JP2000299877A - Image pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image pickup device where white balance is corrected excellently by using optimum color temperature information with respect to various photographing pictures. SOLUTION: In this image pickup device, gain control circuits 3, 4 operated according to correction signals from D/A converters 35, 36 correct a gain of a chrominance signal obtained from an output of an image pickup element 1 to control the white balance. The chrominance signal from the A/D converters 30, 31 are stored in a memory by each of a plurality of areas resulting from dividing an image and a correction signal arithmetic section 34 obtains a white balance correction signal by using a mean value of the entire areas, a means value of only areas corresponding to an achromatic object and color temperature information of a maximum luminance area.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an imaging device,
In particular, the present invention relates to an imaging apparatus having a white balance correction function for correcting a white balance of a video signal obtained from an output of an imaging unit.

[0002]

2. Description of the Related Art Conventionally, in an imaging apparatus for correcting white balance using a signal obtained from an imaging device,
In order to avoid the influence of a chromatic subject, there is known a method of performing white balance correction using only a signal from a subject that is white or close to white or a signal that may be used.

For example, a Y (luminance) signal obtained from a signal processing circuit of a camera and two types of color difference signals R (red)-
Only the above-described signals are extracted from the Y signal and the B (blue) -Y signal, and the white balance is corrected by bringing the extracted color difference signal components closer to zero. Such a method is hereinafter referred to as a white extraction method, and will be briefly described below.

FIG. 21 is a diagram for explaining an example of a signal extraction range in this type of white extraction system. The coordinates in the figure indicate the coordinates of a video signal such as a television signal as a vector.

[0005] Now, the color temperature range is 3000 ° K to 100 ° C.
Consider an imaging device that performs white balance correction at 00 ° K. First, assuming that a white subject photographed at a color temperature of 10000 ° K is corrected to have a white balance, a signal corresponding to the subject corresponds to a point P0 in the figure. . At this time, 300
Assuming that a white subject exists at a color temperature of 0 ° K, the signal of the subject is a point P1 in the figure.

Conversely, if a correction is made so that a white subject photographed at a color temperature of 3000 ° K is in a state of white balance, a signal corresponding to the subject corresponds to a point P0 in the figure. If there is a white subject at a color temperature of 10000 ° K, the signal of the subject is a point P2 in the figure.

That is, the color reproduction of a white subject with a change in color temperature changes along a thick line A in FIG.

This is because x [= (RY) in FIG.
− (BY) = RB] and y [= (RY) + (B−
Considering the two-dimensional coordinates of (Y) = R + B-2Y], it indicates that the effect of the color temperature change is small in the y direction, and that only the x direction changes according to the color temperature change.

Here, as described above, 3000 ° K to 100 ° C
Considering that the white balance is corrected in the range of 00 ° K, if only the signals in the hatched portion range (white extraction range) in FIG. 16 are extracted, all the signals from the white or a subject close to white are extracted. That is, if the white balance control is performed using this, the influence of the chromatic object is small, and sufficient information for white balance control can be obtained.

FIG. 20 is a block diagram showing the configuration of a main part of a conventional image pickup apparatus for performing such white extraction type white balance control.

In FIG. 1, reference numeral 1 denotes an image sensor, which photoelectrically converts subject light incident through a lens 21 and an iris 22. Reference numeral 2 denotes a luminance chromaticity signal for generating a high frequency component (Y _H ) of a luminance signal, a low frequency component (Y _L ) of a luminance signal, a red (R) signal, and a blue (B) signal from the signal from the image sensor 1. The R signal and the B signal generated here are supplied to gain control circuits 3 and 4, respectively. The gain control circuits 3 and 4 have their respective gains controlled by a control signal from a tracking correction circuit 17 described later.
The R signal and the B signal are respectively amplified by the controlled amplification factors.

[0012] Here, when a signal output from the gain control circuit 3, 4 R 'signal, B' signal, the R 'signal and B' signal are input to the color difference signal generating circuit 5 with Y _L signal , The color difference signals (RY), (B-
Y) is generated.

[0013] The color difference signals (R-Y), (B -Y) are input to the encoder 6 with the above-mentioned Y _H signal, is converted into a standard television signal at the encoder 6. An output terminal 28 outputs this standard television signal.

On the other hand, the color difference signals (RY) and (BY) are also input to the automatic white balance correction device 20 and first supplied to the clamp circuits 7 and 8, respectively. In the crimp circuits 7 and 8, these color difference signals (RY) and (B-
Y) The direct current (DC) potentials are adjusted, and their outputs are input to the subtraction circuit 9 and the addition circuit 10, respectively.

In the subtraction circuit 9, the (RY) signal and the (B-
Y), an x signal, that is, a signal component in the coordinate x direction of FIG.
-Y) signal and the (BY) signal are summed to obtain y
A signal, that is, a signal component in the coordinate y direction in FIG. 16 is generated.

The comparators 11 and 12 compare the y signal output from this circuit with reference levels THa and THb corresponding to the line segments indicated by y = a and y = b in FIG. The comparison output is output to an OR circuit 13. The output of the OR circuit 13 becomes a low level (Lo) only when the level of the y signal is in the range of a ≧ y ≧ b in FIG. 16; otherwise, it becomes a high level (Hi) binary signal, and the gate control signal Is supplied to the gate circuit 14.

On the other hand, the x signal output from the subtractor 9, that is, the (RB) signal is supplied to the OR circuit 13 by the gate circuit 14.
Is gated only when the output is Lo, the clipping circuit 18
The signal components corresponding to the portions of x> c and x <d in FIG. 21 are clipped or made non-conductive by the clipping circuit 18, and the white extraction range indicated by hatching in FIG. Of the control signal generation circuit 16
Is output to

The operation of the control signal generation circuit 16 is to output a correction signal for controlling the average value of the input signal to be equal to the reference potentials Rref and Bref corresponding to the average of the white-balanced signal. Become. The output from the control signal generation circuit 16 is supplied to a tracking control circuit 17, which corrects the white balance control along the color temperature change trajectory so that the white balance correction signals Rcont and Bcont are respectively gained. This is output to the control circuits 3 and 4.

With such a configuration, the effect of the chromatic object can be reduced to some extent, and white balance correction is performed so that sufficient control information can be obtained as compared with the case where only the brightest part is extracted as a white object. It became possible.

[0020]

However, in the conventional imaging apparatus described with reference to FIGS. 20 and 21, the followability to the illumination condition of the subject and the stability to the case where the chromatic color enters the screen. It was difficult to ensure compatibility with gender.

For example, if the control speed is set high, giving priority to the change in the lighting conditions, the white balance will change excessively even with a slight movement or change of the subject. The eyes will feel uncomfortable. Also, if the control speed is set slower with emphasis on stability, it will slow down following large changes in shooting conditions, such as from indoors to outdoors, resulting in shooting a screen that is not in white balance for a long time. Will be.

Further, in the conventional image pickup apparatus described with reference to FIGS. 20 and 21, the white balance correction value is calculated only from the area assumed to be achromatic by the above-described white extraction method. Therefore, the following malfunction may be performed.

For example, FIGS. 22 (a1), (b1),
As shown in (c1), taking a case where a person's face is included in a shooting screen with a white background as an example, if it is initially in the state of FIG. (A
As shown in 2), the white balance is accurately corrected, and a signal corresponding to a coordinate point indicated by a circle in FIG. 22A is output.

In this state, when a person's face enters the screen as shown in FIG. 22 (b1), the person's face has a flesh color and corresponds to this flesh color as shown in FIG. 22 (b2). The signal also falls within the white extraction range described above. As a result, the control signal generation circuit 16 calculates the average of the signal components within the white extraction range including the signal corresponding to the flesh color as the reference potential Rre.
The correction signals Rcont and Bcont are output so as to be equal to f and Bref. Therefore, in the state shown in FIG. 22 (c1), the position on the coordinates of the signal corresponding to the skin color subject and the white subject after white balance correction is as shown in FIG.
As shown in (c2), the background, which should be originally white, becomes bluish and the flesh color of the person also fades.

Such a problem is not limited to the case where the background is simply white, and occurs more remarkably when the background is chromatic green or red. That is, in this case, since the white balance is corrected only from the color signal corresponding to the flesh color, the fading of the flesh color portion is further increased, and the result is that correct color reproduction cannot be performed on a screen having such a special composition. I was

As described above, even in the conventional white balance control based on the white extraction method, it is difficult to achieve both tracking performance and stability, and to completely remove the influence of chromatic objects in various objects. .

An object of the present invention is to provide a device for correcting the white balance of a color video signal obtained from an image pickup means as described above, in which both followability and stability are achieved, and
Provided is an imaging apparatus capable of sufficiently removing the influence of a chromatic object on a screen having various patterns, performing almost no visually obstructive erroneous correction, performing stable, and high-speed white balance correction. The purpose is to:

[0028]

For such a purpose,
In the imaging apparatus of the present invention, an imaging unit, an arithmetic unit that calculates a plurality of pieces of color temperature information using a color signal in a color video signal output from the imaging unit, Selecting means for selecting color temperature information that minimizes the amount of white balance correction, and white balance correcting means for correcting the white balance of the color video signal based on the color temperature information selected by the selecting means. .

As described above, by selecting one of a plurality of pieces of color temperature information, it is possible to perform a good white balance correction using various kinds of optimum color temperature information for various photographing screens. It has become possible to minimize the influence of chromatic subjects on any of a wide variety of screen configurations.

[0030]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below in detail.

FIG. 2 is a block diagram showing a schematic configuration of an image pickup apparatus as one embodiment of the present invention. The same components as those in FIG. 15 are denoted by the same reference numerals, and detailed description thereof will be omitted.

In FIG. 2, reference numeral 30 denotes a color difference signal (BY).
Is an analog-to-digital (A / D) converter for converting an analog value into a digital value.
An A / D converter 32 converts Y) from an analog value to a digital value, and an A / D converter 32 converts the _YH signal from an analog value to a digital value.

Reference numeral 33 denotes a memory for storing the outputs from the A / D converters 30, 31, and 32, and reference numeral 34 denotes a correction signal calculation unit for calculating a white balance correction signal. Processor.

An analog-to-digital (D / A) converter 35 converts a B (blue) gain correction signal output from the correction signal calculating section 34 from a digital value to an analog value. D / which converts the output R (red) gain correction signal from a digital value to an analog value
A converter.

Reference numeral 37 denotes an iris position detector comprising a Hall element or the like. As shown in FIG. 3, the iris position detector 37 outputs a detection voltage which is high when the iris is released and becomes low when the iris is maximally closed.

Here, the A / D converters 30, 31, and 32 and the correction signal calculation section 34 are supplied with a synchronizing signal from the synchronizing signal generating circuit 50 for giving a timing necessary for the operation. Needless to say, this synchronization signal is synchronized with the color video signal output from the image sensor.

The A / D converters 30, 31, and 32 and the correction signal operation section 34 operate according to the synchronization signal.
(B-Y), can be divided (R-Y), as shown in FIG. 3 each signal Y _H, and each screen into small regions. Here, in this embodiment, data of eight regions arranged vertically in FIG. 4 can be taken in one field in order to take in data of the entire screen, so that a period of eight fields is required. The shorter the capture period, the better. However, in this embodiment, it is assumed that white balance correction can be performed at a sufficiently high speed even if a period of eight fields is required.

The correction signal calculator 34 calculates (B-
Y), (R-Y) , calculates the average value of signals Y _H.
Here, as shown in FIG. 4, the average value of each (BY) signal of 64 regions divided into (8 × 8) is Bn (n = 1−1).
64), the average value of the (RY) signals is Rn (n = 1 to 6).
4), representing respectively the average values of the Y _H signal YHn (n = 1-64).

The correction signal calculator 34 calculates these values Rn,
Using Bn and YHn, three types of calculations described below are performed, and different color temperature information is calculated by each calculation. Hereinafter, these three types of calculations will be described in detail.

(First Calculation) First, the correction signal calculation section 34
The first calculation in will be described. This calculation is nothing but the calculation of the white balance correction value by the white extraction method described above.

First, the correction signal calculating section 34 calculates the above-described x component and y component for each region based on the input values Rn, Bn, YHn (1 to 64). That is, xn = Rn-B
n = (RY) n- (BY) n, and yn = Rn +
Bn = (RY) n + (BY) n.

Here, white extraction is performed in the same manner as in the above-described conventional example. In this embodiment, the following conditions,
Is extracted only for the signal components of the region satisfying all of the above.

First, the condition is b ≦ yn ≦ a.
b is the same as a and b shown in FIG. The condition is d ≦ x
n ≦ c, and c and d are the same as c and d shown in FIG. The condition is e.ltoreq.YHn.ltoreq.f, where e and f are values for excluding low luminance and high luminance color skip portions.

[0044] Figure 5 is a diagram for explaining a determining value e, f the color jump, coordinates in the figure indicates the level of the signal Y _H, level as shown Y _H signal is 0 or more e When it is less than f and when it exceeds f, it is determined that color skip occurs, and the above signal is not extracted.

From the data group of each area obtained by dividing one screen into a plurality of areas, the total value of Rn extracted by the white extraction operation is defined as Rtotal (w), and the total value of Bn is defined as Btotal.
When the total (w) is set, the number m of these extracted white areas
Are obtained, and are defined as Ravr (w) and Bavr (w), respectively. That is, these Ravr (w) and Bavr (w) are respectively Ravr (w) = Rto
tal (w) / m, Bavr (w) = Btotal (w) / m. The Ravr (w) and Bavr (w) are the color temperature information 1.

(Second Operation) Next, the correction signal operation unit 34
The second calculation in will be described.

In the second operation, an operation of extracting data of an area having the highest luminance level from the data group of the area extracted in white by the first operation is performed.

Then, Rn and Bn in the region having the highest luminance level are set as R (Ymax) and B (Ymax) in the correction signal calculating section 34. The R (Ymax) and B (Ymax) are color temperature information 2.

(Third Operation) Next, the correction signal operation unit 34
The third calculation in will be described.

The third operation is a process for obtaining the average of the color difference signal data of the entire screen. In the case of this embodiment, since one screen is divided into 64, it is obtained by the following operation.

That is, the average value Ravr of the color difference signals (RY) of the entire screen is (R1 + R2 + R3 + R4 +... +
R64) / 64, and the color difference signal (B-
The average value Bavr of (Y) is (B1 + B2 + B3 + B4 +...
.. + B64) / 64. The Ravr and Bavr are the color temperature information 3.

In the correction signal calculating section 34, these three kinds of color temperature information [Ravr (w), Bavr (w)], [R
(Ymax), B (Ymax)], [Ravr, Bavr] nonaka
de, the data of the minimum value, that is, the data that minimizes the white balance correction amount, is selected, and the selected color temperature information is compared with the above-described reference potentials (reference values) Rref and Bref to obtain a value Ravr (w). , R (Ymax) or Ravr and reference value Bavr
(w), B (Ymax) or Bavr is calculated so that the reference value Bref is equal to the reference value Bref, and this correction data is output so that white balance correction along the color temperature change locus is performed. Become.

As described above, by preparing a plurality of pieces of color temperature information and selectively using them, it is possible to perform a good white balance correction on a screen of various patterns and reduce the influence of a chromatic object. Can be more. This effect will be described later in detail.

Next, a plurality of operation modes of white balance correction in the image pickup apparatus of this embodiment will be described.

FIG. 1 is a diagram showing an operation mode of white balance correction in the image pickup apparatus of this embodiment and its transition. As shown, the image pickup apparatus of this embodiment has four white balance correction modes.

The high-speed operation mode shown in FIG. 1 is a mode in which the feedback gain of the white balance correction data is increased and the update cycle is shortened to correct the deviation of the white balance in a short time. is there. On the other hand, the low-speed operation mode is a stability-priority mode in which the white balance shift is slowly corrected by lowering the feedback gain of the white balance correction data and increasing the update cycle.

Both hold modes 1 and 2 in FIG. 1 hold white balance correction data immediately before entering this mode, do not update the correction data, and stop the apparent white balance correction operation. is there.

Transitions between these modes <1> to <12
> Is satisfied by satisfying each transition condition shown in FIG. Hereinafter, the transition conditions a to l in FIG. 10 will be described in detail.

(Condition a) When the luminance signal level is extremely small, as shown in the flowchart of FIG.
Hn total value YHtotal (= YH1 + YH2 + YH3 +
.. + YH64) is compared with a predetermined low luminance reference value Ylow, and is established when the value of YHtotal falls below the value of the low luminance reference value Ylow. When this condition is satisfied, FIG.
The mode transition of the white balance correction shown in <2>, <3>, and <11> is executed.

FIG. 8 is a flow chart showing another example of the judgment for satisfying the condition a. As shown in FIG.
It is also possible to configure so that the condition a is satisfied only when the value of tal is lower than the value of the low luminance reference value Ylow and the output of the iris position detector 37 detects that the iris 22 is in the open state. It is.

(Condition b) This condition is satisfied when the state exits from the condition a, and the condition b is satisfied when <1> in FIG.
Is executed. Note that the low luminance reference value Ylow used when the condition b is satisfied may be different from the low luminance reference value used when the condition a is satisfied.

(Condition c) The condition is satisfied when the change in the luminance level is very large, and an example of the determination is shown in FIG. That is,
In this embodiment, the value of the iris position detector 37 is stored in the memory 33 at regular time intervals, and as shown in the flowchart of FIG.
A difference value Isub (= | Iold-Inew |) between old and the current output value Inew of the iris position detector 37 is calculated, and the difference value Isub is compared with a reference value Ilim of the luminance change.
This is established when the difference value Isub exceeds the reference value Ilim.
The transition of <10> in FIG. 1 is executed by the satisfaction of the condition c.

(Condition d) When white balance is corrected by R (Ymax) and B (Ymax) obtained by the above-described second calculation, when it is determined that the white balance correction value is almost 0 That is, R (Ymax) ≒ Rref and B
It is satisfied when (Ymax) ≒ Bref, and the transition of <8>, <9>, and <12> in FIG. 1 is executed by the satisfaction of the condition d.

(Condition e) When white balance is corrected by Ravr and Bavr obtained in the third operation, the white balance correction value is determined to be almost 0, that is, Ravrav Rref and B
This holds when avr aBref, and the transition of <2> and <3> in FIG. 1 is executed by the fulfillment of the condition e.

(Condition f) When the white balance is corrected by Ravr (w) and Bavr (w) obtained by the above-described first calculation, when the white balance correction value is determined to be almost 0 That is, Ravr (w) ≒ Rref,
If Bavr (w) ≒ Bref, the condition f
Is satisfied, the transitions of <2> and <3> in FIG. 1 are executed similarly to the condition e.

(Condition g) The condition is satisfied when it is determined that there is a change in color temperature using each of the color difference signal data, and when condition f is satisfied, similarly to condition c, <10> in FIG.
Is executed. Hereinafter, an example of the algorithm for determining the color temperature change used in the apparatus of the present embodiment will be described.
explain.

The correction signal calculation section 34 in FIG. 2 stores the data of Rn, Bn, and YHn of a plurality of predetermined areas in the divided areas in the memory 33. In this embodiment, Rn, b of eight regions indicated by hatching in FIG.
n and YHn are stored in the memory 33 at predetermined time intervals. In this embodiment, as shown in FIG. 10, the values Rn, Bn, and YHn are stored for each of the eight areas every second. That is, (R1, B
1, YH1), (R8, B8, YH8), (R19, B
19, YH19), (R22, B22, YH22),
(R43, B43, YH43), (R46, B46, Y
H46), (R57, B57, YH57), (R64,
B64, YH64) in the memory 33
Will be stored.

Then, the correction signal calculating section 34
Then, the change of the color temperature is determined by comparing the past data and the present data stored in 3. Hereinafter, the determination method will be further described.

The determination of the color temperature change is made by detecting the color change for each area. That is, if the time is t3 in FIG. 10, the color change detection is performed based on the 24 pieces of data sampled at t3 and the 24 pieces of data sampled at t2 stored in the memory 33. This is performed by calculating the difference from each data.

Here, assuming that the value of R1 sampled at t2 is R1 (t2) and the value of R1 sampled at t3 is R1 (t3), their difference value ΔR1 is R1 (t3) −R1 ( t2), and similarly Δ
B1, ΔR8,... Are defined as (ΔR1, ΔB
1), (ΔR8, ΔB8), (ΔR19, ΔB19),
(ΔR22, ΔB22), (ΔR43, ΔB43),
(ΔR46, ΔB46), (ΔR57, ΔB57),
Eight sets of 18 difference values of (ΔR64, ΔB64) are obtained.

FIGS. 11 to 13 are diagrams for explaining a method of determining a color temperature change from these color change detection values.
FIG. 11 is a diagram for explaining coordinates used for this determination, FIG. 12 is a diagram for explaining a state in which the color temperature is low using the coordinates in FIG. 11, and FIG. 13 is a diagram for explaining a state in which the color temperature is high. FIG. 12 is a diagram for describing using the coordinates in FIG. 11.

In the determination of the color temperature change, first, the set of the above-described difference values is replaced with a two-dimensional coordinate plane composed of ΔR and ΔB coordinates as shown in FIG. Here, if the color temperature of the light source that illuminates the entire screen changes to a low color temperature between t2 and t3, ΔR of the eight regions all change to positive, and ΔB changes to negative. The vector of (ΔR, ΔB) is shown in FIG.
As shown in FIG. 2, it is on the fourth quadrant on the coordinates of FIG. When the color temperature of the light source illuminating the entire screen changes to a high color temperature between t2 and t3, the vector of (ΔR, ΔB) becomes the second on the coordinates in FIG. 11 as shown in FIG. You will be in the quadrant.

However, when the brightness of the subject is extremely low,
Conversely, when the color jump is extremely high, the color component does not change much even if the color temperature of the light source changes, and thus ΔR and ΔB under such low luminance and high luminance are excluded. At this time, the determination of the high luminance and the low luminance is performed using the aforementioned YHn (t2) and YHn (t3).

FIG. 14 is a diagram showing a color temperature change determination area on the coordinates of FIG. That is, ΔR and ΔB excluding the above-described high-luminance part and low-luminance part exist in area 1 in FIG. 14 for all regions when the color temperature of the light source changes low. In the case of a high change, all areas are present in area 2 of FIG. 14, and this is confirmed to determine a change in color temperature.

Here, when setting the areas 1 and 2, it is considered that the white balance correction operation is being performed even during the determination of the color temperature change. That is, assuming that the color image signal output in one second changes from the point P (t1) to the point P (t2) at the maximum as shown in FIG. 15 by the white balance correction operation during the determination of the color temperature change. The sampled difference values ΔR and ΔB also change by the amount (dr0, db0) corrected for white balance. The value d associated with these maximum white balance corrections
Since the changes of r0 and db0 are not caused by the change of the light source or the object, the determination area of the color temperature change (area 1 and area 2) includes the change of these values dr0 and db0. It must be set so as not to exist.

Therefore, area 1 and area 2 shown in FIG.
Are both a region where the absolute value of ΔR is less than dr0, and Δ
The region where the absolute value of B is less than db0 is set so as not to be included. Thereby, the malfunction was further reduced.

Here, assuming that the color temperature does not change between t1 and t3 and the subject changes as shown in FIGS. 16A and 16B, ΔR and ΔB at t2 are as follows. Become. That is, (ΔR22, ΔB22) and (ΔR1
9, ΔB19) enters the area 1 as shown in FIG. 17, but (ΔR1, ΔB1),
(ΔR8, ΔB8), (ΔR43, ΔB43), (ΔR
46, ΔB46), (ΔR57, ΔB57), (ΔR6
4, ΔB64) are all (0, 0) and do not exist in area 1. Therefore, in this case, it is determined that there is no color temperature change.

(Condition h) This condition is satisfied when there is no area to be extracted by white extraction and there is no data used for the above-described first calculation.
<3> is executed.

(Condition i) The condition is satisfied when Ravr and Bavr obtained by the third operation are not in the white extraction area of FIG. As a specific method for confirming this, first, the x component and the y component in FIG. 21 are detected from the above-mentioned Ravr and Bavr. This x component (xavr) is (Ravr
−Bavr), and the y component (yavr) is (Ravr +
Bavr). Then, the calculated xavr,
If the position on FIG. 21 corresponding to yavr is not within the hatched area, that is, xavr <d, c <xavr, yavr>
This condition i is satisfied when at least one of b, a <yavr is satisfied. By satisfying the condition i, << in FIG.
3> is executed.

(Condition j) This is a condition for limiting the operation time in the high-speed operation mode in FIG. 1, and is satisfied after a predetermined period has elapsed since the high-speed operation mode was entered. That is, <1 in FIG.
> Or <7>, that is, the condition b
Alternatively, when the condition k described later is satisfied and the white balance correction operation enters the high-speed operation mode, a timer built in the correction signal calculation unit 34 is started, and when the time counted by the timer reaches a predetermined time, this condition is satisfied. j is established. When this condition j is satisfied, <5> in FIG.
That is, the transition from the high-speed operation mode to the low-speed operation mode of the white balance correction is executed.

(Condition k) The condition is satisfied when both the condition c (large change in luminance level) and the condition g (color temperature change) are satisfied, and the transition from the hold mode 2 to the low-speed operation mode is satisfied when the conditions c and k are satisfied. However, when the condition k is satisfied, <1 in FIG.
>, <6>, <7> are executed.

(Condition 1) The above conditions e, f, h,
The condition is satisfied when none of the conditions i is satisfied, and <4 in FIG.
> Is executed.

According to the transition conditions a to l described above, the transition of the operation mode of white balance correction is determined as shown in FIGS. As is clear from FIG. 1, when the power is turned on, the timer is reset to enter the high-speed operation mode, and the white balance correction data is initialized to a value corresponding to a light source having a high color temperature. It is configured to change to.

According to the imaging apparatus of the embodiment as described above, once the operation mode is set to the hold mode, the white balance correction is not performed unless the transition condition for restarting the white balance correction is satisfied. It is possible to prevent erroneous white balance correction due to only Also, when the white balance correction is restarted, the white balance correction is performed at the optimal operation speed corresponding to various subject situations according to the transition conditions for restart, so it is affected by the color change of the subject. It is difficult to achieve quick responsiveness according to shooting conditions.

Hereinafter, some specific examples of the effect of the present embodiment will be described in light of the situation of the subject.

(Example 1) First, FIG.
Consider a case where there is a subject change shown in (b1) and (c1). In this case, in the state of FIG. 22 (a1), the color difference signal components should be as shown in FIG. 22 (a2), so that the data [1] obtained by the first, second, and third operations described above [ Ravr (w), Bavr (w)], [R (Yma
x), B (Ymax)] and [Ravr, Bavr] are all reference potentials R
ref and Bref. Accordingly, all of the above-mentioned transition conditions d, e, and f are satisfied, and all of FIG. 1 <2>, <3>, <8>, <9>, and <12> are executed. , The white balance correction becomes the hold mode 2.

In this state, the subject is positioned as shown in FIG.
Even if it changes as shown in (c1), the transition conditions a,
None of c, g, and k is satisfied, and <7> and <10 in FIG.
> And <11> are not executed,
The operation mode remains in the hold mode 2, and the white balance correction state is stabilized in the state of FIG.
Therefore, there is no erroneous correction unlike the white balance correction of the conventional color extraction method.

Then, if this white balance correction state is stable in the state of FIG.
When the color temperature of the light source changes, the color temperature change is determined by the above-described method. Therefore, the transition condition g is satisfied, the transition of <10> in FIG. 1 is performed, and the white balance correction is performed at a low speed. Move to operation mode. This allows
The white balance correction is restarted, and a correction operation corresponding to the new light source color temperature is performed.

(Example 2) Next, a case where a person with a green background is photographed as shown in FIG. 18 will be described. At this time, when the vector of the color difference signal is the background, Pg in FIG.
The person is as shown by Ph in FIG. In such a situation, when the above-mentioned white balance correction of the white extraction method is performed, only the skin color component indicated by Ph is extracted, and as shown in FIG. 19B by the white balance correction. The color difference signal is corrected
This skin color had faded until it became almost white.

On the other hand, in the imaging apparatus of the present embodiment, when Ravr and Bavr of the entire screen are obtained by the third operation, the vectors become as shown by Pa in FIG. It is determined that the Pa point is outside the white extraction area. Then, the above-mentioned transition condition i is satisfied, and the white balance correction is set to the hold mode 1.
Therefore, the white balance does not change from the state of FIG. 19A, and becomes stable in this state.

(Example 3) A case where the shooting situation changes from indoor to outdoor will be described. In this case, since the change in luminance is large and the change in color temperature of the light source is large, it is necessary to quickly perform white balance correction. In this embodiment,
If there is a large change in luminance and a change in color temperature, the above-described transition condition k is satisfied, and the transition <1 in FIG.
By executing>, <6>, and <7>, the white balance correction shifts to the high-speed operation mode, and a white balance state that matches the outdoor color temperature can be quickly achieved.

Thereafter, when the high-speed operation mode continues for a predetermined period, the above-described transition condition j is satisfied, and the white balance correction temporarily transitions to the low-speed operation mode, and then transitions to the operation mode depending on the situation of the subject. .

(Example 4) Next, a case will be described in which the power is turned on accidentally with the lens cap attached, the white balance correction operation is started, and then the lens cap is removed. In this case, when the lens cap is attached, the above-described transition condition a is satisfied, so that the operation mode of the white balance correction is the hold mode 1, but when the lens cap is removed, the transition condition b is satisfied. I do. Therefore, the transition <1> in FIG. 1 is executed, the white balance correction shifts to the high-speed operation mode, and after removing the lens cap, the white balance can be adjusted to the color temperature of the light source in a short time.

In the actual apparatus described in this specification, when averaging the color signal data of the entire screen, data is extracted from all 64 divided areas and the average is calculated. However, if the data is uniformly distributed over the entire screen, it is also possible to extract only the data of a part of the areas and take the average of the data of these areas.

The areas for detecting the color change for judging the color temperature change are eight areas shown by hatching in FIG. 4. Similarly, if the areas are uniformly distributed over the entire screen, the number of these areas is reduced. It can be changed. It is also possible to adopt a configuration in which the position and the number of areas to be detected are changed according to the situation of the subject.

[0096]

As described above, according to the imaging apparatus of the present invention, one of a plurality of pieces of color temperature information can be selected, so that the optimum color temperature information for various photographing screens can be obtained. , It is possible to perform good white balance correction, and it is possible to minimize the influence of chromatic subjects on any of a wide variety of screen configurations.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an operation mode of white balance correction and a transition thereof in an image pickup apparatus according to an embodiment of the present invention.

FIG. 2 is a block diagram illustrating a schematic configuration of an imaging apparatus according to an embodiment of the present invention.

FIG. 3 is a diagram for explaining an output voltage of the iris position detector of FIG. 2;

FIG. 4 is a diagram for describing screen division by the imaging device of FIG. 2, data for each divided region, and a color change detection region.

FIG. 5 is a diagram for explaining a determination value of color skipping by the imaging apparatus of FIG. 2;

FIG. 6 is a diagram showing transition conditions between four operation modes of the white balance correction shown in FIG. 1;

FIG. 7 is a flowchart illustrating an example of a determination for satisfying a condition a in the transition conditions of FIG. 6;

FIG. 8 is a flowchart illustrating another example of a determination for satisfying condition a in the transition conditions of FIG. 6;

FIG. 9 is a flowchart illustrating an example of a determination for satisfying a condition c in the transition conditions of FIG. 6;

FIG. 10 is a diagram for explaining a data sampling period for detecting a color change by the imaging apparatus of FIG. 2;

FIG. 11 is a diagram for explaining coordinates used to determine a color temperature change from a color change detection value.

FIG. 12 is a diagram for explaining a state in which the color temperature has decreased, using the coordinates in FIG. 11;

FIG. 13 is a diagram for explaining a state in which the color temperature has increased, using the coordinates in FIG. 11;

FIG. 14 is a diagram showing a color temperature change determination area on the coordinates of FIG. 11;

FIG. 15 is a diagram for explaining a change in a color image signal due to a maximum white balance correction operation in the apparatus of FIG. 2;

FIG. 16 is a diagram illustrating an example of a change in a subject for explaining the effect of the apparatus in FIG. 2;

17 is a diagram for explaining an operation of determining a change in color temperature in the state of FIG. 16;

FIG. 18 is a diagram showing an example of a subject for explaining the effect of the apparatus shown in FIG. 2;

FIG. 19 is a diagram for describing white balance correction for the subject shown in FIG. 18;

FIG. 20 is a block diagram illustrating a main configuration of a conventional imaging apparatus that performs white balance correction using a white extraction method.

FIG. 21 is a diagram for describing an example of a signal extraction range in a white extraction method.

FIG. 22 is a diagram for explaining a problem of white balance correction of a white extraction method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image sensor 2 Luminance chromaticity signal generation circuit 3,4 Gain control circuit 5 Color difference signal generation circuit 30,31,32 Analog-digital converter 33 Memory 34 Correction signal operation unit 35,36 Digital-analog converter 37 Iris position detection 50 Synchronous signal generation circuit

Claims (5)

[Claims] 1. An image pickup means, an arithmetic means for calculating a plurality of pieces of color temperature information using a color signal in a color video signal output from the image pickup means, and the most white balance correction among the plurality of pieces of color temperature information An image pickup apparatus comprising: a selection unit that selects color temperature information whose amount is reduced; and a white balance correction unit that corrects a white balance of the color video signal based on the color temperature information selected by the selection unit. 2. The image processing apparatus according to claim 1, wherein the calculating unit extracts color signals for a plurality of regions in the photographing screen of the imaging unit, and detects color information according to the extracted color signals for each region. Is color temperature information calculated using at least color information of all of the plurality of regions, and second color temperature calculated using only some of the color information in the plurality of regions. The imaging apparatus according to claim 1, further comprising information. 3. The method according to claim 2, wherein the plurality of regions are a plurality of regions obtained by dividing the entire screen, and the one color temperature information is calculated from an average value of the color information of all the plurality of regions. Item 2. The imaging device according to Item 2. 4. The method according to claim 1, wherein the second color temperature information is calculated from an average value of the color temperature information only in an area of the plurality of areas included in a range in which a color signal corresponding to a white subject has changed. The imaging device according to claim 2, wherein: 5. The imaging apparatus according to claim 2, wherein the second color temperature information is calculated from only the color information of a region having a highest luminance level among the plurality of regions.