JPH0822076B2 - Automatic white balance adjustment device - Google Patents

Description

The present invention relates to an apparatus for automatically adjusting the white balance of a color video camera.

[Conventional technology]

FIG. 3 is a block circuit diagram of a conventional automatic white balance adjusting device to which the technical idea disclosed in Japanese Patent Publication No. 59-43872 is applied.

In the figure, (1) is a lens, (2) is an image sensor,
(3) is a color separation circuit, (4) is an Rch gain control circuit,
(5) is a Bch gain control circuit, (6) is a process circuit,
(7) is an encoder circuit, (8) and (9) are integrating circuits,
(10) and (11) are comparison circuits, (12) is a microcomputer, (13) and (14) are D / A conversion circuits, and (15) is a reference voltage generation circuit.

Next, the operation will be described. The optical image incident from the lens (1) is photoelectrically converted by the image sensor (2) and color-separated into three color signals of R, G, B by the color separation circuit (3). Next, the gain control circuit (4) controls the gain of the R signal, and the gain control circuit (5) controls the gain of the B signal. White balance adjustment is performed by adjusting the gains of the R signal and the B signal, and the luminance signal Y and the color difference signal R- in the process circuit (6).
It is separated into Y and BY. This RY color difference signal, B
The Y color difference signal is integrated by the integrator circuits (8) and (9) and compared with the reference voltage by the comparator circuits (10) and (11), and the signal indicating the comparison result is input to the microcomputer (12). To be done.

FIG. 4 is a flow chart of the software reversible counting means in the microcomputer (12). Each clock pulse is reversibly counted based on the comparison result inputted from the comparison circuits (10) and (11), and the reversible counting result is shown. D / A conversion circuits (13) and (14) respectively perform D / A conversion,
The gain control circuits (4) and (5) are controlled by this analog signal.
Control the gain of each.

The polarities of the comparison circuits (9) and (10), the increasing / decreasing direction of the reversible counting means, and the gain control characteristics of the gain control circuits (4) and (5) are RY color difference when an achromatic subject is imaged. A negative feedback loop in which the signal and the BY color difference signal each become 0 is formed, and the same conditions as when an achromatic subject is imaged by integrating the entire screen by integrating circuits (8) and (9). Can be assumed. A normal subject can be considered as an achromatic color by integrating the entire screen.

With the above operation, it is possible to automatically adjust the white balance even if the light source that refers to the subject changes.

Next, the operation of the reversible counting means will be described based on the flowchart of FIG.

S1. Rch reversible count result RchUDC initial value and Bch reversible count result initial value BchUDC initial value are set.

Outputs S2.RchUDC / BchUDC.

The output value of the S3.Rch comparator (10) is compared with RchUDC. When the output value is low, the operation proceeds to S4 and becomes RchUDC + 1. When the output value is high, the operation proceeds to S5 and RchUDC-1 and then to S6.

The output value of the S6.Bch comparator (11) is compared with BchUDC. When the output value is low, the process proceeds to S7 to BchUDC + 1, and when the output value is high, the process proceeds to S8 to BchUDC-1 and proceeds to S8.

S8. Return to S2 when clock pulse is input.

As a result, the gains of the gain control circuits (4) and (5) are controlled so that the output values of the comparison circuits (10) and (11) always approach RchUDC.BchUDC.

[Problems to be Solved by the Invention]

Since the conventional automatic white balance adjustment device is configured as described above, the number of subjects increases when the distance to the subjects is long, and the white balance adjustment can be performed because the color difference signals from many subjects can be integrated. It is stable, but when the distance to the subject is short, only the color difference signal from a specific subject can be integrated, so the comparison circuit (1
There was a problem that the output level of 0) and (11) frequently changed to high level and low level, and the white balance adjustment became unstable.

The present invention has been made in order to solve the above problems, and an object thereof is to obtain an automatic white balance adjusting device in which white balance adjustment does not become unstable even when a distance to a subject is short. To do.

[Means for solving the problem]

The automatic white balance adjusting device according to the present invention detects the distance to the subject, stores the output value of the comparison circuit for the number of times determined by the distance to the subject, and only when the output values of the plurality of times are the same value. The feature is that the reversible count value is reversibly counted by one level in the positive and negative directions of the value.

[Action]

Since the reversible counting means in the present invention changes the count value only when the output of the comparison circuit is a stable value determined by the distance to the subject, the hypersensitivity of the automatic white balance adjusting device when the distance to the subject is short. Such reactions are suppressed and white balance adjustment is stabilized. [Example] An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a black circuit diagram of this embodiment, in which (16) is a distance detecting device for detecting the distance to a subject, and the distance detection signal is input to the microcomputer (12).

FIG. 2 is a flow chart of the reversible counting means in the microcomputer (12) of this embodiment.

The difference of this embodiment from the conventional example shown in FIG. 3 is a reversible counting means provided with a distance detecting device (16) and carried out by a microcomputer (12) based on the detected distance signal. Since the operation of the part is the same, the operation of the reversible counting means will be described below with reference to the flowchart of FIG.

In Fig. 2, S1.Rch reversible counting result RchUDC and Bch reversible counting result BchUDC
Set the initial value of.

Outputs S2.RchUDC and BchUDC.

S3. Capture a signal indicating the distance to the subject in the microcomputer (12).

S4. Determine the value of N from the distance to the subject. In this embodiment, the value of N is large when the distance to the subject is short, and the value of N is small when the distance to the subject is long.

Set the value of S5.I to 1.

S6.R (I) is used as the output of the Rch comparison circuit (10).

S7.B (I) is used as the output of the Bch comparison circuit (11).

Increase the value of S8.I by 1.

S9. When the clock pulse is input, proceed to S10.

If S10.I = N + 1, proceed to S11, and if I ≠ N + 1, return to S6.

Here, until the clock pulse is input N times, S6 to S10
Repeatedly, each time R (I) ~ R (N), B (I) ~ B
The value of (N) is stored.

If S11.R (I) = R (2) ... = R (N), proceed to S12. If any of R (1) to R (N) has a different value, the process proceeds to S15.

If S12.R (1) is higher than RchUDC, "H", then RchUDC in S13
Decrement by 1 and proceed to S15. If R (1) is low "L", S14
Then, increase Rch UDC by 1 and proceed to S15.

If S15.B (1) = B (2) ... = B (N), the process proceeds to S16, and if any one of B (1) to B (N) has a different value, the process returns to S2.

If S16.B (1) is "H", proceed to S17 and increase BchUDC by 1 and return to S2. If B (1) is "L", proceed to S18 and BchUD.
Lower C by 1 and return to S2.

With the above operation, the reversible counting result changes only when the outputs of the comparison circuits (10) and (11) show the same value the number of times determined by the distance to the subject (N times). Therefore, when the distance to the subject is short and the output value of the comparison circuit (10) or (11) changes frequently, the reversible count result is fixed and does not change, and the white balance adjustment becomes unstable. Never.

Although the reversible counting means is composed of a microcomputer in the above embodiment, it may be realized by hardware using a reversible counting circuit or a memory.

The method of determining the value of N from the distance to the subject is
Any method such as a method by calculation such as primary conversion or a method by table conversion may be used.

Further, the device for detecting the distance to the subject may be any method such as a method of detecting from the position of the focus adjustment lens, a method of detecting with a distance measuring device other than the imaging optical system.

Further, in the above-mentioned embodiment, the value obtained by integrating the color difference signals RY and BY is compared with the reference value, but the color difference signals RY and BY
Alternatively, a value obtained by integrating a signal obtained by matrixing the luminance signal and the luminance signal may be compared with the reference value.

〔The invention's effect〕

As described above, according to the present invention, the distance to the subject is short, the influence of the change of the subject is large, and the comparison circuit (10)
Even if the high level and low level of the output of (11) are unstable, the white balance adjustment does not vibrately change. On the contrary, when the distance to the subject is long and the influence of the change of the subject is small, The effect is to obtain an automatic white balance adjustment device that can quickly respond to changes in the light source.

[Brief description of drawings]

FIG. 1 is a block circuit diagram showing an automatic white balance adjusting device according to an embodiment of the present invention, FIG. 2 is a software flowchart of this embodiment, and FIG. 3 is a block circuit diagram of a conventional automatic white balance adjusting device. FIG. 4 is a flowchart of the software of this conventional example. (2) ... Image sensor, (3) ... Color separation circuit, (4),
(5) ... Gain control circuit, (6) ... Process circuit,
(8), (9) ... Integrator circuit, (10), (11) ... Comparison circuit, (12) ... Microcomputer, (13), (14) ...
D / A conversion circuit, (15) ... Reference voltage generation circuit, (16) ... Distance detection device. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A gain control circuit for controlling the gain of a color signal,
Means for integrating the output signal of the gain control circuit or the signal in which the output chrominance signal of the gain control circuit and the luminance signal are matrixed, the comparison circuit for comparing the integration level and the reference level, and the output signal of the comparison circuit In the automatic white balance adjusting device configured to adjust the white balance by controlling the gain of the gain control circuit by the means for reversibly counting the clock pulses corresponding to the polarity of the And a reversible counting operation in the reversible counting means for executing the reversible counting only when the values of the number of times determined corresponding to the detected distance are the same. Automatic white balance adjusting device.