Efficient LED light geometry for optical printers
AssigneePolaroid Corporation
InventorRichard G. Egan
Life of this patent
Estimating the term…
Abstract
A light source is disclosed for use an optical printer illuminating a spatial light modulator to efficiently and uniformly project light onto a photosensitive medium while providing a simpler design of the spatial light modulator in the optical printer. The light source uses light emitting diodes opposed across a light pipe. The light from the light emitting diodes propagates in the light pipe until striking a redirection structure which redirects the light out of lateral surface of the light pipe.
Claims19
A plurality of color light sources suitable for use in printing on a photosensitive medium, each of said plurality of color light sources comprising:
- light projection means for projecting at least one beam of light;
- a light pipe comprising a first surface and a second surface, said light pipe in optical communication with said light projection means such that said beam of light enters said light pipe and is incident upon said first surface at an angle less than or equal to the critical angle so as to produce a totally internally reflected beam of light within said light pipe;
- and
- optical redirection means disposed at said second surface such that when said reflected beam of light is incident upon said second surface, said reflected beam of light is emitted from said light pipe;
- and
- said plurality of color light sources in adjacent alignment for projecting colored light that is substantially collimated.
A print head for use in an optical printer which prints on a photosensitive medium having a relative motion with respect to the print head, the print head comprising:
- a plurality of color light sources in adjacent alignment for projecting colored light that is substantially collimated, each said light source comprising:
- light projection means;
- and
- a light pipe comprising a first surface and a second surface, said light pipe in optical communication with said light projection means such that said beam of light enters said light pipe and is incident upon said first surface at an angle less than or equal to the critical angle so as to produce a totally internally reflected beam of light within said light pipe;
- and optical redirection means disposed at said second surface such that when said reflected beam of light is incident upon said second surface, said reflected beam of light is emitted from said light pipe;
- and
- a spatial light modulator in optical alignment with said plurality of color light sources, said spatial light modulator comprising a plurality of columns corresponding to a column of pixel locations on the photosensitive medium where each of said plurality of columns is driven independently, said plurality of columns being driven such that an intersection of each of said plurality of color light sources and said plurality of columns defines a line of pixels on the photosensitive medium.
A light source for use in an optical printer that projects light through a conventional lens system having a first light distribution to generate an image on a photosensitive medium, said light source comprising:
- illumination means for projecting light along an optical path;
- and
- light distribution means disposed in the optical path of the illumination means for distributing the light according to a second light distribution where the second light distribution is substantially complimentary to the first light distribution, thus forming a substantially uniform light distribution across the photosensitive medium, said light distribution means comprising a light pipe comprising a first surface and a second surface, such that a beam of light entering said light pipe and incident upon said first surface at an angle less than or equal to the critical angle produces a totally internally reflected beam of light within said light pipe;
- and when said reflected beam of light is incident upon said second surface, said reflected beam of light is emitted from said light pipe.
Dependencies are inferred from the claim text.