JP3612855B2 - White balance circuit and imaging device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a white balance circuit incorporated in an imaging apparatus such as a video camera, for example, and an imaging apparatus incorporating the white balance circuit.
[0002]
[Prior art]
Recently, imaging devices such as video cameras have tended to pursue operability, simplicity, and low price in addition to the basic image quality of the camera.
[0003]
In order to improve operability, automation of lens focus and aperture adjustment, white balance adjustment, and the like has been performed, and technical development has been carried out to minimize the need for manual adjustment.
[0004]
Among them, the auto white balance has different color temperatures (spectral characteristics) depending on the light source, but is designed to obtain the maximum sensitivity and color reproducibility at a specific color temperature. , B are adjusted in advance so that the output ratio is 1: 1: 1. In this case, when a white subject is imaged at different color temperatures, the output ratios of R, G, and B are different, and the captured image is deteriorated.
[0005]
Since the human eye has chromatic adaptation according to the lighting, the white subject looks white in all cases, and when the white subject is imaged even if the color temperature changes to match the camera to the characteristics of the human eye Correction that R = G = B is required. This is white balance adjustment, which includes electrical correction (R and B gain control) and optical correction (color temperature conversion filter). In addition, the control method includes a feed forward method and a feedback method.
[0006]
[Problems to be solved by the invention]
However, the conventional feedforward type white balance adjustment has the following inconvenience because the adjustment is performed based on the color signal before white balance, that is, the color signal not multiplied by the white balance gain.
[0007]
(1) When white balance gain is increased or decreased, it must be predicted how white will change.
(2) In making the above prediction, it is necessary to measure various data in advance for each solid-state imaging device, which requires a lot of labor and cost.
[0008]
On the other hand, in the feedback type white balance adjustment, since the adjustment is performed using the color signal after the white balance, the accuracy is high and the above-described inconvenience does not occur, but there is a risk of oscillation because it is not an open loop. There's a problem.
[0009]
The present invention has been made in view of the above problems, and the object of the present invention is to eliminate the trouble of measuring parameters for each individual solid-state imaging device, which has been a drawback of the feedforward method. It is an object of the present invention to provide a white balance circuit that can improve the accuracy of white balance adjustment without fear of oscillating.
[0010]
Another object of the present invention is to provide an imaging apparatus that can achieve white balance adjustment with high accuracy and improve the image quality of a captured image.
[0011]
[Means for Solving the Problems]
The white balance circuit according to the present invention includes a white balance amplifier circuit having a white balance amplifier circuit having individual gains corresponding to a plurality of color signals, and each of the color signals before being input to the white balance amplifier circuit. Based on the multiplication means for multiplying the gain according to a predetermined rule and each multiplication result from the multiplication means, a new gain that satisfies a predetermined condition is calculated, and the new gain obtained by this calculation is Gain calculating means for supplying the white balance amplifier circuit, and the white balance amplifier circuit amplifies the plurality of color signals with the new gain.
[0012]
Thus, first, the plurality of color signals are multiplied by the multiplying means according to a predetermined rule with gains corresponding to the plurality of color signals before being input to the white balance amplifier circuit used in the white balance amplifier circuit. . Then, in the gain calculation section, based on the multiplication results from said multiplying means, calculating a new gain should meet certain conditions, a new gain obtained in this calculation to the white balance amplifier circuit Supply.
[0013]
The white balance amplification circuit individually amplifies the plurality of color signals with new gains supplied from the gain calculation means. White balance adjustment is performed by this amplification.
[0014]
In the white balance circuit according to the present invention, since the gain at the time of taking the white balance is reflected, the accuracy is improved as compared with the conventional feed forward type white balance circuit. In addition, it is not necessary to measure parameters for each solid-state imaging device, and the cost can be reduced. Also, unlike the feedback method, it is an adjustment method using an open loop, so there is no possibility of oscillation.
[0015]
Next, an imaging apparatus according to the present invention includes an imaging unit that obtains a plurality of color signals from incident light from a subject, and a white balance amplifier circuit that has individual gains corresponding to the plurality of color signals from the imaging unit. In the image pickup apparatus, a plurality of color signals before being input to the white balance amplifier circuit are multiplied by the respective gains according to a predetermined rule, and a predetermined condition is set based on each multiplication result from the multiplication means. Gain calculating means for calculating a new gain to be satisfied and supplying the new gain obtained by the calculation to the white balance amplifier circuit . The white balance amplifier circuit is configured with the new gain. The plurality of color signals are amplified.
[0016]
Thereby, first, a plurality of color signals from the image pickup unit are multiplied by a gain corresponding to the plurality of color signals before being input to the white balance amplifier circuit used in the white balance amplifier circuit and a predetermined rule. Is multiplied according to Then, in the gain calculation section, based on the multiplication results from the multiplier means, calculates a new gain should meet certain conditions, a new gain obtained in this calculation to the white balance amplifier circuit Supply.
[0017]
The white balance amplification circuit individually amplifies the plurality of color signals with new gains supplied from the gain calculation means. White balance adjustment is performed by this amplification.
[0018]
In the white balance adjustment in the image pickup apparatus according to the present invention, the gain at the time when the white balance is taken is reflected, and therefore the accuracy is improved as compared with the conventional feed forward type white balance circuit. In addition, it is not necessary to measure parameters for each solid-state imaging device, and the cost can be reduced. Also, unlike the feedback method, it is an adjustment method using an open loop, so there is no possibility of oscillation.
[0019]
Therefore, in the imaging apparatus according to the present invention, it is possible to improve the quality of the captured image.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment in which the white balance circuit according to the present invention is applied to white balance adjustment of a video camera (hereinafter simply referred to as a white balance circuit according to the embodiment) and a white balance circuit according to the embodiment are described. An incorporated video camera (hereinafter simply referred to as a camera according to an embodiment) will be described with reference to FIGS.
[0021]
As shown in FIG. 1, the camera according to this embodiment has a solid-state imaging device 1 inside, an imaging lens 2 disposed on the front surface thereof, and a preamplifier 3 and a digital signal processing circuit in the subsequent stage of the solid-state imaging device 1. 4 etc. are built in and comprised.
[0022]
Briefly explaining the operation of the camera, first, a subject image incident through the imaging lens 2 is converted into an electrical signal (imaging signal) by the solid-state imaging device 1. The imaging signal from the solid-state imaging device 1 is sampled and held at a predetermined timing by the preamplifier 3 at the subsequent stage, and only necessary signal components are extracted. The extracted signal component is subjected to gain control for adjusting to an appropriate level in the preamplifier 3.
[0023]
An imaging signal from the preamplifier 3 is converted into digital imaging data by an A / D converter (not shown) and then input to the digital signal processing circuit 4. The A / D converter may be included in the digital signal processing circuit 4.
[0024]
Among the imaging data input to the digital signal processing circuit 4, the color signal data R, G, and B are subjected to processing such as white balance and gamma correction in the digital signal processing circuit 4, and then the luminance signal data and The signals are mixed and converted into video data and output from the digital signal processing circuit 4.
[0025]
The video data output from the digital signal processing circuit 4 is converted into an analog video signal by a D / A converter (not shown). This video signal is supplied to, for example, a monitor (not shown) and displayed as a reproduced image. The D / A converter may be included in the digital signal processing circuit 4.
[0026]
The white balance circuit according to the present embodiment is incorporated in the color signal processing system of the digital signal processing circuit 4 and is provided corresponding to R, G, and B as shown in FIG. Two white balance amplifiers (R-WB amplifier 11R, G-WB amplifier 11G, B-WB amplifier 11B) and color signal data R, G, B before being input to these white balance amplifiers 11R, 11G, 11B Te a color temperature detection circuit 12 which performs integration of the range for each field respectively, three integration data iR from the color temperature detection circuit 12, iG, iB and the white balance amplifier 11R, 11G, 11B of the gain data _G R, G _G, multiplied by the G _B with a predetermined rule, the gain data G _R as the multiplication result satisfies a predetermined _condition, G _G, and the setting operation of the G _B , New gain data _rG R which is the set _operation, rG G, the the rG _B white balance amplifier 11R, 11G, is configured to have a supply gain calculating and setting circuit 13 to 11B.
[0027]
The color temperature detection circuit 12 integrates the color signal data R, G, and B, respectively, when the image of the entire field is integrated (when all the colors of the video including various colors are added), the color becomes white. It comes from the assumption.
[0028]
The gain calculating and setting circuit 13, for example, can be configured by a microcomputer, the white balance amplifier 11R, 11G, respectively from 11B current gain data (R gain _G R, G gain _{G G} and B gain _{G B} ), The integrated data receiving means 22 for receiving the three integrated data iR, iG, iB from the color temperature detecting circuit 12, and the three integrated data iR, received by the integrated data receiving means 22. iG, each gain data _G R received by iB and the gain receiving means _21, a multiplier 23 for multiplying G G, and _{G B} a predetermined rule, the multiplication result dR, dG, dB is a predetermined condition and gain data _{G R,} G G, the gain setting means 24 for setting operation the _{G B} so as to satisfy, at the gain setting means 24 Constant has been new gain data _{rG R, rG G,} the white balance amplifier 11R corresponding respectively rG _B, 11G, and gain output unit 25 supplies the 11B is incorporated for example as software.
[0029]
Specifically, the multiplication unit 23, a process of obtaining the R integral multiplication data dR by multiplying the R integral data iR and R gain G _R, G integral multiplication by multiplying the G integrated data iG and G gain G _G a process of obtaining data dG, a B integration data iB and B gain G _B and obtain B integral multiplication data dB and multiplication processing performed.
[0030]
The gain setting means 24 sets the R gain G _R , G gain G _G and B gain G so that the R integral multiplication data dR, the G integral multiplication data dG and the B integral multiplication data dB satisfy any of the following relational expressions. adjust the white balance by operating the _B, performs a process of setting R gain rG R after obtained by the _operation, the _G gain rG _G and B gain rG _B as a new gain, respectively.
[0031]
dR = dG = dB
dR / dG = dB / dG
dR-dG = dB-dG
[0032]
Gain output unit 25, the gain setting means 24 new R gain set by _rG R, the G gain rG _G and B gain rG _B each R-WB amplifier 11R, G-WB amplifier 11G and B-WB amplifier The process of supplying to 11B is performed.
[0033]
As can be seen from these processing operations, in the white balance circuit according to the present embodiment, the color temperature data before the white balance amplifiers (11R, 11G, and 11B) is input is received by the color temperature detection circuit 12, respectively. Individual integration is performed, and the integration data iR, iG, iB is multiplied according to the predetermined rule by the multiplication means 23 in the gain calculation setting circuit 13, and the multiplication results dR, dG, dB match any one of the above relational expressions. White balance amplifier 11R to, 11G, 11B of the gain _{G R, G G,} by operating the _{G B,} gain _rG R obtained through the _operation, rG _G, rG _B each white balance amplifier 11R, 11G, 11B is used as an amplification gain.
[0034]
Therefore, in the white balance circuit according to the present embodiment, the white balance of the color signal data R, G, and B that has passed through the white balance amplifiers 11R, 11G, and 11B is adjusted, and when the white balance is achieved. Therefore, the accuracy is improved as compared with the conventional feed-forward type white balance circuit. In addition, it is not necessary to measure parameters for each solid-state imaging device, and the cost can be reduced. Also, unlike the feedback method, it is an adjustment method using an open loop, so there is no possibility of oscillation. According to the camera incorporating the white balance circuit according to the present embodiment that exhibits such effects, it is possible to improve the image quality of the image displayed on the monitor screen.
[0035]
Next, some modifications of the white balance circuit according to the present embodiment will be described with reference to FIGS. In addition, about the thing corresponding to FIG. 1, the same code | symbol is described and the duplication description is abbreviate | omitted.
[0036]
First, as shown in FIG. 2, the white balance circuit according to the first modification has almost the same configuration as the white balance circuit according to the present embodiment, but the configuration of the color temperature detection circuit 12 and the gain calculation setting. The processing in the circuit 13 is different as follows.
[0037]
In other words, the color temperature detection circuit 12 includes three multipliers (first to third multipliers 31R, 31G, and 31B) and an integration circuit 32, and the R signal data R in the first multiplier 31R. and is multiplied by the R gain _{G R,} and G signal data G in the second multiplier 31G and B gain _{G B} is multiplied, and B signal data B and G gain G _G in the third multiplier 31B multiplies The wiring is connected as shown.
[0038]
The integration circuit 32 integrates the R multiplication data mR from the first multiplier 31R in the range of every field and outputs it as R integration multiplication data dR, and the G multiplication data mG from the second multiplier 31G every field. Are integrated in the range and output as G integral multiplication data dG, and B multiplication data mB from the third multiplier 31B are integrated in the range of each field and output as B integral multiplication data dB. .
[0039]
On the other hand, unlike the gain calculation setting circuit 13 in the white balance circuit according to the above-described embodiment, the gain calculation setting circuit 13 receives the integral multiplication data receiving the three integral multiplication data dR, dG, dB from the color temperature detection circuit 12. R gain G _R , G gain G _G, and B gain G so that any one of the above relational expressions is established between the means 26 and the three integral multiplication data dR, dG, dB received by the integral multiplication data receiving means 26. adjust the white balance by operating _B, the operation R gain after obtained by rG _R, a gain setting means 24 for setting the _G gain rG _G and B gain rG _B as a new gain respectively, the gain setting means new R gain _rG R which is set at 24, respectively G gain rG _G and B gain rG _B R-WB Amplifier 11R, has three means G-WB amplifier 11G and B-WB to be supplied to the amplifier 11B gain output unit 25.
[0040]
As described above, in the white balance circuit according to the first modified example, the color temperature detection circuit 12 receives the color signal data R, G, B before the white balance amplifier (11R, 11G, 11B) is input as the predetermined value. After multiplication according to the rules, each multiplication data mR, mG, mB is individually integrated to obtain multiplication integration data dR, dG, dB. In the gain calculation setting circuit 13, the integration multiplication data dR, dG, dB is gain _G R of the white balance amplifier to meet one _{relationship,} G G, by operating the _{G B,} amplification gain _rG R obtained by the _operation, rG G, the rG _B white balance amplifier It is used as a gain.
[0041]
In the white balance circuit according to the first modified example, as in the white balance circuit according to the above-described embodiment, the accuracy is improved as compared with the conventional feed-forward type white balance circuit. There is no need to measure parameters every time, and the cost can be reduced. There is no risk of oscillation. Therefore, according to the camera incorporating the white balance circuit according to the first modified example having such an effect, the image quality of the image displayed on the monitor screen can be improved.
[0042]
In particular, in the first modification, since it is not necessary to perform data multiplication in the gain calculation setting circuit 13, the software incorporated in the microcomputer constituting the gain calculation setting circuit 13 is configured with a small program capacity. It becomes possible to do.
[0043]
Next, a white balance circuit according to a second modification will be described with reference to FIG.
[0044]
The white balance circuit according to the second modification can be applied when a complementary color checkered color filter is used as the color filter formed in the solid-state imaging device 1, and the white balance circuit is incorporated. Unlike the camera according to the above embodiment, the digital signal processing circuit 4 receives the luminance signal data Y and the two types of color difference signal data Cr and Cb.
[0045]
Therefore, in the digital signal processing circuit 4, the luminance signal data Y and the two types of color difference signal data Cr and Cb are separated into primary colors before the white balance amplifiers 11R, 11G, and 11B, respectively, and R signal data R and G signals are obtained. A primary color separation circuit 41 for data G and B signal data B is inserted and connected.
[0046]
In the white balance circuit according to the second modification, the luminance signal data Y and the two types of color difference signal data Cr and Cb are individually integrated in the range of each field in the color temperature detection circuit 12. A process of outputting the luminance integration data iY and two types of color difference integration data iCr and iCb is performed.
[0047]
On the other hand, the gain calculation setting circuit 13 detects the color temperature received by the integral data receiving means 22 in addition to the gain receiving means 21, the integral data receiving means 22, the multiplying means 23, the gain setting means 24 and the gain output means 25. A primary color separation unit 27 is provided which performs primary color separation processing on the luminance integration data iY from the circuit 12 and the two types of color difference integration data iCr and iCb to obtain R integration data iR, G integration data iG and B integration data iB, respectively.
[0048]
In the multiplying means 23, R gain received through gain receiving means 21 _G R, B gain _{G B} and G gain _{G G} and R integration data iR from primary separation means 27, G integrated data iG and B integration data iB Are individually multiplied to obtain R integral multiplication data dR, G integral multiplication data rG, and B integral multiplication data rB, respectively.
[0049]
Then, in the subsequent gain setting means 24, the supplied R integral multiplication data dR, G integral multiplication data dG and B integral multiplication data dB are represented by the above relational expression, as in the case of the white balance circuit according to the above embodiment. The R gain G _R , G gain G _G and B gain G _B are adjusted to adjust the white balance so that one of them is satisfied, and the R gain rG _R , G gain rG _G and B gain obtained by this operation are adjusted. processing of setting the rG _B as a new gain respectively is performed further in the gain output unit 25, the gain setting means new R gain _rG R which is set at 24, the G gain rG _G and B gains rG _B A process of supplying the signals to the R-WB amplifier 11R, the G-WB amplifier 11G, and the B-WB amplifier 11B is performed. .
[0050]
Thus, in the white balance circuit according to the second modification, the luminance signal data Y and the two types of color difference signal data Cr and Cb before the primary color separation are individually integrated by the color temperature detection circuit 12, respectively. The integration data iY, Cr, Cb are separated into R integration data iR, G integration data iG, and B integration data iB by the primary color separation means 27 in the gain calculation setting circuit 13, and the integration data iR, iG, iB are multiplied. 23, the gains G _R , G _G , and G _B of the white balance amplifiers 11R, 11G, and 11B are set so that the multiplication results dR, dG, and dB match any of the above relational expressions. operation to gain _rG R obtained by the _operation, rG G, the white balance amplifier 11R corresponding respectively rG _B, 11G, 11B is used as an amplification gain.
[0051]
Therefore, in the white balance circuit according to the second modified example, as in the white balance circuit according to the above-described embodiment, the accuracy is improved as compared with the conventional white balance circuit of the feedforward method, and the individual solid state There is no need to measure parameters for each image sensor, and the cost can be reduced. There is no risk of oscillation. Therefore, according to the camera incorporating the white balance circuit according to the second modified example having such an effect, the image quality of the image displayed on the monitor screen can be improved.
[0052]
As described above, the image quality of the white balance circuit according to the embodiment and the white balance circuit according to the first and second modified examples for cameras having an auto white balance adjustment function in consumer, business, and industrial machine cameras. It is possible to contribute to improvement.
[0053]
【The invention's effect】
As described above, according to the white balance circuit of the present invention, in the white balance circuit including the white balance amplifier circuit having individual gains corresponding to a plurality of color signals , the white balance circuit before being input to the white balance amplifier circuit. Multiplying means for multiplying each color signal by each gain according to a predetermined rule, and a new gain that should satisfy a predetermined condition is calculated based on each multiplication result from the multiplying means. Gain calculating means for supplying the obtained new gain to the white balance amplification circuit, and the white balance amplification circuit amplifies the plurality of color signals with the new gain. This saves the trouble of measuring the parameters for each solid-state image sensor, which was a disadvantage of the method, and is similar to the feedback method. No fear, it is possible to improve the accuracy of white balance adjustment.
[0054]
In addition, according to the imaging apparatus of the present invention, an imaging unit that obtains a plurality of color signals from incident light from a subject, and a white balance amplification circuit that has individual gains corresponding to the plurality of color signals from the imaging unit. in the imaging device having a multiplication means for multiplying the respective gain according to a predetermined rule before the plurality of color signals to be input to the white balance amplifier circuit of this, based on the multiplication result from the multiplying means, a predetermined Gain calculating means for calculating a new gain that satisfies the condition and supplying the new gain obtained by this calculation to the white balance amplifier circuit . The white balance amplifier circuit includes the new gain. Thus, since the plurality of color signals are amplified, the white balance can be adjusted with high accuracy and the image quality of the captured image can be improved.
[Brief description of the drawings]
FIG. 1 shows an embodiment in which a white balance circuit according to the present invention is applied to white balance adjustment of a video camera (hereinafter simply referred to as a white balance circuit according to an embodiment), and a white balance according to the embodiment. 1 is a configuration diagram showing a video camera (hereinafter simply referred to as a camera according to an embodiment) in which a circuit is incorporated.
FIG. 2 is a configuration diagram illustrating a first modification of the white balance circuit according to the present embodiment and a camera according to the present embodiment in which the white balance circuit according to the first modification is incorporated;
FIG. 3 is a configuration diagram illustrating a second modification of the white balance circuit according to the present embodiment and a camera according to the present embodiment in which the white balance circuit according to the second modification is incorporated.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Solid-state image sensor, 2 Imaging lens, 3 Preamplifier, 4 Digital signal processing circuit, 11R, 11G, and 11B White balance amplifier, 12 Color temperature detection circuit, 13 Gain calculation setting circuit, 21 Gain receiving means, 22 Integration data receiving means, 23 multiplication means, 24 gain setting means, 25 gain output means, 26 integral multiplication data receiving means, 27 primary color separation means, 31R, 31G and 31B multipliers, 32 integration circuit, 41 primary color separation circuit

Claims (12)

In a white balance circuit including a white balance amplifier circuit having individual gains corresponding to a plurality of color signals,
Multiplying means for multiplying the plurality of color signals before being input to the white balance amplifier circuit by each gain according to a predetermined rule;
Based on the multiplication result from the multiplying means, calculates a new gain should meet certain conditions, a new gain obtained in said calculating a gain calculation means for supplying to said white balance amplifier circuit Yes, and the white balance amplifier circuit white balance circuit, characterized in that amplifying the plurality of color signals in said new gain. 2. The white balance circuit according to claim 1, further comprising a color signal processing circuit that integrates the plurality of color signals and supplies the integrated color signals to the multiplication unit. 3. The white balance circuit according to claim 1, wherein the plurality of color signals are signals relating to three primary colors of red, green and blue. 3. The plurality of color signals are a luminance signal and a color difference signal, and primary color separation means for separating the luminance signal and the color difference signal into signals relating to the three primary colors is provided before the multiplication means. White balance circuit. The predetermined rule is a rule of multiplying a red signal by a red gain, multiplying a green signal by a green gain, and multiplying a blue signal by a blue gain. The white balance circuit according to 1. The predetermined condition is that when the red signal, the green signal and the blue signal after multiplication are dR, dG and dB, respectively.
dR = dG = dB
dR / dG = dB / dG
dR-dG = dB-dG
The white balance circuit according to claim 1, wherein the white balance circuit is any one of the following. In an imaging apparatus including an imaging unit that obtains a plurality of color signals from incident light from a subject, and a white balance amplification circuit having individual gains according to the plurality of color signals from the imaging unit,
Multiplying means for multiplying the plurality of color signals before being input to the white balance amplifier circuit by each gain according to a predetermined rule;
Based on each multiplication result from the multiplication means, there is gain calculation means for calculating a new gain that satisfies a predetermined condition and supplying the new gain obtained by the calculation to the white balance amplifier circuit. The white balance amplifier circuit amplifies the plurality of color signals with the new gain . 8. The imaging apparatus according to claim 7, further comprising a color signal processing circuit that integrates the plurality of color signals and supplies the integrated color signals to the multiplication unit. 9. The imaging apparatus according to claim 7, wherein the plurality of color signals are signals relating to three primary colors of red, green, and blue. 9. The plurality of color signals are a luminance signal and a color difference signal, and primary color separation means for separating the luminance signal and the color difference signal into signals relating to the three primary colors is provided before the multiplication means. Imaging device. 11. The rule according to claim 7, wherein the predetermined rule is a rule of multiplying a red signal by a red gain, multiplying a green signal by a green gain, and multiplying a blue signal by a blue gain. The imaging apparatus according to 1. The predetermined condition is that when the red signal, the green signal and the blue signal after multiplication are Rr, Gg and Bb, respectively.
dR = dG = dB
dR / dG = dB / dG
dR-dG = dB-dG
The imaging apparatus according to claim 7, wherein the imaging apparatus is any one of the following.

Images