Method and apparatus for exposure level setting in machine vision systems
AssigneeSTMicroelectronics (R&D) Ltd.
InventorJustin Richardson
Life of this patent
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Abstract
In a solid state image sensor having a pixel array, a first frame is imaged using varying exposure times in a series of zones. The exposure time for a subsequent frame is selected from the results of the first frame, The exposure times are controlled in a rolling blade manner by controlling the number of lines between reset and readout. The sensor is particularly suited to use in bar code readers.
Claims15
A method of setting an exposure time in a solid state image sensing system comprising an array of pixels, a reset unit for resetting the pixels, and a readout unit for reading out pixel values, the method comprising:
- controlling the reset and readout units for
- exposing a first image frame as a series of frame zones to generate a series of respective zone signals, each frame zone comprising successive groups of rows of pixels and being exposed for a different exposure time, with each frame zone having a progressively increasing exposure time,
- determining a best exposure time based upon the series of zone signals, and with the best exposure time including interpolation between zone exposure times of the first image frame, and
- exposing a second image frame as a whole frame using the best exposure time.
A method of setting an exposure level in an image sensing system comprising an array of pixels, a reset unit for resetting the pixels, and a readout unit for reading out pixel values, the method comprising:
- controlling the reset and readout units for
- exposing a first image frame as a plurality of frame zones to generate a series of readout values, each frame zone comprising successive groups of rows of pixels and being exposed for a different exposure level, with each frame zone having a progressively increasing exposure level,
- selecting an image exposure level based upon the series of readout values, and with the exposure level including interpolation between zone exposure levels of the first image frame, and
- exposing a second image frame using the selected exposure level.
An image sensing device comprising:
- an array of pixels;
- a reset unit for resetting the pixels;
- a readout unit for reading out pixel values;
- and
- a control unit for controlling the reset unit and readout unit to
- expose a first image frame as a series of frame zones to generate a series of respective zone signals, each frame zone comprising successive groups of rows of pixels being exposed for a different exposure time, with each frame zone having a progressively increasing exposure time,
- determine a best exposure time based upon the series of zone signals, and with the best exposure time including interpolation between zone exposure times of the first image frame, and
- expose a second image frame as a whole frame using the best exposure time.
Dependencies are inferred from the claim text.