JP3524464B2 - Imaging device - Google Patents

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art Conventionally, in an image pickup apparatus for correcting white balance using a signal obtained from an image pickup element,
In order to avoid the influence of a chromatic color subject, there is known a method of performing white balance correction using only a signal from a white or near-white subject or a signal that has a possibility of that.

For example, a Y (luminance) signal obtained from a signal processing circuit of a camera and R (red) -which is two kinds of color difference signals.
It is intended to correct the white balance by extracting only the above-mentioned signals from the Y signal and the B (blue) -Y signal and bringing the extracted color difference signal components close to zero. Hereinafter, such a method will be 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 method, and the coordinates in the figure show coordinates in which a video signal such as a television signal is vector-displayed.

Now, the range of color temperature is 3000 ° K-100
Consider an image pickup apparatus that performs white balance correction at 00 ° K. First, assuming that a white object photographed at a color temperature of 10000 ° K is corrected so as to be in a white balanced state, a signal corresponding to the object corresponds to a point P0 in the figure. . At this time, 300
If there is a white subject under the color temperature of 0 ° K, the signal of the subject is a point P1 in the figure.

On the contrary, assuming that a white object photographed at a color temperature of 3000 ° K is corrected so as to have a white balance, the signal corresponding to the object corresponds to the point P0 in the figure. However, if there is a white subject under the color temperature of 10000 ° K, the signal of the subject is the point P2 in the figure.

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

This is because x [= (RY) in FIG.
-(BY) = RB] and y [= (RY) + (B-
Y) = R + B-2Y], it is shown that the influence of the color temperature change is small in the y direction and only the x direction changes in accordance with the color temperature change.

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

FIG. 20 is a block diagram showing a main structure of a conventional image pickup apparatus for performing white balance control by such a white extraction method.

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

When the signals output from the gain control circuits 3 and 4 are R'signals and B'signals, the R'signals and B'signals are input to the color difference signal generation circuit 5 together with the Y _L signal. , The color difference signals (RY), (B-
Y) is generated.

The color difference signals (R-Y) and (B-Y) are input to the encoder 6 together with the above-mentioned _YH signal, and are converted into a standard television signal by the encoder 6. 28 is an output terminal for outputting 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 clamp circuits 7 and 8, these color difference signals (RY) and (B-
The direct current (DC) potentials of Y) 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 (B-
Y signal, the x signal, that is, the signal component in the coordinate x direction of FIG. 16 is generated, and the addition circuit 10 generates (R
-Y) signal and (BY) signal are summed to obtain y
A signal, that is, a signal component in the coordinate y direction of FIG. 16 is generated.

In the comparators 11 and 12, the y signal output from this circuit is compared 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 the OR circuit 13. The output of the OR circuit 13 is a binary signal which becomes a low level (Lo) only when the level of the y signal is in the range of a ≧ y ≧ b in FIG. 16, and becomes a high level (Hi) in other cases, 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.
The output of is gated only when it is Lo, and the clipping circuit 18
21 and the signal components corresponding to the portions of x> c and x <d of FIG. 21 are clipped or made non-conductive by the clipping circuit 18, and the white extraction range shown by hatching in FIG. 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 so that the average value of the input signal becomes equal to the reference potentials Rref and Bref corresponding to the average of the white-balanced signals. Become. The output from the control signal generation circuit 16 is supplied to the tracking control circuit 17, which is corrected so that the white balance control along the color temperature change locus can be performed by the circuit 17, and the white balance correction signals Rcont and Bcont are gained respectively. It will be output to the control circuits 3 and 4.

With such a structure, the influence of the chromatic subject 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 of extracting only the highest brightness portion as a white subject. It has become possible.

[0020]

However, in the conventional image pickup apparatus described with reference to FIGS. 20 and 21, the followability with respect to the illumination condition of the subject and the stability when the chromatic color enters the screen are stable. It was difficult to ensure compatibility with sex.

For example, if the control speed is set to a high speed by giving priority to the followability to the change of the illumination condition, the white balance will be hypersensitively changed even with a slight movement or change of the subject, and the white balance of human beings will be changed. The eyes will feel uncomfortable. Also, if the control speed is set to a slower value with an emphasis on stability, it may be difficult to follow large changes in shooting conditions, such as from indoors to outdoors, resulting in a screen that is out of 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 estimated to be achromatic by the white extraction method described above. Therefore, the following malfunction may occur.

For example, FIG. 22 (a1), (b1),
As shown in (c1), in the case where a person's face is included in a shooting screen with a white background, for example, in the state shown in FIG. 22 (a1) at first, only a white subject is shown in FIG. (A
As shown in 2), the white balance is accurately corrected, and the signal corresponding to the coordinate point indicated by a circle in FIG. 22 (a2) is output.

From this state, when the face of the person comes into the screen as shown in FIG. 22 (b1), the face of the person has a flesh color, which corresponds to this flesh color as shown in FIG. 22 (b2). The signal also enters the white extraction range described above. As a result, the control signal generation circuit 16 calculates the average of the signal components in the white extraction range including the signal corresponding to this skin 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 positions on the coordinates of the signals corresponding to the skin-colored subject and the white subject after white balance correction are shown in FIG.
As shown in (c2), the background that should be white should be bluish, and the skin tones of the person should be faded.

Such a problem is not limited to the case where the background is simply white, and is more remarkable 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 skin color, the fading of the skin color portion becomes larger, and the result is that correct color reproduction cannot be performed on a screen with such a special composition. Was there.

As described above, even in the white balance control by the conventional white extraction method, it is difficult to achieve both the followability and the stability and to completely remove the influence of the chromatic color subject in various subjects. .

It is an object of the present invention to achieve both followability and stability in an apparatus for correcting the white balance of a color video signal obtained from the image pickup means as described above, and
(EN) Provided is an image pickup device capable of sufficiently removing the influence of a chromatic color subject on a screen of various patterns, capable of performing stable and high-speed white balance correction with almost no visually erroneous correction. The purpose is to

[0028]

[Means for Solving the Problems] Under such a purpose,
In the image pickup apparatus of the present invention, an image pickup means, a calculation means for calculating a plurality of color temperature information using color signals in a color video signal output from the image pickup means, and a plurality of color temperature information And a white balance correction means for correcting the white balance of the color video signal based on the color temperature information selected by the selection means. .

[0029]

[Means for Solving the Problems] Under such a purpose,
In the image pickup apparatus of the present invention, an image pickup unit, a calculation unit that calculates a plurality of types of color temperature information from color signals output from the image pickup unit based on a plurality of types of calculation methods, and the plurality of color temperature information items. Of the color signals output from the image pickup means according to the color temperature information selected by the selecting means, the selecting means selecting the color temperature information having the smallest white balance correction amount among the color temperature information in the photographing screen. It is configured to include a white balance correction unit that corrects the white balance.

[0030]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described in detail below.

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

In FIG. 2, 30 is a color difference signal (BY).
Is an analog-digital (A / D) converter for converting an analog value to a digital value, and 31 is a color difference signal (R-
Y) is an A / D converter that converts an analog value into a digital value, and 32 is an A / D converter that converts the _YH signal from an analog value into a digital value.

Reference numeral 33 is a memory for storing the outputs from the A / D converters 30, 31, 32, and 34 is a correction signal calculation unit for calculating a white balance correction signal. The correction signal calculation unit 34 is a microcomputer or the like. It is composed of a processor.

Reference numeral 35 is an analog-digital (D / A) converter for converting the B (blue) gain correction signal output from the correction signal calculation unit 34 from a digital value to an analog value, and 36 is also from the correction signal calculation unit 34. D / that 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 composed of a hall element or the like. The iris position detector 37 outputs a detection voltage which is high when the iris is released and low when the iris is closed as shown in FIG.

Here, the A / D converters 30, 31, 32 and the correction signal calculator 34 are supplied with a synchronization signal from the synchronization signal generation circuit 50, which gives a timing required for operation. Needless to say, this synchronizing signal is synchronized with the color video signal output from the image pickup device.

Since the A / D converters 30, 31, 32 and the correction signal calculator 34 operate according to this synchronizing 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 order to fetch the data of the entire screen, in this embodiment, the data for eight areas arranged vertically in FIG. 4 can be fetched in one field, so that a period of eight fields is required. Although it is preferable that this fetch period is short, in this embodiment, it is assumed that the white balance correction can be performed substantially at a sufficiently high speed even if a period of 8 fields is required.

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

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

(First Calculation) First, the correction signal calculation unit 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 calculation unit 34 calculates the above-mentioned 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 the above-mentioned conventional example, but in the present embodiment, the following conditions,
Only the signal component of the region that satisfies all of is extracted.

First, the condition is b≤yn≤a, and 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. Then, the condition is e ≦ YHn ≦ f, and e and f are values for excluding the low-luminance and high-luminance color skipped portions.

FIG. 5 is a diagram for explaining the values e and f for determining this color skip, and the coordinates in the figure show the level of the signal Y _H , and the level of the Y _H signal is 0 or more e as shown in the figure. When the value is less than the value and when it exceeds f, it is determined that color skipping occurs, and the signal is not extracted.

In this way, the total value of Rn extracted by the white extraction operation from the data group of each area obtained by dividing one screen into a plurality of areas is defined as Rtotal (w), and the total value of Bn is Btotal.
When total (w) is set, the number of white extracted areas is m.
The values obtained by dividing by are taken as Ravr (w) and Bavr (w), respectively. That is, these Ravr (w) and Bavr (w) are Ravr (w) = Rto, respectively.
tal (w) / m, Bavr (w) = Btotal (w) / m. These 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.

The second operation is an operation for extracting the data of the area having the highest brightness level in the data group of the areas extracted in white by the first operation.

Then, Rn and Bn in the area having the highest brightness level are registered in the correction signal calculation unit 34 as R (Ymax) and B (Ymax). The R (Ymax) and B (Ymax) are the color temperature information 2.

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

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

That is, the average value Ravr of the color difference signal (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. These Ravr and Bavr are the color temperature information 3.

In the correction signal calculation unit 34, these three types 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 reference potentials (reference values) Rref and Bref described above to obtain the value Ravr (w). , R (Ymax) or Ravr and reference value Bavr
(w), B (Ymax) or Bavr and the reference value Bref are calculated to be equal to each other, and the correction data is output so that the white balance correction is performed along the color temperature change locus. Become.

By preparing a plurality of pieces of color temperature information as described above and selectively using these pieces of information, it is possible to perform an excellent white balance correction on a screen having various patterns and reduce the influence of a chromatic color subject. Can be more. Note that 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 and its transition in the image pickup apparatus of the present embodiment. As shown in the figure, the image pickup apparatus of the present embodiment has four white balance correction modes.

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

Both the hold modes 1 and 2 in FIG. 1 are modes in which the white balance correction data immediately before entering this mode is held, the correction data is not updated, and the apparent white balance correction operation is stopped. is there.

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

(Condition a) When the luminance signal level is extremely low, Y of the entire screen is displayed as shown in the flowchart of FIG.
Total value of Hn YHtotal (= YH1 + YH2 + YH3 +
(+ YH64) is compared with a predetermined low luminance reference value Ylow, and is established when the value of YHtotal is lower than the low luminance reference value Ylow. By satisfying this condition,
The white balance correction mode transitions <2>, <3>, and <11> are performed.

FIG. 8 is a flow chart showing another example of the judgment that the condition a is satisfied, and as shown in the drawing, YHto
It is also possible to configure the condition a to be satisfied only when the value of tal is lower than 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. Is.

(Condition b) The condition is satisfied when the condition a is exited, and the condition b satisfies <1> in FIG.
Transition is executed. The low brightness reference value Ylow used when the condition b is satisfied can be different from the low brightness reference value used when the condition a is satisfied.

(Condition c) FIG. 9 shows an example of the judgment which is established when the change in the brightness level is extremely large. That is,
In the present embodiment, the value of the iris position detector 37 is stored in the memory 33 at fixed time intervals, and as shown in the flowchart of FIG.
The difference value Isub (= | Iold-Inew |) between old and the current output value Inew of the iris position detector 37 is calculated, and this difference value Isub is compared with the reference value Ilim of the luminance change.
It is established when the difference value Isub exceeds the reference value Ilim.
When the condition c is satisfied, the transition <10> in FIG. 1 is executed.

(Condition d) When the white balance is corrected by R (Ymax) and B (Ymax) obtained by the second calculation described above, it is determined that the white balance correction value is almost zero. That is, R (Ymax) ≈Rref, and B
This is true when (Ymax) ≈Bref, and the transitions <8>, <9>, and <12> in FIG. 1 are executed by the satisfaction of the condition d.

(Condition e) When the white balance is corrected by Ravr and Bavr obtained by the above third calculation, it is determined that the white balance correction value is almost 0, that is, Ravr ≈ Rref and B
This is true when avr≈Bref, and the transition of <2> and <3> in FIG. 1 is executed by the satisfaction of the condition e.

(Condition f) When the white balance is corrected by Ravr (w) and Bavr (w) obtained by the first calculation described above, it is determined that the white balance correction value is almost zero. That is, if Ravr (w) ≈Rref,
Moreover, the condition is satisfied when Bavr (w) ≈Bref, and this condition f
The transition of <2> and <3> of FIG.

(Condition g) This is satisfied when it is determined that there is a change in color temperature using each of the color difference signal data described above, and when this condition f is satisfied, the condition <10> in FIG.
Transition is executed. The following is an example of the algorithm for determining the color temperature change used in the apparatus of the present embodiment,
explain.

In the correction signal calculation unit 34 of FIG. 2, the data of Rn, Bn and YHn of a plurality of predetermined areas in the divided areas are stored in the memory 33 respectively. In this embodiment, Rn, b of eight regions shown 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, each value Rn, Bn, YHn is stored for each of the above eight areas every second. That is, in the sampling operation every 1 second, (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) 8 sets of 24 data are stored in the memory 33
Will be remembered in.

Then, in the correction signal calculation unit 34, the memory 3
The change in color temperature is determined by comparing the past data stored in No. 3 and the present data. The determination method will be further described below.

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

When the value of R1 sampled at t2 is R1 (t2) and the value of R1 sampled at t3 is R1 (t3), the difference value ΔR1 between them is R1 (t3) -R1 ( t2) and similarly Δ
If B1, ΔR8, ... Is defined, (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.

11 to 13 are views for explaining a method of judging a color temperature change from these color change detection values.
11 is a diagram for explaining the coordinates used for this determination, FIG. 12 is a diagram for explaining the state in which the color temperature is low using the coordinates in FIG. 11, and FIG. 13 is a state in which the color temperature is high. It is a figure for demonstrating using the coordinate of FIG.

To determine the change in color temperature, first, the set of each difference value 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, all ΔR of the eight regions change to positive and all ΔB change to negative. The vector of (ΔR, ΔB) is shown in FIG.
As shown in FIG. 2, it is in the fourth quadrant on the coordinates of FIG. When the color temperature of the light source that illuminates the entire screen changes to a high color temperature between t2 and t3, the vector of (ΔR, ΔB) is the second on the coordinates of FIG. 11 as shown in FIG. You will be in the quadrant.

However, when the brightness of the subject is extremely low,
On the other hand, when the color is remarkably high, the color components do not change much even if the color temperature of the light source changes, so such ΔR and ΔB under low brightness and high brightness are excluded. At this time, the high brightness and the low brightness are determined by using the above-mentioned 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 high-luminance portion and the low-luminance portion described above exist in the area 1 of FIG. 14 for all regions when the color temperature of the light source changes low, while the color temperature of the light source is When there is a high change, all areas are present in area 2 of FIG. 14, so this is checked to determine the color temperature change.

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, it is assumed that the white balance correction operation during the determination of the color temperature change causes the maximum color image signal output in one second to change from the point P (t1) to the point P (t2) as shown in FIG. The sampled difference values ΔR and ΔB also change by the amount (dr0, db0) after white balance correction. The value d associated with these maximum white balance corrections
Since the changes in r0 and db0 are not caused by the change in the light source or the subject, the color temperature change determination area (area 1 and area 2) includes the changes in these values dr0, db0. Must be set so that it does not exist.

Therefore, area 1 and area 2 shown in FIG.
Is a region where the absolute value of ΔR is less than dr0, and Δ
The area in which the absolute value of B is less than db0 is set not to be included. As a result, the malfunction can be further reduced.

Here, assuming that there is no change in color temperature 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) will fall within area 1 as shown in FIG. 17, but (ΔR1, ΔB1), and
(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 the color temperature has not changed.

(Condition h) The condition is satisfied when there is no area extracted by the white extraction and the data used for the above-mentioned first calculation does not exist.
<3> transition is executed.

(Condition i) The condition is satisfied when Ravr and Bavr obtained by the third calculation described above are not within the white extraction area of FIG. As a concrete method of confirming this, first, the x component and the y component of FIG. 21 are detected from the Ravr and Bavr. This x component (xavr) is (Ravr
-Bavr) can be calculated, and the y component (yavr) is (Ravr +
It can be calculated by Bavr). Then, the calculated xavr,
When the position in FIG. 21 corresponding to yavr is not within the hatching range, that is, xavr <d, c <xavr, yavr>
The condition i is satisfied when at least one of b and a <yavr is satisfied. When the condition i is satisfied, <
3> transition is executed.

(Condition j) This is a condition for limiting the operation time in the high speed operation mode of FIG. 1, and is satisfied after a predetermined period of time has elapsed since the high speed operation mode was entered. That is, <1 in FIG.
> Or <7> transition is executed, that is, the above condition b
Alternatively, when a 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 measured by the timer reaches a predetermined time, this condition is satisfied. j is established. If this condition j is satisfied, <5> in FIG.
, That is, the transition from the high-speed operation mode of white balance correction to the low-speed operation mode is executed.

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

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

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

According to the image pickup apparatus of the above-described embodiment, once the operation mode becomes 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 optimum operation speed corresponding to the conditions of various subjects depending on the transition condition for restarting, so it is affected by the color change of the subject. It is difficult, and quick follow-up according to the shooting situation can be realized.

Some specific examples of the effects of this embodiment will be described below in light of the situation of the subject.

(Example 1) First, as shown in 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), since the color difference signal component should be as shown in FIG. 22 (a2), the data obtained by the above-mentioned first, second, and third calculations [ Ravr (w), Bavr (w)], [R (Yma
x), B (Ymax)], [Ravr, Bavr] are all reference potentials R
It is almost equal to ref and Bref. Therefore, the above-mentioned transition conditions d, e, and f are all satisfied, and all of <2>, <3>, <8>, <9>, and <12> in FIG. 1 are executed. The white balance correction is the hold mode 2.

In this state, the subject is shown in FIG.
Even if it changes as shown in (c1), the transition condition a,
None of c, g, and k are satisfied, and <7> and <10 of FIG.
> And <11> are not executed,
The operation mode remains the hold mode 2, and the white balance correction state is stable in the state of FIG. 22 (b2).
Therefore, erroneous correction unlike the white balance correction of the conventional color extraction method is not performed.

Then, if the white balance correction state is stable in the state of FIG. 22 (b2),
When the color temperature of the light source changes, the change in color temperature is determined by the above-described method. Therefore, the transition condition g is satisfied, the transition <10> in FIG. 1 is executed, and the white balance correction is slow. Move to operation mode. This allows
The white balance correction is restarted, and the correction operation corresponding to the color temperature of the new light source is performed.

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

On the other hand, in the image pickup apparatus of this embodiment, when Ravr and Bavr of the entire screen are obtained by the third calculation, the vector becomes as shown by Pa in FIG. 19 (C). It is determined that the point Pa is outside the white extraction area. Then, the transition condition i described above is satisfied, and the white balance correction becomes the hold mode 1.
Therefore, the white balance does not change from the state shown in FIG. 19A and is stable in this state.

(Example 3) A case where the photographing condition changes from indoor to outdoor will be described. In this case, the change in brightness is large and the change in color temperature of the light source is also large, so 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-mentioned transition condition k is satisfied, and even if the white balance correction is in any mode at that time, the transition <1
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 obtained.

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

(Example 4) Next, a case will be described in which the lens cap is accidentally turned on to start the white balance correction operation, and then the lens cap is removed. In this case, since the above transition condition a is satisfied with the lens cap attached, the operation mode for white balance correction is the hold mode 1, but the transition condition b is satisfied when the lens cap is removed. To 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 device of the actual sister example described in this specification, when the average of the color signal data of the entire screen is calculated, the data is extracted from all 64 divided areas and the average thereof is calculated. However, if the data is evenly distributed over the entire screen, it is possible to extract only the data in some areas and take the average of the data in these areas.

Further, the eight areas shown by hatching in FIG. 4 are the areas for detecting the color change in order to determine the color temperature change. Similarly, if the areas are evenly distributed over the entire screen, this number of areas is set. It is also possible to change. It is also possible to adopt a configuration in which the position and the number of detected areas are changed according to the situation of the subject.

[0096]

As described above, according to the image pickup apparatus of the present invention, by selecting one of a plurality of color temperature information, the optimum color temperature information for various photographing screens can be obtained. It has become possible to perform good white balance correction by using, and it has become possible to minimize the effect of chromatic subjects on any of a wide variety of screen configurations.

[Brief description of drawings]

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

FIG. 2 is a block diagram showing a schematic configuration of an image pickup 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.

FIG. 4 is a diagram for explaining screen division and data for each divided area and a color change detection area by the image pickup apparatus of FIG.

5A and 5B are diagrams for explaining a judgment value of a color jump by the image pickup apparatus of FIG.

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

FIG. 7 is a flowchart for explaining an example of a judgment for the condition a to be satisfied among the transition conditions of FIG.

FIG. 8 is a flowchart for explaining another example of the determination for the condition a to be satisfied among the transition conditions of FIG.

FIG. 9 is a flowchart for explaining an example of a determination for the condition c to be satisfied among the transition conditions of FIG.

10 is a diagram for explaining a sampling cycle of data for detecting a color change by the image pickup apparatus of FIG.

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 is low, using the coordinates in FIG. 11.

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

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

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.

FIG. 16 is a diagram showing an example of change of a subject for explaining the effect of the apparatus of FIG.

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

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

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

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

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

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

[Explanation 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 calculation unit 35,36 Digital-Analog converter 37 Iris position detector 50 Sync signal generator

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

Claims (5)

(57) [Claims] 1. An image pickup device, and a plurality of types of calculations based on color signals output from the image pickup device.
Calculating means for calculating a plurality of types of color temperature information based on the method, and color temperature information having the smallest white balance correction amount among the plurality of color temperature information as color temperature information in the photographing screen.
And selection means for selecting, the image pickup apparatus characterized by comprising a white balance correction means for correcting the white balance of the color signals output from the imaging unit by the color temperature information selected by said selection means. 2. The calculating means includes a detecting means for extracting a color signal for each of a plurality of areas in a photographing screen of the image capturing means, and detecting color information according to the color signal extracted for each area. The color temperature information of the types is first color temperature information calculated using at least color information of all areas, and second color temperature calculated using partial color information of the plurality of areas. The image pickup apparatus according to claim 1, further comprising information. 3. The entire shooting screen is divided into a plurality of areas
And, the color temperature information imaging apparatus according to claim 1, characterized in that it is calculated from the average value of all said plurality of areas of color information. 4. The color temperature information in the plurality of regions,
The image pickup apparatus according to claim 1, wherein a color signal from a white subject is calculated from an average value of color information in a range in which the color signal changes according to color temperature. 5. The color temperature information in the plurality of regions,
The image pickup apparatus according to claim 1 , wherein the image pickup apparatus is calculated from the color information of the area having the highest brightness level.