JP3701058B2 - Imaging device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an imaging apparatus, and is useful when applied to an imaging apparatus having an automatic exposure control (AE control) function.
[0002]
[Prior art]
Conventionally, AE control in an imaging apparatus has been performed based on information relating to the luminance of a subject. That is, by detecting and integrating the luminance component from the output signal of the imaging means for imaging the subject and controlling the AGC circuit in the iris and preamplifier so that the integrated value of this luminance signal becomes equal to the set value, the imaging means Control the exposure of the camera to an appropriate exposure.
[0003]
[Problems to be solved by the invention]
By the way, the AE control based on the luminance signal as described above is such that red (R), green (G), and blue (B) are present in the entire image of the subject, and when these are integrated, an achromatic color is obtained. This is because it is premised on that. In the NTSC system, the luminance signal Y is obtained based on the following equation.
Y = 0.3R + 0.59G + 0.11B
[0004]
However, depending on the subject, there are cases where there are many specific color components and it is close to a single color. In such a case, there is a problem that the exposure is not properly controlled by the exposure control based on the luminance signal as described above. In particular, the green component is often imaged as a subject, and such a problem appears remarkably.
[0005]
For example, when a main subject (such as a person) is imaged against a green background such as leaves, lawn, or flowers, the luminance signal value is small because there are many green components in the image. It is determined that there is too much aperture, and the main subject that is actually exposed to sunlight is overexposed and flies white.
[0006]
In reality, there are few subjects with many red and blue components, but there are relatively many subjects with many green components. Therefore, it is particularly desirable to take measures against a case where the subject has many green components.
[0007]
Therefore, in view of the above-described prior art, it is an object of the present invention to provide an imaging apparatus having an AE control function capable of performing appropriate exposure control even when a subject has a lot of specific color components such as a green component. .
[0008]
[Means for Solving the Problems]
The present invention for solving the above-described problems includes an imaging means for imaging a subject,
Exposure control signal creating means for creating an exposure control signal using the output signal of the imaging means;
Exposure control means for controlling exposure based on the exposure control signal;
Detecting means for detecting information relating to the hue of the subject from the output signal of the imaging means;
Correction means for correcting the exposure control signal so that the exposure controlled by the exposure control means decreases when it is determined that the subject has a large number of specific color components based on the output of the detection means. ,
The specific color component determined by the correcting means is a green component,
The detection means outputs the integrated value of the color difference signals RY and BY as information relating to the hue of the subject, and the correction means outputs a combined vector of the integrated values of the color difference signals RY and BY. An exposure control signal that determines that the subject has a large amount of green component and the exposure controlled by the exposure control means decreases when the color difference signals RY and BY are within the third quadrant of coordinates having orthogonal coordinate axes. To correct
In addition, in the correction unit, when it is determined that the subject has a large amount of green component while zooming to the wide side, the exposure is maintained as it was before the determination that the green component is large. Features.
[0017]
Therefore, according to the present invention, when a subject with a large amount of green component is imaged, the correction means determines that the subject has a large amount of green component from the information regarding the hue of the subject at this time, and the exposure controlled by the exposure control means is determined. The exposure control signal is corrected so as to decrease. As a result, it is possible to prevent the exposure from becoming excessive.
[0018]
Further, according to the present invention, it is determined that the subject has a large amount of green component when the combined vector of the integrated values of the color difference signals RY and BY is in the third quadrant of coordinates or in a specific region of the third quadrant. Is done.
[0022]
Further, according to the present invention, when it is determined that the subject has a large amount of green component during zooming to the wide side, the exposure is maintained in the previous state, thereby preventing the exposure from becoming excessive. Can do.
[0023]
According to the ninth aspect of the invention, the correction amount is weighted according to which area in the screen it is determined that the specific color component is large.
[0024]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0025]
1 is a block diagram illustrating a configuration of an imaging apparatus according to an embodiment of the present invention, FIG. 2 is a flowchart illustrating processing contents in a brightness determination unit and a control unit of the imaging apparatus illustrated in FIG. 1, and FIG. 3 is illustrated in FIG. FIG. 4, FIG. 5 and FIG. 6 are explanatory diagrams showing a hue determination method in the hue determination unit of the imaging apparatus shown in FIG.
[0026]
As shown in FIG. 1, the imaging apparatus according to this embodiment includes a lens 12, an iris 1, a CCD 2 that is an imaging device, a preamplifier 3 having an AGC circuit 3a, an A / D conversion circuit 4, a signal processing circuit 5, and a signal separation. Circuit 8, integrating circuit 6, microcomputer 7 having brightness determination unit 7 a, hue determination unit 7 b and control unit 7 c, gate circuit 10, D / A conversion circuit 11, and iris driver 9 for driving iris 1 ing.
[0027]
Therefore, light from a subject (not shown) is input to the CCD 2 through the lens 12 and the iris 1 and is converted into an electrical signal by the CCD 2. This electrical signal is sampled and gain controlled by the preamplifier 3 and then converted to a digital signal a by the A / D conversion circuit 4. The digital signal a is input to the signal processing circuit 5 and the signal separation circuit 8 respectively.
[0028]
The signal processing circuit 5 processes the digital signal a and outputs a YC signal (video signal) obtained by mixing the luminance signal and the color signal.
[0029]
On the other hand, the signal separation circuit 8 separates the digital signal a into a luminance signal Y and color difference signals RY and BY and outputs them to the integrating circuit 6. The integration circuit 6 integrates the luminance signal Y and the color difference signals RY and BY output from the signal separation circuit 8, and the integration area at this time is set by the gate circuit 10. In normal AE control, the area at the center of the screen and the area excluding the upper part of the screen are integration areas.
[0030]
Therefore, the integrating circuit 6 integrates the luminance signal Y and the color difference signals RY and BY in the integrating area (such as the area at the center of the screen) set by the gate circuit 10 and integrates the luminance signal integrated value ( Y) and the integrated values (R−Y) and (B−Y) of the color difference signals are output to the microcomputer 7. The integrated value (Y) of the luminance signal is input to the brightness determining unit 7a of the microcomputer 7, and the integrated values (RY) and (BY) of the color difference signal are input to the hue determining unit 7b of the microcomputer 7.
[0031]
As shown in the flowchart of FIG. 2, the brightness determination unit 7a first inputs the position information e of the iris (see FIG. 1) from the iris 1 (S1), and further, as described above, the integrated value (Y) of the luminance signal. Input from the integrating circuit 6 (S2). Subsequently, the brightness (EV value) of the subject is calculated from the input iris position information e and the integrated value (Y) of the luminance signal, the control value of the AGC circuit 3a held in the microcomputer 7 and the sensitivity value of the CCD 2. Then, the calculated EV value is output to the control unit 7c of the microcomputer 7 (S3).
[0032]
As shown in the flowchart of FIG. 2, the control unit 7c determines whether or not the subject has brightness within the normal control region based on the EV value input from the brightness determination unit 7a (S4). If the brightness is outside the normal control region, processing by another routine (detailed explanation is omitted) is performed (S5).
[0033]
On the other hand, if the brightness is within the normal control area, the integrated value (Y) of the luminance signal is compared with the set value SV of the brightness, and the integrated value (Y) of the luminance signal is equal to the set value SV. 1 and the AGC circuit 3a are controlled (feedback control). That is, if the integrated value (Y) of the luminance signal is smaller than the set value SV, the iris control signal c or the AGC control signal d (see FIG. 1) that is the exposure control signal is adjusted to increase the luminance signal Y. If the iris 1 or the AGC circuit 3a is controlled (S7), and if the integrated value (Y) of the luminance signal is larger than the set value SV, the iris control signal c or the AGC control signal d is adjusted to obtain the luminance signal Y. The iris 1 or the AGC circuit 3a is controlled in the decreasing direction (S8). The iris control signal c and the AGC control signal d are converted into analog signals by the D / A conversion circuit 11, and then input to the iris driver 9 and the AGC circuit 3a, respectively.
[0034]
Then, the hue determination unit 7b corrects the iris control signal c or the AGC control signal d according to the hue of the subject. Specifically, as shown in the flowchart of FIG. 3, the integrated values (R−Y) and (B−Y) of the color difference signals are input from the integrating circuit 6 (S11), and “(R−Y) ≦ 0 and (B−Y) ≦ 0 ”holds true, that is, within the third quadrant of coordinates having the color difference signals RY and BY as orthogonal coordinate axes shown in FIG. It is determined whether or not the subject has many green components by determining whether or not the composite vector of Y) exists. In FIG. 4, the vector positions of R, G, B, Cy (cyan), Ye (yellow), and Mg (magenta) are shown for reference.
[0035]
If the combined vector is outside the third quadrant, the brightness setting value SV is set to a standard value (S13). That is, no correction is performed on the brightness setting value SV, so that the iris control signal c and the AGC control signal d are output without being corrected. On the other hand, if the combined vector is present in the third quadrant, it is determined that the subject has a large amount of green component, and a correction value b (see FIG. 1) that decreases the brightness setting value SV is determined by the control unit 7c. Output to. As a result, in the control unit 7c, the brightness setting value SV is lowered based on the correction value b, and the iris control signal c or the AGC control signal d is lowered.
[0036]
Thus, even if a main subject such as a person is photographed against a green background such as a leaf or lawn, it is possible to perform appropriate exposure control, so that the overexposure causes the main subject to fly white. Can be prevented.
[0037]
It should be noted that, as described above, a relatively rough hue that determines whether or not the subject has a large amount of green component depending on whether or not the combined vector of (R−Y) and (B−Y) is in the third quadrant. Although detection is sufficiently practical, more detailed hue detection may be performed as shown in FIG. 5 or FIG.
[0038]
In the detection method shown in FIG. 5, the third quadrant is divided into a plurality of regions (four regions A1, A2, A3, and A4 in the illustrated example) that take into account the color saturation, and any of these regions (R Whether the combined vector of (Y) and (BY) exists is determined by the following determination condition (the determination condition of S12 in FIG. 3 is changed to the following determination condition), and the value of the correction value b for each region It is a method of changing. For example, when the composite vector is in the A1 area, the correction value b is maximized, and the correction value b is decreased in the order of the A2, A3, and A4 areas.
[0039]
Region (A1 + A2 + A3 + A4): (R−Y) ≦ 0 and (B−Y) ≦ 0
Region (A1 + A2 + A3): (R−Y) ≦ R3 and (B−Y) ≦ B3
Region (A1 + A2): (R−Y) ≦ R2 and (B−Y) ≦ B2
Region (A1)...: (R−Y) ≦ R1 and (B−Y) ≦ B1
[0040]
The method shown in FIG. 6 does not simply determine whether the combined vector is in the third quadrant, but based on the following determination condition (the determination condition of S12 in FIG. 3 is changed to the following determination condition) This is a method of limiting to a specific area in three quadrants (that is, limiting hue and saturation), and outputting a correction value b when there is a composite vector in the area.
[0041]
Rm ≦ (R−Y) ≦ Rn and Bm ≦ (B−Y) ≦ Bn
[0042]
As described above, more appropriate exposure control can be performed by dividing the third quadrant into a plurality of regions in consideration of the color saturation, or by limiting the third quadrant to a specific region in the third quadrant.
[0043]
Further, when a green hue is detected as described above, the correction is performed in the direction of decreasing the brightness setting value SV, and the following (1) to (4) are performed. Correction conditions may be provided.
[0044]
(1) Change the correction amount according to the brightness.
That is, the brightness of the subject is determined from the information on the brightness of the subject (EV value), and when the brightness of the subject is high, the subject is often exposed to sunlight outdoors, so the contrast is considered high. For this reason, when the correction amount is increased and the brightness is low, the image is taken indoors and the contrast is not so high in many cases, so the correction amount is reduced. Thereby, more appropriate exposure control can be performed.
[0045]
(2) Change the correction amount according to the amount of green component.
That is, when the detected amount of the green component is large, it is considered that a large part of the subject is occupied by a green object such as a green tree leaf or a lawn, so the correction amount is increased. This also makes it possible to perform more appropriate exposure control.
[0046]
(3) The previous data is retained instead of being corrected.
That is, when the green component increases in the screen during shooting by zooming operation, the values of the iris control signal c and the AGC control signal d are not changed without correcting and changing the brightness setting value SV. It is also possible to hold the exposure in the previous state by holding at this value. For example, consider the case of photographing a white flower in a green leaf. When a white flower is first photographed on the tele side (telephoto) and then gradually pulled to the wide side (wide angle), the area of the green leaf increases in the screen and the value of the luminance signal decreases. Therefore, the iris signal 1 or the AGC circuit 3 is controlled to increase the luminance signal level. As a result, the portion of the white flower that goes to the wide side becomes white as the portion of the CCD 2 is saturated. Therefore, when it is determined that there is a large amount of green component during the zoom operation, the values of the iris control signal c and the AGC control signal d are held at the previous values and the exposure is held at the previous state. good. By controlling in this way, white flowers can be prevented from flying white.
[0047]
(4) The correction amount is weighted by using the data of the division photometry AE control.
An example of a division pattern in the case of performing the division photometry AE control is shown in FIG. In this case, since it is considered that a main subject such as a person often enters the central area 1, the most weight is given. The other areas 2, 3 and 4 are considered to contain backgrounds, so the weights are reduced in order. Since there is a high possibility that the area 5 is empty, the data is deleted or weighted.
When such divided photometry AE control is performed, color signal data is also taken for each area. If the green component is large in area 1, the correction is reduced (or no correction), When the green component is large in 3 and 4, the correction amount is increased. This also makes it possible to perform more appropriate exposure control. However, since the way of division varies depending on the design concept, it is not limited to the division pattern shown in FIG.
[0048]
In the above-described embodiment, it is determined whether or not the subject has a large amount of green component based on the color difference signal. However, the present invention is not limited to this. For example, based on the R, G, and B signals, the G signal If the level is higher than a certain level compared to the other R and B signal levels, it may be determined that the subject has a lot of green and the exposure control signal may be corrected.
[0049]
In the above embodiment, the correction of the exposure control signal based on the green hue having a particularly large effect has been described. Of course, the present invention corrects the exposure control signal based on another hue (red, blue, etc.). It can also be applied to.
[0050]
【The invention's effect】
As specifically described above with the embodiment of the present invention, according to the present invention, since the exposure control signal is corrected according to the hue of the subject, appropriate exposure control can be performed regardless of the hue of the subject. it can. In particular, the effect of the present invention is particularly great when the subject has a large amount of green components, such as when a person or the like is photographed against a green background such as leaves or lawns.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a configuration of an imaging apparatus according to an embodiment of the present invention.
2 is a flowchart illustrating processing contents in a brightness determination unit and a control unit of the imaging apparatus illustrated in FIG. 1;
3 is a flowchart showing processing contents in a hue determination unit of the imaging apparatus shown in FIG. 1;
4 is an explanatory diagram illustrating a hue determination method in a hue determination unit of the imaging apparatus illustrated in FIG. 1; FIG.
FIG. 5 is an explanatory diagram illustrating a hue determination method in a hue determination unit of the imaging apparatus illustrated in FIG. 1;
6 is an explanatory diagram illustrating a hue determination method in a hue determination unit of the imaging apparatus illustrated in FIG. 1;
FIG. 7 is an explanatory diagram showing an example of a division pattern when performing division photometry.
[Explanation of symbols]
1 Iris 2 CCD
3 Preamplifier 3a AGC circuit 4 A / D conversion circuit 5 Signal processing circuit 6 Integration circuit 7 Microcomputer 7a Brightness determination unit 7b Hue determination unit 7c Control unit 8 Signal separation circuit 9 Iris driver 10 Gate circuit 11 D / A conversion circuit 12 Lens RY, BY Color difference signals (RY), (BY) Color difference signal integral value Y Luminance signal (Y) Luminance signal integral value b Correction value c Iris control signal d AGC control signal

Claims (1)

Imaging means for imaging a subject;
Exposure control signal creating means for creating an exposure control signal using the output signal of the imaging means;
Exposure control means for controlling exposure based on the exposure control signal;
Detecting means for detecting information relating to the hue of the subject from the output signal of the imaging means;
Correction means for correcting the exposure control signal so that the exposure controlled by the exposure control means decreases when it is determined that the subject has a large number of specific color components based on the output of the detection means. ,
The specific color component determined by the correcting means is a green component,
The detection means outputs the integrated value of the color difference signals RY and BY as information relating to the hue of the subject, and the correction means outputs a combined vector of the integrated values of the color difference signals RY and BY. An exposure control signal that determines that the subject has a large amount of green component and the exposure controlled by the exposure control means decreases when the color difference signals RY and BY are within the third quadrant of coordinates having orthogonal coordinate axes. To correct
In addition, in the correction unit, when it is determined that the subject has a large amount of green component while zooming to the wide side, the exposure is maintained as it was before the determination that the green component is large. An imaging device that is characterized.

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