Signal processing apparatus and method for photosensitive imaging system

A line imaging system for generating signals representative of detectable conditions of an image bearing surface, comprising:

• an elongated array of thin film photosensitive elements including at least one group of said elements linearly arranged on a common substrate, each of said elements formed from at least one thin film layer of semiconductor material and adapted to convert light energy emanating from a portion of surface and incident upon said elements into an electrical signal corresponding to the amount of light energy emanating from said surface portion;
• means for storing individual values representative of the light intensity sensed by at least certain of the photosensitive elements during the scanning of said surface;
• firt means for comparing the value representing the signal sensed by each of said elements with at least one stored value to determine which of said values represents a greater light intensity, and for causing a sensed signal which said comparision indicates is of greater intensity to be stored in said storage means;
• second means for comparing the sensed signal generated by each element with a threshold value which corresponds to a predetermined fraction of the greatest light intensity yet received by a corresponding element and stored in the storage means;
• and said second comparing means adapted to produce a corresponding electrical output signal representative of the results of said comparison;
• an analog bus having at least one conductor;
• a digital address bus adapted to receive digital addresses from address control means;
• time-division multiplexing circuit means connected to said analog bus and said digital bus for selectively providing a low impedance connection between at least one of said elements from said group and said analog bus upon command from said address control means;
• and
• means for amplifying analog signals from said elements impressed upon said analog bus.

An imaging system for generating signals representative of detectable conditions of an image bearing surface, comprising:

• an elongated array of thin film photosensitive elements, said array including at least a plurality of elongated groups of photosensitive elements;
• each of said groups formed on a discrete common elongated substrate from a plurality of thin film layers;
• each photosensitive element including at least one thin film layer of semiconductor material and at least one conductive layer;
• each photosensitive element adapted to convert light energy into an electrical signal corresponding to the amount of light energy incident thereon;
• means for storing individual values representative of the light intensity sensed by at least certain of the photosensitive elements during the scanning of said surface;
• first means for comparing the value representing the signal sensed by each of said elements with at least one stored value to determine which of said values represents a greater light intensity, and for causing a sensed signal which said comparision indicates is of greater intensity to be stored in said storage means;
• second means for comparing the sensed signal generated by each element with a threshold value which corresponds to a predetermined fraction of the greatest light intensity yet received by a corresponding element and stored in the storage means;
• and said second comparing means adapted to produce a corresponding electrical output signal representative of the results of said comparison;
• sensor board means for mounting the substrates of said elongated groups, said substrates arranged thereon in end-to-end relationship such that the groups form one long continuous array of photosensitive elements;
• a plurality of means for amplifying said electrical signals produced by the photosensitive elements, each amplifier means having at least one output and at least one input associated therewith for receiving signals from said group of elements;
• address control circuit means connected to said groups of photosensitive element for causing the elements of said array to be read in a predetermined order;
• one analog bus associated with each group of photosensitive elements;
• each analog bus including at least one conductor and being selectively connectable to a plurality of photosensitive elements of its respective group and to at least one amplifier means;
• and
• interboard analog bus means for interconnecting respective outputs of said amplifying means together for the delivery thereof to a common node for further processing of analog data.

An imaging system for generating signals representative of detectable conditions of an image bearing surface, comprising:

• sensor means for scanning said surface, said sensor means including an elongated array of photosensitive elements, each element adapted to sense the intensity of light received from a small portion of the surface and generate a corresponding analog signal indicative of the sensed intensity;
• means for storing individual values representative of the light intensity sensed by at least certain of the photosensitive elements during the scanning of said surface;
• first means for comparing the value representing the signal sensed by each of said elements with at least one stored value to determine which of said values represents a greater light intensity, and for causing a sensed signal which said comparison indicates is of greater intensity to be stored in said storage means;
• second means for comparing the sensed signal generated by each element with a threshold value which corresponds to a predetermined fraction of the greatest light intensity yet received by a corresponding element and stored in the storage means;
• and said second comparing means adapted to produce a corresponding electrical output signal representative of the results of said comparision;
• an analog bus having at least one conductor;
• multiplexing means for selectively and successively connecting several of said photosensitive elements to said analog bus;
• means for amplifying analog signals impresssed upon said analog bus from said photosensitive elements;
• and
• sample and hold circuit means connected to the output of at least said amplifier means for sampling for a first predetermined period of time and holding for a second predetermined period of time each of the amplified analog signals successively received from said amplifier means.