JP3475600B2 - White balance adjustment method and white balance adjustment device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a white balance adjusting method and a white balance adjusting apparatus for matching the signal levels of three primary color signals to an achromatic portion of a subject image.

[0002]

2. Description of the Related Art Generally, a video camera is equipped with a non-linear processing device for performing non-linear processing such as γ correction and knee correction on the three primary color signals obtained by a charge image pickup device, and at the same time, the three primary color signals for an achromatic portion of a subject image are processed. It has a white balance adjusting device for matching the signal levels.

Since the color temperature (spectral distribution characteristic) of the subject differs depending on the light source, this white balance adjusting device is set so that maximum sensitivity and color reproduction can be obtained at a specific color temperature. That is, when a white subject is photographed at different color temperatures, the white balance adjustment device outputs different signal levels of red (R), green (G), and blue (B) signals, and the captured image deteriorates. Therefore, even if the color temperature changes,
The signal level ratio of each color signal is automatically corrected to be 1: 1: 1.

[0004]

By the way, the user is
In many cases, I felt that the color was not suitable for the automatic white balance adjustment. However, since the user cannot adjust the desired white balance at the so-called camera processing stage, the user adjusts the desired white balance through the post-processing device after the automatic white balance adjustment. . In addition, the user is inconvenient because he / she can adjust the desired white balance in this way, but cannot easily shift the color temperature direction so that an unnatural image is not obtained.

The present invention has been made in view of such circumstances, and an object thereof is to provide a white balance adjusting method and the like which can easily perform a desired white balance adjustment.

[0006]

In order to solve the above-mentioned problems, a white balance adjusting method according to the present invention detects the signal levels of three types of color signals output through the level adjusting means, and detects each color. Signal levels below the high brightness upper limit slice level are integrated for each signal. Then, the offsets are released from the integrated values of the two types of signal levels among the integrated values of the three types of signal levels, and the three types of color signals in the achromatic portion of the image are based on the integrated values of the three types of color levels. The two kinds of gain adjustment signals for adjusting the level adjusting means are supplied to the level adjusting means so that the ratio of the signal level of 1 becomes 1: 1: 1. Furthermore, a desired offset can be added to the two types of gain adjustment signals, and the gains of the two types of color signal level adjustment means can be adjusted independently.

Further, the white balance adjusting apparatus according to the present invention comprises level adjusting means for outputting three kinds of color signals,
Detecting means for detecting the signal levels of the three types of color signals output via the level adjusting means, and integrating the signal levels below the high brightness upper limit slice level for each color signal,
Based on the offset canceling means for canceling the offset from the integrated values of the two kinds of signal levels among the integrated values of the three kinds of signal levels, and the integrated values of the three kinds of respective color levels,
White balance for supplying two types of gain adjustment signals for adjusting the level adjusting means to the level adjusting means so that the ratio of the signal levels of the three types of color signals in the achromatic portion of the image is 1: 1: 1. The processing means and the offset adding means for adding a desired offset to the two types of gain adjustment signals are provided. And the white balance processing means
The gains of the level adjusting means for the two types of color signals can be adjusted independently based on the gain adjusting signal.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a feedback type white balance adjusting method and a white balance adjusting apparatus according to the present invention will be described below with reference to the drawings.

As shown in FIG. 1, a video camera to which a feedback type white balance adjusting apparatus according to the present invention is applied is a charge image pickup device for converting color-separated three primary color lights from an object into electric color signals. 2A, 2B, 2C
And an automatic gain control circuit 3 for correcting the distortion of the color signal and outputting it.
A, 3B, 3C, analog / digital (hereinafter referred to as A / D) converters 4A, 4B, 4C for converting analog color signals to digital color signals, and white balance adjustment based on the digital color signals The white balance adjusting device 1 is provided.

The feedback type white balance adjusting apparatus 1 detects level of the color signals to be output and level adjusting circuits 5 and 6 for adjusting the output of the color signals, as shown in FIG. From the detection circuit 7 that calculates the integrated value of the signal level, the offset cancellation circuits 8 and 9 that cancels the offset from the integrated value of the signal level calculated by the detection circuit 7, and the detection circuit 7 or the offset cancellation circuits 8 and 9. The white balance processing circuit 10 adjusts the white balance based on the integrated value of the signal level to adjust the gains of the level adjusting circuits 5 and 6.

In the video camera to which the white balance adjusting device is applied, three charge image pickup devices 2 are used.
Imaging light from a subject is separated into three primary color lights of red (R), green (G), and blue (B) and incident on A, 2B, and 2C by a prism or the like not shown. The charge image pickup devices 2A, 2B and 2C pick up the subject images formed by the three primary color lights on the respective image pickup surfaces and supply electric three primary color signals to the automatic gain control circuits 3A, 3B and 3C, respectively. .

The automatic gain control circuits 3A, 3B, 3C supply a color signal without distortion to the A / D converters 4A, 4B, 4C according to the signal level of the supplied color signal.

The A / D converters 4A, 4B and 4C convert the supplied analog color signals into digital color signals and supply them to the white balance adjusting device 1.

In the white balance adjusting device 1, the supplied R and B signals are adjusted in signal level by the level adjusting circuits 5 and 6 and output through the output terminals 9A and 9C. The input G signal is output terminal 9 as it is.
It is output via B.

Here, the detection circuit 7 detects the signal level of each of the R, G and B color signals output from the white balance adjusting apparatus 1 and calculates the integral value of the detected signal level.

Specifically, the detection circuit 7 sets the high luminance upper limit slice level H as the upper limit of the signal level to be processed, for example.
SL is set, and the signal level of the color signal for one field is detected for the signal level equal to or lower than the high brightness upper limit slice level HSL. When the detection circuit 7 finishes detecting the signal level for one field, the lower limit level of high brightness in one field (hereinafter,
“High brightness lower limit slice level LSL”) is calculated. Then, the detection circuit 7 performs integration of signal levels of the high-luminance upper-limit slice level HSL or lower and the high-luminance lower-limit slice level LSL or higher for each of the R, G, B color signals, and the R, G, B signals. Find the integrated value of the level.

The detection circuit 7 supplies the integrated values of the signal levels of the R and B signals thus calculated to the offset canceling circuits 8 and 9, and the integrated value of the signal level of the G signal to the white balance processing circuit 10.

The offset canceling circuits 8 and 9 cancel the offset added to the integrated values of the R signal and the B signal, respectively, and supply the integrated value of each signal level from which the offset has been canceled to the white balance processing circuit 10. .

When the signal level supplied to the offset canceling circuits 8 and 9 is X and the signal level supplied from the offset canceling circuits 8 and 9 to the white balance processing circuit 10 is Y, the offset canceling circuits 8 and 9 are , The offset is canceled according to the equation (1).

Y = X / (1 + OFFSET × LEBEL) (1) The value of OFFSET is a preset value, and LEBEL
The value of is the value set by the user.

The white balance processing circuit 10 compares the integrated value of the R signal and the integrated value of the B signal with the integrated value of the G signal, and sets the ratio of the integrated values of the R, G, and B signal levels to 1 :.
The gain of each color signal output from the level adjusting circuits 5 and 6 is calculated so as to be 1: 1. The white balance processing circuit 10 adds two types of gain adjustment signals for adjusting the gains of the level adjusting circuits 5 and 6 based on the calculated gains of the level adjusting circuits 5 and 6, respectively.
2 to the level adjusting circuits 5 and 6.

At this time, the offset adding circuits 11 and 12
Adds an offset according to the white balance desired by the user to the gain adjustment signal from the white balance processing circuit 10, and outputs the gain adjustment signal to the level adjustment circuit 5,
Supply to 6.

As a concrete calculation method, when the gain adjusting signal supplied to the offset adding circuits 11 and 12 is S and the gain adjusting signal supplied from the offset adding circuits 11 and 12 to the level adjusting circuits 5 and 6 is T, The offset adding circuits 11 and 12 add an offset according to the equation (2).

T = (1 + OFFSET × LEBEL) × S (2) Here, the value of OFFSET is the value preset as described above, and the value of LEBEL is the value set by the user. Is. Therefore, when the user desires automatic white balance adjustment, LEBEL = 0 may be set.

When the offset is added to the gain adjusting signal in this way, the level adjusting circuits 5 and 6 adjust the signal levels of the R and B signals to be output based on the gain adjusting signal. As a result, the user can perform desired white balance adjustment.

Here, the reason why the offset canceling circuits 8 and 9 and the offset adding circuits 11 and 12 which are independent of each other for the R signal and the G signal are provided will be described. Therefore, hereinafter, the offset canceling circuit 8 shown in FIG.
9 and the offset adding circuits 11 and 12 are not provided, and the same circuits are denoted by the same reference numerals.
The signal level of the R signal with respect to the G signal supplied from the detection circuit 7 to the white balance processing circuit 10 is set to RGin
And the signal level of the B signal for the G signal is BGin, the signal level of the R signal for the G signal supplied from the white balance processing circuit 10 to the level adjusting circuits 5 and 6 is RGout, and the signal level of the B signal for the G signal is Level B
Let's call it Gout.

Generally, in the feedback type white balance adjusting apparatus, the relationship between the signal levels of the R signal and the B signal supplied to the white balance processing circuit 10 has linearity, and the equation (3) is established.

BGout = a × RGout + b (where a ≠ 0) (3) When the gain adjustment signals supplied to the level adjustment circuits 5 and 6 become large, the level adjustment circuit 5 The signal level of the color signal output from 6 becomes small, and the level adjusting circuit 5,
When the gain adjustment signal supplied to 6 decreases, the signal level of the color signal output from the level adjustment circuits 5 and 6 increases. That is, RGout at this time is represented by Expression (4) using FIG.

RGout = (RGin + (BGin−b) / a) / 2 (4) BGout is expressed by Expression (5) using Expression (4).

BGout = a × RGout + b = (a × RGin + BGin−b) / 2 + b = (a × RGin + BGin + b) / 2 (5) Therefore, if either RGin or BGin changes, BGout Both RGout and RGout values change. That is, since the white balance adjusting apparatus 1 is of the feedback type, it not only adds an offset to each gain adjusting signal, but also releases the offset from the signal level of the color signal before supplying it to the white balance processing circuit 10. Must. As a result, offset cancellation and addition must be performed independently for each color signal.

As described above, in the white balance adjusting method and the white balance adjusting apparatus, the offset can be released and added independently before and after the white balance adjustment, so that the desired white balance can be easily obtained. Can be adjusted.

The present invention is not limited to the above-mentioned embodiment, and for example, the offset canceling circuit 8,
Of course, the CPU 9, the central processing unit, and the white balance processing circuit 10 and the offset adding circuits 11 and 12 may be combined to operate the above circuits.

[0033]

As described above in detail, according to the white balance adjusting method and the white balance adjusting apparatus of the present invention, the offset is released before the white balance adjustment and the offset is added after the adjustment. Allows you to easily perform the desired white balance adjustment, and adjust the white balance by setting the offset regardless of the operating state such as fixed white balance adjustment, white capture, and automatic tracking. It can be carried out.

[Brief description of drawings]

FIG. 1 is a block diagram showing a circuit of a video camera to which a white balance adjusting apparatus according to the present invention is applied.

FIG. 2 is a diagram illustrating an offset canceling circuit and an offset adding circuit included in the white balance adjusting apparatus according to the present invention.

[Explanation of symbols]

1 ..... White balance adjustment device 5, 6 ... Level adjustment circuit 7 ... Detection circuit 8, 9 ... Offset release circuit 10: White balance processing circuit 11, 12 ... Offset addition circuit

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H04N 9/73 H04N 9/04

Claims (2)

(57) [Claims] 1. A signal level of three types of color signals output via a level adjusting means is detected, and a signal level of a high luminance upper limit slice level or lower is integrated for each color signal to obtain three types of signal levels. The offsets are released from the integrated values of the two types of signal levels among the integrated values of, and the signal level ratios of the three types of color signals in the achromatic portion of the image are calculated based on the integrated values of the three types of color levels. By supplying two types of gain adjustment signals for adjusting the level adjusting means to the level adjusting means so as to be 1: 1: 1, and adding a desired offset to the two types of gain adjusting signals, A feedback-type white balance adjusting method characterized in that the gains of the two kinds of color signal level adjusting means are independently adjusted. 2. A level adjusting means for outputting three kinds of color signals, and signal levels of the three kinds of color signals outputted via the level adjusting means are detected, and the high luminance upper limit slice level or less is detected for each color signal. Based on the detection means for integrating the signal levels, the offset cancellation means for canceling the offset from the integrated values of the two types of signal levels among the integrated values of the three types of signal levels, and the integrated values of the above three types of color levels. Then, two kinds of gain adjustment signals for adjusting the level adjusting means are supplied to the level adjusting means so that the ratio of the signal levels of the three kinds of color signals in the achromatic portion of the image becomes 1: 1: 1. A white balance processing means and an offset adding means for adding a desired offset to the two types of gain adjustment signals are provided. The gain of the level adjusting means of the color signal, based on the gain adjustment signal, white balance adjustment device of the feedback type and adjusting independently.