JP4155559B2 - Signal processing apparatus and method - Google Patents

Description

【００２６】
のように演算する。次に、混合比率演算回路１７において、距離ｄにより混合比率ｒを演算する。例えば、画像中心から最も距離の離れた画素位置までの距離をDmaxとすると、
r = d/Dmax …（４）
のように演算する。このようにすると、中心付近では混合比率ｒが０となり、周辺で１となる。
また、距離ｄと混合比率ｒの関係を図５のように作成しておき、テーブル変換によって距離ｄから混合比率ｒを求めるように構成してもよい。
【００２７】
輝度混合回路８では、上記混合比率ｒを用いて、輝度信号１と輝度信号２を次式（５）のように混合して混合輝度信号Ymixを得る。なお、式（５）において、輝度信号１はＹ１、輝度信号２はＹ２、比率ｒは輝度信号１の混合比率を示すものとする。従って、輝度信号２の混合比率は（１−ｒ）により表される。
Ymix = rY1 + (1-r)Y2 …（５）
【００２８】
図６は、図５に示す比率を用いて、輝度混合回路８により輝度信号１及び輝度信号２を混合した結果を図示したものである。中央部ではSwitch Y方式の輝度が採用され、周辺ではOut Of Green方式の輝度、中間部では両方式の輝度を混合した輝度が採用されている。
【００２９】
以上のように構成することで、画像の中心部分と周辺部分で異なる方式の輝度信号を採用することが可能となり、レンズ系の色収差の影響を受けにくい輝度信号を作成することが可能となる。
【００３０】
即ち、本第１の実施形態によれば、入力した画像信号に基づいて、第１の方式により第１の輝度信号を生成し、同じ画像信号に基づいて、第２の方式により第２の輝度信号を生成し、第１及び第２の輝度信号を混合する割合を決定し、決定した割合に応じて、第１及び第２の輝度信号を混合する。
【００３１】
より具体的には、混合する割合を決定する時には、画像信号の画像における位置を検出し、検出した位置に基づいて、混合する割合を決定する。
【００３２】
更に具体的には、前記第１の方式は、Out of Green方式であって、前記第２の方式は、Switch Y方式である。
【００３３】
＜第２の実施形態＞
本第２の実施形態では、第１の実施形態に加え、さらに、画像の特定個所のみ複数の輝度信号を混合することが可能な実施形態について説明する。
【００３４】
第１の実施形態では、輝度信号１と輝度信号２を被写体によらず、画像の中心からの距離に応じて混合していたが、色の濃い被写体の場合、輝度信号の色構成比の違いにより輝度レベルが異なってくる。例えば、（Ｒ，Ｇ，Ｂ）＝（２００，０，０）という色の場合、色の構成比がＲ：Ｇ：Ｂ＝３：６：１の場合、Ｙ＝６０くらいになるが、色の構成比がＲ：Ｇ：Ｂ＝１：２：１の場合、Ｙ＝５０くらいになる。そのため、色の濃い被写体を撮影した場合、輝度信号１と輝度信号２の輝度レベルの差が激しくなり、切り替えポイントでの輝度段差が気になる場合がある。
【００３５】
これを避けるためには、色の濃い部分については、輝度信号を混合せずに、Out of Green方式で得られた輝度信号１をそのまま用いる。
【００３６】
図７は、本第２の実施形態における撮像装置の構成を示すブロック図である。図７では、図１の構成に信号処理装置４’内に混合位置検出回路１８が加わったもので、その他の構成は図１と同じであるため、同じ構成については詳細説明を省略する。以下、本第２の実施形態における動作を、図８のフローチャートを参照しながら説明するが、第１の実施形態で説明した図２のフローチャートの処理と同様の処理には同じ参照番号を付し、一部説明を省略する。
【００３７】
信号処理装置４は、ＷＢ回路３によりＷＢ処理された信号を受け取とると（ステップＳ１１）、Out of Green輝度回路５において、Out of Green方式により輝度信号１を作成し（ステップＳ１２）、SwichY輝度回路６により、SwichY方式により輝度信号２を作成する（ステップＳ１３）。その後、入力した信号の彩度から、輝度信号混合を行うか否かを判断するが（ステップＳ２１）、この判断は混合位置検出回路１８で行われる。
【００３８】
図９は、本第２の実施形態における混合位置検出回路１８の構成例を示すブロック図である。まず、彩度演算回路１９において、例えば、次式（６）に従って彩度を演算する。なお、式（６）のChmは、彩度である。
【００３９】

【００４０】
次に、混合度合い決定回路２０において、ある閾値より彩度が小さい場合にのみ輝度を混合するように決定する。例えば、閾値ＴＨとＣｈｍを比較し、Ｃｈｍの方が小さい場合には輝度を混合すると判定し、１の信号を発生する。逆の場合にはしないと判定し、０の信号を発生する。
【００４１】
輝度混合回路８’において、この信号を受け取り、１が与えられた場合のみ、輝度の混合を実施するよう構成する（ステップＳ１４〜Ｓ１６）。なお、輝度の混合は、上記第１の実施形態で説明したようにして行われる。０の場合には、Out of Green方式で得られた輝度信号１を出力する。
【００４２】
上記の通り第２の実施形態によれば、彩度が小さい部分のみ輝度の混合が実施されるため、上記問題を回避することが可能となる。
【００４３】
なお、上記第２の実施形態では、混合するかしないかを彩度と閾値とを比較して０、１で判定したが、彩度に応じて０〜１の連続的な数値で混合度合いを決定するように構成してもよい。
【００４４】
即ち、本第２の実施形態によれば、上記第１の実施形態の構成に加えて、画像信号の彩度に応じて、第１及び第２の輝度信号を混合するか否かを判断し、混合すると判断した場合に、第１及び第２の輝度信号を混合する。
【００４５】
より具体的には、上記判断を行う時に、画像信号の彩度を検出し、検出した彩度を予め決められた閾値と比較し、閾値よりも小さい場合に第１及び第２の輝度信号を混合し、大きい場合に前記第１及び第２の輝度信号を混合しないと決定する。
【００４６】
また、別の構成では、上記第１の実施形態の構成に加えて、前記画像信号の彩度に応じて、第１及び第２の輝度信号を混合する割合を判断し、上記決定された２種類の割合に応じて、第１及び第２の輝度信号を混合する。
【００４７】
より具体的には、前記第１の方式は、Out of Green方式であって、彩度に基づく判断で混合しないと判断した場合に、第１の輝度信号をそのまま出力する。
【００４８】
【他の実施形態】
なお、本発明は、複数の機器（例えばホストコンピュータ、インターフェイス機器、スキャナ、カメラヘッドなど）から構成されるシステムに適用しても、一つの機器からなる装置（例えば、デジタルスチルカメラ、デジタルビデオカメラ、複写機、ファクシミリ装置など）に適用してもよい。
【００４９】
また、本発明の目的は、前述した実施形態の機能を実現するソフトウェアのプログラムコードを記録した記憶媒体（または記録媒体）を、システムあるいは装置に供給し、そのシステムあるいは装置のコンピュータ（またはＣＰＵやＭＰＵ）が記憶媒体に格納されたプログラムコードを読み出し実行することによっても、達成されることは言うまでもない。この場合、記憶媒体から読み出されたプログラムコード自体が前述した実施形態の機能を実現することになり、そのプログラムコードを記憶した記憶媒体は本発明を構成することになる。また、コンピュータが読み出したプログラムコードを実行することにより、前述した実施形態の機能が実現されるだけでなく、そのプログラムコードの指示に基づき、コンピュータ上で稼働しているオペレーティングシステム（ＯＳ）などが実際の処理の一部または全部を行い、その処理によって前述した実施形態の機能が実現される場合も含まれることは言うまでもない。ここでプログラムコードを記憶する記憶媒体としては、例えば、フレキシブルディスク、ハードディスク、ＲＯＭ、ＲＡＭ、磁気テープ、不揮発性のメモリカード、ＣＤ−ＲＯＭ、ＣＤ−Ｒ、ＤＶＤ、光ディスク、光磁気ディスク、ＭＯなどが考えられる。
【００５０】
さらに、記憶媒体から読み出されたプログラムコードが、コンピュータに挿入された機能拡張カードやコンピュータに接続された機能拡張ユニットに備わるメモリに書込まれた後、そのプログラムコードの指示に基づき、その機能拡張カードや機能拡張ユニットに備わるＣＰＵなどが実際の処理の一部または全部を行い、その処理によって前述した実施形態の機能が実現される場合も含まれることは言うまでもない。
【００５１】
本発明を上記記憶媒体に適用する場合、その記憶媒体には、先に説明した図２または図８に示すフローチャートに対応するプログラムコードが格納されることになる。
【００５２】
【発明の効果】
上記の通り本発明によれば、より質の高い輝度信号を得ると共に、色収差によるモアレの発生を抑制することができる。
【図面の簡単な説明】
【図１】本発明の第１の実施形態における撮像装置の概略構成を示すブロック図である。
【図２】本発明の第１の実施形態における輝度信号生成手順を示すフローチャートである。
【図３】本発明の第１の実施形態におけるOut of Green輝度回路の構成例を示すブロック図である。
【図４】本発明の第１の実施形態における混合比率変更回路の構成例を示すブロック図である。
【図５】本発明の第１の実施形態における中心から各画素までの距離に対する、混合比率の例を示す図である。
【図６】本発明の第１の実施形態における輝度信号１及び輝度信号２を混合した結果を示す図である。
【図７】本発明の第２の実施形態における撮像装置の構成を示すブロック図である。
【図８】本発明の第２の実施形態における輝度信号生成手順を示すフローチャートである。
【図９】本発明の第２の実施形態における混合位置検出回路の構成例を示すブロック図である。
【図１０】原色ベイヤー配列を示す図である。
【図１１】 Switch Y方式の説明図である。
【図１２】 Switch Y方式で輝度信号生成を行う回路の構成例を示すブロック図である。
【図１３】色収差を説明するための図である。
【符号の説明】
１ 撮像素子
２ Ａ／Ｄ変換回路
３ ホワイトバランス回路
４、４’ 信号処理装置
５ OutofGreen輝度回路
６ SwichY輝度回路
７ 混合比率変更回路
８、８’ 輝度混合回路
９ Ｒ補間回路
１０ Ｂ補間回路
１１ Ｇ補間回路
１２ 輪郭補正回路
１３ 乗算回路
１４ 加算回路
１５ 画素位置検出回路
１６ 距離演算回路
１７ 混合比率演算回路
１８ 混合位置検出回路
１９ 彩度演算回路
２０ 混合度合い決定回路
１０１ 射出瞳
１０２ 固体撮像素子
１２０１ ベース信号補間回路
１２０２ 高域強調回路
１２０３ 加算器[0001]
BACKGROUND OF THE INVENTION
The present invention relates to signal processing, and more particularly to processing for creating a luminance signal from an output signal from an image sensor having a plurality of color filters.
[0002]
[Prior art]
Conventionally, the SwitchY method and the OutofGreen method are known as methods for creating a luminance signal based on an output color signal from a solid-state imaging device. Hereinafter, these methods will be described by taking as an example a case where the solid-state imaging device is covered with a color filter having a primary color Bayer arrangement as shown in FIG.
[0003]
The SwitchY method is a method in which a signal subjected to white balance (hereinafter referred to as WB) processing after A / D conversion of an output signal from a solid-state imaging device is regarded as a luminance signal Y as it is. FIG. 11 is a diagram showing the concept of the obtained luminance signal Y, and the number after Y indicates the pixel position. Usually, in order to suppress the generation of carriers due to sampling, the result of applying a low-pass filter (hereinafter referred to as LPF) having an output of 0 at the Nyquist frequency in the horizontal direction and the vertical direction is used as the base signal. For example, when the filter coefficient of the LPF is [1 2 1] in both the horizontal direction and the vertical direction, the output Y22 ′ from the LPF of the Y22 pixel is
Y22 '= (Y11 + 2 × Y12 + Y13 + 2 × Y21 + 4 × Y22 + 2 × Y23
+ Y31 + 2 x Y32 + Y33) / 16… (1)
[0004]
Can be obtained as follows.
Further, as shown in FIG. 12, a high frequency emphasis signal is created by the high-order Kikyocho circuit 1202 from the base signal obtained from the base signal interpolation circuit 1201, and the original base signal is added by the adder 1203, thereby obtaining a high frequency signal. Can be obtained.
[0005]
However, in an actual imaging system, a lens system is disposed in front of the solid-state imaging device, and light that has passed through the lens system is sampled by the solid-state imaging device. Chromatic aberration occurs in the light that has passed through the lens system, and therefore, the position sampled differs depending on the color when it comes to the periphery of the image.
[0006]
This phenomenon will be described with reference to FIG. In the figure, 101 is an exit pupil of a lens system, and 102 is a solid-state image sensor such as a CCD. FIG. 13 shows light from the exit pupil 101 onto the imaging plane. For example, the solid line indicates blue and the broken line indicates red light. Even if chromatic aberration occurs as shown in FIG. 13A at the center of the image, the center of gravity of sampling does not change. On the periphery of the image, the sampling position differs depending on the color as shown in FIG. 13B.
[0007]
Therefore, particularly in the vicinity of the image, the position of the image to be sampled differs for each color of the image sensor, so that moire due to the sampling position deviation occurs. For example, in the case of the filter array as shown in FIG. 10, the sampling positions at the R position and the B position are substantially deviated from the G position, and an interference pattern is generated in the image.
[0008]
[Problems to be solved by the invention]
As described above, since light passing through the lens system has chromatic aberration, sampling is shifted substantially depending on the color of the color filter even if the arrangement of the solid-state imaging devices is equally spaced. Had occurred.
[0009]
The present invention has been made in view of the above problems, and an object of the present invention is to obtain a higher quality luminance signal and to suppress the occurrence of moire due to chromatic aberration.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, the signal processing apparatus of the present invention includes a first luminance signal generating means for outputting a first luminance signal by an Out of Green method based on an input image signal, and the input image. A second luminance signal generating means for outputting a second luminance signal by the Switch Y method based on the signal; a mixing ratio determining means for determining a ratio of mixing the first and second luminance signals; and the mixing Mixing means for mixing the first and second luminance signals according to the ratio determined by the ratio determining means, and the mixing ratio determining means detects the position of the image signal in the image; The mixing ratio of the second luminance signal is increased as the position of the image signal in the image approaches the center, and the mixing ratio of the first luminance signal is increased as the position of the image signal in the image is away from the center. Yo And a means for determining the mixing ratio.
The signal processing method of the present invention includes a first luminance signal generation step of outputting a first luminance signal by an Out of Green method based on an input image signal, and a Switch based on the input image signal. A second luminance signal generating step of outputting a second luminance signal by the Y method, a step of detecting the position of the image signal in the image, and the second luminance as the position of the image signal in the image approaches the center. The ratio of mixing the first and second luminance signals is determined such that the mixing ratio of the signals is increased and the mixing ratio of the first luminance signals is increased as the position of the image signal in the image is further away from the center. And a mixing step of mixing the first and second luminance signals according to the determined ratio.
According to another configuration, the signal processing apparatus of the present invention includes an input unit that inputs an image signal obtained by the imaging unit, and a first luminance based on the input image signal by an Out of Green method. A first luminance signal generating means for outputting a signal; a second luminance signal generating means for outputting a second luminance signal by the Switch Y method based on the inputted image signal; and the imaging means for the image signal. A means for detecting the distance from the optical axis of the image signal; and the smaller the distance from the optical axis of the image signal, the larger the mixing ratio of the second luminance signal, and the greater the distance from the optical axis of the image signal, In accordance with the ratio determined by the mixing ratio determining means, the mixing ratio determining means for determining the ratio of mixing the first and second luminance signals so as to increase the mixing ratio of the first luminance signal, The first and second luminance signals And a mixing means for mixing the number.
In addition, an input step of inputting an image signal obtained by the imaging means, a first luminance signal generation step of outputting a first luminance signal by an Out of Green method based on the input image signal, and the input A second luminance signal generation step of outputting a second luminance signal by the Switch Y method based on the image signal, a step of detecting a distance of the image signal from the optical axis of the imaging means, and the image signal The mixing ratio of the second luminance signal is increased as the distance from the optical axis is reduced, and the mixing ratio of the first luminance signal is increased as the distance from the optical axis of the image signal is increased. A step of determining a ratio of mixing the first and second luminance signals; and a mixing step of mixing the first and second luminance signals according to the determined ratio.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
[0012]
<First Embodiment>
In the first embodiment, signals from a single-plate image sensor covered with a primary color Bayer array color filter composed of three colors of R (red), G (green), and B (blue) shown in FIG. A case where a luminance signal is obtained will be described.
[0013]
FIG. 1 is a block diagram showing a schematic configuration of an imaging apparatus according to the first embodiment of the present invention. The imaging apparatus includes, for example, a digital still camera and a digital video camera, but is not limited thereto, and an incident optical image is electrically converted by photoelectric conversion using a two-dimensionally arranged solid-state imaging device such as an area sensor. The present invention can be applied if it is acquired as an image.
[0014]
In FIG. 1, 1 is an image sensor such as a CCD (hereinafter referred to as a CCD) that photoelectrically converts incident light and outputs an electrical signal, 2 is an A / D conversion circuit, 3 is a white balance (WB) circuit, 4 Is a signal processing device. In the above configuration, a signal output from the CCD 1 is converted into a digital signal by the A / D conversion circuit 2 and a signal subjected to a known white balance (WB) process by the WB circuit 3 is input to the signal processing device 4. In FIG. 1, for the sake of simplification, a γ conversion circuit, a color generation circuit, and the like that are not directly related to the present invention are omitted.
[0015]
Next, the configuration and operation of the signal processing device 4 according to the first embodiment of the present invention will be described in detail with reference to FIGS. 1 to 6. FIG. 2 is a flowchart showing a luminance signal generation procedure in the first embodiment.
[0016]
As illustrated in FIG. 1, the signal processing device 4 includes an OutofGreen luminance circuit 5, a SwichY luminance circuit 6, a mixing ratio changing circuit 7, and a luminance mixing circuit 8. When the signal processing device 4 receives the signal subjected to the WB processing by the WB circuit 3 (Step S11), the Out of Green luminance circuit 5 creates the luminance signal 1 by the Out of Green method (Step S12).
[0017]
FIG. 3 is a block diagram illustrating a configuration example of the Out of Green luminance circuit 5 according to the first embodiment. An R interpolation circuit 9, a B interpolation circuit 10, and a G interpolation circuit 11 are provided in order to independently process the R, B, and G signals corresponding to the color filter positions of the CCD 1. For example, when processing an R signal, 0 is inserted into pixels other than R, and an LPF having a coefficient of [1 2 1] is applied in the horizontal and vertical directions, and the same applies to the G signal and the B signal. The luminance signal Y is generated by the multiplication circuit 13 and the addition circuit 14 as shown in the following equation.
Y = 0.3R + 0.59G + 0.11B (2)
[0018]
Further, the contour correction circuit 12 creates a high frequency emphasis signal from the G signal and adds it to Y. Thus, since the high frequency emphasis signal is created only from the G signal, the G signal becomes dominant in the luminance signal Y.
[0019]
On the other hand, the luminance signal 2 is created by the SwichY luminance circuit 6 by, for example, the SwichY method described in the prior art (step S13). The SwichY method is a method in which red (R) signal, green (G) signal, and blue (B) signal are regarded as luminance signals as they are, and imaging of the primary color Bayer array employed in the first embodiment is performed. In the case of an element, the color composition ratio of luminance is R: G: B = 1: 2: 1.
[0020]
In the luminance signal 2 obtained by the Switch Y method, as described in the conventional example, moiré is remarkably generated around the image. On the other hand, the luminance signal 1 by the Out of Green method is composed of the G signal as will be described later, so even if the sampling positions of the R signal and the B signal are shifted with respect to the G signal due to chromatic aberration, Insensitive to that. However, since the Out of Green method uses only about half of the CCD pixels as compared to the Switch Y method, it is more advantageous to use the Switch Y method at the center of the image.
[0021]
Therefore, in the first embodiment, the Switch Y method is adopted at the center of the image, the Out of Green method is adopted at the periphery of the image, and both the Switch Y method and the Out of Green method are adopted in the middle.
[0022]
The mixing ratio changing circuit 7 changes the mixing ratio of the luminance signal 1 and the luminance signal 2 according to the pixel position (step S14) (step S15). More specifically, the mixing ratio r is determined according to the distance d from the center (or optical axis) of the screen to each pixel. How to determine the mixing ratio will be described later in detail.
[0023]
Next, in the luminance mixing circuit 8, the luminance signal 1 and the luminance signal 2 are mixed using the mixing ratio r changed by the mixing ratio changing circuit 7 (step S16). This mixing method will also be described later in detail.
[0024]
FIG. 4 is a block diagram showing a configuration example of the mixing ratio changing circuit 7 in the first embodiment. First, the pixel position (x, y) being processed by the pixel position detection circuit 15 is detected. Next, the distance calculation circuit 16 calculates the distance from the image center (xc, yc). For example, the distance d is

[0026]
Calculate as follows. Next, the mixing ratio calculation circuit 17 calculates the mixing ratio r from the distance d. For example, if the distance from the image center to the farthest pixel position is Dmax,
r = d / Dmax (4)
Calculate as follows. In this way, the mixing ratio r is 0 near the center and 1 around.
Further, the relationship between the distance d and the mixing ratio r may be created as shown in FIG. 5, and the mixing ratio r may be obtained from the distance d by table conversion.
[0027]
In the luminance mixing circuit 8, the luminance signal 1 and the luminance signal 2 are mixed as shown in the following equation (5) using the mixing ratio r to obtain a mixed luminance signal Ymix. In equation (5), the luminance signal 1 is Y1, the luminance signal 2 is Y2, and the ratio r is the mixing ratio of the luminance signal 1. Therefore, the mixing ratio of the luminance signal 2 is represented by (1-r).
Ymix = rY1 + (1-r) Y2 (5)
[0028]
FIG. 6 shows the result of mixing the luminance signal 1 and the luminance signal 2 by the luminance mixing circuit 8 using the ratio shown in FIG. Switch Y method brightness is adopted in the center, Out Of Green method brightness in the periphery, and brightness obtained by mixing both types of brightness in the middle part.
[0029]
With the configuration as described above, it is possible to employ different types of luminance signals for the central portion and the peripheral portion of the image, and it is possible to create a luminance signal that is not easily affected by the chromatic aberration of the lens system.
[0030]
That is, according to the first embodiment, the first luminance signal is generated by the first method based on the input image signal, and the second luminance is generated by the second method based on the same image signal. A signal is generated, a ratio of mixing the first and second luminance signals is determined, and the first and second luminance signals are mixed according to the determined ratio.
[0031]
More specifically, when the mixing ratio is determined, the position of the image signal in the image is detected, and the mixing ratio is determined based on the detected position.
[0032]
More specifically, the first method is an Out of Green method, and the second method is a Switch Y method.
[0033]
<Second Embodiment>
In the second embodiment, in addition to the first embodiment, an embodiment capable of mixing a plurality of luminance signals only at a specific portion of an image will be described.
[0034]
In the first embodiment, the luminance signal 1 and the luminance signal 2 are mixed according to the distance from the center of the image regardless of the subject. However, in the case of a dark subject, the difference in the color composition ratio of the luminance signal Depending on the brightness level. For example, in the case of a color of (R, G, B) = (200, 0, 0), when the color composition ratio is R: G: B = 3: 6: 1, Y = 60, When the composition ratio of R: G: B = 1: 2: 1, Y = about 50. For this reason, when a dark subject is photographed, the difference between the luminance levels of the luminance signal 1 and the luminance signal 2 becomes severe, and the luminance level difference at the switching point may be anxious.
[0035]
In order to avoid this, the luminance signal 1 obtained by the Out of Green method is used as it is without mixing the luminance signal for the dark portion.
[0036]
FIG. 7 is a block diagram illustrating a configuration of the imaging apparatus according to the second embodiment. In FIG. 7, the mixed position detection circuit 18 is added to the configuration of FIG. 1 in the signal processing device 4 ′, and the other configurations are the same as those in FIG. 1, so detailed description of the same configurations is omitted. Hereinafter, the operation in the second embodiment will be described with reference to the flowchart of FIG. 8, but the same reference numerals are assigned to the same processes as those in the flowchart of FIG. 2 described in the first embodiment. Some explanations are omitted.
[0037]
When the signal processing device 4 receives the signal subjected to the WB processing by the WB circuit 3 (Step S11), the Out of Green luminance circuit 5 creates the luminance signal 1 by the Out of Green method (Step S12), and the SwichY luminance. The circuit 6 creates the luminance signal 2 by the SwichY method (step S13). Thereafter, it is determined from the saturation of the input signal whether or not luminance signal mixing is performed (step S21). This determination is performed by the mixing position detection circuit 18.
[0038]
FIG. 9 is a block diagram illustrating a configuration example of the mixed position detection circuit 18 in the second embodiment. First, the saturation calculation circuit 19 calculates the saturation according to the following equation (6), for example. Note that Chm in Equation (6) is saturation.
[0039]

[0040]
Next, the mixing degree determination circuit 20 determines to mix the luminance only when the saturation is smaller than a certain threshold value. For example, the threshold values TH and Chm are compared, and if Chm is smaller, it is determined that the luminance is mixed, and a signal of 1 is generated. In the opposite case, it is determined not to generate a 0 signal.
[0041]
The luminance mixing circuit 8 ′ receives this signal and configures the luminance mixing only when 1 is given (steps S14 to S16). Note that the luminance mixing is performed as described in the first embodiment. In the case of 0, the luminance signal 1 obtained by the Out of Green method is output.
[0042]
As described above, according to the second embodiment, since the luminance is mixed only in the portion with low saturation, the above problem can be avoided.
[0043]
In the second embodiment, whether to mix or not is determined by comparing the saturation and the threshold with 0 and 1, but the mixing degree is determined by a continuous numerical value of 0 to 1 according to the saturation. You may comprise so that it may determine.
[0044]
That is, according to the second embodiment, in addition to the configuration of the first embodiment, it is determined whether to mix the first and second luminance signals according to the saturation of the image signal. When it is determined that they are mixed, the first and second luminance signals are mixed.
[0045]
More specifically, when the above determination is made, the saturation of the image signal is detected, the detected saturation is compared with a predetermined threshold value, and if it is smaller than the threshold value, the first and second luminance signals are detected. If they are mixed and are large, it is determined not to mix the first and second luminance signals.
[0046]
In another configuration, in addition to the configuration of the first embodiment, the ratio of mixing the first and second luminance signals is determined according to the saturation of the image signal, and the determined 2 The first and second luminance signals are mixed according to the type ratio.
[0047]
More specifically, the first method is an Out of Green method, and when it is determined that mixing is not performed based on determination based on saturation, the first luminance signal is output as it is.
[0048]
[Other Embodiments]
Note that the present invention can be applied to a system composed of a plurality of devices (for example, a host computer, an interface device, a scanner, a camera head, etc.), or a device composed of a single device (for example, a digital still camera, a digital video camera). , Copying machines, facsimile machines, etc.).
[0049]
Another object of the present invention is to supply a storage medium (or recording medium) in which a program code of software that realizes the functions of the above-described embodiments is recorded to a system or apparatus, and the computer (or CPU or CPU) of the system or apparatus. Needless to say, this can also be achieved by the MPU) reading and executing the program code stored in the storage medium. In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiments, and the storage medium storing the program code constitutes the present invention. Further, by executing the program code read by the computer, not only the functions of the above-described embodiments are realized, but also an operating system (OS) running on the computer based on the instruction of the program code. It goes without saying that a case where the function of the above-described embodiment is realized by performing part or all of the actual processing and the processing is included. Examples of the storage medium for storing the program code include a flexible disk, hard disk, ROM, RAM, magnetic tape, nonvolatile memory card, CD-ROM, CD-R, DVD, optical disk, magneto-optical disk, MO, and the like. Can be considered.
[0050]
Furthermore, after the program code read from the storage medium is written into a memory provided in a function expansion card inserted into the computer or a function expansion unit connected to the computer, the function is determined based on the instruction of the program code. It goes without saying that the CPU or the like provided in the expansion card or the function expansion unit performs part or all of the actual processing and the functions of the above-described embodiments are realized by the processing.
[0051]
When the present invention is applied to the above-described storage medium, the program code corresponding to the flowchart shown in FIG. 2 or FIG. 8 described above is stored in the storage medium.
[0052]
【The invention's effect】
As described above, according to the present invention, it is possible to obtain a higher quality luminance signal and suppress the occurrence of moire due to chromatic aberration.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a schematic configuration of an imaging apparatus according to a first embodiment of the present invention.
FIG. 2 is a flowchart showing a luminance signal generation procedure in the first embodiment of the present invention.
FIG. 3 is a block diagram illustrating a configuration example of an Out of Green luminance circuit according to the first embodiment of the present invention.
FIG. 4 is a block diagram showing a configuration example of a mixing ratio changing circuit in the first embodiment of the present invention.
FIG. 5 is a diagram illustrating an example of a mixing ratio with respect to a distance from the center to each pixel in the first embodiment of the present invention.
FIG. 6 is a diagram showing a result of mixing a luminance signal 1 and a luminance signal 2 in the first embodiment of the present invention.
FIG. 7 is a block diagram illustrating a configuration of an imaging apparatus according to a second embodiment of the present invention.
FIG. 8 is a flowchart showing a luminance signal generation procedure according to the second embodiment of the present invention.
FIG. 9 is a block diagram illustrating a configuration example of a mixed position detection circuit according to a second embodiment of the present invention.
FIG. 10 is a diagram illustrating a primary color Bayer arrangement.
FIG. 11 is an explanatory diagram of a Switch Y method.
FIG. 12 is a block diagram illustrating a configuration example of a circuit that generates a luminance signal by the Switch Y method.
FIG. 13 is a diagram for explaining chromatic aberration.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Image pick-up element 2 A / D conversion circuit 3 White balance circuit 4, 4 'Signal processing apparatus 5 OutofGreen luminance circuit 6 SwichY luminance circuit 7 Mixing ratio change circuit 8, 8' Luminance mixing circuit 9 R interpolation circuit 10 B interpolation circuit 11 G Interpolation circuit 12 Outline correction circuit 13 Multiplication circuit 14 Addition circuit 15 Pixel position detection circuit 16 Distance calculation circuit 17 Mixing ratio calculation circuit 18 Mixed position detection circuit 19 Saturation calculation circuit 20 Mixing degree determination circuit 101 Exit pupil 102 Solid-state image sensor 1201 Base Signal interpolation circuit 1202 High frequency emphasis circuit 1203 Adder

Claims (14)

First luminance signal generating means for outputting a first luminance signal by the Out of Green method based on the input image signal;
Second luminance signal generation means for outputting a second luminance signal by the Switch Y method based on the input image signal;
Mixing ratio determining means for determining a ratio of mixing the first and second luminance signals;
Mixing means for mixing the first and second luminance signals in accordance with the ratio determined by the mixing ratio determining means,
The mixing ratio determining means includes
Means for detecting a position of the image signal in the image;
The mixing ratio of the second luminance signal is increased as the position of the image signal in the image approaches the center, and the mixing ratio of the first luminance signal is increased as the position of the image signal in the image is away from the center. And a means for determining the mixing ratio. A determination means for determining whether to mix the first and second luminance signals according to the saturation of the image signal;
The signal processing apparatus according to claim 1, wherein the mixing unit mixes the first and second luminance signals when the determination unit determines that the mixing is performed. The determination means includes
Means for detecting the saturation of the image signal;
When the detected saturation is compared with a predetermined threshold, the first and second luminance signals are mixed when the detected saturation is smaller than the threshold, and the first and second luminance signals are not mixed when the detected saturation is larger. The signal processing apparatus according to claim 2 , further comprising: a determining unit. A determination means for determining a ratio of mixing the first and second luminance signals according to the saturation of the image signal;
It said mixing means, according to the ratio which is determined by the ratio and the determining means is determined by the mixing ratio determining means, according to claim 1, characterized in that mixing the first and second luminance signals Signal processing equipment. Before SL when it is determined not to mix the determining means, the signal processing device according to any one of claims 2 to 4, characterized in that directly outputs the first luminance signal.   The signal processing apparatus according to claim 1, wherein the input image signal is an image signal obtained by an imaging unit covered with a Bayer color filter. An input unit that inputs an image signal obtained by an imaging unit whose characteristics of chromatic aberration change according to the position of the imaging surface;
The first luminance signal generation unit and the second luminance signal generation unit output the first luminance signal and the second luminance signal, respectively, based on the image signal input from the input unit. the signal processing apparatus according to any one of claims 1 to 6, wherein. Input means for inputting an image signal obtained by the imaging means;
First luminance signal generating means for outputting a first luminance signal by an Out of Green method based on the input image signal;
Second luminance signal generation means for outputting a second luminance signal by the Switch Y method based on the input image signal;
Means for detecting the distance of the image signal from the optical axis of the imaging means;
The mixing ratio of the second luminance signal is increased as the distance from the optical axis of the image signal is decreased, and the mixing ratio of the first luminance signal is increased as the distance from the optical axis of the image signal is increased. in a mixing ratio determining means for determining a ratio of mixing the first and second luminance signals,
A signal processing apparatus comprising: mixing means for mixing the first and second luminance signals in accordance with the ratio determined by the mixing ratio determining means. A first luminance signal generating step of outputting a first luminance signal by an Out of Green method based on the input image signal;
A second luminance signal generation step of outputting a second luminance signal by the Switch Y method based on the input image signal;
Detecting a position of the image signal in the image;
The mixing ratio of the second luminance signal is increased as the position of the image signal in the image approaches the center, and the mixing ratio of the first luminance signal is increased as the position of the image signal in the image moves away from the center. And determining a ratio of mixing the first and second luminance signals;
And a mixing step of mixing the first and second luminance signals in accordance with the determined ratio. An input step of inputting an image signal obtained by an imaging means whose chromatic aberration characteristics change according to the position of the imaging surface;
In the first luminance signal generation step and the second luminance signal generation step, the first luminance signal and the second luminance signal are output based on the input image signal, respectively. The signal processing method according to claim 9 . An input step of inputting an image signal obtained by the imaging means;
A first luminance signal generation step of outputting a first luminance signal by an Out of Green method based on the input image signal;
A second luminance signal generation step of outputting a second luminance signal by the Switch Y method based on the input image signal;
Detecting the distance of the image signal from the optical axis of the imaging means;
The mixing ratio of the second luminance signal is increased as the distance from the optical axis of the image signal is decreased, and the mixing ratio of the first luminance signal is increased as the distance from the optical axis of the image signal is increased. And determining a ratio of mixing the first and second luminance signals;
And a mixing step of mixing the first and second luminance signals according to the determined ratio. A program that can be executed by an information processing apparatus, and that causes the information processing apparatus that has executed the program to function as the signal processing apparatus according to any one of claims 1 to 8 . The program for making an information processing apparatus perform each process of the signal processing method of any one of Claim 9 thru | or 11 . A storage medium readable by an information processing apparatus, wherein the program according to claim 12 or 13 is stored.

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