JP3010373B2 - Imaging device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to an imaging apparatus provided with a white balance adjustment unit.

[Conventional technology]

In imaging devices such as video cameras and electronic still cameras,
A white balance adjusting unit is provided so that the reproduced white color becomes a correct color. In recent years, TT that automatically adjusts white balance based on the output signal of the image sensor
Adjustment of the L (through the taking lens) method is often used. FIG. 17 is a block diagram of a conventional imaging apparatus provided with an integral (averaging) TTL type white balance adjusting means. In the figure, reference numeral 1 denotes a lens, 2 denotes an image sensor that performs photoelectric conversion such as a CCD, 3 denotes a luminance signal processing unit that derives a luminance signal Y from an output of the image sensor 2, and 4 denotes a low luminance signal from the output of the image sensor 2. Frequency component Y _L , red signal R, blue signal B
, And R and B gain control units for changing the signal levels of the output signals R and B of the chroma signal processing unit. Reference numerals 7 and 8 denote the output Y of the chroma signal processing unit 4. _L
From the outputs R 'and B' of the R and B gain controllers 5 and 6,
A matrix amplifier 9 for deriving Y and B-Y, 9 is an output Y of the luminance signal processing unit 3 and an output R of the matrix amplifiers 7 and 8
This is a modulation processing unit that modulates -Y and BY into a prescribed signal and enables recording on a recording medium (not shown) or output to a monitor. 10 and 11 are the outputs R-Y and B- of the matrix amplifiers 7 and 8.
An averaging unit averaging several screens by integrating Y, etc., 32 derives a control voltage appropriate for white balance from the outputs of the averaging units 10 and 11, and controls the R and B gain control units 5 and 6. Control,
This is a control voltage deriving unit.

 Hereinafter, the operation of the conventional example will be described with reference to FIG.

First, the subject image formed on the image sensor 2 is converted into an electric signal, and the output signal is sent to the luminance signal processing unit 3 and the chroma signal processing unit 4, and the luminance signal processing unit 3 outputs the luminance signal Y.
And the chroma signal processing unit 4 derives a low-frequency component Y _{L of the} luminance signal, a red signal R, and a blue signal B. Here Y _L is Y _L = 0.30R + 0.5
This signal is a mixture of red: R, blue: B, and green: G at a ratio of 9G + 0.11B. Among the outputs derived by the chroma signal processing unit 4, the signals R,
B is sent to an R gain control unit 5 and a B gain control unit 6, respectively, where its signal level is changed for white balance adjustment, and signals R 'and B' are derived. Chroma signal processing unit 4
The outputs Y _L and R ′, B ′ of the R and B gain control units 5 and 6 are sent to matrix amplifier units 7 and 8 to obtain color difference signals RY and BY (here, R −Y = 0.70R−0.59G−0.11B B−
Y = 0.89B-0.59G-0.30R).

The signals Y, RY, and BY are sent to the modulation processing unit 9, where they are modulated and output in a prescribed signal form so as to enable recording on a recording medium or the like, or output to a monitor.

On the other hand, the RY and BY signals output from the matrix amplifiers 7 and 8 are also sent to averaging units 10 and 11 to derive an average value of one or more screen parts. Then, in the control voltage deriving unit 32,
The average signal level is 0 level (that is, R = B = G)
The white balance is adjusted by deriving the control voltages to the R and B gain controllers 5 and 6 such that

[Problems to be solved by the invention]

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

Also, in the case of the peak method used for white balance adjustment by sampling a color difference signal of a portion where the luminance level is a certain value or more without using the average value of the color difference signal as in the conventional example, a signal having a certain level or more is not necessarily used. Because it is not achromatic,
Good white balance adjustment is not possible. It has also been proposed to use a combination of both methods,
There is a problem that many components are required and the improvement effect is not remarkable.

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

[Means for solving the problem]

In the present invention, in order to achieve the above object, the imaging device is configured as in the following (I).

(I) an image sensor (2); white balance adjusting means (5, 6, 13) for adjusting a white balance by adjusting a gain of each color signal based on an output of the image sensor; By determining whether or not the color information signals at a plurality of positions (1 to 5 in FIG. 4) in the screen to be formed are similar to each other, it is possible to determine an area in the screen where the approximated color information signal exists. Judgment means (1
3. If the size of the area where the approximate color information signal in the screen is detected by the determination means is smaller than a predetermined value, the gain adjustment range of each color signal is set to the first range. (A range surrounded by klmn in FIG. 7). When the size of the area where the approximate color information signal in the drawing is detected by the determination means is larger than a predetermined value, the respective color signals The control means (1) for switching and controlling the gain adjustment range so that the gain adjustment range is a second range (a range surrounded by, for example, posn in FIG. 7) smaller than the first range.
3) An imaging device comprising:

[Action]

In the present invention, as described above, it is determined whether or not the area having the approximated color information signal occupies a large size in the screen, and the gain adjustment range is switched based on the determination result. Even if a subject having a color similar to the inside occupies a large area, erroneous white balance adjustment is not performed. That is, it is possible to effectively reduce only the adverse effect of a large-area subject, which adversely affects the white balance.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to Examples. FIG. 1 is a block diagram of an "imaging device" according to a first embodiment of the present invention.

In FIG. 1, 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 (hereafter microcomputer), 14 is D / A (digital-analog)
The converter 15 is a photometric sensor that measures the brightness of external light. 2 and 3 are flowcharts showing the operation of the microcomputer 13 in FIG. 1, FIG. 4 is a supplementary explanatory diagram thereof, and FIGS. 5 and 6 are diagrams for explaining the operation of the averaging units 10 and 11. It is a block diagram and a timing chart. FIG. 7 is a view for explaining a limited range of the white balance adjustment in the present embodiment.

 Hereinafter, this embodiment will be described with reference to FIGS.

First, the operations of 1 to 11 in FIG. 1 are the same as those of 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. 5 in the case of the block 10, and the BY signal is input in the case of the block 11. At this time, the switch 16 is
It is closed when INTE is at a high level and open when it is at a low level. Only when closed, each color difference signal RY, B
−Y is resistor 17, capacitor 19, reference voltage source 20, differential amplifier 2
It is input to an integrating circuit consisting of 1. On the other hand, since the switch 18 is closed when RESET in FIG. 6 is at the high level, the charge stored in the capacitor 19 is discharged during that period.

As a result, the outputs of the averaging units 10 and 11 become SIGNA of FIG.
As shown in FIG. 6, the output of the SAMPLE shown in FIG.
The average level in one screen of the Y, BY signal can be detected. VD is a vertical drive signal.

The average values obtained as described above are input to the microcomputer 13 via the A / D converter 12, and the control voltage for white balance adjustment is derived in the microcomputer 13 based on the average value. I do. The operation will be described below with reference to FIGS. 2, 3, 4, and 7.

First, as shown in the steps of the flowchart in FIG. 2, predetermined values as initial values in the microcomputer memory are α, β, A, B, C, D, k, l, m, m, L _O , X, Y, R _C , B _C , F _O
Give as. Next, as shown in the steps of the flowchart, the output L _S of the photometric sensor 15 is read via the A / D converter 12 and divided by a constant L _O to obtain L (see step). Here, L _O is a value indicating the average brightness of outdoor light. When the obtained L is 1 or more, L = 1
And if L <1, the process proceeds directly from step to step. In the step, (RY) ₁ to (RY) ₅ , (BY) ₁ to (BY), which are RY and BY signals at positions on the screen indicated by “□” in FIG. Y)
₅ is read via the A / D converter 12.

Next, the output of the averaging unit (RY) _S , (BY) _S is read (,), and if (RY) _S <-α, _RC = _RC + 1 (RY) _S > α. Then, if R _C = R _C −1 (BY) _S <−β, then B _C = B _C +1 (BY) If _S > β, then B _C = B _C −1, otherwise white. The control voltages R _C and B _C for R gain and B gain for balance adjustment are set as they are, that is, as initial values (（).

Here, if the R gain control voltage R _C has a large value, the gain of the R gain control unit increases and the R signal level increases. Conversely, if the B gain control voltage B _C has a large value, the B gain control voltage B _C increases. The gain of the unit 6 is set to be low and the B signal level is set to be low. The initial values of the control voltages R _C and B _C are set so that the final outputs of R _C and B _C can be quickly determined. It is set as an intermediate value within the range. 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 (). This determination method will be described in more detail with reference to FIG.

In FIG. 3, first, RY,
The (BY) signal (RY) ₁ , (BY) ₁ has a constant value k,
Addition or subtraction of l, m, and n gives (RY) ₁₊ = (RY) ₁ + k (RY) _1- = (RY) ₁ -l (BY) ₁₊ = (B−Y) ₁ + m (B−Y) ₁₋ = (B−Y) ₁₋ n is derived (−1 to −4).

Next, with (P = 2) as an initial value, (RY) _P and (R-
Y) ₁₊ , (R−Y) ₁₋ , and (B−
Y) Compare the magnitude of _P with (BY) ₁₊ , (BY) _1- (-6 to -9), and if any one is NO in steps -6 to -9, That is, the process proceeds to the steps in FIG. On the other hand, if all are YES, it is checked whether P is 5 (−10), and if P ≠ 5, P is incremented by one (
-11), return to step -6 and repeat the same process. If P = 5, the comparison of the five points in FIG. 4 has been completed, so the process proceeds from step -10, that is, to the step in FIG.

As described above, according to the flow of FIG. 3, it can be detected whether or not the color difference signals of the points 2 to 5 shown in FIG. 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 limited range a, b, c, d of the control voltage is set to the initial value A, as in the step.
B, C, and D (see FIG. 7).

On the other hand, if the area occupies a large area, first, the flicker component F of the external light is obtained from the output of the photometric sensor 15 in a step.
Is derived and compared with a reference value F _O. If F <F _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, set to F <F _O If a = (X-A) × L + A b = (B-X) × L + X c = (C-Y) × L + Y d = (Y-D) × L + D (, the 7 see FIG.), F ≧ F _O if a = X, b =
Select B, c = Y, d = D. (See FIG. 7). This is a constant that limits the range that each value of the control voltages R _C and B _C can take in the operation in Steps 1 to 3. That is, if R _C ≧ a is NO, then R _C = a If R _C ≦ b is NO, then R _C = b B _C ≧ c, then B _C = c B _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 and B _C obtained in this manner are converted to a D / A converter 14.
The control is sent to the control units 5 and 6 via the CPU, the color difference signal level is changed, and the operations of steps 1 to 6 are repeated based on the changed output, whereby the white balance adjustment can be suitably performed.

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 the present embodiment, the second
Determines whether an area occupied by the single subject is large in FIG step, the limited range of the control voltage if the state of the occupied area small, the control voltage R _C over a wide range becomes the first of the 7 Figure □ Use klmn, the Bc It is set to take a value ().

On the other hand, in the case of a large occupation area, it is assumed that a high chroma subject may occupy most of the screen, so that the output of the averaging unit is strongly affected by the object color and the white balance may be largely shifted. . 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, 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, If so, it is assumed that the light is completely outdoor light, and the control voltage limited range is □ orlq in FIG. 7 assuming a bluish light source. On the other hand, for example, if L ≦ 0.001, the limited range is almost □ onsp
Becomes In this case, since the light is considerably dark, the limited range may be set by assuming that the light source is reddish assuming 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 is □ osnp as L changes from 0.001 to L = 1
→ It will move to □ orlq.

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

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

FIG. 8 and FIG. 9 are flowcharts for explaining a second embodiment of the present invention.

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

That is, in the step of FIG. 8, the size of the occupied area of the high chroma single subject is determined. The steps are described in more detail in FIG. 9, and the operations in FIGS. 9-1 to 11 are the same as those in the first embodiment. In FIG. 9, in step-1, the absolute value of the color difference signal (R-Y) ₁ at the point 1 shown in FIG. 4 is compared with a constant M, and | (R-Y)
_{If 1} |> M, it is determined that the subject is a high saturation subject, and the process proceeds to −1.

Then, at -2, the color difference signal (B-
Y) _Compare the absolute value of ₁ with the constant N. | (BY) ₁ |> N
If so, it is determined that the subject is a high-saturation subject, and the process proceeds to −1. Then, it is determined that the subject is a low-saturation subject, that is, the process proceeds to the step of FIG.

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

As a result, 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 only the range of the high-saturation subject that has an adverse effect is reduced. Since the width is made narrower, more suitable white balance adjustment becomes possible.

FIG. 10 is a block diagram showing a third embodiment of the present invention.
Numeral 15 is the same block as in the first embodiment, and numeral 22 is an averaging unit having the same configuration as that of 10, 11. The operation of the third embodiment will be described below. The operation of the blocks 1 to 11, 14, and 15 is the same as that of the first embodiment.

In the present embodiment, the signals input to the microcomputer 13 are RY, R
-Y average, B-Y, B-Y average, photometry sensor outputs the other, an averaged signal Y _L output of the chroma signal processing unit 4 in averaging unit 22 through the A / D converter 12 microcomputers Enter in 13. The microcomputer _{13 Y L, R-Y,} B-Y each averaged signal Y _LS of, (R
-Y) _S , (BY) _Deriving R, G, B signals from _S. For example, the following operation is performed.

_{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 R derived in this way, B, The ratio of R to G and the ratio of B to G are derived from the G signal, and the control voltages R _C and B _{C at} which the ratios R / G and B / G become 1 are calculated. Then, the derived R _C and B _C are sent to the R gain control unit 5 and the B gain control unit 6 via the D / A converter 14 to perform white balance adjustment. Also in this 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. Voltage R _C , B _C
The range is further limited. As a result, suitable white balance adjustment can be performed, and at the same time, in the present embodiment, the control voltage is immediately obtained from each of the (RY) _S and (BY) _S Y _LS signals.
Since R _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. Also, once the color difference signal (RY, BY) is obtained,
Since the R, G, and B signals are calculated, the output color of the averaging unit can be easily clipped on the high-saturation object signal, thereby preventing the object object color from being adversely affected. If there is no need for this clip, R, G, B before the color difference signal
The signal may be sent directly to the averaging unit.

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

In this embodiment, the photometric sensor 15 used in the first embodiment to third embodiment is removed, which is a shutter, a configuration of measuring the brightness and the flicker amount of the external light from the aperture and Y _L output instead. That is, the shutter speed and brightness from the aperture when Y _L signal level is controlled by the microcomputer 13 is proper,
The output of the image sensor 2 is intermittently obtained, and the time change of the _YL output is measured to detect the amount of flicker. Based on the above information, the control voltage when the single subject area is large
Determine the limited range of R _C and B _C. In this embodiment, since the photometric sensor 15 can be omitted, the cost can be reduced.

FIG. 12 is a block diagram of a fifth embodiment of the present invention.
Numerals 5 and 22 are the same block diagrams as in the third embodiment, and numeral 25 is a zoom lens for changing the focal length of the image pickup optical system.

In the present embodiment, in particular, in an imaging apparatus such as an electronic still camera which does not need to constantly output an imaging signal, when a single subject area is determined to be large, first, as a data measurement, the focal length of the zoom lens is temporarily reduced, and The control voltages R _C and B _C are determined as the lens state, and the photographing is performed after returning to an arbitrary focal length during the actual photographing. 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. The present embodiment has the same configuration as that of FIG. 1 except for the part relating to the average value.

As can be seen from FIG. 13, in this embodiment, when a large single subject area is determined, the averaging period is partially intermittent. In other words, in such a case, it is assumed that the high-saturation object occupies a large area in the center of the screen. Therefore, as shown in INTE in FIG. 13, the center part (both the horizontal scanning period and the vertical scanning period) is a pulse. By doing so, it is possible to reduce the sampling period of the portion and prevent the influence, thereby enabling the influence with a good white balance.

That is, in the present embodiment, a part of the screen is weighted in averaging. As mentioned above,
Instead of using 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.

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

The operation of the present embodiment will be described below, and the same operations as 1 to 11, 15, and 22 are performed as in the third embodiment. 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 otherwise.

Here E _1, E ₂ 105% of, for example Y _L level, set to correspond to the signal level of 90%.

That if 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 by sampling by A / D12, sends to the microcomputer 13, the signal Y _L, R
White balance is performed by -Y and 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.

In addition the microcomputer 13, the Y _L PEAK combination of detector and white balance adjustment method using the adjustment method using the averaging unit derives a control voltage to compensate for disadvantages of both systems. 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.

In addition, in the present embodiment, when determining the single subject area is large, the influence on the deterioration of the white balance adjustment by the averaging method can be minimized by preferentially using the Y _L PEAK detection method. .

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

Further, in each of the above embodiments, the sampling position and number of the color difference signals are as shown in FIG. 4, but 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 any area equal to or higher than a certain level is detected (any of the regions in the figure). Configuration).

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.

Further, in each of the above embodiments, the color difference signal is used for determining the single subject area, but other signal formats such as a luminance signal may be used.

〔The invention's effect〕

As described above, in the present invention, as described above, it is determined whether or not the area having the approximated color information signal occupies a large size in the screen, and the gain adjustment range is switched based on the determination result. Therefore, even if, for example, a subject of an approximate color occupies a large area in the screen, an erroneous white balance adjustment is not performed by this. That is, it is possible to effectively reduce only the adverse effect of a large-area subject, which adversely affects the white balance.

[Brief description of the drawings]

FIG. 1 is a block diagram of a first embodiment of the present invention, FIGS. 2 and 3 are flowcharts showing the operation of the first embodiment, FIG. 4 is a diagram showing sampling points, and FIG. FIG. 6 is a timing chart of the averaging unit, FIG. 7 is a diagram for explaining a limited range of white balance adjustment, FIG.
9 and 9 are flowcharts showing the operation of the second embodiment of the present invention. FIG. 10 is a block diagram of the third embodiment of the present invention.
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 timing chart of a main part of the sixth embodiment of the present invention, and FIG. Seventh of the present invention
Block diagram of the embodiment, FIG. 15 is a circuit diagram of a Y _L PEAK detector,
FIG. 16 is a diagram showing sampling points, and FIG. 17 is a block diagram of a conventional example. 2 ... Image sensor 5 ... R gain control unit 6 ... B gain control unit 10,11 ... Averaging unit 13 ... Microcomputer

Continuation of front page (56) References JP-A-3-219790 (JP, A) JP-A-64-55996 (JP, A) JP-A-64-46392 (JP, A) JP-A-63-300688 (JP, A) JP-A-63-115489 (JP, A) JP-A-63-141488 (JP, A) JP-A-2-257786 (JP, A) JP-A-2-194792 (JP, A) 64-5286 (JP, A) JP-A-2-250589 (JP, A) JP-A 64-60088 (JP, A) JP-A-63-44581 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04N 9/73 H04N 9/04

Claims (1)

(57) [Claims] An image sensor; a white balance adjusting unit for adjusting a white balance by adjusting a gain of each color signal based on an output of the image sensor; Discriminating means for discriminating whether or not the color information signals at the position are similar to each other, thereby discriminating an area where the approximated color information signal exists in the screen; and approximation in the screen detected by the discriminating means. When the size of the area where the color information signal exists is smaller than a predetermined value, the gain adjustment range of each color signal is set to the first range, and the approximate color information in the drawing detected by the discriminating means is detected. When the size of the region where the signal exists is larger than a predetermined value, the gain adjustment range of each color signal is set to a second range narrower than the first range. Imaging apparatus characterized by comprising control means for controlling switching of the emission adjustment range, the.