient rear projection/diffusion screen exhibiting reduced scatter of light to undesired angles and a reduction in the "hot spot" effect.
In one class of such use, the microlens material performs a straightforward diffusion or light-directing function independently of any projection or optical system. For example, such sheet material may be applied as a film to glass used architecturally, e.g. for glazing windows and doors, or may, for such a purpose, be sandwiched between two sheets of glass or rigid transparent plastics to afford a
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Johnson William N. H.
Phillips Nicholas J.
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