Gray tone reproduction apparatus

Claim 1

Apparatus for recording graytones by selectively placing dots in commonly dimensional matrices, each of which comprises a series of m matrix columns of width p arranged side-by-side in a widthwise direction and extends vertically in a heightwise direction, said apparatus comprising: (a) an arrangement of n marking elements progressively extending in the widthwise direction at a spacing equal to the width of one of said matrices divided by any non-zero positive integer which evenly divides the number m, (b) support means for supporting a print receiving sheet in marking relationship to said marking elements, (c) first transport means for repetitively transporting said recording sheet in the heightwise direction across the active region of said marking elements, (d) second transport means for causing relative movement of said marking elements in the widthwise direction across said marking elements at a speed such that there is a relative widthwise movement of the distance np during the period of one of said repetitive heightwise cycles. (e) memory means for storing strings of bits corresponding to columnar sets of dot patterns collectively comprising a set of matrix patterns which when printed represent all gray levels to be recorded. (f) counting means for counting said repetitive heightwise cycles and generating a counting code representative of said count, (g) a density code generator for generating a series of gray level codes representative of gray levels to be printed by said marking elements, (h) address means responsive to said counting codes and said gray level codes for generating addresses indicating the memory locations of said bit strings, (i) memory control means for causing the bit strings located at said addresses to be written out from said memory, and (j) shift register means for storing the bit strings written out from said memory and generating control signals for controlling the marking action of said marking elements; said number n being selected according to the relationship: n=Im±1 where I is any positive non-zero integer and m is defined as aforesaid.