JP2009261025A - Defective pixel output signal correcting method - Google Patents

Defective pixel output signal correcting method Download PDF

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JP2009261025A
JP2009261025A JP2009185618A JP2009185618A JP2009261025A JP 2009261025 A JP2009261025 A JP 2009261025A JP 2009185618 A JP2009185618 A JP 2009185618A JP 2009185618 A JP2009185618 A JP 2009185618A JP 2009261025 A JP2009261025 A JP 2009261025A
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defective pixel
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JP4900435B2 (en
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Tadao Shinya
忠雄 新屋
Koji Kuriyama
孝司 栗山
Toshihide Kobayashi
敏秀 小林
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Victor Company of Japan Ltd
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Abstract

<P>PROBLEM TO BE SOLVED: To provide a defective pixel correcting method for preventing a defective pixel portion from being colored when the color around a defective pixel is pale or a colorless subject image is captured. <P>SOLUTION: A defective pixel correcting circuit determines whether an incoming signal has been output from a defective pixel or from a normal pixel (S101). When it is output from the normal pixel, the incoming signal is output as an output image signal as it is (S102). When it is output from the defective pixel, it is determined whether the vicinity of the defective pixel is colored or colorless (S103). If the vicinity of the defective pixel is determined as colored, pre-interpolation is used (S104), while if determined as colorless, an image signal of another color component is used to generate an output image signal of the defective pixel so that an image at a position of the defective pixel becomes colorless (S105). Thus, a correction method can be provided for preventing a defective pixel portion from becoming colored if the surrounding color is pale or colorless. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

本発明は、撮像装置に用いる撮像素子の欠陥画素から出力される出力信号を補正する方法に関する。   The present invention relates to a method for correcting an output signal output from a defective pixel of an image sensor used in an imaging apparatus.

多数の画素を持つ撮像素子においては製造過程で発生する結晶欠陥等により正常な信号を出力することができない画素(欠陥画素)が存在しており、従来から、この欠陥画素の出力信号を補正する工夫が行われている（例えば、特許文献１、特許文献２参照）。
このような欠陥画素に対する従来の補正方法を図３ないし図５を用いて説明する。
図３は欠陥画素の補正形態を示すブロック図、図４は欠陥画素補正方法のフローチャート、図５は欠陥画素補正信号の生成方法を表した図である。 In an image sensor with a large number of pixels, there are pixels (defective pixels) that cannot output a normal signal due to crystal defects, etc. that occur during the manufacturing process. Conventionally, the output signal of this defective pixel is corrected. A device has been devised (see, for example, Patent Document 1 and Patent Document 2).
A conventional correction method for such defective pixels will be described with reference to FIGS.
FIG. 3 is a block diagram showing a correction form of defective pixels, FIG. 4 is a flowchart of the defective pixel correction method, and FIG. 5 is a diagram showing a generation method of a defective pixel correction signal.

まず、図３において欠陥画素の補正形態を説明する。
同図の制御回路３０３は、撮像素子３０１に読み出し制御信号Aを供給し、また、撮像素子上の欠陥画素の位置が予め記憶されており、上記読み出し制御信号Aに同期して欠陥画素が読み出されるタイミングで欠陥補正制御信号Bを欠陥画素補正回路３０２に供給する。
撮像素子３０１は、制御回路３０３から供給される読み出し制御信号Aにより、順次被写体の明るさに応じた画像信号Pを欠陥画素補正回路３０２に出力する。欠陥画素補正回路３０２は、制御回路３０３から供給される欠陥補正制御信号Bによって、入来した画像信号Pが欠陥画素の出力か正常画素の出力かを逐次判断し、正常画素である場合は画像信号Pをそのまま出力画像信号Qとして出力し、欠陥画素である場合は所定の処理で出力画像信号Qを生成し出力する。 First, a correction form of defective pixels will be described with reference to FIG.
The control circuit 303 in FIG. 3 supplies a read control signal A to the image sensor 301, and the position of the defective pixel on the image sensor is stored in advance, and the defective pixel is read in synchronization with the read control signal A. The defect correction control signal B is supplied to the defective pixel correction circuit 302 at the same timing.
The image sensor 301 sequentially outputs an image signal P corresponding to the brightness of the subject to the defective pixel correction circuit 302 according to the read control signal A supplied from the control circuit 303. The defective pixel correction circuit 302 sequentially determines whether the incoming image signal P is an output of a defective pixel or an output of a normal pixel based on the defect correction control signal B supplied from the control circuit 303. The signal P is output as it is as the output image signal Q, and if it is a defective pixel, the output image signal Q is generated and output by a predetermined process.

次に、図４のフローチャートを用いて上記欠陥画素補正回路３０２の信号処理を説明する。
今、撮像素子の画素座標nの画素から読み出される画像信号をP(n)、画素座標nの画素が欠陥画素か正常画素かを示す欠陥補正制御信号をB(n)、画素座標nの画素に対する欠陥画素補正回路の出力画像信号をQ(n)とする。
まず、欠陥画素補正回路は、欠陥補正制御信号B(n)によって、入来した画像信号P(n)が欠陥画素の出力か正常画素の出力かを判断する (ステップＳ４０１) 。
上記判断結果が正常画素であった場合は、画像信号P(n)をそのまま出力画像信号Q(n)として出力する (ステップＳ４０２) 。
また、上記判断結果が欠陥画素であった場合は、欠陥画素の近傍に位置する画素の信号から欠陥画素に対する補正信号Qを生成する。この例では、欠陥画素の１つ手前の画像信号P(n-1)を用いて出力画像信号Q(n)として出力する (ステップＳ４０３) 。
以上の流れで信号処理が行われる。 Next, the signal processing of the defective pixel correction circuit 302 will be described using the flowchart of FIG.
Now, P (n) is an image signal read from the pixel at the pixel coordinate n of the image sensor, B (n) is a defect correction control signal indicating whether the pixel at the pixel coordinate n is a defective pixel or a normal pixel, and a pixel at the pixel coordinate n Let Q (n) be the output image signal of the defective pixel correction circuit for.
First, the defective pixel correction circuit determines whether the incoming image signal P (n) is an output of a defective pixel or an output of a normal pixel based on the defect correction control signal B (n) (step S401).
If the determination result is a normal pixel, the image signal P (n) is output as it is as the output image signal Q (n) (step S402).
When the determination result is a defective pixel, a correction signal Q for the defective pixel is generated from a signal of a pixel located in the vicinity of the defective pixel. In this example, the output image signal Q (n) is output using the image signal P (n-1) immediately before the defective pixel (step S403).
Signal processing is performed according to the above flow.

次に、図５を用いて上記欠陥画素の補正の具体例を示す。
今、図５(a)で示すように、(n-2)、(n-1)・・の画素座標の順で画像信号が欠陥画素補正回路に入来し、座標ｎの画素が欠陥画素であるとする。
座標(n-2)の画素はステップＳ４０１で正常画素と判断され、ステップＳ４０２で画像信号P(n-2)がそのまま出力画像信号Q(n-2)として出力される。同様に座標(n-1)の画素も正常画素と判断されP(n-1)がそのままQ(n-1)として出力される。
一方、座標nの画素は欠陥補正制御信号Bによって欠陥画素であることが示されるため、ステップＳ４０１で欠陥画素と判断され、ステップＳ４０３で座標nの１つ手前の座標(n-1)の画像信号P(n-1)が出力画像信号Q(n)として出力される。
座標(n+1)および(n+2)の画素は再び正常画素と判断され、P(n+1)およびP(n+2)がそのままQ(n+1)およびQ(n+2)として出力される。
図５(b)に上記欠陥画素補正回路で補正された出力画像信号Qを示す。この図では欠陥画素の出力画像信号Q(n)は座標(n-1)の画像信号P(n-1)が補正信号として使われていることを表している。 Next, a specific example of the correction of the defective pixel will be shown using FIG.
Now, as shown in FIG. 5 (a), the image signal enters the defective pixel correction circuit in the order of the pixel coordinates of (n-2), (n-1),. Suppose that
The pixel at the coordinate (n-2) is determined to be a normal pixel in step S401, and the image signal P (n-2) is output as it is as the output image signal Q (n-2) in step S402. Similarly, the pixel at the coordinate (n-1) is also determined as a normal pixel, and P (n-1) is output as Q (n-1) as it is.
On the other hand, since the pixel at the coordinate n is indicated as a defective pixel by the defect correction control signal B, it is determined as a defective pixel at step S401, and the image at the coordinate (n-1) immediately before the coordinate n is determined at step S403. The signal P (n−1) is output as the output image signal Q (n).
Pixels with coordinates (n + 1) and (n + 2) are judged as normal pixels again, and P (n + 1) and P (n + 2) remain as Q (n + 1) and Q (n + 2) Is output as
FIG. 5B shows the output image signal Q corrected by the defective pixel correction circuit. In this figure, the output image signal Q (n) of the defective pixel indicates that the image signal P (n-1) at the coordinate (n-1) is used as a correction signal.

特公昭６０−０１３５４９号公報Japanese Patent Publication No. 60-013549 特公昭６２−０４０９１７号公報Japanese Examined Patent Publication No. 62-40917

前記した従来の欠陥画素の補正方法は、欠陥画素の信号を１画素前の信号に置き換える前置補間方式を用いており、一般的な被写体像の撮像では実用的な補正が行えるが、欠陥画素の周囲の色が薄い場合や無彩色の被写体像の場合には、欠陥画素の部分に別の色が着きそこだけ目立つ欠点がある。この現象について図６を用いて説明する。   The above-described conventional defective pixel correction method uses a pre-interpolation method in which the signal of the defective pixel is replaced with the signal of the previous pixel, and a practical correction can be performed in capturing a general subject image. In the case where the surrounding color is light or an achromatic subject image, there is a disadvantage that another color arrives at the defective pixel portion and stands out so much. This phenomenon will be described with reference to FIG.

図６はカラー撮像装置に用いるＲＧＢ３つの撮像素子の欠陥画素補正処理を示している。同図で（ａ）（ｄ）はＲ成分、（ｂ）（ｅ）はＧ成分、（ｃ）（ｆ）はＢ成分の補正である。また、ＲＧＢ３つの色成分の画像信号は夫々PR、PG、PBで表し、同様に欠陥画素補正回路で補正された出力画像信号はQR、QG、QBで表している。
今、被写体像として無彩色（ＲＧＢ各成分のレベルがほぼ等しい場合）で比較的細かい絵柄の場合を例にする。詳細には、同図（ａ）（ｂ）（ｃ）に示すように、座標(n-2)と(n-1)の各信号レベルが小さく、画素座標nと(n+1)、(n+2)の信号レベルが大きいものとし、Ｂ成分の座標nの画素が欠陥画素とする。
このような画像信号に対してＲＧＢ各成分において従来の欠陥画素補正処理を行なうと同図（ｄ）（ｅ）（ｆ）に示すような出力画像信号となる。
ここで、欠陥画素のある座標nのＲＧＢ各成分のレベルを見ると、Ｂ成分の出力画像信号QB(n)のレベルが小さくなっており、したがってこの座標nの部分の画像は無彩色にはならずに色が着くことになる。
このことから、周囲は色が着いていない中で一点だけ有彩色となり、補正したにもかかわらず欠陥画素が認知されてしまう欠点が発生する。 FIG. 6 shows a defective pixel correction process for three RGB image sensors used in a color imaging apparatus. In the figure, (a) and (d) are corrections for the R component, (b) and (e) are corrections for the G component, and (c) and (f) are corrections for the B component. In addition, the image signals of the three RGB color components are represented by PR, PG, and PB, respectively, and the output image signals that are similarly corrected by the defective pixel correction circuit are represented by QR, QG, and QB.
Now, a case where the subject image is an achromatic color (when the levels of RGB components are substantially equal) and a relatively fine picture is taken as an example. Specifically, as shown in FIGS. 5A, 5B, and 5C, the signal levels of the coordinates (n-2) and (n-1) are small, and the pixel coordinates n and (n + 1), ( Assume that the signal level of (n + 2) is high, and the pixel at the coordinate n of the B component is a defective pixel.
When conventional defective pixel correction processing is performed on each of the RGB components for such an image signal, an output image signal as shown in FIGS.
Here, looking at the level of each RGB component of coordinate n where there is a defective pixel, the level of the output image signal QB (n) of the B component is small, and therefore the image at this coordinate n is achromatic. The color will arrive without.
For this reason, there is a drawback in that the surrounding area is chromatic color only in the absence of color, and defective pixels are recognized despite correction.

本発明は、このような従来の問題点に鑑みなされたものであり、その目的は、撮像装置に用いる撮像素子において、欠陥画素の周囲の色が薄い場合や無彩色の被写体像を撮像した場合に欠陥画素部分が有彩色になることを防止する欠陥画素からの出力信号の補正方法を提供するものである。   The present invention has been made in view of such conventional problems, and an object of the present invention is to capture an achromatic subject image when the surrounding color of a defective pixel is light in an imaging device used in an imaging device. The present invention also provides a method for correcting an output signal from a defective pixel, which prevents the defective pixel portion from becoming a chromatic color.

本発明は、（１），（２）により上記課題を解決する。すなわち、
（１）複数の画素がマトリクス状に配列された撮像素子を少なくとも３つ備え、前記撮像素子のいずれかに欠陥画素を有する場合、欠陥画素から出力される出力信号を補正する欠陥画素出力信号補正方法であって、前記欠陥画素が前記撮像素子の内の一の撮像素子にあり、前記欠陥画素の位置が予め記憶されており、前記撮像素子の各画素から順次出力信号が出力され、前記欠陥画素から前記出力信号が出力されるタイミングで欠陥補正制御信号が供給され、前記欠陥補正制御信号が供給された際に、前記欠陥画素からの前記出力信号を欠陥画素出力信号と判断する欠陥画素出力信号判断ステップと、前記一の撮像素子の前記欠陥画素の近傍に位置する第１の近傍画素から出力される第１の近傍画素出力信号の信号レベルと、前記一の撮像素子以外の撮像素子における前記一の撮像素子の前記欠陥画素の座標にそれぞれ対応する座標の対応画素の近傍に位置する第２の近傍画素から出力される第２の近傍画素出力信号の信号レベルとにおける最大値と最小値との差を所定値と比較する信号レベル比較ステップと、前記差が前記所定値より小さい場合には、前記欠陥画素出力信号の信号レベルを、前記対応画素からそれぞれ出力される出力信号の信号レベルの最大値と最小値との間の値として出力する出力信号補正ステップと、を含むことを特徴とする欠陥画素出力信号補正方法。
（２）前記出力信号補正ステップにおいて、前記欠陥画素出力信号のレベルを、前記対応画素からそれぞれ出力される出力信号の信号レベルの平均値として出力することを特徴とする（１）記載の欠陥画素出力信号補正方法。 The present invention solves the above problems by (1) and (2). That is,
(1) Defective pixel output signal correction for correcting an output signal output from a defective pixel when at least three imaging elements in which a plurality of pixels are arranged in a matrix are provided and any of the imaging elements has a defective pixel. In the method, the defective pixel is in one of the imaging elements, the position of the defective pixel is stored in advance, and an output signal is sequentially output from each pixel of the imaging element. A defective pixel output for supplying a defect correction control signal at a timing when the output signal is output from the pixel, and determining the output signal from the defective pixel as a defective pixel output signal when the defect correction control signal is supplied A signal determination step, a signal level of a first neighboring pixel output signal output from a first neighboring pixel located in the vicinity of the defective pixel of the one imaging device, and the one imaging device And the signal level of the second neighboring pixel output signal output from the second neighboring pixel located in the vicinity of the corresponding pixel at the coordinate corresponding to the coordinate of the defective pixel of the one imaging device in the other imaging device. A signal level comparison step for comparing the difference between the maximum value and the minimum value with a predetermined value, and when the difference is smaller than the predetermined value, the signal level of the defective pixel output signal is output from the corresponding pixel, respectively. An output signal correcting step for outputting the output signal as a value between the maximum value and the minimum value of the signal level of the output signal.
(2) In the output signal correcting step, the level of the defective pixel output signal is output as an average value of the signal levels of the output signals output from the corresponding pixels, respectively. Output signal correction method.

欠陥画素からの出力信号の補正において、欠陥画素の近傍の色が薄い場合や無彩色の場合に、欠陥画素部分が着色してしまう現象がなくなり良好な画質の画像信号を得ることが可能となる。   In the correction of the output signal from the defective pixel, when the color near the defective pixel is light or achromatic, there is no phenomenon that the defective pixel portion is colored, and an image signal with good image quality can be obtained. .

本発明による欠陥画素出力補正方法のフローチャートである。3 is a flowchart of a defective pixel output correction method according to the present invention. 本発明による欠陥画素補正信号の生成方法を表した図である。It is a figure showing the production | generation method of the defective pixel correction signal by this invention. 欠陥画素の補正形態を示すブロック図である。It is a block diagram which shows the correction | amendment form of a defective pixel. 従来の欠陥画素補正方法のフローチャートである。It is a flowchart of the conventional defective pixel correction method. 従来の欠陥画素補正信号の生成方法を表した図である。It is a figure showing the production | generation method of the conventional defective pixel correction signal. 従来のカラー信号における欠陥画素補正信号の生成方法を表した図である。It is a figure showing the production | generation method of the defective pixel correction signal in the conventional color signal.

以下、本発明を実施するための最良の形態について、図面と共に説明する。
図１は本発明に係る欠陥画素出力補正方法の一実施例を示すフローチャート、図２は本発明による欠陥画素補正信号の生成方法を表した図である。
また、本発明の欠陥画素の補正形態は図３のブロック図で示すものであるが、これは背景技術で述べたので説明を省略する。なお、本実施例の説明では図３を参照することがある。
本実施例の説明では上記と同様に、ＲＧＢ３つの色成分の画像信号は夫々PR、PG、PBで表し、欠陥画素補正回路の出力画像信号は夫々QR、QG、QBで表してある。
また、図１において、ＲＧＢ３つの色成分のうち、欠陥画素の画像信号をPX、同じく欠陥画素補正回路で補正された出力画像信号をQXとし、欠陥画素でない残り２つの色成分の画像信号を夫々PY、PZ、同じく欠陥画素補正回路の出力画像信号を夫々QY、QZとして表してある。
以下、本実施例ではＢ成分に欠陥画素があるとして説明をする。 The best mode for carrying out the present invention will be described below with reference to the drawings.
FIG. 1 is a flowchart showing an embodiment of a defective pixel output correction method according to the present invention, and FIG. 2 is a diagram showing a defective pixel correction signal generation method according to the present invention.
Moreover, although the correction form of the defective pixel of this invention is shown with the block diagram of FIG. 3, since this was described in background art, description is abbreviate | omitted. In the description of the present embodiment, FIG. 3 may be referred to.
In the description of the present embodiment, similarly to the above, the image signals of the three RGB color components are represented by PR, PG, and PB, respectively, and the output image signals of the defective pixel correction circuit are represented by QR, QG, and QB, respectively.
In FIG. 1, among the three color components of RGB, the image signal of the defective pixel is PX, the output image signal corrected by the defective pixel correction circuit is QX, and the image signals of the remaining two color components that are not defective pixels are respectively shown. PY, PZ, and similarly output image signals of the defective pixel correction circuit are represented as QY and QZ, respectively.
Hereinafter, in the present embodiment, description will be made assuming that there is a defective pixel in the B component.

まず、図１のフローチャートを用いて、図３に示す欠陥画素補正回路３０２の信号処理を説明する。
今、Ｂ成分撮像素子の画素座標nの画素から読み出される画像信号をPB(n)、画素座標nの画素が欠陥画素か正常画素かを示す欠陥補正制御信号をB(n)、画素座標nの画素に対する欠陥画素補正回路の出力画像信号をQB(n)とする。
図３に示す欠陥画素補正回路３０２は、欠陥補正制御信号B(n)によって、入来した画像信号PB(n)が欠陥画素の出力か正常画素の出力かを判断する (ステップＳ１０１) 。
上記判断結果が正常画素であった場合は画像信号PB(n)をそのまま出力画像信号QB(n)として出力する (ステップＳ１０２) 。 First, the signal processing of the defective pixel correction circuit 302 shown in FIG. 3 will be described using the flowchart of FIG.
Now, an image signal read from a pixel at a pixel coordinate n of the B component image sensor is PB (n), a defect correction control signal indicating whether the pixel at the pixel coordinate n is a defective pixel or a normal pixel is B (n), and a pixel coordinate n Let QB (n) be the output image signal of the defective pixel correction circuit for this pixel.
The defective pixel correction circuit 302 shown in FIG. 3 determines whether the incoming image signal PB (n) is an output of a defective pixel or an output of a normal pixel based on the defect correction control signal B (n) (step S101).
If the determination result is a normal pixel, the image signal PB (n) is output as it is as the output image signal QB (n) (step S102).

一方、上記判断結果が欠陥画素であった場合は、欠陥画素の近傍に位置する画素(近傍画素)の彩度(有彩色か無彩色か)を判定する。
本実施例では、近傍画素として座標(n-1)および座標(n+1)の画素を用い、彩度の判定方法として、近傍画素の各色成分のうちレベルが最大の色成分信号から最小の色成分信号を減算し、この減算結果と予め設定した所定の値Kとの比較により近傍画素が有彩色か無彩色かを判定する。この時の判定式は下式となる。
max[PB(n-1),PR(n-1),PG(n-1)]−min[PB(n-1),PR(n-1),PG(n-1)]＜K
max[PB(n+1),PR(n+1),PG(n+1)]−min[PB(n+1),PR(n+1),PG(n+1)]＜K
上記の２つの式が成立したときに近傍画素は無彩色と判定する(ステップＳ１０３)。
なお、Kは一例として最大信号レベルの５パーセント位の値を用いる。 On the other hand, if the determination result is a defective pixel, the saturation (whether chromatic or achromatic) of a pixel (neighboring pixel) located in the vicinity of the defective pixel is determined.
In this embodiment, pixels of coordinates (n-1) and coordinates (n + 1) are used as neighboring pixels, and as a method for determining saturation, the color component signal having the highest level among the color components of neighboring pixels The color component signal is subtracted, and it is determined whether the neighboring pixel is a chromatic color or an achromatic color by comparing the subtraction result with a predetermined value K set in advance. The judgment formula at this time is the following formula.
max [PB (n-1), PR (n-1), PG (n-1)]-min [PB (n-1), PR (n-1), PG (n-1)] <K
max [PB (n + 1), PR (n + 1), PG (n + 1)] − min [PB (n + 1), PR (n + 1), PG (n + 1)] <K
When the above two expressions are satisfied, the neighboring pixels are determined to be achromatic colors (step S103).
For example, a value of about 5 percent of the maximum signal level is used for K.

上記の彩度判定ステップＳ１０３において、近傍画素が有彩色と判定されたときは、欠陥画素の１つ手前の座標(n-1)の画像信号PB(n-1)を欠陥画素の補正信号QB(n)として出力する (ステップＳ１０４) 。
一方、彩度判定ステップＳ１０３において、近傍画素が無彩色と判定されたときは欠陥画素部分の画像も無彩色であると仮定し補正結果が無彩色になるように補正信号を生成する。
本来座標nの画素が無彩色であれば座標nにおける各色間の信号レベルの差は小さいから、逆に無彩色を得るには各色間の信号レベル差が最も小さくなるような補正信号を生成すればよい。そこで、本実施例では、欠陥画素ではない他の２つの色成分の座標nにおける画像信号PR(n)とPG(n)の平均値を欠陥画素の補正信号QB(n)として出力するようにしている (ステップＳ１０５) 。 In the saturation determination step S103, when the neighboring pixel is determined to be a chromatic color, the image signal PB (n-1) at the coordinate (n-1) immediately before the defective pixel is used as the correction signal QB for the defective pixel. Output as (n) (step S104).
On the other hand, in the saturation determination step S103, when the neighboring pixel is determined to be achromatic, it is assumed that the image of the defective pixel is also achromatic, and a correction signal is generated so that the correction result is achromatic.
If the pixel at the coordinate n is originally an achromatic color, the difference in signal level between the colors at the coordinate n is small, so conversely, to obtain an achromatic color, a correction signal that generates the smallest signal level difference between the colors should be generated. That's fine. Therefore, in this embodiment, the average value of the image signals PR (n) and PG (n) at the coordinate n of the other two color components that are not defective pixels is output as the defective pixel correction signal QB (n). (Step S105).

次に、図２を用いて上記欠陥画素の補正の具体例を示す。同図は欠陥画素を持つＢ成分の補正を示している。
今、図２(a)で示すように、(n-2)、(n-1)・・の画素座標の順で画像信号が欠陥画素補正回路に入来し、座標ｎの画素が欠陥画素であるとする。
座標(n-2)の画素はステップＳ１０１で正常画素と判断され、ステップＳ１０２で画像信号P(n-2)がそのまま出力画像信号Q(n-2)として出力される。同様に座標(n-1)の画素も正常画素と判断されP(n-1)がそのままQ(n-1)として出力される。
次いで、座標nは欠陥画素であるからステップＳ１０３において近傍画素の彩度が判定される。この例では、近傍画素は無彩色であるからステップＳ１０５において欠陥画素も無彩色になるように、座標nにおけるR成分画像信号PR (n)とG成分画像信号PG (n)との平均値がＢ成分の補正信号QB(n)として出力される。
図２(b)はこうして補正されたＢ成分の出力画像信号を示している。 Next, a specific example of the correction of the defective pixel will be shown using FIG. This figure shows correction of the B component having defective pixels.
Now, as shown in FIG. 2 (a), the image signal enters the defective pixel correction circuit in the order of the pixel coordinates of (n-2), (n-1),. Suppose that
The pixel at the coordinate (n-2) is determined as a normal pixel in step S101, and the image signal P (n-2) is output as it is as the output image signal Q (n-2) in step S102. Similarly, the pixel at the coordinate (n-1) is also determined as a normal pixel, and P (n-1) is output as Q (n-1) as it is.
Next, since the coordinate n is a defective pixel, the saturation of the neighboring pixels is determined in step S103. In this example, since the neighboring pixels are achromatic, the average value of the R component image signal PR (n) and the G component image signal PG (n) at the coordinate n is set so that the defective pixel also becomes achromatic in step S105. It is output as a B component correction signal QB (n).
FIG. 2B shows the output image signal of the B component corrected in this way.

以上詳述したごとく、本実施例では、欠陥画素の近傍画素が無彩色の場合には、欠陥画素部分の画像が無彩色になるように欠陥画素の補正信号を生成している。これにより周囲が無彩色であるにもかかわらず欠陥画素部分に色が着く問題は生じなくなる。
なお、本実施例では、欠陥画素部分の彩度の判定を行うのに、近傍画素として欠陥画素(座標n)に隣接する２座標(座標n-1とn+1)のＲＧＢ成分を用いたが、これに限らず、上下方向を含むより多くの画素を用いることで近傍画素の彩度判定精度を高めることができる。逆に精度は低下するが隣接１画素(座標n-1)だけを用いて処理を簡素化することも可能である。
また、近傍画素が無彩色の際の欠陥画素に対する補正信号として、残る２つの色成分の平均値レベルを補正信号として用いたが、これに限らず、一方の色成分レベルを用いて処理を簡素化することも可能である。
さらに、本実施例では、カラー信号を構成する成分としてＲＧＢを用いたが、これに限ることなく他の色成分を用いても良い。 As described above in detail, in this embodiment, when the neighboring pixel of the defective pixel is achromatic, the correction signal for the defective pixel is generated so that the image of the defective pixel portion is achromatic. As a result, the problem that the defective pixel portion is colored even though the periphery is achromatic color does not occur.
In the present embodiment, the RGB components of two coordinates (coordinates n−1 and n + 1) adjacent to the defective pixel (coordinate n) are used as neighboring pixels to determine the saturation of the defective pixel portion. However, the present invention is not limited to this, and the saturation determination accuracy of neighboring pixels can be increased by using more pixels including the vertical direction. On the other hand, although the accuracy is lowered, it is possible to simplify the processing using only one adjacent pixel (coordinate n−1).
In addition, the average value level of the remaining two color components is used as the correction signal as the correction signal for the defective pixel when the neighboring pixel is achromatic. However, the present invention is not limited to this, and the processing is simplified using one color component level. It is also possible to
Further, in this embodiment, RGB is used as a component constituting the color signal, but other color components may be used without being limited to this.

３０１：撮像素子
３０２：欠陥画素補正回路
３０３：制御回路 301: Image sensor 302: Defective pixel correction circuit 303: Control circuit

Claims (2)

複数の画素がマトリクス状に配列された撮像素子を少なくとも３つ備え、前記撮像素子のいずれかに欠陥画素を有する場合、欠陥画素から出力される出力信号を補正する欠陥画素出力信号補正方法であって、
前記欠陥画素が前記撮像素子の内の一の撮像素子にあり、前記欠陥画素の位置が予め記憶されており、前記撮像素子の各画素から順次出力信号が出力され、前記欠陥画素から前記出力信号が出力されるタイミングで欠陥補正制御信号が供給され、前記欠陥補正制御信号が供給された際に、前記欠陥画素からの前記出力信号を欠陥画素出力信号と判断する欠陥画素出力信号判断ステップと、
前記一の撮像素子の前記欠陥画素の近傍に位置する第１の近傍画素から出力される第１の近傍画素出力信号の信号レベルと、前記一の撮像素子以外の撮像素子における前記一の撮像素子の前記欠陥画素の座標にそれぞれ対応する座標の対応画素の近傍に位置する第２の近傍画素から出力される第２の近傍画素出力信号の信号レベルとにおける最大値と最小値との差を所定値と比較する信号レベル比較ステップと、
前記差が前記所定値より小さい場合には、前記欠陥画素出力信号の信号レベルを、前記対応画素からそれぞれ出力される出力信号の信号レベルの最大値と最小値との間の値として出力する出力信号補正ステップと、
を含むことを特徴とする欠陥画素出力信号補正方法。 This is a defective pixel output signal correction method for correcting an output signal output from a defective pixel when at least three imaging elements each having a plurality of pixels arranged in a matrix are provided and any of the imaging elements has a defective pixel. And
The defective pixel is in one of the image sensors, the position of the defective pixel is stored in advance, an output signal is sequentially output from each pixel of the image sensor, and the output signal from the defective pixel When a defect correction control signal is supplied at a timing when is output, and when the defect correction control signal is supplied, a defective pixel output signal determination step of determining the output signal from the defective pixel as a defective pixel output signal;
The signal level of the first neighboring pixel output signal output from the first neighboring pixel located in the vicinity of the defective pixel of the one imaging device, and the one imaging device in an imaging device other than the one imaging device The difference between the maximum value and the minimum value of the signal level of the second neighboring pixel output signal output from the second neighboring pixel located in the vicinity of the corresponding pixel at the coordinates corresponding to the coordinates of the defective pixel is predetermined. A signal level comparison step for comparing with the value;
When the difference is smaller than the predetermined value, the output that outputs the signal level of the defective pixel output signal as a value between the maximum value and the minimum value of the signal level of the output signal output from the corresponding pixel, respectively. A signal correction step;
A defective pixel output signal correction method comprising: 前記出力信号補正ステップにおいて、前記欠陥画素出力信号のレベルを、前記対応画素からそれぞれ出力される出力信号の信号レベルの平均値として出力することを特徴とする請求１記載の欠陥画素出力信号補正方法。   2. The defective pixel output signal correction method according to claim 1, wherein in the output signal correction step, the level of the defective pixel output signal is output as an average value of signal levels of output signals output from the corresponding pixels. .
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