United States Patent [19] [ii] Patent Number: 4,562,445
Rich [45] Date of Patent: Dec. 31, 1985
[54] APPARATUS AND METHOD FOR DRIVING INK JET PRINTER
[75] Inventor: Leonard G. Rich, West Hartford,
Conn.
[73] Assignee: Metromedia, Inc., Secaucus, N.J.
[21] Appl. No.: 634,499
[22] Filed: Jul. 26,1984
[51] Int. Q." G01D 15/16
[52] U.S. a 346/140 R; 346/75
[58] Field of Search 346/140 R, 75, 1.1
[56] References Cited
U.S. PATENT DOCUMENTS
4,072,958 2/1978 Hayami 346/140
4,312,007 1/1982 Winfield 346/140
4,499,479 2/1985 Lee 346/140
Primary Examiner—Joseph W. Hartary
Attorney, Agent, or Firm—McCormick, Paulding &
Huber
[57] ABSTRACT
A circuit and related method are provided for driving
an ink jet printer to achieve a consistent velocity of ejected ink drop despite differences in the time elapsing between successive drops. Timing pulses timing the ejection of drops each trigger the production of a fundamental waveform. This waveform is then multiplied by a multiplying factor selected from a look-up table in response to the time elapsing between the timing pulse causing the generation of the waveform and the preceding timing pulse, and the modified waveform so produced is used to drive the printing head through a power amplifier. The multiplying factor is one chosen by experiment as that required to produce the desired ink jet velocity. In a preferred embodiment both the fundamental waveform and the multiplying factor may each be obtained through the use of an associated PROM so that the waveform shape and multiplying factor versus dot frequency characteristic may be readily changed to suit the particular printer head in question.
