US 8,300,125 B2Granted

Method and apparatus for using thin-film transistors and MIS capacitors as light-sensing elements in charge mapping arrays

AssigneePalo Alto Research Center Incorporated

InventorsTse Nga Ng, Sanjiv Sambandan, William S. Wong

Life of this patent

Estimating the term…

Loading patent…

Abstract

A method and apparatus for using TFT transistors or MIS capacitors as light-sensing elements in charge mapping arrays. A bias stress may be applied to a plurality of pixels in a charge map array. As a result, charge carriers may be trapped in each of the plurality of pixels responsive to the bias stress, which may be observed as a value shift such as a threshold voltage VT shift. Light may then be transmitted toward the plurality of pixels in the charge map array causing some of the pixels to absorb the light. The trapped charge carriers are released in the pixels that absorbed the light and not released in the pixels that did not absorb the light. The value shift in each of the pixels can be compared to determine which of the pixels absorbed the light.

Claims10

Dependent claims

A method for sensing light using a charge map array, comprising:

applying a bias stress to a plurality of pixels in the charge map array, thereby trapping charge carriers in each of the plurality of pixels responsive to the bias stress;
transmitting light toward the plurality of pixels in the charge map array, thereby releasing the trapped charge carriers in a first portion of the plurality of pixels responsive to transmitting the light;
determining a threshold voltage shift in the first portion and a second portion of the plurality of pixels by applying a scanning gate pulse to a gate of a switching TFT of each of the plurality of pixels, and reading a current value from a TFT light sensing element of each of the plurality of pixels by applying a read voltage to a source of the switching TFT of each of the plurality of pixels to transfer a read gate voltage to the TFT light sensing element and reading the current value at a drain of the TFT light sensing element to determine the threshold voltage shift in each of the plurality of pixels;
and
comparing the threshold voltage shift in the first portion of the plurality of pixels to the threshold voltage shift in the second portion of the plurality of pixels.

2 more elements

A device, comprising:

a charge map array including a plurality of pixels, each pixel including a switching TFT and a light sensing TFT structured to absorb light;
a gate driver board coupled to the charge map array and structured to apply a bias stress to the plurality of pixels in the charge map array;
and
a data sense board coupled to the charge map array and structured to determine a threshold voltage shift in a first portion and a threshold voltage shift in a second portions of the plurality of pixels responsive to a transmission of light toward the plurality of pixels in the charge map array, the data sense board include a comparator to compare a value shift in the first portion of the plurality of pixels to a value shift in the second portion of the plurality of pixels, the data sense board structured to:
apply a read voltage to a source of the switching TFT of each of the plurality of pixels to transfer a read gate voltage to the light sensing TFT;
apply a scanning gate pulse to a gate of the switching TFT of each of the plurality of pixels;
and
read a current value from a drain of the light sensing TFT in each of the plurality of pixels,
compare the threshold voltage shift in the first portion of the plurality of pixels to the threshold voltage shift in the second portion of the plurality of pixels to determine which of the plurality of pixels in the charge map array absorbed the transmitted light.

6 more elements

Dependencies are inferred from the claim text.