Method of and apparatus for processing image signal

Claim 1

An apparatus for processing an image signal, wherein an original is fed in an auxiliary scanning direction and is scanned in a main scanning direction to produce said image signal, said apparatus comprising: a digital comparator for comparing digital image data and graining reference data to produce grained image data; and a random number generator for producing, as said graining reference data, digital random number data based on an M-sequences coding theory, wherein said random number generator comprises a random number generating circuit based on said M-sequences coding theory and an initial value presetting circuit for setting an initial value in said random number generating circuit, said random number generating circuit having an output port comprising an N-bit shift register (N=2, 3, 4, . . . ), the arrangement being such that N-bit digital random data are updated each time a signal shift clock pulse is applied.

Claim 2

An apparatus for processing an image signal, wherein an original is fed in an auxiliary scanning direction and is scanned in a main scanning direction to produce said image signal, said apparatus comprising: a digital comparator for comparing digital image data and graining reference data to produce grained image data; and a random number generator for producing, as said graining reference data, digital random number data based on an M-sequences coding theory, wherein said random number generator comprises a random number generating circuit based on said M-sequences coding theory and an initial value presetting circuit for setting an initial value in said random number generating circuit, said random number generating circuit having an output port comprising an N-bit shift register (N=2, 3, 4, . . . ), the arrangement being such that N-bit digital random data are updated each time a signal shift clock pulse is applied.

Claim 5

An apparatus for processing an image signal, said apparatus comprising: a digital comparator for comparing digital image data and grain reference data to obtain processed data processed by graining reference data, wherein said processed data is obtained by reading out an original fed in an auxiliary scanning direction and scanned in a main scanning direction; and a random number generator for producing, as said graining reference data, digital random number data based on an M-sequences coding theory, said random number generator comprising a random number generating circuit based on said M-sequences coding theory, said random number generator comprising a plurality of shift registers, and an initial value presetting circuit for setting an initial value in said random number generating circuit, said initial value presetting circuit comprising a plurality of counters wherein the outputs from respective pairs of said counters are supplied as input data to each of said shift registers; wherein said random number generator further comprises a first frequency divider into which a main scanning clock signal is introduced, and said initial value presetting circuit further comprises a second frequency divider into which an auxiliary scanning clock signal is introduced, whereby said digital random number data is updated according to said clock signals corresponding respectively to said main scanning and auxiliary scanning directions.

Claim 6

An apparatus for processing an image signal, said apparatus comprising: a digital comparator for comparing digital image data and grain reference data to obtain processed data processed by graining reference data, wherein said processed data is obtained by reading out an original fed in an auxiliary scanning direction and scanned in a main scanning direction; and a random number generator for producing, as said graining reference data, digital random number data based on an M-sequences coding theory, said random number generator comprising a random number generating circuit based on said M-sequences coding theory, said random number generator comprising a plurality of shift registers, and an initial value presetting circuit for setting an initial value in said random number generating circuit, said initial value presetting circuit comprising a plurality of counters wherein the outputs from respective pairs of said counters are supplied as input data to each of said shift registers; wherein said random number generator further comprises a first frequency divider into which a main scanning clock signal is introduced, and said initial value presetting circuit further comprises a second frequency divider into which an auxiliary scanning clock signal is introduced, whereby said digital random number data is updated according to said clock signals corresponding respectively to said main scanning and auxiliary scanning directions.