Smoothing circuit for display apparatus

Claim 1

A smoothing circuit for a display apparatus in which a desired character composed of selected standard width dots of a matrix of orthogonally disposed rows and columns thereof is displayed on a screen during scanning of the latter in horizontal and vertical directions; comprising: memory means for memorizing data R(t n-1 ), R(t n ), R(t n+1 ), D(t n-1 ), D(t n ) and D(t n+1 ), in which D represents data indicating the presence or absence of a dot in a row of said matrix being currently displayed, (t n ) represents a time interval corresponding to the horizontal scanning of a space being considered in a given one of said rows and which has a width equal to that of each of said dots, (t n-1 ) and (t n+1 ) are equivalent time intervals immediately preceding and following, respectively, said time interval (t n ), and R represents data indicating the presence or absence of a dot in a row of said matrix which is immediately adjacent to said row being currently displayed; logical operation circuit means responsive to said data memorized in said memory means for performing logical operations thereon which satisify predetermined conditions so as to selectively alter said data D(t n ) in correspondence with the addition or removal, in said space being considered, of a small dot having a width one-third of said standard width, said predetermined conditions satisfied by said logical operations being as follows: (a) The condition for altering said data D(t n ) in correspondence with the addition of said small dot in the front third of said space being considered is R(t.sub.n-1)·R(t.sub.n)·D(t.sub.n-1)=1 (b) The condition for altering said data D(t n ) in correspondence with the addition of said small dot in the rear third of said space being considered is R(t.sub.n)·R(t.sub.n+1)·D(t.sub.n+1)=1 (c) The condition for altering said data D(t n ) in correspondence with the removal of said small dot from the front third of a standard width dot in said space being considered is R(t.sub.n-1)·R(t.sub.n)·R(t.sub.n+1)·D(t.sub.n-1)·D(t.sub.n+1)=1 and (d) The condition for altering said data D(t n ) in correspondence with the removal of said small dot from the rear third of a standard width dot in said space being considered is R(t.sub.n-1)·R(t.sub.n)·R(t.sub.n+1)·D(t.sub.-1)·D(t.sub.n+1)=1; and means for displaying on said screen said desired character as modified in accordance with said selectively altered data so that the displayed character has relatively smooth contours.