JP4636743B2 - Imaging apparatus and white balance adjustment method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention has a white balance adjustment operation related to an imaging apparatus capable of capturing moving images and still images.
[0002]
[Prior art]
An imaging device such as a video camera for capturing a moving image or a digital camera for capturing a still image has an RGB signal output ratio so that stable and good color reproduction can be obtained even when the color temperature of the light source changes. A function for automatically adjusting the so-called auto white balance function is provided. This auto white balance function generally reads out color information of an image to be captured in a process of generating a video signal by performing signal processing on an electrical signal from an image sensor, and selects a white subject from the captured image. Detect and adjust the white balance of the captured image.
[0003]
Normally, white balance is adjusted so that white objects appear white, but it may be better to slightly adjust white balance. For example, when the sun is outdoors under sunlight, it is natural to make white appear faithfully white, but in the shade, it is more shaded if the white balance adjustment is slightly shifted in the blue direction. Also, under indoor incandescent lamps, the warm taste of incandescent lamps will appear when the white balance adjustment is slightly shifted in the red / yellow direction.
[0004]
[Problems to be solved by the invention]
In recent imaging apparatuses such as video cameras and digital cameras, there are products that can capture both moving images and still images. For example, in a video camera, moving images are recorded on a magnetic tape such as 8 mm or DV (Digital Video) tape, and still images are recorded on a semiconductor memory such as a multimedia card (MMC). The Of course, different recording media have different media for reproducing recorded video. If it is a moving image recorded on a tape, it is reproduced on a TV monitor, and if it is a still image recorded in a memory, it is displayed on a monitor for a personal computer or printed on paper by a printer.
[0005]
Since these media also have various video recording and playback methods (or output methods), the result is color even though they are the same video that is imaged from the same lens and image sensor and subjected to the same signal processing. The reproducibility of is different. For example, as described above, if the white balance is adjusted slightly deviating from the value considered appropriate in the case of shade or indoors for shooting moving images, for example, color reproduction will not be improved when a still image is printed. It will be.
[0006]
SUMMARY OF THE INVENTION An object of the present invention is to solve the above-described problems and to perform an optimal white balance adjustment regardless of a moving image or a still image.
[0007]
[Means for Solving the Problems]
In order to achieve the above-described object, according to the present invention, a white balance control value for moving images for television playback as a reference and a white for still image for printer printing as a reference corresponding to the control value are provided. Holding means for holding information related to the balance control value, and information regarding the white balance control value used for moving picture shooting and a reference moving picture held by the holding means when switching from moving image shooting to still image shooting A white balance control value for the image and a white balance control value for the still image as a reference corresponding to the control value. Adjusting means for adjusting white balance based on a white balance control value for still images To provide an imaging apparatus characterized by and.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
[0014]
(First embodiment)
FIG. 1 is a block diagram of an imaging apparatus of the present invention.
[0015]
The image pickup apparatus according to the present embodiment includes a lens 11 for entering subject light, a diaphragm 12 for adjusting the amount of light, an image pickup device 13 such as a CCD for converting incident light into an electric signal, and an image signal output from the image pickup device 13. A sample hold / AGC circuit 14 that performs sample hold and gain adjustment for the image hold and the image signal output from the sample hold / AGC circuit 14 (hereinafter referred to as A / D conversion). The signal processing circuit 16 that performs processing such as white balance adjustment, gamma correction, and contour enhancement on the image signal output from the A / D conversion circuit 15 and the A / D conversion circuit 15. The compression / decompression circuit 17 compresses and decompresses the image signal output from the image signal using a predetermined process, and the image signal compressed by the image compression / decompression circuit 17. Based on the image signal obtained from the memory card 18 constituted by a semiconductor memory for recording the image, the image display unit 19 constituted by a liquid crystal monitor for actually displaying the image signal, and the signal processing circuit 16, A white balance control circuit 20 that calculates a white balance control value, a system control circuit 21 that has the white balance control circuit 20 and performs overall control of the entire imaging apparatus, and a still image switch 24 that instructs recording of a still image.
[0016]
The light from the subject received from the lens 11 is imaged on the image sensor surface of the image sensor 13 with its light amount adjusted by the diaphragm 12. Here, after being converted into an electric signal, it is A / D converted by the A / D converter 15 via the sample hold / AGC unit 14 and input to the signal processing circuit 16. In the signal processing circuit 16, the input signal is subjected to processing such as aperture correction, gamma correction, and white balance adjustment for each luminance and color component to generate a video signal, which is output to the liquid crystal monitor 19 as a moving image. . When the still image switch is pressed, the image compression / expansion circuit 17 processes the still image into a file format such as a JPEG file and records the still image on the memory card 18.
[0017]
The white balance control circuit 20 reads color information related to a video signal necessary for white balance adjustment from the video signal processing unit 16 for each field. An image signal that is recognized as a white subject is extracted from the captured image based on the read color information, and a control value is calculated for white balance adjustment. The control value is data for changing the gain of the image signal (RGB signal) output from the A / D converter 15 in the signal processing circuit 16. The white balance control circuit 20 stores and holds information such as a table described later used for white balance adjustment. In this embodiment, the gain of G is fixed, and the white balance is adjusted by varying the gains of the R signal and the B signal using the control value.
[0018]
FIG. 6 is an operation process flowchart of white balance adjustment by the system control circuit 21 in the present embodiment. The white balance adjustment operation of the present embodiment will be described with reference to FIG.
[0019]
In the present embodiment, immediately after activation of the electronic still camera, the system control unit 21 controls each unit so as to generate a moving image. When the still image switch 24 is turned on by a user operation, the system control circuit 21 controls each unit so as to generate a still image only for a predetermined period.
[0020]
First, in step S101, when the main body of the electronic still camera is activated, an imaging operation of a moving image displayed on the image display unit 19 is started. Corresponding to the imaging operation, white balance adjustment for capturing a captured moving image is performed. The white balance adjustment is performed by the white balance control circuit 20. The white balance control circuit 20 adds the color information of the captured image, the brightness information of the subject read out from the video signal processing unit 16, or the current white balance. Based on the value of the balance control value and the like, it is determined what light source the subject is under, and the white balance is adjusted by the light source. Specifically, when it is determined that the sun is outdoors, the neutral color is adjusted. If it is determined that the shade is outdoors, the gain of the B signal is raised from the neutral state to adjust the color to a cold tendency. If it is determined that the lamp is under an incandescent lamp indoors, the gain of the R signal is increased from the neutral state to produce a warm color. Here, the neutral color development means that white appears faithfully white in the finally generated video signal, that is, a state where the signal levels of the color signals R and B components of the white subject portion are zero.
[0021]
In step S102, it is determined whether or not the still image switch 24 is turned on. If turned on, the process proceeds to step S103. If not turned on, the process of step S101 is continued.
[0022]
In step S103, when the still image switch 24 is turned on, a white balance adjustment operation for still image shooting described later is performed.
[0023]
In step S104, it is determined whether a predetermined time has elapsed. When the predetermined time has elapsed, the process returns to step S101, and the white balance adjustment operation for moving image shooting is performed again. If the predetermined time has not elapsed, it is determined that the still image capturing operation has not ended, and the processing in step S103 is continued.
[0024]
Here, the white balance adjustment operation for still image shooting in step S103 will be described using FIGS. 2 to 5 showing the correlation of the gain (white balance control value) with respect to the R signal and the B signal.
[0025]
2 to 5, W1 and W2 indicate reference white balance control values, and Wn indicates a white balance control value Wn for a moving image immediately before a white balance adjustment operation for still image shooting is performed.
[0026]
As shown in FIG. 3, W1s is a white balance control value that is shifted from W1 by an offset Or1 with respect to the gain of the R signal and by an offset Ob1 with respect to the gain of the B signal. Further, as shown in FIG. 4, W2s is a white balance control value shifted from W2 by an offset Or2 with respect to the gain of the R signal and by an offset Ob2 with respect to the gain of the B signal.
[0027]
Here, Or1, Ob1, Or2, and Ob2 are arbitrary values set in advance. For these values, when the white balance control value used for moving image shooting is Wn = W1 or Wn = W2, how much the state of white balance adjustment at the time of a still image is shifted with respect to W1 and W2 in advance in a factory or the like. Determined experimentally.
[0028]
Wns is finally obtained by taking a white balance control value for still image shooting. As shown in FIG. 5, with respect to Wn, the offset Orn and the gain of the B signal are offset with respect to the gain of the R signal. In contrast, the white balance control value is shifted by the offset Obn.
[0029]
Orn and Obn are obtained based on the ratio of the relative position of the control value Wn to W1 and W2. That is, the difference between the control values of the R signal components W1 and W2 is Dr12, the difference between the control values of W1 and Wn is Dr1n, and the difference between the control values of the B signal components W1 and W2 is Db12, W1. When the difference of the control value from Wn is Db1n, Dr12, Dr1n, Db12, and Db1n for Or1, Ob1, Or2, Ob2, Orn, Obn are (Orn−Or1) / (Or2-Or1) = Dr1n / Dr12. (Formula 1)
(Obn-Ob1) / (Ob2-Ob1) = Db1n / Db12 (Formula 2)
There is a relationship. Orn and Obn are calculated as a result of the calculation using (Expression 1) and (Expression 2). Accordingly, white balance control for still image shooting is performed by shifting the white balance control value Wn held in advance before still image shooting by Orn and Obn calculated using (Equation 1) and (Equation 2). A value Wns is determined.
[0030]
As described above, by correcting the white balance control value for moving image shooting, it is possible to perform appropriate white balance control for a still image.
[0031]
(Second Embodiment)
The second embodiment of the present invention will be described below.
[0032]
FIG. 7 is a block diagram of an imaging apparatus according to the second embodiment.
[0033]
The imaging apparatus according to the present embodiment has a memory card 18 composed of a magnetic tape 23 and a semiconductor memory as a storage medium, and a recording medium to be recorded in response to an operation of the tape / memory card switch 25 Switch at 26. In addition, the image pickup apparatus according to the present embodiment can only record still images on the memory card 23, and can record not only still images on the magnetic tape 18 but also moving images by operating the moving image switch 26. And The compression / decompression circuit 22 is a circuit that compresses and decompresses an image to be recorded on the magnetic tape 23 in a TV signal format such as NTSC and digitizes it into a predetermined format. That is, the still image recorded in the file format on the memory card 18 and the still image recorded on the magnetic tape 23 have different recording formats. The other reference numerals identical to those in FIG. 1 denote the same components as those in FIG.
[0034]
In the processing of the present embodiment, the steps of FIG. 6 are performed only when a still image is shot and the memory card 18 is selected as the recording medium by the switching operation of the tape / memory card switch 25. Assume that white balance adjustment for still image shooting is performed in S103. That is, in the white balance adjustment process of the second embodiment, the process of step S103 is performed only when the memory card 18 is selected as the recording medium when the still image switch 24 is turned on in the process of step S102 of FIG. Proceed to the white balance adjustment process. If the magnetic tape 23 is selected as the recording medium, the white balance adjustment process in step S101 is continued regardless of the moving image recording / still image recording.
[0035]
Such processing considers that the possibility that a still image recorded on the memory card 18 is printed out by a printer or the like is high, and the white balance adjustment processing can be further improved.
[0036]
In each embodiment, the reference white balance control values W1 and W2 are not limited, and the number of reference white balance control values is not limited.
[0037]
In the present invention, as an example, the program code of software that realizes the functions of the above-described embodiments is supplied to the imaging apparatus via a network such as the Internet, and the computer (or CPU or MPU) of the imaging apparatus stores it in the storage medium. This can be achieved by reading and executing the programmed program code.
[0038]
In this case, the program code itself read from the storage medium realizes the function of the white balance control circuit 20 of the above-described embodiment, and the storage medium storing the program code constitutes the present invention. .
[0039]
As a storage medium for supplying the program code, for example, a floppy disk, a hard disk, an optical disk, a magneto-optical disk, a CD-ROM, a CD-R, a magnetic tape, a nonvolatile memory card, a ROM, or the like can be used.
[0040]
Further, by executing the program code read by the computer, not only the functions of the above-described embodiments are realized, but also an OS (operating system) operating on the computer based on the instruction of the program code. A case where part or all of the actual processing is performed and the functions of the above-described embodiments are realized by the processing is also included.
[0041]
Further, after the program code read from the storage medium is written to the memory provided in the function expansion board inserted into the computer or the function expansion unit connected to the computer, the function expansion is performed based on the instruction of the program code. The CPU or the like provided in the board 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.
[0042]
When the present invention is applied to the above-described storage medium, the storage medium stores program codes corresponding to the flowcharts described above. In brief, modules essential to the imaging apparatus of the present invention are stored. And stored in a storage medium.
[0043]
【The invention's effect】
As described above, according to the present invention, an appropriate white balance can be adjusted according to a moving image and a still image or a recording medium on which images are recorded, which have different uses of viewing images and different viewing means.
[Brief description of the drawings]
FIG. 1 is a block diagram of an electronic still camera according to a first embodiment.
FIG. 2 is a diagram showing a correlation of gain (white balance control value) with respect to an R signal and a B signal.
FIG. 3 is a diagram illustrating a correlation of gain (white balance control value) with respect to an R signal and a B signal.
FIG. 4 is a diagram showing a correlation of gain (white balance control value) with respect to an R signal and a B signal.
FIG. 5 is a diagram showing a correlation of gain (white balance control value) with respect to an R signal and a B signal.
FIG. 6 is an operation processing flowchart of white balance adjustment in the present invention.
FIG. 7 is a block diagram of a video camera according to a second embodiment.
[Explanation of symbols]
13 Image sensor 16 Signal processing circuit 18 Memory card 19 Image display unit 20 White balance control circuit 21 System control circuit 24 Still image switch 25 Magnetic tape

Claims (7)

A holding means for holding information on a white balance control value for moving images for reference television playback and a white balance control value for still images for printer printing corresponding to the control values; When switching to still image shooting, information on the white balance control value used for moving image shooting, and a white balance control value for a movie to be held by the holding unit and a reference corresponding to the control value A computing means for computing a white balance control value for a still image based on information on the white balance control value for the still image;
An image pickup apparatus comprising: adjusting means for adjusting white balance based on a white balance control value for a still image calculated by the calculating means.   2. The apparatus according to claim 1, further comprising first and second recording means for recording a still image, and performing the calculation by the calculation means only when recording a still image in the first recording means. An imaging apparatus characterized by the above.   3. The imaging apparatus according to claim 2, wherein the first recording unit records on a semiconductor memory, and the second recording unit records on a magnetic tape.   The calculation unit according to claim 1, wherein when calculating from moving image shooting to still image shooting, the calculation means calculates a white balance control value for a still image based on information relating to white balance control data used for immediately preceding moving image shooting. An imaging apparatus characterized by the above.   2. The holding means according to claim 1, wherein the holding means holds at least two reference white balance control values for a moving image, and sets the relative position of the white balance control value used for moving image shooting with respect to these two control values. An image pickup apparatus that calculates a white balance control value for a still image based on the calculated value.   2. The reference white balance control value for a still image held by the holding unit is a color temperature state of a light source in which moving image shooting uses the reference moving image white balance control value. An imaging apparatus characterized by being set sometimes. When switching from movie shooting for TV playback to still image shooting for printer printing, information on the white balance control value used for movie shooting and the white balance control for the movie that is stored in advance as a reference White balance control value for still image is calculated based on the information about the white balance control value for still image as a reference corresponding to the value and the control value, and the white balance for still image calculated by the calculating means is calculated A white balance adjustment method, wherein white balance is adjusted based on a control value.

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