JP3738570B2 - Dot recording method and apparatus, and recording medium recording a program therefor - Google Patents

Description

【００６２】
（３ａ）式の右辺の分子（Ｎｂ×ｋ）は、付加ノズル個数Ｎｂにノズルピッチｋを乗じたものであり、ノズルアレイ内における付加ノズルの範囲を示している。付加ノズルの範囲は、図５の例ではノズル＃１０のラスタ位置からノズル＃１４３ドット下のラスタ位置までの範囲である。パラメータＬは、（Ｎｂ×ｋ）を副走査送り量Ｆで除した値にほぼ等しいので、このパラメータＬは、あるノズル（例えば最上端の付加ノズル＃１０）が付加ノズルの範囲を何回の副走査送りで通過するか、を示す値であると考えることができる。ところで、上述したように、１回の副走査送りによって、各ノズルはその直前のノズルの周期的な位置から１ドットだけずれた位置に配置される。従って、或るパスの後のＬ回の副走査送りを考えると、最上端の付加ノズル＃１０は、Ｌ回の副走査の間はそのバスにおける付加ノズルの範囲内に留まっており、かつ、１回の副走査送り毎にその前のノズルの周期的な位置から１ドットずつずれてゆく。例えば、図５において、パス１の後の２回の副走査送りでは、最上端の付加ノズル＃１０は、パス３までの２回の副走査の間はパス１における付加ノズルの範囲内に留まっており、また、１回の副走査送り毎にその直前のノズルの周期的な位置から１ドットずつずれてゆく。すなわち、パス２では、最上端の付加ノズル＃１０は、パス１における付加ノズルの範囲内において、その直前のパス１におけるノズル＃１２の１ドット後に位置決めされる。また、パス３では、最上端の付加ノズル＃１０は、パス１における付加ノズルの範囲内において、その直前のパス２におけるノズル＃１２の１ドット後に位置決めされる。
【００６３】
このようなノズル位置の移動を考えると、パラメータＬは、「オーバーラップラスタ（基本ノズルと付加ノズルとによって記録されるラスタ）が何本連続して配列されているか」、を示す値であると考えることができる。例えば、図５に示す第１比較例では、Ｌ＝２なので、オーバーラップラスタが２本連続している。（なお、図５には、オーバーラップラスタが３本連続している部分があるが、この理由については後述する。）また、付加ノズルは、ノズルアレイ内においてノズルピッチｋで配列されているので、ｋ本の連続したラスタの中で、はじめのＬ本がオーバーラップラスタとなり、残りの（ｋ−Ｌ）本が非オーバーラップラスタとなる。従って、ラスタの配列としては、Ｌ本のオーバーラップラスタと（ｋ−Ｌ）本の非オーバーラップラスタとで構成されるｋ本のラスタ群が、繰り返し配列されたものとなる。
【００６４】
ところで、Ｎａ本の基本ノズルによる１回の主走査で記録されるＮａ本のラスタの中で、Ｎｂ本の付加ノズルによっても記録されるＮｂ本のラスタがオーバーラップラスタであり、残りの（Ｎａ−Ｎｂ）本のラスタは非オーバーラップラスタである。すなわち、Ｎａ本のラスタの範囲内には、Ｌ本のオーバーラップラスタと（ｋ−Ｌ）本の非オーバーラップラスタとで構成されるｋ本のラスタ群が繰り返し配列され、この結果として、Ｎａ本中のＮｂ本がオーバーラップラスタとなり、残りの（Ｎｂ−Ｎａ）本が非オーバーラップラスタとなる。例えば、図５に示す第１比較例では、ｋ＝４，Ｎａ＝９，Ｎｂ＝５なので、９本のラスタの範囲内で、２本のオーバーラップラスタと２本の非オーバーラップラスタとで構成されるラスタ群が繰り返し配列され、この結果、９本中の５本がオーバーラップラスタとなり、残りの４本が非オーバーラップラスタとなっている。
【００６５】
図５の右端の図には、Ｎａ本毎のラスタの区分が示されている。この例では、Ｎａ本の１組のラスタの中の最後のラスタはオーバーラップラスタであり、また、次の１組の最初のＬ（＝２）本のラスタもオーバーラップラスタである。従って、Ｎａ本毎のラスタの境界において、オーバーラップラスタが３本隣接している。しかし、基本的には、図５のラスタの配列は、Ｌ本のオーバーラップラスタと（ｋ−Ｌ）本の非オーバーラップラスタとで構成されるｋ本のラスタ群が繰り返し配列されていることが理解できる。
【００６６】
このように、第１比較例では、オーバーラップラスタと非オーバーラップラスタとがパラメータｋ，Ｌ，Ｎａ，Ｎｂに応じてほぼ規則正しく配列されている。すなわち、ほぼＬ本ずつ連続するオーバーラップラスタが、ほぼ（ｋ−Ｌ）本の非オーバーラップラスタを挟んでほぼ規則的に配列されている。図６において説明したように、オーバーラップラスタの近傍ではバンディングが目立ちにくくなるので、画質が向上するという利点がある。
【００６７】
主走査を双方向に行う双方向印刷の場合には、上述したような規則的なオーバーラップラスタの配列が以下のような効果も発揮する。すなわち、図３に示したように、６色のインクのノズルアレイが同じラスタを記録するように配置されている場合に、往路では各ラスタ上にＫ，Ｃ，ＬＣ（淡シアン），Ｍ，ＬＭ（淡マゼンタ），Ｙの順に各色のドットが形成される。一方、復路ではこの反対に、各ラスタ上にＹ，ＬＭ，Ｍ，ＬＣ，Ｃ，Ｋの順に各色のドットが形成される。従って、往路で記録されたラスタと、復路で記録されたラスタとでは、多少色が違って見える可能性がある。このとき、オーバーラップラスタを形成せずに、完全なノンオーバーラップ方式でドットを記録すると、往路で記録されたラスタと復路で記録されたラスタとの色の違いが目立ってしまい、画質劣化として認識される。一方、オーバーラップラスタは往路と復路とで記録されるので、往路で記録されるラスタと復路で記録されるラスタとの色の違いがオーバーラップラスタの近傍では緩和される。すなわち、オーバーラップラスタを形成すれば、往路と復路でのラスタの色の違いが目立たなくなるという利点がある。
【００６８】
バンディングを目立たなくさせるという意味からは、すべてのラスタをオーバーラップラスタにすることも考えられる。しかし、すべてのラスタをオーバーラップラスタにすると、すべてが非オーバーラップラスタである場合に比べて約２倍の主走査時間を必要とするので、記録速度が約１／２になる。これに対して、部分オーバーラップでは、オーバーラップラスタと非オーバーラップラスタとが混在しているので、すべてをオーバーラップラスタにする場合に比べて、記録速度の低下を緩和することができるという利点がある。
【００６９】
図７および図８は、第２比較例のドット記録方式を示す説明図である。第２比較例のドット記録方式における各パラメータの値は、Ｎ＝１３，Ｎａ＝１１，Ｎｂ＝２，ｋ＝６，Ｆ＝１１，ｍ＝２，Ｌ＝１である。これらの各パラメータは、上述した（１）〜（４）式を満たしている。なお、ラスタ上のドット位置は、白丸（往動時に基本ノズルで記録される位置）と、黒丸（往動時に付加ノズルで記録される位置）と、白四角（復動時に基本ノズルで記録される位置）と、黒四角（復動時に付加ノズルで記録される位置）の４つに分類されている。
【００７０】
図８には、図５と同様に、パラメータＮａ，Ｌ，ｋの意義が示されている。すなわち、第２比較例も、「ほぼＬ本ずつ連続するオーバーラップラスタが、ほぼ（ｋ−Ｌ）本の非オーバーラップラスタを挟んでほぼ規則的に配列されている」という特徴を有している。
【００７１】
Ｄ．ドット記録方式の実施例：
図９および図１０は、第１実施例のドット記録方式を示す説明図である。第１実施例のドット記録方式における各パラメータの値は、Ｎ＝１３，Ｎａ＝１１，Ｎｂ＝２，ｋ＝６，ｍ＝２，Ｌ＝１である。また、副走査送りは、（８，９，１０，１６，１５，８）ドットの送り量Ｆで１サイクルを構成する変則送りであり、この１サイクルの送り量が繰り返し適用される。これらの各パラメータは、以下に再掲する（１）〜（３）式を満たしている。
【００７２】
Ｎ＝Ｎａ＋Ｎｂ …（１）
Ｎａ＝ｍ×ｋ±１ …（２）
Ｎｂ＝Ｒｄ［Ｌ×Ｎａ÷ｋ］ …（３）
【００７３】
また、第１実施例は、上述した条件Ｃ１〜Ｃ３と類似した下記の条件Ｃ１’〜Ｃ３’も満足している。
【００７４】
条件Ｃ１’：１サイクルの副走査送り回数は、ノズルピッチｋに等しい。
【００７５】
条件Ｃ２’：１サイクル中の各回の副走査送り後のノズルのオフセットＯＦは、０〜（ｋ−１）の範囲のそれぞれ異なる値となる。
【００７６】
条件Ｃ３’：副走査の平均送り量（ΣＦ／ｋ）は、基本ノズル個数Ｎａに等しい。換言すれば、１サイクル当たりの副走査送り量Ｆの累計値ΣＦは、基本ノズル個数Ｎａとノズルピッチｋとを乗算した値（Ｎａ×ｋ）に等しい。
【００７７】
上記条件Ｃ１’，Ｃ２’は、条件Ｃ１，Ｃ２と同じである。条件Ｃ３’は、条件Ｃ３における「使用ノズル個数Ｎ」を「基本ノズル個数Ｎａ」に書き換えたものである。なお、第１実施例は、第２比較例を変則送りに変更したものであり、その他のパラメータは第２比較例と同じである。
【００７８】
図１１は、第１実施例における記録ドット位置の説明図である。図１１には、（Ｎｂ×ｋ）ラスタ分の付加ノズルの範囲が、送り量Ｆずつ順次ずれている様子が示されている。ある１回の主走査のみを考えれば、（Ｎｂ×ｋ）ラスタ分の付加ノズルの範囲内では、付加ノズル（黒丸または黒四角で示す）はｋドットおきに規則的に配置されている。上述した第２比較例のように、副走査送り量Ｆが一定の場合には、この付加ノズルの範囲が一定量ずつずれてゆくので、オーバーラップラスタがほぼ規則的に配置される。これに対して、第１実施例では、副走査送り量Ｆが一定ではなく、異なる複数の送り量が組み合わされて使用されているので、オーバーラップラスタの配置には、第１比較例や第２比較例のような規則性は無い。しかし、第１実施例では、オーバーラップラスタが適度に分散して配置されているので、比較例と同様に、バンディングが目立ちにくくなり、画質が向上するという効果がある。第１実施例では、オーバーラップラスタが規則的に配置されておらず、かなりランダムに分散しているので、第２比較例よりも高画質が得られる可能性がある。
【００７９】
ところで、部分オーバーラップタイプのドット記録方式の記録速度は、基本ノズル個数Ｎａの値にほぼ比例する。すなわち、１回の主走査時に記録されるラスタの正味の本数は基本ノズル個数Ｎａに等しく、付加ノズル個数Ｎｂに依存しない。第２比較例と第１実施例とでは、基本ノズル個数Ｎａが同一なので、同じ記録速度を有している。また、第２比較例も第１実施例も、バンディングが目立ちにくく、画質が向上するという効果を有している。第１実施例では、オーバーラップラスタが規則的に配置されておらず、かなりランダムに分散しているので、第２比較例よりも高画質が得られる可能性があるが、実際に第２比較例と第１実施例のどちらが高画質を達成できるかは、印字ヘッド１におけるノズル間のピッチｋの製造誤差に依存する。そこで、副走査送りとして、第２比較例のような定則送りに限定せず、第１実施例のような変則送りを行うことを許容すれば、ほぼ同じ記録速度の複数のドット記録方式の中から、画質の点で好ましいものを選択して使用することができるという利点がある。
【００８０】
図１２および図１３は、第２実施例のドット記録方式を示す説明図である。第２実施例のドット記録方式における各パラメータの値は、Ｎ＝１５，Ｎａ＝１１，Ｎｂ＝４，ｋ＝６，ｍ＝２，Ｌ＝２である。また、副走査送りは、第１実施例と同じ変則送りである。これらの各パラメータは、上述の（１）〜（３）式および条件Ｃ１’〜Ｃ３’を満たしている。第２実施例は、第１実施例と付加ノズル個数Ｎｂが異なるが、基本ノズル個数Ｎａは同一なので、第１実施例と同じ記録速度を有している。
【００８１】
図１４は、第２実施例における記録ドット位置の説明図である。第２実施例においても、オーバーラップラスタが適度に分散して配置されていることがわかる。従って、第１実施例と同様に、バンディングが目立ちにくくなり、画質が向上するという効果がある。
【００８２】
なお、上記第１、第２実施例の他に、上述した（１）〜（３）式を満足するような種々のドット記録方式を採用することが可能である。図１５は、ｋ＝６でＬ＝１〜３の場合における可能な記録方式のパラメータの組合せを例を示す説明図である。図１５（Ａ）のｋ＝６，Ｌ＝１，ｍ＝２，Ｎａ＝１１，Ｎｂ＝２，Ｎ＝１３の場合は、図９〜図１１に示した第１実施例に相当する。また、図１５（Ｂ）のｋ＝６，Ｌ＝２，ｍ＝２，Ｎａ＝１１，Ｎｂ＝４，Ｎ＝１５の場合は、図１２〜図１４に示した第２実施例に相当する。図１６は、ｋ＝４でＬ＝１〜３の場合における可能な記録方式のパラメータの組合せの例を示す説明図である。これらの例では、上記（３）式の丸め演算Ｒｄ［］として切り上げが使用されているが、切り捨てを使用することも可能である。
【００８３】
図１５および図１６から解るように、ノズルピッチｋの値が与えられたときに、パラメータｍ，Ｌの値を適切に設定することによって、好ましい基本ノズル個数Ｎａと付加ノズル個数Ｎｂとを決定することができ、これらの和から使用ノズル個数Ｎが決定される。逆に、使用したいノズル個数Ｎが決まっている場合には、図１５や図１６を用いて、使用ノズル個数Ｎから好ましい基本ノズル個数Ｎａと付加ノズルＮｂとを決定することも可能である。
【００８４】
図２に示すＰＲＯＭ１５には、ほぼ同じ記録速度を有する複数のドット記録モードのパラメータをそれぞれ含む複数組のドット記録モード情報が格納されており、また、複数のドット記録方式の中から好ましいモードを指定するためのモード指定情報も格納されている。ここで、「ほぼ同じ記録速度を有する記録モード」とは、基本ノズル個数Ｎａの差が約１０％以内であるような記録モードを意味する。例えば、ＰＲＯＭ１５には、第１実施例と第２実施例の２つの記録モードのパラメータをそれぞれ含む２組のドット記録モード情報が格納される。２つのドット記録モードの中のいずれが画質の点で好ましいかは、印字ヘッド１の製造誤差に依存する。そこで、２つの記録モードの中のいずれが好ましいかが個々のインクジェット記録装置毎に決定され、好ましいモードを指定するモード指定情報がＰＲＯＭ１５に格納される。こうすれば、同一の記録速度を有する２つのドット記録モードの中から、画質の点で好ましいモードを選択することが可能である。なお、選択可能な記録モードとしては、３つ以上の多数の記録モードを格納しておいてもよい。また、選択可能な記録モードは、第２比較例のような定則送りを利用するモードを含むようにしてもよい。
【００８５】
上記実施例によれば、部分オーバーラップを使用し、また、副走査送りとして変則送りを使用したので、オーバーラップラスタを適度に分散して配置することができる。この結果、バンディングを目立ちにくくなり、高画質を達成することが可能である。特に、双方向記録を行う場合には、オーバーラップラスタが分散して配置されていることにより、往路と復路でのラスタの色の違いが目立たなくなるという利点がある。また、ほぼ記録速度が等しい複数のドット記録モードの中から、画質の点で好ましいドット記録モードを選択して使用するようにすれば、個々の記録装置毎に、より高い画質を達成できるという利点がある。
【００８６】
なお、この発明は上記の実施例や実施形態に限られるものではなく、その要旨を逸脱しない範囲において種々の態様において実施することが可能であり、例えば次のような変形も可能である。
【００８７】
本発明は、双方向印刷に限らず、決まった主走査方向のみ（たとえば往路のみ）でドットの記録を行う単方向印刷にも適用可能である。
【００８８】
上記実施例では基本ノズルと付加ノズルとが、同一ラスタ上の画素を相補的に記録を行っていたが、基本ノズルと付加ノズルとが同一ラスタ上の画素位置でドットを重複して記録するようにしてもよい。また、これ以外の記録方式を採用することも可能である。例えば、基本ノズルと付加ノズルとで相補的に記録を行い、かつ、付加ノズルにより記録されるドット径の大きさを基本ノズルにより記録されるドット径よりも大きくしてもよい。
【００８９】
この発明はカラー印刷だけでなくモノクロ印刷にも適用できる。また、１画素を複数のドットで表現することにより多階調を表現する印刷にも適用できる。また、ドラムスキャンプリンタにも適用できる。尚、ドラムスキャンプリンタでは、ドラム回転方向が主走査方向、キャリッジ走行方向が副走査方向となる。また、この発明は、インクジェット記録装置のみでなく、一般に、複数のドット形成要素アレイを有する記録ヘッドを用いて印刷媒体の表面に記録を行うドット記録装置に適用することができる。ここで、「ドット形成要素」とは、インクジェットプリンタにおけるインクノズルのように、ドットを形成するための構成要素を意味する。
【００９０】
上記実施例において、ハードウェアによって実現されていた構成の一部をソフトウェアに置き換えるようにしてもよく、逆に、ソフトウェアによって実現されていた構成の一部をハードウェアに置き換えるようにしてもよい。例えば、図２に示した印字データ制御回路１３や、キャリッジ駆動回路５、印刷媒体搬送制御回路９の制御機能を、コンピュータ９０が実行するようにすることもできる。この場合には、プリンタドライバ９６等のコンピュータプログラムが、これらの回路と同じ制御機能を実現する。
【００９１】
このような機能を実現するコンピュータプログラムは、フロッピディスクやＣＤ−ＲＯＭ等の、コンピュータ読み取り可能な記録媒体に記録された形態で提供される。コンピュータシステム９０は、その記録媒体からコンピュータプログラムを読み取って内部記憶装置または外部記憶装置に転送する。あるいは、通信経路を介してプログラム供給装置からコンピュータシステム９０にコンピュータプログラムを供給するようにしてもよい。コンピュータプログラムの機能を実現する時には、内部記憶装置に格納されたコンピュータプログラムがコンピュータシステム９０のマイクロプロセッサによって実行される。また、記録媒体に記録されたコンピュータプログラムをコンピュータシステム９０が直接実行するようにしてもよい。
【００９２】
この明細書において、コンピュータシステムとは、ハードウェア装置とオペレーションシステムとを含む概念であり、オペレーションシステムの制御の下で動作するハードウェア装置を意味している。コンピュータプログラムは、このようなコンピュータシステムに、上述の各回路の機能を実現させる。なお、上述の機能の一部は、アプリケーションプログラムでなく、オペレーションシステムによって実現されていても良い。
【００９３】
なお、この発明において、「コンピュータ読み取り可能な記録媒体」とは、フレキシブルディスクやＣＤ−ＲＯＭのような携帯型の記録媒体に限らず、各種のＲＡＭやＲＯＭ等のコンピュータ内の内部記憶装置や、ハードディスク等のコンピュータに固定されている外部記憶装置も含んでいる。
【図面の簡単な説明】
【図１】本発明の画像処理システムの概略構成を示すブロック図。
【図２】本発明によるインクジェット記録装置の一実施例を示す概念図。
【図３】印字ヘッド１におけるインクジェットノズルの配列を示す説明図。
【図４】非オーバーラップタイプのドット記録方式における副走査送りの基本的条件を示す説明図。
【図５】第１比較例のドット記録方式を示す説明図。
【図６】オーバーラップラスタによるバンディングの防止効果を示す説明図。
【図７】第２比較例のドット記録方式を示す説明図。
【図８】第２比較例のドット記録方式を示す説明図。
【図９】第１実施例のドット記録方式を示す説明図。
【図１０】第１実施例のドット記録方式を示す説明図。
【図１１】第１実施例における記録ドット位置の説明図。
【図１２】第２実施例のドット記録方式を示す説明図。
【図１３】第２実施例のドット記録方式を示す説明図。
【図１４】第２実施例における記録ドット位置の説明図。
【図１５】ｋ＝６でＬ＝１〜３の場合における可能な記録方式のパラメータの組合せの例を示す説明図。
【図１６】ｋ＝４でＬ＝１，２の場合における可能な記録方式のパラメータの組合せを例を示す説明図。
【図１７】従来の記録方式を示す説明図。
【図１８】バンディングの一例を示す説明図。
【符号の説明】
１…印字ヘッド
２…キャリッジ軸
３…キャリッジベルト
４…モータ
５…キャリッジ駆動回路
６…プラテンローラ
７…ギヤ
８…モータ
９…印刷媒体搬送制御回路
１０…固定台
１１…固定台
１３…印字データ制御回路
２０…画像出力装置
２１…カラーディスプレイ
２２…インクジェット記録装置
３０…スキャナ
９０…コンピュータ
９１…ビデオドライバ
９３…ＣＲＴディスプレイ
９５…アプリケーションプログラム
９６…プリンタドライバ
９７…ラスタライザ
９８…色補正モジュール
９９…ハーフトーンモジュール[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a technique for recording dots on the surface of a print medium using a dot recording head.
[0002]
[Prior art]
As a recording apparatus that performs recording using a dot recording head while scanning in the main scanning direction and the sub-scanning direction, there is an ink jet recording apparatus such as a serial scan printer or a drum scan printer. An ink jet recording apparatus forms characters and images on a print medium by ejecting ink from a plurality of nozzles of a print head. That is, each nozzle of the print head is provided with a pressure chamber filled with ink and an electromechanical conversion element. When an electric signal is applied to the electromechanical conversion element, pressure is generated in the pressure chamber, and the nozzle Ink droplets are ejected from.
[0003]
One technique for improving image quality in an ink jet recording apparatus is a technique called an “interlace method” disclosed in US Pat. No. 4,198,642. FIG. 17 is an explanatory diagram of a conventional interlace recording method. The print head 1 has 11 nozzles indicated by numbers # 1 to # 11. The pitch k in the sub-scanning direction of the nozzle is 6 dots. Here, the unit [dot] means the minimum pitch P [inches] of dots recorded on the print medium in the sub-scanning direction, and k dots correspond to k × P inches. In FIG. 17, the position of the print head 1 described as pass 1, pass 2... Indicates the position in the sub-scanning direction during main scanning. Here, “pass” means one main scan. After each main scan, the sub-scan feed is executed with a constant feed amount F of 11 dots.
[0004]
In the conventional interlace recording method, the following two conditions are set in order to record so that there is no missing or overlapping main scanning line (hereinafter also referred to as “raster”).
[Condition 1] The number of used nozzles N and the nozzle pitch k are integers that are relatively prime to each other. (Here, “relatively prime” means that there is no common divisor other than 1.)
[Condition 2] The sub-scan feed amount F is equal to the number N of used nozzles.
[0005]
[Problems to be solved by the invention]
There are two requirements for an ink jet recording apparatus: improvement in printing speed and improvement in image quality. In order to improve the printing speed, the number of nozzles of the print head may be increased. However, in the conventional interlace recording method, the sub-scan feed amount F is set equal to the number N of used nozzles, so that the sub-scan feed amount increases as the number of nozzles increases.
[0006]
However, since the mechanical sub-scan feed accuracy deteriorates almost in proportion to the increase in the sub-scan feed amount, the sub-scan feed accuracy deteriorates when the number of nozzles is increased. In particular, if a plurality of sub-scan feeds are performed between adjacent raster recordings, a plurality of sub-scan feed errors are accumulated, and the pitch between adjacent rasters may deviate considerably from the correct pitch. is there. For example, five sub-scan feeds are performed between the raster recording of raster number 5 and the raster recording of raster number 6 in the lower right of FIG. Therefore, the pitch between these two rasters includes the accumulated sub-scan feed error.
[0007]
FIG. 18 is an explanatory diagram showing the dots recorded in FIG. 17 in more detail. The pitches of the two rasters of raster numbers 5 and 6 are enlarged by the accumulated sub-scan feed error, and as a result, a streak-like image quality deterioration portion that is easily noticeable occurs. Such a streak-like image quality degradation portion is called “banding”. Since banding deteriorates image quality, there has been a demand for reducing banding as much as possible.
[0008]
The present invention has been made in order to solve the above-described problems in the prior art, and an object thereof is to provide a dot recording technique capable of reducing the occurrence of banding.
[0009]
[Means for solving the problems and their functions and effects]
  In order to solve at least a part of the above-described problems, an apparatus according to the present invention is provided in the dot recording head in a dot recording apparatus that records dots on the surface of a printing medium using a dot recording head. During the main scanning, dots of the same color can be recorded on a plurality of main scanning lines, and a constant pitch k × P along the sub-scanning direction (k is an integer of 3 or more, P is a dot on the printing medium) A dot forming element array having a plurality of dot forming elements arranged at a minimum pitch in the sub-scanning direction), a main scanning drive unit that performs main scanning by driving at least one of the dot recording head and the printing medium, A head drive unit that forms dots using at least a part of the plurality of dot forming elements during the main scanning; and the dot recording each time the main scanning ends. Includes a sub-scan driving unit that performs sub-scanning by driving at least one of the head and the printing medium. The sub-scan driving unit repeatedly executes irregular sub-scan feed with k sub-scan feeds combining a plurality of different feed amounts as one cycle.At this time, when it is assumed that a periodic position along the sub-scanning direction of the plurality of dot forming elements when sub-scan feed is not performed is a reference position where the offset is zero, The offsets of the plurality of dot forming elements after each sub-scan feed are M × P (M is an integer from 0 to (k−1)), and the average sub-scan feed amount is set in advance. The irregular sub-scan feed is executed so as to be equal to the basic dot forming element number Na.To do. The head driving unit is used during one main scan.N (N is an integer of 3 or more)Of the dot forming elementsNb (Nb is an integer equal to (N-Na))Using this specific dot forming element, partial overlap recording is performed for each main scan, with dots on the main scan line to be recorded being recorded during other main scans..
[0010]
In partial overlap recording, for the recording of one color dot, the first type main scanning line for which recording is completed with one nozzle and the second type main scanning line for which recording is completed with two nozzles are mixed. Each main scanning line is recorded in such a state. Of these, the second type main scanning line is recorded by two different nozzles, so that the occurrence of banding can be reduced. However, since the second type main scanning line requires twice as much scanning time as the first type main scanning line, the recording speed is ½ for that line. However, if the above (1) to (3) are satisfied, some main scanning lines become the first type main scanning lines, and therefore all the main scanning lines become the second type main scanning lines. Compared to the case, the decrease in recording speed can be alleviated. Further, since this dot recording apparatus uses irregular sub-scan feed, the image quality can be further improved by adjusting the combination of feed amounts.
[0011]
In the above dot recording apparatus, the head driving unit may perform dot recording on the forward path and the backward path when main scanning is performed in both directions in a reciprocating manner.
[0012]
When bidirectional recording is performed, there may be a noticeable color difference between the main scanning line recorded in the forward pass and the main scanning line recorded in the return pass. However, in the case of bidirectional recording, if the partial overlap recording as described above is executed, the difference between the forward path and the backward path becomes inconspicuous in the vicinity of the second type main scanning line recorded by two different nozzles. The image quality is improved.
[0013]
When the pitch in the sub-scanning direction of the plurality of dot forming elements is k × P (k is an integer of 3 or more, P is the minimum pitch of dots on the printing medium in the sub-scanning direction) The number N of dot forming elements used during main scanning (N is an integer of 3 or more) and the parameters Na, Nb, m, and L may satisfy the following expressions (1) to (3). Good.
N = Na + Nb (1)
Na = m × k ± 1 (2)
Nb = Rd [L × Na ÷ k] (3)
Here, m is an integer of 1 or more, L is an integer satisfying 1 ≦ L <k, Nb is the number of the specific dot forming elements, and the operator Rd [] is the decimal part of the value in parentheses. Indicates the rounding operation.
[0014]
In this way, the number of second-type main scanning lines recorded by two different nozzles can be set to an appropriate value from the two viewpoints of suppressing the decrease in recording speed and improving the image quality.
[0015]
The dot recording head is driven so that the dots recorded by the Nb dot forming elements and the dots recorded by the Na dot forming elements have a complementary positional relationship on each main scanning line. You may make it do.
[0016]
Alternatively, the dot recording head may be driven so that the dots recorded by the Nb dot forming elements overlap the dots recorded by the Na dot forming elements on each main scanning line.
[0017]
  The dot recording method according to the present invention can record dots of the same color on a plurality of main scanning lines during one main scanning, and has a constant pitch k × P (k is 3 or more) along the sub-scanning direction. And P is a dot recording head having a dot forming element array having a plurality of dot forming elements arranged at a minimum pitch in the sub scanning direction of dots on the print medium, and is substantially perpendicular to the sub scanning direction. In the method of recording dots on the surface of a printing medium while performing main scanning along the direction, an irregular sub-scan feed in which k sub-scan feeds combining a plurality of different feed amounts are set as one cycle as the sub-scan feed. RepeatedlyAt this time, when it is assumed that a periodic position along the sub-scanning direction of the plurality of dot forming elements when sub-scan feed is not performed is a reference position where the offset is zero, The offsets of the plurality of dot forming elements after each sub-scan feed are M × P (M is an integer from 0 to (k−1)), and the average sub-scan feed amount is set in advance. The irregular sub-scan feed is executed so as to be equal to the basic dot forming element number Na.Used during one main scanN (N is an integer of 3 or more)Of the dot forming elementsNb (Nb is an integer equal to (N-Na))Using this specific dot forming element, partial overlap recording is performed for each main scan, with dots on the main scan line to be recorded being recorded during other main scans.
[0018]
  The recording medium according to the present invention can record dots of the same color on a plurality of main scanning lines during one main scanning, and has a constant pitch k × P (k is 3 in the sub-scanning direction). The above-described sub-scanning is provided in a printing apparatus including a dot recording head having a dot-forming element array including a plurality of dot-forming elements arranged at an integer above, P being a minimum pitch of dots on the printing medium in the sub-scanning direction) A computer-readable recording medium on which a computer program for recording dots on the surface of a printing medium while performing main scanning along a direction substantially perpendicular to the direction is combined with a plurality of different feed amounts Anomalous sub-scan feed is repeatedly executed with k sub-scan feeds as one cycle.At this time, when it is assumed that a periodic position along the sub-scanning direction of the plurality of dot forming elements when sub-scan feed is not performed is a reference position where the offset is zero, The offsets of the plurality of dot forming elements after each sub-scan feed are M × P (M is an integer from 0 to (k−1)), and the average sub-scan feed amount is set in advance. The irregular sub-scan feed is executed so as to be equal to the basic dot forming element number Na.Function to be used during one main scanN (N is an integer of 3 or more)Of the dot forming elementsNb (Nb is an integer equal to (N-Na))The computer executes a function of executing partial overlap recording for each main scan with dots on the main scan line to be recorded during another main scan using a specific dot forming element. A computer-readable recording medium on which a computer program for recording is recorded.
[0019]
Even with such a method and recording medium, the occurrence of banding can be reduced as in the case of the above-described apparatus.
[0020]
Other aspects of the invention
The present invention includes other aspects as follows. A first aspect is a dot recording apparatus that records dots on the surface of a print medium using a dot recording head, and is provided on the dot recording head, and is arranged on a plurality of main scanning lines during one main scanning. A dot-forming element array in which a plurality of dot-forming elements that can form a plurality of dots of the same color at a substantially constant pitch along the sub-scanning direction, Dot formation by using at least one of the plurality of dot forming elements during the main scanning, and a main scanning drive unit that performs main scanning by driving at least one of the dot recording head and the printing medium A head driving unit that performs the scanning, a sub-scanning driving unit that performs sub-scanning by driving at least one of the dot recording head and the printing medium every time the main scanning is completed, and a dot recording operation. Comprising a recording mode storage unit for recording the speed of stores approximately equal plurality of dot recording modes, the. The plurality of dot recording modes are a part of a plurality of dot forming elements used during one main scanning as an irregular feeding dot recording mode using an irregular sub-scan feed combining a plurality of different feed amounts. Including at least one partial overlap type irregular feed dot recording mode in which a part of dots on a main scanning line to be recorded during other main scanning using the specific dot forming element is recorded. The main scanning drive unit, the sub-scanning drive unit, and the head drive unit execute each drive according to a dot recording mode selected from the plurality of dot recording modes.
[0021]
According to the first aspect, since a preferable mode can be selected from a plurality of dot recording modes having substantially the same recording speed, dot recording can be performed by selecting a mode in which high image quality can be obtained for each dot recording apparatus. Can be executed.
[0022]
In the second mode, dots of the same color can be recorded on a plurality of main scan lines during one main scan, and a plurality of dots of the same color are formed at a substantially constant pitch along the sub-scanning direction. Using a dot recording head having a dot forming element array in which a plurality of possible dot forming elements are arranged, dots are recorded on the surface of the print medium while performing main scanning along a direction substantially perpendicular to the sub-scanning direction. A method of performing dot recording according to a dot recording mode selected from a plurality of dot recording modes having substantially the same recording speed that defines a dot recording operation, wherein the plurality of dot recording modes are different from each other. As the irregular feed dot recording mode using the irregular sub-scan feed combined with the feed amount, a specific part of a plurality of dot forming elements used during one main scan is specified. At least one partial overlap type irregularly fed dot recording mode in which a part of dots on a main scanning line to be recorded is recorded during another main scanning by using a dot forming element. To do.
[0023]
In the third mode, dots of the same color can be recorded on a plurality of main scan lines during one main scan, and a plurality of dots of the same color are formed at a substantially constant pitch along the sub-scanning direction. In a printing apparatus having a dot recording head having a dot forming element array in which a plurality of possible dot forming elements are arranged, dots are formed on the surface of the print medium while performing main scanning along a direction substantially perpendicular to the sub-scanning direction. A computer-readable recording medium on which a computer program for performing recording is recorded, wherein dots are recorded in accordance with a dot recording mode selected from a plurality of dot recording modes having substantially the same recording speed that defines the dot recording operation. A computer-readable recording medium recording a computer program for causing a computer to execute the recording of The number of dot recording modes is an irregular feed dot recording mode using irregular sub-scan feed combining a plurality of different feed amounts, and is a part of a plurality of dot forming elements used during one main scan. It includes at least one partial overlap type irregularly fed dot recording mode in which a part of dots on a main scanning line to be recorded is recorded during another main scanning using a specific dot forming element. And
[0024]
DETAILED DESCRIPTION OF THE INVENTION
A. Device configuration:
FIG. 1 is a block diagram showing the configuration of a color image processing system as an embodiment of the present invention. This color image processing system includes a scanner 30, a personal computer 90, and an ink jet recording apparatus 22. The personal computer 90 includes a color display 21. The scanner 30 reads color image data from a color original, and supplies original color image data ORG including three color components of R, G, and B to the computer 90.
[0025]
The computer 90 includes a CPU, RAM, ROM, etc. (not shown), and an application program 95 operates under a predetermined operating system. A video driver 91 and a printer driver 96 are incorporated in the operating system, and print data FNL that is final color image data is output from the application program 95 via these drivers. An application program 95 that performs image retouching or the like reads an image from the scanner and performs a predetermined process on the image, and displays the image on the CRT display 93 via the video driver 91. When the application program 95 issues a print command, the printer driver 96 of the computer 90 receives image information from the application program 95 and receives a signal that can be printed by the inkjet recording apparatus 22 (here, binary for each color of CMYK). Signal). In the example shown in FIG. 1, the printer driver 96 includes a rasterizer 97 that converts color image data handled by the application program 95 into dot unit image data, and an ink jet recording apparatus for the dot unit image data. The color correction module 98 that performs color correction in accordance with the ink colors CMY and color development characteristics used by the color correction module 98, the color correction table CT that the color correction module 98 refers to, and image information after color correction in dot units. A halftone module 99 that generates so-called halftone image information expressing the density in a certain area depending on the presence or absence of ink is provided.
[0026]
FIG. 2 is a conceptual diagram showing the configuration of the inkjet recording apparatus 22. The ink jet recording apparatus 22 includes a print head 1, a carriage shaft 2, a carriage belt 3, a main scanning motor 4, a carriage drive circuit 5 that drives the main scanning motor 4, a platen roller 6, a gear 7, A sub-scanning motor 8, a printing medium conveyance control circuit 9 that drives the sub-scanning motor 8 to convey the printing medium PM, fixed bases 10 and 11, a print data control circuit 13, a programmable ROM (PROM) 15, It has. The platen roller 6, the gear 7, the sub-scanning motor 8, and the printing medium conveyance control circuit 9 constitute a sub-scanning drive unit. The carriage drive circuit 5, the print medium conveyance control circuit 9, and the print data control circuit 13 may be realized by a single control circuit. Further, a control circuit that controls these circuits 5, 9, 13, and 15 in an integrated manner may be provided separately.
[0027]
The main scanning is realized by the carriage driving circuit 5 driving the main scanning motor 4. That is, when the main scanning motor 4 moves the carriage belt 3, the print head 1 fixed to the carriage belt 3 reciprocates between the two fixed bases 10 and 11. The print head 1 ejects ink droplets onto the print medium PM according to the print data supplied from the print data control circuit 13 during the forward or backward operation. When such one main scan is completed, the print medium conveyance control circuit 9 drives the sub-scan motor 8 to move the print medium PM by a predetermined amount.
[0028]
The PROM 15 stores dot recording mode information including a plurality of dot recording mode parameters. Here, the “dot recording mode” means a dot recording method defined by a plurality of parameters such as the number N of nozzles actually used in each nozzle array and the sub-scan feed amount F. In this specification, “recording method” and “recording mode” are used with almost the same meaning. Examples of specific dot recording modes and their parameters will be described later. The PROM 15 further stores mode designation information for designating a preferable mode from a plurality of dot recording modes. For example, when 16 types of dot recording mode information can be stored in the PROM 15, the mode designation information is composed of 4-bit data.
[0029]
The dot recording mode information is read from the PROM 15 by the printer driver 96 when the printer driver 96 (FIG. 1) is installed when the computer 90 is started. That is, the printer driver 96 reads the dot recording mode information for the preferable dot recording mode designated by the mode designation information from the PROM 15. Processing in the rasterizer 97 and the halftone module 99 and main scanning and sub-scanning operations are executed according to the dot recording mode information. The print data control circuit 13 reads dot recording mode information from the PROM 15 and executes dot recording (printing) by the print head 1 in accordance with the information.
[0030]
The PROM 15 may be any rewritable nonvolatile memory, and various nonvolatile memories such as an EEPROM and a flash memory can be used. The mode designation information is preferably stored in a rewritable nonvolatile memory, but the dot recording mode information may be stored in a ROM that cannot be rewritten. The plurality of dot recording mode information may be stored not in the PROM 15 but in other storage means, or may be registered in the printer driver 96.
[0031]
FIG. 3 is an explanatory diagram showing the arrangement of inkjet nozzles in the print head 1. The print head 1 is provided with six nozzle arrays 61 to 66 for six colors of ink. That is, the six nozzle arrays 61 to 66 eject black (K), dark cyan (C), light cyan (LC), dark magenta (M), light magenta (LC), and yellow (Y) ink, respectively. To do. Each nozzle n is provided with a piezo element (not shown) for ejecting ink, and the piezo element is driven according to the print data supplied from the print data control circuit 13, and as a result, Ink is ejected from each nozzle n.
[0032]
The six sets of nozzle arrays 61 to 66 each include a plurality (for example, 32 or 48) of nozzles n arranged in a staggered manner at a constant nozzle pitch k along the sub-scanning direction. Note that the plurality of nozzles n included in each nozzle array need not be arranged in a staggered manner, and may be arranged in a straight line. However, as shown in FIG. 3A, the staggered arrangement has an advantage in that the nozzle pitch k can be easily set small.
[0033]
FIG. 3B shows an arrangement of a plurality of dots formed by one nozzle array. In this embodiment, regardless of whether the arrangement of the ink nozzles is staggered or linear, each nozzle is arranged so that the plurality of dots formed by one nozzle array are aligned in a substantially straight line along the sub-scanning direction. A drive signal is supplied to a piezoelectric element (not shown) for driving. For example, when the nozzle arrays are arranged in a staggered manner as shown in FIG. 3A, the pitch d [inch] between two nozzle rows in the same nozzle array is set to the main scanning drive speed v [inch / inch]. The timing of the drive signals in the two columns is shifted by the time d / v [seconds] divided by [seconds]. In this way, a plurality of dots formed by one nozzle array can be arranged on a straight line along the sub-scanning direction. As will be described later, the total number of the plurality of nozzles provided in each of the nozzle arrays 61 to 66 is not always used, and only some of the nozzles are used depending on the dot recording method. There is also a case.
[0034]
The plurality of nozzles n of the six nozzle arrays 61 to 66 are located at the same position in the sub-scanning direction so that six color dots can be formed on the same plurality of main scanning lines at the time of one main scanning. Is arranged.
[0035]
B. Basic conditions for sub-scan feed:
Before describing the partial overlap type dot recording method in the embodiment of the present invention, first, the basic conditions of the sub-scan feed in the non-overlapping type dot recording method will be described first. The phrase “overlap” means that all dots of the same color on a certain raster are recorded using different nozzles in a plurality of main scans. The “non-overlapping type dot recording method” means a method in which all dots on each raster are recorded by one nozzle during one main scan. In addition, the “partial overlap type dot recording method” is a method in which some rasters are recorded in an overlapping manner and other rasters are recorded in a non-overlapping manner (or among a plurality of nozzles used). Means that only some nozzles are used for overlap). In addition, the term “full overlap type dot recording method” is sometimes used, and this term is a method in which all rasters are recorded in an overlapping manner (or all used nozzles are used for overlapping). System). As will be described later, the present invention relates to a partial overlap type dot recording method. The sub-scan feed condition in the partial overlap type dot recording method can be derived from the sub-scan feed condition in the non-overlapping type dot recording method described below.
[0036]
FIG. 4 is an explanatory diagram for illustrating basic conditions for sub-scan feed in the non-overlapping type dot recording method. FIG. 4A shows an example of sub-scan feed when four nozzles are used, and FIG. 4B shows the parameters of the dot recording method. In FIG. 4A, solid line circles including numerals indicate the positions in the sub-scanning direction of the four nozzles after each sub-scan feed. Numbers 1 to 4 in the circles indicate nozzle numbers. The positions of the four nozzles are sent in the sub-scanning direction every time one main scanning is completed. In practice, however, feeding in the sub-scanning direction is realized by moving the paper by the sub-scanning motor 8 (FIG. 2).
[0037]
As shown at the left end of FIG. 4A, in this example, the sub-scan feed amount F is a constant value of 4 dots. Accordingly, every time the sub-scan feed is performed, the positions of the four nozzles are shifted by 4 dots in the sub-scanning direction. At the right end of FIG. 4A, the number of the nozzle that records dots on each raster is shown.
[0038]
FIG. 4B shows various parameters relating to this dot recording method. The parameters of the dot recording method include the nozzle pitch k [dots], the number of used nozzles N [pieces], and the sub-scan feed amount F [dots]. In this example, the nozzle pitch k is 3 dots, and the number of used nozzles N is 4. The number N of used nozzles is the number of nozzles actually used among the plurality of mounted nozzles.
[0039]
The table of FIG. 4B shows the sub-scan feed amount F, the accumulated value ΣF, and the nozzle offset OF after each sub-scan feed for each sub-scan feed. Here, the offset OF is the period after the sub-scan feed when the periodic position of the first nozzle that is not subjected to the sub-scan feed (positions every 4 dots in FIG. 4) is assumed to be the reference position of the offset 0. This is a value indicating how many dots the nozzle position is away from the reference position in the sub-scanning direction. For example, as shown in FIG. 4A, the first sub-scan feed moves the nozzle position in the sub-scan direction by the sub-scan feed amount F (4 dots). On the other hand, the nozzle pitch k is 3 dots. Therefore, the nozzle offset OF after the first sub-scan feed is 1 (see FIG. 4A). Similarly, the nozzle position after the second sub-scan feed is moved by ΣF = 8 dots from the initial position, and the offset OF is 2. The position of the nozzle after the third sub-scan feed is moved by ΣF = 12 dots from the initial position, and the offset OF is zero. Since the nozzle offset OF returns to 0 by three sub-scan feeds, all the dots on the raster in the printable area can be recorded by repeating this cycle with three sub-scans as one cycle. it can. Here, the “printable area” means an area where dots can be recorded without missing a raster.
[0040]
As can be seen from the above example, when the position of the nozzle is away from the initial position by an integral multiple of the nozzle pitch k, the offset OF is zero. The offset OF is given by a remainder (ΣF)% k obtained by dividing the cumulative value ΣF of the sub-scan feed amount F by the nozzle pitch k. Here, “%” is an operator indicating that the remainder of division is taken. If the initial position of the nozzle is considered as a periodic position, the offset OF can also be considered to indicate the amount of phase shift from the initial position of the nozzle.
[0041]
As will be described below, if the following conditions C1 to C3 are satisfied, dots are recorded so that there is no missing or overlapping raster in the printable area regardless of whether the sub-scan feed amount F is constant or not. It is possible.
[0042]
Condition C1: The number of sub-scan feeds in one cycle is equal to the nozzle pitch k.
[0043]
Condition C2: Nozzle offset OF after each sub-scan feed in one cycle is a different value in the range of 0 to (k−1).
[0044]
Condition C3: The sub-scan average feed amount (ΣF / k) is equal to the number N of used nozzles. In other words, the cumulative value ΣF of the sub-scan feed amount F per cycle is equal to a value (N × k) obtained by multiplying the number of used nozzles N and the nozzle pitch k.
[0045]
Each of the above conditions can be understood by thinking as follows. Since there are (k-1) rasters between adjacent nozzles, recording is performed on these (k-1) rasters in one cycle, and the nozzle reference position (position where the offset OF is zero). In order to return to, the number of sub-scan feeds in one cycle is k times. If the number of sub-scan feeds in one cycle is less than k times, the recorded raster will be lost. On the other hand, if the number of sub-scan feeds in one cycle is greater than k times, the recorded rasters will overlap. Therefore, the first condition C1 is satisfied.
[0046]
When the number of sub-scan feeds in one cycle is k times, only when the offset OF value after each sub-scan feed is a different value in the range of 0 to (k-1), missing or overlapping rasters are recorded. Disappears. Therefore, the second condition C2 is satisfied.
[0047]
If the first and second conditions are satisfied, each of the N nozzles records k rasters in one cycle. Therefore, N × k rasters are recorded in one cycle. On the other hand, if the above third condition C3 is satisfied, as shown in FIG. 4A, the nozzle position after one cycle (after k sub-scan feeds) is N × k from the initial nozzle position. Comes to a raster away position. Therefore, by satisfying the first to third conditions C1 to C3, it is possible to eliminate omissions and overlaps in the recorded raster in the range of these N × k rasters.
[0048]
Note that the above conditions C1 to C3 are not limited to the recording method in which the sub-scan feed amount F is always constant (referred to as “regular feed”), but a plurality of combinations of different values are repeatedly used as the sub-scan feed amount F. The present invention can also be applied to a recording method (referred to as “anomalous feeding”).
[0049]
C. Comparison example of dot recording method:
FIG. 5 is an explanatory diagram showing the dot recording method of the first comparative example. This dot recording method satisfies the following expressions (1) to (4).
[0050]
N = Na + Nb (1)
Na = m × k ± 1 (2)
Nb = Rd [L × Na ÷ k] (3)
F = Na (4)
Here, N represents the number of used nozzles, k represents a nozzle pitch [dot], m represents an integer of 1 or more, L represents an integer satisfying 1 ≦ L <k, and the operator Rd [] represents a value in parentheses. Indicates the operation of rounding the fractional part. The operator ± indicates that either addition or subtraction may be used.
[0051]
The sub-scan feed of the first comparative example is a regular feed in which the sub-scan feed amount F is constant at 9 dots, and the feed amount F and the parameter Na are equal to each other as defined in the above equation (4). On the other hand, the examples of the present invention described later satisfy the above formulas (1) to (3), but the sub-scan feed is an irregular feed that repeatedly uses a combination of a plurality of different sub-scan feed amounts. The above equation (4) is not established. The first comparative example is different from the examples described later in this respect.
[0052]
The parameter values in the dot recording method of FIG. 5 are N = 14, Na = 9, Nb = 5, k = 4, F = 9, m = 2, and L = 2. Here, subtraction is used as the calculation of ± on the right side of equation (2), and rounding up is used as the rounding calculation Rd []. The dot pitch (printing pitch) P in the sub-scanning direction is a value corresponding to the printing resolution of 720 DPI (ie 1/720 inch), for example.
[0053]
As shown in the above equation (1), the number N of used nozzles is given by the sum of two integers Na and Nb. Since the first integer Na is equal to the value of the sub-scan feed amount F, the first integer Na corresponds to the number of nozzles in the conventional recording method shown in FIG. Therefore, hereinafter, the first integer Na is referred to as “basic nozzle number”, and the nozzles included in the basic nozzle number Na are referred to as “basic nozzles”. The second integer Nb is referred to as “additional nozzle number”, and the nozzles included in the additional nozzle number Nb are referred to as “additional nozzle”. In the example of FIG. 5, nozzles # 1 to # 9 are basic nozzles, and nozzles # 10 to # 14 are additional nozzles. The significance of the basic nozzle number Na and the additional nozzle number Nb will be described later.
[0054]
At the right end of FIG. 5, dot positions on the print medium are shown. White circles indicate dot positions recorded by the basic nozzles # 1 to # 9, and black circles indicate dot positions recorded by the additional nozzles # 10 to # 14. The range of the raster existing below the raster in which the white circle and the black circle are drawn is the range (recordable area) that is actually recorded. In FIG. 5, it is not distinguished whether each dot is recorded in the forward pass or the return pass.
[0055]
As can be seen from the recording dot pattern in FIG. 5, the raster to be recorded by the additional nozzles # 10 to # 14 is also the target to be recorded by the basic nozzle. In this specification, rasters recorded by both basic nozzles and additional nozzles are called “overlap rasters”, and rasters recorded only by basic nozzles are called “non-overlapping rasters”.
[0056]
Pixels on the overlap raster are recorded intermittently by one additional nozzle during one main scan, and are recorded so as to complement this by one basic nozzle during another main scan, This completes the recording of all pixels on the overlap raster. In other words, the overlap raster is complementarily recorded by one additional nozzle and one basic nozzle. Here, “complementary” means that all pixels on one raster are recorded without omission or duplication by the additional nozzle and the basic nozzle.
[0057]
The print medium conveyance control circuit 9 (FIG. 2) conveys the print medium PM in the sub-scanning direction by F dots (that is, P × F inches) every time one main scan is completed. For example, it moves from the path 1 to the position of the path 2 in FIG. In pass 5, the three basic nozzles # 3 to # 5 are positioned on the raster already recorded by the additional nozzles # 12 to # 14. In pass 1, the additional nozzles # 12 to # 14 record even-numbered pixels on the overlap raster. In pass 5, the basic nozzles # 3 to # 5 record odd-numbered pixels on these overlap rasters. As a result, complementary recording for the three overlapping rasters is completed. By repeating the above operation, characters and images are formed on the print medium PM.
[0058]
FIG. 6 is an explanatory diagram showing recording dots formed according to the first comparative example. In FIG. 6, white circles indicate dots recorded by basic nozzles, and black circles indicate dots recorded by additional nozzles. In this example, the position of the dot recorded by the additional nozzle is slightly shifted in the sub-scanning direction (vertical direction in FIG. 6) from the position of the dot recorded by the basic nozzle on the same raster.
[0059]
As described in the prior art, when a plurality of sub-scan feeds are performed during recording of adjacent rasters, a plurality of sub-scan feed errors are accumulated, and the pitch between adjacent rasters is changed from the correct pitch. It will deviate considerably, resulting in banding. However, in the first comparative example, even when a sub-scan feed error (conveyance error) is accumulated while two adjacent rasters are recorded, some of the dots on one of the rasters are added nozzles. Since it is recorded, it is difficult to recognize it as banding. The reason for this is that, as shown in FIG. 6, the positions of the dots recorded by the additional nozzles are slightly shifted in the sub-scanning direction from the positions of the dots recorded by the basic nozzles on the same raster.
[0060]
By the way, the significance of each parameter in the above-described equations (1) to (4) can be considered as follows. As can be understood from the equations (2) and (4), the sub-scan feed amount F is set to a constant value of (m × k ± 1) dots. That is, the sub-scan feed amount F is set to a value obtained by adding or subtracting 1 to a value m × k that is an integral multiple of the nozzle pitch k. Assuming that the sub-scan feed amount F is set to an integral multiple m × k of the nozzle pitch k, the position of each nozzle after the sub-scan feed is the periodic position of the nozzle before the sub-scan feed (that is, k). It is arranged again at every other dot). Therefore, when the sub-scan feed amount F is (m × k ± 1) dots, the position of each nozzle after the sub-scan feed is +1 dot or −1 from the periodic position of the nozzle before the sub-scan feed. The dots are arranged at positions shifted in the sub-scanning direction. For example, in FIG. 5, since the value of the sub-scan feed amount F is (2 × 4 + 1) = 9 dots, the nozzle after the sub-scan feed is +1 dot from the periodic position of the nozzle before the sub-scan feed in the sub-scan direction. It is arranged at the position where it has passed.
[0061]
When the rounding operator Rd in the above expression (3) is ignored and the expression (4) is used, the expression (3) can be rewritten as the following expression (3a).

[0062]
The numerator (Nb × k) on the right side of the expression (3a) is obtained by multiplying the number of additional nozzles Nb by the nozzle pitch k, and indicates the range of additional nozzles in the nozzle array. In the example of FIG. 5, the additional nozzle range is a range from the raster position of nozzle # 10 to the raster position below nozzle # 143 dots. The parameter L is substantially equal to the value obtained by dividing (Nb × k) by the sub-scan feed amount F. Therefore, this parameter L is determined by how many times the range of the additional nozzle is determined by a certain nozzle (for example, the uppermost additional nozzle # 10). It can be considered to be a value indicating whether or not to pass in the sub-scan feed. By the way, as described above, each nozzle is arranged at a position shifted by one dot from the periodic position of the nozzle immediately before by one sub-scan feed. Therefore, considering L sub-scan feeds after a certain pass, the topmost additional nozzle # 10 remains within the range of the additional nozzles in the bus during L sub-scans, and Every time the sub-scan feed is performed, the dot is shifted by one dot from the periodic position of the previous nozzle. For example, in FIG. 5, in the two sub-scan feeds after pass 1, the uppermost additional nozzle # 10 remains within the range of the additional nozzles in pass 1 during the two sub-scans up to pass 3. In addition, every time the sub-scan feed is performed, the dot is shifted by one dot from the periodic position of the nozzle immediately before. In other words, in pass 2, the uppermost additional nozzle # 10 is positioned within the range of the additional nozzle in pass 1 and after one dot of nozzle # 12 in pass 1 immediately before that. In pass 3, the uppermost additional nozzle # 10 is positioned within the range of the additional nozzle in pass 1 and after one dot of nozzle # 12 in pass 2 just before that.
[0063]
Considering such movement of the nozzle position, the parameter L is a value indicating “how many overlap rasters (rasters recorded by basic nozzles and additional nozzles) are continuously arranged”. Can think. For example, in the first comparative example shown in FIG. 5, since L = 2, two overlap rasters are continuous. (In FIG. 5, there is a portion where three overlap rasters are continuous. The reason for this will be described later.) The additional nozzles are arranged at a nozzle pitch k in the nozzle array. , Of the k consecutive rasters, the first L are overlap rasters and the remaining (k−L) are non-overlap rasters. Therefore, the raster array is a repetitive array of k raster groups composed of L overlap rasters and (k−L) non-overlap rasters.
[0064]
By the way, among the Na rasters recorded in one main scan by the Na basic nozzles, Nb rasters recorded also by the Nb additional nozzles are overlap rasters, and the remaining (Na -Nb) The rasters are non-overlapping rasters. That is, within the range of Na rasters, k raster groups composed of L overlap rasters and (k−L) non-overlap rasters are repeatedly arranged. As a result, Na Nb of the books are overlap rasters, and the remaining (Nb-Na) books are non-overlap rasters. For example, in the first comparative example shown in FIG. 5, since k = 4, Na = 9, and Nb = 5, two overlapping rasters and two non-overlapping rasters are used within the range of nine rasters. The configured raster groups are repeatedly arranged. As a result, 5 out of 9 are overlap rasters and the remaining 4 are non-overlap rasters.
[0065]
The rightmost diagram in FIG. 5 shows a raster division for each Na. In this example, the last raster in the Na set of rasters is an overlap raster, and the next set of the first L (= 2) rasters is also an overlap raster. Therefore, three overlapping rasters are adjacent to each other at the boundary of the rasters for each Na. However, basically, the raster arrangement of FIG. 5 is such that k raster groups composed of L overlap rasters and (k−L) non-overlap rasters are repeatedly arranged. Can understand.
[0066]
Thus, in the first comparative example, the overlap raster and the non-overlap raster are arranged almost regularly according to the parameters k, L, Na, and Nb. That is, approximately L consecutive overlap rasters are arranged almost regularly across approximately (k−L) non-overlap rasters. As described with reference to FIG. 6, banding is less noticeable in the vicinity of the overlap raster, which has the advantage of improving the image quality.
[0067]
In the case of bidirectional printing in which main scanning is performed in both directions, the regular overlap raster arrangement as described above also exhibits the following effects. That is, as shown in FIG. 3, when the nozzle array of six colors of ink is arranged to record the same raster, K, C, LC (light cyan), M, Each color dot is formed in the order of LM (light magenta) and Y. On the other hand, on the reverse path, on the other hand, dots of each color are formed on each raster in the order of Y, LM, M, LC, C, K. Therefore, there is a possibility that the raster recorded on the forward pass and the raster recorded on the return pass look slightly different in color. At this time, if dots are recorded by a complete non-overlapping method without forming an overlap raster, the color difference between the raster recorded in the forward path and the raster recorded in the backward path becomes conspicuous, resulting in image quality degradation. Be recognized. On the other hand, since the overlap raster is recorded in the forward path and the backward path, the color difference between the raster recorded in the forward path and the raster recorded in the backward path is reduced in the vicinity of the overlap raster. That is, if an overlap raster is formed, there is an advantage that the difference in raster color between the forward path and the backward path becomes inconspicuous.
[0068]
In order to make banding inconspicuous, all rasters can be considered as overlapping rasters. However, if all the rasters are overlapped rasters, the main scanning time is about twice as long as when all the rasters are non-overlapped rasters, so the recording speed is reduced to about 1/2. In contrast, in partial overlap, overlap raster and non-overlap raster are mixed, so the advantage of reducing the recording speed can be alleviated compared to the case where all overlap rasters are used. There is.
[0069]
7 and 8 are explanatory diagrams showing the dot recording method of the second comparative example. The values of the parameters in the dot recording method of the second comparative example are N = 13, Na = 11, Nb = 2, k = 6, F = 11, m = 2, and L = 1. Each of these parameters satisfies the above-described equations (1) to (4). The dot positions on the raster are white circles (positions recorded by basic nozzles during forward movement), black circles (positions recorded by additional nozzles during forward movement), and white squares (recorded by basic nozzles during backward movement). ) And black squares (positions recorded by additional nozzles during backward movement).
[0070]
FIG. 8 shows the significance of the parameters Na, L, k as in FIG. In other words, the second comparative example also has the feature that “approximately L overlap rasters are arranged almost regularly across approximately (k−L) non-overlap rasters”. Yes.
[0071]
D. Example of dot recording method:
9 and 10 are explanatory diagrams showing the dot recording method of the first embodiment. The values of the parameters in the dot recording method of the first embodiment are N = 13, Na = 11, Nb = 2, k = 6, m = 2, and L = 1. The sub-scan feed is an irregular feed that constitutes one cycle with the feed amount F of (8, 9, 10, 16, 15, 8) dots, and this one-cycle feed amount is repeatedly applied. Each of these parameters satisfies the following expressions (1) to (3).
[0072]
N = Na + Nb (1)
Na = m × k ± 1 (2)
Nb = Rd [L × Na ÷ k] (3)
[0073]
The first example also satisfies the following conditions C1 'to C3' similar to the above-described conditions C1 to C3.
[0074]
Condition C1 ': The number of sub-scan feeds in one cycle is equal to the nozzle pitch k.
[0075]
Condition C2 ': Nozzle offset OF after each sub-scan feed in one cycle is a different value in the range of 0 to (k-1).
[0076]
Condition C3 ′: The average sub-scan feed amount (ΣF / k) is equal to the basic nozzle number Na. In other words, the cumulative value ΣF of the sub-scan feed amount F per cycle is equal to a value (Na × k) obtained by multiplying the basic nozzle number Na and the nozzle pitch k.
[0077]
The conditions C1 'and C2' are the same as the conditions C1 and C2. The condition C3 ′ is obtained by rewriting the “number of used nozzles N” in the condition C3 to “the number of basic nozzles Na”. In the first embodiment, the second comparative example is changed to irregular feed, and other parameters are the same as those of the second comparative example.
[0078]
FIG. 11 is an explanatory diagram of recording dot positions in the first embodiment. FIG. 11 shows a state in which the range of additional nozzles corresponding to (Nb × k) rasters is sequentially shifted by a feed amount F. Considering only one main scan, the additional nozzles (indicated by black circles or black squares) are regularly arranged every k dots within the range of additional nozzles for (Nb × k) rasters. As in the second comparative example described above, when the sub-scan feed amount F is constant, the range of the additional nozzles is shifted by a certain amount, so that the overlap raster is arranged almost regularly. On the other hand, in the first embodiment, the sub-scan feed amount F is not constant, and a plurality of different feed amounts are used in combination. There is no regularity like 2 comparative examples. However, in the first embodiment, since the overlap rasters are arranged in a moderately dispersed manner, the banding is less noticeable and the image quality is improved as in the comparative example. In the first embodiment, since the overlap raster is not regularly arranged and is fairly randomly distributed, there is a possibility that a higher image quality can be obtained than in the second comparative example.
[0079]
Incidentally, the recording speed of the partial overlap type dot recording method is substantially proportional to the value of the basic nozzle number Na. That is, the net number of rasters recorded in one main scan is equal to the basic nozzle number Na and does not depend on the additional nozzle number Nb. Since the basic nozzle number Na is the same in the second comparative example and the first embodiment, they have the same recording speed. Further, both the second comparative example and the first example have the effect that banding is not conspicuous and the image quality is improved. In the first embodiment, since the overlap raster is not regularly arranged and is distributed fairly randomly, there is a possibility that a higher image quality can be obtained than in the second comparative example. Which of the example and the first embodiment can achieve high image quality depends on the manufacturing error of the pitch k between the nozzles in the print head 1. Therefore, the sub-scan feed is not limited to the regular feed as in the second comparative example, but if the irregular feed as in the first embodiment is allowed, it is possible to use a plurality of dot recording methods with substantially the same printing speed. Therefore, there is an advantage that a preferable one in terms of image quality can be selected and used.
[0080]
12 and 13 are explanatory diagrams showing the dot recording method of the second embodiment. The values of the parameters in the dot recording method of the second embodiment are N = 15, Na = 11, Nb = 4, k = 6, m = 2, and L = 2. Further, the sub-scan feed is the same irregular feed as in the first embodiment. Each of these parameters satisfies the above-described equations (1) to (3) and conditions C1 'to C3'. The second embodiment differs from the first embodiment in the number of additional nozzles Nb, but has the same recording speed as the first embodiment because the basic nozzle number Na is the same.
[0081]
FIG. 14 is an explanatory diagram of recording dot positions in the second embodiment. Also in the second embodiment, it can be seen that the overlap rasters are arranged in a moderately dispersed manner. Therefore, as in the first embodiment, banding is less noticeable and the image quality is improved.
[0082]
In addition to the first and second embodiments, various dot recording methods that satisfy the above-described equations (1) to (3) can be employed. FIG. 15 is an explanatory diagram illustrating an example of possible combinations of recording method parameters when k = 6 and L = 1-3. The case of k = 6, L = 1, m = 2, Na = 11, Nb = 2, and N = 13 in FIG. 15A corresponds to the first embodiment shown in FIGS. Further, the case of k = 6, L = 2, m = 2, Na = 11, Nb = 4, N = 15 in FIG. 15B corresponds to the second embodiment shown in FIGS. . FIG. 16 is an explanatory diagram showing an example of possible combinations of recording system parameters when k = 4 and L = 1-3. In these examples, rounding up is used as the rounding operation Rd [] in the above equation (3), but rounding down can also be used.
[0083]
As can be seen from FIGS. 15 and 16, when the value of the nozzle pitch k is given, the preferable basic nozzle number Na and the additional nozzle number Nb are determined by appropriately setting the values of the parameters m and L. The number N of used nozzles is determined from these sums. Conversely, when the number N of nozzles to be used is determined, it is possible to determine a preferable basic nozzle number Na and additional nozzle Nb from the number N of used nozzles using FIGS. 15 and 16.
[0084]
The PROM 15 shown in FIG. 2 stores a plurality of sets of dot recording mode information each including a plurality of dot recording mode parameters having substantially the same recording speed, and a preferable mode is selected from a plurality of dot recording methods. The mode specification information for specifying is also stored. Here, “a recording mode having substantially the same recording speed” means a recording mode in which the difference in the number of basic nozzles Na is within about 10%. For example, the PROM 15 stores two sets of dot recording mode information including the parameters of the two recording modes of the first and second embodiments. Which of the two dot recording modes is preferable in terms of image quality depends on the manufacturing error of the print head 1. Therefore, which one of the two recording modes is preferable is determined for each ink jet recording apparatus, and mode specifying information for specifying the preferable mode is stored in the PROM 15. In this way, it is possible to select a mode that is preferable in terms of image quality from two dot recording modes having the same recording speed. As selectable recording modes, a large number of three or more recording modes may be stored. The selectable recording modes may include a mode that uses regular feeding as in the second comparative example.
[0085]
According to the above-described embodiment, since the partial overlap is used and the irregular feed is used as the sub-scan feed, the overlap raster can be arranged in a moderately dispersed manner. As a result, banding becomes inconspicuous and high image quality can be achieved. In particular, when bidirectional recording is performed, there is an advantage that the difference between raster colors in the forward path and the backward path becomes inconspicuous because the overlapping rasters are arranged in a distributed manner. In addition, if a dot recording mode that is preferable in terms of image quality is selected and used from a plurality of dot recording modes having substantially the same recording speed, higher image quality can be achieved for each individual recording apparatus. There is.
[0086]
The present invention is not limited to the above-described examples and embodiments, and can be implemented in various modes without departing from the gist thereof. For example, the following modifications are possible.
[0087]
The present invention is not limited to bidirectional printing, but can also be applied to unidirectional printing in which dots are recorded only in a determined main scanning direction (for example, only in the forward path).
[0088]
In the above embodiment, the basic nozzle and the additional nozzle record the pixels on the same raster in a complementary manner. However, the basic nozzle and the additional nozzle may record dots at the pixel position on the same raster. It may be. It is also possible to employ other recording methods. For example, the basic nozzle and the additional nozzle may perform complementary recording, and the dot diameter recorded by the additional nozzle may be larger than the dot diameter recorded by the basic nozzle.
[0089]
The present invention can be applied not only to color printing but also to monochrome printing. Further, the present invention can be applied to printing that expresses multiple gradations by expressing one pixel with a plurality of dots. It can also be applied to a drum scan printer. In the drum scan printer, the drum rotation direction is the main scanning direction, and the carriage traveling direction is the sub-scanning direction. The present invention can be applied not only to an ink jet recording apparatus but also to a dot recording apparatus that performs recording on the surface of a print medium using a recording head having a plurality of dot forming element arrays. Here, “dot forming element” means a component for forming dots, such as an ink nozzle in an ink jet printer.
[0090]
In the above embodiment, a part of the configuration realized by hardware may be replaced with software, and conversely, a part of the configuration realized by software may be replaced by hardware. For example, the computer 90 can execute the control functions of the print data control circuit 13, the carriage drive circuit 5, and the print medium conveyance control circuit 9 shown in FIG. In this case, a computer program such as the printer driver 96 implements the same control function as these circuits.
[0091]
A computer program for realizing such a function is provided in a form recorded on a computer-readable recording medium such as a floppy disk or a CD-ROM. The computer system 90 reads a computer program from the recording medium and transfers it to an internal storage device or an external storage device. Or you may make it supply a computer program to the computer system 90 from a program supply apparatus via a communication path. When realizing the function of the computer program, the computer program stored in the internal storage device is executed by the microprocessor of the computer system 90. Further, the computer system 90 may directly execute the computer program recorded on the recording medium.
[0092]
In this specification, the computer system is a concept including a hardware device and an operation system, and means a hardware device that operates under the control of the operation system. The computer program causes such a computer system to realize the functions of the above-described circuits. Note that some of the functions described above may be realized by an operation system instead of an application program.
[0093]
In the present invention, the “computer-readable recording medium” is not limited to a portable recording medium such as a flexible disk or a CD-ROM, but an internal storage device in a computer such as various RAMs and ROMs, An external storage device fixed to a computer such as a hard disk is also included.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a schematic configuration of an image processing system according to the present invention.
FIG. 2 is a conceptual diagram showing an embodiment of an ink jet recording apparatus according to the present invention.
FIG. 3 is an explanatory diagram illustrating an arrangement of inkjet nozzles in the print head.
FIG. 4 is an explanatory diagram showing basic conditions of sub-scan feed in a non-overlapping type dot recording method.
FIG. 5 is an explanatory diagram showing a dot recording method of a first comparative example.
FIG. 6 is an explanatory diagram showing an effect of preventing banding by an overlap raster.
FIG. 7 is an explanatory diagram showing a dot recording method of a second comparative example.
FIG. 8 is an explanatory diagram showing a dot recording method of a second comparative example.
FIG. 9 is an explanatory diagram illustrating a dot recording method according to the first embodiment.
FIG. 10 is an explanatory diagram showing the dot recording method of the first embodiment.
FIG. 11 is an explanatory diagram of recording dot positions in the first embodiment.
FIG. 12 is an explanatory diagram showing a dot recording method of a second embodiment.
FIG. 13 is an explanatory diagram showing a dot recording method of a second embodiment.
FIG. 14 is an explanatory diagram of recording dot positions in the second embodiment.
FIG. 15 is an explanatory diagram showing an example of possible combinations of recording method parameters when k = 6 and L = 1 to 3;
FIG. 16 is an explanatory diagram showing an example of possible combinations of recording method parameters when k = 4 and L = 1, 2;
FIG. 17 is an explanatory diagram showing a conventional recording method.
FIG. 18 is an explanatory diagram showing an example of banding.
[Explanation of symbols]
1 ... Print head
2 Carriage shaft
3 Carriage belt
4 ... Motor
5 Carriage drive circuit
6 ... Platen roller
7 ... Gear
8 ... Motor
9: Print medium conveyance control circuit
10 ... Fixing base
11 ... Fixing base
13. Print data control circuit
20 ... Image output device
21 ... Color display
22. Inkjet recording apparatus
30 ... Scanner
90 ... Computer
91 ... Video driver
93 ... CRT display
95 ... Application program
96 ... Printer driver
97 ... Rasterizer
98 ... Color correction module
99 ... Halftone module

Claims (11)

In a dot recording apparatus that records dots on the surface of a print medium using a dot recording head,
Provided in the dot recording head, dots of the same color can be recorded on a plurality of main scanning lines during one main scanning, and a constant pitch k × P (k is 3 or more) along the sub-scanning direction. A dot forming element array having a plurality of dot forming elements arranged at a minimum pitch in the sub-scanning direction of dots on the print medium,
A main scanning drive unit that performs main scanning by driving at least one of the dot recording head and the printing medium;
A head drive unit that forms dots using at least some of the plurality of dot forming elements during the main scanning;
A sub-scanning drive unit that performs sub-scanning by driving at least one of the dot recording head and the printing medium every time the main scanning is finished,
Wherein at the time the sub-scan driving unit, the sub-scan feed of k times a combination of a plurality of different feed amounts repeatedly executes the irregular sub-scan feed of one cycle, this time, the sub-scan feed is not performed more Assuming that a periodic position along the sub-scanning direction of the dot forming elements is a reference position where the offset is zero, the offset of the plurality of dot forming elements after each sub-scan feed in the one cycle is M × P (M is an integer from 0 to (k−1)), and the irregular sub-scan feed so that the average sub-scan feed amount is equal to the preset basic dot forming element number Na. Run
The head driving unit is configured to specify Nb (Nb is an integer equal to (N-Na)) specific N out of N (N is an integer of 3 or more) dot forming elements used during one main scan. A dot recording apparatus, wherein a dot overlap element is used to perform partial overlap recording for each main scan, with dots on a main scan line to be recorded during another main scan being performed. The dot recording apparatus according to claim 1 ,
The head driving unit is a dot recording apparatus that performs dot recording on each of the forward path and the backward path when main scanning is performed in both directions in a reciprocating manner. The dot recording apparatus according to claim 1 or 2 ,
The number N of dot forming elements used during one main scan (N is an integer of 3 or more) and the parameters Na, Nb, m, and L satisfy the following expressions (1) to (3). Dot recording device.
N = Na + Nb (1)
Na = m × k ± 1 (2)
Nb = Rd [L × Na ÷ k] (3)
Here, m is an integer of 1 or more, L is an integer satisfying 1 ≦ L <k, Nb is the number of the specific dot forming elements, and the operator Rd [] is the decimal part of the value in parentheses. Indicates the rounding operation. The dot recording apparatus according to claim 3 ,
The head driving unit is configured so that the dots recorded by the Nb dot forming elements and the dots recorded by the Na dot forming elements have a complementary positional relationship on each main scanning line. A dot recording device that drives a recording head. The dot recording apparatus according to claim 3 ,
The head driving unit drives the dot recording head so that dots recorded by Nb dot forming elements overlap dots recorded by Na dot forming elements on each main scanning line. Recording device. During a single main scan, dots of the same color can be recorded on a plurality of main scan lines, and a constant pitch k × P (k is an integer of 3 or more, P is the print medium) along the sub-scan direction. Using a dot recording head having a dot forming element array having a plurality of dot forming elements arranged at a minimum pitch in the sub-scanning direction of the upper dot, main scanning is performed along a direction substantially perpendicular to the sub-scanning direction. While in the method of recording dots on the surface of the print medium,
As the sub-scan feed, irregular sub-scan feed is repeatedly executed with k sub-scan feeds combining a plurality of different feed amounts as one cycle . At this time, the plurality of dots at the time when the sub-scan feed is not performed. When it is assumed that a periodic position along the sub-scanning direction of the forming element is a reference position where the offset is zero, the offset of the plurality of dot forming elements after each sub-scan feed in the one cycle is M × P. The irregular sub-scan feed is executed such that (M is an integer of 0 to (k-1)) and the average sub-scan feed amount is equal to the preset basic dot forming element number Na. And
Using Nb (Nb is an integer equal to (N-Na)) specific dot forming elements among N (N is an integer of 3 or more) dot forming elements used during one main scan. A dot recording method, wherein partial overlap recording is performed for each main scan, with dots on the main scan line to be recorded being recorded during another main scan. The dot recording method according to claim 6 , wherein
A dot recording method in which, when main scanning is performed in both directions in a reciprocating manner, dot recording is performed in each of the forward path and the backward path. The dot recording method according to claim 6 or 7 , wherein
The number N of dot forming elements used during one main scan (N is an integer of 3 or more) and the parameters Na, Nb, m, and L satisfy the following expressions (1) to (3). Dot recording method.
N = Na + Nb (1)
Na = m × k ± 1 (2)
Nb = Rd [L × Na ÷ k] (3)
Here, m is an integer of 1 or more, L is an integer satisfying 1 ≦ L <k, Nb is the number of the specific dot forming elements, and the operator Rd [] is the decimal part of the value in parentheses. Indicates the rounding operation. The dot recording method according to claim 8 , wherein
On each main scanning line, the dot recording head is driven so that the dots recorded by the Nb dot forming elements and the dots recorded by the Na dot forming elements have a complementary positional relationship. , Dot recording method. The dot recording method according to claim 8 , wherein
A dot recording method in which the dot recording head is driven so that dots recorded by Nb dot forming elements overlap dots recorded by Na dot forming elements on each main scanning line. During a single main scan, dots of the same color can be recorded on a plurality of main scan lines, and a constant pitch k × P (k is an integer of 3 or more, P is the print medium) along the sub-scan direction. A printing apparatus including a dot recording head having a dot formation element array including a plurality of dot formation elements arranged at a minimum pitch in the sub-scanning direction on the top, along a direction substantially perpendicular to the sub-scanning direction. A computer-readable recording medium recording a computer program for recording dots on the surface of a printing medium while performing main scanning,
Anomalous sub-scan feed is performed by repeatedly executing k sub-scan feeds combining a plurality of different feed amounts as one cycle, and at this time, the sub-scan of the plurality of dot forming elements at the time when the sub-scan feed is not performed. Assuming that a periodic position along the direction is a reference position where the offset is zero, the offset of the plurality of dot forming elements after each sub-scan feed in the one cycle is M × P (M is 0 to 0). (An integer of (k-1)) and a function of executing the irregular sub-scan feed so that the average sub-scan feed amount is equal to the preset basic dot forming element number Na ;
Using Nb (Nb is an integer equal to (N-Na)) specific dot forming elements among N (N is an integer of 3 or more) dot forming elements used during one main scan. A function of executing partial overlap recording for each main scan with dots on the main scan line to be recorded during other main scans being recorded;
The computer-readable recording medium which recorded the computer program for making a computer perform.

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