Electrochromic projection and writing device
First Claim
1. Image projection and writing apparatus, comprising:
- an electrochromic cell comprising an electrolyte positioned between an electrochromic material and an ion storage material, said electrochromic cell being positioned between a transparent front electrode and a transparent back electrode, said front electrode and said back electrode being connected to a voltage source in a manner that applies a voltage across said electrochromic cell, a photodiode positioned between the front electrode and the electrochromic cell, said photodiode having electrical resistance that varies in response to light;
a back light source positioned adjacent said back electrode; and
an inscribing light source positioned adjacent said front electrode.
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Accused Products
Abstract
A display and projection apparatus includes an electrochromic material and a photoconductive material deposited in tandem used in conjunction with a light filtering means for filtering light transmitted through the electrochromic material. When an electric field is applied across the electrochromic material and the photoconductive material, light that is incident onto the photoconductive material through the surface of the projection apparatus causes the photoconductive material to conduct current locally in proportion to the amount of light incident on the photoconductive material. The flow of current causes the underlying portions of the electrochromic material to switch from an opaque state to a clear or transmissive state, thereby allowing back-light to propagate through the electrochromic material to create a visible image on the surface of the projection apparatus. Reversal of the electric field causes the electrochromic material to revert back to its opaque state, thereby blocking the transmission of back-light and effectively erasing the image from the surface of the projection apparatus.
26 Citations
17 Claims
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1. Image projection and writing apparatus, comprising:
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an electrochromic cell comprising an electrolyte positioned between an electrochromic material and an ion storage material, said electrochromic cell being positioned between a transparent front electrode and a transparent back electrode, said front electrode and said back electrode being connected to a voltage source in a manner that applies a voltage across said electrochromic cell, a photodiode positioned between the front electrode and the electrochromic cell, said photodiode having electrical resistance that varies in response to light;
a back light source positioned adjacent said back electrode; and
an inscribing light source positioned adjacent said front electrode. - View Dependent Claims (4, 5, 6, 7, 8, 9, 10)
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- 2. The image projection and writing apparatus of clam 1, wherein said photodiode has a total light-absorbing area and said inscribing light source has a light beam that is directed onto an incident area on said photodiode that is smaller than said total light absorbing area.
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11. A method of writing and projecting an image, comprising the steps of:
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positioning an electrochromic cell between a transparent front electrode and a transparent back electrode with a photodiode that has a decreasing electrical resistance in response to incident light of increasing intensity interposed between the front electrode and the electrochromic cell;
applying a bleaching voltage to said front electrode and said back electrode across said electrochromic cell;
directing a back-light through said back electrode onto said electrochromic cell; and
directing an inscribing light beam through the front electrode and onto a portion of the photodiode to decrease electrical resistance of said portion of the photodiode and thereby allow electric current to flow through said portion of the photodiode and through a portion of the electrochromic cell that is adjacent said portion of the photodiode. - View Dependent Claims (12, 13, 14, 15, 16, 17)
directing at least a portion of said back light through a localized area of said electrochromic cell; and
forming an image corresponding to said localized area of said electrochromic cell.
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Specification