JP2005198159A - Image processing method and imaging device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image processing method by which the optimal white balance adjustment is applied to image data only when a spectral characteristic of a light source changes without following movement of an object while a color rolling phenomenon is suppressed and to provide an imaging device which performs the white balance adjustment by the same method. <P>SOLUTION: In the image processing method for applying the white balance adjustment to continuously photographed image data, the white balance adjustment of the image data is performed based on image data of a part where no movement of the object is present among pieces of the photographed image data. In addition, in the imaging apparatus having an image processing means for performing the white balance adjustment, the image processing means performs the white balance adjustment of the image data based on the image data of a part where no movement of the object is present among the pieces of photographed image data. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image processing method and an imaging apparatus having an image processing means.

  Conventionally, when imaging an object such as a digital camera or a video camera, the spectral characteristics (ratio of color components of the three primary colors consisting of red, green, and blue) are automatically set according to the type of light source. The image processing means is determined (hereinafter referred to as “white balance adjustment”) (see, for example, Patent Document 1).

  An imaging apparatus having this image processing means generally performs white balance adjustment when the type of light source changes during shooting, but can also perform white balance adjustment even when shooting with the same light source. there were.

  That is, when a subject is photographed under a light source that periodically flickers, such as a fluorescent lamp, the color tone of the image is periodic due to the fact that the light source blinking cycle is different from the sampling cycle of the imaging device. It is known that a color rolling phenomenon that changes with time is generated, and white balance adjustment has been performed in order to suppress such a color rolling phenomenon.

In order to suppress the color rolling phenomenon, the time interval for executing the white balance adjustment is set narrow, and the color tone region where the white balance adjustment is not performed is set narrow so that the color tone of the image changes periodically. On the other hand, it was necessary to increase the followability of white balance adjustment.
Japanese Patent Laid-Open No. 8-186828

  However, in order to suppress the color rolling phenomenon as in the conventional image pickup device, the white balance adjustment follow-up ability to periodically change the color tone of the image by setting a narrow color tone area where no white balance adjustment is performed. When the image quality is increased, the movement (change) of the subject is recognized as a change in the spectral characteristics of the light source at the time of shooting, and there is a possibility that white balance adjustment may be performed even though there is no change in the spectral characteristics of the light source.

  Specifically, when shooting under a light source that has no change in spectral characteristics, such as natural light, when an object with high contrast such as a human face enters the shooting area, the imaging device May recognize the movement of the subject as a change in the spectral characteristics of the light source and perform white balance adjustment.

  In this way, when the imaging device recognizes the movement (change) of the subject as a change in the spectral characteristics of the light source and performs white balance adjustment, there is a color tone shift between the actual subject color tone and the photographed subject color tone. There was a risk of it occurring.

  Therefore, in the present invention according to claim 1, in the image processing method for performing white balance adjustment on continuously captured image data, the image is based on image data of a portion of the captured image data where no subject moves. We decided to adjust the white balance of the data.

  Further, in the present invention according to claim 2, in the image processing method for performing white balance adjustment on continuously captured image data, the image data is divided into a plurality of blocks, and the presence or absence of subject movement for each block The white balance adjustment of the image data is performed based on the image data of the block in which the subject does not move.

  Further, in the present invention according to claim 3, in the imaging apparatus having the image processing unit for performing white balance adjustment, the image processing unit is configured to perform image data based on image data of a portion where the subject does not move in the captured image data. I decided to adjust the white balance.

  And in this invention, there exists an effect described below.

  In the present invention according to claim 1, in the image processing method for performing white balance adjustment on continuously captured image data, the image data is based on image data of a portion of the captured image data where there is no movement of the subject. Since the white balance adjustment is performed, the optimal white balance adjustment is executed for the image data only when the spectral characteristics of the light source change without following the movement of the subject while suppressing the color rolling phenomenon. Can do.

  Further, in the present invention according to claim 2, in the image processing method for performing white balance adjustment on continuously captured image data, the image data is divided into a plurality of blocks, and the presence or absence of subject movement for each block Since the white balance adjustment of the image data is performed based on the image data of the block where the subject does not move, only the change in the spectral characteristics of the light source appears in the image data of the block where the subject does not move. Thus, it is possible to perform the optimum white balance adjustment on the image data only when the spectral characteristic of the light source is changed without following the movement of the subject while suppressing the color rolling phenomenon.

  Further, in the present invention according to claim 3, in the imaging apparatus having the image processing unit for performing white balance adjustment, the image processing unit is configured to perform image data based on image data of a portion where the subject does not move in the captured image data. Therefore, the optimal white balance adjustment is performed on the image data only when the spectral characteristics of the light source change without following the movement of the subject, while suppressing the color rolling phenomenon. It can be set as an imaging device.

  The imaging apparatus according to the present invention is an imaging apparatus having image processing means for performing white balance adjustment, and in particular, the image processing means performs image processing based on image data of a portion of the photographed image data where there is no subject movement. The white balance adjustment of the data suppresses the color rolling phenomenon, and the optimal white balance adjustment is performed on the image data only when the spectral characteristics of the light source change without following the movement of the subject. ing.

  The image processing method according to the present invention is an image processing method for performing white balance adjustment on continuously captured image data, and is based on image data of a portion of the captured image data where there is no subject movement. The white balance adjustment of the image data is performed and the optimal white for the image data only when the spectral characteristics of the light source change without following the movement of the subject while suppressing the color rolling phenomenon. Balance adjustment can be performed.

  In particular, when detecting a portion where the subject does not move from the image data, the image data is sequentially stored in a memory inside the image processing means for each image, and the image data stored in this memory is stored in a plurality of blocks. By dividing the image and comparing the image data for each block, the presence or absence of the movement of the subject is detected.

  Then, white balance adjustment is performed on the image data using only the image data of the block in which the subject does not move.

  Therefore, only the change in the spectral characteristics of the light source appears in the image data of the block where there is no movement of the subject, so when the spectral characteristics of the light source change without following the movement of the subject while suppressing the color rolling phenomenon Therefore, the optimum white balance adjustment can be executed only on the image data.

  In addition, since the color rolling phenomenon is more likely to occur as the exposure time when photographing a subject is shorter, the range of the color tone region where white balance adjustment is not performed is changed according to the exposure time.

  Then, the range of the color tone region where white balance adjustment is not performed is gradually narrowed as the exposure time is shortened, and further, only the color tone region of the yellow component and the blue component is changed among all the color tone regions. I have to.

  This makes it possible to perform white balance adjustment that further suppresses the color rolling phenomenon while suppressing the followability to the movement of the subject.

  Hereinafter, an imaging apparatus according to the present invention will be specifically described with reference to the drawings.

  In particular, in the following description, the imaging device is described as a monitoring camera device, but is not limited to the monitoring camera device, and can be applied to an imaging device that performs white balance control.

  As shown in FIG. 1, the surveillance camera device 1 displays an image capturing unit 2 that captures video, an image processing unit 3 that processes an image captured by the image capturing unit 2, and an image processed by the image processing unit 3. And an image display unit 4 to be operated.

  The imaging unit 2 includes an image sensor 5 that performs photoelectric conversion of an optical signal S1, such as a CCD (Charge Coupled Device) or CMOS (Complementary Metal Oxide Semiconductor), and an output signal adjustment circuit 6 that adjusts an output signal of the image sensor 5. doing. In the present embodiment, a CCD or a CMOS is taken as an example of the image sensor 5, but is not limited thereto.

  Specifically, the output signal adjustment circuit 6 includes an AGC (Auto Gain Control) 6a and an SH (Sample Hold) 6b.

  The image processing unit 3 includes an ADC (Analog Digital Converter) 8 that converts the analog image data signal S2 input from the imaging unit 2 into a digital image data signal S4 that is a digital image signal, and digital image data converted by the ADC 8. White balance adjustment circuit 9 that performs white balance adjustment on signal S4 and outputs display image signal S7, and image information such as luminance component data and color component data necessary for exposure control based on digital image data signal S4 The detection circuit 10 outputs the signal S9, the motion detection circuit 11 detects the movement of the subject based on the digital image data signal S4, and the microcomputer 12 that controls the white balance adjustment circuit 9.

  Further, the image processing unit 3 is provided with a synchronization signal generating circuit 13, and the synchronization signal S3 generated by the synchronization signal generating circuit 13 is input to the imaging unit 2 to synchronize the imaging unit 2 and the image processing unit 3.

  The white balance adjustment circuit 9 is provided with a white balance amplifier 9a that is a variable gain amplifier for amplifying or attenuating the input signal input from the ADC 8. Based on the white balance control signal S6 input from the microcomputer 12, the white balance adjustment circuit 9 White balance adjustment is performed on the image data of one image of the digital image data signal S4 by changing the gain setting of the balance amplifier 9a.

  As shown in FIGS. 1 and 3 (a) and 3 (b), the motion detection circuit 11 includes a first image memory 11a for sequentially storing the first image data 14b obtained by the digital image data signal S4, and the first image memory 11a. In the one-image memory 11a, the second image memory 11b that sequentially stores the second image data 14a previously stored, the first image data 14b in the first image memory 11a, and the second image data in the second image memory 11b 14a and a comparison circuit 11c for comparing with 14a.

  By comparing the first image data 14b with the second image data 14a as a reference by the comparison circuit 11c, the presence or absence of movement of the subject 15a in the first image data 14b can be detected, and the movement information of the subject 15a Accordingly, still image data in the first image data 14b can be detected.

  In particular, the comparison circuit 11c detects the presence or absence of movement of the subject 15a by dividing the first image data 14b and the second image data 14a into a plurality of blocks and comparing the image data in each block.

  Then, the stationary block 15 which is a block in which the subject 15a does not move (change) is detected, and the position data information of the stationary block 15 is output to the microcomputer 12 as the position data signal S8.

The detection circuit 10 sequentially detects color component data and luminance component data from the digital image data S4, generates an image information signal S9, and outputs it to the microcomputer 12. The microcomputer 12 receives the image information input from the detection circuit 10. Using the signal S9 and the position data signal S8 input from the motion detection circuit 11, the color component data of the stationary block 15 portion is detected, and the spectral characteristic value of the light source is calculated from this color component data.

  At this time, when the spectral characteristic is calculated using only the image information signal S9 without using the position data signal S8, the value of the spectral characteristic of one entire image can be calculated.

  Further, the microcomputer 12 calculates the exposure time of the image sensor 5 based on the image information signal S9 input from the detection circuit 10, and generates a control signal S10 for performing exposure control of the image sensor 5 from the calculation result. As a result, the setting is output to the synchronization signal generation circuit 13, and the setting of the dead zone 16 which is a color tone area where white balance adjustment is not performed is changed according to the calculated exposure time (see FIG. 4).

  That is, as shown in FIG. 5, when the exposure time is relatively long, the area of the dead zone region 16 is set to be relatively wide, and the area of the dead zone region 16 is set to be gradually narrowed as the exposure time is shortened. .

  Then, the gain adjustment amount of the white balance amplifier 9a is calculated based on the value of the spectral characteristic and the dead zone 16, and a white balance control signal S6 is generated, and this white balance control signal S6 is output to the white balance adjustment circuit 9. .

  The synchronization signal generation circuit 13 generates the control clock signal S3 of the imaging unit 2 based on the image clock signal S5 input from the white balance adjustment circuit 9 and the control signal S10 input from the microcomputer 12, and this control clock The signal S3 is output to the imaging unit 2, and the imaging unit 2 and the image processing unit 3 are synchronized.

  The image display unit 4 is configured by a known image display device such as an LCD (Liquid Crystal Display) or a CRT (Cathode Ray Tube), and displays an image based on the display image signal S7 input from the image processing unit 3. ing.

  Next, a white balance adjustment method according to the present invention will be described with reference to the flowchart shown in FIG. 2 and FIGS.

  First, as shown in FIG. 2, the analog image data signal S2 captured by the imaging unit 2 is output to the image processing unit 3 (step T1).

  In the image processing unit 3, the analog image data signal S2 is converted into a digital image data signal S4 by the ADC 8, and then the digital image data signal S4 is input to the white balance adjustment circuit 9 and the digital image data signal S4 is detected. Input to the circuit 10 and the motion detection circuit 11.

  The motion detection circuit 11 sequentially stores the image data detected from the digital image data signal S4 in the first image memory 11a and the second image memory 11b, and the comparison circuit 11c shows them as shown in FIGS. 3 (a) and 3 (b). Thus, the first image data 14b of the first image memory 11a and the second image data 14a of the second image memory 11b are each divided into a plurality of blocks, and the image data of each block is compared with each other to obtain the subject 15a The stationary block 15 having no motion (change) is detected, and the position data signal S8 of the stationary block 15 is generated and output to the microcomputer 12.

  The detection circuit 10 sequentially detects color component data and luminance component data from the digital image data S4 to generate an image information signal S9, and outputs the image information signal S9 to the microcomputer 12 (step T2).

  The microcomputer 12 calculates the spectral characteristic value of the light source of the stationary block 15 part using the image information signal S9 input from the detection circuit 10 and the position data signal S8 input from the motion detection circuit 11 (step T3).

  Next, the microcomputer 12 calculates the exposure time of the image sensor 5 based on the image information signal S9 input from the detection circuit 10 (step T4).

Next, the dead zone region 16 is set according to the exposure time of the image sensor 5. (See Figures 4 and 5.)
That is, as shown in FIG. 5, when the exposure time is relatively long, the area of the dead zone region 16 is set to be relatively wide, and the area of the dead zone region 16 is set to be gradually narrowed as the exposure time is shortened. (Step T5).

  In other words, when shooting the subject, the shorter the exposure time, the higher the rate of color rolling phenomenon, so the sensitivity of white balance adjustment is improved by setting the dead zone 16 narrower as the exposure time becomes shorter, The white balance adjustment can follow the periodic change of the color tone due to the color rolling phenomenon.

  Next, it is determined whether the spectral characteristic value of the light source in the stationary block 15 is inside or outside the dead zone 16.

  Then, as shown in FIG. 4, when the spectral characteristic value of the light source in the stationary block 15 is inside the dead zone 16 (17 in FIG. 5), that is, the spectral characteristic value is relatively uniform. If so, the white balance adjustment is terminated.

  On the other hand, when the spectral characteristic value in the stationary block 15 is outside the dead zone region 16 (18 in FIG. 5), that is, when the spectral characteristic value is biased to a certain color side, white The balance adjustment is continued (step T6).

  Next, if the spectral characteristic value is outside the dead zone 16 in step T4, white can be detected by detecting white within the stationary block 15 based on the image information signal S9 of the stationary block 15. If not, the white balance adjustment is terminated, and if white is detected, the white balance adjustment is continued (step T7).

  Next, the amount of change for shifting the spectral characteristic value of the white part detected in step T5 to the inside of the dead zone 16 is calculated, and the gain adjustment amount of the white balance amplifier 9a is calculated based on this amount of change. The white balance control signal S6 including this gain adjustment amount is output to the white balance adjustment circuit 9 (step T8).

  Next, the white balance adjustment circuit 9 determines white by adjusting the white balance to the digital image data S4 by changing the gain setting of the white balance amplifier 9a based on the white balance control signal S6. The color tone adjustment is also performed for the color based on the white color, and the white balance adjustment is completed (step T9).

It is a block diagram which shows the imaging device which concerns on this invention. 3 is a flowchart illustrating an image processing method according to the present invention. It is explanatory drawing which shows a stationary block. It is explanatory drawing which shows a dead zone area | region and the spectral characteristics of a light source. It is explanatory drawing which shows the relationship between the exposure time and the area of a dead zone area | region.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Surveillance camera apparatus 2 Image pick-up part 3 Image processing part 4 Image display part 5 Image pick-up element 6 Output signal adjustment circuit 6a AGC
6b SH
8 ADC
9 adjustment circuit 9a white balance amplifier 10 detection circuit 11 motion detection circuit 11a first image memory 11b second image memory 11c comparison circuit 12 microcomputer 13 synchronization signal generation circuit 14a second image data 14b first image data 15a subject 15 still block 16 Dead zone area

Claims (3)

In an image processing method for performing white balance adjustment on continuously captured image data,
An image processing method, wherein white balance adjustment of the image data is performed based on image data of a portion of the photographed image data where no subject moves. In an image processing method for performing white balance adjustment on continuously captured image data,
The image data is divided into a plurality of blocks, the presence or absence of subject movement is detected for each block, and white balance adjustment of the image data is performed based on the image data of the block without subject movement. Image processing method. In an imaging apparatus having image processing means for performing white balance adjustment,
The image processing apparatus, wherein the image processing unit performs white balance adjustment of the image data based on image data of a portion where the subject does not move in the captured image data.

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