JP2997234B2 - Imaging device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image pickup apparatus having white balance adjusting means.

[0002]

2. Description of the Related Art Video cameras, electronic still cameras, etc.
Make sure that the imager is white so that the reproduced white color is correct.
The balance adjustment means is provided. And in recent years,
Automatic white balance adjustment based on the output signal of the image sensor
TTL (through the taking lens) method
Is often used. Figure 17 shows the integral type (averaging type)
Conventional TTL white balance adjusting means
It is a block diagram of an imaging device. In the figure, 1 is Len
2, an image sensor that performs photoelectric conversion such as a CCD, and 3 an image sensor
A luminance signal processing unit for deriving a luminance signal Y from the output of the child 2;
Reference numeral 4 denotes a low frequency component Y of the luminance signal from the output of the image sensor 2.
_L Signal processing for deriving red signal R and blue signal B
And 5, 6 are output signals R, B of the chroma signal processing unit 4, respectively.
Gain control unit and B gain control unit for changing the signal level of
7 and 8 are the outputs Y of the chroma signal processing unit 4 _L And R, B gain system
The color difference signals RY, B- are obtained from the outputs R ', B' of the control units 5, 6.
Matrix amplifier for deriving Y; 9 is a luminance signal processing unit
3 and the output R-Y of the matrix amplifiers 7 and 8,
BY is modulated into a prescribed signal, and the signal is transmitted to a recording medium (not shown).
A modulation processing unit that enables recording and image output to a monitor.
10 and 11 are outputs RY of the matrix amplifiers 7 and 8;
Averaging for averaging several screens by integrating BY
32 is a white balance from the outputs of the averaging units 10 and 11
Derive an appropriate control voltage for the lance,
6 is a control voltage deriving unit that controls the control voltage control unit 6.

The operation of the conventional example will be described below with reference to FIG.

First, a subject image formed on the image pickup device 2 is converted into an electric signal, and an output signal thereof is sent to a luminance signal processing unit 3 and a chroma signal processing unit 4, where the luminance signal processing unit 3
In the luminance signal Y, a low-frequency component Y _L and the red signal R of the chroma signal processing section 4, the luminance signal, to derive the blue signal B. Here Y _L red at a ratio of _{Y L = 0.30R + 0.59G + 0.11B} : R, blue: B, green: a mixed signal of the G. Of the outputs derived by the chroma signal processing unit 4, the signals R and B
Are sent to an R gain control unit 5 and a B gain control unit 6, respectively, where the signal level is changed for white balance adjustment, and signals R 'and B' are derived. Output Y _L and R of the chroma signal processing unit 4, the output R and B gain control section 5, 6 ', B' are sent to the matrix amplifier 7 and 8,
The color difference signals RY and BY are obtained (where RY =
0.70R-0.59G-0.11B BY = 0.8
9B-0.59G-0.30R).

[0005] The signals Y, RY and BY are modulated by a modulation processing unit 9.
The signal is modulated into a prescribed signal form and output to enable recording on a recording medium or the like or output to a monitor.

On the other hand, the outputs R of the matrix amplifiers 7 and 8
The −Y and BY signals are also sent to averaging units 10 and 11,
An average value for one or more screens is derived. Then, the control voltage deriving unit 32 derives control voltages to the R and B gain controllers 5 and 6 so that the average signal level becomes 0 level (that is, R = B = G), thereby performing white balance adjustment. Is going.

[0007]

However, in the above-mentioned conventional example, there is a problem that it is difficult to suitably adjust the white balance when capturing a scene in which a high chroma object occupies most of the screen.

Further, in the case of the peak method in which the color difference signal of a portion where the luminance level is equal to or more than a certain value is sampled and the white balance adjustment is performed without using the average value of the color difference signal as in the above-mentioned conventional example, Since the signals are not necessarily achromatic, good white balance adjustment is not possible. Further, it has been proposed to use a combination of the two methods, but there are problems that the number of components increases and the improvement effect is not remarkable.

The present invention has been made under such circumstances, and it is an object of the present invention to provide an imaging apparatus capable of always performing a suitable white balance adjustment regardless of imaging conditions.

[0010]

In order to achieve the above object, according to the present invention, an image pickup apparatus is configured as in the following (1).

The image pickup device (2) and the output of the image pickup device
In a plurality of positions (1 to 5 in FIG. 4) in the screen formed
To determine whether or not the color information signals
And the presence of an approximate color information signal in the screen
(13. 16-1 to 16-3 in FIG. 3)
16-11) and the screen detected by the determination means
Information of the area where the approximated color information signal exists in the area
Sampling the signal discretely compared to the rest of the screen
Sampling means for ringing (INTE signal in FIG. 13)
And after sampling by the sampling means
Forming an average by averaging color information signals
Averaging means (10, 11) and an output of the averaging means.
And a white balance adjusting means (5, 6, 13) for adjusting the white balance.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to examples of an image pickup apparatus.

[0013] In order to ensure that the description does not differ from the original specification and to facilitate comparison with the original specification, the description here is the same as the original specification. The described invention is supported by the description of the sixth embodiment and the description at the end of [Example].

[0014]

The present invention will be described below in detail with reference to examples. FIG.
FIG. 1 is a block diagram of an “imaging device” according to a first embodiment of the present invention.

In FIG. 1, reference numerals 1 to 11 are the same block diagrams as the conventional example shown in FIG. 12 is an A / D (analog-digital) converter, 13 is a microcomputer system (hereinafter referred to as a microcomputer), 14 is a D / A (digital-analog) converter, and 15 is a measurement sensor for measuring the brightness of external light. is there. 2 and 3 show the microcomputer 1 of FIG.
3, FIG. 4 is a supplementary explanatory diagram, and FIGS. 5 and 6 are a configuration diagram and a timing chart for explaining the operation of the averaging units 10 and 11. FIG. 7 is a diagram illustrating a limited range of white balance adjustment in the present embodiment.

This embodiment will be described below with reference to FIGS.

First, the operations of 1 to 11 in FIG. 1 are the same as those in the conventional example, but the operations of the averaging units 10 and 11 will be described with reference to FIGS.

The RY signal is input to the input side of the switch 16 in FIG.
In the case of 1, the BY signal is input. At this time, the switch 16 is closed when INTE in FIG. 6 is at a high level,
Open when the signal is at low level, and only when the signal is closed, the color difference signals RY and BY
9, the reference voltage source 20, and the differential amplifier 21. On the other hand, the switch 18
Is closed when is at a high level, and the electric charge stored in the capacitor 19 during that period is discharged.

As a result, the outputs of the averaging units 10 and 11 have waveforms as shown by SIGNAL in FIG.
A / D outputs its output while SAMPLE is at a high level.
By performing the conversion, the average level in one screen of each of the RY and BY signals can be detected. VD is a vertical drive signal.

Each of the average values obtained as described above is input to the microcomputer 13 via the A / D converter 12, and a control voltage for white balance adjustment is calculated based on the average value. Derived within. Figures 2 and 3 below
The operation will be described with reference to FIGS.

First, step 1 in the flowchart of FIG.
As shown in the figure, predetermined values as initial values in the microcomputer memory are α, β, A, B, C, D, k,
_{l, m, n, L O} , X, Y, R C, B C, previously given as F _O. Next, as shown in Step 2 of the flow chart, the output L _S of the photometry sensor 15 is read through the A / D converter 12 to obtain the L divided by the constant L _O (see step 3). Here, L _O is a value indicating the average brightness of outdoor light. When the obtained L is 1 or more, L
= 1 (4, 5), and if L <1, the process proceeds directly from step 4 to step 6. In step 6, FIG. 4 "□" is a R-Y, B-Y signal of the position on the screen indicated by the _{(R-Y) 1 ~ (} R-Y) 5, (B-Y) 1 ~ (B-
Y) ₅ is read through the A / D converter 12.

Next, the output of the averaging unit (RY) _S , (B-
Y) Read _S (6, 7), (RY) If _S <-α, _RC = _RC +1 (RY) If _S > α, _RC = _RC -1 (BY) _{If S} <-β, B _C = B _C +1 (BY) If _S > β, B _C = B _C -1 otherwise, R gain for white balance adjustment and control voltage R for B gain _C and B _C are left as they are, that is, initial values (8 to 15).

Here, if the R gain control voltage R _C has a large value, the gain of the R gain control section 5 increases and the R signal level increases, while the B gain control voltage B _C has a large value. B
The gain of the gain control unit 6 is set to decrease and the B signal level is set to be low. The initial values of the control signals R _C and B _C are respectively set to speed up the final output of R _C and B _C. Is set to an intermediate value within the range that can be taken. After setting the values of the control voltages R _C and B _C as described above, it is determined whether the state of the captured image is a single subject occupying a large area (16). This determination method will be described in more detail with reference to FIG.

[0024] In FIG. 3, a first R-Y, B-Y signal of the central portion of the screen (see FIG. _{4) (R-Y) 1} , (B-Y) 1
And constant values k, l, m, and n are added to or subtracted from (RY) ₁₊ = (RY) ₁ + k (RY) _1- = (RY) ₁ -l (B- Y) ₁₊ = (BY) ₁ + m (BY) ₁₋ = (BY) ₁ -n is derived (16-1 to 16-4).

Next, with P = 2 as an initial value, (RY) _P
And (RY) ₁₊ , (RY) _1- , and compare the magnitude of (BY) _P with (BY) ₁₊ , (BY) _1-. By comparison (16-6 to 16-9), steps 16-6 to
If any one is NO in 16-9, the result is B, that is, the process proceeds to step 19 in FIG. On the other hand, if all are YES, it is confirmed whether P is 5 (16-10), and if P ≠ 5, P is incremented by one (16-11), and step 16-
Returning to step 6, the same processing is repeated. If P = 5, the comparison of the five points in FIG. 4 has been completed.
Steps 16-10 to C, that is, step 17 in FIG.
Proceed to.

As described above, the flow shown in FIG.
That is, it can be detected whether or not the color difference signals of the points 〜 to 5 are all at an approximate level to the color difference signal of the point 1. Thus, if the levels are all approximate levels, it is determined that the occupied area of the single subject is large.

If the single subject is not in a large area, the control voltage limited range a,
b, c, d are set to initial values A, B, C, D (19, FIG. 7
reference).

On the other hand, if it occupies a large area,
First, we derive the flicker component F of the external light from the output of the photometry sensor 15 in step 17, compared with the reference value F _O, F <F
If it is _O , it is regarded as a non-flicker light source, and if F ≧ F _O , it is regarded as a flicker light source, that is, a fluorescent lamp. Therefore, if F <F _O , a = (X−A) × L + Ab = (B−X) × L + Xc = (C−Y) × L + Y d = (Y−D) × L + D (18, If F ≧ F _O , a = X,
Select b = B, c = Y, d = D (20, see FIG. 7). This is a constant that limits the range that each of the control voltages R _C and B _C can take in the operations in steps 21 to 28. That is, if R _C ≧ a is NO, then R _C = a If R _C ≦ b is NO, then R _C = b R _C ≧ c, B _C = c if R _C ≦ d, then B _C = d. The limited range of the control voltage can be set within the range enclosed by □ klmn shown in FIG.

The control voltages R _C , B thus obtained
_C is sent to the control units 5 and 6 via the D / A converter 14 to change the color difference signal level, and the operations of steps 2 to 29 are repeated based on the changed output to adjust the white balance. It can be suitably performed.

Now, the setting of the limited range of the control voltage according to the first embodiment will be described in detail with reference to FIG. In this embodiment, it is determined whether or not the area occupied by a single subject is large in step 16 in FIG. 2. If the occupied area is small, the limited range of the control voltage is within □ klmn in FIG. The values of the voltages R _C and B _C are set (19).

On the other hand, when the occupied area is large, it is assumed that a high chroma subject may occupy most of the screen, so that the output of the averaging unit is strongly influenced by the object color and the white balance is largely shifted. There is a risk. Therefore, in this case, the limited range of the control voltages R _C and B _C is further narrowed, and the position of the limited range is set to an optimum position based on information from other sensors and the like. In this embodiment, first, at step 17, it is detected whether or not the light source is a fluorescent lamp. If the light source is a fluorescent lamp, the limited range is set to □ oqms. If it is a non-flicker light source, it is determined whether the light is outdoor light or indoor light by the brightness L _{S of the} external light,

[0032]

(Equation 1)

If so, it is assumed that the light is completely outdoor light, and the control voltage limited range is □ orl in FIG. 7 assuming a bluish light source.
q. On the other hand, for example, if L ≦ 0.001, the limited range is almost □ osnp. In this case, since the light is considerably dark, the limited range is set by assuming a reddish light source as indoor light. In general, the darker the tungsten light becomes, the more reddish it becomes, so that it is considered that this setting matches well with the setting of this limited range. If L is an intermediate value, the limited range moves as □ osnp → □ orlq as L = 0.001 → L = 1.

As described above, the size of the single subject area is detected, and in the case of a large subject area, the limited range is narrowed (limited) by the information (brightness of external light and flicker amount) from the measurement sensor 15 so that the object is limited. White balance adjustment can be performed without being strongly affected by color.

In the above embodiment, the control voltage R
_A warning device may be provided to alert the photographer when _C and B _C have reached the limit of the limited range.

FIGS. 8 and 9 are flow charts for explaining a second embodiment of the present embodiment.

In the present embodiment, in the same configuration as in the first embodiment, not only is the size of the occupied area of a single subject on the screen determined, but also the saturation thereof is used as a determination factor.

That is, in step 16 in FIG. 8, the size of the occupied area of the high chroma single subject is determined. Step 16 is described in more detail in FIG.
The operation of -11 is the same as that of the first embodiment. In FIG. 9, in step 16- (1), the absolute value of the color difference signal (RY) ₁ at the point 1 shown in FIG. 4 is compared with a constant M, and if | (RY) ₁ |> M, Judge as a high saturation subject. Proceed to 16-1.

[0039]

(Equation 2)

Then, at 16- (2), the absolute value of the color difference signal (BY) ₁ at the point 1 in FIG.
If | (BY) ₁ |> N, it is determined that the subject is a high chroma subject and 1
Proceed to 6-1

[0041]

(Equation 3)

Then, it is determined that the object is a low-saturation object and the process proceeds to step S19 in FIG.

With the above operation, it is determined whether the area occupied by a single high chroma object is large or small.
As shown in the embodiment, the limited range of the control voltage is narrowed.

Accordingly, when a low-saturation subject that does not adversely affect the white balance adjustment occupies a large area in the screen, the range of the control voltage is not narrowed, and a high-saturation subject that adversely affects the control voltage is not reduced. Only narrow the range,
More suitable white balance adjustment becomes possible.

FIG. 10 is a block diagram showing a third embodiment of the present invention. Reference numerals 1 to 15 denote the same blocks as in the first embodiment.
Is an averaging unit having the same configuration as 10 and 11. The operation of the third embodiment will be described below.
The operation of this block is the same as in the first embodiment.

[0046] In this embodiment, signals R-Y, R-Y average values to be input to the microcomputer 13, B-Y, B- Y mean values, other photometric sensor output, Y _L output of the chroma signal processing unit 4 Is input to the microcomputer 13 via the A / D converter 12. In the microcomputer 13, Y _L , R
−Y and BY average signals Y _LS , (RY) _S ,
(BY) The R, G, and B signals are derived from _S. For example, the following operation is performed.

[0047] _{R = (R-Y) S} + Y LS = R B = (B-Y) S + Y LS = B G = (Y LS -0.30 · R-0.11 · B) /0.59 this R, G, B from the R, B, G signals derived as above
And G are derived, and control voltages R _C and B _{C at} which the respective ratios R / G and B / G become 1 are calculated. And derived R _C ,
B _C is converted into R gain control units 5 and 5 via a D / A converter 14, respectively.
The white balance is adjusted by sending the signal to the B gain control unit 6. Also in the present embodiment, the magnitude of the single subject area is determined, and when the large area is determined, the control is performed based on the light amount value and the flicker amount value obtained from the output of the photometric sensor 15 as in the first embodiment. The range of the voltages R _C and B _C is further limited. Thereby, suitable white balance adjustment can be performed, and at the same time, in this embodiment, each (RY)
_The control voltage R is immediately obtained from the _S , (BY) _S , _YLS signals.
_{Since C} and B _C can be calculated, it is suitable for a white balance adjustment device of an imaging device requiring immediacy such as an electronic still camera. In addition, since the R, G, and B signals are calculated after the color difference signals (RY, BY) are once converted, the output color of the averaging unit can be easily clipped on the high chroma subject signal.
It is possible to prevent adverse effects on the subject object color. If there is no need for this clip, it may be sent directly to the averaging unit in the R, G, B signal state before the color difference signal.

FIG. 11 is a block diagram showing a fourth embodiment of the present invention. Reference numerals 1 to 14, 22 denote the same blocks as in the third embodiment. Reference numeral 23 denotes a shutter for determining the exposure time, and reference numeral 24 denotes an aperture.

[0049] In this embodiment, the photometric sensor 15 used in the first embodiment to third embodiment is removed, turned shutter instead, from the stop and Y _L output configured to measure the brightness and the flicker amount of the external light ing. That is, a is controlled by the microcomputer 13 Y _L signal level brightness and a shutter speed and the aperture value when appropriate, also be used to measure the temporal change of the Y _L outputted intermittently obtained output from the imaging element 2 Detect the amount of flicker. Based on the above information, the limited range of the control voltages R _C and B _C when the single subject area is large is determined. In this embodiment, the cost can be reduced because the photometric sensor 15 can be omitted.

FIG. 12 is a block diagram of a fifth embodiment of the present invention, and 2 to 15, 22 are the same block diagrams as the third embodiment.
A zoom lens 25 changes the focal length of the imaging optical system.

In this embodiment, when the size of a single subject is determined to be large in an image pickup apparatus such as an electronic still camera which does not need to constantly output an image pickup signal, first, the focal length of the zoom lens is temporarily reduced as data measurement. Then, the control voltages R _C and B _C are determined as the wide lens state, and the image is returned to an arbitrary focal length at the time of the actual imaging to perform the imaging. As a result, the area of the high chroma object color in the screen can be reduced as much as possible, and more suitable data of white balance adjustment can be obtained.

FIG. 13 is a timing chart of a main part of the sixth embodiment of the present invention, showing a switching period and an averaging period of the averaging unit corresponding to the averaging units 10 and 11 in FIG. This embodiment has the same configuration as that of FIG.

As can be seen from FIG. 13, in this embodiment, when the single subject area is determined to be large, the averaging period is partially intermittent. That is, in such a case, it is assumed that the high-saturation object occupies a large area in the center of the screen, so that the central portion (horizontal scanning period,
By making intermittent pulses in both vertical scanning periods, the sampling period in that portion can be reduced to prevent the influence of a high-saturation object and to enable good white balance adjustment.

That is, in the present embodiment, a part of the screen is weighted at the time of averaging. As described above, instead of discrete pulses, the color difference signal may be weighted and averaged by applying an appropriate coefficient to the color difference signal in the center area of the screen.

[0055] Figure 14 is a block diagram showing a seventh embodiment of the present invention, 1～15,22 in the same block as the third embodiment, 26 Y _L signal and detects whether within a predetermined level range shows the circuit in FIG. 15 in the comparator unit (Y _L PEAK detector).

The operation of this embodiment will be described below.
Operations similar to those of the third embodiment are shown for 11, 15, and 22. If a certain level range in which Y _L signal comparator unit 26 is E ₂ <is Y _L <E _1, i.e., the high level is outputted, a low level if other than the.

At this time, E ₁ and E ₂ are, for example, 1 of the _YL level.
The setting is made so as to correspond to the signal levels of 05% and 90%.

[0058] If That Y _L level 90 to 105%, Y _L PEAK detector output Y _L P becomes high level. Y of _L P level to the high level, since situations not occurred is high and the color saturation brightness is considered to correspond to the subject of the low-saturation. Therefore, Y _L color difference signal R-Y when the P high, the B-Y and by sampling the A / D12, sends to the microcomputer 13, the signal Y _L, R-Y,
White balance is performed by BY. Signal Y _L, R-
Y, B-Y from the control voltage R _C, means for deriving B _C is the same as the third embodiment.

Further, in the microcomputer 13, the aforementioned Y _L PEA
A white balance adjustment method using a K detector and an adjustment method using an averaging unit are combined to derive a control voltage so as to compensate for the shortcomings of both methods. For example, it is conceivable to preferentially use information of a method in which a signal with lower saturation is detected from both types of detected color difference signals.

[0060] In this embodiment thereon, at the time of determination of a single subject area large, by using a Y _L PEAK detection method preferentially, to minimize the impact on the deterioration of the white balance adjustment by averaging scheme be able to.

In each of the above embodiments, the A / D input terminal for the color difference signal output from the blocks 7 and 8 and the A / D input terminal for the averaged output are provided independently.
When the averaging function of the averaging unit is turned on / off, the input signal is output as a through signal when the averaging function is off, and the averaging output and color difference signals are input to the A / D converter 12 in a time series. The number of input terminals of the D converter can be reduced.

In each of the above embodiments, the sampling positions and the number of color difference signals are set as shown in FIG.
An arbitrary position and number may be selected to determine the size of the single subject area.

For example, in the sixth embodiment, 13 sampling points are set as shown in FIG. 16, and an intermittent pulse is generated only at a position where an area of a certain level or more is detected (one of the regions 1 to 6 in the figure). A configuration (weighting) may be used.

By changing the position and number of sampling points as described above, it is possible to detect and correct a single subject at any position in the screen.

In each of the above embodiments, the color difference signal is used to determine the area of a single subject, but other signal formats such as a luminance signal may be used.

[0066]

As described above, according to the present invention,
Regardless of the condition that a single subject occupies most of the screen, a suitable white balance adjustment can always be performed.

[Brief description of the drawings]

FIG. 1 is a block diagram of a first embodiment of the present invention.

FIG. 2 is a flowchart showing the operation of the first embodiment of the present invention.

FIG. 3 is a flowchart showing the operation of the first embodiment of the present invention.

FIG. 4 is a diagram showing sampling points.

FIG. 5 is a configuration diagram of an averaging unit.

FIG. 6 is a timing chart of an averaging unit.

FIG. 7 is a diagram illustrating a limited range of white balance adjustment.

FIG. 8 is a flowchart showing the operation of the second embodiment of the present invention.

FIG. 9 is a flowchart showing the operation of the second embodiment of the present invention.

FIG. 10 is a block diagram of a third embodiment of the present invention.

FIG. 11 is a block diagram of a fourth embodiment of the present invention.

FIG. 12 is a block diagram of a fifth embodiment of the present invention.

FIG. 13 is a block diagram of a sixth embodiment of the present invention.

FIG. 14 is a block diagram of a seventh embodiment of the present invention.

FIG. 15 is a circuit diagram of a Y _L PEAK detector.

FIG. 16 is a diagram showing sampling points.

FIG. 17 is a block diagram of a conventional example.

[Explanation of symbols]

 2 imaging device 5 R gain control unit 6 B gain control unit 10, 11 averaging unit 13 microcomputer

Claims (1)

(57) [Claims] An image sensor and a plurality of positions in a screen formed by outputs of the image sensor.
Whether or not the color information signals in each other are similar to each other
Of the approximate color information signal in the screen
Discriminating means for discriminating an existing area; and an approximation in the screen detected by the discriminating means.
Color information signal in the area where the
Sampling that samples discretely compared to the area within the screen
Ring means, and color information after sampling by the sampling means.
Average forming the average value by averaging the broadcast signal
Means a, an imaging apparatus characterized by comprising: a white balance adjusting means, for the white balance adjustment based on the output of said averaging means.