Dot matrix printer with half space dot capability

Abstract

A method and apparatus is provided for enhancing the quality of characters printed on a media by a dot matrix printer, and particularly for enhancing edges of characters disposed at an angle to the rows of the matrix. First and second memory matrices contain the information as to the relative position along each row for printing dots to form each character; the first memory containing information to form a basic pattern and the second memory containing information related to an enhancement pattern which, if printed at the same carrier frequency as the basic pattern but phase shifted therefrom by a predetermined relationship (for example, 180.degree.), will enhance those edges of the character being printed disposed at an angle, other than 90.degree., from the rows of dots being printed. The information in the first and second memories are sequenced through first and second shift registers, one of which is sequenced by a clock signal and the other is sequenced by an inverted clock signal. Thus, the shift registers are driven at the same carrier frequency, but at some phase relation (for example, 180.degree.) from each other. The sequenced information from the first and second shift registers are combined to drive a laser gun for the dot matrix printer to print the enhanced character.