JP2529210B2 - White balance adjustment device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a white balance adjusting device for a color video camera.

2. Description of the Related Art A conventional white balance adjusting device is disclosed in, for example, Japanese Patent Laid-Open No. 56-4993. FIG. 4 shows the structure of this conventional white balance adjusting apparatus, and 3 is an external colorimetric circuit for converting light incident from a subject into external color temperature information. Reference numeral 6 is an image sensor, and 7 is an amplifier. Reference numeral 40 is an R / B color signal controller that adjusts the gains of the R / B color signals using the output of the external colorimetric circuit 3. The conventional white balance adjusting device configured as described above uses the external color temperature information obtained from the external colorimetric circuit 3 to control the gains of the R and B color signals with the R and B color signal controller 40. By
The white balance is adjusted so that the ratio of the color signals R, G, B indicating the white part of the subject becomes 1: 1: 1 which is the ratio of the data indicating white.

Another conventional white balance adjusting device is disclosed in, for example, Japanese Patent Application Laid-Open No. 60-180394. FIG. 5 shows the configuration of this conventional white balance adjusting apparatus, in which 6 is an image sensor, 7 is an amplifier, and 41
Is a color process processing circuit, 43 and 44 are level detection circuits, 4
5 is an AND circuit. 42 is a white balance control circuit. The conventional white balance adjusting device configured as described above includes level detectors A, B, 43, 44 and an AND circuit 45.
Thus, the low-saturation state in which the luminance signal Y is equal to or higher than a predetermined level and the chroma signal C is equal to or lower than a predetermined level different from the above is determined. Only in this state, the white balance control circuit 42 White balance adjustment is performed using the output of the color process processing circuit 41.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, in the above-mentioned first conventional technology, when there is a difference in the spectral characteristic and the temperature characteristic of the external colorimetric circuit 3 and the image sensor 6, there is a difference between the detected color temperature and the actual color temperature. Error occurs in the white balance adjustment. Further, since the output of the external colorimetric circuit 3 is directly used for control,
Since the external colorimetric circuit 3 is required to have a high degree of accuracy, the cost tends to increase. Further, in the above-mentioned second conventional technique, since the detection thresholds of the level detection circuits 43 and 44 are constant, even if the magnitude of the chroma signal is measured even if the color temperature changes significantly. However, there is a problem that it becomes difficult to measure the saturation of the subject itself, and the followability of the white balance adjustment with respect to the color temperature deteriorates.

Means for Solving the Problems In order to solve the above problems, the present invention provides an external colorimetric circuit for obtaining external color temperature information and a predetermined color signal of a white portion of a subject using the external color temperature information. A first color signal control circuit for controlling the color signal to be at a level, and when the color signal is smaller than the luminance signal, that is, shows low saturation, the color signal close to the predetermined level is determined as white data. An extraction circuit for extracting the white part of the subject in the output of the first color signal control circuit, an averaging circuit for averaging the outputs of the extraction circuit and averaging the color signals of only the white part of the subject, Data in which the output of the first color signal control circuit is output by using the output of the averaging circuit when the ratio of the white portion of the subject is larger than a predetermined value, and the color signal data when the white subject is imaged indicates white. To become It has a configuration including a second color signal control circuit for controlling.

Effect of the Invention With the above-described configuration, the present invention suppresses an error due to a large change in color temperature by converting the color signal portion obtained by capturing the white portion of the subject into a predetermined level by the first color signal control circuit. , The color signal is smaller than the luminance signal is used to judge the white part, and the accurate white part is extracted by using the average data of the color signal of that part. By using this as a highly reliable white part only when the ratio is large, stable average color signal data of the white part is obtained, and based on this, accurate white balance control with few malfunctions is realized.

Embodiment Hereinafter, a white balance adjusting apparatus according to an embodiment of the present invention will be described with reference to the drawings. The white balance adjusting apparatus according to the embodiment of the present invention has a basic configuration as shown in FIG. 1. An external colorimetric circuit 3 for obtaining external color temperature information, and color signal data of a white subject is predetermined using the external color temperature information. Of the first color signal control circuit 1 for controlling the output level of the first color signal control circuit 1 to extract the low chroma part of the subject in the output of the first color signal control circuit 1, and the white extrusion circuit 4. An averaging circuit 5 for averaging the outputs and a first using the output of the averaging circuit 5
The second color signal control circuit 2 for controlling the output of the color signal control circuit 1 is provided.

With the configuration shown in FIG. 1, the color signal data of the white subject is controlled to a certain predetermined level by using the external color temperature information, and the average of only the color signals in the vicinity of the predetermined level, that is, the low saturation part is controlled. Use the value to finely adjust the white balance.

FIG. 2 is a more detailed block diagram of the white balance adjusting apparatus according to the first embodiment of the present invention. In FIG. 2, 3 is an external colorimetric circuit, 6 is an image sensor, 7 is an amplifier, 8 is a process processing circuit, 9 to 14 are variable gain amplifiers, 16 is a conversion circuit, 17 is a white extraction circuit, and 18 to 20 are. An averaging circuit, 21 and 22 are division circuits, 23 and 24 are sample and hold circuits, and 25 is a ratio detection circuit.

The video signal output from the image sensor 6 passes through the amplifier 7 and is processed by the process processing circuit 8 into the R, G, B signals,
The luminance signal Y is converted. On the other hand, the external temperature information obtained by the external colorimetric circuit 3 controls the gains of the variable gain amplifiers 9 to 11 through the conversion circuit 16 to obtain a ratio of color signals R, G, B when a white subject is imaged. Is controlled to be 1: 1: 1. In this case, it is not exactly 1: 1: 1 due to an error in the external color temperature information, and even if there is some error, it will be corrected by the processing described later. Next, the white extraction circuit 17
By referring to the outputs of the variable gain amplifiers 9 to 11 and the luminance signal Y, only the color signal of the low chroma part of the subject, that is, the part where R: G: B is close to 1: 1: 1 is extracted. The color signal extraction conditions are expressed by Equation 1, Equation 2,
It is shown in Equation 3.

| B−G | <α1 · Y (Equation 1) | R−G | <α2 · Y (Equation 2) Y> β (Equation 3) Here, α1 and α2 are set to relatively small values. Also,
The condition of Expression 3 is necessary to maintain the accuracy of the white balance adjustment, but when considering only the ideal operation, Expression 3
Even if there is no condition, there is no problem in basic operation. The Y signal may be replaced with the G signal. In this way, the output R / G / B of the white extraction circuit 17 for one field is the averaging circuit.
The signals are averaged by 18, 19, 20 and become a signal, and /, / signals are obtained by the division circuits 21, 22. Next, the sample / hold circuits 23 and 24 sample and hold the above-mentioned / and / signals only when the ratio detection circuit 25 causes the low-saturation part of the subject to reach a ratio above a certain level. This prevents an increase in white balance adjustment error when the low saturation portion of the subject is small. The outputs of the sample and hold circuits 23 and 24 control the gains of the variable gain amplifiers 12 and 14 to adjust the white balance. In the above operation, one field is one cycle, but a plurality of fields may be one cycle. Also, the above white balance adjustment operation is controlled so that the ratio of R, G, B signals becomes 1: 1: 1 when a white subject is imaged, but the RY and BY signals are You may control so that it may become zero.

FIG. 3 is a block diagram of a white balance adjusting apparatus according to the second embodiment of the present invention. The operation is such that the color difference signal is controlled to 0 when a white subject is imaged. In FIG. 3, 26 is a process processing circuit,
Reference numeral 27 is a conversion circuit, 28 to 31 are variable gain amplifiers, and 32 is a white extraction circuit.

The video signal obtained from the image pickup device 6 and the amplifier 7 becomes the RY, BY and the luminance signal Y by the process processing circuit 26.
On the other hand, the conversion circuit 27 controls the gains of the variable gain amplifiers 28 and 29 by using the external color temperature information obtained by the external colorimetric circuit 3, and outputs this output by using the adders 36 and 37. When the white subject is imaged by adding to the −Y signal, the RY and BY signals are controlled to be 0. In this case, it is not exactly 0 due to an error in the external color temperature information, and even if it includes a certain amount of error, it will be corrected by the processing described later. Next, the white extraction circuit 32
Refers to the outputs of the adders 36 and 37 and the luminance signal Y to extract the RY and BY signals of the low chroma portion of the subject. The extraction conditions are shown in Equations 4, 5, and 6.

| R−Y | <α3 · Y (Equation 4) | B−Y | <α4 · Y (Equation 5) Y> δ (Equation 6) Here, α3 and α4 are set to relatively small values. Further, the condition of Expression 6 is necessary to maintain the white balance adjustment accuracy, but when considering an ideal operation, Expression 6
Even if there is no condition, there is no problem in basic operation. The RY and BY signals of the low saturation portion of the subject extracted in this way are averaged by the averaging circuit 33.34. Next, the proportion detection circuit 25 causes the sample and hold circuits 23, 2 only when the low-saturation portion of the subject reaches a proportion above a certain level.
4 samples and holds the output of the averaging circuit described above. Then, the gains of the variable gain amplifiers 30 and 31 are controlled using the outputs of the sample and hold circuits 23 and 24, and the outputs are added to the outputs of the adders 36 and 37 by using the adders 38 and 39.
As a result, RY and BY when a white subject is imaged
The signal is controlled so that the signal becomes 0, and the white balance is adjusted.

In the above embodiment, the R, G, B signals and the RY, BY signals are taken into consideration as the color signals, but the same applies when the pixel signals output from the image sensor 6 are used. White balance adjustment is possible.

EFFECTS OF THE INVENTION As described above, according to the present invention, when the white portion of the subject is very small and the data is not stable, this data is invalidated and only when a highly reliable white subject is imaged. Performs white balance operation to achieve white balance with few malfunctions, and uses the fact that the color signal is smaller than the luminance signal to judge, so the white portion color signal when the luminance signal is large or small is accurately extracted. However, an accurate white balance can be realized, and the effect is extremely large.

[Brief description of drawings]

1 is a basic configuration diagram of a white balance adjusting apparatus according to an embodiment of the present invention, FIG. 2 is a block diagram of a first embodiment of the present invention, and FIG. 3 is a block diagram of a second embodiment of the present invention. FIG. 4 is a block diagram of a first conventional white balance adjusting device, and FIG. 5 is a block diagram of a second conventional white balance adjusting device. 1 ... First color signal control circuit, 2 ... Second color signal control circuit, 3 ... External color measurement circuit, 4 ... White extraction circuit, 5,18,1
9,20,33,34 ... Averaging circuit, 6 ... Imaging element, 7 ... Amplifier, 8,26 ... Process processing circuit, 9-14,8-31 ... Variable gain amplifier, 16,27 ... Conversion circuit, 17, 32 ... white extraction circuit, 21, 22 ... division circuit, 23, 24 ... sample and hold circuit, 25 ... ratio detection circuit, 36 to 39 ... adder.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-56-116391 (JP, A) JP-A-61-101187 (JP, A) JP-A-61-140297 (JP, A) Actual development Sho-61- 52885 (JP, U)

Claims (3)

(57) [Claims] 1. An external color measurement circuit for obtaining external color temperature information, and a first color signal control circuit for controlling the color signal of a white portion of a subject to a predetermined level by using the external color temperature information. When the color signal is smaller than the luminance signal, that is, when the color signal shows low saturation, the color signal close to the predetermined level is judged to be white data, so that the object at the output of the first color signal control circuit is detected. An extraction circuit for extracting a white part, an averaging circuit for averaging the outputs of the extraction circuits to average color signals of only the white part of the subject, and a case where the ratio of the white part of the subject is larger than a predetermined value. A second color signal control circuit for controlling the output of the first color signal control circuit using the output of the averaging circuit so that the color signal data when a white subject is imaged becomes data indicating white Characterized by White balance adjustment device. 2. The white balance adjusting device according to claim 1, wherein the extraction circuit also uses, as an extraction criterion, that the image pickup luminance information is within a predetermined level range. 3. A second color signal control circuit determines an initial value of the control value of the color signal based on the external color temperature information, and when the subject does not have a low saturation portion, the control value of the color signal is determined. The white balance adjusting device according to claim 1, further comprising a holding circuit.