Adaptive image acquisition system

An adaptive image acquisition system for optically scanning a media surface bearing static information in a particular direction and providing in real time a digital data representation of the scanned portion of the surface, comprising:

• a hand-held camera comprising an image sensor array of photosensitive pixel elements arranged in R rows and C columns;
• means for exposing said pixel elements during sequential exposure intervals of selectable duration for capturing sequential images of the portion of said media surface within the field of view of said array;
• means for reading out from said imaging array after each exposure interval thereof resulting digital data values for said pixel elements to provide sequential frames of digital image data comprising C columns and R rows of data;
• exposure control means for adaptively selecting the duration of said exposure intervals in dependence on the reflectivity of a background portion of said media surface, said exposure control means comprising means for acquiring a plurality of exposure measurement images of a background portion of said media surface with different exposure interval durations, and means for determining the number of black pixels in said respective images and processing said black pixel numbers to determine an exposure interval duration which yields a minimal number of black pixels for said background portion of said surface;
• means for real time processing of successive ones of said frames of image data to remove data therefrom which is redundant to image data in the preceding image frame, said means comprising:
• means for storing two successive frames of data, the initial frame known as the reference frame and the next frame known as the current frame;
• means for selecting a reference window defined by a subset of the pixel element values comprising said reference frame;
• and
• means for accessing said storing means and comparing selected pixel element values comprising the current frame with the pixel element values comprising said reference window and determining which pixel element data of said current frame is redundant to the pixel element data comprising said reference window;
• and
• means for providing an output image frame data set for each acquired image frame which includes data representative of only the pixel element data determined to be non-redundant to the pixel element data of the next preceding image frame.

An adaptive image acquisition system for optically scanning a media surface bearing static information in a particular direction and providing in real time a digital data representation of the scanned portion of the surface, comprising:

• an image sensor array of photosensitive pixel elements arranged in R rows and C columns;
• means for exposing said pixel elements for capturing sequential images of the portion of said media surface within the field of view of said array;
• means for reading out from said imaging array resulting digital data values for said pixel elements to provide sequential frames of digital image data comprising C columns and R rows of data;
• means for real time processing of successive ones of said frames of image data to remove data therefrom which is redundant to image data in the preceding image frame, said means comprising:
• means for storing two successive frames of data, the initial frame known as the reference frame and the next frame known as the current frame;
• means for selecting a reference window of N image columns, where the number N is less than the number C of pixel columns;
• means for adaptively determining the number N in dependence on the rate of relative movement between the image sensor array and said media surface to decrease the size of the reference window as the rate decreases;
• and
• means for accessing said storing means for comparing the pixel elements comprising selected columns of the current frame with the pixel elements comprising N selected columns of the reference frame within said reference window and determining which columns of pixel data of said current frame are redundant to corresponding columns of data within said reference window;
• and
• means for providing an output image frame data set for each acquired image which includes data representative of only those columns of pixel elements determined to be non-redundant to the columns of the next preceding image frame.

An adaptive image acquisition system for processing sequential frames of digital image data to remove redundant data, comprising:

• an optical camera means for providing sequential frames of digital image data, each frame representing a captured image of a portion of a surface bearing static information, each said frame comprising rows and columns of image pixel data;
• means responsive to a current image frame and the next preceding image frame for:
• (i) selecting a reference frame window size of N columns in relation to the current image frame, where the number N is adaptively selected in dependence on the relative rate of movement between said optical camera means and said surface;
• (ii) comparing selected columns of the current frame image data with the corresponding columns of said preceding frame image data within said reference frame window at a plurality P of alignment positions of the reference frame window, where the number P is selected in dependence on said relative rate of movement, and determining which columns of data of said current frame are redundant with corresponding columns of data of said preceding frame;
• and
• (iii) discarding said redundant columns and providing as a system output only those remaining columns of said current image frame.

A data compression method for processing sequential frames of digitized image data produced by a scanner moving in a predetermined direction in relation to a desired surface bearing static information, comprising a sequence of the following steps:

• (a) providing sequential image frames of digitized image pixel data of the portion of said surface within the field of view of said scanner, each frame comprising R rows and C columns of pixel data;
• (b) as the image frames are provided, storing the current frame and the next preceding reference frame in an addressable digital memory, the addresses for each frame addressable in the Y or row-wise dimension and in the X or column-wise dimension, where said predetermined movement direction is substantially aligned with said X dimension;
• (c) defining a reference frame window formed by N contiguous columns of said reference frame, where the value N is less than the value C, wherein the value N is adaptively determined in dependence on the rate of relative movement between the scanner and the surface to decrease the size of the reference window as the rate increases;
• (d) for each of a plurality of contiguous column-wise alignment positions of said reference frame window in relation to contiguous columns of said current frame, comparing the corresponding respective pixel values in said respective current frame and reference frame window to determine the column-wise alignment position of said reference window in relation to said current frame providing the best match between corresponding pixels;
• (e) from the best match position, determining which columns of pixel values comprising the current frame are redundant to columns of pixel data of the reference window and saving only the non-redundant columns of the current frame.

A method for sequentially acquiring digitized images of a surface bearing static information, comprising a sequence of the following steps:

• (a) providing an optical scanner having an image sensor array of photosensitive pixel elements arranged in R rows and C columns, the rows extending substantially along the X axis and the columns substantially along the Y axis in a Cartesian coordinate system;
• (b) imparting relative motion between the optical scanner and said surface substantially in a predetermined direction along the X axis;
• (c) sequentially exposing the image sensor array for an exposure duration and then reading the values of the pixel elements to provide a sequential series of digitized image data frames of the portion of the surface within the field of view of said scanner;
• (d) correlating each image data frame with a reference frame data window formed by a plurality N of contiguous columns of pixel data values of the preceding frame, where N is less than C, to determine the degree of overlap between the successive image frames and determine a variable value DELTAX representing the number of non-redundant columns for the particular image frame, wherein the value N is adaptively determined in dependence on the rate of relative movement between the image sensor array and the surface to decrease the size of the reference window as the rate increases;
• and
• (e) after the particular image frame has been correlated against the next successive image frame, discarding the (C-DELTAX) columns of image pixel data determined to have been redundant in step (d) and storing only the remaining DELTAX columns of pixel data for that image frame.

An adaptive image acquisition system for optically scanning across a media surface bearing static information in a predetermined scan direction and providing a digital data representation of the scanned portion of the surface, comprising:

• a hand-held optical scanner comprising an image sensor array of photosensitive pixel elements arranged in R rows and C columns, and means for exposing said pixel elements to the media surface during sequential exposure intervals for capturing sequential images of the portion of said medium surface within the field of view of said array, said rows of elements extending generally in the direction of said scan direction and said columns extending generally orthogonally to said scan direction;
• an image frame buffer memory coupled to said imaging array for buffering digitized representations of a plurality of said images;
• a video processor coupled to said optical scanner and said buffer memory for providing control signals to said imaging array and said exposing means for controlling the start and duration of said exposure intervals, for reading out from said imaging array after each exposure interval resulting digital data values for said pixel elements to sequentially provide said digitized representations of said images, and for storing said digitized representations of a plurality of sequential images at selected memory locations within said buffer memory;
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• a central controller coupled to said video processor to control said video processor operations and receive from said video processor compressed digital data representing the non-redundant portions of the sequential images captured by the scanner;
• said video processor and said central controller being cooperatively arranged to provide a means for performing a one-dimensional correlation along said scan direction between each image frame and a selectable window portion of the next preceding image frame comprising N columns thereof to identify redundant columns of pixel data appearing in both said image frame and said selectable window portion, and to provide said compressed digital data to said controller representing only non-redundant image data.

Apparatus for sequentially acquiring digitized images of a surface bearing static information, comprising:

• a handheld optical scanner having an image sensor array of photosensitive pixel elements arranged in R rows and C columns, the rows extending substantially along the X axis and the columns substantially along the Y axis in a Cartesian coordinate system;
• means for sequentially exposing the image sensor array for an exposure duration and then reading the values of the pixel elements to provide a sequential series of digitized image data frames;
• means for determining the effective spatial position of one data frame to the next frame in relation to said surface;
• means responsive to said spatial position means for determining the data in the each frame which is not redundant to the data in the preceding frame, said means comprising means for adaptively selecting a reference window of N rows of the data in the preceding frame, the size N being adaptively selected in dependence on the rate of relative movement between the sensor array and the surface so as to reduce the size N as the rate increases, and means for comparing the reference frame data and next framed data for determining the non-redundant data;
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• means for buffering said non-redundant data with the non-redundant data from previous frames, to assemble a composite image of said surface.

An adaptive image acquisition system for optically scanning a media surface in a particular direction and providing in real time a compressed digital data representation of the scanned portion of the surface, comprising:

• a hand-held camera comprising an image sensor array of photosensitive pixel elements arranged in R rows and C columns;
• means for exposing said pixel elements during sequential exposure intervals of selectable duration for capturing sequential images of the portion of said medium surface within the field of view of said array;
• means for reading out from said imaging array after each exposure interval thereof resulting digital data values for said pixel elements to provide sequential frames of digital image data comprising C columns and R rows of data;
• means for real time processing of successive ones of said frames of image data to remove data therefrom which is redundant to image data in the preceding image frame, said means comprising:
• means for storing two successive frames of data, the initial frame known as the reference frame and the next frame known as the current frame;
• means for selecting a reference window comprising a subset of the pixel element values comprising said reference frame;
• means for adaptively determining the size of said reference window in dependence on the rate of relative movement between said imaging array and said media surface to decrease the size of said reference window as said rate increases;
• and
• means for accessing said storing means and comparing selected pixel element values comprising the current frame with the pixel element values comprising said reference window and determining which pixel element data of said current frame is redundant to the pixel element data comprising said reference window;
• and
• means for providing an output image frame data set for each acquired image frame which includes data representative of only the pixel element data determined to be non-redundant to the pixel element data of the next preceding image frame.

An adaptive image acquisition system for optically scanning a media surface in a particular direction and providing in real time a compressed digital data representation of the scanned portion of the surface, comprising:

• an image sensor array of photosensitive pixel elements arranged in R rows and C columns;
• means for exposing said pixel elements during sequential exposure intervals of selectable duration for capturing sequential images of the portion of said medium surface within the field of view of said array;
• means for reading out from said imaging array after each exposure interval thereof resulting digital data values for said pixel elements to provide sequential frames of digital image data comprising C columns and R rows of data;
• means for real time processing of successive ones of said frames of image data to remove data therefrom which is redundant to image data in the preceding image frame, said means comprising:
• means for storing two successive frames of data, the initial frame known as the reference frame and the next frame known as the current frame;
• means for selecting a reference window of N image columns, where the number N is less than the number C of pixel columns;
• means for adaptively determining the size of said reference window in dependence on the rate of relative movement between said imaging array and said media surface to decrease the size of said reference window as said rate increases;
• and
• means for accessing said storing means for comparing the pixel elements comprising selected columns of the current frame with the pixel elements comprising N selected columns of the reference frame within said reference window and determining which columns of pixel data of said current frame are redundant to corresponding columns of data within said reference window;
• and
• means for providing an output image frame data set for each acquired image which includes data representative of only those columns of pixel elements determined to be non-redundant to the columns of the next preceding image frame.

A method for sequentially acquiring digitized images of an information bearing surface, comprising a sequence of the following steps:

• (a) providing an optical scanner having an image sensor array of photosensitive pixel elements arranged in R rows and C columns, the rows extending substantially along the X axis and the columns substantially along the Y axis in a Cartesian coordinate system;
• (b) imparting relative motion between the optical scanner and the information bearing surface substantially in a predetermined direction along the X axis;
• (c) sequentially exposing the image sensor array for an exposure duration and then reading the values of the pixel elements to provide a sequential series of digitized image data frames;
• (d) correlating each image data frame with a reference frame data window comprising a plurality N of contiguous columns of pixel data values of the preceding frame, where N is less than C, to determine the degree of overlap between the successive image frames and determine a variable value DELTAX representing the number of non-redundant columns for the particular image frame;
• and
• (e) adaptively selecting the size N of the reference window used in correlation the next successive image frame in dependence on the magnitude of the variable value DELTAX, such that the value N has a minimum value and increases with decreasing values of DELTAX to a maximum window size which is less than the number of pixel element columns in the image frame, and
• (f) after the particular image frame has been correlated against the next successive image frame, discarding the (C-DELTAX) columns of image pixel data determined to have been redundant in step (d) and storing only the remaining DELTAX columns of pixel data for that image frame.

A method for sequentially acquiring digitized images of an information bearing surface, comprising a sequence of the following steps:

• (a) providing an optical scanner having an image sensor array of photosensitive pixel elements arranged in R rows and C columns, the rows extending substantially along the X axis and the columns substantially along the Y axis in a Cartesian coordinate system;
• (b) imparting relative motion between the optical scanner and the information bearing surface substantially in a predetermined direction along the X axis;
• (c) sequentially exposing the image sensor array for an exposure duration and then reading the values of the pixel elements to provide a sequential series of digitized image data frames;
• (d) adaptively selecting a reference frame data window comprising a plurality N of contiguous columns of pixel data values of the preceding frame, where N is less than C, in dependence on the magnitude of said relative motion, such that the size N of the window increases as the magnitude of the motion decreases;
• (e) correlating each image data frame with said reference frame data window to determine the degree of overlap between the successive image frames and determine a variable value DELTAX representing the number of non-redundant columns for the particular image frame;
• and
• (f) after the particular image frame has been correlated against the next successive image frame, discarding the (C-DELTAX) columns of image pixel data determined to have been redundant in step (d) and storing only the remaining DELTAX columns of pixel data for that image frame.