JP3636304B2

JP3636304B2 - Electronic zoom device

Info

Publication number: JP3636304B2
Application number: JP2001033921A
Authority: JP
Inventors: 哲也本林; 憲治田部井; 信須部
Original assignee: Panasonic Corp; Matsushita Electric Industrial Co Ltd
Current assignee: Panasonic Corp; Panasonic Holdings Corp
Priority date: 2001-02-09
Filing date: 2001-02-09
Publication date: 2005-04-06
Anticipated expiration: 2021-02-09
Also published as: JP2002238058A

Description

【０００１】
【発明の属する技術分野】
本発明は、三板カメラに特有の画素ずらしを用いて得られた折り返し歪成分を含む映像信号を使用する電子ズーム装置および方法に関するものである。
【０００２】
【従来の技術】
従来、ＣＣＤ等の固体撮像素子からの映像信号をサンプリングすることによって、折り返し歪成分が発生することが知られている。サンプリング周波数が十分高くない場合、折り返し歪成分は、映像帯域内に入り込み、再生画像中にモアレを発生させ、画質を劣化させる。そこで、Ｒ信号用、Ｇ信号用およびＢ信号用のＣＣＤを持つ撮像装置では（したがって、３つのＣＣＤを持つ）、解像度の高い鮮明な映像を得るために、例えば、特開平１１―１１３０１０号公報に記載されている画素ずらしという技術が用いられる。
【０００３】
画素ずらしでは、例えば、Ｇ信号用ＣＣＤの撮像部の各画素は、Ｒ信号用とＢ信号用のＣＣＤの撮像部の対応する各画素に対して、１／２画素ピッチだけずらして配置されている。このように各ＣＣＤの画素を配置することにより、ＲとＢの映像信号の位相は、Ｇの映像信号に対してπずれることとなり、それぞれ発生する折り返し歪成分の位相もπずれることとなる。
【０００４】
図６を用いて画素ずらしを用いた撮像について簡単に説明する。図６（ｂ）において、Ｆｓはサンプリング周波数、Ｆｓ／２はサンプリング周波数の半分の周波数（ナイキスト周波数）である。図６（ａ）において、６０１は被写体によって決まる光学像であり、黒丸はＣＣＤによるサンプル点を示している。また、Ｒ信号用ＣＣＤ６０４、Ｂ信号用ＣＣＤ６０３、Ｇ信号用ＣＣＤ６０２の各画素面の位置は、水平方向の相対的なサンプリング位置を示している。
【０００５】
この図からわかるように、Ｇ信号用ＣＣＤの各画素面が他の２つの信号用CCDの各画素面と１／２画素ピッチずれて配置されているため、被写体像は、画素がずらされていない場合に比して、全体として２倍のサンプリング周波数で撮像したものと考えることができる。そこで、輝度信号生成において、Ｒ、ＧおよびＢの各映像信号に一定の重みを乗じて加算すると、Ｇ信号に含まれる折り返し歪成分と、ＲおよびＢ信号に含まれる折り返し歪成分とが逆位相で加算され、部分的にキャンセルされることとなる。その結果、生成された輝度信号に含まれる折り返し歪成分は低減されることになる。
【０００６】
また、従来の電子ズームの方法としては、例えば、特開平５−１３０４７７号や特開平５−１３０６３２号公報に記載されているように、映像データを一旦メモリに記憶し、ズーム倍率に従ってメモリからデータを読みだし、画素、ライン間の内挿処理を行う方法が知られている。
【０００７】
【発明が解決しようとする課題】
しかしながら、従来の画素ずらしと電子ズームとにより高解像度な電子ズームを実現しようとし、高解像度の輝度信号Ｙを生成する前に電子ズームを行ってしまうと、その後の折り返し歪成分のキャンセルが困難となり、画質の劣化をもたらすという問題がある。
【０００８】
また、上記特開平１１―１１３０１０号に記載されている従来の方法で高解像度の輝度信号Ｙを生成するのでは、倍速処理すなわち、サンプリング周波数（Ｆｓ）の２倍の周波数で高速に動作することが必要となるという問題がある。
【０００９】
また、解像度特性の改善を図るため高解像度の輝度信号Ｙを生成した後では信号が２倍になっているため、その後に電子ズームを行うと、電子ズームに必要となる記憶装置のメモリ容量が２倍必要となってしまうという問題がある。
また、画質向上のためにメモリを使用して輪郭補正処理を行う映像信号補正回路を使用する場合においても、使用するメモリのメモリ容量が２倍となってしまうという問題がある。
【００１０】
さらに、高解像度の輝度信号Ｙを生成してから拡大ズームを行うのでは、打ち消されて軽減された折り返し歪成分の解像度を引き出しているに過ぎないため、高解像度化には限界があるという問題があった。
【００１１】
本発明は、このような問題を解決するためになされたもので、三板カメラに特有の画素ずらしを用いて得られた折り返し歪成分を含む映像信号を使用する電子ズーム装置および方法において、使用メモリのメモリ容量を低減し、拡大内挿の際に発生する折り返し歪成分による画像の劣化を抑えることができる電子ズーム装置および方法を提供するものである。
【００１２】
【課題を解決するための手段】
本発明の電子ズーム装置は、入力された映像信号に電子ズーム処理を施す装置において、前記入力映像信号を用いて再生される画像を垂直方向に拡大するための垂直内挿処理を、前記入力映像信号に施す垂直内挿手段と、前記垂直内挿処理後の映像信号に含まれる折り返し歪成分を軽減するための高域置換処理を、前記垂直内挿処理後の映像信号に施す高域置換手段と、前記高域置換処理後の映像信号を用いて再生される画像を水平方向に拡大するための水平内挿処理を、前記高域置換処理後の映像信号に施す水平内挿手段とを備えた構成を有している。この構成により、高域置換処理を行う前に画像を垂直方向に拡大するための垂直内挿処理を行う垂直内挿手段を具備したことにより、垂直内挿処理の際に必要となる記憶装置のメモリ容量が倍必要となることはない。また、前記高域置換手段の後段に水平内挿処理を行う水平内挿処理手段を具備したことにより、画素ずらしを用いて折り返し歪を軽減した高解像度な電子ズームの実現が可能となる。
【００１３】
また、本発明の電子ズーム装置は、入力された映像信号に電子ズーム処理を施す装置において、前記入力映像信号を用いて再生される画像を垂直方向に拡大するための垂直内挿処理を、前記入力映像信号に施す垂直内挿手段と、前記垂直内挿処理後の映像信号に含まれる折り返し歪成分を軽減するための高域置換処理を、前記垂直内挿処理後の映像信号に施す高域置換手段と、前記高域置換処理後の映像信号を用いて再生される画像を水平方向に拡大するための水平内挿処理を、前記高域置換処理後の映像信号に施す水平内挿手段と、映像信号を所定の割合で間引く処理を行うための間引き手段と、前記間引き処理後の映像信号に所定の映像信号補正処理を施す映像信号補正手段と、前記映像信号補正処理後の映像信号に含まれる折り返し歪成分を軽減するための高域置換処理を施す後段高域置換手段とを備え、前記入力映像信号は、３つの固体撮像素子を用いて行われた撮像後にデジタル化された信号であり、前記３つの固体撮像素子の内の１つの固体撮像素子における各画素は、他の２つの固体撮像素子における対応する各画素に対して水平走査方向に１／２画素ずらして配置され、前記間引き手段は、前記水平内挿処理後の各映像信号のうち、前記１つの固体撮像素子経由の映像信号と前記他の２つの固体撮像素子経由の映像信号とが前記１／２画素分の位相差を持つように間引く構成を有している。この構成により、画像を水平方向に拡大する処理の後に、Ｒ、Ｇ、Ｂのうち１つの映像信号の画素データが他の２つの映像信号の画素データに対して空間的に１／２画素ピッチの位相差を持たせて、映像信号を間引いて出力することにより折り返し歪を復元する間引き回路を具備したことにより、電子ズームの映像信号の水平画素数方向の信号が倍になっていないため、その後、電子ズームに必要となる記憶装置のメモリ容量が２倍必要となることがない。また、例えば、画質向上のためにメモリを使用して輪郭補正処理を行う映像信号補正回路を使用する場合においても、記憶装置のメモリ容量が倍増してしまうという問題がなく、回路規模の小型化、低コスト化につながる。また、復元された折り返し歪を軽減するために再度高域置換処理を行う後段高域置換手段を備えた構成により、水平方向に画素を間引くことによって復元された折り返し歪成分に対して高域置換処理を行い、折り返し歪成分を軽減した高解像度なズーム画質を得ることができる。
【００１４】
また、本発明の電子ズーム装置は、入力された映像信号に電子ズーム処理を施す装置において、前記入力映像信号を用いて再生される画像を垂直方向に拡大するための垂直内挿処理を、前記入力映像信号に施す垂直内挿手段と、前記垂直内挿処理後の映像信号に含まれる折り返し歪成分を軽減するための高域置換処理を、前記垂直内挿処理後の映像信号に施す高域置換手段と、前記高域置換処理後の映像信号を用いて再生される画像を水平方向に拡大するための水平内挿処理を、前記高域置換処理後の映像信号に施す水平内挿手段とを備え、前記高域置換手段は、映像信号の低域成分を抽出するフィルタ処理を行うＬＰＦ手段と、前記映像信号を用いて輝度信号を生成する手段と、前記輝度信号の高域成分を抽出するフィルタ処理を行うＨＰＦ手段と、前記映像信号の低域成分と前記輝度信号の高域成分とを加算する加算手段と、前記ＬＰＦ手段および前記ＨＰＦ手段の制御を行う水平・垂直制御手段とを有し、前記水平・垂直制御手段は、前記電子ズーム処理のズーム倍率に応じて前記制御を行う構成を有している。この構成により、ズーム倍率が大きくなるに従って顕著に現れる折り返し歪に対して、前記ＬＰＦと前記ＨＰＦの特性を制御して、折り返し歪の影響が大きい輝度信号Ｙの高域成分比を変化させ、高解像度なズーム画質を得ることができる。
【００１５】
また、本発明の電子ズーム装置は、入力された映像信号に電子ズーム処理を施す装置において、前記入力映像信号を用いて再生される画像を垂直方向に拡大するための垂直内挿処理を、前記入力映像信号に施す垂直内挿手段と、前記垂直内挿処理後の映像信号に含まれる折り返し歪成分を軽減するための高域置換処理を、前記垂直内挿処理後の映像信号に施す高域置換手段と、前記高域置換処理後の映像信号を用いて再生される画像を水平方向に拡大するための水平内挿処理を、前記高域置換処理後の映像信号に施す水平内挿手段と、映像信号を所定の割合で間引く処理を行うための間引き手段と、前記間引き処理後の映像信号に所定の映像信号補正処理を施す映像信号補正手段と、前記映像信号補正処理後の映像信号に含まれる折り返し歪成分を軽減するための高域置換処理を施す後段高域置換手段とを備え、前記入力映像信号は、３つの固体撮像素子を用いて行われた撮像後にデジタル化された信号であり、前記３つの固体撮像素子の内の１つの固体撮像素子における各画素は、他の２つの固体撮像素子における対応する各画素に対して水平走査方向に１／２画素ずらして配置され、前記間引き手段は、前記水平内挿処理後の各映像信号のうち、前記１つの固体撮像素子経由の映像信号と前記他の２つの固体撮像素子経由の映像信号とが前記１／２画素分の位相差を持つように間引き、前記高域置換手段は、映像信号の低域成分を抽出するフィルタ処理を行うＬＰＦ手段と、前記映像信号を用いて輝度信号を生成する手段と、前記輝度信号の高域成分を抽出するフィルタ処理を行うＨＰＦ手段と、前記映像信号の低域成分と前記輝度信号の高域成分とを加算する加算手段と、前記ＬＰＦ手段および前記ＨＰＦ手段の制御を行う水平・垂直制御手段とを有し、前記水平・垂直制御手段は、前記電子ズーム処理のズーム倍率に応じて前記制御を行う構成を有している。この構成により、ズーム倍率が大きくなるに従って顕著に現れる折り返し歪に対して、前記ＬＰＦと前記ＨＰＦの特性を制御して、折り返し歪の影響が大きい輝度信号Ｙの高域成分比を変化させ、高解像度なズーム画質を得ることができる。
【００１６】
また、本発明の電子ズーム装置は、入力された映像信号に電子ズーム処理を施す装置において、前記入力映像信号を用いて再生される画像を垂直方向に拡大するための垂直内挿処理を、前記入力映像信号に施す垂直内挿手段と、前記垂直内挿処理後の映像信号に含まれる折り返し歪成分を軽減するための高域置換処理を、前記垂直内挿処理後の映像信号に施す高域置換手段と、前記高域置換処理後の映像信号を用いて再生される画像を水平方向に拡大するための水平内挿処理を、前記高域置換処理後の映像信号に施す水平内挿手段と、映像信号を所定の割合で間引く処理を行うための間引き手段と、前記間引き処理後の映像信号に所定の映像信号補正処理を施す映像信号補正手段と、前記映像信号補正処理後の映像信号に含まれる折り返し歪成分を軽減するための高域置換処理を施す後段高域置換手段とを備え、前記入力映像信号は、３つの固体撮像素子を用いて行われた撮像後にデジタル化された信号であり、前記３つの固体撮像素子の内の１つの固体撮像素子における各画素は、他の２つの固体撮像素子における対応する各画素に対して水平走査方向に１／２画素ずらして配置され、前記間引き手段は、前記水平内挿処理後の各映像信号のうち、前記１つの固体撮像素子経由の映像信号と前記他の２つの固体撮像素子経由の映像信号とが前記１／２画素分の位相差を持つように間引く構成を有している。この構成により、ズーム倍率が大きくなるに従って顕著に現れる折り返し歪に対して、前記ＬＰＦと前記ＨＰＦの特性を制御して、折り返し歪の影響が大きい輝度信号Ｙの高域成分比を変化させ、高解像度なズーム画質を得ることができる。
【００１７】
また、本発明の電子ズーム装置は、入力された映像信号に電子ズーム処理を施す装置において、前記入力映像信号を用いて再生される画像を垂直方向に拡大するための垂直内挿処理を、前記入力映像信号に施す垂直内挿手段と、前記垂直内挿処理後の映像信号に含まれる折り返し歪成分を軽減するための高域置換処理を、前記垂直内挿処理後の映像信号に施す高域置換手段と、前記高域置換処理後の映像信号を用いて再生される画像を水平方向に拡大するための水平内挿処理を、前記高域置換処理後の映像信号に施す水平内挿手段と、映像信号を所定の割合で間引く処理を行うための間引き手段と、前記間引き処理後の映像信号に所定の映像信号補正処理を施す映像信号補正手段と、前記映像信号補正処理後の映像信号に含まれる折り返し歪成分を軽減するための高域置換処理を施す後段高域置換手段とを備え、前記入力映像信号は、３つの固体撮像素子を用いて行われた撮像後にデジタル化された信号であり、前記３つの固体撮像素子の内の１つの固体撮像素子における各画素は、他の２つの固体撮像素子における対応する各画素に対して水平走査方向に１／２画素ずらして配置され、前記間引き手段は、前記水平内挿処理後の各映像信号のうち、前記１つの固体撮像素子経由の映像信号と前記他の２つの固体撮像素子経由の映像信号とが前記１／２画素分の位相差を持つように間引き、前記高域置換手段による高域置換処理と前記後段高域置換手段による後段高域置換処理とが連動して行われる構成を有している。この構成により、前記高域置換手段を構成する前記ＬＰＦおよび前記ＨＰＦの特性と、前記後段高域置換手段を構成する前記ＬＰＦおよび前記ＨＰＦの特性とが、連動して変更されるため、前記ズーム倍率に従って変化する折り返し歪成分を軽減した高解像度なズーム画質を得ることができる。
【００１８】
また、本発明の電子ズーム方法は、入力された映像信号に電子ズーム処理を施す方法において、前記入力映像信号を用いて再生される画像を垂直方向に拡大するための垂直内挿処理を、前記入力映像信号に施す垂直内挿ステップと、前記垂直内挿処理後の映像信号に含まれる折り返し歪成分を軽減するための高域置換処理を、前記垂直内挿処理後の映像信号に施す高域置換ステップと、前記高域置換処理後の映像信号を用いて再生される画像を水平方向に拡大するための水平内挿処理を、前記高域置換処理後の映像信号に施す水平内挿ステップとを備えた構成を有している。この構成により、高域置換処理を行う前に画像を垂直方向に拡大するための垂直内挿処理を行う垂直内挿ステップを具備したことにより、垂直内挿処理の際に必要となる記憶装置のメモリ容量が倍必要となることはない。また、前記高域置換処理後に水平内挿処理を行う水平内挿処理ステップを具備したことにより、画素ずらしを用いて折り返し歪を軽減した高解像度な電子ズームの実現が可能となる。
【００１９】
【発明の実施の形態】
以下、本発明の実施の形態について、図面を用いて説明する。
図１に示すように、本発明の第１の実施の形態の電子ズーム装置は、垂直内挿回路３、高域置換回路４および水平内挿回路９から構成される。
【００２０】
以下、第１の実施の形態の電子ズーム装置の動作について説明する。Ｒ、Ｇ、Ｂの各入力映像信号は、垂直内挿回路３に入力され、垂直内挿回路３によって、画像を垂直方向にズームするための垂直内挿処理が施される。垂直内挿処理後の各映像信号は、高域置換回路４に入力され、高域置換回路４によって映像信号から折り返し歪成分をキャンセルするための高域置換処理が施される。高域置換処理後の各映像信号は、水平内挿回路９に入力され、水平内挿回路９によって画像を水平方向にズームするための水平内挿処理が施される。
【００２１】
図２は、本発明の第１の実施の形態の電子ズーム方法における処理の流れを示すフローチャートである。本電子ズーム方法では、Ｒ、Ｇ、Ｂの各入力映像信号に以下の処理が施される。
ステップＳ２０１で、垂直内挿回路３は、画像を垂直方向にズームするための垂直内挿処理をＲ、Ｇ、Ｂの各入力映像信号に施す。ステップＳ２０２で、高域置換回路４は、各映像信号から折り返し歪成分をキャンセルするための高域置換処理を垂直内挿処理後の各映像信号に施す。ステップＳ２０３で、水平内挿回路９は、画像を水平方向にズームするための水平内挿処理を高域置換処理後の各映像信号に施す。
【００２２】
以上のように、本発明の第１の実施の形態の電子ズーム装置は、高域置換回路４の入力段に垂直内挿回路３を設け、高域置換回路４の出力段に水平内挿回路９を設けているので、画素ずらしを考慮した高解像度な電子ズームを行うことができる。
また、本発明の第１の実施の形態の電子ズーム方法は、入力映像信号に垂直内挿処理を施すステップＳ２０１を設け、その後に、高域置換処理を施すステップＳ２０２を設け、高域置換処理後に水平内挿処理を施すステップＳ２０３を設けているので、画素ずらしを考慮した高解像度な電子ズームを行うことができる。
【００２３】
図３は、本発明の第２の実施の形態の電子ズーム装置の構成を示すブロック図である。第２の実施の形態の電子ズーム装置は、画素ずらしを用いた撮像部１、Ａ／Ｄ変換器２、フィールドメモリ１３、水平・垂直制御回路１２、垂直内挿回路３、後述の垂直内挿処理で用いるラインメモリ１４、高域置換回路４、間引き回路１７を有する水平内挿回路９、ラインメモリ１５を有する輪郭補正回路１０および後段高域置換回路１１から構成される。
【００２４】
以下、第２の実施の形態の電子ズーム装置の動作について説明する。
撮像部（ＣＣＤイメージセンサ）１では、同じ画素数のＣＣＤを用いて高解像度な画像を得るため、三板ＣＣＤカメラ特有の画素ずらしと呼ばれる技術が用いられる。撮像部１におけるＲ信号用、Ｇ信号用およびＢ信号用の各ＣＣＤのうち、Ｒ信号用とＢ信号用のＣＣＤは、Ｇ信号用のＣＣＤに対して１／２画素ピッチずらして撮像するよう構成される。撮像部１は、撮像したＲ、Ｇ、Ｂの各映像信号をＡ／Ｄ変換器２に出力する。
【００２５】
Ａ／Ｄ変換器２は、入力された各アナログ映像信号をデジタル映像信号に変換してフィールドメモリ１３に一旦記憶する。このフィールドメモリ１３に記憶された各デジタル映像信号は、垂直内挿回路３に入力され、垂直内挿回路３によって画像を垂直方向に拡大するための補間処理である垂直内挿処理が施される。この垂直内挿処理の際、ラインメモリ１４が用いられる。
【００２６】
垂直内挿処理後の各映像信号は、高域置換回路４に入力され、高域置換回路４によって折り返し歪成分を軽減するための高域置換処理が施される。高域置換処理後の各映像信号は、水平内挿回路９によって画像を水平方向に拡大するための水平内挿処理が施される。水平内挿処理後の各映像信号は、水平内挿回路９内の間引き回路１７によって、Ｇ信号がＲ信号とＢ信号に対して１／２画素分の水平空間位相差を持つように間引かれ、出力される。
【００２７】
Ｇ信号がＲ信号とＢ信号に対して１／２画素分の水平空間位相差を持つＲ、Ｇ、Ｂの映像信号を生成することで、一旦画素ずらしによる折り返し歪成分を復元する。この折り返し歪成分が復元された映像信号は、輪郭補正回路１０によって画質の向上を行うための輪郭補正処理が施される。その際、この輪郭補正処理にラインメモリ１５が用いられる。
【００２８】
上記のように間引き回路１７から出力される映像信号は間引かれているため、ラインメモリ１５に要求されるメモリ容量は、画素ずらしをしない場合と比較して、倍増するという問題がない。
【００２９】
図４を参照して、間引きを行う場合と行わない場合のメモリ容量について比較する。図４の輪郭補正回路１０はラインメモリ１５とフィルタ回路１６とから構成され、各ラインメモリ１５はすべて同じメモリ容量を有する。例えば、１Ｈ遅延用のラインメモリ１５を２個使用する輪郭補正回路１０では、間引きを行わない場合、処理に必要なラインメモリ１５は倍増し、１Ｈ遅延用のラインメモリ１５が４個必要になる。
【００３０】
輪郭補正回路１０から出力される映像信号は、水平内挿回路９内の間引き回路１７によって折り返し歪成分が復元されているため、後段高域置換回路１１で、折り返し歪成分を軽減して高解像度の画質を得るための高域置換処理が行われる。したがって、後段高域置換回路１１からは、折り返し歪成分が軽減された高解像度の画質を得ることができる映像信号が出力される。
【００３１】
以上のように、本発明の第２の実施の形態の電子ズーム装置は、高域置換回路４、および、水平内挿処理を行う際に水平走査方向に信号を間引く間引き回路１７とを設けているので、メモリを使用して画質の向上を行う輪郭補正回路を用いる場合でも、記憶装置のメモリ容量が倍増することなく、回路規模の小型化、低コスト化を図ることができる。
【００３２】
本発明の第３の実施の形態の電子ズーム装置において高域置換処理を行う回路を図５に示す。図５は、第１の実施の形態または第２の実施の形態に記載の高域置換回路４、若しくは、第２の実施の形態に記載の後段高域置換回路１１に適用される回路の具体例を示す図である。したがって、図５に示すＲ、Ｇ、Ｂの各入力映像信号は垂直内挿回路３または輪郭補正回路１０からの出力である。
【００３３】
高域置換回路４または後段高域置換回路１１は、図５において、ＬＰＦ５、輝度信号生成回路６、ＨＰＦ７および加算回路８から構成される。
【００３４】
上記のように構成された高域置換回路または後段高域置換回路の動作について説明する。高域置換回路と後段高域置換回路とは同様の動作をするため、以下では、高域置換回路を代表として説明する。
高域置換回路の入力信号は、低域成分を抽出するためのＬＰＦ５と、輝度信号を生成するための輝度信号生成回路６に入力される。ＨＰＦ７では、輝度信号生成回路６で生成された輝度信号から高域輝度成分を抽出するためのフィルタ処理が行われる。加算回路８は、ＬＰＦ５によって抽出された低域成分とＨＰＦ７によって抽出された高域輝度成分とを加算処理する。これらを加算するによって、折り返し歪成分の影響が大きい輝度信号の高域成分は、折り返し歪成分の軽減がなされる。
【００３５】
また、ズーム倍率の変化に従って折り返し歪成分が現れる帯域が変化することに対応するため、水平・垂直制御回路１１は、ズーム倍率にしたがって前記ＬＰＦ５と前記ＨＰＦ７のフィルタ係数を生成し、前記ＬＰＦ５と前記ＨＰＦ７の特性を制御する。さらに、高域置換回路４での処理と後段高域置換回路１１での処理とを連動させることにより、高域置換回路４を構成するＬＰＦ５およびＨＰＦ７の特性と、後段高域置換回路１１を構成するＬＰＦ５およびＨＰＦ７の特性とが、連動して変更されるため、ズーム倍率に従って変化する折り返し歪成分を軽減した高解像度なズーム画質を得ることができる。
【００３６】
例えば、ズーム倍率が大きくなるに従って顕著に現れる折り返し歪成分に対して、水平・垂直制御回路１１は、ズーム倍率ＬＰＦ５のカットオフ周波数を小さくし、輝度信号のＨＰＦの高域成分の帯域を増やすように制御する。これによって、折り返し歪成分をキャンセルし、画質を向上させることができる。
【００３７】
以上のように、本発明の第３の実施の電子ズーム装置における高域置換処理のための回路は、映像信号の低域成分を抽出するフィルタ処理を行うＬＰＦ５、輝度信号を生成する輝度信号生成回路６、高域輝度信号を抽出するフィルタ処理を行うＨＰＦ７、および、映像信号の低域成分と高域輝度成分を加算する加算回路８を設け、ズーム倍率に応じてＬＰＦ５とＨＰＦ７の制御を行うので、ズーム倍率に応じて折り返し歪成分をキャンセルし、画質を向上させることができる。
【００３８】
なお、上記の実施の形態では、映像信号補正回路として輪郭補正回路を用いた場合について説明したが、本発明は輪郭補正回路のほかに、メモリを使用して画質の向上を図るその他の信号処理回路、例えば、ラインメモリなど記憶手段として使用するノイズリダクション回路等を用いた場合にも同様に適用できる。
【００３９】
【発明の効果】
以上説明したように、本発明は、折り返し歪成分を軽減する高域置換回路と、前記高域置換回路の前段に画像を垂直方向に拡大するための垂直内挿回路と、前記高域置換回路の後段に画像を水平方向に拡大するための水平内挿回路とを備えることにより、記憶装置のメモリ容量が倍増することなく、回路規模の小型化、低コスト化を図ることができる電子ズーム装置を提供することができるものである。
【図面の簡単な説明】
【図１】本発明の第１の実施の形態の電子ズーム装置の構成を示すブロック図
【図２】本発明の第１の実施の形態の電子ズーム装置における処理の流れを示すフローチャート
【図３】本発明の第２の実施の形態の電子ズーム装置の構成を示すブロック図
【図４】本発明の第２の実施の形態の電子ズーム装置における輪郭補正回路のメモリ容量の比較について説明するための図
【図５】本発明の第３の実施の形態の電子ズーム装置における高域置換処理を行う回路のブロック図
【図６】従来技術である、撮像部における画素ずらしについて説明するための概念図
【符号の説明】
１撮像部
２Ａ／Ｄ変換器
３垂直内挿回路
４高域置換回路
５ＬＰＦ
６輝度信号生成回路
７ＨＰＦ
８加算回路
９水平内挿回路
１０輪郭補正回路
１１後段高域置換回路
１２水平・垂直制御回路
１３フィールドメモリ
１４ラインメモリ
１５ラインメモリ
１６フィルタ回路
１７間引き回路[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electronic zoom apparatus and method using a video signal including a aliasing distortion component obtained by using a pixel shift unique to a three-plate camera.
[0002]
[Prior art]
Conventionally, it is known that a aliasing distortion component is generated by sampling a video signal from a solid-state imaging device such as a CCD. When the sampling frequency is not sufficiently high, the aliasing distortion component enters the video band, causes moiré in the reproduced image, and degrades the image quality. Therefore, in an image pickup apparatus having CCDs for R signal, G signal, and B signal (thus having three CCDs), in order to obtain a clear image with high resolution, for example, Japanese Patent Laid-Open No. 11-113010 The technique of pixel shifting described in the above is used.
[0003]
In the pixel shifting, for example, each pixel of the G signal CCD image pickup unit is shifted by a 1/2 pixel pitch with respect to each corresponding pixel of the R signal B signal CCD image pickup unit. Yes. By arranging the pixels of each CCD in this manner, the phases of the R and B video signals are shifted by π with respect to the G video signal, and the phase of the aliasing distortion component generated is also shifted by π.
[0004]
The imaging using pixel shift will be briefly described with reference to FIG. In FIG. 6B, Fs is a sampling frequency, and Fs / 2 is a half frequency (Nyquist frequency) of the sampling frequency. In FIG. 6A, reference numeral 601 denotes an optical image determined by a subject, and black circles indicate sample points by the CCD. Further, the positions of the pixel surfaces of the R signal CCD 604, the B signal CCD 603, and the G signal CCD 602 indicate relative sampling positions in the horizontal direction.
[0005]
As can be seen from this figure, each pixel surface of the G signal CCD is shifted by 1/2 pixel pitch from each other pixel surface of the other two signal CCDs. It can be considered that the image is taken at twice the sampling frequency as a whole as compared with the case where there is no image. Therefore, in the luminance signal generation, when each of the R, G, and B video signals is multiplied by a certain weight and added, the aliasing distortion component included in the G signal and the aliasing distortion component included in the R and B signals are in opposite phases. Will be added and partially canceled. As a result, the aliasing distortion component included in the generated luminance signal is reduced.
[0006]
In addition, as a conventional electronic zoom method, for example, as described in JP-A-5-130477 and JP-A-5-130632, video data is temporarily stored in a memory, and data is stored in the memory according to the zoom magnification. Is known, and interpolation processing between pixels and lines is performed.
[0007]
[Problems to be solved by the invention]
However, if an attempt is made to realize a high-resolution electronic zoom by conventional pixel shifting and electronic zoom, and if the electronic zoom is performed before the high-resolution luminance signal Y is generated, it becomes difficult to cancel the aliasing component thereafter. There is a problem that the image quality is deteriorated.
[0008]
In addition, when the high-resolution luminance signal Y is generated by the conventional method described in the above-mentioned Japanese Patent Application Laid-Open No. 11-113010, the high-speed operation, that is, the high-speed operation at a frequency twice the sampling frequency (Fs). There is a problem that is necessary.
[0009]
In addition, after the high-resolution luminance signal Y is generated in order to improve the resolution characteristics, the signal is doubled. Therefore, when electronic zoom is performed thereafter, the memory capacity of the storage device required for electronic zoom is reduced. There is a problem that it is required twice.
In addition, even when a video signal correction circuit that performs contour correction processing using a memory for improving image quality is used, there is a problem that the memory capacity of the memory to be used is doubled.
[0010]
Furthermore, since the high-resolution luminance signal Y is generated and then the enlargement zoom is performed, the resolution of the aliasing distortion component that has been canceled out and reduced is only extracted, so that there is a limit to increasing the resolution. was there.
[0011]
The present invention has been made to solve such a problem, and in an electronic zoom apparatus and method using a video signal including a aliasing distortion component obtained by using a pixel shift peculiar to a three-plate camera, a memory used An electronic zoom apparatus and method that can reduce the memory capacity and suppress deterioration of an image due to aliasing distortion components that occur during enlargement interpolation.
[0012]
[Means for Solving the Problems]
The electronic zoom device of the present invention is a device that performs an electronic zoom process on an input video signal, and performs a vertical interpolation process for vertically expanding an image reproduced using the input video signal. Vertical interpolation means for applying to the signal, and high-frequency replacement means for applying high-frequency replacement processing for reducing the aliasing distortion component included in the video signal after the vertical interpolation processing to the video signal after the vertical interpolation processing And horizontal interpolation means for performing horizontal interpolation processing on the video signal after the high-frequency replacement processing for horizontally expanding an image reproduced using the video signal after the high-frequency replacement processing. It has a configuration. With this configuration, by including a vertical interpolation unit that performs a vertical interpolation process for enlarging an image in a vertical direction before performing a high-frequency replacement process, a storage device required for the vertical interpolation process is provided. The memory capacity is never doubled. In addition, by providing a horizontal interpolation processing unit that performs a horizontal interpolation process after the high-frequency replacement unit, it is possible to realize a high-resolution electronic zoom that reduces aliasing distortion by using pixel shift.
[0013]
Further, the electronic zoom device of the present invention is a device that performs an electronic zoom process on an input video signal, and performs a vertical interpolation process for vertically expanding an image reproduced using the input video signal. A high-frequency section that performs vertical interpolation on the video signal after the vertical interpolation processing, and a vertical-interpolation unit that performs the high-frequency replacement processing for reducing the aliasing distortion component included in the video signal after the vertical interpolation processing. Replacement means; and horizontal interpolation means for performing horizontal interpolation processing on the video signal after the high-frequency replacement processing for horizontally expanding an image reproduced using the video signal after the high-frequency replacement processing A thinning means for thinning out the video signal at a predetermined rate; a video signal correcting means for performing a predetermined video signal correction process on the video signal after the thinning process; and a video signal after the video signal correction process. Folding distortion included A high-frequency substituting means for performing a high-frequency substituting process for reducing the frequency, and the input video signal is a signal digitized after imaging performed using three solid-state imaging devices, Each pixel in one of the two solid-state image sensors is arranged to be shifted by 1/2 pixel in the horizontal scanning direction with respect to each corresponding pixel in the other two solid-state image sensors. Of each video signal after the horizontal interpolation processing, the video signal via the one solid-state imaging device and the video signal via the other two solid-state imaging devices have a phase difference of ½ pixel. It has a structure to thin out. With this configuration, after the process of enlarging the image in the horizontal direction, the pixel data of one video signal among R, G, and B is spatially ½ pixel pitch with respect to the pixel data of the other two video signals. By providing a thinning circuit that restores the aliasing distortion by thinning out and outputting the video signal with the phase difference of, the signal in the horizontal pixel number direction of the video signal of the electronic zoom is not doubled. Thereafter, the memory capacity of the storage device required for the electronic zoom is not required twice. In addition, for example, when using a video signal correction circuit that performs contour correction processing using a memory to improve image quality, there is no problem that the memory capacity of the storage device is doubled, and the circuit scale is reduced. , Leading to lower costs. In addition, high-frequency replacement is performed for the aliasing distortion component restored by thinning out the pixels in the horizontal direction by using a structure that includes a high-frequency substitution unit that performs high-frequency substitution processing again to reduce the aliasing distortion that has been restored. By performing processing, it is possible to obtain a high resolution zoom image quality with reduced aliasing distortion components.
[0014]
Further, the electronic zoom device of the present invention is a device that performs an electronic zoom process on an input video signal, and performs a vertical interpolation process for vertically expanding an image reproduced using the input video signal. A high-frequency section that performs vertical interpolation on the video signal after the vertical interpolation processing, and a vertical-interpolation unit that performs the high-frequency replacement processing for reducing the aliasing distortion component included in the video signal after the vertical interpolation processing. Replacement means; and horizontal interpolation means for performing horizontal interpolation processing on the video signal after the high-frequency replacement processing for horizontally expanding an image reproduced using the video signal after the high-frequency replacement processing The high-frequency replacement means includes an LPF means for performing a filtering process for extracting a low-frequency component of the video signal, a means for generating a luminance signal using the video signal, and a high-frequency component of the luminance signal. HP that performs filtering Means, an adding means for adding the low frequency component of the video signal and the high frequency component of the luminance signal, and horizontal / vertical control means for controlling the LPF means and the HPF means. The vertical control means is configured to perform the control according to the zoom magnification of the electronic zoom process. With this configuration, the characteristics of the LPF and the HPF are controlled with respect to aliasing distortion that appears conspicuously as the zoom magnification increases, and the high-frequency component ratio of the luminance signal Y that is greatly affected by aliasing distortion is changed. Zoom image quality with resolution can be obtained.
[0015]
Further, the electronic zoom device of the present invention is a device that performs an electronic zoom process on an input video signal, and performs a vertical interpolation process for vertically expanding an image reproduced using the input video signal. A high-frequency section that performs vertical interpolation on the video signal after the vertical interpolation processing, and a vertical-interpolation unit that performs the high-frequency replacement processing for reducing the aliasing distortion component included in the video signal after the vertical interpolation processing. Replacement means; and horizontal interpolation means for performing horizontal interpolation processing on the video signal after the high-frequency replacement processing for horizontally expanding an image reproduced using the video signal after the high-frequency replacement processing A thinning means for thinning out the video signal at a predetermined rate; a video signal correcting means for performing a predetermined video signal correction process on the video signal after the thinning process; and a video signal after the video signal correction process. Folding distortion included A high-frequency substituting means for performing a high-frequency substituting process for reducing the frequency, and the input video signal is a signal digitized after imaging performed using three solid-state imaging devices, Each pixel in one of the two solid-state image sensors is arranged to be shifted by 1/2 pixel in the horizontal scanning direction with respect to each corresponding pixel in the other two solid-state image sensors. Of each video signal after the horizontal interpolation processing, the video signal via the one solid-state imaging device and the video signal via the other two solid-state imaging devices have a phase difference of ½ pixel. The high-frequency replacement means extracts LPF means for performing a filtering process for extracting a low-frequency component of the video signal, means for generating a luminance signal using the video signal, and extracts a high-frequency component of the luminance signal. Filter processing to HPF means, adding means for adding the low frequency component of the video signal and the high frequency component of the luminance signal, and horizontal / vertical control means for controlling the LPF means and the HPF means, The horizontal / vertical control means is configured to perform the control according to the zoom magnification of the electronic zoom process. With this configuration, the characteristics of the LPF and the HPF are controlled with respect to aliasing distortion that appears conspicuously as the zoom magnification increases, and the high-frequency component ratio of the luminance signal Y that is greatly affected by aliasing distortion is changed. Zoom image quality with resolution can be obtained.
[0016]
Further, the electronic zoom device of the present invention is a device that performs an electronic zoom process on an input video signal, and performs a vertical interpolation process for vertically expanding an image reproduced using the input video signal. A high-frequency section that performs vertical interpolation on the video signal after the vertical interpolation processing, and a vertical-interpolation unit that performs the high-frequency replacement processing for reducing the aliasing distortion component included in the video signal after the vertical interpolation processing. Replacement means; and horizontal interpolation means for performing horizontal interpolation processing on the video signal after the high-frequency replacement processing for horizontally expanding an image reproduced using the video signal after the high-frequency replacement processing A thinning means for thinning out the video signal at a predetermined rate; a video signal correcting means for performing a predetermined video signal correction process on the video signal after the thinning process; and a video signal after the video signal correction process. Folding distortion included A high-frequency substituting means for performing a high-frequency substituting process for reducing the frequency, and the input video signal is a signal digitized after imaging performed using three solid-state imaging devices, Each pixel in one of the two solid-state image sensors is arranged to be shifted by 1/2 pixel in the horizontal scanning direction with respect to each corresponding pixel in the other two solid-state image sensors. Of each video signal after the horizontal interpolation processing, the video signal via the one solid-state imaging device and the video signal via the other two solid-state imaging devices have a phase difference of ½ pixel. It has a structure to thin out. With this configuration, the characteristics of the LPF and the HPF are controlled with respect to aliasing distortion that appears conspicuously as the zoom magnification increases, and the high-frequency component ratio of the luminance signal Y that is greatly affected by aliasing distortion is changed. Zoom image quality with resolution can be obtained.
[0017]
Further, the electronic zoom device of the present invention is a device that performs an electronic zoom process on an input video signal, and performs a vertical interpolation process for vertically expanding an image reproduced using the input video signal. A high-frequency section that performs vertical interpolation on the video signal after the vertical interpolation processing, and a vertical-interpolation unit that performs the high-frequency replacement processing for reducing the aliasing distortion component included in the video signal after the vertical interpolation processing. Replacement means; and horizontal interpolation means for performing horizontal interpolation processing on the video signal after the high-frequency replacement processing for horizontally expanding an image reproduced using the video signal after the high-frequency replacement processing A thinning means for thinning out the video signal at a predetermined rate; a video signal correcting means for performing a predetermined video signal correction process on the video signal after the thinning process; and a video signal after the video signal correction process. Folding distortion included A high-frequency substituting means for performing a high-frequency substituting process for reducing the frequency, and the input video signal is a signal digitized after imaging performed using three solid-state imaging devices, Each pixel in one of the two solid-state image sensors is arranged to be shifted by 1/2 pixel in the horizontal scanning direction with respect to each corresponding pixel in the other two solid-state image sensors. Of each video signal after the horizontal interpolation processing, the video signal via the one solid-state imaging device and the video signal via the other two solid-state imaging devices have a phase difference of ½ pixel. In this configuration, the high-frequency replacement processing by the high-frequency replacement means and the subsequent high-frequency replacement processing by the subsequent high-frequency replacement means are performed in conjunction with each other. With this configuration, since the characteristics of the LPF and the HPF constituting the high frequency replacement means and the characteristics of the LPF and the HPF constituting the post-high frequency replacement means are changed in conjunction with each other, the zoom A high-resolution zoom image quality in which the aliasing distortion component that changes according to the magnification is reduced can be obtained.
[0018]
Further, the electronic zoom method of the present invention is a method of performing an electronic zoom process on an input video signal, wherein a vertical interpolation process for enlarging an image reproduced using the input video signal in the vertical direction is performed. A high-frequency band that is applied to the video signal after the vertical interpolation process, and a vertical interpolation step that is applied to the input video signal and a high-frequency replacement process for reducing aliasing distortion components included in the video signal after the vertical interpolation process. A horizontal interpolation step for performing a horizontal interpolation process for horizontally expanding an image reproduced using the video signal after the high-frequency replacement process on the video signal after the high-frequency replacement process; It has the composition provided with. With this configuration, since the vertical interpolation step for performing the vertical interpolation process for enlarging the image in the vertical direction before performing the high-frequency replacement process is provided, the storage device required for the vertical interpolation process is provided. The memory capacity is never doubled. In addition, since a horizontal interpolation processing step for performing horizontal interpolation processing after the high-frequency replacement processing is provided, it is possible to realize a high-resolution electronic zoom with reduced aliasing distortion using pixel shift.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
As shown in FIG. 1, the electronic zoom device according to the first embodiment of the present invention includes a vertical interpolation circuit 3, a high-frequency replacement circuit 4, and a horizontal interpolation circuit 9.
[0020]
Hereinafter, the operation of the electronic zoom device according to the first embodiment will be described. The R, G, and B input video signals are input to the vertical interpolation circuit 3, and the vertical interpolation circuit 3 performs vertical interpolation processing for zooming the image in the vertical direction. Each video signal after the vertical interpolation processing is input to the high-frequency replacement circuit 4, and the high-frequency replacement circuit 4 performs high-frequency replacement processing for canceling the aliasing distortion component from the video signal. Each video signal after the high-frequency replacement processing is input to the horizontal interpolation circuit 9, and the horizontal interpolation circuit 9 performs horizontal interpolation processing for zooming the image in the horizontal direction.
[0021]
FIG. 2 is a flowchart showing a flow of processing in the electronic zoom method according to the first embodiment of the present invention. In this electronic zoom method, the following processing is performed on each of the R, G, and B input video signals.
In step S201, the vertical interpolation circuit 3 performs vertical interpolation processing on the R, G, and B input video signals for zooming the image in the vertical direction. In step S202, the high-frequency replacement circuit 4 performs high-frequency replacement processing for canceling the aliasing distortion component from each video signal on each video signal after the vertical interpolation processing. In step S203, the horizontal interpolation circuit 9 performs horizontal interpolation processing for zooming the image in the horizontal direction on each video signal after the high-frequency replacement processing.
[0022]
As described above, in the electronic zoom device according to the first embodiment of the present invention, the vertical interpolation circuit 3 is provided in the input stage of the high-frequency replacement circuit 4, and the horizontal interpolation circuit is provided in the output stage of the high-frequency replacement circuit 4. 9 is provided, it is possible to perform high-resolution electronic zoom in consideration of pixel shift.
Further, the electronic zoom method according to the first embodiment of the present invention includes step S201 for performing vertical interpolation processing on the input video signal, and thereafter, providing step S202 for performing high frequency replacement processing. Since step S203 for performing horizontal interpolation processing is provided later, high-resolution electronic zoom can be performed in consideration of pixel shift.
[0023]
FIG. 3 is a block diagram showing the configuration of the electronic zoom device according to the second embodiment of the present invention. The electronic zoom device according to the second embodiment includes an imaging unit 1, an A / D converter 2, a field memory 13, a horizontal / vertical control circuit 12, a vertical interpolation circuit 3, and a vertical interpolation described later. The line memory 14 used in the processing, the high-frequency replacement circuit 4, the horizontal interpolation circuit 9 having the thinning circuit 17, the contour correction circuit 10 having the line memory 15, and the subsequent high-frequency replacement circuit 11 are included.
[0024]
The operation of the electronic zoom device according to the second embodiment will be described below.
In the imaging unit (CCD image sensor) 1, a technique called pixel shift unique to a three-plate CCD camera is used in order to obtain a high-resolution image using a CCD having the same number of pixels. Of the CCDs for the R signal, the G signal, and the B signal in the imaging unit 1, the CCD for the R signal and the B signal are imaged with a 1/2 pixel pitch shifted from the CCD for the G signal. Composed. The imaging unit 1 outputs the captured R, G, and B video signals to the A / D converter 2.
[0025]
The A / D converter 2 converts each input analog video signal into a digital video signal and temporarily stores it in the field memory 13. Each digital video signal stored in the field memory 13 is input to the vertical interpolation circuit 3 and subjected to vertical interpolation processing which is interpolation processing for enlarging an image in the vertical direction by the vertical interpolation circuit 3. . In this vertical interpolation process, the line memory 14 is used.
[0026]
Each video signal after the vertical interpolation processing is input to the high-frequency replacement circuit 4, and high-frequency replacement processing for reducing the aliasing distortion component is performed by the high-frequency replacement circuit 4. Each video signal after the high-frequency replacement processing is subjected to horizontal interpolation processing for enlarging the image in the horizontal direction by the horizontal interpolation circuit 9. Each video signal after the horizontal interpolation process is thinned by a thinning circuit 17 in the horizontal interpolation circuit 9 so that the G signal has a horizontal spatial phase difference of 1/2 pixel with respect to the R signal and the B signal. Is output.
[0027]
By generating R, G, and B video signals in which the G signal has a horizontal spatial phase difference of 1/2 pixel with respect to the R signal and the B signal, the aliasing distortion component due to the pixel shift is temporarily restored. The video signal from which the aliasing distortion component has been restored is subjected to contour correction processing for improving the image quality by the contour correction circuit 10. At that time, the line memory 15 is used for the contour correction processing.
[0028]
As described above, since the video signal output from the thinning circuit 17 is thinned, there is no problem that the memory capacity required for the line memory 15 is doubled as compared with the case where pixel shifting is not performed.
[0029]
With reference to FIG. 4, the memory capacities with and without thinning will be compared. The contour correction circuit 10 shown in FIG. 4 includes a line memory 15 and a filter circuit 16, and each line memory 15 has the same memory capacity. For example, in the contour correction circuit 10 using two line memories 15 for 1H delay, if thinning is not performed, the line memory 15 necessary for processing is doubled and four line memories 15 for 1H delay are required. .
[0030]
Since the aliasing distortion component of the video signal output from the contour correction circuit 10 is restored by the decimation circuit 17 in the horizontal interpolation circuit 9, the subsequent high-frequency replacement circuit 11 reduces the aliasing distortion component to achieve high resolution. High-frequency replacement processing is performed to obtain the image quality. Therefore, the post-stage high-frequency replacement circuit 11 outputs a video signal that can obtain high-resolution image quality with reduced aliasing distortion components.
[0031]
As described above, the electronic zoom device according to the second embodiment of the present invention includes the high-frequency replacement circuit 4 and the thinning circuit 17 that thins out signals in the horizontal scanning direction when performing the horizontal interpolation process. Therefore, even when a contour correction circuit that uses a memory to improve the image quality is used, the circuit capacity can be reduced and the cost can be reduced without doubling the memory capacity of the storage device.
[0032]
FIG. 5 shows a circuit for performing high-frequency replacement processing in the electronic zoom device according to the third embodiment of the present invention. FIG. 5 shows a specific example of a circuit applied to the high-frequency replacement circuit 4 described in the first embodiment or the second embodiment or the post-high-frequency replacement circuit 11 described in the second embodiment. It is a figure which shows an example. Therefore, the R, G, and B input video signals shown in FIG. 5 are outputs from the vertical interpolation circuit 3 or the contour correction circuit 10.
[0033]
The high-frequency replacement circuit 4 or the subsequent high-frequency replacement circuit 11 includes an LPF 5, a luminance signal generation circuit 6, an HPF 7, and an addition circuit 8 in FIG.
[0034]
The operation of the high-frequency replacement circuit or the subsequent high-frequency replacement circuit configured as described above will be described. Since the high-frequency replacement circuit and the subsequent high-frequency replacement circuit operate in the same manner, the high-frequency replacement circuit will be described below as a representative.
The input signal of the high frequency replacement circuit is input to the LPF 5 for extracting the low frequency component and the luminance signal generation circuit 6 for generating the luminance signal. The HPF 7 performs filter processing for extracting a high frequency luminance component from the luminance signal generated by the luminance signal generation circuit 6. The adder circuit 8 adds the low frequency component extracted by the LPF 5 and the high frequency luminance component extracted by the HPF 7. By adding these, the high-frequency component of the luminance signal that is greatly influenced by the aliasing distortion component is reduced in the aliasing distortion component.
[0035]
Further, in order to cope with the change of the band where the aliasing distortion component appears according to the change of the zoom magnification, the horizontal / vertical control circuit 11 generates the filter coefficients of the LPF 5 and the HPF 7 according to the zoom magnification, and the LPF 5 and the Control the characteristics of HPF7. Further, by linking the processing in the high-frequency replacement circuit 4 and the processing in the subsequent high-frequency replacement circuit 11, the characteristics of the LPF 5 and the HPF 7 constituting the high-frequency replacement circuit 4 and the subsequent high-frequency replacement circuit 11 are configured. Since the characteristics of the LPF 5 and the HPF 7 to be changed are interlockedly changed, a high-resolution zoom image quality in which the aliasing distortion component that changes according to the zoom magnification is reduced can be obtained.
[0036]
For example, the horizontal / vertical control circuit 11 reduces the cutoff frequency of the zoom magnification LPF5 and increases the high frequency component band of the HPF of the luminance signal with respect to the aliasing distortion component that appears prominently as the zoom magnification increases. To control. Thereby, the aliasing distortion component can be canceled and the image quality can be improved.
[0037]
As described above, the circuit for high-frequency replacement processing in the electronic zoom device according to the third embodiment of the present invention includes the LPF 5 that performs the filter processing for extracting the low-frequency component of the video signal, and the luminance signal generation that generates the luminance signal. A circuit 6, an HPF 7 that performs a filtering process for extracting a high-frequency luminance signal, and an addition circuit 8 that adds a low-frequency component and a high-frequency luminance component of the video signal are provided to control the LPF 5 and the HPF 7 in accordance with the zoom magnification. Therefore, the aliasing distortion component can be canceled according to the zoom magnification, and the image quality can be improved.
[0038]
In the above embodiment, the case where the contour correction circuit is used as the video signal correction circuit has been described. However, in the present invention, in addition to the contour correction circuit, other signal processing that uses a memory to improve the image quality. The present invention can be similarly applied to a circuit, for example, a noise reduction circuit used as a storage unit such as a line memory.
[0039]
【The invention's effect】
As described above, the present invention provides a high-frequency replacement circuit that reduces aliasing distortion components, a vertical interpolation circuit for enlarging an image in the vertical direction before the high-frequency replacement circuit, and the high-frequency replacement circuit. An electronic zoom device capable of reducing the circuit scale and reducing the cost without doubling the memory capacity of the storage device by including a horizontal interpolation circuit for enlarging the image in the horizontal direction at the subsequent stage Can be provided.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of an electronic zoom device according to a first embodiment of the present invention.
FIG. 2 is a flowchart showing a flow of processing in the electronic zoom device according to the first embodiment of the present invention.
FIG. 3 is a block diagram showing a configuration of an electronic zoom device according to a second embodiment of the present invention.
FIG. 4 is a diagram for explaining a comparison of memory capacities of a contour correction circuit in an electronic zoom device according to a second embodiment of the present invention.
FIG. 5 is a block diagram of a circuit that performs high-frequency replacement processing in an electronic zoom device according to a third embodiment of the present invention.
FIG. 6 is a conceptual diagram for explaining pixel shifting in an imaging unit, which is a conventional technique.
[Explanation of symbols]
1 Imaging unit
2 A / D converter
3 Vertical interpolation circuit
4 High-frequency replacement circuit
5 LPF
6 Luminance signal generation circuit
7 HPF
8 Adder circuit
9 Horizontal interpolation circuit
10 Contour correction circuit
11 Subsequent high-frequency replacement circuit
12 Horizontal and vertical control circuit
13 Field memory
14 line memory
15 line memory
16 Filter circuit
17 Thinning circuit

Claims

In an apparatus that performs electronic zoom processing on an input video signal,
Vertical interpolation means for subjecting the input video signal to vertical interpolation processing for vertically expanding an image reproduced using the input video signal;
High-frequency replacement means for performing high-frequency replacement processing for reducing the aliasing distortion component included in the video signal after the vertical interpolation processing on the video signal after the vertical interpolation processing;
Horizontal interpolation means for performing horizontal interpolation processing on the video signal after the high-frequency replacement processing for horizontally interpolating an image reproduced using the video signal after the high-frequency replacement processing An electronic zoom device characterized by the above.

The apparatus for performing the electronic zoom processing further includes thinning means for thinning out the video signal at a predetermined ratio, video signal correcting means for performing predetermined video signal correction processing on the video signal after the thinning processing, Subsequent high-frequency replacement means for performing high-frequency replacement processing for reducing aliasing distortion components included in the video signal after the video signal correction processing,
The input video signal is a signal digitized after imaging performed using three solid-state imaging devices, and each pixel in one solid-state imaging device among the three solid-state imaging devices is the other two The corresponding pixels in the solid-state image sensor are arranged by being shifted by 1/2 pixel in the horizontal scanning direction, and the thinning-out means passes through the one solid-state image sensor among the video signals after the horizontal interpolation process. 2. The electronic zoom device according to claim 1, wherein the video signal is thinned out so that the video signal and the video signal via the other two solid-state imaging devices have a phase difference corresponding to the ½ pixel.

The high-frequency replacement means includes an LPF means for performing a filtering process for extracting a low-frequency component of a video signal, a means for generating a luminance signal using the video signal, and a filtering process for extracting a high-frequency component of the luminance signal HPF means for performing the above, addition means for adding the low frequency component of the video signal and the high frequency component of the luminance signal, and horizontal / vertical control means for controlling the LPF means and the HPF means,
The electronic zoom apparatus according to claim 1, wherein the horizontal / vertical control unit performs the control according to a zoom magnification of the electronic zoom process.

The post-high-frequency replacement means extracts LPF means for performing a filtering process for extracting a low-frequency component of each video signal, means for generating a luminance signal using each video signal, and extracts a high-frequency component of the luminance signal HPF means for performing filtering processing, adding means for adding the low frequency component of each video signal and the high frequency component of the luminance signal, horizontal / vertical control means for controlling the LPF means and the HPF means, Have
3. The electronic zoom device according to claim 2, wherein the horizontal / vertical control means performs the control in accordance with a zoom magnification of the electronic zoom process.

3. The electronic zoom device according to claim 2, wherein the electronic zoom device performs a high-frequency replacement process by the high-frequency replacement unit and a post-high-frequency replacement process by the post-high-frequency replacement unit in conjunction with each other.

In a method of performing electronic zoom processing on an input video signal,
A vertical interpolation step for performing a vertical interpolation process on the input video signal for vertically expanding an image reproduced using the input video signal;
A high-frequency replacement step for performing high-frequency replacement processing for reducing the aliasing distortion component included in the video signal after the vertical interpolation processing on the video signal after the vertical interpolation processing;
A horizontal interpolation step for applying a horizontal interpolation process to the video signal after the high-frequency replacement process to horizontally expand an image reproduced using the video signal after the high-frequency replacement process; An electronic zoom method characterized by the above.