JP2004080158A - Imaging device and white balance control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an imaging apparatus that allows a user to immediately recognize a state wherein normal white balance cannot be adjusted for an image obtained by photographing and shifts to new photographing. <P>SOLUTION: An AWB control processing circuit includes: a gray component extract circuit 41 for extracting a gray component from a color signal by each pixel of an image; an integration circuit 42 for integrating the extracted gray component; a number counter 43 for counting the number of pixels from which the gray component is extracted; a gain setting arithmetic circuit 44 for calculating a white balance value from the integrated value of the integration circuit 42 and the count of the number counter 43; a memory 45 for storing the calculated white balance value; a gain setting output circuit 46 for outputting the calculated white balance value and adjusting the white balance through gain adjustment by each color pixel of the image; a threshold value setting circuit 51 for detecting whether the count of the number counter 43 is a prescribed count or below; and a system control circuit (26) for allowing a display apparatus (28) to inform of a fact of the detection via a display data processing circuit (27) in response to the detection of the threshold value setting circuit 51. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an imaging device and a white balance control method suitable for a digital camera or the like having a solid-state imaging device.
[0002]
[Prior art]
As personal computers have become widespread in ordinary homes, digital still cameras that can acquire images as electronic data, record the images on a memory card, and import the images into a personal computer have been widely and easily handled. ing.
[0003]
FIG. 4 shows a basic circuit configuration of this type of digital still camera. In the figure, a subject image is formed via an optical lens 11 and an aperture 12 on an imaging surface of a CCD 13 on which, for example, a Bayer array (RGB) color filter is arranged.
[0004]
The CCD 13 is driven by a signal from a timing signal generator (TG) 14 and outputs an image signal corresponding to the accumulated charge level of each color pixel. The output image signal is sent to the CDS 15.
[0005]
The CDS 15 samples the image output of the CCD 13 based on the signal from the timing signal generator 14 synchronized with the driving of the CCD 13 and sends it to the AGC amplifier circuit 16.
[0006]
The AGC amplifier circuit 16 multiplies the image signal sampled by the CDS 15 by a predetermined gain and outputs the multiplied image signal to an A / D converter 17 in the next stage. The data is converted into 10-bit digital data for each pixel and output to the digital clamp circuit 18.
[0007]
The digital clamp circuit 18 performs black level clamping on the image data and outputs the image data to an RGB weighting circuit 19. The RGB weighting circuit 19 performs white balance adjustment by performing weighting for each pixel of RGB. , To the gamma correction processing circuit 20.
[0008]
The gamma correction processing circuit 20 multiplies the image data supplied from the RGB weighting circuit 19 by a predetermined gamma curve coefficient, and stores the image data in the form of Bayer pixel data in the memory 22 by DMA transfer via the memory bus interface 21. Let it.
[0009]
When the image data stored in the form of Bayer pixel data stored in the CCD 13 becomes equal to or larger than a predetermined image processing block unit such as 8 pixels × 8 pixels or 16 pixels × 16 pixels, these image data are The data is sequentially read from the memory 22 by DMA transfer, and transferred to the Bayer input buffer 23 via the memory bus interface 21.
[0010]
The image data in image processing block units transferred to the Bayer input buffer 23 is sent to the Y generation circuit 24 and the C generation circuit 25.
[0011]
The Y generation circuit 24 generates a Y (luminance) component image data for each image processing block by performing a matrix operation on the received image data, and sends the generated image data to the AE control processing circuit 30. On the other hand, the data is transmitted to the memory 22 via the memory bus interface 21 and stored.
[0012]
Similarly, the C generation circuit 25 generates a Cb, Cr (color difference) component image data for each image processing block by performing a matrix operation on the received image data, and converts the generated image data to AWB. While being sent to the control processing circuit 31, it is transferred to and stored in the memory 22 via the memory bus interface 21.
[0013]
The image data of the luminance / color difference system stored in the CCD 13 is read out to a display data processing circuit 27 controlled by a system control processing circuit 26 via a memory bus interface 21, and the image read out by the display data processing circuit 27 is read out. Display data is created from the data, and is displayed on a monitor 28 which is a liquid crystal display panel provided on the back of the camera body.
[0014]
Further, the display device 28 can display various information as user auxiliary information under the control of the system control processing circuit 26 in addition to the captured image to be displayed on the monitor.
[0015]
The system control processing circuit 26 controls the operation of the entire digital still camera in accordance with various key operation signals input from the key input device 29 in response to a key operation by the user. Control signals are also output to the AE control processing circuit 30 and the AWB control processing circuit 31 in addition to the processing circuit 27.
[0016]
The AE control processing circuit 30 provides a control signal to an aperture control circuit 32 that variably controls the aperture value of the aperture 12 according to the signal level of the image data of the luminance component obtained by the Y generation circuit 24, The exposure time is varied by controlling the drive timing of the signal generator 14 to the CCD 13 and the CDS 15, and the gain of the AGC amplifier circuit 16 is controlled.
[0017]
That is, the AE control processing circuit 30 generally opens the aperture 12 to the maximum when the brightness level of the subject image is small (dark), makes the exposure time as long as possible, and furthermore, in that state, a sufficient output image If the level (integrated level of the low-frequency luminance signal) cannot be obtained, the gain in the AGC amplifier circuit 16 is increased. The detailed operation thereof depends on the state of the exposure mode set at that time and the like. It is controlled by the control processing circuit 26.
[0018]
On the other hand, the AWB control processing circuit 31 executes a white balance calculation based on the color difference component image data obtained by the C generation circuit 25, and issues an instruction from the system control processing circuit 26 according to the white balance mode set at that time. The RGB weighting circuit 19 performs weighting control for each of the RGB pixel components based on the contents to be performed.
[0019]
FIG. 5 shows a detailed circuit configuration of the AWB control processing circuit 31. The color difference image signals Cb and Cr from the C generation circuit 25 are input to a gray component extraction circuit 41.
[0020]
The gray component extraction circuit 41 converts the value of each pixel into a gray zone GyZ as shown in FIG. 6 by a combination of the color difference signals Cb and Cr given by, for example, 10 bits (“0” to “1023”). It is determined whether or not they belong to each other. If it is determined that they belong to each other, a signal indicating the magnitude is sent to the integrating circuit 42 and, at the same time, a count-up signal is sent to the number counter 43.
[0021]
The integration circuit 42 integrates a signal indicating the magnitude of each color component of a series of gray pixels sent from the gray component extraction circuit 41 and outputs the result to the gain setting operation circuit 44.
[0022]
The number counter 43 performs a counting operation according to the count-up signal from the gray component extraction circuit 41, and outputs the count value to the gain setting operation circuit 44 as described above.
[0023]
The gain setting calculation circuit 44 calculates a gain setting value based on the integration result from the integration circuit 42 obtained corresponding to the color difference signal for one screen and the count value of the number counter 43, and writes it into the memory 45.
[0024]
In the memory 45, in addition to the gain setting value written by the gain setting operation circuit 44 at that time, for example, sunlight, shade, fluorescent light, incandescent light, or the like according to the specification of the digital still camera. A gain setting value corresponding to the color temperature of each light source is stored in advance.
[0025]
Under the control of the system control processing circuit 26, the gain setting arithmetic circuit 44 calculates the gain of the camera under the control of the system control processing circuit 26 corresponding to the setting state of the camera, that is, the white balance selection state by the key input operation of the user. One of light gain, shade gain, fluorescent lamp gain, and incandescent lamp gain is selected and sent to the gain setting output circuit 46.
[0026]
The gain setting output circuit 46 outputs the gain setting value sent from the gain setting operation circuit 44 to the RGB weighting circuit 19 to execute white balance adjustment.
[0027]
[Problems to be solved by the invention]
As described above, in the AWB control processing circuit 31, the gray component extraction circuit 41 determines a sufficient number of pixels having color difference data values belonging to the gray zone GyZ shown in FIG. It is assumed that automatic white balance adjustment is performed on the premise of extraction.
[0028]
Therefore, if the color difference signal corresponding to gray cannot be obtained at all from the image data for one screen, or if the number thereof is very small, the number counter The count value of 43 becomes “0” or a very small value, and a normal gate setting value for performing automatic white balance adjustment cannot be calculated.
[0029]
In addition, when shooting is performed in a state where a normal gate setting value cannot be calculated as described above, there is no means for notifying the user in real time of this, and a normal image cannot be obtained. Cannot be recognized by the user, and as a result, an important shutter chance may be missed.
[0030]
The present invention has been made in view of the above-described circumstances, and its purpose is to allow a user to immediately recognize a state in which normal white balance adjustment cannot be performed on an image obtained by shooting, It is an object of the present invention to provide an imaging device and a white balance control method capable of shifting to a new shooting.
[0031]
[Means for Solving the Problems]
According to a first aspect of the present invention, there is provided a gray extracting means for extracting a gray component value from a color signal for each pixel of a captured image, an integrating means for integrating the gray component value extracted by the gray extracting means for each color component, Counting means for counting the number of pixels from which the gray component value has been extracted by the gray extracting means, and calculation for calculating a white balance value based on the integrated value for each color component obtained by the integrating means and the count value obtained by the counting means Means, a storage means for storing the white balance value obtained by the calculation means, and a gain adjustment for each color pixel of the photographed image using the white balance value obtained by the calculation means to adjust the white balance of the image. White balance adjusting means, detecting means for detecting whether or not the count value obtained by the counting means is equal to or less than a predetermined value, and detecting the count value by the detecting means. When it is detected that is less than, characterized by comprising a notification means for notifying to that effect.
[0032]
With such a configuration, it is possible to promptly notify the user of a state in which normal white balance adjustment cannot be performed on an image obtained by shooting and to prompt the user to recognize the state, thereby promptly shifting to a new shooting. It becomes.
[0033]
According to a second aspect of the present invention, in the first aspect of the present invention, the notifying unit displays a message on a monitor display unit that displays a captured image on a monitor.
[0034]
With such a configuration, in addition to the effect of the invention described in the above-described claim 1, a state in which normal white balance adjustment could not be performed is displayed on the monitor instead of notifying by an indicator display or a buzzer sound. For example, by displaying a message by superimposing it on an actual captured image and notifying the user, the user can accurately recognize the current situation.
[0035]
According to a third aspect of the present invention, in the first aspect of the present invention, the white balance adjustment means is obtained by an arithmetic means stored in the storage means when the notification by the notification means is performed. The white balance adjustment is performed using the white balance value.
[0036]
With such a configuration, in addition to the operation of the invention described in the first aspect, it is possible to immediately shift to white balance adjustment using a normal white balance value already acquired at the time before that.
[0037]
According to a fourth aspect of the present invention, in the first aspect of the present invention, the storage unit stores a preset white balance value in addition to the white balance value obtained by the arithmetic unit, and stores the information. When notifying by the means, stored in the storage means, further comprising a selection means for selecting one from a white balance value obtained by the arithmetic means and a preset white balance value, The white balance adjustment means performs white balance adjustment using the white balance value selected by the selection means.
[0038]
With such a configuration, in addition to the operation of the invention described in the first aspect, a normal white balance value already acquired at the time before that and a white balance corresponding to various preset light sources are set. When the user selects one of the values, the user can immediately shift to white balance adjustment using the selected white balance value.
[0039]
According to a fifth aspect of the invention, there is provided a gray extraction step of extracting a gray component value from a color signal of each pixel of a captured image, an integration step of integrating the gray component value extracted in the gray extraction step for each color component, A counting step of counting the number of pixels from which a gray component value has been extracted in the gray extraction step, and an operation of calculating a white balance value based on the integration value for each color component obtained in the integration step and the count value obtained in the counting step A white balance value obtained in the calculation step; and a gain adjustment for each color pixel of the photographed image using the white balance value obtained in the calculation step to adjust the white balance of the image. A white balance adjusting step, a detecting step of detecting whether the count value obtained in the counting step is equal to or less than a predetermined value, and When it is detected that is less than, characterized in that and a notification step of notifying to that effect.
[0040]
According to such a method, it is possible to promptly notify the user of a state in which normal white balance adjustment cannot be performed on an image obtained by shooting, thereby allowing the user to recognize the state, and promptly shift to a new shooting. It becomes.
[0041]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment in which the present invention is applied to a digital still camera will be described with reference to the drawings.
[0042]
FIG. 1 shows the circuit configuration, which is basically the same as that shown in FIG. 4 above. Therefore, the same portions are denoted by the same reference numerals and description thereof will be omitted.
[0043]
The AWB control processing circuit 31 ', which inputs the image data of the color difference component from the Y generation circuit 24, sends a signal directly to the system control processing circuit 26 as necessary, and outputs a signal other than the white balance value calculated at that time. Is output to the RGB weighting circuit 19.
[0044]
FIG. 2 shows a detailed circuit configuration of the AWB control processing circuit 31 ', which is basically the same as the content shown in FIG. 5, so that the same parts are denoted by the same reference numerals. Description is omitted.
[0045]
However, the count value counted by the number counter 43 is output not only to the gain setting operation circuit 44 but also to the threshold value setting circuit 51. The threshold value setting circuit 51 detects whether or not the count value of the number counter 43 is equal to or less than a preset threshold value, and when detecting that the count value is equal to or less than the threshold value, the system control processing circuit 26 as described above. Output the detection signal to
[0046]
Next, the operation of the above embodiment will be described.
[0047]
FIG. 3 mainly shows the contents of the processing relating to the white balance adjustment in the system control processing circuit 26 and the AWB control processing circuit 31 '. At the beginning of the processing, it waits for the execution of the image capturing (step S01). ) When it is determined that the execution has been performed, the count value n of the number of pixels constituting the captured image is cleared to “0” (step S02), and the number m of gray component pixels counted by the number counter 43 is also changed. Similarly, it is cleared to "0" (step S03).
[0048]
Next, the color difference signal C (Cb, Cr) for one pixel is taken into the AWB control processing circuit 31 '(step S04). After the count value n is updated and set to "+1" (step S05), the gray component It is determined whether or not the extraction circuit 41 has been able to extract a gray component from the color difference signal (step S06).
[0049]
Only when it is determined that the extraction has been successful, the integration circuit 42 executes an integration process for each color component based on the extraction result and outputs the integrated value to the gain setting operation circuit 44 (step S07). The counter 43 updates the count value m by "+1" (step S08).
[0050]
Thereafter, it is determined whether or not the count value n has reached the total number N of pixels constituting the image, thereby determining whether or not the gray component counting process for the color difference signals of all the pixels has been completed (step S1). S09) If it is determined that the count value n has not reached the total number of pixels N, the process returns to step S04.
[0051]
In this way, by repeatedly executing the processing of steps S04 to S06, (S07, S08,) S09, the number m of pixels, which are gray components, in all the pixels constituting the image for one screen is counted.
[0052]
Then, when it is determined in step S09 that the count value n has become the total number N of pixels forming the image, the threshold value setting circuit 51 then sets the count value m of the number counter 43 to a value equal to or smaller than a preset threshold M. It is determined whether or not there is (step S10).
[0053]
Here, when it is determined that the count value m of the number counter 43 is larger than the threshold value M and that the white balance can be sufficiently adjusted, the signal from the threshold value setting circuit 51 to the system control processing circuit 26 is not transmitted, and the gain The setting calculation circuit 44 calculates a gain setting value for adjusting the white balance based on the integration value of the integration circuit 42 and the count value m of the number counter 43, and updates and sets the gain setting value in the memory 45 (step S11). The set gain set value is output to the RGB weighting circuit 19 by the gain setting output circuit 46 (step S12), and a series of processes related to white balance adjustment is completed to prepare for the next image shooting in step S01. Return to the processing from.
[0054]
If it is determined in step S10 that the count value m of the number counter 43 is equal to or smaller than the threshold value M and the gray component cannot be extracted enough to perform the white balance adjustment, the threshold value setting circuit 51 sends the system control processing A signal to the circuit 26 is sent.
[0055]
The system control processing circuit 26 sends display data set in advance corresponding to the signal from the threshold setting circuit 51 to the display data processing circuit 27 to indicate that an appropriate white balance cannot be obtained on the display device 28. Message, for example, "Cannot adjust image white balance"
Is superimposed on the monitor image and displayed (step S13), and the calculated white balance value stored in the memory 45 at the time before that is compared with the fixed sunlight, shade, A list screen for selecting any one of the white balance values such as a fluorescent lamp and an incandescent lamp is displayed on the display device 28 (step S14). The operation waits in response to the key operation (step S15).
[0056]
When one of the white balance values is selected and operated in step S15, the gain setting operation circuit 44 reads out the selected white balance value from the memory 45, and the gain setting output circuit 46 outputs the RGB weighting circuit 19. (Step S16), and a series of the processes relating to the white balance adjustment is completed as described above, and the process returns to Step S01 to prepare for the next image capturing.
[0057]
In this way, a state in which normal white balance adjustment cannot be performed on an image obtained by shooting can be immediately notified to the user to be recognized, and a new shooting can be promptly performed.
[0058]
In this case, for example, a state in which normal white balance adjustment could not be performed is superimposed on, for example, an actual captured image by a display device 28 that performs a monitor display instead of notifying by a display of an indicator or a buzzer sound. By displaying and notifying a message as described above, the user can be made to recognize the current state more accurately and easily.
[0059]
In addition, each time a captured image is obtained, its white balance value is updated and set in the memory 45. If a normal white balance value cannot be obtained, the updated white balance value and the memory 45 are set. The user can arbitrarily select one of the white balance values, such as sunlight, shade, fluorescent light, incandescent light, etc., which is fixedly set and stored in advance, and can utilize it for white balance adjustment. By selecting a white balance value suitable for the intention of the user, it is possible to immediately shift to white balance adjustment using the selected white balance value.
[0060]
In the above embodiment, the CCD 13 has the color filters of the primary color system Bayer array, and the white balance adjustment is performed by making the weights of the respective color components of the primary color signals RGB different from each other. Also has a complementary color filter, it is possible to adjust the white balance value by the same concept. In this case, each color component of Y (yellow), Mg (magenta) and Cy (cyan) can be adjusted. Each weighting is individually and variably set.
[0061]
Further, in the above embodiment, the case where the present invention is applied to a digital still camera is described. However, the present invention is not limited to a digital still camera, and performs photographing using a solid-state imaging device and adjusts the white balance. As long as the image pickup apparatus can be adjusted, the present invention can be similarly applied to both analog / digital video cameras and various medical / industrial camera apparatuses.
[0062]
In addition, the present invention is not limited to the above-described embodiment, and can be variously modified and implemented without departing from the gist thereof.
[0063]
Furthermore, the above embodiments include inventions at various stages, and various inventions can be extracted by appropriately combining a plurality of disclosed constituent features. For example, even if some components are deleted from all the components shown in the embodiments, at least one of the problems described in the column of the problem to be solved by the invention can be solved and the effects described in the column of the effect of the invention can be solved. When at least one of the effects described above is obtained, a configuration from which this component is deleted can be extracted as an invention.
[0064]
【The invention's effect】
According to the first aspect of the present invention, it is possible to promptly notify the user of a state in which normal white balance adjustment cannot be performed on an image obtained by shooting, thereby prompting the user to recognize the state, and promptly shift to new shooting. Becomes possible.
[0065]
According to the second aspect of the present invention, in addition to the effect of the first aspect of the present invention, a state in which normal white balance adjustment cannot be performed, not a notification by lighting of an indicator or a buzzer sound, etc. For example, by superimposing a message on an actual captured image and displaying a message on the monitor display unit to notify the user, the user can accurately recognize the current situation.
[0066]
According to the third aspect of the present invention, in addition to the effect of the first aspect of the present invention, it is possible to immediately shift to white balance adjustment using a normal white balance value which has been obtained at a previous time. .
[0067]
According to the fourth aspect of the present invention, in addition to the effects of the first aspect of the present invention, a normal white balance value already obtained at a time before that, and various preset light sources are supported. When the user selects one of the white balance values, it is possible to immediately shift to white balance adjustment using the selected white balance value.
[0068]
According to the fifth aspect of the present invention, it is possible to promptly notify the user of a state in which normal white balance adjustment cannot be performed on an image obtained by shooting, thereby prompting the user to perform a new shooting. Becomes possible.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a circuit configuration of a digital still camera according to an embodiment of the present invention.
FIG. 2 is a block diagram showing an internal circuit configuration of the automatic white balance control processing circuit of FIG. 1;
FIG. 3 is a flowchart showing processing content of white balance control according to the embodiment;
FIG. 4 is a block diagram showing a circuit configuration of a general digital still camera.
FIG. 5 is a block diagram showing an internal circuit configuration of the automatic white balance control processing circuit of FIG. 4;
FIG. 6 is a diagram showing the details of gray extraction performed by the gray component extraction circuit of FIG. 5 on a color difference signal.
[Explanation of symbols]
11 optical lens 12 diaphragm 13 CCD
14. Timing signal generator (TG)
15 CDS
16 AGC amplification circuit 17 A / D converter 18 Digital clamp circuit 19 RGB weighting circuit 20 Gamma correction processing circuit 21 Memory bus interface 22 Memory 23 Bayer input buffer 24 Y generation circuit 25 C generation Circuit 26 System control processing circuit 27 Display data processing circuit 28 Display device 29 Key input device 30 AE control processing circuits 31 and 31 ′ AWB control processing circuit 32 Aperture control circuit 41 Gray component extraction circuit 42 Integrating circuit 43 Number counter 44 Gain setting operation circuit 45 Memory 46 Gain setting output circuit 51 Threshold setting circuit

Claims (5)

Gray extraction means for extracting a gray component value from a color signal for each pixel of a captured image,
Integrating means for integrating the gray component value extracted by the gray extracting means for each color component;
Counting means for counting the number of pixels from which the gray component value has been extracted by the gray extraction means;
Calculating means for calculating a white balance value based on the integrated value for each color component obtained by the integrating means and the count value obtained by the counting means;
Storage means for storing the white balance value obtained by the calculation means;
White balance adjustment means for performing gain adjustment for each color pixel of a captured image using the white balance value obtained by the arithmetic means, and adjusting the white balance of the image;
Detecting means for detecting whether the count value obtained by the counting means is equal to or less than a predetermined value,
When the detecting means detects that the count value is equal to or less than a predetermined value, the notifying means for notifying the fact is provided. 2. The image pickup apparatus according to claim 1, wherein the notifying unit displays a message on a monitor display unit that displays the captured image on a monitor. The white balance adjusting means performs white balance adjustment using the white balance value obtained by the arithmetic means, stored in the storage means, when the notification by the notifying means is performed. The imaging device according to claim 1. The storage means stores a preset white balance value in addition to the white balance value obtained by the calculation means,
When the notification by the notification means is performed, the information processing apparatus further includes a selection means for selecting one from a white balance value obtained by the calculation means and a preset white balance value stored in the storage means. And
2. The imaging apparatus according to claim 1, wherein the white balance adjustment unit performs white balance adjustment using the white balance value selected by the selection unit. A gray extraction step of extracting a gray component value from a color signal for each pixel of the captured image,
An integration step of integrating the gray component value extracted in the gray extraction step for each color component;
A counting step of counting the number of pixels from which the gray component value has been extracted in the gray extraction step,
A calculating step of calculating a white balance value from the integrated value for each color component obtained in the integrating step and the count value obtained in the counting step;
A storage step of storing the white balance value obtained in the calculation step,
A white balance adjustment step of performing gain adjustment for each color pixel of the captured image using the white balance value obtained in the calculation step, and adjusting the white balance of the image;
A detection step of detecting whether the count value obtained in the counting step is equal to or less than a predetermined value,
And a notifying step of notifying when the count value is equal to or less than a predetermined value in the detecting step.

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