Method for controlling a photosensitive device with low image retention, and photosensitive device implementing same
AssigneeThomson Tubes Electroniques
InventorsThierry Ducourant, Christophe Chaussat
Life of this patent
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Abstract
A drive process for an array of photosensitive points produced on a semiconductor material. Each of the points has a photodiode connected in series with a switch element. The photodiode is reverse-biased and produces charges when it is exposed to a light signal during an imaging phase. Before the imaging phase, the photosensitive points are illuminated with an additional light flux whose intensity causes the photodiode to conduct in the forward direction and then in applying a biasing pulse to the photosensitive points in order to return the photodiode to reverse bias. Thus, a current is produced which has the effect of reducing a remanence effect in the semiconductor material.
Claims24
A drive process for a photosensitive device comprising a matrix of photosensitive points, the photosensitive points are arranged in at least one row and in at least one column and each photosensitive point of said photosensitive points comprises a switch element connected in series with a photodiode to have a common point, the drive process comprising:
- exposing at least one photosensitive point of said photosensitive points of the matrix to an erasing light having an intensity and a duration such that a first plurality of charges generated in said at least one photosensitive point modify a voltage of said common point until said voltage of said common point reaches an elbow voltage of the photodiode and the photodiode conducts in a forward direction;
- reverse-biasing said photodiode;
- exposing said at least one photosensitive point to a light signal such that a second plurality of charges produced in said at least one photosensitive point by said light signal modify a bias voltage of said photodiode;
- and
- reading said at least one photosensitive point after said exposing.
A photosensitive device comprising:
- a matrix of photosensitive points that are arranged in at least one row and at least one column, each photosensitive point of said photosensitive points lying at an intersection of said at least one row and said at least one column, each photosensitive point comprising:
- a switch element, and
- a photodiode, wherein
- said switch element is formed in series with the photodiode,
- each photodiode is reverse-biased during an imaging phase,
- a junction between the photodiode and the switch element have a common point having a floating potential, and
- charges produced by the photodiode are accumulated at said common point;
- a first voltage source configured to expose the matrix to an erasing light flux such that said photodiode produces charges that accumulate at said common point and causes said photodiode to conduct in a forward direction;
- and
- a second voltage source configured to reverse-bias said photodiode after an application of the erasing light flux and before the imaging phase, wherein
- said photosensitive device implements a process comprising:
- exposing at least one photosensitive point of said photosensitive points of the matrix to the erasing light having an intensity and a duration such that a first plurality of charges generated in said at least one photosensitive point modify a voltage of said common point until said voltage of said common point reaches an elbow voltage of the photodiode and the photodiode conducts in a forward direction;
- reverse-biasing said photodiode;
- exposing said at least one photosensitive point to a light signal such that a second plurality of charges produced in said at least one photosensitive point by said light signal modify a bias voltage of said photodiode;
- and
- reading said at least one photosensitive point after said exposing.
Dependencies are inferred from the claim text.