Apparatus and method for controlling the adjustment of optical elements in an electrophotographic apparatus

An apparatus for optimumly adjusting the optical elements of a copier to positions forming images of lines, on an illuminated background, which have the greatest background-to-line illumination contrast;

• including an electronic scanner for examining, point-by-point, target line and background images;
• wherein the invention is characterized by means for indicating the optical adjustment at which there is greatest contrast, comprising:
• means for detecting, during scanning, the light level and position of each background point and line examined and supplying at an output light level signals;
• last-in/first-out (LIFO) storage means, connected to the detecting means output for retaining, in each of a plurality of storage positions, the light level signals and for retaining corresponding optical adjustment signals;
• first means, interconnecting the detecting and the LIFO storage means, for sequentially pushing into the LIFO storage the light level as the scanner passes across a target line;
• a background register, for storing signals which are a function of light levels;
• comparsion means, connected to the LIFO storage and background register, for comparing light level signals in the background register with the average of the light level signals in all of the LIFO storage positions, and supplying at an output a "compare" signal if the average is less than the signals in the background register;
• second means, interconnecting the background register and LIFO storage means, operable by a "compare" signal from the comparison means output, to enter into the background register aforesaid average of the signals in all of the LIFO storage positions;
• and
• utilization means, conncted to the storage and comparison means, for supplying at an output signals identifying the optical adjustment at which the lowest amount of light is relfected.

In a system, wherein focus is determined by scanning an image for the point of greatest illumination contrast between a background and a line on the background, apparatus comprising:

• scanning means, for examining the image point-by-point and indicating, as digital data, the illumination value of each point examined;
• background calculation means, connected to the scanner, for calculating and retaining a background illumination value from the digital data resulting from the scanning of a plurality of background points of the image;
• a data exchange bus, connected to the background calculating means;
• a storage stack, connected to the bus, comprising a plurality of locations, each selectively arranged to exchange data either with the bus or with an adjacent location;
• first control means, connected to the scanning calculation, bus and stack means, for entering directly into each location the background illumination value and for pushing into the stack successive illumination values from the scanning means;
• comparison means, connected to the background calculation means and the stack, for indicating when the background illumination value differs from the average of all the values in the stack;
• second control means, connected to the scanning, calculation, bus, stack and comparison means, for retaining in said calculation means the average of all the illumination values in the stack, if the comparison means indicates that the current background illumination value differs from the average in the stack;
• and
• third control means, connected to the first and second control means, for indicating that the illumination value most different from the background illumination value has been retained in the calculation means, and supplying the illumination value thereof.

In combination:

• a master document, carrying lines on a backgroung;
• an illumination source, operable to illuminate selected areas of the master document;
• a scanner arranged to receive images of illuminated areas of the master document;
• a digitizer, connected to the scanner, for supplying digital data representing the illumination intensity of the master document images;
• averaging means, connected to the digitizer, operable to receive digital data and compute therefrom current averages of a plurality of successively received digital data;
• a first storage, connected to the averaging means, operable to store the current averages one at a time;
• a second storage, connected to the averaging means, operable to receive previous averages one at a time;
• a comparator, connected to the first and second storages, operable when the current average in the first storage is less than the previous average in the second storage, to transfer the current average to the second storage;
• and
• controls, connected to the scanner and comparator, operable to cause the scanner to continue to receive images when the current average is less than the previous average and to cause the scanner to receive a predetermined number of images when the current average is not less than the previous average.

In a combination for automatically adjusting a copier optical system for optimum focus by determining the apparent darkness of a line on a light background while changing the relationship of optical elements in the system to achieve the darkest apparent line;

• the invention comprising apparatus for indicating the optical relationship giving the darkest line;
• including:
• receiving means, operable to receive the light level signals as the image is scanned, and to supply digital data representing the light levels and the optical adjustment corresponding thereto;
• level logic means, connected to the receiving means, operable in accordance with the light level data to initially supply data which is a function of the light level of the background and, subsequently, when a first decrease in light level occurs, to supply data which indicates the light level of a line;
• a first position means, connected to the receiving and level logic means, for recording the idicia of the optical relationship at which said first decrease in light level occurs;
• a last-in/first-out storage stack, connected to the receiving means, comprising a plurality of individually accessible storage register locations, operable initially to hold in each register aforesaid background light level data and, subsequently, after the first decrease in light level, to receive in an input register aforesaid line light level data as data is pushed into the stack;
• averaging logic, connected to the push-up stack, for receiving data stored in all the stack registers, calculating the average of the data and providing a best-focus signal when the stack average is less than a precalculated value;
• and
• second position means, connected to the receiving means and the averaging logic, for recording the optical relationship at which the best focus signal occurs.

In a combination for automatically controlling the adjustment of a copier optical system by examining a number of lines on a background;

• the invention comprising apparatus for finding the edge of a line in accordance with the level of light reflected from an image carrying the line as points on the image are scanned;
• including:
• receiving means, operable to receive the light level signals for each point of the image scanned, and to supply digital data representing the light levels and the position on the image of the point corresponding thereto;
• level logic means, connected to the receiving means, operable in accordance with the light level data to initially supply data which is a function of the light levels of points on the background;
• averaging logic, connected to the receiving means, for calculating the average of portions of the digital data, providing an indication of light level data that is significantly less than the average, and providing an edge-of-line signal when the line light level data is less than the average;
• and
• position means, connected to the receiving means and the averaging logic, for recording the position on the image at which the edge-of-line signal occurs.

A method for optimumly adjusting the optical elements of a copier to positions forming images of lines, on an illuminated background, which have the greatest background-to-line illumination contrast, comprising the steps of:

• (a) examining, point-by-point, target line and background images while changing the optical element relationships;
• (b) detecting, during scanning, the light level and position of each background point and line point examined;
• (c) supplying, at an output, light level signals;
• (d) retaining, in each of a plurality of storage positions, the light level signals;
• (e) sequentially entering into a selected one of said storage positions the light level;
• (f) recording the position of each current target point in sequence as the scanner progresses across a target line;
• (g) causing the contents of each storage position to be moved to an adjacent position;
• (h) comparing light level signals in all of the storage positions with the lowest previous value;
• and
• (i) supplying at an output signals identifying the optical element relationship at which the lowest amount of light is reflected.

A process for focus determination, comprising the steps of:

• (a) scanning an image for the point of greatest illumination contrast between a background and a line on the background;
• (b) changing the focus setting elements between each scan;
• (c) examining the image point-by-point;
• (d) indicating, as digital data, the illumination value and focus for each scan;
• (e) calculating a background illumination value from the digital data resulting from the scanning of a plurality of background points and the image;
• (f) entering directly into each position of a last-in/first-out (LIFO) stack the background illumination value and separately storing the value;
• (g) pushing into the stack each illumination value;
• (h) indicating when the separately stored value differs from the average of all the values in the stack;
• (i) indicating when the stack average is the most different from the background illumination;
• and
• (j) supplying the illumination value and the focus setting thereof.