JP4342158B2 - LED drive system - Google Patents

Description

［式１］を行列の形で表現すると［式２］とすることができる。
【００４７】
【式２】

ここで必要となるのは出力となる階調データＲｒ、Ｇｒ、Ｂｒであるので、逆行列を掛けると［式３］とすることができる。
【００４８】
【式３】

このようにして求められた階調データＲｒ、Ｇｒ、Ｂｒを対応する各ＬＥＤに出力することにより、目標とする赤色のＣＩＥ三刺激値「Ｘ_０、Ｙ_０、Ｚ_０」に値を集束することができる。すなわち、ここでは、同一空間にＣＩＥ三刺激値が存在するので色度補正だけでなく輝度補正をも一括して行うことができる。
【００４９】
より詳細に説明すれば、初めの段階でΔＸＲ、ΔＹＲ、ΔＺＲ、ΔＸＧ、ΔＹＧ、ΔＺＧ、ΔＸＢ、ΔＹＢ、ΔＺＢをそれぞれ求める際、すなわち色調を一定とし階調データｒ毎の「Ｘｏ、Ｙｏ、Ｚｏ」を測定する際における階調データｒが入力となり、その入力に対する「Ｘｏ、Ｙｏ、Ｚｏ」が目標のＣＩＥ三刺激値となる。そして、そのＣＩＥ三刺激値を実現するために必要な赤色ＬＥＤ、緑色ＬＥＤおよび青色ＬＥＤそれぞれに対する出力が［式３］によって求められるのである。すなわち、階調データｒ毎の「Ｘｏ、Ｙｏ、Ｚｏ」を測定する際における階調データｒを入力、それから得られるＲｒ、Ｇｒ、Ｂｒを各ＬＥＤに対する出力とし、それぞれをプロットすることにより、関数３ｒ（Ｒ）、３ｒ（Ｇ）、３ｒ（Ｂ）を求めることができる。なおここでは、階調データｒに注目して関数３ｒ（Ｒ）、３ｒ（Ｇ）、３ｒ（Ｂ）について説明したが、関数３ｇ（Ｒ）、３ｇ（Ｇ）、３ｇ（Ｂ）、３ｂ（Ｒ）、３ｂ（Ｇ）、３ｂ（Ｂ）についても同様にして求めることができる。なお、目標とする色の「Ｘｏ、Ｙｏ、Ｚｏ」を測定する際には、画素毎、ＬＥＤユニット毎、あるはそれよりも大きな単位で任意に行うことができる。また、目標とする色の「Ｘｏ、Ｙｏ、Ｚｏ」を測定する、つまり上記所定の関数を求める際に各色のＬＥＤに流す駆動電流の大きさと、実際にＬＥＤを駆動する際に各色のＬＥＤに流す駆動電流の大きさをＬＥＤ毎に同一にすることにより、測定時と駆動時の間で色調の変化を伴わずに駆動させることができる。具体的には、例えば、赤色ＬＥＤ、緑色ＬＥＤ、青色ＬＥＤをそれぞれ測定し、該測定の結果に基づいて各々のＬＥＤに対する所定の関数を決定し、かつ測定時の駆動電流と同じ大きさの駆動電流を用いて各ＬＥＤを実際に駆動することができる。また、本件発明においては、後に説明するように、実際にＬＥＤを駆動させて得られる目的とする輝度の範囲を考慮して、測定時の電流の大きさを決定することもできる。なお、何色のＬＥＤを測定するか、その測定に基づいて何色のＬＥＤに対して階調データを変換するかは設定者側で任意に設定することができる。
【００５０】
また例えば、赤色のＣＩＥ三刺激値「Ｘ_ｏ、Ｙ_ｏ、Ｚ_ｏ」を測定する際は、本来赤色ＬＥＤに対応する赤色に関する階調データを利用して所定の輝度を得るために必要な駆動電流よりも大きな駆動電流を流して、赤色ＬＥＤ、緑色ＬＥＤまたは青色ＬＥＤの発光特性をそれぞれ測定することがこのましい。すなわち、駆動電流を大きくして各ＬＥＤを駆動することを考慮して測定することができる。以下に、階調データｒ、ｇ、ｂに基づく赤色ＬＥＤの発光を例にとって、その理由について説明する。
【００５１】
本実施の形態においては、赤色ＬＥＤに対する階調データに注目すると、階調データｒ、ｇ、ｂに基づいて赤色ＬＥＤに対する階調データＲｒ、Ｒｇ、Ｒｂが出力される。そして階調データＲｒ、Ｒｇ、Ｒｂは、後に記載するように階調データ加算部（階調データ加算工程）を備える場合、１つの階調データ「Ｒｒ＋Ｒｇ＋Ｒｂ」として赤色ＬＥＤに対して出力される。ここで、階調データ「Ｒｒ＋Ｒｇ＋Ｒｂ」は対応するメモリに一旦書き込まれ、それを読み出すことにより赤色ＬＥＤが発光するが、階調データ「Ｒｒ＋Ｒｇ＋Ｒｂ」が備えられたメモリに対して大きすぎる場合が生じる。
【００５２】
すなわち、所望の画像を得るには、ＬＥＤの明滅の繰り返し期間を短縮させ、画像の点灯が常時行われているように見せる（ヒュージョン）必要があるが、その影響で、階調データ制御のみでは、一定以上の輝度を得ることができない。もし、一定以上の輝度を得ようと一定時間以上の点灯を行えば、画像にフリッカーがはしることとなり、また、最悪の場合は、輝度が逆に落ちる場合もある。そのため、本発明の輝度補正および色調補正を考慮した点灯になるために必要な輝度を得ることができなくなる。
【００５３】
そこで、予め大きな駆動電流での使用を考慮しておき、測定時のその「大きな駆動電流」を実際に流して各ＬＥＤを発光させることで、色調の変化は伴わずにより短い階調データで所定の輝度を得ることができ、且つ画像のちらつきを伴うことなく輝度補正及び色調補正を行うことができる。尚、「大きな駆動電流」を流すことにより当然色調は変化するが、同じ大きさの駆動電流を流して測定を行うので当然補正後は所望の輝度及び色調を得る事ができる。すなわち、本件発明は、所定の関数を決定するためにＬＥＤの発光特性を測定する際に各色のＬＥＤそれぞれに流す駆動電流の大きさと、実際にＬＥＤを駆動する際に各色のＬＥＤに流す駆動電流の大きさを各色のＬＥＤそれぞれにおいて一定にすることにより、測定時と駆動時の間で色調の変化を伴わずに駆動させることができる。このため本件発明においては、実際にＬＥＤを駆動させて得られる目的とする輝度の範囲を考慮して、測定時の電流の大きさが決定されるのである。なお、ここでは、より大きな輝度を得ることを目的として、「大きな駆動電流」としたが、前に説明したように測定時の電流と駆動時の電流の大きさが同じであればよいのであって、例えば通常使用される電流値よりも小さい「小さな駆動電流」を用いて所定の関数を決定することもできる。なお、前に記載したように何色のＬＥＤを測定するか、その測定に基づいて何色のＬＥＤに対して階調データを変換するかは設定者側で任意に設定することができる。
【００５４】
図３は階調データ加算部４に注目して本実施の形態のＬＥＤ駆動システムを描いたブロック図である。図３に示すように本実施の形態においては、階調データ加算部４が第１の階調データ加算部４Ｒ、第２の階調データ加算部４Ｇ、第３の階調データ加算部４Ｂを備える。すなわち階調データ加算部４は、階調データ変換部３にて変換された新たな９つの階調データＲｒ、Ｇｒ、Ｂｒ、Ｒｇ、Ｇｇ、Ｂｇ、Ｒｂ、Ｇｂ、Ｂｂを、対応する赤色ＬＥＤ、緑色ＬＥＤ、青色ＬＥＤ毎に加算し１つの階調データとして各ＬＥＤに対して出力する。
【００５５】
具体的には、階調データ変換部３で変換された赤色ＬＥＤに対する３つの階調データＲｒ、Ｒｇ、Ｒｂが第１の階調データ加算部４Ｒにて加算され１つの階調データ「Ｒｒ＋Ｒｇ＋Ｒｂ」となる。同様に、階調データ変換部３で変換された緑色ＬＥＤに対する３つの階調データＧｒ、Ｇｇ、Ｇｂが第２の階調データ加算部４Ｇにて加算され１つの階調データ「Ｇｒ＋Ｇｇ＋Ｇｂ」となり、階調データ変換部３で変換された青色ＬＥＤに対する３つの階調データＢｒ、Ｂｇ、Ｂｂが第３の階調データ加算部４Ｂにて加算され１つの階調データ「Ｂｒ＋Ｂｇ＋Ｂｂ」となる。このように階調データ加算部４は、赤色ＬＥＤ、緑色ＬＥＤ、青色ＬＥＤそれぞれに対して、新たに生成した階調データ「Ｒｒ＋Ｒｇ＋Ｒｂ」、「Ｇｒ＋Ｇｇ＋Ｇｂ」、「Ｂｒ＋Ｂｇ＋Ｂｂ」を出力し、その階調データに基づいて赤色ＬＥＤ、緑色ＬＥＤ、青色ＬＥＤをそれぞれ発光させる。
【００５６】
なお本発明においては、第１の階調データ変換工程、第２の階調データ変換工程および第３の階調データ変換工程それぞれにおいて新たに出力される階調データを、赤色ＬＥＤ、緑色ＬＥＤおよび青色ＬＥＤ毎に加算してそれぞれ１つの階調データとする工程を階調データ加算工程と言う。すなわち、本実施の形態においては、各階調データ変換工程にて変換された赤色ＬＥＤに対する３つの階調データＲｒ、Ｒｇ、Ｒｂが第１の階調データ加算工程にて加算され１つの階調データ「Ｒｒ＋Ｒｇ＋Ｒｂ」となる。同様に、各階調データ変換工程にて変換された緑色ＬＥＤに対する３つの階調データＧｒ、Ｇｇ、Ｇｂが第２の階調データ加算工程にて加算され１つの階調データ「Ｇｒ＋Ｇｇ＋Ｇｂ」となり、階調データ変換工程にて変換された青色ＬＥＤに対する３つの階調データＢｒ、Ｂｇ、Ｂｂが第３の階調データ加算工程にて加算され１つの階調データ「Ｂｒ＋Ｂｇ＋Ｂｂ」となる。
【００５７】
図５は、加算された新たな階調データによる各ＬＥＤの発光期間の関係を説明するための模式的なタイムチャートである。ここでは所定の階調基準クロックを基準として、階調データ「Ｒｒ＋Ｒｇ＋Ｒｂ」により赤色ＬＥＤが期間ｗ（Ｒｒ＋Ｒｇ＋Ｒｂ）で発光し、階調データ「Ｇｒ＋Ｇｇ＋Ｇｂ」により緑色ＬＥＤが期間ｗ（Ｇｒ＋Ｇｇ＋Ｇｂ）で発光し、階調データ「Ｂｒ＋Ｂｇ＋Ｂｂ」により青色ＬＥＤが期間ｗ（Ｂｒ＋Ｂｇ＋Ｂｂ）で発光する一実施の形態について説明する。
【００５８】
なお、図５の各ＬＥＤに対応するタイムチャートそれぞれにおいては、横軸が時間的な流れを示し、縦軸が駆動電流の大きさを示す。本発明においては前に記載したように各ＬＥＤを発光させる際、ＬＥＤそれぞれにおける駆動電流の大きさは常に一定とする。ところで、例えばＲＧＢのＬＥＤそれぞれに所定の割合で駆動電流を供給し発光させ、その駆動電流の供給割合を維持したまま各ＬＥＤに供給される駆動電流の大きさを変化させると、駆動電流の供給割合が一定であるにも係わらず色調が変化してしまう。これは前に記載したように１つのＬＥＤにおいて駆動電流の大きさが変化すると色調もが変化してしまうためである。なお、駆動電流を一定とした場合、発光期間を増減させることにより色調は変化せず輝度のみを変化させることができる。本発明はこれらを考慮してなされたものであり、ＬＥＤを発光させる際に各色のＬＥＤそれぞれに供給される駆動電流の大きさは各色のＬＥＤ毎に常に一定とし階調データの長さのみを考慮することで、色調を一定としながらも輝度を任意に制御することができるというものである。
【００５９】
図５に示すように、赤色ＬＥＤに対する３つの階調データが加算された新たな階調データ「Ｒｒ＋Ｒｇ＋Ｒｂ」により赤色ＬＥＤが発光する期間ｗ（Ｒｒ＋Ｒｇ＋Ｒｂ）に注目すると、期間ｗ（Ｒｒ＋Ｒｇ＋Ｒｂ）は実質的に、階調データＲｒによる発光期間ｗ（Ｒｒ）と階調データＲｇによる発光期間ｗ（Ｒｇ）と階調データＲｂによる発光期間ｗ（Ｒｂ）に分割して考えることができる。すなわち、本発明においては各色のＬＥＤ毎に駆動電流を一定の大きさとし且つ階調データ変換部３にて各ＬＥＤの発光期間を決定する階調データのみを変化させているので、階調データの加算は発光期間の加算となり、換言すれば輝度の加算と同様の意味を持つ。
【００６０】
同様に、緑色ＬＥＤに対する階調データ「Ｇｒ＋Ｇｇ＋Ｇｂ」により緑色ＬＥＤが発光する期間ｗ（Ｇｒ＋Ｇｇ＋Ｇｂ）に注目すると、期間ｗ（Ｇｒ＋Ｇｇ＋Ｇｂ）は実質的に、階調データＧｒによる発光期間ｗ（Ｇｒ）と階調データＧｇによる発光期間ｗ（Ｇｇ）と階調データＧｂによる発光期間ｗ（Ｇｂ）に分割して考えることができる。また、青色ＬＥＤに対する階調データ「Ｂｒ＋Ｂｇ＋Ｂｂ」により青色ＬＥＤが発光する期間ｗ（Ｂｒ＋Ｂｇ＋Ｂｂ）に注目すると、期間ｗ（Ｂｒ＋Ｂｇ＋Ｂｂ）は実質的に、階調データＢｒによる発光期間ｗ（Ｂｒ）と階調データＢｇによる発光期間ｗ（Ｂｇ）と階調データＢｂによる発光期間ｗ（Ｂｂ）に分割して考えることができる。なお、図５に示すタイムチャートは説明を容易にするためにＬＥＤ毎に３つの発光期間に分割したものであって、実際には各ＬＥＤの発光期間において境目は存在しない。
【００６１】
ここで、図５に示す階調データ「Ｒｒ＋Ｒｇ＋Ｒｂ」に基づく赤色ＬＥＤの発光期間と、階調データ「Ｇｒ＋Ｇｇ＋Ｇｂ」に基づく緑色ＬＥＤの発光期間と、階調データ「Ｂｒ＋Ｂｇ＋Ｂｂ」に基づく青色ＬＥＤの発光期間に注目すると、発光期間が最も長い赤色ＬＥＤの発光期間内に、緑色ＬＥＤの発光期間および青色ＬＥＤの発光期間が含まれることが好ましい。すなわち、発光期間が最も長いＬＥＤの発光と他のＬＥＤの発光が時間的に重複していることが好ましい。これにより、色のちらつき（以下、「色フリッカー」ともいう）の発生を効果的に軽減することができる。なお図５においては、各ＬＥＤの発光が同時に開始される例について説明したが、各発光を時間差で開始することもできる。
【００６２】
また、本実施の形態においては、色フリッカーを最大に軽減するために発光期間が最も長いＬＥＤの発光期間内に、他の２つのＬＥＤの発光期間が含まれる例について説明したが、もちろん、発光期間が最も長いＬＥＤの発光期間内に他の２つのＬＥＤの発光期間が含まれる場合に比較して色フリッカー軽減の効果は多少落ちるが、他の１つのＬＥＤの発光期間のみを含むようにしてもよい。
【００６３】
また、階調データ加算部４にて各ＬＥＤに対する階調データが加算されずに、階調データｒ、ｇ、ｂそれぞれに基づく各ＬＥＤの発光が個々に行われる場合も同様に、発光期間が最も長いＬＥＤの発光期間内に、補正用の他のＬＥＤの発光期間が含まれることが好ましい。例えば図２において階調データ加算部３が備えられておらず、階調データ変換部３で変換された各階調データが赤色ＬＥＤ、緑色ＬＥＤ、青色ＬＥＤにそのまま入力される例について考える。すなわち、階調データｒに基づく各ＬＥＤの発光においては、階調データＲｒに基づいて赤色ＬＥＤが発光している期間内に、階調データＧｒに基づく緑色ＬＥＤの発光と階調データＢｒに基づく青色ＬＥＤの発光が行われるように制御することが好ましい。同様に、階調データｇに基づく各ＬＥＤの発光においては、階調データＧｇに基づいて緑色ＬＥＤが発光している期間内に、階調データＢｇに基づく青色ＬＥＤの発光と階調データＲｇに基づく赤色ＬＥＤの発光が行われるように制御し、階調データｂに基づく各ＬＥＤの発光においては、階調データＢｂに基づいて青色ＬＥＤが発光している期間内に、階調データＲｂに基づく赤色ＬＥＤの発光と階調データＧｂに基づく緑色ＬＥＤの発光が行われるように制御することが好ましい。これにより、階調データ加算部４にて各階調データを加算せずに単色で発光させる場合においても、色フリッカーを容易に軽減することができる。
【００６４】
また、ここでは倍速表示について言及しなかったが、もちろん画像のちらつきを軽減するために倍速表示を行ってもよい。すなわち、１ＶＳＹＮＣ期間を複数に分割し、その分割期間毎に同じ画像を表示することにより、画像のちらつきを効果的に軽減することができる。本発明を倍速表示に適応させる場合は、分割期間毎に、本来１色のＬＥＤで発光させるべき色に関する階調データに基づき主に発光するＬＥＤとそのＬＥＤの発光を補正するためのＬＥＤの発光が分割期間内に行われる。これにより、画像のちらつきだけでなく色フリッカーの発生も効果的に軽減することができる。さらに、同じ画像を表示する分割期間毎に、階調データ（輝度）を増減させることもできる。このように構成することにより、見かけ上の階調（グレースケール）を増やすことができる。
【００６５】
また、本実施の形態においては、データ供給部２が階調データ変換部３および階調データ加算部４を備える構成について説明したが、本発明はこれに限定されない。つまり、階調データ変換部３および階調データ加算部４はデータ供給部１またはＬＥＤユニット５が具備することもできる。また、例えばデータ供給部２が階調データ変換部３を備え、ＬＥＤユニットが階調データ加算部４を備えることもできる。すなわち、階調データ変換部３と階調データ加算部４を分離して構成することもできる。さらに、本発明のＬＥＤ駆動システムにおいて分配器であるＴＡは必ずしも必要なく、ＣＵからＤＵにデータを直接入力することもできる。この場合、ＣＵが本発明のデータ供給部に対応することになる。
【００６６】
また、本実施の形態においては、通信ラインＬ２を上位の通信ラインとし、通信ラインＬ１を下位の通信ラインとした２階層から構成される接続としたが、通信ラインの階層は３以上の複数階層から構成してもよい。この場合、階層に応じたＴＡが配置される。また、ＴＡおよびＤＵの数、ＴＡおよびＤＵの接続形態はこれに限定されないことは言うまでもない。すなわち、図１に示すように本実施の形態においては、ＴＡがＺ字状に配置され各ＴＡにおいてＤＵがＺ字状に配置された構成となるが本発明はこれに限定されず、例えば各ＴＡが一直線に配列され各ＴＡにおいてＤＵがＴＡの配列方向と異なる方向に（例えばＴＡの配列方向とＤＵの配列方向が垂直になるように）一直線に配列させてもよい。
【００６７】
また、本実施の形態においては、第１の色に発光する第１のＬＥＤ、第２の色に発光する第２のＬＥＤ、第３の色に発光する第３のＬＥＤからなる計３種のＬＥＤがＬＥＤユニット５に配置された構成について説明したが、本発明はこれに限定されない。すなわち、本発明のＬＥＤ駆動システムは、異なる色に発光する２種以上のＬＥＤが存在していればよく、例えば、第１の色に発光する第１のＬＥＤと第２の色に発光する第２のＬＥＤからなる計２種のＬＥＤ、あるいは計４種以上のＬＥＤがＬＥＤユニットに配置されていてもよい。この場合、異なる色を発光するＬＥＤの数を考慮して、階調データ変換部および階調データ加算部がそれぞれ構成されることになる。
【００６８】
また、ここでは、本来一種のＬＥＤで発光させるべき階調データに対して複数色の各ＬＥＤがそれぞれ一種の関数を有する構成としたが、複数色のＬＥＤそれぞれにおいて予め複数の大きさの駆動電流を用いて所定の関数を設定し、それぞれの大きさの駆動電流に対する関数を複数に設定することもできる。これにより、例えば、比較的大きな駆動電流を用いて各関数を決定することにより昼間用の比較的大きな輝度を容易に確保できると共に、比較的小さな駆動電流を用いて各関数を決定することにより夜間用の比較的小さな輝度を色フリッカーを伴うことなく確保することができる。いずれの場合も、複数色のＬＥＤそれぞれにおいて、測定時の駆動電流の大きさと駆動時の駆動電流の大きさを同じにすることにより、色調の変化を伴うことなく各ＬＥＤを発光させることができる
【発明の効果】
【００６９】
これまで説明したように、本発明によれば輝度補正および色調補正を一括して行うことができる。すなわち、一般には、本来１色のＬＥＤに対応させるべき階調データに基づく発光において、輝度が調整でき且つ色調が常に一定に保たれることが好ましい。しかしながら、ＬＥＤによって輝度および色度のバラツキが存在すること、駆動電流の大きさを変化させると色調までもが変化してしまうことを考慮すると、色調を一定に保ちつつ輝度を任意に調整することは容易ではない。
【００７０】
しかしながら、本発明のＬＥＤ駆動システムおよびその制御方法によれば、実際に各ＬＥＤを発光させる際に駆動電流を常に一定の大きさとし且つ各ＬＥＤに対する階調データを利用するという比較的簡単な構成にも拘わらず、輝度補正と色調補正を両立せさせて同時に効率よく行うことが可能となる。
【図面の簡単な説明】
【００７１】
【図１】 本実施の形態のＬＥＤ駆動システムの構成を示す概略図である。
【図２】 図１に示すＬＥＤ駆動システムの階調データ変換部に注目した概略図である。
【図３】 図１に示すＬＥＤ駆動システムの階調データ加算部に注目した概略図である。
【図４】 本実施の形態のＬＥＤ駆動システムの階調データ変換部に記憶された関数をしめす模式図である。
【図５】 本実施の形態における各ＬＥＤの発光期間を示す模式図である。
【図６】 ＬＥＤに駆動電流が供給される状態を説明するための概略図である。
【符号の説明】
【００７２】
１…データ制御部、２…データ供給部、３…階調データ変換部、３ｒ…第１の階調データ変換手段、３ｇ…第２の階調データ変換手段、３ｂ…第３の階調データ変換手段、４…階調データ加算部、４Ｒ…第１の階調データ加算手段、４Ｇ…第２の階調データ加算手段、４Ｂ…第３の階調データ加算手段、５…ＬＥＤユニット、１０…ディスプレイ、１１…ＴＡブロック、２０…ＬＥＤ、２１…共通ライン、２２…電流ライン、Ｌ１、Ｌ２…通信ライン。BACKGROUND OF THE INVENTION
[0001]
The present invention includes an LED unit including a plurality of LEDs that can emit different colors, and a data supply unit that supplies gradation data that determines at least the light emission period of each LED to each LED arranged in the LED unit. More particularly, the present invention relates to an LED drive system and a control method thereof capable of performing luminance correction and color tone correction collectively according to variations in light emission characteristics of LEDs.
[Prior art]
[0002]
Today, as light emitting elements capable of emitting light with high brightness such as LEDs (hereinafter also referred to as “light emitting diodes”) have been developed for each of RGB (red, green, blue), large self-luminous type Full color displays are being made. Above all, full-color displays using LEDs as light-emitting elements have features such as light weight, thinness and low power consumption, and the demand for large-sized displays that can be used not only indoors but also outdoors increases rapidly. Yes.
[0003]
For example, in the case of a large display installed outdoors, one display is generally configured by combining a plurality of LED units. In other words, the LED unit includes, for example, a set of RGB LEDs arranged on the substrate for each pixel, and each LED unit displays an image assigned to it. In a full color display using LEDs as light emitting elements, each pixel is generally composed of a combination of three or more types of LEDs capable of emitting light in RGB.
[0004]
In addition, as a driving method of the LED unit, a dynamic driving method is usually used. For example, in the case of an LED display in which pixels are arranged in m rows and n columns as shown in FIG. 6, the anode terminals of the LEDs 20 located in each row are connected in common to one common line 21, and the LEDs 20 located in each column The cathode terminal is commonly connected to one current line 22. In this way, the m common lines 21 are sequentially turned on at a predetermined cycle, and a drive current is supplied to the n columns of current lines 22 in accordance with data corresponding to the common lines that have been turned on. As a result, a drive current corresponding to the data is applied to the LED 20 of each pixel (corresponding to an arrow in the figure), and an image is displayed.
[0005]
Here, in order for the data to be accurately reproduced on the LED display, it is necessary that the light emission characteristics (luminance, color tone, etc.) of each LED are uniform. If the light emission characteristics are not uniform, even if the LEDs are caused to emit light under the same conditions, the light emission characteristics vary from LED to LED, and a desired color cannot be obtained using a single color or a mixed color. However, LEDs are formed on a wafer by semiconductor technology, and variations in brightness and color tone occur depending on the production lot, wafer or chip. For this reason, it is necessary to arbitrarily adjust the driving conditions in accordance with variations in the light emission characteristics of the respective LEDs constituting each pixel.
[0006]
For example, conventional brightness variation correction (hereinafter also referred to as “brightness correction”) is performed by increasing or decreasing the drive current in accordance with the brightness variation of each LED. In other words, by adjusting the magnitude of the drive current supplied to each LED, correction has been made so that the same luminance can be obtained even with different LEDs having variations in luminance.
[0007]
In addition, the conventional color tone variation correction (hereinafter, also referred to as “color tone correction”), for example, turns on LEDs of other colors using a correction drive current in accordance with the color tone variation of each LED. It was realized by. Specifically, in accordance with the color tone variation of each LED, drive currents of different magnitudes are supplied to the LED that mainly emits light and the correction LED that corrects light emission by the LED. As a result, the same color tone can be obtained as a whole even with different LEDs having different color tones.
[Problems to be solved by the invention]
[0008]
However, in the conventional luminance correction or color tone correction, it is very difficult to accurately reproduce input information on the LED unit.
[0009]
That is, in the conventional luminance correction, although correction for luminance can be performed, correction for color tone cannot be performed. Specifically, since the color tone of the LED changes depending on the magnitude of the drive current, the color tone is completely controlled even though the luminance can be controlled by adjusting the magnitude of the drive current. There was a problem that it was difficult.
[0010]
Also, in the conventional color tone correction, the mainstream is not correcting the color tone variation of the LED but emphasizing the color reproducibility of the LED display. In addition, due to the characteristics of the LED, by performing luminance correction using current, the emission color change of the LED itself occurs, and it is impossible to perform accurate color correction.
[0011]
The present invention has been made in view of such problems, and by performing luminance correction and color correction at the same time regardless of variations in luminance and color tone for each LED, the luminance can be maintained while keeping the color tone constant. An object of the present invention is to provide an LED drive system that can be controlled and a control method thereof.
[Means for Solving the Problems]
[0012]
The LED drive system according to the present invention includes an LED unit in which at least a first LED that emits light in a first color and a second LED that emits light in a second color are arranged for each pixel, and the LED unit connected to the LED unit. In an LED drive system comprising: a data supply unit that supplies gradation data for determining at least the light emission period of each LED to each of the first LED and the second LED; The data supply unit includes a gradation data conversion unit connected to the data control unit, and a gradation data addition unit connected to the gradation data conversion unit and the LED unit. The gradation data converter is Data control unit Based on the first function, the gradation data relating to the color that should be emitted from the first LED, which is supplied from the above, is corrected based on the first function, and the light emission by the first LED is corrected. Gradation data for the second LED for When Conversion to And output to the gradation data adder First gradation data converting means for Data control unit The gradation data relating to the color that should be emitted from the second LED originally supplied from the second LED is corrected based on the second function, and the gradation data for the second LED and the light emission by the second LED are corrected. Gradation data for the first LED for When Conversion to And output to the gradation data adder Second gradation data conversion means.
[0013]
Further, the gradation data conversion unit has a third function and a fourth function obtained by a drive current having a magnitude different from that of the drive current passed when obtaining the first and second functions. And above Data control unit The gradation data relating to the color to be emitted by the first LED, which is originally supplied from the first LED, is corrected based on the third function, the gradation data for the first LED and the light emission by the first LED. Gradation data for the second LED to When Conversion to And output to the gradation data adder A third gradation data converting means, and Data control unit The gradation data relating to the color to be emitted by the second LED originally supplied from the second LED is corrected based on the fourth function, and the gradation data for the second LED and the light emission by the second LED are corrected. Gradation data for the first LED to When Conversion to And output to the gradation data adder And a fourth gradation data converting means. The gradation data adding unit converts the gradation data relating to the color originally emitted from the first LED supplied from the data control unit based on the first or third function. The second LED obtained by converting the gradation data for the LED and the gradation data relating to the color to be emitted by the second LED originally supplied from the data control unit based on the second or fourth function. The first gradation data adding means for adding the gradation data for the first LED for correcting the light emission due to the light and outputting the result to the LED unit; and the second gradation data originally supplied from the data control section The gradation data relating to the color to be emitted by the LED is converted based on the second or fourth function, the gradation data for the second LED, and the original first supplied from the data control unit. The gradation data on the color to be emitted by the LED is converted based on the first or third function, and the gradation data for the second LED for correcting the light emission by the first LED is added. Second gradation data adding means for outputting to the LED unit. When obtaining the first to fourth functions, the magnitude of the drive current passed through the first LED and the second LED, and when driving the LED unit, the first LED and the second LED. The magnitudes of the drive currents flowing through are the same.
[0014]
In the LED driving system of the present invention, at least a first LED that emits light in the first color, a second LED that emits light in the second color, and a third LED that emits light in the third color are provided for each pixel. And a data supply unit that supplies gradation data that determines at least the light emission period of each LED to each of the first LED, the second LED, and the third LED connected to the LED unit. Prepare. In particular, the LED drive system further includes a gradation data conversion unit connected to the LED unit and the data supply unit, and the gradation data conversion unit is originally the first LED supplied from the data supply unit. The gradation data relating to the color to be emitted is based on the first function, the gradation data for the first LED, the gradation data for the second LED for correcting the light emission by the first LED, and the first First gradation data conversion means for converting to gradation data for the third LED for correcting light emission by the LED, and gradation data relating to a color to be emitted by the second LED originally supplied from the data supply unit On the basis of the second function, the gradation data for the second LED, the gradation data for the first LED for correcting light emission by the second LED, and the second LED. Second gradation data conversion means for converting to gradation data for the third LED for correcting light emission, and gradation data relating to the color to be emitted by the third LED originally supplied from the data supply unit, Based on the third function, the gradation data for the third LED, the gradation data for the first LED for correcting the light emission by the third LED, and the second for correcting the light emission by the third LED. And at least one gradation data conversion means selected from the third gradation data conversion means for converting to gradation data for the LED of the LED, and the first to third functions are obtained when the first to third functions are obtained. The driving current flowing through the first to third LEDs is the same as the driving current flowing through the first to third LEDs when the LED unit is driven.
[0015]
In addition, the LED drive system of the present invention can have a gradation data conversion section and a gradation data addition section connected to the previous LED unit. In this gradation data addition unit, the gradation data conversion unit includes a first gradation data conversion unit, a second gradation data conversion unit, and a third gradation data conversion unit, and is originally a first LED. At least one of light emission based on gradation data relating to a color to be emitted, light emission based on gradation data relating to a color to be originally emitted by the second LED, and light emission based on gradation data relating to a color that should be originally emitted by the third LED When color mixing is performed for each pixel using two light emission, the gradation data for the first LED converted by the first gradation data conversion means and the first gradation data converted by the second gradation data conversion means. First gradation data adding means for adding the gradation data for the first LED and the gradation data for the first LED converted by the third gradation data converting means into one gradation data; 1 gradation The gradation data for the second LED converted by the data conversion means, the gradation data for the second LED converted by the second gradation data conversion means, and the conversion by the third gradation data conversion means The second gradation data adding means for adding the gradation data for the second LED to be one gradation data, and the level for the third LED converted by the first gradation data conversion means. The tone data and the gradation data for the third LED converted by the second gradation data conversion means are added to the gradation data for the third LED converted by the third gradation data conversion means. It is characterized by comprising at least one of third gradation data adding means for making one gradation data.
[0016]
Further, in the light emission of each LED based on the gradation data for each LED added by each gradation data adding means, the light emission period of the other LED is included in the light emission period of the LED having the longest light emission period. Features. Thereby, the flicker of the color by the shift | offset | difference of the light emission period of each LED can be reduced significantly.
[0017]
Each gradation data converting means inputs gradation data inputted to itself when converting gradation data inputted to itself into gradation data for a predetermined LED and gradation data for the LED for correcting light emission by the predetermined LED. And using the input grayscale data as a common input, a new grayscale for each LED based on the input and a predetermined function corresponding to each of the first LED, the second LED, and the third LED. It is characterized by outputting data. Thereby, the gradation data input to itself can be efficiently converted into new gradation data.
[0018]
The predetermined function is non-linear. As a result, other corrections such as gamma correction can be performed collectively.
[0019]
The first LED, the second LED, and the third LED are respectively a red LED that emits red light, a green LED that emits green light, and a blue LED that emits blue light. Thereby, it can be set as the LED drive system in which full color light emission is possible.
[0020]
The LED driving system control method according to the present invention is such that each LED emits light for each of a red LED that emits red light, a green LED that emits green light, and a blue LED that emits blue light. In this control method, gradation data for determining a period is supplied, and each LED emits light based on the gradation data. In particular, the control method of this LED drive system corrects the gradation data related to the red light that should be emitted by the red LED, based on the first function, and the gradation data for the red LED that mainly emits light and the light emission by the red LED. First gradation data conversion step for converting the gradation data for the green LED and the gradation data for the blue LED for correcting the light emission by the red LED, and the gradation data regarding the green color originally to be emitted by the green LED Based on the second function, the gradation data for the green LED that mainly emits light, the gradation data for the blue LED for correcting the light emission by the green LED, and the level for the red LED for correcting the light emission by the green LED. A second gradation data conversion step for converting to gradation data, and a gradation data for blue that should originally be emitted by the blue LED. Based on the third function, the gradation data for the blue LED that mainly emits light, the gradation data for the red LED for correcting light emission by the blue LED, and the green LED for correcting light emission by the blue LED A third gradation data conversion step for converting to gradation data, and at least one gradation data conversion step selected from the above, and when driving the LED unit, the red LED, the green LED, and the above The magnitude of the drive current that flows through the blue LED is the same as the magnitude of the drive current that flows through the red LED, the green LED, and the blue LED when obtaining the first to third functions. .
[0021]
The LED driving system control method of the present invention includes a first gradation data conversion step, a second gradation data conversion step, and a third gradation data conversion step, and is based on the gradation data relating to red. The red color converted in the first gradation data conversion step when at least two of the light emission based on the light emission and green gradation data and the light emission based on the blue gradation data are mixed for each pixel. The gradation data for the LED, the gradation data for the red LED converted in the second gradation data conversion process, and the gradation data for the red LED converted in the third gradation data conversion process are added to 1 Converted into grayscale data for the green LED converted in the first grayscale data conversion step and the second grayscale data conversion step. A second gradation data addition step of adding the gradation data for the green LED and the gradation data for the green LED converted in the third gradation data conversion step into one gradation data; The gradation data for the blue LED converted in the gradation data conversion process of the above, the gradation data for the blue LED converted in the second gradation data conversion process, and the conversion in the third gradation data conversion process It is characterized in that it includes at least one of the third gradation data addition steps to add gradation data for the blue LED thus obtained to form one gradation data. Thereby, the configuration of the control method can be further simplified, and gradation data can be easily controlled.
[0022]
Further, the light emission of the red LED based on the gradation data for the red LED added in the first gradation data addition step and the green color based on the gradation data for the green LED added in the second gradation data addition step. In the light emission of the blue LED based on the gradation data for the blue LED added in the light emission of the LED and the third gradation data addition step, the light emission period of the other LED is within the light emission period of the LED having the longest light emission period. It is controlled to be included. Thereby, the flicker of the color by the shift | offset | difference of the light emission period of each LED can be reduced significantly.
[0023]
Further, in each gradation data conversion step, the gradation data input to itself is converted into gradation data for a predetermined LED and gradation data for the LED for correcting light emission by the predetermined LED. To output new gradation data to each LED based on the input and a predetermined function corresponding to each of the red LED, green LED and blue LED. Features. Thereby, the gradation data input to itself can be efficiently converted into new gradation data.
[0024]
The predetermined function is non-linear. As a result, other corrections such as gamma correction can be performed collectively.
[0025]
In addition, by using each gradation data regarding red, green and blue, a driving current larger than a driving current necessary for obtaining a predetermined luminance is supplied, and the light emission characteristics of the red LED, green LED or blue LED are respectively measured. A predetermined function corresponding to each LED is determined based on the measurement result. Thereby, a desired luminance can be obtained without making the gradation data longer than necessary.
DETAILED DESCRIPTION OF THE INVENTION
[0026]
Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the embodiment described below is for embodying the technical idea of the present invention, and the present invention is not limited to the following. In addition, the size and positional relationship of components shown in each drawing are exaggerated for clarity of explanation.
[0027]
FIG. 1 shows a configuration example of an LED drive system according to the present invention. In the LED driving system according to the present embodiment, at least a first LED that emits light in the first color, a second LED that emits light in the second color, and a third LED that emits light in the third color are provided for each pixel. The arranged LED unit 5 (hereinafter also referred to as “DU (Display Unit)”) and a data supply unit 2 connected to the LED unit 5 and supplying gradation data for determining at least the light emission period of each LED. (Hereinafter also referred to as “TA (Terminal Adapter)”) includes a gradation data conversion unit 3 connected to the LED unit 5 and the data supply unit 2. Here, a red LED that emits red light as the first LED, a green LED that emits green light as the second LED, and a blue LED that emits blue light as the third LED are used, and each pixel has RGB (red, An example composed of green and blue LEDs will be described.
[0028]
As shown in FIG. 1, the LED drive system of the present embodiment includes a data control unit 1 (hereinafter also referred to as “CU (Control Unit)”). The data control unit 1 supplies control data and gradation data for driving LEDs input from the outside to each LED unit 2 via the data supply unit 2. In this specification, the control data is various data for controlling and driving each LED. For example, vertical synchronization data (hereinafter also referred to as “VSYNC”) indicating the start and end of one image frame, Horizontal synchronization data (hereinafter also referred to as “HSYNC”) indicating a separation for each line, a gradation reference clock (hereinafter also referred to as “GCLOCK”) indicating a reference of gradation, and the like. This is data for determining the light emission period of each LED based on the clock.
[0029]
Further, the LED drive system of the present embodiment includes a gradation data addition unit 4 as will be described later, and the gradation data addition unit 4 is connected to the gradation data conversion unit 3 and the LED unit 5. That is, the LED drive system of the present embodiment has a configuration in which the data control unit 1, the data supply unit 2, the gradation data conversion unit 3, the gradation data addition unit 4, and the LED unit 5 are sequentially connected. Here, in the LED drive system of the present embodiment, the data supply unit 2 includes a gradation data conversion unit 3 and a gradation data addition unit 4.
[0030]
As shown in FIG. 1, in the LED drive system of the present embodiment, a plurality of data supply units 2 are connected to a data control unit 1 via a communication line L <b> 2, and a plurality of LED units 1 are provided for each data supply unit 2. They are connected via a communication line L1. That is, in this embodiment, the TA that serves as the data supply unit 2 has a function as a distributor that distributes the data input from the CU that serves as the data control unit 1 to each of a plurality of DUs connected to itself. With this configuration, a larger display 10 can be formed. Further, in FIG. 1, in order to simplify the description, the data control unit 1 is expressed as CU, the data supply unit 2 is expressed as TA, and the LED unit 5 is expressed as DU. Here, in order to perform smoother communication, the communication in the communication line L2 is preferably performed at a higher speed than the communication in the communication line L1.
[0031]
On the other hand, reference numeral 10 denotes an entire display that performs display based on control data and gradation data, and the display 10 is divided into a plurality of TA blocks 11. That is, one TA is arranged in each TA block 11, and in this embodiment, the display 10 is composed of 24 TA blocks 11 in which TA1 to TA24 are arranged. Furthermore, each TA block 11 is composed of a plurality of DUs, and in this embodiment, each TA block 11 is composed of 12 DUs (DU1 to DU12). That is, in the present embodiment, the display 10 is composed of 288 DUs in total of 24 × 12.
[0032]
Here, in the LED drive system and the control method thereof according to the present invention, the gradation data that should originally correspond to one color LED in the gradation data conversion unit 3 or the gradation data conversion step described later is assigned to a plurality of LEDs. It is characterized by converting into key data. When the gradation data that should originally correspond to one color LED is converted into gradation data for a plurality of color LEDs, and each corresponding LED is driven based on this new gradation data, The magnitude of the drive current supplied to the LEDs is always equal at least for each color LED. That is, the luminance is determined by the magnitude of the drive current and the length of the light emission period, but in the present invention, the drive supplied to the LED corresponding to each new gradation data converted by the gradation data conversion unit 3. The present invention is characterized in that the brightness is arbitrarily controlled as a whole by the new gradation data converted by the gradation data conversion unit 3 while the magnitude of the current is constant. In other words, the luminance can be arbitrarily adjusted while keeping the color tone constant by adjusting the light emission period of each LED based on the gradation data without changing the magnitude of the drive current. In addition, the magnitude | size of each drive current supplied to LED of each color should just be determined in consideration of the target predetermined color (for example, white).
[0033]
In the present specification, “gradation data that should originally correspond to one color LED” means “gradation data that has not been subjected to luminance correction and color tone correction considering the light emission characteristics of the LED to a degree that can be substantially satisfied. ". That is, in the present invention, even when at least one of the luminance correction and the color tone correction is performed by a known method, if it is necessary to substantially perform further correction, the gradation data is updated to a new one. By converting into other gradation data, more excellent luminance correction and color tone correction can be performed.
[0034]
Hereinafter, the flow of control data and gradation data will be described in more detail with reference to FIGS. First, for example, control data is input to the data control unit 1 from a computer such as a PC, and gradation data is input from a video reproduction device such as a video player. In this specification, as shown in FIGS. 2 and 3, gradation data relating to red that should be emitted by the red LED is “r”, and gradation data relating to green that should originally be emitted from the green LED is “g”. The gradation data relating to blue that should be emitted by the blue LED is expressed as “b”. That is, the gradation data r, g, and b mean gradation data of each color that is directly input from the CU to the TA and is not corrected.
[0035]
On the other hand, as described above, the LED driving system according to the present embodiment includes the data control unit 1, the data supply unit 2, the gradation data conversion unit 3, the gradation data addition unit 4, and the LED unit 5 sequentially connected. Yes. FIG. 2 is a block diagram depicting the LED driving system of the present embodiment, paying attention to the gradation data conversion unit 3. As shown in FIG. 2, in the present embodiment, the gradation data conversion unit 3 includes the first gradation data conversion means 3r, the second gradation data conversion means 3g, and the third gradation data conversion means 3b. Prepare.
[0036]
That is, the gradation data r input to the first gradation data conversion means 3r is converted into gradation data represented by “Rr”, “Gr”, and “Br”, respectively. Here, Rr is gradation data for the red LED, Gr is gradation data for the green LED for correcting light emission of the red LED based on Rr, and Br is for correcting light emission of the red LED based on Rr. It refers to gradation data for blue LEDs. Similarly, the gradation data g input to the second gradation data conversion means 3g is converted into gradation data represented by “Gg”, “Bg”, and “Rg”, respectively. Here, Gg is the gradation data for the green LED, Gb is the gradation data for the blue LED for correcting light emission of the green LED based on Gg, and Gr is for correcting the light emission of the green LED based on Gg. This refers to the gradation data for the red LED. Similarly, the gradation data b input to the third gradation data conversion means 3b is converted into gradation data represented by “Bb”, “Rb”, and “Gb”, respectively. Here, Bb is gradation data for the blue LED, Rb is gradation data for the red LED for correcting the light emission of the blue LED based on Bb, and Gb is for correcting the light emission of the blue LED based on Bb. It refers to the gradation data for the green LED.
[0037]
In the present invention, the step of converting gradation data that should originally correspond to one color LED into gradation data for a plurality of LEDs is called a gradation data conversion step. Specifically, the gradation data conversion step in the method for controlling the LED driving system of the present embodiment includes a first gradation data conversion step, a second gradation data conversion step, and a third gradation data conversion step. Including. That is, in the first gradation data conversion step, the gradation data r is converted into gradation data represented by “Rr”, “Gr”, and “Br”, respectively. Similarly, in the second gradation data conversion step, the gradation data g is converted into the gradation data represented by “Gg”, “Bg”, and “Rg”, respectively, and the third gradation data conversion step. Then, the gradation data b is converted into gradation data represented by “Bb”, “Rb”, and “Gb”, respectively.
[0038]
Further, when the gradation data r, g, b is converted by the gradation data conversion unit 3, respectively, based on the input gradation data r, g, b and a predetermined function provided in advance. Thus, gradation data for each LED is output. That is, a predetermined function is stored in advance in the gradation data conversion unit 3, and an output as new gradation data is determined by associating the function with the input of gradation data. This will be explained in more detail below.
[0039]
FIG. 4 is a schematic diagram for explaining the gradation data conversion unit 3 of the present embodiment in more detail. As shown in FIG. 4, in this embodiment, the gradation data conversion unit 3 includes a first gradation data conversion unit 3r, a second gradation data conversion unit 3g, and a third gradation data conversion unit 3b. In each of the means, a total of three functions corresponding to the red LED, the green LED, and the blue LED are stored. That is, the first gradation data conversion means 3r corresponds to the function 3r (R) corresponding to the red LED, the function 3r (G) corresponding to the green LED, and the blue LED having the gradation data r as a common input. The function 3r (B) is stored in advance. Similarly, the second gradation data conversion means 3g corresponds to the function 3g (R) corresponding to the red LED, the function 3g (G) corresponding to the green LED, and the blue LED having the gradation data g as a common input. Function 3g (B) is stored in advance, and the third gradation data conversion means 3b corresponds to the function 3b (R) corresponding to the red LED having the gradation data b as a common input, and corresponding to the green LED. Function 3b (G) and function 3b (B) corresponding to the blue LED are stored in advance. In each function shown in FIG. 4, the horizontal axis corresponds to the input of gradation data r, g, and b (corresponding to “IN” in the figure), and the vertical axis represents the output of gradation data for each LED (in the figure). Corresponds to “OUT”).
[0040]
Here, paying attention to the first gradation data converting means 3r, the gradation data r relating to red is inputted in common to each of the functions 3r (R), 3r (G), 3r (B) provided in itself, New gradation data is output by the function of. That is, the function 3r (R) outputs new gradation data Rr for the red LED based on the gradation data r input to itself. Similarly, the function 3r (G) outputs new gradation data Gr for the green LED based on the gradation data r input to itself, and the function 3r (B) converts the gradation data r input to itself to the gradation data r. Based on this, new gradation data Br for the blue LED is output.
[0041]
Next, paying attention to the second gradation data conversion means 3g, the gradation data r relating to green is inputted in common to the functions 3g (R), 3g (G), 3g (B) provided in itself, New gradation data is output for each function. That is, the function 3g (R) outputs new gradation data Rg for the red LED based on the gradation data g input to itself. Similarly, the function 3g (G) outputs new gradation data Gg for the green LED based on the gradation data g input to itself, and the function 3g (B) converts the gradation data g input to itself to the gradation data g. Based on this, new gradation data Bg for the blue LED is output.
[0042]
Next, paying attention to the third gradation data conversion means 3b, the gradation data b relating to blue is inputted in common to each of the functions 3b (R), 3b (G) and 3b (B) provided in itself, New gradation data is output for each function. That is, the function 3b (R) outputs new gradation data Rb for the red LED based on the gradation data b input to itself. Similarly, the function 3b (G) outputs new gradation data Gb for the green LED based on the gradation data b input to itself, and the function 3b (B) converts the gradation data b input to itself to the gradation data b. Based on this, new gradation data Bb for the blue LED is output.
[0043]
In the present embodiment, each function is nonlinear in consideration of gamma correction and the like. With this configuration, it is possible to perform not only luminance correction and color tone correction but also gamma correction by changing only the gradation data. In the present embodiment, each function is non-linear, but each function may be linear, that is, a linear function.
[0044]
Next, how to obtain each function stored in advance in the gradation data conversion unit 3 will be described. An object of the present invention is to use the gradation data to arbitrarily change the luminance while keeping the color tone constant. Here, paying attention to the gradation data r relating to red, the gradation data r is converted into gradation data Rr, Gr, Br for each LED, whereby the luminance is arbitrarily changed while keeping the color tone constant. A method for determining the functions 3r (R), 3r (G), and 3r (B) that can be used will be described as an example.
[0045]
First, it is assumed that the target red color tone / brightness is “(xo, yo), Yo”, and this is converted to CIE tristimulus values as “Xo, Yo, Zo”. The target red CIE tristimulus values “Xo, Yo, Zo” vary depending on the gradation data. This is because “Xo, Yo, Zo” fluctuate when the color tone is constant (the height of the drive current is constant) and the luminance is changed by the gradation data r. Here, the magnitude of the drive current supplied to the red LED, green LED, and blue LED is made constant for each LED, and the change in CIE tristimulus value in one gradation of the red LED to be corrected is expressed as “ΔXR, ΔYR”. , ΔZR ”, changes in CIE tristimulus values in one gradation of the green LED are“ ΔXG, ΔYG, ΔZG ”, and changes in CIE tristimulus values in one gradation of the blue LED are“ ΔXB, ΔYB, ΔZB ”. When the gradation data to be output to the red LED is “Rr”, the gradation data to be output to the green LED is “Gr”, and the gradation data to be output to the blue LED is “Br”. (Rr, Gr, and Br correspond to FIG. 4), and the target red CIE tristimulus values “Xo, Yo, Zo” can be expressed by [Equation 1].
[0046]
[Formula 1]

[Expression 1] can be expressed as [Expression 2] in the form of a matrix.
[0047]
[Formula 2]

Since what is required here is output gradation data Rr, Gr, and Br, [Equation 3] can be obtained by multiplying the inverse matrix.
[0048]
[Formula 3]

By outputting the gradation data Rr, Gr, Br thus obtained to the corresponding LEDs, the target red CIE tristimulus value “X” ₀ , Y ₀ , Z ₀ The value can be focused on. That is, here, since CIE tristimulus values exist in the same space, not only chromaticity correction but also luminance correction can be performed collectively.
[0049]
More specifically, when obtaining ΔXR, ΔYR, ΔZR, ΔXG, ΔYG, ΔZG, ΔXB, ΔYB, ΔZB at the initial stage, that is, “Xo, Yo, Zo for each gradation data r with a constant tone. "Xo, Yo, Zo" corresponding to the input is the target CIE tristimulus value. And the output with respect to each of red LED, green LED, and blue LED required in order to implement | achieve the CIE tristimulus value is calculated | required by [Formula 3]. That is, the gradation data r when measuring “Xo, Yo, Zo” for each gradation data r is input, and Rr, Gr, Br obtained therefrom are output to each LED, and each is plotted to obtain a function. 3r (R), 3r (G), and 3r (B) can be obtained. Here, the functions 3r (R), 3r (G), and 3r (B) have been described focusing on the gradation data r, but the functions 3g (R), 3g (G), 3g (B), 3b ( R), 3b (G), and 3b (B) can be similarly determined. In addition, when measuring “Xo, Yo, Zo” of a target color, it can be arbitrarily performed for each pixel, for each LED unit, or for a larger unit. In addition, the target color “Xo, Yo, Zo” is measured, that is, when the predetermined function is obtained, the magnitude of the drive current passed through each color LED, and when the LED is actually driven, By making the magnitude of the drive current to flow the same for each LED, it is possible to drive without any change in color tone between the measurement time and the drive time. Specifically, for example, a red LED, a green LED, and a blue LED are measured, a predetermined function for each LED is determined based on the measurement result, and a drive having the same magnitude as the drive current at the time of measurement is performed. Each LED can actually be driven using current. In the present invention, as will be described later, the magnitude of the current during measurement can be determined in consideration of the target luminance range obtained by actually driving the LED. Note that it is possible for the setter to arbitrarily set what color LED is measured and what color LED is to be converted based on the measurement.
[0050]
For example, the red CIE tristimulus value “X _o , Y _o , Z _o Is measured by using a gradation data related to red, which originally corresponds to the red LED, and a driving current larger than a driving current necessary for obtaining a predetermined luminance is applied to the red LED, the green LED, or the blue LED. It is preferable to measure the emission characteristics of each. That is, the measurement can be performed in consideration of driving each LED by increasing the drive current. Hereinafter, the reason for this will be described by taking light emission of a red LED based on the gradation data r, g, and b as an example.
[0051]
In the present embodiment, paying attention to the gradation data for the red LED, the gradation data Rr, Rg, and Rb for the red LED are output based on the gradation data r, g, and b. The gradation data Rr, Rg, and Rb are output to the red LED as one gradation data “Rr + Rg + Rb” when a gradation data addition unit (gradation data addition step) is provided as described later. Here, the gradation data “Rr + Rg + Rb” is once written in the corresponding memory, and when it is read, the red LED emits light. However, there is a case where the gradation data “Rr + Rg + Rb” is too large for the memory provided with the gradation data “Rr + Rg + Rb”.
[0052]
In other words, in order to obtain a desired image, it is necessary to shorten the repetition period of blinking of the LED and to make it appear that the image is always turned on (fusion). It is not possible to obtain a certain level of brightness. If lighting is performed for a certain period of time or more in order to obtain a certain level of brightness, flicker will be applied to the image, and in the worst case, the brightness may decrease. For this reason, it is not possible to obtain the luminance necessary for lighting that takes into account the luminance correction and color tone correction of the present invention.
[0053]
Therefore, in consideration of the use with a large drive current in advance, each LED is caused to emit light by actually flowing the “large drive current” at the time of measurement. The luminance correction and the color tone correction can be performed without flickering of the image. Although the color tone naturally changes when a “large drive current” is applied, since the measurement is performed with the same amount of drive current applied, it is naturally possible to obtain a desired luminance and color tone after correction. That is, according to the present invention, the magnitude of the drive current that flows to each LED of each color when measuring the light emission characteristics of the LED to determine a predetermined function, and the drive current that flows to the LED of each color when actually driving the LED By making the size of each of the LEDs of each color constant, it is possible to drive without any change in color tone between the time of measurement and the time of driving. Therefore, in the present invention, the magnitude of the current at the time of measurement is determined in consideration of the target luminance range obtained by actually driving the LED. Here, “large driving current” is used for the purpose of obtaining higher luminance, but as described above, it is sufficient that the current during measurement and the current during driving are the same. Thus, for example, a predetermined function can be determined by using a “small drive current” smaller than a normally used current value. Note that, as described above, it is possible to arbitrarily set the color of the LED to be measured and the color data to be converted for the color of the LED based on the measurement.
[0054]
FIG. 3 is a block diagram depicting the LED driving system of the present embodiment, paying attention to the gradation data adding unit 4. As shown in FIG. 3, in the present embodiment, the gradation data adding unit 4 includes a first gradation data adding unit 4R, a second gradation data adding unit 4G, and a third gradation data adding unit 4B. Prepare. That is, the gradation data adding unit 4 converts the nine new gradation data Rr, Gr, Br, Rg, Gg, Bg, Rb, Gb, and Bb converted by the gradation data conversion unit 3 to the corresponding red LEDs. Are added for each green LED and blue LED, and output to each LED as one gradation data.
[0055]
Specifically, the three gradation data Rr, Rg, Rb for the red LED converted by the gradation data conversion unit 3 are added by the first gradation data addition unit 4R, and one gradation data “Rr + Rg + Rb” is added. It becomes. Similarly, the three gradation data Gr, Gg, and Gb for the green LED converted by the gradation data conversion unit 3 are added by the second gradation data addition unit 4G to become one gradation data “Gr + Gg + Gb”. The three gradation data Br, Bg, Bb for the blue LED converted by the gradation data conversion unit 3 are added by the third gradation data addition unit 4B to become one gradation data “Br + Bg + Bb”. In this way, the gradation data adding unit 4 outputs the newly generated gradation data “Rr + Rg + Rb”, “Gr + Gg + Gb”, “Br + Bg + Bb” to each of the red LED, the green LED, and the blue LED, and the gradation data thereof. Based on the above, red LED, green LED, and blue LED are caused to emit light.
[0056]
In the present invention, the gradation data newly output in each of the first gradation data conversion step, the second gradation data conversion step, and the third gradation data conversion step are red LED, green LED, and The process of adding each blue LED to form one gradation data is called a gradation data addition process. That is, in the present embodiment, three gradation data Rr, Rg, and Rb for the red LED converted in each gradation data conversion process are added in the first gradation data addition process, thereby obtaining one gradation data. “Rr + Rg + Rb”. Similarly, the three gradation data Gr, Gg, Gb for the green LED converted in each gradation data conversion process are added in the second gradation data addition process to become one gradation data “Gr + Gg + Gb”. The three gradation data Br, Bg, Bb for the blue LED converted in the tone data conversion process are added in the third gradation data addition process to form one gradation data “Br + Bg + Bb”.
[0057]
FIG. 5 is a schematic time chart for explaining the relationship between the light emission periods of the respective LEDs based on the added new gradation data. Here, on the basis of a predetermined gradation reference clock, the red LED emits light in the period w (Rr + Rg + Rb) by the gradation data “Rr + Rg + Rb”, and the green LED emits light in the period w (Gr + Gg + Gb) by the gradation data “Gr + Gg + Gb”. An embodiment in which a blue LED emits light in a period w (Br + Bg + Bb) based on gradation data “Br + Bg + Bb” will be described.
[0058]
In each time chart corresponding to each LED in FIG. 5, the horizontal axis indicates the time flow, and the vertical axis indicates the magnitude of the drive current. In the present invention, as described above, when each LED emits light, the magnitude of the drive current in each LED is always constant. By the way, for example, when a drive current is supplied to each of the RGB LEDs at a predetermined ratio to emit light, and the magnitude of the drive current supplied to each LED is changed while maintaining the supply ratio of the drive current, the drive current is supplied. Although the ratio is constant, the color tone changes. This is because, as described above, when the magnitude of the drive current changes in one LED, the color tone also changes. Note that when the driving current is constant, the luminance can be changed only by changing the light emission period without changing the color tone. The present invention has been made in consideration of these, and the magnitude of the drive current supplied to each LED of each color when the LED emits light is always constant for each LED of each color, and only the length of the gradation data is determined. By taking this into consideration, the luminance can be arbitrarily controlled while keeping the color tone constant.
[0059]
As shown in FIG. 5, when attention is paid to the period w (Rr + Rg + Rb) in which the red LED emits light by the new gradation data “Rr + Rg + Rb” obtained by adding the three gradation data for the red LED, the period w (Rr + Rg + Rb) is substantially equal. Further, the light emission period w (Rr) based on the gradation data Rr, the light emission period w (Rg) based on the gradation data Rg, and the light emission period w (Rb) based on the gradation data Rb can be considered. That is, in the present invention, the driving current is made constant for each LED of each color, and only the gradation data for determining the light emission period of each LED is changed in the gradation data conversion unit 3, so that the gradation data The addition is the addition of the light emission period, in other words, has the same meaning as the addition of luminance.
[0060]
Similarly, when attention is paid to the period w (Gr + Gg + Gb) in which the green LED emits light based on the gradation data “Gr + Gg + Gb” for the green LED, the period w (Gr + Gg + Gb) is substantially equal to the emission period w (Gr) and the level of the gradation data Gr. The light emission period w (Gg) based on the tone data Gg and the light emission period w (Gb) based on the gradation data Gb can be divided into consideration. When attention is paid to the period w (Br + Bg + Bb) in which the blue LED emits light based on the gradation data “Br + Bg + Bb” for the blue LED, the period w (Br + Bg + Bb) is substantially equal to the light emission period w (Br) and gradation according to the gradation data Br. The light emission period w (Bg) based on the data Bg and the light emission period w (Bb) based on the gradation data Bb can be considered. Note that the time chart shown in FIG. 5 is divided into three light emission periods for each LED for ease of explanation, and actually there is no boundary in the light emission period of each LED.
[0061]
Here, the light emission period of the red LED based on the gradation data “Rr + Rg + Rb” shown in FIG. 5, the light emission period of the green LED based on the gradation data “Gr + Gg + Gb”, and the light emission period of the blue LED based on the gradation data “Br + Bg + Bb”. When attention is paid to the above, it is preferable that the light emission period of the green LED and the light emission period of the blue LED are included in the light emission period of the red LED having the longest light emission period. That is, it is preferable that the light emission of the LED having the longest light emission period and the light emission of other LEDs overlap in time. Thereby, the occurrence of color flicker (hereinafter also referred to as “color flicker”) can be effectively reduced. In addition, although FIG. 5 demonstrated the example in which light emission of each LED was started simultaneously, each light emission can also be started by a time lag.
[0062]
In this embodiment, an example has been described in which the light emission period of the other two LEDs is included in the light emission period of the LED having the longest light emission period in order to reduce the color flicker to the maximum. Compared to the case where the light emission period of the other two LEDs is included in the light emission period of the LED having the longest period, the effect of reducing the color flicker is slightly reduced, but only the light emission period of the other one LED may be included. .
[0063]
Similarly, when the gradation data adding unit 4 does not add gradation data for each LED and each LED emits light based on each of the gradation data r, g, and b, the light emission period is similarly set. It is preferable that the light emission period of another LED for correction is included in the light emission period of the longest LED. For example, consider an example in which the gradation data adding unit 3 is not provided in FIG. 2 and each gradation data converted by the gradation data converting unit 3 is directly input to a red LED, a green LED, and a blue LED. That is, in the light emission of each LED based on the gradation data r, it is based on the light emission of the green LED based on the gradation data Gr and the gradation data Br within the period in which the red LED emits light based on the gradation data Rr. It is preferable to control the light emission of the blue LED. Similarly, in the light emission of each LED based on the gradation data g, the light emission of the blue LED based on the gradation data Bg and the gradation data Rg within the period in which the green LED emits light based on the gradation data Gg. Based on the gradation data Rb, the light emission of each LED based on the gradation data b is controlled based on the gradation data Rb within the period in which the blue LED emits light based on the gradation data Bb. It is preferable to control so that the red LED emits light and the green LED emits light based on the gradation data Gb. Thereby, even when the gradation data adding unit 4 emits light in a single color without adding each gradation data, the color flicker can be easily reduced.
[0064]
Although the double-speed display is not mentioned here, of course, double-speed display may be performed in order to reduce the flicker of the image. That is, by dividing the 1VSYNC period into a plurality of parts and displaying the same image for each divided period, it is possible to effectively reduce the flicker of the image. When the present invention is applied to the double speed display, the LED that mainly emits light and the light emission of the LED for correcting the light emission of the LED based on the gradation data related to the color that should be emitted by the LED of one color for each divided period. Is performed within the split period. Thereby, not only the flicker of the image but also the occurrence of color flicker can be effectively reduced. Furthermore, the gradation data (luminance) can be increased or decreased for each divided period in which the same image is displayed. With this configuration, the apparent gradation (gray scale) can be increased.
[0065]
In the present embodiment, the configuration in which the data supply unit 2 includes the gradation data conversion unit 3 and the gradation data addition unit 4 has been described. However, the present invention is not limited to this. That is, the gradation data conversion unit 3 and the gradation data addition unit 4 can be included in the data supply unit 1 or the LED unit 5. Further, for example, the data supply unit 2 may include the gradation data conversion unit 3, and the LED unit may include the gradation data addition unit 4. That is, the gradation data conversion unit 3 and the gradation data addition unit 4 can be configured separately. Furthermore, the TA which is a distributor in the LED drive system of the present invention is not necessarily required, and data can be directly input from the CU to the DU. In this case, the CU corresponds to the data supply unit of the present invention.
[0066]
In the present embodiment, the communication line L2 is an upper communication line, and the communication line L1 is a lower communication line. The communication line has three or more hierarchies. You may comprise. In this case, a TA corresponding to the hierarchy is arranged. Needless to say, the number of TAs and DUs and the connection form of TAs and DUs are not limited to this. That is, as shown in FIG. 1, in the present embodiment, TA is arranged in a Z-shape and DU is arranged in a Z-shape in each TA, but the present invention is not limited to this. TAs may be arranged in a straight line, and in each TA, DUs may be arranged in a straight line in a direction different from the TA arrangement direction (for example, the TA arrangement direction and the DU arrangement direction are perpendicular to each other).
[0067]
Further, in the present embodiment, a total of three types including a first LED that emits light in the first color, a second LED that emits light in the second color, and a third LED that emits light in the third color. Although the configuration in which the LEDs are arranged in the LED unit 5 has been described, the present invention is not limited to this. That is, the LED drive system of the present invention only needs to have two or more types of LEDs that emit light of different colors. For example, the first LED that emits light in the first color and the second LED that emits light in the second color. Two types of LEDs composed of two LEDs or a total of four or more types of LEDs may be arranged in the LED unit. In this case, the gradation data conversion unit and the gradation data addition unit are configured in consideration of the number of LEDs that emit different colors.
[0068]
In addition, here, each of the LEDs of a plurality of colors has a type of function with respect to gradation data that should originally be emitted by a type of LED. However, a driving current having a plurality of magnitudes in advance in each of the LEDs of the plurality of colors. It is also possible to set a predetermined function using and to set a plurality of functions for each magnitude of drive current. Thereby, for example, by determining each function using a relatively large driving current, it is possible to easily ensure a relatively large luminance for daytime, and at the same time determining each function using a relatively small driving current. Therefore, a relatively small luminance can be ensured without color flicker. In any case, in each of the LEDs of a plurality of colors, each LED can emit light without a change in color tone by making the magnitude of the driving current at the time of measurement the same as the magnitude of the driving current at the time of driving.
【The invention's effect】
[0069]
As described above, according to the present invention, luminance correction and color tone correction can be performed collectively. That is, generally, it is preferable that the luminance can be adjusted and the color tone is always kept constant in the light emission based on the gradation data that should originally correspond to one color LED. However, considering that there are variations in brightness and chromaticity depending on the LED, and that the color tone changes when the magnitude of the drive current is changed, the luminance can be arbitrarily adjusted while keeping the color tone constant. Is not easy.
[0070]
However, according to the LED driving system and the control method thereof of the present invention, when the LEDs are actually caused to emit light, the driving current is always set to a constant magnitude and gradation data for each LED is used. Nevertheless, it is possible to achieve both luminance correction and color correction simultaneously and efficiently.
[Brief description of the drawings]
[0071]
FIG. 1 is a schematic diagram showing a configuration of an LED drive system according to the present embodiment.
FIG. 2 is a schematic view focusing on a gradation data conversion unit of the LED driving system shown in FIG.
3 is a schematic view focusing on a gradation data adding unit of the LED driving system shown in FIG.
FIG. 4 is a schematic diagram showing a function stored in a gradation data conversion unit of the LED drive system according to the present embodiment.
FIG. 5 is a schematic diagram showing a light emission period of each LED in the present embodiment.
FIG. 6 is a schematic diagram for explaining a state in which a drive current is supplied to an LED.
[Explanation of symbols]
[0072]
DESCRIPTION OF SYMBOLS 1 ... Data control part, 2 ... Data supply part, 3 ... Gradation data conversion part, 3r ... 1st gradation data conversion means, 3g ... 2nd gradation data conversion means, 3b ... 3rd gradation data Conversion means, 4... Gradation data addition unit, 4R... 1st gradation data addition means, 4G... 2nd gradation data addition means, 4B... 3rd gradation data addition means, 5. ... display, 11 ... TA block, 20 ... LED, 21 ... common line, 22 ... current line, L1, L2 ... communication line.

Claims (1)

An LED unit in which at least a first LED that emits light in the first color and a second LED that emits light in the second color are arranged for each pixel, and the first LED and the second LED connected to the LED unit A data supply unit that supplies gradation data for determining at least the light emission period of each LED to each of the LEDs,
The data supply unit includes a gradation data conversion unit connected to a data control unit, and a gradation data addition unit connected to the gradation data conversion unit and the LED unit.
The gradation data converter is
The gradation data relating to the color that should be emitted from the first LED, which is supplied from the data control unit , is based on the first function, the gradation data for the first LED, and the first LED. a first gray-scale data conversion means for outputting the gradation data addition unit is converted into the gradation data for the second LED for correcting the light emission,
Based on the second function, the gradation data relating to the color to be emitted by the second LED, which is supplied from the data control unit , is based on the gradation data for the second LED and the second LED. emission has a, a second tone data conversion means for outputting the gradation data addition unit is converted into the gradation data for the first LED for correcting,
Further, the gradation data converter is
A third function and a fourth function obtained by a drive current having a magnitude different from that of the drive current passed when obtaining the first and second functions;
Gradation data relating to the color originally emitted from the first LED supplied from the data control unit, gradation data for the first LED based on the third function, and the first LED a third gradation data conversion means for converting the gradation data and outputs the gradation data addition unit for a second LED for correcting the emission by,
Based on the fourth function, the gradation data for the second LED, the gradation data relating to the color that should originally be emitted from the second LED, supplied from the data control unit , and the second LED and and a fourth gradation data conversion means for outputting the gradation data addition unit is converted into the gradation data for the first LED for correcting the emission by,
The gradation data adding unit
The gradation data for the first LED, which is converted from the gradation data relating to the color to be emitted by the first LED, supplied from the data control unit based on the first or third function, The gradation for correcting the light emission by the second LED, which is converted from the gradation data relating to the color to be emitted by the second LED originally supplied from the data control unit based on the second or fourth function. First gradation data adding means for adding gradation data for one LED and outputting the result to the LED unit;
The gradation data for the second LED, which is converted from the gradation data related to the color to be emitted by the second LED and supplied from the data control unit based on the second or fourth function, A gradation data for correcting the light emission by the first LED, which is obtained by converting the gradation data relating to the color to be emitted by the first LED supplied from the data control unit based on the first or third function. Second gradation data adding means for adding the gradation data for the two LEDs and outputting the result to the LED unit;
The magnitudes of drive currents that flow through the first LED and the second LED when obtaining the first to fourth functions, and the first LED and the second LED when the LED unit is driven. The LED drive system characterized in that the magnitudes of the drive currents flowing through are the same.

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