Method and apparatus for grey level printing

Claim 1

A method of printing which uses an array of radiation-emitting elements, the method comprising the steps of: (a) advancing an imaging surface relative to the array; (b) selectively enabling the elements to emit radiation for predetermined periods of time during a cycle of operation to form an image on the surface, each of said predetermined periods of time being related to a respective one of plural image data related multi-bit digital signals; (c) operating a digital counting means having a plurality of output lines with signals thereon representing in digital form a time-changing count that is independent of said image data related signals; (d) generating exposure clock pulses, that are independent of said image data related signals, to change the count represented on the output lines; (e) comparing the time-changing count with each of several different image data related predetermined counts that are each defined by a respective one of said image data related multi-bit digital signals, and generating respective enablement pulses in response to respective image data related predetermined counts, a time duration of each enablement pulse being different dependent upon a respective image data-related predetermined count, and a set of enablement pulses determines enabling times of elements selected to be enabled; and wherein in step (d) the exposure clock pulses are generated by reading a digital word of exposure clock data signals from memory, at least one digital word representing at least two successive exposure clock pulses and storing said exposure clock data signals in a serial shift register and then serially shifting said exposure clock data signals out from said shift register as said successive exposure clock pulses.

Claim 2

A method of printing which uses an array of radiation-emitting elements, the method comprising the steps of: (a) advancing an imaging surface relative to the array; (b) selectively enabling the elements to emit radiation for predetermined periods of time during a cycle of operation to form an image on the surface, each of said predetermined periods of time being related to a respective one of plural image data related multi-bit digital signals; (c) operating a digital counting means having a plurality of output lines with signals thereon representing in digital form a time-changing count that is independent of said image data related signals; (d) generating exposure clock pulses, that are independent of said image data related signals, to change the count represented on the output lines; (e) comparing the time-changing count with each of several different image data related predetermined counts that are each defined by a respective one of said image data related multi-bit digital signals, and generating respective enablement pulses in response to respective image data related predetermined counts, a time duration of each enablement pulse being different dependent upon a respective image data-related predetermined count, and a set of enablement pulses determines enabling times of elements selected to be enabled; and wherein in step (d) the exposure clock pulses are generated by reading a digital word of exposure clock data signals from memory, at least one digital word representing at least two successive exposure clock pulses and storing said exposure clock data signals in a serial shift register and then serially shifting said exposure clock data signals out from said shift register as said successive exposure clock pulses.

Claim 16

The apparatus for grey level printing which comprises: an array of radiation emitting elements; means for selectively enabling at least some of the elements for predetermined periods of time during a cycle of operation to form radiation for use in recording image data; the enabling means including circuit means for generating a pulsewidth modulated set of enabling pulses for determining different durations of enabling periods of time of said at least some of the elements; and wherein the circuit means includes: digital counting means having a plurality of output lines representing in digital form a time changing numerical count during a count mode; exposure clock means coupled to the digital counting means and generating exposure clock pulses, that are independent of image data, for changing the count represented by the output lines, the clock means including a master clock for generating a series of uniformly spaced master clock pulses, and address counter means responsive to a signal representing 1/N master clock pulses, wherein N is an integer greater than one, for generating an address signal, a memory means responsive to said address signal for outputting in parallel a series of signals representing exposure clock pulses, and means for shifting out serially said exposure clock pulses; and comparator means coupled to the output lines and comparing the time changing count with each of several different predetermined counts related to image data to be recorded and generating respective enabling pulses, each of the enabling pulsed having a duration that is related to a respective one of the predetermined counts.

Claim 17

The apparatus for grey level printing which comprises: an array of radiation emitting elements; means for selectively enabling at least some of the elements for predetermined periods of time during a cycle of operation to form radiation for use in recording image data; the enabling means including circuit means for generating a pulsewidth modulated set of enabling pulses for determining different durations of enabling periods of time of said at least some of the elements; and wherein the circuit means includes: digital counting means having a plurality of output lines representing in digital form a time changing numerical count during a count mode; exposure clock means coupled to the digital counting means and generating exposure clock pulses, that are independent of image data, for changing the count represented by the output lines, the clock means including a master clock for generating a series of uniformly spaced master clock pulses, and address counter means responsive to a signal representing 1/N master clock pulses, wherein N is an integer greater than one, for generating an address signal, a memory means responsive to said address signal for outputting in parallel a series of signals representing exposure clock pulses, and means for shifting out serially said exposure clock pulses; and comparator means coupled to the output lines and comparing the time changing count with each of several different predetermined counts related to image data to be recorded and generating respective enabling pulses, each of the enabling pulsed having a duration that is related to a respective one of the predetermined counts.