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US 8,508,656 B2Granted
Control of a dynamic image sensor
AssigneeStmicroelectronics (Grenoble2) SAS
InventorPaul Varillon
Life of this patent
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Abstract
A method and a circuit for controlling a dynamic image sensor defining, for each image, several successive time intervals of exposure of photodiode cells, starting from successive decreasing reset levels, wherein the time intervals of exposure of the image respect a homogeneous distribution of the amount of cells in ranges of brightness levels.
Claims17
A method for controlling a dynamic image sensor comprising photodiode cells, each providing an information representative of a brightness level, comprising for each image the steps of:
- defining ranges of brightness levels;
- defining several successive time intervals of exposure of the cells for the next image, the cells being reset at the beginning of each interval, said intervals being calculated from the brightness levels of a present image and from the desired brightness level distribution for the next image;
- and
- adapting the time intervals of exposure as a function of a homogeneous distribution of the number of cells in the ranges of brightness levels, wherein the time intervals T(i) between resets for the next image are calculated by the following formula:
- T
- (
- i
- )
- =
- PvalN
- +
- 1
- (
- i
- )
- -
- PvalN
- +
- 1
- (
- i
- -
- 1
- )
- Sen
- ·
- (
- LvalN
- +
- 1
- (
- i
- )
- -
- LvalN
- +
- 1
- (
- i
- -
- 1
- )
- )
- ,
- where
- PvalN+1(i) designates the upper threshold of interval i for the next image,
- PvalN+1(i-1) designates the upper threshold of interval i−1 for the next image,
- LvalN+1(i) designates the brightness value of interval i for the next image,
- LvalN+1(i-1) designates the brightness value of interval i−1 for the next image, and
- Sen designates the sensitivity of a cell.
47 more elements
A method for controlling an image sensor including sensor cells, comprising:
- determining, by an image sensor control circuit, brightness values of a next image corresponding to limits of a desired cell value distribution, based on values of a current image;
- and
- determining, by the image sensor control circuit, time intervals between resets of the sensor cells and corresponding cell reset values for the next image, based on the determined brightness values and the limits of the desired cell value distribution of the next image, wherein the time intervals between resets of the sensor cells are adjusted to achieve the desired cell value distribution of the next image, wherein the time intervals T(i) between resets for the next image are calculated by the following formula:
- T
- (
- i
- )
- =
- PvalN
- +
- 1
- (
- i
- )
- -
- PvalN
- +
- 1
- (
- i
- -
- 1
- )
- Sen
- ·
- (
- LvalN
- +
- 1
- (
- i
- )
- -
- LvalN
- +
- 1
- (
- i
- -
- 1
- )
- )
- ,
- where
- PvalN+1(i) designates an upper threshold of interval i for the next image,
- PvalN+1(i-1) designates an upper threshold of interval i−1 for the next image,
- LvalN+1(i) designates a brightness value of interval i for the next image,
- LvalN+1(i-1) designates a brightness value of interval i−1 for the next image, and
- Sen designates the sensitivity of a cell.
46 more elements
A method for controlling an image sensor including sensor cells, comprising:
- determining, by an image sensor control circuit, brightness values of a next image corresponding to limits of a desired cell value distribution, based on values of a current image;
- and
- determining, by the image sensor control circuit, time intervals between resets of the sensor cells and corresponding cell reset values for the next image, based on the determined brightness values and the limits of the desired cell value distribution of the next image, wherein the time intervals between resets of the sensor cells are adjusted to achieve the desired cell value distribution of the next image, wherein levels Prst(i)of the successive resets for the next image are calculated by the following formula:
- Prst(i)=PvalN+1(i)−(T(i)·Sen·LvalN+1(i)), where
- T(i) designates the exposure time interval of rank i between resets for the current image,
- PvalN+1(i) designates an upper threshold of interval i for the next image,
- LvalN+1(i) designates a brightness value of interval i for the next image, and
- Sen designates the sensitivity of a cell.
5 more elements
An image acquisition device comprising an image sensor including sensor cells and a control and processing circuit encoded with instructions that, when executed, are configured to:
- determine brightness values of a next image corresponding to limits of a desired cell value distribution, based on values of a current image;
- and
- determine time intervals between resets of the sensor cells and corresponding cell reset values for the next image, based on the determined brightness values and the limits of the desired cell value distribution of the next image, wherein the time intervals between resets of the sensor cells are adjusted to achieve the desired cell value distribution of the next image, wherein the time intervals T(i) between resets for the next image are calculated by the following formula:
- T
- (
- i
- )
- =
- PvalN
- +
- 1
- (
- i
- )
- -
- PvalN
- +
- 1
- (
- i
- -
- 1
- )
- Sen
- ·
- (
- LvalN
- +
- 1
- (
- i
- )
- -
- LvalN
- +
- 1
- (
- i
- -
- 1
- )
- )
- ,
- where
- PvalN+1(i) designates an upper threshold of interval i for the next image,
- PvalN+1(i-1) designates an upper threshold of interval i−1 for the next image,
- LvalN+1(i) designates a brightness value of interval i for the next image,
- LvalN+1(i-1) designates a brightness value of interval i−1 for the next image, and
- Sen designates the sensitivity of a cell.
46 more elements
An image acquisition device comprising an image sensor including sensor cells and a control and processing circuit encoded with instructions that, when executed, are configured to:
- determine brightness values of a next image corresponding to limits of a desired cell value distribution, based on values of a current image;
- and
- determine time intervals between resets of the sensor cells and corresponding cell reset values for the next image, based on the determined brightness values and the limits of the desired cell value distribution of the next image, wherein the time intervals between resets of the sensor cells are adjusted to achieve the desired cell value distribution of the next image, wherein levels Prst(i) of the successive resets for the next image are calculated by the following formula:
- Prst(i)=PvalN+1(i)−(T(i)·Sen·LvalN+1(i)), where
- T(i) designates the exposure time interval of rank i between resets for the current image,
- PvalN+1(i) designates an upper threshold of interval i for the next image,
- LvalN+1(i) designates a brightness value of interval i for the next image, and
- Sen designates the sensitivity of a cell.
5 more elements
Dependencies are inferred from the claim text.