Microlens screens, photopolymerisable materials and artifacts utilising the same

• US 5,442,482 A
• Filed: 12/18/1992
• Issued: 08/15/1995
• Est. Priority Date: 05/21/1990
• Status: Expired due to Term

• Current Assignee: Microsharp Corporation Limited
• Original Assignee: Nicholas J. Phillips, William N.H. Johnson
• Inventors: Phillips, Nicholas J., Johnson, William N. H.
• Primary Examiner(s): Lerner, Martin
• Application Number:
  US07/958,329
• Time in Patent Office: 970 Days
• Field of Search: 359/654, 359/652, 359/463, 359/618-624, 359/599, 264/2.6, 264/2.7, 430/4
• US Class Current: 359/619
• CPC Class Codes: G02B 2006/12102 Lens
• CPC Class Codes: G02B 2006/1219 Polymerisation
• CPC Class Codes: G02B 3/0031 Replication or moulding, e.g. hot embossing, UV-casting, injection moulding
• CPC Class Codes: G02B 3/0056 arranged along two different directions in a plane, e.g. honeycomb arrangement of lenses G02B3/0043 takes precedence; miniaturised objectives for electronic devices employing wafer level optics G02B13/0085
• CPC Class Codes: G02B 3/0087 with index gradient
• CPC Class Codes: G02B 6/1221 made from organic materials
• CPC Class Codes: G03B 21/625 Lenticular translucent screens

Abstract

There are disclosed variations on a basic technique for forming a diffusion or rear-projection screen comprising an array of microlenses formed by selective light exposure and consequent selective polymerization of a sheet of photopolymerizable material. Thus, the lenses may be made elongate in a preferred direction transverse to the lens axes by exposure through a mesh formed with an array of slots. The lenses may be graded refractive index lenses having a surface relief adding to the lens power, such relief being formed naturally or by molding. The photopolymerizable material may be exposed by laser light, for example to a holographic pattern and such exposure may be made through a quarter-wave plate continuously rotated to eliminate micro defects. Enhanced lens powers may be achieved by heating the photopolymerizable material to close to the softening temperature of the associated polymer before exposure to light and maintaining the material at that temperature during the resultant polymerization.

Claims

1. A sheet of transparent material comprising a layer of a photopolymer which has been formed with an array of integral graded refractive index microlenses by selective exposure of a photopolymerisable monomer to polymerising radiation wherein each microlens terminates, on at least one of the surfaces of the sheet, in a surface relief formation which adds to the power of the respective microlens.

2. A method of making a light diffusing material comprising providing a sheet of light-transmitting base material, having a surface thereof configured to form an array of microlenses, coating the base material with a layer of a medium, said medium being a photopolymerisable monomer, of which the refractive index can be varied by exposure to light, then exposing the variable refractive index medium to light through the said base material having said microlenses formed thereon, whereby the localised variation in intensity of said light, through the variable refractive index medium, produced by said microlenses, causes corresponding variations in refractive index in said medium whereby there is produced, in said medium, an array of graded refractive index lenses each aligned with, and adding its optical effect to, a respective said microlens of the base material.

3. A method of making a light diffusing material comprising forming a sheet or layer of a medium, said medium being a photopolymerisable monomer, of which the refractive index can be varied by exposure to light, one surface of said sheet or layer being moulded or embossed to afford form an array of microlenses, exposing the sheet or layer of said medium to light through said moulded or embossed surface, whereby the localised variation in said light, through the variable refractive index medium, produced by refraction at said moulded or embossed surface, causes corresponding variations in refractive index in said medium, whereby there is produced, in said medium, an array of graded refractive index lenses each aligned with, and adding its optical effect to, a respective microlens surface defined by said moulding or embossing.

4. A method of making a light diffusing material comprising forming a sheet or layer of a medium, said medium being a photopolymerisable monomer of which the refractive index can be varied by exposure to light, exposing the sheet or layer of said medium to light through an optical mask consisting of an array of light transmitting areas in an opaque field whereby the localised variation in said light, through the variable refractive index medium, produced by said mask causes corresponding selective polymerisation of said medium in said light transmitting areas with corresponding variations in refractive index in said medium, whereby there is produced, in said medium, an array of graded refractive index lenses, the method including leaving at least one surface of said sheet or layer free during exposure and photopolymerisation, whereby said sheet or layer undergoes a surface modification associated with said selective polymerisation to produce an array of microlenses defined by the surface contour of said surface, each of said microlenses defined by said surface contour being aligned with, and adding its optical effect to, a respective said graded refractive index lens.