Self aligning raster input scanner

A method of calibrating an raster input scanning device for detecting an image on a preselected surface, including the steps of:

• providing a linear array of photosensitive sensors arranged along a first axis for sensing and generating an electrical representation of an image;
• moving a sensor readable test target along a second axis, transverse to said first axis, from a predetermined starting point, said sensor readable test target including at least one selected alignment feature;
• measuring the distance traveled along said second axis by said target from said starting point until said sensors detect said selected alignment feature;
• comparing said measured distance with a second axis reference value;
• storing a second axis value representative of said comparison in a device storage memory;
• and
• using said stored second axis value as a second axis offset reference.

In an apparatus for scanning an image in a line by line fashion to produce data representative of the image scanned, including

• a linear scanning array comprised of a plurality of discrete photoelectric sensors arranged along a first axis for detecting images on a preselected surface;
• and means for moving at least one of a surface to be scanned and said scanning array relative to the other along a second axis transverse to said first axis, starting from a predetermined start position;
• a sensor detectable target image removably mountable on said surface to be scanned;
• second axis measuring means for determining the distance traveled by said at least one of a surface to be scanned and said scanning array relative to the other along said second axis from said predetermined starting position until a selected feature on said target image is detected;
• second axis comparison means for comparing said distance with a reference to derive a second axis offset value;
• and
• a memory storing said second axis offset value.

In an apparatus for scanning an image to produce data representative of the image thus scanned, including:

• a scanning array comprised of a plurality of discrete photoelectric sensors arranged along at least a first axis for radiation indicative of images on a preselected surface;
• a sensor detectable target image supported for detection by said sensors;
• a controller for detecting the position of a selected and detected feature on said target image with respect to a selected axis on said scanning array;
• a comparator for comparing said position with a reference to derive a axis offset value;
• and
• a memory storing said axis offset value.

A system for calibrating a raster input scanning device, including:

• a linear photoelectric sensor array comprising a plurality of discrete photosensitive elements arranged along a first axis, for sensing and generating electrical representations of an image on a surface;
• a carriage assembly movable along a second axis, transverse to said first axis, and supporting a photoelectric sensor detectable target image having selected alignment features;
• a drive system for driving said carriage assembly from a starting position along said second axis;
• a motor drive controller producing a series of control signals for controlling said drive system;
• a diagnostic memory for storing reference information representative of a selected alignment feature and a desired location thereof;
• a system controller for comparing images detected by said photosensitive elements with said stored reference information to identify the detection of a selected alignment feature by said photosensitive elements, receiving said control signals from said motor drive controller as indications of distance traveled by said carriage assembly along said second axis and comparing said distance traveled by said carriage with said desired location of said alignment feature;
• and
• a calibration memory for storing a y-axis offset value from said system controller derived by comparing said distance traveled by said carriage assembly along said second axis until said photosensitive elements detect a a selected feature on said target image, with the desired locations of a selected feature for use as a y-axis offset value.

A system for calibrating a raster input scanning device, including:

• a linear photoelectric sensor array comprising a plurality of discrete photosensitive elements arranged along a first axis, for sensing and generating electrical representations of an image on a surface;
• means for moving at least one of said image and said sensor array relative to the other along a second axis, transverse to said first axis;
• measuring means for measuring the relative movement of said image and said sensor array;
• and
• means for identifying a selected feature on said image;
• and
• means for determining the positional difference between said identified selected feature and a reference position.

A system for calibrating magnification in a raster input scanning device including:

• a linear photoelectric sensor array comprising a plurality of discrete photosensitive elements arranged along at least a first axis, for sensing and generating electrical representations of an image on a surface;
• a sensor detectable target image supported for detection by said sensors and including a selected magnification feature;
• a controller for determining the number of photosensitive elements detecting said selected magnification feature;
• a comparator for comparing the actual number of photosensitve elements detecting said selected magnification feature with a reference value and determining a magnification constant;
• a memory for storing the magnification constant.

A system for calibrating focus in a raster input scanning device including:

• a linear photoelectric sensor array comprising a plurality of discrete photosensitive elementsh arranged along at least a first axis, for sensing and generating electrical representations of an image on a surface;
• a sensor detectable target image supported for detection by said sensors and including a selected focus feature;
• a light source for illuminating said target image;
• a focusing lens for focusing light from said target image, sensor array, arranged between said sensor array and said target image, said lens controllably movable therebetween to vary focus of the light rays.
• a controller for determining the number of sensors detecting said selected focus feature, and the intensity of light from said detected feature as an indication of focus at any selected position;
• a temporary memory for storing focus indications at successive selected positions of said focusing lens between said sensor array and said target image;
• and
• a calibration memory for storing the selected position of said focusing lens deriving the optimum focus indication.